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20 


-y^ 


A    TREATISE    ON     THE 


PRINCIPLES   AND   PRACTICE 


OF 


DOCK    ENGINEERING. 


A    TREATISE    ON    THE 


PRINCIPLES   AND   PRACTICE 


OF 


DOCK    ENGINEERING. 


CHARLES  GRIFFIN  &  Co.,  Ltd.,  Publishers. 


I  ♦  I 


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4 


A   TREATISE    ON   THE 


PRINCIPLES   AND    PRACTICE 


OF 


DOCK    ENGINEERING. 


BY 

BRYSSON    CUNNINGHAM,    B.E., 

ASSOC.M.INST.C.E., 

OF  THE  ENGINEER'S  DEPARTMENT,  MERSEY  DOCKS  AND  HARBOUR  BOARD;    EXHIBITIONER 
.     OF  THE  ROYAL  UNIVERSITY  OP  IRELAND;    MEDALLIST  OF  THE  CITY  AND  GUILDS 
OF  LONDON  INSTITUTE;    AUTHOR  OF   "BUILDING  CONSTRUCTION,"  ETC 


mub  34  foVbin^^pltiUB  and  468  JUudtrationa  in  tbe  XLcit 


LONDON: 
CHARLES    GRIFFIN   &   COMPANY,   LIMITED; 

EXETER    STREET,    STRAND. 

1904. 

[A//  Rights  Reserved,^ 


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-J 


(^ 


\ 
\ 


PREFACE. 


Maritime  EngineeriDg  is  a  science  of  peculiar  and  vital  importance 
to  the  national  and  commercial  welfare  of  an  insular  people. 


The  subject,  however,  in  its  entirety,  is  much  too  extensive  to 
be  dealt  with  within  the  limits  of  a  single  volume,  and,  even  in 
treating  that  section  of  it  relating  to  docks,  the  author  feels  that 
he  is  but  touching  on  the  fringe  of  a  theme  fraught  with  manifold 
possibilities  and  capable  of  great  future  development. 

His  aim  throughout  has  been  to  deal  thoroughly  rather  than 
extensively,  and  to  investigate  in  detail  rather  than  in  general, 
leaving  nothing  undone,  in  order  that  premises  and  conclusions 
alike  might  be  presented  in  their  completest  and  most  intelligible 
form.  And  here  it  may  be  remarked  that,  while  the  book  has 
been  written  largely,  and  even  mainly,  for  the  student,  it  is  hoped 
that  it  will  not  be  without  some  value  for  reference  purposes  to 
the  expert  and,  indeed,  to  all  who  are  in  any  way  concerned  with 
this  branch  of  engineering  and  its  cognate  interests. 

The  compilation  of  such  a  work  has  naturally  entailed,  in 
addition  to  a  basis  of  long  personal  experience,  much  correspondence 
and  research,  and  the  author  takes  this  opportunity  of  acknow- 
ledging his  indebtedness  to  many  professional  friends,  who  have 
contributed  valuable  information  and  who  have  otherwise  rendered 
him  assistance  in  a  task  of  no  inconsiderable  difficulty.  To  the 
Councils  of  the  Institution  of  Civil  Engineers,  the  Institution  of 
Mechanical  Engineera,  the  Institution  of  Naval  Architects,  the 
American  Society  of  Civil  Engineers,  and  the  Liverpool  Engineering 
Society,  he  tenders  his  thanks  for  permission  to  reproduce  diagrams 
and    to   make  extracts  from  papers  published    in    their  respective 


J  H7350 


VI  PREFACE. 

Minutes  of  Proceedings,  as  well  as  to  the  writers  of  the  papers 
for  their  personal  sanction.  In  addition  to  these  gentlemen,  the 
author  feels  that  he  cannot  omit  to  specify  his  great  obligation 
to  Mr.  A.  G.  Lyster,  Engineer-in-Chief  to  the  Mersey  Docks  and 
Harbour  Board,  for  the  privilege  of  making  use  of  much  valuable 
material;  to  M.  Pastakoff',  of  St.  Petersburg;  M.  Delachanal,  of 
Havre;  and  to  many  other  English  and  Continental  engineers  for 
esteemed  contributions  relating  to  recent  practice  at  various  ports. 

The  Editors  of  Engineering  and  of  TIte  Engineer  are  thanked 
for  permission,  very  courteously  accorded,  to  make  extracts  from 
the  columns  of  their  journals.  A  number  of  well-known  engin- 
eering firms  have  also  kindly  placed  at  the  author's  disposal  diagrams 
of  plant  and  appliances  manufactured  by  them. 

Whilst  every  care  has  been  taken  to  ensure  the  accuracy  of 
statistics  and  calculations,  it  is  possible  that  a  few  errors  may 
have  crept  in  and  escaped  detection.  It  is  trusted  that  these,  if 
discovered,  may  prove  to  be  of  minor  importance;  but,  in  any 
case,  the  author  will  be  very  grateful  for  an  intimation  of  them. 

BRYSSON    CUNNINGHAM. 

Liverpool,  Jamvary,  1904. 


CONTENTS. 


CHAPTER  I.— Historical  and  Dlseursive. 

PAGB 

Introductoey  Definitions — Pouts  and  thbib  Functions — The  Development 
OF  Maritime  Engineering—The  First  Wet  Dock—The  Howland 
Great  Wet  Dock — Regent  Progress — Dock  Administration — Historical 
Notices  of  the  Ports  of  London,  Liverpool,  New  York,  Glasgow, 
Hamburg,  Antwerp,  Marseilles,  Rotterdam,  Cardiff,  and  of  the 
Tyne  Ports,        .........  1 

CHAPTER  II.— Doek  Design. 

Necessity  for  Docks — Relative  Advantages  of  Docks  and  Basins- 
Restrictions  IN  Design — Considerations  in  regard  to  Position  and 
Outline — Various  Forms — A  Model  Dock  System— Ratio  of  Quay 
Space  to  Water  Area — Ratio  of  Periphery  to  Surface — Grouped 
Docks — Internal  Dispositions — Cost  of  Construction— Fresh  Water 
Supply— Ship  Design — Typical  Dock  Systems  at  Liverpool  and 
Birkenhead,  Barry,  Buenos  Ayres,  Tilbury,  Glasgow,  Calcutta, 
Hull,  Hamburg,  London,  Sunderland,  Swansea,  Havre,  and 
Marseilles — Statistics  of  Representative  Docks,  .  .  .17 

CHAPTER  III.— Constructive  Appliances. 

Classification— Positive,  Negative,  and  Auxiliary  Appliances— Piling 
Apparatus— Hand,  Steam,  Electric,  and  Hydraulic  Machines- 
Ram  AND  Fall— Quiescence- Limit  of  Driving— Supporting  Power 
OF  Piles  —  Concrete  Mixers  —  Messent,  Taylor,  Carey-Latham, 
Sutcliffe,  and  Gravity  Machines— Concrete  Moulds — Block -setting 
Appliances — Excavators — French  and  German  Machines — Ruston, 
Simpson-Porter,  and  Whitaker  Steam  Navvies — Hydraulic  Navvy — 
Drilling  Appliances — Hand  and  Machine  Drills— Blasting  Agents 
— Haulage  and  Traction — Dredgers  and  Hoppers— Suction,  Ladder, 
Dipper,  and  Grab  Dredgers — Buckets— Shoots — Tumblers — Power 
— Cost — Dams  of  Earth,  Timber,  Stone,  Concrete,  and  Iron— Coffer- 
dams—  Strength  and  Stability  —  Pumps  and  Pumping  —  Cranes  — 
Overhead  Travellers — Skips — Lewis  Bars  and  Clips— List  of  Con-  rCo 
structive  Plant  at  Keyham  Dock  Works,  .  .  .       m 

CHAPTER  IV.-Materlals. 

Concrete — The  Aggregatb— The  Matrix — Portland  Cement— Its  Fineness, 
Strength,  Rate  of  Setting,  and  Soundness— Adulterants  of  Cement — 
Proportion  of  Water— Action  of  Sea  Water  upon  Concrete — Case  of 


Viii  CONTENTS. 


PAGE. 


Disintegration  at  Aberdeen^Official  Explanation  and  Possible 
Causes— De.  MiCHAftLis  on  Cement  in  Sea  Water — Suggested  Protec- 
TivB  Measures— Practical  Notes  on  Mixing  Concrete— Strength  of 
Concrete— Sample  Compositions — Iron  and  Steel— Alloys  with  Man- 
ganese AND  Nickel — Impurities— Varieties  of  Cast  Iron,  Wrought 
Iron,  and  Steel — Defects  in  Manufactured  Iron— Specifications  for 
Castings,  Plates,  and  Bars^— Working  Strength — Tests— Weights- 
Corrosion  OF  Iron  and  Steel — Effect  of  Sea  Water  on  Dock  Gates 
— Preservative  Agents— Timber— Varieties  used  for  Dock  Work — 
Selection  of  Timber — Destruction  and  Deoat — Means  of  Preservation 
—Stone— Kinds  Employed — Destructive  Agencies,  .  .  .      IIT 

CHAPTER  v.- Dock  and  Quay  Walls. 

Definition — ^Functions  under  Various  Conditions — Stresses  in  Retaining 
Walls — Overturning  Forces— Angles  of  Repose— Theory  of  Conjugate 
Pressures  —  Coulomb's  Theorem — Chaudy*s  Theorem  —  Weight  of 
Earthwork  —  Surcharge  —  Restraining  Forces  —  Counterforts  —  Tie 
Bars  —  Weight  of  Masonry  —  Empirical  Formuue  —  Conditions  of 
Stability — ^Centres  of  Gravity — Typical  Example — Practical  Points 
— Natural  Foundations— Stratified  Sites— Artificial  Foundations- 
Piling — Wells  and  Cylinders— General  Methods  of  Construction, 
with  Examples  op  Quay  Walls  at  Newcastle,  Cork,  Glasgow, 
Liverpool,  Belfast,  Ardrossan,  Marseilles,  Antwerp,  Rotterdam, 
Dublin,  Kurrachee,  Suez,  Bougie,  and  Sfax  —  Consideration  of 
Instances  of  Failure  at  Altona,  London,  Southampton,  Calcutta,  and 
Liverpool — Underpinning — Miscellaneous  Types  of  Wall  at  Hull, 
Greenock,  London,  Liverpool,  and  Manchester,  ....      156 

CHAPTfiR  VL— Entrances,  Passages,  and  Locks. 

General  Aspects  of  the  Subject — Site — Effect  of  Wind,  Wave,  and 
Current — Direction — Size — Draught  of  Water  in  Approach  Channel 
— Arrangement  and  Types— Simple  Entrances,  Locks,  and  Half-tide 
Basins — Maintenance  of  Fairway— Sluicing— Velocity  of  Efflux — 
Friction  of  Culverts— Coefficients  of  Discharge — Sluicing  Arrange- 
ments AT  Liverpool,  Ostend,  Honfleur,  Ramsgate,  Dover,  and  Dublin 
— Scraping  and  Scuttling— Dredging— Lock  Foundations —Boils  and 
Springs — Instances  at  Hull  and  Liverpool — Suggestions  for  Treat- 
ment— Grouting— Stock-ramming — Sand  Concrete— Lock  Construction 
— Sills  —  Platforms  —  Recesses  —  Waixs  —  Culverts  —  Penstocks  or 
Cloughs  —  Stoney  Sluices  —  Fan  Gates  —  Pivotted  Gates  —  Duration 
OF  Levelling  Operations^-Examples  of  Dock  Entrances  at  Liverpool, 
Dunkirk,  Buenos  Ayres,  Kiddbrpur,  Eastham,  Barry,  Ardrossan, 
Hull,  and  Bremerhaven,         .......      225 

CHAPTER  VII.-Jetties,  Wharfs,  and  Piers. 

Definitions— Stresses— Wave  Action— Force  of  Impact — Results  of  Impact 
— ^Observed  Pressures — Instances  of  Wave  Action— Design  of  Jetties 
AND  Piers — Construction  —  Concrete  Mass,  Bag,  and  Block  Work  — 
Dressed  Masonry  and  Rubble  Mounds — Fascine  Work— Open  Timber 
Framing  and  Crib  Work — Columnar  Structures  and  Frameworks  of 


CONTENTS.  ix 

PAGB 

Iron  and  Steel — Monier  and  Hennebique  Systems — Typical  Examples 
AT  Aberdeen,  Zbebruogb,  Havre,  Kingstown,  Algiers,  Hook  of 
Holland,  Blyth,  Liverpool,  Newcastle,  Soukhoum,  Touaps^,  Belfast, 
Dundee,  Dunkirk,  Tilbury,  Madras,  Sunderland,  Greenock,  and 
Hull,       ..  ....•••      268 

CHAPTER  VIIL— Doek  Gates  and  Caissons. 

Definition  and  Relative  Advantages  of  Gates  and  Caissons — Metal  versus 
Wooden  Gates — Weight,  Cost,  Dttrability,  and  Strength— Single-leaf 
AND  Double-leaf  Gates— Horizontal  and  Vertical  Girder  Types- 
Storm  Gates— Strut  Gates — Stresses  in  Gates — Statical  Forces — 
Methods  of  Finding  Resultant  Pressure— Zones  of  Equal  Pressure — 
Rise  of  Gates — Analysis  of  Resultant — Graphic  Representation — 
Limits  of  Stress — Typical  Examples — Vertical  Co-planar  Girders — 
Stress  is  Panels — Exemplification  of  Gate  Calculations — ^Fittings — 
Examples  of  Gates  at  Liverpool,  Birkenhead,  Manchester,  Hull, 
Buenos  Ayres,  Calcutta,  South  Shields,  and  Dunkirk— Table  of  Dock 
Gates — Stresses  in  Caissons — Classification  of  Caissons — Swinging, 
Traversing,  Sliding,  Rolling,  Floating,  and  Ship  Caissons— Lowering 
Platforms— Examples  of  Caissons  at  Malta,  Bruges,  Blackwall, 
Cardiff,  Calcutta,  Belfast,  Liverpool,  and  Greenock — Table  of  Dock 
Caissons,  .........      301 

CHAPTER  IX.— Transit  Sheds  and  Warehouses. 

Extent  of  Accommodation  Required— Proportion  of  Goods  to  Quayage — 
Statistics  of  Sample  Cargoes — Accessibility  of  Sheds — Proximity  to 
Edge  of  Quay— Level  of  Floor — General  Diversity  of  Practice- 
Features  OF  Construction— Doors  and  Doorways— Compartments — 
Lighting — Materials  for  Floors  —  Fire-resisting  Construction  — 
Monier,  Hennebique,  and  C0TTAN91N  Systems — Pressure  Sustained  by 
Floors— Columns  and  Piers— Strength  of  Columns— Roof  Coverings — 
Weight  of  Shed  Roofs— Examples  of  Sheds  and  Warehouses  at 
Tilbury,  Liverpool,  Dundee,  Greenock,  Glasgow,  Manchester, 
Antwerp,  Rotterdam,  Havrie,  Marseilles,  Calais,  Dunkirk,  Dieppe, 
Rouen,  Bremen,  Hamburg,  Calcutta,  and  Buenos  Ayres,  .  .      364 

CHAPTER  X.— Dock  Bridges. 

Classification — Floating  Bridges — Traversing  Bridges — Dra^vbridges — 
Bascules — Lifting  Bridges— Swing  Bridges— Single-leaf  verstis  Double- 
leaf  Bridges— Stresses  in  Movable  Bridges — Case  of  the  Double 
Cantilever — Case  of  the  Cantilever  and  Beam— Case  of  the  Arch — 
Case  of  the  Continuous  Beam — The  Theorem  of  Three  Moments- 
Effect  OF  Counterpoise— Loads  imposed  on  Movable  Bridges — Weight 
OP  Structure — Weights  of  Typical  Locomotives — Equivalent  Live 
Loads — Weight  of  Vehicles  and  Men — Practical  Example  of  the 
Calculations  for  a  Swing  Bridge — Distinctive  Features  of  Movable 
Bridges— The  Pivot— Balanced  Rollers  and  Wheels— The  Counter- 
poise— Setting  Apparatus — Interlocking  Apparatus — Notes  on  Design 
— Illustrations  of  Movable  Bridges  at  Greenock,  Antwerp,  Rotterdam, 
Chicago,  Marseilles,  Liverpool,  Leith,  and  Ridderpur,  .  ,      405 


CONTENTS. 


CHAPTER  XL— Graving  and  Repairing  Doeks. 


PAGE 


Vabious  Methods  of  effboting  Repatbs  to  Ships — Careening — Beaching — 
The  Gbidiron — The  Slipway— The  Hydraulic  Ldbt— The  Graving 
Dock — The  Floating  Dock — Essential  Requirements  of  a  Repairing 
Dep6t — Comparison  of  the  various  Types  in  regard  to  Accessibility, 
Ventilation,  Light,  Capacity,  Initial  Cost,  Maintenance  and  Repairs, 
Working  Expenses,  Durability  and  General  Adaptability— Design 
AND  Construction  of  Slipways  —  Foundation  —  Permanent  Way  — 
Cradle— Sliding  Slipways— Broadside  Slipways— Stresses  in  Slipways 
— Design  and  Construction  of  Graving  Docks — Types  of  Floating 
Docks— Process  of  Overhauling— Equipment  of  Repairing  Docks — 
Distribution  of  Pressure  on  Keel  Blocks— Description  of  Gridirons 
AT  Liverpool,  Hydraulic  Lift  at  London,  Slipway  at  Dover,  Graving 
Docks  at  Bremerhaven,  Liverpool,  Glasgow,  Barry,  and  London, 
AND  Floating  Docks  at  Cartagena  and  Bermuda,  .  .  .      462. 

CHAPTER  XIL— Working  Equipment  of  Doeks. 

Sources  of  Power— Compressed  Air— Steam— Water  under  Pressure- 
Electricity — Comparative  Expenditure  of  Energy — Crane  Tests— Cost 
OF  Power — Hydraulic  Machinery — Systems  of  Electrical  Distribution 
— Applications  to  Dock  Equipment — Gate  Machinery— Power  of  Gate 
Machines— Sluicing  Machinery — Capstans — Quay  and  Floating  Cranes 
— Jiggers  and  Transporters — ^Coal  Tips  and  Lifts- Grain  Elevators 
— Slipway  Haulage — Pumping  Installations — Petroleum  Storage- 
General  Equipment — List  of  Appliances  in  Use  at  Hamburg,  Havre, 
AND  Liverpool,  ........      50^ 


LIST   OF  ILLUSTRATIONS. 


FIG.  PAOK 

1.  Southampton  Docks, 21 

2.  Model  dock  system, Plate  I.,  ^o /ace  22 

3.  Amidships  section  of  typical  vessels, 27 

4.  Longitudinal  section  of  modem  cargo  vessel, 28 

5.  Liverpool  Docks, Plate  II.,  to  face  32 

6.  Birkenhead  Docks, Plate  IIL,     „  32 

7.  Barry  Docks, 35 

8.  Docks  of  Buenos  Ajrres, 37 

9.  TUbury  Docks, 39 

10.  Glasgow  Harbour  and  Docks, 41 

11.  Eidderpur  Docks,  Calcutta, 42 

12.  Alexandra  Dock,  Hull, 43 

13.  Hamburg  Docks, 44 

14.  MiUwall  Dock,  London, 45 

15.  London  and  St.  Katharine  Docks,  London, 46 

16.  East  and  West  India  Docks,  London, -.47 

17.  Royal  Victoria  and  Albert  Docks,  London, 48 

18.  Surrey  Commercial  Docks,  London, 49 

19.  Sunderland  Harbour  and  Docks, 50 

20.  Swansea  Docks, 51 

21.  Port  of  Havre, 52 

22.  Port  of  Marseilles, 63 

23.  Pile  driving  machine, 58 

24.  Whitaker's  steam-hammer  pile  driver, 59 

25.  Electric  pile  driver, .62 

26.  27,  28.  Hennebique  piles, 63 

29.  Messent  concrete  mixer, .        .  67 

30.  Taylor             do.,             68 

31.  32.  Carey- Latham  concrete  mixer, 70 

33.  Sutcliffe  concrete  mixer, 71 

34.  Do.                 do.,            72 

35.  Gravity             do 72 

36.  37,  38.  Concrete  moulds, 73 

39.  Concrete  mould, 74 

40.  "Goliath," 75 

41.  "Titan," 76 

42.  43.  French  steam  excavator,     ......  ...  78 

44,  45,  46.  Grerman  steam  excavator, .  80 

47.  Ruston  steam  excavator, 82 

48.  Simpson  and  Porter  steam  excavator, 83 

49.  Hydraulic  excavator, 85 

50.  Suction  hopper  dredger,  Seine  navigation, 90 


XU  LIST  OP  ILLUSTRATIONS. 

na.  PAGE 

51,  Hopper,  fitted  with  adjustable  coamings, 91 

52,  53.  Bates'  dredger,  with  clay-cutting  appliances, 93 

54.  Ladder  dredger,  "  Caimdhu,"  Clyde  navigation, 95 

55,  56, 57, 58.  Do.,            do.,                   do.,                   96 

59,  60,  61.  Hopper  barge,  Clyde  navigation, 99 

62,  63.  Peters'  grab, 101 

64,  65.  Priestman  grab, 102 

66.  Cofferdam  at  Liverpool, 107 

67.  Do.          HuU, 108 

68.  Do.          Limerick 109 

69,70.  Dams  at  Ardrossan, 110 

70a.  Pulsometer, 112 

71,  72,  73,  74,  75,  76.  Lewis  bars  and  clips, 114 

77)  78.  Stresses  in  retaining  walls, 157 

79.  Angle  of  repose, 157 

81.  Stresses  in  retaining  walls, 159 

81a.  Conjugate  pressures, 160 

82,83.            Do.,                     161 

84,  85.            Do.,                     162 

86,87.           Do.,                     163 

88.  Direction  of  thrust 165 

89.  ReiUy's  resultant, 166 

90, 91.  Coulomb's  theorem,     . 168 

92,  93.  Chaudy's      do., 168 

94.  Surcharge, 171 

95,  96.  Distribution  of  pressure  on  bed  joint, 175 

97.  Do.               do.               do.,                  176 

98,  99,  100,  101,  102.  Loci  of  centres  of  gravity, 177 

03,  104.  Combined  centres  of  gravity, 178 

05.  Diagram  of  stresses  in  quay  wall, 179 

06.  Old  dock  wall  at  Leith,   .        .    ^ 181 

07.  Quay  wall  at  Sheemess, '181 

08.  Do.          Kidderpur, 182 

09.  Transverse  fracture  of  foundations, 183 

10,111.  Herculaneum  dock  wall,  Liverpool, 184 

12.  Dock  wall  at  Ardrossan, 184 

13.  Quay  wall  at  Rotterdam,         ...                 186 

14.  Dock  wall  at  Limerick, 187 

15.  Quay  wall  at  Rouen, 187 

16,117.   Wrought-iron  curb, 188 

18.  Quay  wall  at  Newcastle-on-I^e, 190 

19,  120.  Quay  wall  at  Cork 191 

21,  122.        Do.            Glasgow, 192 

23,  124,  125,  126.  Cylinder  shoe  at  Glasgow, 193 

26a.  Joint,  cylinder  shoe  at  Glasgow, 194 

27,  128,  129.  Quay  wall  at  Newcastle, 196 

30.  Dock  wall  at  Liverpool, 198 

31.  Timbered  trench, 199 

32.  Quay  wall  at  Belfast, 199 

33.  Construction  within  temporary  dam, 200 

34.  Dam  and  quay  wall  at  Ardrossan 200 


LIST  OF  ILLUSTRATIONS. 


xin 


FIO.  PAOB 

135.  Dock  wall  at  Maraeilles,  type  A, 201 

136.  Do.                 do.,          do.  B, 202 

137.  138.  Caiflson  for  walla  at  Marseilles, 203 

139.  Dock  wall  at  Marseilles,  type  C, 206 

140.  Quay  wall  at  Antwerp, 206 

141.  142.  Pneumatic  construction  at  Antwerp, 206 

143.  Pneumatic  construction  at  Rotterdam, 207 

144,  146.  Cast-iron  washer 200 

146.  Quay  wall  at  Dublin 210 

147.  Do.          Cork, 210 

148.  149.  Monoliths  at  Cork, 211 

150.  Blockwork  at  Kurrachee, 211 

151.  Quay  wall  at  Bougie 212 

152.  Monolith         do.,             213 

153.  Quay  wall  at  Sfax, 213 

154.  Quay  at  Altona, 214 

L56,  156.  Anchorage  for  stays, 216 

L57.  Dock  wall  at  Southampton, 217 

158.  Do.          Liverpool, 218 

159.  Underpinning  at  Ardrossan, 218 

160.  Do.              Liverpool 219 

161.  Do.                   do., 220 

162.  163,  164.  Dock  waU  at  HuU, 221 

165,  166.  Dock  walls  at  Greenock, 222 

167.  Dock  wall  at  Hull, 222 

168.  Quay  wall  at  Tilbury, 222 

169.  Dock  wall  at  Liverpool, 223 

170.  Do.          Manchester, 223 

171.  Velocity  of  water  in  sluices, 239 

L72,  173.  Sluicing  system  at  Liverpool, Plate  YV.,  to  fact  244 

174.  Section  through  outlet, 244 

175.  PortofOstend, Plate  V.,  ^o /ace  250 

176.  Elevation  of  a  dock  entrance, 251 

177.  178.  Hollow  quoins 253 

179.  Caisson  recess  at  Greenock, 254 

180,  181.  Stoney  sluice, 255 

182.  Fan  door  at  Dunkirk, 256 

183.  Section  of  Old  Canada  Lock,  Liverpool, 258 

L84.  Section  of  Canada  Lock,  Liverpool,  as  deepened 259 

.85.  North  Lock  at  Dunkirk, Plate  VI.,  fo /ace  260 

186.  Dam  at  Dunkirk, 261 

187.  Section  of  North  Lock,  Dunkirk, 262 

188.  189,  190,  191,  192,  193.  North  Lock  at  Buenos  Ayres,   .      Plate  VIL,  to  fact  262 

194.  Eastham  Locks Plate  VIIL,      „  262 

195,  196, 197, 198, 199, 200.  Kidderpur  Dock,  entrances  and  lock,  Plate  IX.,    „  264 

201.  Entrance  to  Eglinton  Dock,  Ardrossan 264 

202,  203,  204,  205.  Alexandra  Lock,  Hull,     ....         Plate  X.,  to  fact  266 

206.  Bremerhaven  Lock, 266 

207,  208,  209,  210.  Caisson  at  Zeebrugge 278 

^11.  Jetty  at  Zeebrugge, 279 

^12.  Pier  at  Havre, 280 

213.  Jetty  at  Dover, 280 


xiv  LIST  OF  ILLUSTRATIONS. 

FIG.  PAGI 

214.  Jetty  at  Algiers, 281 

215,  216,  217.  Fascine  work, 28a 

218.  Mole  at  Hook  of  Holland, 283 

219,  220.  Jetties  at  Blyth, 284 

221,  222.  Jetties  at  Liverpool,  types  A  and  B, 285 

223.  Jetty  at  Liverpool,  type  C, 286 

224.  Crib  frame, 286 

225.  226.  Pier  at  Soukhoum, 288 

227.  Jetty  at  Zeebrugge, 288 

228.  Do.,                        289 

229.  230.  Jetty  at  Touaps^, 290 

231,  232,  233,  234.  Hennebique  sheeting  pile 291 

235,  236,  237.  Hennebique  sheeting  pile, 292 

238.  Wharf  at  Belfast, 292 

239,  240.  Wharf  at  Dundee, 294 

241.  Jetty  at  Dunkirk 294 

242,  243.  Pierhead  at  Madras 296^ 

244,  245.  Piers  at  Sunderland, 298 

246.  Wharf  at  HuU, 300 

247,  248,  249.  Single-leaf  gate  at  Birkenhead, 311 

250,  251.  Water  pressure  on  dock  gates, 316 

252.  Water  pressure  on  dock  gates, 317 

253.  Diagram  of  resultant  pressure, 31& 

254.  Do.                  do.,                      319 

255.  Range  of  position  of  line  of  pressure, 320 

256.  Diagram  of  resultant  pressure, 320 

257.  258.  Zones  of  equal  pressure, 322 

259.  Ratio  of  rise  to  span, 324 

260.  Analysis  of  resultant  pressure, 325 

261.  262.  Amount  and  range  of  stress, 327 

263.  Stress  in  connecting  piece, 328 

264.  Centre  of  section 331 

265.  Distribution  of  pressure  on  vertical  girders, 331 

266.  267,  268.  Wooden  dock  gate  at  Liverpool,     .        .        .       Plate  XL ,  <o /ace  332 
269,  270,  271,  272,  273.  Steel  dock  gates  on  river  at  Blyth,   .       Plate  XII. ,     „  334 

274.  Section  of  rib, 335 

275.  Do 336 

276.  277,  278.  Gate  rollers  at  Liverpool, 338 

279.  Gate  roller  at  Dublin, 339 

280.  Clapping  sill 339 

281.  Gate  anchorage  at  Liverpool, 339 

282.  Do.             on  the  l^e, 339 

283.  Do.             at  Dublin, 340 

284.  285.  Gate  footsteps 341 

286,  287.        Do.,                     342 

288,  289.  Dock  gate  at  Liverpool, 343 

290,  291,  292, 293, 294,  295, 296.  Manchester  Ship  Canal  gates,  Plate  XIIL,  to  face  344 

297,  298,  299.  Dock  gates  at  Hull, 344 

300,  301,  302,  303.  Lock  gates  at  Buenos  Ayres, 346 

304,  305,  306,  307,  308,  309.  Dock  gates  at  Calcutta, 347 

310,  311,  312.  Pock  gates  on  the  Tyne,  ....      Plate  XIV.,  to  face  348 

313.  Graving  dock  entrance  on  the  Tyne, 348. 


LIST  OF  ILLUSTRATIONS. 


XV 


FIG.  PAGE 

314,  315,  316,  317,  318,  319.  Dock  gatee  at  Dunkirk,  .  Platk  XV.,  to  face  348 

320,  321.  Dock  gate  at  Dunkirk, 348 

322,  323,  324.  Diagrams  of  flotation, 351 

325,  326,  327,  328,  329.  Swinging  caisson  at  Dundee, 352 

330.  Sliding  caisson  at  Malta, 353 

331.  Section  of  sliding  caisson  at  Malta, 354 

332.  333,  334,  335.  Rolling  caisson  at  Bruges,                              Platk  XVI.,  to  face  356 
336,  337,  338.  Floating  caisson  at  Blackwall,                  .        .    Platb  XVIL,      .,  356 

339.  Plan  of  caisson  at  Limekiln, 357 

340.  Ship  caisson  at  Cardifi^ 357 

341.  342,  343.  Ship  caisson  at  Calcutta, 35& 

344.  Ship  caisson  at  Belfast, 359 

345,  346,  347.  Ship  caisson  at  Liverpool,       .        .  .  Platk  XVIII., /o  ,ac€  360 

348.  Caisson  at  Greenock, 361 

349.  Shed  and  warehouse  at  Bremen, 369 

350.  Shed  compartment  at  Liverpool, 370 

351.  352.  Wooden  shed  door, 371 

363,  354.  Iron  shed  door, 372 

355,  356.  Folding  door  at  Dundee 373 

357,  358,  359,  360.  Details  of  shutter  and  mechanism, 374 

361,  362.  Shed  upper  floors, 376 

363,  364.  Monier  floors, 377 

365,  366.  Hennebique  floor, 378 

367,  368,  369.  Cottan9in's  systems, 379 

370.  Single-storey  shed  at  Liverpool 388^ 

371.  Double-storey  shed  at  Liverpool, 388 

372.  Shed  at  Liverpool, 38» 

373.  Shed  and  warehouse  at  Dundee, 390 

374.  Shed  at  Manchester 392 

375.  Do.,  393 

376.  377.  Sheds  at  Antwerp, 393 

378.  Shed  at  Havre, 395 

379,  380.  Sheds  at  Marseilles, 396 

381.  Shed  at  Calais, 396 

382.  Do.      Dunkirk, 397 

383.  Do.      Dieppe, 397 

384.  Do.      Rouen, 397 

385.  Sheds  and  warehouse  at  Bremen, 398 

386.  Do.  do.,  399 

387.  388.  Sheds  at  Hamburg, 399 

389,  390,  391.  Sheds  and  warehouse  at  Buenos  Ayres, 402 

392.  Shed  at  Zeebrugge, 403 

393.  Do.      Emden,      ....  403 

394.  Warehouse  at  Amsterdam, 404 

395.  Bascule  Bridge, 408 

396.  397.  Bridge  diagrams 412 

398,  399.  Do.,  414 

400.  Stresses  in  continuous  beam, 415 

401.  Diagram  of  moments, 418 

402.  Stresses  in  continuous  beam, 419 

403.  Stresses  due  to  ballast, 422 

404.  Bridge  diagram, 427 


XVI  LIST  OF  ILLUSTRATIONS. 

no.  PAGE 

406.  Bridge  pivot  at  Velsen, 429 

406.  Do.            Rotterdam, 430 

407.  409.  Bridge  pivots  at  Liverpool, 430 

408.  Raritan  bridge  pivot, 430 

410,  411.  Bridge  pivot  at  Hawarden, 431 

412,  413.            Do.            Liverpool, 432 

414,  416.            Do.            Fleetwood 433 

416,  417.            Do.            Marseillea, 434 

418.  Swing  bridge  at  Dublin, 436 

419,  420,  421.  Balancing  rollers  and  roller  path, 436 

422.  Balancing  lever, 437 

423,  424,  426,  426,  427,  428.  Bearing  blocks, 440 

429,  430.  Folding  bridge  at  Greenock, Plate  XIX.,  ^o /ace  442 

431.  Swing  bridge  at  Antwerp, 443 

432,  433.  Traversing  bridge  at  Antwerp, 444 

434.  Bascule  bridge  at  Rotterdam, 446 

436,  436.  Rolling  bascules  at  Chicago, 448 

437,  438,  439.  Swing  bridge  at  MarseiUes 460 

440.  Tilting  bridge  at  Marseilles, 462 

441,  442,  443.  Swing  bridge  at  Liverpool, 463 

444,  446.  Swing  bridge  at  Leith, Plate  XX.,  ^o. Ace  464 

446.  Swing  bridge  at  Liverpool, 466 

447,  448.  Swing  bridge  at  Liverpool, 466 

449,  460,  461.  Foot  bridge  at  Liverpool, 467 

462,  463,  454.        Do.                   do.,               458 

466,  466.  Double  swing  bridge  at  Calcutta, 469 

467.  Swing  bridge  at  Calcutta, 460 

468.  Travelling  bridge  at  Greenock,        . 461 

469,  460.  Slipway  construction, 471 

461.  Halifax  Graving  Dock,  Nova  Scotia 478 

462.  Cartagena  Floating  Dock, 479 

463.  Depositing  dock, 480 

464.  Off-shore  dock, 480 

465.  466.  Stability  of  vessels  under  water  ballast, 481 

467,  468,  469,  470,  471,  472,  473,  474.  Process  of  overhauling  a  floating  dock,      .  482 

476.  Keel-block,  Belfast, 483 

476,  477,  478,  479.  The  8.  s.  **Fulda"  and  graving  blocks 486 

480.  Curve  of  maximum  pressures  on  keel-blocks, 487 

481.  Distribution  of  weight,  S.S.   "Umbria"  and  "Etruria,"        ....  490 

482.  Gridiron  at  Liverpool, 491 

483.  Hydraulic  lift,  London, 492 

484.  486,  486,  487.  Dover  Slipway, 494 

488,  489,  490,  491.  Cradle  of  Dover  Slipway, 495 

492,  493,  494,  496,  496,  497,  498,  499.  Kaiser  Graving  Dock,  Bremerhaven, 

Plate  XXL,  t'  fare  496 

600,  601.  Canada  Graving  Dock,  Liverpool,  ....  Plate  XXII,     ,,  498 

602.  No.  3  Graving  Dock,  Glasgow, 600 

.503,  504.  Commercial  Graving  Dock,  Barry,  .        .        .         Plate  XXIII.,  to  face  502 

606.  Pumping  Station,  Barry, 503 

606,  607,  508,  609.  Tilbury  Graving  Docks  and  Lock,  .          Plate  XXIV. ,  to  face  504 

510,  611.  Bermuda  Floating  Dock, Plate  XXV.,     „  506 

512,  613.      Do.                   do., 507 


LIST  OF  ILLUSTRATIONS.  XVU 

FIO.  PAGE 

514,  515.  Bermuda  Floating  Dock, 50S 

516.  Combined  piston  and  ram, 517 

517.  Two  concentric  rams, 518 

518.  519.  Rotary  gate  machine, Plate  XXVI.,  to  face  522 

520.  521.  Arrangement  of  gate  chains, 524 

522.  Leith  Docks —Gates  and  machinery  for  60-foot  entrance,  Plate  XXVII. ,  to  face  524 

523.  Do.,  do.  do.  do.,  Plate  XXVIII.,    „      524 

524.  525.  Leith  Docks — ^Gate  machines  at  SO-foot  lock,  .  Plate  XXIX,  tojace  524 
526,  527.  Do.,  do.  70-  do.,  .  .  Plate  XXX.,  „  524 
528,  529.  Electric  dough  at  Ymuiden  Locks, 528 

530.  Electric  comiections  to  gates  and  sluices  at  Ymuiden, 529 

531,  532,  533,  534.  Hydraulic  capstan, 530 

535.  Hydraulic  capstan  valves, 531 

536.  Electric  capstan, 531 

537.  538,  539,  540,  541.  Hydraulic  quay  cranes,  .  .  .Plate  XXXI.,  to  face  532 
542,  543,  544,  545,  546.  Quay  cranes, 53a 

547.  Floating  crane, 534 

548.  Plan  of  floating  crane 535 

549.  550.  Hydraulic  jigger, 535 

551,  552,  553.  Hydraulic  crane  at  Malta,      .        .        .       Plate  XXXII.,   to  face  536 

554.  Temperley  transporter, 537 

555,  556.  Dayd^  and  Pill^  transporter,  .  .  -  .  .  Plate  XXXIIL,  ^oyace  538 
557,  558,  559.  Hydraulic  coal  hoist  and  tip  at  Dundee, .  Plate  XXXIV.,  „  538 
560,  561.  Pneumatic  grain  apparatus, 540 

562.  Hydraulic  rams  for  slipway  haulage 542 

563.  Do.  do.,  543 

564.  Buoy  with  anchorage 546 

565.  566.  Mooring  stagings, 547 

567,  568.  Mooring  posts, 547 

569.  Mushroom, 547 


xviil  UST  OF  TABLEI3. 


LIST  OP  TABLES. 


TABLE  PAQB 

I.  Foreign  trade  of  principal  ports  in  United  Kingdom 15 

II.            Do.             do.         '    Foreign  and  Colonial  ports,         .  16 

III.  Liverpool  and  Birkenhead  Docks, 31 

IV.  Barry  Docks, 36 

IVa.  Madero  Docks,  Buenos  Ayres 38 

V.  Representative  Docks  and  Basins, 54 

VI.  Interstices  in  broken  material, 118 

Vn.  Compressive  strength  of  concrete, 131 

VIII.  Strength  of  iron  and  steel, 139 

IX.  Coefficients  of  corrosion, 141 

X.  Corrosion  of  iron  and  steel, 142 

XI.          Do.                do.,             146 

XII.  Durability  of  timber 147 

XIII.  Weight  and  strength  of  timber, 150 

XIV.  Compressive  strength  of  stone, 154 

XV.  Angles  of  repose .  158 

XVI.  Weight  of  earths, 171 

XVII.  Weight  of  mineral  substances, 173 

XVni.  Force  of  wind, 228 

XIX.  Height  of  waves, 230 

XX.  Record  of  docking  conditions  at  Liverpool, 230 

XXI.  Suspended  material  in  Mersey  water, 232 

XXII.  Velocity  of  currents, 232 

XXHL  Lockage, 236 

XXIV.  Cost  of  lock  gates,  Manchester  Ship  Canal, 305 

XXV.  Dock  gates, 349 

XXVI.  Dock  Caissons, 362 

XXVIL            Do.            at  French  ports, 363 

XXVIII.  Tonnage  and  berthage  of  cargo  vessels, 365 

XXIX.  Volume  and  weight  of  merchandise, 380 

XXX.  Coefficients  for  Gordon's  formula, 384 

XXXI.  Weight  of  shed  roofs, 386 

XXXII.  Weight  of  bridge  girderwork, 424 

XXXIII.  Weight  of  modem  locomotives, 425 

XXXIV.  Live  loads  on  single  railway, 426 

XXXV.  Dimensions  of  largest  modern  vessels, 466 

XXXVL  Overhang  of  ships,        . 491 

XXXVII.  Comparison  of  power  supply 513 

XXXVUI.  Expenditure  of  energy  by  cranes, 514 

XXXIX.              Do.                       do.,                   515 

XL.              Do.                       do.,                   615 

XIjI.  Cost  of  hydraulic  and  electric  power  supply, 516 

XLIL  Fluctuations  in  hydraulic  pressure, 520 

XUII.  Gate  machines, 527 


DOCK   ENGINEEEING. 


") 


CHAPTER  I. 

HISTOBICAIi  AND   DISCUBSIVE. 

Intboductoby  DKFiirinoNS — ^Pokts  and  thiib  Functions — The  Dsvelopmxnt  of 
Mabitihe  Enoineebino— The  Fibst  Wet  Dock— The  Howland  Gbeat  Wet 
Dock — Regent  Pboobess— Dock  Administbation — ^Histobical  Notices  op  the 
Pobts  of  London,  Liyebpool,  New  Yobk,  Glasgow,  Hambubo,  Antwebp, 
Mabseilles,  Rottebdam,  Cabdiff,  and  of  the  Tyne  Pobts. 

Introductory  Definitions. — In  the  terminology  of  maritime  engineering,  a 
Dock  is  an  artificial  repository  for  shipping. 

This  definition,  admittedly  vague,  and  at  first  sight  unsatis&<;tory,  not 
to  say  incomplete,  is,  nevertheless,  the  only  one,  apparently,  which  can  be 
devised  to  cover  the  manifold  and  diverse  applications  of  the  word.  On 
consideration,  it  will  be  seen  that  its  terms  do  not  admit  of  further 
restriction. 

Docks  are  divisible  into  three  classes,  with  widely  different  charac- 
teristics and  functions,  viz. : — Wet  Docks;  Dry  or  Graving,  and  Slip  Docks; 
and  Floating  Docks. 

Wet  Docks  are  areas  of  impounded  water  within  which  vessels  can 
remain  afloat  at  a  uniform  level,  independent  of  external  tidal  action. 
They  have  also  been  termed  Floating  Docks,  in  which  case  the  epithet 
denotes  the  object  for  which  the  dock  exists ;  but  as  this  name  is  liable  to 
be  confused  with  that  in  which  the  epithet  is  descriptive  of  the  dock  itself, 
it  is  not  at  all  suitable,  and  should  be  avoided. 

Dry  Docks  are  those  from  which  water  can  be  temporarily  excluded,  in 
order  that  repairs  to  the  hulls  and  keels  of  vessels  may  be  effected.  When 
the  vessel  is  floated  into  the  dock,  and  the  water  removed  by  natural  or 
artificial  means,  the  term  Graving  Dock  is  appropriate.  When  the  vessel 
is  partially  withdrawn  from  the  water  by  means  of  ways,  the  remaining 
water  being  excluded  as  before,  the  term  Slip  Dock  is  used. 

Floatifig  Docks  are  frames  or  structures  capable,  by  reason  of  their  own 
flotation,  of  raising  ships  completely  above  water,  and  of  maintaining  them 
in  that  position  during  the  execution  of  repairs. 

The  term  dock  is  also  applied,  though  somewhat  loosely,  to  tidal  basins — 
that  is,  to  areas  of  partially-enclosed  water  in  free  communication  with 

1 


2  DOCK   ENGINEERING. 

the  sea.  The  functions  of  basins  in  many  cases  coincide  with  those  of 
docks,  so  that  some  elasticity  of  nomenclature  is  not  without  justification. 
At  the  same  time,  it  must  be  affirmed  that  the  term  is  not  correctly  ap- 
plicable to  basins,  though  the  distinction  will  not  be  too  rigidly  insisted 
upon  in  the  course  of  this  work. 

Primarily,  it  appears  that  a  dock  was  devoted  entirely  to  shipbuilding 
and  ship-repairing  purposes.  When  fitted  with  appliances  for  the  exclusion 
of  tidal  water,  it  was  distinguished  as  a  dry  dock ;  otherwise,  it  was  a  wet 
dock,  and  the  ship  was  only  accessible  during  periods  of  low  water. 

Ports  and  their  Fanctions. — Though  by  no  means  a  unique  or  even  an 
essential  feature,  a  dock-system  nevertheless  constitutes  the  most  important 
appendage  of  a  port. 

Ports  may  be  regarded  from  two  distinct  points  of  view — either  as  the 
termini  of  great  ocean  trunk  lines  of  communication,  or  as  intermediate 
stations  on  the  entire  route  from  the  manufactory  to  the  mart,  from  the 
producer  to  the  consumer.  Each  aspect  has  its  own  special  characteristics 
and  problems,  alike  interesting  to  the  engineer.  As  a  terminus,  the  port 
must  be  provided  with  ample  accommodation  and  sheltered  berths.  As 
an  intermediate  station,  it  must  be  readily  accessible  and  fully  equipped 
with  all  necessary  appliances  for  the  speedy  transfer  of  merchandise  between 
ship  and  shore. 

The  subject  of  ports  as  a  whole,  however,  exceeds  the  scope  of  the 
present  treatise,  for  it  would  involve  the  discussion,  not  only  of  docks,  but 
also  of  harbours,  channels,  waterways,  and  roadsteads. 

Natural  havens  and  roadsteads  do  not  fall  within  our  purview  at  all, 
neither  have  we  to  concern  ourselves  with  those  large  areas  of  safe  anchorage 
which  are  formed  and  protected  by  breakwaters.  Upon  smaller  areas,  more 
completely  enclosed  and  designated  harbours  and  basins,  we  shall  touch  but 
lightly.  Our  immediate  purpose  is  to  deal  with  spaces  of  moderate  extent, 
more  or  less  continuously  cut  off  from  external  influences,  and  properly 
called  docks. 

The  Development  of  Maritime  Engineering — While  harbours  have  con- 
stituted prominent  features  in  connection  with  maritime  intercourse  from 
the  remotest  times,  docks  are  a  comparatively  modem  innovation.  We 
should  have  to  go  very  far  back  indeed  into  the  history  of  navigation  to 
trace  the  origin  of  artificial  harbours.  Natural  harbours  and  creeks  have, 
of  course,  always  been  available;  but  their  situation  and  accommodation, 
even  in  early  days,  sometimes  proved  not  altogether  satisfactory.  Accord- 
ingly, we  find  that  the  Phcenicians  protected  their  ancient  ports  of  Tyre  and 
Sidon  on  the  Levantine  Coast  by  means  of  rubble  breakwaters.  Carthage, 
the  home  of  their  descendants,  likewise  possessed  a  harbour  enclosed  by 
moles.  Rome,  the  vanquisher  of  Carthage,  has  left,  despite  the  ravages  of 
time  and  disuse,  many  traces  of  maritime  engineering  structures  along  the 
coasts  of  Italy ;  nor  is  Greece  lacking  in  striking  examples  of  harbour  works 
upon  her  classic  shores.     With  the  downfall  of  the  Koman  Empire  commer- 


THE  FIRST   WET   DOCK.  3 

cial  enterprise  found  a  home  in  the  still  flourishing  ports  of  Venice  and 
Genoa.  Later,  Spain  set  her  grasp  upon  ocean  trade,  investing  Barcelona 
and  Cadiz  with  a  glory,  some  vestiges  of  which  cling  to  them  still.  Later 
again,  the  phlegmatic  Dutch  took  over  the  supremacy,  and,  with  patient  toil 
and  perseverance,  laid  the  foundations  of  their  ports  within  the  very  domain 
of  the  sea  itself. 

In  our  own  country,  notwithstanding  the  spirit  of  naval  adventure  which 
animated  the  Cabots,  the  Drakes,  the  Ealeighs,  the  Frobishers,  the  Hawkins, 
and  many  other  heroes  of  the  Tudor  period,  little  was  done  to  improve  such 
facilities  as  were  naturally  possessed  by  towns  upon  the  seaboard.  Dover 
was  for  a  long  time  perhaps  the  only  port  of  real  note  developed  in  any  way 
by  artificial  agency.  Subsequently  Bristol,  Plymouth,  London,  and  Leith, 
amongst  others,  rose  to  importance,  but  most  of  our  present  leading  ports 
are  of  quite  recent  growth.  Liverpool,  Hull,  Glasgow,  and  Newcastle 
afforded  very  trifling  accommodation  for  shipping  a  century  ago.  Cardiff, 
Barrow,  and  Middlesbrough  have  existed  as  ports  for  little  more  than  fifty 
years.  Twenty  years  ago  Barry  was  unknown,  and  Manchester  an  inland 
town. 

The  First  Wet  Dock. — The  distinction  of  having  created  the  first  wet 
dock  has  been  the  subject  of  some  discussion  and  the  cause  of  not  a  little 
rivalry  between  the  ports  of  London  and  Liverpool.  According  to  such 
evidence  as  is  forthcoming — and  some  of  it  is  conflicting  and  inconclusive  to 
a  degree — the  balance  appears  to  incline  in  favour  of  the  former  place.  As 
regards  Liverpool,  it  is  generally  admitted  that  parliamentary  authority  was 
obtained  for  the  construction  of  a  wet  dock  in  the  year  1708,  during  the 
reign  of  Queen  Anne.  This  dock  was  built  and  opened,  apparently,  very 
shortly  afterwards,  the  engineer  being  Thomas  Steers.  But,  according  to 
the  "  City  Annals "  appended  to  Gore's  Directory  of  Liverpool,  the  dock 
was  already  in  existence  in  1700,  and  a  date  (June  8)  is  given  on  which  the 
first  ship,  the  "  Marlborough,"  entered  it.  Possibly  these  conflicting  state- 
ments are  reconcilable  if  we  regard  the  earlier  dock  as  having  been  of  the 
nature  of  a  tidal  basin,  which  was  afterwards  converted  into  a  wet  dock  by 
the  addition  of  entrance  gates.*  Some  interest  attaches  to  this  "  Old  Dock  '* 
as  it  is  termed.  It  was  four  acres  in  extent,  and  was  designed  to  afford 
accommodation  for  100  vessels,  and  so  arranged  as  to  have  not  less  than 
10  feet  of  water  within  it  at  low  neap  tides,  with  a  sufficiency  at  spring 
tides  to  take  the  smaller  class  of  warships.  The  dock  no  longer  exists 
except  in  name,  although  the  level  of  its  sill  still  supplies  the  zero  or 
datum  in  vogue  throughout  the  Mersey  Dock  Estate  in  preference  to  the, 
elsewhere,  more  generally  accepted  Ordnance  Datum. 

On  the  other  hand,  as  regards  London,  the  inception  of  the  Surrey  Com- 
mercial Docks  is  said  to  date  from  1660  or  1666 ;  at  any  rate,  there  is 
decisive  evidence  that  an  Act  of  Parliament  for  the  construction  of  a  wet 
dock  at  Rotherhithe  received  the  Royal  Assent  in  1696.     The  date  when 

*  This  is  mere  conjecture,  and  a  dubious  solution  at  the  best. 


4  DOCK   ENGINEERING. 

the  dock  wa-s  opened  is  not  recorded,  but  that  it  was  in  use  in  the  year  1703 
is  testified  by  an  old  description  (undated)  of  the  dock  which,  with  an 
engraving,  is  retained  in  the  Board-room  of  the  Surrey  Commercial  Dock 
Company.  Being  not  without  interest  as  an  old-world  document,  throwing 
light  upon  conditions  which  prevailed  two  centuries  ago  in  regard  to  the 
management  of  ships  in  port,  a  copy  of  it  is  reproduced  here.*  The  original 
name  of  the  dock,  "  The  Rowland  Great  Wet  Dock,"  has  since  been  replaced 
by  that  of  the  "  Greenland  Dock."  Mrs.  Elizabeth  Rowland  was  the  wife 
of  John  Rowland,  of  Streatham,  Surrey,  and  the  mother-in-law  of  the 
Marquis  of  Tavistock,  afterwards  second  Duke  of  Bedford. 


Rowland  Great  Wet  Dock, 

In  the  Parifli  of  Rotherhithe^  or  Redriff^   belonging  to   Mrs,  Ho^vland^  of 

Streatham. 

This  dock  hath  been  found  a  very  fafe  repofitory  for  fJiips^  which  was 
fully  proved  in  that  terrible  and  violent  ftorm  which  happened  on  the 
21  th  November^  i7o3>  when  by  the  extremity  of  the  wind  all  the  fhips  in 
the  river,  which  rode  eitlier  at  chains  or  their  own  moorings^  were  fordd 
adrift,  and  confufedly  driven  on  the  North  fliore,  w/iere  fome  were  lefty 
and  moft  received  great  damage.  Then,  of  all  the  feveral  fhips  depofited  in 
this  wet  dock  there  was  only  one  injured,  andflie  only  in  her  bowfprit,  which 
wcK  in  a  great  meafure  imputed  to  too  fecure  a  negligence  in  the  perfons 
who  Tnoof'd  her  there.  This  may  remain  a  lofting  evidence  of  t/ie  great 
fervice  fuch  a  repofitory  for  fhipping  is  to  our  navigation ;  efpecially  if 
it  be  confidered  that  this  fatal  ftorm  happened  foon  after  the  planting  of 
thofe  trees,  which  are  on  the  fouih  and  north  as  a  fence  to  the  dock  from 
winds,  and  which  are  now  grown  to  a  confiderable  bulk;  and  alfo  before 
that  range  of  houfes  were  built  to  the  weft,  and  the  pailings  fet  up  to  the 
eaft,  and  on  each  fide;  fo  that  now,  in  the  hardeft  gales  of  wind  that  have 
within  ihefe  late  years  happened,  notwithftanding  the  large  extent  of 
the  water,  the  wind  does  not  give  any  fuch  motion  to  it,  as  can  endanger 
tho  fmalleft  boat  in  pajfing  it  any  way  over,  and  thd  very  deep  loaded. 
And  as  fhips  are  here  fo  well  fecur^d  from  any  ftorm  that  may  happen, 
fo  they  are  entirely  defended  from  the  hazard  and  damage  which  accrueth 
to  them  often  in  the  river,  by  hard  frofts.  For  by  the  driving  of  the  ice 
in  the  river,  if  they  /hould  continue  in  the  ftream  on  float,  their  cables 
would  be  cut ;  to  prevent  which  and  to  preferve  their  bottom,  they  are 
for^d  to  take  up  with  fhore  births,  which  often  are  f  training  and  uneafy 
to  the  fhips,  and  require  a  conftant  care  and  charge  to  preferve  them,  by 
fhoring  or  fhifting,  as  it  may  happen,  by  the  icis  driving  under  them. 
And  notwithftanding  all  the  care  which  can  be  taken,  the  bottoms  of 

*  Vide  Min.  Proc,  Inst.  C.E,,  voL  c,  p.  93. 


REGENT  PROGRESS.  5 

Jhips  are  fo  raked  by  the  ice,  thai  it  is  often  a  confiderahle  addition  in 
the  charge  of  refitting^  if  no  other  more  material  damage  happens  to  them 
thereby,  Whtreas  the  fhips  here  depofited,  lye  always  water  borne, 
without  the  leaft  rubbing  of  the  ice,  or  any  further  care  or  charge  for 
their  prefervation,  as  fully  appeared  by  the  laft  great  froft  in  1715. 
Ships  are  likewife  here  more  effectually  fecur^d  from  the  peril  of  fire ; 
there  being  proper  cook  rooms  provided  on  fliore,  and  no  fire  fuffered  to 
be  on  board.  But  if  neither  ftorms,  tior  ice,  nor  fire,  be  confldered,  fhips 
are  here  depofited  at  a  much  lefs  charge  and  a  mtuh  greater  fecurity 
than  in  the  river ;  which  any  one  may  eafily  evince,  if  he  will  calculate 
the  wearing  their  cables  or  the  charge  of  the  chain,  the  frequent  fhifting 
of  the  moorings,  and  other  neceffary  incidents,  which  do  and  will  happen 
in  the  river,  and  compare  them  with  the  moderate  rates  wet-docking  is  by 
this  work  reduced  to, 

Defcription  of  the  Dock. — The  outward  gates  of  the  wet-dock,  leading 
to  the  Thames,  21  foot  high,  and  ^^foot  wide,  opet^d  to  let  in  the  f hip. 

The  bafon,  or  gut,  leading  to  the  great  wet-dock,  44  foot  wide,  150  foot 
long. 

The  inward  gates,  of  the  fame  height  and  breadth  with  the  outward, 
but  ftronger,  by  reafon  they  bear  the  great  tueight  of  water  in  the  dock, 
which  fometimes  flo7vs  within  a  foot  of  the  top  of  thefe  gates,  and  is  kept 
pent  up  within  /^foot  thereof. 

The  great  wet-dock,  wherein  at  good  fpring  tides  there  is  feventeen  foot 
of  water,  over  the  cell  againft  which  the  bottom  of  the  gates  fhut ;  fo  that 
it  would  commodioufly  receive  his  Majefifs  third-rate  fhips. 

The  dimenfions  of  the  dock  are  from  eaft  to  weft  1,070  feet;  from  north 
tofouth,  at  the  weft  end,  ^^o  feet,  and  from  north  to  fouth,  at  the  eaft  end, 
500  feet;  fo  that  it  would  contain  upwards  of  120  fail  of  the  largeft 
merchant  fhips,  without  the  trouble  of  fhifting,  mooring,  or  unmooring 
any  in  the  dock,  for  taking  in  or  out  any  other. 

This  dock  when  full  at  a  fpring  tide,  contains,  by  a  moderate  computa- 
tion of  \o  foot  f olid  to  the  ton,  228,712  tons  of  water,  being  much  larger 
than  the  famous  bafon  of  Dunkirk,  or  any  pent  water  in  the  world. 

The  maft  crain,  for  taking  out  and  fetting  in  mafts  in  fhips  in  the  wet- 
dock,  which  anfwers  the  end  of  an  hulk,  with  proper  pits  and  crab  for 
careening  three  or  four  fhips  at  once. 

Recent  Progress. — To  whichever  of  the  two  rival  ports  the  honour  be 
aillocated  (and  this  is  a  matter  of  no  great  moment),  at  any  rate  it  is  apparent 
that  the  first  English  dock  dates  back  no  further  than  the  commencement  of 
the  18th  century.  But  what  perhaps  is  more  remarkable  still,  is  that 
■during  the  next  hundred  years,  despite  the  enormous  increase  in  oversea 
trade  and  the  great  development  of  lines  of  inland  navigation,  no  works  of 
Any  note  were  undertaken  for  the  extension  or  improvement  of  dock 
accommodation. 


6  DOCK  ENGINEERING. 

It  is  very  difficult  to  realise  that,  up  to  the  last  decade  of  the  18th 
century,  the  Thames  only  possessed  its  one  dock  (and  that  devoted  to  the 
whaling  trade),  while  Liverpool  had  but  three,  and  these  of  inconsiderable 
extent. 

It  was  left  to  the  19th  century  to  witness  a  great  revival  in  dock  and 
harbour  engineering.  Great  forces  which  had  been  slowly  gathering 
throughout  the  Georgian  period  eventually  came  to  a  head.  The  sudden 
growth  of  commerce  consequent  upon  the  advent  of  steam  power,  the 
expansion  of  the  empire  and  the  opening  up  of  virgin  territory,  gave  an 
impetus  to  national  policy  which  resulted  in  the  adoption  everywhere  of 
vigorous  and  energetic  measures.  The  history  of  the  Victorian  era  is  a 
long  and  triumphant  record  of  feats  of  maritime  engineering  skill  adorned 
by  the  names,  amongst  others,  of  Rennie,  Smeaton,  Stevenson,  Hawkshaw, 
Messent,  Coode,  Hartley,  and  Lyster,  and  attested  by  the  splendid  array 
of  docks  and  harbours  which  line  the  English  coast  to-day. 

Nor  is  there  any  sign  yet  of  a  diminution  in  the  activity  which  has 
produced  such  magnificent  results.  Fresh  undertakings  are  demanded  daily 
to  correspond  with  each  succeeding  development  of  naval  architecture  and 
with  each  access  of  national  prosperity.  From  the  point  of  view  of  national 
vitality  this  is,  indeed,  no  time  for  relaxation  of  efTort.  Powerful  trade 
competitors  have  arisen  in  nations  who,  admittedly  outdistanced  before, 
now  openly  dispute  the  British  claim  to  the  sovereignty  of  the  seas. 
Renewed  exertions  will  have  to  be  made,  both  to  retain  trade  and  to  cope 
with  its  altered  conditions.  Hence  the  necessity,  on  the  part  of  port 
authorities,  for  a  watchful  and  attentive  attitude,  ready  to  note  each 
impending  change  and  its  probable  consequences ;  to  seize  each  favourable 
opportunity  for  fresh  enterprise,  and  by  decision  and  energy  to  utilise  it  to 
the  fullest  extent.  Only  in  this  way  can  ports,  as  well  as  nations,  hold  their 
own. 

Dock  Administration. — Docks  are  to  be  found  under  five  difTerent  systems 
of  management,  and  though  the  question  of  administration  is  one  of 
economics  rather  than  of  mechanical  science,  it  merits  at  least  a  passing 
reference.  The  five  systems  of  administration  may  be  enumerated  as 
follows : — 

(1)  Private  or  Public  Companies,  ad  hoc. 

(2)  Railway  Companies, 

(3)  Municipalities, 

(4)  Public  Trusts, 

(5)  Government  Departments, 

Of  these  it  may  be  said  that  private  companies  are  in  the  least  favourable 
position  for  maintaining  their  docks  in  an  efficient  condition,  or  for  meeting 
the  needs  of  a  growing  port.  Dock  engineering  works  are  particularly 
costly,  and  the  return  on  capital  thus  invested,  except  in  rare  instances,  will 
not  bear  favourable  comparison  with  dividends  arising  from  securer  sources. 


DOCK  ADMINISTRATION.  7 

Henoe  there  must  inevitably  be  undue  economy  and  even  parsimony  in 
management,  and  a  reluctance  to  undertake  fresh  expenditure  on  works, 
however  beneficial  or  necessary. 

Railway  Companies  derive  a  considerable  amount  of  indirect  benefit  by 
the  proprietorship  of  docks  in  touch  with  their  respective  systems,  quite 
apart  from  any  specific  receipts  locally.  The  facilities  for  the  direct  transfer 
of  goods  from  rail  to  ship,  and  vice  versdy  are  greatly  increased  without  any 
corresponding  augmentation  of  staff  and  without  friction  of  negotiation. 
The  diversion  of  traffic  to  their  lines  is  often  sufficient  to  compensate  a 
company  for  the  otherwise  unremunerative  working  of  their  docks. 

Municipal  CounciU,  nominally  the  controlling  authorities,  generally 
delegate  their  powers  of  dock  management  to  a  sub-committee,  with  results 
that  have  not  been  uniformly  successful.  Town  Councillors  are  elected  on 
a  variety  of  grounds,  sometimes  personal,  but  mainly  political,  cmd  often 
without  the  remotest  bearing  on  shipping  matters.  Now,  however  versed 
in  the  direction  of  purely  urban  affairs  a  councillor  may  be,  it  is  obvious 
that,  without  some  active  participation  in  maritime  affairs,  he  will  lack  the 
requisite  technical  knowledge  to  enable  him  to  deal  satisfactorily  with 
important  questions  affecting  the  mercantile  marine.  Hence  in  such  a 
committee  the  likelihood  of  uncertain  counsels,  sometimes  unduly  timorous, 
sometimes  the  reverse. 

Public  Trusts,  specially  elected  from  the  classes  most  intimately 
associated  with  the  use  and  exploitation  of  docks,  constitute  perhaps  the 
most  satisfactory  of  all  forms  of  government.  On  a  body  of  this  kind  would 
be  proper  representatives,  chosen  by  an  electorate  of  shipbuilders,  ship- 
owners, merchants,  and  traders;  of  all,  in  fact,  who  were  connected  with  the 
shipment  of  goods,  the  qualification  being  the  payment  of  dock  or  port  dues. 
The  particular  knowledge  possessed  by  sudi  a  body  would  be,  and  is 
eminently  calculated,  to  develop  the  efficiency  and  prosperity  of  a  port,  the 
efforts  of  the  members'  being  stimulated  by  a  certain  amount  of  self-interest. 
It  must  not  be  overlooked  that  the  welfare  of  the  port  involves  the  welfare 
of  the  town,  and  that  the  two  suffer  or  flourish  together.  Hence  the 
necessity  for  specialist  management  in  both  cases. 

Control  by  a  Government  Department,  which  would  naturally  involve  the 
inclusion  of  all  ports  within  one  national  jurisdiction,  cannot  be  considered 
a  desideratum.  Speaking  generally,  it  is  admitted  that  there  is  a  lack  of 
initiative  and  a  diffusion  of  authority  in  governmental  departments  which 
are  not  adapted  to  the  successful  carrying  on  of  commercial  undertakings. 
The  almost  inevitable  result  of  this  system  would  be  the  stifling  of  private 
enterprise,  and  the  abandonment  of  that  local  patriotism  which  constitutes 
the  best  guarantee  of  the  vitality  and  energy  of  a  port,  at  the  same  time 
that  it  affords  the  best  augury  for  its  continued  prosperity. 

We  now  pass  on  to  a  brief  resume  of  the  more  prominent  historical  facts 
connected  with  the  development  of  some  of  the  most  important  ports  of  the 
world.     It  would  be  difficult  to  asdign  to  them  any  satisfactory  order  of 


8  DOCK  ENGINEERING. 

precedence.  Navigation  returns  fluctuate  considerably,  and  with  them  the 
relative  positions  of  the  ports  concerned.  No  attempt,  then,  will  be  made 
to  preserve  any  particular  sequence  except  that  attaching  to  general  pro- 
minence and  representative  character. 

The  Port  op  London. 

The  Port  of  London  has  long  maintained  an  indubitable  supremacy.  At 
the  beginning  of  last  century,  however,  it  received  no  more  than  4,000  ships 
annually,  of  which  number  more  than  half  were  coasting  vessels,  and  the 
aggregate  tonnage  scarcely  exceeded  half  a  million.  In  1901  the. number  of 
ships  which  entered  and  cleared  the  port  was  53,230,  and  the  tonnage 
31,157,015. 

The  Greenland  (or  Howland)  Dock,  with  its  area  of  12  acres  and 
quayage  under  a  mile,  held  its  unique  position  until  the  year  1790,  when  the 
Brunswick  Dock  was  constructed  by  a  shipbuilder  on  the  site  of  the  present 
West  India  Dock.  The  shipping  at  this  time  was  mainly  accommodated  at 
"  legal  wharves  "  at  the  river  side  or  at  moorings  amidstream.  The  delay 
which  arose  in  this  way  from  stoppages  of  the  navigable  channel  and  the 
enormous  losses  sustained  by  robberies,  created  a  scandal  of  such  moment 
that  the  Government  of  the  day  was  obliged  to  take  action,  and  parliamen- 
tary powers  were  obtained  for  the  redemption  of  some  of  these  legal  wharves 
by  compensating  their  owners.  At  the  same  time  an  Act  was  passed 
authorising  the  construction  of  the  West  India  Dock.  This  dock  was  so 
named  from  its  appropriation  to  the  West  Indian  trade,  and  all  vessels 
engaged  in  that  trade  were  compelled  to  use  the  dock,  which  had  the  mono- 
poly conferred  upon  it  for  twenty-one  years.  The  date  of  opening  was  1802. 
It  was  followed  in  1805  by  the  London  Dock,  which  was  endowed  with  a 
monopoly  of  vessels  engaged  in  the  conveyance  of  wine,  spirits,  and  tobacco. 
The  East  India  Dock  was  opened  on  equally  protective  lines  in  1806.  The 
first  free  dock  (St.  Katharine's)  did  not  come  into  existence  until  the  years 
1827-28.  After  this  a  long  interval  elapsed,  until  the  construction  of  the 
Royal  Victoria  Dock  in  1855.  This  dock,  situated  nearly  opposite  Wool- 
wich, is  a  very  important  one.  Its  length  is  3,000  feet  and  its  width  1,050 
feet ;  and,  with  its  appurtenances,  it  added  90  acres  to  the  water  area  of  the 
port. 

The  MiLLWALL  Docks — in  reality  but  one,  shaped  like  the  letter  L — 
were  next  built  in  1868.  They  have  a  water  area  of  35  acres.  In  1870 
came  the  opening  of  the  South-West  India  Dock,  parallel  to  the  other  two 
India  Docks ;  like  them,  stretching  across  the  Isle  of  Dogs,  and  having  a 
river  connection  at  each  end. 

In  1880  another  large  dock,  the  Kotal  Albert,  added  very  materially 
to  the  extent  of  the  port.  With  its  entrance  basin  it  has  an  area  of  84  acres. 
It  is  in  close  connection  with  the  Victoria  Dock,  being  joined  to  it  by  a 
channel. 


THE   PORT   OF  LIVERPOOL.  9 

The  available  space  in  the  higher  reaches  of  the  river  was  now  becoming 
xery  restricted,  and,  moreover,  the  congestion  of  traffic  caused  much  inter- 
ference with,  and  even  prevented,  any  rapidity  of  navigation.  Accordingly, 
the  next  group  of  docks,  the  Tilbury  Docks,  were  built  lower  down  the 
river,  opposite  Gravesend.  They  consist  of  a  main  dock  with  three  parallel 
branches,  in  addition  to  a  tidal  basin,  entrance  locks,  and  graving  docks. 
By  this  group,  opened  in  1886,  the  port  was  enlarged  by  57 J  acres. 

The  water  area  of  the  port  now  amounts  to  about  570  acres,  exclusive  of 
shallow  timber  ponds,  and  it  is  being  added  to  by  important  improvements 
at  the  8uRRET  Commercial  Docks.  These  docks,  which  are  situated  on  the 
south  side  of  the  river,  consist  of  two  groups — the  Commercial  Docks,  dating 
back  to  the  Howland  Dock,  reconstructed  in  1807,  and  the  Surrey  Docks, 
-opened  in  1812.     They  are  mainly  used  for  cargoes  of  timber  and  grain. 

The  present  position  of  London  as  a  port  cannot,  however,  be  regarded  as 
satisfactory.  The  navigation  of  the  river  is  impeded  by  tortuous  channels 
beset  with  shallows,  while  trade  is  hampered  by  insufficient  dock  accom- 
modation and  diversity  of  management.  The  docks  in  London  are  the 
property  of  several  distinct  companies,  with  conflicting  interests  and  indepen- 
dent jurisdictions.  They  are  under  the  necessity  of  paying  dividends,  and 
their  capital  is  insufficient  to  meet  the  growing  demands  made  upon  it.  The 
amount  of  interest  earned  can  only  be  described  as  meagre,  so  that  there  is 
little  inducement  to  find  additional  capital  for  investments  of  so  compara- 
tively unremunerative  a  nature.  Yet,  without  this  expenditure  the  docks 
must  rapidly  pass  into  a  state  of  inefficiency  and  disuse. 

How  to  provide  funds  for  the  purpose  is  a  delicate  and  difficult  question. 
Shipowners  complain  that  port  charges  and  dues  are  already  excessive,  while 
other  sources  of  revenue  are  not  available.  Radical  constitutional  changes 
are  impending,  including  the  formation  of  a  Port  Trust,  with  the  absorption 
of  all  interests  in  one  body.  This  '^ill  undoubtedly  lead  to  considerable 
economy  in  management,  and  a  solution  of  the  financial  difficulty  will,  no 
doubt,  be  forthcoming.  The  matter  has  little  interest  from  an  engineering 
point  of  view,  and  concerns  but  indirectly  the  province  of  the  dock  engineer. 
Hence,  we  may  with  advantage  leave  so  thorny  a  topic  for  debate  in  other 
and  more  appropriate  quarters. 


The  Port  op  Liverpool. 

The  second  port  in  the  kingdom,  has  a  history  dating  back  to  the  year 
1338,  when  it  was  first  made  an  independent  port.  Up  to  the  beginning  of 
the  19th  century,  however,  the  docks,  for  which  it  is  now  famous,  did 
not  cover  a  greater  area  than  18  acres,  nor  in  1816  were  there  more  theui  34 
acres ;  but  in  1846  the  water  space  had  increased  to  108  acres,  and  in  1857, 
after  the  inclusion  of  the  Birkenhead  docks,  to  209  acres,  until  at  length,  in 
1901,  the  combined  system  comprised  no  less  than  558  acres,  with  a  quayage 


lO  DOCK   ENGINEERING. 

of  35  miles,  the  latter  being  equivalent  to  two-thirds  of  that  of  the  quayage 
of  all  other  wet  docks  in  the  world,  excluding  British  ports. 

The  docks  constructed  during  the  latter  half  of  the  18th  century 
were  the  Salthouse,  the  George's,  the  King's,  and  the  Queen's.  These 
were  devoid  of  quays,  and  much  time  and  labour  were  wasted  in  the  transfer 
and  cartage  of  goods.  The  Fringes  Dock  was  opened  in  1821,  and  five  years, 
later  the  Old  Dock  was  closed.  The  Clarence  Dock  was  built  in  1830,  the 
Waterloo  in  1834,  and  the  Victoria  and  Trafalgar  Docks  in  1836. 
These  earlier  docks  were  of  very  small  size,  rarely  exceeding  10  acres.  The 
Canada  and  Huskisson  Docks,  constructed  between  1850  and  1860,  marked 
a  decided  advance  in  this  respect,  and  the  size  was  still  further  increased  in 
the  case  of  the  Langton  and  Alexandra  Docks,  opened  in  1881,  the  former 
of  which  contains  21  acres  and  the  latter,  44^  acres.  Larger,  again,  than 
these  are  the  East  and  West  Floats,  on  the  Cheshire  side  of  the  river, 
containing  59|  acres  and  52  acres  respectively  ;  but  none  of  the  docks  in  the 
Mersey  Estate  approach  the  size  of  the  Victoria  and  Albert  Docks  at 
London. 

An  immense  floating  landing  stage,  built  in  1847,  forms  a  prominent 
feature  of  the  river  frontage.  It  was  burned  down  in  1874,  but  after- 
wards restored.  There  are  similar,  but  smaller,  floating  stages  at  Woodside 
and  Wallasey. 

The  tonnage  of  vessels  entering  and  leaving  the  port,  which  in  1831  only 
amounted  to  1^  millions,  had  nearly  reached  19  millions  before  the  end  of 
the  century,  with  a  total  of  about  40,000  vessels.  For  the  year  just  closed 
(Midsummer,  1903)  the  tonnage  exceeded  23|  millions. 

The  management  of  the  dock  system,  which  is  perhaps  the  finest  under 
single  control  in  the  world,  passed  from  the  hands  of  a  committee  of  the 
Town  Council  in  1858  into  those  of  a  public  Trust,  created  by  Act  of 
Parliament,  and  called  the  Mersey  Docks  and  Harbour  Board,  which,  since 
that  time,  has  administered  it  with  striking  success. 

The  Port  op  New  York. 

The  premier  city  and  port  of  the  United  States  is  possibly  somewhat 
lacking  in  attraction  for  the  dock  engineer  in  that  it  has  no  docks,  in  the 
strict  sense  of  the  word.  What  are,  by  courtesy,  termed  docks  are  open 
areas  of  water  formed  by  the  projection  of  numerous  timber  jetties  from  the 
face  line  of  the  river  quays.  The  city  itself  lies  on  an  island  between  the 
Hudson  and  East  rivers,  in  a  well-sheltered  position  which  calls  for  no 
further  protection,  while  at  the  same  time  it  is  close  to  the  open  sea.  A 
further  reason  for  the  absence  of  docks  is  the  small  range  of  tide,  which  does 
not  exceed  5  feet,  on  an  average.  The  construction  of  the  river  wharves, 
despite  some  supervision  introduced  at  the  beginning  of  last  century,  seems 
to  have  proceeded  on  no  definite  plan  or  system  until  the  year  1870,  when  a 
special  department  was  constituted  for  that  purpose.      The  city  is  now 


THE   PORT  OF  GLASGOW.  II 

gradually  possessing  itself  of  the  river  frontages,  expanding  and  improving 
them  on  systematic  lines.  In  1870  the  length  of  whar£age  was  28  miles  ;  in 
1890  it  had  increased  to  37  mUes,  and  since  that  date  it  has  been  consider- 
ably augmented. 


The   Port   op   Glasgow. 

Glasgow  is  a  notable  example  of  a  port  existing  in  the  face  of  many 
natural  disabilities.  For  a  long  period  the  Clyde,  afflicted  with  the  dual 
evils  of  shaUowness  and  tortuousness,  was  little  better  than  a  ditch.  Goods 
were  despatched  by  pack-horses  a  distance  of  over  30  miles  from  Glasgow,, 
to  be  shipped  at  the  ports  of  Troon  and  Irvine,  on  the  Ayrshire  coast. 
At  one  time  it  was  despaired  of  ever  rendering  the  river  navigable,  and  the 
inhabitants,  in  1668,  acquired  a  plot  of  land,  some  13  acres  in  extent,  near 
the  village  of  Newark,  about  18  miles  distant,  where  they  built  a  harbour 
and  christened  it  Port-Glasgow. 

The  colony  thrived  for  a  time.  It  even  grew  into  importance.  In  1710 
it  was  the  principal  Custom  House  port  on  the  Clyde.  In  1762,  it  became 
the  site  of  the  first  graving  dock  in  Scotland,  built  under  the  direction  of 
James  Watt.  In  1812,  the  famous  "Comet" — the  pioneer  of  steam  naviga- 
tion in  Europe— was  built  here.  This  vessel  plied  the  i^ver  for  passengers,  ajid 
it  is  recorded  that  it  sometimes  took  seven  hours  to  accomplish  the  journey 
from  Greenock  to  Glasgow — a  distance  of  less  than  20  miles.  The  zenith  of 
Port-Glasgow's  prosperity  was,  however,  at  length  reached.  The  citizens  of 
the  parent  city  never  abandoned  their  efforts  to  increase  the  navigability  of 
the  river,  and  by  dint  of  perseverance  they  succeeded  in  effecting  some 
improvement.  Shipping  was  naturally  attracted  to  the  more  important 
trade  centre  and  the  fortunes  of  Port-Glasgow  declined.  It  is  at  the  present 
time  dependent  upon  its  shipbuilding  yards  for  its  existence. 

In  1768,  John  Golbome,  of  Chester,  reported  to  the  Glasgow  magistrates 
that  by  suitable  works  it  might  be  possible  to  obtain  a  depth  of  4,  or  even 
5,  feet  as  far  as  the  town.  He  was  considered  over-sanguine  by  some,  but 
he  more  than  fulfilled  his  word,  the  depth  actually  obtained  being  7  feet. 
In  1799,  John  Rennie,  of  London,  advocated  a  system  of  low  rubble  training 
walls,  and  these  were  carried  out  with  such  success  that  the  navigable 
depth  in  1806  had  been  increased  to  8^  feet  on  spring  tides ;  but  im- 
provement for  some  time  thereafter  was  slow.  Up  to  1836  the  depth  in 
the  harbour  had  only  been  increased  to  7  or  8  feet  at  low  water,  making 
12  feet  at  high  water  of  neap  tides,  and  15  feet  at  high  water  of  spring 
tides. 

In  1824,  an  impetus  was  given  to  deepening  operations  by  the  introduc- 
tion of  the  steam  dredger ;  and,  whereas  in  1821,  the  maximum  draught  of 
vessels  navigating  the  river  was  13 J  feet;  in  1830,  it  was  14  feet;  in  1870, 
21  feet;  in  1880,  22  feet;  in  1890,  23  feet,  and  in  1900,  26^  feet.     The 


12  DOCK   ENGINEERING. 

present  condition  and  prospects  of  the  river  are  thus  stated  by  the  Engineer, 
Mr.  W.  M.  Alston  ♦:— 

"The  deepening  and  widening  of  the  river  is  still  going  on,  the 
constantly  increasing  draught  of  vessels  demanding  more  depth,  and  more 
depth  involving  greater  widths  in  order  that  the  banks  may  stand. 
Dredging  is  presently  being  executed  to  20  feet  below  extreme  low  water, 
•or  22|^  feet  below  average  low  water  of  spring  tides,  corresponding  with 
About  32^  feet  at  high  water,  spring  tides,  at  Port-Glasgow,  and  33|  feet  at 
high  water,  springs,  at  Glasgow ;  and  with  this  depth,  the  bottom  widths 
range  from  120  feet  at  the  River  Kelvin  to  500  feet  at  Port-Glasgow.  Out 
of  the  16  miles  of  channel  between  the  harbour  and  Port-Glasgow,  about  10 
miles — not  continuous — may  be  said  to  have  attained  this  depth ;  while  in 
the  remaining  6  miles  the  depth  varies  from  about  19  feet  to  22^  feet  below 
average  low  water  of  spring  tides." 

Owing  to  the  comparatively  small  range  of  tides — about  11^  feet  at 
springs  and  9  feet  at  neaps — ^it  has  not  been  deemed  necessary  to  equip 
the  Glasgow  docks  with  gates.  They  are,  therefore,  properly  speaking,  tidal 
basins  in  which  the  water  is  free  to  rise  and  fall  with  the  tide.  •  The  first 
dock,  the  Kingston,  with  an  area  of  5^  acres  was  opened  in  1867.  The 
Queen's  Dock  was  completed  in  1880,  and  added  33f  acres  to  the  available 
accommodation.  This  dock  is  situated  on  the  north  side  of  the  river. 
Parallel  to  it  on  the  9<yith  side  has  been  constructed,  between  the  years  1892 
and  1897,  the  Prince's  Dock,  with  an  area  of  35  acres.  These  constitute  the 
present  extent  of  the  dock  accommodation  at  Glasgow.  Developments, 
however,  are  in  hand,  and  a  dock  of  16f  acres  is  in  course  of  construction 
at  Clydebank,  6  miles  below  Glasgow  Bridge,  for  the  service  of  the  coal  and 
mineral  trades. 

The  shipping  at  Glasgow,  which  in  1810  only  registered  24  sailing 
vessels  and  1,956  tons,  in  1900  had  increased  to  1,605  sailing  and  steam 
vessels  with  a  tonnage  of  1,582,229.  The  vessels  arriving  and  clearing  at 
Glasgow  in  1900  numbered  21,800,  with  a  tonnage  of  7,461,417. 

The  Poet  of  Hamburg. 

The  leading  port  of  the  Continent  conducted  all  its  loading  and  unloading 
opei'ations  prior  to  1866  by  means  of  open  barges,  the  ships  being  moored  to 
dolphins,  arranged  in  long  rows  in  natural  bays,  along  the  banks  of  the  Elbe, 
or  in  the  river  itself.  The  earliest  basins  to  be  constructed  were  the 
Sandthor  (24  acres),  and  the  Grasbrook  (16 J  acres),  and  these  were  brought 
into  existence  between  the  years  1860  and  1870.  In  1881,  the  port  joined 
the  Customs  Union  of  the  German  Empire,  and  a  period  of  great  activity  in 
dock  construction  commenced.  From  the  year  1884  onwards  the  port  has 
been  extended  by  the  formation  of  the  Beacon  Basin  (44  acres),  the  Hansa 

*  Alston  on  "  The  River  Clyde  and  Harbour  of  Glasgow,"  International  Engineering 
Congress,  Glasgow,  1901. 


THE   PORT   OF   MARSEILLES.  I J 

Basin  (90^  acres),  the  India  Basin  (27  acres),  the  Petroleum  Basin  (19} 
acres),  the  Moldau  Basin  (62  acres),  the  Saale  Basin  (30  acres),  and  the 
Spree  Basin  (27J  acres). 

Up  to  the  year  1895,  the  total  water  area  of  the  free  port,  including  the 
river,  canals,  and  side  basins,  amounted  to  941  acres,  of  which  the  basins 
for  sea-going  ships  occupied  328  acres,  and  those  for  river  vessels  136  acres. 
There  were  also  14^  miles  of  deep-water  quayage.  Since  that  date  a  large 
scheme  of  dock  extension,  on  the  south  side  of  the  river,  has  been  in  hand,, 
and  is  now  practically  completed.  It  includes  a  deep-water  basin,  for  sea- 
going ships,  having  an  area  of  55^  acres,  and  a  shallow-water  basin,  for 
river  craft,  having  an  area  of  96J  acres. 

In  the  year  1900,  13,102  vessels  entered  the  port  with  a  tonnage  of 
7,909,913,  and  of  these,  8,933  were  steamships  with  a  tonnage  of  7,124,145. 

The  Port  op  Antwerp. 

Antwerp  is  of  ancient  origin  and  long  held  one  of  the  most  splendid 
positions  in  the  history  of  European  commerce.  But,  in  the  year  1648, 
the  Dutch  inflicted  upon  its  prosperity  a  blow  from  which  it  did  not 
recover  for  many  long  years.  Victorious  in  their  struggle  with  the 
Spaniards,  who  at  that  time  were  proprietors  of  the  North  Sea  littoral,, 
they  insisted,  in  the  treaty  of  Munster,  upon  the  closing  of  the  Scheldt  on 
this  side  of  the  sea;  in  other  words,  on  the  destruction  of  Antwerp  as  a 
seaport.  It  was  not  until  the  year  1795  that  the  unfortunate  city  regained 
its  freedom  by  the  terms  of  the  treaty  of  the  Hague.  Since  then  Antwerp 
has  made  notable  strides  towards  regaining  its  lost  position,  and  to-day  it 
ranks  as  the  second  Continental  port. 

Early  in  the  19th  century  there  were  only  two  docks  and  some 
river  quays  in  existence.  The  docks  had  an  area  of  21  acres  only,  and 
this  remained  the  extent  of  the  enclosed  accommodation  until  the  year 
1860,  when  the  Kattendyke  Dock  was  opened.  Twenty  years  later  it 
was  extended  to  a  total  area  of  120  acres.  The  Africa  Dock  for  large 
transatlantic  steamers,  and  the  America  Dock  for  the  petroleum  trade — 
making  an  addition  of  50  acres  in  all — were  begun  in  1883  and  finished  in 
1886.  Apart  from  these  there  is  a  magnificent  stretch  of  over  3  miles  of 
quay  frontage  to  the  River  Scheldt. 

In  the  year  1900,  11,488  vessels  with  a  tonnage  of  6,688,272  entered 
the  port. 

The  Port  of  Marseilles. 

Up  to  the  year  1889,  Marseilles  was  the  principal  Continental  port. 
From  that  date  Hamburg  assumed  the  lead,  and,  in  1894,  Antwerp  wrested 
the  second  place  in  order  of  importance  from  her  former  superior.  Despite 
these  successive  misfortunes,  Marseilles  still  retains  a  high  position  amongst 


14  DOCK   ENGINEERING. 

European  ports.  The  town  is  a  very  ancient  one,  but  the  harbour  accom- 
modation has  only  really  been  developed  within  the  last  fifty  years.  Prior 
to  1852,  there  was  only  the  Old  Harbour,  67  acres  in  extent,  which,  with 
a  small  canal  and  basin,  made  the  total  water  area  72  acres.  In  this  year, 
the  JoLiETTE  Basin,  which  had  been  commenced  in  1844,  was  opened,  and 
gave  an  additional  area  of  54  acres,  or,  with  its  outer  harbour,  56  acres. 
In  1863  followed  the  Lazaret  and  Arenc  Basins  adding  51  acres,  and 
the  Railway  Basin  with  41  acres.  The  National  Basin  was  completed 
in  1881,  and  its  105  acres  raised  the  total  accommodation  of  the  port  to 
325  acres.  In  1893  the  construction  of  a  new  basin  called  the  Pin&de 
Basin  was  authorised,  the  works  for  which  are  not  yet  completed.  It 
will  add  65|  acres  to  the  sheltered  water  area. 

In  1900  the  number  of  vessels  which  entered  and  cleared  the  port  was 
17,254,  and  the  tonnage  12,178,245.  In  1901  the  figures  were  16,802  and 
12,877,731  respectively. 

The  Port  op  Rotterdam. 

The  port  of  Rotterdam  possessed  a  small  dock  at  the  close  of  the 
16th  century.  This,  called  the  Herring  Basin,  is  shown  upon  a  plan 
dated  1599.  For  the  next  twenty-five  years  there  was  steady  progress.  A 
plan,  dated  1623,  demonstrates  the  existence  at  that  time  of  the  Leuve 
Basin,  the  Wine  Basin,  and  the  Shipbuilder's  Basin.  But  for  the 
ensuing  two  hundred  years  very  little  appears  to  have  been  done  in  the 
direction  of  increasing  the  amount  of  enclosed  water  space.  The 
Salmon  Basin  was  brought  into  existence  at  the  commencement  of  the 
18th  century.  At  this  date  Rotterdam  was  only  accessible  to  ships  drawing 
less  than  11  feet  of  water. 

It  was  not  until  1873  that  a  further  impetus  was  given  to  the  expan- 
sion of  the  port,  when  the  King's  Basin  and  the  Railway  Basin  were 
constructed.  Between  1874  and  1879  the  Inner  Basin  and  the  Ware- 
house Basin  were  opened.  These  were  followed,  in  1885,  by  the  Rhine 
Basin,  in  1894  by  the  Katendrecht  Basin,  and,  in  1898,  by  the  Park 
Basin.  In  the  last-named  year  was  commenced  the  construction  of  the 
Meuse  Basin,  which  adds  145  acres  to  the  dock  accommodation  of  a  port 
already  possessing  147  acres  on  the  right  bank  of  the  Meuse  and  162  acres 
on  the  left  bank,  making  454  acres  in  all,  exclusive  of  river  berths  and 
moorings. 

The  number  of  vessels  which  entered  Rotterdam  during  the  year  1900 
was  7,268,  with  a  tonnage  of  6,483,6t55. 

The  Port  op  Cardiff. 

The  staple  export  of  Cardiff  is  coal,  and  its  position  in  reference  to  the 
great  coalfields  of  South  Wales  has  caused  the  rise  of  the  town  from  a 


FOREIGN  TRADE   IN  UNITED  KINGDOM. 


^5 


population  of  2,000,  at  the  beginning  of  the  19th  century,  to  one  of 
160,000,  at  the  beginning  of  the  20th.  The  development  of  the  port  is 
•due  to  the  Marquis  of  Bute,  who,  between  1840  and  1850,  commenced 
the  construction  of  the  docks  known  by  his  name.  In  1901  the  docks 
covered  an  area  of  153  acres  (including  the  new  Roath  Dock).  The 
quantity  of  coal  shipped  amounted  to  8,000,000  tons,  and  the  number  of 
vessels  entering  the  port  was  14,695,  with  a  tonnage  of  9,290,785. 


The  Tynb  Ports. 

What  Cardiff  is  to  South  Wales,  the  cluster  of  ports  at  the  mouth  of 
the  Biver  Tyne  is  to  the  North-East  coast  of  England.  From  ancient 
times  Newcastle  has  been  a  great  coaling  centre,  with  North  and  South 
Shields  and  Tynemouth  in  close  competition.  The  growth  of  the  trade 
bas  been  remarkable.  At  the  beginning  of  the  19th  century  the  export 
amounted  to  half  a  million  tons;  at  the  end  it  was  over  12,000,000.  The 
docks  are  of  qidte  recent  origin,  the  Northumberland,  Ttne,  and  Albert 
Edward  Docks,  with  their  combined  area  of  129  acres,  having  been  brought 
into  existence  during  the  latter  half  of  last  century.  In  1901  the  number 
of  vessels  entering  the  ports  was  14,072,  with  a  tonnage  of  8,491,535. 

The  following  tables,  condensed  from  information  published  by  the 
Board  of  Trade,  will  afford  some  means  of  instituting  an  interesting 
comparison  of  the  ports  enumerated.  It  will  be  noted,  however,  that  the 
statistics  relate  to  foreign  trade  only. 

■ 

TABLE  I. — Foreign  Trade  op  Principal  Ports  in  the  United 

Kingdom. 

Tonnaok  of  Sailing  and  Steam  Vessels  Entered  and  Cleared  with  Cargoes  and 
in  Ballast  in  the  Foreign  Trade  during  the  Years  1900- 1902. 


Port. 

1900. 

1901. 

1902. 

Bntraoces. 

Clearances. 

Entrances. 

Clearances. 

Entrances. 

Clearances. 

Tons. 

Tons. 

Tons. 

Tons. 

Tons. 

Tons. 

Belfast, 

435,980 

249,770 

447,855 

226, 168 

479,377 

149,660 

Cardiff, 

5,132,623 

7,636,717 

4,953,980 

7,783,077 

4,688,088 

7,868,656 

Dover, 

973,074 

964,476 

955,472 

960,477 

986,908 

980,984 

Glasgow, 

1,462,023 

2,229,574 

1,558,301 

2,267,589 

1,618,663 

2,525,554 

HuU, . 

2,666,598  i  2,274,137 

2,460,830 

1,964,526 

2,514,663 

1,965,875 

Leith, 

1,055,291  1      982,309 

1,023,669 

922,085 

989,914 

890,357 

Liverpool, . 

6,001,563 

5,666,145 

6,465,153 

6,171,072 

6,843,200 

6,314,514 

London, 

9,580,854 

7,119,673 

9,992,753 

7,282,892 

10,179,023 

7,385,085 

Southampton,     . 

1,613,913    1,395,486 

1,645,166 

1,417,556 

1,689,525 

1.534,966 

Tyne  ports, 

3,897,142    4,894,157 

3,831,554 

4,840,256 

3,615,046 

4,754,301 

i6 


DOCK  ENGINEERING. 


TABLE  II. — Foreign  Trade  op  Principal  Foreign  and  Colonial  Ports. 


Tonnage  of  Sailing  and  Steam  Vessels  Entered  and  Cleabed  with  Cargoes 
AND  in  Ballast  in  the  Foreign  Trade  during  the  Years  1899-1901. 


Port. 

1899. 

1900. 

1901. 

Entrances. 

Clearances. 

Entrances. 

Clearances. 

Entrances. 

! 

Clearances. 

Tons. 

Tons. 

Tons. 

Tons. 

Tons. 

Tons. 

Antwerp,   . 

6,837,801  ,  6,735,656 

6,696,370 

6,669,712 

7,466,463 

7,518,292 

Buenoe  Ayres,    . 

3,302,145  1  2,969,196 

2,789,581 

2,505,323 

returns  not 

available. 

Grenoa, 

3,990,306  1  3,679,973 

4,313,604 

4,119,372 

4,503,895 

4,309,075 

Gibraltar,  . 

4,328,859    4,299,678 

4,455,083 

4,414,654 

4,171,360 

4,159,272 

Hamburg,  . 

7,037,294    7,157,576 

7.322,476 

7,404,112 

7.623,098 

7,671,938 

Hong-Kong, 

6,720,769  1  6,716,378 

7,021,982 

7,000,185 

7,383,683    7,340,586 

Marseilles, 

4,695,168    4,933,946 

4,629,599 

4,933,945 

4,936,095 

5,286,640 

New  York, 

7,707.477 

7,496,279 

8,176,761 

7,843,529 

8.679,273 

8,118,427 

Rotterdam, 

5,956,437 

5,828,331 

5,970,395 

5,762,967 

5,950,446 

5,733,763 

Singapore, . 

4,416,260 

4,409,913    4,836,048    4,833,989 

5,456,032 

5,453,999 

17 


CHAPTER  II. 

DOCK     DESIGir. 

Necessity  for  Docks — Rblativb  Advantages  of  Docks  ai^d  Basins— Restriction 
IN  Design— Considerations  in  regard  to  Position  and  Outlike— Various 
Forms — A  Model  Dock  System— Ratio  of  Quay  Space  to  Water  Area — 
Ratio  of  Periphery  to  Surface — Grouped  Docks— Internal  Dispositions — 
Cost  of  Construction —Fresh  Water  Supply— Ship  Design — Typical  Dock 
Systems  at  Liverpool  and  Birkenhead,  Barry,  Buenos  Ayrbs,  Tilbury, 
Glasgow,  Calcutta,  Hull,  Hamburg,  London,  Sunderland,  Swansea,  Havre^ 
and  Mabseillbs— Statistics  of  Representative  Docks. 

Necessity  for  Docks. — In  the  days  before  steamships  were  known,  when 
vessels  traversing  the  ocean  highways  of  the  world  were  built  entirely  of 
wood,  the  question  of  the  provision  of  docks  for  the  accommodation  of 
shipping  had  not  assumed  that  aspect  of  importance  and  urgency  which  it 
has  since  acquired.  It  was  no  uncommon  occurrence  for  a  vessel  to  take  the 
ground  at  the  quayside  during  periods  of  low  water,  and  this  could  be  done 
with  impunity  when  hulls  were  short  and  stout,  and  sides  thick  and  strong. 
In  fact,  the  experience  was  a  recognised  incident  in  the  ordinary  course  of 
navigation,  and  we  find  one  of  the  advantages  claimed  for  the  port  of 
Bristol,  two  centuries  ago,  was  that  the  harbour  afforded  a  ''soft  bed, 
suitable  for  the  grounding  of  vessels." 

In  one  respect  naval  architecture  has  degenerated  since  those  times. 
Nowadays,  the  attenuated  plating  of  an  ocean  steamer,  coupled  with  its 
enormous  length  and  weight,  would  inevitably  suffer  serious  strain, 
if  not  collapse,  under  such  drastic  treatment.  Indeed,  to  such  an  extent 
have  strength  and  stiffness  been  sacrificed  to  speed,  that  the  foundering  of 
at  least  one  modern  craft  *  is  attributed  to  the  fact  that  the  ends  of  her  keel 
were  lifted  momentarily  upon  the  crests  of  two  waves,  while  the  central 
portion  spanned  the  trough  between,  and,  being  unsupported,  was  fractured 
by  the  mere  weight  of  the  vessel  and  its  internal  fittings. 

Except  then  for  small  fishing  craft,  deep  water  berths  in  the  form  of 
harbours,  basins,  or  docks,  capable  of  maintaining  shipping  continuously 
afloat,  are  necessary  features  of  every  modem  port.  River  frontage  quays 
may  suffice  in  minor  cases  in  sheltered  situations,  but,  as  a  rule,  the  accom- 
modation thus  afforded  is  insufficient. 

The  question  whether  open  basins  or  closed  docks  are  more  suitable  for 

*This  was  a  torpedo  boat  destroyer,  it  is  true— the  ill-fated  *' Cobra" — bat  the 
vessel  and  the  disaster  are  typical  of  modem  tendencies  and  their  results. 

2 


1 8  DOCK  ENGINEERING. 

adoption  in  a  locality  depends  upon  the  range  of  tide  and  the  meteorological 
conditions. 

In  an  inland  sea,  such  as  the  Mediterranean,  which  is  practically  tideless, 
an  open  basin  will  serve  all  the  requirements  of  commerce,  in  so  far  as  the 
provision  of  quayage,  for  the  reception  of  cargo,  is  concerned.  Nor  is  there 
much  inducement  to  construct  closed  docks  when  the  range  of  tide  is 
moderate,  say  not  exceeding  about  10  feet,  instances  of  which  occur,  amongst 
other  places,  at  Glasgow,  Belfast,  and  Hamburg ;  but  when  the  rise  and  fall 
of  the  water  level  is  very  great,  as  at  Liverpool,  Bristol,  and  elsewhere, 
where  there  is  a  difference  in  level  of  between  30  and  50  feet,  the  necessity 
for  enclosed  areas,  in  which  the  water  may  be  impounded  at  a  fairly  constant 
depth,  becomes  evident  and  imperative. 

The  advantages  attaching  to  tidal  basins,  where  practicable,  are  the 
speedy  and  unrestricted  arrival  and  departure  of  vessels,  and  the  absence  of 
costly  appliances  for  closing  the  entrances.  On  the  other  hand,  the  main- 
tenance of  an  unchanging  and  uniform  water  level  in  tidal  situations,  is  of 
undoubted  benefit  in  facilitating  the  loading  and  discharging  of  cargoes,  in 
avoiding  the  chafing  of  vessels  against  the  quayside,  and  in  obviating  the 
necessity  of  constant  attention  to  and  alterations  in  the  moorings. 

Apart  from  the  tidal  question,  an  enclosed  and  sheltered  dock  has  the 
advantage  of  providing  a  quiescent  area  unaffected  by  external  waves  and 
storms. 

In  a  determination  of  the  particular  design  suitable  for  a  dock  or  basin, 
such  great  influence  is  esterted  by  considerations  of  a  purely  local  nature, 
and  there  is  so  much  scope  for  the  exercise  of  ^idividual  judgment  and 
opinion,  that  it  is  quite  impossible  to  lay  down  any  hard  and  fast  rules  to  be 
observed  universally,  or  even  in  a  majority  of  cases. 

Very  rarely  does  the  Engineer  find  himself  absolutely  unfettered  by 
restrictions  arising  from  fixed  conditions,  such  as  those  relating  to  site, 
expediency,  and  economy.  Commerce  is  erratic  to  this  extent  that  it  does 
not  necessarily  favour  ports  possessing  admirable  natural  facilities  for  the 
accommodation  of  shipping.  A  port  is  only  one  of  several  stages  in  the 
journey  from  the  manufacturer  to  the  consumer.  Consequently,  any  par- 
ticular merits  it  may  possess  as  a  harbour,  are  entirely  subservient  to  its 
position  in  regard  to  the  great  trade  routes.  In  the  maintenance  of  well- 
established  lines  of  communication  much  inconvenience  has  been  endured 
from  natural  obstacles,  and  large  sums  have  been  expended  upon  their 
mitigation  and  removal ;  whereas  other  ports,  more  favourably  endowed  by 
nature,  have  languished  in  obscurity.  Trade,  therefore,  cannot  be  created 
at  will ;  but  much  may  be  done  to  induce  and  foster  it,  just  as  it  may  be 
injured  by  indifference  and  n^lect. 

It  is  mainly,  then,  within  areas  already  occupied  and  probably  densely 
populated,  that  provision  has  to  be  made  for  the  formation  and  extension  of 
dock  accommodation.  In  such  cases  the  acquisition  of  adjoining  property 
has  to  be  kept  within  remunerative  or,  at  any  rate,  strictly  utilitarian  limits, 


POSITION.  1 9 

and  very  often  the  new  boundaries  are  so  irregular  as  to  need  the  exercise 
of  much  thought  and  skill  in  order  to  utilise  the  enclosed  space  to  its  fullest 
extent.  Many  docks  owe  the  complexity  and  apparent  eccentricities  of  their 
outlines  to  such  conditions  of  evolution. 

As,  however,  in  a  treatise  of  (this  kind  we  must  have  some  basis 
upon  which  to  found  our  observations,  which  are  to  be  as  complete  and 
comprehensive  as  possible,  there  is  no  alternative  but  to  assume  a  freedom 
of  choice  and  design  which  will  rarely,  if  ever,  be  realisable  in  practice. 
Upon  such  an  assumption  the  following  points  claim  foremost  attention : — 

The  most  convenient  poeition,  and 

The  most  suitable  sh^pe  for  a  dock ; 

The  best  nUio  hettoeen  quay  space  and  uxxter  area;  and 

That  between  periphery  amd  swrface. 

Position. — In  regard  to  this  point  certain  obvious  requirements  im- 
mediately present  themselves  —  accessibility,  shelter,  accommodation. 
Accessibility  will  depend,  in  the  first  place,  upon  the  depth  of  water  in 
the  approach  channel.  This,  of  course,  is  susceptible  of  improvement  by 
artificial  means,  but  a  naturally  deep  fairway  is  a  great  saving  in  cost, 
both  of  construction  and  of  maintenance.  In  the  second  place,  accessibility 
will  depend  upon  the  absence  of  dangerous  shore  eddies  and  currents;  in 
the  third  place,  upon  proximity  to  the  open  sea,  and,  lastly,  upon  the  range 
and  duration  of  the  tide.  The  amount  of  shelter  will  be  governed  by  the 
configuration  of  the  coast  line,  by  the  vicinity  or  otherwise  of  promontories 
and  headlands,  and  by  local  experience  in  the  matter  of  storms  and  cyclones. 
The  accommodation  will  depend  upon  the  area  available  and  its  disposition. 

Apart  from  considerations  of  exposure,  a  position  upon  the  seaboard 
is  preferable  to  one  some  distance  up  a  river,  for  large  ocean-going 
steamers.  The  navigation  of  a  river,  often  tortuous  in  course  and 
crowded  with  craft  of  various  sizes,  is  a  slow  and,  in  fogs  and  darkness, 
a  hazardous  proceeding,  rarely  attended  by  any  compensating  advantages. 
Such  ports  as  Antwerp  and  Bremen  are  undoubtedly  handicapped  by  their 
inland  situations.  The  disadvantage  has  perhaps  not  been  fully  apparent 
in  the  past,  but  it  is  bound  to  make  its  influence  felt  in  the  future. 
Joined  to  the  difficulty  of  manoeuvring  mammoth  vessels  will  be  the 
attendant  loss  of  time,  which  busy  mercantile  communities  can  ill  afiEbrd  to 
endure.  No  doubt  engineering  operations  are  quite  capable  of  maintaining 
and  improving  the  accessibility  of  these  ports,  but  only  at  considerable 
outlay  in  initial  and  current  expenditure.  Forts  like  Marseilles  and 
Havre,  on  the  other  hand,  will  always  naturally  enjoy  the  privilege  of 
direct  and  unimpeded  communication  with  the  ocean.  But  it  must  not  be 
overlooked  that  such  ports  are  subject  to  the  whole  violence  of  the  open 
sea  in  time  of  storm,  and  that  the  provision  of  shelter  from  such  destructive 
agencies  will  often  necessitate  very  expensive  protective  works. 

Taking  all  things  into  consideration,  an  estuarine  situation  is  perhaps 


20  DOCK  ENGINEERING. 

most  to  be  recommended,  combining,  as  it  does,  the  advantages  of  both  the 
previous  cases  without  any  of  their  drawbacks  in  an  acute  form.  But,  in 
order  to  fulfil  the  ideal  conditions,  the  estuary  must  be  broad  and  well 
sheltered,  free  from  shoals  and  from  a  shallow  bar. 

Shape. — ^The  outline  of  a  dock  or'basin  may  be  that  of  any  geometrical 
figure,  or  of  several  figures  in  combination.  Figures  approaching  the 
curvature  of  the  circle,  unless,  indeed,  the  radius  be  extremely  great,  are 
obviously  unsidtable  for  enclosures  destined  to  accommodate  long  straight 
vessels  in  contact  with  their  sides.  Curves  are  undoubtedly  employed  to 
advantage  in  many  cases,  in  connecting  outlying  arms  and  branches,  and 
in  training  ships  through  changes  of  direction,  but  their  effective  use  is 
limited  and  otherwise  to  be  deprecated.  The  most  suitable  forms  are 
rectilinear,  and  those  generally  available  for  the  purpose  are  the  triangular, 
the  square,  the  rectangular,  the  diamond  (or  lozenge),  the  machicolated,  and 
the  digital. 

The  trianfftdar  form  is  rarely  used,  not  so  much,  perhaps,  on  the  ground 
of  any  inherent  defect,  as  that  the  quay  arrangements  are  not  always  con- 
formable to  a  plan  of  that  character.  It  has  possible  advantages  for  an 
entrance  basin  acting  as  a  vestibule  to  a  group  of  docks,  as  exemplified  in 
the  basin  leading  to  the  Albion  and  Island  Docks  at  Botherhithe  (fig.  18). 
This  example,  however,  be  it  noted,  is  somewhat  defective,  though  not 
radically  so.  Other  triangular  outlines,  more  or  less  complete,  are  to  be 
found  in  the  Prince  of  Wales  Dock  at  Swansea  (fig.  20),  the  Morpeth  Branch 
Dock  at  Birkenhead  (fig.  6),  and  the  Manchester  Dock  at  Liverpool  (fig.  5). 

The  sqitare  dock  offers  the  advantage  of  plenty  of  space  for  the  turning 
of  the  vessels  it  accommodates.  In  the  majority  of  instances  a  vessel 
leaves,  and  should  leave,  a  dock  stem  first.  As  she  generally  makes  her 
entry  in  the  same  manner,  it  behoves  that  sufficient  room  be  provided  for 
turning  her  within  the  dock.  This  proviso  is  of  most  importance  in  exposed 
situations  with  narrow  entrance  channels.  With  a  wide  open  fairway, 
sufficiently  sheltered,  it  is  a  matter  of  indifference  whether  the  turning 
takes  place  within  or  without  the  dock.  Many  ships  will  take  advantage 
of  an  outer  basin  in  order  to  make  their  entry  stem  first,  so  as  to  be  ready 
for  direct  departure.  The  disadvantage  attaching  to  the  square  dock  is  the 
excessive  proportion  of  its  water  area  to  the  amount  of  quayage,  which 
renders  it  unsuitable  for  the  accommodation  of  large  vessels.  It  is  doubtful 
whether  any  existing  dock  is  absolutely  square,  but  the  Albert  and  Colling- 
wood  Docks,  at  Liverpool  (fig.  5),  are  sufficiently  close  approximations 
for  the  purpose  of  illustration. 

The  rectangtUar  dock  is  a  modification  of  the  square  dock,  designed  to 
overcome  the  defect  just  mentioned.  By  proper  manipulation  the  length 
and  breadth  may  be  arranged  so  as  to  give  the  maximum  amount  of  quay 
frontage  consistent  with  the  water  space  absolutely  required  for  manoeuvring 
purposes.     This  ratio  will  be  discussed  later. 

The  rectangular  form  is  common.     A  few  instances  of  its  adoption  may 


SHAPE. 


21 


be  cited  from  Avonmouth,  Cardiff  (Roath  Dock),  and  London  (West  India 
Dock,  fig.  16). 

The  lozenge,  or  diamond,  is  a  slight  deformation  of  the  square,  resulting 
in  an  improvement  of  form  when  the  entrance  is  at  one  of  the  acute  angles, 
as  is  the  case  in  the  most  noteworthy  instance  of  its  use — viz.,  at  the 
Empress  Dock,  Southampton  (fig.  1). 

The  machicolcUed  form  consists  of  any  rectilinear  outline  in  conjunction 
with  a  number  of  internal  projections,  often  of  the  nature  of  jetties  or 
staiths.  It  constitutes  an  admirable  means  of  utilising  large  docks  to  their 
fullest  extent,  as  will  be  evident  from  an  inspection  of  the  plans  of  the 
Alexandra  Dock  at  Hull  (fig.  12),  the  Victoria  Dock  at  London  (fig.  17), 
Penarth  Dock,  and  others. 


Fig.  1. — Southampton  Docks.     Scale,  j^^. 


A  particular  variation,  or  possibly  an  evolution,  of  the  previous  type  is 
the  tridentine,  in  which  a  main  dock  is  provided  with  three  important 
arms  or  branches,  perpendicular  to  it.  Such  is  the  shape  adopted  for  the 
Tilbury  Docks  at  London  (fig.  9),  the  Alexandra  and  Huskisson  Docks  at 
Liverpool  (fig.  5),  and  the  Prince's  Dock  at  Glasgow  (fig.  10).  There  is  no 
essential  limit  to  the  number  of  branches,  but  three  appears  to  be  a  very 
serviceable  number  consistent  with  compactness  of  design.  For  reasons  of 
traffic,  the  branches  should  be  arranged  to  the  landward  of  the  main  dock. 

Finally,  we  come  to  yet  another  evolution  of  the  machicolated,  which, 
from  its  resemblance  to  the  outspread  fingers  of  a  hand,  may  appropriately 


22  DOCK  £N6I^  BERING. 

be  termed  the  digikd.  It  is  illustrated  in  fig.  2.  The  suggestion  emanated, 
in  the  first  instance,  from  the  late  Thomas  Stevenson,  but  the  design  in  the 
figure  embodies  several  important  modifications  of  the  original  sketch,  and 
includes  an  entrance  scheme  which  has  not,  to  the  author's  knowledge, 
appeared  elsewhere.  The  idea  is  that  the  dock  is  situated  on  the  margin 
of  a  tidal  river,  or  estuary,  and  the  dual  entrance,  as  explained  in 
Chapter  vi.,  is  intended  to  permit  of  the  dock  being  accessible  at  all 
stages  of  the  tide.  When  the  flow  is  up  the  river,  vessels  will  enter  by 
the  upstream  locks  and  depart  by  the  downstream  locks.  Vice  versd,  when 
the  tide  is  running  out,  incoming  vessels  will  use  the  downstream  locks,  and 
those  departing,  the  upstream  locks.  In  this  way  the  dock  will  be  worked 
without  intermission  and  without  obstruction.  It  is  assumed  that  the 
outer  sills  are  deep  enough  to  allow  vessels  to  pass  over  them  at  low  water. 
The  scheme  has  been  amplified  so  as  to  include  all  the  features  essential 
to  a  dock  system.  Graving  docks  of  various  sizes  are  arranged  between  the 
entrance  locks,  with  ample  intermediate  space  for  ship-repairing  depdts. 
In  order  to  have  shoreward  connection  for  these,  it  will  be  necessary  for 
the  locks  to  be  spanned  by  movable  bridges. 

The  central  portion  of  the  dock  is  semi-circular  in  form,  and  designed  to 
afford  turning  room  for  vessels  up  to  1,000  feet  in  length.  There  are  also 
four  utilisable  berths,  each  275  feet  long. 

The  branches,  of  which  there  are  five,  though  irregular  in  form  are  all 
similar,  and  each  provides  quay  accommodation  in  pairs  of  lengths  of  1,000, 
600,  and  400  feet  successively,  together  with  an  end  berth  of  350  feet.  The 
indentations  permit  of  ships  overlapping,  while  at  the  same  time  berths  are 
afforded  for  small  craft  of  100  to  120  feet  in  length.  A  further  advantage 
of  the  indentations  is  that  moored  vessels  are  well  recessed  out  of  the  way 
of  those  passing  in  and  out  of  the  branches ;  in  fact,  provision  is  made  for 
vessels  being  attended  in  their  berths  by  rows  of  lighters  on  each  side 
without  obstructing  the  main  waterway. 

The  sides  of  the  branches,  generally,  are  lined  with  sheds,  from  100  to 
120  feet  in  width,  of  varying  lengths,  and  of  heights  taken  at  two  storeys, 
but  capable  of  adjustment  to  circumstances.  The  sheds  are  recessed  40  feet 
from  the  edge  of  the  quay,  to  allow  of  lines  for  quay  cranes  and  railway 
trucks.  These  lines,  as  well  as  others  at  the  rear  of  the  sheds,  are  all  in 
inter-communication  by  means  of  a  circular  railway  along  the  landward 
boundary  of  the  estate,  which  is  supposed  to  be  connected  with  trunk  lines 
leading  to  other  towns. 

Special  berths  are  provided  at  one  branch  dock  for  petroleum  and  coal, 
and  at  another  for  grain  and  timber.  The  petroleum  berth  has  both  tank 
storage  and  shed  accommodation  for  barrels.  The  coal  berth  consists  of  an 
open  quay,  laid  with  numerous  sidings  and  furnished  with  projecting  jetties 
for  hoists  and  tips.  Grain  is  received  direct  into  warehouses,  the  face  line 
of  which  is  within  5  feet  of  the  edge  of  the  coping.  Timber  may  be 
discharged  into  a  single  storey  shed  or  on  to  a  low  quay,  or  it  may  be  floated 


i^»  fat,  pott  n. 


RATIO  OF  QUAY  SPACE  TO  WATER  AREA.        2$ 

into  the  timber  pond.  The  river  frontage  is  also  available  for  timber  storage, 
as  well  as  for  a  cattle  wharf,  if  required,  with  a  lairage  at  the  rear. 

There  are  four  surplus  plots  of  land,  triangular  in  shape,  between  the 
branches.  These  can  be  utilised  as  sites,  partly  for  administrative  buildings 
and  offices,  and  partly  for  warehouses  and  goods  dep6ts,  timber  yards,  and 
l^e  like  commercial  adjuncts  of  a  dock  system.  The  land  immediately 
adjoining  the  entrance  locks  will  be  advantageously  occupied  by  the  dock- 
master's  office  and  residence,  and  by  dwellings  for  dockgatemen  and  other 
officials  whose  constant  attendance  upon  the  spot  is  desirable.  A  convenient 
site  wiU  also  be  found  in  the  vicinity  of  the  graving  docks  for  a  pumping 
station  and,  if  hydraulic  power  is  to  be  employed,  for  one  or  more  accumula- 
tors, though  possibly  the  requisite  power  may  be  as  readily  obtained  from 
an  external  source,  such  as  the  mains  of  a  private  company  or  of  a  municipal 
body. 

The  design  is  an  ideal  one  in  this  respect,  that  it  presupposes  an  entire 
freedom  of  action  in  regard  to  site  and  outlay  which  is  rarely  attainable. 
There  is  nothing,  however,  to  prevent  the  carrying  out  of  the  scheme 
partially  or  in  instalments,  as  may  be  found  necessary. 

Ratio  of  Quay  Space  to  Water  Area. — ^The  ratio  of  quay  space  to  water 
area  will  depend  upon  the  relationship  between  the  carrying  capacity  and 
the  length  of  vessels  which  occupy  berths  in  the  dock  in  question.  The 
following  is  an  approximate  statement  of  the  nett  registered  tonnage  of 
vessels  per  lineal  foot,  averaged  from  a  considerable  number  of  cases.  It 
must  be  emphasised,  however,  that  there  is  much  variation  dependent  on  the 
design  of  the  vessel,  whether  for  cargo  solely  or  for  cargo  and  passengers 
combined : — 


Veasels  between  200  and  300  feet  long,  5  to   6  tons  per  lineal  foot. 

.300  „  400  „  6  to  7 
400  „  500  „  8  to  10 
500  ,,  600  „  10  to  12 
600  ,,    700        „        12  to  15 


i» 
ft 
ft 


»»  $9 

99  »> 

»>  »> 

it  is  evident  that  the 


Assuming  a  cubic  equivalent  of  40  feet  to  the  ton, 
volume  of  space  required  for  the  reception  of  cargo  will  range  between  200 
cubic  feet  per  lineal  foot  for  small  vessels  and  600  cubic  feet  per  lineal  foot 
for  large  ships.  This  accommodation  may  be  provided,  either  in  open  quay 
space  or  within  covered  sheds,  in  which  latter  case  the  available  area  will  be 
doubled  or  trebled,  if  the  shed  have  two  or  three  storeys.  But  as  goods  will 
rarely  be  piled  or  stacked  to  a  greater  height  than  10  feet,  and  as  allowance 
must  be  made  to  the  extent  of  33  per  cent,  for  alley  ways  and  passages,  it 
will  probably  be  equitable  to  take  an  average  of  5  feet  in  height  over  the 
whole  surface.  -  Accordingly,  a  superficies  of  from  40  to  120  feet  per  foot 
lineal  will  be  required  for  the  accommodation  of  cargo,  but  this  is  on  the 
assumption  that  the  whole  is  deposited  upon  the  quay  before  the  removal  of 
any  portion.  On  the  other  hand,  no  provision  has  been  made  for  the  simul- 
taneous reception  of  outward-bound  merchandise.    The  whole  problem,  in 


24  DOCK  ENGINEERING. 

fact,  is  so  beset  with  possibilities  and  contingencies  as  to  admit  of  no  definite 
solution.  Experience  alone  will  demonstrate  the  adequacy  or  otherwise  of 
the  quay  space  appropriated  to  any  particular  vessel  or  class  of  goods. 

Ratio  of  Periphery  to  Surfkce. — ^The  proper  proportion  between  the 
surface  of  a  dock  and  its  periphery  is  largely  dependent  upon  the  combination 
of  length  and  breadth  which  is  most  suitable  for  the  twofold  purpose  in 
view — ^viz.,  the  provision  of  sufficient  space  for  manoeuvring  ships  and  of 
sufficient  quayage  for  berthing  them.  Of  the  two  dimensions  which  produce 
the  area,  the  length  will  either  be  the  greatest  available,  or  that,  at  least, 
which  is  judged  adequate  for  present  and  future  requirements.  In  assigning 
a  breadth  to  a  dock,  it  must  be  borne  in  mind  that  a  steamship  will  not 
infrequently  coal  from  hulks  alongside  during  the  same  period  in  which  she 
is  receiving  and  discharging  cargo.  She  may  also  have  several  lighters  in 
attendance  for  goods  destined  to  be  forwarded  by  river  or  canal.  In  fact, 
employing  a  concrete  example,  it  will  be  well  to  make  allowance  for  a  row  of 
barges,  20  feet  in  width,  to  lie  between  the  vessel  and  the  quay  and  for  two 
rows  of  similar  craft  on  the  other  side  of  the  vessel.  Taking  the  beam  of  the 
latter  at  between  60  and  70  feet,  it  is  evident  that  the  berth  must  extend  to 
some  120  or  130  feet  in  width.  Doubling  this  for  two  sides,  and  allowing  a 
central  margin  of  100  feet  for  the  passage  of  ships  in  and  out  of  the  berths, 
it  is  clear  that  350  feet  is  no  excessive  width  for  a  dock.  Indeed,  an 
examination  of  Table  v.  will  show  that  this  dimension  is  frequently 
exceeded.  At  the  same  time,  it  must  be  observed  that  in  cases  of  extreme 
width  the  dock  will  generally  be  found  intersected  by  projecting  arms  or 
jetties. 

It  has  already  been  remarked  that  the  square  form  is  not  economical 
from  the  point  of  view  of  obtaining  the  greatest  amount  of  quayage  from 
a  given  area.  This  discrepancy  is  most  marked  in  docks  of  large  size. 
If  the  side  of  the  dock  be  s,  the  ratio  of  surface  to  periphery  is  8^  to  4«, 
or  «  to  4,  so  that  the  disparity  increases  with  the  length  of  the  side.  In 
a  rectangle  of  length,  /,  and  breadth,  6,  the  ratio  is  /6  to  2Z  +  26,  or  if 
^  =  nZ  where  n  is  any  proper  fraction :  «^  to  2Z  (1  +  n),  i,e. — 

^  ^  2  (1  +  n) 
n 

By  giving  n  the  values,  in  succession,  of  J,  J,  J,  ^,  &c.,  we  get  the 
following  ratios  :— 

Z  :  6,  8,  10,  12. 

When  n  =  1,  the  figure  is  a  square  and  the  ratio  becomes  Z  :  4  as  before. 

Grouped  Docks. — ^The  growth  of  trade  being  gradual,  docks  increase  in 
number  as  circumstances  at  each  port  demand.  Where  a  series  of  docks 
are  thus  brought  into  existence  they  will  generally  be  placed  in  intercom- 
munication by  means  of  passages.  Grouping  can  be  effidcted  systematically 
in  various  ways,  as  will  be  evident  from  a  consideration  of  what  may  be 
called  the  "  chain  "  system  at  Buenos  Ayres  (fig.  8),  the  "  comb  "  system  at 


INTERNAL  DISPOSITIONS.  25 

Liiverpool  (fig.  5),  and  the  "barb"  system  at  Hamburg  (fig.  13).  In  the 
majority  of  instances,  however,  there  is  no  system  at  all,  the  docks  being 
grouped  in  an  irregular  and  involved  manner  only  explicable  on  the  ground 
of  unforeseen  expansion. 

Internal  Dispositions. — The  internal  dispositions  of  a  dock  system  have 
already  been  indicated  in  the  description  of  the  model  plan  (p.  22),  but  it 
will  be  advisable  to  enlarge  a  little  further  upon  them. 

In  large  ports  it  is  a  commendable  (and  even  a  necessary)  arrangement 
to  have  separate  docks  for  the  reception  of  special  classes  of  merchandise 
(coal,  for  instance,  and  petroleum)  which  it  is  not  desirable  to  mix  with 
cargo  of  a  more  general  character. 

A  very  frequent  disposition  at  coaling  ports  is  to  provide  along  one  or 
more  sides  of  a  dock  a  series  of  projecting  coal  tips,  or  shoots,  served  by 
lines  and  sidings.  When  one  side  of  a  dock  is  sufficient  for  the  purpose, 
the  others  may  be  devoted  to  miscellaneous  cargo,  but  the  dust  arising  from 
the  shipment  of  coal  renders  it  advisable  to  conduct  tipping  operations  as 
far  as  possible  from  any  goods  likely  to  be  contaminated  thereby.  At 
ordinary  ports  where  coal  is  shipped  for  fuel  mainly,  if  not  altogether, 
loading  can  be  performed  from  hulks  ranged  alongside  each  vessel,  while 
her  cargo  is  being  dealt  with  on  the  quay — a  method  which  saves  much 
time. 

Petroleum  is  brought  either  in  barrels  or  in  bulk.  For  the  latter 
system,  which  is  the  most  general,  tank  steamers  are  essential,  the  oil 
being  pumped  from  the  steamer  direct  through  mains  to  storage  tanks 
upon  the  quay.  On  account  of  the  extreme  danger  of  fire,  petroleum 
berths  must  be  thoroughly  isolated. 

Orain  is  discharged  either  by  small  portable  elevators  over  a  ship's 
side  into  lighters  and  barges,  or  by  means  of  stationary  elevators  direct 
into  warehouses,  which  for  this  purpose  are  built  close  to  the  edge  of 
the  quay. 

Timber  used  to  be  conveyed  almost  exclusively  in  sailing  ships,  and  the 
logs  were  drawn  out  through  apertures  in  their  bows  on  to  a  low  quay  or 
into  the  dock.  This  method  still  prevails,  but  a  considerable  quantity  of 
timber  nowadays,  particularly  deals,  comes  by  steamship,  and  has  to  be 
discharged  from  the  deck  or  the  hold  in  the  ordinary  way.  On  account 
of  the  great  amount  of  quay  space  monopolised  by  timber  cargoes,  it  is  in 
many  cases  found  a  convenient  arrangement  to  load  the  timber  on  to  bogies 
or  small  trucks  ashore,  or  on  to  large  pontoons,  afloat,  for  removal  to  a 
•convenient  storage  ground ;  or,  again,  logs  and  sleepers  may  be  formed  into 
rafts  to  be  floated  into  timber  ponds. 

Flour  is  one  of  the  most  delicate  kinds  of  merchandise.  It  is  very  sus- 
ceptible to  deterioration  and  readily  acquires  a  flavour  from  its  environment. 
Accordingly  it  should  not  be  discharged  in  the  immediate  neighbourhood  of 
substances  with  strong  odours,  such  as  fresh  fruit. 

Cattle  necessitate  special  wharves  with  isolation  zones  and  lairages.    The 


26  DOCK  ENGINEERING. 

regulations  of  the  Board  of  Agricultnre  require  the  animals  to  be  inspected 
before  any  part  of  the  cargo  is  discharged,  and  to  be  slaughtered  at  the  point 
of  disembarkation. 

Cost  of  Dock  Gonstmction. — A  point  of  very  marked,  and  even  vital^ 
interest  to  the  engineer  is  the  approximate  cost  of  a  projected  undertaking, 
and  any  guidance  in  forming  his  estimates,  or  in  affording  a  basis  for  com- 
parison with  works  of  a  similar  nature  elsewhere,  is  readily  welcomed ;  but 
information  sufficiently  reliable  for  the  purpose  is  rarely  available  in  dock 
engineering,  on  account  of  the  extreme  diversity  of  circumstances  under 
which  its  operations  are  carried  out.  The  cost  of  dock  construction  varies 
exceedingly,  depending,  as  it  does,  upon  such  mutable  conditions  as  the 
difficulties  appertaining  to  each  particular  site,  the  current  price  and  trans- 
port rate  of  material,  the  cost  of  labour,  combined  with  an  extremely  wide 
range  of  equipment.  Some  docks  have  gates;  others  do  not  need  them. 
Some  are  bordered  by  open  quays  ;  others  are  provided  with  sheds,  several 
storeys  in  height.  There  is,  in  fact,  absolutely  no  uniformity  of  treatment, 
and  anything  in  the  nature  of  comparison  is  practically  impossible.  The 
following  statistics  are  inserted  by  way  of  interest  merely.  They  are  of  no 
value  whatever  as  a  standard  of  cost  in  localities,  and  under  circumstances 
other  than  those  which  they  actually  represent: — 

Actual  Cost  of  Docks  and  their  Equipment  per  Acre  of 

Water  Surface. 


Victoria  Dook,  Dundee,  .  .  £10,600 
Barry  Docks,  South  Wales,  .  12,950 
West  India  Docks,  London,  .  15,000 
Prince  of  Wales  Dock,  Swansea,  18,000 
Victoria  Harbour,  Greenock,  .       21,730 


Alexandra  Dock,  Liverpool,  .  £23,300 
Albert  Dock,  Hull,  .  .  .  24,300 
Queen's  Dock,  Glasgow,  .  .  24,450 
Alexandra  Dock,  Hull,  .  .  28,900 
Canada  Branch  Dock,  Liverpool,    40,000 


Fresh  Water  Supply. — ^An  important  point  in  dock  design,  which  must 
not  be  overlooked,  is  the  provision^of  a  supply  of  clean  water  to  replenish 
the  waste  due  to  leakage  and  other  causes,  and  also  to  prevent  the  dock  from 
becoming  foul  and  insanitary.  The  writer's  experience  of  leakage  through 
gates  and  of  losses  through  lockage  under  normal  circumstances  at  the  port- 
of  Liverpool,  is  that  the  combined  depression  does  not  exceed  an  inch  per 
hour  over  the  whole  water  surface,  but  in  other  localities  it  may  be  more  or 
less  according  to  the  conditions  which  obtain.  On  the  sea  coast  and  in 
estuaries,  the  tide  may  be  relied  upon  to  effect  the  necessary  augmentation 
and  changes  in  an  efficient  manner,  but  in  rivers  highly  charged  with  sedi- 
ment, such  extraneous  means  of  supply  cannot  be  adopted  without  incurring 
considerable  expense  in  the  removal  of  sand  and  silt  from  the  interior  of  the 
dock.  In  this  case  it  is  preferable  to  seek  fresh  water  from  some  inland 
source  to  feed  the  dock,  the  water  in  which  must  always  be  maintained  at  a 
higher  level  than  that  of  the  river.  Where  this  plan  is  inapplicable  the 
difficulty  may  be  overcome  by  constructing  between  the  river  and  the  dock  a. 


SHIP  DESIGN. 


27 


long  canal,  the  leisurely  flow  through  which  for  a  considerable  distance  causes 
the  sediment  to  be  deposited  before  entering  the  dock*  The  material  has 
still  to  be  dredged  by  this  method,  but  the  operation  is  confined  to  a  limited 
space,  and  can  be  carried  on  without  interfering  with  shipping.  The  system 
has  been  successfully  tried  at  Calcutta  (fig.  11),  where  the  feed-canal  is 
3,300  yards  long,  and  it  is  found  that  the  whole  of  the  water-borne  mud 
brought  in  from  the  River  Hooghly  is  deposited  within  the  first  thousand 
yards. 

Ship  Design. — ^The  question  of  ship  design  is  so  much  akin  to  that  of 
dock  design  that  no  apology  is  needed  for  a  few  passing  remarks  upon  the 
former  subject.  Within  recent  years  very  great  strides  have  been  made  in 
naval  construction,  and  the  profile  of  ships  has  undergone  a  considerable 
change.  The  graceful  curved  outlines  amidships  and  the  deep  keel  of  a 
generation  ago  have  now  given  way  to  a  square  box-like  section,  with  a  flat 
bottom  and  with  sides  perfectly  upright,  or  having  an  inward  inclination 
towards  the  top.  These  new  features,  shown  on  fig.  3,  obviously  demand 
quays  with  absolutely  perpendicular  faces  and  entrances  with  level  sills. 


Fig.  3. — Amidahip  Sections  of  Typical  Vessels. 

In  a  paper  read  before  the  Institution  of  Naval  Architects  in  1899,  Mr, 
G«  B.  Hunter  "^  thus  describes  the  design  of  a  modem  vessel,  suitable  for 
carrying  large  cargoes  across  the  Atlantic  economically  and  safely  on  a 
moderate  draught.  '^  With  docks,  harbours,  and  markets  as  they  are  and 
will  be,  a  typical  American  freight  steamer  of  the  present  or  early  future 
may  be  designed  to  carry  not  less  than  12,000  tons  deadweight,  with  cubic 

*  Hunter  on  **Large  Atlantic  Cargo  Steamers,"  Min,  Proc.  Inst.  N.A.^  1899. 


28 


DOCK  ENGINEERING. 


;2s 


3 


iil 


-1     i 


i  I 

I 

i 


I 


f 


i 


3        O 

§ 

OQ 

s 

■Q, 

a 


I      3 

i      I 


capacity  for  20,000  tons  of  cargo  at 
40  feet  per  ton  and  1,000  tons  of  fuel. 
This  would  require  dimensions  approxi- 
mately as  follows  : — Length  between 
perpendiculars,  500  feet;  breadth,  60 
feet;  depth,  moulded,  36  feet  to  main 
deck;  44  feet  to  shelter  deck.  The 
draught  of  water  loaded  would  be 
about  27  feet  6  inches."  The  longi- 
tudinal section  of  such  a  vessel  is 
shown  in  fig.  4. 

These  remarks  were  made  with- 
out reference  to  the  advent  of  the 
"Oceanic,"  but  they  will  serve  as 
the  approximate  standard  of  an  aver- 
age purely  cargo  -  carrying  vessel. 
Vessels  built  for  passenger  traffic 
are,  of  course,  on  somewhat  diflferent 
lines.  Most  steamships  combine,  in 
varying  proportions,  the  functions  of 
passenger  transport  with  freight- 
carrying. 

The  largest  vessels  at  prasent 
under  construction  are  760  feet  long 
by  78  feet  beam  and  52  feet  deep. 
There  can  be  no  doubt  that  even 
such  large  dimensions  as  these  will 
be  exceeded  in  the  near  future.  The 
1,000-foot  vessel  is  almost  within  the 
range  of  practical  politics. 

Naturally,  these  conditions  do  not 
apply  to  all  ports,  but  they  serve  as 
an  indication  of  modem  tendencies. 
And  as  it  behoves  a  dock  engineer, 
above  all  things,  to  exercise  foresight 
and  to  be  prepared  for  growth  and 
expansion,  he  will  lay  his  plans  accord- 
ingly. 

The  following  table  gives  an  aver- 
age of  the  leading  dimensions  of 
the  twenty  largest  steamships  in 
existence  at  each  of  the  years  named, 
between  1881  and  1901,  and  an 
approximate  forecast  for  the  year 
1911 :— 


LIVERPOOL  AND  BIRKENHEAD  DOCKS. 


29 


1881. 

1891. 

1901. 

1911  (forecast). 

Length, 
Breadth,     . 
Depth. 

Loaded  draught. 
Tonnage,     . 

feet, 

»» 
f » 

460 

45 

30 

24 

4,900 

507 

64J 

31 

27 

6,980 

599 

65 

39 

32 

14,150 

1 

780 

82        j 
50 
39 

26,000 

We  now  proceed  to  consider  the  arrangements  adopted  under  conditions 
actually  prevailing  at  various  ports. 


Liverpool  and  Birkenhead  Docks. 

The  port  of  Liverpool  (including  Bootle  and  Birkenhead)  possesses  a 
system  of  docks  which  for  extent,  completeness,  and  efficiency  may  be 
described  as  unrivalled.  To  what  degree  these  results  are  due  to  its 
administration  by  one  authority  it  is  difficult  to  say,  but  there  can  be  no 
doubt  that  the  single  jurisdiction  of  the  Mersey  Docks  and  Harbour  Board, 
as  a  public  trust,  has  conferred  greater  benefit  upon  the  town  and  port  of 
Liverpool  than  the  conflicting  interests  of  a  number  of  separate  dividend- 
earning  companies  have  been  able  to  afford  to  the  Metropolis. 

Liverpool,  it  must  be  admitted,  possesses  great  natural  advantages. 
The  town  is  favourably  situated  close  to  the  seaboard  of  the  St.  George's 
Channel,  upon  a  wide  and  sheltered  estuary,  affording  it  a  water  frontage 
of  over  6  miles.'"'  It  stands  at  the  portal  of  the  great  manufacturing 
districts  of  Lancashire  and  the  Midlands,  and  it  is  in  close  proximity  to 
the  coal-fields  and  the  mineral  wealth  of  the  North  of  England  and  North 
Wales.  Furthermore,  it  is  linked  by  railways  and  canals  with  the  whole 
of  the  interior  of  Great  Britain.  It  is,  in  fact,  the  great  door  of  the  West, 
and  as  a  port  for  goods,  and,  in  a  lesser  degree,  for  passenger  traffic,  is 
the  principal  channel  of  communication  with  the  United  States  and  with 
Canada. 

The  tidal  area  of  the  estuary  of  the  Mersey  is  about  22,500  acres,  the 
greater  portion  of  which  is  filled  with  a  deposit  of  sand,  resulting  in  about 
four-fifths  of  the  area  being  above  low  water  level  of  spring  tides.  The 
deposit  is  only  prevented  from  permanent  accretion  and  consolidation  by 
the  erratic  action  of  the  upland  water,  which  ploughs  its  way  to  the  sea 
in  constantly  changing  channels.  This  roving  disposition  of  the  stream 
is  looked  upon  in  many  quarters  as  the  salvation  of  the  port,  for  were 
the  estuary  to  become  restricted  by  the  accumulation  of  sand  within  it, 
its  capacity  to  receive  tidal  water  would  be  correspondingly  diminished, 
and  the  result,  as  regards  the  maintenance  of  the  outer  channel  and 
approaches  of  the  port,  would  be  serious.  Hence  it  is  that  the  Biver 
Mersey,  though  by  no  means  a  model  river,  is  left  severely  alone. 

*  The  recent  inclusion  of  Garston  within  the  municipal  area  increases  the  amount 
of  river  frontage  to  10  miles. 


30  DOCK  ENGINEERING. 

The  deep  water  channel  extends  from  New  Brighton,  on  the  left  bank, 
at  which  place  the  river  is  5,600  feet  wide,  to  Dingle  Point,  on  the  right 
bank,  where  the  width  is  7,200  feet.  At  an  intermediate  point  opposite 
the  centre  of  Liverpool,  the  width  becomes  reduced  to  3,000  feet. 
Throughout  this  distance  there  is  ample  depth  of  water  for  vessels  at  all 
stages  of  the  tide,  the  depth  at  low  water  of  ordinary  spring  tides  being 
70  feet,  40  feet,  and  50  feet  at  the  above-mentioned  stations  respectively. 
On  the  Liverpool  side,  unfortunately,  this  deep  channel  is  bordered  by  a 
sand  bank,  known  as  the  Pluckington  Bank,  which  shoals  the  river  bed 
to  such  an  extent  as  to  seriously  diminish  the  value  and  utility  of  the 
central  docks,  and  interfere  with  the  use  of  the  passengers'  floating  landing- 
stage,  which  flanks  the  river  quays  at  this  part.  Various  remedial  ex- 
pedients have  been  tried  trom  time  to  time,  but  whatever  success  has  been 
obtained  has  never  been  otherwise  than  of  a  temporary  nature. 

The  navigable  depth  over  the  crest  of  the  bar  of  the  river  at  the  present 
date  is  27  feet  at  lowest  low  water  of  ordinary  spring  tides.  This  result 
has  only  been  obtained  by  a  vigorous  policy  of  continuous  dredging  with 
sand  pumps.  Bather  more  than  a  decade  ago  the  navigable  depth  was 
only  10  feet  at  lowest  low  water  of  spring  tides. 

The  range  of  tide  at  Liverpool  is  31^  feet  at  equinoctial  springs,  27|  feet 
At  ordinary  springs,  and  13  feet  at  ordinary  neaps.  The  local  datum  is  the 
Old  Dock  sill,  4  feet  8  inches  below  ordnance  datum.  The  Old  Dock  has 
long  since  disappeared,  but  the  level  of  its  sill  has  been  scrupulously 
preserved. 

The  following  table  presents  a  suocint  but  complete  statement  of  the 
extent  of  accommodation  afforded  by  the  Liverpool  and  Birkenhead  Docks 
at  the  present  time : — 


LIVERPOOL  DOCKS. 


31 


TABLE    III. 

The  Datum  is  iht  Level  qfthe  Old  Dock  Sill,  which  is  marked  on  a  Tide  Gauge  on  the 
River  Face  of  the  Centre  Pier  of  the  ShUranees  to  the  Canning  Half- Tide  Dock, 

Liverpool  Docks. 


liyerpool  Docki. 


FodticnaDd 

Width  of  EntrmDce 

or  Paasage. 


Hornby  Dock, 

Branch  Dock, 


Sonth 


f  > 


Alexandra  Dock, 


Ft.  la 

90  0 

.1      „      .     60  0 

>g/£a8t    90  0 

•  act  West  150  0 

Branch  Dock,  No.  3, 

2, 

1. 
Langton  Dock, 

Lock,  238  ft.  long,    .  ^  /  West  65  0 

„      119        „          .  oqI  East    65  0 

Branch  Dock,    .        .  j  West   .     60  0 

Brocklebank  Dock, .                 .    South  .    80.  0 


9* 


99 
>f 
If 


>» 
99 


S.  East     50   0 


Lock,  110  ft.  long, 


»> 


>f 


f9 
91 


North  Carriers'  Dock,     . 
South  ,, 

Canada  Lock,  600  ft.  long, 
(a)  „     Dock, . 

„     Branch  Dock,  No.  1, 
Hme^isBon  Dock, 

Branch  Dock,  No.  3, 

Sandon  Half-lHile  Dock, !' 
„       (Lock,  130  ft.  long), 
>»       (    f>      166      „      ), 
»»       (    >»     130      ,,      ), 

Wellington  Lock,    . 

Bramley-Moore  Dock, 

Nelson  Dock,  . 

Canal  Basin,  Lightbody  Street, 

Stanley  Lock, 
Collingwood  Lock, 


Salisbury  Look,    . 

Stanley  Dock, . 
Collingwood  Dock, . 

Salisbury  Dock, 


^ 


{ 


^  f  North  32  0 

.    . 20  0 

^  *  South  60  0 

40  0 

40  0 

100  0 

90  0 


f  I  Mid. 
^  ISoutl 
West 

North 
South 


South  .     90   0 


fNorth  80  0 
^Mid.  40  0 
I  South  100   0 


West  . 

ft      • 
North. 

South  . 

»f      • 

Passage 

West   . 

f»      • 

f»      • 

Inner  Sill 


90 
70 
60 
60 
60 
18 

18 
18 
18 


Outer 
West 


9» 


61 
60 


0 
0 
0 
0 
0 
0 

0 
0 
0 


0 
0 


S /North  60  0 
£\South  60   0 


SUl 

Coping  at 
Hollow 

below 

Qooini 

Dstnm. 

above 
Datum. 

rt  In. 

Pt  In. 

12    0 

27    0 

O.D.S. 

27    0 

20    6 

27   01 
27   0/ 

•  *  • 

12    0 

■  •  • 

•  «  * 

•  •  • 

9    0 

•  ■  • 
« •  • 

27   0 

12   0 

30   0 

12   0 

30   0 

12   0 

27   0 

7    9 

28   0 

6   0 

28   0 

6   0 

28    0 

7    9 

28   0 

6   0 

27   0 

6   0 

27    0 

14   0 

28   0 

14   0 

28   0 

•  •  • 

20   6 

•  •  • 

•  •  • 

•  •  • 

31    0 

•  ■  • 

•  •  • 

•  •  • 

■  •  • 

20   6 

■  •  • 

•  •  • 

36   0 

16   0 

36   0 

20   6 

36   0 

20   6 

31    0 

6   6 

31    0 

6   0 

26   01 
26   0/ 

6   0 

6   6 

26   0 

O.D.8. 

26   0 

Above 

2   6 

29   0 

2   6 

26   0 

•  ■  • 

26   0 

2    6 

• « • 

Below 

6   0 

•  ■  • 

6   6 

29   0 

6   9 

26   0 

6  11 

26   0\ 
26   0/ 

611 

Water  Axea. 


Acres.  Yards. 

16  4454 
0  3354 

17  4281 

7  3420 

9  2667 

9  673 

18  689 
0  1719 
0  860 
2  4549 

11  1010 


2  3423 

1  4616 

1  2018 

24  913 

7  2313 
12  4273 

8  780 
7  692 

9  1126 
14  466 


10  100 

7  4120 

9  3106 

7  4786 

0  920 


3   3343 
5     244 

3   2146 


Lineal 
Qoayage. 


HUes.  Yards. 
0    1461 
0      308 

0  1068 


0 
0 


846 
1024 
0  983 
0  1322 
160 
81 

671 
1002 


0 
0 
0 
0 


0  641 

0  616 

0  469 

0  1696 

0  823 


0 
0 
0 
0 


711 
990 
910 
083 


0    1081 


0 
0 


0 
0 


867 
820 

936 

803 
110 


0 
0 


662 
663 


0      406 


Note  (a). — The  water  in  the  Canada  and  Huskisson  Docks  can  be  raised  to  give  any 
additional  depth  of  water  required  in  the  Canada  Dock  and  its  South  Passage,  so  that 
that  passage  may  have  the  same  effective  depth  as  the  river  entrances  to  Sandon  Half- 
Tide  Dock— vis.,  20  feet  6  inches  below  Old  Dock  SilL 


32 


DOCK   ENGINEERING. 


TABLE  III.  {Continued), — Liv£kpool  Docks. 


1 

Coping  a1 
Hollow 

t 

Position  and 

I 

Sill 

I                 TT  *        -.       1 

Liverpool  Docks. 

Width  of  Entrance 
or  Passage. 

below 
Datum. 

Quoins 

above 

Datum. 

Water  Area. 

Lineal 
Quayage. 

Ft. 

In. 

Ft.  In. 

Ft.  In. 

Acres.  Yards. 

Miles.  Yards. 

Clarence  Gravmg  Dock  Basin,  -j 

North  .    45 
South  .     44 

0 
6 

4    9 
4    6 

26    0\ 
26    6/ 

1 

1056 

0      291 

„       Half -Tide  Dock, 

West   .     50 

0 

5    0 

26    8 

4 

1794 

0      635 

%  y                    J-/01#Jk.f                       •                      •                      a 

„       .     47 

0 

3    2 

26    0 

6 

273 

0      914 

Trafalgar  Lock, 

North  .     45 

0 

6    7 

23  10 

0 

2937 

0      256 

„         Dock, 

»»           ^^ 

3 

6    7 

21  11 

6 

459 

0      724 

Victoria  Dock, 

South  .     50 

0 

6    6 

26    0 

5 

4374 

0      701 

West  Waterloo  Dock,      . 

M       .     60 

0 

8    0 

22    1 

3 

2146 

0      533 

East          „            ,f         .        . 

n       .     60 

0 

8    0 

22    1 

2 

3375 

0      506 

Prince's  Ha^-Tide  Dock, 

^  [  North  65 

0 

8    0 

31    0] 

,,        Lock,  110  ft.  long,     . 

I-  Mid.     32 
^  (South  65 

0 

8    0 

31    0 

4 

3250 

0      434 

»»          ..... 

0 

8    0 

31    0 

, ,             LfOGSLf              ... 

North  .     45 

0 

5  11 

27    5 

11 

1490 

0    1194 

*George's  Dock  Passage, 

South  .     40 

3 

4    6 
Above 

24    5 

0 

1033 

0      152 

Manchester  Dock,   . 

West   .     32  10 

0    3 

23    3 

1 

595 

0      339 

Below 

,,            Lock,  86  ft.  long, 

,,       .33 

8 

3   9 

24    3 

0 

315 

0        57 

*Canning  Dock, 

,,      .     45 

0 

H    1 

26    2 

4 

376 

0      585 

♦      „        Half-Tide  Dock,       . 

§  /  North  45 
^  t  South  45 

0 
0 

6    3 
6   3 

28    3\ 
28    3j 

2 

2688 

0      429 

♦Albert  Dock,                  .        j 

North  .     45 
East     .     45 

0 
0 

6    4 
6    0 

26    01 
26    0/ 

7 

3542 

0      885 

*Salthouse  Dock,     . 

North  .     45 

0 

6    0 

26    0 

6 

2019 

0      784 

r 

,,      .     50 

0 

5    8 

26    0] 

*Wapping  Basin,     . 

South  .     50 

0 

6    0 

26    0 

1 

3151 

0      454 

West   .     40 

0 

5    8 

25    0) 

Duke's  Dock,  .        .        .        -[ 

40 
Middle     40 

0 
0 

4    2 

4    7 

25  10  1 
22    9/ 

2 

1336 

0    1138 

*Wapping  Dock,     . 
*King  8  Dock, 

South  .     50 

0 

6    0 

26    0 

5 

499 

0      815 

East     .     50 

0 

6    0 

26    0 

7 

3896 

0      875 

Queen's  Half-Tide  Dock, 

•  ■  •                 •  •  • 

•  ■ « 

•  •  ■ 

3 

3542 

0      445 

,,           J^OCK,               ... 

South  .  100 

0 

17    6 

29    5 

10 

3124 

0    1114 

„       Branch  Dock,  No.  1,  . 

• » •                 •  •  « 

•  •  • 

•  ■  • 

4 

4384 

0      654 

♦Coburg  Dock, 

West   .     70 

0 

5    7 

30   6 

7 

3157 

0      939 

♦Brunswick  Dock,  . 

North  .  100 

0 

17    6 

29   0 

12 

3533 

0    1070 

Half-Tide  Dock,  . 

West   .     45 

0 

6   0 

26    6 

1 

1399 

0      250 

•Union  Dock, .        .        .        -{ 

North  .     60 
South  .     60 

0 
0 

6    6 
12    0 

27    01 
31    0/ 

1 

1941 

0      361 

Toxteth  Dock, 

„      .     60 

0 

12    0 

31    0 

11 

1075 

0    1134 

,,       Lock,  177  ft.  long,     . 

West   .     50 

0 

8    0 

31    0 

0 

1013 

0      118 

Harrington  Dock,    . 

South  .     60 

0 

12    0 

31    0 

9 

256 

0    1023 

,,          Lock,  131  ft.  long, 

West   .     22 

0 

5    9 

31    0 

0 

320 

•  •  • 

Herculaneum  Dock, 

1  j  North  80 
^  t  South  60 

0 
0 

12    0 
12    0 

31    01 
31    0/ 

7 

2581 

0      596 

, ,            Branch  Dock,    . 

«  •  •                 •  •  • 

■ « • 

■  •  • 

2 

853 

0      577 

Total  Water  Area  and  Lineal  Quayage  of  the  . 

Liverpool  Docks, 

389 

3751 

24    1542 

*  The  water  in  the  group  of  Docks  from  Canning  to  Brunswick  Docks,  inclusive,  is 
impounded  over  low  neap  tides,  and  any  loss  made  good  by  pumping  from  the  river. 
By  these  means  the  effective  depth  of  these  docks  is  made  not  less  than  that  of  the 
lowest  Sills  over  which  they  can  be  approached — viz.,  12  feet  below  datum. 


T 
I 


PLAr 


32 


Live 


Clarence  Or 


»» 


Trafalgar 


»» 


Victoria  X-^o 
West  W8i*t>© 

East  »* 

Prince's  Ha 


*George's   XI 
Manchestior 


*) 


•Canning  I^ 


91 


♦Albert  Do< 
♦Salthouse 

Wapping  J 


Duke's  Doo. 

•Wapping  3 
♦King's  DcK 
Queen's  Ha^ 

•Coburg  Do 
•Bninswick 

♦Union  Doo 

Toxteth  Do* 

„       Lo< 

Harrington 

Herculaneu: 


»» 


Total  Wate 


♦Thews 
impounded  c 
By  these  met 
lowest  Sills  c 


J 


N 


N 


>«-■>«     • ' 


RTRITIfTJWBAT^ 


-  Mersey  Dock  Estate 

.AN  OF  Birkenhead  Docks 


PQCKS. 


wtmm 


BIRKENHEAD  DOCKS. 


33 


TABLE  III.  {CknUintted), — ^Liverpool  Basins. 


lirerpool  Basins. 


Canada  Basm, 

George's  Ferry  Basin, 
Chester  Basin, 
Anderton  Basin, 
South  Ferry  Basin, 


Width  of 
Bntranoe. 


Ft.    In. 
390    O-f 

67  0 

36  0 

46  0 

60  0 


Height  of 

Pieis  above 

Datum. 


Ft.  In. 
N30  0 
S  32 

23 

22 

25 

30 


0 
8 
2 
7 
6 


) 


Water  Area. 


Acres.  ITards. 

9   2806 

0  1344 

0  2668 

0  1422 

0  2927 


Lineal 
Quayage. 


Miles.  Yards. 
0      846 


0 
0 
0 
0 


160 
288 
175 
205 


Total  Water  Area  and  Lineal  Quayage  of  the  Liverpool  Basins, 

Docks, 


i> 


f> 


If 


»» 


11  1386 
389  3751 


0  1674 
24  1542 


Total, 


401  297 


25  1456 


BlRKBNHIAD  DoCKS. 


Coping  at 

Hollow 

Quoins 

aboye 

Datum. 

Birkenhead  Docks. 

Position  and 

Width  of  Entrance 

or  Passage. 

8U1 

below 

Datum. 

1 
Water  Area. 

Lineal 
Quayage. 

Ft. 

In. 

Ft.  In. 

Ft.  In. 

Acres.  Yards. 

Miles.  Yards. 

West  Float,     .        .        .        . 

East     . 

100 

0 

7    6 

26    6 

52     319 

2 

210 

Basins  near  Canada  Works — 

- 

West  Basin, 

North. 

50 

0 

•  SB 

•  •  • 

1    2554 

0 

543 

East      „              .        .        . 

ft             * 

50 

0 

•   «   ■ 

•  •  • 

1        84 

0 

390 

East  Float,      .        .        .        . 

•  •   B 

■  •  • 

•   ■   ■ 

•  •  • 

59   3786 

1 

1673 

Com  Warehouse  Dock,   . 

South  . 

30 

0 

O.D.S. 

26    0 

1      453 

0 

555 

Railway  Companies'  Basin,     . 
Wallasey  Dock, 

■  •  • 
•  •  • 

•  •  • 

•  »  • 

•  •  • 

•  •  • 

Below 
9   0 

•  •  • 
■  «  • 

0     606 
12   3813 

0 
0 

113 
1261 

Passage  to  Wallasey  Dock,  . 

West   . 

49 

2 

26    0 

0    1333 

0 

234 

Inner  Northern  E2ntrances, 

North  . 

100 

0 

9    0 

26    0 

B    •   • 

0 

242 

Lock,  198  ft.  long. 

Middle 

30 

0 

•  •  • 

26    0 

0     667 

0 

264 

Inner  SiU, 

■  •  • 

*   ■    B 

9    0 

B   •   ■ 

•    ■    B 

•  •  • 

Outer    „           .        .        . 

•    B    « 

■    •    • 

12    0 

•  •   • 

BBS 

■  •  • 

Lock,  274  ft.  long. 

South  . 

50 

0 

•  •  • 

26    0 

0    1522 

0 

300 

Inner  Sill, 

a  •  » 

■    B    B 

9   0 

•  •  • 

■  «  ■ 

■  ■  ■ 

Outer    „           .        .         . 

•  ■  • 

B   ■    • 

12    0 

•  •  • 

■    »    B 

i  ■  ■ 

Alfred  Dock,  .... 

m  9  m 

■   •    • 

•  •  ■ 

■  «  • 

8   3276 

0 

511 

Outer  Northern  Entrances— 

Lock,  480  ft.  long. 

North  . 

100 

0 

18    6 

31  a 

0   3888 

0 

352 

,,       ISro         ,,                  .           . 

Middle 

30 

0 

12   0 

26    0 

0     667 

0 

377 

,,      398       ,,               . 

South  . 

49 

8 

12   0 

26    0 

0    2222 

0 

391 

Eeerton  Dock, 
Morpeth  Dock, 

West  . 

70 

0 

7    4 

25    0 

4     469 

0 

704 

»f      • 

70 

0 

5   5 

25    0 

11    2404 

0 

1299 

„        Lock,  398  ft.  long,    . 

East     . 

85 

0 

12   0 

26    0 

0   3777 

0 

441 

Railway  Company's  Basin, 
Morpeth  Branch  Dock,    . 

South  . 

25 

0 

O.D.S. 

26    0 

0   3144 

0 

319 

West   . 

85 

0 

•  •    B 

26    0 

4     248 

0 

637 

Total  Water  Area  and  Lineal  Qi 

layage  of  the  Birkenhead  Docks, 

160    1347 

9 

256 

NoTK. — The  water  in  the  Birkenhead  Docks  is  impounded  over  low  neap  tides,  and 
any  loss  made  good  by  pumping- from  the  river.  By  these  means  the  effective  depth  of 
these  docks  is  made  not  less  than  that  of  the  lowest  Sills  over  which  they  can  be 
approached — viz.,  18)  feet  below  datum. 

3 


34 


DOCK  ENGINEERING. 


TABLE  IIL  {Continued).— BiKKENBXAD  Basin. 


Birkenhead  Basin. 


North  Basin, 


Width  of 
Bn  trance. 


Ft.    In. 
500     0 


Height  of 

Piers  above 

Datum. 


Pt.  In. 
31    0 


Total  Water  Area  and  Lineal  Quayage  of  the  Birkenhead  Basin, 

Docks, 


>> 


if 


9i 


>> 


Total, 


Water  Area. 


Acres.  Yards. 
4    2843 


4    2843 
160    1347 


164   4190 


Lineal 
Quayage. 


Miles.  Yards. 
0      669 


0      669 
9      256 


9      925 


Barry  Docks. 

The  special  feature  of  the  Barry  Docks  is  the  accommodation  provided, 
almost  exclusively,  for  the  coal  and  timber  trades,  and  it  is  on  this  account, 
principally,  that  these  docks  have  been  selected  for  illustration.  The  town, 
which  is  of  quite  modem  growth,  having  developed  from  a  population  of 
100  in  1884  to  one  of  30,000  in  1902,  is  situated  at  the  southernmost  point 
of  the  Welsh  coast-line,  forming  an  outlet  from  the  coalfields  in  that  locality, 
in  close  contiguity  to  CardiflT,  Newport,  and  Swansea. 

The  docks  are  the  property  of  the  Barry  Railway  Company.  The  entrance 
lies  under  the  convenient  shelter  afforded  by  the  high  land  of  Barry  Island, 
which  protects  it  from  westerly  and  south-westerly  winds.  The  only  points 
of  exposure — viz.,  to  the  southward  with  a  sesrrange  of  14  miles  and  to 
the  south-east  with  a  sea-range  of  16  miles — are  covered  by  breakwaters. 
There  is  also  good  anchorage,  extending  from  Barry  Island  to  Sully  Island,  a 
distance  of  3  miles. 

The  range  of  tide  at  Barry  is  36  feet  at  ordinary  springs  and  20  feet  at 
ordinary  neaps. 

The  shipment  of  coal  takes  place  at  the  north  side  of  both  No.  1  and 
No.  2  docks,  and  on  both  sides  of  the  mole  in  the  former  dock.  It  is  stated 
that  a  steamer  has  entered  the  dock,  loaded  1,900  tons  of  coaJ,  and  left  again 
on  the  same  tide. 

Table  iv.  gives  all  the  particulars  necessary  for  following  the  arrange- 
ments exhibited  in  the  plan. 

The  timber  trade  is  accommodated  at  the  east  end  of  No.  2  dock,  where 
there  are  two  timber  ponds  of  6  and  35  acres  respectively.  Railways  are 
provided  alongside,  so  that  timber  can  be  loaded  direct  from  the  ponds  into 
the  railway  waggons. 


BARKY   DOCKS. 


36 


DOCK  ENGINEERING. 


I 

li 


a 


"|||8Si 


■iiiS%    l|a 


Docks  at  Buenos  Atbes. 

l^is  system  of  docks  exem- 
plifies (see  fig.  8)  the  case  in 
which  an  enclosed  basin  has 
been  rendered  necessary  by  other 
than  strictly  tidal  reasons.  The 
average  range  of  tide  does  not 
exceed  2  feet  7  J  inches,  the 
highest  recorded  for  four  years 
being  3  feet  in  the  month  of 
December,  and  the  lowest  2  feet 
3^  inches  in  the  month  of  June. 
The  flood  waters  of  the  "Santa 
Rosa,"  however,  cause  the  water 
to  rise  to  a  height  of  8  feet 
above  their  normal  height,  and 
the  river  has  been  known  to  fall 
below  zero  to  the  same  extent 
on  one  occasion  at  least.  The 
principal  reasons,  therefore, 
which  operated  in  favour  of 
entrance  locks  are  thus  set  forth 
by  Mr.  Dobson* : — 

"  In  the  first  place,  the  gates 
were  provided,  not  so  much  with 
the  object  of  maintaining  the 
water  in  the  docks  at  a  nearly 
constant  level,  as  for  the  pur- 
pose of  preventing  it  from  falling 
below  the  level  of  zero  or  low 
water,  thereby  enabling  vessels 
always  to  remain  afloat  in  the 
docks,  and,  at  the  same  time, 
to  allow  all  ships  of  light 
draught  to  leave  them,  if  neces- 
sary, when  the  level  of  the  river 
was  below  zero.  In  the  second 
place,  the  southernmost  pair  of 
gates,  which  point  outwards, 
are  constructed  with  the  object 
of  preventing  the  water  of  the 
Biachuelo,   when    in    a    turbid 

*  Dobson  on  ' '  Buenoa  Ayrw 
Harbour  Works,"  ilin.  Proc.  Intt. 
C.B.,  vol.  oiXKviii. 


DOCKS   AT  BUENOS   AYBES, 


38 


DOCK   ENGINEERING. 


state,  from  entering  the  docks,  and  also  to  enable  the  docks  to  be  more 
thoroughly  sluiced,  if  required.  By  closing  these  gates  at  low  water  the 
rising  tide  would  be  compelled  to  enter  at  the  north  end,  and  then  by  closing 
the  north  lock-gates  at  high  water  the  falling  tide  would  have  to  run  out 
through  the  south  lock,  thus  entirely  changing  the  water  in  the  docks 
and  preventing  the  possibility  of  its  becoming  stagnant  and  consequently 
dangerous  to  the  health  of  the  city. 

"  Since  the  works  have  been  completed  and  the  north  basin  opened  it 
has  been  found,  from  experiments  made  with  floats,  that  the  current  in  the 
docks  is  even  better  than  was  anticipated,  and  that,  with  a  good  average 
tide  and  a  strong  north  or  south  wind,  there  is  as  much  as  850  feet  per  hour, 
so  that  the  closing  of  the  gates  in  order  to  sluice  will  be  only  occasionally 
needed." 

The  following  is  a  statement  of  the  dimensions  of  the  various  docks : — 


TABLE  lYa.     '. 

Dimensions 

OP  THE  Madero  Docks,  Buenos  Atres. 

Length. 

Breadth. 

Area. 

Quayage. 

Depth 
below  25ero. 

Dock  No.  1,   .     . 
Dock  No.  2,   .     . 
Dock  No.  3,  .     . 
Dock  No.  4,   .     . 

Tarda. 
623 
623 
756 
689 

Tarda. 
175 
175 
175 
176 

Acres. 
23 
23 
27 
26 

Tarda. 
1,553 
1,553 
1,815 
1,679 

Feet. 

23f 

23$ 

23$ 

23f 

The  south  basin  has  an  area  of  35  acres  and  a  depth  of  water  of  21^  feet 
below  zero.  The  south  lock  is  443  feet  long  and  65^  feet  wide  at  coping 
level,  with  sills  21 J  feet  below  zero.  The  north  lock  is  508^  feet  long, 
82  feet  wide,  with  sills  22  feet  below  zero.  The  north  basin  has  an  area  of 
41  acres  and  a  depth  of  21^  feet.  The  total  water  area  of  the  two  basins 
and  four  docks  is  174  acres,  and  the  total  quayage  9,276  yards. 


TiLBURT  Docks,  London. 

These  docks  (see  fig.  9)  are  planned  on  the  tridentine  system.  They  are 
approached  by  means  of  a  tidal  basin,  having  an  area  of  17^  acres,  with  an 
entrance  from  the  River  Thames,  364  feet  in  width,  flanked  on  each  side  by 
splayed  timber  jetties.  Landing  places  for  passengers  are  provided  in  the 
tidal  basin,  so  that  they  may  disembark  before  a  vessel  enters  the  dock. 
There  is  also  a  coaling  jetty.  The  lock  between  the  tidal  basin  and  the  inner 
docks  is  946  feet  long  over  all,  with  two  chambers  555  feet  and  145  feet 
long  respectively,  both  80  feet  wide,  and  with  a  depth  of  44  feet  below 
Trinity  high  water  mark  on  the  outer  and  intenaediate  sills.  The  main  and 
branch  docks  have  a  water  area  of  52^  acres,  with  quayage  accommodation 
for  31  vessels,  averaging  400  feet  in  length.  Each  berth  in  the  branch  docks 
is  provided  with  a  shed,  301  feet  long  and  120  feet  wide,  and  has  direct 


TILBURY   DOCKS,   LONDON. 


oommunication  wiih  the  LondoQ,  Tilbury,  and  Southend  Railway.  There  are 
two  graving  docks  placed  parallel  to  the  lock  and  of  the  same  extreme 
length.     They  can  be  entered  either  from  the  dock  or  from  the  basin,  and 


Fig.  g.— TilbuT}-  Docks,  Loudon. 


can,  if  necessary,  be  used  as  auxiliary  locks.  The  depths  of  the  basin  and 
lock  are  so  arranged  that  a  ship  drawing  33  feet  of  water  can,  even  at  low 
water  of  spring  tides,  proceed  direct  to  her  berth  in  the  inner  docks. 


40  DOCK   ENGINEERING. 

Glasgow  Docks. 

The  dock  system  at  Glasgow  is  an  exemplification,  also  on  the  tridentine 
principle,  of  the  method  adopted  in  localities  where  gates  are  not  rendered 
necessary  by  any  considerations.  The  '*  docks  "  are,  in  fact,  strictly  speaking, 
tidal  basins. 

The  docks  are  in  two  groups.  On  the  right  hand  bank,  or  north  side  of 
the  Clyde,  the  Queen's  Dock  has  a  water  area  of  33^  acres,  with  3,334  lineal 
yards  of  quay  frontage,  and  a  depth  of  20  feet  at  low  water.  The  entrance 
is  100  feet  wide,  and  it  is  spanned  by  a  single  leaf  swing  bridge.  The  dock 
is  subdivided  into  an  outer  or  canting  basin,  1,000  feet  long  by  695  feet 
wide,  and  two  inner  basins,  the  one  1,891  feet  long  by  270  feet  wide,  and 
the  other  1,668  feet  long  by  230  feet  wide,  separated  by  a  pier  195  feet 
wide. 

On  the  south  side  of  the  Clyde  the  Prince's  Dock  has  a  total  water  area 
of  35  acres,  with  3,737  lineal  yards  of  quay  frontage.  The  canting  basin  is 
1,150  feet  long,  with  a  width  of  from  505  to  676  feet  and  there  are  three 
branch  basins,  each  200  feet  wide,  and  1,168  feet,  1,461  feet,  and  1,528  feet 
long  respectively.  The  north  basin  has  a  depth  of  20  feet,  the  centre  and 
south  basins,  25  feet,  and  the  outer  basin,  20  to  28  feet  below  low  water. 
The  entrance  is  bell-mouthed  in  shape,  with  a  minimum  width  of  156  feet, 
and  is  not  crossed  by  a  bridge.* 

The  Kidderpur  Docks,  Calcutta. 

The  tidal  and  fluvial  conditions  prevailing  in  the  River  Hooghly  are 
irregular  and  conflicting.  The  port  of  Calcutta  is  situated  some  90  miles 
from  the  sea,  but  the  tides,  when  not  checked  by  freshets  during  rains,  exert 
their  influence  beyond  that  distance.  "  From  March  to  July,  when  strong 
southerly  winds  prevail,  the  current  at  spring  tides  during  the  early  portion 
of  the  floods  attains  a  velocity  of  5  to  6  miles  an  hour.  During  the 
rainy  season,  whea  the  discharge  of  fresh  water  by  the  branches  from  the 
Ganges  is  considerable,  the  down-stream  current  during  the  ebb  tide  runs  at 
about  the  same  rate ;  and  during  heavy  freshets  in  the  river,  the  upward 
current  at  the  flood  tide  is  hardly  perceptible,  although  the  level  of  the  water 
is  raised  for  many  miles  above  Calcutta.  At  neap  tides  there  is  no  up-stream 
current  at  all  if  there  are  freshets ;  the  water  is  headed  up  and  the  level 
rises,  but  the  current  is  always  down  stream.  During  the  rains  the  spring 
tides  rise  to  a  mean  height  of  20^  feet,  and  fall  to  8^  feet  above  (zero) 
datum,  while  neap  tides  rise  to  15  feet  and  fall  to  about  10  feet  above 
datum.  In  the  dry  season,  which  lasts  from  November  to  June,  the  spring 
tides  rise  to  an  average  height  of  15  feet  and  faU  to  2|  feet;  while  neap  tides 
rise  on  an  average  to  12  feet  and  fall  to  5  feet  above  datum.     The  tidal 

*  Alston  on  '*The  River  Clyde  and  the  Harbour  of  Glasgow/'  International 
Engineering  Congress,  Glasgow,  1901. 


42  DOCK  BNOINBERING. 

range  between  low  water  of  spring  tides  in  the  dry  season,  and  the  average 
high  w&ter  in  the  rainy  season  is  about  18  feet,  but  during  heavy  floods  has 
been  as  much  as  22^  feet."* 

Such  conflicting  conditiona 
call  for  a  special  arrangement 
of  dock  entrances  to  permit  of 
vessels  entering  or  leaving  on 
the  flood  tide,  or  when  tiie 
current  in  the  river  is  continu- 
ously down  stream,  and  the 
arrangement  adopted  is  shown 
in  fig.  11.  It  consists  of  a  lock, 
400  feet  long  by  60  feet  wide, 
and  a  single  entrance,  80  feet 
J  wide,  pointing  in  opposite  direc- 

,  tions,  the  reasons  for  and   ad- 

vantages   of    which    are   fully 
discussed  in  Chapter  vi. 

The  half-tide  basin  is  600 
feet  by  680  feet,  and  No.  1  dock 
is  2,600  feet  long  by  600  feet 
wide,  with  a  water  area  of  34^ 


The  Alexandra  Dock,  Hull. 


I 


This  dock  i 
example  of  the  machicolated 
system.  It  is  situated  near  the 
mouth  of  t^e  Biver  Humber, 
bos  a  water  area  of  46^  acres,  a 
quayage  of  2  mites,  covering 
160  acres ;  and  is  provided  with 
a  lock,  550  feet  long  by  85  feet 
wide,  and  two  graving  docks. 
The  entrance  to  the  lock  is 
splayed. 

"The  navigable  channel  of 
the  Humber  approaches  close  to 
the  northern  shore  in  front  of 
Hull ;  but  at  the  Alexandra 
Dock  the  northern  edge  of  the 
deep  channel  was  960  feet  from 
the  outer  lock  sill.    The  channel 


■Bruce  on  "  The  Eidderpur  Doclu,  Calcutta,"  if  in.  Proc  Intl.,  C.S,,-rt>L  <x 


HAMBUBG  DOCKS.  43 

there  is  30  to  40  feet  deep  at  low  'water  spring  tides,  having  an  almost 
vertical  face  in  places  on  its  nortiiero  side,  the  depth  increasing  suddenly 
from  5  to  30  feet,  owing  to  the  scour  of  the  tidal  current  against  this  side, 
the  channel  having  been  eroded  by  it  out  of  the  hard  clay  of  the  '  Hebbles,' 
a  shoal  extending  ^  mile  above  and  2  milefl  below  the  Alexandra  Dock. 
The  Hebbles  shoal  is  moatly  composed  of  very  hard  boulder  clay,  with  large 


Fig.  12.— Alexandra  Dock,  HuIL 


boulders  reaching  up  to  ^  ton  in  weight,  and  smaller  stones  strewn  over 
the  surface,  and  beds  of  peat  were  also  found."*  The  origmal  surface  of 
the  foreshore  and  river  bed  and  the  deepening  effected  by  the  dredging 
operations  previous  to  the  opening  of  the  dock  for  traffic  are  shown  on  the 
plan  in  fig.  12. 

Hah  BUBO  Docks. 
The  town  of  Hambu^  is  situated  62  miles  above  the  outlet  of  the  river 
Elbe.  As  in  the  case  of  Glasgow,  the  range  of  tide,  which  averages  6  feet, 
ia  not  sufficient  to  render  gates  an  absolute  necessity,  and  they  have  been 
dispensed  with,  although  the  maximum  difference  between  high  and  low 
water  reaches  19J  feet.  One  reason  which  operated  in  favour  of  this 
decision  was  that  locks  would  have  seriously  hindered  the  considerable 
traffic  between  sea^:oing  ships  and  the  river  boats  which  ply  between 
*  Hnrlzig  on  "The  Alexandra  Dock,  Hall,"  Mn.  Proe.  In*t.  O.E.,  voL  zcii. 


44  DOCK  ENGINEERING. 

Hamburg  and  Bohemia.    Again,  the  Elbe  leaves  little  deposit  near  ita  tidal 
limit,  30  that  no  need  for  gates  arises  from  this  cause. 


The  basiiiB  B,  C,  and  D  are  now  practically  completed.  Basin  B  is  surrounded 
by  sloping  sides  with  suppoTting  pilework  at  the  foot  and  with  maeoDry  jetties  at 
intervals.     Basins  C  and  D  ore  lined  throughout  with  quay  wbIIb. 


MILLWALL  DOCK. 


45 


Vaeious  Ports. 

As  additional  examples  of  the  variatioiis  in  dock  design,  a  number  of 
diagrams  are  here  given,  showing  arrangements  adopted  at  the  ports  of 
London,  Sunderland,  Swansea,  Havre,  and  Marseilles. 


Appended  is  also  a  table  giving  statistics  of  representative  docks  in  the 
British  Isles  and  throughout  the  world  (pp.  54,  55). 


46 


DOCK  ENGINEERING. 


EAST  AKD  WEST  INDIA  DOCKS. 


47 


48 


DOCK  ENGINEERING. 


SURREY   COMMEBCtAL  DOCKS. 


50 


DOCK  ENGINEEBING. 


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CHAPTER  III. 
CONSTRUCTIVE   AFFIiIANCES. 

Ct^assification— Positive,  Negative,  and  Auxiliary  Appliakces— Piling  Apparatus 
— Hand,  Steam,  Electric,  and  Hydraulic  Machines— Ram  and  Fall — 
Quiescence  —  Limit  of  Driving  —  Supporting  Power  op  Piles  —  Concrete 
MixsRR— Mbssbnt,  Taylor,  Carey-Latham,  Sutcuffe,  and  Gravity  Machines 
"—Concrete  Moulds — Block-setting  Appliances— Excavators— French  and 
German  Machines — Ruston,  Simpson- Porter,  and  Whitaker  Steam  Navvies — 
Hydraulic  Navvy— Drilling  Appliances— Hand  and  Machine  Drills- 
Blasting  Agents — Haulage  and  Traction— Dredgers  and  Hoppers— Suction, 
Ladder,  Dipper,  and  Grab  Dredgers — Buckets— Shoots — Tumblers — Power 
..^osT — Dams  of  Earth,  Timber,  Stone,  Concrete,  and  Iron — Cofferdams — 
Strength  and  Stability — Pcmps  and  Pumping— Cranes-Overhead  Travel- 
lers—Skips— Lewis  Bars  and  Clips— List  of  Constructive  Plant  at  Eeyham 
Dock  Works. 

The  speediest  and,  at  the  same  time,  the  most  economical  methods  of  carry- 
ing out  projected  works  are  points  of  the  utmost  importance  to  the  engineer. 
Time  and  capital  are  alike  too  valuable  to  be  utilised  to  any  but  their  fullest 
extent.  Hence  some  consideration  of  the  various  types  of  appliances  used 
in  dock  construction,  especially  in  regard  to  their  capabilities,  efficiency,  and 
cost,  will  not  be  without  both  interest  and  advantage. 

Classification. — A  chapter  which  has  to  deal  with  a  number  of  discon- 
nected items  must  perforce  exhibit  some  break  of  continuity,  and  in  order  to 
minimise  this  effect  and,  at  the  same  time,  to  link  together  the  different 
sections,  the  following  classification  is  proposed : — Positive  appliances  will 
include  all  those  employed  in  definite  constructive  operations — that  is  to  say, 
piling  machines,  concrete  mixers,  setting  machines,  and  the  like.  Negative 
alliances  will  be  understood  to  mean  those  engaged  in  the  removal  of 
existing  obstacles  and  superfluous  material,  such  as  excavators  and  dredgers, 
boring  apparatus  and  blasting  agents.  A  third  class,  designated  Attxiliary 
appliances,  will  include  all  those  used  in  conjunction  with  each  of  the  fore- 
going, indifferently  and  for  either  object,  as  dams,  pumps,  waggons,  skips, 
and  locomotives.  The  classification  is,  of  course,  purely  artificial,  but  it  will 
serve  a  useful  purpose  if  it  admits  of  the  systematic  treatment  of  a  hetero- 
geneous subject. 

POSITIVE   APPLIANCES. 

Pile  Drivers  and  Driving. — The  process  of  driving  a  pile  generally  con- 
sists in  causing  a  heavy  weight,  called  a  ram  or  monkei/y  to  fall  from  some 
height,  in  a  series  of  blows,  upon  the  head  of  the  pile.     For  this  purpose  a 


STEAM   PILING   MACHINES.  57 

piling  machine  is  constructed,  with  two  long  vertical  guides  or  runners,  up 
and  down  the  face  of  which  the  monkey  slides,  being  kept  in  position  by  a 
lug  or  projection  fitting  into  the  groove  between  the  guides. 

The  simplest  kind  of  pile  driver  is  the  ringing  machine^  in  which  the 
work  is  performed  entirely  by  hand.  The  monkey  rarely  weighs  more  than 
one-third  of  a  ton,  and  it  is  lifted  by  a  rope  which,  after  passing  over  the 
pulley  at  the  head  of  the  frame,  is  connected  with  a  number  of  short  lengths, 
so  as  to  afford  a  hold  to  a  corresponding  number  of  men,  in  the  proportion  of 
about  40  lbs.  weight  per  man.  The  lift  does  not  exceed  4  feet.  At  a  given 
signal  the  monkey  is  allowed  to  fall,  the  men  taking  advantage  of  each 
rebound  to  raise  the  monkey.  Driving  is  usually  carried  on  in  spells  of 
three  or  four  minutes'  duration,  with  intervals  of  rest,  and  in  this  way 
men  are  said  to  be  capable  of  delivering  from  4,000  to  5,000  blows  per 
day. 

The  explosion  of  a  cartridge  has  been  utilised  to  augment  the  effect  of  the 
blow  upon  the  pile  and  to  increase  the  recoil  of  the  ram.  The  cartridges  are 
inserted  in  a  small  hollow  in  the  pile-head,  and,  after  percussion,  are  replaced 
by  fresh  ones  during  the  ascent  of  the  ram.*  The  cartridges  are  either  of 
gunpowder  or  of  dynamite;  in  the  latter  case  the  head  of  the  pile  is  protected 
by  an  iron  plate.  Explosive  drivers  can  readily  make  from  30  to  40  blows 
of  from  5  to  10  feet  per  minute. 

In  another  pile  driver,  called  a  crctb  engine^  the  rope,  instead  of  being 
directly  held  by  hand,  passes  round  the  drum  of  a  crab  or  windlass,  by  means 
of  which  the  monkey  can  be  given  a  fall  of  10  or  12  feet. 

Such  merely  manual  methods,  however,  are  primitive ;  they  are  really 
only  suitable  for  driving  small  piles  in  insignificant  numbers,  and  are 
entirely  superseded  in  works  of  importance  by  steam  piling  machines. 

Steam  Piling  Machines  are  of  various  design.  In  the  earlier  examples 
steam  power  simply  replaced  manual  effort  in  lifting  the  weight.  A  hook 
or  trigger  at  the  end  of  the  lifting  chain  engaged  in  a  staple  in  the  head  of 
the  pile,  and  was  released  by  pulling  a  counter-weighted  lever.  The  chain 
had  to  be  lowered  after  each  blow. 

The  intermittent  action  involved  in  this  arrangement  has  been  obviated 
by  the  device  of  an  endless  lifting  chain,  characteristic  of  the  machines  of 
Messrs.  Sissons  &  White  (fig.  23).  The  chain  passes  up  the  groove  between 
the  leaders  and  down  over  a  spur  wheel  in  the  gearing,  by  means  of  which 
it  is  kept  running  continuously.  The  ram,  which  weighs  from  15  to 
25  cwts.,  is  raised  by  a  tongue  passing  through  its  centre  and  capable  of 
engaging  in  the  moving  chain,  through  the  medium  of  a  rack  and  pinion 
movement  actuated  by  a  lever.  The  man  in  charge  of  this  apparatus  pulls 
the  cord  attached  to  the  end  of  the  lever,  causing  the  tongue  to  shoot  out  at 
the  back  of  the  monkey  into  the  nearest  open  link.  The  tongue  is  with- 
drawn at  any  desired  level  by  the  other  end  of  the  lever  coming  in  contact 
with  a  staple  fixed  to  the  face  of  one  of  the  guides.     The  holes  for  these 

*  Sir  F.  Bramwell,  Presidential  Address,  1885,  Min,  Proc,  Inst,,  CE.,  vol.  Ixxx. 


58 


DOCK   ENGINEERING. 


staples  are  set  at  short  intervals,  so  that  the  amount  of  fall  can  be  regulated 
fairly  uniformly. 

The  services  of  three  men  are  required  for  each  machine — one  to  work 
the  winch,  another  to  actuate  the  lever,  and  a  third  to  watch  the  pile,  mark 
its  progress,  and  shift  the  staple.  Steam  should  be  partially  cut  off  while 
the  ram  is  falling,  in  order  to  reduce  the  speed  of  the  chain  for  reattachment. 

The  pile  is  pitched  by  an 
auxiliary  chain  passing  over 
a  separate  pulley  at  the 
frame  head.  It  is  kept  in 
position  by  a  toggle  bolt 
passing  right  through  the  pile 
near  the  top,  and  also  through 
a  wood  block  in  the  groove 
behind  it,  to  the  back  of  the 
leaders,  where  it  is  secured 
by  an  iron  bearing  plate, 
nut,  and  screw.  After  the 
necessary  preliminaries  the 
monkey,  which  has  been 
temporarily  raised  out  of  the 
way,  is  lowered  upon  the 
pile  and  is  ready  for  action. 
The  rate  of  working  is  about 
six  blows  per  minute  under 
steam  pressure  of  55  to  60 
lbs.  per  square  inch.  Piles 
can  be  driven  vertically,  or 
at  any  required  inclination, 
"~  by  adjusting  a  screw  at  the 
foot  of  the  ladder  at  the  rear 
of  the  platform. 

When  the  pile  has  been 
driven  below  the  level  of  the 
foot  of  the  leaders,  the  pro- 
cess is  continued,  either  by 
the  interposition  of  a  punch 
or  dolly  (a  short  log  of  the 
same  scantling  as  the  pile)  between  the  pile  and  the  ram,  or  by  the  use  of 
telescopic  leaders  (fig.  23).  The  first  method  involves  considerable  loss  of 
driving  power,  as  the  dolly  absorbs  fully  one-half  of  the  kinetic  energy  of 
the  blow. 

The  frame  of  a  Whiiaker  steam-hammer  pile  driver  is  not  dissimilar  from 
that  just  described.  The  principal  difference  of  the  contrivance  lies  in  the 
application  of  the  power.     Driving  is  done  by  means  of  a  piston  and  cylinder, 


Fig.  23. — Pile-driving  Machine  fitted  with 
Teleecopio  Leaders. 


-  Cylinder-cover  removed . 


© 


Pipt.miagiBr^UiigtHMWilh 
i  ntvrt  tAi9  distance. 


Fi(!.  24. — Section  of  Whitaker'B  Steam-hammer  Pile  Driver. 


6o  DOCK   ENGINEERING. 

but  the  action  is  the  reverse  of  ordinary  usage.  The  piston  (fig.  24)  is  kept 
stationary  and  in  continuous  contact  with  the  pile  head,  while  the  blow  is 
administered  by  the  lower  end  of  the  heavy  cast-iron  cylinder,  moving  up 
and  down  under  steam  pressure.  The  movement  of  the  cylinder  is  guided 
by  rollers  behind  the  main  leaders,  and  the  arrangement  involves  a  sliding 
steam  feed  pipe  (which  is  a  special  feature  of  the  system),  with  a  flexible 
rubber  connection  to  the  supply  pipe  from  boiler.  At  the  head  of  the 
cylinder  is  a  two-way  cock,  regulated  by  a  double-armed  lever,  which,  when 
pulled  down  on  one  side,  exhausts  the  cylinder,  and  on  the  other  admits 
fresh  steam.  There  is  also  a  double-action  machine,  in  which  steam  pressure 
is  applied  alternately  to  each  side  of  the  piston,  thus  increasing  the  force  of 
the  blow.  The  stroke  is  about  3  feet,  and  blows  can  follow  one  another  with 
great  rapidity.  From  observations  of  a  Whitaker  machine  in  single  action 
with  80  to  90  lbs.  steam  pressure,  the  author  finds  that  35  blows  per  minute 
can  be  delivered  at  full  stroke,  or  60  blows  per  minute  with  a  stroke  of 
12  inches.  In  double  action  45  blows  per  minute  were  delivered  with  a 
stroke  of  2  feet.     The  weight  of  the  cylinder  was  1  ton. 

A  similar  machine,  known  as  the  Cram  Pile  Driver,  manufactured  in 
America,  has  a  hammer  fastened  to  the  lower  end  of  the  cylinder,  and  is 
supplied  with  steam  through  a  hollow  piston-rod.  The  original  Nasmyth 
hammer  is  also  used,  in  which  the  hammer  is  attached  to  the  piston,  the 
cylinder  remaining  stationary  and  being  confined  between  the  upper  ends  of 
two  vertical  and  parallel  X  or  channel  beams,  the  lower  ends  of  which  enclose 
a  hollow,  conical  bonnet  casting,  fitting  over  the  head  of  the  pile.  This  cast- 
ing is  open  at  the  top,  and  through  it  the  blow  is  administered.  When  steam 
is  admitted  to  the  cylinder,  the  hammer  is  lifted  about  30  to  40  inches  and 
then  allowed  to  fall,  generally  by  the  automatic  opening  of  an  escape  valve. 

Piling  machines  of  the  steam-hammer  type  consume  from  1  to  2  tons  of 
coal  per  day,  working  with  a  boiler  pressure  of  50  to  75  lbs.  per  square  inch> 
and  can  deliver  blows  at  the  rate  of  about  60  per  minute.  They  need  three 
men  in  attendance. 

The  disadvantage  attending  them  is  the  liability  of  the  pilehead  to 
crushing  or  brooming y  which,  combined  with  the  escape  of  moisture  from  the 
cylinder,  reduces  it,  if  in  the  least  degree  soft  or  sappy,  to  a  saponaceous 
condition.  The  effect  of  this  is  to  materially  diminish  the  force  of  the  blow, 
as  is  evidenced  by  the  following  particulars  of  the  driving  of  a  green  Norway 
pile  by  a  Nasmyth  steam  hammer  *  : — 

The  3rd  foot  of  penetration  required 5  blows. 

15 

20 

73 

153 

684 

*Whittemore  on  "The  Efficiency  of  Pile  Driving,"  Min.  Proc.  Imt,  C.E.,  vol. 
Ixxvi.,  p.  399. 


ff          -xvu 

„      5th 

„    10th 

„    12th 

„    14th 

STEAM   PILING   MACHINES.  6l 

Head  adzed  off. 

The  15th  foot  of  penetration  required 213  blows. 

,1    18th      ,,  ,,  ,,  .....  825     ,f 

Head  sawn  off. 

The  19th  foot  of  penetration  required 213  blows. 

„    22nd      „  „  „  378    „ 

The  total  number  of  blows  was  5,228.  A  similar  pile,  which  was  not 
adzed  or  sawn,  required  9,923  blows  to  descend  to  the  same  depth.  The  ram 
weighed  2,800  lbs.  and  fell  3  feet  sixty-five  times  per  minute.  The  friction 
caused  by  the  working  of  the  fibres  on  each  other,  under  the  blows  of  the 
hammer,  was  sufficient  to  ignite  and  bum  the  interior  of  the  head  of  the  pile 
from  side  to  side. 

A  third  type  of  pile  driver  is  the  Electric  Pile  Driver,  in  which  advantage 
is  taken  of  the  temporary  magnetisation  of  wrought  iron  to  make  an  electro- 
magnet of  that  material  attach  itself  by  contact  to  the  cast-iron  monkey. 
The  two  parts  are  then  lifted  by  the  winch.  On  switching  off  the  current 
the  monkey  falls,  and  the  magnet  is  caused  to  follow  it  down  ready  for  lifting 
again.  The  monkey  is  of  the  ordinary  kind,  with  an  upper  planed  surface. 
The  magnet  is  connected  by  wires  to  the  motor  on  the  winch.  The  illustra- 
tion (fig.  25)  is  of  one  manufactured  by  the  New  Southgate  Engineering 
Co.,  Ltd. 

Hydraviic  Method, — While  piles  readily  respond  to  the  motive  force  of 
the  ram  in  ordinary  ground,  and  even  in  stiff  clay,  their  progress  through 
sand  and  gravel  is  not  so  satisfactory,  and  the  ordinary  methods  of  driving 
have  generally  to  be  abandoned,  either  wholly  or  partially,  in  favour  of  the 
water  jet.  The  principle  of  this  method  consists  in  transforming  the  sand 
immediately  beneath  the  pile  into  quicksand,  by  saturating  it  with  water 
under  pressure,  a  condition  which  enables  the  pile  to  sink  by  its  own  weight 
or  with  very  little  assistance.  The  water  is  conducted  to  the  foot  of  the  pile 
by  means  of  wrought  iron  gas  piping  having  a  short  returned  end,  provided 
with  a  nozzle  or  pierced  with  holes,  which  passes  underneath  the  pile.  This 
last  is  not  usually  pointed,  but  left  with  a  butt  end,  which  favours  perpen- 
dicularity in  driving.  The  descent  of  the  pile  may  be  expedited  by  a  static 
weight,  or  by  the  direct  downward  pull  of  a  rope  passing  through  sheaves  to 
a  winch.  When  the  pile  has  been  sunk  to  a  sufficient  depth,  the  nozzle  of 
the  water  pipe  is  turned  through  a  quadrant  to  clear  the  pile  and  brought 
up  to  the  surface  again  by  the  same  means  which  accomplished  its  descent. 
The  sand  is  then  allowed  to  consolidate  round  the  pile,  which  it  does  rapidly 
and  satisfactorily.  No  difficulty  is  experienced  from  boulders  or  large 
stones  for,  if  met  with,  they  can  be  displaced  or  lowered  by  a  preliminary 
action  of  the  jet  below  them. 

This  hydraulic  method  of  sinking  piles  is  often  used  in  conjunction  with 
the  falling  ram  in  earth  of  a  compact  nature.  The  pile  in  Uiis  case  is 
naturally  furnished  with  a  pointed  end,  preferably  conical. 

Timber  piles  are  universally  in  evidence,  but  iron  and  concrete  piles  also 


DOCK   ENGINEERING. 


Fig.  2fi.— Eleclrio  Pile  Driver. 


PILING. 


63 


have  their  uses.  The  drawback  to  timber  piles  is  that,  although  extremely 
durable  while  completely  protected  from  atmospheric  influence,  they  are  very 
susceptible  to  decay  in  air  and,  more  particularly,  "betwixt  ydnd  and  water, ^' 
and  to  perish  from  the  attacks  of  insects. 

Iron  pOes  with  pointed  ends,  and  concrete  piles  on  the  Hennebique 
system  (figs.  26  and  27),  (vide  also  Chap,  vii.)  should  only  be  driven  through 
the  interposition  of  a  wooden  dolly  (fig.  28). 

For  untrustworthy  strata  of  indefinite  depth,  piles,  whether  of  wood  or 
iron,  are  occasionally  furnished  with  a  broad  screw  end  to  the  extent  of  a 
single  turn  or  slightly  more.  This  considerably  increases  the  bearing 
surface.  Such  piles  have  to  be  lowered  by  rotation,  either  by  means  of 
manual,  animal,  or  mechanical  power 

ARRANOENENT  FOf? 
SHEET     PILE  DRIVING  PILE 


I! 


I" 


Fig.  27.— Bearing  Pile. 


I 


Otabag 


Fig.  26. — Hennebique  Pile. 


Fig.  28. — Hennebique  Pile. 


'  Ram  Qfnd  FaU, — Piles  may  theoretically  be  driven  at  the  same  rate  with 
a  light  ram  and  a  long  fall  as  with  a  heavy  ram  and  short  fall,  but  the  second 
method  is  preferable  in  practice.  A  long  fall  means  greater  oscillation  in  the 
ram  and  a  consequent  jar  in  the  delivery  of  the  blow,  which  tends  to  rupture 
the  pile.  From  extensive  experience  in  the  driving  of  wooden  piles,  the 
author  finds  a  monkey  of  1  ton  weight,  with  a  fall  of  8  or  10  feet,  a  very 
suitable  combination.  For  concrete  piles  on  the  Hennebique  system,  even 
less  fall  is  desirable,  and  a  monkey  of  2^  tons,  with  4^  feet  drop,  has 
answered  very  satisfactorily  at  Southampton. 

Quiescence. — If  the  driving  of  a  pile  be  interrupted  for  a  short  time,  it  is 
found  that  the  resistance  offered  to  driving  is  materially  increased.  Piles 
which  have  been  left  partially  driven  overnight  have  exhibited  a  resistance 
nearly  three  times  as  great  on  the  resumption  of  work  in  the  morning.    This 


64  DOCK   ENGINEERING. 

effect  is  no  doubt  due  to  the  consolidation  round  the  pile  of  the  earth  which 
had  been  maintained  in  a  state  of  disintegration  and  vibration  during  a 
sequence  of  rapid  blows. 

Limit  of  Driving. — ^The  limit  of  adequate  driving  and  the  maximum 
supporting  power  of  piles  are  equally  moot  points  among  engineers.  To  a 
certain  extent  they  are  interdependent. 

The  practice  at  Liverpool  has  been  to  regard  a  total  depression,  not 
exceeding  ^  inch  in  10  blows  of  a  20-cwt.  ram  falling  10  feet,  as  evidence 
of  sufficient  driving,  or,  in  other  words,  an  expenditure  of  mechanical  energy 
at  the  rate  of  896,000  ft. -lbs.  per  inch.  At  New  York  river  wall  the  piles 
were  specified  not  to  penetrate  more  than  y*^  foot  with  the  last  blow  of  a 
3,000-lb.  monkey  falling  through  8  feet,  involving  energy  to  the  extent  of 
20,000  ft.-lbs.  per  inch.  According  to  Rankine,  some  of  the  best  authorities 
consider  the  test  of  a  sufficiently  driven  pile  to  be  a  depression  of  not  more 
than  i  inch  by  30  blows  of  an  800-lb.  ram  falling  5  feet,  or  mechanical 
energy  represented  by  600,000  ft.-lbs.  per  inch.  These  standards  are 
evidence  of  the  great  diversity  of  opinion  there  is  on  the  subject. 

Supporting  Power. — Various  theoretical  and  empirical  formulse  have  been 
suggested  for  determining  the  relationship  between  the  blow  required  to 
drive  a  pile  to  a  given  depth  and  the  greatest  load  it  will  sustain  without 
sinking  further. 

Rankine  *  puts  forward  the  following  equation,  supposing  the  pile  to  be 
supported  by  uniformly  distributed  friction  against  its  sides  : — 

in  which 

w  =  Weight  of  ram  in  lbs. 

E  =  Modulus  of  elasticity. 

8  =  Sectional  area  of  pile  in  square  inches. 

H  :=  Fall  of  ram  in  feet. 

L  =  Length  of  pile  in  feet. 

p  =  Maximum  load  in  lbs. 

D  =  Depression  of  the  pile  in  feet  by  the  last  blow. 

A  factor  of  safety  of  not  less  than  3  should  be  used;  preferably  one  of 
5  to  10. 

A  very  well-known,  but  merely  approximate,  rule  devised  by  Major 
Saunders  of  the  U.S.  Engineers  is 

•^^^D" ^^^ 

/  being  the  safe  load  in  lbs.  and  the  other  notation  as  before. 
The  formula  recommended  by  Trautwine  is 

51-5  w  »/H 

^=-f2DTr <'> 

with  a  factor  of  safety  of  from  2  to  12  according  to  circumstances. 

*  Manual  of  Civil  Enginuringj  p.  604. 


SUPPORTING   POWER. 


65 


The  majority  of  the  formulsB  enunciated  for  dealing  with  the  question  of 
the  supporting  power  of  piles  are  of  a  very  complicated  nature,  and  comprise 
elements  which  are  but  remotely  connected  with  it.  Mr.  C.  H.  Has  well  has 
the  following  pertinent  remarks  upon  the  subject  *  : — 

"  The  resistance  opposed  by  a  pile  to  the  blow  of  a  ram  is  the  measure  of 
its  value  to  sustain  stress  whatever  may  be  its  diameter,  weight,  length,  or 
modulus  of  elasticity.  The  diameter  and  length  of  a  pile  do  not  affect  the 
question,  their  effect  is  to  limit  penetration.  The  weight  of  the  pile  is 
worthy  of  consideration  only  as  affecting  the  weight  of  the  ram  employed. 
The  relative  elasticity  is  of  little  moment,  for  when  a  pile  approaches  the 
limit  of  its  penetration  its  head  is  dressed  off,  if  broomed,  and  if  split  or 
liable  to  be  so,  it  is  confined  by  a  ring.  In  fact,  the  weight  of  the  ram  being 
proportioned  to  the  duty  required  of  it,  the  diameter,  length,  and  elasticity 
of  the  pile  are  inconsiderable,  where  so  great  factors  of  safety  ranging,  in 
various  formulae,  from  tS^  to  ^,  are  employed." 

Mr.  HasweU's  own  formula  is 


/= 


32w^H 


(4) 


in  which  the  constant  (C)  has  values  ranging  between  3  and  6,  according  to 
the  nature  and  condition  of  the  soil,  the  character  of  the  piles,  and  the 
excellence  of  their  driving. 

The  following  table  exhibits  a  comparative  view  of  the  results  obtained 
by  the  foregoing  expressions,  assuming  a  depression  of,  say,  ^  inch  from  the 
final  blow  of  the  ram  in  each  case.  Sectional  area  of  pile  =  100  square 
inches : — 


Safe  Load  in  Lbs. 

Bankine. 

Saunders. 

Trautwine. 

Haswell. 

1 ,000  Ibe.  f alUng  20  feet,    . 
2,000  lbs.  falling  25  feet,    . 
3,500  Ibe.  falling  9  feet,      . 

66,425 

129,249 

93,312 

60,000 

150,000 

94,500 

/   46,609  \ 
\     7,768/ 
/ 100,296  \ 
1    16,716/ 
/ 124,974 1 
t   20,829/ 

f   47,680  \ 
I    23,840  J" 
f  106,666 
L   53,333 
r  112,0001 
[  56.000/ 

Rankine's  empirical  rule  for  the  safe  load  on  a  pile,  driven  till  it  reaches 
firm  ground,  is  1,000  lbs.  per  square  inch  of  area  of  head.  The  author  con- 
siders 10  cwts.  per  square  inch  well  within  the  limit  of  practical  safety^ 

When  the  arrangement  of  the  strata  is  such  that  it  is  impossible  to  i*each 
firm  ground  with  a  pile,  the  conditions  of  equilibrium  are  different.  The 
pile  will  then  only  be  able  to  sustain  a  superimposed  weight  by  reason  of  the 
friction  of  the  ground  against  its  sides.  Under  such  circumstances  Rankine 
recommends  200  lbs.  per  square  inch  as  the  maximum  load.     Mr.  Hurtzig 

•  Haswell  on  "  Formulas  for  Pile  Driving,"  Min.  Proc,  Inst.  C.E.,  vol.  cxv. 

5 


66  DOCK   ENGINEERING. 

gives  the  following  equation,*  from  experience  gained  in  drawing  a  number 
of  piles  against  the  frictional  resistance  of  clay. 

the  weight  of  the  ram  (W)  being  taken  in  tons.  P  is  the  extreme  resistance 
of  the  pile,  also  in  tons.  H  and  D,  as  before,  are  the  height  of  fall  and  the 
depression  under  the  last  blow  respectively,  both  in  feet. 

Concrete  Mixers. — Concrete  can  be  very  efficiently  mixed  by  hand,  but 
the  process  is  slow  and  only  suitable  in  dealing  with  small  quantities.  When 
the  requirements  are  large,  as  in  block  and  mass  work,  it  will  be  much  more 
economical  and  expeditious  to  employ  mechanical  agency. 

So  many  varieties  of  concrete  mixers,  each  with  its  own  particular 
merits,  are  on  the  market,  that  it  is  an  utter  impossibility  within  the  limits 
of  a  moderate  chapter  to  review  them  all ;  and  although  it  is  a  somewhat 
invidious  task  to  select  one  or  two  examples  for  illustration,  such  a  step  is 
inevitable,  and  must  not  be  understood  to  convey  any  depreciation  of  those 
machines  which  afe  un&voidkbly  excluded. 

The  principal  features  of  an  efficient  concrete  mixer  are  a  thorough  and 
intimate  incorporation  of  the  ingredients  and  a  rapid  and  regular  discharge 
of  material. 

Concrete  mixers  are  of  two  kinds — intermittent  and  continuous.  In  the 
.former  cla^s,  charges  are  mixed  separately ;  in  the  latter,  they  follow  one 
another  in  unbroken  sequence.  More  perfect  incorporation  of  the  in- 
gredients is  the  particular  claim  of  the  intermittent  mixers,  .while  the 
continuous  mixers  afford  greater  regularity  of  supply..  In  both  instances, 
that  machine  must  be  reckoned  best  in  which  the  churning  action  is  most 
thorough. 

Intermittent  Mixers — Messent  Mixer. — ^The  best  known  of  the  earlier 
types  of  mixer  is  that  due  to  the  late  Mr.  P.  J.  Messent,  of  Tynemouth,  and 
the  following  description  of  it  is  extracted  from  the  circular  of  the  makers, 
Messrs.  Stothert  <fe  Pitt,  of  Bath : — 

"It  consists  of  a  closed  box  or  chamber,  A  (fig.  29),  revolving  on  an  axle, 
and  of  such  a  form  as,  when  half-filled  with  the  materials,  to  cause  them  to 
be  turned  over  sideways,  as  well  as  endways,  four  times  in  each  revolution 
of  the  chamber,  so  that  in  from  six  to  twelve  revolutions  (the  number 
necessary  being  varied  according  to  the  weight  and  nature  of  the  materials) 
a  more  perfect  mixture  is  effected  than  could  possibly  be  produced  by  hand, 
or  (except  in  a  much  longer  time)  by  any  other  machine. 

"  For  filling  concrete  into  a  trench,  or  the  hearting  of  a  pier,  the  machine 
is  supported  over  the  opening,  on  two  balks  of  timber ;  a  waggon  containing 
the  gravel  (and  cement  in  bags)  follows  on  the  same  line.  The  hopper, 
shown  in   the   figure,  suspended   from   a  davit,  is   made  to  contain  the 

♦Hurtzig  on  "The  Friction  of  Timber  Piles  in  Clay,"  Min.  Proc,  Inst,,  C.E., 
vol.  Ixiv. 


INTERMITTENT  M1XEK8.  67 

proper  measure  of  gravel  for  a  charge,  whilst  the  bags  contain  the  proper 
i^uantity  of  cement,  and  a  cistern  near  at  hand  (filled  by  a  flexible  hose) 
the  proper  quantity  of  water.  Two  men  standing  on  the  waggon  (the 
sides  of  which  are  generally  raised  so  that  it  contains  about  twice  the 
quantil^  of  an  ordinary  earth  waggon)  are  able  to  All  the  hopper  in  the 
time  employed  by  four  men  to  give  the  mixer  the  requisite  number  of 
turns.     For  counting  these  a  tell-tale  is  provided,  which  indicates  when  the 


Fig.  29. — Messenl  Concrete  Mixer. 

proper  number  of  turns  is  completed ;  the  mixer  is  then  stopped  with  the 
door  downwards.  The  door  fastening  is  released  and  the  charge  of  concrete 
falls  into  its  place,  the  discharge  being  instantaneous.  The  opening  of  the 
mixer  is  then  turned  upwards,  as  in  the  figure,  the  door  is  opened  (through 
the  dotted  arc  as  shown),  the  hopper,  suspended  from  the  davit,  is  brought 
over  the  opening  and  at  once  discharged  into  it,  and  the  water  is  run  in  from 
the  cistern  at  the  same  time.     The  door,  which  closes  water-tight,  is  then 


68 


DOCK   ENGINEERING. 


shut  and  the  mixing  resumed,  the  hopper  being  meanwhile  refilled  for  the 
next  charge. 

"  With  the  hand  mixer,  above  described,  a  gang  of  six  men,  with  a  boy 
for  attending  to  the  water  cistern,  can  make  from  30  to  40  cubic  yards  of 
concrete  blocks,  and  a  larger  quantity  of  concrete  in  bulk  in  a  trench  in  a 
day,  of  better  quality  and  at  a  cheaper  rate  than  can  be  done  by  shovel 
mixing,  and  when  the  mixers  are  turned  by  steam,  twice  the  above 
quantities  are  made."  The  usual  standard  sizes  have  capacities  of  |  and  1 
cubic  yard. 


Fig.  30. — Taylor  Concrete  Mixer. 

The  Messent  mixer  has  been  used  at  Tynemouth  breakwater ;  Aberdeen 
harbour  works;  the  Surrey  Commercial  Docks,  London;  dock  works  at 
Kurrachee,  and  elsewhere. 


CONTINUOUS  MIXERS.  69 

Tayhr^a  Mixer. — A  later  adaptation  of  the  same  type  of  mixer  has  the 
revolving  chamber  in  the  form  of  a  double  cone  (fig.  30). 

"  In  mixing  concrete  the  materials  are  filled  into  the  measuring  hopper 
in  the  usual  proportions ;  the  sliding  door  is  then  withdrawn  and  they  are 
admitted  into  the  revolving  mixing  cones,  to  mix  dry  first ;  water  is  then 
supplied  through  the  hollow  supporting  shaft. 

"A  few  revolutions,  say  15,  serve  to  thoroughly  mix  the  materials,  and 
the  delivery  doors,  which  are  closed  perfectly  tight  while  the  mixing  is 
proceeding,  being  simultaneously  opened  by  the  lever  and  clutch,  the 
contents  are  dropped  through  a  shoot  into  suitable  trucks  or  skips,  or 
directly  on  to  the  work  in  hand. 

"A  one-yard  mixer  can  produce,  in  ordinary  working,  24  cube  yards 
of  the  very  best  concrete  in  one  hour  at  a  cost  for  labour  of  about  4d.  per 
yard.  If  fitted  with  a  steam  hoist  and  special  service  trucks  an  output 
of  30  yards  per  hour  of  thoroughly  well  mixed  concrete  can  be  guaranteed, 
the  cost  being  greatly  reduced.  The  machines  are  made  either  stationary 
or  portable,  and  of  capacities  varying  from  ^  to  I^  cube  yards"  {Mcmufnc- 
iurera^  Circular), 

The  machines  can  also  be  worked  by  gas  engine  or  electric  motor.  They 
are  supplied  by  Messrs.  Henry  Balfour  k  Co.,  Ltd.,  of  Leven,  Fife. 

The  Taylor  mixer  has  been  employed  at  the  Keyham  Dockyard 
extension  works,  at  Barry  Dock,  at  Methil  Dock  extension,  at  Seaham 
Harbour,  &c. 

Continaoas  Mixers — Carey-Lathcmi  Mixer, — In  this  machine  the  sand 
and  ballast  are  supplied  systematically,  by  means  of  ascending  buckets,  to 
the  mixing  cylinder  (figs.  31  and  32),  where  they  are  met  by  a  supply  of 
cement^  the  quantity  of  which  is  regulated  by  an  archimedean  screw. 
The  process  can  thus  be  carried  on  uninterruptedly  for  any  length  of 
time. 

Incorporation  is  "  carried  out  in  a  revolving  cylinder  in  which  are  fitted 
inclined  blades  or  vanes,  which  lift  and  tumble  the  materials  some  50  times 
before  delivery,  first  in  the  dry  and  afterwards  in  the  wet  state.  During 
this  process  the  blades  or  vanes,  which  are  carried  from  a  central  shaft, 
revolve  with  the  cylinder  in  the  same  direction,  but  at  a  slightly  less  speed, 
whereby  they  are  constantly  changing  their  position,  acting  as  scrapers, 
and  thus  prevent  the  setting  of  the  cement  on  the  blades  and  inner  surface 
of  the  mixing  cylinder.  The  water  required  for  the  concrete  passes  through 
the  central  shaft,  and  is  sprayed  out  on  the  materials  as  they  are  tumbled 
about  in  the  mixer." 

The  machines  are  manufactured  by  Messrs.  John  H.  Wilson  k  Co., 
Ltd.,  of  Liverpool,  in  sizes  capable  of  discharging  from  10  to  30  cubic 
yards  per  hour. 

The  Carey-Latham  mixer  has  been  used  in  connection  with  dock  and 
harbour  works  at  Peterhead,  Newhaven,  Sydney,  Hong  Kong,  Yokohama, 
Odessa,  Bilbao,  New  York,  «fec. 


DOCK   ENGINEERING. 


CONTINUOUS  MIXERS. 


71 


Stitcliffe  Mixer, — The  principle  of  this  machine  (fig,  33)  is  embodied  in 
the  method  adopted  for  measuring  the  quantities  of  material.  The  cement 
is  discharged  into  the  uppermost  hopper  (fig.  34),  the  floor  of  which  is  a 
cylinder  with  three  grooves  of  equal  area  and  capacity  in  its  surface.  The 
cylinder  is  turned  by  a  hand  wheel,  and  an  angular  displacement  of  60* 
causes  the  contents  of  one  of  the  grooves  to  be  emptied  into  the  lower 
hopper  where  it  meets  with  the  proper  supply  of  gravel.  The  gravel  is 
discharged  from  hand  barrows,  and  the  cement  grooves  are  so  regulated 
that  one  grooveful  corresponds  to  a  barrow  load.  When  the  lower  hopper 
is  full,  the  contents  are  allowed  to  fall  through  three  trap  doors,  opened 
consecutively,  on  to  a  moving  band  which  conveys  the  dry  materials  to  a 


a 


Cement 


fimeyin^iBttnd 


Hopper 


Gjvyeland 
SandSapa 


L 


Fig.  33.— Sutpliffe  Concrete  Mixer — Elevation. 

series  of  trays  at  the  top  of  a  shoot,  water  -  being  added  from  a  supply  pipe 
at  the  level  of  the  topmost  tray.  Each  side  of  the  machine  is  symmetrical, 
and,  by  means  of  an  oscillating  vane  for  the  deflection  of  the  cement  supply, 
the  machine  becomes  double  acting,  so  that  there  is  absolutely  no  break 
in  the  discharge,  which  takes  place  from  each  side  of  the  lower  hopper 
alternately. 

This  machine  has  been  very  extensively  used  at  the  Liverpool  Docks 
for  a  number  of  years.  It  has  proved  capable  of  turning  out  over  300  cubic 
yards  of  concrete  in  a  working  day  of  ten  hours,  but  the  normal  rate  of 
supply  lies  between  200  and  300  cubic  yards  per  day. 

Gravity  Mixer. — An  American  machine  in  which  there  are  no  moving 
parts,  the  whole  process  of  mixing  being  performed  by  numerous  rows  of 
pins,  which  intercept  and  sift  the  material  during  its  descent  through  a 
shoot,  is  effectively  illustrated  in  fig.  35.  The  ingredients  are  first  deposited 
in  measured  quantities  upon  the  platform,  and  then  shovelled  by  hand  to 


DOCK   ESGINEERTNG. 


DiscJuaye  to  Mixer 
Fig.  34— Sutcliffe  Concrete  Mixer -Section  of  Hoppers. 


Fig.  35, — The  Gravity  Concrete  Mixer. 


CONCRETE   MOULDS. 


73 


the  shoot,  at  the  top  of  which  the  water  supply  is  added.  The  concrete, 
however,  does  not  actually  become  wetted  until  it  reaches  the  fifth  row  of 
pins,  the  process  prior  to  this  being  that  of  dry  mixing.  A  gate,  or  valve, 
at  the  foot  of  the  shoot,  regulates  the  discharge  if  not  required  to  be 
continuous. 

The  machine  has  been  used  in  England  at  the  Liverpool  Docks,  the 
London  and  India  Docks,  and  at  Chatham  Dockyard.  At  the  Canada 
Branch  Dock  (No.  2  contract),  Liverpool,  it  proved  capable  of  discharging 
rather  less  than  100  cubic  yards  per  day  when  fed  continuously.  This 
represents  a  much  more  moderate  output  than  those  of  the  machines 
previously  described,  but  the  concrete  was  of  a  very  satisfactory  quality. 
The  advantages  possessed  by  a  mixer  of  this  type,  when  used  in  undertakings 
not  necessitating  a  rapid  supply,  are  lightness,  mobility,  and  economy. 

Concrete  Moulds. — Closely  connected  with  concrete  mixers  are  the  tem- 
porary wooden  moulds  within  which  the  fluid  concrete  is  deposited. 


^■ii' 

•^■- 

n 

■ 

•    * 

•      • 

o.   ■ 

'     •  .  •  . 

Fig.  37.— Concrete  Mould. 


'%'boUs 


^••.^:! 


•  ■  r»v*     1-   .  ■  •'   •••■.' 
\y..  I- ,.  .    .    . 

• .  •  •   •  ■  •  I   •  ••  i 


U.^;_t 


C&natte 


Fig.  36.— Concrete  Mould  : 
Section. 


Fig.  38. — Section  through  Concrete 
Mould  in  position. 


Per  the  back  of  a  dock  or  quay  wall,  which  is  usually  designed  in  a  series 
of  horizontal  offsets,  ordinary  deals  on  edge  forma  sufficient  and  satisfactory 
enclosure.  The  offsets  are  rarely  more  than  a  few  planks  in  height ;  these 
are  stiffened  by  short  verticals  at  the  back,  and  the  whole  rests  upon  the 
ledge  next  below.  The  same  method,  with  a  slight  modification,  may  be 
adopted  for  the  altar  courses  of  a  graving  dock.  The  profile  is  rounded  and 
the  face  of  the  mould  carefully  planed  (fig.  36). 

For  the  front  of  a  dock  or  quay  wall,  the  moulds  are  prepared  in  uniform 
sizes  of  any  convenient  dimensions.  Two  methods  of  supporting  them  are 
illustrated. 

In  the  first  case  the  moulds  (^g.  37)  rest  upon  short  cantilevers  project- 
ing from  the  wall.  These  cantilevers  (fig.  38)  are  of  timber,  about  4  by  3 
inches  section,  with  their  ends  laid  upon  the  previously  completed  work 


74 


DOCK  ENGINEERING. 


and  there  built  in,  the  whole  being  carefully  levelled.  After  the  wall  is 
completed  the  cantilever  pieces  are  sawn  off^  and  if  the  appearance  of  the 
ends  be  deemed  unsightly,  they  are  cut  out  of  the  wall  for  an  inch  or  two 
find  the  face  floated  over. 

In  the  second  method  (fig.  39)  long  timber  uprights  are  arranged  at 
regular  intervals.  At  each  side  of  the  uprights  is  a  groove,  within  which 
a  mould  can  slide  up  or  down  as  required.  When  raised  to  each  fresh 
position,  it  is  temporarily  secured  by  wooden  wedges. 

In  every  case  the  surface  of  a  concrete  mould  should  be  coated  with  a 
suitable  oil,  or  gpreasy  preparation,  to  minimise  adhesion. 


SiKMfMI 


■% 


Fig.  39. — Concrete  Mould  supported  by  Standards. 

Block-setting  Appliances. — For  the  purpose  of  dealing  with  massive  con- 
crete blocks,  used  for  construction  in  exposed  situations,  two  types  of 
appliances  are  generally  employed,  known  by  the  generic  titles  of  Goliath 
and  Titcm  respectively. 

•  

The  GolicUk  is  an  overhead  traveller,  with  rectilinear  motions.  The 
frame,  consisting  of  two  vertical  sides  connected  by  an  upper  horizontal 
platform,  travels  backwards  and  forwards  upon  two  lines  of  rails  at  the 
ground  level.  The  platform  supports  a  track  for  the  transverse  motion  of 
the  hoisting  machine.  The  general  function  of  a  Goliath  is  the  removal  of 
the  blocks  from  the  moulds,  in  which  they  have  been  formed,  to  the  stacking 
yard.  An  illustration  of  one  is  given  in  fig.  40,  which  represents  a  42-ton 
steHm  Goliath,  constructed  by  Messrs.  Ransomes  &  Eapier,  of  Ii)swich,  for 
'harbour  work  at  Dover.  The  span  of  the  main  girders,  which  are  138  feet 
over  all,  is  100  feet  l^  inches  between  centres  of  tracks,  and  the  clear  head- 
way is  25  feet,  while  the  total  lift  is  120  feet.  The  speeds  of  the  various 
movements  are : — Lifting,  10  feet ;  crab  travel,  50  feet ;  main  travel,  GO  feet 
per  minute.     The  weight  of  the  machine  in  working  order  is  216  tons.* 

The  Titan  is  also  an  overhead  traveller,  but  on  the  cantilever  principle, 
which  admits  of  rotary  as  well  as  rectilinear  motion.  Its  function  is  to 
take  the  blocks  from  the  yard  and  deposit  them  in  their  places.  The  earlier 
type  of  Titan  did  not  possess  the  turning  movement,  but  this  latter  is  very 
useful  in  setting  apron  blocks  alongside  the  main  work.     The  Mormugaa 

*  Engineering,  September  29,  1899. 


BLOCK-BBTTING  APPUANCES. 


76 


DOCK   ENGINEERING. 


machine,  constructed  by  Messrs.  Stothert  &  Pitt,  of  Bath,  illustrated  in 
fig.  41,  used  for  constructing  a  breakwater  at  the  port  of  Goa  in  India,  is  of 
this  kind.  The  overhang  is  25  feet,  measured  from  the  front  leg  to  the 
extreme  position  of  the  load ;  the  extreme  range  of  cross  travel  is  18  feet 
and  the  vertical  range  of  lift  40  feet;  the  clear  height  under  the  croRS 
girder  is  16|  feet  and  the  working  load  40  tons.''*' 


f  I  I  I  I  1 1  I  I  1 1 1 


Seal0 


LL 


-i 


/we 


Fig.  41. — Titan  Overhead  Traveller. 


NEQATIVE  AFFIilANCES. 

Excavators. — The  various  classes  of  implements  for  the  removal  of  earth- 
work, in  bulk  and  in  the  dry,  from  the  site  of  a  proposed  dock  may  be 
enumerated  as 

Land  Dredgers. 

Steam  Navvies, 
Grabs. 

Land  Dredgers  are  an  adaptation  of  the  principle  of  sea  dredgers  to  land 
work.  They  are  a  foreign  product,  and  subdivisible  into  twb  types,  which 
may  be  distinguished  as  the  French  and  the  German  respectively,  according 
to  the  country  of  their  origin.  Both,  however,  are  one  in  mode  of  action, 
and  the  distinction  between  them  simply  lies  in  the  fact  that  the  former 
discharges  its  load  into  waggons  entirely  to  the  rear,  while  the  latter 
discharges  into  waggons  which  pass  underneath  its  framing.  This  arrange- 
ment gives  the  German  machine  a  wider  base  and  greater  stability.     There 

*  Pitt  on  **  Plant  for  Harbour  and  Sea  Works,"  Mhu  Proc,  Inst,  CE,^  vol.  cxiii. 


LAND   DREDGERS.  *]*] 

are  occasions  recorded  in  which  the  French  machine  has  overturned  when 
working  in  light,  marshy  clays. 

While  the  principle  of  the  land  dredger  is  identical  with  that  of  the  sea 
dredger,  there  is  a  difference  in  the  method  of  working.  In  the  sea  dredger 
the  buckets  excavate  downwards,  away  from  the  vessel,  whereas  in  the  land 
dredger  the  cutting  action  is  upwards,  towards  the  machine.  The  buckets 
of  a  land  dredger  are  much  shallower  and  lighter  than  those  of  a  sea  dredger, 
but  both  machines  are  alike  in  that  they  are  fitted  with  two  tumblers,  about 
which  the  buckets  revolve,  discharging  their  contents  in  passing  over  the 
upper  tumbler. 

A  very  important  advantage  attaching  to  the  use  of  land  dredgers  is  the 
saving  of  a  considerable  amount  of  haulage  up  inclines.  The  machines  not 
only  excavate  cuttings  to  a  depth  of  15  or  20  feet,  but  they  also  deliver  the 
spoil  at  a  level  of  6  or  8  feet  above  the  ground  upon  which  they  travel. 
This  means,  of  course^  a  marked  saving  in  time,  as  well  as  in  locomotive  or 
winding  power. 

On  the  other  hand,  the  first  cost  of  these  machines  is  very  great, 
amounting  to  about  <£2,400  each  ;  and  they  require  much  heavier  roads  than 
machines  of  lighter  build.  Under  very  favourable  circumstances  the  cost 
of  excavation  with  these  machines  has  amounted  to  l^d.  per  cubic  yard 
excavated,  but  this  figure  may  very  easily  be  doubled  in  cases  where  space 
is  circumscribed  and  action  impeded.  Such  conditions  often  prevail  in  dock 
construction. 

French  Machine. — A  land  dredger  constructed  by  Messrs.  J.  Boulet  et 
Cie.,  of  Paris,  is  illustrated  in  figs.  42  and  43.  It  was  employed  in 
excavating  the  site  of  Canada  Branch  Dock  No.  2,  Liverpool,  and  formed 
one  of  four  engaged  upon  the  formation  of  the  Manchester  Ship  Canal. 
Experience  showed  that  it  is  only  suitable  for  use  in  connection  with 
light  soils,  such  as  earth  filling,  sand,  loam,  and  gravel.  It  is  of  no 
value  in  stiff  clay  or  in  rock,  however  soft.  Being  heavy  in  build  (about 
80  tons  weight),  a  strong  and  expensive  road  is  entailed  to  carry  the 
machine  upon  the  soft  ground  in  which  alone  it  is  effective.  For  this 
purpose  steel  rails,  weighing  80  lbs.  per  yard,  are  required,  resting  upon 
cross  sleepers  2  feet  apart,  and  sometimes  upon  longitudinal  sleepers 
in  addition. 

Another  important  consideration  is  the  fact  that  a  special  locomotive 
is  required  in  attendance  upon  the  machine  to  move  the  waggons  along 
under  the  discharge  shoot,  as,  although  the  excavator  has  motive  power, 
it  is  not  sufficiently  rapid  to  keep  pace  with  the  rate  of  filling.  About 
forty  men  are  also  required  to  be  in  attendance,  tending  and  laying  the 
road. 

At  the  Canada  Branch  Dock  the  French  machine  has  excavated  770 
cubic  yards  of  soft  material  in  a  day  of  ten  hours,  and  its  average  has 
been  600  cubic  yards  per  diem,  but  the  area  in  which  it  worked  was 
restricted  and  the  material  not  altogether  favourable,  so  that  it  did  not 


i 


LAND  DREDGERS.  79 

have  a  fair  chance  of  displajing  its  maximum  capabilities.  On  the 
Manchester  Ship  Canal,  where  there  was  much  greater  scope,  Sir  E. 
Leader  Williams  records  the  following  as  being  the  best  single-day 
performances  on  different  sections  of  the  work:* — No.  3  section,  1,943 
oabic  yards;  No.  5  section,  1,624  cubic  yards;  No.  7  section,  2,250  cubic 
yards;  No.  8  section,  2,025  cubic  yards.  "These,"  observes  Sir  Edward, 
''are  remarkable  figures;  but  the  soil  and  other  circumstances  must  be 
suitable  in  order  to  afford  such  results.  The  average  day's  work  on  all 
the  districts  was  about  1,500  cubic  yards.  If  440  waggons,  containing 
1,650  cubic  yards,  were  filled  per  day  on  No.  8  section,  it  was  considered 
A  fair  day's  work.  A  bonus  of  a  penny  per  cubic  yard  was  paid  to  the 
men  on  everything  above  this  quantity.  For  the  excavation  of  this 
quantity  the  average  daily  expenses  of  the  machine  in  wages  of  crew, 
coal,  stores,  and  repairs,  the  last  item  being  heavy,  were  about  60s.,  or 
0*44d.  per  cubic  yard  excavated.  There  were  employed  upon  the  excavator 
an  engine-driver  and  a  stoker,  and,  round  it,  a  number  of  men,  varying 
from  28  to  43,  the  average  number  being  35,  the  roads  requiring  frequent 
moving." 

Oenmam  Mcuhine. — The  land  dredger,  illustrated  in  figs.  44,  45,  and  46, 
was  made  by  the  Liibecker  Maschinenbau-Gesellschaft.  Similar  in  principle 
•and  in  mode  of  action  to  the  French  machine,  it  will  only  be  necessary  to 
touch  upon  the  points  of  difference,  which  are  of  but  secondary  importance. 
The  German  excavator  has  greater  stability,  owing  to  its  broader  base, 
and  its  motive  power  is  sufficient  to  propel  it  forward  at  a  rate  com- 
mensurate with  the  speed  of  filling  the  waggons ;  hence,  an  attendant 
locomotive  is  unnecessary.  The  machine  is  some  10  tons  less  in  weight 
than  the  French  machine,  and  is  generally  of  lighter  build,  but  the  initial 
cost  is  about  the  same.  The  following  particulars  of  its  work  upon  the 
Manchester  Ship  Oanal  are  taken  from  the  paper  by  Sir  K  Leader  Williams 
already  referred  to : — 

"The  best  day's  performances  that  are  recorded  in  its  favour  are  as 
follows : — No.  3  section,  2,073  cubic  yards ;  No.  4  section,  1,736  cubic 
yards;  No.  5  section,  1,725  cubic  yards;  and  No.  6  section,  2,400  cubic 
yards.  The  average  day's  work  is  1,416  cubic  yards,  with  an  average 
number  of  36  men.  The  average  daily  expenses  of  the  machine  in  wages 
of  crew,  coal,  stores,  and  repairs  are  about  60s.,  or  0'5d.  per  cubic  yard 
excavated,  which  is  increased  to  l*6d.  per  cubic  yard  by  the  wages  of  the 
labourers  who  attend  on  the  excavator." 

"  Summarising  the  results  of  experience  in  the  working  of  land  dredgers 
in  England,  it  may  be  said  that  in  light  material  and  on  level  ground 
they  will  fill  waggons  at  considerable  speed  and  with  economy ;  and  where 
large  excavations  of  soft  material  have  to  be  made  with  rapidity,  the 
bucket  dredging  system  gives  the  cheapest  and  best  results,     fiut  they 

*  WilliamB  on  **  Mechanical  Appliances  employed  in  the  CoDstruction  of  the  Man- 
chester Ship  Canal,"  Min,  Proc,  /.  Mech.  E.,  1891,  p.  418. 


STEAM  NAVVIES.  8 1 

will  not  excavate  heavy  or  strong  material ;  they  are  difficult  and  expen- 
sive to  maintain,  and  therefore  cause  delay  to  the  work;  they  require 
a  costly  and  a  heavy  road,  and  special  precautions  on  soft  ground  to 
prevent  them  from  tilting  over  into  the  cutting ;  and  they  are  expensive 
to  move  from  one  cutting  to  another." 

Steam  Navvies  represent  a  class  in  which  excavation  is  performed  by 
a  single  bucket  working  at  the  end  of  an  arm  or  lever.  The  machines 
travel  along  the  bottom  of  the  cutting,  and  the  mode  of  action  is  an 
upward  curved  sweep  of  the  bucket  against  the  face  of  the  ground  in 
front.  Steam  navvies  or  excavators,  as  they  are  sometimes  called,  are 
characterised  by  great  power.  They  are  capable  of  working  in  the  stiffest 
clay  and  the  hardest  marl.  They  will  also  take  soft  rock  unaided,  and 
hard  rock  with  the  assistance  of  a  little  blasting. 

The  Rvaton  Steam  Nawy,  manufactured  by  Messrs.  Euston,  Procter  k  Co,j 
Ltd.,  of  Lincoln,  has  a  strong  spaodril-shaped  jib,  intersected  at  its  centre 
by  a  long  arm,  at  the  lower  end  of  which  is  the  bucket.  The  arm  is  capable 
of  forward  motion  by  means  of  rack  and  pinion  gearing,  and  it  also  rotates 
about  the  pinion  under  the  tension  of  a  chain  leading  from  the  bucket  to 
the  head  of  the  jib.  The  method  of  action  is  clearly  indicated  in  fig.  47. 
The  size  usually  employed  for  dock  work  is  that  developing  10  H.P.,  in 
which  case  the  capacity  of  the  bucket  ranges  from  1^  cubic  yards  for  stiff 
ground  to  2^  cubic  yards  for  sand.  The  best  results  are  obtained  when 
the  excavation  has  a  depth  of  from  20  to  25  feet.  Under  such  circum- 
stances from  1,700  to  2,000  cubic  yards  of  sand,  and  very  dry,  friable 
material,  have  been  obtained  in  a  day  of  10  hours,  but  a  fair  average  in 
mixed  earth,  under  ordinary  conditions,  would  be  600  to  700  cubic  yards 
per  diem.  In  hard  material,  such  as  rock  and  rocky  marl,  the  output  is 
necessarily  less  again  than  this.  At  Barry  Docks  from  450  to  500  cubic 
yards  per  day  were  excavated,  the  marl  being  first  loosened  by  powder. 
Of  soft  material,  1,000  cubic  yards  were  obtained  in  a  single  day,  on  several 
occasions,  at  the  same  place. 

The  disadvantages  attaching  to  the  machine,  undoubtedly  powerful  and 
useful  though  it  be,  are  its  great  weight  (about  45  tons),  which  necessitates 
a  very  solid  road,  and  its  inability  to  work  otherwise  than  directly  forward. 
The  waggons  to  be  filled  must  be  ranged  alongside,  as  the  pivot  only 
rotates  through  a  semicircle,  and  a  wide  base  is  required  to  accommodate 
two  waggon  roads  in  addition  to  the  navvy  road.  The  first  cost  of  the 
machine  is  about  £1,200,  and  the  working  expenses,  including  wages, 
amount  to  about  30  shillings  per  day. 

The  Simpson  cmd  Porter  ExcoAyator  (fig.  48),  manufactured  by  Messrs. 
J.  H.  Wilson  <fe  Co.,  Ltd.,  of  Liverpool,  is  a  lighter  machine,  but  very 
effective  in  suitable  soil.  The  special  point  in  its  favour  is  its  ability  to 
revolve  through  a  complete  circle,  and  therefore  to  deliver  the  excavated 
material  into  waggons  at  its  extreme  rear,  if  necessary;  and  further,  by 

disconnecting  the  bucket  gear,  the  machine  is  readily  available  for  use 

6 


82 


DOCK  ENGINEERING. 


r 


I 

t 

H 

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I 

I 
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STEAM  NAVVIES. 


83 


84  DOCK  ENGINEERING. 

as  an  ordinary  crane.  The  rate  of  work  claimed  for  a  12-ton  machine^ 
fitted  with  a  IJ-yard  bucket,  is  from  800  to  1,200  cubic  yards  per  day 
of  1 1  hours,  according  to  the  nature  of  the  ground.  It  has  been  known 
by  the  writer  to  maintain  an  average  of  570  cubic  yards  of  stiff  clay  per 
day  of  10  hours,  under  normal  conditions,  with  the  attendance  of  10  men 
and  2  horses.  The  cost  is  about  £1,200,  and  the  ordinary  working  expenses 
amount  to  about  25  shillings  per  day. 

The  method  of  action  is  somewhat  different  from  that  of  the  Ruston 
navvy.  The  bucket  is  operated  by  a  direct-acting  steam  cylinder,  the 
piston  of  which  has  a  stroke  of  6  inches  to  2  feet  in  any  position  of  the 
face.  Being  lighter  in  build,  the  machine  is  not  so  well  adapted  to  rock- 
getting  as  the  Buston  machine. 

Very  similar  in  design  is  the  Whitaker  Excavator,  made  by  Messrs. 
Whitaker,  of  Horsforth,  near  Leeds,  and  its  capabilities  are  also  about  the 
same.  It  requires  the  attendance  of  a  dozen  men,  with  two  horses,  and 
its  daily  working  expenses  lie  between  25  and  30  shillings.  The  cost  of  a 
10-ton  machine  with  li-yard  bucket  is  about  £1,250. 

A  very  interesting  application  of  hydraulic  power  to  dock  construction 
is  illustrated  in  the  Hydraulic  Navvy  (fig.  49),  designed  by  Sir  W.  G. 
Armstrong  k  Oo.,  and  used  in  the  formation  of  the  Alexandra  Dock  at 
Hull.  The  jib  is  similar  to  that  of  the  Huston  navvy.  The  lifting  ram 
and  multiplying  sheaves  are  placed,  in  an  inclined  position,  at  the  rear  of 
the  machine,  so  that  their  weight  may  exercise  the  greatest  counter- 
balancing effect  when  the  bucket  is  making  a  cut.  The  diameter  of  the 
ram  is  141  inches  and  the  stroke  4  feet  5  inches.  The  hydraulic  working 
pressure  at  Hull  was  700  lbs.  per  square  inch,  which  afforded  a  maximum 
cutting  force,  allowing  for  friction,  of  about  12  tons.  The  capacity  of  the 
bucket  was  1|  cubic  yards,  and  the  machine  could  excavate  600  cubic 
yards  of  suitable  ground  in  10^  hours.  Its  speed  of  working,  compared 
with  a  steam  navvy,  was  as  13  to  10,  and  the  ordinary  repairs  as  10  to  14. 
The  cost  of  the  machine  complete  was  about  <£1,300,  and  its  weight  30  tons. 
The  average  daily  consumption  of  water  was  17,000  gallons. "^ 

Hydraulic  appliances  are  not  generally  feasible  for  constructive  work^ 
unless  the  power  be  pre-existent.  A  contractor  would  scarcely  deem  it 
worth  while  to  lay  down  a  special  installation  for  the  purpose.  But^ 
where  available,  the  system  offers  the  following  advantages  over  steam 
power.  It  is  more  rapid  and  more  reliable  in  action,  with  less  vibration 
and  less  noise.  There  are  fewer  repairs  to  be  made,  and,  in  the  absence 
of  coal  and  of  water  boilers,  there  is  less  weight  to  be  carried  over  soft  or 
uncertain  ground. 

Grabs  are  also  used  as  excavators,  but  their  rate  of  working  is  much 
inferior,  and  they  are  best  adapted  to  confined  situations  and  to  the 
removal  of  light  surface  soil,  under  which  conditions  an  average  output 
of  300  cubic  yards  per  10-hour  day  has  been  obtained.     They  can  excavate 

*  Vide,  Hurtzig  on  "The  Alexandra  Dock,  Hull,"  Min.  Proc.  Inst.  C,E.,  vol.  xcii. 


DRILLING  APPLIANCES.  85 

cla;.  but  ftt  a  much  slower  rate — about  100  cubic  yards  per  diem.  In 
accordance  with  their  more  appropriate  inclusion  amongst  dredging 
appliances,  a  description  of  them  is  relegated  to  that  section. 


Drilling  Appliances. — For  the  removal  of  rock,  old  masonry,  and  other 
hard  material,  in  large  quantities,  blasting  is  the  expedient  commonly 
adopted.  For  this  purpose,  and  for  others,  such  as  the  insertion  of  the 
ends  of  jetty  piles  in  a  foundation  of  natural  rock,  dec,  drilling  appliances 


are  neoessarf . 


86  DOCK   ENGINEERING. 

Drilling  tools  are  divisible  into  two  classes — hand  drills  and  machine 
drills. 

Hand  drills  are  round  bars  of  iron  or  steel,  with  a  steel  catting  edge, 
either  cruciform  or  chisel  shaped,  and  are  of  two  sizes.  The  short  hand 
drill  can  be  manipulated  by  one  man.  He  holds  the  drill  in  the  left  hand 
and  strikes  it  with  a  hammer  in  his  right.  Sometimes  two  men  are 
engaged — one  as  a  holder  and  the  other  as  a  striker.  The  drill  should 
be  slowly  rotated. 

Long  hand  drills,  or  jumpers,  necessitate  the  attendance  of  several 
men.  If  driven  vertically,  the  drill  is  lifted  by  their  combined  effort 
and  allowed  to  fall,  being  caught  at  its  rebound  and  at  the  same  time 
turned  through  a  slight  angle.  If  the  cutting  be  horizontal,  the  drill  is 
projected  backwards  and  forwards  by  a  swaying  movement  of  the  holders. 

Hand  drilled  holes  are  from  |  inch  to  2  inches  in  diameter,  and  the 
depth  varies,  of  course,  according  to  circumstances.  For  blasting  purposes 
from  2  to  4  feet  will  suffice.  The  rate  of  drilling  depends  upon  the  nature 
of  the  material,  but  may  be  taken  between  the  limits  of  5  to  10  feet  yter 
10-hour  day.  The  cutting  edge  will  require  re-sharpening,  at  intervals 
represented  by  from  6  to  18  inches  of  excavation  in  depth. 

Machine  drills  are  much  more  rapid  in  action  than  hand  drills,  and  they 
also  work  more  economically,  but  their  installation  is  expensive  and  only 
justiGable  in  the  case  of  extensive  operations. 

Machine  drills  are  of  two  kinds — percussive  and  rotary.  The  former 
are  identical  in  principle  with  hand  drills,  the  distinction  lying  simply  in 
the  nature  of  the  motive  power  applied,  which  may  be  steam,  compressed 
air,  or  electricity.  Instead  of  using  a  single  cutting  edge,  however,  several 
chisels  may  be  worked  in  combination,  especially  where  large  holes  are 
required.  For  vertical  boring  the  drill  is  often  surged  by  a  wire  rope  leading 
over  sheaves  to  a  winch.  The  chisels  vary  in  width  up  to  24  inches,  but 
the  vibration  due  to  such  a  heavy  chisel  as  this  last  is  apt  to  cause  frequent 
breakages  in  the  rods. 

Rotary  drills  are  tubular,  with  extremities  fitted  with  hardened  steel 
teeth  or  diamonds,  the  latter  being  more  general.  The  drill  consists  of  two 
parts — the  boring  bit  and  the  core  lifter.  In  the  course  of  action  the  former 
makes  an  annular  cutting,  leaving  an  internal  core  upstanding,  which,  when 
the  operation  is  finished,  is  gripped  by  a  loose  toothed  ring  contained  within, 
and  caught  in  its  turn  by,  the  coned  inner  surface  of  the  drill.  The  core, 
being  thus  jammed  in  the  drill,  is  broken  away  at  the  root  by  a  few 
additional  revolutions. 

In  ordinary  rock,  machine  drills  can  bore  holes,  2  to  3  inches  in 
diameter,  at  rates  varying  from  1  to  10  feet  per  hour. 

Blasting  Agents. — The  agents  most  commonly  used  are : — 
Ounpotjoder  ; 

Niiro-glycerine  and  its  compounds^  such  as  dynamite  ;  and 
Gum,  cotton  and  its  compounds,  such  as  tonite. 


HAULAGE  AND  TRACTION.  87 

Gunpowder  is  a  mixture  of  snlphnr,  nitre,  and  charcoal.  It  exerts  an 
explosive  force  of  from  18  to  40  tons  per  square  inch,  and  weighs  about 
62 J  lbs.  per  cubic  foot.  For  blasting  purposes  the  lower  power  is  used, 
and  a  cubic  yard  of  quarry  rock  requires  a  charge  of  from  ^  lb.  to  2  lbs., 
according  to  nature  and  position ;  in  tunnels  and  shafts  as  much  as  6  lbs. 
has  been  used. 

A  formula  given  by  Haswell  for  computing  the  quantity  required  is — 

Charge  in  lbs.  =  —  , 

where  I  is  the  length  of  the  line  of  least  resistance  in  feet,  and  x  a  factor 
ranging  from  25  for  limestone  to  32  for  granite.  The  line  of  least  resistance 
should  not  exceed  one-half  the  depth  of  the  hole. 

Nitro-glycerine  results  from  the  action  of  nitric  and  sulphuric  acids  upon 
glycerine.  The  addition  of  a  granular  absorbent  constitutes  dtftiamite. 
This  absorbent  may  be  either  inert  or,  in  itself,  an  explosive.  Dynamite, 
containing  75  per  cent,  of  nitro-glycerine,  has  from  four  to  six  times  the 
explosive  force  of  gunpowder. 

Gun  cotton  is  cotton  dipped  in  a  mixture  of  nitric  and  sulphuric  acids. 
Tonite  is  gun  cotton,  in  a  finely  divided  state,  mixed  with  nitrate  of  barium. 
The  power  of  tonite  may  be  said  to  be  equal  to  that  of  dynamite,  but  the 
efifect  is  somewhat  less  shattering. 

Haulage  and  Traction. — The  question  as  to  the  relative  merits  of  loco- 
motives and  stationary  winding  engines  for  the  haulage  of  excavated 
material  from  a  lower  to  a  higher  level,  depends  entirely  upon  local  circum- 
stances. Where  there  is  ample  space  for  the  comparatively  flat  incline  upon 
wiiich  locomotive  traction  is  practicable  that  method  is,  generally  speaking, 
preferable  on  the  grounds  of  economy  in  working  and  of  saving  in  time. 
The  waggons  can  be  conveyed  direct  from  the  excavator  to  the  tipping 
station,  whereas  with  the  winding  engine  there  are  at  least  two  breaks  in 
the  journey — one  at  the  foot  of  the  incline,  where  the  waggons  have  to  be 
connected  with  the  hauling  apparatus,  either  singly  or  in  small  detached 
groups,  and  the  other  at  the  summit,  where  they  have  to  be  disconnected 
and  coupled  up  again.  In  the  former  case,  under  convenient  circumstances, 
one  locomotive  may  serve  all  requirements,  both  taking  the  waggons  to  the 
tipping  station  and  bringing  them  back  again.  In  the  latter  instance  two 
locomotives,  in  addition  to  the  winding  engine,  are  absolutely  essential — 
one  working  at  the  higher  and  the  other  at  the  lower  level. 

Winding  engines  can,  however,  be  satisfactorily  employed  where  space  is 
much  restricted,  since  the  incline  may  practically  be  made  at  any  angle  and 
as  steep  as  is  considered  desirable.  A  slope  of  about  1  in  20  represents  the 
critical  pitch  at  which  traction  by  locomotives  begins  to  lose  its  superior 
etficiency.  A  very  steep  pitch  throws  considerable  strain  upon  the  working 
parts;  and,  indeed,  in  any  case,  it  is  advisable  to  arrange  a  triangular- 
shaped  siding  in  order  that  the  engines  may  be  reversed  frx)m  time  to  time. 


88  DOCK   ENGINEERING. 

A  turntable  for  such  temporary  purposes  would,  of  course,  be  impracticable 
on  grounds  of  expense.  The  waggons  also  need  reversing  at  intervals,  as 
there  is  a  tendency  for  the  flanges  of  the  wheels  to  wear  unequally  when 
the  curves  of  the  roads  have  one  prevailing  direction.  This  can  be  done  by 
a  crane. 

Waggons  are  of  three  kinds — ballast  or  permanent  way,  side-tipping,  and 
end-tipping.  Ballast  waggons  have  fixed  bodies,  and  thus,  being  steady  in 
travelling,  are  employed  for  the  conveyance  of  spoil  to  great  distances.  The 
contents,  about  5  cubic  yards  of  material  each,  have  to  be  discharged  by 
hand,  unless  the  waggons  be  lifted  bodily  and  overturned,  as  is  some- 
times done.  Side-tipping  waggons  generally  have  their  bodies  supported  on 
rockers  formed  by  curved  channel  bars  bearing  upon  short  cross  rails. 
They  are  temporarily  secured  by  pins  and  catches,  upon  releasing  which 
tilting  becomes  possible  and  the  contents  are  shot  out.  End-tipping 
waggons  have  bodies  hinged  at  one  end  to  longitudinal  bearers.  They  can 
be  lifted  in  order  to  discharge,  but  are  usually  driven  with  some  impetus 
against  a  wooden  log  fixed  as  a  buffer  upon  the  rails.  The  abrupt  stoppage 
causes  the  tail-end  of  the  waggon  to  jump  up.  The  method  involves,  as  can 
readily  be  imagined,  considerable  wear  and  tear.  Tipping  waggons  contain 
rather  less  than  ballast  waggons,  say,  from  3i  to  4  cubic  yards  of  material. 

Dredgers  and  Dredging  Plant — All  operations  involving  the  removal  of 

material  under  water  are  comprehended  in  tlje  term  dredging,  whether  the 

mode  of  action  be  dragging,  sucking,  or  digging. 

As  a  primary  distinction  all  dredgers  may  be  included  in  one  of  two 

classes : — 

Compound  hopper-dredgers. 

Simple  dredgers  wUh  attendant  hopper  barges. 

The  hopper-dredger  is  self-contained  and  complete  in  itself,  being  pro- 
vided not  only  with  apparatus  for  raising  material,  but  also  with 
compartments  for  its  reception  when  raised.  The  dredger  loads  itself, 
conveys  its  load  to  the  assigned  position,  discharges  it  there  and  returns, 
all  under  its  own  engine  power. 

An  obvious  disadvantage  is  the  discontinuity  of  its  dredging  operations, 
with  the  attendant  repetition  of  mooring  manoeuvres.  Where  new  works 
are  being  carried  out  there  is  a  corresponding  loss  of  time,  which  is  a  matter 
of  serious  importance  from  several  points  of  view.  For  maintenance  works 
and  minor  undertakings  the  objection  has  possibly  not  so  much  weight;  but, 
in  either  case,  the  drawback  is  emphasised  by  the  possibility  of  the  dredger 
being  weatherbound  and  unable  to  leave  a  sheltered  position  in  order  to 
proceed  to  sea  and  discharge. 

On  the  other  hand,  the  combined  hopper  dredger  costs  less  in  initial 
expenditure  and  subsequent  upkeep  than  a  separate  dredger  and  hopper 
with  corresponding  or  even  greater  capacity.  It  also  monopolises  less  valu- 
able water  space  in  restricted  areas,  such  as  the  interior  of  docks.  Only 
one  crew  is  required  to  carry  out  all  duties ;  the  working  expenses  are  less. 


DREDGERS  AND   DREDGING  PLANT.  89 

and  the  time  taken  up  in  sea  trips  may  be  usefully  employed  in  overhauling 
the  buckets  and  pins  and  in  effecting  any  necessary  repairs.  A  possible 
demur  to  this  last  contention  on  the  ground  that  both  machinery  and  crew 
would  be  too  fully  occupied  with  purely  navigatory  functions  to  admit  of 
ftuch  extraneous  duties,  may  be  met  by  the  explanation  that  repairs  would 
be  limited  in  each  voyage  to  those  buckets  which  were  actually  accessible, 
and  that  the  presence  of  one  or  two  additional  hands  in  order  to  attend 
to  them  would  be  fully  compensated  for  by  the  saving  in  time. 

In  undertakings  of  considerable  magnitude,  where  time  and  interest  on 
capital  are  factors  of  the  highest  importance,  it  will,  on  the  whole,  be 
found  expedient  to  adopt  the  separate  system  with  a  large  fleet  of  hopper 
barges  in  constant  attendance  upon  the  dredgers ;  for,  though  the  outlay 
may  be  greater,  the  increased  rapidity  of  execution  will  fully  compensate 
for  it. 

Apart  from  the  foregoing  classification,  dredgers  are  capable  of  inclusion 
in  a  great  variety  of  divisions,  according  to  the  very  varied  manner  in 
which  they  individually  discharge  their  functions.  Indeed,  the  subject  is 
one  of  such  wide  scope  and  importance  as  to  claim  a  special  treatise,  if  any- 
thing of  the  nature  of  an  adequate  dissertation  were  to  be  attempted.  In 
the  limited  space  at  our  disposal  we  can  only  afford  to  deal  in  a  general  way 
with  the  relative  merits  of  the  more  important  types,  and  to  give  a  brief 
description  of  their  salient  features.  For  this  purpose  we  will  adopt  the 
following  succinct  classification  : — 

Suction  dredgers. 
Ladder  dredgers. 
Dipper  dredgers. 
Grab  dredgers. 

Suction  dredgers^  hydraulic  dredgers^  or  sa/nd  pump  dredgers,  as  they  are 
Tery  commonly  called,  consist  essentially  of  a  continuous  pipe  or  tube 
through  which,  by  means  of  suitable  machinery,  sand  or  other  light  material 
is  sucked  up  from  the  bottom  (see  fig.  50).  The  sand  is  naturally  accom- 
panied by  a  very  large  volume  of  water  which  is  delivered  with  it  into  the 
iiopper,  and  this  fact,  combined  with  the  disposition  of  the  water  to  escape 
over  the  sides  of  the  hopper  with  the  sand  still  in  suspension,  causes  a  great 
deal  of  unremunerative  pumping,  the  loss  in  sand  amounting  to  as  much  as 
20  per  cent,  of  the  quantity  actually  raised.  Considerable  diminution  of 
this  waste  has  been  effected  by  a  device  introduced  by  Mr.  A.  G.  Lyster,  the 
engineer  to  the  Mersey  Docks  and  Harbour  Board ^  (fig.  51).  The  hopper  is 
entirely  covered  over  with  the  exception  of  a  narrow  central  portion,  4  feet 
wide,  provided  with  adjustable  coamings,  raised  to  a  height  of  5  feet.  The 
sand  is  delivered  near  the  sides  of  the  hopper,  and  having  a  considerable 
distance  to  travel  before  it  can  reach  the  top  of  the  central  opening,  the 
greater  portion  settles  en  route  and  the  efiSuent  is  comparatively  clear.     It 

*  Lyster  on  "Sand  Pump  Dredgers,"  Min,  Proc,  Inst,  C,E,,  vol.  cxxxviii. 


DOCK  BNGINBERING. 


I 


SUCTION  DREDGERS. 


91 


should  not  be  overlooked,  however,  that  this  arrangement,  whilst  extremely 
effective  for  its  particular  purpose,  somewhat  reduces  the  useful  capacity 
of  the  hopper  for  solid  material,  by  adding  to  the  gross  load  carried. 

The  suction  pump  dredger  would  also  be  applicable  to  silt  and  mud,  were 
it  not  that  the  lower  specific  gravity  of  such  material  renders  it  practically 
impossible  to  secure  its  deposition  within  the  limits  of  the  receiving  hopper. 
Silt  will  take  nearly  as  many  hours  to  settle  as  sand  takes  minutes.  It  is 
sometimes,  however,  an  advantage  to  bring  a  suction  pump  to  bear  on  mud 
in  situations  otherwise  inaccessible,  such  as  gate  platforms  and  recesses. 
The  mud  thus  disturbed  settles  in  more  open  positions,  where  it  can 
conveniently  be  removed  by  other  appliances.  The  discharge  of  the  muddy 
effluent  of  a  suction  pump  into  a  tidal  or  other  current  is  a  simple  but 
efficacious  means  of  maintaining  a  waterway,  provided  that  the  deposit  be 
light  and  the  current  sufficiently  powerful  to  retain  it  in  suspension  until 
it  reaches  a  place  where  its  settlement  will  do  no  harm. 


AdJustablB  Coaming 


Adjushabl9  Coaming 


Oischorye 
From  Pump 


Discharge 
From  Pump 


Fig.  51. — Section  of  Hopper  fitted  with  Adjustable  Coamings. 

Suction  pumps  possess  very  great  advantages  in  exposed  situations,  where 
the  incessant  motion  of  the  waves  materially  interferes  with  the  working 
of  other  forms  of  dredging  apparatus.  Equipped  with  telescopic  pipes  and 
flexible  joints,  they  can  adjust  themselves  to  the  rise  and  fall  of  the 
vessel  and  be  quite  independent  of  variations  of  level,  either  momentary  or 
prolonged.  The  manifest  convenience  and  safety  attaching  to  dredgers  of 
this  class  has  led  to  repeated  attempts  to  adapt  them  to  the  removal  of 
material  other  than  sand.  With  this  object  in  view  the  lower  end  of  the 
suction  pipes  has  been  fitted  with  a  number  of  cutting  blades,  the  revolu- 
tion of  which,  by  suitable  gearing,  is  intended  to  disintegrate  clay,  marl,  and 
other  compact  material  to  such  a  degree  as  will  admit  of  their  being  drawn 
up  the  suction  pipe. 

This  is  the  basis  of  the  Bates,  the  von  Schmidt,  and  other  systems 
of  dredger.      The   cutters,   generally    speaking,    are    cylindrical,    hollow, 


92  DOCK   ENGINEERING. 

straight,  or  spiral  blade  milling  cutters,  mounted  around  and  concentrically 
-with  the  end  of  the  suction  pipe.  They  consist  of  a  number  of  knives 
•{from  10  to  15)  united  by  suitable  discs,  or  rings,  at  one  or  both  ends. 
The  whole  cutter  may  be  secured  to  the  end  of  the  suction  pipe  and 
rotary  motion  imparted  to  them  together,  or  the  cutter  shaft  may  be 
journalled  in  a  suitable  bearing  provided  in  the  end  of  the  suction  pipe, 
which  is  then  made  stationary. 

The  use  of  cutters  is  only  practicable  in  fairly  smooth  water ;  in 
situations  where  there  is  much  swell,  other  means  must  be  found  for 
loosening  and  disintegrating  the  material  to  be  removed.  One  alternative 
expedient  is  the  application  of  numerous  water  jets  through  a  series  of 
orifices,  specially  provided  for  the  purpose  in  the  bars  which  traverse  the 
mouth  of  the  drag-piece,  and  communicating  by  means  of  suitable  ports 
with  a  pipe  running  along  the  front  of  the  mouthpiece.  This  system  of 
nozzles  is  supplied  with  water  under  pressure  through  a  flexible  pipe.  The 
result  is  much  inferior  to  that  attained  by  the  action  of  cutters,  and,  in 
order  to  obtain  the  best  effect,  it  is  necessary  to  concentrate  the  pressure  of 
the  jets  upon  a  small  surface,  and  to  direct  the  stream  towards  the  intake 
pipe. 

The  value  of  the  cutter  appliance  in  dealing  with  beds  of  hard  sand  has 
been  abundantly  demonstrated  on  the  Mississippi,  the  Scheldt,  and  the 
Volga  But  after  witnessing  a  number  of  trials  of  a  similar  type  of  dredger 
upon  stiff  clay,  the  writer  is  inclined  to  doubt  the  efficacy  of  the  system  in 
dealing  with  material  of  an  argillaceous  character,  though  he  is  prepared 
to  admit  that  much  may  depend  upon  the  precise  form  of  cutter  adopted. 
In  this  view  he  is  confirmed  by  some  remarks  made  by  Mr.  J.  H.  Apjohn 
at  a  recent  engineering  conference,  which,  indeed,  are  worth  quoting  as 
demonstrating  the  scope  existing  for  experimental  investigation.''^ 

''The  author's  experience  of  rotary  cutters  has  been  with  a  dredger 
designed  for  the  purpose  of  excavating  clay  for  dock  extension.  The  clay 
being  silty,  it  was  thought  it  would  be  easily  broken  up  by  the  cutter,  but 
this  was  not  the  case.  The  cutter  had  fourteen  straight  knives,  set  at  an 
angle  of  26"*  to  the  tangent  of  the  circle  round  which  they  were  placed  and 
overlapping  each  other  to  a  slight  extent.  The  dredger  was  first  operated 
at  a  small  depth  where  the  soil  was  brittle  and  the  cutter  proved  efficient, 
but  when  the  clay  was  reached  at  a  greater  depth,  the  openings  between 
the  blades  of  the  cutter  clogged  with  the  tenacious  plastic  clay,  with  the 
result  that  the  proportion  of  clay  found  in  the  water  discharged  through 
the  pipe-line  was  extremely  small.  The  cutter  was  then  unshipped,  and 
a  width  of  some  inches  was  cut  off  the  inner  edge  of  each  blade,  so  that  the 
overlap  was  done  away  with,  and  at  the  same  time  the  circular  opening  at 
the  bottom  of  the  cutter  was  reduced  in  area.  When  again  tried  the 
cutter  worked  better,  there  being  but  little  clogging  between   its  blades, 

*  Apjohn  on  "Dredging  with  special  reference  to  Rotary  Cutters,"  Proc.  Eng. 
Conf.,  London,  1903. 


94  I>OCK   ENGINEERING. 

but  these  did  not  cut  the  clay  very  well.  A  new  cutter  was  then  built, 
with  narrow  spiral  knives,  and  proved  to  be  more  efficient  than  the  first ; 
but  even  with  this  cutter  the  quantity  turned  out  per  hour  was  never  more 
than  60  per  cent,  of  that  contracted  for.  The  clay,  which  it  discharged 
behind  the  walls  was  in  the  form  of  nodules,  varying  in  size  between  that 
of  an  egg  and  that  of  a  Dutch  cheese." 

Notwithstanding  some  disappointing  experiences,  such  as  the  foregoing, 
the  clay-cutting  gear  has  very  strong  partisans.  Mr.  A.  W.  Robinson  * 
claims  for  a  dredger,  the  "J.  Israel  Tarte,"  designed  by  himself,  and  working 
in  blue  clay  in  the  channel  of  the  river  St.  Lawrence  below  Montreal,  <'a 
world's  record  for  output,  measured  by  the  output,  of  any  dredger  under  any 
•conditions. "t  And  Mr.  C.  W.  Darley,  in  his  description  of  "Dredging  in 
New  South  Wales,"!  speaks  of  them  as  valuable  for  cutting  new  channels 
through  **  tough  or  hard  clay  formations."  Any  definite  pronouncement  on 
the  value  of  the  cutter  dredger  must  therefore  remain  in  abeyance,  pending 
the  completion  of  more  extensive  trials  and  the  determination  of  the  best 
form  of  cutting  apparatus. 

The  illustration  (figs.  52  and  53)  is  one  of  a  dredger  on  the  Bates  system 
constructed  for  the  Russian  Government.  The  cutters,  of  which  there  are 
four,  are  shown  at  the  stem.  The  forward  end  is  in  connection  with  a 
discharge  pipe. 

Ladder  Dredgers,  or  bucket-ladder  dredgers  (figs.  54  to  58),  consist,  in 
principle,  of  an  endless  chain  connecting  a  series  of  buckets  which  traverse 
in  succession  an  inclined  orbit,  approximately  elliptical,  about  two  pivots  or 
tumblers,  excavating  material  at  the  lower  tumbler  and  discharging  it  into 
.a  shoot  while  passing  over  the  upper  tumbler. 

Bucket  dredgers  of  this  type  have  either  one  or  two  ladders — "  ladder  " 
being  the  name  applied  to  the  frame,  with  its  roller  bearings,  on  which  the 
buckets  travel.  In  single-ladder  dredgers  the  ladder  coincides  with  the 
longitudinal  axis  of  the  vessel.  The  ladders  of  double  dredgers  are  situated 
jit  each  side  of  the  vessel. 

A  single-ladder  dredger  of  the  same  capacity  as  a  double  dredger  has  the 
advantage  of  fewer  moving  parts  and,  consequently,  of  less  working  friction. 
The  central  position  of  the  ladder  also  admits  of  a  more  convenient  outline 
for  the  vessel,  from  the  point  of  view  of  propulsion,  and  affords  greater 
steadiness  in  a  sea  way.  The  broad  beam  of  double-ladder  dredgers  renders 
it  impossible  for  them  to  pass  through  narrow  locks,  though  this  difficulty 
has  been  overcome,  in  one  case  at  least,  by  constructing  a  dredger  in 
detachable  halves. 

On  the  other  hand,  a  side-ladder  dredger  can  work  in  greater  proximity 

*A.  W.  Robinson  on  *' Modem  Machinery  for  Excavating  and  Dredging," 
Engineering  Magazine^  vol.  xxv.,  No.  1,  April,  1903. 

tXhis  performance  is  stated  to  have  consisted  in  the  removal  of  1,180,000  cubic 
^ards  of  material  daring  a  period  of  two  months,  comprising  52  working  days. 

:;:  Eng.  Conf.,  London,  1903. 


LADDER   DREDGERS.  97 

to  the  face  of  a  dock  or  quay  wall  than  is  feasible  in  the  case  of  a  central 
ladder.  But,  under  these  circumstances,  the  discharge  of  dredged  material 
has  to  take  place  across  the  whole  width  of  the  vessel  (unless  it  be  a  hopper 
dredger,  which  is  unlikely,  from  its  unsuitable  form  for  navigation),  and 
either  the  cross  shoot  will  be  too  flat  to  be  thoroughly  effective,  or  else  the 
lift  of  the  buckets  is  excessively  high  for  ordinary  purposes.  It  will 
generally  be  found  necessary  to  employ  an  auxiliary  pump  to  flush  the  shoot. 

A  central  ladder  dredger  can  discharge  indifferently  to  either  side,  but 
again,  if  any  mishap  occur  to  a  link  or  bucket,  the  whole  dredger  is  placed 
out  of  action,  whereas  in  a  double  ladder  dredger  one  ladder  may  be 
quite  disabled  without  interfering  with  the  work  of  the  other.  In  cases 
where  very  powerful  machines  are  required,  double  dredgers  have  the 
recommendation  of  providing  greater  lifting  capacity  with  buckets  of  a 
less  unwieldy  size. 

The  bucket  dredger  is  eminently  suitable  for  steady  continuous  work 
in  hard  material.  It  is  the  only  form  of  dredger  which  will  excavate  rock, 
and  it  has  proved  capable  of  raising  boulders  much  larger  than  its  own 
buckets.  In  stiff  clay  it  is  much  superior  to  dredgers  of  any  other  type. 
Altogether,  it  is  an  excellent  machine,  but  it  cannot  be  worked  in  a  swell 
nor  in  very  shallow  water. 

It  is  nut  an  economical  machine  in  the  matter  of  power.  Owing  to  the 
necessity  of  discharging  through  a  shoot,  in  cases  where  an  attendant 
hopper  is  employed  to  receive  the  dredged  material,  lifting  has  to  be 
performed  by  the  machinery  to  the  extent  of  25  or  30  feet  (the  writer 
knows  of  a  case  of  35  feet)  above  the  water  line,  representing  a  corre- 
sponding waste  of  energy. 

The  difficulty  of  dealing  with  shoals  and  banks  has  been  solved  by  a 
special  form  of  dredger,  devised  by  Messrs.  Wm.  Simons  <k  Co.,  of  Renfrew, 
called  the  traversing  bucket  dredger.  The  ladder  is  supported  upon  a 
horizontal  longitudinal  framing,  by  means  of  which  it  can  be  projected  in 
advance  of  the  dredger,  and  thus  enabled  to  cut  the  flotation  of  the  latter 
through  shallow  places.  By  the  same  arrangement  the  ladder  can  be 
entirely  removed  from  the  water,  and  less  obstruction  is,  in  consequence, 
offered  to  its  passage,  when  acting  as  a  carrier  hopper  or  otherwise. 

Central  ladder  dredgers  are  themselves  susceptible  of  subdivision  into 
two  classes,  according  as  the  well  is  situated  at  the  bow  or  the  stern  of  the 
vessel.  The  former  is  the  more  general  type  for  simple  dredgers,  but  a 
stem  well  hopper  dredger  derives  the  advantage  of  increased  speed  from 
a  normal  stem,  with  improved  manoeuvring  qualities  and  a  better  shaped 
hull  for  encountering  heavy  seas. 

The  following  are  points  of  practical  importance  in  connection  with  the 
utility  of  bucket  dredgers. 

Buckets, — No  object  is  gained  by  bringing  the  lip  of  the  bucket  too  far 
forward.  The  limit  of  filling  will  generally  be  the  horizontal  line  through 
the  inner  edge  when  in  the  inclined  position ;  hence  the  bucket  is  equally 

7 


98  DOCK   ENGINEERING. 

effective  with  a  short  face  as  with  a  long  one,  and  the  former  outline  is 
better  adapted  for  discharging.  The  mouthpieces,  or  lips,  should  be  of  hard 
steel  ri vetted  to  the  face  of  the  buckets  which,  together  with  the  links  and 
pins,  are  also  of  steel  of  special  quality.  A  hole  or  two  in  the  front  is 
useful  for  the  escape  of  water.  Large  buckets  free  themselves  better  than 
small  buckets  from  adhesive  material. 

Shoots. — The  least  inclination  for  the  unassisted  discharge  of  mis- 
cellaneous material  is  somewhere  about  1  in  4 ;  but  this  is  not  always 
obtainable.  With  the  assistance  of  continuous  and  ample  flushing,  together 
with  some  manual  appliance,  such  as  a  pricker,  the  limit  may  be  raised  to 
1  in  10  for  mud,  1  in  15  for  clay,  and  1  in  20  for  sand. 

Tumblers. — The  top  tumbler  actuates  the  rotary  motion  of  the  buckets 
and  should  be  as  small  as  possible,  in  order  to  reduce  the  amount  of  inter- 
mediate gearing.  The  ideal  form  would  be  the  circular,  but  with  straight 
links  and  flat  backed  buckets,  a  square  or  pentagonal  section  must  be 
adopted.  The  latter  is  preferable,  as  it  brings  all  faces  of  the  tumbler 
equally  in  contact  with  the  buckets.  To  achieve  this  condition  with  a 
square  tumbler,  an  additional,  or  "  hunting,"  link  would  have  to  be  inserted 
at  some  point  in  the  chain.  The  bottom  tumbler  does  not  transmit  power 
and  should  be  made  of  large  diameter  to  diminish  friction,  say,  with  six 
or  more  sides.  It  is  suspended  from  a  cross  beam  on  the  dredger,  and  has 
to  be  readily  adjustable  to  the  depth  of  water  in  which  the  dredger  may 
be  working.  For  the  guidance  of  the  buckets,  the  lower  tumbler  should  be 
provided  with  large  flanges. 

Power, — Mr.  J.  J.  Webster,*  from  observation  of  a  large  number  of 
indicator  diagrams,  submits  the  following  empirical  formulae  for  determining 
the  indicated  horse-power  required  to  dredge  different  qualities  of  material 
under  varying  conditions  of  lift.  If  H  be  the  height  of  the  upper 
tumbler  shaft  from  the  surface  of  the  ground  to  be  dredged,  and  W  the 
number  of  tons  per  hour  to  be  dredged,  then  the  indicated  horse-power 
required  is  approximately — 

04  W  ^H  for  very  stiff"  clay  or  mud. 

•034  W  ^H  for  hard  clay  and  indurated  mud. 

•026  W  ^H  for  soft  mud  and  light  sand. 

The  illustrations  (figs.  54-61)  are  of  the  dredger  "  Cairndhu  "  and  one  of 
her  attendant  hopper  barges,  belonging  to  the  Clyde  Navigation. 

The  Dipper  Dredger,  which  is  almost  exclusively  an  American  type, 
being  much  used  in  connection  with  the  improvement  and  maintenance  of 
river  beds  and  channels  in  the  United  States,  is  so  identical  in  principle 
and  mode  of  action  with  the  steam  navvy  (p.  81  ante),  or  land  excavator, 
already  described,  that  there  is  no  necessity  to  make  more  than  a  very 
brief  and  passing  reference  to  it. 

*  Webster  on  *' Dredging  Operations  and  Appliances/*  Miiu  Proc  Inst,  C.E,, 
vol.  Izxxiz. 


HOPPER  BARGE. 


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lOO  DOCK   ENGINEERING. 

The  apparatus,  consisting  of  a  single  bucket  at  the  end  of  a  long  arm, 
is  mounted  upon  a  barge  in  any  suitable  position,  working,  for  instance, 
either  through  a  well  in  the  centre,  or  from  one  end.  After  being  lowered 
the  bucket  makes  a  curved  upward  cut^  the  contents  being  discharged  into 
a  hopper  through  the  bottom  of  the  bucket,  which  is  hinged.  The  machine 
is  capable  of  executing  cuts  at  anj  required  level,  down  to  a  depth  of  about 
35  feet.  Like  the  ladder  dredger,  it  is  not  suitable  for  use  in  an  exposed 
seaway,  but  it  has  done  very  elective  service  in  sheltered  positions,  and 
when  operating  under  favourable  conditions,  its  capabilities  may  be  gauged 
by  the  performances  of  its  prototype,  the  steam  navvy. 

A  machine  employed  in  the  construction  of  a  canal  connecting  the 
rivers  St.  Lawrence  and  Grasse,  with  a  bucket  capacity  of  2^  cubic  yards 
and  excavating  to  a  depth  of  20  feet  below  the  surface  of  the  water, 
removed  138,000  cubic  yards  of  indurated  material  in  a  period  of  183 
working  days  of  10  hours  each,  at  an  average  cost  of  4d.  per  cubic  yard, 
including  attendance,  upkeep,  and  renewals,  both  for  itself  and  the 
attendant  barges  and  tug."^ 

Grab,  or  Grapple,  Dredgers,  known  also  as  Clam-shell  dredgers  in  the 
United  States  (the  country  of  their  origin),  are  essentially  segmental 
scoops,  generally  two  quadrants,  which  rotate  about  a  central  pivot,  and 
which,  on  meeting  in  the  closed  position,  form  a  semi-cyliudrical  receptacle 
or  bucket.  On  the  same  principle,  grabs  have  been  constructed  with 
spherical  sides  in  two  or  three  parts.  This  latter  type  is  principally 
adapted  to  excavation  for  cylinder  and  circular  well  foundations.  Either 
apparatus  is  manipulated  in  connection  with  a  crane. 

The  grab  dredger  is  based  on  two  distinct  systems — the  single  chain 
and  the  double  chain.  The  former  system  is  exemplified  in  the  patents 
of  Wild,  Ooles,  Peters,  Cooper  and  Holds  worth,  and  others ;  the  latter  in 
the  Friestman  and  the  Kingston  dredgers. 

The  Wild  grab  has  a  single  chain,  leading  from  the  jib-head  of  the 
crane,  fitted  with  a  catch  in  the  form  of  a  half  ball,  or  hemisphere,  with 
the  flat  surface  uppermost.  Such  a  form  permits  the  downward  passage 
of  the  catch  between  two  small  tumblers,  but  prevents  its  rising  again, 
and  the  grab  from  closing,  until  the  bottom  is  reached,  when  the  chain 
becomes  slack  and  the  tumblers  are  opened  by  the  weight  of  a  sliding 
sleeve.  The  grab  can  then  be  closed  and  drawn  up  until  it  reaches  a 
point  where  a  ring  in  the  lifting  gear  engages  two  steel  hooks,  from 
which  the  grab  is  suspended  whilst  being  discharged.  The  hooks  are 
withdrawn  by  a  simple  contrivance  when  the  grab  is  slightly  lifted. 

The  action  of  the  Peters  machine  (figs.  62  and  63)  depends  upon  the 
gripping  of  the  lifting  chain,  prior  to  the  opening  process,  by  a  pair  of 
steel  arms,  which  are  actuated  and  controlled  by  a  roller,  bearing  against 
the  chain,  and  a  governing  rod,  attached  to  the  upper  edge  of  the  bucket. 

*Bogart  on  ''Dredging  Machines  in  Recent  Excavations  in  Large  Magnitude," 
Ninth  Int.  Navigation  Cong. ,  Dusseldorf ,  1902. 


GRAB,  OR  GRAPPLE,  DREDGERS.  lOI 

In  excavftting,  the  bucket  is  closed  hy  the  chKin,  which  continuee  taut 
during  lifting.  When  the  chain  is  slackened  the  roller  falls  and  allows  the 
grippers  to  engage.     Then,  on  hoisting,  tlie  grab  is  pulled  open. 

In  the  double  chain  system  of  the  Priettman  type  (figs.  64  and  65)  the 
outer  corners  of  the  bucket  are  connected,  by  hinged  arms,  to  a  horizontal 
bar,  or  crosa  piece,  which  is  capable  of  vertical  movement  in  the  central 
groove  of  the  frame.  One  chain  from  the  jib-head  ia  attached  to  this  bar, 
and  any  tension  in  it  causes  the  bucket  to  open  ;  the  other  chain,  from  the 
jib-head,  is  wound  round  a  drum  on  the  pivot,  the  unwinding  of  which, 
with  the  assistance  of  two  subsidiary  chains  connected  to  the  horizontal 
bar  previously  mentioned,  palls  the  latter  down  and  causes  the  bucket  to 


Figa.  62  and  63.— Section  and  Elevation  of  Peters'  Grab. 


The  single  chain  system  has  the  advantage  of  being  alhxable  to  an 
ordinary  crane,  while  the  double  chain  syatem  involves  the  provision  of  a 
special  crane,  but  it  has  the  following  important  points  in  ita  favour : — 

1.  It  has  fewer  working  parts,  and  those  of  less  delicate  adjustment, 

2.  The  opening  and  closing  of  the  bucket  can  be  effected  at  any  point 
in  the  lift,  whereas,  with  the  one  exception  of  the  Feters  machine,  a  single 
chain  grab  haa  always  to  he  lifted  to  the  height  of  the  suspending  piece 
before  discharge  can  be  made.  If  the  latter  should  close  upon  some 
immovable  object  below  water,  it  could  not  be  opened  again  without 
lowering  the  suspending  piece,  or  without  the  aid  of  a  diver.  A  falae 
or  empty  lift  bos  to  be  completed  as  well  as  a  full  one. 


DOCK  ENGINEERING. 


3,  The  strain  upon  a  single  chain  from  some  unseen  obstacle  might  cause 
a  fracture,  with  the  coneequeiit  loss  of  the  bucket.     With  a  double  chain 


the  risk  of  fracture  is  diminislied,  and  loss  of  the  bucket  could  only  occur 
in  the  event  of  both  chains  giving  way, 

i.  A  double  chain  grab  can  discharge  its  load  as  gradually  ss  may  be 


DAMS.  103 

considered  desirable,  whereas  the  action  of  a  single  chain  grab  is  instan- 
taneous. 

A.  grab  dredger  with  a  bucket  capacity  of  1  ton  may  be  assumed  capable, 
froui  actual  trial,  of  raising  from  50  to  GO  tons  of  mud  per  hour,  when  working 
in  from  15  to  20  feet  of  water.  Of  clay,  very  little  more  than  one-half  this 
amount  can  be  reckoned  upon. 

The  grab  is  an  excellent  tool  and  invaluable  in  con6ned  situations,  but  it 
is  scarcely  suitable  for  general  adoption  in  works  on  a  large  scale.  It  is  not 
an  economical  instrument  for  the  removal  of  stiff  clay;  its  best  performances 
are  in  regard  to  mud  and  soft  earth.  It  cannot  be  counted  upon  to  work 
with  the  same  regularity  and  evenness  as  the  ladder  dredger ;  in  fact,  its 
tendency  is  to  pit  the  surface  of  the  ground  with  a  series  of  hollows  and 
depressions.  But,  in  spite  of  these  drawbacks,  it  has  demonstrated  its 
utility  to  such  an  extent  that  it  is  looked  upon  as  an  essential  accompani- 
ment of  most  dock  and  harbour  undertakings. 

Cost  of  Dredging. — The  conditions  prevailing  in  regard  to  dredging  are 

of  so  variable  a  nature  that  no  information  respecting  the  cost,  at  any 

locality,   is  of  much   use   elsewhere.      Further    than   this,   the   available 

statistics  are  far  from   uniform,   and   there   is  considerable   diversity  of 

extent  in  the  operations  included.      It   can   only  be  said  broadly  that, 

within  ordinary   limits,   dredging   is   effected  at   some   price   between   a 

penny  and  half  a  crown  a  cubic  yard,  dLstributed,  roughly,  somewhat  as 

follows : — 

Suction  dredging,  Id.  to  6d. 

Grab  dredging,  3d.  to  8d. 

Bucket  dredging,  6d.  to  2s.  6d. 

These  figures  do  not  apply  to  rock-dredging,  the  cost  of  which  exceeds  the 
higher  limit,  often  very  considerably. 

AUXILIARY    APPLIANCES. 

Dams. — In  dock  construction,  a  dam  is  a  temporary  contrivance  for  the 
exclusion  of  water  from  a  site  during  the  progress  of  the  undertaking.  It 
is  accordingly  composed  of  material  susceptible  of  easy  removal,  either  in 
bulk  or  in  parts.  Timber  aud  clay  form  two  of  the  most  prominent  sub- 
stances for  the  purpose.  Stone  and  concrete  are  occasionally  used,  under 
restrictions  to  be  noted  later.  Iron  is  rarely  employed,  and  then  only 
with  a  view  to  its  ultimate  incorporation  in  the  permanent  work. 

In  spite  of  its  temporary  character,  a  dam  should  be  substantially  made. 
The  damage  and  delay,  to  say  nothing  of  possible  loss  of  life,  resulting  from 
the  failure  of  any  part  of  it,  during  a  critical  period,  would  far  more  than 
counterbalance  any  economy  in  construction.  Too  much  stress  cannot  be 
laid  upon  this  point.  It  is  infinitely  better  to  err  on  the  side  of  excessive 
strength  than  to  run  the  risk  of  disaster  through  an  insufficient  margin  of 
stability. 


104  DOCK   ENGINEERING. 

In  nearly  every  case,  clay  is  the  material  mainly  relied  upon  for  the 
staunchness  of  a  dam.  It  must  be  judiciously  selected  :  free  from  stones, 
roots,  and  soil;  not  of  a  marly  or  brittle  nature,  but  tenacious  and  adhesive; 
well  tempered,  watered,  and  worked  to  a  proper  consistency.  When  these 
points  are  carefully  attended  to,  the  resultant  clay  pitddUf  as  it  is  termed, 
is  capable  of  forming  a  thoroughly  impervious  barrier.  If  clay  of  an 
inferior  quality  be  used,  there  is  sure  to  be  trouble  with  leaks  and 
in  bursts. 

Temporary  dams  may  be  classified  according  to  their  composition,  as 

follows : — 

Earth  danis, 

Timhivr  dams. 

Stone  dams. 

Concrete  dams. 

Iron  dams. 

Earth  Dams  are  peculiarly  appropriate  to  situations  where  there  is  ample 
space  and  where  a  very  slight  elevation  is  required,  as  in  shallow  water. 
They  simply  consist  of  a  mound  of  clay,  or  of  a  hearting  of  earth,  covered 
with  an  outer  layer  of  clay,  deposited  by  tipping  from  waggons,  skips,  or 
hopper  barges.  Under  the  action  of  tipping,  the  mound  has  a  decided 
tendency  to  subside,  and  this  is  still  further  accentuated  by  the  softening 
effect  of  water  upon  the  material,  so  that,  in  any  case,  long  flat  slopes  are 
inevitable,  and  hence  plenty  of  room  is  an  absolute  necessity  for  this  class 
of  dam.  It  is  advisable  where  the  natural  surface  of  the  ground  is  mud  or 
silt,  to  excavate  the  site  of  the  dam  down  to  a  solid  stratum,  better  able 
to  support  an  imposed  load  and  to  make  a  watertight  joint  with  it.  This 
last  is  an  important  point,  as,  if  the  stratum  below  a  dam  be  pervious,  water 
may  be  forced  through  it  under  external  hydrostatic  pressure.  An  example 
of  an  earth  dam  is  given  in  ^g,  186. 

Tiinher  Dams  are  frames  of  woodwork  with  or  without  an  enclosure  of 
clay  puddle.     They  are  subdivisible  into 

(a)  Skin  dams  or  sheeting  dams. 
(6)  Cofferdams. 

Skin  Dams  consist  of  a  single  row  of  sheeting  piles,  of  whole  or  half 
timber,  retained  by  tiers  of  horizontal  walings.  Lacking  sufficient  stiffness 
in  themselves,  they  have  to  be  supported  by  perpendicular  or  raking  shores 
abutting  upon  a  firm  surface.  Skin  dams  are  very  suitable  for  adoption  in 
front  of  quay  walls  which  it  is  desired  to  underpin,  reface,  or  repair.  In 
such  cases  the  wall  forms  a  convenient  surface  for  the  shore  abutments,  and 
the  outer  hydrostatic  pressure  is  transmitted  to  the  wall  through  the 
medium  of  the  shores.  The  walings  should  be  spaced  at  intervals  corre- 
sponding as  nearly  as  possible  with  the  extent  of  zones  of  equal  hydrostatic 
pressure.  The  amount  and  distribution  of  this  pressure  is  calculable  upon 
the  same  principles  as  those  formulated  in  Chapter  viii.,  for  dock  gates. 


COFFERDAMS.  IO5 

On  grounds  of  stiffness  and  strength,  whole  timber  piling  is  preferable 
to  half  timber  piling,  though  a  method  very  commonly  adopted  is  that  of 
-driving  whole  timber  guide  piles,  with  intervening  bays,  or  panels,  of  half 
timber  piles.  The  guide,  or  king  piles  are  provided  with  pointed  shoes,  but 
the  intermediate  piles  are  shod  with  wedge-shaped  shoes.  If  an  edge  or  side 
of  each  pile  foot  be  splayed,  the  process  of  driving  will  cause  it  to  draw 
more  closely  to  the  adjoining  one,  and  so  produce  continuous  contact.  For 
the  same  reason  it  is  a  good  plan  to  pitch  or  set  a  whole  bay  of  piles  and 
filightly  drive  them  all,  before  proceeding  to  a  conclusion  of  the  process  with 
any  one  of  them.  Furthermore,  the  sides  of  adjoining  piles  may  be  alter- 
nately tongued  and  grooved  or,  alternatively,  both  grooved,  for  the  reception 
of  a  vertical  strip  of  flat  iron,  say,  from  2  to  3  inches  wide  by  ^  inch  in 
thickness.  The  former  method  is  of  greater  service  for  maintaining  the 
regularity  of  the  piles  in  driving. 

Skin  dams  need  not  necessarily  be  piled.  A  method  very  successfully 
practised  at  Liverpool  (fig.  160)  is  that  of  constructing  skin  dams  ashore,  in 
flitches  of  100  lineal  feet  or  more.  They  are  then  launched  from  the  quay, 
xip-ended  with  the  aid  of  a  floating  crane  and  some  iron  rail  ballast,  and 
inserted  in  a  trench  previously  dredged  to  receive  them.  The  dam  is  finally 
-shored  to  the  wall  at  uniform  intervals,  forming  bays  of  from  10  to  12  feet 
in  length.  The  edges  of  adjoining  piles  are  rendered  a  watertight  joint  by 
means  of  1-inch  triangular  wooden  fillets  nailed  to  the  piles  and  closely 
•cramped  together.  Torch-wick  has  also  been  used  as  a  watertight  packing. 
These  flitches  proved  very  successful  and  were  used  repeatedly,  being  trans- 
ferred from  one  site  to  another  as  occasion  required.  A  length  of  over  4,500 
feet  of  dock  walls  was  underpinned  in  this  manner.  The  cost  of  the  flitches, 
including  maintenance  and  removal,  varied  between  £13  and  £18  per  lineal 
foot. 

A  skin  dam  has  been  made  self-supporting  by  constructing  it  in  the 
form  of  a  bottomless  box  for  work  which  could  be  carried  on  in  the  interior. 
The  outer  faces  then  afford  one  another  mutual  support  through  the  medium 
of  cross  shores  and  struts.  The  method  as  applied  to  the  construction  of  a 
dock  wall  at  Liverpool  is  shown  in  fig.  133.  It  will  be  noticed  that  the 
outer  sheeting  consists  of  a  series  of  horizontal  timbers,  ranging  in  thickness 
from  12  inches  at  the  bottom  to  3  inches  at  the  top.  Water- tightness  is 
effected  by  means  of  torch-wick  joints.  Inside  the  sheeting  there  is  a 
continuous  row  of  piles  driven  down  to  a  rock  substratum,  and  acting  as  a 
support  for  an  overhead  crane  road.  The  dam  in  question  was  246  feet  long, 
in  15-foot  bays.     The  cost  was  rather  less  than  £35  per  foot  run. 

In  all  cases  the  foot  of  a  skin  dam  has  to  be  amply  protected  and  covered 
by  a  thick  layer  of  clay  puddle,  which  will  need  replenishing  from  time  to 
time  as  the  clay  subsides. 

Cofferdams  consist  essentially  of  two  timber  faces  enclosing  a  hearting, 
generally  of  clay  (fig.  66),  but  occasionally  of  stone.  They  are  of  more  solid 
^construction  than  skin  dams,  but,  at  the  same  time,  they  offer  some  risks  of 


Io6  DOCK  ENGINEERING. 

failure  from  which  the  former  are  exempt.  The  continual  subsidence  of  the 
clay  hearting  involves  more  than  the  mere  replacement  of  the  disappearing 
material,  since  the  latter  in  sinking  exerts  powerful  pressure  of  a  hydro- 
static character  against  the  sides  of  the  dam,  producing  a  strong  tendency  to 
rupture,  which  has  indeed  taken  place  in  at  least  one  instance  to  the 
author's  knowledge.  Again,  the  presence  of  horizontal  walings  in  the 
interior  of  the  dam  for  the  guidance  of  the  piles  in  their  descent,  and  of 
transverse  ties,  is  a  source  of  much  troublesome  attention,  because  the 
clay,  in  settling,  leaves  cavities  and  interstices  immediately  underneath 
these  parts,  which  serve  as  channels  and  ducts  for  leakages.  The  evil  may 
be  minimised  by  the  withdrawal  of  the  inner  waling,  after  the  driving  of  the 
piles  and  before  the  insertion  of  the  clay,  also  by  the  substitution  of  timber 
diaphragms,  extending  from  top  to  bottom,  for  transverse  tie-rods.  Where 
rods  or  bars  are  used,  several  flat  washers  or  plates  of  large  area  with  per- 
forations near  the  upper  edge,  for  the  insertion  of  the  through  bolts,  will 
sometimes  serve  to  check  the  passage  of  water  in  case  of  a  slight  sinkage 
of  the  clay. 

From  these  considerations  it  is  clear  that  no  useful  object  per  se  is 
served  by  any  great  thickness  of  clay  puddle ;  the  disruptive  force  is  only 
increased  thereby,  and  sources  of  leakage  are  more  difficult  to  locate.  A 
minimum  width  of  5  feet  in  the  interior  of  a  cofferdam  will  generally 
prove  an  adequate  allowance  for  impermeability,  but,  on  the  other  hand,  as 
regards  the  stability  under  external  pressure,  the  height  of  the  dam  will 
exercise  most  influence  in  determining  its  width,  though  this  factor  can  be 
discounted  to  some  extent  by  the  use  of  auxiliary  shoring. 

The  only  external  force  at  work  upon  a  cofferdam  is  the  hydrostatic 
pressure  against  its  outer  face.  If  we  call  this  P,  the  height  of  the  water  A, 
and  the  weight  of  a  cubic  foot  w^  then  the  pressure  per  foot  run  (as  explained 
in  detail  in  Chapter  viiL),  is 

2  ' 

and  the  overturning  moment  about  the  base,  the  centre  of  pressure  being  at 
one-third  of  the  height  from  the  ground, 

Now,  the  dam  derives  its  stability  in  varying  proportions  from  three 
sources.  These  are — (1)  its  dead  weight  or  inertia,  treated  as  a  heavy, 
detached  mass  ;  (2)  its  resistance  to  transverse  stress,  treated  as  a  cantilever 
firmly  fixed  in  the  ground ;  and  (3)  the  support  afforded  by  the  external 
strutting,  if  any. 

(I)  The  moment  of  resistance  due  to  the  intrinsic  weight  of  the  struc- 
ture is 

Mi  =  wx  ^,         .        .        .        •         (6) 


COFFERDAMS.  107 

where  w  is  the  weight  of  the  whole  dam  per  lineftl  foot  and  b  the  breadth  of 
the  base. 

(2)  Conaidered  as  a  loaded  caatilever,  the  outer  row  of  pilea  will  be 
subjected  to  tension  and  the  inner  row  to  compression,  or  both  rows  will  be 
subjected  to  tension  and  compression  alike,  according  to  whether  we  treat 
the  atructure  as  rigid  or  deformable.  Assuming  the  former  condition,  if  o 
be  the  sectional  area  of  single  piling  per  foot  ran  andy,  and/,  the  resistance 
of  the  material  per  unit  area  to  tension  and  compreaaion.  respectively,  then 
the  linear  moment  of  resistance  is 

Mj  =  a/.6  or  o/.* (7) 

ABsamiDg  the  latter  condition,  the  resistance  of  each  row  of  piles  must  be 
cocsi'lered  disconnectedly,  and 

M,-i«/.rfand  Ja/,rf.     ...         (8) 
where  d  stands  for  the  depth,  or  thickness,  of  the  piles. 


Fig.  66.~Coff^rdaiD  at  Liverpool. 

(3)  If  a  be  the  sectional  area  of  one  of  the  external  struts  at  a  distance,  S, 
from  the  base,  and  s  the  horizontal  distance  apart  of  the  struts,  then  the 
linear  moment  of  resistance  due  to  any  number  of  such  struts  is 

M,.j!4-' (9) 

This  is  on  the  assumption  that  the  struts  lie  directly  in  the  axis  of  stress. 
Should  this  not  be  the  case,  and  the  angle  of  inclination  to  the  horizontal  be 
#,  we  must  write 

M,.2"--^^~"-'        ....      (10) 

A  similar  and  additional  modification  would  have  to  be  made  it  the  struts 
were  also  raking  on  plan. 


I08  DOCK  ENGINEERING. 

'  Combining  all  these  elements,  we  have  for  equilibrium 

The  exact  distribution  of  stress  being  inde term i  Date,  a  very  large  factor  of 
safety  is  essential. 

The  stress  in  the  internal  tie-rods  can  only  be  adequately  covered  by 
asauming  the  clay  to  be  in  a  fluid  condition  and  exerting  a  pressure  propor- 
tionate to  its  specific  gravity. 

Fig.  66  shows  a  cofferdam  as  employed  in  doolc  constrnction  at  Liver- 
pool. It  was  straight  in  plan  between  its  extreme  abutments  for  a  total 
length  of  260  feet,  divided  into  15-feet  bays  by  cross  diaphragms  of  3-inch 
planking,  thus  obviating  tlie  use  of  internal  tie-roda.  The  height  was 
38  feet  and  the  bottom  and  top  internal  widths  2u  feet  and  1 2  feet  respec- 
tively. It  derived  some  additional  support  from  raking  shores  not  shown 
in  the  figure.  A  dam  of  this  type  can  be  constructed,  maintained,  and 
removed  at  a  cost  ranging  from  £35  to  £50  per  foot  run,  much  depending 
upon  the  nature  of  the  site  and  the  duration  of  the  work. 


Fig.  67.— Coflenlam  at  Hull. 

Fig.  67  shows  a  cofferdam  used  at  the  Alexandra  Dock,  Hull.  It  was 
segmental  in  form,  with  a  radius  of  2561  feet  and  a  length  of  461  feet.  The 
piles  were  driven  vertically,  enclosing  a  space  5  feet  wide.  Five  sluice 
openings  were  formed  to  allow  the  tide  to  flow  in  and  out  until  the 
completion  of  the  dam.* 

■  Hurtzig  on  "  The  Alexandra  Dock.  Hull,"  Jfiw.  Proc.  Jnsl.  C.E.,  vol  xcii. 


CONCRETE  DAMS.  IO9 

Fig.  68  is  the  section  of  a  cofferdam  adopted  »t  Limerick  in  coimectioQ 
with  the  rebuilding  of  a  dock  wall  whicb  had  failed,  the  length  being 
430  feet.* 

Stone  Dame  are  similar  in  construction  to  earthwork  dams,  consisting  of 
a  mound  of  light  stone  rubble  (such  as  chalk)  deposited  and  overlaid  with 
claj  to  form  a  watertight  skin.  Tliis  material  is  also  used  as  filling  for  the 
interior  of  a  cofferdam,  as  exemplified  at  Ardrossan  harbour  t  (figs.  €9  iiud 
70). 

Concrete  Dams. — A  somewhat  novel  and  ingenious  experiment  in  dam 
construotioa  has  been  successfully  tried  at  Liverpool.  A  wall  was  built  of 
large  concrete  blocks  (each  containing  100  cubic  feet)  bedded  in  hydraulic 
mortar,  with  a  sheet  of  ordinary  brown  paper  laid  between  the  blocks  in 
each  joint.  The  paper  adapted  itself  to  the  surface  of  the  bed  and  allowed 
the  blocks  to  obtain  a  uniform  bearing  upon  one  another,  while  at  the  same 


Fig.  68.— CofferdacD  at  Limerick. 

time  it  prevented  any  actual  adhesion.  The  stability  of  the  structure 
depended,  therefore,  entirely  upon  the  resistance  of  the  blocks  to  sliding 
friction,  which  proved  to  be  ample  for  the  purpose.  The  dam  in  question 
was  built  upon  the  outer  sill  of  a  lock,  100  feet  wide  between  side  walls. 
The  sill  had  a  straight  outer  face  and  a  curved  inner  one  for  the  ultimate 
reception  of  gates.  The  area  of  the  sill  was  nearly  400  square  yards,  with  a 
minimum  width  of  25  feet.  The  front  of  the  dam  was  a  vertical  plane,  the 
back  being  stepped.  The  total  height  above  the  sill  was  42  feet,  at  which 
level  a  roadway  was  formed  for  traffic.     High  water  of  ordinary  spring  tides 


no  DOCK   BNGINEEBING. 

«ame  up  to  33  feet  above  the  aill,  but  during  equinoctial  galea  the  waves 
frequently  surged  to  the  top  of  the  dam  and  broke  over  tlie  roadwaj. 

Iron  Dams  usually  take  the  form  of  caiasonB,  but  they  are  bj  no  means 
common.  The  most  striking  iastaace  of  their  adoption  is  perhaps  in  con- 
nection with  the  construction  of  the  Thames  Embankment.  The  caiesons 
were  of  wrought-iron  in  half  oval  segments,  with  upright  Sanges  at  each 
end,  so  that  when  the  halves  were  bolted  together  they  formed  a  complete 
oval,  12  feet  6  inches  long  by  7  feet  wide  in  the  centre  and  4  feet  6  inches 
deep.     The  plates  were  J  and  |  inch  thick.     Angle  irons  were  bolted  round 


—Dam  Bt  Ardrossan, 


Fig.  70. — Dam  at  Ardrossan. 

the  top  of  the  rings,  enabling  them  to  be  firmly  secured  to  each  other  in  the 

vertical  position.  A  watertight  joint  was  formed  by  a  guide  pile,  lOJ  by 
6^  inches  section,  fitting  into  a  groove  between  adjoining  caissons.  The 
dam  was  further  stayed  by  a  few  surrounding  piles  which  maintained  the 
caissons  rigid  and  vertical  in  their  descent.  The  gross  cost  of  this  dam  was 
£30  per  lineal  foot  as  compared  with  £20,  the  gross  cost  of  a  timber  cofferdam 
in  a  similar  position.  Some  of  the  iron  caissons  were  incorporated  in  Che 
permanent  work  at  an  allowance  of  £%  per  lineal  foot.     With  this  qualili- 


PUMPS.  1 1 1 

•cation  it  may  be  added  that  the  nett  costs  of  the  two  dams  were  about  £15 
and  £17  respectively. 

For  tidal  work  a  dam  may  be  conveniently  contrived  by  sinking  iron 
pontoons  and  banking  them  up  and  between  with  clay.  The  height  of  such 
a  dam  is  necessarily  small,  but  it  materially  increases  the  period  of  working 
within  the  enclosed  area. 

Pomps. — The  subject  of  pumping  demands  the  most  careful  and  earnest 
attention  of  the  dock  engineer,  seeing  that  the  practicability  and  success  of 
his  undertakings  depend  largely  upon  the  efficiency  of  his  pumping  arrange- 
ments. Some  evidence  of  this  will  be  afforded  in  subsequent  chapters,  but 
the  fact  is  almost  sufficiently  obvious  in  itself. 

There  are  many  varieties  of  pumps  on  the  market,  each  with  its  own 
special  features  and  capabilities.  A  study  of  the  catalogues  of  well-known 
manufacturers  will  generally  enable  a  satisfactory  selection  to  be  made  for 
the  particular  purpose  required,  and  the  following  remarks  are  simply 
appended  by  way  of  indicating  such  practical  points  as  seem  worthy  of 
consideration  in  exercising  a  choice. 

Valve  Pumps — that  is  to  say,  lift  pumps  and  force  pumps,  or  any  com- 
bination of  these  in  which  the  action  depends  upon  the  alternate  opening 
and  closing  of  small  valves — are  only  suitable  for  comparatively  clear  water. 
Water  which  is  highly  charged  with  solid  matter  in  suspension  and  with 
floating  objects  is  very  likely  to  derange  these  delicately  adjusted  parts  and 
to  put  the  pump  out  of  action.  The  gritty  nature  of  sand  causes  excessive 
wear  of  the  leather  washers  and  packings,  necessitating  frequent  renewals. 
Ohips  and  gravel  lodge  in  the  valves  and  prevent  them  from  closing.  The 
jambing  of  the  bucket  packings  may  cause  serious  trouble  owing  to  the 
great  force  frequently  required  to  release  the  bucket.  For  drainage 
purposes  in  trench  excavations,  a  lift  pump  has  this  advantage  over  a  force 
pump,  in  that,  if  the  working  should  by  any  accident  become  suddenly 
flooded,  the  lift  pump  can  still  discharge  its  function,  being  actuated  from 
the  summit  level,  whereas  the  machinery  of  a  force  pump  is  in  the  bottom 
and,  consequently,  would  be  submerged. 

A  very  handy  drainage  pump  for  use  in  confined  situations  is  the 
PuUometer.  It  represents  a  rather  unusual  principle  in  pumping.  The 
action  consists  in  the  alternate  admission  and  exclusion  of  steam  to  and 
from  adjoining  chambers.  The  water  is  forced  out  of  one  of  tlie  two 
chambers  by  steady  pressure  until  it  sinks  to  the  level  of  the  discharge 
orifice,  at  which  point  the  steam  obtains  a  free  vent,  and  being  in  contact 
with  a  large  surface  is  so  rapidly  condensed  as  to  cause  a  vacuum  in  the 
chamber  and  draw  over  the  steam  ball  at  the  top  which  closes  the  aperture 
and  transfers  the  supply  to  the  next  compartment.  Meanwhile,  continued 
condensation  in  the  empty  chamber  increases  the  vacuum,  which  is  filled  by 
a  fresh  supply  of  drainage  water  through  the  lower  valve  leading  from  the 
suction  pipe.  The  apparatus  is  compact  and  easily  suspended  by  a  rope  or 
chain  in  any  desired  position. 


1 1  2  DOCK   ENGINEERING. 

Other  appliances  for  dealing  with  small  quantities  of  water  are  the 
simple  haml-piimp  and  the  ejector.  The  former  is  of  the  ordinary  bucket 
type  of  pump,  worked  by  iiand.  The  ejector  is  actuated  by  hydraulic  or 
by  steam  pressure.     The  principle  is  that  of  forcing  a  small  jet  or  current 


Fig.  TOn. — Pulsomete 

A,  Pump  chamber. 

B,  Air  cbaniber. 

C,  Suction  pipe. 

D,  Diachsrgi!  orifice. 

E,  Inlet  valve. 

F,  Outlet  valve. 


I,  Steam  inlet  valve 

J,  Neck. 

K,  Steampipe. 


through  a  nozzle  in  the  interior  of  a  discharge  pipe  of  slightly  greater 
diameter.     Drainage  water  is  drawn  up  from  the  sump,  by  suction,  to  fill 

s  created. 

g  "slurry"  or  liquid  mud,  water  charged  with  sand,  gravel, 
cement  scum,  floating  material,  and,  in  fact,  the  general  drift  and  debris 


PUMPS.  113 

which  find  their  way  into  a  pumping  well  in  excavations  carried  on  under 
circumstances,  perhaps  more  peculiarly  characteristic  of  dock  work  than 
of  any  other  branch  of  engineering,  pumps  of  the  strongest  and  simplest 
construction  are  advisable.  Such,  for  instance,  are  the  chain  pump  and 
the  centrifugal  pump. 

The  first  of  these  which  has  demonstrated  its  utility  from  remote  ages, 
being  originally  an  invention  of  the  Chinese,  consists  of  a  series  of  flat 
blades,  strung  at  regular  intervals  upon  two  parallel  endless  chains.  These 
chains  liang  vertically,  being  suspended  from  a  revolving  reel  or  barrel  at 
the  summit,  over  which  they  travel  continuously.  The  descent  is  in  the 
open,  but  on  reaching  the  bottom  the  blades  enter  the  splayed  orifice  of 
a  rectangular  funnel  extending  upwards  to  the  point  of  discharge.  The 
blades  tit  the  interior  of  the  funnel  sufficiently  closely  to  take  the  bulk  of 
the  enclosed  water  with  them  without  incurring  excessive  friction  against 
the  sides.  The  pump  acts  admirably  in  lifting  with  absolute  impartiality 
water,  mud,  pieces  of  brick,  wood,  stone,  and  concrete ;  any  substance,  in 
short,  which  can  enter  the  funnel.  The  only  thing  to  check  its  action  is 
the  intrusion  of  a  chance  wedge  or  plank  end,  transversely,  between  the 
buckets  and  the  orifice  The  blades,  which  are  of  wood,  are,  of  course, 
subject  to  a  considerable  amount  of  abrasion  and  have  to  be  replaced  from 
time  to  tiuie,  but  repairs  of  this  kind  are  easily  effected.  A  stock  of  fresh 
blades  is  kept  at  hand,  and  the  operation  of  removing  a  damaged  blade 
is  simply  that  of  taking  out  the  split  keys  which  hold  it  in  position  on 
the  chain. 

Cliain  pumps  with  rectangular  blades,  2  feet  long  and  6  inches  wide, 
14^inch  centres,  running  at  a  speed  of  500  feet  per  minute  have  proved 
capable  of  discharging  regularly  600  tons  of  water  per  hour,  which 
represents  an  efficiency  of  slightly  less  than  70  per  cent.  The  speed  may 
be  increased  to  600  or  700  feet  per  minute,  with  a  corresponding  greater 
discharge,  but  such  speeds  throw  an  undue  strain  upon  the  apparatus. 

The  action  of  a  centriftugal  pump  is  the  revolution  of  a  series  of  blades 
radiating  from  a  common  axis,  by  means  of  which  the  water  is  whirled 
round  in  a  confined  space  until  it  acquires  sufficient  velocity  to  be  projected 
up  the  discharge  pipe.  The  blades  are  short,  tliick,  and  curved  in  form. 
This  class  of  pump  will  '*  throw  "  a  good  deal  of  extraneous  material,  but 
there  is  always  the  possibility  of  a  fairly  large  object  being  drawn  through 
the  suction  pipe  and  getting  jambed  in  the  blades,  which  are  less  accessible 
for  repairs  than  those  in  a  chain  pump.  The  usual  sizes  of  such  pumps  for 
temporary  duties  varies  between  6  and  18  inches  diameter. 

Before  leaving  the  subject,  it  will  be  well  to  observe  that  the  provision 

of  a  duplicate  pumping  system  is  a  commendable  arrangement.     One  set  of 

pumps  might  easily  break  down  at  a  critical  moment,  and  even  if  the 

amount  of  pumping  is  sufficiently  small  to  allow  a'dequate  intervals  for 

cleaning  and  repairs,  yet  an  auxiliary  pump  is  an  advisable  precaution 

for  unforeseen  contingencies. 

8 


114 


DOCK  ENGINEERING. 


The  placing  of  pumps  upon  the  framework  of  dams,  though  sometimes 
unavoidable,  is  always  to  be  deprecated.  The  vibration  set  up  by  the 
machinery  inevitably  causes  settlement  and  induces  leakage. 

Cranes  for  constructive  work  are  mostly  of  the  locomotive  type,  and 
the  power  usually  ranges  from  3  to  10  tons  lifting  weight.  The  heavier 
machines  are  fitted  with  two  gearings,  by  which  a  light  load  can  be  lifted 
speedily,  or  the  full  working  load  at  a  more  moderate  rate.  There  are 
four  motions — travelling,  jibbing,  lifting,  and  slewing.  For  raising  and 
depositing  heavy  loads  within  a  short  distance,  derrick  cranes  may  be 
employed.  Owing  to  the  broader  base  afforded  by  their  outlying  arras, 
these  cranes  have  greater  stability  than  the  locomotive  cranes,  but  they 
lack  the  rapid  travelling  movement  of  the  latter. 


■It 


Figs.  71,  72,  73,  74,  76,  and  76.— Lewis  Bars  and  Clips. 


Overhead  travellerSy  or  ga/ntries^  are  useful  appliances  for  dealing  with 
excavation  in  trenches.  They  are  built  on  the  same  principle  as  the 
Goliath,  illustrated  in  fig.  40,  but  are  generally  much  lighter,  and  the 
lifting  power,  in  the  generality  of  cases,  does  not  exceed  about  1 5  tons. 

Ships  are  buckets  of  various  forms,  used  for  the  transfer  of  material  by 
means  of  cranes  or  travellers.     They  hold  from  ^  to  1^  cubic  yards,  and 


CONSTRUCTIVE   PLANT. 


115 


are  genei*ally  either  round  with  a  pivoted  handle,  or  square  with  a  hinged 
bottom. 

Lewis  bars  and  clips^  for  the  lifting  of  masonry  and  concrete  blocks, 
are  of  various  designs.  In  the  former  case,  the  hold  is  obtained  either 
by  turning  the  bar  through  an  angle  or  by  wedging  it.  In  the  latter 
case,  the  tension  in  the  chain  causes  a  closing  of  the  jaws,  and  the  block 
cannot  be  released  until  the  chain  is  slackened.  A  number  of  them  are 
illustrated  in  figs.  71-76. 

Coiutructive  Plant  at  Keyham  Dock  Works, 

As  an  example  of  the  variety  and  amount  of  plant  required  for  dealing 
with  dock  work  on  a  large  scale,  a  statement  of  the  plant  used  at  Keyham 
Dockyard  Extension  Works  is  quoted  from  Mr.  Whately  Eliot's  paper  on 
the  subject : — * 

**  The  works  occupy  ground  to  the  extent  of  113  acres,  of  which 
35  acres  are  situated  above  high  water  mark,  being  chiefly  land  which 
has  been  reclaimed,  in  former  years,  from  that  part  of  the  Tamar  called 
the  Hamoaze.  The  remainder  of  the  area,  78  acres  in  extent,  is  the 
foreshore  of  mud  from  high  water  line  to  about  low  water  of  spring 
tides,  the  range  of  tide  being  15^  feet.  The  works  compose  a  tidal  basin 
of  10  acres  and  a  closed  basin  of  35^  acres,  divided  by  a  space  about 
900  feet  iti  width,  in  which  there  will  be  three  large  graving  docks  and 
an  entrance  lock.  The  whole  of  the  river  front  of  the  site  is  enclosed, 
during  construction,  by  a  cofferdam,  to  exclude  the  tidal  and  river  water. 
This  cofferdam  is  more  than  a  mile  in  length." 


List  of  Plant. 


Ten  vertical  boilers, 

Six  40-H.P.  winding  engines, 

Six  20-H.P. 


f » 


»f 


>i 


>> 


f » 


11 


>f 


f» 


Two  40-H.P.  fixed 
Three  25-H.P.  portable 
Seven  20-H.P. 
Four  1.S-H.P. 

Four  15-inch  cylinder  locomotives, 
Four  12-inch 
Four  10-inch 
Two  9-inch 


i> 


»} 


»i 


)» 


f » 


>f 


6-wheeled, 

4 

4 

4 


If 


t) 


Eight  10-ton  steam  cranes. 
Two  7-ton  ,,  ,, 

Thirty-seven  5-ton  steam  cranes. 


Used  for  hauling  waggons  and  mud 
scoops. 

Used  for  dynamos,  pumps,  sawmills, 
and  other  purposes,  in  the  yard. 

Used  in  conveying  materials  from 
landing  jetties  and  to  various  parts 
of  works. 

Used  in  landing  goods  at  jetties,  lift- 
ing materials  from  the  trenches, 
lowering  concrete  and  masonry  into 
the  trenches  and  setting  masonry, 
and  various  other  purposes.  Four 
of  the  10- ton  cranes  are  fitted  to  be 
worked  as  steam  navvies. 


Min,  Proc  I.  Mech,  E.,  and  Engineering,  28th  July,  1899. 


ii6 


DOCK   ENGINEERIJNG. 


Sixteen  lO-ton  derrick  cranes, . 
Two  10-ton  Goliaihs,  60-feet  span,  . 
Ten  steam  winches,  8-inch  cylinders, 
Four  gas  engines,     .... 
One  oil 
Four  gas 


»» 


>f 


a 


Six  dynamos. 

Forty  Wells'  lamps. 

Five  rock  drills,  *'LarmuthJ 

Four        „  "Little  Hercules." 

Two  air  compressors. 

Six  Taylor  concrete  mixers. 

Two  Sissons  and  White  pile  drivers. 

Four  Ruston  and  Procter  steam  navvies. 

Two  Baxter  stone  breakers. 

Eight  Hone  grabs ;  four  other  grabs. 

Seven  patent  mud  scoops. 

One  18-inch  duplex  pump. 


Used  for  setting  masonry. 

Used  for  stacking  granite  in  yard. 

For  pile  engines,  kc. 

I    For  concrete  mixers. 

For  workshops  and  yard. 

One  18-inch  large  rocker  pump. 
Three  12-inch  centrifugal  pumps. 
Two  10-inch  „  „ 

Sixteen  6-inch    to   8-inch    direct-acting^ 

pumps. 
Two  tugs,  500  I.  H.  P. 

300      „ 
Two  suction  dredgers;  suction  pipe  22 

inches  in  diameter. 
Two  800-ton  steam  hopper  barges. 
Six  1,250- ton  ordinary  ,,         „ 
Twelve  f^mall  barges  of  various  sizes. 


117 


CHAPTER   IV. 

MATERIALS. 

Concrete  — The  Aggregate  —  The  Matrix  —  Portland  Cement  — Its  Fineness, 
Strength,  Rate  of  Setting,  and  Soundness— Adulterants  of  Cement— Propor- 
tion OF  Water— Action  of  Sea  Water  upon  Concrete— Case  of  Disintegration 
AT  Aberdeen— Official  Explanation  and  Possible  Causes— Dr.  Micha£lis  on 
Cement  in  Sea  Water— Suggested  Protective  Measures — Practical  Notes  on 
Mixing  Concrete- Strength  of  Concrete— Sample  Compositions — Iron  and 
Steel— Alloys  with  Manganese  and  Nickel — Impurities— Varieties  of  Cast 
Iron,  Wrought  Iron,  and  Steel — Defects  in  Manufactured  Iron— Specifica- 
tions FOR  Castings,  Plates,  and  Bars — Working  Strength — Tests— Weights — 
CoRKOSioN  of  Iron  and  Steel — Effect  of  Sea  Water  on  Dock  Gates— Pre- 
servative Agents — Timber— Varieties  used  for  Dock  Work — Selection  of 
Timber — Destruction  and  Decay — Means  of  Preservation— Stone— Kinds 
Employed — Destructive  Agencies. 

The  dock  engineer  has  to  deal  with  a  great  variety  of  materials  common 
to  many  other  branches  of  constructive  work,  and  the  bulk  of  the  informa- 
tion requisite  for  a  tliorough  appreciation  of  their  respective  qualities  and 
uses  must  naturally  be  sought  in  treatises  dealing  exclusively  with  such 
matters.  At  the  same  time,  there  are  other  materials  not  so  commonly 
employed,  and  there  are  applications,  adaptations,  and  standards  peculiarly 
characteristic  of  dock  work,  and  it  is  mainly  with  a  view  of  treating  these 
special  features  that  the  following  notes  have  been  compiled.  In  order  to 
maintain  some  continuity  of  form,  however,  it  will  be  necessary  to  touch 
upon  each  subject  in  its  general  aspect,  but  this  will  be  done  in  the  lightest 
possible  manner,  and  details  will  be  reserved  for  those  questions  more 
particularly  germane  to  the  province  of  maritime  engineering. 

The  materials  selected  will  be  dealt  with  in  the  following  order : — 

Concrete.  Timber, 

Iron  and  Steel,  Stone, 


CONCRETE. 

Concrete  is  the  term  applied  to  an  admixture  of  various  mineral  sub- 
stances which  become  incorporated  into  a  solid  body  under  chemical  action. 
It  consists  essentially  of  two  parts — the  aggregate  and  the  matrix. 

The  aggregate  is  a  heterogeneous  mass  of  one  or  any  number  of  the 
following  materials : — Slag,  shingle,  burnt  clay  or  earthenware,  broken 
stone,  broken  brick,  gravel  and  sand,  mixed  in  varying  proportions. 

The  mairix  consists  of  hydraulic  lime  or  cement,  combined  with  water. 


ii8 


DOCK   ENGINEERING. 


The  above  definition  and  classification  do  not  include  three  compositions, 
commonly  called  concrete,  but  which  differ  fundamentally  therefrom  in  that 
no  chemical  action  is  required  to  solidify  them.  Apart  from  this,  their  use 
in  constructive  work  is  very  limited,  and  they  are  quite  unimportant.  The 
compositions  are  as  follows  : — 

Tar  concrete^  made  of  broken  stones  and  tar. 

Iron  concretCj  composed  of  iron  turnings,  asphalte,  bitumen,  and 
pitch ;  and  - 

Lead  coTicrete^  which  consists  of  broken  bricks  immersed  in  lead. 

Reverting  to  the  first  and  most  prevalent  conception  of  concrete,  we  will 
discuss  its  composition  a  little  more  in  detail. 

The  aggregate  should  be  clean  and  perfectly  free  from  impurities,  such 
as  dust,  dirt,  and  greasy  matter.  Ballast,  therefore,  which  has  been 
carried  as  such  by  a  ship  should  not  be  used.  The  material  should 
also  be  sharp  and  contain  as  many  angular  fragments  as  possible.  Bough, 
porous  surfaces  are  better  adapted  for  the  adherence  of  the  matrix  than 
those  which  are  smooth  and  vitreous.  Hence  brick  and  gravel  offer 
certain  advantages  over  shingle  and  flints,  though  these  latter  are  often 
preferred  for  a  reason  given  below.  Fragments  of  different  size  should 
be  employed,  so  that  the  smaller  material  may  fill  up  the  interstices  in 
the  larger,  and  it  is  to  be  noted  in  this  connection  that  equal  measures 
of  large  and  small  stone,  when  combined,  make  less  than  double  the  volume 
of  either.  No  individual  fragment  should  have  a  dimension  exceeding 
4  inches,  and  the  material  is  often  specified  to  pass  through  a  ring 
of  1^  inches  diameter.  Weight  is  a  desirable  feature  in  dock  walls,  and 
accordingly  for  this  class  of  work  preference  should  be  given  to  aggregates 
of  high  specific  gravity.  The  amount  of  sand  and  cement  will  evidently  be 
governed  by  the  volume  of  the  remaining  cavities  to  be  filled.  Tiiese  may 
be  estimated  from  the  following  table,  quoted  from  Mr.  Sandeman's  paper 
on  "Portland  Cement  and  Concrete"  : — * 


TABLE  VI. 


1.  Broken  limestone,  the  greater  part  of  which  would  be 

gauged  by  a  8-inch  ring, 

2.  GraveX  screened  free  from  sand,  varying  in  size  between 

small  pebbles  and  pieces  gauged  by  a  2^ -inch  ring, 

3.  The  above  limestone  and  gravel,  well  mixed  in  equal 

proportions, 

4.  Sandstone  varying  in  size  between  pieces  gauged  by  a 

4-inch  ring  and  pieces  gauged  by  an  8-inch  ring,  . 
6.  Sandstone  varying    in    size   between   sand    and  pieces 

gauged  by  a  4-inch  ring, 

6.  The  above  sandstones  mixed  in  equal  proportions,    . 


Weight  of 
Material. 


Lbs.  per 
cubic  foot. 

95 

llli 

113i 

74 

92 
91i 


Ratio  of 
Interstices. 


Per  cent. 
60-9 

33-6 

33-6 

60  0 

34-0 
36  0 


*  Min,  Proc,  Inst.  CE,,  vol.  cxxi. 


PORTLAND   CEMENT.  I  1 9 

Mr.  Morrison*^  recommends  the  following  procedure,  which,  he  states, 
he  has  always  found  a  safe  rule  : — 

**  Decide  tentatively  on  quantity  of  large  and  small  stones,  if  necessary 
trying  two  or  three  proportions.  Add  sand  by  degrees,  till  the  mixture, 
after  being  well  turned  over  and  shaken  down,  shows  a  decided  increase  in 
bulk,  at  least  5  per  cent;  then  add  cement  to  an  amount  equal  to  between 
one-third  and  one-half  of  the  sand,  and  draw  up  a  specification  taking  the 
amount  of  sand  as  unity." 

A  proportion  of  2  parts  of  sand  to  1  of  cement  will  be  found  most 
effective  for  marine  work,  and  it  should  be  noted  that  the  mortar  made  from 
sand  and  cement  diminishes  by  one-fourth  of  the  volume  of  the  same 
materials  mixed  dry.  The  quantity  of  mortar  should  be  from  10  to  15  per 
cent,  in  excess  of  that  required  to  just  fill  the  interstices. 

The  sand  should  not  be  too  fine  or  dust-like,  and  the  particles  should 
not  be  rendered  too  spherical  by  attrition.  Hence  pit  sand  is  better  than 
river  or  shore  sand. 

The  matrix  is  almost  universally  Portland  cement.  Hydraulic  lime 
and  Roman  cement  are  also  employed,  but  the  range  of  their  application  is 
restricted.  The  former  is  useful  for  the  foundations  of  buildings  and  the 
latter  in  cases  of  urgency,  such  as  sometimes  occur  in  tide  work.  Both  are 
much  inferior  to  Portland  cement  in  strength  and  durability. 

Portland  cement  is  an  artificial  product  obtained  by  calcining  clay,  or 
shale,  with  chalk,  or  other  limestone,  at  a  high  temperature.  It  is  outside 
the  province  of  the  dock  engineer  to  inquire  into  systems  of  manufacture, 
of  which  there  are  several,  or  to  investigate  too  closely  the  chemical  com- 
position of  the  cement  he  uses.  Ohemical  analysis  takes  no  account  of  the 
degree  of  calcination  and  fails  to  distinguish  between  free  and  combined 
lime. 

It  certainly  does  become  necessary  to  acquire  some  knowledge  of  the 
constituents  of  cement  in  their  relation  to  sea-water,  but  this  question 
will  be  considered  later,  and,  for  the  present,  the  following  may  be  stated  as 
the  approximate  composition  of  an  average  sample  of  sound  cement : — 

Lime,        * 60  per  cent. 

Silica, 23  „ 

Alumina, 7  „ 

Oxide  of  iron 4  j> 

Sulphuric  acid, *^  if 

Alkalies, '5  u 

Magnesia, 1*5 

Moisture, 3*5 


f  I 

9» 


100 


Of  the  above  ingredients,  sulphur  and  magnesia  are  objectionable  in 
excess  of  limits  which,  in  the  former  case,  are  about  1,  and  in  the  latter, 
about  5  per  cent. 

*  Morrison  on  "Cement  Concrete,"  Min.  Proc,  Inst.  C,E.,  vol.  cxxxix* 


I20  DOCK   ENGINEERING. 

From  the  point  of  view  of  the  user,  the  matter  of  greatest  moment  is 
the  actual  behaviour  of  the  cement  under  the  projected  conditions.  Hence 
the  attention  of  engineers  has  been  largely  directed  to  a  determination  of 
those  features  which  are  of  vital  importance.  The  experience  gained  by 
means  of  numerous  experiments  has  resulted  in  the  selection  of  four  charac- 
teristics for  purposes  of  comparison,  viz. : — 

1.  Fineness  of  grinding. 

'2.  Resistance  to  stress. 

3.  Rate  of  setting. 

4.  Integrity  or  soundness. 

Fineness, — The  importance  of  fineness  is  due  to  the  fact  that  the  coarse 
particles  of  a  badly-ground  cement  hydrate  more  gradually  than  the  finer 
particles,  and,  consequently,  expand  at  a  later  stage  to  the  detriment  of  the 
work.  Fine  cement,  again,  will  take  more  sand  than  coarse  cement  and 
makes  a  proportionately  stronger  concrete.  It  also  possesses  greater  capa- 
bility of  rendering  the  concrete  w;itertight,  which  under  certain  conditions 
is  imperative.  Finally,  the  coarse  particles  are  denser  and  add  considerably 
and  needlessly  to  the  cost  of  carriage.  Fineness  is  tested  by  sieves  with 
meshes  ranging  from  1,600  to  32,000  holes  to  the  square  inch,  of  which 
standards  the  former  is  as  extremely  low  as  the  ktter  is  inordinately  high. 
General  practice  at  present  seems  to  favour  either  a  residue  not  exceeding 
5  per  cent,  on  a  2,500  mesh  sieve,  or  a  residue  not  exceeding  10  per  cent,  on 
a  5,800  mesh  sieve. 

One  caution  is  needful :  a  finely-ground  cement  may  be  obtained  by 
supplying  the  mills  with  comparatively  soft  '*  clinker,"  which  is  inferior  to 
that  which  is  heavily  burnt.  Also,  there  is  a  point  at  which  any  increase 
in  the  fineness  of  the  cement  causes  additional  expense  without  compensat- 
ing advantages.  To  prevent  the  use  of  light,  underburnt  clinker,  the  weight 
or  the  specific  gravity  of  the  cement  is  often  specified.  The  former  lies 
between  100  and  120  lbs.  per  bushel  and  the  latter  between  3  and  3*15,  the 
higher  values  corresponding  to  the  better  samples,  provided  that  the  coarse 
particles  (which  have  a  high  density)  be  sifted  before  weighing.  A  very 
heavy  cement,  however,  is  likely  to  contain  an  excess  of  lime,  which,  in  the 
free  state,  is  eminently  deleterious.  The  weight,  moreover,  is  not  a  very 
satisfactory  criterion;  cements  decrease  in  weight  as  they  grow  old — as 
much  as  4  per  cent,  in  the  first  month,  with  a  total  of  15  per  cent,  for  the 
year. 

Strength. — With  good  Portland  cement,  mixed  neat,  a  tensile  strength 
of  500  lbs.  per  square  inch  should  be  obtained  at  the  end  of  28  days  after 
mixing — 1  day  in  air  and  27  immersed  in  water.  Very  frequently  a 
strength  of  450  lbs.  is  required  at  the  end  of  7  days,  but  a  7  days'  test  is  a 
somewhat  unreliable  guide  to  the  strength  ultimately  attained,  as  cements 
showing  but  moderate  results  (say,  350  to  400  lbs.)  at  the  end  of  a  week 


PORTLAND   CEMENT.  121 

offcen  develop  the  highest  ultimate  values.  Uniformity  of  results  is  a  great 
desideratum.  Considerable  divergency  in  the  results  is  a  most  unsatisfactory 
feature,  no  matter  how  high  the  average  may  stand.  It  should  not  fail  to 
be  noted  that  the  care  taken  in  the  preparation  of  the  specimen  briquette, 
and  the  method  of  applying  the  testing  weight,  exercise  a  very  considerable 
influence  on  the  results  obtained. 

In  Germany,  much  importance  is  attached  to  a  test  in  which  the  cement 
is  mixed  with  standard  sand,  on  the  ground  that  the  cementitious  power  of 
the  cement  can  only  be  estimated  properly  on  this  basis.  Indeed,  it  has 
been  found  that  of  two  samples  of  cement,  one  finely  and  the  other  coarsely 
ground,  the  finer  cement  was  the  weaker  of  the  two  in  the  neat  condition, 
but  much  the  stronger  in  combination  with  sand.  The  test  has  also  been 
intr«)duced  into  this  country,  not  with  any  unanimity  of  approval.  It  is 
•difficult  to  procure  a  standard  sand  of  rigid  uniformity,  and  the  efficiency  of 
the  lest  suffers  in  consequence.  The  criterion  usually  adopted  is  passage 
through  a  400-raesh  sieve  and  retention  by  a  900-mesh  sieve,  A  briquette 
made  with  3  parts  of  such  sand  to  1  of  cement  should  exhibit  a  tensile 
strength  of,  at  least,  150  lbs.  per  square  inch  at  the  end  of  a  week,  with  a 
regular  increase,  as  the  period  is  lengthened,  to  250  lbs.  at  the  end  of  a 
month. 

Compressive  testa  are  also  used  in  Germany,  and  not  without  reason,  for 
•concrete  is  particularly  designed  to  withstand  compression,  whilst  its  use  in 
positions  of  tension  is  strictly  prohibited.  The  ratio  of  the  compressive 
strength  of  Portland  cement  to  its  tensile  strength  may  he  taken  at  about 
10  to  1.  The  only  objection  urged  against  this  course  apparently  is  that 
"Portland  cement  will  bear  a  greater  (c« impressive)  stress,  without  fracture, 
than  it  can  be  subjected  to  in  practice."* — an  argument  which,  like  the 
•boomerang,  has  a  curiously  reflex  action.  It  may  pertinently  be  asked 
wherein  the  distinction  lies,  that  the  statement  is  inapplicable  to  tensile 
stress.  The  author  is  of  opinion  that  an  extensive  series  of  experimental 
results  in  compression  would  be  a  very  valuable  addition  to  our  data  on 
Portland  cement. 

Time  of  Setting. — The  time  of  setting  for  ordinary  cement,  under  normal 
conditions,  will  vary  between  two  and  five  hours.  Slowness  in  setting  is, 
generally  speaking,  indicative  of  strength.  A  quick-setting  cement  probably 
contains  an  excess  of  clay,  but  fine  grinding  has  also  an  appreciable  eftect  in 
accelerating  the  setting  action,  in  some  instances  to  such  an  extent  as  to 
justify  special  retardative  measures.  The  usual  way  is  to  thoroughly  aerate 
the  cement  by  spreading  it  over  a  floor,  under  cover,  to  "  cool,"  by  which 
means  the  aluminate  of  lime  becomes  f)artially  hydrated  and  its  activity 
moderated.  Sulphate  of  lime  or  gypsum,  added  to  the  cement  during 
manufacture,  retards  the  setting  action,  but  any  excess  over  2  per  cent,  is 
harmful.     Common   soda  accelerates   hardening,   though   it   weakens   the 

♦  Shaw  on  "Portland  Cement,"  Min,  Proc,  L.E.S.,  vol.  xix. 


122  DOCK   ENGINEERING. 

cement.*  Bicarbonate  of  soda,  on  the  other  hand,  retards  it  considerably, 
as  also  do  sugar,  glycerine,  and  salt,  slightly. 

Integrity  or  Soundness. — This  may  be  tested  by  Faija's  steaming  apparatus 
or  by  simple  immersion  in  water.  The  former  is  the  more  rapid  method, 
occupying  about  as  many  hours  as  the  other  occupies  days.  In  both  cases 
thin  pats  are  made,  j^  inch  thick  at  the  centre  and  as  thin  as  possible  at  the 
edges.  Signs  of  cracking,  blowing,  or  expansion  indicate  a  cement  either 
unsound  or  too  hot  for  use. 

Adulterants  of  Cement. — Two  common  adulterants  of  Portland  cement 
are  furnace  slag  and  Kentish  ragstone,  the  introduction  of  which,  though 
defended  by  some  manufacturers,  must  be  held  a  reprehensible  practice. 
The  first,  besides  being  injuriously  impregnated  with  sulphur,  possesses 
scarcely  any  hydraulic  properties  whatever,  and  the  second  is  an  inferior 
variety  of  carbonate  of  lime.  Effervescence  under  the  action  of  hydrochloric 
acid  will  betray  the  ragstone.  The  slag,  which  is  a  crude  mixture  of  silicates 
of  lime,  iron,  <fec.,  has  a  high  specific  gravity,  and  confers  a  mauve  tint  upon 
the  powdered  cement. 

The  toater  may  be  either  salt  or  fresh,  unless  for  important  surface  work 
above  ground,  in  which  case  salinity  is  objectionable,  on  account  of  the 
resulting  efflorescence.  The  amount  of  water  required  cannot  be  stated  with 
exactitude.  It  will  depend  upon  the  proportion  of  the  aggregate  and  its 
porosity.  It  is  best  determined  by  experience  in  each  particular  case. 
Without  being  profuse  enough  to  drown  the  concrete  or  wash  away  the 
cement,  it  should  be  used  in  sufficient  quantity  to  act  as  an  efficient  inter- 
mediary between  the  matrix  and  the  aggregate.  Some  authorities  advocate 
a  very  sparing  use,  but  the  author's  experience  is  to  the  effect  that  a 
plentiful  supply  is  advantageous,  for  several  reasons  :  it  serves  to  intimately 
incorporate  the  materials ;  if  the  aggregate  be  very  porous  it  prevents 
undue  absorption  of  moisture  from  the  matrix,  and  it  allows  a  scum  of 
inert  or  limey  cement  to  rise  to  the  surface  and  pass  away  with  the  drainage. 
In  certain  parts,  such  as  the  floors  and  walls  of  graving  docks,  founded  on 
water- 1  tearing  strata,  and  sea  piers,  impermeability  of  the  work  is  essential 
to  its  stability,  and  it  has  been  claimed  by  somef  that  a  minimum  of  water 
in  mixing  produces  a  maximum  of  watertightness  in  the  mixture,  but  this 
is  far  from  being  the  case,  and  the  labour  involved  in  manipulating  the 
concrete  under  such  conditions  is  greatly  increased,  since,  in  order  to  secure 
the  complete  penetration  of  the  scanty  allowance  of  water,  the  mixture  has 
to  be  beaten  in  a  manner  such  as  would  be  adopted  to  cause  moisture  to 
appear  on  the  surface  of  damp  sand.     For  the  majority  of  dock  walls,  in 

*  Mr.  F.  E.  Priest,  of  Liverpool,  has  been  kind  enough  to  communicate  to  the  author 
the  results  of  some  experiments  which  he  undertook  in  reference  to  this  point,  from 
which  it  appears  that  the  weakening  is  only  a  transitory  feature,  and  that  at  the  end  of 
four  years  the  testing  of  the  briquettes  indicated  perfectly  normal  results. 

t  Vide  Deacon  on  "Liverpool  Waterworks,"  Min,  Proc.  Iiist.  CE,,  vol.  cxxvi.^ 
pp.  42,  43. 


ACTION  OF  SEA-WATER  UPON  CONCRETE.  1 23 

which  impermeability  is  not  essential,  the  excessive  time  and  labour  required 
for  such  an  operation  would  be  wasteful  and  unremunerative  ;  and,  further, 
there  is  absolutely  no  reason  to  believe  that  concrete  mixed  with  a  good 
supply  ot  water  is  any  the  less  impervious  on  that  account.  Available 
testimony  rather  demonstrates  the  contrary,  and  the  following  experiment* 
of  Mr.  Bamber,  F.I.C.,  is  both  interesting  and  instructive. 

He  made  three  sets  of  blocks  of  concrete,  in  duplicate,  with  the  following 
proportions  : — 4  parts  of  shingle,  2  of  sand,  and  1  of  cement.  The  first 
pair  were  mixed  with  the  full  quantity  of  water  that  the  cement  would  take 
up,  which  proved  to  be  10  lbs.  for  each  block.  The  second  were  mixed  with 
only  7i  lbs.  of  water,  or  three-fourths  of  the  full  quantity.  The  third  pair 
were  mixed  with  5  lbs.  of  water  or  half  the  full  quantity.  After  standing 
for  a  fortnight,  one  of  each  of  these  pairs  was  placed  on  a  sea  wall,  and  they 
were  covered  and  uncovered  by  each  tide.  They  stood  there  twelve  months, 
and  at  the  end  of  that  time  were  brought  on  land  and  carefully  broken 
through  the  middle.  The  results  were  as  follows  : — No  1,  with  the  full 
quantity  of  water  (10  lbs.)  was  very  hard  and  perfectly  sound  and  dry  quite 
through  to  the  surface.  No.  2,  with  three  quarters  of  the  full  quantity  of 
water  (7J  lbs.)  was  dry  in  the  middle,  but,  on  every  side,  the  water  had 
penetrated  about  3  inches,  and  had  much  weakened  the  block.  Ko.  3,  with 
half  the  full  quantity  of  water  (5  lbs.)  was  wet  quite  through,  and  was  very 
easily  broken  up,  the  water  having  been  able  to  percolate  continually 
through  the  block,  and  havin^^  dissolved  much  of  the  lime.  The  fellow  pair 
of  each  of  these  was  placed  in  fresh  water,  and  remained  the  same  time,  with 
exactly  similar  results  as  to  penetration  of  water  and  strength  of  blocks,  but 
in  these  cases  another  result  could  be  observed.  In  the  case  of  No.  1,  with 
the  full  quantity  of  water  (10  lbs.),  the  water  in  which  it  stood  remained 
clear.  In  the  case  of  No.  2  (7J  lbs.  of  water)  the  water  in  which  it  stood 
became  milky  and  turbid  from  the  formation  of  carbonate  of  lime.  In  the 
case  of  No.  3  (5  lbs.  of  water)  the  water  became  quite  white ;  and,  at  the 
end  of  twelve  months,  the  whole  block  was  covered  with  crystals,  a  quarter 
to  half  an  inch  in  thickness.  The  lime  had  been  gradually  dissolved  and 
crystallised  on  the  surface  in  the  form  of  calcium  carbonate.  Similar 
blocks  subsequently  exposed  in  the  sea  wall  for  nearly  three  years  gave  the 
same  results. 

Action  of  SearWater  npon  Concrete. — A  great  deal  of  discussion  has 
arisen,  and  many  conflicting  opinions  have  been  expressed,  in  reference  to 
the  durability  of  cement  concrete  in  submarine  situations.  On  the  one 
hand,  there  are  those  who  hold,  with  much  practical  exemplification,  that 
concrete  is  in  general  a  thoroughly  reliable  and  durable  material  for  use 
under  such  and,  indeed,  any  normal  conditions;  and,  on  the  other  hand, 
there  are  those  who  point  to  the  indubitable  evidence  of  deterioration 
manifested  in  several  well-known  instances.  It  is  a  somewhat  difficult 
matter  to  decide  with  any  finality  whether  these  failures  are  due  to  purely 
*  Bamber  on  **  Portland  Cement,"  Min.  Proc.  Inst,  C.E.,  vol.  evil. 


124  DOCK   ENGINEERING. 

local  conditions,  or  whether  they  arise  from  causes  of  a  more  general  and 
widespread  nature.  The  writer  has  seen  to  the  construction  of  a  good  deal  of 
•concrete  work,  executed  without  any  special  precautions,  the  whole  of  which 
during  a  number  of  ensuing  years  has  been  exposed  either  to  constant 
immersion  or  to  tidal  alternations,  without  the  slightest  sign  whatever  of 
deterioration.  Indeed,  from  specimens  which  have  been  cut  out  of  the  solid 
mass,  he  is  convinced  that  a  harder  and  more  compact  material  for  its 
purpose  would  be  difficult  to  find.  At  the  same  time,  the  evidence  in  favour 
of  adopting  certain  measures,  of  the  nature  of  preventives  against  possible 
degeneration,  is  so  weighty  and  backed  by  such  influential  authority 
that  it  cannot  be  lightly  disregarded  or  passed  over  without  due  con- 
sideration. 

In  order  then  to  present  some  evidence  bearing  on  the  question,  a 
typical  instance  will  be  taken  in  which  concrete,  composed  of  Portland 
cement  and  a  mineral  aggregate,  has  proved  abortive  and  exhibited  un- 
doubted signs  of  disintegration  and  decay. 

The  case  is  that  of  the  entrance  walls  of  a  graving  dock,  at  Aberdeen, 
opened  in  1885.  They  were  built  as  a  '^  homogeneous  mass  of  concrete, 
deposited  inside  frames,  composed  of  1  of  cement,  2  of  sand,  and  3  of  stone, 
for  one-third  of  the  depth  of  the  frame,  and  of  1  of  cement,  3  of  sand,  and 
4  of  stone,  in  the  upper  two-thirds."  It  had  also  been  intended  to  provide 
the  wall  with  a  facing  of  2  of  cement,  3  of  sand,  and  4  ot  stone,  but  this 
waH  omitted  and  the  surface  was  plastered  instead.  The  sand  used  was 
clean,  sharp,  quartzose  sand,  screened  through  a  sieve  of  40  meshes  to  the 
inch,''^  and  containing  a  small  proportion  of  minute,  water-worn  pebbles. 
The  stones  consisted  of  smooth  water-worn  pebbles,  granite,  trap  or  whin- 
stone,  macadam,  and  granite  chips. 

Shortly  after  the  opening  of  the  dock  symptoms  of  disruption  appeared, 
and  in  June,  1887,  Mr.  Wm.  Smith,  the  engineer  at  that  period,  reported 
that  ''the  Portland  cement  concrete  entrance  walls  have  expanded  2^ 
inches  on  the  height  of  the  walls,  their  surfaces  have  cracked  and  bulged, 
and  the  joints  of  the  caisson  quoin  stones  have  opened  up,  causing 
considerable  leakage.'' 

Professor  Brazier,  of  Aberdeen  University,  Mr.  P.  J.  Messent,  M.  Inst. 
C.E.,  and  Mr.  Pattinson,  a  Public  Analyst,  were  consulted  on  the  subject. 

The  tirst-named  reported  as  follows  : — 

"  The  analyses  of  the  series  of  decomposed  cements  show  a  remarkable 
diflerence  to  the  original  cement,  inasmuch  as  that  in  all  these  samples 
there  is  found  a  large  quantity  of  magnesia,  and  a  large  proportion  of  the 
lime  in  the  form  of  carbonate.  I  believe  this  alteration  is  brought  about 
entirely  by  the  action  of  sea-water  upon  the  cement.  There  is  no  other 
source  for  either  the  magnesia  or  the  carbonic  acid.'* 

*  Although  not  specifically  stated,  apparently  the  linear  inch  is  intended,  and 
accordingly  there  would  be  1 ,600  meshes  to  the  square  inch,  the  more  generally  accepteJ 
unit. 


ACTION   OF  SEA-WATER   UPON   CEMENT. 


125 


Analyses  of  Samples  op  Cemeni\ 


Original 

Decomposed  Cement. 

Cement  of 
Test 

I 

'  Briquette. 

I. 

II. 

in. 

n'. 

V. 

Alumina  and  oxide  of  iron,      13*10 

26-76 

28-42 

105 

1-53 

5-60 

Silica,       .... 

20-92 

18  04 

19-55 

1-33 

1-31 

10-87 

Carbonate  of  lime,  . 

8-18     1 

6-61 

15-78 

45-72 

35-42 

38-37 

Hydrate  of  lime, 

11-26 

30-54 

16  94 

27-85 

17-17 

19-21 

Caustic  lime,    . 

45-39     , 

•  •  • 

■  ■  1 

• « ■ 

•  •  ■ 

■  ■  • 

Magnesia, 

Hydrate  of  magnesia, 

0-33 

... 

■  ■  • 

• »  • 

•  ■  « 

■  •  • 

•  •  • 

13-57 

15-08 

2103 

39-96 

22-30 

!  Sulphuric  acid. 

'      0-82 

2-98 

4-23 

1-31 

0-90 

0-85 

Soluble  in  water,     . 

»                    •  •  • 

1-50 

■  •  • 

1-71 

3-71 

2-80 

Mr.  Pattinson's  report,  based  on  a  separate  series  of  samples,  contained 
the  following  conclusions  : — 

"  On  comparing  the  analyses  of  the  concrete  used  in  the  work  with 
those  of  the  original  briquettes,  it  is  evident  that  very  considerable  changes 
have  occurred  in  the  composition  of  the  cement  used  in  the  concrete. 
1st.  Much  of  the  lime  has  disappeared  from  six  samples.  2nd.  A  great 
increase  of  the  magnesia  has  taken  place  in  the  same  samples.  3rd.  An 
increase  in  the  amount  of  sulphuric  acid  has  taken  place  in  the  same 
samples.     This  sulphuric  acid  exists  as  hydrated  sulphate  of  lime. 

*^  There  can  be  no  doubt,  I  think,  that  this  deterioration  is  caused  by^ 
the  action  of  the  sea  water  with  which  the  cement  has  come  in  contact. 
According  to  Thorpe  and  Morton's  analysis,"*^  1,000  grains  of  sea  water 
contains  3*151  grains  of  chloride  of  magnesium  and  2*066  grains  of 
sulphate  of  magnesia.  The  magnesia  of  both  these  salts  is  precipitated 
as  hydrate  of  magnesia  on  coming  into  contact  with  lime,  with  the 
simultaneous  formation  of  soluble  chloride  of  calcium  and  partially 
soluble  sulphate  of  litue.  This  chemical  action  of  sea  water  has  evi- 
dently taken  place  in  the  cemeut  used  in  the  six  samples,  and  notably 
in  one  of  them,  from  which  about  two- thirds  of  the  lime  has  been 
removed,  and  in  which  about  twenty  times  the  original  quantity  of 
magnesia,  and  more  than  three  times  the  original  quantity  of  sulphate 
of  lime,  have  been  deposited,  thereby  causing  the  friable  and  disintegrated 
condition  which  marked  this  sample.  Tiie  same  result,  in  a  lesser  degree, 
is  observable  in  the  other  samples." 

Mr.  Messent,  commenting  on  these  analyses,  observed : — *^  In  their  exam, 
ination  of  the  deteriorated  concrete,  both  agree  that  the  presence  of  too 
much  magnesia  in  the  cement  is  the  cause  of  the  deterioration,  and  that, 
as  the  same  proportion  or  quantity  was  not  found  in  the  briquettes  made 
of  the  neat  cement  used,  the  additional  quantity  found  in  the  spoiled 
concrete  must  have  been  supplied  by  the  sea-water,  in  contact  with  the 

•  Chem,  Soc,  Joum,,  vol.  xxiv.,  p*  606. 


126  DOCK   ENGINEERING. 

cement  portion  of  the  concrete,  which  sea- water,  whilst  precipitating  the 
magnesia  that  it  contains,  takes  away,  in  an  altered  form,  a  portion  of  the 
lime  from  the  cement." 

Mr.  Messent  made  experiments  as  to  the  quantity  of  water  absorbed 
by  briquettes  of  neat  cement,  and  of  cement  and  sand,  and  found  that  by 
repeated  absorption  and  drying,  the  solids  contained  in  the  sea- water  were 
left  in  the  briquettes,  the  strength  of  which  decreased  by  from  37  to  70 
per  cent. 

He  went  on,  in  his  report,  to  add : — '*  I  am  of  opinion  that  the  cause 
of  the  damage  referred  to  is  the  injurious  eifect  of  sea-water,  which  entered 
through  holes  in  the  plaster,  .  .  .  percolated  the  concrete  of  the  inter- 
mediate portion  of  the  wing  walls,  and  of  the  mass  behind  the  altars  of 
the  dock  walls,  and,  in  so  percolating,  extracted  lime  from,  and  deposited 
magnesia  in,  the  cement  portion  of  the  concrete,  causing  it  to  deteriorate 
and  expand ;  and  that  the  injurious  percolation  was  facilitated  by  the 
inappropriate  relative  proportions  of  the  cement,  sand,  and  stone,  or  the 
insufficient  quantity  of  cement  in  the  original  composition  of  the  deterior- 
ated concrete." 

So  much  for  one  side  of  the  question.  The  unanimity  of  conclusion  is 
af)parently  convincing,  but,  at  the  same  time,  it  must  be  admitted  that 
other  solutions  of  the  problem  are  equally  admissible. 

In  the  first  place,  there  are  one  or  two  inconsistencies  in  the  individual 
reports  which  call  for  notice.  Mr.  Pattinson  asserts  that  much  of  the 
lime  has  disappeared  from  his  samples — as  much  as  two-thirds  in  one 
case — while  an  examination  of  the  analytical  tables  of  Professor  Brazier 
demonstrates  as  remarkable  an  increase  in  that  constituent.  These  state- 
ments are,  of  course,  not  necessarily  conflicting.  The  lime  may  have  been 
washed  away  by  tidal  action  from  Mr.  Pattinson's  specimens,  but  thr 
uniformity  of  its  absence  is  curious  and  striking.  Then,  no  explanation 
is  offered  to  account  for  the  very  singular  fluctuations,  both  above  and 
below  the  normal  quantity,  of  the  amount  of  alumina  and  oxide  of  iron. 
A  decrease  is  intelligible,  but  there  is  no  manifest  source  of  supply  for  an 
increase.'"'  Aluminium  salts  are  not  present  in  ordinary  sea- water,  nor  is 
oxide  of  iron  a  common  constituent. 

Without  personal  knowledge  of  the  facts  and  circumstances,  it  is 
difficult  to  express  a  definite  opinion,  but  it  occurs  to  the  author  to 
suggest — 

1.  That  the  cement  actually  used  in  the  construction  of  those  portions 
of  the  wall  in  which  decay  occurred  might  have  been  of  different  com- 
position, and  of  inferior  quality,  to  that  of  the  original  test  briquette. 

2.  That  the  aggregate  was  impregnated  with  impurities  of  an  argil- 
laceous nature. 

(One  or  other  of  these  hypotheses  would  appear  necessary  to  account  for 
the  large  increase  of  alumina  in  some  of  the  specimens  of  decomposed 
*  Increase  by  difference  in  ratio  is  not  supported  by  an  examination  of  the  tables. 


ACTION   OF   SEA- WATER   UPON   CONCRETE.  I  27 

cement,  and  the  second  would  also  admit  of  an  explanation  for  a  decrease 
by  reason  of  fluxion.) 

3.  That  the  sand  was  much  too  fine  for  the  purpose  of  making  concrete, 
and  was  used  in  excessive  quantities.  A  1,600-mesh  sieve  for  sifting  sand 
is  absurdly  fine.  In  confirmation  of  this  view,  Mr.  Messent's  report  may 
be  quoted,  in  which  it  is  said  that  *'  the  deterioration  was  chiefly  confined 
(so  far  as  could  be  ascertained  by  examination)  to  the  concrete  which 
contained  the  largest  proportion  of  sand — viz.,  3  to  1  and  upwards." 
Supplementary  evidence  is  afforded  by  Mr.  Leedham  White,*  who  stated 
that — 

"Twenty  years  ago  he  was  in  Aberdeen,  and  examined  one  of  the 
concrete  blocks  made  at  the  beginning  of  that  particular  work.  The  block 
was  pointed  out  to  him  as  not  giving  satisfaction  to  the  engineers ;  and, 
although  it  had  been  made  several  weeks,  he  had  no  difficulty  in  crumbling 
a  piece  off  in  his  hands,  part  of  which  he  took  home  and  washed,  which 
disclosed  that  the  sand,  which  had  been  used  very  liberally,  was  so  minute 
in  the  grain  that,  though  sharp  and  clean,  it  was  little  better  than  dust. 
He  was  so  impressed  with  the  faulty  character  of  the  sand  that  he  took  a 
sample  of  the  cement  to  the  manufacturer,  and  told  him  that  he  would 
certainly  hear  complaints  of  the  cement,  and  ought  to  know  how  it  had 
been  treated.  He  did  not  know  whether  sand  of  that  quality  was  subse- 
quently used  in  the  work,  but,  as  a  manufacturer,  he  afiirmed  that  if  such 
sand  was  used  at  the  Aberdeen  works  during  successive  years,  it  was  a 
miracle  that  the  concrete  had  ever  stood  at  all." 

Mr.  Faija,t  one  of  the  greatest  authorities  on  the  subject  of  Portland 
cement,  expressed  himself  as  follows  : — 

*' Magnesia,  as  precipitated  from  sea-water,  was  simply  in  the  form  of 
a  hydrate  or  carbonate,  and  was  a  perfectly  inert  material.  The  lime  was 
dissolved  from  the  cement,  and  the  magnesia  precipitated  from  the  sea- 
water;  but  the  lime  was  not  dissolved  to  the  destruction  of  the  cement  if 
it  was  sound,  and,  as  the  lime  from  the  outside  surface  was  dissolved,  a 
crust  of  lime  and  magnesia  was  formed  which  rendered  the  mass  impervious 
to  further  destructive  action.  He  had  passed  sea- water  through  blocks 
under  a  head  of  21  feet  and  found  that,  after  a  time,  percolation  ceased, 
because  the  pores  of  the  concrete  became  filled  with  the  deposit  of  carbonate 
of  lime  and  magnesia,  so  that  the  briquettes  through  which  the  sea-water 
had  percolated  were  stronger  than  those  left  in  the  sea- water  without 
percolation.  The  analyses  given  by  Mr.  Smith  showed  that  the  failure  at 
Aberdeen  was  due  to  bad  cement  or  bad  manipulation." 

Mr.  Carey, t  who  has  also  largely  contributed  to  the  scientific  data  of 
Portland  cement,  summed  up  the  matter  as  follows : — 

"  The  real  point  at  issue  is  whether  the  salts  of  magnesia,  which  are 
admittedly  deposited  from  the  sea  in  porous  concrete  structures,  are,  or 
*  Min.  Proc.  Inst,  C.K,  vol.  cvii.,  p.  109.  fibid,,  vol.  ovii.,  p.  118. 

$  Carey  on  "Portland  Cement,"  Min.  Proc,  Inst.  G.E,^  vol.  cvii. 


128  DOCK   ENGINEERING. 

are  not,  inert.  In  his  opinion  no  conclusive  evidence  has  been  adduced 
to  prove  that  the  precipitates  from  sea- water  induce  disintegration,  even 
of  fissured  or  porous  concrete,  when  sound  cement  is  used.  Had  such 
evidence  been  forthcoming  it  would  throw  doubts  on  the  durability  of 
all  such  structures  in  the  sea.  In  the  Aberdeen  experiments  it  was 
demonstrated  that  free  caustic  lime  had  been  washed  out  of  the  concrete, 
and  magnesia,  as  magnesium  hydrate,  precipitated,  with  the  formation  of 
calcium  chloride  and  sulphate.  The  analyses  prove  nothing  beyond  the 
fact  that  the  caustic  lime  present  was  the  cause  of  such  precipitation,  and 
that  the  lime  in  this  form  is  an  unstable  and  soluble  body.  The  inference, 
that  by  similar  action  long  continued  a  dangerous  portion  of  the  lime  may 
be  dissolved  out  of  the  cement  present  in  a  concrete  structure,  is  without 
proof.  Tlje  precipitation  of  magnesian  or  other  salts  from  sea-water  is 
merely  the  deposition,  without  active  chemical  change  and  consequent 
change  of  volume,  of  bodies  which  already  exist  there  in  solution.  Sum- 
ming up  the  facts,  of  which  undoubted  evidence  has  been  produced,  it  may 
be  stated  that  an  excess  of  caustic  lime  or  caustic  magnesia  causes  (1) 
disintegration  by  the  expansion  due  to  hydration;  and  (2)  being  soluble, 
when  conditions  permit  of  their  washing  out,  they  leave  the  concrete  in  a 
honeycombed  state." 

It  would  be  impossible  to  close  so  vexed  a  question  without  a  quotation 
of  the  views  of  that  eminent  specialist,  Dr.  Wilhelm  Michaelis,  of  Berlin. 
He  states  his  opinion  that — 

''  The  magnesia,"*^  which  is  deposited  during  the  action  of  sea- water 
upon  hydraulic  mortar,  is  a  preservative  agent  which  tends  to  close  the 
pores  of  the  mass.  It  would  be  more  correct  to  speak  of  the  injurious 
action  of  the  sulphates  in  sea- water,  than  to  attribute  such  action  to  the 
magnesia  salts,  although  it  is  true  that  magnesium  sulphate  is  the  special 
salt  which  acts  in  sea-water.  The  sulphates  of  lime  or  of  alkalies,  in  fact, 
any  soluble  sulphate  have  the  same  destructive  action,  but  do  not  act  with 
the  same  degree  of  energy." 

'^  The  main  points  f  to  be  considered  in  erecting  permanent  structures  in 
sea-water,  with  the  aid  of  hydraulic  cements — in  other  words,  concrete — 
are — 

*^  I.  From  the  physical  point  of  view,  completely  impermeable  mixtures 
should  be  made,  composed  of  one  part  of  cement  with  two  or,  at  the  most, 
two  and  a-half  parts  of  sand  of  mixed  grain,  of  which  at  least  one-third 
must  be  very  fine  sand.  To  this  the  requisite  quantity  of  gravel  and 
ballast  should  be  added.  This  impermeable  layer  should  surround  the 
porous  kernel  on  all  sides  in  sufficient  thickness,  even  underneath.  It 
would,  perhaps,  be  unnecessary  waste  of  material  in  the  case  of  thick  walls 
to  use  the  impermeable  mixture  throughout;  but,  so  far  as  possible,  the 

*  Miohaelis  on  '*Sea>  water  and  Hydraulic  Cements,*'  if  in.  Proc.  Inst,  C.B,, 
vol.   cxxix. 

t  Michaelis  on  "Portland  Cement  in  Sea- water,"  Min.  Proc,  Inst,  G.E,,  voL  oviL 


-, 


I 


ACTION   OF  SEA- WATER   UPON   CONCRETE.  1 29 

compact  shell  and  the  poorer  kernel  should  be  made  in  one  operation. 
Where  this  is  not  possible,  and  the  shell  is  added  subsequently,  numerous 
iron  ties  should  be  used. 

"  2.  From  the  chemical  point  of  view,  cements  or  hydraulic  limes,  rich 
in  silica  and  as  poor  as  possible  in  alumina  and  ferric  oxide,  should  be  used, 
for  aluminate  and  ferrate  of  lime  are  not  only  decomposed  and  softened 
rapidly  by  sea- water,  but  they  also  give  rise  to  the  formation  of  double 
compounds,  which  in  their  turn  destroy  the  cohesion  of  the  mass  by 
producing  cracks,  fissures,  and  bulges.  The  salts  contained  in  sea-water, 
especially  the  sulphates,  are  the  most  dangerous  enemies  of  hydraulic 
cements.  The  lime  is  either  dissolved  and  carried  off  by  the  salts,  and  the 
mortar  thus  loosened,  or  the  sulphuric  acid  forms  with  it  crystalline 
compounds  as  basic  sulphate  of  lime,  alumino-sulphate  and  ferro-sulphate 
of  lime,  which  are  segregated  forcibly  in  the  mortar,  together  with  a  large 
quantity  of  water  of  crystallisation,  and  a  consequent  increase  in  volume 
results.  The  separation  of  hydrate  of  magnesia  is  only  the  visible  but 
completely  innocuous  siga  of  these  processes.  The  magnesia  does  not  in 
any  way  enter  into  an  injurious  reaction  with  silica,  alumina,  or  ferric 
oxide,  it  is  only  displaced  by  the  lime  from  its  solution  in  the  shape  of  a 
flocculent,  slimy  hydrate,  which  may  be  rather  useful  in  stopping  the  pores, 
but  can  never  cause  any  strain  or  expansion,  even  if  it  subsequently 
absorbed  carbonic  acid.  The  carbonic  acid,  whether  derived  from  air  or 
water,  assists  the  hydraulic  cement  as  a  preservative  wherever  it  comes 
into  contact  with  the  solid  mortar.  It  could  only  loosen  the  latter  if 
present  in  such  an  excess  that  bicarbonate  of  lime  might  be  formed. 

^*  3.  The  use  of  substances  which  render  the  mortar,  at  any  rate  in  its 
external  layers,  denser  and  more  capable  of  resistance.  Such  substances 
are — 

"(a)  Sesquica/rhonate  of  Ammonia  (from  gas  liquor)  in  all  cases  where 
long  exposure  to  the  air  is  impossible.  Such  a  solution  applied  with  the 
brush,  or  as  a  spray,  and  then  allowed  to  dry,  converts  the  hydrate  of  lime 
into  carbonate  of  lime.  The  latter  is  not  acted  upon  by  the  neutral 
sulphates  present  in  sea-water.  It  must  be  repeated  that  it  is  a  decidedly 
erroneous  opinion  that  the  texture  of  otherwise  sound  cements  is  injured  by 
the  action  of  carbonic  acid  ;  on  the  contrary,  it  renders  them  more  capable 
of  resistance,  except  in  the  above-mentioned  case,  which  is  extremely  rare, 
when  bicarbonate  of  lime  is  formed  and  goes  into  solution. 

'*  (j8)  Fluosilicatea^  among  which  magnesium  fluosilicate  is  most  to   be 

recommended.     The  free  lime  is  converted  into  calcium  fluoride  and  silicate 

of  lime,  and,  in  conjunction  with  the  liberated  hydrate  of  magnesia,  these 

new  products  close  the  pores  of  the  mortar.     Both  salts  are  sufficiently 

cheap  to  be  used  on  a  large  scale. 

"  (7)  Last,  not  least,  Ba/rium  Chloride.     Two  or  three  per  cent,  of  the 

weight  of  the  cement  is  dissolved  in  the  water  with  which  the  concrete 

is  mixed.    This  forms  perfectly  insoluble  barium  sulphate  with  the  sulphates 

9 


I30  DOCK  EN6INEEBIN6. 

of  the  sea- water,  while  the  magnesia  remains  in  solution  as  magnesium 
chloride.  Although  in  this  case  there  can  be  no  further  closing  of  the 
pores,  yet  the  insoluble  barium  sulphate,  which  is  formed,  affords  some 
protection  and  does  not  give  rise  to  any  increase  of  volume  (swelling). 
From  2  to  3  per  cent,  of  barium  chloride  does  not  in  any  way  diminish 
the  strength,  as  has  been  proved  by  the  comparative  tests  of  English  and 
German  cements.  Frequently  the  strength  of  the  mortar  is  increased  by 
this  addition.  This  substance  is  only  to  be  used  in  the  external,  perfectly 
watertight  skin  of  concrete ;  in  other  words,  in  the  4  to  8-inch  coating,  com- 
posed of  1  cement,  1  to  2  sand,  and  3  to  4  coarse  gravel,  flint,  broken 
stone,  &c," 

Practical  Notes  on  Mixing  Concrete  for  Marine   Work. 

1.  A  heavy  aggregate  is  desirable.  If  mixed  by  hand,  the  materials 
should  be  laid  out  on  a  platform  of  deals,  in  order  to  secure  freedom  from 
dirt  and  impurities,  and  covered  by  the  cement  in  a  thin  layer.  The  whole 
should  be  turned  over  thrice  dry,  and  as  many  times  wet,  before  depositing. 

2.  The  concrete  should  not  be  tipped  from  a  height  greater  than  6  feet, 
or  there  will  be  a  tendency  for  the  heavier  portions  of  the  aggregate  to 
separate  from  the  lighter.  For  great  depths,  shoots  may  be  employed  with 
men  stationed  at  the  foot  to  shovel  the  mass  immediately  into  position. 
I'he  work  should  be  well  rammed  and  consolidated. 

3.  As  many  rubble  burrs,  or  stone  plums,  should  be  imbedded  as  the  fluid 
concrete  can  adequately  enclose.  No  two  burrs  should  be  in  contact,  and 
none  should  be  set  within  12  inches  of  the  face  of  the  wall.  If  the  burrs 
are  porous,  they  should  be  wetted  before  insertion. 

4.  The  concrete  should  be  deposited  without  delay  after  mixing,  and 
should  remain  entirely  undisturbed  during  setting.  ALfter  the  setting 
of  each  layer,  the  surface  should  be  prepared  for  the  reception  of  the  next 
layer  by  picking,  washing,  and  sweeping.  In  mass  work,  layers  should  not 
exceed  2  to  4  feet  in  height. 

5.  Concrete  blocks  should  not  be  used  under  14  days  after  mixing,  and 
preferably  the  period  will  be  extended  to  three  or  four  weeks. 

6.  Concrete  bags  have  a  tendency  to  break  away  at  the  ends.  Con- 
sequently, they  should  be  slightly  longer  than  the  nett  length  required. 

7.  Wind  screens  should  be  provided  in  windy  weather,  otherwise  the 
cement  will  be  largely  wasted,  even  if  the  concrete  be  not  allowed  to  suffer 
thereby. 

8.  Concrete  mixing  should  be  avoided  as  far  as  possible  during  keen 
frost,  except  in  situations  where  the  concrete  is  deposited  directly  under 
water,  or  is  soon  afterwards  covered  by  the  tide.  Where  continuous  opera- 
tions are  essential  on  shore,  artificial  warmth  from  braziers  and  fires  may 
be  utilised  to  raise  the  surrounding  temperature,  and  salt-water  may  be 
employed  in  mixing  on  account  of  its  lower  freezing  point.     An  American 


i' 


TRANSVERSE  STRENGTH. 


131 


practice  is  to  dissolve  1  lb.  of  salt  in  18  gallons  of  water  when  the  temper- 
ature is  32"*  F.,  and  to  add  3  ounces  for  every  3**  of  lower  temperature. 
The  surface  of  such  work,  left  for  the  night,  must  be  protected  by  boards, 
tarpaulins,  sacking,  gravel,  or  littered  straw. 

Strength  of  Concrete. 

Compressive  Strength. — The  following  results  were  obtained  by  Mr. 
Grant. ''^  Experiments  were  undertaken  with  12-inch  cubes  of  compact 
concrete  made  with  Portland  cement,  weighing  1 10*56  lbs.  ]>er  bushel^  and 
having  a  tensile  stress  of  427  lbs.  per  square  inch  after  seven  days*  immersion 
in  water.     The  tests  took  place  at  the  end  of  twelve  months. 


TABLE    VII. 


1 
I 

Composition  of  Concrete. 

Crushing  Weight  in  Tons. 

1 

Blocks  kept  in  Air. 

Blocks  kept  in  Water. 

1  cement,    1  ballast, 

107 

170-5 

1        ,,         2       „ 

149                                     160 

1        „         3       „ 

113                                    115-5 

1         »         4       „ 

103                                    108-6 

1        „         5       „ 

89                    j                  99-5 

1         »         6       „ 

80-5                                 91 

1           M            7          „ 

76                                     80-5 

1        »         8       „ 

61-5                                 76 

1        „         9       ,, 

54 

68-5 

1        „        10       „ 

48-5 

48 

Experiments  made  with  9-inch  cubes  of  the  concrete  (6  of  gr^ivel  and 
broken  stone  to  1  of  Portland  cement)  used  in  the  construction  of  the 
Vymwy  Dam  gave  84*23  tons  per  square  foot  as  the  lowest  resistance  to 
compression  in  the  case  of  a  block  little  more  than  three  months  old,  and 
298*6  tons  per  square  foot  as  the  highest  resistance  in  the  case  of  a  block 
three  years  old.  The  mean  resistance  to  cracking,  under  compression,  of  all 
the  blocks  tested  between  two  and  three  years  after  moulding  was  215*6 
tons.  Still  higher  results  were  obtained  from  blocks  cut  out  of  the  hearting 
of  the  actual  work.  The  mean  resistance  to  cracking,  under  compression,  of 
19  blocks,  between  one  and  two  years  old,  was  263  tons  per  square  foot. 

Transverse  Strength. — In  an  experiment  by  Mr.  Oolsonf  a  beam  of 
9  to  1  concrete,  28  days  old,  21  inches  wide,  9  inches  deep,  and  3  feet 
9  inches  clear  span,  fractured  with  a  weight  of  1*044  ton  applied  centrally. 
The  coefficient  derived  from  this,  for  the  unit  beam,  1  foot  wide,  1  foot  deep, 
and  1  foot  span,  becomes  4  tons. 


*  Grant  on  "  Strength  of  Portland  Cement,"  Min.  Proc,  Inst.  C.E.t  vol.  xzxii. 
+  MtTi,  Proc.  Inst,  C,K,  vol.  liv.,  p.  270. 


132  DOCK   ENGINEERING. 

In  an  experiment  by  Mr.  Sutcliffe  with  a  concrete  block  cut  from  a  dock 
wall  at  Liverpool,  and  composed  of  8  parts  of  gravel  and  broken  brick  to  1 
of  Portland  cement,  with  rubble  burrs  incorporated,  the  size  of  the  block 
being  25  inches  wide  by  23  inches  deep,  and  the  clear  span  12  feet,  fracture 
resulted  from  a  central  concentrated  load  of  3*25  tons,  giving  a  coefficient  of 
5  tons  for  the  unit  beam. 

Sir  Benjamin  Baker's  experiments,'^  in  which  the  weight  of  the  beam 
itself  was  included,  yielded  the  following  unit  breaking  weights  : — 

4*85  tons  for  .         .         .         8  to  1  concrete. 

6  to  1 
13 


18 


4  to  1        „ 
pure  cement. 


Some  Sample  Compositions  of  Concrete, 

1.  At  Arbroath,  used  by  Mr.  W.  Dyce  Cay,  in  1887,  for  a  dock  entrance — 

1  Portland  cement,  7  sand,  gravel,  and  broken  stone. 

2.  At  Sydney,  used  by  Mr.  C.  W.  Young,  in  1883,  for  a  graving  dock — 

1  Portland  cement,  1  *5  sand, 

3*61  bluestone,  gauged  through  a  2i-inch  ring. 

3.  At  Belfast,  by  Mr.  W.  Redfern  Kelly,  in  1888,  for  a  graving  dock. 

(a)  For  foundations  in  tideways — 

1  Portland  cement,  1^  gravel, 

2  sand,  1^  whinstone  metal. 

(6)  For  hearting  to  walls — 

1  Portland  cement,  2^  whinstone  metal, 

2  sand,  3}  coarse  gravel. 

(c)  For  facing  to  walls — 

1  Portland  cement,  3  fine  gravel. 

1  sharp  sand, 

4.  At  Newport,  Mon.,  by  Mr.  G.  D.  Pickwell,  in  1889,  for  a  graving  dock — 

1  Portland  cement, 
10  broken  steel  slag,  weighing  26  feet  per  ton,  in  pieces  not  larger  than 
2i-inch  cubes  for  bulk  and  j-inch  cubes  for  face  work — in  both  cases 
unscreened  from  dust. 

5.  At  Greenock,  by  Mr.  W.  R..  Kinipple,  between  1878-86,  for  dock  walls — 

1  Portland  cement,  3  ballast, 

3  coarse  sand,  6  large  stones. 

6.  At  Ardrossan,  by  Mr.  R  Robertson,  circa  1889,  for  dock  walls. 

(a)  For  rubble  concrete — 

1  Portland  cement,  1  '4  gravel, 

2  broken  stone,  passed  through    2*2  sand, 

screen  with  2-inch  mesh. 

(6)  For  concrete  in  bags — 

1  Portland  cement,  1  '4  gravel, 

2*2  broken  stone,  1*2  sand. 

*  Min.  Proc,  Inst,  0,E,,  vol.  cxi.,  p.  95. 


IKON  AND  STEEL.  1 33 

IBON  AND   STEEL. 

Cast  iron,  wrought  iron,  and  steel  are  essentially  the  same  substance  in 
•combination  with  different  proportions  of  other  constituents.  The  prin- 
cipal ingredient  in  thici  connection  is  carbon,  and  the  following  percentages 
are  generally  recognised  as  forming  the  distinctive  compositions  of  the 
three  classes  of  metal,  viz. : — 

From  '0  to    *!  per  cent  for  wrought  iron, 

>i      *«'  >»  1'"       »>  >i  steel. 

„    2*0  „  5*0       „  „  cast  iron. 

Unfortunately,  this  quantitative  differentiation  is  not  susceptible  of  too 
strict  interpretation,  because  other  ingredients,  besides  carbon,  exercise  a 
powerful  modifying  influence  upon  the  compounds.  Their  properties  also 
depend  upon  the  form  in  which  the  carbon  is  present — whether  as  specks  of 
graphite,  or  free  carbon,  mechanically  mixed  and  easily  detected,  or  in 
such  intimate  chemical  combination  as  to  be  indistinguishable  from  the 
metal  itself. 

A  practical  distinction  is  founded  upon  the  behaviour  of  a  bar  of  metal 
under  certain  treatment,  as  follows  : — 

Steel  attains  great  hardness  when  suddenly  cooled,  from  a  high  tem- 
perature, by  immersion  in  water  or  oil.  This  process  has  no  effect  upon 
wrought  iron. 

Steel  which  has  been  hardened  in  this  way  may  be  softened  again,  or 
tempered,  by  heating  it  and  allowing  it  to  cool  gradually.  Oast  iron  may 
be  hardened,  but  it  cannot  be  tempered 

One  drawback  to  the  efficacy  of  these  tests  is  that  some  modern  steels, 
•containing  elements  other  than  carbon  and  iron,  are  made  softer,  and  not 
harder,  by  sudden  cooling. 

A  third  attempt  at  drawing  a  distinction  relies  upon  the  results  obtained 
in  the  testing  machine,  but  this  method  is  too  artificial  to  be  of  any  practical 
value. 

Altogether,  it  must  be  confessed  that,  while  the  differences  in  the 
physical  properties  of  iron  and  steel  are  sufficiently  marked  to  preclude 
any  misconception,  it  is  no  easy  matter  to  lay  down  any  definite  line  of 
demarcation  between  the  metals  themselves.  Steels  containing  less  than 
'5  per  cent,  of  carbon  form  an  intermediate  class  insensibly  shading  into, 
and  gradually  acquiring  the  characteristics  of,  wrought  iron.  Such  steels 
are  commonly  designated  mild  ateeU,  and  they  furnish  the  bulk  of  the 
material  used  for  structural  purposes.  Those  compounds  containing  a 
higher  percentage  than  1*5  imperceptibly  merge  into  the  class  of  cast 
irons. 

The  influence  exerted  by  carbon  in  modifying  the  physical  charac- 
-teristics  of  iron,  while  largely  dependent  upon  the  manner  in  which  it 
•enters  into  combination  with  it,  may  be  stated  in  general  terms  as  follows: — 


134  '  DOCK  ENGINEERING. 

A  relatively  large  proportion  of  carbon  induces  hardness,  strength,  incom- 
pressibilitj,  brittleness,  and  fusibility.  A  small  proportion  tends  to 
toughness,  malleability,  weldability,  and  tenacity. 

Mcmganese  Sted, — But,  as  already  remarked,  there  are  other  constituents,, 
besides  carbon,  which  are  capable  of  entering  very  largely  into  combination 
with  iron,  and  of  exercising  an  influence  equally  powerful  in  determining 
its  characteristics.  By  far  the  most  remarkable  is  an  element  which, 
according  to  the  proportion  in  which  it  is  incorporated,  imparts  the 
most  opposite  qualities  to  the  compound.  'J'he  addition  of  manganese 
to  iron  was  suggested  as  far  back  as  the  18th  century,*^  and  Mushet, 
who  published  in  1840  the  results  of  some  very  interesting  experiments, 
recommended  it  as  an  essential  accompaniment  to  the  Bessemer  process. 
The  quantity  recommended  was  small  and  in  the  form  of  spiegeleisen,  and 
a  limit  was  found  at  which  the  steel  apparently  ceased  to  beuefit  by  the 
admixture.  A  recent  and  more  deeply  experimental  investigation,  by 
Mr.  R.  A.  Hadfield,  has  established  the  important  fact  that  there  ia 
a  second  limit  beyond  the  first,  at  which  the  deterioration  ceases,  and 
the  compound  commences  to  regain  in  greater  intensity  the  characteris- 
tics which  it  had  seemingly  lost.  Mr.  Hadfield's  conclusions  are  as 
follows : — t 

**  Whilst  the  belief,  hitherto  held,  that  steel  becomes  brittle  and  com- 
paratively worthless  when  the  manganese  exceeds  about  2*75  per  cent, 
is  correct,  yet  it  has  now  been  proved  that,  by  adding  more  of  the  same 
metal  in  such  quantities  as  to  obtain  in  the  material  under  treatment  not 
less  than  about  7  per  cent,  of  manganese,  the  result  is  a  metal  with  entirely 
different  characteristics  ;  in  fact,  the  product  is  a  new  metal.  The  apparent 
paradox  thus  takes  place  that,  whilst  manganese,  alloyed  with  iron,  the 
former  being  present  in  the  proportion  of  not  less  than  2*75  and  up  to 
about  7  per  cent.,  gives  a  very  brittle  product,  when  its  proportion  is 
increased  to  not  less  than  7  and  up  to  about  20  per  cent.,  .  .  .  the  result 
is  a  material  possessing  peculiar  and  extraordinary  strength,  toughness^ 
and  other  qualities." 

Manganese  steel  is  more  free  from  blow  holes  than  are  ordinary  castings, 
and  the  addition  of  silicon,  in  order  to  prevent  unsoundness  or  honeycombs, 
is  unnecessary.  Whilst  molten,  it  gives  off  a  peculiarly  strong  sulphuroua 
odour,  and,  though  at  first  very  fluid,  it  cools  more  rapidly  than  ordinary 
steel ;  its  contraction  is  also  greater. 

Nickel  is  a  second  agent  capable  of  entering  into  an  effective  combina- 
tion with  iron,  and  of  producing  a  valuable  compound.     The  following 

*  Early  experiments  upon  manganese  were  made  by  Glauber  in  1656,  and  by  Wartz 
in  1705.  Rinman  (1773)  melted  equal  parts  of  grey  pig-iron  and  manganese  ore,  obtaining, 
a  non-magnetic  product.  Reynolds  attempted  its  use  in  the  manufacture  of  steel  in 
1799. 

+  Hadfield  on  ''Manganese  Steel,"  Min,  Proc.  Inst.  C,E,,  vol.  xciii. 


IKON  AND  STEEL.  1 35 

concise  statement  of  its  influence  is  given  by  Mr.  White,  of  the  Bethlehem 
Iron  and  Steel  Co.,  U.S.  A. : — * 

'*  The  tensile  strength  and  elastic  limit  of  nickel  iron  alloys  and  nickel 
steel  rise  with  increasing  proportions  of  nickel,  reaching  a  maximum  at 
about  20  per  cent.  Passing  this  they  begin  to  fall,  and  elongation 
increases  abnormally  up  to  30  per  cent.  The  hardening  eflect  of  quench- 
ing ceases  at  about  10  per  cent.,  but  is  quite  marked  in  the  lower  per- 
centages. In  this  case  the  eflect  is  heightened  by  the  manganese,  but 
with  '06  per  cent,  manganese  it  is  still  decided.  Between  10  and  20  per 
cent,  nickel,  neither  quenching  nor  annealing  exerts  any  decided  effect. 
Above  20  per  cent.,  quenching  produces  a  softening  eflect,  which  is  decided 
at  30  per  cent.  Perhaps  it  would  be  better  to  call  it  a  weakening  effect, 
as  the  tensile  strength  and  elastic  limit  are  much  lowered,  the  elongation 
increased,  but  the  cutting  properties  shown  by  turning  in  a  lathe  are  not 
perceptibly  changed. 

**  These  results  refer  to  alloys  of  nickel  and  iron  containing  carbon  from 
*06  to  '1  per  cent.,  which  practically  can  be  considered  carbonless  alloys,  as 
it  is  impracticable  to  make  them  lower.     The  manganese  ranged  between 
06  and  '1  per  cent. 

**  There  are  many  difficulties  to  be  overcome  in  handling  nickel  steel 
as  commercially  made.  It  is  very  susceptible  to  changes  of  temperature 
when  containing  the  usual  amounts  ('2  to  '9  per  cent.)  of  carbon  and 
manganese,  requiring  considerable  care  in  heating  and  working  to  bring 
out  its  best  qualities." 

The  question  of  alloys  is  a  very  wide  one,  and,  in  view  of  the  extensive 
range  of  modern  chemical  research,  the  student  will  do  well  to  consult 
technical  literature  for  a  more  complete  and  detailed  statement  of  the 
behaviour  of  the  various  products.  It  would  be  out  of  place  here  to  enter 
into  the  subject  seriously,  and  we  must  dismiss  other  known  combinations 
with  the  briefest  possible  notice. 

Tungsten  and  chromium  have  the  effect  of  hardening  steel  and  increasing 
its  tenacity.  Copper  and  antimony,  on  the  other  hand,  produce  brittleness. 
Titanium  increases  the  ductility. 

The  following  constituents  are  usually  accounted  impurities  : — 

Silicon  produces  brittleness  in  iron  and  is  generally  excluded  as  slag.  It 
is  not  detrimental  to  steel  when  present  in  a  very  minute  quantity,  as  it 
tends  to  repress  agitation  and  bubbling  during  the  process  of  cooling.  Its 
effect  on  cast  iron  is  somewhat  similar  to  that  of  carbon. 

Phosphorus  hardens  cast  iron,  makes  it  more  fusible,  and  lessens  its 
ductility.  Steel  is  deteriorated  by  a  very  small  quantity,  say,  '08  per  cent. 
Wrought  iron  is  rendered  more  weldable  by  -01  per  cent.,  but  above  that 
limit  the  metal  becomes  brittle  and  ''cold  short" — t.e.,  it  cracks  if  bent  cold. 

Sulphur  makes  wrought  iron  *'  red  short,"  or  brittle,  at  high  tempera- 
tures.    It  renders  both  steel  and  cast  iron  more  fusible  and  more  brittle. 

*  Min,  Proc  Inst.  C,E.,  voL  cxxxviii.,  p.  53. 


136  DOCK   ENGINEERING. 

Classification  of  Iron. — A  description  of  the  various  processes  employed 
in  the  manufacture  of  iron  and  steel  is  quite  beyond  the  scope  of  the  present 
work.  A  brief  classification  of  mercantile  products,  with  their  most  note- 
worthy features,  is  all  that  can  be  attempted. 

Pig  iron  is  the  name  given  to  the  coarse  bars  of  unpurified  metal  run 
off  from  the  blast  furnace.  These  are  roughly  divisible  into  two  kinds — 
those  having  a  dark  grey  fracture,  due  to  a  large  proportion  of  uncomhined 
carbon,  and  those  having  a  silvery  fracture,  with  very  little  uncombined 
carbon.  The  first  are  distinguished  as  foundry  pigs,  being  particularly 
suitable  for  castings,  and  the  second  as  /orge  pigs,  being  only  adapted  for 
conversion  into  wrought  iron.  Special  varieties  of  pig  are  generally 
assigned  to  the  manufacture  of  steel.  For  what  is  known  as  the  acid 
process  (see  below),  the  metal  must  be  comparatively  free  from  phosphorus 
and  sulphur,  such,  for  instance,  as  the  pig  produced  from  haematite  ores. 
By  the  basic  process  much  impurer  ores,  containing  a  large  proportion  of 
phosphorus,  can  be  utilised,  but  the  product  is  scarcely  so  satisfactory. 

Ccut  iron  is  obtained  by  remelting  pis:  iron  to  eliminate  its  impurities. 
The  process  may  be  repeated  with  beneticial  results  as  many  as  a  dozen 
times.  After  that  point  has  been  reached  the  metal  begins  to  deteriorate. 
According  to  Sir  William  Fairbairn,  the  transverse  strength  and  elasticity 
decrease  after  the  twelfth  remelting,  and  the  compressive  strength  after  the 
fourteenth.  Cast  iron  comprises  three  classes — grey,  mottled,  and  white 
oast  iron,  following  the  structural  nature  of  the  pigs  from  which  they  are 
cast.  The  first  contains  a  profusion  of  carbon  in  graphitic  specks,  the  last 
is  free  from  uncombined  carbon,  and  the  second  represents  an  intermediate 
condition. 

Chilled  iron  is  a  product  of  casting  in  which  the  surface  of  the  metal  is 
allowed  to  come  into  contact  with  a  cold  substance,  with  the  result  that  it 
becomes  hard  and  brittle  while  the  interior  remains  tough. 

Wrotight  iron  is  iron  from  which  all  carbon  has  been  eliminated  as  far 
as  practicable.  It  is  developed  in  a  pasty  mass  which  is  much  improved  by 
cutting,  piling,  and  rolling.  Hence  there  are  three  qualities,  each  an 
amelioration  on  the  preceding  by  a  repetition  of  the  process — viz.,  puddled 
bars,  merchant  bars,  and  best  bars. 

Steel  is  capable  of  production  on  two  systems  (1)  by  eliminating  the 
carbon  from  pig  iron  until  the  requisite  proportion  is  left,  and  (2)  by  adding 
a  definite  amount  of  carbon  to  wrought  iron. 

The  cementation  process  based  on  the  second  system  produces,  first, 
blister  steel  of  very  unequal  quality,  and  secondly,  shear  steel,  in  which  the 
metal  is  rendered  more  homogeneous  by  piling  and  rolling.  Cast  steel  is 
obtained  by  melting,  in  crucibles,  wrought  iron  which  has  been  previously 
bedded  in  charcoal  powder  in  a  furnace. 

The  Bessemer  process  yields  a  steel  of  that  name,  which  is  due  to  the 
combustion  of  the  carbon  contained  in  suitable  pig  iron,  by  means  of  a 
volume  of  air  forced  at  high  pressure  through  the  molten  masR,  leaving 


DEFECTS  IN  CASTINGS.  1 37 

the  iron  either  at  the  exact  composition  required,  or  comparatively  pure, 
so  that  the  requisite  carbon  may  be  added  to  it. 

Siemens- Martin  steel  results  from  the  reduction  of  a  mass  of  crude  iron, 
often  with  the  admixture  of  an  ore  rich  in  oxide,  the  whole  being  melted 
in  an  open  hearth  exposed  to  the  intense  heat  of  a  regenerative  furnace. 
It  is  a  much  slower  process  than  the  Bessemer,  but  it  produces  a  steel  of  a 
more  generally  trustworthy  character,  and  it  is  frequently  specified  for 
bridgework. 

Of  the  above  processes,  two  modifications  exist — viz.,  (a)  the  Acid,  and 
{b)  the  Basic — according  to  whether  the  lining  of  the  converters,  or  of  the 
furnaces  is  siliceous  or  calcareous.  In  the  basic  process,  additions  of 
calcined  lime  are  made  to  the  bath  of  molten  metal  in  order  that  it  may 
combine  with  the  excess  of  phosphorus,  and  remove  it  in  the  form  of  slag. 
In  the  acid  process  this  step  is  not  taken,  and  hence  the  necessity  for  purer 
ores. 

Practical  Observations  on  Manufactured  Iron, 

Defects  in  Castings. — The  engineer  should  have  sufficient  acquaintance 
with  foundry  methods  to  enable  him  to  appreciate  the  difficulties  of  success^ 
ful  casting,  to  understand  the  proper  distribution  of  the  metal  for  the 
purpose  intended,  and  to  distinguish  between  defects  which  are  trifling  and 
those  which  are  of  vital  importance.  Founders  incur  considerable  risks 
and  many  failures  in  their  endeavours  to  reproduce  large  and  intricate 
patterns,  and  such  work  should  not  lightly  be  rejected  on  account  of  some 
insignificant  surface  blemish,  when  otherwise  sound  and  serviceable.  On 
the  other  hand,  there  are  surface  indications,  apparently  slight,  which 
reveal  serious  internal  defects. 

The  necessity  for  having  the  metal  thoroughly  fluid,  in  order  that  it  may 
penetrate  to  all  parts  of  a  large  mould,  sometimes  causes  it  to  be  heated  to 
such  an  extent  that  it  burns  into  the  sand  of  the  mould,  and  instead  of 
producing  the  clear  blue  skin  of  the  ideal  casting,  a  rough  white  surface 
is  the  result  This  aflects  green  sand  moulds  rather  than  those  of  loam 
or  dry  sand. 

The  most  common  defects  of  castings  are  the  presence  of  blow  or  air  holes 
due  to  the  generation  of  steam  and  gases  by  the  damp  sand,  the  want  of 
sufficient  venting,  and  an  imperfect  supply  of  metal.  A  certain  amount 
of  dampness  in  the  sand  of  moulds  and  cores  is  necessary  to  secure 
adhesion  of  the  particles,  but  an  excess  of  moisture  produces  steam.  An 
insufficient  number  of  vents  causes  particles  of  air  to  be  imprisoned  in 
the  various  parts,  and  an  imperfect  supply  of  molten  metal  lacks  the  head 
to  secure  homogeneity.  Very  often  these  blowholes  are  not  manifest 
until  the  casting  is  machined,  and  occasionally  they  escape  notice 
altogether.  It  is  obvious  that  they  are  a  source  of  weakness  wherever  they 
occur.  The  author  has  noticed  a  hydraulic  pressure  pipe  develop  an  almost 
imperceptibly  fine  jet  through  the  thickest  part  of  the  flange,  while  the 


138  DOCK  ENGINEERING. 

thinner  stem  remained  intact.  To  remedy  such  defects  in  large  pieces^ 
without  having  recourse  to  a  fresh  casting,  the  hole  may,  under  certain 
circumstances,  be  bored,  tapped,  and  fitted  with  a  steel  screw,  or  a  wrought 
iron  patch  may  be  raised  to  a  white  heat  and  hammered  in.  A  sound 
casting  is,  however,  always  preferable  to  one  that  has  been  doctored  up. 

Another  defect  is  the  presence  of  extraneous  matter,  such  as  loose  sand 
from  the  mould,  or  even  impurities  in  the  iron  itself  These  latter  should 
be  skimmed  off  the  surface  of  the  casting  ladle.  But  it  is  difficult  to  avoid 
loose  sand  in  a  mould  which  takes  some  time  to  close,  and  light  projections 
are  frequently  washed  away  by  the  influx  of  metal.  Such  foreign  matter 
will  naturally  rise  to  the  top  of  the  casting,  and  by  making  the  latter  a 
little  higher  than  the  nett  size  required  the  objectionable  material  can  be 
removed  later  by  the  planing  machine. 

Imperfectly  adjusted  cores  cause  the  metal  to  be  thicker  on  one  side  of 
a  hollow  casting  than  on  the  other.  While  perfect  adjustment  is  perhaps 
not  always  attainable,  yet  limits  of  deviation  should  be  fixed  and  adhered  to. 

Shortage  in  the  supply  of  metal  to  a  mould  cannot  be  made  good  by  a 
second  charge.  No  matter  how  quickly  applied,  a  shut  or  flaw  will  be  the 
inevitable  result. 

Castings  which  become  cracked  or  twisted  are  frequently  due  to  defective 
design.  Considerable  variation  in  the  thickness  of  the  metal,  abrupt 
changes,  and  outlying  projections  cause  irregular  contraction.  The  thinner 
portions  cool  more  quickly  than  the  thicker  portions,  and  internal  stresses, 
often  unsuspected,  are  set  up.  Sudden  changes  in  sectional  area  should, 
accordingly,  be  avoided,  and  projections  should  be  graduated  from  the 
main  body. 

Specification  for  Castings, 

'*  Castings  are  to  be  clean,  true,  and  free  from  twist,  having  regular 
surfaces  both  inside  and  outside,  with  sharp,  well-defined  angles  and  lines. 
They  must  be  sound  and  free  from  air  or  sandholes,  cold  shuts,  and  other 
imperfections,  in  the  case  of  columns,  pipes,  drc,  care  should  be  taken  that 
the  lengths  are  exactly  equal  to  the  dimensions  given ;  that  the  bearing 
surfaces  of  flanges  are  perfectly  smooth  and  regular  planes,  perpendicular  to 
the  centre  line ;  that  the  bolt  holes  are  of  the  proper  size  and  in  their  exact 
positions,  and  that  the  thickness  of  the  metal  in  the  shafts  is  quite  uniform 
throughout,  of  which  evidence  may  be  taken  by  drilling  holes,  if  necessary. 
Any  casting  will  be  liable  to  rejection  which  deviates  more  than  ^  inch  in 
thickness  and  \  inch  in  length  from  the  given  dimensions." 

Defects  in  Rolled  Plates  and  Bars. — Loose  and  open  fibres,  flaws,  and 
signs  of  lamination  are  due  to  imperfect  rolling  and  welding. 

Coarse  crystals  or  blotches  of  colour  are  caused  by  an  insufficiently 
purified  metal,  contaminated  with  scarice  and  other  impurities. 

A  crystalline  fracture  does  not  necessarily  imply  an  inferior  iron.    When 


TESTS. 


139 


wrought  iron  breaks  suddenly  a  crystalline  fracture  is  the  invariable  result, 
A  truer  test  is  a  slowly  applied  breaking  weight,  which  should  cause  a 
fibrous  fracture.     Bad  iron  is  never  fibrous. 

Specification  for  Plates  and  Bars, 

"  Every  plate  and  bar  must  be  sound,  straight,  and  free  from  all  flaws,  and 
any  piece  which  shows  signs  of  lamination  or  other  defect  will  be  rejected. 
The  edges  of  all  plates  are  to  be  planed  so  that  they  may  bear  truly  at  their 
joints.  All  joggles  are  to  be  thoroughly  well  and  neatly  formed.  The 
butting  ends  of  all  ties,  angles,  and  bars  are  to  bear  fairly  and  firmly 
throughout,  and  all  comers  and  edges  to  be  neatly  finished  off.  Every 
piece  is  to  be  of  the  full  thickness  specified,  to  be  tested  by  gauging,  weigh- 
ing, or  otherwise." 

Working  Strength. — The  following  table  gives  the  amount  of  stresa 
generally  permissible,  in  tons,  per  square  inch  of  sectional  area : — 


TABLE   VIII. 


Cast  Iron. 

SteeL                Wrought  Iron. 

Tension, 

Compression,*    .... 
Shearing 

• 

8 
2 

8 

12 

6 

5 

4 
4 

These  figures  are  based  on  a  factor  of  safety  of  4.  The  Board  of  Trade 
has  fixed  the  limit  of  stress  for  bridges  of  wrought  iron  at  5  tons  per  square 
inch,  and  of  steel  bridges  at  6^  tons.  The  strength  of  steel  depends  on  the 
precise  nature  of  its  composition,  and  the  values  given  above  are  merely 
approximate  and  general. 

Tests. — Cast  iron  is  usually  specified  to  be  tested  as  follows  : — A  sample 
bar  is  cast,  3  feet  6  inches  long,  2  inches  deep,  and  1  inch  wide.  It  is 
supported  on  bearings  3  feet  apart,  and  loaded  at  the  centre  with  a  weight 
variously  stated  at  from  25  to  30  cwts.,  which  it  is  required  to  sustain 
without  fracture  and  without  exhibiting  a  deflection  greater  than  ^-^  inch. 
Test  bars  should,  if  possible,  be  cut  from  the  casting,  but  in  any  case 
should  be  cast  under  exactly  the  same  conditions.  A  tensile  test  is  rarely 
required. 

Wrought  iron  is  generally  required  to  stand  a  minimum  tensile  stress 
before  breaking,  the  contraction  of  area  at  fracture  not  being  less  than  a 

*  These  values  only  apply  in  the  case  of  short  struts.  When  the  length  is  consider- 
able, failure  is  more  likely  to  take  place  through  flexure,  and  special  calculations  are 
necessary  for  determining  the  nature  and  extent  of  the  stress.  The  problem  is  dealt 
with  in  Chapter  ix. 


I40 


DOCK   ENGINEERING. 


'Certain  amount.     According  to  the  quality  desired  the  following  figures  are 
^iven : — 


intimate  Stress. 

ContractioD. 

Round  or  square  bars, 

Flat  bars, 

Angle  or  tee  iron, 

Plates  with  grain  lengthways,     . 

Plates  with  grain  crossways. 

23  to  27  tons. 
22  to  26    „ 
21  to  25    „ 
20  to  24    „ 
17  to  22    „ 

20  to  45  per  cent. 

16  to  40 

12  to  30        „ 

8  to  20        „ 

3  to  12 

In  addition  to  this,  certain  forge  tests  are  required.  Thus,  1-inch  plates 
for  the  Admiralty  are  to  be  capable  of  bending  without  fracture  while  hot 
from  90''  to  125**  along  the  grain  and  from  60"*  to  90*"  across  the  grain, 
And  while  cold,  10**  to  15°  along  the  grain  and  5**  across  the  grain.  For 
^inch  plates  the  cold  tests  are  55''  to  TO**  and  20"  to  SO**  respectively. 

Sied,  according  to  Admiralty  requirements,  must  have  an  ultimate 
tensile  strength  of  between  26  and  30  tons  per  square  inch,  combined  with 
AD  elongation  of  20  per  cent,  in  a  length  of  8  inches.  Lloyd's  specification 
raises  the  limits  to  between  27  and  31  tons  with  the  same  elongation. 
JBoth  tests  apply,  indifferently,  along  or  across  the  grain. 

As  regards  temper,  strips  cut  from  a  plate  heated  to  a  low  cherry-red 
and  cooled  in  water  at  82°  F.  must  stand  bending  round  a  curve  of 
which  the  diameter  is  1^  or  3  times  the  thickness  of  the  plate,  according 
as  the  authority  is  Lloyd's  or  the  Admiralty. 

Rivets,  if  of  wrought  iron,  should  be  capable  of  being  bent  double,  cold, 
without  sign  of  fracture.  When  hot  they  should  stand  being  hammered 
down  to  less  than  ^  inch  in  thickness  without  cracking  at  the  edge.  If  of 
Bteel  they  should  have  an  elongation  of  25  per  cent.,  with  26  to  28  tons 
per  square  inch  tensile  strength,  in  test  pieces  of  ten  diameters,  and  should 
be  capable  of  bending  double  after  the  same  tempering  as  that  applied  to 
steel  plates. 

Weight  of  Iron  and  Steel. — Plates  of  metal,  12  inches  square  and  1  inch 
in  thickness,  weigh  37|,  40,  and  40|  lbs.  respectively  for  cast  iron,  wrought 
iron,  and  steel. 

Corrosion  of  Iron  and  SteeL — It  is  to  be  regretted  that  on  a  point  of 
such  vital  importance  to  the  dock  engineer  as  the  durability  of  metal 
structures  exposed  to  atmospheric  and  aqueous  agencies,  the  evidence  is  so 
scanty  as  to  be  inconsiderable,  so  incomplete  as  to  be  inconclusive,  and 
so  conflicting  as  to  be  actually  perplexing.  This  state  of  things  arises  from 
a  variety  of  causes.  In  the  first  place,  it  is  only  within  the  last  fifty  years 
that  iron  has  begun  to  usurp  the  pre-eminence  hitherto  enjoyed  by  wood 
and  stone  in  maritime  construction,  and  steel  is  an  intrusion  of  still  later 
■date.  Consequently  there  has  hardly  yet  been  sufficient  time  in  which  to 
.acquire  data  for  the  determination  of  the  actual  life  of  metallic  structures 


CORROSION   OF   IRON   AND   STEEL. 


141 


under  such  conditions,  even  if  systematic  experiments  had  been  carried  out 
from  the  earliest  possible  moment,  which  has  not  been  the  case.  Again  the 
variation  in  atmospheric  conditions  is  extremely  great,  the  seasons  being 
marked  by  enormous  fluctuations  in  sunshine,  rainfall,  and  temperature  not 
only  for  different  seasons  in  the  same  year,  but  for  the  same  season  in 
consecutive  years.  The  question  is  still  further  complicated  by  the  factor 
of  locality.  Then,  as  regards  aqueous  influences,  there  is  no  definite 
standard  of  comparison  whatever.  The  salinity,  acidity,  density,  and 
temperature  difler  in  almost  every  unit  volume  of  sea- water,  so  that  it  is 
never  precisely  the  same  at  any  two  ports.  Rivers,  sewers,  and  ocean 
currents  all  contribute  to  diflbrentiate  its  composition. 

It  would,  perhaps,  be  a  comparatively  easy  solution  of  the  difficulty  to 
lay  down  one's  individual  experience  as  a  dogma  for  general  acceptance,  but 
the  wiser  and  more  judicious  course  will  be  to  set  forth  such  information 
on  the  subject  as  is  available,  and  leave  the  reader  to  draw  his  own 
conclusions. 

The  following  coefficients,  given  by  Thwaite  and  quoted  by  Molesworth,"^ 
represent  the  amount  of  corrosion  in  lbs.  per  square  foot  of  surface  during 
twelve  months*  exposure  : — 

TABLE   IX. 


Material. 


Cast  iron, 

Wrought  iron, 

Cast  iron  (skin  removed  by  planing), 
(surface  galvanisea), . 


>> 


Corrodiiig  Agents. 


Foul 
Sea- 
Water. 


•0656 
•1956 
•1944 
•2301 
•0895 


Clear 
Sea- 
Water. 


•0635 
•1285 
•0970 
•0888 
•0359 


Foul 
Biver- 
Water. 


•0381 
•1440 
•1133 
•0728 
•0371 


Pure  Air 

or  Clear 

Biver- 

Water. 


•0113 
•0123 
•0125 
•0109 
•0048 


City  Air 

or 
Sea  Air. 


•0476 
•1254 
•1262 
•0884 
•0199 


Sea- 
Water  of 
Average 
Foulness. 


in  contact  with  brass, 
„  ,,    copper, 

„  „    gun-metal, 

Best  wrought  iron  in  contact  with  brass, 
„  ,,  „        copper, 

„  ,,  „        gun-metal, 


f  > 


•1908 
•2003 
•3493 
•2779 
•4012 
•4537 


If  the  metal  be  painted  once  a  year  the  coefficient  to  be  divided  by  2 ; 
if  once  in  two  years,  by  1-8 ;  and  if  once  in  three  years,  by  1*6. 

Trautwine  t  states,  in  apparent  contradiction  of  the  above,  that  while 
"fresh-water  corrodes  wrought  iron  more  rapidly  than  cast,  the  reverse 
appears  to  be  the  case  with  sea- water,"  and  that  "  the  corrosion  of  iron  or 
steel  by  sea-water  increases  with  the  carbon."     He  admits,  however,  that 

*  Pocket-hook  of  Engijieering  Formtdoe,  25th  edition,  p.  33. 
+  CivU  Ehigmeera^  Pocket-hook^  17th  edition,  p.  218. 


142 


DOCK  ENGINEERING. 


wrought  iron  is  affected  very  quickly,  so  that  thick  flakes  may  be  detached 
from  it  with  ease.  The  following  instances  are  cited  : — "  Oast-iron  cannons 
from  a  vessel  which  had  been  sunk  in  the  fresh- water  of  the  Delaware 
river  for  more  than  40  years,  were  perfectly  free  from  rust."  The  cast-iron 
work  of  the  "  Royal  George ''  and  the  "  Edgar/'  sunk  in  the  sea  for  62  years 
-and  133  years  respectively,  when  examined  by  Gen.  Pasley  had  become 
quite  soft  and  resembled  plumbago.  The  wrought  iron  was  not  so  much 
injured,  except  when  in  contact  with  copper,  or  brass  gun-metal. 

Two  other  experimentalists — Kennie  and  Mallet — adopt  antithetical 
opinions  as  to  the  relative  corrosion  of  cast  and  wrought  iron  in  salt-water. 
The  former  maintains  a  higher  rate  for  cast  iron;  the  latter,  for  wrought 
iron.* 

The  following  table  extracted  from  a  paper  on  the  corrosion  of  iron  and 
steel,  by  Mr.  David  Phillips,*  relates  to  a  series  of  experiments  made  by 
him  with  five  sets  of  iron  and  steel  plates,  4  inches  square  by  |  inch  thick, 
•exposed  to  various  corrosive  agencies.  ''To  avoid  even  a  suspicion  that 
galvanic  action  had  any  influence  in  these  cases,  all  the  plates  were 
suspended  on  glass  rods,  and  each  plate  was  separated  from  its  neighbour 
by  glass  ferrules."  It  is  important  to  note  that  Mr.  Phillips  attributed  the 
generally  greater  corrosion  during  the  first  period  of  trial  to  the  fact  that 
the  weather  in  the  summer  of  1879  was  much  more  changeable  than 
that  in  1880. 


TABLE  X. — CoEROSioN  op  Iron  and  Steel. 


Metal. 

Water. 

Loss  of  Weight. 

First 
12  Months. 

Second 
ISMonths. 

Total. 

Average 
perSq.Pt. 
of  Surface. 

Grs. 

Grs. 

Grs. 

Grs. 

N  Bessemer  steel,    . 

Rain-water,    . 

186-7 

141-4 

328-1 

1,246-9 

Y  Siemens  steel, 

i»             •        • 

1741 

147-0 

321  1 

1,220-3 

B  B  Stafibrdshire  iron, 

»>             •        • 

165-3 

119-0 

284  3 

1,080-5 

D  D  Yorkshire  iron,    . 

>f             • 

1861 

1.36-2 

321-3 

1,221  1 

N  Bessemer  steel,    . 

Sea-water, 

42-4 

36-9 

79-3 

301-4 

Y  Siemens  steel, 

>i             • 

33-5 

34-7 

68-2 

259-2 

B  B  Staffordshire  iron, 

>»             •        • 

35-4 

35-6 

71-0 

269-8 

D  D  Yorkshire  iron,    . 

»>             •        • 

36-9 

31-6 

68-5 

260*3 

N  Bessemer  steel,    . 

(  Exposed  to  weather  j 
<      and  dipped  in  sea-  > 
(      water  daily,         .  ) 

1,044-7 

501-6 

1,545-6 

5,8740 

B  B  Staffordshire  iron, 

417-9 

259-1 

6770 

2,572-9 

Y  Siemens  steel. 

/Exposed    to    the\ 
\     weather  only,     .  / 

234-4 

135-9 

370-3 

1.407-3 

D  D  Yorkshire  iron,    . 

147-6 

62-7 

200-0 

761-2 

In  the  discussion  which  followed  the  reading  of  the  paper,  much 
emphasis  was  laid  by  Dr.  Siemens,  Mr.  Barnaby,  Mr.  Farquharson,  and 
others,  on  the  importance  of  removing  the  magnetic  oxide  scale  from  the 

*  Phillips  on  *'The  Comparative  Endurance  of  Iron  and  Steel  when  Exposed  to 
Corrosive  Influences,"  Min.  Proc,  Inst,  C.E.,  voL  Ixv. 


CORROSION   OF   IRON   AND   STEEL.  1 43 

fiurface  of  steel,  and  this  received  the  confirmation  of  Sir  W.  H.  White,  at 
a  later  meeting  of  the  institution,  when  he  declared  that  *'  as  regards  the 
relative  corrosion  of  iron  and  steel  when  immersed  in  sea-water,  the 
experience  of  the  Admiralty  during  the  last  six  years  (1876-1882)  showed 
that  if  the  manufacturers'  scale  (black  oxide)  was  thoroughly  removed, 
and  equal  care  taken  in  protecting  the  surfaces  by  paint  or  composition, 
iron  and  steel  had  about  the  same  average  rate  of  corrosion,  the  steel 
wearing  somewhat  more  uniformly  than  the  iron."* 

The  question  of  corrosion  principally  concerns  the  dock  engineer  in 
regard  to  the  duration  and  maintenance  of  metal  gates  and  fittings. 
Decay  mainly  takes  place  below  the  water-line,  where  inspection  and 
repairs  are  alike  difficult.  In  this  connection  the  following  data  taken  from 
a  report  t  by  Messrs.  Brandt  and  Hotopp  to  the  Ninth  International 
Navigation  Congress  possess  much  interest : — 

"  I.  In  the  case  of  the  floodgates  at  Gliickstadt,  erected  in  1874  and  to 
be  renewed  this  year  (1902),  the  first  isolated  rust  spots  on  the  outer  skin 
are  to  be  found  at  4  inches  below  ordinary  low  water  level ;  the  spots 
increase  in  number  at  6  inches  below  low  water,  and  are  thickly  distributed 
all  over  the  metal  at  a  depth  of  10  inches.  The  greatest  depth  to  which 
decay  has  penetrated  in  the  strip  (k>mprised  between  this  line  and  another, 
lying  about  3  feet  3  inches  below  low  water,  is  about  ^inch ;  below  this 
level  the  metal  skin  is  covered  with  a  layer  of  short-stalked  moss,  mixed 
with  shells,  the  thickness  of  which  increases  downwards,  and  below  which 
the  depth  and  extent  of  decay  grows  gradually  less  and  less  (to  about  |-inch 
deep  near  the  sill),  so  that  the  plates  near  the  sill  are  almost  sound.  A  few 
of  the  rivet  heads,  starting  at  a  depth  of  14  inches  below  low  water,  begin 
to  show  signs  of  decay  and  are  furrowed;  the  decay  gradually  increases 
with  the  depth,  so  that  when  the  rows  of  rivets,  situated  between  18  and 
22  inches  below  low  water,  are  reached,  not  only  have  all  their  heads  been 
completely  eaten  ofiT,  but  their  shanks  have  also  been  already  attacked  in 
isolated  cases.  The  decay  in  this  case  also  becomes  less  and  less  with 
increased  depth.  The  water  of  the  River  Elbe,  at  GlUckstadt,  is  only  on 
exceptional  occasions  somewhat  brackish,  but  in  the  outer  harbour  there  is 
a  great  deal  of  deposit,  and  several  drains  full  of  water  from  the  moors 
empty  into  it. 

"II.  The  gates,  and  more  especially  the  floodgates,  in  the  harbour  at 
Geestemtinde,  erected  in  1861,  show  a  furrow,  the  rust  in  places  penetrating 
as  deep  as  -^  inch  into  the  outer  metal  skin,  just  above  the  cover  strips 
lying  close  below  low-water  line,  and  it  may  be  assumed  that  similar  rusty 
places  exist  also  above  the  cover  strips  in  lower  situations,  the  upper 
portions  of  the  outside  rivet  heads  lying  close  under  low  water  mark  have 
also  rusted  away.     The  cause  to  which  this  damage  is  ascribed  is  the  layer 

*  Min.  Proc.  Inat,  C.E,,  vol.  bdx.,  p.  35. 

t Brandt  and  Hotopp  on  "Iron,  Steel,  and  Wooden  Gates,"  IrU.  Navt  Cong., 
DUaaddorf,  1902. 


144  DOCK  ENGINEERING. 

of  mud  deposited  on  the  upper  edges  of  the  cover  strips  and  on  the  rivet- 
heads,  the  mud  being  highly  charged  with  acids  derived  from  the  decaying 
river  deposit  and  the  salt-water  and  water  from  the  moors  conveyed  by  the 
lower  Weser  and  the  Geste.  The  corrosive  influence  of  the  deposit  is 
proved  by  the  fact  that  the  decay  in  question  is  specially  noticeable  on  the 
convex  side  of  the  curved  floodgates,  the  outer  skin  of  which  is  permanently 
immersed  in  the  very  muddy  water  of  the  outer  harbour,  whereas  on  their 
concave  side  they  are  often  washed  by  the  water  in  the  harbour  which  is 
not  so  turbid. 

'^  III.  The  dock  gates  of  the  new  harbour  at  Bremerhaven  were  erected 
in  1852,  and  removed  as  worn  out  in  1900.  The  thinning  down  of  the  plate 
was  especially  noticeable  where  projecting  edges  formed  ledges  upon  which 
mud  could  settle.  Those  parts  of  the  gates  which  had  been  in  contact  with 
oak  timber  were  also  in  worse  condition.  At  Bremerhaven  the  water  is 
fairly  full  of  salt  and  heavily  laden  with  mud. 

^'  lY.  The  inner  gates  of  the  great  lock  at  Harburg,  erected  in  1880 
and  removed  in  1901  for  alteration,  were  found  in  very  good  condition  with 
the  exception  of  a  strip  about  2  feet  wide  near  the  low  water-line,  where 
the  outer  skin  was  very  rough  and  showed  rust  spots  penetrating  ^  inch 
into  the  metal.  The  river-water  is  completely  free  from  salt  and  almost 
free  from  mud  at  Harburg,  but  the  water  in  the  harbour  is,  as  yet,  strongly 
polluted  by  the  surface  and  house  drainage  of  the  town,  and  several 
chemical  factories,  besides,  discharge  their  waste  water  into  it  full  of 
impurities,  the  oxidation  of  all  which  takes  place  on  the  surface  of  the 
water ;  consequently,  the  plating  of  the  gates  is  principally  damaged  near 
the  water-line." 

The  following  statement  of  results,  obtained  by  the  author  in  some 
experiments,  covering  a  period  of  twelve  months,  serves  to  illustrate  the 
difficulty  of  deducing  reliable  coefficients  of  corrosion  from  any  but  the 
most  extensive  investigation.  The  data  obtained  are  not  without  intrinsic 
interest,  but  in  order  to  be  of  any  practical  value,  such  observations  would 
have  to  be  extended  over  a  considerable  number  of  years.  It  is  a  note- 
worthy feature  that  the  galvanised  specimens  apparently  suflered  more  than 
the  ungalvanised,  and  that,  during  the  first  three  months,  the  latter,  instead 
of  losing,  actually  gained,  weight.  This  is  due  partly  to  the  conditions  of 
immersion,  and  partly  to  the  fact  that  weight  is,  after  all,  no  very  reliable 
criterion  of  the  amount  of  corrosion  actually  taking  place,  since  some 
forms  of  oxidation  involve  no  loss  in  this  respect. 

The  first  six  specimens  were  suspended  in  a  disused  clough-shaft,  to 
which  the  tidal  water  of  the  River  Mersey  had  free  access,  the  specimens 
being  placed  at  mean  tide  level,  so  that  they  were  in  and  out  of  water  for 
about  equal  periods.  The  water  was  somewhat  impregnated  with  sewage 
discharged  from  a  neighbouring  outfall  sewer,  and  the  ungalvanised  speci- 
mens became  coated  with  a  hard  deposit,  apparently  of  a  calcareous  nature, 
which  was  removed  as  far  as  possible  before  each  weighing  by  washing  in 


PRESERVATION  OF  IRON  AND  STEEL. 


145 


clear  water  and  using  a  stiff  scrubbing  brush.  The  gain  in  weight  of 
certain  of  the  specimens  represents  the  amount  of  deposit  which  could  not 
be  removed  in  this  way.  No  further  measures  were  taken  to  remove  the 
deposit,  because  it  was  deemed  desirable  to  maintain  the  normal  conditions 
of  corrosion. 

The  last  three  specimens  were  kept  continuously  immersed  in  the  water 
of  an  inner  dock,  which  was  free  from  contamination. 

Precautions  were  taken  to  prevent  any  contact  between  the  various 
pieces,  and  all  were  well  washed  prior  to  each  weighing.'"' 

TABLE  XI. 


Nett  ' 

Weight 

Weight 

Weight 

Weight 

Total 

Loss  per 

Nature  of  Specimen. 

Area  of    Initial 
Surface!  Weight. 

at  end 
ofl 

at  end 
OfS 

at  end 
of  6 

at  end 
of  12 

Loss 
In  12 

sq.  in.  of 
exposed 

expoBed 

Mouth. 

Months. 

Months. 

Months. 

Months. 

Surface. 

Sq.  ina. 

Grains. 

Graina. 

Grains. 

Grains. 

Grains.    Grains. 

Grains. 

Casting,  plain, 

3712 

19,473 

19,499 

19,526 

19,510 

19,467  1     16 

•43 

„       galvanised, 

36-87 

18,-272 

18,228 

18,170 

18,197 

18,069 

203 

6-50 

Wrought-iron  bar,  plain, 

54-96 

31,126 

31,176 

31,173 

31,167 

31,083 

43 

-78 

,,          galvanised, 

54-38 

31,437 

31,351 

31,282 

31,278 

31,243 

194 

3-66 

,,          turned, 

58-35 

31,172 

31,187 

31,185 

31,143 

30,988 

184 

316 

Steel  bar,  plain,    . 

23-80 

6,662 

6,672 

6,680 

6,671 

6.633  1    29 

1-21 

Cast-iron  plate, 

77-5      16,979 

16,976 

16,965 

16,943 

16,972  '      7 

•09 

Wrought-iron  plate, 

76-26  !  12,903 

12,883 

12,838 

12,814 

12,854 

49 

-65 

Mild  steel  plate,    . 

75-25  •  13,519 

13,503 

13,483 

13,453 

13,406 

113 

1-60 

It  may  be  useful,  as  well  as  interesting,  to  insert  here  an  analysis  of  the 
water  of  the  River  Mersey,  made  by  Mr.  Charles  C.  Moore,  F.I.C.,  in  Sep- 
tember, 1897.  The  sample  was  taken  about  the  time  of  high  water,  and  its 
specific  gravity  was  found  to  be  1-02254.  The  water  contained  the  following 
salts  in  solution  : — 


Sodium  chloride,     .        .        .        . 

22-35 

grammes  per 

litre 

Sodium  bromide,      .        .         .         . 

032 

Potassium  chloride. 

0-54 

Magnesium  chloride. 

2^78 

Magnesium  sulphate. 

1  -785 

Calcium  sulphate,    .         .        .         . 

1-9 

Calcium  carbonate. 

0-04 

Total  dissolved  salts, 

29-715 

Preservation  of  Iron  and  Steel. — The  two  principal  measures  adopted 
for  preventing  corrosion  are  painting  and  galvanising. 

Painting  is  an  operation  which  should  be  repeated,  at  least,  once  in 
three  years  under  normal  conditions,  and  oftener  in  exposed  situations. 

*  In  regard  to  this  last  operation,  the  author  desires  to  acknowledge  the  kind  assist- 
ance he  received  from  Messrs.  H.  Pooley  ft  Son,  Ltd. 

10 


146  IX)CK  ENGINEERING. 

As  a  general  rule,  lead  paints'^  are  employed,  but  it  has  been  suggested  that 
preference  should  be  given  to  oxide  of  iron  paints,  to  avoid  any  tendency 
to  galvanic  action  between  two  metallic  substances.  Oare  should  be  taken 
to  remove  all  rust  and  scale  before  applying  the  paint. 

Cast  iron  on  leaving  the  mould  has,  or  should  have,  a  hard  bluish  skin, 
which  should  be  kept  intact  by  an  immediate  coat  of  (hydro-carbon)  oil  or 
paint.  Wrought  iron  is  also  sometimes  specified  to  be  dipped  in  oil  while 
hot,  but  the  method  is  not  a  very  successful  preservative,  and  ironworkers 
dislike  it  on  account  of  its  messiness. 

Dock  gates  and  other  marine  structures  of  iron  and  steel  should  be 
thoroughly  scraped,  cleaned,  and  painted  at  frequent  intervals — in  some 
cases  annually.  The  materials  usually  employed  for  the  purpose  include — 
red  lead  and  oil  paint,  mineral  tar,  vegetable  tar,  black  varnish,  and 
siderosthen.  The  surfaces  of  ironwork  in  close  contact  should  be  painted 
before  being  put  together.  The  interior  walls  of  ballast  boxes,  and  other 
generally  inaccessible  surfaces,  are  frequently  floated  with  a  thick  wash  of 
Portland  cement. 

Gcdvanising  consists  in  immersing  the  iron  in  a  bath  of  molten  zinc, 
whereby  a  skin  of  that  metal  is  formed  upon  the  surface.  The  process  is 
successful  so  long  as  the  zinc  covering  remains  intact.  When  it  cracks,  or 
becomes  defective  in  any  way,  rapid  corrosion  ensues  in  the  presence  of  the 
least  damp.  The  writer's  experience  of  galvanised  iron,  employed  as  a 
material  for  dock  sheds,  is  that  sea  air,  highly  charged  with  salt  and 
moisture,  works  havoc  with  it.  Several  such  sheds,  after  being  a  few 
years  in  existence,  have  had  to  be  completely  coated  with  black  varnish 
to  preserve  them  from  imminent  destruction. 

The  Angus-Smith  treatment^  largely  adopted  for  cast-iron  pipes,  consists 
in  dipping  them,  at  a  temperature  of  700°  F.,  into  a  mixture  of  coal  tar, 
pitch,  linseed  oil,  and  resin,  at  a  temperature  of  SOO""  F.  The  process  is 
an  admirable  method  of  preservation,  and  enjoys  a  considerable  reputation. 


TIMBEB. 

The  varieties  of  timber  principally  in  demand  for  the  purposes  of  dock 
engineering  may  be  enumerated  as  follows  : — 

PUea, — Greenheart,  Jarrah,  Karri,  Mora,  Pitchpine,  Oak,  Elm,  Beech. 

*A  very  common  constituent  of  modem  paints  is  sulphate  of  barium,  of  which 
there  are  two  forms,  viz.: — (1)  the  finely-ground  mineral  barytes,  and  (2)  blanc  Jixe, 
or  precipitated  sulphate  of  barium.  While  both  these  substances  have  the  same 
chemical  composition,  there  is  a  wide  difierence  in  their  physical  conditions,  which 
results  in  the  ground  mineral  being  worthless  as  an  ingredient  of  paint,  whereas  the 
precipitate  is  just  as  valuable,  owing  to  its  covering  power  and  unalterability.  Examin- 
ation of  a  sample  of  each  paint  under  the  microscope  will  easily  show  the  difierence 
between  the  fragments  of  crystals  in  the  first  case  and  the  amorphous  condition  of 
the  other. 


TIMBER. 


147 


Gates  and  Cloughs, — Greenheart,  Jarrah,  Mora,  Oak,  Pitchpine,  Pine, 
and  Fir. 

Deckings  (for  wharfs  and  bridges). — Greenheart,  Oak,  Teak,  £lm. 

Fenders.  — Elm . 

Temporary  Dams, — Pitchpine. 

Timbering  for  Excavatiorhs. — Pitchpine,  Spruce  deals,  Greenheart  sheet- 
ing piles. 

Graving  Dock  Blocks. — Oak,  Birch,  Elm,  Pitchpine. 

As  indicative  of  their  comparative  values  in  maritime  situations,  the 
following  classification  of  timbers  for  shipbuilding  purposes,  by  a  committee 
of  Lloyd's,  will  be  useful : — 


TABLE   XIL 


Estimated 

Durability 

in  Yean. 


12 
10 
9 
8 
7 
6 
5 
4 


Timber. 


Teak,  British  oak,  mora,  greenheart,  ironbark,  saL 

Bay  mahogany,  cedar. 

European  Continental  oak,  chestnut,  blue  gum,  stringy  bark. 

North  American  white  oak  and  chestnut. 

Larch,  hackmatack,  pitchpine,  English  ash. 

Cowrie,  American  rock  elm. 

Ked  pine,  grey  elm,  black  birch,  spruce  fir,  English  beech. 

North  American  hemlock,  pine. 


Greenheart  is  a  product  of  British  Guiana  and  the  north  coast  of  South 
America.  It  is  a  wood  of  extreme  hardness  and  durability,  with  a  colour 
ranging  from  green  to  black.  Its  resistance  to  crushing  is  enormous,  but 
it  is  very  brittle  and  splits  under  the  least  provocation.  Particularly  is  this 
the  case  during  the  months  of  April  and  May.  Great  care  is  therefore 
required  in  working  it,  and  when  a  log  is  about  to  be  sawn  in  two,  it  is 
often  advisable  to  bind  it  on  each  side  of  the  proposed  cut  with  chains  and 
wedges.  The  wood  has  a  very  fine  grain  and  exhibits  no  distinct  annual 
rings.  It  is  very  heavy,  ranging  from  62  to  75  lbs.  per  cubic  foot,  so  that 
it  does  not  float  in  water.  It  contains  an  essential  oil  which  is  very 
poisonous,  and  which  apparently  confers  upon  it  some  immunity  from  the 
attacks  of  sea-worms.  The  evidence  on  the  last  point,  however,  is  not 
conclusive.  Greenheart  is  obtainable  in  logs  from  12  to  24  inches  square 
and  up  to  70  feet  in  length. 

Mora  is  a  light  red  wood  with  similar  uses  to  greenheart  and  is  a  native 
of  the  same  district.  It  is  very  tough  and  close-grained,  difficult  to  saw  and 
split,  and  extremely  durable.  It  can  be  obtained  in  logs  18  to  24  inches 
square  and  as  much  as  100  feet  in  length. 

Purpleheart,  another  neighbouring  tree,  is  also  noted  for  its  qualities  of 
durability  and  strength.      It  is  hard  and  close-grained,  and  its  colour  is 


148  IX)CK  ENGINEERING. 

indicated  by  its  name.     Owing  to  its  great  toughness  it  is  capable  of  resist- 
ing great  shocks.     Logs  can  be  obtained  from  18  to  30  inches  square. 

Bullet  tree  is  a  dark  red  wood  said  to  be  an  excellent  substitute  for 
greenheart.  It  saws  easily,  takes  a  smooth  finish,  and  is  thoroughly  tough 
and  durable.  The  size  of  the  logs  runs  up  to  3  feet  in  quarter  girth  and  50' 
feet  in  length. 

Kakaralli,  though  a  less  known  tree,  is  described  as  even  surpassing, 
greenheart  in  its  qualities  for  marine  situations,  such  as  durability  and 
resistance  to  the  attacks  of  worms.  It  is  close-grained,  tough  and  difficult 
to  saw,  but  easy  to  plane.  It  has  one  drawback  in  that  it  can  only  be- 
obtained  in  small  logs,  10  to  14  inches  square,  and  rarely  exceeding  40  feet 
in  length. 

Jarrah  is  an  Australian  timber,  resembling  mahogany  in  colour,  also 
recommended  as  a  valuable  substitute  for  greenheart.  It  is  hard  and  close- 
grained,  very  liable  to  warp  and  split  and  full  of  clefts,  filled  with  resinous 
matter.  The  fibres  contain  an  acid  having  a  pungent  odour,  said  to  be  very 
efficacious  against  sea-worms  and  insects.  Its  extreme  durability  compared 
with  other  timbers  is  incontestible,  and  it  is  on  record  that  it  has  survived 
the  attacks  of  marine  borers  long  after  other  woods  have  succumbed.  On 
the  other  hand,  there  are  some  authenticated  instances  of  its  destruction 
by  the  white  ant  and  the  teredo. 

Karri,  another  Australian  native,  is  hard,  heavy,  straight-grained,  and 
tough.  It  is  stronger  than  jarrah  but  less  durable  in  damp  situations, 
though  when  entirely  immersed  it  is  said  to  last  well.  No  decisive  evidence 
is  forthcoming  as  to  its  capacity  to  resist  worms. 

Bed  Gum  is  another  tree  possessing  the  same  characteristics  as  jarrah,. 
with  strength  and  toughness  in  a  higher  degree,  while  its  durability  is 
rather  less. 

Ironbsurk  is  one  of  the  hardiest  and  strongest  woods  in  existence,  but 
it  is  not  so  durable  in  marine  situations  as  the  preceding  varieties,  being 
admittedly  readily  attacked  by  the  teredo.  In  spite  of  this  fact  it  is  much 
used  for  piles  in  harbour  works  in  New  South  Wales.  The  wood  has  a  close,, 
straight  grain,  is  very  tough  and  heavy,  and  is  white  or  yellowish  in  colour. 

Bine  Gum,  though  an  undoubtedly  useful  timber,  is  only  suitable  for  dry 
and  open  situations,  and  it  is  depreciated  by  a  tendency  to  warp  and  shrink 
under  exposure  to  the  sun.     It  is  straw-coloured. 

Stringy  bark  is  a  hard,  heavy,  straight-grained  wood,  occasionally 
employed  for  the  superstructure  of  engineering  works.  This  concludes  the 
Australian  series. 

Keyaki  is  a  very  important  timber  in  Japan,  being  strong,  durable,  and 
easily  worked.  It  is  durable  in  situations  alternately  wet  and  dry,  and  is 
much  used  for  piles. 

Deodar,  supposed  to  be  a  variety  of  the  Oedar  of  Lebanon,  is  a  wood 
of  great  stiffness,  strength,  hardness,  and  durability,  well  adapted  for 
engineering  purposes  in  India. 


TIMBER.  1 49 

Sal,  or  Saul,  is  a  close-grained,  straight-fibred  wood,  possessing  the  same 
useful  characteristics  as  the  deodar,  but  much  stronger  and  more  durable. 
The  wood  is  heavy  and  coarse  in  grain. 

Teak,  perhaps  the  best  known  of  Indian  trees,  is  endowed  with  consider- 
•able  strength  and  durability.  It  has  been  designated  the  Indian  oak,  but 
it  is  also  found  in  Burmah,  Siam,  and  Java.  The  grain  is  fine  and 
straight,  the  wood  light  and  easily  worked,  with  a  tendency  to  splinter. 
Teak  contains  an  aromatic  oil  of  a  resinous  nature,  which  coagulates  to 
such  a  degree  of  hardness  as  to  spoil  the  edges  of  cutting  tools.  The  oil 
is  further  reputed  to  be  a  preservative  from  the  white  ant  and  from  sea- 
worms.  Marketable  logs  do  not  exceed  40  feet  in  length,  with  a  quarter- 
girth  of  15  inches  downwards.     Teak  is  mainly  used  in  small  scantlings. 

Elm  is  a  wood  of  great  strength  and  toughness,  found  generally  on  the 
continent  of  Europe  and  in  North  America.  The  grain  is  smooth,  close, 
4ind  fibrous,  offering  great  resistance  to  crushing.  English  elm  is  brownish 
in  colour,  with  a  curly  grain  not  easy  to  split,  and  it  is  a  noteworthy  feature 
that  the  sap  wood  is  equally  durable  with  the  heart  wood,  provided  the  con- 
ditions be  those  of  total  immersion  or  complete  dryness.  Alternations  of 
wet  and  dry  bring  about  speedy  decay.  In  American  elm,  which  is  lighter 
in  colour,  stringy  in  the  grain,  and  liable  to  split  under  exposure,  the 
heartwood  alone  is  durable,  and  that  only  when  kept  constantly  under 
water. 

Beech  is  a  light,  compact,  fine-grained  wood,  grown  in  Europe  and  the 
United  States.  It  is  readily  cleavable  and  easily  worked.  Like  elm  it  is 
subject  to  decay  under  changes  of  condition,  but  is  fairly  durable  if 
maintained  in  either  the  wet  or  the  dry  state. 

Oak  is  possibly  the  most  valuable  timber  of  northern  latitudes,  and 
English  oak  is  particularly  renowned  for  its  strength  and  toughness.  It  is 
Mnfortunately  liable  to  the  attacks  of  insects,  and  it  contains  an  acid  which 
has  a  tendency  to  corrode  iron  fastenings.  American  oak  is  considered 
somewhat  inferior  to  the  English  and  European  varieties. 

Pitchpine  is  a  product  of  the  Southern  States  of  North  America.  It  is 
a  strong,  h6avy  resinous  wood,  extremely  durable,  when  not  exposed  to 
marine  insects,  but  difficult  to  work,  and  subject  to  cupshakes.  It  is 
procurable  in  logs,  reaching  up  to  70  or  75  feet  in  length,  with  10  to  20 
inches  quarter-girth. 

Pine,  Deal,  Fir,  and  Spruce  are  terras  covering  a  large  variety  of  timber 
of  the  same  generic  character,  which  it  is  not  necessary  to  discuss  here  at 
any  length,  more  especially  as  the  wood  plays  no  part  of  unique  importance 
in  dock  work.  Its  uses  are  confined  to  purposes  common  to  most  structures. 
It  is  a  very  handy  material,  with  a  considerable  range  of  strength  and 
toughness  among  the  various  species.  It  will  be  sufficient  to  remark  that 
wood  from  the  Baltic  is  generally  superior  to  that  from  North  America. 
Red  pine  from  Scandinavia  makes  the  best  timber  for  framing,  and  spruce 
•deals  from  the  same  locality  make  admirable  sheeting  piles.     The  former  is 


ISO 


DOCK  ENGINEERING. 


imported  in  logs,  12  to  14  inches  square,  and  the  latter  in  scantlings  of  9^ 
inches  by  3  inches  and  in  lengths  up  to  16  feet.  Oregon  pine  is  noted  for 
the  great  length  and  girth  of  its  logs,  but  it  is  not  a  very  strong  or  durable 
wood.  Signs  of  decay  have  been  observed  in  a  very  short  time.  It  is, 
however,  very  useful  for  temporary  shoring,  and  can  be  obtained  from  30  to 
130  feet  in  length  with  12  to  30  inches  quarter-girth.  Hemlock,  from  the 
Southern  States  of  South  America,  is  in  demand  for  deals  and  sleepers. 


TABLE  XIII. — Weight  and  Strength  op  Timber. 


Weight 

Transverse 

1 

Weight 

Trausverse 

Timber. 

iD  Lbs.  per 

Streugth 

Timber. 

in  Lbs.  per 
Cub.  Ft. 

Strength 

Cub.  Ft. 

in  Lbs. 

in  Lbs. 

Greenheart,     . 

62  to  75 

900  to  1,500 

Kim, 

34  to  37 

350  to  450 

Mora, 

57  „  68 

1,100  „  1,250 

Beech,     . 

43  „  53 

560  „  700 

Purpleheart,  . 
Bullet  tree,     . 

62 

•  •  • 

Oak, 

49  „  61 

500  „  650 

67 

•  •  • 

Pitch  pine. 

41  „  58 

500  „  700 

Kakaralli, 

63 

•  •  • 

Birch, 

45„49 

550  „  650 

Jarrah,    . 

63  to  64 

500  to     660 

Fir, 

34  „  36 

400  „  700 

Karri,     . 

63„64 

650  „      850 

Pine, 

32,,  34 

360  „  500 

Red  gum, 

53,,  63 

650  „      7'20 

Spruce,   . 

29„32 

400  „  600 

Ironbark, 

72 

950  „  1,050 

Chestnut, 

36„41 

650  „  650 

Blue  gum, 

63  to  71 

550  „      850 

Cedar,     . 

35„47 

400  „  600 

Stringy  bark, . 

58 

450  „      650 

Ash, 

43  „  53 

600  „  700 

Teak,      . 

41  to  52 

600  „      700 

Note. — The  transverse  strength  given  above  is  the  concentrated  central  breaking 
weight  of  a  beam  1  inch  wide,  1  inch  deep,  and  1  foot  clear  span. 

Selection  of  Timber. — A  thorough  insight  into  the  merits  and  defects  of 
different  logs  can  only  be  obtained  by  much  experience  and  close  personal 
investigation.  The  selection  of  timber  for  important  marine  works  should, 
accordingly,  only  be  entrusted  to  a  competent  and  reliable  man.  It  would 
be  a  difficult  matter  to  enumerate  all  the  indications  of  weakness  in  logs, 
and  many  defects  are  quite  latent  to  the  inexperienced  eye.  Shakes  or 
splits  should  be  looked  for  and  their  extent  gauged  by  tapping.  Discolora- 
tion is  a  bad  sign,  as  also  are  sponginess  and  the  appearance  of  wormholes 
on  the  surface.  Timber  with  large  or  dead  knots  is  unsuitable.  The  heart 
should  be  central.  Rankine'^  states  the  following  general  indications  of 
strong  and  durable  timber  : — 

*'  In  the  same  species,  that  specimen  will  in  general  be  the  strongest  and 
the  most  durable  which  has  grown  the  slowest,  as  shown  by  the  narrowness 
of  the  annual  rings. 

"  The  cellular  tissue,  as  seen  in  the  medullary  rays  (when  visible),  should 
be  hard  and  compact. 

''  The  vascular  or  fibrous  tissue  should  adhere  firmly  together,  and  should 
show  no  woolliness  at  a  freshly  cut  surface,  nor  should  it  clog  the  teeth  of 
the  saw  with  loose  fibres. 

*  A  Manual  of  Civil  Engineering,  p.  441. 


DECAY  AND  DESTRUCTION  OF  TIMBER.  151 

''  If  the  wood  is  coloured,  darkness  of  colour  is,  in  general,  a  sign  of 
strength  and  durability. 

"The  freshly-cut  surface  of  the  wood  should  be  firm  and  shining,  and 
should  have  somewhat  of  a  translucent  appearance.  A  dull,  chalky 
appearance  is  a  sign  of  bad  timber. 

"  In  wood  of  a  given  species,  the  heavier  specimens  are,  in  general,  the 
stronger  and  the  more  lasting. 

'*  Among  resinous  woods,  those  which  have  the  least  resin  in  their  pores, 
and  amongst  non-resinous  woods,  those  which  have  least  sap  or  gum  in 
them,  are,  in  general,  the  strongest  and  most  lasting." 

Decay  and  Destruction  of  Timber. — Timber  is  subject  to  dry  and  wet  rot 
and  to  the  depredations  of  worms  and  insects.  Dry  rot  is  a  disintegration 
of  the  fibres  accompanied  by  the  growth  of  a  fungus,  due  to,  and  accelerated 
by,  inadequate  ventilation.  It  attacks  woodwork  in  confined  situations 
free  from  moisture,  and  reduces  it  to  the  condition  of  a  fine  powder.  The 
disease  is  infectious,  and  spreads  with  startling  rapidity.  Once  attacked, 
no  remedy  can  save  the  affected  parts,  and  the  only  efficient  preventive  is 
thorough  ventilation.  Wet  rot  is  a  decomposition  of  the  fibres  under  the 
influence  of  moisture,  resulting  in  putrefaction  and  decay.  It  is  not 
infectious  like  dry  rot,  but  is  communicable  to  sound  timber  by  actual 
contact. 

Of  worms  and  insects  which  attack  timber,  impair  its  strength,  and  in 
some  cases  bring  about  its  utter  destruction,  the  most  important  are  the 
Teredo  navcUis,  the  Limnoria  terebrans,  the  Chelv/ra  terebrans,  and  the  Termes 
or  white  ant. 

The  Teredo  is  found  in  all  British  waters,  and,  indeed,  frequents  the 
majority  of  seaports.  It  has  a  preference  for  clear  salt  water,  and  the 
available  evidence  seems  to  point  to  the  fact  that  it  avoids  fresh,  sewage- 
polluted,  and  muddy  water  with  equal  impartiality.  Its  depredations  take 
the  form  of  tunnellings  or  excavations  into  the  timber,  generally  along  the 
grain,  and  these  it  lines  with  a  chalky  secretion.  It  is  no  uncommon 
experience  to  find  holes  ^  inch  or  f  inch  in  diameter.  Some  specimens  of 
the  Teredo  are  very  large,  measuring  as  much  as  2  feet  in  length. 

The  Limnoria  is  a  small  insect,  which  is  troublesome  on  account  of  the 
vast  numbers  in  which  it  infests  certain  localities.  It  appears  to  be 
indifferent  to  the  foulness  of  the  water,  provided  it  be  saline.  Its  ravages 
are  confined  to  the  range  of  the  tide,  and  it  generally  works  about  high- 
water  level  of  neap  tides. 

The  Chelv/ra  is  a  shrimp,  which  undercuts  woodwork  and  causes  it  to 
fall  away  in  flakes.  This  insect  manifests  a  decided  partiality  for  pure  sea- 
water,  and  is,  consequently,  more  often  found  along  the  open  coast  than  in 
enclosed  harbours. 

The  Fholas  dactylus,  while  principally  regarded  as  an  enemy  of  masonry, 
has  also  been  known  to  attack  wood.  It  bores  a  number  of  holes  close 
together. 


152  IX)CK  ENGINEERING. 

Above  groand,  timber  is  subject  to  the  depredations  of  ants — particu- 
larly, in  tropical  climates,  the  wkUe  ant.  Even  the  hardest  woods  succumb 
to  its  attacks.  The  boring  is  most  insidious,  the  whole  of  the  interior  being 
eaten  away,  while  the  surface  remains  intact. 

Preservation  of  Timber. — Of  all  artificial  means  available  for  the  protec- 
tion of  timber,  alike  from  destruction  and  decay,  by  far  the  most  satisfactory 
is  the  process  of  creosoting.  It  coagulates  the  albumen  and  fills  the  pores 
with  an  antiseptic  substance,  which  excludes  moisture,  repels  worms  and 
insects,  and  prevents  dry  rot. 

Creosote  is  an  oily  liquid  contained  in  the  second  distillation  of  tar.  Its 
composition  is  somewhat  variable ;  but,  in  order  to  be  effective,  it  should 
contain  over  40  per  cent,  of  naphthaline,  about  4  or  5  per  cent,  of  carbolic 
acid,  and  as  little  pitch  as  possible.  The  process  is  as  follows : — The  timber 
to  be  treated,  after  being  dried,  is  placed  in  a  vacuum,  and  there  heated  to 
vaporise  the  sap  and  expel  all  traces  of  moisture.  Creosote  at  a  temperature 
of  about  120**  F.  is  then  introduced  into  the  containing  cylinder  under 
considerable  pressure.  The  liquid  is  absorbed  by  the  wood  to  an  extent 
ranging  between  3  and  16  lbs.  per  cubic  foot.  The  former  figure  applies  to 
oak  and  other  hard  woods,  which  are  rather  unsuitable  subjects  for  treat- 
ment. Soft,  and  even  green,  woods  are  better  adapted  on  account  of  their 
higher  power  of  absorption.  ' 

Other  substances  have  been  advocated  for  the  impregnation  of  timber, 
notably  solutions  of  sulphate  of  copper  (Boucherie's  process),  corrosive' 
sublimate  (kyanizing),  and  chloride  of  zinc,  but  they  do  not  give  such 
good  results  as  oil  of  tar.  A  Commission  appointed  by  the  Dutch 
Government  some  time  ago,  for  the  purpose  of  investigating  the  claims 
of  various  preservative  agencies,  reported  that  'Hhe  only  process  which 
could  be  relied  upon  for  the  protection  of  wood  from  the  attacks  of  the 
Teredo  was  that  of  creosoting." 

Apart  from  internal  treatment,  various  superficial  applications  have 
been  tried,  with  more  or  less  success.  Paint  is  a  very  usual  agent  and  an 
efiective  preservative,  provided  it  be  applied  only  to  well-seasoned  timber 
and  periodically  renewed.  If  applied  to  green  timber,  it  imprisons  the  sap 
and  induces  decay.  In  sea-water  the  coating  is  liable  to  be  softened  and 
eroded.  Tar,  verdigris,  and  paraffin  have  also  been  employed  as  external 
coverings. 

The  extremities  of  timber  posts  let  into  the  ground  are  frequently 
charred  to  a  height  of  a  few  inches  above  the  ground  level. 

For  open  woodwork  in  marine  situations  the  following  measures  have 
been  adopted,  with  generally  favourable  results,  more  particularly  in  regard 
to  the  attacks  of  worms  : — 

Metallic  Sheeting. — A  thin  covering  of  copper-plate  has  proved  to  be  a 
most  satisfactory  protection  for  piles,  but  it  must  extend  from  below  the 
surface  of  the  mud  to  somewhat  above  high  water  mark,  otherwise  the 
insect  may  intrude  itself  between  the  metal  and  the  wood.     The  drawback 


GRANITE.  153 

to  its  extensive  use  is  its  expense.     A  zinc  covering  has  been  tried,  but  it 
is  soon  corroded  by  sea-water.     Muntz  metal  is  another  substitute. 

Pipe  Ciuings, — Piles  encased  in  earthenware  pipes,  such  as  drain  pipes, 
'with  the  intervening  space  filled  in  with  sand  or  cement  grout,  make  a 
durable  combination  in  situations  free  from  shocks  and  erosion.  A  coating 
of  Portland  cement  will  often  answer  the  same  purpose,  but  it  is  more 
likely  to  crack.  Tubes  of  steel  wire  netting,  embedded  in  concrete  on 
the  Monier  principle,  have  been  found  very  effective. 

Compound  Coverings, — The  following  method,  used  on  the  Pacific  coast, 
has  attracted  attention: — "After  removing  the  bark,  the  surface  of  the 
pile  is  covered  with  a  prepared  compound,  some  of  the  ingredients  of  which 
are  paraffin,  powdered  limestone,  and  kaolin.  The  pile  is  then  wrapped  in 
jute  burlap,  and  another  application  of  the  compound  is  made.  Wooden 
battens  are  then  nailed  along  the  surface,  which  receives  a  final  coat  of 
the  paint.  Piles  thus  protected  have  been  in  use  for  ten  years.  The 
•  coating  protects  the  piles  from  the  teredo,  limnoria,  and  similar  animals, 
but  its  duration  is  not  known." '"' 

Close  Nailing, — ^The  driving  in,  very  closely  together,  of  broad-headed 
scupper-nails  is  an  expedient  of  some  antiquity.  The  heads  are  apt  to 
rust,  and  though  this  is  sometimes  held  to  be  a  further  protection  from 
worms,  the  statement  lacks  confirmation.  The  method  has  been  applied 
to  dock  gates,  but  it  is  troublesome  and  expensive. 

A   natural  protection  is  very  often  provided  by  the  accumulation  of 
barnacles,  mussels,  and  other  shellfish  upon  the  surface  of  the  wood.     Sea 
thorns  act  in  the  same  way  when  the  surface  has  been  covered  with  their 
•discs. 

STONE. 

There  are  many  varieties  of  stone  suitable  for  constructive  work,  but 
the  dock  engineer  confines  his  attention  to  a  comparative  few,  which,  by 
long  experience,  have  gained  a  reputation  for  durability  and  strength.  The 
principal  of  these  is  granite. 

Granite  is  a  very  bard  and  extremely  durable  rock,  of  igneous  origin, 
crystalline  in  structure,  and  of  great  value  in  dock  work  on  account  of  its 
heavy  and  massive  proportions.  In  its  true  form  it  is  composed  of  crystals 
of  quartz,  felspar,  and  mica;  but  there  are  other — so-called — granites  con- 
taining hornblende  (syenitic  granite),  quartz  diorite,  kc. 

The  quartz  is  a  very  hard  substance,  with  a  vitreous  lustre,  and  prac- 
tically indestructible.  It  renders  the  granite  very  difficult  to  work.  The 
felspar  is  lustrous  and  granular,  and,  being  present  in  greatest  volume, 
gives  the  granite  its  distinctive  colour,  which  may  be  white,  grey,  pink, 
red,  or  brown.  It  is  less  hard  and  less  durable  than  quartz.  Mica 
is  a  thin,  fiaky  substance,  with  a  bright,  metallic  *  lustre.  It  is  easily 
•decomposed. 

*  Snow  on  "  Marine  Woodborers,"  Engineering ,  Oct.  7,  1898. 


154 


DOCK  ENGINEERING. 


Granite  is  principally  used  in  situations  where  great  strength  is  required^ 
such  as  for  copings  and  facings  to  dock  walls,  quoins  and  sills  to  entrances 
and  locks,  column  and  pivot  bases,  girder  beds,  paving  setts,  and  road 
metal. 

The  stone  is  procured  in  various  parts  of  the  United  Kingdom,  chiefly 
in  Aberdeenshire,  Kirkcudbrightshire,  Cornwall,  Devonshire,  Leicester- 
shire, Wicklow,  Wexford,  and  the  Channel  Isles.  Cornish  granites  have 
generally  a  very  coarse  grain. 

.  Sandstone  has  a  crystalline  structure  composed  of  grains  of  quartz 
cemented  together  by  various  substances,  such  as  carbonate  of  lime, 
carbonate  of  magnesia,  <&c.,  upon  the  weathering  qualities  of  which  the 
durability  of  the  stone  depends.  A  good  sandstone  should  possess  a 
uniform,  compact,  bright,  well-cemented  grain.  A  dull  appearance  is 
not  a  good  sign.  Some  sandstones  are  very  friable,  others  are  but  moder- 
ately durable,  but  a  few  of  the  harder  varieties  are  very  serviceable  for 
dock  work,  such  as  those  from  the  reputed  quarry  of  Bramley  Fall,* 
near  Leeds,  from  the  Forest  of  Dean,  in  Gloucestershire,  and  elsewhere. 


TABLE  XIV. — Compressive  Strength  op  Stone.! 


Cruahlng 

Cnifihing 

stone. 

Weight 
in  Tons  per 

Stone. 

Weight 
in  Tons  per 

Square  Foot. 

Square  Foot. 

1 

Granite— Aberdeenshire,  . 

800  to  1,200 

Limestone — Chilmark, 

400 

ComiBh,     . 

600  ,.  1,000 

Ma^nesian,    . 

430 

Mount  Sorrel,    . 

850 

Sandstone — ^Craigleith,     . 

360 

Trap — Penmaenmawr, 

1,060 

York,     . 

.S60 

Limestone —Portland, 

260 

Bramley  Fall, 

390 

Bath,     . 

90  to  100 

Cheshire, 

130 

Pur beck, 

680 

Limestone  is  a  somewhat  vague  term  for  a  stone,  the  principal  con- 
stituent of  which  is  carbonate  of  lime ;  and  a  class  which  includes  chalk, 
Portland  stone,  Kentish  rag '  and  marble,  has  a  very  wide  range  of 
characteristics  indeed.  The  most  durable  specimens,  as  a  rule,  are  heavy, 
dense,  and  homogeneous,  with  a  fine,  crystalline  grain.  Portland  and 
Purbeck  limestones,  perhaps  the  best  known  varieties  in  general  use, 
differ  slightly  from  this  criterion;  the  first  has  a  fairly  large  grain,  and 
the  second  is  conchoidal  and  non-crystalline.  Both  these  stones,  and, 
indeed,  limestones  generally,  and  in  a  lesser  degree  sandstones,  are  vulner- 
able under  the  attacks  of  the  Fholas,  and  this  acts  as  a  deterrent  to  their 
extensive  use  in  marine  situations.     The  limestone   blocks  at  Plymouth 

*  The  original  quarry  of  Bramley  Fall  is  reported  to  be  practically  worked  out, 
but  much  of  the  stone  from  neighbouring  quarries  goes  by  the  same  name. 

t  For  a  very  valuable  and  complete  series  of  experimental  results,  dealing  with  the 
crushing  strength  of  .stone,  the  reader  is  referred  to  a  paper  on  *^  The  Building  Stones  of 
Great  Britain,"  by  Professor  T.  Hudson  Beare. — Vide  Min.  Proc.  Inst.  CE.,  vol.  cvii. 


DESTRUCTION  OF  STONE.  155 

breakwater  had  to  be  replaced  by  granite  blocks  owing  to  the  ravages  of 
the  mollusc  Apart  from  this,  the  growing  popularity  and  the  ready 
adaptability  of  concrete  have  caused  it  to  largely  supersede  natural  rock 
for  dock  construction  and  harbour  works. 

Destmction  of  Stone. — The  softer  kinds  of  stone  will  frequently  wear 
away  under  continued  attrition  and  the  chemical  action  of  an  unsuitable 
atmospheric  environment,  but  the  destructive  agencies  most  in  evidence, 
in  regard  to  the  more  adamantine  varieties  used  in  dock  work,  are  living 
organisms. 

The  PJioloa  dactylus  is  a  mollusc,  living  in  sea- water,  which  bores  into 
limestone,  shale,  sandstone,  and  timber,  but  does  not  attack  granite.  It 
is  a  small  animal,  with  a  maximum  length  of  about  5  inches,  but  one 
which  is  quite  capable  of  doing  extensive  mischief  by  boring  its  holes 
in  close  proximity  to  each  other,  causing  the  ultimate  collapse  of  the 
masonry. 

The  Saaicava  is  another  mollusc  known  to  bore  into  limestone  to  a 
depth  of  6  inches.  It  )ias  manifested  its  presence  at  Plymouth,  Folke- 
stone, and  elsewhere. 

There  is  apparently  no  remedy  for  the  ravages  of  these  marine  borers, 
except  the  substitution  of  some  other  kind  of  material  for  the  stone 
attacked. 


156 


CHAPTER  V. 

DOCK  AND   QUAY  WAIiLS. 

Definition — Functions  undeb  Vabious  Conditions — Stresses  in  Retaining  Walls 

— OVEKTUIINING  FOBCES— AnOLES  OF  REPOSE — ThEOBT  OF  CONJUGATE  PbESSITRES — 

Coulomb's  Theobem — CHAxn)T's  Theorem — Weight  of  Earthwork — Surcharge 
— Restraining  Forces — Counterforts — Tns  Bars — Weight  of  Masonry — Em- 
pirical FoRMUUB — Conditions  of  Stability — Centres  of  Gravity — Typical 
Example— Practical  Points— Natural  Foundations— Stratified  Sites— Arti- 
ficial Foundations — Piling — Wells  and  Cylinders— General  Methods  of 
Construction,  with  Examples  of  Quay  Walls  at  Newcastle,  Cork,  Glasgow, 
Liverpool,  Belfast,  Ardrossan,  Marseilles,  Antwerp,  Rotterdam,  Dublin, 

KURRACHEE,  SUEZ,  BOUGIE,  AND  SfAX— CONSIDERATION  OF  INSTANCES  OF  FAILURE 

AT  Altona,  London,  Southampton,  Calcutta,  and  Liverpool — Underpinning — 
Miscellaneous  Types  of  Wall  at  Hull,  Greenock,  London,  Liverpool,  and 
Manchester. 

Definition. — A  dock  wall  may  be  said  to  be  a  special  case  of  a  class  of  walls 
termed  Retaining  or  Revetment  walls.  Under  normal  conditions  it  derives 
a  certain,  albeit  varying,  amount  of  support  from  the  hydrostatic  pressure 
on  its  face,  which  more  or  less  neutralises  the  earth  pressure  from  the  rear. 
Should,  however,  the  dock  at  any  time  be  allowed  to  run  dry,  the  identity 
of  its  functions  with  those  of  an  ordinary  retaining  wall  would  be  complete. 
This  is  a  possibility  which  may  have  to  be  faced,  voluntarily,  on  account  of 
repairs  and  alterations,  or  involuntarily,  for  other  reasons,  such  as  an 
accident  to  the  entrance  gates.  Accordingly,  it  is  advisable  to  neglect  any 
frontal  sustaining  force  and  to  treat  a  dock  wall  as  if  it  were  a  retaining 
wall,  pure  and  simple. 

But,  even  in  so  doing,  it  must  be  admitted  that  the  range  of  contingen- 
cies to  which  a  dock  wall  is  liable  far  exceed  those  affecting  an  ordinary 
retaining  wall.  ''Hydrostatic  pressure  alone  may  more  than  double  or 
halve  the  factor  of  safety  in  a  given  wall.  Thus,  with  a  well  puddled  dock 
bottom,  the  subsoil  water  in  the  ground  at  the  back  of  the  wall  will 
frequently  stand  far  below  the  level  of  the  water  in  the  dock,  and  the 
hydrostatic  pressure  may  thus  wholly  neutralise  the  lateral  thrust  of  the 
earth,  or  even  reverse  it.  On  the  other  hand,  with  a  porous  subsoil  at  a 
lock  entrance,  the  back  of  the  wall  may  be  subjected,  on  a  receding  tide,  to 
the  full  hydrostatic  pressure  due  to  the  range  of  that  tide  plus  the  lateral 
pressure  of  the  filling.  Again,  the  water  may  stand  at  the  same  level  on 
both  sides  of  the  wall,  but  may  or  may  not  get  underneath  it.  If  the  wall 
is  founded  on  rock  or  good  clay,  there  is  no  more  reason  why  the  water 


OVERTDRNINO  FORCES.  157 

should  get  under  the  wall  thiin  that  it  should  creep  under  aaj  stratum  of  a 
well-conatructed  masonry  or  puddle  dam,  and  under  those  ciroumatanceB  the 
presence  of  the  water  will  increase  the  atability  by  diminisliing  the  lateral 
thrust  of  the  filling.  If,  however,  as  is  perhaps  more  frequently  the  case, 
the  wall  ia  founded  on  a  porous  stratum,  the  full  hydrostatic  pressure  will 
act  OD  the  base  of  the  wall,  and  reduce  its  stability  in  practical  cases  by 
About  one-half."  •  These  mutable  conditions  can  manifestly  only  be  met  by 
providing  a  considerable  margin  of  strength. 

Stresses  in  Retaining  Walls. — The  forces  at  work  iu  the  case  of  an 
ordinary  retaining  wall  are  three  in  number: — 

(1)  There  ia  the  overturning  influence  of  a  wedge-shaped  mass  of  earth, 
I)  C  E  (fig.  77),  behind  the  wall,  which  tends  to  slide  down  some  plane  of 
rupture,  C  E,  in  the  absence  of  proper  support. 

(2)  To  this  mu^t  be  added  the  effect  of  any  snrcharge  upon  the  surface 
of  the  ground  constituting  the  wedge. 


Fig.  77.  Fig.  78. 

(3)  And,  lastly,  there  is  the  weight  of  the  wall  acting  vertically  down- 
ward, and  consequently  oSering  resistance  to  the  overturning  tendency.     If 
the  bock  of  the  wall  be  not  vertical,  as  in  fig.  78,  it  is  obvious  that  the 
perpendicular  line,    CD,    must  still    be  con- 
sidered the  virtual  boundary  of  the  opposing 
influences  and  that  the  weight  of  the  earth- 
work, F  C  D,  must  be  included  in  the  weight 
of  the  wall. 

It  will  be  well  to  consider  these  forces  a  ^^    ^ 

little  more  in  detail. 

Orertornlng  Forces. — The  actual  extent  of  the  wedge  and  its  effective 
pressure  can  only  be  matters  of  conjecture.  It  is  common  experience  that 
unsupported  earthwork  stands  at  widely  differing  slopes,  according  to  the 
nature  and  condition  of  the  particles  of  which  it  is  composed.  To  a  limited 
degree,  experiments  have  determined  some  of  these  slopes  and  fixed  what  ia 
termed  an  Angle  of  Repoge  (p,  fig.  79)  for  the  more  prominent  kinds  of 

•Baker  on  "Lateral  Presaure  of  Earthwork,"  Mm.  Proe.  Int-t.  O.E.,  vol.  Ixv., 
p.  ISO. 


158 


DOCK  ENGINEERING. 


•earth.  But  the  values  attached  to  these  angles  can  only  be  regarded  as  of 
an  approximate  nature,  as  will  be  evident  from  a  glance  at  the  following 
table  comprising  maximum  and  minimum  results  obtained  by  different 
•experimentalists : — 

TABLE  XV. 


Material. 

Range  of  Angle  of  Bepoee. 

From 

To        - 

Gravel  and  shingle, 

Dry  sand, 

Vegetable  earth,     .... 
Compact  earth,       .... 
Well-drained  clay, 
Peat, 

35' 
21' 
28' 
40' 
40' 
14' 

48' 
37' 
55' 
60' 
46' 
46' 

Ranges  so  extensive  render  it  an  exceedingly  difficult  matter  to  assign 
any  angle  to  a  variety  of  soil,  however  specific,  especially  in  view  of  a  further 
modification  due  to  its  degree  of  humidity.  The  amount  of  moisture  present 
in  the  sample  under  consideration  very  materially  influences  the  experi- 
mental result  obtained  for  its  angle  of  repose.  A  slight  quantity,  just 
sufficient  to  occupy  the  interstices  between  the  grains  of  solid  matter,  has 
been  found  to  increase  the  frictional  resistance  to  movement,  and,  accord- 
ingly, to  produce  a  correspondingly  greater  angle  of  repose.  Any  excess 
of  moisture,  however,  over  and  above  this  trifling  amount,  results  in  a 
diminution  of  the  frictional  resistance ;  and  if  the  humidity  be  indefinitely 
increased,  the  material  eventually  acquires  a  muddy  consistency  to  which 
there  is  no  angle  of  repose  worth  noting.  Ordinary  clay,  for  instance,  in 
the  dry  condition  crumbles  at  40° ;  moderately  moist,  its  inclination  may  be 
increased  to  as  much  as  50° ;  allowed  to  become  saturated,  it  subsides  at  an 
angle  of  10°. 

Argillaceous  earths  are  most  susceptible  to  the  deteriorating  influences 
of  moisture,  and  any  admixture  of  sand  with  the  clay  only  produces  an 
accentuation  of  the  evil,  because  the  impermeability  of  the  clay  ofiers  an 
obstacle  to  the  escape  of  water  which  has  entered  through  the  pores  of  the 
sand.  A  striking  instance  of  this  is  afforded  in  a  notable  landslip  behind 
a  quay  wall  at  Altona,  to  be  dealt  with  at  a  later  stage. 

The  foregoing  considerations  distinctly  emphasise  the  necessity  for  the 
prompt  and  adequate  drainage  of  earthwork,  and  particularly  so  in  the  case 
of  dock  and  river  walls,  where  the  earth  backing  is  generally  in  a  state  of 
intermittent  immersion.  Under  the  head  of  a  rising  tide,  water  penetrates 
to  an  equal  height  behind  the  wall,  and,  unless  there  be  adequate  means 
for  its  withdrawal  with  the  ebb,  the  volume  of  water  thus  confined  will 
prove  a  serious  augmentation  of  the  overturning  forces. 


THE  THEORy  OP  CONJUGATE  PRESSURES. 


159 


Quite  apart,  however,  from  the  question  of  humidity,  there  is  another 
difficulty  in  the  way  of  estimating  the  angle  of  repose  for  cases  in  practice. 
The  earth  behind  a  dock  wall  is  often  anything  but  homogeneous.  With 
the  most  moderate  foundation  depths,  a  series  of  totally  different  strata 
will  generally  be  passed  through,  each  having  its  own  particular  angle  of 
repose.  And  even  supposing  the  most  favourable  case — that  of  filling  of  a 
fairly  uniform  texture — it  is  manifest  that  the  increased  pressure  upon 
the  lower  layers  will  confer  upon  them  a  greater  density,  and  so  modify 
their  conditions  of  stability  that  the  line  of  rupture,  instead  of  being 
straight,  will  become  more  and  more  inclined.  Further,  the  absence  of 
pressure  upon  the  topmost  layers  will  enable  these  to  stand  at  a  steeper 
inclination,  so  that  the  natural  outline  of  the  mass  would  present  the  form 
of  an  ogee  curve  (fig.  80).  Altogether,  it  must  be  frankly  confessed  that 
it  is  practically  impossible  to  arrive  at  any  thoroughly 
reliable  data  for  dealing  with  each  case  in  situ,  and, 
in  the  absence  of  definite  information,  the  only  course 
open  is  to  make  certain  assumptions,  approximately 
accurate,  and  to  allow  a  sufficient  margin  of  safety  to 
cover  attendant  errors. 

Several  theories,  accordingly,  have  been  put  forward  in  regard  .to  the 
magnitude  and  direction  of  the  resultant  pressure  of  earthwork  on  a 
retaining  wall.  It  would  be  impossible,  within  the  limits  of  this  work, 
to  investigate  all  these  theories  exhaustively,  but  it  will  be  noticed  that, 
however  distinct  in  development,  they  contain  a  common  elemental  factor. 

Considering  the  wall  as  of  unit  length,  calling  the  height  h  ( A  B  or 
C  D,  fig.  77),  and  the  angle  of  rupture  $,  the  sectional  area  of  the  earth 

wedge  may  be  stated  as  — ^ ,  and  its  weight  as -: ,  w  being  the 

weight  per  unit  volume.     The  various  theories  may 
then  be  covered  by  the  following  general  expression : — 


Fig.  80. 


P  =  ^'  X  C, 


(11) 


Fig.  81. 


in  which  P  stands  for  resultant  pressure,  and  C  is  a 
variable  coefficient  dependent  upon  several  considera- 
tions, such  as  the  angle  of  repose,  f,  the  surface 
slope,  a,  of  the  earth  behind  the  wall,  the  batter,  /3,  of 
the  back  of  the  wall,  and  the  direction,  7,  of  the 
resultant. 

In  the  ensuing  examination  of  some  of  these  theories,  the  foregoing 
symbols  will  retain  their  respective  significations  throughout. 

The  Theory  of  Coiyugate  Pressures.— Professor  Rankine,  in  his  work 
on  CivU  Engineering  (pp.  167  and  318),  has  developed  a  theory  of  earth 
pressure  which  ignores  the  existence  of  any  cohesion  between  the  particles. 
It  is  based  on  the  following  principle,  primarily  enunciated  in  a  paper  on 


l6o  DOCK  ENGINEERING. 

"  The  Stability  of  Loose  Earth,"  contributed  to  the  Philosophical  Transac- 
tions of  the  year  1856,  viz. : — "The  resistance  to  displacement,  by  sliding 
along  a  given  plane,  in  a  loose  granular  mass,  is  equal  to  the  normal 
pressure  exerted  between  the  parts  of  the  mass  on  either  side  of  that 
plane,  multiplied  by  a  specific  constant."  The  restriction  renders  the 
theory  somewhat  defective  in  its  relationship  to  ordinary  revetment  walls 
with  well-consolidated  backing,  but  it  is  nevertheless  apparent  that  any 

calculations  made  on  this  basis  will  err  only 
on  the  side  of  excessive  strength. 

Starting  with  a  definition  of  conjugate 
stresses  as  a  pair  of  stresses  acting  upon  two 
planes  supposed  to  traverse  a  point  in  a  body, 
such  tliat  each  stress  is  parallel  to  the  plane 
upon  which  the  other  acts,  and,  futher,  dis- 
tinguishing as  principal  stresses  those  stresses 
Fie.  81a.  which    are    mutually    normal,  *    we    may    go 

on  to  show  that  there  are  three  cases  in 
which  the  intensity  and  direction  of  the  resultant  stress  can  be  deter- 
mined, viz.  : — 

1.  When  the  principal  stresses  are  of  the  same  kind — i.e.,  either  both 
positive  (compressive)  or  both  negative  (tensile),  with  equal  intensities. 

2.  When,  with  equal  intensities  the  stresses  are  not  of  the  same  kind ; 
and, 

3.  When  the  stresses  are  of  either  kind,  but  with  unequal  intensities. 

Case  I. — The  resultant  stress  must  clearly  be  of  the  same  kind  as  the 
principal  stresses,  and  have  an  intensity  equal  to  that  of  either  of  them.  In 
fig,  82,  A  B  and  B  C  are  planes  upon  which  two  principal  stresses,  P  and  Q, 
are  supposed  to  act.  Since  these  are,  by  hypothesis,  equal  in  intensity, 
heir  magnitudes  will  be  proportional  to  the  sides,  AB  and  B  C,  respec;- 
tively.  If,  then,  from  the  point  of  intersection  we  set  off  O  X  to  represent 
P  =  j9  X  A  B,  and  O  Y  to  represent  Q  =  q  (or  p)  x  B  0,  O  Z  will  give  the 
magnitude  and  direction  of  the  resultant,  R.  Since  the  triangles,  ABC 
and  O  X  Z,  are  similar,  it  follows  that  R  is  perpendicular  to  the  plane,  A  C, 
and  is  proportional  to  the  side,  A  C  {i.e.,  R  =  r*  x  A  C),  and,  therefore, 
that  the  intensity  of  pressure  of  the  resultant  is  equal  to  the  intensity  of 
each  of  the  principal  stresses,  which  is  equivalent  to  stating  that  r  =  p  =^  q. 

Case  II. — When  the  sense  of  one  of  the  principal  stresses  is  altered, 
the  intensities  remaining  equal,  the  effect  is  to  change  the  direction  of  the 
resultant,  but  not  its  amount  or  intensity.  In  fig.  83  the  principal  stresses 
are  P  and  Q,  as  before,  but  the  sense  of  P  is  inverted.     By  a  construction 

*  If  two  planes,  X  X  and  Y  Y,  be  supposed  to  traverse  a  point,  0,  in  any  body,  and 
if  the  direction  of  the  stress,  p,  on  the  plane  X  X  be  parallel  to  the  plane  Y  Y,  then  the 
direction  of  the  stress,  q,  on  the  plane  Y  Y  is  parallel  to  the  plane  X  X,  and  the  two 
stresses  are  said  to  be  conjugate.  When  X  X  and  Y  Y  are  at  right  angles  the  stresses 
become  principal  stresses  (fig.  81a). 


THE  THEORY  OF  CONJUGATE  PRESSURES. 


l6l 


similar  to  that  in  Case  I.,  and  readily  understood  from  the  diagram,  the 
direction  of  R  is  foand,  and  it  will  be  noticed  that  it  makes  the  same 
angle,  &,  with  the  direction  of  Q,  as  the  resultant  in  Oase  I.,  but  on  the 
opposite  side. 

Yi TiZ 


Fig.  82. 

Case  II Ly  with  which  we  are  mainly  concerned,  is  a  combination  of  the 
conditions  obtaining  in  the  preceding  instances  and  may  be  solved  from 
them.  For  it  is  possible  to  take  two  subsidiary  intensities  such  that  the 
principal  intensity,  g,  is  equal  to  their  sum  and  the  principal  intensity,  p, 
to  their  difference,  thus — 

+  — ?i  ~ 


P^ 


2 
q+p     q-p 


2 


2 


Dealing  with  these  subsidiary  intensities  in  pairs,  the  problem  resolves 
itself  into  finding,  first,  the  resultant  of  two  like  intensities,  each  equal  to 

—^j  as  in  Case  I. ;  secondly,  the  resultant  of  two  unlike  intensities,  each 

equal  to  ^-^  as  in  Case  II. ;  and,  lastly,  the  combined  resultant  of  these 
two. 

In   fig.    84,   set  off  O  X  =  ,  perpendicular  to  the  plane   A  C,   to 

It 

represent  the  resultant  intensity  due  to  two  like  equal  intensities  of  that 

amount.     Next  set  off  O  Y  =  ^^~  at  an  angle  X  O  Y  =  2  tf,  to  represent  the 

resultant  of  two  unlike  equal  intensities.  Completing  the  parallelogram, 
OZ  =  r  will  be  the  resultant  of  these  component  intensities  in  direction  and 
magnitude. 

The  same  result  may  be  demonstrated  by  a  slightly  modified  diagram, 
which  lends  itself  to  a  clearer  analysis  of  the  range  of  stress. 

In  fig.  85  draw  0  H  at  right  angles  to  the  plane  A  0,  from  the  point  of 

intersection  O,  and  set  off  O  M  =  ^       .     Produce  the  line  of  action  of  the 

stress  Q  to  L,  taking  the  point  L  such  that  O  M  L  is  an  isosceles  triangle 

11 


l62 


DOCK  ENGINEERING. 


with   the   sides   MO    and    ML    equal.      With    centre    M    and    radius 

M  N  =  ~~  describe  the  arc  Nq  N  N^  Ng  cutting  M  L  in  N.     Join  N  O, 

which  thus  becomes  the  measure  of  the  resultant  intensity  r. 

The  angle  ^  being  variable,  the  angle  H  M  L  =  2  ^  will  also  vary,  and 
with  it  the  angle  M  O  N,  which  is  the  obliquity  of  the  direction  of  the 
resultant  in  reference  to  O  M,  the  normal  to  the  plane,  A  0.  The  locus  of 
the  point  N  is  the  semicircumference  NQNNg.  The  angle  M  OjN  attains 
its  maximum  value,  manifestly,  when  the  direction  of  r  is  a  tangent  to 


the  curve — i.e.,  when  the  point  N  coincides  with  N^.      When  this  is  the 
case  the  angle  M  N  O  is  a  right  angle,  and  the  angle  M  O  N  becomes 

.     ,  MN        .     .q  -  p 
O  M  9  ^  P 


Write 


Whence 


sin  9  = 


9  -  P 


q  +  p 
p      \  -  sin 


(12) 


q       1  +  sm  9 

In  applying  this  theory  to  earth  pressure,  it  is  to  be  noted  that  the  angle 
MON  represents  the  limiting  angle  consistent  with  equilibrium;  in 
other  words,  the  angle  of  repose  (^).  Equation  (12)  then  determines  the 
minimum  intensity,  />,  of  horizontal  pressure  necessary  to  maintain  the 
stability  of  a  mass  of  earth,  the  measure  of  whose  vertical  pressure  intensity 
is  q. 

In  the  case  of  a  retaining  wall,  the  earthwork  behind  which  does  not 
rise  above  a  horizontal  surface  level  with  the  coping,  q  is  equal  to  the  weight 
of  a  unit  column  of  earth  of  height,  h — i.e., 

q  =wh. 
The  mean  intensity  is 

wh 


"j 


THE  THEORY  OF  CONJUGATE  PRESSURES. 


163 


and  the  total  pressure 


Hence,  siuce 


Q  = 
P  = 


"2  • 


1  -  sin  (p 


(13) 


1  +  Sin  (f> 

The  line  of  action  of  P  is,  as  in  the  case  of  water  pressure,  at  one-third 
of  the  height  of  the  wall  above  its  base. 

A  simple  graphical  construction  for  obtaining  the  numerical  value  of 

A2  ; — i  may  advantageously  be  inserted  here.     Take  a  vertical  line,  A  B 

1  +  sin  9       "^ 

(fig.  86),  to  represent  A,  the  height  of  the  wall,  to  any  convenient  scale,  and 
A  C 


Fig.  86. 

from  B  draw  B  C,  making  the  angle  9  with  A  B.     Draw  A  0  horizontally, 
and  with  centre,  C,  and  radius,  C  A,  describe  the  arc  A  D.     Then  B  D  is 


the  line  whose  length  measures  U;  :i?^^- to  the  same  scale. 

*  \  1  +  Sin  9 


For  B  D*  =  (B  C  -  C  D)2  =  (B  C  -  A  C)2 

h  ^2 

,cos  <p 

I  -  sin  (p\^ 


=  (  -  A  tan  0  ) 

\oos  <p  ^  J 

\    cos  (p    ) 

(1  -  sin  y)» 
1  -  sin^  9 


=  A2 


1  -  sin  9 


1  +  sin  <p 

The  case  of  conjugate  stresses — viz.,  that  in  which  the  stresses  are  not 
mutually  perpendicular — is  perhaps  not  strictly  essential  to  the  present 
purpose,  as  its  application  is  confined  to  those  retaining  walls  in  which  the 
surface  of  the  earth  backing  is  not  horizontal — a  condition  of  such  rare 
occurrence  in  the  practice  of  dock  engineering  as  scarcely  to  warrant  any- 
thing in  the  nature  of  a  lengthy  demonstration,'^     It  may  be  of  interest, 

*  There  is  only  the  poesibility  of  a  river  wall  being  surcharged  by  a  sloping  embank- 
ment. 


1 64  I^OCK  ENGINEERING. 

however,  to  give  a  succinct  description  of  the  method  by  which  the  general 
formula  is  evolved. 

In  fig.  87,  let  the  angle  N  O  M  (  =  f)  represent  the  limiting  angle  of 
repose,  and  the  semicircle  Ng  N  Kq,  the  locus  of  the  point  N,  as  in  fig.  85. 

Through  O  draw  the  line  O  X  Y,  making  the  angle  M  O  Y  =  a,  the 
obliquity  of  the  conjugate  pressures,  and  cutting  the  semicircle  in  X  and  Y. 
Then  the  limits  of  the  ratio  of  the  intensities  of  the  conjugate  pressures  are 
OX  OY 

OY*       OX" 

The  angle  a  may  have  any  value  between  zero  and  (p.  In  the  former 
limit,  which  is  the  case  when  the  conjugate  pressures  are  perpendicular  to 
each  other,  and  become  principal  stresses,  O  X  Y  coincides  with  O  Nj  Nq  and 

_— -i-  (  = ^ — L.\  is  the  minimum  value  of  -.     When  the  obliquity  is 

O  N^   \      1  +  sin  9/  q 

the  greatest  possible,  such  that  a  ^  (p,  the  points  Ng  and  Nq  coalesce  in 

N,  and  the  limit  of  the  ratio  of  the  conjugate  pressures  becomes  unity. 

For  any  intermediate  position  in  which  a  =  X  O  M ,  the  limiting  ratio 

(^j  of  the  conjugate  pressures   may  be  determined   as  follows: — Draw 

S  M   perpendicular  to  X  Y,  and  join  M  X,   M  Y,  each  line  making  the 
angle  &  with  X  Y. 

p^_QX_OS-XS_|  (q+p)co%  «-^  (y-jp)cos  6 
^'~OY""OS  +  YS"'|  {q  +p)  cos  a  + 1  {q  -p)  cos  & 


Then 


—  -  COS  a -COS  B 

-  —^  cos  a  +  cos  9 
q^p 


.     (U> 


Now,  8in^  =  t^2±^8ina, 


=  y-g^ 


.    />)2 

.  COS  &=    A  /  1  -  7^ To  sin2  a 


And  as 


/(^  "  P)^  "  (5'  ■*"  P)^  sin2  a 

sin^  =  ^  /    ':, 


-j'^ 


,  ^■,     pY  sii^^  ^  -  (q+P)^  sin^  a 
cos  tf^  


(9-pr 


9  +  P       /     .     o  ^ ^-o- 

= V  sm^  ©  -  sin^  a 

q-p 

=  - — —  J  cos^  a  -  cos^  4>. 

q-p 


THE  THEORY  OF  CONJUGATE  PRESSURES. 


165 


Hence,  substituting  in  (14),  and  cancelling 


a—  v 


p      cos  a  -  n/cos'^  a  -  cos^  ^ 
9      cos  a  +  >/co82  a  -  cos-  9 


(15) 


Now,  as  the  stresses  are  inclined  to  one  another  at  the  angle  a,  the 
intensity  of  the  vertical  pressures  in  the  case  of  earthwork  will  be  equal  to 
the  weight  of  a  unit  column  multiplied  by  cos  a. 

g'  =  wh  cos  a. 

The  mean  intensity,  therefore,  is 

wh 


7i  = 


cos  a 


and  the  total  pressure 


Accordingly, 


P  = 


whT- 


cos 


Q  =  -rr-  COS  a. 


^  cos  a  -  vcos^  a  —  cos^  0 
cos  a  +  V  cos-  a  -  cos^  ^ 


(16) 


It  will  be  seen  that  when  the  surface  of  the  ground  is  horizontal  as=0, 
-cos  a  =  1,  and 

p  _  wh^      1  -  sin  9 

~    2     ■  1  +  sin  (p' 
as  previously  demonstrated. 

For  a  surface  sloping  upwards  at  the  angle  of  repose,  a  =  ^  and 


P  =  -^—  cos  ^. 


(17) 


According  to  Professor  Rankine,  the  line  of  action  of  the  resultant 
force  is  always  parallel  to  the  surface  of  the  ground.  A  modification  of  the 
theory,  due  to   Dr.  Scheffler,  determines  the 

direction  of  the   earth   thrust  as  inclined  to  ^^ 

the  horizontal  at  a  constant  angle,  identical 
with  the  angle  of  repose.  In  this  way, 
although  the  total  amount  of  the  thrust  is 
greater  by  Scheffler' s  hypothesis  (being  as  E  G 
to  EF,  fig.  88),  yet,  except  in  one  instance, 
the  overturning  effect  is  less,  owing  to  the 
nearer  approach  of  the  line  of  thrust  to  the 
vertical.  The  one  exception  is  the  case  in 
which  the  surface  of  the  ground  has  an  in- 
clination ^  to  the  horizontal,  and  then  the 
two  theories  lead  to  the  same  result. 

Another   modification,   due    to    Professor 


Fig.  88. 


Keilly,  takes  into  consideration  the  batter,  or  inclination  to  the  vertical^ 


1 66  DOCK  ENGINEERING. 

of  the  back  of  the  wall.     In  fig.  89,  the  point  X  is  determined  by  drawing 
MX  at  an  angle,  OMX  -  2^. 

^^ ^^  Then  the  total  thrust  is  measured  graphically 

by 

wh^      OX 
ON, 


^x       if       -Nf.  ^  =  -ir-rri^. 


0 


Fig.  89. 
or  analytically  by 

p  _  J^.     >/r+  sin*  9  -  2  sin  ^  cos  2 p  /^S) 

2  1  +  sin  <p 

When  the  back  of  the  wall  is  vertical,  i8  =  0,  and  the  equation  reduces 

to 

wh^     1  -  sin  f> 

2       l+sm^ 

which  agrees  with  Kankine's  result  for  similar  conditions.  The  direction 
of  the  resultant  is  constant  at  an  angle  /  to  the  horizontal,  such  that 
y  =  /?  +  X,  the  last-named  angle  being  deduced  from  the  equation — 

.    ^  sin  ©sin  2/3  ,-^. 

8inX= — ■  ^  .         .     (19) 

V 1  +  sin^  (p  -  2  sin  ^  cos  2  /? 

It  will  be  observed  that  in  none  of  the  foregoing  expressions  is  any 
account  taken  of  the  friction  exerted  by  the  particles  against  the  back  of 
the  wall — ^a  factor  which  tends  to  resist  displacement.  In  fact,  the  assumed 
conditions  only  hold  good  at  a  suitable  distance  from  the  wall  beyond  the 
range  of  its  frictional  influence. 

A  formula  has  been  devised  by  Professor  Boussinesq  to  cover  this  defect. 
If  >(/  be  the  angle  of  friction  between  the  wall  and  the  earth,  and  x  the 
horizontal  distance  from  the  face  of  the  wall,  the  following  expressions  are 
given  by  him  for  the  intensity  of  horizontal  and  vertical  prossure  for  valuea 

of  X  less  than  .  A  "  ^^^'^  ^  ._ 

\  1  +  sin  ^ 

/r         J.       ,.  1  -  sin^ 
w  (h  ■{•  X  tan  -^z) -. — - 

Horizontal  pressure  = .     -;        .     (20) 


>  1  H  sin  z 


1  + 

^  \  -\  sm  p 

Vertical  pressure  = ^^=^ — — .      .      .     (21) 

\  1  +  sin  9 
At  the  face  of  the  wall  a;  =  O,  and  the  expressions  become — 

,  1  -  sin  0 
toh~ : — - 

Horizontal  pressure  = ^ ;  ,     (22) 

.  /I  -  sin  0  , 

1  +  V  r '• —  tan  -vj/ 

\  I  +  sin  ^         ^ 


COULOMB'S  THEOREM.  167 

Vertical  pressure  ■■ — •       •       •     (23) 

\  1  +  sin  f>         ^ 

CoiUomb'a  Theorem. — What  is  practically  the  same  formula  as  that 
enunciated  by  Kankine  has  been  developed  by  MM.  Prony  and  Coulomb, 
on  somewhat  different  lines,  as  follows : — 

In  fig.  90,  C  E  is  the  line  of  repose.  Were  the  wedge  of  earth,  D  C  E, 
a  solid  mass  it  would  have  no  tendency  to  slide  down  the  plane,  C  E,  the 
frictional  resistance  between  the  two  surfaces  being  sufficient  to  counteract 
movement.  Evidently,  then,  if  the  earth  yield  at  all,  it  must  do  so  by 
fracturing  along  some  other  plane,  the  position  of  which  remains  to  be 
determined.     Meanwhile,  assume  a  position,  0  F. 

Through  the  centre  of  gravity  of  the  wedge,  D  C  F,  draw  K  O,  vertically, 
to  represent  its  weight,  W.  Draw  L  O,  making  an  angle,  ^,  with  the  normal 
to  the  plane,  C  F,  to  represent  the  ultimate  reaction  of  the  plane,  and  L  K 
a  horizontal  line  through  K.  Then  the  pressure  on  the  back  of  the  wall  is 
measured  by 

P  =  L  K  =  W  tan  d  =  -2-  tan  tf  cot  (tf  +  (p).      .         (24) 

It  is  now  necessary  to  find  the  angle  which  gives  the  greatest  possible 
value  to  P.  Take  the  variable  factors  in  the  preceding  expression,  differ- 
entiate, and  equate  to  zero. 

d  tan  ^  cot  (tf  +  0)  «  .        , .         ^       ,       .  ,  .,         .       ^ 
"^ -^  =  sec*  tf  cot  (tf  +  9)  -  tan  ^  cosec*  (^  +  ^)  =  0. 

This  reduces  to 

sin  (2  tf  +  2  ^)  =  sin  2  tf,       .         .         .         (25) 

and,  therefore,  since  the  sines  of  supplementary  angles  are  equal, 

,'.2&  +  p=  2 

whence  it  is  evident  that  the  greatest  thrust  is  obtained  when  the  line  of 
rupture,  C  F,  bisects  the  complement,  D  C  E,  of  the  angle  of  repose.  In 
this  case, 

P  =  -TT—  .  tan*  d, 
2  ' 


which  is  a  variant,  in  form  only,  of  Rankine's  expression,  since 

G  - 1)- 


'    -•'»'•    fn' 


1  +  sin  p 
There  are,  in  fact,  several  different  methods  of  arriving  at  the  same 


1 68 


DOCK  ENGINEERING. 


result.  For  -instance,  without  using  the  angle  of  friction,  as  in  the  pre- 
ceding investigation,  take  the  forces  acting  at  the  point,  O,  in  tig.  91,  and 
resolve  them  along  the  plane  of  rupture,  0  F.  Then  equate  them  for 
equilibrium.     The  coefficient  of  friction  being  tan  ^,  we  have 

P  (sin  &  +  cos  &  tan  p)  =  W  (cos  tf  -  sin  6  tan  ^) ; 

...P.!fi^^J^f»»5.^,     .       (26) 

2       1  -•-  cot  tf  tan  ^*  ^ 

which,  when  tf  and  9  are  angles  such  that  ^  =  — - — ^ ,  is  readily  trans- 
formable  into 


or. 


p  __  t^?A-    1  -  sin  <p 

2       1  +  sm  <p 


A              D 

F 

1 

V 

L 

W      / 
/ 

K  / 

• 

h     ^E 

B 


C 
Fig.  90. 


Chaud'i/s  Theorem.* — The  undoubtedly  excessive  values  attributed  to 
earth  pressure,  in  the  preceding  investigations,  have  led  a  French  engineer 
to  approach  the  problem  from  a  fresh  standpoint,  and  to  evolve  a  solution 
which,  despite  its  complexity,  yields  results  more  in  accordance  with  prac- 
tical observation. 

A       F        D  X  E 


/ 

'X^ 

\\ 

\ 

y 

r/ 

.4' 

— «-         ...        N 

1; 

h. 

> 

a 

V 

/ 

/ 

\  7   / 

^/ 

\ 

\ 

^G 

B 

\ 

A 

Fig.  92. 


B 


Fig.  93. 


M.  Ohaudy  starts  with  the  postulate  that  a  pressure,  Q,  applied  to  the 

surface  of  a  mass  of  earth  causes  an  oblique  thrust,  P,  and  the  object  of  his 

investigation  is  to  find  the  amount  of  this  thrust,  and  the  angle  at  which 

•  M&moirt8  tt  Corrvptes  Rtndus  des  Trat'uux  de  fa  SociiU  dett  Ing^nieurs  Civile  de 
France,  Bulletin  de  Decembre,  1895. 


CHAUDY'S  THEOREM.  169 

it  exercises  its  greatest  effect.  He  proceeds  to  do  this  by  resolving  the 
pressure,  Q  (fig.  92),  into  its  component  parts,  Q  sin  7,  and  Q  cos  7,  along, 
and  perpendicular  to,  the  direction  of  the  oblique  thrust,  assumed  to  make 
an  angle,  7,  with  the  horizontal,  and,  in  this  way,  he  determines  the  amount 
of  the  oblique  pressure  as 

P  =  Q  sin  7  -  Q  cos  7  tan  f>  =  Q  sin  7  (l  -  ^^),     •     (27) 

the  last  term  being  the  deduction  due  to  friction. 

Considering,  now,  an  element,  x,  of  the  surface,  A  0,  as  undergoing  an 

intensity  of  pressure,  g,  and  noting  that  y,  the  corresponding  element  of 

the  surface  exposed  to  the  oblique  intensity,  p,  is  x  sin  7,  we  can  derive 

from  the  above  equation — 

/         tan  ^\ 
py  =  pxsiny  =  5a:  sm  7(^1  -  ^^j, 

whence, 

'■-'('-^)'  •  ■  •  w 

which  gives  the  relative  intensities  of  the  two  pressures. 

Applying  this  to  the  case  of  a  retaining  wall,  A  B  C  F  (fig.  93),  we  see 
that  the  vertical  force  for  each  element  of  surface  is  the  weiglit  of  a  strip 
of  earth,  toxa,  and,  therefore,  that 


P  =  M?x2a;ax  sin  y  ( 1  -   -) 

^  \         tan  7/ 


=  areaFCE  x  w;  sin  7  fl  -  ^?5_?\ 

^  \         tan  7/ 


tan  7, 
Now,  the  area  FOE  =  iFG.CE, 

in  which  F  G  =  F  C  cos  (  7  -  ^)  =  A  sec  /?  cos  (7  -  p), 

and  C  E  =  A  cosec  7 ; 

A2 


.  • .  the  area  F  0  E  =  —  cosec  7  sec  /?  cos  (7  -  ^), 

and  P  =  :5?2^'.8ecjScos(7-/?)(l  -  ^^y     .        (29) 

When  the  back  of  the  wall  is  vertical,  ^  =  0,  and  the  equation  simplifies 
into 

tan  7, 

To  determine  the  value  of  7,  which  will  give  the  maximum  value  to  the 
equation,  differentiate  the  variable  factors,  as  before,  and  equate  to  zero : — 


T>       w;A2  /         tan  0\  ,.,^, 


dy 


170  DOCK  ENGINEERING. 

sm^y  ^'       '^^  \         tan  7/ 

Multiply  by  ^^^jfy 

.  • .  — — -  -  tan*  y  tan  (y  -  P)  +  tan  9  tan  7  tan  (y  -  /?)  =  0. 
co8^  y 

Substitute 

1  +  tan*  y  for  — =— -,  and  :; 7 ^       r»  for  tan  (7  -  /?). 

'         cos*  7  1   +  tan  7  tan  p  mi/ 

Then, 

^     ,  2  tan  9  +  tan /?^     «  tan  9  ,«-. 

tan*  7  -  1 —  ^ 5  tan*  7  =  ,—   - —  -~z — nj,    .     (31) 

'        1  -  tan  <p  tan  p  '       \  -  tan  (p  t&np  ^ 

a  cubic  equation  which  determines  the  direction  of  the  resultant  and  its 
maximum  value. 

The  case  of  a  retaining  wall  with  a  horizontal  ground  surface  has  alone 
been  dealt  with,  the  investigation  of  the  general  case  being  far  too  lengthy 
and  involved  for  insertion.  It  may  be  stated,  however,  that  the  general 
formula  is  deduced  as 


p  ^  ur^  cos  (7  -  13)    /j   _   tan^N    sin  7  cos  (/?  -  a) 

2    '       cos  P       '  \         tan  7/  '  sin  (7  -  a)  cos  /?'   '    ^ 

and  the  direction  of  the  resultant  is  to  be  derived  from  the  following: — 

^     «  2  tan  ^  +  tan  /? 

'        1  -  tan  (p  tan  p  +  tan  p  tan  a 


(tan  Q)  +  tan  Q)  tan  a 
1  —  tan  9  tan  ^  +  tan  ^  tan  a         '^ 

tan  p  -  tan  a  ( 1  -  tan  (p  tan  /?) 
1  -  tan  <p  tan   ^  +  tan  /?  tan  a* 


(33) 


So  much  for  the  purely  theoretical  aspect  of  the  question  which,  how- 
ever, is  by  no  means  exhausted.  Should  the  student  be  desirous  of  still 
further  investigation,  he  will  find,  at  the  end  of  the  chapter,  reference  to  a 
few  of  the  sources  from  which  he  may  obtain  additional  information. 

Weight  of  Earthwork. — The  weight,  w^  per  unit  volume  of  the  earth- 
work behind  a  retaining  wall  can  only  be  estimated  from  experimental 
results,  a  number  of  which  are  embodied  in  the  following  table.  Much, 
however,  depends  on  the  degree  of  humidity  of  the  earth  in  question,  as 
well  as  on  its  actual  chemical  composition,  which,  within  the  limits  of  the 
same  generic  name,  may  vary  considerably.  Then  it  must  also  be  borne 
in  mind  that  unless  the  backing  consist  entirely  of  carefully  selected  filling, 
it  is  a  practical  impossibility  to  accurately  gauge  for  the  full  extent  of  the 
wall  the  depths  of  the  dlfierent  strata  to  be  met  with.  In  the  majority  of 
cases  an  estimate  has  to  be  founded  upon  the  information  derived  from  a 
few  isolated  borings,  which  may  entirely  fail  to  take  account  of  pot-holes  or 
adventitious  beds  of  treacherous  material. 


RESTRAINING  FORCES. 


171 


TABLE  XVI. — Approximate  Weight  per  Cubic  Foot  op  Various 

Kinds  of  Earth. 

Lbs. 

90 

98 

100 

118 

170 


Fine  dry  sand,  loose, 

„  ,,     well  shaken, 

Coarse  pit  sand, 
Damp  river  sand,    . 
Quartz  sand, 


Gravel, 90  to  95 

106 

102 

95 

106 

126 

125 

100  to  120 


Loose,  dry  shingle, 

Mud 

Dry,  common  earth,  loose, 
Common  earth,  slightly  moistened, 
Densest  and  most  compact  earth,    . 

Loam, 

Marl, 


Clay, 120  to  135 

Chalk, 117  to  174 

Shale, 162 

Rubble  filling  (with  interstices), 100 

Surcharge. — The  amount  of  surcharge  upon  a  quay  or  dock  wall  can  be 
determined  by  reference  to  the  weights  of  cargo  to  be  deposited  there  and 
of  any  superstructure  upon  the  quay.  A  definite  limit,  however,  is 
generally  fiixed  in  the  former  case,  beyond  which  wharfingers  and  others 
should  not  be  permitted  to  load  quay  spaces  or  shed  fiioors,  and  an  allowance 
of  about  3  tons  per  superficial  yard  will  generally  be  found  adequate  to 
cover  all  reasonable  contingencies  of  sur- 
charge. The  effect  of  the  surcharge  should 
be  considered  as  extending  from  the  vertical 
back  (actual  or  virtual)  of  the  wall  to  the 
intersection  of  the  line  of  rupture  with  the 
quay  surface,  and  its  line  of  action  taken 
as  passing  downwards  through  the  centre  of 
this  distance.  Fig.  94  shows  the  method 
of  combining  the  effective  pressures  due  to 
the  earth  wedge  and  the  surcharge.  The 
distance,  F  G,  between  their  respective 
centres  of  gravity  is  divided  inversely  in 
the  ratio  of  their  weights,  and  the  sum  of  the  latter  is  taken  as  acting 
through  the  point,  K,  thus  found.  It  will  be  noticed  that,  in  this  way,  the 
effect  of  the  surcharge  is  not  merely  to  increase  the  direct  horizontal  thrust 
against  the  back  of  the  wall,  but,  at  the  same  time,  to  raise  its  point  of 
application  and  thus  still  further  increase  the  overturning  moment. 

Having  dealt  with  those  forces  which  tend  to  disturb  equilibrium,  we 
now  turn  our  attention  to  those  which  tend  to  maintain  it. 

Restraining  Forces. — The  magnitude  and  line  of  action  of  the  restraining 
forces  are  open  to  less  controversy  and  difference  of  opinion  than  is  the  case 
with  the  overturning  forces.     If  the  wall  have  a  vertical  back  the  dead 


A            D 

—  %% 

w 

s    / 

pU 

y 

p 

I 

r           i 

/ 

Fig.  94. 


172  DOCK  ENGINEERING. 

'weight  of  its  structure  constitutes  the  one  and  only  element  of  stability, 
and  its  line  of  action  is  obviously  vertical  through  the  centre  of  gravity. 
If,  however,  the  back  of  the  wall  be  inclined  to  the  vertical  at  an  angle, 

/?,  as  in  fig.  81,  the  nett  weight  of  the  wall  must  be  increased  by  — ^—  tan  /?, 

the  weight  of  the  earth  directly  supported  by  the  wall  and  manifestly 
assisting  to  maintain  equilibrium.  The  combined  weights  must  be  taken 
as  acting  through  a  common  centre  of  gravity. 

Such,  at  any  rate,  is  the  legitimate  course  to  adopt  from  a  purely 
theoretical  point  of  view.  At  the  same  time  it  must  be  admitted,  on 
unimpeachable  testimony,  that  the  assumption  is  not  borne  out  by  actual 
experiment.  Sir  Benjamin  Baker  states  that  "  he  has  invariably  observed 
that  when  a  retaining  wall  moves  by  settlement  or  otherwise,  it  drops  away 
from  the  filling  and  cavities  are  formed.  A  settlement  of  but  -^^  of  an 
inch,  after  the  backing  had  become  thoroughly  consolidated,  would  suffice  to 
relieve  the  offsets  of  all  vertical  pressure  from  the  superimposed  earth,  and 
the  latter  cannot  therefore  be  properly  considered  as  contributing  to  the 
moment  of  stability."*  Considering,  however,  that  the  purely  theoretical 
aspect  of  the  problem  involves  equal,  if  not  greater,  discrepancies  on  the  other 
side,  in  unduly  augmenting  the  effective  overturning  thrust,  it  is  no  inequit- 
able arrangement  to  regard  the  advantages  accruing  to  the  weight  of  the  super- 
imposed earth  as  compensating  for  the  neglect  of  the  cohesive  power  of  the 
backing.  Where  the  offsets  at  the  back  of  the  wall  are  continued  to  some 
depth,  it  may  reasonably  be  urged  that  any  indisposition  of  the  earthwork  to 
follow  settlement  in  the  wall  argues  a  correspondingly  high  degree  of  cohesion 
between  the  particles  and  a  considerable  modification  of  the  calculated  thrust. 

Another  point  which  calls  for  attention  is  the  extreme  likelihood  of 
water  finding  a  passage  beneath  the  wall,  especially  in  porous  foundations, 
for,  in  this  way,  the  effective  weight  of  the  wall  is  decreased  by  the  weight 
of  a  volume  of  water  equivalent  to  the  immersed  section.  This  may  amount 
to  as  much  as  45  or  50  per  cent. ;  a  reduction  of  great  importance.  The 
effect,  however,  is  only  felt  when  the  dock  is  full  of  water,  and  then  the 
support  derived  from  the  hydrostatic  pressure  on  the  face  of  the  wall  is 
sufficient  to  compensate  for  the  diminution  in  weight,  unless  the  water  in 
the  dock  be  lowered  rapidly  while  the  earth  backing  is  imperfectly  drained. 
The  liquid  head  due  to  the  water  imprisoned  behind  the  wall,  combined 
with  percolation  through  the  foundation,  is  sufficient  to  produce  a  dangerous 
complication,  resulting  in  more  than  one  instance,  from  actual  experience,  in 
movement  and  disruption. 

Counterforts,  or  narrow  pilasters,  are  often  built  at  regular  intervals 
behind  a  retaining  wall  with  the  view  of  adding  to  its  stability.  Their 
value  in  this  respect  is  entirely  a  question  of  adhesion.  In  the  case  of 
masonry  walls  it  has  frequently  been  found  that  a  separation  has  taken 
place  between  the  counterfort  and  the  body  of  the  wall.     Such  a  separation, 

*  Min.  Proc,  Inst.  C.E,,  vol.  Ixv.,  p.  181. 


WEIGHT  OF  WALLS. 


175 


however  minute,  is  sufficient  to  nullify  the  advantages  of  counterforts,  and 
even  to  invest  them  with  dangerous  potentialities,  for,  in  falling  back,  they 
add  some  portion  of  their  own  weight  to  the  earth  pressure  against  the  wall. 
Provided,  however,  the  counterforts  be  adequately  bonded  into  the  body  of 
the  wall  (and  this  may  be  effected  very  satisfactorily  in  the  case  of  walls  con- 
structed of  Portland  cement  concrete),  there  can  be  no  doubt  as  to  the 
advantage  to  be  derived  from  their  aid.  The  thickness  of  the  wall  may  then, 
for  theoretical  investigation,  be  regarded  as  increased  to  the  extent  of  th& 
thickness  of  the  counterforts,  divided  by  the  distance  apart  at  which  they 
are  set ;  in  other  words,  the  wall  may  be  taken  at  its  mean  thickness.  At 
the  same  time  it  is  a  matter  of  opinion  as  to  whether  the  material 
may  not  be  more  economically  distributed  uniformly. 

In  instances  where  it  is  rendered  necessary,  additional  security  may  he 
afforded  by  the  use  of  tie-rods  or  tie-bars  firmly  connected  to  the  wall  near 
the  top  and  carried  to  a  secure  anchorage  in  the  ground  some  distance  away. 
The  very  great  leverage  (measured  from  the  base)  at  which  such  a  tensile 
force  would  act,  renders  a  comparatively  slight  rod  capable  of  counteracting 
a  considerable  degree  of  earth  thrust.  The  expedient  has  often  been 
adopted  for  the  purpose  of  strenj^thening  walls  which  have  showed  signs  of 
yielding.  Means  should  be  provided  for  properly  tightening  up  the  bars 
or  rods  by  means  of  gibs  and  cotters,  screw  shackles,  or  other  contriv- 
ances. A  rough  and  ready  way  is  to  heat  the  whole  length  of  the  bar 
before  completing  the  attachment ;  the  contraction  in  cooling  will  generally 
be  found  sufficient  to  bring  the  bar  into  stress. 

Weight  of  Walls. — The  weight  in  air  of  the  various  kinds  of  material  of 
which  a  dock  wall  may  conceivably  be  composed  is  stated  below : — 

TABLE  XVIL — Approximate  Weight  per  Cubic  Foot  of 

Mineral  Substances. 


Lbs. 

Lbs. 

Basalt,  .... 

187 

Masonry,                         .    116  to  144 

Brick,    .... 

115  to  135 

Mortar,          .... 

109 

Brickwork  in  mortar,     . 

112 

Quartz,           .... 

165 

Felspar^ 

162 

Sandstone— 

Flint,     .... 

164 

Gatton  (Surrey),     . 

103 

Granite — 

Calverley  (Kent),    . 

118 

Cornish, 

164 

Whitby  (Yorks.),    . 

126 

Aberdeen, 

166 

Red  (Cheshire), 

133 

Dublin,    . 

170 

Craigleith  (Edinburgh), 

141 

Guernsey, 

187 

Darley  Dale  (Derby), 

148 

Limestone — 

Talacre  (Flint), 

150 

Bath,      . 

120 

York,      . 

157 

Portland, 

130 

Auchray  (Dimdee), 

159 

Chalk,     . 

145 

Abercarnc  (Monmouth), 

168 

Purbeck, 

150 

Slate- 

Chilmark, 

155 

Cornwall, 

157 

Kentish  rag,    . 

166 

Westmoreland, 

173 

Marble, 

170 

Welsh,    . 

180 

Magnesian, 

175 

Trap,      .... 

17a 

174  ^^^^  ENGINEERING. 

Empirical  Formnlse. — General  Fanshawe's  rule  was  to  make  the  thickness 
of  rectangular  revetment  walls  of  brickwork,  sustaining  ordinary  earth,  the 
following  percentages  of  the  height : — 


For  a  batter  of 

1 

T 

:     24 

per  cent. 

1 

15- 

:     25 

1 

:     26 

1 
TI7 

:     27 

iV 

:     28 

« 

1 
24 

.     30 

For  a  vertical  v 

^all 

:     32 

A  rule  sometimes  adopted  for  perpendicular  retaining  walls  on  railways 
is  to  divide  the  height  into  three  equal  parts  and  make  the  thicknesses  ^, 
^,  and  ^  respectively  of  the  total  height. 

The  following  general  observations  on  the  subject  are  given  on  the 
authority  of  Sir  Benjamin  Baker*  : — 

'*  Experience  has  shown  that  a  wall  ^  of  the  height  in  thickness  and 
battering  I''  or  2""  per  foot  on  the  face  possesses  sufficient  stability  when  the 
backing  and  foundation  are  both  favourable.  It  has  been  similarly  proved 
by  experience  that  under  no  conditions  of  surcharge  or  heavy  backing  is  it 
necessary  to  make  a  retaining  wall  on  a  solid  foundation  more  than  double 
the  above,  or  |  of  the  height  in  thickness.  Within  these  limits  the 
engineer  must  vary  the  strength  in  accordance  with  the  conditions  affect- 
ing the  particular  case."  As  the  result  of  his  own  experience  Sir  Benjamin 
Baker  '*  makes  the  thickness  of  retaining  walls  in  ground  of  an  average 
character  equal  to  ^  of  the  height  from  the  top  of  the  footings." 

Conditions  of  Stability. — Having  duly  selected  a  provisional  sectional 
profile  for  a  dock  wall,  and  having  defined  in  magnitude  and  line  of  action 
the  overturning  and  restraining  forces,  it  now  remains  to  take  the  resultant 
of  the  latter  and  consider  its  efiect  upon  the  wall  as  a  whole.  The  possi- 
bilities of  failure  are  threefold — 

1.  The  wall  may  fail  by  overturning  about  the  outer  edge  of  its  base  or 
of  any  bed  joint.  To  achieve  such  a  result  the  overturning  moment  about 
these  points  must  exceed  the  moment  due  to  the  restraining  force.  When 
the  moments  are  equal  there  is  theoretical  equilibrium  ;  but,  in  order  to 
ensure  a  sufficient  margin  of  safety,  the  axis  of  overturning  should  be 
assumed  to  lie  some  little  distance  within  the  wall — say,  at  least,  ^  of  the 
width  of  the  base. 

2.  The  outer  edge  of  the  wall  at  any  horizontal  section  may  be  crushed 
in  consequence  of  excessive  compression.  This  is  not  likely  to  arise  so 
much  from  the  actual  total  weight  upon  any  section  as  from  the  unequal 
distribution  of  stress.  Unless  the  resultant  thrust  pass  exactly  through 
the  centre  of  gravity  of  each  horizontal  plane  the  stress  intensity  is  not 
uniform  throughout.     Uniformity  of  stress  is  possible  in  revetment  walls 

*  Min,  Proc,  Inst,  C,E,,  vol.  lxv»,  p.  181. 


CONDITIONS  OF  STABILITY. 


175 


having  a  considerable  backward  slope,  but  from  the  very  nature  of  their 
functions  this  ideal  is  unattainable  in  dock  walls,  and  it  follows  that  a 
certain  portion  of  each  bed  joint  is  more  highly  stressed  than  the  remainder. 
The  intensity  is  greatest  at  the  outside  edge,  and,  assuming  the  joint  to  be 
a  perfect  one,  it  diminishes  uniformly  as  it  recedes  from  the  face.  If  it 
reach  a  zero  value,  it  may  do  so  either  at  the  back  of  the  wall  or  at  some 
point  within  the  wall.  The  latter  alternative  should  be  avoided,  as  it 
entails  a  tensile  stress  beyond  the  compressive  limit — a  stress  which  bed 
joints  are  ill  adapted  to  resist,  and  which,  accordingly,  they  should  not  be 
called  upon  to  undergo.  In  fig.  95,  A  B  is  a  horizontal  bed  joint  and  R  0 
represents,  in  line  of  action  and  magnitude,  the  resultant  pressure  upon  the 
joint.  Resolve  R  into  its  two  components,  NR  and  NO  respectively, 
parallel  and  perpendicular  to  A  B.  The  former  constitutes  a  shearing  stress, 
which  will  be  considered  later;  the  latter  is  the  total  direct  compression 

N  C 
upon  AB.     At  A  set  up  the  perpendicular  AD=2   ^-^.      Then,  assum- 
ing compression  to  vanish  at  the  point  B,  join  D  B  and  the  triangle  A  D  B 

D 


Fig.  96. 


Fig.  96. 


will  be  the  graphical  representation  of  the  amount  and  distribution  of  pres- 

NC 


.         /     N  (J  \ 

sure  over  the  joint,  A  B.    For  the  area  of  the  triangle  A  D  B  =  ^(  2  -j-=  x  A  B ) 

=  N  0.  And,  since  the  effect  of  any  system  of  loading  is  equivalent  to 
supposing  the  whole  concentrated  at  its  centre  of  gravity,  the  line  NC 
necessarily  passes  through  the  centre  of  gravity  of  the  triangle  A  D  B  in 
order  to  conform  to  the  condition  of  zero  stress  at  B.     Clearly,  then,  this 

A  B 

entails  A  C  ==  —^ .     In  other  words,  the  resultant  thrust  passes  through  the 

extremity  of  the  middle  third  of  the  wall,  but  if  tension  in  the  joint  is  to  be 

avoided,  it  may  not  exceed  this  limit. 

The  resultant  passes  through  the  centre  of  section  (E,  fig.  96)  when 

AD 
there  is  uniformity  of  stress    throughout,   and  AK  =  —^   is  the  mean 

intensity.     The  stress  diagram  in  this  case   is,   accordingly,  a  rectangle 

A  B  A  B 

having  the  same  area.     Between  the  two  limits  AE=—  -  and  AC  =  — s- 

(for  we  may  disregard  as  inapplicable  all  values  exceeding  these)  the  diagram 


\y» (^^) 


176  DOCK  ENGINEERING. 

will  assume  some  intermediate  trapezoidal  form.  For  instance,  let  G 
(fig.  96)  be  the  point  of  application  of  the  thrust :  the  corresponding  stress 
area  will  be  H  A  B  N.  The  line  H  N  is  defined  by  the  necessity  of  passing 
through  the  point  F,  and  by  the  following  condition : 

in  which  a  =  A  K,  is  the  mean  intensity  of  stress,  a:  =  G  E,  is  the  eccentricity 

of  the  thrust,  and  ^  =  A  B,  is  the  length 
H  of  the  base. 

The  demonstration  of  this  condition 
^  depends  upon  a  simple  theorem  in 
J        mechanics. 

KABM    (fig.  97)    being   any  body 
whose     weight     is    W    and     centre    of 
Fig.  97.  gravity    G^,    if   by   the  transposition  of 

any  part  of  its  volume  M  O  N  with 
weight  Wy  its  form  is  altered  to  the  outline  H  A  B  N,  then  the  new  centre 
of  gravity,  Gg,  is  determined  by  the  proportion 

G2  G|  _  w? 

92  9i 

and  the  horizontal  projections  of  Gg  G^  and  ^2  9i  follow  the  same  law. 

Now,  let  us  apply  this  result  to  the  pressure  diagram.     Call  MN  y. 

In  fig.  96  H  K  F  and  F  M  N  are  equal  triangles,  and  the  horizontal  distance 

between  their  respective  centres  of  gravity  is,  clearly,  |  L     Then,  in  the 

ly 
foregoing  equation  (34),  writing  v)  =r  ^  and  W  =  a  /,  we  have 

3.1?        ly 
21  "  ial 

_  6aa; 
y  —      J-  ......     \*^0) 

which  defines  the  position  of  the  point  N  corresponding  to  any  assigned 
value  of  X, 

A  table  giving  the  resistance  to  compression  of  various  kinds  of  stone 
will  be  found  in  Chapter  iv.,  and  the  safe  loads  on  foundations  are  given 
on  p.  183. 

3.  The  wall  may  fail  by  shearing  horizontally  along  some  bed  joint. 
The  amount  of  shear  is  N  R  (fig.  95),  the  horizontal  component  of  the 
resultant  thrust.  The  resistance  of  masonry  joints  to  actual  shearing, 
which  depends  largely  upon  their  cohesion,  is  usually  abandoned  in  favour 
of  their  resistance  to  sliding,  which  depends  on  friction  alone,  and,  having 
a  lower  value,  affords  a  margin  of  safety  to  cover  defects  in  workmanship. 
In  any  case  this  is  all  the  duty  which  can  be  expected  from  the  base  joint 
between  the  wall  and  its  foundation.  The  amount  of  resistance  to  sliding 
is  CN,  the  vertical  component  in  fig.  95,  multiplied  by  the  tangent  of 


LOCI  OF  CEan:RE8  OP  GRAVITY. 


177 


the  angle  of  repose — i.e.,  of  the  steepest  inclination  at  which  a  block 
of  the  substance  in  question  will  remain  stationary.  This  frictional 
resistance  is  quite  independent  of  the  area  of  the  surfaces  in  contact,  but 
its  intensity  at  any  point  corresponds  to  the  intensity  of  pressure  at  the 
same  point.  The  following  are  values  for  the  tangent  of  the  angle  of  repose 
of  several  surfaces,  usually  designated  the  coefficient  of  friction : — 

Dry  masonry  and  brickwork,  0*6  to  0*7. 
Masonry  and  brickwork,  with  wet  mortar,  0-47. 
Masonry  and  brickwork,  with  slightly  damp  mortar,  0*74. 

Before  applying  the  foregoing  principles  to  a  definite  example  it  may  be 
as  well  to  explain  one  or  two  methods  adopted  for  finding  the  centre  of 
gravity  of  the  section  of  a  dock  or  other  retaining  wall. 

Loci  of  Centres  of  Gravity, — The  centre  of  gravity  of  a  square  or 
rectangle  lies  at  the  intersection  of  the  diagonals  (O,  fig.  98). 

The  centre  of  gravity  of  a  triangle  is  at  two-thirds  of  the  length  of  a 
median  measured  from  the  apex  (O,  fig.  99). 

The  centre  of  gravity  of  a  trapezoid  is  at  a  point  O,  fig.  100,  on  the  line 

AB,  bisecting  the  parallel  sides  such  that  -j-=  =  — — , 

and  h  are  the  lengths  of  the  sides  bisected  at  A  and  B  respectively. 

A 


where    a 


Fig.  98. 


Fig.  99. 


The  result  may  be  obtained  by  means  of  a  simple  graphical  construction. 
Let  A  C  D  B  (fig.  101)  be  a  trapezoid.  Bisect  A  B  and  C  D  at  the  points 
E  and  F  respectively,  and  join  E  F.     Produce  B  A  to  G,  so  that  A  G  is 


J^z 


equal  to  C  D.  Produce  C  D  to  H,  so  that  D  H  is  equal  to  A  B.  Join  G  H. 
The  intersection,  O,  of  the  lines  E  F  and  G  H,  is  the  required  centre  of 
gravity. 


178 


DOCK  EN6INEERIN0. 


The  same  principle  may  be  applied  to  finding  the  common  centre  of 
gravity  of  two  areas.  Let  A  C  D  B  (fig.  102)  and  C  F  H  E  be  two  areas, 
whose  respective  centres  of  gravity  are  Gj  and  Gg.  Join  Gj  Gj.  From  G^ 
and  G2  draw  two  parallel  lines,  in  this  case  horizontal,  but,  generally 
speaking,  preferably  perpendicular  to  Gj  Gg,  and  make  G^J  proportional 
to  the  area  C  F  H  E,  and  G^  K  proportional  to  the  area  A  C  D  B.  Join  J  K. 
The  intersection  of  J  K  and  G^  Gq  at  the  point,  O,  gives  the  common  centre 
of  gravity  of  the  two  areas. 

Sections  of  dock  walls,  when  not  actually  forming  any  simple  geometrical 
figure,  may  be  subdivided  into  a  number  of  such  figures.  The  combined 
centre  of  gravity  for  the  whole  figure  can  then  be  obtained  by  the  method 
just  described,  taking  the  areas  successively  and  finding  the  joint  centre  for 
each  pair.     Or  any  of  the  following  methods  may  be  employed  : — 

1.  In  fig.  103  a  wall  section  is  shown  divided  into  3  rectangles.  E  is 
the  centre  of  gravity  of  the  topmost  rectangle,  A  C  D  B,  found  by  inter- 


Fig.  104. 

secting  diagonals.     F  and  H,  in  like  manner,  are  the  centres  of  gravity 

for  the  other  two  rectangles.     Join  EF  and  take  a  point  G  such  that 

EG      areaOLMJ       _,,       ^.     , 

GF  ~  —    ATDB'       ^^^^  G  18  the  common  centre  of  gravity  for  the  two 

rectangles.     Join  G  H  and  take  a  point  K  such  that 

GK  areaLNOP 


KH      areas  ACDB  +  CLMJ* 
K  is  the  centre  of  gravity  of  the  whole  figure. 

2.    The  point  K  may  be  found  by  combining  the  co-ordinates  of  the 


LOCI  OF  CENTRES  OF  GRAVITY. 


179 


subsidiary  centres  of  gravity  ;    thus,  in  fig.  104,  calling  the  areas  of  the 
rectangles  A,  B,  and  C  respectively — 

Y  _  Aajj  +  BiCj  +  Cx^ 

^         aTb  rc      ' 

A  +  B  +  C       * 


Surface    of    Quay 


ock  Bottom 


Scales :  12  feet  =  1  inch.    30  tons  .-=  1  inch. 

Fig.  106. 

3.  A  very  close  approximation  may  be  made  by  the  practical  expedient 
of  cutting  out  the  profile  of  the  wall  in  stout  cardboard,  and  suspending  it 


i8o 


DOCK  ENGINEERING. 


from  two  consecutive  comers.  The  intersection  of  the  vertical  lines 
through  the  points  of  suspension  gives  the  centre  of  gravity  of  the  figure. 
It  is  better  to  suspend  from  three  points ;  the  third  line  acts  as  a  check 
against  possible  error. 

In  all  three  instances  the  assumption  has  been  made  that  the  wall  is 
homogeneous.  When  this  is  not  the  case,  it  will  be  necessary  to  deal  with 
the  weights  of  the  different  sections,  instead  of  their  areas.  Thus,  if  two 
adjoining  sections  of  a  wall  have  areas  A  and  B  and  unit  weights,  w^  and  W2 
respectively,  their  common  centre  of  gravity  will  be  found  by  dividing  the 

an      Jk 

line  joining  their  individual  centres  inversely  in  the  ratio     ^      . 

Typical  Example. 

Fig.  105  is  the  profile  of  an  actual  dock  wall,  constructed  at  Liverpool,  to 

which  the  methods  of  stress  investigation  just  described  have  been  applied, 

with  the  following  results.     The  material  of  the  wall  is  Portland  cement 

concrete ;  the  foundation,  sound  rock ;  the  filling,  selected  earth  and  rock 

rubbish,   moistened  and  well  consolidated.      The  wall   is  taken  at  unit 

length : — 

Area  of  section  of  wall  (deducting  pipe  trench), 

Weight  of  wall  at  145  lbs.  per  cubic  ft., 

Area  of  section  of  filling  resting  upon  wall, 

Weight  of  filling  at  112  lbs.  per  cubic  ft., 

Angle  of  repose  assumed  at     . 

90**  -  45° 
Angle  of  rupture  to  vertical ^ ,    . 


Area  of  hypothetically  raptured  wedge, 

Weight  of  wedge  at  112  lbs.  per  cubic  ft., 

Extent  of  surcharge,       .... 

Amount  of  surcharge  at  I  ton  per  sq.  ft. , 

Total  vertical  thrust  at  back  of  wall. 

Resolved  horizontal  thrust  against  wall. 

Total  effective  weight  of  wall  and  filling, 

Resultant  thrust  on  foundation,     . 

Overturning  moment  about  outer  edge  of  toe. 

Moment  of  stability  about 

Factor  of  safety,     . 

Width  of  foundation. 

Eccentricity  of  thrust,    . 

Average  intensity  of  pressure  on  foundation  per  sq.  ft. , 

Maximum  intensity, 

Average  intensity  of  shearing  stress  per  sq.  ft.  at  base, 
Maximum  intensity, 


If 


876  sq.  ft. 

66-7  tons. 
310  sq.  ft. 

15*5  tons. 

45^ 


22"  30'. 

648  sq.  ft. 
32-4  tons. 
23-18  lin.  ft. 

7*7  tons. 
40*1  tons. 
16-6  tons. 
72-2  tons. 
74  tons. 
340-3  ft. -tons. 
1101      ft. -tons. 

3-2. 
26-5  lin.  ft. 

2-66  ft. 

2-7  tons. 

3 '8  tons. 

0-6  ton. 

0-8  ton. 


Pra>ctical  Points, 

The  two  essential  features  of  a  well-designed  dock  wall  are  weight  and 
grip  on  the  foundation,*     Without  these  qualifications  even  a  high  moment 

*Proc.  Inst,  C,E,,  vol.  Ixv.,  p.  180. 


PRACTICAL  POINTS.  l8l 

of  stability  has  proved  useleas.  The  atability  of  a  wall  depends  to  as  large 
an  extent  upon  the  immobility  of  its  foundation  aa  upon  its  own  inherent 
resistance  to  overturning. 

The  importance  of  adequate  drainage,  in  this  connection,  has  already  been 
alluded  to.  Where  springs  or  other  sources  of  continuous  flow  are  met 
with  during  the  building  of  the  wall,  they  should  be  conducted  to  some 
suitable  vent  where  they  may  escape  freely.  Any  attempt  at  repressing 
them  will  only  result  in  an  outburst  elsewhere.  Infiltrations  of  water  into 
the  foundation  should  be  dealt  with  by  a  temporary  drain  at  the  base  of  the 
wall  leading  to  a  pumping  well. 

With  the  same  object  in  view,  the  filling  behind  a  wall  for  a  thickness  of 
2  feet  or  so  will  advisedly  be  composed  of  packed  rubble  stone  and  broken 
brick,  the  interstices  of  which  will  act  as  conduits  for  subsoil  water  leading 
to  weep-holes,  or  outlets,  running  through  the  wall  at  stated  intervals. 
These  weep-holes  may  he  formed  by  drain  pipes  of  from  4  to  9  inches 
diameter,  and  they  will  generally  be  placed  at  distances  of  from  50  to  100 
feet,  ai^ording  to  the  nature  of  the  backing. 


Fig.  lOa.— Old  Dock  Wall  at  Leith  (1806).  Fig.  107.— Quay  Wall  at  Hheemere. 

In  order  to  derive  as  much  benefit  as  possible  from  the  cohesion  of  the 
particles,  the  earth  backing  should  be  carefully  punned  in  12-inch  layers,  and 
well  watered  to  ensure  thorough  consolidation. 

OffaeU  in  the  back  of  the  wall,  for  the  purpose  of  reducing  its  thickness, 
should  be  narrow  and  shallow,  in  preference  to  being  broad  and  deep,  par- 
ticularly in  cases  where  the  foundation  is  at  all  unsatisfactory,  as  the  former 
.arrangement  is  conducive  to  greater  uniformity  of  pressure. 

The  bailer  usually  assigned  to  a  wall,  when  the  face  is  not  plumb,  varies 
between  1  in  8  and  I  in  24.  A  battering  face  to  a  wall  naturally  increases 
its  stability,  but,  at  the  same  time,  it  detracts  from  its  efficiency.  Modern 
ships  have  vertical  sides  with  an  upper  "  tumble  home,"  or  inward  inclina- 
tion, so  that  the  advisability  of,  and  even  the  necessity  for,  walls  with  plumb 


1 82  DOCK  ENGINEERING. 

faces  become  apparent.  Old  walla  are  frequently  to  be  found  with  consider- 
able batter,  both  straight  and  curved,  as  in  fig.  106,  an  old  wall  at  Leith,  and 
fig.  107,  a  wall  at  Sheemeas,  constructed  by  the  late  Sir  John  Rennie.  These 
may  be  compared  with  the  latest  type  of  quay  wall  at  Liverpool  shown  in 
fig.  169. 

A  curved  or  splayed  toe  to  a  wall  is  a  valuable  feature,  provided  it  be 
Dot  canied  so  high  as  to  nullify  the  advantage  of  a  vertical  face.  Prolonged 
to  some  distance  beyond  the  face  line,  the  "  toe "  becomes  an  apron.  The 
former  is  illustrated  in  figs.  165  and  169,  the  latter  in  fig.  223.  The  object 
of  an  apron  is  to  prevent  any  abrading  or  softening  action  upon  the  ground 
in  front  of  the  wall,  whereby  any  forward  movement  would  be  assisted. 


Pig.  108.— Wall  at  Kidderpur  Dooka,  CalcatU. 
Counterforts  should  be  disposed,  as  far  as  possible,  to  form  foundations 
for  the  bases  of  columns  of  sheds,  or  other  structures  intended  to  be  built 
upon  the  quay.  They  can  be  carried  up  from  any  ofi'set  level.  The  inter- 
vening spaces,  instead  of  being  occupied  with  filling,  may  in  certain  coses  be 
arched  over,  and  the  vaults  thus  formed  left  vacant  in  order  to  relieve  the 
pressure.  Such  arched  counterforts  are  often  arranged  in  two  or  more  tiers. 
Where  circumstances  render  it  desirable  to  still  further  lighten  a  wall, 
pockets  may  be  introduced  into  its  interior,  either  to  be  left  empty  or  filled 
with  light  material.  Fig.  108  shows  the  Kidderpur  Dock  wall  treated  in 
this  way,  because  of  its  weak  foundation.     Walla  thus  constructed,  however, 


FOUNDATIONS.  1 83 

are  very  liable  to  slide  forward  on  their  bases,  owing  to  insufficient  weight, 
as  actually  happened  in  this  instance. 

A  trench  or  gallery,  for  hydraulic  supply  pipes  and  water  and  gas 
mains,  may  often  be  managed  within  the  body  of  the  wall,  at  a  short 
depth  below  the  coping  level.  Access  to  this  will  be  obtained  by  man- 
holes placed  at  convenient  distances  apart,  say,  76  to  100  feet. 

In  setting  out  the  line  of  a  dock  wall,  it  is  by  no  means  desirable  to 
make  it  absolutely  straight,  even  if  intended  to  be  so.  Apart  from  the 
possibility  of  some  slight  forward  movement  producing  an  appreciable  and 
unsightly  bulge,  there  is  the  effect  of  an  optical  illusion  which  causes  a 
perfectly  straight  coping  to  appear  curved  outwards.  This  latter  can  be 
counteracted  by  giving  the  wall  an  almost  infinitesimal  curvature  in  the 
opposite  direction.  A  versed  sine  of  6  inches  in  1,000  feet  will  generally  be 
found  sufficient. 

Fonndations. — The  foundation  constitutes  so  important  a  feature  in 
connection  witi)  the  construction  of  dock  walls  as  to  call  for  some  detailed 
observations.  Care  should  be  taken  to  see  that  in  each  case  certain  essential 
conditions  are  fulfilled.     These  conditions  may  be  stated  as  follows  : — 

1.  The  inclination  to  the  vertical  of  the  resultant  pressure  upon  the 
surface  of  the  foundation  should  not  exceed  the  angle  of  repose  of  the  earth 
in  question.  This  ensures  what  is  termed  stability  of  friction — i.e.,  there 
will  be  no  likelihood  of  the  wall  sliding  bodily  forward  upon  its  base.  The 
condition  can  always  be  met  by  giving  a  suitable  bevel  to  the  surface,  so 
that  it  slopes  downward  from  tiie  front  of  the  wall  to  the  back. 

2.  The  deviation  of  the  resultant  pressure,  from  the  centre  of  symmetry 
of  the  foundation,  should  not  be  more  than  on&sixth  of  the  width.  This 
condition  is  necessary  to  maintain  absence  of  tension  at  the  back. 

3.  The  maximum  intensity  of  pressure,  at  any  point,  should  not  exceed 
a  certain  limit,  dependent  upon  the  nature  of  the  ground.  The  safe  intensity 
of  pressure  on  natural  foundations  has  been 

determined  as  follows  : — 

Oo  Imrd  rock,  9  or  10  tons  per  sq.  ft. 

On  soft  rock  and  hard  cl&y,  2  to   3     „       „ 
On  sand  and  gr&vel,  1}  ,,    2     „         ,, 

On  compact  earth,  I    •>     li   ,.        „ 

On  soft,  uncertain  ground,    .         .   1   ,.         ., 

Where  an   artificial    foundation    has   been  

prepared,  the   following  intensities  should  pj      jqj 

not  be  exceeded : — 

Por  Portland  oement  concrete,    .  10  to  12  tons  per  84.  ft. 

For  rubble  010801117 '»  hydraulic  mortar,    .  4  „    6    ,,  „ 

In  the  case  of  natural  foundations,  care  must  be  taken  that  there  is  no 
possibility  of  lateral  escape,  and,  in  the  case  of  artificial  foundations,  the 
prepared  bed  must  have  sufficient  depth  to  prevent  transverse  fracture,  as 
indicated  in  fig.  109.    The  depth  of  the  bed,  d,  will  depend  upon  the 


1 84  I>OCK  ENGINEERIKQ. 

amouut  of  projection,  x.     Assumisg  an  ultimate  tensile  resistance,  for  good 
concrete,  of  100  tba.  per  square  inch,  and  treating  the  portion  a;  as  a  canti- 
lever, fracture  would  occur,  with  a  uniformly  distributed  load, 
100  rf" 


whence,  considering  w  as  the  pressure  on  the  foundation,  in  tons  per  square 
foot,  and  taking  a  factor  of  safety  of  2, 

d=   Jl^.x (36) 

4.  The  texture  and  chemical  composition  of  the  foundation  should  be 
such  that  it  is  not  liable  to  deterioration  from  external  influences.  Certain 
varieties  of  rock  are  softened  and  washed  away  by  the  action  of  water.  The 
writer  has  seen  sandstone,  which  required  the  use  of  the  pick  to  excavate  it, 
degenerate  into  the  consistency  of  quicksand  after  a  short  exposure  to  a 
running  stream.  Clays  are  very  susceptible  to  atmospheric  influences, 
expanding  and  contracting  under  changes  of  temperature.  Such  strata 
should  be  covered  as  rapidly  as  possible. 

5.  An  unyielding  foundation  is,  par  excdl«ncr,  the  best,  but  where  this 
cajinot  be  realised,  the  foundation  must  be  but  slightly  and  uniformly 
compressible. 


^; 


Fig.  110.— Section  of  WaU.  Fig.  Ul.— Plan. 

Berculaneum  Dock,  Liverpool. 

The  following  are  a  few  remarks  on  prominent  varieties  of  earths  : — 
Rock,  if  of  a  good  character,  is  the  most  valuable  of  all  bases.  It  is 
firm,  durable,  and  unyielding.  It  involves,  perhapa,  a  little  more  labour  in 
dressing  to  a  level  surface,  but,  in  many  cases,  inequalities  in  this  direction 
may  be  met  by  benching  in  steps.  Any  fissures  should  be  made  good,  and 
unsound  parts  cut  away.  If  the  rock  be  of  a  soft  nature,  inclined  to  pasti- 
ness, it  diould  be  well  drained,  and  not  allowed  to  remain  long  exposed. 
If  the  site  be  such  that  the  rock  rises  very  nearly  to  the  surface,  the  dock 


STRATIFIED  SITES.  1  85 

wall  may  be  comparatively  economically  constructed  in  the  form  of  a  thin 
veneer  of  masonry  or  concrete,  securely  attached  by  dovetailing,  at  intervals, 
to  the  vertical  face  of  the  rock.  Such  was  the  method  adopted  at  the 
Herculaneum  Dock,  Liverpool,  where  the  rock  cutting  was  faced  by  2  to 
4  feet  of  masonry,  with  vertical  dovetails  5  feet  wide  and  4  feet  deep,  at 
20-feet  intervals,  as  shown  in  figs.  110  and  111.  If,  however,  the  rock 
be  very  hard  and  durable,  the  necessity  for  veneering  is  obviated,  as  at 
Ardrossan  (fig.  112). 

Clay  is  a  very  uncertain  material.  It  varies  in  volume,  texture,  and 
consistency.  When  thoroughly  dry,  it  is  hard  and  friable ;  when  saturated, 
it  becomes  soft  and  viscous.  Mixed  with  lime,  it  forms  a  brittle  compound, 
known  as  marl.  When  the  adulterant  is  sand,  the  more  tenacious  product 
is  called  loam.  Clays  possess  so  many  purely  local  attributes  that  little  can 
be  said  of  their  efficiency,  as  a  class,  for  foundation  purposes,  beyond  that 
they  are  usually  satisfactory,  if  properly  protected.  One  variety  of  clay — 
the  blue  clay — however,  possesses  striking  and  dangerous  characteristics, 
which  call  for  especial  precautions.  Several  instances  of  failures  in  dock 
walls  have  occurred  by  reason  of  its  treacherous  nature.  Apparently  firm 
in  itself,  it  often  conceals  planes  of  non-adhesion — surfaces  in  such  a  state 
of  greasiness  that  they  slide  over  one  another  with  the  greatest  facility. 
These  planes  may  be  some  distance  below  the  foundation  level,  and  involve 
the  upper  stratum  of  clay  in  the  forward  movement  of  the  wall,  as  actually 
took  place  at  the  S.-W.  India  Dock.*  A  blue  clay  foundation  has  been 
responsible  for  the  sliding  of  dock  walls  at  Southampton,  Calcutta,  Avon- 
mouth,  and  elsewhere.  Nominally  and  generally  bluish  in  colour,  the 
upper  layers  of  this  clay  are  sometimes  yellow,  due  to  the  change  of  a 
protoxide  of  iron  into  a  peroxide,  by  the  action  of  air  and  moisture. 

Sa/tid  and  Gravd  are  usually  firm  and  durable  foundations,  practically 
incompressible,  but  they  must  be  confined  laterally.  They  need  protection 
from  the  action  of  currents.  Very  often  beds  or  pockets  of  these  substances 
are  met  with  in  the  boulder,  drift,  or  glacial  clay.  If  too  deep  for  excava- 
tion, they  may  be  rendered  very  serviceable  by  the  expedient  of  mixing 
some  neat  cement  with  the  topmost  layer. 

Stratified  Sites. — The  question  of  the  depth  at  which  it  is  desirable  to 
found  a  quay  wall  depends  not  only  on  the  projected  level  of  the  dock 
bottom,  but,  to  a  far  greater  degree,  upon  the  nature  and  disposition  of  the 
strata  met  with.  Having  reached  a  depth  adequate  from  the  point  of  view 
of  design,  a  problem  presents  itself  which  may  be  resolved  into  four  heads, 
the  first  and  simplest  of  which  has  just  been  dealt  with. 

1.  A  sufficiently  firm  foundation  of  indefinite  extent.  The  wall  may 
be  erected  thereon,  with  such  precautions  as  the  nature  of  the  case 
requires. 

2.  A  hard  stratum  overlying  a  soft  one.  Here  it  is  essential  to  preserve 
the  hard  covering  intact.     For  example,  if  a  bed  of  clay  overlie  a  quicksand 

*  Min,  Proc,  hist,  CS.,  vol.  cxxi.,  p.  120. 


1 86  DOCK   BNOINEERING. 

it  is  evident  that  any  perforation  of  the  clay  will  allow  the  quicksand  to 
escape  under  the  superimposed  pressure. 

3.  A  Moft  atratum  of  moderate  depth  overlying  a  hard  oae.  In  this  case 
it  is  advisable  to  found  at  the  lower  depth.  If  actual  excavation  of  the  site 
be  impitLcticable,  the  desired  object  may  be  attained  by  the  use  of  bearing 
piles,  cylinders,  piers,  and  the  like. 

4.  A  soft  stratum  of  considerable  depth.  Means  must  be  taken  to 
lighten  the  wall  as  far  as  ia  consistent  with  its  stability,  and  to  distribute 
the  weight  over  a  large  area.  Framed  timber  rafts,  mats  of  fascine  work, 
layers  of  rubble  pitching,  rows  of  logs  laid  horizontally — these  are  a  few  of 
the  methods  adopted  for  equalising  and  reducing  the  pressure  intensity  over 
foundations  of  this  nature. 

Artificial  FonndationB — PUed  Fmindations.—Aa  the  use  of  piles  is  of 
wider  application  than  the  range  of  this  chapter,  they  have  been  dealt  with 


Fig.  Iia— Quay  Wall  at  Rotterdam. 

generally  in  a  previous  section  (Chapter  iii.).  It  only  remains  to  add  that, 
for  the  purpose  of  dock  walls,  a  very  considerable  advantage  accrues  to  the 
use  of  raking  piles.  Owing  to  the  obliquity  of  the  resultant  pressure,  there 
is  a  considerable  transverse  strain  upon  vertical  piles,  whereas  it  is  quite 
feasible  to  drive  the  piles  at  such  an  inclination  that  this  transverse  strain 
may  be  avoided,  and,  with  it,  the  tendency  to  plough  up  the  ground  in 
front  Instances  of  piled  foundations  are  shown  at  Rotterdam  (fig.  113), 
Limerick  (fig.  114),  Sheemeea  (fig.  107),  and  Rouen  (fig.  116). 

Well  Foundations.— libe  principle  of  a  well  foundation  consists  in 
cau.Hing  a  hollow  shaft  or  cylinder  to  sink  through  a  soft  stratum  by 
excavating  operations  carried  on  from  the  interior,  aided  by  weighting  the 
circumfei-ence,  if  necessary,  untU  a  firm  bottom  is  reached,  whereupon  the 


ARTIFICIAL   FOUNDATIONS.  187 

ahaft  or  cylinder,  as  the  case  may  be,  ia  filled  in  solid,  and  the  superstrui:- 
ture  erected  upon  it.  The  wells  are  of  brick,  iron,  or  concrete,  or  a 
combination  of  any  of   these.      Cylinders  being  much  more  common   for 


Fig.  114.— Dock  Wall  at  Limerick. 


Hard  Chalk 

;.  116.— Quay  Wall  at  Rouen. 


1 88 


DOCK  ENGINEERING. 


well  foundations  than  rectangular  shafts,  the  former  word  will  be  used  in 
the  sense  of  a  generic  term. 

1.  Brick  Cylinders, — In  point  of  antiquity  this  type  of  foundation  is 
pre-eminent,  having  been  used  from  time  immemorial  for  the  purpose  of 
well  sinking.  The  method  of  operations  consists  in  laying  upon  the  surface 
of  the  ground  a  circular  curb — formerly  of  wood,  but  now  universally  of 


Vertical  Section 


Half  Plan. 
Scale  4  ft'  J  inch. 

Figs.  116  and  117.— Wrought-iron  Curb. 


metal — in  shape  like  the  letter  L  placed  thus  F,  or  an  angle  iron  with  its 
uppermost  side  horizontal.  The  two  wings  are  strengthened  by  gusset 
plates  or  stiffeners,  set  at  intervals.     The  curb  is  not  necessarily  in  one 


IRON  CYLINDERS.  189 

single  piece  :  for  large  cylinders,  such  a  base  would  be  inconvenient  and  im- 
practicable ;  it  is  generally  composed  of  segments  bolted  together.  Details 
of  a  wrought-iron  curb  for  a  bridge  foundation  in  India*  are  shown  in 
figs.  116  and  117.  The  height  of  the  curb  is  4  feet,  and  the  width  of  the 
brickwork  base,  3  feet  7  inches.  The  diameters  of  the  outer  and  inner 
edges  of  the  curb  are  12  feet  6  inches  and  5  feet  4  inches  respectively. 
"  The  gusset  plates,  A,  twelve  in  number,  framed  with  angle  irons,  E,  were 
fixed  in  pasition  and  temporarily  bolted  to  the  outside  circular  plates,  from 
which  they  radiated  inwards,  forming  in  cross-section  a  V  shape ;  the  top  of 
the  V  being  the  top  segmental  plates,  C,  which  were  placed  upon  the  gusset 
frames  and  fixed  with  bolts  and  drifts  to  the  angle-iron  ring,  H,  the  whole 
being  riveted  together.  Finally,  the  inside  sloping  plates,  D,  were  fixed 
and  riveted  to  the  angle  irons,  E,  which  finished  the  operation."  The 
spaces  between  the  gussets  were  filled  in  with  concrete. 

Upon  curbs  similar  to  the  foregoing  the  brickwork,  or  ateining,  is 
founded,  vertical  bolts  (K,  fig.  116)  being  employed  to  firmly  connect  the 
two  parts.  Excavation,  carried  on  in  the  interior  of  the  cylinder  and 
beneath  its  base,  causes  the  cylinder  to  descend,  the  action  of  the  cutting 
edge  being  assisted  by  the  weight  of  brickwork  above.  As  the  cylinder 
sinks,  brick  rings  are  added  continuously  until  the  required  depth  is 
obtained. 

Great  care  has  to  be  taken  during  these  operations  to  maintain  the  per- 
pendicularity of  the  cylinder.  This,  of  course,  depends  upon  the  equal  and 
uniform  settlement  of  the  cutting  edge.  The  mast  trying  time  is  during  the 
sinking  of  the  first  10  feet  or  so,  and  it  is  recommended  that,  where  possible, 
the  curb  should  be  sunk  alone  to  this  depth.  The  first  layer  of  brickwork 
may  then  be  some  5  feet  in  height,  and  no  succeeding  layer  should  be  more 
than  10  feet.  It  is  further  recommended  that  the  topmost  course  of  brick- 
work of  each  layer  should  be  removed  before  commencing  the  next  layer,  so 
as  to  ensure  a  joint  perfectly  clean  and  free  from  any  trace  of  fallen  earth. 

Where  there  is  much  side  friction,  the  mere  intrinsic  weight  of  the 
cylinder  may  not  be  sufficient  for  the  purpose  of  driving.  Additional  weight 
is  best  added  in  the  form  of  iron  rails  and  kentledge,  which  are  compact  and 
easily  handled.  The  actual  amount  of  friction  to  be  encountered  will 
depend  on  local  circumstances,  but  under  ordinary  conditions  it  has  been 
found  to  vary  between  3  and  5  tons  per  square  yard.  The  average  rate  of 
sinking  in  the  instance  quoted  above  was  6  feet  in  eight  hours. 

Iron  Cylinders, — Metal  cylinders  are  almost  invariably  built  of  cast  or 
wrought  iron,  in  tiers  of  tubular  castings  or  of  circular  plating,  the  cutting 
edge  being  furnished  by  the  lower  edge  of  the  bottom  tier.  Adjacent  parts 
in  the  case  of  cast  iron  are  connected  by  internal  flanges,  and  in  the  case  of 
wrought  iron  by  fish-plates  also  arranged  internally,  with  tie  and  angle- 
iron  stiffeners  at  intervals.     Horizontal  flanged  joints  offer  facilities  for  the 

*  "Cylinder  Foundations"  by  Imrie  Bell  and  John  Milroy,  Min,  Proc,  Inst,  C,E., 
vol.  xzviii. 


I90  DUCK  BNGINESRINQ. 

placing  of  iron   kentledge  for  weighting  purposes,    and  brackets  may  be 
specially  cast  for  the  same  object.     This  method  wa^  adopted  in  the  case  of 
foundations  for  the  piers  of  a  bridge  in  the  River  Clyde,  the  bed  of  which  is 
running  sand  to  a  depth  of  80  feet*     Four  piles  were  driven  as  vertical 
guides  for  each  cylinder,  and  uniform  subsidence  wa^  obtained  by  systematic 
distribution  of  the  kentledge.     Brackets,  6  inches  long,  were  cast  on  the 
lower  flange  of  each  length  {6  feet  6  inches)  of  the  cylinder,  which  last  had 
a  dianieter  of  8  feet  4  inches.    The  kentledge  was  cast  in  the  form  of  circular 
segments,  12  inches  thick,  so  as  to  fit  the  concavity  of  the  sides  of  the  cylin- 
der, and  rest  upon  the  brackets.     In  this  way  lOi  tuns  dead  weight  was 
deposited  in  live  rings  upon  each  tier.     Owing  to  their  symmetry  and  the 
mutual  support  afforded  by  contiguous  sur- 
faces, there  was  no  tendency  to  displacement 
in  any  of  the  pieces.     The  rate  of  sinking 
was  5  feet  per  working  day. 

Cast-iron  cylinders,  5  feet  diameter  and 
25  feet  apart  longitudinally,  centre  to 
centre,  were  adopted  for  the  substructure 
of  the  earlier  quays  at  Newcastle-on-Tyne 
(fig.  H8).t  They  were  sunk  under  atmos- 
pheric pressure.  Over  the  intervening 
spaces,  masonry  and  brick  arches  were 
turned,  springing  from  cast-iron  beams  which 
connected  the  front  and  back  cylinders. 
Crescent-shaped  rows  of  metal  sheet  piling 
joined  the  front  cylinders  below  low  water 
level.  The  superstructure  consisted  of  ashlar 
facing  with  concrete  backing  and  granite 
coping.  The  wall,  however,  showed  signs 
of  weakness  before  the  dredging  in  front  of 
_,.      ii8T_Qua     \v  i]  ^^  '^  reached  the  intended  depth,  and  the 

Newcastle-on-Tyna.  '  work  had  to  be  strengthened  by  a  trench  of 

concrete  at  the  back. 
Elliptically  shaped  "cylinders"  of  cast  iron  in  continuous  rows  were 
then  experimented  with,  the  sheet  piling  being  discarded,  but  the  result  was 
equally  unsuccessful.  They  were  found  to  be  too  weak  to  resist  lateral 
pressure.  Apparently  the  failure  was  due  to  insufficient  thickness  of  metal, 
for  the  substructure  of  the  deep  water  quays  at  Cork  was  satisfactorily 
carried  out  in  oval-shaped  "cylinders"  of  concrete  (figs.  119  and  120). 

Concrete  cylinders  present  no  essential  structural  difference  from  thase 
of  brick,  as  already  described,  their  only  distinguishing  feature  being  the 
employment  of  concrete  instead  of  brickwork  for  the  steining.     Perhaps  at 

•  Min.  Proe.  hut.  O.E„  vol,  xxviii, 

+  Scott  on  "Deep  Water  Quays,   Newcastle-on-Tyne,"   Mm.   Pror.   Infl.   C.E., 


CONCRETE  CYLINDERS. 


191 


no  place  have  they  been  practised  so  extensively  or  developed  bo  such  & 

degree  as  in  the  foundation  for  the  quay  walls  of  the  River  Clyde.     From 

the  elementary  series  of  single  cylinders  has  been  developed  a  dual,  and, 

finally,  a  triple  form  shown 

in    figs.   121    and    122,    and 

described    in    the    following 

extract     from    a    paper     on 

"  Clyde  Navigation  "  by  the 

late    Mr.  James  Deas,  *  the 

information     being      revised 

and  supplemented  to  date  by 

the  courtesy  of  Mr.  Archibald 

Hamilton  : — 

"  The  cylinders  for  carry- 
ing the  quay  walls  are  triple, 
9  feet  7J  inches  outside  and 
5  feet  9^  inches  inside  dia- 
meter. They  are  made  in 
rings  2  feet  6  inches  deep 
by  1  foot  U  inches  thick,  in 
movable  wooden  moulds  on  a 
platform.  The  concrete  con- 
sisted of  5  of  gravel  or  broken 
stones  and  sharp  sand  te  1 
of  Portland  cement  of  the 
strongest  description,  mixed 
together  by  steam  power  in 
mixers  designed  for  the  pui^ 
pose,  water  being  added  to 
bring  the  mass  into  a  plastic 
stete.  To  facilitate  lifting, 
the  rings  were  divided  into 
three  and  four  segments,  al- 
ternately, so  as  to  break  bond 
when  built  into  the  cylinders. 
The  division  was  effected  in  a 
simple  manner:  malleable-iron 
dividing  plates,  |  inch  thick, 
were  placed  radially  across 
the  empty  wooden  moulds  in 
the  position  required ;  the 
concrete  was  then  filled  in  and 
well  punned  with  hammers, 
weighing  25  lbs.,  bo  as  to  secure  homogeneity  and  a  smooth  surface.     Twelve 


Pigs.  1 19  and  190.— Quay  WaU  at  Cork. 


•Jfin.  Pnc  I.  Mwh.  E.,  1896. 


CONCRETE  CYUNDBR8. 


193 


hoars  afterwards  the  dividing  plates  were  withdrawn,  and  two  days  later 
the  wooden  moulds  themselves ;  and  in  periods,  varying  from  nine  days 
in  hot  summer  weather  to  three  weeks  in  the  rains  of  winter,  the  rings 


Couet'Crorv  Shoe  for  CyLuuLer. 


PLcuv  of  Shoe 


iimn  6  0 

^uliiliilnl 


Sc4Ue    f^4S^ 
12       3       4 


SeclCorh 
at  XX.    1 


SecUorv 
at  YY.    VI 


SecUon 
at  ZZ.   I 


SoclU  VZ4*^ 


Figs.  123, 124,  125,  and  126.— Cylinder  Shoe  at  Glasgow. 


were  ready  for  removal  and  building.  The  volume  of  one  ring  complete 
was  10^  cubic  yards,  and  the  weight  18  tons,  the  heaviest  segments  weigh- 
ing about  6  tons  each. 

13 


194  ^^^^  ENGINEERING. 

"  The  bottom  ring,  differing  from  the  others,  is  called  a  corbelled  ring, 
because  it  is  made  less  in  thickness  all  round  the  bottom  edge,  in  order  to  fit 
into  a  cast-iron  shoe  (figs.  123  to  126),  and  is  tapered  inwards  and  upwards 
to  the  full  thickness  of  I  foot  1 1  inches.  The  shoe  is  of  V-shape,  2  feet 
deep,  of  I -inch  metal,  and  the  same  external  size  as  the  rings ;  the  under 
side  of  the  bottom  concrete  ring  rests  on  a  shelf  in  the  shoe,  6  inches  from 
the  top.  The  wedge-shaped  space  below  is  filled  with  concrete.  The  shoe 
weighs  about  4^  tons,  and  Is  in  six  parts  for  convenience  of  placing  in  the 
trench,  which  was  excavated  along  the  line  of  the  quay  wall.  The  bottom 
of  the  trench  was  about  2  feet  below  low-water  level,  where  it  was  made 
19  feet  wide,  the  sides  sloped  upwards  with  a  batter  oi  l^  horizontal  to 

1  perpendicular.  Staging  was  erected  to  carry  the  travelling  cranes  and 
digging  apparatus.  On  the  bottom  of  the  trench  the  shoes  were  placed 
exactly  along  the  line  of  the  quay  wall,  and  the  corbelled  ring,  being  placed 

on  the  shelf  in  the  shoe,  was  bolted  to  it  by  thirteen 
I^inch  bolts.     A  malleable-iron  washer  plate,  5  inches 
broad    by   ^    inch    thick,    was    sunk    into     the     top 
surface  of   the    corbelled   ring,    in    which   the   recess 
for  this    plate  and  the    holes    for  the   bolts  passing 
through  the  ring  had  been  made  in  the  moulding  of 
the   concrete  ring.     The  cyUnders,  being  triple,  were 
"R"     iQfl«  — M  ihnH     P^*<5^  ^^  ^^®  treuch  so  as  to  dovetail  into  one  another 
of  forminff  Joint        — ^^®  ^^  front  and  two  behind,  alternating  with  two 
at  J  fig.  123.         ^  front  and  one  behind.      The  sides  of    the   groups, 

where  they  pressed  against  each  other,  were  flattened 
for  a  breadth  of  5  feet  so  as  to  ensure  a  good  bearing. 

"  When  the  building-up  of  the  rings  forming  one  group  of  cylinders  was 
completed  to  the  full  height,  the  sand  and  gravel  were  dug  out,  simul- 
taneously, from  within  each  of  the  three  cylinders  by  means  of  cranes  or 
excavators  specially  designed  for  that  purpose.  From  400  to  600  tons  of 
east-iron  segmental  weights,  of  the  same  shape  as  the  rings,  were  generally 
required  to  force  each  group  of  cylinders  down  to  the  required  depth,  which 
is  nearly  60  feet  below  the  coping  level  of  the  quay.  The  tops  of  the 
cylinders  finish  about  12  inches  above  low- water  level.  The  average  rate  of 
sinking  was  about  1  foot  per  hour ;  in  good  working  sand  as  much  as  3  feet 
per  hour  was  attained.  When  the  group  had  been  sunk,  each  cylinder  was 
cleaned  out  by  means  of  the  excavators  to  the  level  of  the  bottom  of  the  shoe, 
and  was  then  filled  to  the  top  with  Portland  cement  concrete.  On  this 
foundation  the  quay  wall  is  built.  In  order  to  effectually  close  up  the 
apertures  between  the  adjoining  groups  of  cylinders  a  timber  chock  pile, 
30  feet  long  by  12  inches  square,  was  driven  behind,  angleways,  so  that  a 
sharp  comer  bears  hard  against  each  of  the  adjoining  cylinders. 

**  The  walls  are  of  concrete  rubble,  and  many  of  the  stones  weigh  from 

2  to  3  tons  each.  The  walls  are  faced  with  concrete  ashlar,  in  courses 
ranging  from  18  to  15  inches  thick ;  the  concrete  blocks  are  not  less  than 


CONCRETE  CYLINDERS.  1 95 

4  feet  long  by  2  feet  broad  on  the  beds,  and  the  headers  not  more  than 
10  feet  apart  from  centre  to  centre.  The  cope  is  of  granite,  3J  feet  broad 
by  17  inches  thick,  in  lengths  of  not  less  than  4  feet. 

"  To  increase  the  stability  of  the  quay  walls  of  the  Prince's  Dock,  tie-rods, 
2^  inches  diameter  and  60  feet  long,  were  put  in,  fixed  to  blocks  of  concrete 
masonry,  12  feet  long  by  6  feet  broad  and  8  feet  deep  (fig.  121).  Where  a 
depth  of  20  feet  at  low  water  is  afforded,  the  tie-rods  are  64  feet  apart,  and 
where  there  is  25  feet  depth  at  low  water,  they  are  32  feet  apart.  Where 
28  feet  depth  at  low  water  was  desired,  the  single  row  of  triple  cylinders  was 
supplemented  behind  by  a  row  of  twin  cylinders,  and  the  tie-rods  were 
increased  to  3^  inches  diameter  and  70  feet  length,  and  placed  64  feet  apart. 

*' Including  tie-rods  and  excavation  of  trenches,  the  cost  of  the  walls 
to  give  20  feet  depth  at  low  water  was  £80  per  lineal  yard;  to  give 
25  feet,  £90  per  lineal  yard ;  and  to  give  28  feet  depth,  £120  per  lineal 
yard." 

The  same  method  of  construction,  with  some  slight  modifications,  has  been 
employed  in  constructing  the  later  quay  walls  at  Newcastle-on-Tyne.  The 
"  cylinders  "  in  this  case  were  rectangular  in  plan,  30  feet  long,  20  feet  wide, 
and  37  feet  deep,  with  a  rectangular  internal  cavity  20  by  10  feet,  leaving 
walls  5  feet  thick  (figs.  127,  128,  and  129).  The  process  of  sinking  was 
carried  out  as  follows  : — 

"  The  curb  was  6  feet  in  height,  the  cutting  edge  being  an  iron  casting  of 
V-shaped  section,  2  feet  1  inch  deep,  with  vertical  wrought-iron  straps 
attached,  and  timber  lining.  The  cast-iron  toe  was  made  in  four  parts, 
which  were  bolted  and  riveted  together  at  the  comers.  In  constructing  the 
curb,  the  castings  were  first  set  and  bolted  temporarily  together,  after  which 
the  timber  lining  (elm  or  beech)  was  fitted  and  bolted  upon  it.  The  finished 
curb  was  let  down  into  position  in  four  parts,  which  were  bolted  together  at 
their  comers  in  the  bottom.  Sometimes  a  little  concrete  was  put  into  the 
curbs  before  they  were  let  down.  The  bottom  was  levelled  to  receive  the 
shoes,  and  was  made  up,  where  necessary,  to  3  or  4  feet  above  low-water 
level.  Straps  were  put  across  the  corners  on  the  inside  at  the  top  of  the 
curb  to  prevent  the  sides  from  bulging  out.  The  curbs,  being  set  level,  were 
filled  with  6  to  1  concrete,  and  on  this  the  sides,  6  feet  thick,  were  built  all 
round.  The  shutters  for  concreting  were  3  feet  deep,  and  were  carried  on 
9-inch  by  3-inch  standards.  After  each  3-foot  filling  sufficient  time  was 
allowed  for  the  concrete  to  set.  When  the  structure  had  been  built  to  a 
height  of  9  or  1 2  feet  above  the  top  of  the  curb,  it  was  stripped  and  sunk, 
the  interior  being  taken  out  by  grab  dredgers  until  the  top  was  3  or  4  feet 
above  low-water  level."  By  repeating  the  process  of  alternately  building  and 
sinking  in  stages  of  9  or  12  feet,  the  full  depth  of  37  feet  was  attained,  when 
the  toe  of  the  curb  fairly  entered  into  a  stratum  of  hard  ballast.  "  The 
sinking  blocks  were  not  guided  or  suspended  in  any  way,  but  were  left 
entirely  free  and  were  thus  liable  to  work  a  little  out  of  place.  Sometimes 
.a  block  would  heel  over  considerably  on  one  side,  but  could  generally  be 


196  DOCK  ENGINEERING. 


SlgB.  127,  12S,  and  129.— Nencnatle  Quay,WaU. 


CONSTRUCTION  IN  THE  OPEN.  1 97 

righted  again  by  the  excavation."  Old  rails  and  kentledge  were  used  as 
sinking  weights.     The  heaviest  load  was  350  tons. 

Having  reached  a  satisfactory  depth,  a  little  copper  slag  was  put  in  the 
bottom  of  the  wells  prior  to  filling  the  whole  with  7  to  1  concrete  containing 
rubble.  Small  bags  of  concrete  were  packed  by  divers  all  round  the  toe 
under  the  curb,  and  then  the  bulk  of  the  concrete  was  lowered  in  skips 
through  the  water  to  the  bottom,  and  gently  released. 

The  intervening  spaces  of  about  2  feet  between  adjacent  piers  were  piled, 
back  and  front,  and  concreted. 

The  superstructure  consisted  of  a  sandstone  ashlar  facing,  backed  by 
5  to  1  cement  concrete  with  granite  coping.  The  face  has  a  batter  of 
1  in  12.* 

General  Methods  of  Construction. 

Apart  from  the  means  adopted  to  secure  a  firm  and  reliable  foundation 
on  sites  more  or  less  unsatisfactory  and  untrustworthy,  there  are  a  great 
variety  of  methods  practised  in  constructing  the  dock  wall  itself ;  so  varied, 
in  fact,  as  to  scarcely  admit  of  any  classification,  though  an  attempt  will  be 
made  here  to  include  some  of  the  more  prominent  and  typical  systems  under 
five  heads,  viz. : — 

(a)  Ordinary  constrtictton — 

In  the  open. 
In  trenches. 
Within  temporary  dams. 

(P)  Subaqueous  construction — 

In  pneumatic  chambers. 
With  monoliths. 

Construction  in  the  Open. — A  description  of  this  method  calls  for  little  or 
no  amplification.  Where  the  base  rests  upon  the  natural  surface  of  the 
ground,  the  wall,  if  of  masonry,  is  built  in  the  ordinary  way,  generally  with 
the  aid  of  overhead  travellers.  If  of  concrete,  it  will  be  necessary  to 
provide  means  for  the  support  of  the  face  moulds.  This  may  be  done  by 
the  use  of  temporary  uprights,  sometimes  called  "  soldiers."  These  uprights 
(fig.  39),  placed  at  convenient  distances  apart,  have  a  rebate  on  their  inner 
faces,  within  which  the  moulds  are  free  to  move  vertically.  When  the  latter 
have  been  lifted  or  lowered  to  their  assigned  position,  they  are  temporarily 
fixed  by  means  of  wedges.  The  swivel  hooks  shown  in  the  fig.  are  for  the 
purpose  of  raising  the  moulds.  Alternatively,  the  moulds  may  be  supported 
by  wooden  cantilevers  built  into  the  wall  at  each  succeeding  course,  as  shown 
in  fig.  38,  and  temporarily  counterweighted  by  concrete  blocks.  These 
cantilevers  can  be  afterwards  cut  away  to  an  inch  or  so  within  the  face  line 

*  Scott  on   **  Deep-water    Quays,    Newcastle-on-Tyne,"  Min.    Proc.   Inst,   0,E,n 
voL  cxix. 


198 


DOCK  ENGINEERING. 


of  the  wall,  and  covered  with  a  thin  veneer  of  cement.  Or  if  their  ends 
be  not  considered  unsightly  they  may  be  simply  sawn  flush  with  the  surface 
of  the  concrete. 

Where  the  base  of  the  wall  lies  below  the  ground  level,  the  earth  may  be 
excavated  at  any  suitable  slope  until  the  required  depth  is  reached.  If  the 
strata  will  admit  of  it,  it  is  preferable  to  bench  out  the  ground  in  a  series  of 
steps  to  avoid  the  formation  of  a  possible  plane  of  rupture  between  the 
filling  and  the  natural  earth.  The  steps  may  even  with  advantage  be  sloped 
downwards  away  from  the  wall.  Fig.  130  is  an  illustration  of  a  masonry 
dock  wall  built  under  a  combination  of  the  foregoing  circumstances.  The 
ground  in  front  of  the  wall  had  previously  been  excavated  to  the  proposed 
depth  ;  that  at  the  rear  of  the  wall  is  partially  sloped  and  partially  benched. 
The  projection  from  the  back  of  the  wall  near  the  coping  level  is  to  form  the 
floor  of  a  trench  for  hydraulic  and  other  pipes. 


Md  bom 


Boulder 
Clay 


^^T^-VT^T' 


18  6' 


Fig.  130.— Dock  Wall  at  Liverpool. 

Constmction  in  Trenches. — The  means  adopted  for  obtaining  the  required 
depth  for  the  base  of  a  wall  by  means  of  timbered  trenches  is  illustrated  in 
fig.  131,  which  exhibits  the  actual  strata  passed  through  in  a  definite 
instance  on  the  banks  of  the  Mersey.  The  vertical  series  of  shores  are 
placed  at  intervals  of  from  1 0  to  1 2  feet.  The  width  of  the  trench  at  the 
top  is,  of  course,  greater  than  the  assigned  foundation  width,  by  the  sum  of 
the  thicknesses  of  the  timber  settings.  The  small  "  grip,"  or  trench,  in  the 
bottom  is  for  drainage  purposes.  The  method  of  construction  presents  no 
essential  difference  from  those  already  indicated.  The  shores  and  walings 
which,  together  with  the  sheeting  piles,  are  withdrawn  as  the  wall  is  built, 
offer  facilities  for  the  support  of  concrete  moulds.  By  this  system  the  earth 
in  front  of  the  wall  is  excavated  at  a  later  stage.  In  the  meantime,  any 
space  between  the  front  of  the  wall  and  the  side  of  the  trench  is  occupied  by 


CONSTRUCTION  WTTHIN  TEMPOKAEY   DAMa  I99 

filling  tipped  in  as  the  wall  rises  in  height.     Care  must  be  taken  to  bring  the 

wall  up  in  regular  lifts  as  far  as  possible,  contemporaneous,  and  to  avoid  any 

extenaive  "  racking  back,"  which  causes  inequality  of  pressure  on  the  founda* 

tion,  and   necessitating    abrupt 

changes  in  the   timbering,  may  _,  ^*?r^*«L_^«?' 

induce  vertical    cracks    in    the 

wall. 

Trenching  was  adopted  for  » 
quay  wall  at  Belfast  as  indicated 
in  fig.  132,  which  also  shows  the 
nature  of  the  strata  dealt  with. 
Sleetoh  is  the  local  name  for 
slightly  indurated  or  compact 
mud. 

Constrnctlon  within  Tem- 
porary Dams. — The  foregoing 
sections  have  dealt  with  3ite.i 
more  or  less  inland  during  the 
period  of  construction.  Of  the 
many  ways  in  which  the  work 
may  be  carried  on  when  the  .site 
is  continuously  under  water,  the 
following  is  one  which   admits 


Fig.  131.— Timbered  Trench. 


Sckl*.  W  het  to  1  iDub. 
Fig.  133.— Quay  Wall  at  Belfaat. 
of  constructive  work,  under  normal  conditions,  after  the  initial  provision 
of  a  watertight  compartment. 


200  1>0CE  BNOIMEBRIKO. 

Fig.  133  shows  a  section  of  a  timber  d&m  (a  description  of  it  will  be 
fovnd  on  p.  105,  antt)  which  has  been  floated  over  the  site  (at  LiveTpool), 
weighted,  sunk,  and  ^ited.  The  bottom  edge  of  the  dam  has  been  made 
watertight  by  means  of  a  tipped  bank  of  clay  puddle,  which  La  prevented 
from  slipping  away  under  the  softening  influence  of  water  by  barges  sank 
on  the  outer  side.     Within  the  enclosed  area  thus  provided,  work  may 


Fig.  133.— Conatniclion  within  Temporary  Dam. 


Fig.  134.— Dam  and  Quay  Wall  at  ArdroBBan. 

proceed  as  usual.  Pumping  power,  however,  is  in  this  case  a  more  essential 
feature,  not  only  on  account  of  emptying  the  dam  in  the  first  instance,  but 
also  for  dealing  with  leakage,  which  ia  sure  to  be  continuous,  and  the  pos- 
sibility of  an  inburst  of  water.  Inbursts  are  most  likely  to  occur  in  faulty 
ground,  the  water  being  forced,  under  the  great  head,  through  a  pervious 
stratum  m  the  dock  bottom.     It  is,  therefore,  advisable  to  dredge  the  site 


CONSTRUCTION  IN  PNEUMATIC  CHAMBERS.  201 

clear  of  all  mud  and  Hilt  before  berthing  the  rlam.  A  good  supply  of  clay 
will  be  neceavaty  to  replace  wa^itage  in  the  puddle. 

The  length  of  the  dam  in  <iueation  was  246  feet,  divided  into  16  bays 
of  15  feet  each,  with  an  overlap  at  one  end.  On  the  conclusion  of  the 
work  the  piles  were  drawn,  and  the  sides  of  the  dam  removed  separately. 
In  a  similar  manner  the  concrete  walls  of  a  tidal  basin  at  Ardrossan  were 
constructed.*  Fig  134  is  a  section  of  the  wall  and  of  the  box  dam  within 
which  it  was  built. 

Constmction  in  PneoMallc  Cbambers.— ^This  system,  in  one  or  other  of 
its  forms,  represents  a  very  considerable  proportion  of  Continental  practice, 
but  it  does  not  seem  to  have  been  adopte<l  in  any  noteworthy  instance  in 
English  ports,  if,  as  is  intended,  we 
restrict  the  use  of  the  diving  bell  to 
the  actual  construction  of    the  wall. 
The  system  dates  back  sonie  consider- 
able time,  and  walls   have  been  con- 
structed on  its  principles,  notably  at 
Antwerp,  Marseilles,  Genoa,  and  elae- 

The  following  account  of  its  appli- 
cation to  the  recently  constructed  quay 
walls  of  the  Bassin  de  la  PinMe,  at 
Marseilles,  is  extracted  and  condensed 
from  an  article  by  M.  Batard-RazeliJire, 
Engineer  -  in  -  Chief  of  the  harbour  , 
works  there :— + 

"  The  foundation  of  the  quay  walls 
is  laid  on  stiff  ground  (ballast,  grit,  or 
hard  clay),  when  that  ground  is  met 
with  above  a  level  of  40  feet  below 

the  datum  of  ordinary  low-water  level.  The  profile  of  the  wall  is  then 
represented  by  fig.  1 35.  The  masonry  is  bedded  into  the  ground  for  a  width 
of  about  10  feet  at  its  base.  When  stifi'  ground  is  only  to  be  found  below 
the  above-named  level,  the  site  is  dredged  to  that  depth,  the  material  con- 
sisting mainly  of  mud,  sand,  and  decayed  seaweed.  A  bank  of  rubble 
stone  is  then  formed  and  brought  up  to  a  level  of  30  feet  below  datum, 
having  at  this  level  a  width  of  41  feet,  and  the  normal  section  of  the  wall 
is  founded  upon  this  base,  as  in  fig.  136. 

To  within  5  feet  of  low-water  level  the  work  is  executed,  by  means  of 
compressed  air,  in  the  interior  of  large  metallic  chambers  (caissons  I),  acting 
like  diving   bells.      From  5  feet  below  to   18  inches  above   datum    it  is 

*  Robertson  on  "Ardrossaii  Harbour  EitenisiunB,"  .Win.  Pnc  Inal.  C.E.,  vol.  cxx, 
+  Butleiin  dr.  la  fiocUti  ScUiili^iit  Indaitrittte  lU  MarwilU,  2me  Trimeetre,  1900. 
X  The  word  "  caisaon  "  in  this  connection  ha*  not  quite  the  signification  which  it 
has  when  applied  to  the  apparatus  for  cloeing  a  dock  entrance. 


202  DOCK   ENGINEERING. 

executed  in  the  open  air,  by  pumping  the  enclosed  water  from  the  interior 
of  a  large,  bottomless,  metallic  chamber,  forming  a  cofferdam.  The  remainder 
of  the  wall,  to  its  full  height  of  nearly  8  feet  above  datum,  is  constructed  in 
the  ordinary  way. 

The  walls  are  entirely  constructed  in  ordinary  rubble  masonry,  with  the 
exception  of  a  dressed  stone  coping  and  a  picked  facing  down  to  low  water 
level. 

Five  caissons  are  allocated  to  the  execution  of  the  work  under  compressed 
air.  These  caissons  are  movable,  and  the  work  is  carried  out  in  such  a  way 
as  to  obtain  a  continuous  block,  without  any  interposition  of  metal  in  ita 
interior. 


Kig.  136.— Dock  Wall  at  .MarBeillca— Section  li. 

Four  of  these  caissons  are  identical  in  disposition  (figs.  137  and  138). 
The  interior  height  of  the  working  chamber  is  6  feet  6  inches  uniformly, 
but  the  dimensions  in  plan  vary  somewhat.  The  size  of  the  largest  chamber 
is  66  feet  3  inches  by  21  feet  9  inches,  the  smallest  59  feet  by  17  feet 
9  inches.  Above  the  working  chamber  is  a  compartment  having  the  same 
horizontal  dimensions,  in  which  is  depositefl  the  necessary  ballast.  This 
ballast  is  formed  partly  by  a  layer  of  masonry,  or  of  concrete,  and  partly  by 
iron  kentledge.  From  the  roof  of  the  working  chamber  rise  three  vertical 
shafts,  situated  on  the  longitu<linal  axis  of  the  caisson,  each  surmounted  by 
an  air  lock  above  the  water  level.  The  middle  shaft  serves  for  the  work- 
men ;  ita  diameter  ia,  according  to  circumstances,  2  feet  3  inches  or  3  feet 
6  inches.  The  entrance  ]o<:k  is  a  cylindrical  chamber  8  feet  3  inches  dia- 
meter. The  other  two  shafts  serve  for  the  raising  of  excavations  and  the 
lowering  of  materials ;  they  are  3  feet  6  inches  diameter,  as  also  are  their 

The  working  chamber  is  lighted,  and  the  lifts  are  worked,  by  electricity 


PLAN  OF  CAISSON  AT  MARSEILLES. 


203 


The  compressed  air  is  despatched,  from  a  central  station  on  shore,  by  means 
of  a  conduit  branching  into  flexible  tubes  supported  on  piles,  and  is  intro- 
duced into  the  top  of  the  central  shaft  immediately  below  the  floor  of  the 
lock.     The  electric  wires  follow  the  same  route. 


Fig.  137. — LoDgitudinal  Section  of  Caisson  at  Marseilles. 


Fig.  138  — Plan  of  Caisson  at  Marseilles. 


204  I>OCK  ENGINEERING. 

The  total  weight  of  a  caisson  is,  on  an  average,  nearly  410  tons,  including 
350  tons  of  kentledge.  This  weight  is  reduced  to  about  290  tons  when  the 
caisson  is  immersed,  and  to  30  tons  when  it  is  sunk  and  the  working 
chamber  full  of  air. 

Having  dredged  and  prepared  the  site,  as  before  described,  the  caisson  is 
conducted  to  its  place  between  two  barges  connected  by  a  framing  which 
forms  a  deck  above  the  caisson.  The  latter  is  then  lowered  into  position  and 
detached  from  its  supports.  The  working  chamber  having  been  filled  with 
compressed  air,  the  surface  of  the  ground  uncovered  is  cleared  and  levelled, 
and  a  block  of  masonry  built  upon  it  about  4  feet  in  height,  its  other 
dimensions  corresponding  to  the  size  of  the  chamber  and  the  width  of  the 
wall,  with  a  slight  clearance  in  the  former  case.  This  completed,  the  caisson 
is  removed  to  an  adjoining  site  by  a  reversal  and  renewal  of  the  process,  the 
blocks  being  constructed  as  closely  together  as  possible  and  leaving  only  an 
interval  of  about  3  feet  between  them.  A  second  caisson  following  the  first 
builds  the  second  course,  and  at  the  same  time  by  sitting  over  the  joints 
between  the  blocks  fills  up  the  vacant  spaces  with  the  aid  of  a  diver,  who 
rapidly  constructs  a  brick  wall,  back  and  front  of  the  spaces,  which  are  then 
pumped  dry  and  filled  with  masonry. 

The  fifth  caisson  is  self-acting ;  it  can  sink  or  float  by  its  own  appliances. 
It  is  larger  and  heavier  than  the  others,  and  is  intended  to  be  worked  at 
variable  depths,  being  used  principally  for  constructing  the  bottom  course  of 
blocks.  Its  functions  generally,  however,  are  the  same  as  those  of  the  other 
four  chambers. 

Ordinarily,  no  excavations  were  made  within  the  caissons  except 
such  as  were  necessary  to  prepare  a  level  seat  for  the  wall ;  in  certain 
cases,  however,  it  was  possible  to  descend  about  6  feet  below  the  initial 
position  of  the  chamber,  but  there  would  have  been  risk  in  sinking 
lower,  on  account  of  the  possibility  of  not  being  able  to  liberate  the 
caisson. 

Where  firm  earth  is  met  with  above  the  floor  of  the  basin,  which  is  the 
case  along  and  in  the  neighbourhood  of  the  landward  side,  the  wall  is  only 
built  to  its  full  width  above  that  level.  The  lower  portion  of  the  wall  is 
simply  constructed  as  a  retaining  wall  or  revetment  of  about  5  feet  in  thick- 
ness, as  shown  in  fig.  139.  In  this  case  the  caisson  is  sunk  to  rest  upon  the 
higher  level,  and  the  firm  stratum  below  being  practically  impermeable,  the 
revetment  is  put  in  by  means  of  a  trench,  and  the  upper  portion  of  the  wall 
is  proceeded  with  as  usual. 

The  rate  of  working  has  depended  on  the  nature  of  the  foundation ;  in 
the  case  of  very  hard  ground  requiring  the  pick,  the  rate  of  descent  of  the 
caisson  did  not  exceed  6  inches  per  day  of  24  hours.  In  the  building  of 
the  wall  each  mason  executes  about  88  cubic  feet  of  masonry  in  a  shift  of 
eight  hours.  The  construction  of  one  block  of  masonry  absorbed  three 
days,  including  the  manipulation  of  the  caisson  and  the  making  good  of 
the  joint  in  the  course  below.     The  cost  of  the  masonry,  exclusive  of  the 


l-NEUMATIC  PB0CE8S  AT  ANTWERP.  305 

hydraulic  lime,  which  is  supplied  to  the  coatractor  by  the  Adminiatntion, 
amouiits  to  about  18  shilliuga  a  cubic  yard. 

The  system  just  described  is  by  no  means  uew,  having  been  practised  at 
the  ports  of  Paimbceuf,  St.  Malo,  La  Pallioe,  and  Genoa  by  the  same 
contractor  (.M.  Conrad  Zschokke),  but  the  vork  now  or  recently  carried  out 
at  Marseilles  represents  its  full  aiid  perfected  development. 

With  this  system  may  be  contrasted  the  pneumatic  process  adopted  at 
Antwerp  as  far  back  as  tlie  year  1877,  and  still  employed  for  the  construc- 
tion of  additionsl  quays  within  the  last  few  years.  The  following  is  an 
account,  necessarily  succinct,  of  the  process  in  its  most  modem  form  : — * 

The  wall  (fig.  140)  is  built  of  brickwork  mainly,  with  a  facing  of  dressed 
stone  from  3  feet  below  low-water  level  up  to  a  coping  of  ashlar  masonry. 
It  rests  upon  a  foundation  of  concrete  of  varying  thickness,  according  to  the 
depth  of  excavation  required,  but  ranging  generally  between  6  and  16  feet. 


Fig.  140.— Quay  Wall  st 
Antwerp. 

The  batter  of  the  face  is  1  in  10  for  the  lower  portion  and  1  in  20  above  low- 
water  level.  The  thickness  of  the  wall  at  the  base  is  21  feet  4  inches.  The 
depth  of  the  base  is  24  feet  8  inches  below  low-water  level. 

A  bottomless  metallic  caisson,  rectangular  in  plan,  is  floated  out  over  the 
site  of  the  foundation  between  two  barges,  connected  by  overhead  framing. 
In  plan  the  caisson  is  t'8  feet  4  inches  long  by  31  feet  2  inches  wide.  The 
structure  of  the  caisson  will  be  readily  understood  from  the  cross  and  longi- 
tudinal sections  shown  in  &gs.  141  and  142.  It  is  lowered  into  place  and 
sunk  to  a  firm  clay  foundation  by  excavating  inside  of  it  the  alluvial  bed 
of  the  river.     In  sinking  it  is  assisted  by  the  weight  of  the  concrete  ballast 

*  Vide  "  Anvers,  port  de  Mer,  aveo  appendice,"  1898.  Vernon- HaroourC  on  "Mari- 
time Navigstion  Works  in  Belgium,"  Min.  Proc.  Inst.  C.E.,  vol.  oxxxvi. 


2o6  DOCK  ENGINEBRINO. 

immediately  above  the  working  chamber,  aad  of  the  qnay  wall,  which  is 
built   up  gradually  from  its   roof  within    an  auxiliary   cofferdam.      The 


Flga.  141  and  1^— Pnenmatio  Ccoutrnctdcti  at  Autwerp. 


PNEUMATIC  CONSTRUCTION  AT  ROTTERDAM.  207 

nrorking  ch&mber  is  finally  filled  with  concrete  through  the  vertical  shafta 
which  have  previonaly  served  for  purposes  of  scceas.  The  interval  of  about 
18  inches,  nnavoidably  left  between  adjacent  lengtjis  of  foundation,  and  the 
gap  of  about  42  inches  between  the  sections  of  wall,  are  made  good  hj 
cement  concrete,  the  joint  being  strengthened  hj  vertical  grooves  in  the 
connected  ends.  The  wall  is  continuous  above  a  level  of  3  feet  above  low 
water.  The  height  of  the  working  chamber  is  a  little  over  5  feet,  and  it 
projects  6  feet  in  front  of  the  base  of  the  wall,  in  order  to  afford  a  sufScient 
area  of  foundation  to  support  the  imposed  pressure.  The  present  cod- 
tractors  are  Messrs.  Hersent  &  Son,  succeeding  the  original  firm  of 
Oouvreux  &  Hersent,  who  initiated  the  syatetn. 

In  contradistinction  to  the  preceding  instances,  the  use  of  the  pneumatic 
chamber  has  been  applied  at  the  port  of  Rotterdam  to  the  construction  of  a 
portion  of  the  wall  considerably  above  the  dock  bottom*  {see  fig.  143). 


Fig.  143. — Pneumatic  ConBtmctiou  at  Rotterdam. 

The  wall  is  built  upon  a  timber  platform,  supported  hy  fir  piles  driven 
into  the  bed  of  the  River  Meuse  through  fascine  mattrasses  and  a  layer  of 
sand  previously  deposited  in  a  dredged  trench.  The  piles  are  provisionally 
sawn  off  at  low  water,  and  the  caisson,  70  feet  long  by  29  feet  wide,  ia 
floated  over  their  heads  in  such  a  manner  that  the  ends  occupy  spaces  of 
4  feet,  specially  provided  at  intervals  between  the  piles,  which  are  otherwise 
driven  at  centres  of  3  feet  3  inches.  The  caisson  is  then  sunk  until  it  takes 
its  bearing  on  the  landward  side,  and  at  one  end  upon  a  portion  of  the  plat- 
form already  placed  in  position.  At  this  stage,  suitable  adjustments  of 
water  ballast  are  made,  to  maintain  equilibrium,  and  workmen  enter  the 
oompresBod  air  chamber,  which  hat  previously  been  occupied  by  water.  The 
*  Le  Port  de  Rotterdam,  hy'^  A,  van  Ysaelsteyn,  8oas.director  des  tiavaiuc  de  la  ville. 


208  DOCK  ENGINEERING. 

piles  are  cut  off  to  the  desired  height  and  fitted  with  iron  collars  to  support 
the  cross  beams,  9  to  12  inches  square,  which,  in  turn,  carry  the  flooring, 
4  inches  thick.  Two  consecutive  lengths  of  platform  are  prepared  in  this 
way,  and  then  the  caisson  is  berthed  over  the  interval  between  them,  and 
the  decking  made  continuous.  In  one  week,  14  men  working  within  the 
pneumatic  chamber  can  completely  prepare  a  length  of  more  than  22  yards 
of  platform. 

Upon  the  foundation  thus  constructed,  the  wall  is  built  to  its  full  height 
with  concrete  blocks,  8  feet  long,  3  feet  high,  and  as  wide  as  the  wall  is 
thick,  having  a  facing  of  basalt.  Brickwork  has  been  tried,  with  unsatis- 
factory results. 

The  fascine  work  is  made  good  between  the  beams  to  the  underside  of 
the  decking,  and  an  additional  mattrass  is  sunk  behind  the  timber  work  so 
as  to  present  an  upper  surface  level  with  the  planking.  Finally,  a  mattrass 
is  laid  partly  upon  the  platform  and  partly  upon  the  fascine  work  behind, 
and  the  whole  is  filled  with  sand. 

A  lineal  yard  of  wall  constructed  in  this  manner  costs  at  the  present  day 
900  florins,  of  which  one-third  may  be  assigned  to  the  fascine  mattrass  work. 
Fig.  113  shows  a  cross  section  of  the  completed  wall. 

Gonstniction  with  Monolithic  Blocks. — By  this  system,  which  consists  in 
building  the  submerged  portion  of  a  quay  wall  in  a  series  of  massive  blocks, 
the  use  of  cofferdams  is  avoided,  and  also  that  of  diving  bells,  except  in  so 
far  as  the  latter  are  found  necessary  for  providing  a  suitable  and  level 
foundation  for  the  blocks.  The  blocks  themselves  may  be  set  by  means  of  a 
floating  crane  or  sheers,  and  accurately  adjusted  with  the  assistance  of  a 
diver,  who  may  also,  under  favourable  circumstances,  be  able  to  prepare  the 
site  for  their  reception. 

Perhaps  the  most  notable  instance  of  the  adoption  of  this  method  is  to  be 
found  at  Dublin,  where  the  quay  walls  have  a  monolithic  base  course, 
27  feet  in  height,  reaching  to  3  feet  above  equinoctial  low  water.  The 
width  of  each  block  at  the  base  is  21  feet  4  inches,  forming  the  entire 
thickness  of  the  wall ;  the  face  length  is  12  feet,  and  the  total  contents  are 
nearly  5,000  cubic  feet  of  masonry,  weighing  350  tons.  Adjacent  blocks 
are  connect3d  by  means  of  dowels,  formed  by  filling  with  concrete  long 
vertical  grooves,  3  feet  square  in  plan,  one-half  of  which  is  arranged  in  the 
side  of  each  block. 

The  following  particulars  relate  to  the  quay  wall  of  a  tidal  basin  built, 
in  1871,*  under  the  direction  of  Dr.  Stoney,  F.R.S.,  the  engineer  to  the 
Port  Trust. 

The  necessary  preparation  and  levelling  of  site  were  effected  by  the 
agency  of  a  diving  bell,  covering  an  area  of  400  square  feet,  and  furnished 
with  a  shaft,  3  feet  in  diameter,  rising  from  its  roof  above  the  surface  level 
of  the  water,  where  it  was  connected  to  an  air-lock  for  the  passage  of  men 

*  Stoney  on  **  The  ConBtruction  of  Harbour  and  Marine  Works  with  Artificial  BlockB 
of  Large  Size,"  i/m.  Proe,  Inst,  G.E,,  vol.  xxxvii. 


CONSTRUCTION  WITH  MONOLITHIC  BLOCKS. 


209 


and  materials.  Operations  were  carried  on  at  a  maximum  depth  of  44  feet. 
With  two  gangs  of  six  men,  each  working  alternately  in  4-hour  shifts,  at  a 
cutting  4  feet  deep,  in  stiff  clay,  the  preparation  of  the  foundation  for  one 
block  occupied  about  62  hours. 

The  masonry  of  which  the  blocks  were  composed  consisted  of  a  bulk  of 
irregularly  bonded  rubble,  in  pieces  not  exceeding  2  tons  weight,  set  in 
cement,  with  a  facing  of  calp  limestone,  squared  and  jointed,  the  mortar 
being  composed  of  4  parts  sand  to  I  of  Portland  cement.  The  blocks  were 
built  in  wooden  frames  at  a  wharf  some  distance  away,  and,  when  ready  for 
depositing,  were  lifted  by  a  pair  of  floating  sheers.  For  the  purposes  of 
lifting,  four  wrought-iron  suspension  bars,  5  inches  diameter,  having 
±-shaped  extremities,  passed  through  vertical  rectangular  holes  in  each 
block,  at  the  foot  of  which  were  circular*  cast-iron  washers,  2  feet  2  inches 
diameter  (figs.  144  and  145),  to  distribute  the  pressure.  By  turning  them 
through  an  angle  of  90°  the  bars  could  be  engaged  or  released. 


-A-f  — 


\ 


---fji-::--a.--  — 


Fig.  144. — Plan  of  Cast-iron  Washer. 


Ovss  Secoon  on  Line  AB. 

Fig.  145. 


IBoUamof Block 


Conveyance  was  usually  made  with  the  block  submerged  to  half  its 
height^  thus  relieving  the  strain  on  the  lifting  tackle  by  some  80  to  100 
tons.  Arrived  at  the  site,  no  difficulty  was  found  in  bringing  the  block 
rapidly  into  its  assigned  position.  Ranging  was  performed  while  it  was 
about  3  or  4  inches  off  the  ground,  by  means  of  short  timber  uprights 
wedged  into  the  dowel  grooves  at  each  side  of  the  block.  These  were 
brought  into  line  against  a  horizontal  balk,  extending  from  and  attached  to 
the  blocks  already  set.  Close  contact  of  adjoining  blocks  was  achieved  by 
the  use  of  a  small  tackle,  the  average  joint  in  a  length  of  300  feet  being 
only  \  inch.  The  dowel  grooves  were  then  filled  with  concrete  and  the 
operation  was  concluded. 

The  upper  portion  of  the  wall  was  built  by  tide  work  to  a  height  of 
18  feet  10  inches  above  equinoctial  low  water,  giving  a  total  height  to  the 

*  This,  however,  is  a  later  improvement ;  the  earliest  type  of  washer  was  girder- 
shaped. 

14 


2  to  DOCK  ENGINEERING. 

wall  of  42  feet  10  inches.  The  coping  is  of  granite  in  blocks  of  from  2  to  4 
tons  weight.     The  profile  of  the  wail  is  showa  in  fig.  146. 

The  cost  of  a  quay  wall  constructed  in  this  way  and  to  these  dimensions 
came  to  £40  per  foot  run,  includinj^  7  per  cent,  interest  on  a  sum  of 
.£33,800  for  plant.     The  rate  of  construction  was  400  lineal  feet  per  annum. 

On  the  same  principle,  but  with  blocks  of  smaller  dimensions,  a  quay 
wall  (fig,  147)  some  500  yards  in  length,  was  constructed  at  Cork  about  tlie 
year  1877.*  The  submerged  portion  of  the  wall  consisted  of  three  rows  of 
blocks,  rectangular  in  plan,  weighing  from  35  to  4i)  tons  eaoli.  As  in  the 
case  of  the  Dublin  blocks,  they  were  constructed  at  a  wharf  some  distance 
away  and  transported  to  their  respective  positions  by  a  floating  sheers. 
The  composition  of  the  monoliths,  however,  was  different,  in  that  they 
were  made  entirely  of  concrete  in  the  proportion  of  7  to  l^viz.,  5  parts 
river  ballast,  3  parts  broken  limestone  passed  through  a  3-inch  ring,  and 
1  part  Portland  cement 


Fig.  146.— Quay  WaU  at  Dublin.  Fig.  147.— Quay  WaU  at  Cork. 

The  foundation  consisted  mainly  of  fine  compact  gravel  and  sand.  After 
being  dredged  to  within  2  feet  of  the  required  depth  the  remaining  material 
was  removed  by  divers.  A  rectangular  frame  of  angle  iron  slightly  larger 
than  the  block  was  then  laid  on  the  ground  and  adjusted  by  soundings  from 
above.  The  surface  inequalities  within  the  enclosure  were  levelled  by  an 
iron  straight  edge. 

The  blocks  (figs.  148  and  149)  were  suspended  by  four  stirrup-rods  pass- 
ing down  vertical  grooves,  10  inches  by  5  inches,  in  the  sides  of  the  blocks, 
*  Barry  on  "  Deep  Water  Qoays  at  the  Port  of  Cork,"  Min.  Proc.  Inst.  C.B.,  vol  c 


CONSTRUCTION  WITH  MONOLITHIC  BLOCKS.  2  1 1 

which  were  afterwards  used  for  the  reception  of  lO-inch  square  atoae 
dowels,  3  to  4  feet  loDg,  to  connect  adjoining  lengths.  The  ends  of  two 
small  wrought-iron  girders  in  recfssea,  at  or  near  the  liottom  of  each  block, 
rested  in  the  stirrup-rods,  and  all  were  withdrawn  together  at  the  close  of 
the  setting  operations. 

The  superstructure  consisted  of  a  facing  of  regularly  coursed  limestone 
ashlar,  backed  by  6  to  1  concrete,  with  a  coping  of  Cktrnish  granite. 

Another  instance  of  monolithic  construction,  with  yet  smaller  blocks  of 
concrete,  is  to  be  found  at  Kurrachee  (tig.  150).  The  dimensions  of  th« 
blocks  were  12  feet  by  8  feet  by  i^  feet,  and  their  weight  27  tons  each. 
Lifting  and  setting  were  performed  entirely  by  land  carriage  with  the  aid 
of  a  Titan,  which  travelled  over  the  sections  of  work  already  executed  and 
deposited  the  blacks  in  front  of  it.  The  depth  of  the  foundation  bed  was  15 
feet  below  the  surface  level  of  the  water,  and  the  blocks  were  laid  in  three 
horizontal  tiers  or  courses  to  a  total  height  of  24  feet  6  inches.  The  blocks 
were  not  set  vertically,  but  with  a  slight  backward  ittcllDation  as  shown  in 
fig.  150.  The  sea  bottom  was  sandy  at  a  depth  of  25  to  30  feet,  and  was 
surmounted  with  a  rubble  foundation,  levelled  by  divers,  and  upon  which 
the  blocks  were  laid. 


Fig.  148.  Fig.  149.  Fig.  150.— Block  work  at  Kurrachee. 

A  similar  method  wai  adopted  for  building  the  quay  walla  at  Suez.  The 
blocktt,  which  were  about  the  same  size  as  those  at  Kurrachee,  were 
conveyed  to  their  destination  in  barges. 

Other  examples  may  be  quoted  from  ports  iu  the  Mediterranean,  at 
Marseilles  and  elsewhere.  The  French  were,  in  fact,  the  pioneers  of  the 
system,  when  they  inaugurated  it  at  Algiers  as  far  back  as  the  year  1840. 
It  is  still  being  practised  for  harbour  work  in  Algeria  at  the  present  time, 
and  the  following  particulars,  furnished  by  the  courtesy  of  the  Engineer  in 
charge,  M.  Georges  Boisnier,  relate  to  a  quay  wall  at  the  port  of  Bougie, 
now  under  construction  (see  fig.  151). 

The  sea  bottom  is  mud  to  a  considerable  depth,  and  in  order  to  obtain  a 
sufficiently  broad  area  for  the  pressure,  a  foundation  of  rubble  stone,  llj 
feet  in  depth,  is  deposited  within  a  trench  dredged  to  a  bottom  width  of  55 
feet.  The  wall  consists  of  five  tiers  of  masonry  blocks  of  varying  size,  only 
one  of  which  is  above  the  surface  of  the  water.  The  blocks  are  constructed 
on  a  neighbouring  quay  with  limestone  from  a  local  quarry.     Those  in  the 


212  DOCK  ENCraEERING. 

two  lowermost  tiers  weigh  about  39  tona  each,  the  upper  tiers  average 
5  tons  less.      An  interval  of  from  three  to  four  mouths  is  allowed  to  elapse 
Nj  between  making  and  using, 

S  when  the  mortar  is  com- 

posed of  hydraulic  lime, 
bub  only  three  weeks, 
when  of  cement.  The 
blocks  are  set  by  a  float- 
ing crane  with  the  assist- 
ance of  a  diver.  VVhen  the 
four  submerged  courses 
have  been  constructed,  the 
\  wall  ia  weighted    with    a 

temporary  surcharge  of 
two  tiers  of  blocks,  which 
i  causes  the  structure  to 
W  settle  bodily  to  tlie  extent 
*  of  about  3J  feet  in  a 
*  (lei'iod  of  two  months,  at 
3  the  end  of  which  time  the 
!»  rate  of  settlement  is  found 
Q  to  be  insignificant,  the  Bur- 
's charge  is  removed  and  a, 
S  coping  course  substituted. 
S  The  hacking  behind  the 
I  wall  is  of  rubble  with  a 
3  covering  layer,  3  feet  thick, 
(jj    of    quarry    spalls,    above 


f-     whi 


discharged     the 
the 


mud    dredgec 
^'  foundations. 

The  cost  of  this  type  of 
wall  works  out  to  rather 
more   than  £14   per  foot 
run,    made    up,    approxi- 
mately, as  follows  : — 
Dredging  Bite,     .£110 
Rubble  filling,     .       4  15    0 
Artificial  blocks,        6    3    0 
Suroharge,  0    9    0 

Coping,      .  0  11     0 

General,    .  ISO 

Experience  has  shown  inadequate  stability  in  a  portion  of  the  wall,  as 
constructed  above,  and  several  important  modifications  are  being  introduced 
into  another  section  of  tlie  same  undertaking.     The  dredged  mud  is  no 


FAILUHES. 


213 


longer  ased  for  any  part  of  the  bkcking,  its  place  being  takea  by  dry 
quarry  rubbish.  The  blocks  are  made  to  larger  dimenBioDB,  but,  in  order 
to  racilitate  setting  operations,  they  are  rendered  temporarily  lighter  than 
they  would  otherwise  bo  by  the  arrangement  of  voids  or  pockets  in  their 
interiors,  as  shown  by  the  plan  in  fig.  152.  The  lowermost  blocks  weigh 
some  50  tons  prior  to  the  filling  of  the  pockets  with  concrete,  an  operation 
which  is  performed  when  they  are  in  position.  The  former  face  batter  of 
I  in  10,  found  to  be  unsuitable  for  vessels  with  vertical  sides,  is  now  reduced 
to  1  in  20. 

'"'  The  profile  thus  adopted  may  bo  compared  with  that  of  a  quay  wall  at 
the  neighbouring  port  of  Sfax*  in  Tunis,  similarly  constructed,  hut  with  the 
face  receding  in  a  series  of  ofiaeta  as  shown  in  fig.  153, 


Fig.  152.  ■  Fig.  153.-Quay  Wall  at  Sfax. 

The  difficulty  caused  by  excessive  gettlement  in  walla  of  this  class  is 
well  illustrated  hy  the  case  of  a  wall  at  Smyrna,  where  no  less  than  six  or 
seven  tiers  of  blocks  bad  to  be  superimposed,  instead  of  four,  as  originally 
intended,  while  the  front  of  the  wall  had  to  be  supported  by  a  rubble  mound 
carried  up  to  within  7  feet  of  mean  sea-level. 

FaUuroB. 

Failures  of  dock  walls  are  by  no  means  scarce,  and  they  often  present 
interesting  and  instructive  features,  but,  in  nearly  every  case,  the  cause  can 
be  traced  to  a  bad  foundation.  Movement  to  a  greater  or  less  degree  is  to 
be  expected,  and  has  been  experienced  in  all  walls  founded  upon  any  other 
stratum  than  hard  rock.  It  is  stated  as  the  experience  of  Voisin  Bey,  the 
Engineer- in-Chief  of  the  Suez  Canal,  that  he  had  never  found  a  long  line  of 
quay  wall  which,  on  close  inspection,  proved  to  be  perfectly  straight  in  line 
and  free  from  indications  of  movement. 

*  Baron  de  Rochemont  on  "  Quelques  Forts  de  la  Meditemu^,"  IrU.  Nav.  Cong., 
Paris,  1900. 


DOCK  ENGINEERING. 


As  has  already  been 
IKiinted  out,  the  moat 
treacherous  of  all  strata, 
from  the  point  of  fouada- 
tiou  for  a  quay  wall,  is 
the  blue  clay.  Out  of 
many  instances,  wliicli 
might  be  cited  as  evi- 
dence of  its  dangerous 
nature,  tlie  following  ac- 
count of  the  sliding  for- 
ward of  a  wall  at  the 
])OTt  of  Altona  is  selected 
as  affording  an  interesting 
example  of  remedial  mea- 
sures adopted  with  perfect 
success : — * 

The  town  of  Altona  is 
g  situated  on  the  right  bank 
J  of  the  River  Elbe,  and  the 
^  level  of  the  ground  rises 
*  gradually  from  the  river 
I  bank  inland  to  a  heiglit 
I  of  105  feet.  The  town 
^  stauds  partly  upon  this 
"    slope  and  [lartly  npon  its 

The  uppermost stratnm 

of  the  site  (fig.  154)  con- 
sists of  very  Gne  sand, 
interspersed  with  numer- 
ous water  streaks.     Below 


this 


lai 


■yer 


of 


clay,  which  rises  to  the 
liills  at  an  angle  rather 
less  than  the  surface  in- 
clination. The  clay  is 
firm  when  not  saturated 
with  moisture.  It  is,  bow- 
ever,  soluble  in  water, 
and  becomes  a  smooth, 
soapy  body,  ofi'ering  no 
effective  resistance  to  slid- 
*MiH.  Proc.  Am.  Soc.  C.E., 


FAILURES.  2  1 5 

ing.  As  long  as  the  water  from  the  hills  can  percolate  freely  through 
the  sand  and  escape  there  is  no  danger,  but  when  the  outlet  is  blocked  the 
sand  becomes  sodden,  and  the  clay  acquires  a  slippery  surface  conducive  to 
landslip. 

The  quay  wall  consists  of  a  solid  face  of  three  thicknesses,  4^,  6,  and 
9  feet  respectively,  formed  by  offsets  at  5^  and  9^  feet  above  the  base.  It 
is  backed  by  a  series  of  counterforts,  arranged  at  intervals  of  about  30  feet, 
and  well  bonded  into  the  wall.  The  spaces  between  the  counterforts  are 
spanned  by  two  tiers  of  arches,  the  lower  of  which  sustains  the  sand  filling 
behind  the  wall,  and  the  upper  forms  a  foundation  for  the  line  of  steam 
cranes  which  serve  the  quay  front.  The  materials  of  which  the  wall  is 
constructed  are  hard  bricks  and  cement  mortar,  the  latter  in  the  propor- 
tion of  1  of  cement  to  4  of  sand. 

The  wall  rests  upon  a  level  base,  formed  by  a  strong  honzontal  mortised 
framing  of  longitudinal  and  transverse  timbers,  covered  with  planking  and 
supported  by  vertical  and  oblique  bearing  piles.  A  row  of  tongued  and 
grooved  sheet  piling  is  driven  to  retain  the  bank  of  earth  below  the  platform 
level.  A  corrugated  iron  shed,  founded  upon  a  distinct  system  of  piling, 
stands  a  little  distance  back  from  the  face  of  the  quay. 

In  August,  1890,  shortly  after  the  completion  of  the  work,  cracks  were 
observed  in  the  wall  and  in  the  brick  gables  of  the  shed,  and  it  was  found 
that  both  the  quay  and  the  shed  had  perceptibly  shifted  their  positions. 
The  backing  at  the  rear  of  the  wall  was  removed  forthwith,  in  order  to 
lighten  the  pressure.  Very  shortly  afterwards  the  movement  of  the  shed 
was  found  to  have  been  arrested,  evidently  by  the  resistaace  of  its  founda- 
tion piles  on  the  landward  side,  which  had  been  driven  well  into  the 
lower  clay. 

Meanwhile,  the  quay  wall  continued  a  slow  but  uniform  movement 
outwards ;  so  gradual  and  minute,  however,  as  to  permit  a  series  of 
observations  to  be  taken  systematically,  from  which  the  source  of  the 
mischief  was  accurately  traced,  and  the  means  devised  for  remedying  it. 
It  was  found  that  the  whole  stratum  of  earth  above  the  clay,  extending 
as  far  as  the  hill  top,  was  sliding  bodily  forward  towards  the  Elbe,  and, 
as  the  lower  ends  of  the  quay  piles  were  bedded  in  the  clay,  the  upper 
masonry  was  turning  about  the  feet  of  the  piles  as  about  a  pivot. 

In  order  to  check  this  movement,  and  restore  the  stability  of  the  wall, 
a  series  of  29  iron  stays,  placed  about  lo  feet  apart,  were  secured  to  the 
upper  face  of  the  quay  piles,  and  led  to  anchorages,  some  164  feet  back, 
sunk  well  below  the  surface.  These  stays  consisted  of  links  about  16  feet 
long  and  10  square  inches  sectional  area,  alternately  of  round  and  bar 
iron,  the  latter  being  double  and  attached  to  the  rods  by  bolts  passing 
through  their  ends.  At  the  quay  face  the  extremity  of  the  stay  was 
made  fast  to  a  heavy  iron  plate,  bearing  against  horizontal  beams  below 
the  surface  of  the  water,  which  transmitted  the  pressure  evenly  to  the 
foundation  piles.     The  anchorage  on  the  landward  side  (figs.  155  and  156) 


2l6 


DOCK  ENGINEERING. 


consisted  of  a  stout  shield  of  nearly  70  feet  surface,  made  of  strong  logs, 
abutting  against  a  smooth  vertical  face  in  the  clay. 

As  a  further  precaution,  the  soil  behind  the  quay  was  excavated  to 
below  low-water  level,  and  the  void  filled  with  broken  brick,  which  gave 
a  backing  of  a  lighter  character,  while,  at  the  same  time,  it  resulted  in 
more  efficient  drainage.  The  arches  between  the  counterforts  having  been 
destroyed  by  unequal  settlement,  a  light  concrete  wall  was  formed  behind 
them,  to  take  the  surface  pressure  and  transmit  it  to  the  bearing  piles  at 
the  base  of  the  wall.  The  quay  line  of  rails  is  now  carried  on  iron  joists 
6  feet  apart,  bedded  in  concrete,  and  spanning  the  space  intervening 
between  the  two  walls. 

The  work  took  eighteen  months  to  carry  out,  cost  about  £30  per  lineal 
foot,  and  has  proved  satisfactory,  in  every  way,  since  the  quays  were  re- 
opened to  full  traffic  in  1892. 


lAl  _i_ 

==rzi^^;-i_i_i_ 

Elevation  of 
Anchorage. 


Vertical  Section 
of  Anchorage. 


0  n  3  i  5 


10  Feet 
Figs.  155  and  156. 

In  the  instance  above  recorded,  the  landslip  occurred  above  the  clay. 
The  South- West  India  Dock,  London,  built  in  1868,  furnishes  an  example 
of  a  slip  within  the  clay.  Some  portions  of  the  dock  wall  were  founded 
upon  a  hard  bed  of  natural  concrete,  composed  of  gravel  and  shells,  resting 
upon  a  layer  of  London  clay.  When  the  wall  came  to  be  backed  up,  it  slid 
forward.  In  the  course  of  excavation,  for  the  purpose  of  rebuilding  the  wall 
from  a  deeper  foundation,  two  disconnected  surfaces  of  clay  were  found, 
one  having  slipped  on  the  top  of  the  other,  showing  that  the  slip  had 
actually  taken  place  some  distance  below  the  bottom  of  the  wall  itself.* 

Another  well-known  instance  of  sliding,  due  to  the  same  kind  of  founda- 
tion, is  that  of  the  walls  of  the  Empress  Dock,  at  Southampton,  built  in 
1888.  A  section  is  given,  in  fig.  157,  showing  the  position  taken  up  by  the 
east  wall  of  the  dock  after  movement.  It  will  be  noticed  that  the  earth  in 
front  of  the  toe  has  been  heaped  up  above  its  original  level.  The  buttress 
shown  in  the  figure  is  one  of  a  series,  each  20  feet  long,  15  feet  wide,  and 
12  feet  deep,  set  at  about  30  feet  apart,  with  the  intention  of  strengthening 
the  wall  after  a  previous  experience  of  its  weakness.! 

The  walls  of  the  Kidderpur  Dock,  at  Calcutta,  have  already  been  men- 
tioned (p.  182,  ante)  and  a  section  given.     In  one  case  there  was  a  central 

*  Min,  Proc,  In«t.  CE,^  vol.  cxxi.,  p.  120.  \  Ibid.t  p.  127. 


FAILURES. 


217 


forward  projection  of  7  feet  5^  inches  in  a  length  of  2,080  feet;  an  adjoining 
wall  was  thrust  forward  no  less  than  13  feet -in  a  length  of  only  450  feet. 
In  neither  case  was  the  deviation  from  the  vertical  of  any  consequence, 
apparently  demonstrating  that  the  slip  of  the  backing  extended  to  a  greater 
depth  than  the  foundation  of  the  wall.''^  Immediately  upon  the  occurrence 
of  the  slip,  which  took  place  during  the  process  of  backing  the  wall,  the 
water  was  admitted  to  the  dock,  and  no  further  movement  has  since 
been  manifested.  The  author  is  personally  aware  of  another  case  where 
the  hydrostatic  pressure  in  front  of  a  dock  wall  constitutes  its  principal 
element  of  stability.  Built,  in  the  first  place,  with  a  view  to  merely 
temporary  uses,  the  wall  was  allowed  to  remain  in  conjunction  with  work 


SoaZey  Zc^ti^  1^ 


Fig.  157. — Dock  Wall  at  Southampton. 

of  a  more  durable  and  solid  character.  An  experimental  lowering  of  the 
water  in  the  dock,  on  a  recent  occasion,  had  to  be  abandoned  owing  to 
serious  signs  of  failure  showing  themselves  in  the  form  of  cracks  and 
fissures  behind  the  wall. 

Another  instance  of  failure,  but  of  a  different  kind  and  somewhat 
puzzling  as  to  its  origin,  is  that  exhibited  in  fig.  158,  part  of  which  repre- 
sents the  section  of  an  old  wall  at  the  Huskisson  Dock,  Liverpool.  Some 
years  ago  when  the  wall  came  to  be  examined  it  was  found  that  a  portion 
of  the  front  masonry,  at  a  depth  of  15  feet  below  the  surface  level  of  the 
water,  had  by  some  means  been  displaced,  had  fallen  out  and  was  then  lying 
in  the  dock  bottom.  The  length  affected  was  about  400  lineal  feet,  the 
disturbance  varying  from  a  crack  to  the  maximum  gap  exhibited  in  the 

*  Min,  Proc,  hist,^  C.E,,  p.  104  et  seq. 


2  1 8  DOCK  ENGINEERING. 

figure.  The  strange  thing  was  that  the  wall  showed  no  signs  of  collapsing 
altogethei-.  The  cause  of  the  mischief  is  still  obscure.  An  examination 
of  the  stability  of  the  section  by  theoretical  principles  revealed  no  weak- 
ness. Apjiarently  had  there  been  eKcessire  aompression  on  the  face,  the 
upper  part  of  the  wall,  deprived  of  its  support,  should  have  collapsed,  but 
this  is  what  did  not  happea.  The  wall  was  repaired  by  a  refacing  of 
concrete,  3  feet  thick,  and  as  an  improvement  of  the  dock  was  in  contempla- 
tion at  the  same  time,  advantage  was  taken  of  the  opportunity  to  deepen 
the  foundations  of  the  wall  by  an  operation  about  to  be  describt>d. 


Fig.  158. — Dock  Wall  at  Liverpool.  Pig.  159. — UnderpiDning  at  Ardrosavi. 

Usderp inning. — Occasionally  an  engineer  has  to  face  the  problem,  not  of 
constructing  a  new  wall,  but  of  adapting  an  old  one  to  conditions  far 
other  than  those  contemplated  at  the  time  of  its  construction.  A  common 
instance  ia  that  in  which  it  is  requisite  to  deepen  an  existing  dock  in 
order  to  accommodate  vessels  with  greater  draught.  This  necessitates  a 
corresponding  lowering  of  the  quay  wall  and  its  foundations,  a  process 
called  underbuilding  or  underpinning. 

When  the  work  can  be  carried  out  in  the  open — that  is,  with  the  dock 
run  dry — it  is  attended  by  no  more  than  the  usual  difficulties,  though  much, 
of  course,  depends  on  the  nature  of  the  strata  to  be  undercut.  More  arduous 
and  less  secure  is  the  operation  when  it  has  to  be  performed  with  the  dock 
under  normal  conditions. 

Fig.  159  is  a  section  of  a  quay  wall  of  Eglintoii  Dock,  Ardrossan,  to 
which  the  following  extract  refers  : —  * 

•Robertsou  on  "  Ardroasan  Harbour  Extenfliona,"  Jtfin.  Proc.  IjuI.  C.E.,  voL  cxi. 


UNDERPINNING.  219 

"The  portions  of  the  north  and  soutli  walls  of  the  old  tidal  harbour, 
extending  along  the  side  of  the  new  dock,  were  retained,  but  having  been 
founded  on  clay  they  were  underbuilt  to  the  rock  with  rubble  concrete,  to 
a  depth  varying  between  2  feet  and  20  feet.  The  clay  below  the  walla  was 
excavated  back  5  feet  from  the  face  of  the  wall,  and  the  front  of  the  wall 
was  supported  from  the  rock  by  raking  shores.  The  rubble  concrete  under- 
building has  a  unilorm  thickness  of  5  feet,  where  the  depth  is  less  than  10 
feet,  but  for  greater  depths  the  underbuilding  is  6  feet  thick  at  the  top, 
increasing  downwards  with  the  batter  of  the  wall.  The  excavation  was 
taken  out  in  alternate  lengths  of  about  10  feet,  and  the  clay  left  between 
until  the  blocks  on  each  side  were  thoroughly  set  j  then  the  intermediate 


Jtvci 

Fig.  160,— Underpinning  at  Liverpool. 

spaces  were  excavated  and  built  up.  The  rubble  concrete  was  built  in  layers 
of  about  18  inches  or  2  feet,  until  too  close  to  the  underside  of  the  old 
walls  for  men  to  go  in  below  ;  it  was  then  built  from  the  front  and  the  con- 
crete carefully  rammed  into  the  back.  When  the  concrete  was  within  1 
inch  or  2  inches  of  the  underside  of  the  wall,  an  additional  board,  bevelled 
outwards,  was  put  in  the  front  of  the  frame ;  liquid  grout  of  cement  and 
sand  was  poured  in,  filling  up  the  small  space  between  the  concrete  and  the 
wall.  This  proved  most  satisfactory,  as  shown  by  au  examination  of  the 
side  of  each  block  on  excavating  the  intermediate  space.  No  trouble  was 
experienced  in  supporting  the  walls,  and  no  settlement  took  place  during 
the  underbuilding." 

Equally  satisfactory,  though  attended  by  more  risk,  has  been  the  result 


220  DOCK  ENGINEERrao. 

of  underpinning  operations  as  carried  out  at  certain    of  the    Liverfiool 
-docks.      Owing  to   the  exigencies  of  traflio  the  work  bftd  to  be  done  in 
sections,  with  the  dock  full  of  water,  so  as  to  interfere  as  little  aa  possible, 
with  shipping  occommodalion.     Fig.  160  shows  a  section  of  the  old  wall,  at 
the  commencement  of  the  underpinning,  and  fig.  161  is  a  section  of  the 
completed  undertaking.     It  will  be  observed  that  the  work  was  carried  on 
under  cover  of  a  sheeting  dam,  described  elsewhere  (p.  105,  ante),  strutted  and 
shored  to  the  old  wall,  at  b  distance  of  about  17  feet.     Below  the  level  of 
the  dock  bottom,  an  inner  trench  was  excavated  between  two  rows  of  sheet- 
ing piles,  one  of  wliich  was  situated  at  the  extreme  back  of  the  wall  and  the 
other  in  front  of  it.     Within  these  limits  the  underpinning  was  effected  on 
similar  lines  to  the  underbuilding  at  Ardrosaan.    The  ba^s  were  from  10  to 
15  feet  in  length  and  were  dealt  with  singly,  the  work  being  attacked  at 
several  points  simultaneously.     The  new  work  consisted  entirely  of  6  to  1 
concrete,   carefully  tongued    into   tbe 
old  masonry,  the  surface  of  which  was 
well  washed  und  picked  rough.    When 
the  concrete    had   been    deposited  to 
within  3  feet  of  the  onderside  of  the 
existing    base,    the    remaining    layer 
was  pub  in,  in  three  sections,  advanc- 
ing from  the  back  towards  the  front, 
V)ehiDd  roughly  coostriicted  barriers  of 
rubble,  the  concrete    lieing  carefully 
rammed  tight  and  the  whole  grouted. 
Miscellaneons  Types  of  Wall.— It 
will  be  as  well  to  conclude  the  chapter 
with  some  miscellaneous  examples  of 
the  very  varied  range  of  types  to  be 
found  among  dock  walls.     Figs.  162 
to    164  are  plan  and  sections  of  the 
Fig.  161.-Dock  Wall  aa  Underpinned.        A'*«'"''  ^'"^^  **"  *'  Hull,*  or,  rather, 
ihe  wall    as  originally  designed    and 
only  executed  for  a  part  of  its  length,  owing  to  modifications  introduced  as 
the  work  proceeded.     This  type  of  wall  with  an  arched  front  is  unusual, 
and  it  has  obvioos  inconveniences,  though  as  regards  its  structural  qualities, 
a  broad  base  with  a  minimum  of  masonry  was  held  to  counterbalance  these 
drawbacks  on  ft  foundation  which  wss  incapable  of  sustaining  much  pressure. 
A  similar  type  of  wall,  consisting  of  alternate  piers  and  arches,  is  to  be  found 
at  Bordeaux. 

The  sections  (figs.  165  and  166)  of  two  dock  walls  at  Greenock  are  self- 
explanatory  and  do  not  call  for  any  remarks,  except  that  it  may  I>e  well 
to  add    that  the  quarry  refuse    filling  behind  the  western  tidal  harbour 

•Hawkshawon  "The  Albert  Dock,  Hull,"  J/in.  Proc.  hi»t.  O.E.,  voU  xli. 


DOCK  WALL  AT  HULL. 

wall  waa  washed  in  with  Portland  cement  in  the  proportion  of  1  t 
high  as  low-water  level.* 


I     WALL     SECTIO 


I.  162,  163,  and  164.— Dock  WaU  at  Hull. 


Fig.  167  is  a  section  of  the  Alexandra  Dock  wall  at  Hull.     Originally- 
designed  to  bo  constructed  with  an  ashlar  atone  face  and  rubble  chalk  back- 

•  Kiaipple  on  "Greonocli  Harbour,"  Min.  Proc,  Intl.  CE.,  vol.  cxxx. 


DOCK  ENGINEERING. 


Figs.  165  and  166.—Dock  Walls  at  Greenock. 


Fig.  167.  -Dock  Wall  at  HiilL  Fig.  168.— Quay  WaU  at  Tilbury. 


DOCK  WALI^  AT  LIVERPOOL  AND  MANCHESTER.  223 

ing  up  to  14  feet  below  coping,  tt  strike  of  maaona  led  to  the  subatitntion 
of  Portland  cement  concrete.  The  upper  part  of  the  wall,  14  feet  in 
height,  was  built  as  designed  with  ashlar  facing,  projecting  0  inches  to 
form  a  fender,  and  with  granite  coping.  The  weep-holes  are  at  75  feet 
interval  a.* 

The  section  of  the  tidal  basin  wall  at  Tilbury  Docka,  London,  is  given 
in  eg.  168.  The  material  used  for  the  bulk  of  the  wnll  was  concrete, 
composed  of  10  parts  of  ballast  to  1  of  Portland  cement.  The  concrete  work 
was  faced  above  low-water  mark  with  blue  bricks,  having  a  stock  brick 
backing^the  whole  being  9  inches  in  thickness,  with  half  brick  piers,  about 
4  feet  apart,  dovetailing  into  the  concrete.f 

The  latest  type  of  Liverpool  wall  (fig.  169)  is  built  entirely  of  concrete, 


Mum      iiidit1»Hftailtms;-lX'^ 


Reek  FHundation  Oty 

Fig.  169.— Dock  Wall  at  LiverpooL  Fig.  170.— Dock  Wall  at  Manchester. 

with  the  exception  of  a  granite  coping.  The  hearting  is  composed  of  8  parta 
of  gravel  to  1  of  Portland  cement,  with  as  many  burra  or  plums  of  clean 
rubble  and  old  masonry  as  can  conveniently  be  bedded  in.  The  facing, 
13  inches  thick,  iaof  6  to  1  concrete  without  burrs. 

The  new  wall  for  the  extension  of  the  Manchester  Docka  is  also  mainly 
composed  of  concrete  (fig.  170).  It  haa  a  blue  brick  facing  above  water 
level,  surmounting  a  limestone  fender  course.     The  coping  is  of  granite. 

*Hurtzigon  "  The  Alexandra  Dock,  Hall,"  Jfin.  Proe.  Inst.  O.E.,  voL  »cii. 
t  Scott  on  "The  Tilbury  Docks,  London,"  Jfin.  Proc.  Inst.  G.E.,  voL  ox«. 


2  24  JyOCK  ENGINEERING. 

REFERENCE  WORKS. 

The  following  are  a  few  of  the  sources  from  which  the  student  may  obtain  additional 
information  on  the  vexed  question  of  earth  pressure  against  retaining  walls  : — 

**  The  Actual  Lateral  Pressure  of  Earthwork."  By  Sir  B.  Baker.  Min»  Proc,  Inst, 
C,E.,  vol.  Ixv.,  p.  140. 

«*  The  Slopesof  Cuttings."    By  Wilfrid  Airy.     Min.  Proc,  Inst.  C,E.,  vol.  Iv.,  p.  241. 

*  *  Theory  of  the  Stability  and  Pressure  of  Loose  Elarth,"  in  A  Manual  of  Civil  Engineer- 
ing,    By  Professor  J.  W.  M.  Rankine.     18th  edition,  p.  318. 

^'Essai  th^oretique  sur  I'^uilibre  des  massifs  pulv^rulents,  compart  ^  celui  des 
massifs  solides ;  et  sur  la  pouss^  des  terres  sans  coh^ion."  By  Professor  J.  Boussinesq. 
Abstract  in  Min.  Proc.  Inst,  G,E,,  vol.  li.,  p.  277. 

**  Earth  Pressures  on  Retaining  Walls."  By  G.  C.  Maconchy.  Article  in  Engineer- 
ing, vol.  Ixvi.,  p.  256. 

«*  Dock  Walls."    By  J.  R.  Allen. 

**  Some  Experiments  on  Conjugate  Pressures  in  Fine  Sand."  By  G.  Wilson.  Min, 
Proc.  Inst.  C.E.y  vol.  cxlix. 


225 


CHAPTER  VI. 

ENTBANCE8,   PASSAGES,    AND   LOCKS. 

Gbniral  Aspbcts  of  the  Subject— Site— Effect  of  Wind,  Wave,  akd  Current — 
Direction — Size— Draught  of  Water  in  Approach  Channel — Arrangement 
AND  Types — Simple  Entrances,  Locks,  and  Half-tide  Basins — Maintenance  of 
Fairway— Sluicing— Velocity  of  Efflux — Friction  of  Culverts— Coefficients 
of  Discharge  —  Sluicing  Arrangements  at  Liverpool,  Ostend,  Honfleur, 
Ramsgate,  Dovkr,  and  Dublin — Scraping  and  Scuttling— Dredging — Lock 
Foundations  —  Boils  and  Springs  —  Instances  at  Hull  and  Liverpool  — 
Suggestions  for  Treatment— Grouting  — Stock-ramming — Sand  Concrete — 
Lock  Construction  —  Sills  —  Platforms  —  Recesses  —  Walls  —  Culverts  — 
Penstocks  or  Cloughs  —  Stonky  Sluices  —  Pan  Gates  —  Pivotted  Gates  — 
Duration  of  Levelling  Operations  —  Examples  of  Dock  Entrances  at 
Liverpool,  Dunkirk,  Buenos  Ayres,  Kiddbrpur,  Eastham,  Barry,  Ardrossan^ 
Hull,  and  Brkmerhavbn. 

General  Aspects  of  the  Subject. — The  subject  of  dock  entrances  is  one 

demanding  the  most  careful  attention,  seeing  that  the  utility  and  value  of 

an  entire  dock  system  depend  to  a  very  large  extent,  if  not  mainly,  upon 

the  safety  and  accessibility  of  its  entrances. 

If  the  docking  and  undocking  of  ships  could  be  carried  on  invariably  in 

calm  weather,  and  with  smooth  water,  many  of  the  most  acute  difficulties 

of  the  problem  would  at  once  disappear.     But  ships  have  to  be  docked  in 

foul  weather  as  well  as  fair,  and,  apart  altogether  from  the  desirability  of 

their  obtaining  shelter  at  the  earliest  possible  moment  from  rough  winds 

and  tempestuous  seas,  there  is  the  more  cogent  reason  that  the  exigencies 

of  modern  commerce  will  not  allow  of  a  ship  missing  her  berth  in  dock  by 

one  hour  more  than  is  absolutely  necessary  for  her  actual  voyage ;  neither 

will  they  admit  of  her  failing  to  leave  her  berth  at  the  specified  time. 

Every  hour  of  extra  detention  in  port  represents  to  her  owners  a  large  sum 

in  wages,  maintenance  and  interest,  unprofitably  expended.     Consequently, 

it  becomes  a  qualification  of  the  highest  importance  for  a  dock  entrance  to 

be  available  at  all  times  and  under  all  conditions.     It  must  certainly  be 

admitted  that,  as  yet,  many  commercial  seaports  are  unable  to  comply  with 

this  requirement,  owing  to  obstacles  arising  from  natural  causes,  such  as  an 

extreme  range  of  tide,  a  shallow  bar,  strong  currents,  and  sudden  floods. 

But  it  is  increasingly  evident  that  the  qualification  will  ultimately  become 

the  sine  qud  non  of  a  flourishing  port.     At  the  present  time  extensive 

operations  are  in  progress  at  various  places,  notably  at  Liverpool,  with  the 

object  of  increasing  the  period  of  accessibility  and  eventually  of  transform- 

16 


2  26  DOCK   ENGINEERING. 

ing  an  intern) ittent  into  a  continuous  service.  In  the  dredging  of  bars,  f  he 
lowering  of  dock  sills  and  floors,  two  of  the  main  obstacles  to  the  ideal 
condition  can  be  artificially  overcome,  and  the  problem  then  simfily  resolves 
itself  into  a  question  of  fixing  a  judicious  limit  to  the  expenditure  incurred, 
80  as  to  achieve  the  most  beneficial  result  commensurate  with  the  port's 
resources  and  prospects. 

Docks  in  tideless  seas,  as  the  Mediterranean  ;*  in  inland  situations,  as  at 
Eouen  and  Bremen  ;  and  in  localities  where  there  is  only  a  small  range  of 
tide,  as  is  the  case  at  Glasgow  and  Southampton,  are  endowed  by  Nature 
with  signal  advantages  in  this  respect,  which  enable  them  to  dispense  with 
all  the  costly  apparatus  necessary  for  periodically  closing  their  entrances, 
together  with  all  the  time  and  labour  involved  in  the  operation,  while,  at 
the  same  time,  it  confers  upon  them  special  facilities  for  the  prompt 
reception  and  discharge  of  shipping.  On  the  other  hand,  such  docks 
reproduce  every  fluctuation  of  the  external  water  level,  and  from  the  very 
continuity  of  their  systems,  their  entrances  are  liable  to  constitute  quiescent 
depositing  areas  for  silt  and  detritus,  brought  in  by  passing  cuiTents.  This 
last  drawback,  however,  is  one  from  which  tidal  ports  themselves  are  not 
altogether  exempt. 

In  determining  the  dispositions  to  be  adopted  for  a  dock  entrance,  the 
following  points  have  primary  importance,  viz. :  — (1)  Site;  (2)  direction ; 
and  (3)  size. 

Site. — The  site  should  obviously  be  the  most  sheltered  spot  available 
for  the  purpose.  Exposure  during  docking  operations  to  the  direct  influ- 
ence of  even  a  moderate  gale  may  render  a  vessel  temporarily  unmanage- 
able, and  cause  her  to  drift  into  situations  dangerous  alike  to  herself  and 
to  neighbouring  craft.  The  writer  has  seen  several  lineal  yards  of  granite 
coping  at  a  dock  entrance  detruded  by  the  stem  of  a  vessel,  under  no  way, 
but  imperfectly  controlled,  while  docking  in  a  heavy  swell.  The  strain 
upon  entrance  gates  at  such  times  is  likewise  exceedingly  great,  especially 
immediately  after  they  have  been  closed.  Until  suflicient  head  is  acquired 
on  the  inner  side,  by  the  fall  of  the  tide,  to  keep  them  fairly  mitred,  the 
leaves  are  undergoing  a  series  of  chafings  and  concussions  against  one 
Another  and  the  sill,  and  even  when  actual  movement  in  them  has  ceased, 
they  are  still  dynamically  stressed  by  the  impact  of  breaking  waves. 

For  this  reason  direct  communication — and  by  this  is  meant  communi- 
cation in  an  uninterruptedly  straight  line — with  the  open  sea  is  to  be 
avoided,  wherever  practicable.  In  the  case  of  ports  on  the  seaboard, 
outer  harbours  or  entrance  channels  should  be  provided  of  length,  at 
least,  sufficient  to  admit  of  a  vessel  losing  the  way  which  she  may 
have  gathered  in  making  for  her  destination  under  stress  of  weather. 
The  length  of  sheltered  reach  necessary  for  this  purpose  will  vary  with 
particular  circumstances,   but  the  following   instances   may  be   cited  as 

*  The  Mediterranean  is  not  strictly  tideless,  but  the  range  of  tide  is  so  small  as  to 
be  negligible. 


WIND. 


227 


generally  representative  of  practice  in  this  respect : — Barry  has  an 
-entrance  channel,  between  breakwaters,  470  yards  long.  At  Leith,  a 
similar  channel  extends  to  660  yards.  Sunderland  has  an  enclosed  outer 
harbour  affording  a  run  of  900  yards.  At  Dover  the  present  protected 
length  is  750  yards,  but  when  the  new  works,  now  in  progress,  are  com- 
pleted there  will  be  a  sheltered  reach  of  at  least  1,100  lineal  yards  within 
the  breakwaters. 

The  objections  attending  a  sea-exposed  entrance  are,  of  course,  equally 
potent  in  the  case  of  ports  situated  on  broad  river  estuaries,  flanked  by 
low-lying  country.  Though  the  river  mouth  may  be,  to  a  certain  extent, 
•considered  as  supplying  the  functions  of  an  entrance  channel,  yet  it  is 
often  found  expedient  to  provide  a  vestibule  to  the  docks,  in  the  form 
of  a  tidal  basin,  having  free  communication  with  the  river.  This  is  the 
plan  adopted  at  the  Liverpool  and  Birkenhead  Docks,  the  Tilbury  Docks 
■at  London,  the  Boyal  Dock  at  Grimsby,  and  others.  The  Canada  Basin 
at  Liverpool  has  an  entrance  width  of  390  feet  and  a  water  area  of 
9^  acres.  The  North  Basin  at  Birkenhead  has  an  entrance  width  of 
^00  feet  and  a  water  area  of  4^  acres,  while  at  the  Tilbury  Basin  the 
entrance  is  364  feet  wide  and  the  water  area  17}  acres. 

In  wide  estuaries  sheltered  by  ranges  of  hills,  and  narrow  estuaries 
generally,  in  land-locked  bays  and  lagunes,  and  on  inland  rivers,  the  fore- 
going precautions  are  rendered  unnecessary,  except  for  other  and  purely 
local  reasons. 

The  three  natural  agencies  influencing  the  eligibility,  or  otherwise,  of 
a  site  for  a  dock  entrance  are  (a)  wind,  (b)  wave,  and  (c)  current.  It  will 
be  well  to  subject  them  to  a  brief  consideration. 

For  the  purpose  of  the  present  section  we  need  not  investigate  the 
•effect  of  these  natural  forces  except  in  so  far  as  they  favour  or  interfere 
with  the  effective  use  of  entrances,  and  the  manipulation  of  vessels.  Any 
inquiry  in  regard  to  their  action  upon  permanent  structures  will  be 
deferred  until  we  come  to  the  chapter  dealing  with  the  parts  most 
affected — viz.,  jetties,  wharfs,  and  piers. 

Wind. — The  power  exerted  by  the  wind  is  often  sufficient  to  greatly  impede, 
if  not  absolutely  prevent,  the  manoeuvring  of  vessels  (more  particularly 
those  with  a  high  freeboard),  into  and  through  a  narrow,  exposed  water- 
way. The  effect  is  greatest  when  the  direction  of  the  wind  is  broadside 
on,  causing  the  vessel  to  fall  off  to  the  leeward.  A  head  wind  can  always 
be  counteracted  by  adequate  tractive  or  propelling  power ;  in  a  side  wind 
this  is  of  no  avail,  and  the  vessel  has  to  be  kept  in  her  course  by  means  of 
ropes.  Occasionally  accidents  happen  through  the  breaking  of  these  ropes 
from  excessive  strain.  Cases  have  occurred  in  which  all  the  retaining 
ropes  to  a  vessel  have  snapped  in  quick  succession,  leaving  her  entirely 
helpless.  It  is  to  be  regretted  that,  at  the  present  time,  there  is  so  little 
reliable  evidence  in  regard  to  the  actual  pressure  exerted  on  large  surfaces 
by  air  in  motion.     Records  have,  indeed,  been  obtained  showing  very  great 


228 


DOCK  ENGINEERING. 


pressures,  but  the  area  affected  has  been  comparatively  trifling,  and  it  i» 
tolerably  certain  that  the  intensity  of  pressure  registered  by  a  small 
anemometer  can^  in  no  wise,  be  considered  representative  of  surfaces  of 
indefinite  extent.  Eminent  authorities  are  inclined  to  take  this  view, 
and  Sir  John  Wolfe  Barry,  in  his  Presidential  Address  to  the  Mechanical 
Section  of  the  British  Association  meeting,  in  1898,  pointed  out  that  of 
two  wind  gauges  of  300  and  1*5  square  feet  respectively,  at  the  Forth 
Bridge,  under  the  same  conditions  of  wind  and  exposure,  the  larger 
registered  a  pressure  of  38*7  per  cent,  less  per  square  foot  than  the 
smaller,  while  of  two  other  gauges  with  more  greatly  contrasted ,  areas, 
at  the  Tower  Bridge,  the  divergency  amounted  to  over  70  per  cent. 
Prior  to  the  Tay  Bridge  disaster,  in  1879,  the  recognised  maximum 
allowance  for  wind  pressure,  in  Great  Britain,  on  exposed  surfaces,  waa 
40  lbs.  per  square  foot.  Acting  under  the  influence  of  public  opiifion,, 
the  Board  of  Trade,  in  1880,  raised  the  safe  limit  to  56  lbs.,  at  which 
figure — an  undoubtedly  excessive  one — it  now  stands. 

The  following  table  shows  the  ratio  of  wind  pressure  to  velocity,  as 
originally  published  by  Smeaton  in  the  Philosophical  Transactions  of  1759, 
and  as  recently  modified  by  Mr.  W.  H.  Dines  after  a  long  and  exhaustive 
series  of  experiments.'"'  Taking  the  pressure,  P,  in  lbs.  per  square  foot^ 
and  the  velocity,  Y,  in  miles  per  hour,  Smeaton  and  Dines*  formulae  are — 

P  =  *00492  V^ 
and 

P  =  003  V2, 
respectively : — 


TABLE  XVIII. — Force  of  Wind  in  Lbs.  per  Square  Foot. 


Velocity  in  Miles  per  Hour. 

10 

20 

SO 

40 

60 

60 

17-7 
10-8 

70 

80 

90 

100 

110 

120 

Smeaton,    . 
Dines,    .     . 

•5 
•3 

20 
1-2 

4*4 
2-7 

7*9 

4*8 

12*3 
7-5 

241 
14-7 

31-5 
19*7 

39*8 
24*3 

49*2 
30*0 

59*3 
36-6 

70*8 
43-2 

The  connection,  however,  between  velocity  and  pressure  is  one  which 
cannot  be  exactly  determined  by  a  simple  coefficient,  and  all  such  expres- 
sions must  inevitably  give  results  more  or  less  erroneous,  except  within 
the  narrow  experimental  limits  upon  which  they  are  founded. 

To  obtain  immunity  for  an  entrance  from  gales  blowing  from  all  points 
of  the  compass  is,  of  course,  a  manifest  impossibility,  but  something  may  be 
done  towards  minimising  the  effect  of  the  more  noxious  winds.  Advantage 
should  be  taken  of  any  natural  features — headlands,  promontories,  and  the 
like— or  even  of  moderately   high  ground  in  order  to  secure  a  leeward 

♦  Vide  Engineer,  Nov.,  1897. 


WAVES.  229 

position.  Where  this  is  not  available,  artificial  shelter  may  be  created  in 
the  form  of  parapet  walls,  wind  screens,  and  buildings  generliUy.  Offices, 
huts,  and  sheds,  for  the  use  and  shelter  of  the  dock  master  and  his  staff,  may 
be  grouped  at  the  more  exposed  points  so  as  to  break  the  force  of  the 
wind. 

The  wind  which  blows  with  greatest  frequency  at  any  place  is  usually 
(termed  the  prevailing  wind,  but  it  does  not  by  any  means  follow  that  it  is 
the  wind  attended  by  the  most  disastrous  results.  More  harm  may  be  done 
by  a  single  gale  from  an  unusual  quarter  than  by  a  whole  twelvemonth  of 
the  prevailing  wind.  In  this,  as  in  all  other  matters,  it  is  necessary  to 
Jicquire  locally  the  fullest  information  possible. 

Waves. — The  action  of  waves,  apart  from  tidal  waves,  depends,  primarily, 
of  course,  upon  the  wind,  but,  once  agitated,  the  sea  maintains  a  momentum 
which  may,  and  usually  does,  outlast  the  duration  of  the  wind  itself  so  as  to 
•constitute  an  entirely  distinct  source  of  activity. 

The  inception  of  waves  being  due  to  the  wind,  their  development  will 
largely  depend  upon  the  amount  of  surface  acted  upon.  The  greater  the 
length  of  open  sea,  ceteribus  paribus,  the  higher  the  wave  which  breaks  upon 
the  shore,  provided  always  there  is  sufficient  depth  of  water  to  admit  of  its 
formation.  Intervening  shoals  will  break  up  a  wave,  so  that  the  effective 
length  of  sea  may  be  much  less  than  the  apparent  length. 

This  length,  or  distance  within  which  the  wave  attains  its  development, 
is  termed  the  fetch,  and  Stevenson  has  devised  an  empirical  formula  from 
which  the  probable  height  of  waves  may  be  estimated.  Taking  H  as  the 
height  of  the  wave  in  feet,  and  L  as  the  length  of  fetch  in  miles,  it  has  been 
ibund  that  approximately — 

H  =  1-5^F; (a) 

•or,  for  short  fetches,  less  than  30  miles, 

H=  1-5^F  +  (2-5- VF).  .  .     (/3) 

In  Table  xix.  are  one  or  two  examples  of  the  height  of  waves  as  deduced 
^y  the  formulae  and  as  determined  by  actual  observation. 

The  maximum  fetch  alone  cannot,  however,  be  considered  as  a  criterion 
•of  the  exposure  of  an  entrance.  The  severest  gales  may  not  blow  from  that 
particular  quarter  of  the  compass,  and,  on  the  other  hand,  heavy  rolling  seas 
may  be  deflected  so  as  to  bring  their  influence  to  bear  upon  an  apparently 
sheltered  area. 

In  exposed  situations  it  is  possible,  by  artificial  means,  to  cause  a  wave 
to  spend  its  force  before  reaching  the  spot  where  its  unchecked  onset  would 
be  dangerous.  Breakwaters,  either  in  the  form  of  parapet  walls  or  as  sub- 
merged mounds,  may  accordingly  be  employed  to  reduce  the  amount  of 
fetch  and  to  provide  areas  of  comparative  quiescence.  These  works,  how- 
>ever,  form  a  distinct  branch  of  harbour  engineering  which  cannot  be  entered 
•upon  here. 


230 


DOCK  ENGINEERING. 


TABLE   XIX. 


Calculated  Height. 

Place  of  Observation. 

Length  of  Fetch. 
Nautical  Miles. 

Observed  Height 
of  Waves,  in  Feet. 

* 

Formula. 

Formula. 

(•) 

03) 

Feet. 

Feet. 

Scalpa  Flow, 

1-0 

4-0 

1-5 

3-0 

Firth  of  Forth,      . 

1-3 

1-8 

18 

3-2 

Loush  Foyle,         .        • 
Clyde,   .... 

7-5 

4-0 

2-5 

3-75 

9  0 

4  0 

4-5 

5 -20 

Colon.say, 
Lough  Foyloj 

9  0 

5-0 

4-5 

5-25 

110 

5  0 

5-0 

5-7 

Anstruther,  . 

24  0 

6-5 

7-5 

7-7 

Lake  of  Geneva,    . 

30  0 

8-2 

8-2 

8  37 

Buckie, 

40  0 

8-0 

9-55 

•  •  • 

Douglas,  I.O.M.,  . 

65  0 

10-12 

12  0 

•  •  • 

lanffstown,   . 
Sunderland,  . 

114  0 

15-0 

16-0 

■  •  • 

165  0 

15  0 

19-3 

•  •  t 

Peterhead,     . 

400  0 

22-6 

30-0 

•  •  • 

TABLE   XX. 


Date.     I  Tide 


1902. 
Aug.  20,1  P.M. 

Sept.   2   A.M. 

„     16  A.M. 


ti 


ti 


17 


17 


8 

•^   . 

TS  J3 

£5 

Direction  of 

Wind. 

^K 

>»« 

■^  s 

"SiJ 

o;;: 

•3^ 

> 

N.W. 

IS 

s.w. 

23 

s.w. 

24 

A.M.     W.N.W. 


A.M. 


20 


W.N.W.  i    24 


W.S.W. 


Oct.  15|A.M. 

„  15 1  P.M.  S.W. 

„  16  A.M.  N.W. 

„  16   P.M.  N.W. 


15 
24 

21 

25 


9»a  CO 


H 

^ 


3h 


H 

3 
5 

4^ 

5i 


„     17  A.M. 

N.W. 

20 

H 

Dec.  18    P.M. 

W.N.W. 

32 

5i 

„     19  A.M. 

W.N.W. 

25 

5 

„     25    P.M. 
„     29   P.M. 
,,     30   A.M. 

W.S.W. 

W. 

N.W. 

20 
35 
20 

4i 
5S 
4' 

Largest  Vessel 
Docked  or 
Undocked. 


"Majestic." 


4) 


c        — 


I 


565 


"Teutonic."      565 


"Workman." 


>» 


450 


450 


26^ 
27^ 
18 

18 


"Majestic."      565   25^ 


■  •  •      >      •  ■  • 


"Turcoman.'    450:23^ 
I  None  of  im-  "l 
\   portance.   /      ••  ,  ••• 


portance 
"Saxonia." 


600124 


i  None  of  im-  \ 


\  portance. 


"Bavarian." 


600  26 


•  •  •  •  •  • 


■  •  •      1      •  •  • 


5ZJ 


5 


Remarks. 


I  Undocked 
j    without 
(    trouble. 

Do. 
i  Attempted 
!    to  undock, 
f    but  failed. 
.  Locked  out 
<    3  hours  be- 
(    foreH.W. 
LeftatH.W. 
20  minutes 
in  basin. 


{Three  small 
steamers. 
J  Docked  at 
t   H.W. 
/  Two  small 
\   steamers. 

{Undocked  at 
H.W. 


CURRENT.  2  3  I 

It  has  been  stated  that  2  feet  is  the  greatest  height  of  waves  oonsistent 
with  the  safe  working  of  dock  gates.*  The  writer's  experience  convinces  him 
that  this  estimate  is  too  low,  for  he  is  acquainted  with  instances  in  which 
the  gates  of  exposed  entrances  have  been  worked  without  difficulty  in 
waves  of  at  least  twice  that  height.  Furthermore,  vessels  have  safely 
weathered  the  pierhead  of  an  entrance  lock  with  a  rise  and  fall,  due  to 
surging,  of  7  or  8  feet  in  the  level  of  their  decks.  It  may  be  said  that  while 
no  definite  limit  can  be  fixed  as  the  point  at  which  the  working  of  an 
entrance  becomes  dangerous,  the  practicability,  or  otherwise,  of  docking 
operations  will  largely  depend  on  the  tug  and  capstan  power  available,  on 
the  strength  of  the  ropes  and  hawsers  employed,  and,  above  all,  on  the  skill 
and  capability  of  those  who  superintend  and  carry  out  the  necessary 
manoeuvres. 

For  the  record  (Table  xx.)  of  noteworthy  conditions  during  a  period 
of  four  months,  at  the  Canada  Basin  entrances,  Liverpool,  the  writer  is 
indebted  to  the  Dockmaster,  Captain  Parkes. 

Current, — In  contradistinction  to  the  intermittent  character  of  the 
previous  agencies,  the  third  is  continuous  and  cumulative  in  action.  To  the 
influence  of  the  littoral  current  is  due  the  maintenance  or  closing  of  the 
fairway  of  an  entrance.  Currents  arise  from  several  causes  and  their  work- 
ings are  often  complex  and  conflicting.  At  one  period  of  the  day  the  tidal 
current  will  predominate  in  a  river  and  cause  an  inward  flow,  at  another  it 
will  reverse  its  direction,  augmented  by  the  fluvial  current.  At  different 
stages  of  the  tide  there  will  be  zones  of  slack  water,  counter-currents,  and 
eddies.  It  is  no  uncommon  feature  for  the  tide  to  be  flowing  into  the 
mouth  of  an  estuary  at  one  side  while  it  is  ebbing  on  the  opposite  shore. 
The  course  of  a  river  is  never  straight,  and  the  current  is  greater  at  the 
concave  side  of  each  bend  than  at  the  convex  side.  Hence  it  is  that 
currents  are  perhaps  the  most  erratic  and  least  understood  of  all  aqueous 
agencies.t 

In  tidal  estuaries,  just  about  the  time  at  which  the  tide  reaches  its 
highest  and  lowest  levels,  there  are  periods  of  slack  or  still  water,  in  which 
matter,  hitherto  kept  in  suspension  by  the  movement  of  the  current,  is 
deposited.  If  allowed  to  accumulate  in  the  vicinity  of  an  entrance,  the  silt 
thus  formed  becomes  a  danger  to  navigation.  It  may,  possibly,  be  removed 
by  a  succeeding  current ;  if  not,  it  will  be  necessary  to  remove  it  either  by 
dredging,  scouring,  or  sluicing. 

•  Sncyclopoidia  Britannica,  9th  ed.,  Art.  "  Harbours."  It  is  not  quite  clear  whether 
the  measurement  is  from  trough  to  crest  or  merely  above  mean  water  level.  The  author 
assumes  the  former. 

t  Lord  Kelvin  is  reported  to  have  said  to  a  Parliamentary  Committee,  in  reply  to 
an  enquiry  respecting  his  investigation  into  the  probable  effect  of  certain  works  upon 
tidal  currents,  that  he  had  considered  the  question  seriously,  had  made  many  calcula- 
*  tioDB,  and  was  quite  unable  to  arrive  at  any  satisfactory  result.  Vide  Farren  on  the 
'*  Silting  of  Small  Harbours,"  Min.  Proc,  Liverpool  Engiiieering  Society ^  vol.  xviii.^ 
p.  226. 


232 


DOCK  ENGINEERING. 


As  illustrative  of  the  variation  in  the  amount  of  material  carried  in 
suspension  by  tidal  rivers  the  following  table  is  inserted  : —  * 

TABLE  XXL — Showing  Amount  op  Material  in  Suspension  in  1  Gallon 
OP  Mersey  Water  at  Various  Times  op  the  Tide. 


Flood  Tide. 

Flood  Tide. 

Ebb  Tide. 

Ebb  Tide. 

Ebb  Tide. 

A.M. 

Grains. 

AM. 

Grains. 

P.M. 
1.15 

Grains. 

P.M. 

Grains. 

P.M. 

Grains. 

8.45 

7  0 

11.15 

12-95 

5-25 

3.45 

19-95 

6.15 

30-8 

9.0 

8-4 

11.30 

12-95 

1.30 

5-25 

4.0 

13-65 

6.30 

30*45 

9.15 

20-3 

11.45 

15-05 

1.45 

6-3 

4.15 

1-05 

6.45 

54-25 

9.30 

22-92 

12.0 

15-75 

2.0 

3-5 

4.30 

5-6 

7.0 

43-06 

9.45 

2012 

2.15 

1-75 

4.45 

14-0 

7.15 

38-86 

10.0 

24-85 

P.M. 

2.30 

2-8 

5.0 

34-65 

7.30 

46-56 

10.15 

24-15 

12.15 

12-25 

2.45 

2-8 

515 

18-9 

7.45 

52-6 

10.30 

23-62 

12.30 

10-85 

3.0 

10-85 

6-30 

25-2 

8.0 

32-2 

10.45 

17-5 

12.45 

9-8 

3.15 

5-95 

5.45 

30-8 

8.15 

46-65 

11.0 

21-7 

1.0 

9-8 

3.30 

8-4 

1    G.O 

1 

22  05 

8.30 

38-5 

The  sediment  in  the  River  Hooghly,  at  time  of  flood,  amounts  to  3 
inches  per  cubic  foot.     In  the  River  Plate  it  is  1  in  10,000  bj  weight. 

Great  variation  is  to  be  found  in  the  rate  at  which  silting  takes  place. 
The  quantity  which  collects  in  the  Tilbury  tidal  basin  is  stated  to  bo  I  ^  to 
2  inches  daily.  At  Avonmouth  Dock  entrance,  the  accumulation  amounts 
to  only  15  inches  per  month. 

Purely  maintenance  dredging  at  some  ports  reaches  very  high  flgui-es. 
At  Kidderpur,  it  is  37,000  cubic  yards  per  annum;  at  Bordeaux,  380,000 
cubic  yards ;  at  Ostend,  500,000  cubic  yards ;  at  Hull,  830,000  cubic  yards ; 
and  at  Glasgow,  870,000  cubic  yards  per  annum. 

The  power  of  currents  to  disturb  deposited  material  may  be  gauged 
from  the  following  table  which  indicates  the  critical  velocity,  or  the 
velocity  at  which  moving  water  just  begins  to  exert  its  erosive  power.     To 


TABLE  XX IF. 


Material. 


Silt,  mud,  very  soft  clay, 

Fine  sand,  loam,   . 

Ordinary  clay, 

Coarse  sand,  fine  gravel, 

Fairly  coarse  gravel. 

Coarse  ballast  (1-inch  pebbles), 

Large  shingle  (Ij^-inch  pebbles), 

Heavy  shingle,  broken  stone, 

Soft  rock,      .... 


Critical  Velocity. 


3  incites  per  second. 

5 

6 


12 


»» 


2  feet' 

3  „ 

4  „ 

5  „ 


>» 

a 
it 
fi 

I) 


*  A.  G.  Lyster  on  **  Manchester  Ship  Canal,"  Min.  Proc.  Liverpool  Engineeriiig 
Society,  vol.  vii. 


DIMENSIONS.  233 

retain  in  suspension  and  transport  material,  the  current  will  have  to  exceed 
this  limit,  and,  in  some  cases,  to  he  very  much  greater. 

The  figures  in  Table  xxii.  relate  to  the  bottom  or  bed  velocity,  which, 
according  to  Professor  Rankine,  varies  between  f-and  ^  of  the  surface  velocity. 

A  moderate  current  in  the  fairway  of  an  entrance  is  a  desideratum  from 
more  points  of  view  than  one.  It  prevents  silting  and  it  assists  in  the 
manceuvring  of  vessels.  For  this  reason  it  will  be  advisable  to  locate  an 
entrance  in  the  vicinity  of  a  concavity  in  a  river's  bank  rather  than  at  a 
convexity.  But  the  question  is  somewhat  too  complicated  for  generalities, 
and  the  engineer  will  have  to  rely  largely  upon  his  own  judgment,  aided 
by  such  local  information  as  he  is  able  to  procure. 

Direction. — Having  determined  the  site,  the  next  point  to  be  settled  is 
the  direction  of  the  entrance.  There  are  three  main  directions  in  which  an 
entrance  may  point — viz.  (a)  down-stream,  (6)  up-stream,  and  (c)  amid* 
stream,  or  at  right  angles  to  the  direction  of  flow. 

(a)  A  downrhlream  entrance  is  not  convenient  for  vessels  entering  on  a 
flood  tide.  The  way  on  a  ship  is  maintained  or  increased  by  the  tidal  flow, 
and  effective  control  is  more  difficult.  It  is  better,  for  purposes  of  naviga- 
tion, to  dock  or  undock  a  ship  against  the  tide  or  current.  Hence  such  an 
entrance  would  only  be  suitable  for  vessels  docking  after  high  water  or 
undocking  before  high  water.  In  non-tidal  rivers,  or  those  portions 
unaffected  by  the  tide,  the  circumstances  are  in  favour  of  a  down-stream 
entrance,  especially  if  the  current  is  at  all  strong. 

(b)  'J'he  advantages  and  disadvantages  of  an  up-stream  entrance  are  the 
converse  of  those  appertaining  to  a  down -stream  entrance.  There  is  the 
additional  consideration  that  an  up-stream  entrance  is  more  likely  to  be 
silted  up  by  detritus  brought  down  by  the  river  and  deposited  in  the 
mouth  of  the  entrance. 

(c)  An  entrance  pointing  amidstream  is  at  once  the  least  convenient 
And  the  most  convenient  form  for  general  purposes.  In  itself  it  offers  grave 
drawbacks  to  navigation,  for  the  moment  a  vessel's  bow  comes  within  its 
shelter,  the  unprotected  stern  will  be  swung  round  by  the  force  of  the 
current,  unless  it  exceptionally  happens  to  be  dead  high  water  at  the 
moment;  but  if  it  be  provided  with  a  bell-mouth,  or  with  trumpet-shaped 
wing  walls,  this  drawback  is  overcome  and  the  entrance  becomes  avail  ible 
for  both  ebb  and  flood  tides,  since  a  vessel  may  thus  gain  the  leeward  of 
either  of  the  wing  walls  for  her  entire  length  before  engaging  in  the 
entrance  proper. 

Dimensions. — The  dimensions  to  be  assigned  to  an  entrance  will 
obviously  be  regulated  by  the  size  of  the  largest  ship  frequenting  the  port, 
with  a  due  allowance  for  future  increment. 

Half  a  century  ago,  under  the  regime  of  paddle  steamers,  entrances  and 
locks  had  to  be  constructed  of  very  considerable  tvidths.  When,  in  process 
of  time,  screws  and  propellers  displaced  paddles,  the  necessity  for  a  great 
width  of  waterway   temporarily  disappeared,   but   with   the   growth   and 


234  I^^CK  ENGINEERING. 

deyelopment  of  ocean  leviathans  in  recent  years,  the  need  of  wide  entrances 
is  returning.  In  1857  the  Canada  Lock  was  constructed  at  Liverpool,  lOO 
feet  wide.  It  was  not  until  the  year  1902  that  another  entrance  of  the  samo 
width  was  opened  for  traffic.  During  the  interval  the  width  considered 
requisite  had  fallen  to  65  feet,  from  which  it  has  gradually  risen  to  its 
former  dimension.  No  doubt  a  width  of  100  feet  is  in  excess  of  present- 
day  requirements,  the  maximum  breadth  of  a  ship  being  as  yet  70  feet,  but 
another  decade  will  probably  see  a  large  increase,  so  that  the  margin 
provided  is  no  more  than  prudent  foresight  would  warrant. 

Another  factor  involved  in  the  determination  of  width  is  the  ratio 
between  the  sectional  area  of  the  entrance  and  the  cubic  capacity  of  the 
dock,  or,  what  is  the  same  thing,  between  the  width  of  the  entrance  and  the 
area  of  the  dock.  If  a  dock  entrance  remains  open  for  any  length  of  time 
after  high  water,  a  gradually  increasing  current  is  generated  owing  to  the 
fall  of  the  tidal  level  outside,  and  the  consequent  discharge  of  the  water 
from  within  the  dock  through  a  narrow  passage.  If  allowed  to  continue 
too  long  the  current  may  become  so  rapid  as  to  render  the  closing  of  the 
gates  a  hazardous  proceeding.  The  limit  of  safety  may  be  considered 
reached  when  the  velocity  is  3  feet  per  second.  When  the  dock  is  of 
considerable  area  it  may  be  necessary  to  provide  two  or  more  entrances,, 
as  much  for  facilities  of  traffic  as  for  the  reason  given  above. 

As  regards  depth,  the  sill  of  the  old  Canada  Lock  was  such  as  to  afford  a 
depth  of  26  feet  6  inches  of  water  at  high  water  of  ordinary  spring  tides  at 
Liverpool,  and  19  feet  4  inches  at  high  water  of  ordinary  neaps.  The  latest 
entrances  constructed  at  that  port  provide  for  39  feet  2  inches  and  32  feet 
respectively.  The  loaded  draught  of  modern  vessels,  it  is  true,  does  not 
exceed  about  32  feet  as  yet,  but  the  greatest  length  consistent  with  that 
draught  has  now  been  reached,  and  an  increment  in  length  will  necessitate 
a  corresponding  increase  in  depth.  The  obstacle  to  this  development  in 
depth  has  been  the  limited  draught  of  water  obtainable  at  the  ports  which 
the  vessels  frequent,  and  there  can  be  no  doubt  that  with  increased  depth 
of  water  there  will  come  increased  depth  of  ships.  The  following  abridged 
remarks  of  Dr.  Francis  Elgar,"^  made  in  1893,  are  equally  applicable  at  the 
present  date  : — 

''The  deep  draught  of  water  is  a  most  important  element  of  speed  at 
sea,  and  it  is  now  strictly  limited  by  the  depth  of  water  in  the  ports  and 
docks  used  by  the  fast  passenger  steamships  on  both  sides  of  the  Atlantic. 
The  result  is  that  it  is  only  a  question  of  time,  and  not  of  a  very  long  time 
with  our  present  materials  of  construction  and  type  of  propulsive  machinery, 
to  find  an  absolute  limit  of  speed  imposed  by  the  restriction  of  draught  of 
water.  The  Atlantic  trade  is  increasing  at  such  a  rapid  rate  that  larger  and 
swifter  ships  are  certain  to  be  soon  called  for ;  but  much  deeper  harbours 
and  docks  will  be  required  if  further  great  increases  of  speed  at  sea  are  to  be 
obtained  without  excessive  difficulty  and  cost." 

*  Elgar  on  "  Fast  Ocean  Steamships/'  Min.  Proc.  Inst,  N,A.y  1893. 


ARRANGEMENT  AND  TYPES  OF  ENTRANCES.        235 

Commenting  on  and  emphasising  this  statement  in  1898,  Dr.  Elmer 
Oorthell*  added  the  following  rider : — 

"It  may  be  stated  as  a  fact,  palpable  and  undoubted,  that  no  port  of 
the  world  will,  in  the  near  future,  be  classed  or  used  as  a  first-class  port 
which  will  not  readily  admit  steamers  drawing  at  least  30  feet  of  water. 
This  means  35  feet  in  the  entrance  channels  through  sea- bars,  32  feet  in 
river  channels  and  other  entrance  approaches,  and  31  feet  in  harbours,, 
basins,  and  along  the  quays  and  wharves." 

The  length  to  be  given  to  an  entrance  will  depend  upon  its  arrangement,, 
either  as  a  lock  with  two  pairs  of  gates,  or  as  a  simple  entrance  with  one  pair. 
In  the  latter  case,  apart  from  the  wing  walls  adopted  for  entrances  pointing 
amid  stream,  the  length  need  not  be  more  than  will  accommodate  the  gates- 
and  their  side  recesses.  The  length  to  be  given  to  a  lock  entrance  will,  of 
course,  be  governed  by  the  length  of  vessel  which  the  lock  is  intended  to 
receive.  The  largest  lock  on  the  Thames  is  the  Tilbury  entrance  lock, 
700  feet  long,  followed  by  the  northern  entrance  lock  of  the  Albert  Dock, 
550  feet  long.  The  largest  lock  at  Liverpool  is  602  feet  long  ;  at  Barry 
there  is  a  lock  647  feet  in  length  ;  at  Barrow,  700  feet ;  and  at  Cardiff, 
800  feet.  This  last  represents  the  maximum  length  yet  obtained.  The  new 
lock  at  Bremerhaven  is  705  feet  long.  Swansea  has  an  800- feet  lock  in 
hand. 

Arrangement  and  Types  of  Entrances.— Following  local  dispositions  and 
requirements,  there  are  three  varieties  of  dock  entrance,  which  are  used 
either  singly  or  in  combination,  viz  : — 

(1)  A  simple  entrance,  provided  with  one  pair  of  ebb-gates. 

(2)  A  lock,  with  at  least  two  pairs  of  ebb-gates. 

(3)  A  half-tide  basin,  intervening  between  the  river  and  the  dock  and 
separated  from  each  by  a  pair  of  gates. 

Referring  to  these  seriatim,  it  may  be  remarked  that  (1)  a  simple  entrance 
is  only  available  for  navigation  at  or  about  the  time  of  high  water.  Where 
the  rise  and  fall  in  the  tide  is  sufficient  to  necessitate  the  use  of  gates,  the 
working  period  will  generally  be  confined  to  a  period  of  three  hours,  or  less, 
in  each  tide.  Furthermore,  a  single  pair  of  gates  is  but  inadequate  pro- 
vision against  contingencies.  Should  an  accident  by  any  means  happen  to 
the  gates  so  that  they  could  not  be  closed,  a  very  grave  risk  would  be 
incurred.  The  unexpected  running  dry  of  a  dock  would  probably  cause 
irreparable  damage  to  the  shipping  berthed  within  it. 

(2)  A  lock  offers  additional  facilities  for  the  docking  of  vessels,  since  it 
can  discharge  its  functions  for  some  time  after  the  water  within  the  dock 
has  been  impounded  ;  to  be  precise,  as  long  as  there  is  sufficient  depth  of 
water  on  the  outer  sill  to  admit  of  boats  entering  the  lock.  It  is  a  particu- 
larly useful  arrangement  when  the  dock  is  frequented  by  barges,  lighters^ 
and  other  small  craft ;  and  its  value  is  enhanced  by  dividing  the  lock,  by 

*  Corthell  on  "Maritime  Commerce,'*  3/ih.  Proc.  American  Af^^ociation  for  the 
Advancement  of  Science,  vol,  xlvii. 


236 


DOCK  ENGINEERING. 


means  of  a  pair  of  intermediate  gates,  into  two  sections  or  lengths,  so  that 
it  can  be  accommodated  to  the  reception  of  large  or  small  vessels,  as  the 
•case  may  be,  with  the  minimum  expenditure  of  water  during  the  process. 
The  quantity  of  water  withdrawn  from  the  dock  will  be  a  matter  for 
•consideration  if  the  operation  of  locking  be  very  prolonged.  The  following 
table,  modified  from  one  in  Rankine's  work  on  Civil  Engine&ring,  shows 
the  results  of  lockage  under  various  conditions. 

Let  L  denote  a  lockful  of  water — ^that  is,  the  volume  contained  in  the 
lock  chamber,  between  the  upper  and  lower  water  levels ;  let  B  denote  the 
volume  displaced  by  a  boat. 

TABLE  XXIII.— Lockage. 


One  boat  undocking, 


)} 


»» 


,,        docking,  . 

Two  n  boats  docking  and  \ 

undocking  alternately,  / 

Seriesofn  boats  undocking, 

»»  »»  »» 

„  „   docking,  . 

Two    series,   each   of  n\ 

boats,  the  first  undock-  j- 

ing,  the  second  docking,  j 


Lock  Found 


Water 
DiBcharged. 


Lock  Left 


Empty. 

Full. 

Empty  or  full. 

{Undocking,  full.  \ 
Docking,  empty./ 
Empty. 
Full 
Empty  or  full. 

Full. 


L-B. 

•  ■  • 

L  +  B. 
71  L. 

n  L  -  n  B, 

(n-l)L-nB. 
71 L  +  n  B. 

(2n-l)L. 


Empty. 
Empty. 
I  Full. 

{Undockinff,  empty. 
Docking,  full. 
Empty. 
Empty. 

Fuli: 

Full. 


Against  the  advantages  afforded  by  the  use  of  a  lock  have  to  be  set  the 
greatly  increased  cost  of  construction  over  that  of  a  simple  entrance  and  the 
additional  space  required.  The  projection  of  the  inner  end  of  a  lock  into 
the  dock  itself  is  a  plan  which,  though  often  adopted,  is  attended  by  a 
decrease  in  the  utilisable  length  of  quay  and  in  the  convenience  of  berthing. 

In  large  ports,  the  combination  of  a  simple  entrance  with  one  or  more 
locks  is  no  uncommon  feature.  The  former  is  used  for  docking  large  ships 
during  the  period  in  which  there  is  free  communication  between  the  dock 
and  the  river ;  the  latter,  which  are  often  in  two  widths,  are  brought  into 
active  service  when  the  entrance  is  closed,  or  they  may  be  utilised  contem- 
poraneously as  subsidiary  entrances.  At  Barry  there  is  a  single  entrance, 
80  feet  in  width,  and  a  lock  adjoining,  647  feet  by  60  feet.  The  recently 
constructed  entrances,  at  the  north  end  of  the  Liverpool  dock  system, 
comprise  an  entrance,''^  100  feet  wide,  an  80- foot  lock,  130  feet  long,  and  a 
40-foot  lock,  165  feet  long.  These  are  all  parallel  in  direction,  pointing 
up-stream,  but  at  Kidderpur  docks,  advantage  has  been  taken  of  a  bend  in 
tlie   waterway   to   arrange  a  lock,  400  feet  by  60  feet,  in  an  up-stream 

*  This  entrance  is,  strictly  speaking,  a  lock,  being  provided  with  two  pairs  of  ebb- 
gates  ;  but  it  is  rarely,  if  ever,  used  as  such,  the  chamber  being  only  130  feet  long, 
and  the  provision  of  two  pairs  of  gates  is  really  a  safeguard  against  the  contingencies 
previously  referred  to* 


MAINTKNANCE  OF   FAIRWAY. 


237 


direction,  and  an  80-foot  entrance  pointing  down-stream.  Ships  docked 
before  high  water,  anchor  above  the  upper  entrance,  and,  when  the  gates  can- 
be  opened,  are  breasted  in  alongside  the  jetty-head.  The  lower  entrance  ia 
intended  for  the  use  of  vessels  which  cannot  arrive  before  high  water ;  it  ia 
also  required  during  freshets  in  the  rainy  season,  when  the  current  in  the 
river  is  always  down-stream. 

In  connection  with  parallel  entrances  it  has  been  noted,  in  the  Mersey,, 
that  during  the  time  in  which  they  are  open,  a  circulating  current  has  been 
set  up,  the  water  entering  through  one  passage  and  making  its  exit  by  the 
other,  and  this  quite  regardless  of  any  change  in  the  tide. 

At  the  entrance  to  the  Manchester  Ship  Canal  there  are  three  parallel 
locks— 30  feet  by  150  feet,  50  feet  by  350  feet,  and  80  feet  by  600  feet 
respectively. 

(3)  Half-tide  basins,  which  are  practically  locks  on  a  very  large  scale,  are 
said  to  be  due  to  the  initiative  of  the  late  Mr.  Jesse  Hartley.  They  differ 
only  from  locks  in  regard  to  their  irregular  shape  and  great  size.  The  gatea 
of  the  dock  proper  are  closed  at,  or  soon  after,  high  water,  whereas  the 
gates  of  the  half- tide  basin  are  kept  open^  as  the  name  implies,  for  several 
hours  afterwards,  so  that  belated  vessels  can  enter  as  long  as  there  ia 
sufficient  depth  of  water  over  the  outer  sill  which,  of  course,  is  necessarily 
lower  than  that  of  the  inner  dock.  Vessels  may  remain  in  the  half-tide 
dock  until  the  ensuing  flood  tide  and  discharge  part  of  their  cargo  there,  or, 
if  it  be  desirable  to  establish  immediate  communication  with  the  inner 
dock,  this  can  be  done  by  pumping  water  into  the  half- tide  dock  from  some 
external  supply,  usually  the  river  itself.  To  equalise  the  level  by  running 
down  the  water  in  the  inner  dock  would  generally  prove  to  be  too  wasteful 
of  water,  unless  the  latter  were  relatively  much  larger  than  the  half-tide 
basin.  This  last  condition  may,  of  course,  be  fulfilled  by  grouping  several 
inner  docks  together.  The  Sandon  half-tide  dock  at  Liverpool  has  an 
area  of  14  acres,  and  is  in  direct  communication  with  the  Sandon  Dock  (10* 
acres),  the  Huskisson  Dock  and  branches  (36  acres),  the  Wellington  Dock 
(8  acres),  and  the  Bramley  Moore  Dock  (10  acres) — 64  acres  in  all.*  The 
North  Dock  (13  acres)  at  Swansea  is  approached  by  two  half -tide  basins, 
one  at  each  end,  with  areas  of  2^  and  1^  acres,  respectively.  At  Sunderland 
there  is  a  half-tide  basin  of  2|  acres,  acting  as  a  vestibule  to  the  Hudson 
Docks,  of  over  40  acres  in  extent. 

Maintenance  of  Fairway. — ^The  absolute  necessity  for  a  sufficient  and 
continuous  depth  of  water  in  the  channel  leading  to  a  dock  entrance  is  self- 
evident.  The  tendency,  which  the  channel  has,  to  become  silted  up,  must  be 
checked  by  some  corrective  agency,  either  natural  or  artificial.  The  natural 
means  would  be  the  utilisation  of  some  beneficial  current.  Where  this  is  im- 
practicable, recourse  must  be  had  to  sluicing,  scouring,  scraping,  or  dredging^ 

Sluicing, — This  method  consists  in  forming  an  aqueduct  or  culvert  in  the 
side  walls  of  an  entrance,  communicating  with  the  dock  at  its  inner  end,. 
*  And  indirectly  with  others,  the  total  impounded  area  being  over  100  acres. 


a^S  DOCK   ENGINEERING. 

And  branching  into  a  series  of  outlets,  discharging  as  low  as  possible,  at 
<;onvenient  intervals  along  the  channel  frontage.  During  the  lowest  period 
•of  ebb-tide,  water  from  the  dock  is  allowed  to  run  off  through  these 
-culverts  and  the  velocity,  which  it  possesses  in  consequence  of  the  head 
-of  water  within  the  dock,  enables  it  to  stir  up  and  remove  the  mud  in 
front  of  the  outlets.  The  quantity  of  water  run  off  is  controlled  by  a 
penstock,  or  paddle,  near  the  entrance  of  the  culvert,  and,  in  addition  to 
this,  other  pe  stocks  are  often  provided,  one  at  each  outlet  in  order  to 
regulate  the  numVier  of  exits,  for  it  may  often  be  desirable  to  concentrate 
the  whole  discharge  at  a  few  points  in  order  to  obtain  the  maximum  effect. 
Where  this  system  is  adopted,  it  is  very  essential  to  provide  a  masonry  or 
-concrtite  apron  in  front  of  the  wall,  otherwise  there  will  be  a  decided  risk 
of  the  wall  becoming  undermined.  For  the  same  reason  the  discharge 
should  be  perfectly  horizontal,  as  any  downward  inclination  causes  the 
water  to  act  the  part  of  an  excavator.  The  ground  in  such  cases  is 
])loughed  up,  and  the  excavated  material  is  deposited  a  short  distance  away 
as  soon  as  the  current  slackens,  in  such  a  manner  as  to  form  a  ridge,  which, 
being  out  of  range  of  the  sluice,  is  very  dangerous,  and  can  only  be 
removed  by  dredging. 

This  tendency  to  excavate  below  the  toe  of  a  wall  is  one  of  the  draw- 
backs of  a  mural  sluice ;  another  is  that  its  effective  action  is  restricted  to 
a  very  small  area  immediately  in  front  of  the  opening,  so  that  it  lowers 
the  sides  of  the  channel  at  the  expense  of  the  middle  of  the  bed.  A  third 
objection  lies  in  the  fact  that  the  formation  of  numerous  outlets  at  the  base 
of  the  wall  weakens  the  wall  at  the  locus  of  greatest  intensity  of  pressure. 
A  fourth  objection  is  the  very  seriouc^  loss  of  head  due  to  friction  and  bends, 
whereby  the  force  of  the  discharge  is  materially  diminished. 

Accordingly,  it  is  not  surprising  that  the  alternative  method  of  sluicing 
through  apertures  in  the  dock  gates  has  been  adopted  in  many  cases. 
There  is  an  absence  of  skin  friction,  there  are  no  bends,  and  the  only  loss 
of  head  is  that  due  to  discharge  through  a  thin  orifice,  which  is  much  less 
than  the  loss  due  to  friction  in  a  long  conduit.  Furthermore,  by  this  means 
a  large  body  of  water  is  discharged  along  the  axis  of  the  channel,  the  bed  of 
which  is  thus  kept  clear  without  endangering  the  stability  of  the  wing  walls. 
On  the  other  hand,  the  provision  of  sluice  valves  and  gear  adds  considerably 
to  the  weight  of  the  gates  and  entails  greater  strength  in  their  structure. 

Velocity  of  Efflux  from  Sluices. — The  velocity  of  efflux,  from  which  the 
scouring  effect  of  a  sluicing  current  can  be  gauged,  is  calculated  from 
formulie  based  upon  the  following  principles  : — 

The   theoretical  velocity  of  a  liquid  issuing  from  an  outlet  under  a 

given   head  or  charge,  considered   without  reference   to  friction,  is  the 

same  as  that  acquired  by  a  solid  particle  in  falling  freely  from  a  height 

.equal  to  the  head — i.e., 


*=2? 


VELOCITY  OF  KPFLUX   FROM  SLUICES.  239 

or, 

V  =  J2gh (37) 

In  the  case  of  a  liquid  whose  motion  is  impeded  by  friction,  the  rate  of 
flow  is  naturally  less.  The  amount  of  reduction  may  be  expressed  by  a 
fractional  coetlicient,  attached  to  the  preceding  equation,  denoting  the 
proportion  of  head  expended  in  overcoming  the  frictional  resistance. 
Thus,  the  total  head  may  be  considered  as  divided  into  two  portions, 
only  one  of  which  is  available  for  producing  velocity — 


v2 


whence 


A  =  (1.F)-. 


/   2</A 


The  laws  of  fluid  friction,  which  it  will  be  useful  to  state  at  this  point, 
differ  materially  from  those  relating  to  the  surface-contact  of  solid  bodies. 
They  are  as  follows  : — 

1.  The  friction  is  independent  of  the  head,  or  pressure. 

2.  It  varies  directly  as  the  area  of  the  surface  exposed  to  action. 

3.  It  varies  directly  (or  very 
nearly  so)  as  the  square  of  the  —  7*- 
velocity.  This,  however,  is  only  liter-  ^ 
ally  true  so  long  as  the  rate  of  flow  E:z^zZ- 
is  sufficient  to  prevent  the  adherence  z7^2^ 
of  water  to  the  surface  in  question.  ^ 


"SC 


3 


Now,  let  us  consider  the  case  of  p. 

a    horizontal    culvert    of    length,    x 

(fig.  171),  and  sectional  area,  a,  in  which  water  is  running  full.     Agree- 
ably to  the   foregoing   laws,   we    may   express    the    amount    of   surface 

friction  as 

S  =  /.  p  .  a; .  v^, 

where  y  is  a  coefficient  to  be  determined  later,  and  p  is  the  perimeter  of 
fluid  section. 

Now,  assume  the  surface  friction  to  be  just  counteracted  by  the  differ- 
ence of  pressure  upon  the  two  faces  of  the  length,  x.     That  is — 

But  this  resultant  pressure,  {q^  -  q^  a,  is  due  to  a  difference  in  head 
on  each  side  of  the  culvert.  Hence,  we  may  substitute  for  it  the  expres- 
sion for  the  pressure  of  the  differential  head — viz.,  wh^a,  in  which  w  is 

the  weight  of  a  cubic  foot  of  water.     At  the  same  time,  let  R  =  -,  and  the 
equation  becomes 

^  B,    to 


i 


240 


DOCK  ENGINEERING. 


v-^yjgh, (39) 


This  \ralue  for  h^  determines  the  amount  of  head  absorbed  in  overcoming 
friction.     Its  ratio  to  that  given  above  (37)  for  simple  discharge  is  expressed 

by  the  coefficient:  ^  =/Tr«     ^^^  factor,  f,  varies  with  the  nature  of  the 

surface  of  the  conduit,  and  it  is  also  found  to  depend,  to  a  certain 
extent,  on  the  relative  diameter  of  the  conduit  and  the  rate  of  flow,  being 
greater  in  small  pipes  than  in  large  culverts,  and  at  low  velocities  than 
at  high  speeds.  Its  value  is  found,  however,  to  lie  between  -005  and  -01, 
and  *0075  may  be  taken  as  a  serviceable  mean  for  general  use  under  normal 
conditions. 

The  symbol,  R,  standing  for  the  area  of  fluid  section  divided  by  the 
perimeter,  is  referred  to  as  the  hydraulic  mean  radius,  or  the  hydraulic 
mean  depth.  For  circular  and  square  culverts  running  full,  and  for 
circular  culverts  running  half  full,  it  is  obviously  equal  to  one- fourth 
of  the  diameter. 

There  are  other  sources  of  friction  than  that  investigated  above,  and 
these  cannot  be  overlooked  in  estimating  the  efficiency  of  the  current 
issuing  from  a  sluicing  culvert : — 

I.  There  is  the  friction  due  to  the  form  of  inlet  at  the  reservoir.  If 
an  orifice  in  a  thin  plate,  it  has  been  found  by  experiment  that 

Fg  =  -055. 

If  the  inlet  has  a  square-edged  entrance, 

Fj  =  -505. 

II.  There  is  the  friction  at  sudden  enlargements  or  contractions  of 
culvert  area.  Let  the  ratio  in  which  the  effective  area  is  suddenly 
enlarged  or  contracted  be  designated  r.     Then,  for  abrupt  enlargements, 

F3  =  (r  -  If, 

and  for  abrupt  contractions  the  same  formula  may  be  used,  although  the 
actual  ratio  of  contraction  is  somewhat  uncertain,  being  greater  than  the 
apparent  ratio.  The  loss  of  head  is  due  to  the  enlargement  succeeding 
contraction. 

III.  For  bends  in  circular  culverts, 


P,-^[0-131+ 1-847  (A)ij, 


I 


I 


I 


I 


Now,  the  term  —  (10  =  64  lbs.  for  salt  water)  deviates  by  so  little  from  ' 

that  we  can  replace  it  by  the  latter,  without  sensible  error.     Whence, 

K     -   f    ^     ^ 

or,  


VELOCITY  OF  EFFLUX  FROM  SLUICES.  24 1 

and  in  rectangular  culverts, 

F,=  i{0-124  +  3104(^)^}. 

are  formulse  ennnciated  by  Weisbach,  r  being  the  radius  of  curvature  of 
the  centre  line,  and  6  the  angle  through  which  the  culvert  is  bent  For 
very  sharp  turns,  or  knees, 

F4  =  0-946  sin2  ~  +  205  sin*  ^. 

The  head  necessary  to  overcome  all  these  varied  sources  of  friction  must 
be  deducted  from  the  total  head,  and  the  residue  will  then  represent  the 
head  available  for  producing  velocity  of  exit,  in  accordance  with  the 
formula 

The  theoretical  quantity  of  water  discharged  is 

where  A  is  the  area  of  opening,  but  in  practice  it  is  further  necessary  to 
take  into  account  a  modification  due  to  the  contraction  of  the  free  effluent 
leaving  the  culvert,  by  which  the  effective  area  of  the  current  is  less  than 
the  total  area  in  a  certain  ratio,  dependent  on  the  shape  of  the  outlet. 
This  is  brought  about  by  the  convergence  of  the  particles  into  a  vena  con- 
tracta,  or  contracted  vein. 

Calling  the  pipe  or  culvert  area  unity,  the  following  are  coefficients  (c) 
of  actual  discharge  in  the  formula  Q  =  c  Av. 

For  wide  openings,  whose  bottom  is  on  a  level  with 
that  of  the  reservoir ;  for  culverts  with  walls  in  a 
line  with  the  orifice,       .         .         .         .         .         .       -96. 

For  narrow  openings,  whose  bottom  is  on  a  level  with 

that  of  the  reservoir, '86. 

For  sluices,  without  culverts  or  side  walls,   .         .  *61. 

In  the  foi*egoing  investigation  we  have  only  credited  the  fluid  current 
with  the  energy  due  to  motion  and  to  head  or  pressure,  this  being  the  case 
when  the  culvert  is  truly  horizontal.  When,  however,  there  is  a  fall  or 
inclination  in  the  culvert  the  water  possesses  another  source  of  energy, 
viz.,  energy  of  position,  and  this  leads  us  to  undertake  an  investigation  into 
the  principles  which  govern  the  flow  of  water  in  inclined  pipes  and  culverts. 

Reverting  to  the  laws  of  fluid  friction  stated  on  p.  239,  and  remem- 
bering thatwhen  motion  has  become  uniform,  the  acceleration  and  retardation 
of  a  current  neutralise  each  other,  we  can  form  the  following  equation 
connecting  the  two.  The  acceleration  is  that  due  to  the  action  of  gravity 
on  a  body  falling  down  an  inclined  plane  of  height,  h,  and  length,  Z.  Accord- 
ingly, 


g  -J  =  pv^  X  constant ; 


16 


24^  I>OCK  KNGINEERINO. 

A  1      « 

or,  substituting  S  for  -?-,  the  sine  of  slope,  and  introducing  ^  =  -  instead  of  p, 

so  as  to  express  the  equation  in  terms  of  the  hydraulic  mean  radius,  we  have 

^S  =  ^^  X  constant, 

Iv 

which  reduces  to  the  form 

V  =  Os/nrs; (40) 

and  this  constitutes  the  basis  of  a  very  large  number  of  expressions  for  the 

velocity,  the  values  for  0  ranging  from  70  to  100,  according  to  the  personal 

observation  of  different  experimentalists. 

Kutter's  value  for  C,  though  complex,  is  recognised  as  the  most  generally 

reliable,  and  it  is  here  given 

,,  ^       1-811        00282 
41-6  +  +  — - — 

•00282\     a  '         '         '     ^  ^^ 


1        /^i  «       '0{)26'2\     a 


in  which  a  has  the  following  numerical  equivalents  : — 

•009  for  well-planed  timber  channel. 

'010  „  cement  plaster  channel. 

Ol  1  „  cement  and  sand  plaster  channel. 

*012  „  common  boards,  unplaned. 

'013  „  ashlar  and  neatly-jointed  brickwork. 

•017  „  rubble  masoniy. 

•025  „  earth  surface. 

'03  „  detritus  and  uneven  ground. 

Strictly  speaking,  the  amount  of  head  introduced  into  the  foregoing 
equation  should  be  the  total  head  reduced  by  that  portion  required  to  over- 
come the  friction  of  entrance  into  the  culvert,  but  when  this  latter  is  very 
small  in  comparison  with  the  foimer,  as  it  is  in  long  conduits  with  moderate 
heads,  the  total  head  may  be  used  without  sensible  error. 

For  the  sake  of  example  let  us  take  the  case  of  a  horizontal  culvert, 
6  feet  high  by  4  feet  wide,  and  find  the  amount  of  head  required  to  produce 
an  exit  velocity  of  4  feet  per  second.  Assume  a  length  of  100  feet,  a  square- 
edged  entrance,  and  one  bend  of  60'  in  direction,  with  a  radius  of  5  feet. 

Then,  by  the  preceding  formulae, 

*  _   0075  X  100  _ 

»"•'& r2     •     •     •     •  -   «»^» 

Fj =     -505 

F,  =  i{0-124  + 3-104(2^)^} 


=  l{  0-124.  3-104  Q^} 


=    '045 


F  =  R  +  F,  +  F,  =  1-175 


8 


V  = 


1  +  ^41-6  +  •J??^282_x  iUO  X   12\  ■01_     V  i00~x-r2 
V  7  J  J 1-2 


VELOCITY  OF  EFFLUX  FROM  SLUICES.  243 

H  =  (1  -  F)g 

=  2175  X  If  =  -644  foot,  or  6J  inches. 

The  head  required  to  produce  the  same  velocity  through  a  simple  sluice 
opening,  as  in  a  gate,  will  be  as  follows : — 

F,  =   055. 

H  =  (I  +  Fi)  -   =  1  055  X  i«  =  -264  foot,  or  a  little  over  3  inches— 

«bout  one-half  of  the  head  required  in  the  former  case. 

It  may  be  interesting  to  compare  the  foregoing  problems  with  a  kindred 
one  calculated  by  Kutter's  formula.  Suppose  the  culvert,  as  above,  to  have 
an  inclination  equal  to  that  afforded  by  the  head — viz.,  6^  inches— or,  to 
simplify  calculation,  say  7  inches  in  100  feet. 

,,  ^       1-811       -00282  X  100  X  12 

•01  7        ^    /  -12  X  7 

\  -01 

090.10 
=    -Too     ^    '^^'^^'^  =  1^1  ^  '084  =  13-52  feet  per  second. 

The  difference,  even  allowing  for  the  additional  ^  inch  fall,  is  very 
marked,  but  the  results  are  not  really  comparable,  being  calculated  on 
widely  divergent  lines  from  dissimilar  conditions. 

A  very  complete  and  interesting  example  of  sluicing  on  an  extensive 
scale  is  shown  by  the  plan  in  fig.  173,  which  refers  to  the  Canada  tidal  basin 
at  Liverpool.''^  The  main  culverts  are  constructed  partly  in  masonry  and 
partly  in  iron.  Those  of  iron  are  circular  in  section  and  lined  with  a  layer 
of  Portland  cement  ^  inch  tliick,  which  is  secured  by  dovetailed  ribs  or 
keys  at  close  intervals  along  the  castings.  This  work,  although  completed 
twenty  years  ago,  is  still  sound  and  intact,  exhibiting  no  signs  of  erosion  or 
decay. 

The  centre  of  the  basin  is  brought  within  the  scope  of  the  discharge  by 
outlets  in  the  floor  of  the  northern  portion,  which  is  laid  with  concrete. 
The  sluicing  pipes  are  arranged  in  radiating  lines  beneath  the  floor 
(fig.  172),  each  being  provided  with  a  series  of  upper  outlets  along  its 
length,  and  terminating  in  a  splayed  opening.  To  protect  these  openings 
heavy  frames  or  discs  of  greenheart  (fig.  174)  are  laid  over  them  as  covers, 
being  secured  by  four  strong  links  to  foundation  anchorages.  When  the 
sluices  are  not  in  use,  these  discs  lie  at  rest  upon  their  respective  outlets, 
but  under  the  pressure  of  flowing  water  within  the  culvert  they  are  raised 
to  the  full  extent  allowed  by  the  links,  and  the  water  rushes  out  in  the 
form  of  annular  jets,  sweeping  the  circular  area  within  its  range. 

This  arrangement  has  been  found  extremely  effective  for  the  purpose 

*  6.  F.  Lyster  on  **  Dock  Extensions  at  Liverpool,"  Min^  Proc,  Inst.  C,E.,  vol.  c. 


244 


DOCK  ENGINEERING. 


intended,  but  in  view  of  the  increase  in  depth  continually  demanded  hj 
modern  shipping,  a  concrete  floor  to  a  basin  is  a  feature  which  cannot  be 
considered  free  from  inconveniences.  No  deepening  of  the  basin  is  possible 
without  its  removal,  which  must  prove  a  costly  and  troublesome  under- 
taking. 

Sluicing  is  carried  on  daily  at  the  Canada  Basin,  but  the  maximum 
effect  is  obtained  at  low  water  of  spring  tides,  a  time  when  the  basin  ia 
very  shallow,  and  when  the  inner  docks  can  afford  to  part  with  a  consider- 
able amount  of  the  water  impounded  on  the  flood  tide.  The  water  in  the 
docks  is  always  levelled  with  the  incoming  tide  two  hours  before  high- 
water,  within  which  period  tlie  operations  of  docking  and  undocking  are 
carried  on. 


Xov  Wittmr  of 


aax  lOicr  utrnt-  o.ik.9. 


ENLARGED  SECTION  THROUGH  OUTLET. 


*-'\lL-LJLl_J_£ 


aoaU^J%T9^^1Jn 


y--'^"^^ 


JlpTkbtf. 


Fig.  174. 

Sluicing  on  a  large  scale  is  a  prominent  feature  of  ports  bordering  on 
the  English  Channel.  The  method  usually  adopted  is  that  of  impounding 
a  quantity  of  water  during  the  flood  tide,,  in  a  basin  specially  constructed 
for  the  purpose.  At  high  water  the  sluice  gates  of  this  basin  are  closed, 
and  the  contents  retained  until  a  suitable  period  about  low  water,  when 
the  gates  are  opened  again.  The  discharge  of  a  large  volume  of  water  is 
found  to  be  absolutely  essential  to  the  maintenance  of  entrance  channela 
so  subject  to  the  introduction  of  sand  by  a  littoral  current,  with  ita 
attendant  deposition.  The  rate  of  discharge  provided  at  Dunkirk  and 
Calais  is  about  500  cubic  yards  per  second,  and  the  effective  duration 
about  three-quarters  of  an  hour. 

The  recent  improvement  works  at  the  port  of  Ostend  (fig.  175)  com- 
prise a  considerable  enlargement  of  area  in  the  sluicing  enclosure  there, 
concerning  which  M.  Van  der  Schueren''^  makes  the  following  obser- 
vations : — 

"  Ships  drawing  much  water  will  be  able  to  enter  the  port  by  favour  of 

*  Van  der  Schueren  on  **Travaux  ex^ut^  r^oemment  et  en  oours  d'ex6cution  au 
port  d'Ostende,"  Ii\i,  Nav,  Cong.,  Paris,  1900. 


I 


SLUICES  AT  OSTEND. 


245 


the  tide,  to  reach  the  qaaj  of  the  new  outer  harbour,  and  to  remain  there 
afloat ;  but,  to  this  end,  it  is  necessary  to  maintain  a  draught  of  26  feet  at 
low  water. 

'*  If  it  were  considered  essential  to  obtain  this  result  by  means  of 
<lredging,  it  is  to  be  feared  that  the  cost  of  the  undertaking  would  be 
-considerable,  even  excessive,  and  that  the  cumbersome  appliances  neces- 
sarily employed  for  its  execution  would  be  found  only  too  often  usurping, 
in  front  of  the  quay  walls,  berths  destined  for  commercial  vessels. 

"  Dredging,  therefore,  would  constitute  a  drawback — a  serious  danger 
•even — for  navigation  at  the  port;  and  the  maintenance  of  great  depths 
could  with  difficulty  be  assured  by  this  means  alone. 

"  In  regard  to  ports  on  the  Belgian  littoral,  the  rapidity  with  which 
•deposits  of  mud  accumulate,  in  channels  withdrawn  from  the  action  of 
natural  or  artificial  currents,  is  well  known. 

*' Under  these  circumstances,  the  utility  of  a  sluicing  basin  would  appear 
to  be  incontestible.  The  sluices  are  designed  to  supplement  the  action  of 
the  upper  waters  and  of  tidal  currents,  with  a  view  to  maintaining  uninter- 
ruptedly, along  the  tidal  quay  of  the  new  outer  harbour,  the  assigned 
-depth  of  26  feet,  without  having  recourse  to  continual  dredging. 

"The  sill  of  the  Bluice  is  located  13  feet  below  datum,  differing  in 
this  respect  from  existing  sluices,  the  sills  of  which  are  level  with,  or  not 
below,  low  water  datum. 

**  The  arrangement  adopted  is  justified  in  respect  of  the  efficacy  of  the 
current.  Calculation,  in  accordance  with  observed  results,  enables  it  to 
be  determined  to  what  degree  the  useful  work  of  the  sluice  is  increased 
in  this  way. 

'*  In  his  inquiry  into  the  improvement  of  ports  on  a  sandy  beach  the 
late  M.  Mey  demonstrates,  in  efioct,  that  in  ordinary  conditions,  relative 
to  the  dimensions  of  the  sluice  and  the  reservoir  basin,  the  useful  efiect 
of  the  effluent  varies  in  the  ratio  of  about  1  to  6 '5  when  the  sill  of  the 
sluice,  assumed  primarily  at  the  level  zero  (low  water),  is  lowered  after- 
wards to  13  feet  below  this  datum/' 

The  following  are  particulars  of  the  sluicing  arrangements  at  Ostend : — 


Nuin))er 

Width                Level  of  Sill 

Nanie  of  Basin. 

Area. 

of 

of                '  with  reference 

Acres. 

Sluices. 

Opening.           '  to  Local  Zero. 

Feet.                       Feet. 

£cluse  Militaire, 

29^ 

3 

JTwoeachl9i\               ^i 
j       One  39                 "    ^^ 

l^cluse  Fran9ai8e, 

64 

2 

19i             1       +      J 

^cliise  Leopold, 

m 

6 

13                      +14 

New  Basin, 

192^ 

6 

16i                    -  13 

To  prevent  the  sluicing  basin  itself  from  being  silted  up,  it  is  in  some 
•cases  allowed  to  be  filled  only  on  the  top  of  high  water,  when  the  influent 
is  comparatively  clear.     This  is  the  case  at  Honfleur.     Elsewhere,  as  at 


246  DOCK  ENGINEERING. 

RanuigRte  and  Dover,  the  basin  haa  been  divided  into  two  separate  sections 
by  a  dividing  bank,  and  one  of  these  sections  has  occasionally  been  used  ta 
cleanse  the  other.  Another  expedient  is  to  feed  the  reservoir  with  inland 
fresh  water.  In  this  connection,  it  is  desirable  to  note  that  the  specific 
gravity  of  fresh  water  being  less  than  that  of  salt  water,  there  is  a  marked 
tendency  for  fresh  water  to  flow  over  the  surface  of  the  salt  water,  and  it 
has  been  stated  that  the  eflect  of  scouring  with  the  former  does  not  extend 
to  depths  greater  than  9  feet.  * 

At  the  port  of  Dublin  a  considerable  area  of  strand  of  the  estuary  of  the 
River  Liffey  is  enclosed  by  a  low  retaining  wall,  which  is  submerged  above 
half-tide  level.  When  the  tide  falls  below  this  level,  the  ebbing  water 
converges  to  a  contracted  outlet,  and  produces  a  very  effective  scour  at  the 
mouth  of  the  harbour. 

It  is  very  necessary  to  emphasise  the  danger  of  excavation  in  front  of  a 
discharging  sluice.  Even  when  a  masonry  apron  of  considerable  width  has 
been  provided,  the  ground  immediately  beyond  it  has  been  found  eroded  to 
such  an  extent  that  measures  have  had  to  be  taken  to  prevent  serious 
damage.  A  hole,  6  feet  deep,  was  formed  at  the  edge  of  a  stone  apron,. 
80  feet  in  width,  at  the  low- water  basin,  Birkenhead,  and  all  attempts  to- 
fill  up  and  reduce  the  hole  by  the  discharge  of  large  blocks  of  rubble  stone 
into  it  were  ineffectual.  The  same  results  were  experienced  at  Dunkirk,, 
where  the  sill  of  a  former  sluicing  basin  was  found  undermined  to  a  depth 
of  13  feet. 

Scraping  and  Scuttling, — This  method  consists  in  stirring  up  the  deposit 
by  mechanical  means,  to  enable  it  to  be  carried  away  by  an  existing  outward 
current.  At  Tilbury  basin,  harrows  are  employed  for  the  purpose,  aided  by 
high-pressure  water  jets  worked  from  a  small  tug  during  the  ebbtide.  The 
commotion  caused  by  the  revolving  propeller  itself  of  a  tug  with  light 
draught  in  shallow  water  will  also  cause  a  very  eflective  disturbance  of 
mud.  The  same  method  with  a  larger  vessel  has  been  successfully  employed 
for  removing  sandy  bars  at  the  mouths  of  rivers. 

Dredging, — Dredging,  as  a  means  of  channel  maintenance,  and  distinct 
from  deepening  work,  is  open  to  the  objection  already  stated,  that  it 
obstructs  the  navigable  way.  Having  in  view  the  soft  nature  of  the  material 
to  be  dealt  with  and  the  necessity  for  continuous  removal  of  shallow  deposits 
rather  than  the  intermittent  excavation  of  large  accumulations,  suction 
dredgers  form  the  most  useful  type  for  maintenance  work.  Grab  dredgers 
are  also  valuable  in  confined  spaces,  but  the  bucket  dredger  can  only  be 
usefully  employed  in  large  and  unconfined  areas,  where  a  considerable  bulk 
of  material  has  to  be  excavated. 

In  the  case  of  a  suction  dredger,  the  mud  in  the  intake  pipe  forms  a- 
comparatively  small  percentage  of  its  contents — ^averaging,  say,  from  30  to- 
40  per  cent. — and  of  this  a  large  proportion  may  be  expected  to  pass  out 
with  the  overflow  water  from  the  hopper  into  which  it  is  discharged.     The 

*  Mm,  Proc.  Int<t.  C.E.y  vol.  Ixvii.,  p.  461. 


LOCK  FOUNDATIONS.  247 

qaantity  of  escaping  material  19  oqisble,  however,  of  being  greatly  reduced 
by  a  device  due  to  Mr.  A.  G.  Lyster  and  already  referred  to  (p.  89). 

We  now  pass  on  to  a  consideration  of  the  structural  features  of  looks 
and  entrances. 

Lock  Foundations. — On  the  subject  of  foundations  much  that  is  stated  in 
the  chapter  on  Dock  and  Quay  Walls  is  equally  applicable  in  the  present 
instance  and  need  not  be  here  repeated.  There  are,  however,  some  contin- 
gencies and  expedients  peculiarly  characteristic  of  lock  construction  which 
call  for  special  notice  and  explanation. 

The  walls  of  locks  differ  from  the  ordinary  type  of  dock  walls  in  that 
they  derive  a  considerable  amount  of  support  from  the  floor,  especially  if, 
as  is  usually  the  case,  the  latter  has  the  form  of  an  inverted  arch  or,  if  a  flat 
floor,  has  curved  haunches  tangential  to  the  side  walb,  or,  failing  that,  is 
sufficiently  thick  to  admit  of  the  existence  of  a  virtual  arch  within  its  limits. 

The  floor,  on  the  other  hand,  without  much  assistance  from  hydrostatic 
pressure,  has  frequently  to  restrain  the  uplifting  tendency  induced  by  this 
lateral  weight.  The  efiect  is  more  particularly  felt  in  cases  such  as  the  lock 
at  Bremerhaven  (fig.  206),  where  there  is  no  artificial  floor,  though  in  the 
instance  cited  the  stress  is  minimised  by  the  use  of  bearing  piles  beneath 
the  walls. 

As  a  general  rule,  hard  rock  and  stifl*  clay,  in  which  there  are  no  springs, 
do  not  call  per  ae  for  any  artificial  covering,  except  such  as  may  be  judged 
necessary  to  protect  their  surfaces  from  the  softening  and  scouring  action  of 
water.  On  the  other  hand,  alluvial  deposit,  sand,  gravel,  and  other  inco- 
hesive  strata,  need  the  confinement  aflbrded  by  a  superimposed  mass  in 
addition  to  the  lateral  support  of  sheet-piles.  Earth  of  a  porous  nature, 
moreover,  is  not  only  unsuitable  for  a  natural  fioor,  but  is  equally  undesir- 
able as  a  foundation  for  an  artificial  floor,  owing  to  its  efficacy  as  a  medium 
for  the  transmission  of  water  pressure,  on  which  account  any  covering  laid 
upon  it  should  be  both  strong  and  impervious. 

The  point  of  perhaps  the  greatest  importance  in  connection  with  lock 
foundations  is  that  of  the  treatment  of  boils  or  springs,  such  as  are  often 
encountered  in  works  of  this  class.  The  type  of  foundation  roost  likely  I0 
cause  trouble  in  this  respect  is  that  in  which  a  pervious  stratum  lies  between 
two  others  of  an  impervious  nature,  the  upper  of  which  has  been  pierced  or 
is  fissured  by  a  natural  fault.  The  water-bearing  stratum  may  then  discharge 
copiously  under  considerable  head,  owing  to  a  connection  with  some  external 
supply  located,  often  unsuspected ly,  at  some  remote  inland  source.  The 
following  may  be  cited  as  an  illustration  germane  to  the  point. 

The  site  of  the  Albert  Lock  at  Hull*  consists  of  consecutive  layers  of 
silt,  peat,  boulder  clay,  sand,  boulder  clay,  sand,  and  chalk.  Soon  after  the 
lower  bed  of  clay  had  been  laid  bare  in  the  course  of  excavation  there 
occurred  numerous  and  powerful  inbursts  of  brackish  water  charged  with 
yellow  sand.  The  source  of  the  trouble  was  primarily  attributed  to  the 
*  Hawkshaw  on  "  The  Albert  Dock,  Hull,"  Min.  Proc,  Itist,  C,E.,  vol.  xli. 


248  POCK  ENGINEERING. 

River  Humber,  but  the  fact  that  the  sand  between  the  two  beds  of  clay  was 
grey  and  loamy,  whereas  the  water-borne  sand  was  yellow,  induced  the 
engineers  to  make  trial  borings  through  the  lower  clay.  This  was  found  to 
be  a  stiff  brown  layer,  42  feet  in  thickness,  and  the  borehole  remained 
quite  dry  until  the  bottom  was  reached,  when  water  charged  with  yellow 
sand  flowed  up  tlie  hole  with  considerable  force,  showiug  that  the  boils  had 
their  origin  in  the  sand  bed  which  immediately  overlay  the  chalk.  As  the 
chalk  wolds  extend  over  a  large  area,  attaining  an  elevation  of  500  feet  at 
no  great  distance  from  Hull,  and  giving  rise  to  copious  springs  at  their  base, 
it  was  then  considered  probable  that  the  influent  was  mainly  due  to  land 
water  accumulated  in  the  chalk,  though  the  fact  that  the  stream  was 
brackish  indicated  some  connection  with  the  sand  beds  of  the  River 
H  umber. 

Sometimes  the  source  of  leakage,  being  nearer  at  hand,  is  more  obvious. 
In  the  reconstruction  of  the  Oanada  Lock  at  Liverpool,  the  site  of  which 
comprises  an  alluvial  bed  overlying  two  layers  of  boulder  clay,  intersected 
by  a  bed  of  sand  and  gravel  of  varying  thickness,  considerable  difficulty  was 
experienced  at  first  owing  to  inbursts  from  the  river  through  the  sand. 
Excavations  at  the  time  were  in  progress,  continuously  within  the  lock 
chamber,  under  protection  of  the  gates,  and  intermittently  at  the  outer  sill, 
at  low  water  of  spring  tides.  The  removal  of  the  upper  clay  in  both  situa- 
tions was  coincident  with  the  flooding  of  the  lock  chamber  at  high  tide, 
clearly  under  the  head  afforded  by  the  water  in  the  river.  It  was  found 
impossible  to  keep  down  the  water  in  the  lock,  and  the  interior  work  had 
to  remain  in  abeyance  until  the  outer  sill  was  completed. 

The  larger  area  involved  in  the  construction  of  locks  and  entrances 
generally  renders  it  difficult,  and  not  always  advisable,  to  adopt  the  method 
of  treatment  recommended  for  infiltrations  of  water  to  wall  foundations — 
viz.,  to  lead  them  to  some  suitable  spot  where  they  can  be  provided  with  a 
vent.  Discharge  within  the  lock  itself  is  inconvenient  in  the  case  of  small 
streams  and  impracticable  in  the  case  of  large  ones.  On  the  other  hand,  to 
convey  a  discharge  outside  the  lock  area  would  be  a  matter  often  attended 
by  needless  difficulty  and  expense.  Furthermore,  there  is  the  risk  that  the 
effluent  might  carry  with  it  material  in  suspension,  unless  it  were  entirely 
checked  by  a  counteracting  head. 

In  view  of  the  divei-sity  of  conditions  under  which  constructive 
operations  have  to  be  carried  on,  it  would  be  obviously  impossible  to  lay 
down  any  general  rules  of  procedure  in  case  of  leakage  arising  from  boils  or 
springs.  All  that  is  permissible  is  to  briefly  indicate  a  few  of  the  methods 
which  have  been  successfully  adopted  in  actual  cases,  putting  on  one  side 
altogether  the  question  of  their  applicability  elsewhere. 

1.  Where  the  discharge  has  been  slight  and  of  the  nature  of  an  infiltra- 
tion, it  has  been  easily  checked  by  the  rapid  deposit  of  a  large  bulk  of 
concrete  upon  the  spot,  the  concrete  being  mixed  fairly  dry,  so  as  to  allow 
for  its  admixture  with  the  water  in  situ. 


LOCK  FOUNDATIONS.  249 

2.  Where  the  discharge  has  been  greater,  but  sufficiently  moderate  not 
to  interfere  with  work  in  the  vicinity,  it  has  been  allowed  to  find  its  way 
into  the  pumping  well  in  the  ordinary  manner  (t.e.,  by  open  "  grip  "  or 
drain  pipe),  and  any  sand,  which  accompanied  it,  filtered  by  laying 
straw,  bags,  strips  of  canvas,  &c,,  over  the  source  and  weighting  them 
down. 

3.  Where  the  discharge  has  been  more  rapid  still,  proceeding  from 
a  definite  "  blow,"  with  a  tendency  to  diffusion,  it  has  been  concentrated 
into  a  special  iron  pipe  which  led  temporarily  to  a  pumping  well,  or 
in  another  case  was  carried  up  to  a  height  equal  to  the  head  of  discharge. 
There  is  a  danger,  however,  attached  to  this  method  of  repressing  the  flow 
by  a  counteracting  head.  The  general  pressure  is  in  no  way  relieved, 
and  there  is  every  likelihood  of  the  blow  re-asserting  itself  at  another 
weak  spot,  so  that  the  horizontal  duct  is  a  preferable  course  to  adopt.  At  a 
later  period,  the  pipes  referred  to  were  grouted  with  cement  under  pressure, 
and  in  due  time,  after  the  cement  had  set,  the  projecting  portions  were  cut 
off.  The  connection  between  the  pipe  and  the  blowhole  necessitated  care- 
ful and  ample  packing  with  rubble  and  clay  or  cement  in  bags,  so  as  to 
secure  a  thoroughly  watertight  joint.  In  one  instance  a  hollow  hemi- 
spherical casting  was  employed  to  collect  the  outflow.  It  was  3  feet  in 
diameter,  with  an  upper  flanged  connection  for  a  C-inch  pipe,  and  sat  upon 
a  ledge  surrounding  the  hole,  below  the  foundation  level,  in  which  position 
it  was  concreted. 

4.  Where  the  discharge  has  been  so  great  as  threaten  to  overpower  the 
pumps,  it  has  been  deemed  advisable  to  block  the  holes,  temporarily,  with 
rubble  and  clay  puddle,  tipped  in  large  quantities,  until  the  affected  area 
could  be  isolated  by  an  enclosure  of  whole  timber  sheet  piling.  One  hole, 
treated  in  this  way,  is  recorded  as  having  absorbed  several  hundred  cubic 
yards  of  puddle. 

5.  Finally,  where  the  pumps  have  actually  been  overpowered,  the  water 
has  been  allowed  to  rise  to  its  natural  head  and  the  excavation  completed 
by  dredging.  The  foundation  was  then  piled  and  the  pile-heads  cut  off  by 
divers  to  one  uniform  level.  A  covering  of  jute  cloth  was  next  laid  over 
them  and  fastened  there  while  concrete  was  deposited  upon  the  site  by  skips 
opening  at  the  bottom.  Wlien  the  concrete  had  reached  a  height  sufficient 
to  counteract  the  under-pressure,  the  area  was  pumped  out  again  and  the 
work  resumed  in  the  open. 

One  essential  feature  stands  out  prominently  as  the  outcome  of  much 
experience — the  necessity  for  adequate  pumping  power.  It  is,  in  fact,  wiser 
to  provide  it  in  excess  of  all  anticipated  requirements,  rather  than  to  run 
the  risk  of  a  stoppage  of  the  works  at  some  critical  and  momentous  period. 
At  the  same  time,  it  must  be  borne  in  mind  that  there  is  a  judicious  limit 
to  be  observed.  If  the  water  be  continuously  and  heavily  charged  with 
silt  or  sand,  which  cannot  be  checked,  it  is  evident  that  a  void  is  being 
formed    somewhere,  and  that  settlement  of  the  foundation    will    be   the 


250   .  DOCK  ENGINEERING. 

probable  result.      Under  such  circumstances   a   suspension   of   pumping 
operations  becomes  imperative. 

Occasionally,  leaks  have  been  found  to  develop  in  the  floor  or  sills  of  a 
lock  or  entrance  subsequent  to  the  completion  of  the  work.  In  such 
cases  the  loecUe  of  the  leak  has  been  bored  through  to  the  underlying 
stratum  and  stand  pipes,  fitted  into  the  boles,  have  been  filled  with  cement 
grout,  from  a  considerable  height,  to  be  cut  off  later  as  already  described. 
This  operation  is  best  carried  out  at  a  time  when  the  pressure  of  water 
within  and  without  the  lock  is  the  same.  Provided  the  holes  are  sufii- 
ciently  close  together,  the  whole  of  the  underside  of  the  floor  may  be 
coated  in  this  way  with  a  thin  watertight  diaphragm.  Fissures  in  rock  can 
be  treated  by  the  same  process,  and  it  is  a  common  method  for  grouting 
up  the  interior  of  a  cast-iron  roller  path  after  it  has  been  adjusted  by 
wedges  and  holding-down  bolts  to  its  proper  level  on  the  gate  platform. 

Another  course  of  treatment  for  cracks  and  fissures  is  that  called 
stock-rammtTig,  and  consists  in  inserting  into  the  borehole  pipe  lumps  of  clay 
worked  up  with  cement  or  hydraulic  lime,  sand  mixed  with  iron  filings  and 
sal  ammoniac  (rust  cement)  or  stiff  concrete,  the  material  being  forced  home 
by  blows  from  a  heavy  ram  worked  by  hand  or  steam-power. 

Open  joints  may  be  caulked  by  rolls  of  canvas,  partially  filled  with  soft 
cement.  Large  fissures  are  sometimes  cut  out,  so  as  to  form  a  rectangular 
recess  into  which  a  block  of  masonry  is  fitted,  wedged  up,  and  grouted. 

Oracks  will  often  occur  near  the  centre  of  a  lock  fioor,  owing  to  the 
unequal  distribution  of  pressure  over  the  foundation  area,  arising  from  the 
greater  weight  of  the  side  walls.  These  manifestations  of  weakness  may 
be  prevented  by  adopting  a  floor,  the  section  of  which  constitutes  an 
actual  or  virtual  inverted  arch. 

The  problem  of  the  proper  distribution  of  pressure  over  a  lock  area  is 
a  very  important  one,  particularly  if  the  strata  be  irregular  and  water- 
bearing.   A  variety  of  methods  have  been  exemplified  in  different  localities. 

If  the  ground  be  of  an  uncertain  or  treacherous  character,  such  as  clay 
interspersed  with  pot  holes  of  quicksands,  it  will  be  well  to  effect  the 
uniform  distribution  of  the  superimposed  weight  by  the  interposition  of 
timber  planking  laid  horizontally  and  arranged  so  as  to  break  joint. 

A  loose  sandy  foundation  may  be  somewhat  consolidated  by  driving  a 
series  of  short  piles  at  close  intervals.  A  row  of  external  sheet  piling 
should  not  be  neglected. 

An  ingenious  method  has  been  devised  for  transforming  a  sand  or  gravel 
foundation  into  one  of  concrete,  by  impregnating  it  with  Portland  cement 
under  air  pressure.  The  following  details  relate  to  the  manner  in  which  the 
operation  was  carried  out  at  the  Port  of  Vegesack,  near  Bremen,  on  the 
River  Weser : — * 

A  pipe  or  shaft,  1^  inches  in  diameter,  pointed  at  its  lower  end  and  per- 

*  Neukerch  on  "  Constructing  Foundations  by  forcing  Cement  into  Loose  Sand  and 
Gravel  by  Air,"  Min.  Proc.  Am.  Sor.  CA'-.-vol.  xxx.,  p.  284. 


I 


SILLS.  25 

forated  there  with  three  or  four  boles  of 
f  inch  dUmeter,  was  sunk  ander  com- 
preraed  air  into  the  sand  until  it  reached 
a  depth  varjing  from  16  to  19  feet.  In 
the  air  pressure  supplj  pipe  provision 
wag  made,  br  means  of  suitable  branches 
and  stopcocks,  for  connecting  therewith 
on  apparatus  which,  with  the  aid  of  an 
injector  device,  enabled  any  desired  quan- 
tity of  cement  powder  to  be  fed  into  the 
»ir  current.  While  this  was  being  done, 
the  pipe  was  slowly  withdrawn  in  an 
upward  direction,  so  that  the  cement 
was  thoroughly  diffused  throughout  the 
bed,  which  was  full  of  natural  moisture. 
The  cement  was  supplied  dry  and  warn 

air  was   used.     Consecutive  areas,  from  fi 

S  to  13  inches  square,   were  treated  in  E 

this  way,  and  the  concrete  allowed  suffi- 
cient time  to  set  before  being  built 
upon. 

Frincip&l    ConBtractire    Featores. —  Z 

Apart   from    the    question  of  the    floor  c 

and  its  foundations,  the  following  (illus-  ''§ 

trated    in    fig.   ITG)    are  the    most    im-  £ 

portant  features  in  the  construction  of  | 

entrances    and     passages     generally : —  f£ 

(1)  the  sills,  (3)  the  platforms,  (3)   the  "1 

side  recesses  and  chambers,  (4)  the  walls,  S 

and  (5)  the  levelling  culverts.  The  sub- 
ject of  the  means  adopted  for  closing  the 
entrance  is  resei'ved  for  an  independent 
chapter. 

1.  Sille. — If  for  caissons,  these  will 
constitute  straight  lines  Id  plan,  normal 
to  the  axis  of  the  waterway  ;  if  for  gates, 
each  will  consist  of  two  straight  or 
curved  lines  intersecting  at  the  centre. 
The  level  of  the  sill  will  generally  be 
somewhat  higher  than  the  floor  ol  the 
chamber  in  order  tn  avoid  sinking  the 
gate  or  caisson  plutform  below  the  floor 
level.  This,  however,  is  often  done, 
more  especially  in  the  case  of  caisson 
platforms,   which    are   not  so  extensive 


252  DOCK  ENGINEERING. 

&8  gate  platforms.  The  objection  is  the  great  tendency  for  any  depres- 
sion in  the  floor  to  form  a  mud  trap,  but  this  may  be  partially  obviated 
by  arranging  the  culvert  inlets  so  as  to  exercise  their  influence  at 
such  parts.  The  sectional  profile  of  a  sill  is  often  curvilinear,  but  the 
outlines  of  modern  naval  architecture  render  it  desirable  that  the  sill 
should  be  as  flat  as  possible.  The  height  of  the  sill  depends  upon  the 
amount  of  cover  required  to  form  a  watertight  joint  with  the  gate  or 
•caisson,  and  the  clearance  necessary  for  truck-wheels,  rollers,  or  slides,  as 
the  case  may  be.  Six  or  eight  inches  will  generally  be  sufficient  in  the  first 
case,  and  the  total  depth  usually  varies  from  18  inches  to  3  feet.  The 
vertical  abutment  face  of  the  sill  may  be  formed  by  stone,  wood,  or  iron, 
assuming  that  there  is  always  a  wooden  member  of  the  gate  or  caisson  to 
•come  into  contact  with  it.  The  dressing  of  this  timber  face  necessitates 
great  care  and  good  workmanship,  for  upon  a  close-fitting  joint  depends 
the  absence  of  leakage. 

On  account  of  their  proximity  to  the  unprotected  earthen  floor  of  a 
dock,  the  sills  of  passages  and  the  inner  sills  of  locks  are  at  times  subject  to 
Tery  great  hydrostatic  pressure,  if  the  underlying  stratum  be  in  any  degree 
porous.  Instances  have  even  occurred  in  which,  with  a  rock  foundation, 
water  has  percolated  into  the  bed  joint  between  the  sill  and  the  rock, 
causing  the  former  to  uplift.  To  minimise  the  danger  arising  from  this 
caude  it  will  be  advisable  to  pierce  the  sills  with  a  series  of  vent  holes, 
lightly  covered  with  pieces  of  flagstone.  If  thp  bed  joint  remain  intact 
these  vents  will  not  be  called  into  action,  but  if  through  any  mischance 
water  should  penetrate  beneath  the  sill  at  a  time  when  there  is  little  or 
no  hydrostatic  counteraction,  it  is  infinitely  preferable  that  there  should 
be  a  means  of  escape  for  the  water  rather  than  that  the  full  effect  of 
th3  fluid  pressure  should  be  exerted  against  the  underside  of  the  sill  to 
its  detriment  and  possible  disruption.  From  the  foregoing  considerations 
it  is  obvious  that  weight  and  homogeneity  are  distinct  advantages  to  a 
sill. 

To  prevent  undermining  by  the  wash  of  the  tide  or  the  scour  of  a 
•current,  the  outer  sills  of  entrances  should  be  provided  with  a  masonry  or 
concrete  apron  extending  some  distance  in  front  of  the  sills. 

2.  Platf(yrm8, — These  form  the  floor  over  which  gates  and  caissons  are 
moved  in  and  out  of  position.  If  for  gates  fitted  with  truck  wheels  or 
caissons  with  rollers  or  slides,  they  will  be  provided  with  granite,  or  iron, 
or  steel  tracks,  the  last  two  firmly  bolted  down  to  the  masonry  or  concrete. 
Metal  roller  paths  for  gates  form  segments  of  circles  in  plan,  and  their 
upper  surfaces  are  bevelled  to  the  inclination  of  the  truck  wheels,  which  are 
truncated  cones,  on  account  of  the  greater  amount  of  travel  to  be  performed 
by  the  outer  edge.  The  axis  of  the  cone  will  intersect  the  axis  of  the 
pivot.  Caisson  tracks  are  either  flat  metal  surfaces  or  rails.  Occasionally, 
the  wheels  are  attached  to  the  floor,  and  the  track  or  sliding  surface  to 
the  underside  of  the  caisson.      A  platform  should  be  sufficiently  strong 


PRINCIPAL  CONSTRUCTIVE  FEATURES. 


255 


to  support  without  settlement  any  weight  which  may  be  concentrated  on 
a  limited  portion  of  its  area.  The  excess  weight  of  a  large  greenheart 
gate,  over  and  above  its  flotation,  may  amount  to  as  much  as  50  tons,  and 
this  has  to  be  divided  between  the  pivot  and,  say,  two  truck  wheels,  so  that 
the  three  points  of  contact  are  undergoing  a  stress  equivalent  to  a  pressure 
of  nearly  600  feet  of  water  more  than  the  remainder  of  the  platform  area» 
The  disparity  in  pressure  will  be  greatly  accentuated  for  intermediate  and 
outer  gates  at  such  times  as  when  the  lock  happens  to  be  dry ;  and  aa 
caissons  are  frequently  utilised  as  avenues  for  traffic,  it  is  well  to  remember 
that  the  effect  of  any  dead  or  moving  load  which  they  carry  is  transmitted 
direct  to  the  platform  below.  The  bedding  and  adjustment  of  the  wheel 
tracks  is  then  a  matter  for  careful  attention. 

3.  Side  recesses  for  gates  are  usually  curved  in  form  and  sufficiently  deep 
to  admit  of  the  gate  receding  well  beyond  the  face  line  of  the  side  walls,  in 
order  to  avoid  concussion  with  passing  vessels.  A  gate  recess  terminates  in 
two  returns,  or  quoins,  called  from  their  shape  the  hollow  quoin  and  the 
squctre  quoin  respectively.     The  former  receives  the  heel  post  of  the  gate 


Fig.  177.  FifiT.  178. 

and,  accordingly,  is  concave  in  plan,  forming  a  circular  segment.  Combined 
with  its  curved  junction  with  the  side  wall  it  may  be  described  as  a  modi- 
fied Ogee  or  Cyma  Recta.  There  are  two  types  of  hollow  quoin.  One, 
which  finds  favour  in  this  country,  provides  a  cylindrical  surface  in  close 
contact  with  the  heel  post  for  a  considerable  portion  of  its  circumference;. 
This  design  (tig.  177)  entails  very  accurate  and  careful  dressing,  and 
is  attended  by  the  inevitable  wear  of  the  contiguous  surfaces,  resulting  in 
leakage,  though  not  to  the  extent  which  might  be  supposed.  The  alter- 
native plan  (fig.  178),  in  vogue  in  Holland,  is  to  limit  the  amount  of  water- 
tight contact  to  a  narrow  straight  face,  about  8  inches  in  width,  the  dressing 
and  polishing  of  which,  being  a  plane  surface,  is  accomplished  with  greater 
facility  than  that  of  a  cylindrical  quoin.  At  the  outer  edge  of  the  quoin 
there  is  another  close-fitting  strip  to  prevent  the  passage  of  small  floating 
objects.  In  both  forms  of  quoin  the  friction  of  movement  may  be 
diminished  by  affording  a  slight  play  in  the  pivot,  by  which  the  gates 
revolve  out  of  contact  with  the  quoin.  Hydrostatic  pressure  causes  the 
surfaces  to  resume  their  watertight  abutment.  The  joints  of  hollow  quoins 
are  preferably-  bedded  in  lead  for  a  depth  of  6  inches  from  the  face.     Tho 


254  ^'^'^^  ENGINEKBING. 

stone  Bhould  be  of  a  very  hard  and  durable  quality.  Oranite  is  almost 
iuTariablj  used,  but  greenheart  timber  has  also  been  employed  with,  it  is 
stated,  moat  satis&ctory  results.  The  wear  of  the  heelpost  is  said  to  be 
less,  aud  the  cost  of  dressiug  the  surface  of  the  quoin  much  veduced.* 

At  the  base  of  the  hollow  quoin  is  situated  the  foundation  stone  to 
receive  the  gate-pivot  casting. 

Id  cases  where  chains  are  used  for  manteuvring  the  gates,  it  will  be 
advisable  to  attach  a  check  chain  from  the  top  of  the  mitre  post  to  a  volute 
«r  other  spring  fixed  in  the  neighbourhood  of  the  square  quoin,  to  avoid 
violent  impact  against  the  sill. 

Beceases  for  sliding  and  rolling  caissons  (fig.  179)  are  usually  rectangular 
chambers  constructed  normally  to  the  axis  of  the  passage.     They  require  to 


Fig.  179. — Caisaon  RecesB  at  Greeoock. 

be  slightly  longer  than  the  width  of  waterway,  and  to  be  slightly  wider  than 
the  caisson  itself.  In  some  cases  sufficient  room  is  left  between  the  caisson 
and  tbe  side  wall  of  the  chamber  to  allow  of  men  conveniently  effecting 
repairs  to  the  caisson  should  such  be  necessary,  the  chamber  being  rendered 
watertight,  temporarily,  by  timber  dams.  A  strong  covering  is  expedient 
■on  account  of  the  traffic  overhead. 

i.  The  tide  uxdla  of  a  lock  are  preferably  constructed  without  any  batter 
on  the  face.  With  the  water  at  widely  varying  levels  there  would  be  a 
danger  of  two  vessels,  locking  outwards  side  by  side,  nipping  each  other 
unless  the  walls  were  plumb.  Where  a  ship  caisson  is  used  for  closing 
the  entrance,  and,  for  that  purpose,  is  floated  into  grooves  in  the  walls,  a 
slight  batter  is  inevitable,  bnt  the  method  is  unusual  for  lochs  and  the 
-contingency  remote. 

'MoncrieffoQ  " Dock  Gales  of  Ircm  and  Steel,"  Jlfia.  Five.  Inst.  C,E.,  vol  cxvii. 


PRINCIPAL  CONSTRUCTIVE  FEATURES. 


255 


Sluice 


SuMpenaion. 
of  Sluice. 


Jcunh 


And  friction. 
RolUrt 


5.  The  levelling  calvert*  may  with  advaataf^e  be  arrangeil  so  that  their 
inlets  are  behind  the  holloir  qtioin  and  oik  n  level  with  the  gate  platform. 
In  this  way  they  assist  to 
keep  the  platform  and 
wheel  tracks  clear  of  mud. 
Where  caissons  are  em- 
ployed, the  culverts  may 
have  their  openings  into 
the  caisson  chamber  with 
the  same  object  in  view. 

The  flow  of  water 
through  culverts  is  regu- 
lated in  several  ways,  one 
or  two  of  which  will  be 
briefly  described. 

{a.)  At  a  certun  point, 
usnally  near  the  inlet,  the  ^iref^Ccn 
culvert  is  intersected  by  a  ^f  Pressure — 
elough-paddU  or  penstock 
(fig.  223).  This  consists 
of  a  substantia)  frame  of 
wood  or  iron,  faced  with  a 
plane  surface  sliding  in  side  ^^ 

grooves,  and  having  hori-  ¥"' 

zontal  bearings  against  a 
bear)  and  sill  in  the  roof 
and  floor  of  the  cnlvert 
respectively.  A  vertical 
shall  above  the  culvert 
permits  the  ]>addlB  to  be 
entirely  withdrawn  from 
the  sectional  Ojiening  of 
the  culvert.  Raising  and 
lowering  are  performed  by 
manual  labour  or  by  hy- 
draulic or  other  power. 
When  the  cnlvert  is  not 
Id  use  the  [)addle  is  kept 
down.  By  lifting  it  com- 
munioatioa  between  the 
outer  and  inner  water  is 
established,  and  if  there 
be  any  difference  of  level  a 
current  is  immediately  formed.  Ordinary  doughs  are  provided  with  atone 
(generally  granite)  jambs,  head,  and  sills,  the  slidiug  surfiMieB  being  polished. 


m. 


SiU 


Verlic^U    S  ecUan, . 


StoMiuJuttq 


Sluice. 


Jamb 


-iction, 
era 


Figs.  1 


Plan.. 

0  and  181.— Stooey  Sluice. 


256 


DOCK  ENGINEERING. 


The  paddle  is  slightly  larger  than  the  opening — about  6  to  12  inches  each 
way — and  may  be  either  tapering  in  thickness  or  with  parallel  faces.  It 
is  a  judicious  arrangement  to  have  duplicate  paddles,  one  being  actuated 
by  hand  in  case  of  mishap  to  the  other  worked  by  machinery. 

(fi)  Stoney  sluiceSy  so-called  from  the  name  of  their  inventor,  have  the 
friction  of  the  bearing  surfaces  during  movement  very  much  reduced  by  the 
employment  of  rollers.  The  doors  are  of  steel,  and  a  watertight  joint  ia 
formed  by  the  engagement  of  a  rod  in  a  V-shaped  groove.  Figs.  180  and  18.1 
explain  the  arrangements  adopted. 

(y)  Fan  doors  {partes  en  eventail)  are  adopted  in  some  instances  abroad. 
They  are  in  the  shape  of  a  right-angled  triangle  in  plan  (fig.  182),  with  a 
vertical  axis  at  the  corner,  formed  by  the  intersection  of  two  plane  surfaces 
of  unequal  area.  When  in  position  the  smaller  wing,  bearing  against  a 
wood-lined  frame,  cuts  off  the  culvert  connection.  To  open  the  gate  the 
larger  wing  has  to  revolve  within  a  cylindrical  chamber.     A  small  discharge 


— T~ 


S 


'"■'  '.■'//.' 

'.'/■I  /'it 


,///.'/.'//j//A 


1^ 


Fig.  182.— Plan  of  Fan  Door  at  Dunkirk. 


pipe  fitted  with  a  valve  serves  to  set  the  gate  in  motion.  While  the  valve 
remains  closed  the  up-stream  pressure  keeps  the  gate  shut.  As  soon, 
however,  as  the  valve  is  opened  the  water  in  the  cylindrical  chamber  escapes, 
down-stream  pressure  is  introduced  into  the  chamber,  and  the  difference 
causes  the  gate  to  revolve  on  its  pivot,  in  virtue  of  the  unequal  areaa 
exposed. 

(d)  Other  doors  or  gates  are  in  one  plane  surface  throughout,  turning 
upon  a  vertical  axis  slightly  out  of  centre.  By  opening  a  small  valve  in  the 
wider  panel  the  pressure  on  that  panel  is  reduced  below  the  pressure  on  the 
other  panel,  and  the  gate  revolves  so  as  to  set  itself  in  a  line  with  the 
stream.  Closing  the  valve  and  giving  the  gate  a  slight  sideways  displace- 
ment causes  the  current  to  act  with  greater  effect  on  the  larger  surface,  so 
that  the  gate  automatically  swings  to.  It  is  locked  in  position  by  a  turn  of 
.the  wooden  side  post 


DURATION  OF  LEVELLING  OPERATIONS.  257 

Duration  of  Levelling  Operations. — It  is  often  desirable  to  know  how  long 
it  will  take  to  level  up  a  lock  from  a  lower  to  a  higher  level  through  the 
medium  of  a  culvert.  If  the  source  from  which  the  water  for  the  purpose 
is  drawn  be  maintained  at  a  constant  level,  or  so  nearly  constant  as  to  be 
conceivably  treated  as  such,  the  calculation  is  a  simple  one.  The  theoretical 
velocity  is  v  =  S  Jh^  as  previously  explained.  This  multiplied  by  the 
sectional  area  of  the  culvert,  or  of  the  culverts  if  there  be  more  than  one, 
combined  with  a  suitable  coefficient  of  discharge,  gives  the  quantity  of  water 
passing  in  unit  time,  whence  the  total  time  is  obtained  by  dividing  into  the 
quantity  of  water  required  to  fill  the  lock.  Therefore,  algebraically,  the 
time  in  seconds, 

^^  Sacjh ^^^^ 

where  Q  is  the  quantity  required  in  cubic  feet,  a  the  culvert  area  in  square 
feet,  and  c  the  coefficient  of  discharge — varying  from  '5  to  *6,  according  as 
the  culvert  is  long  or  short. 

If  the  source  of  supply  be  not  maintained  at  a  sensibly  constant  level 
during  the  process  of  filling,  as  when  two  docks,  whose  areas  are  not 
very  excessively  unequal,  have  to  be  brought  to  a  common  level  by  inter- 
communication, a  suitable  formula  maybe  deduced  from  the  same  principles, 
as  follows  : — 

In  addition  to  the  previous  notation,  let  A^  and  A3  represent  the  areas 
of  the  docks  in  question,  h^  the  height  by  which  the  lower  dock  (A J  is 
raised,  and  h^  that  by  which  the  higher  dock  (A2)  is  lowered.  Then 
h^  +  h^  =  h. 

The  initial  velocity  of  influx  iaS  Jh,  the  final  velocity  is  zero ;  the  mean 
velocity,  therefore,  is  ^  J  h.     The  rate  of  influx  thus  becomes  4  ac  Jh, 

The  quantity  of  water  required  to  be  transferred  is,  indifferently,  Aj  h^ 

or  A2  h^ — that  is, 

Aj  Aj  =  Ag  Ag  ', 

but  h^  =  h  —  hy 

Therefore  A^  h^  =  Ag  (A  -  h^), 

or  7*1  (Aj  +  A2)  =  Ag  ^. 

That  is,  h,  =  j^-^  k. 

Substituting  this  value  for  A^  in  A^  h^,  the  quantity  of  water  required  to  be 
transferred  (Q),  and  completing  the  equation  as  in  the  previous  example  (42), 
we  finally  obtain — 

Aj  +  Aj       4  a  c  ^     ' 

Throughout  the  remarks  which  have  been  made  in  connection  with 
structural  operations  it  has  been  found  convenient  to  use  the  word  Lock 
as  a  more  or  less  generic  term  to  include  Entrance  and  Passage  as  well. 

17 


258  DOCK  ENGINEERING. 

Unless  the  sense  absolutely  precludes  such  an  interpretatioa  the  reader  will 
consider  the  principles  laid  down  as  applicable  and  common  to  all  forms  of 
narrow  dock  waterways.  In  one  respect  alone  does  a  passage  materially 
differ  in  design  from  a  lock.  A  lock  provided  with  gates  has  them  all  (with 
the  possible  exception  of  storm  gates)  pointing  in  the  same  direction, 
whereas,  in  a  passage,  the  gates  point  in  opposite  directions  in  order  to 
exclude  water  from  either  of  the  docks  which  it  serves  to  connect. 

Having  commented  as  fully  as  is  practicable  within  the  limits  imposed 
by  restrictions  of  space,  upon  the  various  matters  appertaining  to  the  design 
and  construction  of  locks,  we  now  pass  on  to  a  brief  review  of  some 
prominent  examples  selected  from  harbours  in  various  parts  of  the  world. 


Canada  Itook,  Iiirerpooi. 

Constructed  in  1857,  with  a  single  chamber,  having  an  effective  length 
of  498  feet,  a  width  of  100  feet,  a  depth  of  35  feet  9  inches  below  coping, 
and  a  draught  of  26  feet  9  inches  on  sill  at  h.w.o.s.t.,  this  lock  was 
deepened  in  1895  to  a  draught  of  33  feet  on  sill,  lengthened  to  602  feet,  and 
divided  by  a  pair  of  intermediate  gates  into  two  chambers  of  200  and  402 
feet  respectively.  In  addition  to  the  three  pairs  of  gates,  the  lock  pierheads 
are  fitted  for  the  reception  of  ship  caissons  in  the  event  of  repairs  being 
necessary  to  the  outer  sills. 


Fig.  183,— Section  ot  Old  Canada  Lock,  Liverpool. 

The  old  lock  was  constructed  entirely  in  masonry  and  intended  to  serve 
the  additional  purpose  of  a  graving  dock.  Henoe  the  peculiar  form  of 
section  adopted  and  shown  in  fig.  183.  The  recessed  panels  in  the  side 
walls  were  for  the  abutments  of  shores  to  the  sides  of  vessels.  In  the  course 
of  alteration  these  panels  were  filled  up,  as  also  were  the  lower  sluicing 
culverts,  except  for  short  lengths  on  each  side  of  the  gates,  where  they  are 
now  utilised  as  levelling  culverts. 

The  improvement  work  of  1895  consisted  in  removing  the  old  masonry 
floor  and  replacing  it  by  one  of  concrete,  at  a  depth  of  3  feet  3  inches  lower 
than  the  new  sill  level,  founded  on  the  boulder  clay  which  underlies  the 
whole  site.     The  concrete  was  composed  of  8  parts  of  gravel  to  I  of  Portland 


CANADA  LOCK,  LIVERPOOL. 


259 


•cement,  with  a  laige  proportion  of  sandstone  and  granite  burrs  thrown  in. 
The  thickness  of  the  new  floor  averages  7  feet,  and  the  upper  surface  is 
•coated  with  a  6-inch  layer  of  granolithic  concrete.  A  transverse  section 
'(fig.  184)  shows  the  floor  to  be  flat  for  a  width  of  80  feet  and  connected  with 
the  sides  by  circular  curves  of  10  feet  radius.  The  side  walls  were  under- 
pinned with  concrete  in  bays  of  from  12  to  15  feet  in  length.  A  gas-  and 
water-pipe  culvert,  5  feet  in  diameter,  is  arranged  below  the  floor  level. 

The  stone  work  comprises  copings,  hollow  quoins,  culvert  quoins,  caisson 
•quoins,  gate  sills,  caisson  sills,  calvert  sills  and  heads — all  of  Scotch  granite, 
with  square  quoins  of  sandstone. 

The  work  was  carried  out  in  the  following  manner : — ^The  outer  sill  in 
the  tidal  basin  was  reconstructed  during  low  water  of  spring  tides  in  small 
sections,  within  a  piled  dam,  which  was  pumped  out  on  each  occasion.  On 
the  completion  of  the  work  a  stank  of  concrete  blocks  was  built  across  it 


II 1 1 ,i.iji.....^ 


iii4ih  VaC^    OmUniMry    Spring     Tides 


x 


Mi^k^  WttUr   Orduvar^  -  ^«aM   Tides 


Floor  \  cf  Slit 


FUw  '-21  ^    CAamher 


J^M. 


.0 


Boulder       Clay 

Fig.  184.— Section  of  Canada  Lock,  Liverpool,  as  deepened. 


between  the  side  walls  of  the  lock,  and  carried  up  above  the  level  of  high 
water.  These  blocks  were  of  uniform  size,  1 1  feet  3  inches  by  3  feet  by 
3  feet^  each  containing  about  100  cubic  feet.  They  were  made  in  wooden 
moulds  at  least  a  fortnight  before  using,  and  were  deposited  by  means  of 
overhead  steam  travellers,  double  tracks  for  which,  64  feet  wide,  ran  the 
whole  length  of  the  lock.  To  ensure  watertightness,  the  blocks  were  bedded 
in  cement  mortar.  At  the  same  time,  to  facilitate  their  later  removal,  a 
Bheet  of  common  brown  paper  was  interposed  between  the  block  and  the 
mortar.  The  plan  answered  admirably,  the  blocks  being  perfectly  bedded 
without  the  undesired  adhesion.  It  is  needless  to  add  that  the  stability  of 
the  dam  in  no  way  depended  upon  the  tenacity  of  the  joints. 

The  inner  end  of  the  lock  was  enclosed  by  a  cofferdam,  constructed  of 
piles  and  timber  framing  and  filled  with  clay  puddle.  A  section  of  the  dam 
is  illustrated  in  fig.  66  (p.  107).  When  the  dams  were  completed  no 
difficulty  was  experienced  in  bringing  the  work  to  a  rapid  and  successful 
•conclusion.     Three  chain  pumps  with  wooden  blades,  2  feet  6  inches  by 


26o  DOCK  ENGINEERING. 

6  inches,  running  alternately  and  intermittently,  -were  found  adequate  to 
deal  with  all  infiltrations  of  water. 

The  North  Lock  at  Dunkirk.^ 

Prior  to  1896  the  port  of  Dunkirk  was  served  by  three  entrance  locks,, 
the  largest  of  which,  the  west  lock,  had  a  serviceable  length  of  only  384  feet 
and  a  width  of  69  feet.  As  far  back  as  1883  this  accommodation  was  found 
to  be  insufficient,  and  in  1887  the  project  of  a  large  new  lock  (fig.  185)  was 
approved,  at  an  estimated  cost  of  9|  million  francs.  The  dimensions  decided 
upon  were :  a  width  of  82  feet  and  lengths  of  687  feet  over  all,  580  feet 
between  outer  sills  and  558  feet  available  for  actual  use.  The  level  of  the 
sills  was  fixed  at  16  feet  6  inches  below  the  local  datum  (zero  of  marine 
charts),  so  that  there  is  an  available  draught  of  30  feet  at  lowest  neap  tides,. 
32  feet  6  inches  at  mean  neaps,  and  35  feet  9  inches  at  mean  springs.  The 
works  were  completed  and  the  lock  opened  for  traffic  in  1896. 

The  lock  is  provided  with  three  pairs  of  metal  ebb  gates,  by  means  of 
which  it  can  be  divided  into  two  chambers,  with  lengths  of  351  and  229  feet 
respectively,  for  the  purpose  of  reducing  the  period  of  locking  for  vessels  of 
moderate  or  short  length.  The  outer  gates  are  furnished  with  strut  frames 
as  a  support  against  rough  seas. 

The  filling  and  emptying  of  the  lock  are  achieved  by  means  of  two 
longitudinal  culverts  of  11  feet  6  inches  by  5  feet  9  inches  sectional  opening 
running,  one  on  each  side,  from  one  end  of  the  lock  to  the  other.  These 
culverts  are  closed  at  the  extremities  and  near  the  middle  by  swing  gates, 
of  the  type  called  fan  gates  (partes  en  eventaU),  and  they  are  in  permanent 
connection  with  the  lock  chamber  by  means  of  16  transverse  openings,  each 
6  feet  6  inches  wide.  The  dimensions  given  to  the  culverts  are  .such  that 
the  lock  can  be  filled  in  six  minutes  under  a  head  of  10  feet. 

Ship  caissons  can  be  berthed  at  both  ends  of  the  lock  in  case  of  accidents 
and  repairs.  The  opposite  quays  are  in  communication  by  means  of  a- 
centrally  situated  two-leaved  swing-bridge,  with  a  single  cart  track,  including 
a  line  of  rails.  A  metallic  culvert  of  circular  section,  6  feet  9  inches  in 
diameter,  forms  a  syphon  under  the  floor  for  the  transmission  of  water,  gas,, 
electric,  and  hydraulic  supply  mains. 

The  area  of  10  acres  which  formed  the  site  of  the  lock  between  the  outer 
channel  and  the  inner  docks  was  enclosed  by  means  of  two  cofferdams,  one 
at  each  end. 

The  outer  dam  (fig.  186)  was  based  on  the  sill  of  an  old  sluicing  lock 
after  the  removal  of  the  masonry,  closing  the  opening  between  the  side 
walls.  It  consisted  of  a  bank  of  sand  having  its  outer  slope  covered  by  a 
thick  layer  of  stiff  earth  (ipaiase  couch^  de  terre  forte),  with  stone  pitching 
superadded  as  a  protection  against  wave  action.  The  inner  dam  formed  a 
semicircle  in  plan,  projecting  into  the  adjoining  basin.     As  in  the  previous- 

*  Vide  L'Ecluee  Nord  et  sea  Aborda,  Dunkirk,  1896. 


?<^T 


I 


-case,  it  consiated  of  fine  cle&n 
s&nd  filling,  carefully  watered 
-and  rammed  in  thin  I&yers. 

The  foundatioDB  of  a  neigh- 
bouring lock  rest  directly  upon 
a  very  thick  bed  of  fioti  sand 
■which  underlies  the  district,  and 
a  similar  mode  of  foundation 
was  contemplated  in  the  first 
instance  for  the  new  lock.  But 
the  work  also  occupies  a  portion 
of  the  site  of  the  old  sluicing 
basin,  and,  on  examination,  it 
was  found  that  very  extensive 
excavation  liad  reentted  from 
water  scour  in  front  of  the 
sluice  gates,  and  that  the  sand 
bed    had    been  disturbed    to  a 

considerable      depth.        Conse-  ^ 

quently,  as  it  was  desirable 
that  so  im]iortant  an  under- 
taking should  rest  upon  a  * 
homogeneous  base,  it  was  de-  9 
cided  to  carry  out  a  general  | 
scheme  of  close  piling.                                                                                         J^ 

The  piles  employed  were  of 
oak,   of    10    inches    mean    dia.  g 

meter,  14  feet  9  inches  long 
under  the  floor  of  chamber, 
16  feet  3  inches  long  under  the 
sills,  and  It)  feet  long  under  the 
ftjirons.  The  piles  were  pitched 
at  distances  proportionate  to 
the  thickness  of  the  masonry, 
which  nttains  62  feet  in  the 
side  walls  of  the  pierheads  and 
is  reduced  to  13  feet  within 
the  chamber.  The  number  of 
piles  was  6,300,  and  they  were 
driven  by  ten  steam  -  piling 
machines  and  three  ringing 
machines. 

The  floor,  which  varies  in 
thickness  from  13  to  18  feet,  is 
formed  by  a  layer  of  brickwork, 


362  DOCK  ENQINEERINO. 

Bet  upon  a  concrete  bed  and  covered  b;  ashlar  masoniy  (^iitoaUon*  dCappai-eUj. 
[The  concrete,  6  feet  6  inches  thick  in  the  floor  of  the  lock,  10  feet  thick  in 
the  gate  platforms,  and  12  feet  thick  in  the  aprons,  was  composed  of  equal 
parts  of  hydraulic  lime  mortar  (Toumai  lime,  trass,  and  sand),  pebblM 
(jfolttt),  utA  broken  material  (briquei  roehta  eoncatsies).  The  Bectional  pro- 
file of  the  fioor  (fig.  167)  exhibits  a  fiat  centre,  42  feet  6  inches  in  extent, 
flanked  by  ourres  which  are  tangential  to  the  aide  walls. 


Fig.  1S7.— North  Look,  Dunkirk— Section. 

The  side  walls  were  executed  generally  in  local  brick  and  limestone,  set 
in  Portland  cement  mortar,  with  a  facing  of  ashlar  masonry.  Normandy  or 
Brittany  granite  was  used  for  the  sills,  hollow  quoins,  caisson  quoins, 
copings,  square  quoins,  culvert  apertures,  and  for  the  rounds  of  the 
pierheads  above  low  water.  The  mortar  was  composed  of  1  to  1^  parts  of 
Portland  cement  to  1  of  aand. 


The  NorttL  Iiook  at  Buenos  Ayres.* 

It  was  at  first  proposed  to  lay  out  the  northern  entrance  to  the  Madero 
Docks  in  a  north-easterly  direction  from  the  north  basin  to  the  outer  roads, 
where  there  is  a  long  stretch  of  water  having  an  average  depth  of  20  feet 
3  inches  below  low-water  level,  and  thence  in  a  S.E,  direction  to  the 
bar  anchort^.  This  line,  however,  waa  abandoned  as  likely  to  involve  an 
increase  in  silting,  owing  to  its  directly  transverse  situation  in  regard  to  the 
stream,  and  it  was  eventually  decided  to  turn  the  channel  as  quickly  as 
possible  into  the  rim  of  the  river  (see  iig.  8,  p.  37). 

The  north  lock  is  82  feet  wide  at  the  coping,  has  a  length  of  508  feet 

6  inches  between  sills,  and  a  draught  of  22  feet  over  sills  at  low  water.     It 
is  traversed  by  a  swing  bridge.    A  main  service  subway,  9  feet  10  inches  by 

7  feet  6  inches,  in  rubble  masonry,  lined  with  brickwork,  passes  under  the 
floor.     The  general  disposition  of  the  lock  will  be  readily  grasped  from  an 

"  Dobaon  on  "Buenos  Ayroa  Harbour  Works,"  Mm.  Proe.  Inet.  C.E.,  vol.  cxxxviii. 


iiiMiilWillliiiiiliUiliiliJiM^iiliiiliiiliiiiililililMiiL^ 


ENTRANCES  AT  BARRY  DOCKS.  263 

inspection  of  figs.  188  to  192.    The  following  interesting  experience  occurred 
during  its  construction  : — 

A  very  large  bed  of  running  sand  was  met  with  just  at  the  intended 
level  of  the  bottom  of  the  foundation  of  the  north  sill.  The  sand  was  so 
troublesome  that  all  pumping  had  to  be  at  once  suspended,  and  the  level  of 
the  bottom  of  the  foundations  raised  and  widened  out  so  as  to  reduce  the 
weight  per  unit  area  on  the  soft  white  to9ca  overlying  the  running  sand. 
To  overcome  the  difiiculty  an  iron  cylinder,  8  feet  in  diameter  (fig.  193), 
was  sunk  through  both  strata  into  the  hard  tosca  below,  the  excavation 
being  performed  by  a  diver.  When  the  cylinder  was  well  down,  a  good 
layer  of  strong  concrete  was  put  in,  making  the  cylinder  quite  watertight 
below,  while  it  was  allowed  to  receive  by  lateral  holes  the  drainage  from  the 
upper  white  tosca,  at  a  level  between  the  bottom  of  the  foundations  and  the 
top  uf  the  running  sand.  A  centrifugal  pump,  working  continuously,  kept 
the  water  in  the  cylinder  below  foundation  level.  Before  building  the 
masonry  of  the  north  sill,  the  entire  surface  was  covered  with  a  layer  of 
concrete,  25  inches  thick.  Laying  the  concrete  in  bags,  which  was  the 
method  first  attempted,  did  not  succeed,  and  canvas  in  long  strips  was  sub- 
stituted, with  the  joints  so  placed  that  the  water  would  run  underneath. 
This  plan  answered  well,  and  although  the  level  at  which  the  canvas  was 
laid  was  only  2  feet  above  the  running  saod,  the  whole  of  the  concrete  was 
put  in  quite  dry.  When  the  invert  was  completed,  the  cylinder  was  filled 
with  concrete  and  built  over. 

Eastham  Entrance  Looks. 

Manchester  Ship  Canal, — There  are  three  entrance  locks  (fig.  194)  con- 
structed in  parallel  lines  pointing  down  the  River  Mersey,  600  feet  by  ^  0 
feet,  350  feet  by  50  feet,  and  150  feet  by  30  feet,  respectively.  The  lower 
sill  of  the  largest  lock  Is  42  feet  below  liigh  water  of  ordinary  spring  tides. 
This  lock  has  culverts  on  each  side,  12  feet  high  by  6  feet  wide,  which 
enable  it  to  be  filled  or  lowered,  so  that  a  vessel  can  pass  through  in  less 
than  ten  minutes.  Two  20-foot  Stoney  sluices  adjoin  the  locks  and  assist 
to  fill  and  lower  the  canal  at  tide  and  flood  times  respectively. 

Entrances  at  Kidderpur  Docks,  Calcutta. 

Flans  and  sections  ef  tlie  entrance  locks  and  passages  at  these  docks 
which  have  already  been  referred  to  (p.  236)  are  shown  in  figs.  195  to  200. 

Entrances  at  Barry  Docks. 

The  harbour  is  approached  by  a  sheltered  channel,  450  yards  long, 
enclosed  by  two  breakwaters,  the  heads  of  which  are  350  feet  apart.  There 
are  two  entrances — one,  leading  to  a  basin,  is  available  for  2^  hours  before 
and  2^  hours  after  high  water  ;  the  other,  known  as  the  Lady  Windsor 


264 


DOCK  ENGINEERING. 


Lock,  can  be  used  at  any  state  of  the  tide,  having  a  depth  of  16  feet  of  water 
at  low  water  of  ordinary  spring  tides.  The  basin  entrance  and  the  passage 
between  the  basin  and  No.  1  Dock  are  each  80  feet  wide.  The  sills  are 
curved,  with  a  versed  sine  of  3  feet,  and  a  central  draught  of  40 '7  feet  at 
high  water  ordinary  springs,  and  32 '3  feet  at  high  water  ordinary  neaps. 
Timber  guiding  jetties,  200  feet  in  length,  are  erected  seaward  of  the  basin 
entrance,  and  a  masonry  jetty,  with  timber  fenders,  600  feet  long,  leads  to 
the  Lady  Windsor  Lock.  This  last  ha»  a  length  of  647  feet,  a  depth  of  60 
feet  and  a  width  of  65  feet.  It  is  divided  into  two  compartments  by  an 
intermediate  pair  of  gates.  The  depth  at  the  centre  of  the  curved  sills  is 
52*8  feet  at  high  water  of  ordinary  springs,  and  44*4  feet  at  high  water  of 
ordinary  neaps. 


Eglinton  Dock  Entrance,  Ardrossan.* 

The  walls  of  the  entrance  (fig.  201)  were  founded  on  rock  excavated  4  J 
feet  below  the  sill,  which  is  level  with  the  bottom  of  the  dock  and  tidal 
basin ;  the  gate  floor  is    18  inches  lower  than  the  sill.      The  sluices  on 


Fig.  201. — Entrance  to  Eglinton  Dock,  Ardrossan. 

each  side  of  the  entrance  are  3  feet  wide  and  4  feet  high,  with  inlet  sluices, 
2  feet  wide  and  2  feet  high,  at  the  bottom  of  the  gate  recess.  The  sill- 
stones,  hollow  quoins,  and  sluice  chamber  guides  are  of  granite,  the  rest  are 
built  in  rubble  concrete,  except  the  sill,  gate  floor,  and  aprons,  which  are  of 
concrete. 

♦Robertson  on  "Ardrossan  Harbour  Extensions,"  Min.  Proc.  Imt,  C.E.,  vol.  cxx. 


{To  fam  raft  tCA. 


^4 


THE  ALEXANDRA  LOCK,  HULL.  265 

The  Alexandra  Look,  Hull.^ 

This  lock  is  85  feet  wide  and  550  feet  long,  divided  into  two  compart- 
ments of  325  and  225  lineal  feet  respectively.  The  filling  and  emptying  of 
the  lock  are  done  by  means  of  two  pairs  of  5-foot  culverts,  constructed  in 
the  walls  at  low-water  level.  On  one  side  of  the  sill  these  culverts  open 
into  the  gate  recesses,  and  their  inlets  are  closed  by  external  paddles  of 
greenheart,  resting  against  granite  faces  and  worked  by  hydraulic  power. 
The  two  outer  sills  are  18  inches  deeper  than  the  inner  one.  The  outer 
gates  weigh  176  tons,  exceeding  the  weight  of  the  inner  gates  by  6  tons. 
The  roller  path  is  of  cast  steel,  accurately  and  carefully  bedded  on  granite. 

The  difficulties  encountered  during  the  construction  of  this  lock  are  very 
instructive.  The  site  was  covered  with  toarp  or  river  mud,  which  was  stiff 
and  sticky  inshore,  but  softer  further  out,  encrusting  in  drying,  with  a  soft 
interior.  It  varied  in  thickness  up  to  27  feet,  and  below,  beds  of  warp, 
sand,  gravel,  clay,  and  peat  were  met  with  in  no  definite  order. 

The  foundations  of  the  lock  were  designed  to  be  laid  at  48^  feet  below 
high-water  spring  tides,  or  32^  feet  below  the  level  of  the  mud.  The  walls 
at  the  south  end  of  the  lock  were  commenced  in  deep  trenches,  owing  to  the 
impossibility  of  excavating  the  fluid  mud  in  the  open.  In  the  western 
trench,  clay  was  not  met  with  until  51  feet  below  high- water  spring  tides,  or 
2 J  feet  deeper  than  was  anticipated.  A  "blow  "  occurred  at  one  point,  but 
was  promptly  remedied  before  any  extensive  disturbance  could  result.  An 
iron  pipe  was  placed  in  the  hole,  and  surrounded  by  chalk  rubble,  filling 
the  hole  to  the  surface  level  of  the  clay,  which  was  then  covered  over  with 
Portland  cement  concrete  in  bags,  upon  which  the  foundation  concrete  was 
laid.  A  good  deal  of  fine  silt  was,  at  first,  brought  up  with  the  water,  but, 
eventually,  the  effluent  became  quite  clear,  and  was  led  away  in  a  horizontal 
pipe  to  a  pumping  well,  the  vent  being  kept  open  to  the  last.  One  or  two 
other  cases  occurred  and  were  similarly  treated.  The  source  of  the  leaks 
was  practically  only  the  water  contained  in  the  strata,  the  connection  with 
the  river^  as  indicated  by  the  variations  in  tidal  level  and  head,  being  very 
remote. 

At  the  north  end  of  the  lock  the  foundations  caused  more  serious 
trouble.  After  clay  had  been  reached  through  remarkably  dry  excavation, 
the  bottom  of  the  trench  suddenly  began  to  heave,  and  water  burst  up  in 
several  places  in  such  quantities  as  to  master  the  pumps.  Additional 
pumping  power  failed  to  make  any  impression.  The  sides  of  the  trench 
began  to  be  undermined  by  the  escape  of  silt ;  the  ground  settled,  and  large 
holes  appeared  in  the  vicinity.  These  last  were  staunched  with  clay  puddle, 
stable  litter,  straw,  and  bags  loosely  filled  with  Portland  cement  concrete. 
Soundings  showed  a  layer  of  silt,  5|  feet  thick,  at  the  bottom  of  the  trench, 
while  a  40-foot  rod  failed  to  reach  the  bottom  of  the  blowhole.  The  total 
collapse  of  the  trench  was  threatened,  so  that  strong  lacings  had  to  be 

♦  Hurtzig  on  "The  Alexandra  Lock,  Hull,'*  Min.  Proc.  Inst.  C.E.,  vol.  xcii. 


266  DOCK   ENGINEERING. 

ioserted  and  other  preventive  steps  taken.  Pumping  was  reduced  to  the 
miuimum  necessary  for  getting  in  a  piled  foundation  for  the  side  walls  at 
the  highest  jMSsibie  level.  The  boles  were  filled  with  chalk  rubble  and  the 
whole  area  covered  with  it  in  order  to  intercept  the  flow  of  silt.  Bearing  ■. 
piles  were  then  driven  between  a  network  of  temgwrary  timbering,  connected 
at  the  top  by  whole  timber  caps  and  covered  with  a  double  thickness  of  elm 
planking.  As  regards  the  origin  of  the  water  in  the  blows,  investigations 
seemed  to  iudicate  the  existence  of  parallel  water-courses  below  the  bed  of 
clay  mnniiig  transversely  to  the  lock. 

The  pfincipal  difficulty  being  anticipated  at  the  inner  gate  platform,  it 
was  proposed  to  excavate  the  foundation  in  small  areas,  enclosed  by  half 
timber  sheeting,  grooved  and  tongued,  but  after  a  few  piles  had  been  driven 
some  blows  occurred  at  the  surface,  which  was  a  little  above  dock  bottom, 
and  water  came  up  in  considerable  quantities.  Large  holes  formed,  and  some 
of  the  sheeting  disappeared.  Cast-iron  pipes  were  driven  vertically  into  the 
two  priiioipa!  springs,  and  in  one  of  these  the  water  reached  a  height  of 
14  feet  above  dock  bottom.  Several  hundred  yards  of  clay  puddle  were 
absorbed  by  one  hole  alone.  To  reach  the  origin  of  the  disturbance  it  was 
clearly  necessary  to  carry  the  sheeting  lower  down,  and  accordingly  pitch 
pine  piles,  14  inches  square  and  50  feel  long,  grooved  and  tongued,  were 
driven  so  as  to  enclose  the  disturbed  area  and  cut  ofl'  the  flow  of  water, 
which  was  eSectively  done  and  the  foumlatious  completed.  The  roller 
path  stones  and  sills  were  laid  on  elm  plaiforms  over  hearing  piles.  The 
discharge  through  one  of  the  blowhole  pipes  was  stopped,  but  the  water 
continued  to  flow  through  the  other  until  the  pipe  was  closed  at  the 
completion  of  the  works. 

New  Look  at   Bremerhaven. 
This  lock  (6g.  206)  has  an  efficient  length  of  656  feet,  or  a  length  of 
705  feet  between  gates.     The  breadth  of  the  entrance  is  92  feet,  and  of  the 


Fig.  206.— Bremerharen  Lock. 

chamber  147  feet,  so  that  the  largest  passenger  steamers  can  lie  there 
preparatory  to  starting  and  receive  cargo  from  lighters.  The  depth  is 
sufficient  to  accommodate  ships  drawing  31  feet  during  neap  tides.     An 


SeCTIOIr      ACROSS     LOCK 


NEW  LOCK   AT  BREMERHAVEN.  267 

invert  in  the  floor  of  the  lock  has  been  dispensed  with  as  unnecessary,  since 
no  sprins^s  were  likely  to  be  found  in  the  stiff  clay  on  which  the  lock  stands. 
The  walls,  which  contain  the  levelling  culverts,  are  founded  on  inclined 
piles,  in  rows,  4  feet  apart.  They  are  inclined  alternately  in  opposite 
directions,  an  arrangement  which  secures  a  favourable  distribution  of  the 
forces  acting  on  the  piles,  and  has  the  further  advantage  that  the  pile-heads 
are  not  so  near  together,  and  the  piles  can  consequently  be  driven  deeper 
into  tlie  solid  ground.  The  inner  end  of  the  lock  is  closed  by  a  sliding 
caisson,  the  outer  end  by  a  pair  of  iron  gates.  The  former  was  selected  on 
grounds  of  economy  and  utility  as  a  movable  bridge,  the  latter  by  reason  of 
their  greater  strength,  for  during  spring  tides  a  strong  current  flows  through 
the  lock  into  the  Kaiser  Dock,  which  during  southerly  winds  is  considerably 
increased  by  the  heaping  up  of  the  tide  on  the  Bremerhaven  shore.  This 
current,  aided  by  the  force  of  the  waves  and  the  pressure  of  the  wind, 
exerts  a  force  which,  it  was  considered,  could  not  be  so  well  resisted  by  a 
sliding  caisson,  supported  at  one  end  only,  as  by  two  strong  gates. 


268 


CHAPTER  VII. 

JETTIES,   WHABFS,   AND   FIEBS. 

Definitions — Stresses — Wave  Action — Force  of  Impact — Results  of  Impact — 
Observed  Pressures — Instances  of  Wave  Action  —  Design  of  Jetties  and 
Piers  —  Construction  —  Concrete  Mass,  Bag,  and  Block  Work  —  Dressed 
Masonry  and  Rubble  Mounds — Fascine  Work — Open  Timber  Framing  and 
Crib  Work— Columnar  Structures  and  Frameworks  of  Iron  and  Steel — 

MONIER    AND    HeNNEBIQUE    SySTEMS  —  TVPICAL    EXAMPLES    AT    ABERDEEN,    ZSE- 

brugge,  Havre,  Kingstown,  Algiers,  Hook  of  Holland,  Blyth,  Liverpool, 
Newcastle,  Soukhoum,  Touaps^,  Belfast,  Dundee,  Dunkirk,  Tilbury,  Madras, 
Sunderland,  Greenock,  and  Hull. 

In  one  sense,  and  that  perhaps  the  most  important,  jetties,  wharfs,  and 
piers  may  be  looked  upon  as  constituting  the  outlying  or  advance  works 
of  a  dock  system.  It  is  quite  true  that  they  are  by  no  means  exclusive, 
or  even  indispensable  features,  being  found  at  many  ports  which  have  no 
docks  and  absent  from  others  where  docks  are  numerous.  Furthermore, 
they  do  not  always,  or  necessarily,  occupy  outlying  positions,  being  often 
located  in  sheltered  basins  and  even  within  docks  themselves. 

Seeing,  however,  that  their  most  important  functions  are  discharged  in 
connection  with  exposed  situations,  we  shall  deal  with  them  mainly  from 
this  standpoint,  and  afterwards  consider  their  adaptation  to  more  sheltered 
areas.  And  as  to  the  strict  propriety,  or  otherwise,  of  treating  such 
structures  as  forming  an  integral  part  of  a  dock  system,  we  need  not 
concern  ourselves  too  closely.  The  fact  that  they  do  play  so  prominent 
a  r6le  in  many  cases,  and  that  they  have  indubitably  demonstrated  their 
ability  as  accessory  features  generally,  is  sufficient  justification  for  treating 
the  subject  in  its  broadest  aspect. 

Definitions. — Our  first  duty  is  a  delimitation  of  the  respective  con- 
stituents of  the  group. 

It  is  no  easy  matter  to  draw  a  strict,  or  even  a  serviceable,  distinction 
between  the  various  types.  A  jetty  is  radically  that  which  juts  out  or 
projects,  and  the  term  is  appropriately  applied  to  all  structures  which 
project  from  the  general  contour  of  any  littoral.  But  it  shares  this 
signification  in  common  with  piers  and  moles,  both  of  which  are  similar 
projections.  The  primary  meaning  of  the  word  pier  is  apparently  con- 
nected with  the  notion  of  support,  and  it  is  commonly  used  in  engineering 
to  indicate  the  intermediate  props  or  supports  of  a  series  of  arches. 
Probably  from  this  association,  an  idea  of  isolation  or  detachment  has  been 


DEFINITIONS.  269 

acquired,  and  hence  its  application  to  maritime  structures,  the  connection  of 
which  with  the  mainland  is  of  a  slight  and  restricted  nature.  This  feature, 
however,  is  equally  characteristic  of  jetties  and  moles.  The  word  mole  ia 
evidently  derived  from  the  Latin  moles,  a  mass,  and  is  indicative  of  a 
large  mound,  or  long  ridge  of  material,  heaped  more  or  less  regularly,  in 
such  a  way  as  to  constitute  some  protection  from  rough  external  seas.  In 
this  respect  it  fulfils  the  functions  of  a  breakwater,  with  which  it  is  closely 
allied,  though,  in  later  times,  it  has  acquired  the  special  significance  of  a 
breakwater  provided  with  a  broad  superstructure  capable  of  being  used  as 
an  ordinary  quay.  Perhaps  the  position  may  be  best  summarised  thus : — 
Outlying  works  in  exposed  situations,  used  for  protective  purposes  alone, 
are  breakwaters.  When  joined  to  the  shore,  and  equipped  for  commercial 
operations,  they  become,  almost  indifferently,  piers,  jetties,  and  moles» 
Accordingly,  the  latter  terms  will  be  employed,  in  the  present  chapter,  as 
practically  synonymous. 

A  wharf  may  be  defined  as  a  continuous  structure,  occasionally  acting 
as  a  retaining  wall,  along  the  open  margin  of  a  sea,  or  along  the  banks  of 
a  river,  canal,  or  other  waterway.  The  application  of  the  word  is  some- 
what loose,  and  it  is  sometimes  taken  as  identical  with  quay,  though  ita 
use  in  connection  with  dock  and  basin  walls  is  rare.  Wharfs  have 
obviously  provided  the  most  natural  sites  for  the  berthing  of  vessels 
from  the  earliest  times,  being  employed  for  this  purpose  long  before  the 
ideas  of  outlying  jetties  and  enclosed  basins  were  conceived.  In  this 
connection,  they  are  subdivisible  into  two  classes — legal  wharfs  and  suffer- 
ance  wharfs.  The  former  are  certain  wharfs,  in  all  seaports,  at  which 
goods  were  required  to  be  landed  and  shipped  by  Act  1  Eliz.,  cap.  11  (now 
repealed),  and  subsequent  acts.  Some  wharfs,  as  at  Chepstow,  Gloucester,, 
d^.,  are  deemed  legal  from  immemorial  usage ;  others  have  been  made 
legal  by  special  Acts  of  Parliament.  Sufferance  wharfs  are  places  where 
certain  goods  may  be  landed  and  shipped — as  hemp,  fiax,  coal,  and  other 
goods — by  special  sufferance,  granted  by  the  Crown  for  that  purpose.* 
These  legal  distinctions,  however,  have  no  bearing  on  the  engineering, 
aspect  of  the  question. 

From  their  close  relationship  to  ordinary  quays,  much  that  has  been 
said  in  Chapter  v.  is  equally  applicable  to  wharfs,  but  need  not  be 
repeated  here. 

As  part  of  a  dock  system,  external  jetties  and  piers  serve  a  twofold 
purpose.  In  the  first  place,  they  act  as  protective  works,  by  means  of  which 
vessels  are  guided  and  sheltered  during  their  entry.  Secondly,  they  serve 
as  directive  agencies  for  the  deflection  or  regulation  of  currents.  Whether 
intentionally  on  the  part  of  the  designer  or  not,  this  second  function  is  on& 
which  must  inevitably  be  performed  by  any  artificial  projection  beyond  the 
normal  contour  of  a  littoral.  Hence  it  behoves  the  engineer  to  exercise 
great  care  in  determining  the  location  and  disposition  of  a  proposed  jetty  or 

*  Dr.  Ogilvie. 


270  DOCK  ENGINEERING. 

pier,  lest  serious  or  even  disastrous  consequences  ensue.     The  effect  of  a 
misplacement  might  be  the  shoaling  of  a  hitherto  navigable  channel. 

Unfortunately,  the  conditions  affecting  fluvial,  estuarine,  and  marine 
currents  are  too  complex  for  anything  of  the  nature  of  a  brief  and  satisfactory 
resume,  and  the  subject,  in  deed,  constitutes  a  branch  of  maritime  engineering 
which  scarcely  comes  within  the  purview  of  the  present  treatise.  There  can, 
however,  be  no  doubt  that  the  influence  of  training  workH,  in  the  foim  of 
walls  and  dykes,  upon  the  augmentation  and  maintenance  of  waterways  is 
very  powerful,  and  that,  judiciously  employed,  they  are  a  valuable  means 
for  increasing  the  accessibility  of  a  port.  There  are  several  instances  of 
such  works  in  existence,  notably  at  the  mouths  of  the  Tees  and  the  Kibble, 
where  training  works  have  been  recently  constructed  in  order  to  afford  a 
navigable  channel,  in  the  iirst  instance  to  the  ports  of  Middlesbrough  and 
Stockton,  and  in  the  second  to  the  town  of  Preston. 

External  jetties  are  either  detached  or  arranged  in  pairs.     Of  double 

jetties  there  are  three  forms — viz.,  parallel,  convergent,  and  divergent. 
Parallel  jetties  are  mainly  used  for  training  purposes,  as  at  Leith  and 
Ostend ;  convergent  jetties  enclose  a  sheltered  basin  or  outer  harbour,  as  at 
Barry  and  Sunderland ;  divergent  jetties  afford  guidance  and  direction  to 
vessels  entering  a  narrow  waterway,  as  at  the  Alexandra  Dock,  Hull,  the 
Canada  Basin,  Liverpool,  and  the  Tilbury  Docks,  London. 

Jetties  are  also  to  be  found  in  the  interior  of  many  docks,  especially 
those  of  large  size,  with  the  object  of  increasing  the  proportion  of  quayage 
to  water  area.     Thus  the  south-west  India  Dock,  London,  with  an  area  of 

26|  acres,  is  furnished  with  16  jetties,  affording  accommodation  to  32  vessels. 

The  Victoria  Dock,  at  the  same  port,  has  13  jetties  in  an  area  of  74  acres. 

The  Alexandra  Dock,  at  Hull,  has  4  jetties  in  an  area  of  46^  acres. 

Wide  projections,  of  solid  construction,  into  the  interior  of  a  dock  are 

designated  Tongties,  such  as  the  Canada  Tongue  at  Liverpool.     They  really 

constitute  an  integral  part  of  the  dock  outline. 

Short  tongues  or  jetties  used  for  coaling  purposes  are  called    Staiths, 

There  are  13  staiths  at  the  Penarth  Dock  and  31  at  Barry  Docks. 

Stresses  in  Piers  and  Jetties. — In  Chapter  vi.  some  consideration  has 

already  been  given  to  the  character  and  influence  of  various  natural  agencies 

in  so  far  as  they  affect  the  navigability  and  usefulness  of  dock  entrances. 

In  the  present  section  it  will  be  necessary  to  supplement  this  information 

by  some  observations  on  the  effect  of  these  agencies  upon  the  stability  and 

durability  of  exposed  structures. 

Wave  action  alone  calls  for  serious  notice.     The  effect  of  wind  pressure 

upon  the  superstructure  of  a  pier  is  trifling  compared  with  that  of  the  onset 

of  waves  upon  its  base.     The  only  danger  to  be  apprehended  from  currents 

is  their  tendency  to  undermine  the  foundations,  and  this  can  readily  be 

guarded  against  by  the  exercise  of  the  precautions  indicated  in  Chapter  v. 
The  mathematical  theory  of  waves  is  a  physical  question  too  purely 

academic  for  discussion  in  an  engineering  treatise.     Students  who  desire 


STRESSES  IN  PIERS  AND  JETTIES.  27 1 

information  on  the  subject  are  referred  to  the  articles  on  "  Wave  "  in  each 
of  the  Encyclopsedias,  Britannica  and  Metropolitana. 

The  points  which  more  immediately  concern  the  engineer  are  the  nature, 
direction,  and  magnitude  of  the  disruptive  forces,  as  determined  by  actual 
observation. 

Although  waves  have  been  divided  into  two  classes — those  of  oscillation 
and  those  of  translation — it  is  probable  that  all  waves  are  more  or  less 
waves  of  translation,  causing  the  particles  of  which  they  are  composed  to 
move  forward  iiorizontally  to  some  extent.  Certainly  this  is  the  case  with 
all  lar:^e  and  important  waves  affecting  the  stability  of  maritime  works. 

When  a  wave  advances  into  water  which  becomes  increasingly  shallow, 
its  energy  is  communicated  to  successively  decreasing  masses,  and  there  is 
consequently  a  tendency  to  produce  in  those  masses  a  greater  and  more 
violent  agitation  ;  but  this  effect  is  generally  diminished,  and  sometimes 
entirely  counteracted,  by  the  loss  of  energy  due  to  friction  along  the  bottom, 
and  to  eddies  and  surging. 

The  bottom  friction  produces  a  distortion  of  the  elliptical  orbits  of  the 
particles  of  water,  causing  the  crest  to  advance  more  quickly  than  the 
trough.  At  length  the  crest  overhangs  the  face  slope,  fails  forward,  and 
breaks  into  surf.  At  this  point  the  forward  motion  of  the  particles  is  equal 
to  the  velocity  of  the  wave,  and  the  stroke  represents  the  maximum  effort 
of  the  latter.  Now,  the  velocity  of  a  wave  in  shallow  water  is  found  to  be 
nearly  the  same  as  that  which  would  be  acquired  by  a  heavy  body  in  falling 
freely  from  rest,  under  the  action  of  gravity,  through  a  height  equal  to  the 
semi-depth  of  the  water  plus  three-fourths  of  the  height  of  the  wave. 
Accordingly,  we  have 

V  ^  ^9  (d  ^  yj,      ....     (44) 

where  v  is  the  velocity  of  the  wave,  h  its  height,  and  d  the  depth  of  the 
water. 

When  the  depth  of  water  exceeds  the  length  of  the  wave,  the  speed  of 
the  latter  is  practically  independent  of  the  depth,  and  is  almost  exactly 
equal  to  the  velocity  acquired  by  a  body  falling  through  half  the  radius  of  a 
circle  whose  circumference  is  the  length  of  the  wave. 

The  reaction  of  a  surface  subjected  to  the  force  of  continuous  impact  is 
measured  by  the  rate  at  which  momentum  is  destroyed.  Hence,  if  to  be  the 
weight  of  a  unit  volume  of  water,  wv  is  the  mass  which  impinges  on  unit 
surface  in  unit  time,  and  wv^  is  therefore  the  amount  of  momentum.  And 
since  the  weight  of  1  lb.,  falling  freely,  generates  in  one  second  t/  units  of 
momentum,  the  reaction  of  the  surface  will  be  equivalent  to  a  weight  of 

'  and  this  represents  the  pressure  per  unit  area  due  to  the  impact. 

y 

Lieut.  Gaillard  (Corps  of  Engineers,  U.S.  Army),  has  demonstrated  by 

experiments   upon   small  areas  that  the  maximum   intensity  of  force  in 

breaking  waves  in  such  cases  occurs  at  a  level  slightly  above  still  water, 


272  DOCK  ENGINEERING. 

diminishing  to  zero  at  the  crest,  and  to  one-half  the  maximum  at  the 
bottom.  But  like  wind-pressure  data,  results  on  small  areas  are  no  guide 
to  stresses  over  exten8iye  surfaces. 

If  a  wave,  before  breaking,  reaches  a  wall  or  other  obstruction  having 
an  abrupt,  vertical  face,  it  is  reflected  in  the  following  manner: — The 
particles  of  water  in  contact  with  the  wall  move  up  and  down  through  a 
height  double  the  height  of  the  original  wave.  At  a  distance  away  from 
the  wall  equal  to  a  quarter  of  the  length  of  the  wave,  the  particles  move 
horizontally  backwards  and  forwards.  Between  these  two  points  the  motion 
of  the  particles  is  a  compound  one,  and  movement  takes  place  at  various 
angles. 

Consequently,  the  action  of  waves  upon  a  pier  or  jetty  must  be  t&ken  as 
resulting  in  the  creation  of  four  distinct  forces  : — 

1.  A  direct  horizontal  force  exerting  compression. 

2.  A  deflected  vertical  force,  acting  upwards  and  tending  to  shear  any 
projections  beyond  the  surface  of  contact. 

3.  A  vertical  downward  force  upon  the  base  of  the  wall,  due  to  the 
collapse  of  the  wave. 

4.  The  suction  of  the  back  ilrauglit  upon  the  foundation. 

Apart  from  the  hydrostatic  pressure,  augmented  to  a  very  considerable 
degree  by  tlie  force  of  impact,  the  following  subsidiary  results  will  take 
place,  viz.  : — 

1.  A  vibration  of  the  structure  tending  to  weaken  the  connection  of  the 
various  parts. 

2.  A  series  of  impulses  imparted  to  particles  of  water  contained  in  the 
pores  and  joints  of  the  structure,  producing  internal  pressure  in  various 
directions. 

3.  The  condensation  and  expansion  of  air  confined  in  cavities  and  inter- 
stices, causing  disruption. 

It  is  impossible  on  any  purely  theoretical  basis  to  determine  with  the 
least  degree  of  accuracy  and  precision  the  magnitude  of  these  various 
stresses.  Practical  observation  must  therefore  be  called  in  to  supply  the 
deficiency,  by  providing  data  as  to  the  maximum  stresses  likely  to  be 
encountered.  Investigations  have*been  made  in  several  instances  with  the 
aid  of  a  marine  dynamometer,  devised  by  Stevenson,  with  the  result  that 
in  the  most  exposed  cases,  the  pressure  registered  did  not  exceed  3^  tons  per 
square  foot.  With  waves  10  feet  high,  a  mean  pressure  of  1*36  tons  was 
indicated.     Other  instances  are  as  follows  : — 

At  Skerry vore,  from  2 J  to  2 J  tons  per  square  foot. 

At  Bell  Rock  (German  Ocean),  1^  tons  per  square  foot. 

At  Dunbar  (East  Lothian),        3^     „      „  „ 

At  Buckie  (Banffshire),  3       „      „  „ 

Experiments  by  Mr.  Frank  Latham,  at  Penzance,  showed  a  pressure  of 
18  to  20  cwts.  per  square  foot,  at  right  angles  to  a  sea  wall,  in  10  feet  of 
water,  with  a  wind  pressure  of  15  to  18  lbs.  per  square  foot. 


INSTANCES  OF  WAVE  ACTION.  273 

At  Cherbourg,  the  force  of  waves  in  storms  has  been  found  to  vary  from 
600  to  800  lbs.  per  square  foot. 

Instances  of  Wave  Action, — The  following  are  a  few  recorded  instances 
of  the  feats  performed  by  waves  : — 

During  a  summer  gale,  in  the  year  1869,  fourteen  stones,  each  2  tons  in 
weight,  part  of  the  structure  of  the  Dhu  Heartach  Lighthouse,  which  had 
been  laid  in  Portland  cement  and  fixed  in  their  places  by  joggles,  at  a  level 
of  35  feet  6  inches  above  high  water,  were  torn  up,  and  eleven  of  them  swept 
off  the  rock  into  deep  water.* 

During  the  storms  of  December,  1896,  and  January,  1897,  blocks, 
weighing  40  tons  each,  used  in  the  construction  of  Peterhead  breakwater, 
were  displaced  in  courses  bedded  respectively  at  the  levels  of  17  feet  1^  inches 
and  23  feet  7^  inches  below  low  water  of  spring  tides.  One  of  these  blocks 
lodged  on  a  concrete  platform,  30  feet  7  inches  below  low  water,  and  was 
washed  away  during  a  storm  in  the  following  March,  t 

The  destruction  of  the  outer  extremity  of  the  breakwater  at  Wick,  in 
December  of  the  year  1872,  is  described  in  a  report  by  Messrs.  Stevenson 
to  the  directors  of  the  British  Fishery  Society.  J  The  end  of  the  work  was 
protected  by  a  mass  of  cement  rubble  work.  It  was  composed  of  three 
courses  of  large  blocks  of  80  to  100  tons,  which  were  deposited  as  a  founda- 
tion on  the  rubble.  Above  this  foundation  there  were  three  courses  of  large 
stones  carefully  set  in  cement,  and  the  whole  was  surmounted  by  a  large 
monolith  of  cement  rubble,  measuring  about  26  feet  by  45  feet  by  11  feet 
in  thickness,  and,  at  16  feet  to  the  ton,  weighing  upwards  of  800  tons.  This 
block  was  built  in  situ.  As  a  further  precaution,  iron  rods,  3|  inches  in 
diameter,  were  fixed  in  the  uppermost  of  the  foundation  courses  of  cement 
rubble.  These  rods  were  carried  through  the  courses  of  stonework  by  holes 
cut  in  the  stone,  and  were  finally  embedded  in  the  monolithic  mass  which 
formed  the  upper  portion  of  the  pier.  Incredible  as  it  might  seem,  this 
huge  mass,  weighing  not  less  than  1,350  tons  and  presenting  an  area  of  496 
square  feet  to  the  sea,  was  gradually  slewed  round  by  successive  strokes 
until  it  was  finally  removed  and  deposited  on  the  rubble  inside  the  pier, 
having  sustained  no  damage  beyond  a  slight  fracture  at  the  edges.  The 
lower  or  foundation  course  of  80-ton  blocks,  which  were  laid  on  the  rubble, 
at  a  depth  of  15  feet  below  low  water,  retained  their  positions  unmoved. 
The  second  course  of  cement  blocks,  on  which  the  1,350  tons  rested,  was 
swept  off  after  being  relieved  of  the  superincumbent  weight,  and  some  of 
the  blocks  were  found  entire  near  the  end  of  the  breakwater. 

The   displaced  mass   was  succeeded   by  a  still  more  enormous  block, 
weighing  no  less  than  2,600  tons,  which,  after  remaining  undisturbed  for 

♦  Stevenson  on  "  The  Dhu  Heartach  Lighthouse,"  Min.  Proc,  Inst,  C,E.,  vol.  xlvi. 
t Shield  on  "The   Effects  of  Waves  on  Breakwaters,"  Min,  Proc,  Inst,   C.E,, 
vol.  oxxzviii. 

J  Vide  3fin,  Proc,  Inst.  CK,  vol.  xliii. 

18 


2  74  1>0CK  ENGINEERING. 

three  years,  was  carried  away  bodily  by  a  storm  in   January,  1877,  and 
deposited  in  two  pieces  within  the  line  of  the  breakwater. 

But  even  this  is  not  the  limit  of  wave  power.  Daring  the  storm  of 
October,  1898,  which  is  said  to  have  been  as  severe  as  any  that  have  been 
witnessed  in  Peterhead  Bay,  the  waves  were  30  feet  in  height,  and  a 
section  of  the  breakwater  there,  down  as  far  as  10  feet  7^  inches  below 
low  water  and  weighing  3,300  tons,  was  bodily  slewed  to  the  extent  of 
2  inches,  without  the  brickwork  being  dislocated.  This  enormous  mass 
slid  upon  the  surface  of  the  course  immediately  below  it,  the  blocks  in 
which  were,  strange  to  say,  quite  unmoved.  In  the  waves  which  were 
responsible  for  this  feat,  the  water  was  thrown  up  to  a  height  of  about 
115  to  120  feet,  and  the  surface  upon  which  they  acted  measured  33  feet 
by  44  feet^  or  1,122  square  feet.  In  order  to  form  an  idea  of  the  force 
required  to  slew  such  a  mass,  the  Engineer,  Mr.  William  Shield,  ascer- 
tained the  coefficient  of  friction  of  blocks  similar  to  those  forming  the 
breakwater,  by  causing  them  to  slide  upon  a  concrete  floor.  The  floor 
was  well  wetted,  and  the  average  of  several  trials  with  blocks  up  to  68 
tons  weight,  gave  a  coefficient  of  0*7.  In  moving  the  mass,  the  waves 
must  therefore  have  exerted  a  force  of  2,310  tons  over  the  whole  area 
exposed  to  them,  or  slightly  over  2  tons  per  square  foot.  Although  about 
one-third  of  the  mass  was  below  the  level  of  low  water,  the  troughs  of 
the  waves  would  be  considerably  below  its  lowest  point,  and  taking  all  the 
circumstances  into  consideration,  little,  if  any,  allowance  need  be  made  for 
flotation.  If  such  allowance,  however,  be  considered  necessary,  it  is  prob- 
able that  some  deduction  should  also  be  made  from  the  area  exposed  to 
the  wave-stroke,  so  that  the  above  force  per  square  foot  would  not  be  much 
affected.  * 

After  this  incident  it  is,  perhaps,  not  surprising  to  find  that  a  20-ton 
block  at  Ymuiden  breakwater,  in  Holland,  was  lifted  to  a  height  of  12  feet 
vertically  up  the  face  of  the  pier  and  landed  on  the  top  of  it.f  « 

The  Design  of  Jetties,  Wharfs,  and  Piers. — ^The  principles  of  the  stability 
of  quays  have  already  been  set  forth,  and  they  are  equally  applicable  to 
those  wharfs  of  solid  construction  which  act  as  retaining  walls.  The 
depth  of  a  wharf  or  river  wall,  however,  will  generally  require  to  be  greater 
than  that  of  a  dock  wall,  on  account  of  the  vertical  disturbance  of  vessels  by 
waves.  Open  timber  wharfs  in  front  of  pitched  slopes,  allow  the  waves  to 
pass  through  and  expend  themselves  upon  the  bank,  so  that  the  wharf 
structure  does  not  encounter  the  full  force  of  the  waves,  but  this  arrangement 
is  only  feasible  in  situations  where  the  exposure  is  not  great. 

In  considering  the  stability  of  structures  subjected  to  external  forces  of 
great  magnitude,  it  will  be  found  that  there  are  two  distinct  sources  of 
resistance,  upon  either  of  which  a  design  may  be  based — viz.,  the  resistance 

♦Shield  on  "The  EflFect  of  Waves  and  Breakwaters,"  Min.  Proc.^Inst.   C.E,, 
vol.  oxxxviii. 
t/Wd. 


CONCRETE  MASS  WORK.  275 

due  to  the  inertia  of  a  solid  mass  and  the  resistance  offered  by  the  inherent 
strength  of  a  scientifically  framed  structure.  The  first  case  is  exemplified 
by  piers  constructed  in  huge  blocks  of  masonry  and  concrete,  and  in  the 
second  by  trussed  open  work  piers  of  timber,  iron,  or  steel.  Nature,  it  is 
to  be  noted,  opposes  the  violent  onset  of  stormy  seas  with  huge  boulders 
and  rocky  headlands,  and  accordingly  such  natural  features  constitute  an 
obvious  type  of  massive  construction.  Framed  structures,  on  the  other 
hand,  represent  the  result  of  human  thou<;htand  adaptation.  Theoretically, 
both  principles  would  seem  to  be  equally  effective,  but  in  practice  it  will  be 
realised  that  the  joints  in  framed  structures  are  a  source  of  weakness,  owing 
to  their  tendency  to  loosen  under  vibration  ;  and  further,  that  there  is  the 
very  important  factor  of  deterioration  and  decay,  which  gives  a  decided 
advantage  to  the  employment  of  a  practically  indestructible  material,  such 
as  stone  or  concrete,  over  less  durable  substances,  such  as  timber,  iron,  and 
steel.  In  the  latter  cases,  there  must  be  a  constant  expenditure  on  main- 
tenance and  repair. 

Where  there  is  an  important  littoral  current,  which  it  is  undesirable  to 
divert  in  any  way,  the  use  of  columnar  piers  becomes  a  necessity.  The 
current  then  passes  through  the  openings  without  perceptible  obstruction. 

Gonstraction  of  Jetties. — Jetties,  wharfs,'and  piers,  considered  as  forming 
a  single  class,  may  be  constructed  on  any  of  the  following  systems,  either 
singly  or  in  combination  : — 


(  Mass  work. 
Concrete,     .         .  <  Bag  work. 

(  Block  work. 

c,.  {  Dressed  masonrv. 

Steele, .        .        .  I  ^^^^^^  ^^^^^  J^ 


Fascine  work. 
Timber,       .        .  \  Open  framework. 

.  Crib  work. 

r-.^  ««r7  Qt^^i       i  Columnar  structures. 
Ir<m  aiid  Steel,    •  |  close  framework. 


Composite,         ,        .        •  { Hen^eWqu^^^^^ 

It  will  be  useful  to  deal  with  the  salient  features  of  each  of  these  various 
systems  seriatim. 

Concrete  Mass  Work  consists  in  the  deposition  of  a  large  bulk  of  fluid 
concrete  within  an  enclosure,  formed  either  by  a  boundary  of  sheet  piling  or 
by  temporary  retaining  moulds,  which  latter  are  removed  when  the  concrete 
is  sufficiently  set.  The  method  is  not,  generally  speaking,  satisfactorily 
adapted  to  subaqueous  construction,  as,  apart  from  the  awkwardness  of 
setting  wooden  moulds  under  water,  it  is  difficult  to  prevent  excessive 
dilution  and  washing  away  of  the  cement  particles,  whereby  the  strength  of 
the  concrete  is  seriously  impaired.  Accordingly,  the  method  is  mainly 
restricted  to  situations  in  which  it  can  be  carried  out  in  the  open — that  is  to 
say,  either  above  low- water  line  or,  when  below  that  level,  by  tide  work  and 
within  the  shelter  afforded  by  cofferdams.  Notwithstanding  this,  there  are 
undoubtedly  instances  in  which  fluid  concrete  has  been  successfully  deposited 
under  water,  but  the  local  conditions  in  such  cases  have  been  peculiarly 
favourable.  One  of  the  main  elements  of  success  is  perfectly  quiescent 
water.     Where  the  water  level  fluctuates  rapidly  and  erratically,  as  in  an 


276  I>OCK  ENGINEERING. 

exposed  tidal  way,  with  its  attendant  ground-swells  and  rapid  currents,  the 
risk  is  sufficiently  great  to  render  other  methods  preferable. 

Concrete  Bag  Work,  introduced  in  1865  by  Mr.  P.  J.  Messent  for  the 
purpose  of  repairs  at  Tynemouth,  and  developed  into  a  system  of  subaqueous 
construction  about  the  year  1870  by  Messrs.  Oay  and  Barton  at  Aberdeen 
and  Greenore  respectively,  consists  in  filling  jute  bags  with  fluid  concrete 
and  depositing  them  immediately  in  situ  with  the  aid  of  divers.  If  the  work 
be  carried  out  expeditiously,  before  the  concrete  has  had  time  to  set,  the 
bags  will  adapt  themselves  to  the  inequalities  of  the  surface  upon  which  they 
are  laid,  and  so  ensure  a  complete  and  uniform  bearing  for  each  successive 
course.  The  size  of  the  bags  used  in  various  instances,  ranges  from  a 
capacity  for  5,  to  one  for  100  tons  of  concrete,  or  even  more.  The  material 
used  is  jute  sacking,  weighing  from  25  to  30  ounces  per  superficial  yard. 
The  bags,  after  being  filled  at  the  mixing  station,  are  conveyed  to  their 
respective  positions  and  lowered  in  wrought-iron  skips,  through  the  hinged 
bottom  of  which  they  are  discharged.  Adjustment  and  flattening  is 
performed  by  the  divers.  As  there  is  a  tendency  for  the  exposed  ends  of 
thti  outermost  bags  to  break  away  under  heavy  wave  action,  it  is  advisable 
to  construct  the  work  slightly  wider  than  the  nett  width  desired.  Bag 
work  forms  an  admirable  method  of  dealing  with  irregular  foundations  too  in- 
durated for  dredging,  such  as  hard  rock  and  clay  containing  massive  boulders. 

Concrete  Block  Work  is  an  adaptation  of  the  principles  of  masonry  on  a 
large  scale  to  concrete  construction.  The  blocks  are  prepared  on  shore  in 
the  ordinary  way,  by  means  of  wooden  moulds  of  the  shape  required.  For 
foundation  and  interior  work  the  rectangular  or  square  form  is  the  most 
usual.  The  blocks  are  of  any  convenient  size,  ranging  from  5  tons  to  a 
weight  limited  only  by  the  power  available  for  lifting  and  depositing.  In 
order  to  facilitate  setting,  -each  block  is  sometimes  constructed  with  two 
vertical  or  slightly  inclined  perforations,  through  which  are  passed  iron  bars 
with  T  or  angle  ends,  capable  of  engaging  against  the  under  side  of  the  block 
when  turned  through  a  right  angle.  These  are,  of  course,  removed  after  the 
block  has  been  set.  Other  appliances  for  lifting  and  depositing  are  illustrated 
on  p.  114,  ante.  Setting  operations  may  be  carried  out  by  a  floating  crane^ 
by  a  traveller  running  upon  a  temporary  staging,  or  by  a  crane  traversing 
the  portion  of  the  work  previously  constructed  and  able  to  set  a  block  some 
distance  in  front  of  its  leading  wheels.  Except  in  the  case  of  very  smooth 
water,  the  traveller  and  the  land  crane  constitute  by  far  the  steadier  agents. 
The  blocks  are  set  on  the  outer  faces  of  the  structure,  and  are  ranged  as 
closely  as  possible  in  order  to  admit  of  being  connected  by  cramps  and 
joggles.  Where  the  circumstances  render  such  a  process  feasible,  the  joints 
may  be  pointed  in  cement,  or,  if  too  wide  for  this,  the  openings  may  be  made 
good  with  brickwork  in  cement.  The  interior  of  the  work  will  then  be 
filled  with  blocks,  arranged  so  as  to  break  joint,  and  well  bedded  in  concrete 
grouting,  which  may  be  run  through  a  pipe  under  a  considerable  head  after 
the  blocks  are  set. 


MASS  WORK. 


277 


All  three  of  the  foregoing  systems  may  be,  and  have  been,  used  in 
combination,  such  as,  for  instance,  a  construction  of  block  work  below 
low-water  level,  resting  upon  a  bag-work  foundation  course,  and  having  a 
superstructure  of  mass  concrete. 

The  south  breakwater  at  Aberdeen  was  carried  out  in  this  manner,  and 
as  the  statement  of  expenditure  affords  a  comparison  of  the  cost  of  the 
several  methods,  it  is  appended  here : — * 


Cubic 
Yanls. 

Expenditure. 

1 
Cost  per 
Cubic  Yard. 

Bag  work  in  foundations,         .... 
Block  work,  including  blocks  inserted  in  fluid 

concrete, 

Mass  concrete  in  frames, 

3,202 

22,851 
23,356 

£4,045 

18,175 
18,868 

25/3 

15/11 

16/2 

1 

A  better  appreciation  of  the  relative  cost  will  be  gained  by  a  brief 
statement  of  the  precise  conditions  obtaining  in  each  case.t 

Bag  Work, — The  bags  were  deposited  by  iron  skips,  the  greater  part 
by  two  skips  each  holding  5^  tons  of  concrete,  their  inside  dimensions 
being  6  feet  by  4  feet  by  3^  feet  deep.  In  the  last  year,  a  skip  of  16  tons 
capacity  was  used,  its  dimensions  being  9  feet  by  6  feet  by  6  feet.  The 
bottoms  of  the  skips  opened  on  hinges,  the  hook  which  held  them  being 
released  by  a  trigger.  In  the  larger  skip  the  closing  of  the  doors,  after 
the  bag  was  deposited,  was  assisted  by  counterbalance  weights.  The  bag, 
of  the  same  shape  as  the  skip  but  rather  larger,  was  fitted  into  it  and 
temporarily  lashed  at  the  top  so  as  to  line  the  skip.  It  was  then  filled 
with  liquid  concrete  (1  cement,  2^  sand,  3^  gravel),  the  temporary  lashings 
removed,  and  the  mouth  of  the  bag  sewn  up.  The  skip,  with  its  contents, 
was  lowered  by  a  crane  to  the  divers,  and  moved  about,  in  obedience  to 
their  signals,  until  close  over  the  required  position,  when  the  trigger  was 
pulled  by  a  rope  from  above,  and  the  bag  discharged. 

Block  Work, — The  blocks  were  all  4  feet  high  and  usually  6  feet  wide. 
At  first,  they  were  of  sizes  varying  in  weight  from  7^  to  18  tons ;  latterly, 
the  small  blocks  were  mostly  used  for  incorporation  among  the  fluid 
concrete  or  mass  work,  and  the  larger,  from  10^  to  24  tons  weight,  for 
block  building.  The  blocks  were  cast  in  wooden  moulds  in  the  usual 
manner,  the  proportions  of  the  concrete  being  1  cement  to  4  of  sand 
and  5  of  gravel,  with  large  pieces  of  broken  stone  imbedded.  They  were 
staked  by  cranes  in  the  block-yard  to  harden,  and  then  taken  down  an 
incline,  on  waggons,  to  the  staging  cranes,  by  means  of  which  they  were 
lowered  to  and  set  by  the  divers. 

Maaa  Work, — A  framework  of  posts  was  erected  round  the  site  of  the 
building,  excepting  at  the  ends  of  the  completed  work,  which  formed  one 

*  This  statement  does  not  include  items  for  preparatory  works,  plant,  staging,  &c. 
t  Cay  on  **The  South  Breakwater,  Aberdeen, '^  Mxn,  Proc.  Inst,  C.E,,  vol.  xxxix. 


278 


DOCK  ENGINEERING. 


side  of  the  case.  The  posts  were  provided  with  grooves,  into  which  panels 
were  slid,  extending  from  post  to  post.  The  bottom  and  sides  of  the  case 
were  lined  with  jute  bagging,  and  tie-rods,  passing  through  the  posts  and 
from  side  to  side,  prevented  the  case  from  being  burst  open  by  the  lateral 
pressure  of  the  fluid  concrete.  The  heart  of  each  post  was  a  piece  of  Baltic 
fir,  20  feet  long  by  12  inches  by  6  inches,  scantling ;  the  pieces  of  wood  for 
forming  the  grooves  were  fixed  to  the  larger  sides.  The  panels  were  built 
up  of  short  pieces  of  plank  2  feet  long,  placed  vertically,  so  as  to  form  a 
slab  7  feet  9  inches  by  2  feet  by  3  inches,  and  they  were  backed  by  two 
horizontal  planks  7  feet  4  inches  by  11  inches  by  3  inches.  The  ends 
of  these  formed  the  tongues  which  slid  in  the  grooves  in  the  sides  of  the 
posts.  The  tie-rods  were  of  wrought  iron  f  inch  diameter,  in  convenient 
lengths,  connected  by  f-inch  shackle&  The  jute  bagging  was  39  inches 
wide  and  weighed  29^  ozs. ;  it  cost  8d.  per  lineal  yard  and  could  generally 
be  used  twice.  The  proportions  of  the  concrete  found  best  for  the  work 
were  1  cement  to  3  sand  and  4  gravel ;  much  of  it  was  executed,  however, 
in  the  proportion  of  1  cement  to  4  sand  and  5  gravel. 


LONGITUDINAL    SECTION 


CROSS  SECTION 


iS  oj 


Jl^' 


Figs.  207,  208,  209,  and  210.— Caisson  at  Zeebrugge. 

A  special  adaptation  of  the  concrete  block  system,  as  practised  in  the 
construction  of  the  outermost  portion  of  a  mole  at  Zeebrugge,  merits  some 
notice.  It  consisted  in  the  formation  of  hollow  blocks  of  concrete  of  height 
sufficient  to  reach  above  low  water  from  the  ground  level.  These  were 
floated  out  into  position,  sunk,  and  filled  with  concrete.  The  circumstances 
at  Zeebrugge  were  favourable  to  this  method,  the  depth  of  water  not 
exceeding  30  feet  at  low  water  and  being  generally  26  feet. 

The  blocks,  or  caissons  (tigs.  207  to  210),  were  moulded  about  an  iron 
frame  with  plated  sides,  and  were  80  feet  long  by  30  feet  wide  by  30  feet  deep. 
This  gives  a  -volume  of  72,000  cubic  feet  each,  and  a  total  weight  of  about 


Masonry  piers.  279 

4,500  toDB.  The  underside  of  each  caisson  had  a  knife  edge  to  penetrate 
the  ground.  The  concrete  was  composed  of  33  parts  of  small  atone  and 
11}  of  sand  to  6  of  cement.  The  caisson  was  designed  with  three  compart- 
ments, and  in  each  of  the  walls  there  was  provided  an  orifice  for  filling 
them  with  water.  The  orifices  were  temporarily  plugged  while  the  caisson 
was  being  towed  into  position.  On  removing  the  plugs,  the  block  foundered. 
The  interior  was  then  filled  with  concrete  by  means  of  skips  opening  at  the 
bottom.  The  top  layer  of  3  feet  was  deposited  in  the  dry  at  low  water, 
with  concrete  very  rich  in  cement.  Large  pieces  of  rock  were  then  sunk 
to  the  seaward  of  the  block,  and  along  its  base,  to  prevent  any  danger  of 
undermining  by  the  water.     The  ground  was  a  clayey  sand. 

Upon  the  foundation  course  thus  laid,  the  upper  blocks,  of  5&  tons  weight 
each,  were  set  by  a  Titan  crane.  The  jetty  was  constrncted  with  horizontal 
o£Faets,  in  order  to  partially  destroy  the  downward  effect  of  a  breaking 
wave  upon  the  foot  of  the  wall  (fig.  211). 


5        IB       SO       30F**e 

Fig.  211.— Jetty  at  Zeebrugge. 

Other  examples  of  bag  work  are  to  be  found  at  Sunderland  (figs.  344 
and  245),  of  block  work  at  Dover  (fig.  313),  and  of  mass  work  at  Liverpool 
(figs.  221,  223,  and  223).  The  subject  of  concrete  work  has  also  been 
treated  in  the  chapter  on  Dock  Walla,  and  instances  are  there  given  of 
quays  constructed  on  the  same  or  kindred  lines. 

Masonry  Piers  are  not  so  common  as  they  used  to  be  in  the  days  before 
the  introduction  of  cement  concrete.  They  are  only  executed  now  in 
places  where  suitable  stone  is  very  plentiful  and  skilled  labour  cheap. 
In  other  situations,  concrete  ofiers  every  inducement  for  its  adoption. 
Masonry   piers  usually  have  iacings  of  ashlar  with  heartings  of  rubble, 


28o  DOCK  ENGINEERING. 

though  in  some  caaea,  pockets  of  earth  irork  have  been  employed.  With 
either  ayatera  of  construction,  it  is  essential  for  the  stability  of  the  work 
that  the  oppoaite  facings  should  be  securely  tied  together  by  well  bonded 
cross  walls,  or  by  horizontal  lacing  courses  at  regular  intervals.  The 
largest  possible  atones  should  be  choaen  for  the  outer  blocks,  and  they 
should  be  secured  to  one  another  by  dowels  and  plugs  as  well  as  dovetailed 


l-'ig.  212.— Pier  at  Havre. 

into  the  hearting  by  an  efficient  system  of  bonding.     The  south  pier  at 

Havre  (£;;.  312)  is  a  typical  example  of  masonry  conatruction.     It  has 

inclined  ashlar  facings,  averaging  5  feet  in  thickness,  connected,  at  intervals 

of  5  feet  in  height,  by  lacing  courses,  2  feet  thick.     The  bottom  width  is 

36  feet  6  inches,  and  the  top  width,  between  parapet 

walls,  18  feet  6  inches.    The  pavement  is  7  feet  6  inches 

above   high    water  of  equinoctial    tidea,  and    33  feet 

4  inchea  above  ground  level. 

A  combination  of  a  granite  ashlar  facing  with  a 
hearting  of  concrete  blocka  is  exemplified  in  a  pier 
at  Dover,  constructed  about  the  year  ISHS.  Present 
practice  at  that  port  favours  the  concrete  block  system 
throughout,  with  a  thin  facing  of  granito  rubble  above 
Fig.  213. -Jetty  at     lo"'"**"  level  (fig.  213). 

2>}Ter.  Piers  wholly  of  loose  rubble  are  indistinguishable 

from  breakwaters,  their  principal  function  being  the 
destruction  of  waves.  There  are  but  few  inatancas  of  such  works  being 
uaed  for  landing  purpoaea.  There  is  one,  however,  at  Eingatown  Harbour, 
near  Dublin,  where  a  long  inclined  mound  of  looae  rubble,  with  slopes 
ranging  from  1  to  1  to  5  to  1,  ia  crowned  with  a  pitched  surface  on  the 
inner  side,  38  feet  in  width.  The  maintenance  of  such  disorganised  masses 
is  apt  to  be  costly,  aa  they  suffer  considerably  from  the  effecta  of  wave 
action. 


MASONRY  PIERS. 


251 


Since  upright  piers  from  the  sea  bottom  are  inevitably  expensive  in 
construction,  where  the  depth  is  at  all  considerable,  and  further,  since  the 
rubble  mound  offers  a  suitable  means  of  bringing  the  foundation  level 
tolerably  near  the  water  level  without  incurring  too  much  danger  of 
disturbance,  a  combination  of  the  two  types  is  a  very  common  feature 
of  modern  practice. 

The  level  at  which  loose  rubble  of  different  sizes  may  be  trusted  to 
remain  stationary  in  stormy  weather  is  a  matter  of  considerable  importance 
in  piers  of  this  type.  Sir  John  Ooode  states  that  he  found  the  shingle  of 
Ohesil  Beach  in  motion  during  winter  storms,  at  a  depth  of  8  fathoms. 
The  line  of  permanent  mud,  which  marks  at  any  rate  the  extreme  limit  of 
wave  action,  whatever  other  agencies  may  assist  in  its  determination,  lies  at 
a  depth  of  12  to  16  fathoms  below  low  water  off  the  coast  of  Holland,  and  at 


Exterior 
Level    of   the 


<  500  X     7  00    > 


^  ■  ^  »■  m^i^r^^^mm 


"^ 


»*i**MM^k^M*^li**aM 


I 

^9 


Interior 
Lowest    tides 


1400 

Artificial     Blocks 

of  15  Cubic     I 
Metres        ^ 


.<5\ 


■s -^^'O  »  ^ -s^  .^^  V^ 


Blocks    from    1337  to  SOZS    -^^>? 

Floc?iS    fYom   100  toJ337^  ^-^  ^^ 

Fragments    fYom  v^  >^ 

to  WO  kHogmmmes  in  weight     v^  ^Sa? 

Fig.  214.— Jetty  at  Algiers. 


v*.-\,?f- 


a  depth  of  80  to  90  fathoms  in  the  vicinity  of  the  Shetlands.  But  even 
assuming  the  motion  of  waves  to  be  perceptible  throughout  so  great  a 
range,  it  is  manifest  that  the  force  diminishes  with  the  distance  below  the 
surface,  and  that,  at  a  certain  depth,  the  effects  become  of  trifling  import- 
ance. In  fact,  it  appears  that  the  really  injurious  effects  of  wave  action  are 
confined  to  a  zone  extending  from  the  surface  level  to  a  distance  of  about 
25  or  30  feet  below.  Beyond  this  point,  small  rubble  and  quarry  rubbish 
may  be  deposited,  with  comparative  impunity,  in  mounds  which  will  stand 
at  slopes  of  1  or  1^  to  1.'"'  Upwards  of  this,  stones  of  larger  bulk  and 
greater  weight  must  be  employed,  culminating  in  blocks  of  not  less  than 

*  There  are,  of  course,  abnormal  cases  in  which  these  statements  do  not  accord  with 
experience.  For  instance,  at  Peterhead  Harbour  in  October,  1898,  blocks  weighing 
upwards  of  41  tons  each  were  displaced  by  the  waves  at  a  depth  of  36^  feet  below  low 
water  of  ordinary  spring  tides,  but  this  and  one  or  two  other  examples  at  Wick  and 
•elsewhere  are  exceptional. 


282  DOCK  ENGINEERING. 

25  to  30  tons  weight  at  the  summit.  Owing  to  the  difficulty  of  quarrying 
such  blocks,  concrete  monoliths  are  now  generally  adopted  for  the  upper- 
most layer.  No  benefit  is  derived  from  any  attempted  consolidation  of  the 
work  by  intermixing  large  and  small  pieces.  On  the  contrary,  the  result  is 
likely  to  be  harmful,  since  the  dislocation  of  the  larger  blocks  will  be 
facilitated  in  consequence  of  the  small  pieces  getting  under  and  between 
them.  Blocking  the  interstices  with  cement  concrete,  in  bags  or  otherwise, 
is  a  much  more  satisfactory  course. 

As  an  illustration  of  the  combined  system  of  construction,  we  may  take 
the  North  Jetty  at  Algiers  (fig.  214).  The  bottom  hearting,  16  feet  in 
height,  consists  of  rubble  from  30  to  200  lbs.  per  piece.  Overlying  this 
there  are  two  layers,  each  10  feet  high,  of  natural  blocks,  ranging  in  the 
lower  layer  from  y\y  to  IJ  tons,  and  in  the  upper  layer  from  1 J  to  8  tons  in 
weight.  The  remaining  distance  of  32^  feet  to  low- water  level  is  occupied 
by  artificial  blocks  containing  about  550  cubic  feet.  The  superstructure  is 
carried  to  a  height  of  16  feet. 

Timber  Piers  are  less  substantial  than  those  of  masonry  or  concrete,  but 
they  possess  certain  advantages  as  regards  economy  and  rapidity  of  execu- 
tion. Where  the  ground  is  suitable  for  the  reception  of  piling,  and  in 
localities  where  storms  are  infrequent  and  of  no  great  severity,  timber 
jetties  and  piers  can  be  constructed  at  a  cost  much  less  than  that  of  more 
massive  structures.  In  ice-bound  ports,  too,  such  as  those  in  the  Baltic, 
the  prosecution  of  the  work  of  piling  is  independent  of  the  season  and  can 
be  carried  on  uninterruptedly  through  the  winter,  which  is  an  important 
consideration. 

The  simplest,  and  certainly  the  most  primitive,  system  of  timber  jetty 
work  is  that  inaugurated  by  the  Dutch,  who  build  their  quays  very  largely 
with  the  aid  of  fascines  (Dutch,  ryshoot),  or  bundles  of  brushwood  derived 
from  copses  of  willows,  osiers,  &c.  Mattrasses  of  this  material,  weighted 
with  stone,  are  sunk  in  position  in  successive  courses,  the  whole  structure 
being  secured  by  rows  of  vertical  and  inclined  piling.  The  advantages 
claimed  for  the  use  of  brushwood  are  (1)  its  elasticity,  which  renders  it  less 
liable  to  injury  from  the  impact  of  waves,  and  (2)  its  solidification  under 
the  accumulation  of  sand  and  drift  in  the  interstices.  To  these  may  be 
added  its  convenience  and  cheapness. 

The  following  particulars  relate  to  the  piers  at  the  Hook  of  Holland^, 
near  Rotterdam  (see  figs.  216,  216,  and  217)  : — 

The  piers  were  constructed  of  successive  layers  of  zinkatukken,  or 
mattrasses,  54*7  yards  long  by  26 '2  yards  broad,  and  1  foot  8  inches  thick, 
constructed  as  follows : — Two  stakes  were  driven  into  the  ground,  about 

2  feet  6  inches  apart,  to  which  a  cross  stick  was  secured  about  2  feet 

3  inches  from  the  ground.  A  series  of  these  frames  were  erected,  2  feet 
apart,  the  number  depending  on  the  size  of  the  zinkstuk.  The  fascines 
were  then  placed  on  the  cross  sticks,  being  drawn  out  lengthways,  so- 
that  each  bundle  overlapped  and  bonded  well  into  the  next.     They  were 


TIMBER  PIERS.  283 

laid  of  such  thicknesa  that  oo  being  bound  round  in  the  fonn  of  a  rope, 
tbe  circumference  was  17  inches.  When  the  full  lengtii  for  one  rope,  or 
ufi^,  bad  been  laid  out,  the  fascines  were  tied  at  15-inch  intervals  with 
oaier  bands,  tightly  twisted  and  with  their  ends  tucked  in.  Light 
intermediate  bands,  i  inches  apart,  were  then  added.  The  wiepen  were 
next  laid  in  parallel  rows  upon  the  ground,  about  3  feet  apart,  to  the  full 
width  of  tbe  proposed  mattrass.  Tbey  were  crossed  by  a  second  layer  at 
right  angles  to  the  first,  thus  forming  a  network,  which  was  secured  by 


SECTION   A.B. 


Figs.  216,  218,  and  217.— Fasohie  Work. 


Fig.  218.— Mole  at  Hook  of  Holland. 

lashings  of  ^inch  tarred  rope  with  free  ends,  and  withes.  Two  such 
networks,  upper  and  lower,  enclosed  three  layers  of  ryshout,  set  crossways, 
18  inches  thick  in  all,  and  were  tied  together  by  the  rope  ends.  This 
completed  the  mattrass.  In  order  to  cause  sinkage,  it  was  weighted  with 
atone,  and  the  loading  was  afterwards  continued  until  it  amounted  to 
10  cwts.  per  square  yard.  The  body  of  the  piers  took  from  five  to  six 
mattrasses,  averaging  with  the  stones,  about  3  feet  3  inches  thick ;  these 
were  further  held  in  place  by  five  rows  of  piles,  driven  about  11  or  12  feet 


2S4  I>OCK  ENGINEERING. 

through  the  mass  into  the  sand  below.  The  outer  slopes  and  edges  of  the 
mattrasses  were  covered  with  a  coating  of  stone,  averaging  13  cubic  feet 
per  lineal  foot  of  pier.  The  part  above  water  was  covered  with  larger 
stones,  retained  bj  rows  of  small  oak  piles,  the  ends  of  which  project  above 
the  level  of  the  work,  with  a  view  to  breaking  the  force  of  the  waves. 

A  cross-section  of  the  north  pier  is  given  in  fig.  218.  It  has  a  width  of 
29  feet  6  inches  between  the  main  piles. 

The  crown  of  the  south  pier  is  26  feet  3  inches  wide,  rounded  on  the 
upper  surface,  which  attains  the  level  of  ordinary  high  water.  The  piles 
connecting  the  mattrasses  are  carried  to  a  height  of  9  feet  10  inches  above 
this  level.  A  timber  roadway,  carrying  two  lines  of  rails,  is  attached  to 
the  piles. 

Open  Timber  Frames  are  very  often  employed  for  piers  and  wharfs 
where  the  water  is  tolerably  quiescent  and  but  moderately  deep.  The 
frames  may  be  either  fixed  or  movable.  In  the  first  instance,  the  verticals 
consist  of  whole  timber  piles,  generally  greenheart  or  creosoted  pitch  pine, 
driven  down  to  a  solid  stratum  and  connected  transversely  above  the 
water  level  by  cross  pieces  and  inclined  struts,  as  at  Hull  (fig.  246).  In 
the  second  case  the  verticals  are  tenoned  into  and  rest  upon  a  timber 
sole-plate,  set  upon  a  naturally  hard  bottom,  as  at  Blyth  (figs.  219 
and  220).     In  both  cases,  the  frames  are  erected  at  distances  apart,  usually 


Figs.  219  and  220.— Jetties  at  Blyth. 

from  10  to  15  feet,  and  the  bays  thus  formed  are  faced  with  horizontal 
walings  and  fenderings.  The  movable  frames  have  necessarily  to  be 
weighted  down  with  heavy  stone  filling,  and  this  is  frequently  added  in 
the  case  of  fixed  frames,  in  order  to  stiffen  the  work.  A  foundation  of 
concrete  is  occasionally  to  be  found,  as  at  Liverpool,  and  exemplified  in 
three  instances  (figs.  221,  222,  and  223),  especially  when  it  can  be  utilised 
in  the  formation  of  culverts  with  sluice  openings  to  maintain  the  required 
depth  of  water  in  situations  where  there  is  a  tendency  to  silting.  A 
concrete  apron  must  then  be  £tdded  to  the  structure,  or  it  will  inevitably 
be  undermined  by  the  current.  Filed  timber  jetties  have  also  been 
constructed  upon  a  rock  bottom.  At  Newcastle,  for  the  uprights  of 
coaling  staiths,  holes,  3  inches  in  diameter,  were  drilled  into  the  rock 
and  into  these  the  pile  shoes,  which  had  4-inch  square  spikes,  6  feet  long 
at  their  ends,  were  driven.  At  Liverpool,  similar  but  larger  holes  were 
drilled  for  the  Prince's  jetty,  the  holes  being   25  inches  diameter,  and 


OPEN  TIMBER  FRAMES.  285 


Lower     Clay- 
Fig.  221.— Jettj  at  Liverpool— Typo  A. 


Ltnver    Clay 
Fig.  2!^— Jetty  »t  Livarpool— Type  B. 


DOCK  EHGINBEBINQ. 


consequently  capable  of  receiving  the  whole  butt  ends  of  greenheart  pilw, 
14  inches  square,  which  were  grouted  in  concrete  after  being  adjusted. 


.-— Jl 


-T-i-t-r-i^ 

li 

r^ 

=^^.„ 

^ 

Concrete 

' 

Fig.  223.— Jetty  «t  Liverpool— Type  C. 

Crib  Work  is  a  mode  of  constrnction  peculiarly  characteristic  of  jetties 
in  the  large  North  American  lakes.  From  the  crudeness  of  its  build  and 
the  perishability  of  the  material,  the  ayatem  must  be  regarded  as  mainly  of 


Kg.  224.— Crib  Frame. 


IRON  COLUMNAR  PIERS.  287 

the  nature  of  a  temporary  structure ;  indeed,  it  is  doubtful  whether  it  is 
applicable  to  other  than  the  particular  localities  in  which  it  has  been 
devised  and  practised,  admittedly  with  success,  wliere  timber  is  plentiful 
and  cheap,  and  where  ])resent  requirements  outweigh  considerations  of 
future  contingencies.  Cribs  are  box-shaped  frames  of  timber  (pine,  cedar, 
ash,  tamarac,  or  elm),  constructed  in  open-work,  with  numerous  compart- 
ments formed  by  means  of  transverse  and  longitudinal  ties.  They  range 
from  30  to  50  feet  in  length  and  are  never  narrower  than  the  total  height, 
with  a  minimum  in  the  shallowest  cases  of  20  feet.  The  main  timbers 
are  12  inches  square  throughout,  except  in  the  lowermost  course,  or 
grillage,  where  they  are  12  inches  by  18  inches.  The  traus verse  and 
longitudinal  ties  are  about  10  inches  by  12  inches,  and  the  structure  is 
held  firmly  together  by  l^inch  wrought -iron  bolts.  This  method  of 
construction  will  be  tolerably  clear  from  an  inspection  of  fig.  224. 

The  preparation  of  the  site  for  the  cribs  is  a  matter  of  importance. 
A  sandy  bottom  is  not  very  suitable,  giving  rise  to  unequal  settlement. 
A  mound  of  rubble  has  been  found  to  answer  the  purpose  best. 

The  cribs  are  framed  on  a  sheltered  beach,  within  easy  reach  of  a 
draught  of  10  or  12  feet  of  water.  After  three  or  four  courses  have  been 
bolted  together  the  structure  is  launched,  and  additional  courses  put  on 
until  the  height  is  several  feet  greater  than  the  depth  of  the  jetty  site. 
The  crib  is  then  towed  into  position  and  weighted  with  stone  until  it 
sinks,  after  which  it  is  filled  level  with  the  top.  After  the  final  settle- 
ment, all  the  cribs  are  levelled  up  with  wedges,  and  a  roadway  of  planking 
is  laid  at  a  height  of  5  or  6  feet  above  water  level.  The  cost  of  crib  work 
in  24  feet  of  water  at  Chicago,  in  1871,  amounted  to  about  £30  per  lineal 
foot. 

Iron  Columnar  Piers  form  light,  ornamental  structures,  and  they  are 
often  adopted  where  the  traffic  is  mainly  in  passengers.  The  open  columns 
also  cause  practically  no  interference  with  the  movements  of  the  sea,  and 
consequently  the  type  is  a  suitable  one  in  situations  where  there  is  a 
littoral  current  which  it  is  inadvisable  to  deflect  in  any  way.  The  columns 
are  either  piles  themselves  or  are  bolted  to  the  heads  of  piles,  unless  the 
bottom  surface  be  rock,  in  which  case  there  is  no  need  for  piling.  Screw 
piles  are  very  generally  employed,  on  account  of  the  broad  bearing  afforded 
by  the  surface  of  the  screw.  The  columns  are  arranged  in  bays,  and  are 
connected  just  below  the  decking  by  longitudinal  and  transverse  girders, 
the  depth  and  design  of  which  will  depend  upon  the  distance  apart  of  the 
columns.  There  is  so  much  scope  for  individual  taste  and  opinion  that 
it  is  impossible  to  lay  down  any  rules,  of  a  general  nature,  in  regard 
to  the  design  of  iron  columnar  piers.  Two  examples  will  suffice  by  way 
of  illustration. 

At  the  port  of  Soukhoum,  in  the  Black  sea,  there  is  an  iron  pier  (figs. 
225  and  226),  about  154  feet  long,  constructed  in  1889.  The  bays  are  each 
14  feet  in  extent,  with  one  of  7  feet  at  the  end.    There  is  also  a  further 


IRON  COLUMNAR  PIERS.  289 

projection  of  7  foet  e.t  the  outer  extremity,  forming  a.  support  to  a  stairway. 
The  columns  are  arranged  in  parallel  rows  of  five,  the  middle  columns 
being  7  feet  10^  iaches  apart  and  the  outer  ones  5  feet  3  ioches.  They  are 
5  inches  in  diameter,  connected  by  3'inch  by  3-inuh  by  g-inch  angle-iron 
bracing.  The  deck  is  planked  upon  whole  timber  bearers,  at  a  height  of 
14  feet  above  the  water  level. 

In  order  to  allow  freedom  of  movement  to  the  littoral  current  a  portion, 
410  jards  long,  of  the  jetty  or  mole  at  Zeebrugge,  on  the  North  Sea,  is 
constructed  of  mild  steel  in  openwork.     The  structure  (figs.  227  and  3:it!) 
is  composed  of  SO  bays  of  16^  feet  each,  and  is  carried  by  parallel  rows  of 
piles  or  columns,  six  in  number,  of  which  four  support  a  double  line  of 
rails  and  trwo  the  side  extremities 
of  the  platform.     The  heads  of  the       *"*" 
piles   are    connected    by  a    lattice 
girder,     and    at    low- water    level, 
there  is  a  second  horizontal  mem- 
ber formed  of  two  channel  irons. 
The  diagonal    bracing   is  2  inches 
in  diameter,  fitted  with  tightening- 
up  shackles.  Each  column  is  formed 
of    four    quadrant    irons,    ri vetted 
together     at     their      longitudinal 
flanges.      The    internal    diameter 
is    0^    inches    and    the    thickness 
I  inch.    The  sectional  area  of  each 
pile  is  about  31  square  iaches.    At 

the  foot  of  each  pile  is  a  wooden  -;,-  -      -pr  -,t;  -_^-i,r^-.      ^rr- : 

shoe,  16  inches  in  diameter  and  a  ''-'  ^'  '.■     "  ■.',,' 

yard  lone,  bearin"  airainst  a  collar  Sealma. 

onthenile  ?   ^^  1^^  ^    ^  ^    ?  fP  M.tr,^. 

on  tne  pile.  b     A     fy  SO  30F«»e 

The  rows  of  piles  are  connected  pig,  228.-Jetty  at  Zeebnigfe-e. 

longitudinally  by  plate  girders,  four 

of  which  are  2  feet  6  inches  deep  and  the  outer  two  2  feet  deep,  with 
6-inch  by  J-inch  flat-bar  wind  bracing.  The  decking  comprises  5-inch 
by  2J-inch  oak  joists,  set  IJ  inches  apart  clear,  to  allow  a  passage  for 
waves.     The  cover-plates  in  the  railways  are  of  cast  iron,  pierced  pattern. 

On  the  outer  face  of  the  jetty,  there  is  a  plate  superstructure,  15  feet 
9  inches  in  height,  suitably  stifieued,  to  afi'ord  shelter  to  trains.  This 
superstructure  carries  a  gangway  for  pedestrians. 

An  interesting  example  of  a  jetty  of  a  somewhat  unusual  type  for  iron, 
though  not  for  wood,  is  given  in  figs.  229  and  230,  which  is  a  section  of 
one  constructed  at  the  port  of  Touaps^,  on  the  Black  Sta,  in  1896-97.  The 
jetty  is  800  feat  long  and  has  two  inclined  faces,  each  formed  of  a  row  of 
railway  metals  oa  end,  driven  into  the  ground  some  10  inches  apart,  being 
guided  and  strengthened  by  two  rows  of  longitudinals ;  the  upper,  9  feet 

19 


290  DOCK  ENGINEERING. 

above  the  water  line,  an  angle  iron  6  inches  by  6  inches  by  ^  inch,  and  the 
lower,  a  channel  iron  10  inches  by  3  inches  by  }  inch,  connected  in  each 
case  by  transverse  through-bolts.  The  interior  of  the  jetty  ia  filled  with 
rubble.     The  top  width  is  U  feet,  providing  acoommodation  for  a  single 

line  of  rails. 


Figs.  229  and  230.— Jetty  at  Tonape^ 

Composite  Systeme. — Perhaps  the  most  remarkable  development  of 
recent  years  is  the  intimate  combination  of  iron  and  concrete  for  buildiag 
purposes,  and  not  the  least  important  application  of  the  method  is  in 
reference  to  piling.  The  earlier  open-work  systems,  whether  of  iron  or 
wood,  are  subject  to  deterioration  and  decay — in  the  first  case  from 
corrosion,  and  in  the  second  from  the  ravages  of  sea  worms.  Hence  a 
combination  of  two  materials,  in  wliich  the  durability  of  the  one  acts  as 
a  preservative  to  the  strength  of  the  other,  is  an  undoubted  advantage. 
Such  is  the  principle  of  several  well-known  systems,  in  all  of  which  iron 
rods  and  bars  are  completely  imbedded  in.  concrete,  so  as  to  be  beyond  the 
reach  of  external  destructive  agencies.  Two  of  these  systems,  from  their 
primary  application  to  building  construction,  are  more  fully  described  in 
the  chapter  on  Sheds  and  Warehouses.  Here  we  are  only  concerned  with 
their  adaptability  to  jetties  and  piers. 

The  Monier  system,  consisting  of  a  mesh  of  metal  wire  incorporated  in  a 
slab  of  concrete,  has  been  used  as  an  external  cover  for  timber  piles,  and 
also,  in  the  form  of  cylinders,  for  bridge  foundations.  Monier  tubes,  in  3  feet 
6  inch  lengths,  21  inches  internal  diameter.  If  inch  thick,  with  a  hearting 
of  steel  wire  netting,  1^  inch  mesh,  So.  16  gauge  wire,  have  been  used  by 
Mr.  De  Burgh  for  the  protection  of  ironbark  piles  in  Australia.  In  a 
second  instance,  the  cylinders  were  3  feet  6  inches  in  diameter,  with  a 
thickness  of  3^  inches.  Both  applications  were  successful,  and  indicate  the 
possibility  of  utilising  Monier  tubes  on  a  more  extended  scale  for  marine 
foundation  work. 


COMPOSITE  SYSTEMS. 


291 


LU 


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;V>'i%.i*i>*>.t»i^; 

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Ts  .;  ;'7 

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The  Hennebiqiie  system  has  been  more  directly  applied  to  the  formation 
of  piles.  As  practised  in  recent  examples,  it  consists  in  enclosing  rows  of 
iron  rods,  bound  at  intervals  by  iron  ties,  in 
a  casing  of  concrete.  Figs.  23 1  to  234  are  the 
elevation  and  sections  of  a  sheet  pile,  con- 
structed in  this  manner.  There  are  three 
rows  of  pairs  of  vertical  rods,  connected,  at 
10-inch  intervale,  by  horizontal  bands  or  clips. 
The  pile  is  moulded  with  cylindrical  grooves 
in  each  side,  in  which  the  spur,  C,  of  an 
adjoining  pile  engages,  for  guidance  in  driv- 
ing. When  two  consecutive  piles  have  been 
driven,  their  combined  grooves  form  a 
cylinder,  which,  after  being  cleansed  by 
forcing  water  through  it  under  pressure,  is 
grouted  with  cement.  The  lower  ends  of  the 
piles,  which  can  be  made  either  wedge- 
shaped  or  pointed,  are  protected  by  steel 
shoes  secured  to  the  body  of  the  pile  in  the 
moulding  process. 

In  fig.  27  (p.  63)  is  a  plan  showing  the 
method  adopted  for  the  construction  of  bear- 
ing piles.  Piles  of  this  description,  14  inches 
square  and  42  feet  long,  have  been  driven 
to  the  number  of  1,300  for  a  cold  storage 
foundation  at  Southampton.  A  monkey  weigh- 
ing 2^  tons  was  used,  and  the  piles  were  driven 
until  10  blows,  with  4  feet  6  inches  fall,  failed 
to  produce  an  additional  inch  of  depression. 
It  is  better  for  this  class  of  work  to  use  a  heavy 
weight  with  a  short  fall,  rather  than  a  light 
weight  with  a  long  fall.  Owing  to  the  brittle 
nature  of  the  concrete,  the  head  of  the  pile 
during  driving  must  be  protected,  as  shown 
in  figs.  235  and  236,  by  a  sheet  helmet  bedded 
on  sawdust  or  sand  in  bags  on  the  head  of  the 
pile,  with  the  further  interposition  of  a  wooden 
dolly  between  the  monkey  and  the  helmet. 
The  loss  of  energy  by  this  arrangement  is  very 
great,  though  eventually  the  sawdust  hardens 
into  a  compact  mass. 

The  brittleness  and   rigidity  of  the  thin 
concrete  covering  are  the  only  drawbacks  of 

the  composite  system  in   positions  such  as  jetties,  where  it  is  liable  to 
concussions  and  shocks.      It  has,  however,   been  used  with  satisfactory 


'V: 


i4  f  *  **^P*'"'^I« 
••        ••        ,i 

■I      ?•      :; 


1: 


-f— 


)  ■  i< 

iiii 


SMEIT     PILC 

•iCTtoa    A  ■. 

ticTioa  C.9. 

Figs.  231,  232,  233,  and  234. 
Hennebique  Sheeting  Pile. 


292 


DOCK  ENGINEERING. 


results  in  the  construction  of  a  jettj  at  Woolston,  near  Southampton,  and 
possibly  in  other  cases. 

HENNEBIQUE    SHEETING   PILES 


Sfet  Heimeh 


V     \^  Sawdust 

\ 

■ 

i 


I 


I 

I ^T 


Figs.  235,  236,  and  237. 

Jetties  and  Wharfs  at  Belfast.^ 

Fronting  the  Victoria  Channel  and  flanking  the  entrance  to  the  Alex- 
andra Graving  Dock  at  Belfast,  two  timber  jetty  quays  or  wharfs  have  been 
erected,  the  former  510  feet  long  and  the  latter  840  feet.  The  structures 
comprise  eight  jetties,  connected  by  a  narrow  wharf  (fig.  238),  extending 


TO...  c 


Teet,  to  $ 

'--■•'-- 


K> 


«o 


SO 


«c 


XF^et 


Fig.  238.— Wharf  at  Belfast. 
Kelly  on  '*The  Alexandra  Graving  Dock,  Belfast,"  Min,  Proc,  Inst,  C*E»,  vol.  czi» 


TIMBER  WHARF  AT  DUNDEE.  293 

70  feet  from  the  quay  face.  The  jetties  are  20  feet  and  the  wharf  15  feet 
wide.  All  the  timber  work  is  of  pitchpine  except  the  fenders,  which  are  of 
American  rock  elm.  The  coping  timber  is  protected  by  a  sheathing  of 
malleable  iron,  2^  feet  broad  and  \  inch  thick.  The  pitchpine  was  creosoted 
with  4  lbs.  of  creosote  per  cubic  foot,  which,  owing  to  the  density  of  the 
timber,  was  with  difficulty  forced  into  it.  Twenty-five  mooring  bollard 
piles,  48  feet  long,  were  driven  and  secured  to  the  main  framing  of  the 
jetties  and  quays,  and  titted  on  the  top  with  cast-iron  bollard  caps.  The 
bays  of  piling  of  the  jetties  are  9  feet  apart,  and  of  the  quays  between  the 
jetties,  8  feet.  The  slopes  behind  the  jetty  quays  down  to  the  lowest  low- 
water  mark  are  protected  with  16-inch  rubble  whinstone  pitching,  laid  on  a 
6-inch  bed  of  gravel. 

A  quay  wall,  80  feet  in  length,  and  three  piers  and  foundations  for 
supporting  a  100-ton  derrick  crane  were  constructed  of  concrete  in  the  tide- 
way, within  two  rows  of  sheeting  piles,  38  feet  long.  The  three  crane  piers 
are  raised  '22  feet  above  the  quay  level;  they  are  20  feet  square  at  the  base 
and  1 7^  feet  square  at  the  top,  and  have  wrought-iron  holding-down  bolts. 
Plate  castings  are  built  into  the  piers  for  securing  the  granite  seats  and  the 
foundation  castings  of  the  crane.  Along  both  sides  of  the  derrick  crane 
seat,  a  timber  wharf,  very  economical  and  serviceable  in  form  where  the 
depth  of  water  in  front  of  the  quay  is  not  greater  than  about  10  feet  at 
ordinary  low  water,  was  constructed  for  a  total  length  of  220  feet.  Forty- 
five  bays  of  supporting  piles,  in  front,  and  stay  piles,  four  in  each  bay,  behind, 
were  driven,  5  feet  apart,  along  the  wharf.  A  row  of  sheeting  piles,  22  feet 
long  and  7  inches  thick,  was  driven  along  the  face  of  the  wharf.  For  a 
depth  of  14  feet  below  the  coping  level,  close  4-inch  planking  was  spiked  to 
the  back  of  the  front  row  of  supporting  piles,  and  a  coping  timber,  18  inches 
by  10  inches,  was  secured  along  the  quay  face  to  the  pile-heads.  The 
wharfing  was  tied  back  by  iron  bolts  to  the  stay  piles,  and  the  space  imme- 
diately behind  the  face-work  was  filled  in  with  ashes,  brick  rubbish,  &c. 
The  cost  of  such  a  wharf  facing  amounts  to  between  £10  and  J&12  per  lineal 
foot  of  frontage. 

Timber  Wharf  at  Dundee.* 

The  landing  wharf  (figs.  239  and  240)  at  present  in  use  for  the  discharge 
of  steamers,  and  available  at  any  time  of  the  tide  for  vessels  whose  draught 
is  too  great  to  admit  of  entrance  into  the  docks,  has  a  length  of  2,800  feet, 
and  is  provided  with  shed  accommodation  at  the  rear  to  the  extent  of 
24,650  square  yards.  It  is  12  feet  6  inches  in  width,  is  constructed  of  two 
rows  of  main  piles,  9  feet  apart  centre  to  centre,  with  sheeting  between  the 
piles  of  the  first  row,  and  is  tied  back  by  iron  tie-rods  f  inch  diameter  and 
50  feet  long.  There  are  bollards  along  the  face  of  the  wharf,  18  feet  apart, 
and  numerous  ladders  down  to  low- water  level.     The  timber  wharf  being  of 

*  Buchanan  on  "  The  Port  of  Dundee,"  Min.  Proc.  Inst.  C.E,f  vol.  cxlix. 


294  I**^^  ENGINEERING. 

a  temporary  D&ture,  and  more  shed  accommodation  being  required,  the 
construction  of  a  permanent  river  wall,  140  feet  outaide  the  present  wharf, 
is  about  to  be  commenced. 


Figa.  239  and  240.— Wharf  at  Dundee. 

Jett7    at   Dunkirk.* 
The  new  east  jetty  at  Dunkirk  (fig.  241)  has  a  foundation  of  masonry, 
instructed  on  the  compressed  air  system  described  in  Chapter  v.     The 


•BarW 
Eighth  Int.  Nav.  Cong.,  Faria,  190a 


Fig.  241.-Jettj  at  Dunkirk. 
Travaui  les  plus  r^enta  execute  dam  lea  principaux  ports  fran^ais," 


PIERHEAD   AT  MADRAS.  295 

jetty  is  938  yards  long,  and  42  caissons  were  employed,  generally  68  feet 
long,  with  widths  ranging  from  15  feet  6  inches  to  21  feet  for  the  jetty  and 
31  feet  for  the  pierhead.  These  caissons  were  sunk  into  the  fine  sand  of 
the  beach  to  depths  of  16  to  26  feet  below  zero.  The  joints  between  the 
caissons  were  at  the  most  20  inches  wide  :  they  were  simply  closed  by  wood 
panels.  The  superstructure  consists  of  an  open  timber  framework  adjoining 
the  mainland,  650  feet  loDg,  a  half-fiUed-in  framework,  490  feet  long,  and  a 
solid  breakwater  for  the  remaining  length,  bordered  on  tlie  inner  side  by  a 
stockade  and  on  the  outside  by  a  mole,  having  a  hearting  of  sand  protected 
by  a  facing  of  masonry.  In  the  open-work  jetty  the  masonry  base  is  carried 
to  a  level  of  8  feet  above  datum  and  to  a  level  of  16  feet  6  inches  in  the 
half  solid  portion.  The  platform  is  constructed  throughout  at  a  height  of 
29  feet  6  inches  above  zero,  or  6  feet  above  high  water  of  equinoctial  spring 
tides. 

Biver  Jetties  at  Tilbury.* 

The  jetties  at  the  entrance  to  the  tidal  basin  are  45  feet  in  width,  and 
project  in  the  tideway  into  about  45  feet  of  water  at  high  water  of  spring 
tides,  or  48  feet  below  Trinity  high-water  mark.  The  centres  of  the  rounded 
ends  of  the  jetties  were  formed  of  cast-iron  cylinders,  15  feet  in  diameter, 
sunk  to  a  chalk  foundation  at  about  75  feet  below  the  level  of  the  deck. 
These  cylinders  were  afterwards  filled  with  concrete.  Immediately  around 
the  cylinders,  and  hooped  at  intervals  to  them,  was  driven  a  double  row  of 
piles,  from  which  radial  and  cross  strutting  was  carried  to  the  outer  piles. 
The  straight  portions  of  the  jetty  were  formed  by  a  double  row  of  piles  on 
each  side  in  10-foot  bays,  with  four  horizontal  struts,  and  cross  strutting 
extending  the  full  width  of  the  structure.  The  whole  of  the  piles  and  main 
timbers  were  of  sawn  pitchpine  logs,  averaging  about  1 4^  inches  square  and 
65  feet  in  length.  The  decks  were  formed  of  3-inch  planking  in  4|-inch 
widths,  laid  upon  1 1-inch  by  2-inch  bearers.  The  shore  end  of  the  west 
jetty  was  similar  in  construction  to  the  outer  ends,  and  the  corresponding 
end  of  the  east  jetty  was  connected  with  the  solid  knuckle  formed  by  the 
return  of  the  south  wall  of  the  tidal  basin. 

Pierhead  at  Madras.! 

The  pierheads  at  Madras  Harbour  are  formed  of  cylindrical  monoliths, 
consisting  of  a  plating  of  iron  with  a  concrete  interior  (figs.  242  and  243). 

For  each  pierhead  a  watertight  iron  caisson  was  provided,  with  outside 
diameters  of  42  feet  and  41  feet  5^  inches  at  the  base  and  summit  respec- 
tively, and  53  feet  in  height.  The  bottom  and  sides  were  covered  with 
J-inch  plating,  the  latter  being  built  up  in  a  series  of  tiers  or  horizontal 

*  Scott  on  **  The  Tilbury  Docks,"  Min.  Proc.  Inet,  G.E.,  vol  cxx. 
t  Thompson  on  *'  The  Caisson  at  the  North  Pierhead,  Madras  Harbour,"  Min,  Proc, 
Inst.  C,E,,  vol.  cxxv. 


296  DOCK   ENGINEERING. 

bands,  each  consisting  of  eight  curved  plates,  16  Teet  6  inches  long  and 
4  feet  in  height.  Both  sides  and  bottom  were  strengthened  with  ribs  of 
lattice  girders.  Across  the  bottom,  each  along  the  cimtre  of  a  row  of  plates, 
ten  girders,  2  feet  in  height,  were  placed,  3  feet  9/^  incJies  apart  from 
centre  to  centre.  The  sides  were  supported  by  fifteen  circular  girders, 
placed  horizontally,  and  varying  in  breadth  from  1  foot  9  inches  to  1  foot 
6  inches,  and  also  by  twelve  vertical  girders  from  2  feet  to  1  foot  9  inches 


FigB.  242  and  243.  — Pierhoftd  at  Madraa. 


in  width.  The  vertical  girders  were  set  at  equal  distances  apart,  and  only 
their  inner  flanges  were  continuous  throughout  the  height  of  the  caisson,  the 
outer  flanges  being  arranged  in  sections  between  the  horizontal  girders. 
The  inner  flange  consisted  of  a  3-inch  by  3-inch  by  f-inch  angle  iron, 
connected  at  a  single  joint  by  a  bar  cover.  To  these  girders  the  side 
plating  was  fixed  by  ^-iach  rivets  at  5-inch  pitch,  the  tiers  being  rivetted 
together  with  |-incb  rivets  at   SJ-inch  pitch  and  arranged  telescopically, 


PIERS  AT  SUNDERLAND  HARBOUR.  2Q7 

so  that  each  tier  is  |  inch  less  in  diameter  than  that  immediately 
below  it. 

The  caisson  was  furnished  with  four  12-inch  sluice  valves,  fitted  to  the 
outside  of  the  eighth  tier,  27  feet  7  inches  from  the  bottom.  Eighteen 
3-inch  wrought-iron  pipes,  rivetted  over  3-inch  holes  in  the  bottom,  were 
also  provided  for  the  purpose  of  grouting  the  rubble  base  beneath  the 
•caisson.  They  were  built  to  a  height  of  50  feet,  in  three  lengths,  vvith 
screw  ends.  This  great  height  was  necessary,  as  the  b^se  could  not  be 
grouted  until  the  caisson  was  nearly  filled  with  concrete,  but  it  entailed 
considerable  difficulty  in  affixing  successive  lengths,  a  step  which  had  to  be 
undertaken  while  the  caisson  was  afioat  and  by  no  means  quiescent.  Being 
too  slender  to  support  themselves,  they  had  to  be  stiifened  by  bracing  to  the 
sides  of  the  caisson,  an  arrangement  which  interfered  with  the  lowering  of 
material  and  plant.  Any  damage,  moreover,  to  the  pipes  below  the  water 
line  would,  in  all  probability,  have  involved  the  foundering  of  the  caisson. 

The  caissons  for  the  north  and  south  pierheads  were  similar  in  construc- 
tion, with  the  exception  that  the  former  had  an  additional  bracing  of  three 
transverse  bottom  girders,  2  feet  deep,  rivetted  over  the  tops  of  the  other 
ten,  at  right  angles  to  them.  The  north  caisson  was  brought  over  from 
England  in  sections  and  put  together,  to  a  height  of  23  feet,  within  a 
temporary  dock  or  enclosure  on  the  beach.  At  this  stage  it  was  launched, 
and  received  a  solid  floor  of  concrete  4  feet  thick.  Above  this  floor,  concrete 
was  deposited,  to  a  height  of  3  feet,  in  such  a  manner  as  to  leave  seven 
circular  wells  or  pits,  which,  with  the  exception  of  the  centre  one,  used  as  a 
tide  gauge- well,  were  filled  later.  The  lining  for  these  and  the  sides  was 
built  by  means  of  wooden  moulds,  5  feet  6  inches  in  height,  set  upon 
wooden  putlogs  as  the  sides  were  raised.  When  the  iron  sides  with  their 
concrete  lining  were  completed  the  caisson  drew  36  feet  of  water.  At  this 
draught  it  was  V)erthed  over  the  site,  which  had  a  prepared  rubble  founda- 
tion, with  a  slight  inclination,  to  cause  the  caisson  to  tilt  slightly  inwards 
towards  the  blockwork  of  the  pierhead  and  the  wave-breakers,  which  would 
lean  against  it.  When  in  position,  the  sluice  valves  were  opened,  the  caisson 
grounded,  and  about  500  tons  of  water  were  admitted,  sufficient  to  keep  it 
secure.  The  pits  were  then  utilised  for  the  reception  of  a  number  of  concrete 
blocks,  ranging  from  25  to  150  tons  in  weight,  and  the  caisson  was  subse- 
quently emptied  of  water  by  a  pulsometer.  After  this,  the  work  of 
completing  the  concrete  interior  was  proceeded  with  without  interruj>tion. 
The  sluices  were  removed  at  the  close  of  the  work. 

Piers  at   Sunderland  Harbour. 

These  piers  consist  of  two  curved  arms,  projecting  from  the  shore  line 
and  converging  to  a  distance  apart  of  480  feet  at  the  pierheads.  The  area 
thus  enclosed  is  100  acres. 

The  Roker  Pier  (fig.  244),  on  the  north  side  of  the  River  Wear,  has  a 


298 


DOCK  ENGINEERING. 


length  of  2,800  feet.  For  2,340  feet  of  this  length,  the  width  at  the  top  ia 
35  feet,  while  for  the  remaining  portion,  the  width  is  4 1  feet.  The  width  at 
the  bottom  varies  with  the  depth,  and  is  generally  120  feet  at  a  depth  of 
40  feet  below  low  water.  The  top  of  the  pier  is  10  feet  above  high  water. 
A  subway,  6J  feet  high  by  4  feet  wide,  runs  the  entire  length  of  the  pier, 
and  aflTords  access  to  the  lighthouse  in  stormy  weather.  The  shoreward 
portion  of  this  pier,  for  a  length  of  385  feet,  is  constructed  of  concrete 
en  masse,  faced  with  granite  blocks ;  for  the  remainder  of  the  pier,  the  super- 
structure is  formed  of  granite-faced  concrete  blocks,  varying  in  weight  from 
43  to  54  tons,  set  in  lengths  of  42  feet  7  inches  each,  by  a  radial  hydraulic 
block-setting  crane,  which  could  set  a  60-ton  block  60  feet  in  advance  of  its 
leading  wheel.  The  interior  of  each  length  is  filled  with  concrete  blocks 
and  mass  concrete.  The  superstructure  is  set  on  a  foundation  levelled  to- 
2^  feet  above  low  water.  This  foundation  was  formed  of  56-ton  and  116-ton 
bags  of  4  to  1  concrete  deposited  in  a  plastic  condition  on  the  rock.  The 
concrete  was  enclosed  in  bags  of  jute  sacking,  weighing  27  ounces  per  yard, 
30  inches  wide.  These  bags  were  made  in  boxes  slung  in  the  well  of  a. 
Wake  twin-screw  bag-barge  and  suspended  from  hydraulic  cylinders.     The 


ROKER     PIER 


SOUTH      PIER 


H  <*  p_St 


Fig.  244.— Pier  at  Sunderland. 


Fig.  245. — Pier  at  Sunderland. 


barge  steamed  alongside  a  concrete  mixing-house,  where  the  bag  was  filled 
with  plastic  concrete  and  laced ;  the  barge  then  proceeded  to  sea  and  waa 
moored  directly  over  the  place  where  the  bag  was  required.  The  box  and 
bag  were  then  lowered  as  near  the  bottom  as  possible  and  the  bag  deposited. 
For  a  length  of  460  feet  at  the  outer  end  of  the  pier,  the  rock  was  covered 
with  a  layer  of  sand,  varying  in  thickness  from  1  to  17  feet,  and  this  was 
removed  by  a  sand  pump  dredger  before  the  bags  were  deposited. 

The  pierhead  is  formed,  in  the  first  place,  of  an  iron  caisson,  100^  feet 
long,  69  feet  wide,  and  26^  feet  deep,  set  on  a  specially  prepared  foundation 
of  concrete  bags,  levelled  to  23  feet  below  low  water.  The  caisson  was 
floated  out  with  a  draught  of  22  feet,  containing  3,500  tons  of  concrete,  and 
sunk  on  its  site  by  partly  filling  it  with  water.  It  was  then  built  up  with 
15-ton  and  2o-ton  blocks,  mass  concrete  and  cement-grouted  granite  rubble 
until,  when  completed,  its  weight  amounted  to  10,000  tons.  On  top  of  this- 
the  pierhead  superstructure  was  constructed  in  blockwork  and  surmounted 
by  a  lighthouse,  giving  a  total  weight  of  23,000  tons  for  the  whole  structure. 

The  new  south  pier  (fig.  245),  on  the  south  side  of  the  harbour  is 
constructed  in  a  similar  manner  to  the  Roker  Pier,  but  varies  somewhat  in 


WHARFS  AT  GREENOCK.  299 

details.  The  length  of  the  pier  is  2,844  feet,  the  width  is  35  feet  for  three- 
fourths  of  this  length  and  41  feet  for  the  remainder.  The  top  of  the  pier  is 
9  feet  above  high  water,  and  there  is  a  parapet  wall,  9  feet  high  by  9  feet 
wide,  mainly,  but  14  feet  wide  at  the  outer  end,  running  along  its  entire 
length.  The  weight  of  the  blocks  used  on  this  pier  was  15  tons ;  they  were 
set  on  a  bagwork  foundation  by  a  20-ton  block-setting  crane  worked  by  a 
gas  engine.  The  crane  revolved  completely,  and  could  set  a  20-ton  block 
64  feet  in  advance  of  its  leading  wheel.  The  foundation  was  constructed  in 
the  same  manner  as  that  at  Roker  Pier. 


Wharfs  at  Greenock. 

The  wharfs  constructed  along  the  frontage  of  the  River  Clyde,  at 
Greenock,*^  between  the  entrances  to  the  East  and  West  Harbours  and 
westward  of  the  West  Harbour,  in  order  to  obtain  a  greater  depth  of 
water  than  existed  at  the  old  quays,  are  known  as  the  Steamboat  Quay 
and  the  West  Quay  respectively.  These  wharfs  were  erected  parallel  to 
and  25  feet  back  from  an  improved  channel  way,  adding  about  5,380  super- 
ficial yards  to  the  old  irregular  quays — which  are  much  used  for  coasting 
traffic — and  a  depth  of  28  feet  at  high  water  has  been  provided  in  front 
of  them.  Borings,  taken  along  the  line  of  the  new  work,  showed  that  a 
firm  stratum,  fit  for  quay  wall  foundations,  was  only  reached  at  great 
depths,  attaining  70  feet  below  high  water  in  one  or  two  places,  and 
therefore  timber  work  was  adopted.  A  trench  was  first  dredged  along 
the  front  line  of  the  new  work,  and,  after  driving  the  piles,  a  bank  of 
whinstone  rubble  was  deposited,  to  serve  as  a  toe  to  the  filling  between 
the  new  and  the  old  work.  To  increase  the  resistance  of  the  main  piles 
to  outward  thrust,  wrought-iron  shields,  5  feet  by  3i  feet,  were  bolted  to 
the  faces  of  the  front  piles  before  driving,  and  then  driven  down  so  that 
their  tops  were  2 J  feet  below  the  level  of  the  finished  dredged  bottom.  Sheet- 
ing piles  and  horizontal  planking  were  placed  along  the  line  of  the  front 
piles  to  retain  the  bank  of  rubble  stone,  and  for  the  retention  of  the 
filling  behind  the  back  line  of  main  piles,  a  double  row-  of  sheeting  piles 
was  driven,  the  lower  ends  of  which  extended  about  4  feet  into  the 
rubble  bank,  and  between  the  sheeting  piles,  a  wall  of  8  to  1  concrete 
was  brought  up  to  the  deck  planking.  The  greenheart  front  and  back 
piles,  14  to  16  inches  square,  8  feet  apart,  and  driven  into  the  hard 
clay,  are  joined  by  half-timber  ties,  and  whole-timber  struts  were  inserted 
between  the  piles,  and  the  ties  and  struts  bolted  together.  The  quay 
surface  is  planked  with  3-inch  Gardnerised  fir  planking,  with  whinstone 
pitching  laid  thereon,  on  a  bed  of  Portland  cement  mortar.  The  face  of 
the  quay  is  protected  by  segmental  rubbing  irons. 

•  Kinipple  on  "Greenock  Harbour,"  Min.  Proc,  InaL  C.E,,  vol.  cxxx. 


300 


DOCK  ENGINEERING. 


Wharfs  at  Hidl. 

The  splayed  wings  of  the  entrance  to  the  Alexandra  Lock,  at  Hull,* 
are  lined  with  timber  wharfs,  which  are  returned  for  a  length  of  300  feet 
up  and  down  the  River  Humber.  The  wharfs  (fig.  246)  were  constructed 
in  bays,  generally  10  feet  in  length,  but  3  feet  at  the  corners,  the  framing 
being  braced  both  longitudinally  and  transversely,  and  covered  with  a 
6- inch  decking.  The  river  bed  in  front  of  the  wharfs  had  been  dredged 
away  to  about  40  feet  below  the  top  of  the  piles,  so  that  the  piles,  which 
were  61  feet  in  length  and  about  15  inches  square,  penetrated  only  about 


r?'.  <'. 


Fig.  246.— Wharf  at  Hull. 

20  feet  into  the  ground.  Grooved  and  tongued  sheet  piling,  25  feet  long 
and  8  inches  thick,  was  driven  along  the  front,  the  top  being  just  above 
low  water.  The  sheeting  was  driven  in  lengths  of  6  feet  at  a  time,  all 
the  piles  in  one  bay  being  previously  pitched  in  position  so  as  to  ensure 
tight  contact.  This  sheeting  held  up  the  material  at  the  back  when  the 
river  bed  was  deepened  in  front.  During  construction  the  mud  accumu- 
lated so  rapidly,  in  the  recesses  behind,  that  whole-timber  sheeting  had  to 
be  driven  at  the  back  to  retain  it,  the  space  enclosed  between  the  front 
and  back  piles  being  excavated  to  enable  the  cross  bracing  to  be  fixed  at 
the  lowest  possible  level.  The  wharfing  was  constructed  from  a  staging 
on  piles  driven  by  piling  machines  on  barges.  The  sheet  piling  was  driven 
by  piling  machines  with  telescopic  leaders. 

*  Hurtzig  on  "The  Alexandra  Dock,  Hull,"  Min.  Proc.  Inst.  C.E,,  vol.  xcii. 


30I 


CHAPTER  VI IT. 

DOCK    GATES   AND    CAISSONS. 

Definition  and  Relative  Advantages  of  Gates  and  Caissons — Metal  rersiuf 
Wooden  Gates — Weight,  Cost,  Durability,  and  Stren(;th— Single-leaf  and 
Double-leaf  Gates— Horizontal  and  Vertical  Girder  Types— Storm  Gates — 
Strut  Gates — Stresses  in  Gates — Statical  Forces— Methods  of  Finding 
Resultant  Pressure— Zones  of  Equal  Pressure — Rise  of  Gates — Analysis 
of  Resultant — Graphic  Representation — Limits  op  Stress — Typical  Examples 
— Vertical  Co-planar  Girders — Stress  in  Panels — Exemplification  of  Gate 
CAI^'ULATIONs — Fittings — Examples  of  Gates  at  Liverpool,  Birkenhead, 
Manchester,  Hull,  Buenos  Ayr&s,  Calcuti'a,  South  Shields,  and  Dunkirk — 
Table  of  Dock  Gates — Stresses  in  CaiSvSons — Classification  of  Caissons — 
Swinging,  Traversing,  Sliding,  Rolling,  Floatincj,  and  Ship  Caissons 
—Lowering  Platforms— Examples  of  Caissons  at  Malta,  Bruges,  Blackwall, 
Cardiff,  Calcutta,  Belfast,  Liverpool,  and  Greenock — Table  of  Dock 
Caissons. 

In  localities  where  there  is  considerable  tidal  range  and  where  circum- 
stances render  it  desirable  to  maintain  the  surface  of  the  water  set  apart 
for  the  reception  of  shipping  at  a  fairly  constant  level,  it  is  evident  that 
the  entrance  or  entrances  to  a  dock  must  be  closed  in  order  to  impound  the 
water,  and  must  remain  closed  during  those  portions  of  each  day  in  which 
the  tide  falls  below  a  certain  limit.  This  is  usually  effected  by  means  of 
(1)  gates  or  (2)  caissons,  and  occasionally  provision  may  be  found  for  both 
forms  of  closure.  Graving  and  repairing  docks  are  treated  in  like  manner, 
but  for  a  different  purpose,  the  object  in  this  case  being  to  exclude  the 
external  water  during  the  time  of  occupancy. 

Definitions. — The  distinctive  feature  of  a  gate  is  that  it  revolves  about 
an  axis,  in  most  cases  vertical,  but  occasionally  horizontal,  while  the  motion 
of  a  caisson  is  either  rectilinear  or  altogether  untrammelled.  As  with 
many  other  terms,  however,  employed  in  dock  engineering,  this  definition 
is  not  susceptible  of  too  rigid  interpretation.  There  is  an  intermediate 
class  of  gate-caissons  combining  the  hinge  or  axis  of  the  gate  with  the 
broad  beam  of  the  caisson,  and  exemplified  at  Bristol,  Dundee,  Havre,  and 
other  places,  though,  taken  on  the  whole,  the  type  is  rare. 

The  Relative  Merits  of  Caissons  and  Gates,  considered  as  two  distinct, 
though  comprehensive,  classes  based  on  the  foregoing  definitions,  may  be 
broadly  gauged  as  follows  : — 

1.  Gates  with  vertical  axes  need  side  recesses  into  which  they  may  be 
swung  when  the  entrance  is  to  be  opened  for  the  passage  of  vessels.     This 


302  DOCK  ENGINEERING. 

necessitates  a  considerable  and  expensive  addition  to  the  length  of  the  side 
walls,  especially  when  the  lock  or  entrance  is  of  great  width,  as  often 
-obtains  at  the  present  day.  Oaissons  do  not  occasion  any  increase  in  the 
length  of  the  side  walls,  but,  on  the  other  hand,  there  must  be  reckoned  the 
■cost  of  a  special  chamber  for  sliding  and  rolling  caissons.  Ship  caissons  do 
not  need  a  chamber,  but,  when  out  of  use,  they  have  to  be  berthed 
somewhere,  and  this  leads  to  a  certain  amount  of  inconvenience  in  the 
iippropriation  of  useful  space. 

2.  Oaissons  are  generally  of  stronger  build  and  broader  beam  than 
gates,  and  they  afford  accommodation  for  the  transmission  of  rail  and  road 
traffic  across  a  waterway,  thus  discharging  the  functions  of  a  bridge  in 
addition  to  those  peculiarly  their  own. 

3.  The  first  cost  of  a  caisson  is  undoubtedly,  in  most  cases,  greater 
than  that  of  a  pair  of  gates,  but  if  the  cost  of  a  swing  bridge  for  vehicular 
traffic,  which  is  a  necessary  adjunct  in  the  case  of  gates,  be  also  taken  into 
consideration,  the  advantage  will  be  found  to  lie  with  the  caisson.  This 
advantage  is  still  further  emphasised  where  a  lock  or  passage  is  fitted  with 
double  gates  to  alternately  impound  or  exclude  water.  A  caisson  can  be 
constructed  to  act  equally  in  both  directions. 

4.  Caissons  obviate  the  necessity  for  pointed  sills  and  gate  platforms  of 
large  area,  but  those  of  the  ship  type,  fitting  into  grooves  so  as  to  be 
capable  of  acting  in  two  directions,  call  for  battered  side  walls  to  allow  of 
their  floating  clear  when  manoeuvring  in  and  out  of  position,  and  this  gives 
the  entrance  an  unsuitable  profile  for  modern  vessels  of  square  amidship 
section  and  with  bilge  keels. 

5.  Floating  caissons  are  not  always  manageable  in  boisterous  weather 
and  strong  currents,  and  oftentimes  they  are  only  workable  with  difficulty. 
Sliding  caissons,  too,  have  to  encounter  the  effect  of  wind  pressure,  especi- 
ally if  there  be  much  clearance  between  their  keels  and  the  sliding  ways. 
Neither  can  rolling  caissons  be  said  to  be  altogether  exempt  from  the 
abrading  or  wearing  effect  due  to  the  action  of  friction  on  the  moving  parts 
under  lateral  pressure.  So  that,  on  the  whole,  it  may  be  claimed  that 
gates  are  easier  of  movement  and  are  more  completely  under  control  during 
manipulation. 

Dock    Gates. 

Gates  are  sometimes  distinguished  as  wooden  gates  or  iron  (including 
steel)  gates,  according  to  the  nature  of  the  bulk  of  the  material  of  which 
they  are  composed.  As  a  matter  of  fact,  both  materials  enter  essentially, 
though  in  varying  proportions,  into  the  construction  of  all  gates.  It  would 
be  impossible  to  connect  the  various  members  of  a  wooden  gate  without  the 
aid  of  metal  bolts,  straps,  and  other  fastenings,  while  iron  gates  depend  for 
their  watertightness  (except  in  rare  instances)  on  wooden  posts  and  plates 
at  the  abutting  surfaces. 


EFFECTIVE  WEIGHT.  303 

As  regards   the   relative  advantages   of  wood   veraits  iron  gates,  the 
following  points  may  be  noted : — 

1.  Dead  Weight. — For  a  given  width  of  entrance,  wooden  gates  are 
considerably  the  heavier.  Greenheart  is  the  wood  now  most  extensively 
adopted  in  this  country,  but  in  spite  of  the  fact  that  its  specific  gravity, 
though  high  for  timber,  is  considerably  less  than  that  of  either  wrought 
iron  or  steel,  being  only  1*1  to  1*2  as  compared  with  7*6  and  7*8  for  the 
metals  respectively,  yet  it  outweighs  them  both  by  reason  of  the  excessive 
bulk  required  to  offer  an  equal  resistance  to  stress.  This  disparity  in 
strength  is  still  further  emphasised  in  the  case  of  the  lighter  woods,  such 
as  oak  and  pitch  pine,  considerably  in  vogue  at  Continental  ports.  And 
it  must  also  be  observed  that  no  inconsiderable  addition  is  made  to  the 
weight  of  a  pair  of  gates  by  the  unavoidably  extensive  use  of  metal  fittings 
and  connections.  The  weight  of  a  pair  of  iron  gates,  25^  feet  deep,  at 
Dublin,  for  a  70-foot  entrance  is  stated  to  be  90  tons.  A  similar  pair  of 
steel  gates  at  Limerick  are  about  the  same  weight,  while  a  69-foot  lock  at 
Dunkirk  possesses  iron  gates,  24  feet  deep,  weighing  88  tons.  As  against 
these  fairly  representative  values  for  metal  gates  may  be  set  the  weight, 
204  tons,  of  the  wooden  gates  (48  feet  deep)  to  a  70-foot  lock  at  Avon- 
mouth.  These  gates  are  mainly  framed  in  pitch  pine  and  memel,  the 
heelposts  and  mitreposts  alone  being  of  greenheart.  The  weight  of  the 
iron  fittings,  including  a  cast-iron  roller  path,  amounts  to  42  tons.  At 
the  south  lock  of  Buenos  Ayres  Harbour,  the  waterway  is  5  feet  less  in 
width  and  13  feet  less  in  depth,  but  the  gates  weigh  as  much  as  206  tons, 
owing  to  their  entire  construction  in  greenheart.  For  entrances  of  greater 
width,  wooden  gates  attain  enormous  figures,  as,  for  example,  the  green- 
heart gates  (44  feet  deep)  at  a  90-foot  passage  at  Liverpool,  which  weigh  no 
less  than  330  tons.  It  is  quite  safe  to  assert  that  a  pair  of  metal  gates  of 
the  same  size  would  not  exceed  half  that  amount. 

2.  Effective  Weight. — Not  only  is  the  dead  weight  of  wooden  gates 
necessarily  much  in  excess  of  that  of  iron  gates,  but  the  practicability  of 
forming  watertight  compartments  in  the  latter,  constitutes  a  means  of  still 
further  reducing  the  actual  working  load,  since  the  flotation  power  thus 
obtained  may  be  arranged  so  as  to  practically  counterbalance  the  weight 
of  the  gates,  leaving  only  a  small  margin  for  stability.  By  this  means  the 
power  required  for  opening  and  closing  the  gates  is  reduced  to  a  minimum. 
Even  in  localities  where  there  is  very  great  tidal  range,  and  where  anything 
like  an  exact  counterbalance  would  be  attended  with  much  difficulty  and 
some  danger,  the  reduction  in  weight  which  can  be  safely  made  is  far  from 
negligible.  At  Dunkirk  there  were,  some  short  time  back,  two  similar 
entrances,  69  feet  wide,  one  fitted  with  iron  and  the  other  with  wooden 
gates.  When  immersed  at  mean  sea  level,  the  weight  of  the  iron  gates 
was  reduced  from  98  to  16  tons,  to  which  16  tons  of  water  ballast  was 
added  making  32  tons  in  all.  The  wooden  gates,  when  immersed,  weighed 
just  double  this  last  amount.     They  have  now  been  replaced  by  iron  gates. 


304  I>OCK  ENGINEERING. 

3.  Initial  Cost. — Generally  speaking,  gate  materials  may  be  placed  as 
regards  cost  in  the  following  order,  commencing  with  the  most  expen- 
sive : — Greenheart,  iron,  oak,  and  creosoted  pine.  The  exact  proportion, 
of  course,  depends  on  current  prices.  At  the  present  time,  greenheart  logs 
of  large  size  can  hardly  be  obtained  for  less  than  Ss.  6d.  to  4s.  per  cubic 
foot,  and  for  great  lengths,  the  price  will  run  as  high  as  5s.  or  6s.  Under 
such  circumstances,  greenheart  gates,  for  entrances  ranging  between  60  and 
100  feet  in  width,  may  be  expected  to  cost,  under  normal  conditions,  from 
40s.  to  50s.  per  superficial  foot  of  gate.  Oak  may  be  priced  in  this  country 
at  3s.  to  4s.  6d. ;  red  pine  at  2s.  3d.  to  Ss.  3d. ;  and  pitch  pine  at  Is.  3d.  to 
2s.  3d.  per  cubic  foot.  Gates  of  these  last  named  timbers  will  be  relatively 
cheaper  with  a  corresponding  decrease  in  durability  and  strength.  The 
cost  of  iron  gates  has  fluctuated  somewhat.  In  1857  the  Dublin  graving 
dock  gates  cost  46s.  9d.  per  square  foot  of  gate  area,  but  the  figure  is  a 
high  one,  and  due,  no  doubt,  to  special  and,  possibly,  local  circumstances. 
The  price  of  iron  was  certainly  inordinately  high  about  the  year  1873,  for 
the  original  intention  of  fitting  the  Avonmouth  Lock  with  iron  gates  was 
abandoned  in  favour  of  wooden  gates  for  that  very  reason.  Iron  gates 
constructed  at  Antwerp  in  1873-74  cost  46s.  lOd.  per  square  foot.  But 
in  187D,  when  estimates  were  obtained  for  a  pair  of  gates  at  Dunkirk,  the 
tender  for  ungalvanised  iron  had  fallen  to  21s.  per  square  foot,  and  for 
galvanised  iron  it  was  only  26s.  per  square  foot,  including  in  both  cases 
four  coats  of  paint.  About  the  same  period  Mr.  Harrison  Hayter,  Past 
Fres.  Inst.  C.E.,  stated  in  the  course  of  a  discussion,*  that  he  was  in  the 
habit  of  estimating  the  cost  of  wrought-iron  gates  at  from  30s.  to  40s.  per 
square  foot.  Within  the  succeeding  decade  a  pair  of  steel  gates  was 
erected  at  Limerick  Dock  entrance  tor  258.  4d.  per  square  foot.  At  the 
present  time,  allowing  for  market  fluctuations,  a  pair  of  iron  or  steel  gates 
might  be  expected  to  cost  from  25s.  to  30s.  per  square  foot,  with  a  slight 
margin  in  favour  of  steel. 

On  the  Manchester  Ship  Canal,  two  pairs  of  gates  were  recently 
constructed  for  the  same  lock — one  pair  of  greenheart  and  the  other  of 
steel.  A  statement  (Table  xxiv.)  of  their  actual  cost  will  be  useful,  if  only 
as  aflbrding  a  basis  of  comparison  between  the  two  materials.f 

From  particulars  of  the  cost  of  seventeen  gates  of  oak  for  small 
entrances  at  German  seaports,  ranging  between  25  and  45  feet  in  width, 
Messrs.  Brandt  and  Hotopp  have  deduced  15s.  per  square  foot  as  the 
average  cost  of  such  gates.  |  They  further  state  that  "  the  proportion  in 
the  cost  of  wooden  gates  to  that  of  iron  or  steel  gates  may,  under  present 
conditions,  be   taken  as    4:5,  within  the  limits  fixed  for   comparison." 

*  Mill,  Proc.  Inst.  C,E.^  vol.  Iv.,  p.  72. 

t  Hunter  on  **Lock  Gates  of  Greenheart  and  Steel,"  Min,  Proc.  Ninth  Int.  Nav, 
Cony.,  Dtisseldorf,  1902. 

:^ Brandt  and  Hotopp  on  "Iron,  Steel,  and  Wooden  Gates,"  Min.  Proc.  Ninth 
Int.  Nav.  Cong.,  Diisseldorf,  1902. 


COST  OF  MAINTENANCE. 


305 


From  which  the  cost  of  small  metal  gates  in  Germany  may  be  considered 
as  about  198.  per  square  foot — a  figure  very  much  lower  than  that  quoted 
from  Mr.  Hunter's  report,  but  some  allowance  must  be  made  for  the  locale 
of  the  statistics,  as  well  as  for  the  difference  in  size  of  the  gates. 


TABLE  XXIV. 

Cost  of  Construction  and  of  Erection  of  One  Pair  of  Gates  for  a  Lock^  65 
feet  in  undthy  with  40  feet  of  toater  over  sill,  exclusive  of  Operating 
Machinery  and  of  Cliains, 


GrBEN  HEART  GaTES. 

Timber, £4,642 


Iron  and  steel  work,  . 

Labour, 

Erection,    . 


1,604 

1,640 

60.3 


Steel  Gates 

Steel  and  iron  work,  . 
Pumps  and  valves, 
Sheaves,  &c., 

Greenheart  posts  and  sills. 
Pitch-pine  fenders, 
Ballast, 
Erection,     . 


Total,  . 


£8,489 


i.e.,  49s.  9d.  per  square  foot  of  gate, 

or     65s.  3d.  „  waterway. 


Total,    . 


£4,523 
18a 
85 
425 
200 
206 
138 

£6,760 


i,e.y  338.  9d.  per  square  foot  of  gate, 

or    44s.  3d.  .,  waterway. 


it 


Area  of  waterway  =  width  of  lock  (65  feet)  x  greatest  depth  of  water  on  sill  (40  feet). 

Mr.  Nelemans  states  that,  for  a  lock  40  feet  to  60  feet  in  width,  the 
cost  of  creosoted  pine  gates  may  be  taken  at  one-half  of  that  of  iron  gates, 
and  from  two-thirds  to  three-fourths  of  that  of  oak  gates.*  He  also  gives 
it  as  his  experience  that,  for  locks  ranging  from  4d  to  65  feet  in  width,  iron 
gates,  with  double  plating,  cost  an  average  of  20  per  cent,  in  excess  of  oak 
gates,  and,  for  locks  of  about  40  feet  in  width,  gates  with  an  iron  frame 
and  creosoted  planking  cost  an  average  of  15  per  cent,  in  excess  of  oak 
gates.  These  conclusions  are  based  exclusively  on  statistics  obtained  from 
the  more  important  maritime  canals  of  the  Netherlands. 

4.  Cost  of  Maintenance. — Reliable  and  extensive  data  for  general 
application  on  this  point  are  not  forthcoming.  The  writer's  experience  is 
that,  in  regard  to  greenheart  gates,  the  cost  of  maintenance  is  practically 
nil.  Gates  of  oak  and  pine  are  stated  by  Messrs.  Brandt  and  Hotopp  to 
require  an  annual  upkeep  expenditure  of  ^  to  1  per  cent,  of  their  prime 
cost.  Some  iron  and  steel  gates  are  recorded  as  costing  as  much  as  1  to 
1^  per  cent.  Mr.  Nelemans  places  the  several  materials  in  the  following 
order  as  regards  maintenance,  commencing  with  the  costliest : — Creosoted 
pine,  iron,  oak.  He  states,  in  this  connection,  that  'Hhe  maintenance 
expenses  of  wooden  lock  gates  exceed  those  of  iron  gates  by  50  per  cent., 

*  Nelemans  on  "  Iron  and  Wooden  Lock  Gates,"  Min,  Proc,  Ninth  Int,  Nav,  C<mg.y 
Dosseldorf,  1902. 

20 


306  DOCK   ENGINEERING. 

and  exceed  those  of  gates  with  iron  framework  and  planking  by  25 
per  cent." 

Owing  to  the  variability  of  local  practice,  there  is  no  absolute  standard 
of  comparison. 

5.  Durability* — As  regards  this  point,  the  advantage,  on  the  whole, 
lies  with  wooden  gates.  Salt  water,  especially  if  in  any  way  contaminated 
with  sewage,  is  extremely  deleterious  to  ironwork.  As  has  already  been 
pointed  out  in  Chapter  iv.,  the  metal,  if  unprotected,  is  speedily  reduced 
to  a  condition  resembling  graphite  or  plumbago  in  structure.  Painting,  the 
preservative  agency  most  usually  adopted,  is  merely  a  temporary  expedient 
calling  for  constant  renewal,  while  the  more  expensive  process  of  galvanising 
adds  bnt  a  few  years  to  the  natural  life  of  a  gate  at  the  expense  of  some 
reduction  in  the  strength  of  the  material.  The  life  of  an  iron  gate,  under 
normal  circumstances,  can  scarcely  be  expected  to  exceed  thirty  years,  and 
the  following  are  actually  recorded  instances  of  the  rate  of  decay  : — A  pair 
of  iron  gates  at  a  lock  on  the  Dedemsvaart  Oanal  in  Holland,*^  constructed 
in  1880,  were  removed  for  repairs  in  1894,  when  it  was  found  that  the  frame- 
work was  covered  with  a  layei*  of  rust  which  had  to  be  scraped  away,  while 
the  sluice  paddles  and  their  grooves  were  completely  worn  out  so  as  to  need 
replacing.  The  galvanised  sheeting  was  intact,  but  it  was  deemed  advis- 
able to  coat  it  with  black  varnish.  A  pair  of  gates  at  GlUckstadt  Harbour, 
on  the  Elbe,  built  in  1874,  were  condemned  in  1902.  Dock  gates  at 
Bremerhaven,  erected  in  1852,  were  removed  in  1900  as  completely  worn 
out,  the  plates  being  eaten  away  below  low  water  to  a  depth  of  ^  of  an  inch, 
and  the  rivet  heads  either  badly  decayed  or  entirely  destroyed,  t  Naturally, 
the  life  of  an  iron  gate  depends  very  largely  on  the  amount  of  care  devoted 
to  its  maintenance,  and,  in  order  to  keep  such  gates  in  proper  condition, 
they  should  be  scraped,  cleaned,  and  painted  annually,  or  at  intervals  not 
exceeding  three  years.  The  lock  gates  at  Terneuzen  and  Ymuiden  are 
thus  treated. 

Apart  from  the  attacks  of  sea  worms  (and  some  ports  are  apparently 
exem])t  from  these  pests),  wooden  gates,  more  particularly  those  of  oak  and 
greenheart,  are  extremely  durable  and  need  no  attention.  Mr.  Blandy  X 
mentions  the  case  of  the  old  Waterloo  Dock  gates  at  Liverpool,  constructed 
of  oak,  which,  when  removed  on  account  of  alterations  and  taken  to  pieces, 
were  found  to  be  in  a  perfect  state  of  preservation  after  forty  years' 
exposure  to  tide,  wind,  and  weather.  §  The  100-foot  greenheart  gates  at 
the  Canada  Lock  of  the  same  port  were  in  active  use  for  a  like  period,  1856 
to  1895,  and,  when  removed  on  similar  grounds  and  taken  asunder,  were 
found  to  be  in  an  absolutely  sound  condition  and  as  good  as  on  the  day 


♦.. 


Min.  Proc,  Seventh  IrU,  Nav.  Cong,,  Brussels,  1898,  p.  326. 
+  Brandt  and  Hotopp  on  "Iron,  Steel,  and  Wooden  Gates,"  Min,  Proc,  Ninth 
Int.  Nav,  Cong,,  Diisseldorf,  1902. 

t  Blandy  on  **  Dock  Gates,"  Min,  Proc,  IiiM,  C.E.,  vol.  lix. 

§  The  gates  lay  on  the  beach  for  several  ykoxs  prior  to  being  broken  up. 


DURABILITY.  307 

when  they  were  built.  Owing  to  the  deepening  of  the  lock,  new  verticals 
had  to  be  introduced,  but  the  old  horizontal  ribs  were  replaced,  and  are 
now  doing  duty  as  effectively  as  the  new  timber,  with  every  prospect  of  an 
indefinite  existence.  The  greenheart  storm-gates  of  the  Sandon  entrance, 
built  about  the  year  1848,  were  taken  to  pieces  in  1902  and  found  to  be  in 
•excellent  condition.  The  Bramley-Moore  Dock  gates,  of  English  oak,  built 
about  1835,  were  overhauled  in  1902 ;  below  the  water-line,  the  wood  was 
in  perfect  preservation,  but  decay  had  occurred  in  some  sapwood  in  the 
upper  part  of  the  gate,  which  had  to  be  made  good.  The  greenheart 
gates  at  the  Del  am  ere  Dock,  at  the  entrance  to  the  Eiver  Weaver,  were 
constructed  in  1862.  No  repairs  of  any  kind  have  been  executed  to 
them,  and  they  are  still  in  admirable  condition.*  The  greenheart  gates  at 
the  sea  entrance  to  Hendon  Dock,  Sunderland,  were  constructed  in  1866. 
With  the  exception  of  some  caulking  to  the  planking,  no  repairs  have  been 
•carried  out,  and  the  gates  are  still  practically  as  good  as  new.f 

Where  the  timber  is  of  less  trustworthy  character  the  same  durability 
cannot  be  reasonably  expected.  Continental  gates  often  contain  a  large 
proportion  of  ordinary  pine  and  pitchpine,  timbers  which  do  not  possess 
the  lasting  qualities  of  oak  and  greenheart.  It  is  not  surprising,  there- 
fore, to  find  that  the  average  life  of  such  gates  is  about  twenty-five  years, 
though,  with  constant  care,  Mr.  Nelemans  states  that  very  good  results 
have  been  obtained,  after  nearly  forty  years'  trial,  with  creosoted  pine, 
^^  although  the  gates  concerned  are  not  usually  worked,  excepting  those  in 
the  old  Ymuiden  Locks.  It  should  be  observed,  however,  that  gates 
which  are  nearly  always  in  their  recesses  do  not  last  longer  than  those 
which  are  regularly  worked."  J 

The  one  recdly  weak  point  in  the  argument  for  the  longevity  of  wooden 
^ates  is  their  liability  to  the  depredations  of  sea  worms.  The  Limnoria 
Urehrans  and  the  Teredo  navcUis  (vide  Chapter  iv.,  p.  151)  are  two  extremely 
persistent  and  troublesome  borers,  but  they  do  not  infest  sewage-polluted 
waters,  at  any  rate  to  any  serious  extent,  and  greenheart  appears  to  be 
little,  if  at  all,  susceptible  to  their  ravages,  §  possibly  on  account  of  a 
poisonous  oil  which  it  contains.     A  splinter  of  greatheart  in  the  flesh  will 

•Hunter  on  **Dock  Gates  of  Greenheart  and  Steel," //li.  Nav,  Cong,,  Dusseldorf, 
1902. 

flbid, 

t  Nelemans  on  "Iron  and  Wooden  Lock  Gates,"  Int.  Nav.  Cong.,  Dusseldorf, 
1902. 

§  The  testimony  on  this  point  is  not  altogether  unanimous.  Mr.  Squire  states  that 
'*  Greenheart  ofiers,  perhaps,  the  best  resistance  to  the  ravages  of  the  Photcta  and 
Limnoria  on  the  exterior,  and  of  the  Teredo  on  the  interior,  of  the  wood,  but  it  is  by  ' 
no  means  invulnerable.  In  the  Bombay  Docks,  greenheart  gates  were  freely  attacked 
by  all  these  animals,  especially  on  the  seaward  side  of  the  gates  and  on  the  underside  of 
the  ribs.  For  the  first  few  years  they  appeared  only  in  the  corners  of  the  large  ribs 
where  the  less  mature  timber  would  be  found,  but  ultimately  they  penetrated  the  heart- 
wood."— On  "  Lock  Gates,"  Niiith  Int.  Nav.  Cong.,  Dusseldorf,  1902. 


308  DOCK   ENGINEERING. 

certainly  produce  a  nasty,  festering  wound ,  difficult  to  heal.  There  are 
sundry  precautions  which  may  be  adopted  to  minimise  the  mischief  caused 
to  gates  by  marine  vermin.  They  have  already  been  dealt  with  in  the 
chapter  on  Materials  of  Construction. 

6.  Strength. — Another  respect  in  which  timber  gates  have  an  advantage 
over  iron  gates  is  their  more  solid  construction  and  consequent  greater 
ability  to  stand  the  peculiarly  rough  usage  to  which  dock  gates  are  unavoid- 
ably subjected.  Entrances  sometimes  have  to  be  closed  in  the  face  of  a 
strong  outflow  of  water,  and  at  such  times  there  is  a  tendency  for  the 
gates  to  strike  the  sill  with  considerable  force,  in  spite  of  the  restraint  of 
check  chains  and  springs.  Occasionally,  moreover,  the  leaves  do  not  reach 
the  sill  simultaneously,  and  the  top  part  of  the  leaf,  meeting  with  no  sup- 
port, is  jerked  violently  forward.  An  instance  is  on  record  where,  in  the 
absence  of  a  check  chain,  the  topmost  outer  corner  of  a  gate  at  Birkenhead 
was  projected  momentarily  some  10  or  12  feet  out  of  plumb.*  The  leaf 
then  recoiled,  and,  fortunately,  mitred  fairly  with  its  neighbour  without- 
further  mishap ;  but  the  shock  must  have  been  tremendous,  and  nothing 
save  the  elasticity  and  flexibility  of  a  wooden  frame,  with  broad  tenoned 
joints,  could  possibly  have  withstood  the  strain.  As  another  instance  of 
the  almost  disastrous  nature  of  some  of  the  conditions  to  which  a  gate  may 
be  subjected,  mention  may  profitably  be  made  of  a  serious  accident  which 
quite  recently  befell  a  pair  of  wooden  gates  at  Liverpool,  closing  a  passage 
90  feet  wide  between  two  adjoining  docks.  One  of  these  is  a  half-tide 
dock,  in  which  the  water  is  allowed  to  fall  with  the  tide  for  some  hours 
after  high  water.  The  passage  gates  were  carefully  mitred  at  the  turn  of 
the  tide,  and  attention  was  directed  to  them  until  a  steadily  increasing 
head  of  some  15  or  18  inches  of  water  was  registered.  At  this  point, 
being  night-time,  they  were  left,  apparently  secure.  Unfortunately,  by 
some  carelessness  or  oversight,  water  for  levelling  purposes  was  run  off 
from  the  inner  dock  at  too  rapid  a  rate,  and  the  accumulated  head  was 
dissipated,  with  the  result  that  the  gates  parted.  Shortly  afterwards,  when 
the  sluices  were  closed  and  at  a  time  when  the  tide  was  ebbing  fast,  the 
gates  came  together  again,  probably  with  some  impact,  certainly  imperfectly,, 
and  in  such  a  way  as  to  cause  nipping  between  the  outer  edge  of  one  mitre- 
post  and  the  inner  edge  of  the  other.  The  falling  tide  soon  produced  a 
fresh  head  of  4  feet  or  so,  at  which  point  the  foully  mitred  gates  yielded 
with  a  loud  crack.  The  alarm  being  raised,  immediate  steps  were  taken 
to  avert  any  further  evil  consequences.  The  gates  were  found  to  be  badly 
strained,  and  one  leaf  had  to  be  taken  into  the  graving  dock  for  repairs. 
Despite  the  resistance  of  the  connecting  straps,  the  topmost  ribs  were 
torn  out  of  the  heel-post,  and  the  upper  portion  of  the  latter  was  so  split 
as  to  need  splicing  with  new  timber.  The  nipped  edge  of  the  mitre-posts 
were  also  badly  detruded.  However,  the  damage  was  soon  made  good 
at  a  moderate  cost,  and  though  the  incident,  at  first  sight,  demonstrates 
*  This  is  the  authentic  statement  of  an  expert  eyewitness. 


STRENGTH.  309 

the  vulnerability  of  timber  gates,  yet  it  may  be  claimed  that  the  injury 
was  far  from  vital,  that  the  repairs  were  speedily  effected,  and  that  in 
undergoing  a  similar  experience,  the  damage  to  a  pair  of  iron  gates  would 
have  been  well-nigh  irreparable.  The  veriest  trifle,  indeed,  may  cause  them 
serious  if  not  fatal  injury,  owing  to  the  thinness  of  their  skins,  the  rigidity 
of  their  rivetted  joints,  and  the  delicate  adjustment  of  their  buoyancy 
<3hambers.  Several  instances  might  be  cited,  but  the  following  extract,* 
relating  to  a  pair  of  iron  gates  at  Limerick,  will  suffice : — 

"About  1867,  the  bottom  plates  were  unaccountably  injured.  The 
air-cells  tilled  with  water,  which  it  was  found  impossible  to  eject,  as  no 
provision  had  been  left  for  pumping.  The  result  was  a  total  loss  of 
buoyancy,  the  whole  weight  of  the  gates  being  thrown  on  the  bottom 
pintles  and  rollers.  Temporary  repairs  to  the  damaged  plates  were 
•eflected  by  divers,  and  sluice  doors  were  placed  over  the  inlets  on  the 
river  face,  so  that  the  effect  contemplated  by  the  designer  was  reversed, 
the  air-cells  and  water-cells  changing  their  functions.  This  arrangement 
was  partially  successful,  but  had  the  disadvantage  of  imparting  such  an 
excess  of  buoyancy  to  the  gates  that  during  rough  weather,  at  spring 
tides,  they  were  nearly  floated  off  the  hinges,  whilst  at  neaps  as  many 
as  twelve  men  were  often  required  to  move  them.  The  state  of  things 
grew  worse,  for  the  roller  carriages  became  disabled  under  the  undue 
stress,  causing  the  gates  frequently  to  jamb  in  the  closing,  allowing  the 
water  to  leave  the  dock."  After  this,  it  is  not  surprising  to  learn  that  the 
estimated  cost  of  repairs  rendered  an  entirely  new  pair  of  gates  advisable. 

After  receiving  a  number  of  reports  on  the  relative  merits  of  wood  and 
iron  gates,  followed  by  a  general  discussion,  the  Ninth  International 
Navigation  Congress,  sitting  at  Dusseldorf  in  1902,  came  to  the  conclusion 
that  no  definite  opinion  could  be  expressed  as  to  the  preference  to  be 
accorded  to  wood  or  iron  gates,  the  question  depending  almost  entirely 
upon  local  considerations.  They  adopted  a  further  conclusion,  however, 
*^  that  for  locks  of  great  width,  iron  gates  offer  the  advantage  over  wooden 
gates  that  they  can  be  more  easily  constructed  with  suitable  stiffness  and 
durability,  more  readily  and  expeditiously  moved,  and  more  expeditiously 
and  less  expensively  installed  and  removed."  The  reader  will  be  able  to 
form  his  own  conclusions  from  the  evidence  which  has  been  laid  before 
him. 

From  a  German  official  of  public  works,  Herr  Fiilscher,  comes  a  novel 
suggestion  for  compound  gates.  Since  wood  is  durable  under  water  and 
perishable  above,  while  for  iron  and  steel  the  conditions  are  reversed,  Herr 
Fiilscher  advocates  the  employment  of  each  material  in  the  situation  which 
is  particularly  favourable  to  it,  so  that  the  lower  part  of  a  gate  would  be  of 
wood  and  the  upper  part  of  iron.  The  idea  is  ingenious  and  plausible,  but 
no  attempt  has  yet  been  made  to  carry  it  into  effect,  and  there  are  several 
serious  difficulties  in  the  way  of  its  realisation.     It  would  manifestly  be  an 

•  Mill,  Proc,  Inst.  C.E,,  vol.  xcvii.,  p,  336. 


310  DOCK   ENGINEERING. 

Unsuitable  design  for  localities  in  which  there  was  any  important  change  in 
tidal  level,  and  it  is  chiefly  in  such  places  that  gates  are  required. 

Classification  of  Gates. — Gates  may  be  most  efficiently  classified  as — 

(a)  Those  consisting  of  a  single  leaf. 
(/J)  Those  having  double  leaves. 
In  the  former  case  the  axis  of  rotation  may  be  either  horizontal  or  vertical ; 
in  the  latter,  it  is  necessarily  vertical. 

Single  Leaf  Gates. — A  single  leaf  gate  with  a  vertical  axis  can  only  be 
advantageously  employed  for  a  very  narrow  waterway.  When  swung  back 
to  allow  a  passage  for  vessels,  it  occupies  a  side  recess  of  considerable 
extent,  rendering  the  entrance  or  lock  unduly  long  and  correspondingly 
expensive.  Such  a  gate  is  rarely,  if  ever,  constructed  for  dock  work,  and  is 
almost  entirely  confined  to  canals.  The  following  conclusion,  voted  by  the 
International  Navigation  Congress  sitting  at  Brussels  in  1 898,  sums  up  the 
advantages  and  disadvantages  in  a  clear  and  concise  manner. 

''  Single  gates,  turning  on  a  pivot,  claim  the  attention  of  engineers. 
Notwithstanding  the  lengthening  of  the  lock  which  they  involve,  they  are 
not  more  expensive  than  mitred  gates ;  they  are  subject  to  less  strain, 
cause  less  loss  of  water,  and  are  more  easily  adjusted,  repaired,  and 
replaced  ;  and  their  working  is  simpler  and  more  regular.  Nevertheless, 
the  great  expenditure  of  water,  and  the  increase  in  the  period  of  locking, 
resulting  from  the  elongation  of  the  chamber,  are  inconveniences  which,  as 
regards  the  lower  gates,  counterbalance  and  even  outweigh  the  advantages 
mentioned  above."* 

A  single  leaf  gate,  however,  w^ith  a  horizontal  axis,  is  capable  of  much 
wider  application.  It  turns  upon  a  hinge  or  pivot,  fixed  slightly  below  the 
level  of  the  sill  of  the  entrance.  When  open,  it  lies  prone  upon  a  platform, 
below  and  outside  the  sill,  so  contrived  that  no  part  of  the  gate  in  this 
position  projects  above  the  sill  level.  The  process  of  closing  consists  in 
raising  the  outer  edge  of  the  gate  until  it  is  vertically  over  the  pivot. 
When  this  is  done,  the  gate  has  a  bearing  against  the  two  side  quoins  and 
against  the  face  of  the  sill.  The  raising  may  be  efiected  by  means  of  a 
suitable  attachment  of  wire  ropes  or  chains,  leading  from  the  topmost 
member  to  a  winch  or  other  winding  apparatus  on  the  quay,  but  the  action 
can  be  aided  to  a  considerable  extent  by  the  formation  of  watertight  com- 
partments within  the  gate,  the  flotation  power  of  which  reduces  the 
external  lifting  force  required. 

Messrs.  Clover,  Clayton  &  Co.,  of  Birkenhead,  have  a  gate  constructed 

on  this  principle  at  one  of  their  private  graving  docks.     It  is  illustrated  in 

figs.  247  to  249. t     It  closes  an  entrance  of  rather  more  than  40  feet  mean 

width  and  its  height  is  27  feet  7  inches.     The  framing  consists,  on  the 

inside,  of  four  horizontal  tiers  of  bulb-angle  iron,  ranging  from  6  by  3  inchea 

to  9  by  3  inches,  with  a  lowermost  tier  of  10  by  6  inches  bulb  tee  iron ;  and 

•  Proceedings,  p,  638. 

+  Vide  Brodie  on  "Dock  Gates,"  Min.  Proc,  L,E,S.,  vol.  xviii. 


SINGLE   LEAF  GATE  AT  BIRKENHEAD, 


312  DOCK   ENGINEERING. 

on  the  outside,  of  20  vertical  bulb-angle  irons,  each  7  by  3  inches,  spaced 
about  2  feet  apart.  The  plating  between  the  framings  varies  in  thickness 
from  \  inch  at  the  top  to  |  inch  at  the  bottom.  The  topmost  member  is 
arranged  as  an  air  chamber,  and  it  also  serves  the  purpose  of  a  stiffening 
girder.  The  meeting  surfaces  of  the  gate,  the  sill  and  the  jambs,  consist  of 
pieces  of  pitchpine,  faced  with  strips  of  indiarubber,  2  inches  wide  and 
f  inch  thick,  to  secure  watertightness.  The  method  is  apparently  very 
effective,  and  the  joint  a  perfectly  durable  one,  as  the  author  found  from 
personal  inspection.  At  the  end  of  seven  years  the  indiarubber,  which  is 
fastened  by  copper  nails,  was  quite  undeteriorated.  The  gate  is  swung  on 
two  hinges,  having  pins  4  inches  diameter.  A  sluice  at  each  side  of  the 
lowermost  panel  completes  the  equipment  of  the  gate. 

The  success  attending  this  type  of  gate,  of  which  the  foi*egoing  is 
probably  the  principal  existing  example  in  this  country,*  is  sufficient  to 
warrant  its  introduction  on  a  larger  scale.  The  main  objections  attending 
such  a  step  are  the  necessity  for  a  platform  deep  enough  to  contain  the 
buoyancy  chambers,  and  the  possibility  of  some  unseen  obstacle  preventing 
the  gate  from  falling  back  to  its  full  extent,  and  thereby  endangering 
vessels  passing  over  it.  These  disadvantages  cannot  be  considered  insuper- 
able. Special  recesses  might  be  formed  in  a  comparatively  shallow 
platform  to  receive  the  buoyancy  chambers,  and  these  would  be  kept  clear 
of  deposit  by  an  efficient  system  of  sluicing.  An  additional  element  of 
strength  could  be  imparted  to  the  gate  by  the  adoption  of  a  sill  curved  in 
plan,  to  which  the  turning  axis  would  be  tangential  at  its  centre,  as 
exemplified  in  the  lower  portion  of  a  railway  carriage  door.  This  would 
entail  somewhat  longer  hinges  at  the  sides,  in  order  to  cover  which,  and 
the  curved  profile  of  the  gate,  the  sill  would  also  require  to  be  curved  in 
elevation — an  objectionable  arrangement  for  passages  frequented  by  flat- 
bottomed  vessels. 

Gates  with  ttoo  Leaves. — By  far  the  more  general  method  is  that  of  gates 
in  two  symmetrical  leaves,  each  a  little  longer  than  the  semi-width  of  the 
waterway,  meeting,  when  closed,  at  its  centre  line  in  such  a  way  as  to 
afford  one  another  mutual  support  by  pointing  in  the  direction  of  the 
impounded  water. 

Of  this  class  of  gate  there  are  two  varieties,  representing  distinct  forms 
of  construction,  viz.: — 

(a)  Those  with  horizontal  girders. 
(3)  Tliose  with  vertical  girders. 

The  first  case  represents  the  type  most  commonly  met  with  in  British 
ports.  It  is  founded  on  the  principle  of  the  arch,  and  consists  essentially 
of  a  series  of  horizontal  ribs  or  girders.  In  timber  structures,  these  are 
grouped  more  or  less  into  << cesses"  throughout  the  height  of  the  gate,  the 

*  The  author  is  only  aware  of  one  other  example,  viz.  : — A  gate  closing  the  entrance 
(35  feet  wide)  to  a  graving  dock  at  Port  Dinorwic,  North  Wales. 


STORM   GATES.  313 

intermediate  spaces  being  faced  with  planking.  In  the  larger  gates,  the 
cesses  are  not  continuous  from  one  end  of  the  leaf  to  the  other,  but  are 
intersected  by  verticals  which  divide  each  leaf  into  a  series  of  v&ussoirs. 
In  iron  gates  the  horizontal  members  are  single  girders,  continuous 
throughout,  with  intermediate  connecting  pieces,  or  stiffeners,  and  plating. 
There  are  at  least  two  continuous  vertical  members  in  both  kinds  of 
gate — the  heel-post,  or  axis  of  rotation,  set  in  the  hollow  quoin  of  the 
entrance,  and  the  mitre-post y  forming  the  abutment  at  the  outer  end  of 
the  leaf.  In  timber  gates  the  horizontal  ribs  are  tenoned  into  and  between 
these  two  main  verticals,  and  for  small  gates  they  are  sufficient.  But  for 
medium  sized  leaves  of  arched  form,  ranging  from  30  to  40  feet  in  length, 
an  additional  vertical  called  the  middle-liead  is  economically  introduced, 
dividing  the  leaf  into  two  voussoirs.  For  larger  entrances  still,  the 
middle-head  can  be  duplicated,  the  two  posts  being  distinguished  as  the 
heel-^midcUe-head  and  the  mitre-middle-hsad,  according  to  their  respective 
positions.  In  extreme  cases,  where  the  length  of  the  leaf  reaches  from 
50  to  60  feet,  three  intermediates  will  be  required. 

In  the  second  type  the  method  of  construction  is  reversed,  and  the 
principle  of  the  beam  adopted.  There  are  only  two  continuous  horizontal 
members,  one  at  the  sill  level,  forming  a  watertight  abutment,  and  the 
other  at  the  summit  of  the  gate.  Between  these  are  set  a  series  of  verticals 
at  regular  intervaU  from  heel-post  to  mitre-post.  The  intervening  space 
is  made  good  with  planking  or  plating,  as  the  case  may  be,  the  thrust 
upon  which  is  transmitted  by  the  verticals  to  the  upper  and  lower 
transoms,  and  these,  accordingly,  receive  the  whole  hydrostatic  pressure 
in  a  ratio  to  be  determined  later.  For  curved  timber  gates  the  verticals 
may,  in  certain  cases,  be  arranged  in  contiguity  as  the  voussoirs  of  an 
arch,  but  the  necessity  for  having  them  in  such  close  contact  is  remote, 
and  the  system  is  more  generally  characteristic  of  flat  gates,  such  as  are 
in  evidence  at  Dunkirk,  on  the  North  Sea  Canal  and  elsewhere. 

For  the  sake  of  offering  some  basis  of  comparison  of  the  merits  of  the 
two  systems,  it  may  be  remarked  that  the  vertical  tyf)e  is  more  readily 
adaptable  to  the  accommodation  of  large  sluice  openings  in  the  gate  itself, 
as  these  can  be  arranged  between  the  verticals  without  impairing  the 
strength  of  the  framing.  On  the  other  hand,  the  horizontal  system  has 
obvious  advantages  in  respect  to  the  more  eflfective  distribution  of  the 
material,  and,  in  the  case  of  wooden  gates,  at  any  rate,  it  undoubtedly 
represents  the  soundest  and  most  economical  form  of  construction. 

Storm  Gates, — A  class  of  gates  differing  in  function,  rather  than  in  mode 
or  form  of  construction,  is  that  known  as  storm  or  flood  gates.  They  are 
employed  in  entrances  subjected  periodically  to  floods  or  to  extraordinarily 
high  tides  accompanied  by  cyclones  and  tempestuous  weather.  During 
such  periods  it  is  often  necessary  to  exclude  part  of  the  tidal  water  from 
a  dock,  and  the  gates  consequently  point  in  the  opposite  direction  to  those 
used  for  impounding  water.     From  the  nature  of  their  du.ies  it  is  evident 


314  DOCK   ENGINEERING. 

that  they  call  for  exceptional  strength  and  careful  construction.  In  some 
instances  a  ship  caisson  is  employed  for  the  purpose,  especially  when  the 
circumstances  are  of  rare  occurrence. 

Strut  OcUes  are  auxiliary  frames  or  shores  which  support  the  main  ebb 
gates  in  their  closed  position  and  enable  them  to  withstand  a  slight  head 
on  the  outer  face,  and  to  resist  the  onset  of  waves  at  or  about  high- water 
level.  They  assist  ebb  gates  to  act  to  a  certain  extent  as  storm  gates,  and 
are  accordingly  found  to  be  a  useful  adjunct  in  exposed  situations  (fig.  201). 

Stresses  in  Gates. — Proceeding  now  to  an  investigation  of  the  stresses 
to  which  gates  are  subjected,  it  will  be  found  on  consideration  that  the 
causes  to  which  they  are  due  may  be  ranged  under  five  heads : — 

1.  The  excess  of  \vater  pressure  on  the  inner  side,  or  back  of  the  gates, 
when  closed. 

2.  The  tension  of  chains,  or  the  thrust  of  rams,  during  the  operations 
of  opening  and  closing. 

3.  Concussions  and  irregularities  of  movement  in  consequence  of  unseen 
obstacles  and  incomplete  control  of  the  motive  power.  In  this  connection 
it  is  to  be  noted  that  a  strong  current  sometimes  forms  a  very  great  part 
of  the  motive  power. 

4.  Wind  pressure  and  the  impact  of  waves. 

5.  Collisions  with  passing  vessels. 

Of  these,  the  three  last  are  of  a  more  or  less  abnormal  nature,  and 
their  magnitude  cannot  be  estimated  with  any  degree  of  exactitude  or 
certainty.  Nevertheless,  they  constitute  very  potent  factors  in  the  deter- 
mination of  the  life  and  stability  of  a  gate.  In  boisterous  weather,  not 
only  do  external  waves  break  against  the  outer  face  of  a  gate  in  a  succession 
of  shocks  of  varying  intensity  (the  effect  at  high  water  being  especially 
destructive),  but  even  the  water  confined  within  the  dock  will  often  become 
considerably  agitated,  especially  if  there  be  any  extensive  area  exposed  to 
the  action  of  the  wind.  This  last  named  agent  also  exerts  direct  unbalanced 
pressure  upon  the  surface  of  the  gate  above  the  water  line,  but  as  the 
unimmersed  portion  is,  as  far  as  possible,  constructed  in  openwork,  the 
result  is  minimised. 

During  the  operations  of  opening  and  closing,  the  gates  are  liable  to 
jars  and  shocks  from  contact  with  sunken  obstacles,  from  abrupt  stoppages 
due  to  occasional  fluctuations  in  hydraulic  pressure,  where  such  is  employed, 
from  the  sudden  impetus  of  wind,  wave,  and  tidal  current,  and  even  from 
irregularities  in,  and  silt  accumulations  upon,  roller  paths.  If  the  tide  be 
running  out  with  any  degree  of  swiftness,  a  rapid  current  is  generated  in 
narrow  entrances,  in  which  it  is  difficult  with  rams,  and  almost  impossible 
with  chains,  to  prevent  the  gates  from  striking  the  still  with  some  force, 
instances  of  which  have  already  been  noticed. 

Collisions  are  occurrences  more  or  less  frequent  during  the  time  the 
entrance  or  passage  is  being  worked.  Accordingly,  it  is  very  essential  that 
the  open  gate  should  be  completely  recessed  beyond  the  face  line  of  the 


RESULTANT  WATER   PRESSURE.  315 

waterway.  Even  when  this  point  is  carefully  attended  to,  it  is  impossible 
to  avoid  chance  contact,  and  the  abrading  action  can  only  be  neutralised  by 
the  provision  of  stout  and  ample  fendering.  Perhaps  the  best  form  of  gate 
to  suit  these  conditions  is  that  with  a  straight  inner  face,  and  when  the  gate 
is  segmental,  it  is  desirable  that  the  fendering  should  be  arranged  so  as  to 
form  a  chord  to  the  segment.  This  gives  a  straight  lead  to  shipping,  and 
prevents  the  arch  voussoirs  from  receiving  a  pressure  from  the  quarter  in 
which  they  are  least  fitted  to  resist  it. 

For  all  these  and  other  varieties  of  stress,  more  or  less  intermittent  in 
character,  uncertain  in  direction  and  unknown  in  amount,  provision  can 
only  be  made  in  a  crude  and  wholesale  manner  by  the  employment  of  a  high 
factor  of  safety.  It  is  not  too  much  to  say  that  the  actual  strength  of  a 
gate  should  be  at  least  ten  times,  and,  in  certain  cases,  as  much  as  twenty 
times,  in  excess  of  its  calculated  requirements  under  normal  statical  con- 
ditions. This  factor  of  safety  attains  its  higher  values  in  the  case  of 
wooden  gates,  where  the  material  has  a  wide  range  of  strength.  The  resist- 
ance of  iron  and  steel  can  be  estimated  with  greater  exactitude,  and 
therefore  admits  of  a  closer  approximation. 

Statical  Forces. — The  only  statical  forces  are  those  called  into  action  by 
the  excess  of  water  pressure  on  the  back  of  the  closed  gate,  and  by  its  own 
weight,  and  it  is  inevitable  to  limit  the  calculations  for  the  stability  of 
gates  to  a  consideration  of  these  simple  elements.  Calculations  are  some- 
times carried  out  to  a  theoretical  nicety,  which,  however  ingenious  and 
interesting,  is  of  questionable  expediency  in  view  of  the  wide  margin  of 
safety  ultimately  adopted.  Inordinate  detail  in  calculation  entails  two 
evils  j  it  not  only  involves  a  waste  of  time,  but  leads  to  an  exaggerated  view 
of  the  accuracy  and  importance  of  the  result.  In  investigating,  therefore, 
the  internal  stresses,  caused  by  external  agency,  an  attempt  must  be  made 
to  steer  a  middle  course  between  the  Scylla  of  useless  refinement  and  the 
Chary bd is  of  superfluous  strength. 

When  a  pair  of  dock  gates  is  closed  and  the  water  within  the  dock  is  at 
a  higher  level  than  that  outside,  the  horizontal  external  forces  at  work  are 
four  in  number : — 

1.  The  resultant  pressure  of  the  water  against  the  back  of  the  gate. 

2.  The  mutual  reaction  of  the  mitre-posts. 

3.  The  reaction  of  the  hollow  quoins  on  the  heel-posts. 

4.  The  reaction  of  the  sill  against  the  bottom  of  the  gate. 

The  conditions,  in  fact,  are  those  of  a  loaded  vault  closed  at  one  end. 

It  will,  perhaps,  be  preferable  to  consider  primarily  the  joint  effect  of 
the  first  three  forces,  and  then  to  estimate  the  modification  caused  by  the 
fourth  force,  which  does  not  in  any  way  aflfect  the  relationship  existing 
between  the  other  three.  The  forces  being  symmetrical  for  each  half  of  the 
gate,  it  will  only  be  necessary  to  deal  with  a  single  leaf  in  each  case. 

1.  Reaultaiit  Water  Pressure, — This  force  is  completely  defined,  since  it 
is  known  in  magnitude,  line  of  action  and  sense. 


3i6 


DOCK  ENGINEERING. 


(a)  Magnitude. — The  weight  of  a  cubic  foot  of  fresh  (distilled)  water  is 
1,000  ozs.  av.  or  62^  lbs.  The  weight  of  a  cubic  foot  of  salt  water  depends 
upon  its  impurities,  which  vary  in  different  localities.  Within  the  limits 
of  the  British  Isles,  it  ranges  from  1,000  to  1,025  ozs.,  and  will  be  taken 
here  at  its  maximum  value  of  64  lbs.,  and  symbolised,  when  necessary, 
by  the  letter  w.  The  intensity  of  water  pressure  on  the  back  of  a  gate 
increases  from  zero  at  the  surface  level  to  an  amount  at  any  other  level  due 
to  the  height  of  the  column  of  water  above  it.  Thus,  at  a  depth  of  10  feet 
below  the  surface,  the  pressure  is  10  to  =  640  lbs.  per  square  foot.  When 
there  is  no  water  on  the  front  of  the  gate  this  represents  the  resultant 
intensity  of  pressure  at  that  level.     If  the  height  of  the  water  behind  the 


gate   be   designated  A,  then  the  mean  intensity  of  pressure  is 
the  total  resultant  pressure  per  lineal  foot  of  gate. 


wh 


and 


P  = 


(45) 


If  there  be  a  height,  h^,  of  water  at  the  front  of  the  gate,  it  is  manifest 
that  this  expression  must  be  modified  into 


w 


A*       w  hi 


w 


Pi  =  ^ o-   =  V  (A*  -  A.'). 


2 


2 


(46) 


(/9)  Line  of  Action, — The  centre  of  pressure  is  situated  at  the  level  of 
the  centre  of  gravity,  D,  of  the  triangle,  ABC,  representing  the  distri- 
bution of  pressure  (fig.  250).  That  is  to  say,  the  line  of  action  is  horizontal, 
at  one-third  of  the  height  of  the  water.  When  there  is  water  on  only  one 
side  of  the  gate,  this  applies  to  the  resultant  pressure  also.  With  water  on 
both  sides,  the  resultant  pressure  will  act  at  a  point  determined  by  the 
centre  of  gravity  of  the  quadrilateral,  A  C  F  D  (fig.  251),  formed  by  deduct- 
ing the  lesser  triangle  of  pressure  from  the  greater.  If  the  gate  be  curved, 
the  line  of  action  will  be  normal  to  the  curve. 

A 


A. 


^'^'^^''^^^S^ 


Fig.  250.  Fig.  251. 

(y)  The  Sense  is  obvious,  being  al  ways  towards  the  gate. 

2.  Tiie  Jieaction  of  the  Alitre-jyosts  is  a  force  perpendicular  to  the  plane 
of  their  abutting  surfaces,  and,  therefore,  also  perpendicular  to  the  longi- 
tudinal axis  of  the  waterway.    Even  with  perfectly  fitting  gates,  it  would  not 


REACTION   OF   THE   SILL.  317 

be  justifiable  to  assume  that  the  line  of  action  of  the  force  passed  through 
the  centre  of  the  meeting  faces,  and,  in  practice,  it  must  inevitably  happen 
that  the  gates  are  the  veriest  trifle  too  long  or  too  short,  in  either  of  which 
cases  the  gates  will  nip  one  another  ;  if  too  long,  on  the  inner  edge,  and  if 
too  short,  on  the  outer  edge,  of  the  mitre-post  (fig.  255).  Nipping  may  also 
be  due  to  the  accidental  intrusion  of  some  small  floating  substance,  such  as 
a  chip  of  wood.  Under  these  circumstances,  the  line  of  action  would  pass- 
near  to  the  inner  or  outer  edge  of  the  mitre-post.  For  the  present,  how- 
ever, the  assumption  will  be  made  that  it  bisects  the  meeting  surfaces. 

3.  If  friction  be  left  out  of  account,  the  Reaction  of  the  Hollow  Quoins^ 
will  pass  through  the  centre  of  the  heel-post,  and  further  (the  three  forces 
being  in  equilibrium),  through  the  point  of  intersection  of  the  other  two 
forces,  and  these  two  points  are  sufficient  to  determine  its  line  of  action. 
When  the  gates,  however,  are  just  closed,  and  during  the  period  in  which 
the  parts  are  taking  up  their  respective  stresses,  there  is  some  inevitable, 
albeit  almost  infinitesimal,  yielding  of  the  wooden  heel-post,  and  a  corre- 
sponding movement  along  the  face  of  the  rigid  masonry,  which  brings  into- 
play  a  frictional  force,  Btan  ^,  where  R  is  the  thrust  on  the  heel-post  and 
f  the  angle  of  repose  of  wood  on  stone.  If  r  be  the  radius  of  the  heel- post, 
the  reaction  of  the  hollow  quoin  will  accordingly  pass  at  a  distance,  rsin  9, 
from  its  centre.  The  deviation  is  generally  slight,  and,  unless  the  thrust 
be  very  great,  its  effect  may  be  ignored. 

4.  The  Reaction  of  the  Sill  upon  the  lowermost  horizontal  member  of 
the  gate  is  frequently  overlooked,  but  that  it  is  capable  of  affording  no- 
inconsiderable  assistance  to  a  gate  under 
pressure  is  manifest  from  the  fact  that 
it  is  quite  theoretically  possible  to  con- 
struct a  gate  deriving  its  entire  support 
from  the  sill  alone.    This  will  be  apparent 
from  a  glance  at  flg.  252,  in  which  the 
top  of  the  sill  coincides  with  the  centre 
of  gravity  of  the  water  pressure  against 
the  gate.    The  latter,  accordingly,  is  in 
critical  equilibrium,  which  the  least  in-  %^^?^^^>!?^^^^^^ 
crease  in  its  depth  below  the  sill  renders  Yia,  252 

stable.     The  inconvenience,  however — if 

not  the  impracticability — of  providing  so  deep  a  sill,  with  a  perfectly 
watertight  joint,  constitutes  an  insuperable  objection  to  such  an  ar- 
rangement. The  reaction  of  an  ordinary  shallow  sill  is  not  altogether 
easy  to  determine,  but  it  may  be  considered  in  two  ways.  It  may 
be  deemed  to  raise  the  level  of  the  centre  of  pressure,  though,  in 
this  respect,  its  effect  is  scarcely  appreciable.  It  may  also  be  taken  as 
exerting  a  moment  about  the  top  edge  of  the  sill,  contrary  to  and  partially 
counteracting  the  moment  due  to  the  water  pressure  above  the  sill.  This- 
latter,  however,  would  only  be  a  legitimate  aspect  of  the  problem,  provided 


— N- 


r-«-^ 


— V— 


^C 


3i8 


DOCK   ENGINEERING. 


the  gate  were  constructed  mainly  or  altogether  of  verticals,  for  the  joints 
between  successive  tiers  of  horizontal  ribs  are  not,  and  cannot  be  supposed, 
capable  of  resisting  transverse  stress.  In  the  absence  of  such  joints,  it  is 
justifiable  to  state  that  the  pressure  on  the  watertight  surface  of  the  sill  is 
sufficient  to  counterbalance,  at  least,  the  pressure  on  an  equal  height  of 
the  unsupported  portion  of  the  gate  immediately  above  the  sill.  The 
case  is  that  of  a  cantilever,  the  moiety  of  whose  length  is  unsupported 
and  loaded  with  a  weight  something  less  than  the  weight  on  the  sup- 
ported half.  In  flat  gates  of  the  vertical  type,  the  sill  plays  a  most 
important  part,  supporting,  as  will  be  seen  later,  two-thirds  of  the  total 
water  pressure  upon  the  gate. 

So  much  for  the  horizontal  forces.  The  vertical  forces  are  two  in 
number : — 

1.  The  dead  weight  of  the  gate,  acting  downwards  through  its  centre 
of  gravity. 

2.  The  upward  reaction,  due  either  separately  or  jointly  to  (a)  flotation 
of  buoyancy  chambers  or  the  water  pressure  on  the  underside  of  the  gate, 
(6)  truck  wheels  or  rollers  bearing  upon  a  platform,  and  (c)  inclined  straps 
connected  with  the  top  of  the  heel-post. 

We  need  not  consider  these  at  greater  length.  Obviously,  equilibrium 
can  be  secured  by  a  suitable  adjustment  of  the  opposing  forces.  We  pro- 
ceed to  deal  with  the  more  complex  problem  presented  by  the  horizontal 
forces. 

To  find  the  Resultant  Pressure  on  any  Section  of  a  Gate, 

Fig.  253  represents  the  plan  of  one  leaf  of  a  pair  of  gates.  P  is  the  total 
water  pressure  upon  the  back  of  the  leaf,  assumed  concentrated  at  its  centre. 


Fig.  253. 

Kj  is  the  mitre  reaction  of  the  adjoining  leaf,  taken  as  passing  through  the 
centre  line  of  the  abutting  surfaces.     R^  ^^  ^^^  reaction  of  the  hollow  quoin 


RESULTANT  PRESSURE.  319 

assumed  to  act  through  the  axis  of  the  heel-post.  These  three  forces  being 
in  equilibrium,  the  triangle  of  forces,  or  a  (fig.  254),  can  be  drawn,  having 
its  sides  parallel  to  the  forces,  P,  R^,  and  Rg  re- 
spectively, and,  since  the  magnitude  of  P  is 
known,  the  magnitudes  of  the  other  two  may 
readily  be  determined. 

If,  now,  it  be  required  to  find  the  position 
and  amount  of  the  resultant  stress  across  any 
section,  A  B  (fig.  253),  of  the  gate,  we  proceed 
as  follows: —Join  the  point.  A,  to  each  of  the 
two    extremities,    K,  L,    of    the    water-bearing 

surface  of  the  leaf;  bisect  these  lines  at  U  and  V  respectively,  and  draw 
perpendiculars  to  represent  the  total  water  pressure  on  each  section.  Each 
section  is  in  equilibrium  under  the  action  of  these  forces :  in  one  case, 
the  water  pressure,  the  heel-post  reaction,  and  the  stress  across  A  B ;  in 
the  second  case,  the  water  pressure,  the  mitre-post  reaction,  and  also  the 
stress  across  AB,  acting,  of  course,  in  the  opposite  direction.  Since 
this  stress  must  have  the  same  line  of  action  in  both  cases  and  must 
pass  through  the  points  of  intersection  of  each  of  the  other  pairs  of  forces 
in  order  to  fulfil  the  conditions  of  equilibrium,  we  have  obviously  only  to 
join  the  two  points  of  intersection  to  obtain  the  line  of  action  of  the 
resultant  pressure  at  the  section  A  B.  Its  magnitude  maybe  determined  by 
drawing  a  parallel  line  in  the  force  diagram  from  the  point,  o,  and  complet- 
ing the  triangle  by  drawing  the  line  representing  the  water  pressure  on 
either  surface  of  the  gate.  Thus,  in  fig.  254,  the  mitre-post  reaction  being 
already  determined,  r^  is  the  water  pressure  on  the  surface  of  the  gate 
between  the  point,  A,  and  the  mitre-post,  and  qo  i^  the  stress  across  the 
section  A  B.  Similarly,  for  the  heel  portion,  a  line,  qs^  might  have  been 
drawn  parallel  to  the  water  pressure  on  that  section.  Thus  the  point,  q,  is 
not  only  obtained,  but  confirmed. 

By  taking  a  series  of  sections  in  this  way,  it  will  be  found  that  the  locus 
of  the  point  q  is  sensibly  the  arc  of  a  circle,  and  therefore  that,  except 
perhaps  \\\  the  case  of  vei*y  flat  gates,  the  resultant  pressure  is  so  nearly 
constant  as  to  be  justifiably  considered  so  without  serious  error.  Also,  it 
will  be  found  that  the  line  of  pressure  is  a  circular  curve.  This  is  perfectly 
true  for  all  gates  which  present  the  form  of  a  continuous  arc  when  closed. 
It  is  also  approximately  and  practically  true  for  all  segmental  gates  varying 
between  the  straight  line  and  the  continuous  arc,  provided  the  versed  sine 
or  rise  of  the  gates  (T  M,  fig.  253)  do  not  exceed  one-fifth  of  the  span.  For 
a  greater  ratio  of  rise  to  the  span  the  divergency  of  the  line  of  pressure  from 
the  circular  arc  begins  to  be  appreciable,  and  ultimately,  in  the  ca.se  of  the 
flatter  gates,  becomes  very  marked,  so  that  it  is  necessary  to  find  by  trial  a 
series  of  points  through  which  the  curve  may  be  drawn.  Fig.  255  shows  the 
curves  of  pressure  in  a  segmental  gate  for  a  central  reaction  at  the  mitre- 
post  and  also  in  case  of  nipping  on  .the  inner  or  outer  edges  of  the  mitre-post. 


320 


DOCK  ENGINEERING. 


Fig.  265.— Range  of  Position  of  Line  of  Pressure  due  to  Nipping. 

V 


Fig.  2o6. 


RESULTANT   PRESSURE.  32 1 

Another  method  of  procedure,  which  has  the  advantage  of  including  both 
diagrams  in  a  single  drawing,  is  as  follows: — From  one  extremity,  K 
(fig.  256),  of  the  water-bearing  surface  of  the  leaf  draw,  perpendicular  to  the 
direction  of  the  heel-post  reaction,  a  line,  K  O,  to  intersect  at  O,  the  centre 
line  of  the  passage,  which  itself  is  perpendicular  to  the  mitre-post  reaction. 
In  this  way  a  triangle,  KLO,  is  formed,  having  its  sides  respectively 
perpendicular  to  the  lines  of  action  of  the  forces  and  therefore  proportional 
to  their  magnitudes.     And  as  P,  the  total  water  pressure,  is  measured  by 

the  length  of  the  leaf,  K  L,  multiplied  by  -,^  ,  so  the  heel  and  mitre-post 

reactions  are  K  O  x  —  -  and  L  O  x  — ^  respectively  and  indifferently,  for 

they  are  equal,  as  we  have  already  seen.  The  reaction  at  any  section  of  the 
gate  can  be  obtained  by  drawing  a  line  from  O  to  that  point  of  the  water- 
bearing surface  which  lies  on  the  section  line  in  question.     The  length  of 

9/)  ft" 
this  line  multiplied  by  —^  gives  the  required  reaction. 

It  may  be  convenient  to  obtain  an  expression  for  the  value  of  the  heel- 
post,  the  mitre-post,  and  the  sectional  reactions  generally,  in  terms  of  the 
span  and  rise  of  the  gates.  This  can  be  done  with  very  close  approximation 
as  follows: — By  the  span  of  the  gates  is  to  be  understood  the  distance 
between  the  centres  of  the  two  heel-posts  and  by  the  rise,  the  vertical 
distance  from  this  line  to  the  centre  of  the  abutting  surfaces  of  the  mitre- 
posts.  From  an  inspection  of  fig.  256  it  will  be  seen  that  the  line  H  M 
joining  the  centre  of  the  heel-post  to  the  centre  of  the  mitre  meeting 
surface — that  is,  joining  the  extremity  of  the  span  to  the  extremity  of  the 
rise — is  practically  and  sensibly  parallel  to  the  line  K  L  which  connects  the 
extremities  of  the  water-bearing  surface.  Consequently  we  may  imagine 
the  angle  H  M  T  equal  to  the  angle  K  L  T  without  appreciable  error.  Then 
from  similar  triangles,  HTM  and  O  S  L,  we  have 

OL  ^  HM 
S  L  *"    M  T  ' 

Now,  S  L  =  one-half  the  total  water  pressure  on  the  surface  of  the  leaf 

A2  7 

=  —J — ;  and  OL  is  to  all  intents  and  purposes  a  measure  of  the  resultant 

pressure  on  any  section — i.e.,  R. 

Again,  H  M  is  the  length  of  the  leaf  minus  the  radius  of  the  heel-post 
^  I  -  p\  and  M T  is  the  rise  of  the  gate  =  r. 
Substituting,  we  obtain 

R="^'y/^> ^^^^ 

If  we  choose. to  neglect  f>,  which  is  a  very  small  quantity  in  comparison 

,2 

with  I,  and  to  substitute  for  Z*  its  component  value  -r  +  r*,  we  arrive  at  an 

4 

21 


322 


DOCK  ENGINEERING. 


approximate  expression  for  the  resultant  pressure  in  terms  of  the  rise  and 
span  of  the  gates,  viz.  : — 

...     (48) 


R  =  wA2  f  -—  + 
16r 


(l6r  ■*"  i}     • 


The  following  data  apply  to  a  pair  of  gates  closing  a  70-foot  entrance : — 

;  =  39-75;  «  =  76-3;  r=lM6;  f»=lj  A  =  30— all  in  feet. 
By  formula  (47) 

64  X  30  X  30  X  39-75  x  38-75 


R  = 


By  formula  (48) 


4  X  11-16 
=  1,987,500  lbs.,  or  887-3  tons. 


R  =  64  X  30 


X  30  (■ 


76-3  X  76-3     11-16 


) 


16  X  11-16         4 
=  2,038,500  lbs.,  or  910  tons. 

The  discrepancy  between  the  two  results,  it  will  be  observed,  is  less  than 
2  J  per  cent. 

Zones  of  Equal  Pressure, — ^The  surface  of  a  gate  may  be  divided  into  a 
series  of  zones,  in  which  the  total  hydrostatic  pressure  is  equal,  in  the 
following  simple  and  graphical  manner : — 

With  the  height  of  the  gate  between  the  sill  and  the  surface  of  the  water 
as  diameter,  describe  a  semicircle  (fig.  257).     Subdivide  the  diameter  into 


B 
Mg.  257.  Fig.  268. 

any  number  of  equal  parts  (say  five)  by  the  points  a,  6,  c,  d.  Through  these 
points  draw  horizontal  lines  to  the  semicircle,  intersecting  it  at  the  points 
*>y>  9y  ^'  Then,  with  A  as  centre,  describe  circular  arcs  ek,  /I,  gm,  An, 
cutting  the  gate  surface  at  the  points  k,  I,  m,  and  n.  Ak,  kl,  Im,  m n,  and 
n  B  will  then  be  a  series  of  consecutive  zones  upon  which  the  hydrostatic 
pressure  is  in  each  case  equal  to  one-fifth  of  the  total  pressure  upon  the 
surface  of  the  gate. 

This  may  be  proved  by  reference  to  fig.  258. 
from  similar  triangles 


There  it  will  be  seen  that 


or 


AC 
AD 
AO 


AD 
AB' 
AD2 


AB^XS^' 


RISE  OF  GATES.  323 

That  is  (since  the  water  pressure  on  any  surface  is  proportional  to  the 
square  of  the  depth),  the  pressure  on  A  D  is  to  that  on  A  B  in  the  same 
ratio  as  the  depth  A  C  to  the  depth  A  B. 

Having  divided  the  sectional  area  of  material  required  into  equal 
portions,  the  cesses  or  girders  can  be  located  at  the  centres  of  pressure  of 
the  respective  zones. 

Bise  of  Gates, — The  ratio  which  the  versed  sine  or  rise  of  a  pair  of  gates 
bears  to  the  span  varies  in  practice  between  the  limits  of  one-third  and 
one-sixth.  The  best  proportion  is  a  matter  of  individual  experience  and 
local  requirements,  rather  than  of  theoretical  calculation.  Much  depends 
upon  the  nature  of  the  material  of  which  the  gate  is  constructed,  its 
distribution  and  maximum  resistance  to  stress,  but  the  practical  exigencies 
of  the  situation  often  outweigh  them  all  in  importance. 

It  has  been  stated  that  the  most  economical  rises  are  about  one-third 
and  one-fifth  for  cylindrical  and  straight  gates  respectively.*  But  gates  are 
rarely  constructed  with  parallel  faces,  and  the  disposition  of  the  material 
may  be,  and  often  is  such,  that  the  longitudinal  axis,  which  is  the  true 
curve  of  the  gate,  follows  a  path  in  no  way  concentric  with  either  of  the 
faces.  Further,  it  should  be  noted  that  mere  economy  in  gate  construction 
is  a  question  of  minor  importance  to  those  of  stability,  durability,  and 
convenience.  A  great  rise,  combined  with  cylindrically-curved  backs,  calls 
for  long  and  deep  recesses  in  the  side  walls,  and  exposes  a  large  gate  surface 
to  contact  with  passing  vessels.  On  the  other  hand,  at  graving  dock 
entrances  the  rise  of  the  gates  adds  somewhat  to  the  available  length  of  the 
dock. 

Considering  the  question  for  a  moment  merely  from  the  point  of  view  of 
the  amount  of  stress  due  to  different  ratios  of  rise  to  span,  let  us  refer  to 
the  closely  approximate  formula  already  devised  for  the  value  of  the 
resultant  stress  in  terms  of  the  rise  and  span  of  the  gates,  viz. : — 

Re-arrange  and  let  r  =  vs,  so  that  v  may  have  any  value,  integral  or 
fractional,  of  which  the  latter  alone  calls  for  serious  consideration.     Then 

In  this  equation  we  have  an  expression  for  the  resultant  in  terms  of  the 

water  pressure  per  unit  length  of  the  gate  (  —^  j,  multiplied  by  a  coefficient 

involving  the  rise  and  span  of  the  gates  only. 

Now  assign  to  t;  a  series  of  values  ranging  from  '1  to  1 — that  is,  from 
^jf  to  unity — and  calculate  therefrom  the  corresponding  values  for  the 
coefficient 

1  +  4t^ 
81; 
*  Min,  Proc,  Ivst,  C.E,,  vol.  xviii.,  pw  474 ;  voL  zxxi,  p.  344. 


324 


DOCK  ENGINEERING. 


The  results  form  a  series  of  co-ordinates  from  which  the  curve  in  fig.  259 
has  been  plotted.  The  line  A  B  constitutes  the  span,  and  along  it  have 
been  marked  off  distances  corresponding  to  the  ratio  of  rise  to  span.  From 
an  inspection  of  the  figure  we  see  that  the  resultant  pressure  is  least  with  a 
ratio  of  ^,  and  that  it  increases  in  amount  with  any  change  from  this  ratio. 
The  increment  is  comparatively  small  as  the  value  of  t;  approaches  unitj^ 
but,  as  it  approaches  zero,  the  rate  of  increase  is  very  rapid,  becoming 
ultimately  infinite.  With  a  rise  equal  to  ^  span,  the  excess  over  the 
minimum  is  inconsiderable,  and  thence  to  a  rise  of -^,  it  is  but  moderate, 
but  for  rises  beyond  ^,  the  value  of  the  coefficient  becomes  excessive. 

In  conjunction  with  the  question  of  the  total  amount  of  stress,  it  must 
be  borne  in  mind  that  the  pressure  between  the  gate  framing  has  to  be 
taken  by  metal  plating  and  wood  planking,  as  the  case  may  be,  and  that 
there  is  a  practical  limit  to  their  effective  and  useful  resistance. 


B 


Fig.  259. 

Taking  everything  into  consideration — design,  material,  permissible 
stress,  contingencies  of  manufacture — no  definite  rule  can  be  laid  down 
beyond  the  statement  of  the  usual  range  already  given. 

AncUysis  of  the  Hesukant  Pressv/re. — Having  obtained  an  expression  for 
the  resultant  pressure  on  the  cross-section  of  a  gate,  we  now  proceed  to 
consider  it  with  reference  to  its  point  of  application. 

The  simplest,  and  theoretically  ideal,  gate  would  be  that  in  which  the 
line  of  pressure  passed  through  the  centre  of  gravity  of  successive  cross- 
sections.  In  this  way  the  joints  would  simply  be  called  upon  to  sustain 
direct  compression,  uncomplicated  by  any  bending  moment.  It  has  been 
pointed  out  that  this  does  not  necessarily  imply  that  the  back  and  front 
of  the  gate  would  be  circular  arcs  concentric  with  the  line  of  pressure. 
A  straight  gate  might  be  constructed  to  fulfil  the  required  condition  by  a 
suitable  adjustment  of  the  material,  so  that  the  centre  of  gravity  of  each 
section  fell  upon  the  line  of  pressure. 

In  most  cases,  however,  practical  considerations  cause  the  axis  of  the 
gate  to  deviate  more  or  less  from  the  ideal  curve. 

Fig.  260  is  the  plan  of  a  portion  of  a  gate  leaf,  A  A  being  the  longi- 
tudinal axis — 1.6.,  the  line  passing  through  the  centres  of  gravity  of 
successive  sections — and  L  M  a  line  perpendicular  thereto. 


ANALYSIS  OF  RESULTANT  PRESSURE. 


325 


Now,  let  X  be  the  point  of  application,  in  the  curve  of  pressures,  of  the 
resultant,  E,  acting  on  the  plane  of  section,  L  M.  Then,  if  the  angle 
between  the  line  of  action  of  B  and  the  sectional  line  L  M  be  designated 
6,  the  force,  R,  may  be  resolved  into  two  component  forces — viz.,  R  sin  ^, 
parallel  to  the  axis,  A  A,  and  R  cos  ^,  at  right  angles  to  it.  The  former  is 
a  direct  compressive  stress  and  the  latter  a  shear. 

By  introducing  two  opposite  forces  at  the  point  O,  each  equal  to  R  sin  0, 
a  step  which  in  no  way  interferes  with  the  equilibrium  of  the  section,  wq 
may  conceive  the  line  of  action  of  R  sin  0  transferred  to  the  axis,  A  A, 
provided  that  this  change  be  taken  in  conjunction  with  a  couple,  the 
moment  of  which  is  R  a?  sin  tf,  and 
which  tends  to  turn  in  a  clockwise 
direction. 

The  section,  L  M,  is  thus  subjected 
to  the  action  of  the  following  forces  : — 

1.  A  shearing  stress,  R  cos  &,  along 
LM. 

2.  A  direct  compressive  stress  of  uni- 
form intensity  throughout  the  section, 
the  total  amount  of  which  is  R  sin  0, 

3.  A  bending  moment,  R  x  sin  ^,  producing  compression  from  O  to  L 
and  tension  from  O  to  M,  both  these  stresses  varying  in  intensity  and 
increasing  with  the  distance  from  the  neutral  axis  at  O. 

The  force  R  cos  ^,  being  a  simple  shear,  calls  for  no  further  comment. 
With  regard  to  the  force  R  sin  ^,  it  will  simplify  the  notation  in  the 
ensuing  investigation  if,  from  this  stage,  we  symbolise  it  by  the  letter  F. 
If  the  area  of  section  be  A,  the  uniform  intensity  of  direct  compression  is 

F  F 

— ,  and  if  the  vertical  depth  be  taken  as  unity,  it  is  ^,  where  b  is  the 

breadth  of  section  «  L  M. 

The  intensity  of  stress  at  any  point  in  the  section  due  to  the  bending 
moment,  F  or,  may  be  obtained  from  the  well-known  relationship, 


Fig.  260. 


y 


M 
I' 


where  y  is  the  distance  from  the  neutral  axis  of  the  fibre  sustaining  the 

stress  intensity,  /,  M  is  the  moment  of  resistance,  equal  to  the  bending 

moment,  F  x,  and  I  is  the  moment  of  inertia. 

The  greatest  intensity  of  stress  is  manifestly  that  in   the  outermost 

fibres,  at  L,  where  the  maximum  compressive  efiect  of  the  bending  moment 

is  added  to  the  direct  compression.     Indicating  the  distance,  O  L,  by  the 

letter  p^  and  taking  the  depth  as  unity,  the  intensity  of  stress  due  to  direct 

^compression  is 

F 

/     =   -T>       .  •  •  •  •  C^") 


326  DOCK  ENGINEERING, 

and  that  due  to  bending  is 

r-^; (50) 

whence  the  total  intensity  of  stress  at  L — 

/  =  /+/- =F(J  +  y).  .        .        .        (61) 

At  the  point  M,  on  the  other  side  of  the  neutral  axis,  we  roust  give 
the  tensile  stress,/'',  a  negative  value,  and  the  equation  becomes 

Graphic  Bepresentation  of  iTiterncU  Stress, — Fig.  261  is  a  diagram  showing 
the  combined  effect  of  the  stresses,  /'  and  /",  throughout  the  section,  L  M. 
The  quadrilateral,  K  L  M  N,  represents  direct  compression,  and  accordingly, 

F 

The  two  triangles,  LOP,  M  0  R^  represent  respectively  the  compres- 
sive and  tensile  values  of  the  bending  moment ;  so 

It  will  be  noticed  that,  in  the  etched  portion  of  the  figure,  the  com- 
pression and  tension  more  or  less  neutralise  one  another,  and  that  at  the 
point  Q  there  is  exact  equilibrium.  From  Q  to  M  tension  predominates, 
and  compression  from  Q  to  L.     Calling  the  distance  O  Q,  q,  we  may  obtain 

its  value  by  equating, 

F  _  F_ag 

b   "  "1"  ' 


whence 


«  =  ^ (5^) 


When  it  is  undesirable  to  allow  a  tensile  stress  in  any  part  of  the 
section,  as  in  the  case  of  a  curved  gate  built  up  of  a  series  of  vertical 
voussoirs,  evidently  the  section  must  be  so  arranged  that 

F  _  F  a;  (ft  -  p) 

b~  I 

whence 

^  "  b(b  -  p) ^^^^ 

This  agrees  with  (53)  when  q  =  b  —  p,  which  is  the  condition  for  coinci- 
dence of  the  points  M  and  Q. 

Limits  of  Stress. — It  is  manifest  that  there  is  a  limiting  value  for  the 
stress  intensity  at  L,  beyond  which  it  would  be  unsafe  to  compress  the 
leaf  without  risk  of  collapse.  Let  us  call  this  limiting  value  7,  and 
consider  its  relationship  to  the  resultant  pressure. 


LIMITS  OF  STRESS. 


327 


Substituting  in  (51),  we  have 

F      ¥xv 

For  any  rib  of  given  dimensions,  6,  p,  and  I  are  fixed  ;  in  other  words, 
they  are  constants,  and  the  only  variables  are  F  and  x, 
Re-ar ranging,  we  get 


<j^  *')-'- 


(66) 


P^         /        P 
which  is  an  equation  of  the  form 

F(Ci  +  x)^Q^ 

where  C^  and  C,  are  constants.  Now,  this  is  the  equation  of  a  rectangular 
or  equilateral  hyperbola,  one  of  whose  asymptotes  is  the  line  L  M,  and  the 
other  is  a  line  parallel  to  the  longitudinal  axis  and  at  a  distance, 


Fig.  262. 

from  it  on  the  inner  side.  Consequently,  if  we  ^:l  upon  a  limiting  value 
for  y,  we  may  vary  F  and  x  within  the  range  shown  in  fig.  262,  where 

—.  +  X  constitutes  the  abscissa,  and  F  the  corresponding  ordinate  for  any 

point  of  the  hyperbolic  curve,  Y  Z.  The  point  O  is  the  intersection  of  the 
asymptotes.  Given  the  distance,  x,  from  the  longitudinal  axis  of  the 
resultant,  its  maximum  value  is  determined  by  the  ordinate ;  and  vice  versdy 
given  the  magnitude  of  the  resultant,  the  extreaie  limit  of  its  position 
may  be  deduced. 

The  diagram,  fig.  262,  is  only  applicable  to  resultants  on  the  compressive 
side  of  the  axis.  For  loci  of  F  between  O  and  M,  it  would  be  necessary  to 
draw  another  hyperbola,  with  its  origin  on  the  other  side  of  O ;  but 
instances  of  this  kind  do  not  usually  occur  in  practice  and  need  not 
be  further  considered. 


328 


DOCK   ENGINEERING. 


L      X 


Connecting  Pieces. — Timber  gates  of  the  voussoir  type  are  generally 
stiffened  by  horizontal  connecting  pieces  (vide  fig.  288)  on  the  front  of  the 
gate,  forming  chords  to  the  arc  of  the  gate.  The  total  moment  of  resistance 
in  such  cases  is  compounded  of  the  separate  moments  due  to  the  voussoir 
and  the  connecting  piece,  and  since  the  angle  of  deflection  producing  the 
moment  of  resistance  is  the  same  in  both  members,  it  is  evident  that  the 
distribution  of  stress  due  to  bending  will  be  similar,  the  amount  and 
maximum  intensity  being  determined  by  the  relative  breadths  of  the 
voussoir  and  connecting  piece. 

To  draw  the  diagram  of  stress,  find  first  the  stress  area,  L  F  O  B  M 
(fig.  263),  for  the  voussoir,  considered  as  acting  alone.    Then  through  C  the 

neutral  axis  of  connecting  piece  draw  Q  S  parallel 
to  P  R.  The  area  M  Q  0  S  N  represents  the 
proportionate  stress  in  the  connecting  piece.  We 
must  now  reduce  both  areas  in  the  same  propor- 
tion until  their  sum  is  equal  to  the  area  of  stress 
caused  by  the  bending  moment — that  is,LPOBM. 
To  do  this,  divide  L  F  in  the  point  X  such  that 
L  X  :  X  P  :  :  O  L*  :  C  M2.  Draw  XX'  through  the 
point  O  and  Y  Y'  parallel  to  it  through  the  point 
C.  Then  the  etched  portion,  L  X  O  X'  M  Y  C  Y'  N, 
is  the  required  stress  diagram  as  regards  bending  moment  only.  The  direct 
compressive  stress  is  taken  by  the  voussoir  as  before. 

The  proof  of  the  diagram  is  as  follows  : — The  triangles,  O  X  P  and 
0  M  Y,  must  be  equal  to  fulfil  the  required  conditions.     Hence 

XP  X  LO  =MY  X  CM 


Voussoir 


Connecting' 
Piece 


S  Y'  ^ 
Fig.  263. 


MY  = 


XP  X  LO 
CM      ' 


Also,  since  X  X'  and  Y  Y'  are  to  be  parallel, 

MY  :CM  :  :X'M  :  MO 

L  X  :  LO 


MY  = 


Equating  the  two  values  of  M  Y, 

XP  X  LO 


CM 


XP 
LX 


CMx  LX 

LO 

CM  X  LX 

LO 

CM2 

L  02 


So  delicate  an  adjustment  of  stress  depends  upon  conditions  which 
cannot  be  obtained  in  practice,  and  it  is  certainly  advisable  to  construct  the 
voussoirs  of  a  gate  so  that  they  may  be  able  to  take  the  whole  of  the  stress 
unaided  by  the  connecting  pieces. 


HORIZONTAL   IRON   GIRDERS.  329 

6 
Typical  Examples — 1.  Horizontal  Rectangtdar  Rib, — In  this  case  p  =  ^\ 

I  =  r-j,  when  the  depth  is  unity  ;  and  F  is  the  total  stress,  divided  by  the 

number  of  ribs. 

The  value  for  L  P  (fig.  261)  is 

Yxp  __  6Fa5 

"I      "  ~W 
and  the  neutral  axis  of  a  rectangular  beam  being  assumed  to  coincide 
with  its  horizontal  axis  of  symmetry,  the  same  value  is  equally  applicable 
to  MR. 

When  the  resultant  passes  through  the  point  L — i.e.,  when  ^  ^  k»  ^^ 

F       S  F       4-  F 
<K)mpre8sion    at    L    becomes     -  +  -7-  =  -t->   or  exactly   four   times    the 

intensity  which  it  has  when  the  resultant  passes  through  the  point  O. 

2.  Vertical  Voussoira, — Here  it  is  necessary  to  avoid  tension  in  any 
part  of  the  joints,  no  duty  being  expected  from  the  connecting  bolts  in 
this  respect. 

The  point  Q  is  given  from  (53)  by 

I    ^    6g 
^  ~  hx"  Ux 

&nd  when  q  is  made  equal  to  -^  which,  as  we  have  already  demonstrated,  is 

the  limit  consistent  with  the  absence  of  tension,  we  have 

2  ""  12a;' 

so  that  X  =  -^y 

6 

which  signifies  that  the  line  of  pressures  must  lie  within  the  middle  third 
of  the  thickness  of  the  gate. 

3.  Horizontal  Iron  Girders, — Assuming  the  web  horizontal  and  the 
flanges  vertical,  so  that  the  plane  of  the  resultant  coincides  with  that  of 
the  web,  supposed  indefinitely  thin,  no  difference  exists  between  the 
formulae  in  this  case  and  those  for  rectangular  ribs,  beyond  the  complica- 
tion introduced  by  the  somewhat  involved  expressions  for  the  value  of  the 
moment  of  inertia. 

With  flanges  of  equal  area,  symmetrically  disposed  about  the  centre  of 
gravity  of  the  section,  the  value  of  I  may  be  conveniently  expressed  as  the 
difference  between  the  moments  of  inertia  of  two  rectangles  : — 

"*  iT      "12"' ^  ^ 

where  d^  and  h^  are  the  dimensions  of  the  combined  side  recesses  of  the 
irder. 


330  DOCK   ENGINEERING. 

The  intensity  of  stress  due  to  direct  compression  is 


F  F 

'^'  "  A  "  (d  -  rfi)  (6  -  61)'        •         •         *     ^^^^ 

and  the  maximum  stress  due  to  the  bending  moment  is 

¥xp  6F6aj 

whence,  combining,  we  obtain  the  maximum  and  minimum  intensities  in 
the  outer  and  inner  flanges  respectively, 


(59) 


Aiiother  expression  for  the  value  of  I,  which  neglects  the  thickness  of 
the  flanges  and  assumes  their  areas  concentrated  on  a  centre  line  in  each 
case  situated  a  distance,  d,  apart,  with  k  as  the  area  of  the  web,  is 


=  '^(*n>  •        •        •        •    (60) 


k 
If  only   an  approximation   be  required,  ~   may  be  ignored  as   very 

small  and 

I  =  — ^«      ......     (61) 

When  the  cross-section  of  the  girder  is  not  symmetrical  about  the 
centre  of  gravity,  the  position  of  the  latter  may  be  obtained  by  dividing  the 
depth  of  the  girder  inversely  as  the  ratio  of  the  flange  areas.  Thus,  if  o^  be 
the  area  of  the  smaller  flange  and  ag  that  of  the  larger,  the  distance  of  the 
centre  of  gravity  from  the  larger  flange  will  be 

""^      6, (62) 

«!  +  ^2 

where  b  is  the  horizontal  dimension  of  the  girder.     Or  it  may  be  obtained 

graphically,  thus  : — Let  A  B  (fig.  264)  represent  the  web  of  the  girder  as  a 

single  line ;  set  off  horizontally  A  C  =  area  of  flange  B,  and  B  D  =  area  of 

flange  A.     Join  0  D,  and  O  is  the  required  centre  of  gravity. 

Using  the  notation  of  (62)  a  fairly  approximate  value  for  I  is 

For  built  girders,  the  moment  of  inertia  will  have  to  be  calculated  in 
detail  from  its  component  parts. 

Gates  toith  Vertical  Co-planar  Girders, — For  straight  or  flat  gates  with 
discontinuous  horizontal  members,  a  different  method  of  stress  investigation 
is  necessary.  The  system  of  co-planar  vertical  girders  which  derive  no 
support  from  each  other,  such  as  contiguous  vertical  voussoirs  do,  involves, 
as  has  already  been  pointed  out,  the  use  of  two  horizontal  transoms,  one  at 
the  head  and  the  other  at  the  sill,  to  afford  them  the  necessary  support. 


STRESSES  IN  PANELS. 


331 


As  the  pressure  increases   with  the   depth,   the  total   pressure,    —^ ,  is 
distributed  unequally  between  these  two  members,  in  the  proportion  of 

TO  ^2 

1  to  2,  the  amount  being  — ^  at  the  top  and  -^  at  the  sill. 

The  verticals  may  accordingly  be  treated  as  independent  beams,  sus- 
taining a  uniformly  increasing  load.  Under  these  conditions  it  is  evident 
that  the  maximum  bending  moment  cannot  be  at  the  centre.  The  bending 
moment  at  any  point  X  may  be  found  thus  : — The  pressure  on  the  surface 


wa^ 


X 


AX  (fig.  265)  of  the  gate  is  — «-,  acting  at  a  point  k  above  X.     Cons^ 
quently  the  bending  moment  at  X  is 

«-**«=  _«^  =  '^(A2_^).    .        .        .    (64) 


M.  = 


6 


B 


Fig.  264.  Fig.  265. 

To  obtain  the  maximum  value  of  this  expression  it  is  only  necessary  to 
differentiate  with  respect  to  ;r  and  equate  to  zero. 


ax  ax 


whence 


J3x  =  A (65) 

In  other  words,  the  maximum  bending  moment  is  situated,  not  at  the 

h  h 

centre  of  pressure  ^,  but  at  a  point  -y^  below  the  surface  of  the  water. 

The  maximum  bending  moment  at  this  point  is 

wh^        wh^        wh^  ,^^^ 

.     (66) 


M 


max 


6^3      18^3       9^3'       ' 

and  the  dimensions  of  the  girder  can  easily  be  calculated  by  any  of  the 
methods  applied  to  instances  of  beams  under  similar  conditions  of  loading. 

Subsidiary  horizontal  members  are  introduced  between  the  verticals  to 
transmit  the  pressure  from  the  plating,  which  is  made  as  thin  as  is  con- 
sistent with  durability  and  strength. 

Stresses  in  Panels. — For  all  practical  purposes  the  pressure  on  each 
unsupported  area  of  plating  or  planking  between  the  gate  framing  may  be 
taken  as  uniform,  an  assumption  which  is,  of  course,  to  a  certain  extent. 


332  DOCK   ENGINEERING. 

-erroneous.  The  variation  from  the  truth  is  greatest  in  the  case  of  the 
topmost  panels,  and  the  approach  to  accuracy  increases  with  the  depth. 
No  account  is  taken,  generally  speaking,  of  the  support  derived  from  the 
fixture  of  the  ends,  nor,  in  cambered  gates,  of  that  due  to  the  curvature, 
Any  excess  of  strength  in  these  respects  being  set  oif  against  possible  loss 
from  corrosion  or  decay. 

Calling  the  shorter  unsupported  length  of  the  panel  ^,  and  d  the  depth 
of  the  centre  of  the  panel  below  the  surface,  the  maximum  bending  moment 
.    wdl^ 

Then,  if  t  be  the  thickness  of  the  plate  and  /  the  safe  maximum  fibre 
stress,  the  moment  of  resistance  iB—-;  and,  equating. 


8 


/3    tod 
whence  i  =  ^  ^  -  •  — (67) 


=  ^  V  VF (^^) 


In  the  foregoing  expression  the  unit  is  the  foot.  It  will  be,  perhaps, 
more  convenient  to  express  t  and  I  in  inches.  Giringw  its  numerical  value, 
the  expression  then  becomes- 

'd 

W 

Mr.  Ivan  C.  BoobnofT,  naval  architect  of  the  Imperial  Russian  Navy, 
proposes  to  calculate  the  thickness  of  plating  for  ships  by  a  similar  formula, 
deduced  in  a  rather  more  elaborate  manner — 

'''s/~i"i^7    ....    (69) 

These  are  theoretical  thicknesses.  There  is  in  practice  a  minimum  of 
f  inch  for  iron  and  steel  and  3  inches  for  wood,  beyond  which  it  is  not  safe 
to  go,  on  account  of  the  exceptionally  rough  usage  to  which  the  panels  are 
subjected  and  their  liability  to  corrosion  and  decay. 

Practical  Illustrations. — It  will  be  useful  at  this  stage  to  take  an  actual 
pair  of  gates  and  see  how  far  their  construction  conforms  to  the  theoretical 
requirements  of  the  preceding  formulse.  Examples  of  both  wood  and  iron 
gates  have  been  selected  for  this  purpose,  as  representing  two  widely  distinct 
types,  the  main  dimensions  of  the  entrances  which  they  close  being,  as  far 
as  possible,  alike,  in  order  that  a  certain  comparison  may  be  instituted 
between  them.  For  the  plans  and  particulars  relating  to  the  metal  gates 
the  author  is  indebted  to  the  courtesy  of  Mr.  J.  M.  Moncrieff,  of  Messrs. 
Sandeman  k  Moncrie£P,  Newcastle-upon-Tyne. 

Case  1, —  Wooden  Gates, — A  pair  of  gates  at  Liverpool,  each  leaf  consisting 
of  a  series  of  curved  horizontal  ribs,  built  in  two  voussoirs  with  connecting 
pieces,  as  shown  by  the  drawings  in  figs.  266,  267,  and  268.     With  the 


Ft. 

Ins. 

60 

0 

63 

8 

10 

0 

10 

6 

0 

12 

34 

6 

WOODEN   GATES.  333 

exception  of  the  two  topmoflt  connecting  pieces  and  a  rubber  on  the  front  of 
the  gate,  which  are  of  pitchpine,  the  whole  of  the  framing  and  panelling  is 
of  greenheart,  fastened  with  galvanised  iron  bolts  and  straps. 
The  data  for  calculation  are  as  follows  : — 

Width  of  waterway,        .... 

Span  of  gates  (between  heel-post  centres). 

Rise  or  versed  sine  of  sill,*     . 

Rise  or  versed  sine  of  gates,* 

Radius  of  heel-post,         .... 

Length  of  leaf  (water-bearing  surface),    . 

Distance  from  centre  of  heel-post  to  centre  of 

meeting  faces  of  mitre-posts,        ...         33       6 

The  gates  are  segmental  in  form,  and  so  designed  that  the  curve  of 
pressure  coincides  with  the  back  of  the  gate  at  the  centre  of  each  leaf.  The 
thickness  of  the  middle  head  is  2  feet. 

The  total  height  of  each  leaf  is  34  feet  3  inches,  of  which  9  inches  forms 
a  sill  abutment,  leaving  a  height  of  33  feet  6  inches  capable  of  sustaining 
water  pressure. 

Adopting   first  the   approximate   formula   (47)   for  the   resultant,    we 

obtain — 

^      wh^lU-p)      64  X  33-5  X  33-5  X  34-5  X  33-5       ,n^^,,„,^ 

R  = 7^ =  -. — =7r-« =  1,976,442  lbs. 

4r  4  X  lO'D 

This  may  be  checked  by  drawing  in  the  diagram  of  stresses  as  illustrated 
in  fig.  256,  from  which  it  will  be  found  that  the  radius  of  curvature  is 

55  feet.     Hence 

^       55  X  64  X  33-5  x  335       -  ^„„  _^^  ,, 
R  = 2 ==  1,975,160  lbs. 

The  agreement  is  very  close.  Let  the  result  be  taken  in  round  numbers 
at  882  tons. 

Now,  the  maximum  bending  moment  is  at  the  middle  head,  where  the 
curve  of  pressure  is  situated  12  inches  outside  the  longitudinal  axis  of  the 
gate.  At  this  point  its  direction  is  normal  to  the  back  of  the  gate,  so  there 
will  be  no  shearing  stress  along  the  joints  on  either  side  of  the  middle  head. 

In  the  preliminary  investigation  it  will  be  recollected  that  when  the 

curve  of  pressure  lay  upon  the  outer  edge  of  a  horizontal  rib  the  intensity 

of  stress  in  the  outermost  fibres  was  found  to  be  four  times  that  of  the 

simple  compression  due  to  a  resultant  acting  along  the  gate  axis.     The 

882 
compressive  intensity  is  -^  tons,  the  gate  being  24  inches  in  thickness. 

ftftO       A. 

Accordingly  the  maximum  stress  intensity  is  — ;tj —  =  147  tons  over  the 

whole  depth  of  the  gate. 

*  The  versed  sine  is  measured  in  each  case  from  the  line  through  the  centres  of  the 
heel-posts  and  extends  to  the  point  of  the  sill  and  the  centre  of  the  meeting  faces  of  the 
mitre-posts  respectively. 


334  DOCK  ENGINEEiaNG. 

Taking  the  ultimate  compressive  stress  of  greenheart  at  8*5  tons  per 
square  inch,  it  is  evident  that  a  minimum  depth  of  some  18  inches  of 
solid  rib  is  needed  to  withstand  the  147  tons  compression.  This,  however, 
is  the  critical  value,  when  the  material  is  tested  to  breaking  point,  and  as 
it  is  inadvisable  to  take  a  less  factor  of  safety  than  10,  180  inches,  or  15  feet, 
in  depth  is  actually  required.  As  a  matter  of  fact,  in  the  gate  in  question 
the  total  depth  of  solid  rib  amounts  to  over  20  feet,  so  that  the  factor  of 
safety  adopted  lies  between  13  and  14 — a  by  no  means  excessive  value  for  a 
wooden  gate,  having  regard  to  the  duties  which  it  is  called  upon  to  perform. 

In  the  foregoing  calculation  no  account  has  been  taken  of  the  connecting 
pieces,  for  reasons  which  have  already  been  given.  They  can  only  be  looked 
upon  as  affording  a  reserve  of  strength  for  contingencies. 

Allowing  a  working  stress  of  1^  tons  in  the  outermost  fibres  of  the  green- 
heart  planking,  the  thickness  of  the  bottom  panel  is  deduced  from 


<  =  1-25  J.^-^  =  3  05  inches. 


Ft. 

Ins. 

60 

0 

61 

0 

64 

6 

10 

9 

26 

6 

27 
3xli 

This  is  an  ample  allowance,  for  it  takes  no  account  of  the  fixture  of  the 
ends,  and  as  the  stress  on  the  other  panels  is  much  less,  a  uniform  thickness 
of  3  inches  has  been  adopted  throughout. 

Case  11. — Steel  Gates. — A  pair  of  gates  for  a  graving  dock  on  the  River 
Blyth,  constructed  in  mild  steel,  with  greenheart  heel  and  mitreposts  and 
clapping  sill,  as  shown  by  the  drawings  in  figs.  269  to  273. 

Data : — 

Width  of  waterway,  between  fenders,    . 

„  „  between  faces  of  walls, 

Span  of  gates  (between  heel-post  centres), 
Rise  of  versed  sine  of  gates,* 
Height  of  gate  above  dock  sill^ 
Depth  of  lowest  compartment  in  body  of  gate, 

in  order  to  allow  ample  room  for  rivetters, 

not  less  than 2      0 

Width  of  leaf  at   each  end,    for  reasons  of 

access, 19 

Width  of  leaf  at  centre,  in  order  to  ensure 

line  of  pressure  passing  within  the  gate,   .  3       9 

Dealing  with  the  question  of  buoyancy  in  the  first  place,  the  horizontal 
sectional  area  of  one  leaf,  as  measured  from  plan,  is  about  108  square  feet, 
so  that  the  displacement,  with  the  five  lowermost  compartments  formed  into 
a  buoyancy  chamber,  is  roughly, 

IItV  feet  depth  x  108  square  feet  area  x  64  lbs.       «.,  , 
-IS ! ^^ =  34i  tons, 

while  the  actual  weight  of  one  leaf  complete  =:  41^  tons  nearly,  leaving 

*  See  footnote,  p.  333. 


f 


I 


t 

I 
I 


Alfib 


STEEL   GATES. 


335 


7  tons  as  the  nett  positive  weight  keeping  the  leaf  down,  and  preventing 
its  rising  o£P  the  heel  pivot,  when  the  gates  are  open  and  the  water  level 
is  not  lower  than  the  top  of  the  buoyancy  chamber.  When  the  gates  are 
closed  and  the  dock  is  pumped  dry,  the  upward  lifting  effort  of  the  water 
on  each  leaf  exceeds  34}  tons,  owing  to  the  fact  that  the  clapping  sill 
projects  behind  the  body  of  the  leaf,  but  even  with  the  water  level  right 
up  to  the  top  of  the  gates,  which  would  be  a  very  remote  contingency,  the 
additional  lifting  force  per  leaf  only  amounts  to  about 

9  square  feet  x  27^  feet  x  64  lbs.       _  ,  , 

— 2240 "  nearly, 

making  a  total  lifting  force  of  41}  tons,  or  just  equal  to  the  weight  of  one 
leaf.  But  this  lifting  force  could  only  exist  when  the  gates  were  exerting 
an  enormous  thrust  against  the  hollow  quoin,  and  the  friction  would  be 
amply  sufficient  to  prevent  the  gates  rising,  even  under  such  exceptional 
circumstances. 

Owing  to  the  water-bearing  surface  for  the  five  lower  compartments 
being  the  curved  outer  plating,  while  for  the  five  upper  compartments  it 
is  the  straight  inner  plating,  it  is  necessary  to  lay  down  two  lines  of 
pressure,  and  these  are  shown  in  fig.  273 ;  but  it  will  be  noticed  that  they 
differ  only  very  slightly  from  each  other,  and  that  the  centres  of  the 
circular  curves  are  practically  coincident  with  a  common  radius  of  53  feet 
9  inches,  say  54  feet.  Also,  because  the  ribs  are  not  disposed  according 
to  zones  of  equal  pressure,  it  will  be  necessary  to  treat  each  one  separately, 
instead  of  dealing  with  the  gate  as  a  whole,  as  in  the  previous  example. 
Space  will  not  permit  of  our  taking  more  than  two  cases,  which,  however, 
will  be  sufficient  to  indicate  the  method  of  dealing  with  the  rest. 

First  take  the  rib  at  a  depth  of  24  feet  3^  inches,  and  deal  with  the 
section  5-5.     The  section  of  the  rib  is  shown  in  fig.  274. 


Flat  rr^^/w 
note  Z5\^/£ 


23-3 


23-3" 


r  ^'"ii 


^1       wtb  ^ 


angles  ..  ^ 


45 


i  « 


Fig.  274. 


The  water  pressure  on  the  face  of  the  rib  is 

2-08  X  24-3  X  64  =  3,240  lbs.,  say. 

Hence,  the  resultant  pressure : 

R  =  3,240  X  54  =  175,000  lbs.,  nearly, 
and,  since  the  direction  of  R  is  parallel  to  the  centre  of  section,  R 


=  F. 


336 


DOCK  ENGINEERING. 


The  cross-sectional  area  is  as  follows : — 


.  45  X  ^ 


Web, 

Two  plates,  each,   25  x  ^^^ 


91 


)} 


8  X 


8 


Four  angles,     4  x  3  x  ^^  = 


18  square  inches. 
20 

6-4 
10-56 


54-96 


>> 


Say,  55  square  inches.     From  formula  (51)  we  have — it  being  noted  that 
the  flanges  are  symmetrical  about  the  centre  of  section — 

^  175,000  ^  175,000  x  17  x  23-3 
""       55       ~  21,808 

=  3,182  ±  3,178  lbs., 

that  is,  2*84  tons  per  square  inch  on  the  outer  flange  and  4  lbs.  per  square 
inch  on  the  inner  flange. 


Flat  9\ 
Angles 


• 

I 


I 

web    I  ^/zo" 


i    s  I 


m 


4\3\W^ 


I  %Flat 

lie- 1745  "  -.►;     Plate  Vx^ 
—      39" 


3lV^k 


Jl..:l. 


Fig.  275. 


Now,  take  the  rib  at  a  depth  of  12  feet  9^  inches,  and  deal  with  section 
3-3,  shown  in  fig.  275.  In  this  case  the  inner  plating  is  the  water- 
bearing surface,  whose  radius  =  51  feet,  nearly. 

Water  pressure  =  2-6  x  12-8  x  64  =  2,130  lbs., 

F  =  R  =  2,130  X  51  =  109,000  lbs., 
in  round  numbers. 

Cross-sectional  area  of  rib — 9  x  ^^^  =     3*6  square  inches. 

39  X  3^  =  15-6 

31  X  /^  =  12-4 


>» 


8  X  /^  =     3-2 


Four  angles,  4  x  3  x  ^=  10*56 

45-36 


99 


Say,  45  square  inches.     In  this  case  the  flanges  are  not  symmetrical  about 


ROLLERS  AND   ROLLER  PATHS.  337 

the  centre  of  section.     Accordingly,  we  must  find  the  stress  in  each  flange 
separately. 

Outer  F/ange.  Inner  Flange. 

F     Yxp  F     Yx{b-p) 

^"A"^    I  -^"A  I 

109,000     109,000x17-45x251"        _  109,000     109,000  x  1745  x  15-1 
"      45      "^  11,957  "'45       ■  11,957 

=  2*86  tons  per  square  inch.  =  20  lbs.  per  square  inch. 

It  will  be  observed  that  all  the  foregoing  stresses  are  well  within^the 
safe  limits  for  mild  steel. 

The  thickness  of  the  lowermost  plating  works  out  as  follows  : — 

All  the  plates  are  actually  made  ^j^  inch  =  '4  inch. 

Such  is  a  very  condensed  outline  of  the  calculations  entailed  in  con- 
nection with  the  design  of  dock  gates. 

Gate  Fittings.  —  We  now  turn  our  attention  to  some  of  the  more 
prominent  details  connected  with  gate  construction,  leaving  aside  for  the 
present  those  matters  which  relate  to  the  working  of  the  gates.  These 
will  be  more  advantageously  dealt  with  in  the  chapter  on  Working 
Equipment. 

Rollers  and  Roller  PcUhs, — Gates  may  be  entirely  hung  upon  a  pivot  or 

axis  at  the  heel-post,  or  they  may  derive  partial  support  from  truck  wheels, 

or  rollers,  placed   under  them  at  one  or  more  points.      There  is  much 

conflict  of  opinion  among  engineers  as  to  the  value  or  otherwise  of  the 

latter  method.     On  the  one  hand,  it  is  urged  that  rollers  add  unnecessarily 

to  the  weight  and  expense  of  the  gates,  that  they  are  liable  to  get  out  of 

order,  that  they  are  diflicult  to  adjust  and  repair,  and  that,  generally,  they 

are  a  source  of  much  anxiety  and  inconvenience.     On  the  other  hand,  it 

is  contended  that  they  are  a  valuable  means  of  support,  that  they  reduce 

the  friction  on  the  heel-post  and  relieve  the  stress  on  the  anchor  blocks, 

and  that  they  can  be  maintained  in  a  state  of  efficiency  with  very  little 

trouble.     Generally  speaking.  Continental  (more  especially  Dutch)  practice 

inclines  to  the  former  view,  English  practice  to  the  latter,  but  there  is  no 

absolute  uniformity  in  either  case.      Rollers  have  been,  and  are  being, 

dispensed  with  at  Hull,  while  on  the  Mersey,  the  Manchester  Ship  Oanal, 

and  elsewhere  they  are  still  the  invariable  rule.      It  may,  however,  be 

fietirly   conceded   that  for  small    wooden   gates   and   for  iron  gates  with 

buoyancy  chambers,  rollers  are  not  absolutely  essential.      Heavy  wooden 

gates  of  large  span  certainly  do  gain  in  steadiness  by  the  attachment  of 

rollers  to  their  outer  extremities.     Types  of  rollers  in  use  at  various  ports 

are  illustrated  in  figs.  276  to  278,  279,  and  294. 

22 


338  DOCK  ENGINEERING. 

Clapping  SilU. — The  fiuiing  of  the  lovermost  horizotital  member  of  » 
gate,  formiDg  a  watertight  joint  irith  the  dock  sill,  is  almost  invariably  of 
wood,  in  wood  and  iron  gates  alike.     Indiambber,  as  a  watertight  material, 


Ba£/c  EkvaUm 


Side  EUvatim 


Plan. 

PigH.  276,  277,  and  278.— Gate  BoUera  at  LiverpooL 
is  not  employed  to  any  noticeable  extent,  though  there  is  no  apparent 
objection    to    its    more    extended    use.      An    arrangement    proposed    by 


CLAPPING  SILLS. 


M.  Barret,  dock  engineer  at  MorseUlea,  in  1879,  is  itlnstrated  in  fig.  380. 
It  consists  of  a  buffer  of  plaited  hemp  covered  with  leather,  with  a 


z-j;—- 

W" 

Fig.  279.— Gate  Roller  at  Dublin. 


Fig.  281. — Gate  Anohorage  at  LiverpooL 


Fig.  282.— Gate  Anchorage  on  the  Tyne. 


DOCK   ENGINEERING. 


FOOTSTEPS.  341 

pendant  to  absorb  any  play  between  the  lower  part  of  the  gate  section  and 
the  silL 

Siuicet. — Sluices  for  levelling  the  water  on  both  sides  of  a  pair  of  lock 
gates  preparatory  to  opening  them,  ma;  be  fitted  in  the  gates  themselvei, 
alternatively  to  locating  them  in  the  side  walls.  The  arrangement, 
however,  has  the  disadvant&ge  of  adding  very  considerably  to  the  weight 
'Of  the  gates,  by  reason  of  the  apparatus  required  for  opening  and  closing 
the  sluices.     The  question  is  discussed  somewhat  more  fully  in  Chap.  vL 


W^^^^""^ 


Fig.  2S4.— Gate  FooUtep. 

PUuformt. — Gates  are  usually  fitted  with  a  gangway  at  or  about  coping 
level.    It  is  usually  carried  on  brackets  fixed  to  the  topmost  member  of 
the  gate.     The  handrail  or  chain  guard  should  be  removable,  in  order  to 
facilitate  the  passing  of  warps  and  ropes 
when  the  passage  is  open. 

Anchorage. — The  top  of  the  heel-post, 
or  the  upper  pintle  of  a  gate,  revolves 
in  a  horizontal  collar,  bolted  to  and 
forming  part  of  a  suitable  heavy  casting, 
known  as  the  anchor  block,  from  which 
tie-rods  or  bars  radiate  to  some  distance, 
their  ends  being  bedded  in  massive 
masonry.  Several  types  of  anchort^e 
are  shown  in  figs.  281,  282,  and  283. 

Footttept. — The    lower    end    of    the 
heel-post  may  either  be  arranged  as  a         g^^.^^^  EUvatlon. 
pintle,    etting   into    a    circular    socket.  Fig.  285.-Gste  Footstep. 

or    it    may    be    fitted    with    a    hollow 

casting  to  revolve  upon  a  spherical  surface.  The  latter  arrangement  is 
illustrated  in  two  forms  in  figs.  284  and  285.  The  first  of  these  is  more 
suitable  for  small  gates.  In  the  second  example,  the  play  between  the 
cylindrical  pivot  and  the  sides  of  the  lover  casting,  or  cup,  is  designed 
to  allow  of  a  slight  clearance  between  the  heel-post  and  the  hollow  quoin, 
during  the  movement  of  the  former,  so  as  to  diminish  the  iriction.      A 


342 


DOCK  ENGINEERING. 


Boitable  composition  for  the  bronze  alloys  of  the  various  parts  as  adopted 
at  Liverpool  is  as  follows : — 


Pivot,  . 
Ball,  . 
Heel-hoop, 


Copper. 

Tin. 

16  oza. 

2^  0Z8. 

16    „ 

34    „ 

16    „ 

2     „ 

Zinc. 


i  oz. 


The  addition  of  a  small  portion  of  phosphorus  is  said  to  have  the  effect 
of  preserving  the  surface  of  the  metal  from  corrosion.  Aluminium  bronze, 
containing  90  parts  of  copper  to  10  of  aluminium,  is  a  very  strong  alloy, 
which  does  not  readily  corrode,  but  it  is  very  expensive.  Manganese  bronze 
is  another  compound  possessing  equal  durability  and  strength.  Steel  is 
quite  out  of  the  question.     It  is  speedily  destroyed  by  the  salt  water. 


Plan  of  Base  of  heelpost  inverted.  pi^m  of  Cup . 

Fig.  286.  Fig.  287. 

Check  chains  from  the  mitre-post  to  volute  or  other  suitable  spring  at  the 
square  quoin  of  the  gate  recesses,  are  a  useful  means  of  checking  the  impetus 
of  a  gate  at  the  sill  and  preventing  distortion. 


Examples  of  Dock  G-ates. 

It  only  remains  to  conclude  this  section  with  a  few  selected  examples  of 
wood  and  iron  gates. 

Liverpool  is  par  excellence  the  port  of  wooden  gates.  Throughout  the 
vast  system  controlled  by  the  Mersey  Docks  and  Harbour  Board,  there  is 
not  a  single  iron  gate  in  existence  up  to  the  time  of  writing.  Several  of  the 
locks  and  entrances  are  no  less  than  100  feet  in  width,  but  they  are  all 
fitted  with  wooden  gates.  A  pair  of  gates  closing  a  60-foot  entrance  has 
already  been  treated.  By  way  of  exemplification  of  the  larger  structures^ 
the  plan  and  vertical  section  of  a  leaf  of  the  Canada  Lock  gates  are  shown 
in  tigs.  288  and  289.  The  timber  is  greenheart,  connected  by  galvanised 
iron  straps  and  bolts. 

The  principal  feature  of  the  gates  along  the  great  waterway  leading  to 
the  Port  of  Manchester  is  their  great  solidity.  Perhaps  this  is  also  their 
most  essential  requirement,  for  several  serious  accidents  have  already  taken 
place  in  connection  with  them.  For  example,  a  few  years  back  a  steamer, 
improperly  controlled,  ran  into  a  pair  oi  gates  and  drove  one  leaf  completely 


DOCK  GATE  AT   LIVERPOOL. 


I 


!• 


'  t  t  (  I" 


344  DOCK   ENGINEERING. 

over  the'Bill  by  shearing  the  mitre-post.     Such  eui  accident  is,  fortnoatelf, 
flxceptioD&l,  bat  demotiatrateB  the  posaibilities  which  have  to  be  contended 


SeCTIOM     OM      A. A  SECTION     ON     •-■.  PLAN. 

Figs.  297,  29S,  and  299.  — Dock  Gates  at  Hull, 
vith.     FigB.  290  to  396  are  plana,  Bections,  and  elevation  of  a  pair  of  80-foot 
gates,  constructed  in  greenheart,  with  iron  straps  and  bolts.* 

*  WilliamB,  Eliot,  and  Meade-King  on  "  Tlie  Maochesler  Ship  Cana),"  Jtfin.  Proe, 
7nM.  CB.,  vol.  cixxi. 


i 


U  I ,  I- . 


DOCK    GATES.  345 

m 

Figs.  297,  298,  and  299  illustrate  the  Outer  lock  gates  of  the  Alexandra 
Dock  at  HnlL*  Each  leaf  consists  of  three  framed  greenheart  voussoirs, 
similar  in  design  to  the  Liverpool  gates. 

-  In  all  the  preceding  cases  the  wood  panels  are  framed  in  between  the 
ribs.  In  the  diagrams  of  tho  gates  at  the  North  and  South  Locks,  Bnenos 
Ayres  f  (figs.  300  to  303),  it  will  be  observed  that  the  sheeting  is  continuous 
throughout  the  height  of  the  gates. 

The  iron  gates  at  Kidderpar  Docks,  Calcutta,}  are  shown  in  figs.  304  to 
309.     The  heel  and  mitre-posts  are  of  greenheart. 

A  particular  interest  attaches  to  the  pair  of  metal  gates  exhibited  in 
figs.  310to312,  as  indicating  an  extremely  ingenious  device  for  overcoming 
a  natural  difiiculty.  The  gates  close  the  entrance  to  a  graving  dock  on  the 
River  Tyne.§  The  longitudinal  axes  of  dock  and  river  meet  at  an  acute 
angle  (fig.  313).  Had  the  gates  been  constructed  in  the  ordinary  manner, 
with  symmetrical  leaves,  and  the  line  through  the  heel-post  centres  perpen- 
dicular to  the  axis  of  the  dock,  a  considerable  length  of  one  quay  would 
have  been  excluded  from  the  graving  dock,  which  would  have  been 
much  shorter  in  consequence.  By  adopting  the  form  of  two  unequal 
leaves,  the  designer,  Mr.  J.  M.  MoncriefiF,  has  been  enabled  to  utilise 
the  axial  length  to  its  fullest  extent.  The  dock  entrance  is  49  feet 
wide,  and  the  lengths  of  the  leaves  are  41^  and  22^  feet  respectively,  their 
chord  forming  an  angle  of  about  12°  35'  with  the  normal  to  the  dock  centre 
line.  Under  this  arrangement  the  heel-post  of  the  larger  gate  turns  through 
a  greater  angle  than  is  usually  the  case,  and  the  hollow  quoin  has  been 
purposely  kept  narrow  to  enable  the  end  of  the  leaf  to  clear  it.  The  inner 
and  outer  faces  of  the  shorter  leaf  are  concentric  throughout,  but  the  longer 
leaf  needed  the  stiffening  which  could  only  be  afibrded  by  increasing  the 
thickness  or  width  at  the  centre,  and  accordingly  a  flatter  curve  has  been 
adopted  for  the  inner  face. 

A  pair  of  iron  gates  at  DaDkirk||  (figs.  314  to  319)  are  included  as  an 
example  of  the  type  of  vertical  girders.  They  have  flat,  parallel  faces,  and 
bear  against  a  pointed  sill.  The  extreme  length  of  each  leaf  is  38  feet 
4  inches,  and  the  entrance  closed  is  69  feet  wide.  The  plating  covers  the 
whole  of  the  outer  and  the  lower  half  of  the  inner  face,  forming  a  watertight 
chamber  there.  In  a  later  type  of  gate  erected  at  the  same  port  the  arrange- 
ment of  the  watertight  compartments  is  slightly  modified,  as  shown  in  the 
line  diagrams,  figs.  320  and  321. 

*  Hurtzig  on  **The  Alexandra  Dock,  Hull,"  Min.  Proc,  Inst.  C.E.,  vol.  xcii. 

tDobeon  on  "Buenos  Ayres  Harhour  Works,"  Min,  Proc.  Inst.  Ci^.,  vol. 
cxzxviii. 

:t  Bruoe  on  **The  Kidder  pur  Docks,  Calcutta,"  Min.  Proc,  Inst.  C»E,,  vol. 
oxxi. 

§Moncrieff  on  **Dock  Gates  of  Iron  and  Steel,"  Min,  Proc.  Inst.  CE,,  vol. 
cxvii. 

II  Vide  Discussion  on  "  Dock  Gates,"  Min,  Proc.  Inst.  C.E.,  vol,  lix. 


346 


DOCK  ENGINEEKING. 


B-aaaa^ai-galJa!!; 


DOCK   GATES. 


,  308,  anil  ;j09.— DiK'k  GaCes 


348 


DOCK   EKGINEEUING. 


Fig.  313.— Graving  Dock  Entrance,  River  Tyne. 


-n 

i 

s' 

Sh 

ice 
iber 

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A- 

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— 1 

1 

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—l 

I 


S  Recess  for 
"TChain.  pull^ 


\_Lower  ThmsoTti 


42'  9" 

Fig.  3dO.— Elevation  of  Dock  Gate  at  Dunkirk. 


^1:1:] 


J^ 


Tlie  annexed  table  affurda  some  statistics  relating  to  ditferent  types  of 
gate,  collected  from  various  sources.  The  writer  is  indebted  in  m&n;  cases 
to  engineers  at  the  several  ports  for  the  inroriuation. 


f 

/ 


E    XV. 


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I 

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i 


hnd  319.- 


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DOCK   GATES. 


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'Is 

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Sq.  Foot  of 
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^l, 

^       KS  ^  S¥i?!««^2p  .       =  .„  .S=, 

Sill. 

£  3  S"  2  325S2S2SS  S  S  =  2  *SESZJi2^ 

OmLnf. 

|Sg5SS£3  ■  ■  'i  -3  '^SSS  -SSIS  -SSTS  ■«  ■  ■  ■    ■  BSSggg 

Height  of 
Oitas. 

Bepthof 
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B.W.O.B.T. 

^«    0          a          ^       *S                   o«?,^«3S S 

Width  oi  1    ?■""                                                                  ^B         S                ^y    i 
VXUTW.J.  \   1  a  52  S  SSSSiSSSS  S  SSSSSSSi3S8SSSS3S  K  KSSSSS    | 

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iii-i'-Wlh 

350  DOCK   ENGINEERING. 


Dock  Caissons. 

The  primary  meaning  of  the  word  caisson  appears  to  be  a  box  or  chest 
(Fr.  caisse),  but  its  use  has  been  extended,  in  maritime  engineering,  to 
include  all  hollow  structures,  not  being  gates,  used  to  close  entrances  or 
passages.  Generally  speaking,  though  not  universally  so,  the  horizontal 
axis  of  a  caisson  is  a  straight  line,  differing  in  this  respect  from  gates,  the 
leaves  of  which  usually  meet  at  an  angle.  Any  absolute  distinction,  how- 
ever, between  gates  and  caissons  is  difficult  to  draw,  owing  to  the  extreme 
variety  of  types  in  both  classes. 

Stresses  in  Caissons. — The  stresses  induced  in  a  horizontally-framed 
caisson  in  situ  are  those  incurred  by  a  series  of  beams  uniformly  loaded 
and  supported  at  each  end.  It  is  only  necessary  to  find  the  proportion  of 
hydrostatic  pressure  on  each  beam  and  then  to  consider  it  as  a  uniformly 

72 

distributed  load.     The  bending  moment  at  the  centre  will  be  -5-,  where  I 

is  the  length  of  the  unsupported  portion.  The  moment  of  resistance  will  be 
afdf  where/  is  the  maximum  permissible  unit-stress  in  either  flange,  with 
area  a,  and  d  the  distance  between  the  centres  of  gravity  of  the  flanges. 
Equating  the  two  moments,  and  noting  that  a  and  d  are  the  only  variables, 
we  get 

in  which,  by  selecting  a  value  for  the  width  of  the  caisson,  we  determine 
the  corresponding  sectional  area  in  the  flanges  of  the  horizontal  beams  of 
which  it  is  composed. 

Where  the  horizontal  members  are,  however,  discontinuous,  and  the 
external  thrust  is  sustained  by  a  series  of  verticals,  it  will  be  necessary  to 
provide  a  substantial  transom  at  the  top  capable  of  taking  one-third  of  the 
total  pressure.  The  distribution  of  stress  in  this  case  has  already  been 
investigated  in  connection  with  gates  constructed  on  identical  lines. 

Apart  from  the  resistance  of  a  caisson  to  lateral  pressure,  it  is  further- 
more necessary  to  take  into  account  its  conditions  of  stability  under  the 
upward  pressure  of  the  water.  This  upward  pressure,  which  is  equal  in 
amount  to  the  weight  of  the  volume  of  water  displaced  by  the  caisson,  may 
cause  its  derangement  and  ultimate  capsisal,  if  not  properly  provided  for. 

In  every  floating  body,  there  are  two  points  which  determine  the 
stability  of  its  position.  One  is  the  centre  of  gravity  (G,  ^g,  322)  of  the 
body  itself,  and  the  other,  the  centre  of  gravity  (B)  of  the  fluid  displaced, 
otherwise  designated  the  centre  of  buoyancy.  These  may  have  any  number 
of  positions  relative  to  one  another,  but  as  long  as  they  remain  in  the  same 
vertical  line  the  equilibrium  is  complete.  If,  however,  after  a  slight 
displacement  of  the  body,  the  points  are  no  longer  in  the  same  vertical, 
it  is  manifest  that  there  is  a  couple,  W  x  (W  ==  weight  of  displaced  fluid  ; 


SWINGING   CAISSONS. 


351 


X  =  horizontal  distance  between  verticals),  tending  either  to  restore  the 
body  to  its  former  position,  or  to  completely  overturn  it. 

In  fig.  323  a  floating  body  is  represented  as  having  undergone  a  slight 
displacement.  The  centres  of  gravity  and  buoyancy  now  occupy  relatively 
different  positions,  unless  the  body  be  a  homogeneous  sphere.  Assuming 
that  it  is  not,  if  the  centre  of  gravity  lie  below  the  centre  of  buoyancy,  the 
couple  is  clearly  a  righting  one.  If,  on  the  other  hand,  the  centre  of 
buoyancy  lie  below  the  centre  of  gravity,  the  couple  will  not  necessarily  be 
an  overturning  one ;  its  effect  will  depend  upon  the  following  condition. 
Premising  that  the  point,  in  which  the  vertical  through  the  centre  of 
buoyancy  after  a  slight  displacement  intersects  the  vertical  through  the 
centre  of  buoyancy  in  its  former  position  of  equilibrium,  is  designated  the 
metacerUre,  the  condition  for  the  restoration  of  equilibrium  is  that  the 
metacentre  shall  lie  above  the  centre  of  gravity  of  the  body,  otherwise  the 
latter  will  tend  to  depart  still  further  from  the  position  of  equilibrium. 
The  two  effects  are  illustrated  in  figs.  323  and  324. 


Figs.  322,  323,  and  324. 

In  the  case  of  caissons,  it  is  particularly  desirable  that  the  metacentre 
should  be  well  above  the  centre  of  gravity,  say  not  less  than  2  to  3  feet, 
but  the  stability  of  the  caisson  will  be  more  completely  assured  by 
ballasting  it  until  the  centre  of  gravity  falls  below  the  centre  of  buoyancy. 
A  margin  of  18  inches  or  so  will  be  found  sufficient  for  safe  working.  If 
the  caisson  be  fitted  with  air  chambers  and  a  tidal  deck,  it  will  certainly 
be  advisable,  if  not  imperative,  to  adopt  the  latter  precaution. 

GlaBBiflcation  of  Caissons. — Caissons  are  of  very  diverse  design,  but  they 
admit  of  a  broad  classification  into  swinging,  traversing,  and  ship  caissons. 

Swinging  Caissons  have  already  been  referred  to,  under  the  name  of  gate 
caissons,  as  forming  an  intermediate  class  possessing  characteristics  common 
to  both  gates  and  caissons.  Like  the  former,  they  turn  or  swing  upon 
a  vertical  axis  fixed  at  one  side  of  a  waterway,  and  they  have  all  the 
drawbacks  attaching  to  a  single  leaf  gate,  in  regard  to  the  excessive  length 
of  side  recess  required  for  their  accommodation  when  out  of  use.  On  the 
other  hand,  they  are  built  with  much  broader  beam  than  gates,  and  this 
gives  them  the  compensating  advantage  of  a  wide  roadway  for  traffic  at 
quay  level,  which  would  otherwise  be  impracticable  without  the  aid  of 
a  special  swing  bridge.     This  feature,  however,  is  more  or  less  common 


352 


DOCK  ENGINEERING. 


to  all  clasRCB  of  caisson.      Swinging  caissons  are  not  numerous.      One  is 
chosen  for  illustration  from  the  entmncs  to  a  graving  dock,  leading  out  of 
the  Victoria  Dock  at  Dundee  (fig.  325).     In  plan,  its  only  distinguishing 
feature  from  a  caisson  of  the  ordinary  rectangular  type  is  the  hinge  about 
which  it  turns,  which  is  situated  at  the  apex 
of  a  triangular  arm.     One  side  of  the  arm 
forms  a  continuation  of  the  outer  face  of  the 
caisson,  so  that  the  latter  can  be  swung  well 
clear  of  the  entrance.     The  entrance  itself  is 
splayed  in   order  to  admit   of   this  arrange- 
V  t  ment      When   in    the   closed    position,     the 

caisson  is  suspended  from  corbels  in  the 
masonry  at  each  side,  and  the  process  of 
opening  consists  in  floating  it  off  these  sup- 
ports, by  pumping  air  into  a  pneumatic 
chamber.  The  reverse  operation  of  allowing 
the  compressed  air  to  escape  causes  the  caisson  to  settle  upon  its  bearings. 
Figs.  326  to  329  exhibit  the  construction  of  the  caisson  in  detail. 


Fig.  325. 


and  329.— Swinging  Caistoa  at  Dundee. 


Traversing  Caisaotu  include  all  those  whose  motion  is  rectilinear.  They 
may  be  subdivided  into  sliding,  rolling,  and  floating  caissons,  according  to 
the  mode  of  travelling,  but  in  each  case  they  occupy  a  rectangular  recess, 


SLIDING  CAISSON  AT  MALTA. 


354 


DOCK  ENGINEERING. 


constructed  in  a  aide  wall  at  right  angles  to  the  axis  of  the  waterway,  and 
in  a  direct  line  with  the  path  along  which  they  travel  to  close  the  entrance. 
These  caissons  are  almost  universally  of  the  box  type  (bence  sometimes 
called  box  caiMons)^  consisting  of  a  floor,  side  and  end  plating,  and  a  water- 
tight deck,  the  whole  being  divided  into  compartments  according  to  the 
requirements  of  buoyancy  and  the  mutability  of  design. 

Sliding  Caissons  are  provided  with  keels  or  rubbing  plates  on  their 
undersides,  by  which  they  are  hauled  over  sliding  ways  set  in  the  floor  of 
the  caisson  berth.  This  method  gives  rise  to  a  certain  amount  of  friction, 
which  may  be  diminished  to  some  extent  by  suitable  flotation  adjustment. 
Sliding  caissons  have  been  constructed  at  Malta,  Portsmouth,  Mil  ford,  and 
elsewhere.  The  following  is  a  brief  description  of  one  used  to  close  the 
Hamilton  Graving  Dock  at  Malta, ''^  (see  figs.  330  and  331)  : — 

"  The  rectangular  sliding  caisson,  made  of  mild  steel,  is  40^  feet  high  and 
16^  feet  wide,  exclusive  of  the  keel  and  stem  timbers,  and  is  strengthened 
by  two  watertight  decks,  and  bracing  and  framing.     As  the  position  of  the 

entrance  precludes  heavy  traffic  passing  over 
TH  1  °**^"^;  J  ^^^    caisson,   the   roadway  deck  could    be 

;  Ik  JiTJl*.  i  Ul._^.^         placed  low  enough  to  pass  under  the  cover- 

ing  of  the  camber,  1 J  feet  below  the  coping, 
connection  being  made  with  the  quay  by  a 
hinged  flap.  The  caisson  can  be  floated  out 
from  its  normal  position  to  the  outer  stop, 
thereby  adding  38  feet  to  the  available 
length  of  the  dock.  The  air-chamber,  92 
feet  by  16 J  feet  by  8j-  feet,  in  the-  middle 
of  the  caisson,  is  reached  through  two  shafts. 
The  caisson  is  ballasted  by  concrete  blocks 
on  the  floor  of  the  air-chamber,  and  by 
water  in  the  tanks  under  the  roadway 
deck  at  each  end.  Without,  any  ballast, 
the  caisson  would  float  with  the  top  of  the 
air-chamber  2  inches  above  the  water,  but 
the  concrete  ballast  more  than  balances  the 
flotation,  producing  a  normal  pressure  on 
the  sliding  ways  of  10  to  20  tons.  The  water  ballast  is  adjusted  by  means 
of  a  three-way  stopcock  in  the  4-incb  pipe  connecting  the  tanks,  enabling 
the  water  to  be  run  from  one  tank  to  the  other,  or  one  or  both  tanks  to 
be  emptied.  The  caisson  can  be  hauled  in  or  out  of  the  camber  in  five 
minutes,  by  two  steel  pitch  chains  connected  with  the  hydraulic  hauling 
gear,  and  exerting  a  pull  of  30  tons  on  the  two  projecting  arms  of  the 
caisson  to  which  they  are  attached.  The  caisson  is  guided  into  the  camber 
by  the   keels  and  granite  rubbing  pieces  below,  and  by  the  fenders  and 

•  C.  and  C.  H.  Colsonon  <*  Hamilton  Graving  Dock,  Malta,"  Min,  Proc,  Inst,  CE,, 
vol.  oxv. 


^^5®SS555S5 


«M«rilA«ll^,A(fa 


CROSS 


•  CCTION 


Fig.  331. 


ROLLING   CAISSONS.  355 

rubbing  pieces  above,  and  tilting  is  prevented  by  the  adjustment  of  the 
water-ballast,  and  by  rollers  on  the  underside  of  the  camber  girders.  The 
caisson  is  stopped  automatically  at  the  end  of  its  course  into  or  out  of  the 
camber,  and  buffers  are  placed  in  the  recess  opposite  the  camber,  in  case 
of  a  failure  of  the  automatic  stopping  gear.  The  maximum  tensile  strain 
on  the  plating  of  the  caisson  does  not  exceed  6^  tons  per  square  inch, 
when  one  side  of  the  caisson  is  dry  and  the  water  is  up  to  deck  B  on  the 
other  side.  The  keels  and  stems  are  greenheart,  10|  by  8  inches,  and  the 
rubbing  pieces  and  fenders  are  American  elm.  Two  sluice  valves,  3|  feet 
in  diameter,  and  li  feet  above  the  deck  floor,  furnish  an  auxiliary  means 
of  filling  the  dock.  A  4-inch  hand-pump  serves  to  remove  water  from  the 
air-chamber.  The  hauling  arms  can  be  readily  moved  when  the  caisson  has 
to  be  floated  out  of  place." 

In  Rolling  CatMsons,  as  the  epithet  implies,  the  sliding  ways  are  replaced 
by  rollers  which  are  attached  either  to  the  underside  of  the  caisson  or  to  the 
pathway.  This  method  of  guidance  obviates  an  impediment  to  movement, 
due  to  the  slight  side  clearance  between  a  caisson  and  its  sliding  ways. 
Often  while  travelling,  the  projecting  portion  of  such  a  caisson  comes  under 
the  influence  of  the  wind,  which  results  in  its  getting  jambed  diagonally. 
There  is  also  less  friction  with  rollers  than  with  sliding  surfaces,  and, 
•consequently,  less  abrasion.  There  is  the  risk,  however,  that  the  rollers 
themselves  may  get  out  of  order,  in  which  case  any  advantages  they  may 
have  are  more  than  counterbalanced  by  the  trouble  and  difficulty  of  effecting 
repairs.  At  the  same  time,  it  is  only  fair  to  admit  that,  from  experience  of 
many  cases,  it  has  been  found  that  the  likelihood  of  such  a  contingency  is 
remote. 

As  an  example  of  a  rolling  caisson,  the  following  description  of  one 
constructed  at  the  sea-lock  of  the  new  Bruges  Canal,*  within  the  past  few 
years,  may  be  useful  (see  figs.  332  to  335)  : — 

The  caisson  is  a  steel  framework,  with  plating  of  the  same  metal,  of 
14j  feet  uniform  width,  presenting  in  elevation  the  form  of  a  trapezium, 
whose  top  and  bottom  lengths  are  80^  feet  and  67^^  feet,  respectively.  The 
height  of  the  caisson  is  41§  feet,  the  upper  surface  being  8  inches  above  the 
highest  tide  level.  A  watertight  deck  is  laid  about  16  feet  above  the  keel, 
and  the  chamber  thus  formed  is  occupied  only  by  the  kentledge  necessary 
for  preserving  equilibrium.  The  upper  part  of  the  caisson,  though  enclosed, 
is  adapted  to  the  free  entry  of  water  from  either  side,  by  the  formation  of  a 
series  of  orifices,  14  inches  in  diameter,  in  each  face,  at  the  level  of  the 
watertight  deck.  Under  the  fluctuations  of  water  level,  the  volume  of 
displacement  remains  constant,  and,  consequently,  the  weight  on  the  wheels 
remains  unchanged  after  once  being  regulated  by  ballasting.  These  orifices 
are  opened  and  closed,  as  required,  by  valves  worked  from  the  top  deck.  The 
caisson  is  carried  on  eight  wheels,  each  3^  feet  in  diameter,  on  four  axles, 

*  Vide  Piens  on  '*  Portes  It  un  seul  vantail  de  I'^cluse  Maritime  du  nouveau  Canal 
de  Bruges,"  Seventh  Int,  Nav,  Con.,  BmsselB,  1898. 


356  DOCK  ENGINEERING. 

arranged  in  pairs.  The  working  parts  are  open  to  inspection  by  means  of  & 
pneumatic  shaft  leading  to  the  chambers  in  which  the  axles  are  placed. 
The  buoyancy  chamber  is  also  accessible  by  means  of  a  similar  shaft. 
Watertightness  at  the  abutting  surfaces  of  the  caisson  is  established  by 
greenheart  facings.  The  caisson  is  designed  to  stand  a  head  of  water  from 
either  side.  Its  displacement  is  about  420  tons  ;  its  own  weight,  196  tons  ; 
and  the  ballast,  273  tons ;  leaving  some  49  tons  excess  weight  to  insure 
stability  during  movement. 

The  general  framework  of  the  structure  comprises  eight  large  vertical 
girders,  placed  at  intervals  of  8  feet,  and  extending  to  the  full  height  and 
width  of  the  caisson.  The  flanges  of  these  girders  serve  as  bearing  surfaces 
for  the  plating ;  they  are  formed  of  6  bv  2^  by  3  inches  channel  iron.  The 
horizontal  struts  are  similarly  composed,  but  double. 

Six  tiers  of  horizontal  joists,  14  inches  deep,  connect  the  vertical  girders 
on  each  face.  These  joists  are  spaced  at  varying  distances  apart,  according 
to  the  intensity  of  hydrostatic  pressure.  Between  the  vertical  girders  are 
three  rows  of  intermediate  bearers,  only  the  centre  one  of  which  is 
prolonged  above  the  watertight  deck.  These  bearers  are  of  channel  iron 
of  the  same  section  as  the  vertical  flanges.  The  watertight  decking  is 
carried  by  the  horizontal  struts  of  the  main  girders,  with  deck  joists 
between  and  at  right  angles  to  them.  The  thickness  of  the  plating  varies 
from  I:  to  f  inch. 

Floating  Caissons  may  either  be  of  the  box  or  the  ship  type.  In  the 
former  case,  they  are  generally  rectangular  in  plan  and  similar  to  the 
examples  of  box  caissons  already  described.  Their  distinction  lies  simply 
in  the  fact  that  they  are  moved  entirely  by  flotation,  without  guides  or 
rollers.  Figs.  336  to  338  illustrate  a  floating  caisson  used  at  Blackwall, 
London.* 

The  caisson  has  only  one  meeting  face,  and  that  of  teak,  14  by  7  inches. 
There  is  a  lower  air-chamber  extending  the  whole  length  of  the  caisson, 
formed  by  a  watertight  deck  at  a  height  of  1 1  feet  6  inches  above  the 
bottom.  Above  this  level,  the  caisson  is  divided  into  three  compartments 
by  vertical  bulkheads,  which  are  also  watertight.  The  ballast  at  the 
bottom  of  the  air  chamber  consists  of  cast-iron  kentledge,  set  in  Portland 
cement  concrete.  Three  sluices,  each  3  feet  in  diameter,  allow  water  to  be 
transmitted  through  the  caisson,  the  valves  being  controlled  by  spindles 
passing  through  the  air-chamber  to  the  upper  deck.  The  following  are  the 
sizes  and  general  dimensions  of  the  framing : — Angle  irons  at  sides,  3  by  3 
by  f  and  18  inches  apart ;  angle-iron  cross  beams,  4  by  4  by  ^  inches  to  high- 
water  level,  and  3  by  3  by  f  inches  above ;  centre  uprights,  4  by  4  by 
f  inches,  also  18  inches  apart;  deck  beams,  3  by  3  by  f  inches.  The  plating 
is  -j^  inch  thick  up  to  the  watertight  deck,  and  above  that  level,  f  and  ^ 
inch  thick.     Rock  elm  fenders,  10  by  10  inches,  and  a  decking  of  English 

*  Vide  Macalister  on  "Caissons  for  Dock  Entrances/*  Min.   Proc.   Inst.   C,E., 
vol.  Ixv. 


ITo  fatt  page  ass. 


356 


DOCK  ENGINEERING. 


[To  fwu  page  856, 


BfyuUiiju*g  Vali-^  S'dia". 


SHIP  CAISSONS. 


357 


oak  complete  the  general  features  of  the  caisson,  which  was  constructed 
in  1878  from  designs  by  Messrs.  Kinipple  and  Morris. 

That  a  caisson  of  this  type  is  not  necessarily  rectilinear  in  plan  is 
evidenced  by  the  instance  of  a  caisson  (fig.  339),  designed  in  1864  by  the 


Fig.  339. 

late  Mr.  W.  K.  Kinipple,  and  built  the  following  year  for  a  graving  dock 
at  Limekiln,  London.  Beyond  the  eccentricity  of  its  form,  inspired  by  the 
desire  to  obtain  the  axial  advantage  of  a  mitred  sill,  there  is  nothing  very 
remarkable  about  its  construction.  As  in  the  preceding  case,  it  is  furnished 
with  a  lower  air-chamber  and  two  watertight  bulkheads,  which  latter, 
however,  pass  right  through  the  air- 
chamber  and  completely  trisect  the 
caisson. 

Ship  Caissons  have  more  or  less  the 
form  of  an  ordinary  navigable  vessel,  but 
the  curvature  of  their  sides  varies  very 
much  with  the  depth  of  water  in  which 
they  have  to  float.  At  the  Bute  Docks, 
Cardiff,  where  the  draught  of  water  on 
occasion  is  as  little  as  9^  feet,  the  caisson 
has  had  to  be  designed  with  sufficient 
buoyancy  space  at  that  depth  to  support 
the  upper  weight.  This  and  the  necessity 
for  a  margin  of  stability,  has  necessitated 

the  somewhat  peculiar  profile  shown  in 

/.      o  J  A  Fig.  340.— Ship  CaiBBon  at  Cardiff. 

The  more  general  section  of  ship  caisson  is  similar  to  that  in  fig,  341, 
which  is  the  section  of  one  at  the  Kidderpur  Docks,  Calcutta.''^  A  plan 
And  elevation  are  given  in  figs.  342  and  343.  The  keels  and  stems  of  the 
•caisson  are  faced  with  greenheart. 

A  caisson  differing  somewhat  in  construction  and  internal  arrangements 
is  that  (fig.  344)  closing  the  entrance  to  the  Alexandra  Graving  Dock  at 
Belfast,!  a  short  description  of  which  is  appended. 

*  Bruce  on  *'The  Kidderpur  Dock,  Calcutta,"  Jftn.  Proc.  Inst.  C.E.,  vol.  qxxu 
+  Kelly   on  "The   Alexandra   Graving   Dock,   Belfast,"  J/iw.   Proc,  InsU   C.E,^ 
vol.  oxi. 


358  DOCK  ENGINEERING. 


359 


NAL^  MIDSHIP  StCTlON 


HALF    CUD    ELEVATION. 


J555^5555^^5^^^^5^???^s^fe^ 


I 


l-^^m^^SM 


^^^<J^SS5^^^^\\^^;^i^^ 


^'mC   q_ 


SHIP        QAISSON 

4         «         1         o         


Fig.  344.-  Ship  Caisson  at  Belfast. 


360  DOCK   ENGINEERING. 

"  The  hull  is  of  wrought  iron,  framed  and  braced  together.  There  are 
four  decks,  the  three  lower  of  which  are  open  lattice  work,  connecting  the 
deck  stringer-plates  of  both  sides.  The  keel-  and  stem-plates  are  2^  inches 
thick,  and  the  keel- base  is  formed  of  two  angle-irons  ri vetted  in  the  wake 
of  the  garboard  strakes.  On  both  sides  of  the  keel  and  stems,  heavy  pieces 
of  greenheart  are  bedded  on  and  bolted  to  the  ironwork,  the  timber  on  both 
sides  of  the  keel  and  stems  being  planed  true  to  iit  the  polished  masonry 
faces  of  the  grooves,  with  which  they  form  a  thoroughly  watertight  joint. 
The  frames  of  the  caisson  are  of  angle-iron ;  below  the  level  of  deck,  6, 
they  are  spaced  at  distances  apart  of  3  feet.  The  deck  beams  are  of 
angle-iron.  The  skin  plating  ranges  in  thickness  from  f  inch  at  the 
upper  part,  to  |  inch  at  the  lower  part  of  the  caisson.  The  large  plates 
are  laid  with  their  greatest  lengths  horizontal,  in  alternate  inside  and 
outside  strakes,  with  vertical  butt  joints.  Between  decks,  A  and  6,  in 
the  centre  of  the  caisson,  is  a  room  with  watertight  floor  and  bulkheads, 
in  which  the  engine,  boiler,  and  pumping  machinery  are  placed.  Hatch- 
ways in  the  upper  deck  give  access  to  the  engine-room  and  other  parts  of 
the  interior  of  the  caisson.  The  roadway  deck  has  strong  angle-iron  deck 
beams  and  stringers,  and  it  is  cleaded  with  4-inch  Dantzlc  oak  planking, 
caulked  and  payed  with  marine  glue.  ^A  horse- track,  along  the  centre  of 
the  roadway,  is  formed  of  American  rock  elm  slabs,  spiked  to  the  deck  flat ; 
and  on  each  side  of  it,  tracks  of  wrought-iron  ^-inch  bars  are  screwed  down 
to  the  decking ;  guides  of  angle-iron  are  fitted  along  their  outsides ;  and 
a  hinged  handrail  of  wrought-iron  gaspipe  is  fixed  along  both  sides  of 
the  roadway." 

The  caisson  illustrated  in  figs.  345  to  347,  forming  one  of  a  number  of 
interchangeable  caissons  in  the  service  of  the  Mersey  Dock  and  Harbour 
Board,  is  mainly  used  for  work  of  a  temporary  nature  during  the  absence 
of,  or  in  case  of  accident  to,  the  dock  gates.  It  consists  of  four  decks, 
below  the  lowest  of  which  is  located  the  concrete  ballast.  It  will  be 
noticed  that  the  upper  deck,  which  is  of  wrought-iron  plating,  is  not 
available  for  traffic.  There  are  three  bulkheads,  two  transverse  and  one 
running  fore  and  aft.  These  caissons  do  not  tit  into  grooves,  as  in  the 
previous  instance,  but  have  a  single  plane  bearing  surface  against  a  sill, 
and  quoins  arranged  in  the  curved  pierhead  of  an  entrance,  so  that  the 
same  caisson,  which  is  100  feet  long,  can  serve  in  several  situations. 

Lowering  Platforms, — The  difl&culty  of  entirely  recessing  a  traversing 
caisson  under  cover  of  the  quay,  and  of,  at  the  same  time,  equipping  it  with 
a  suitable  deck  at  quay  level  for  the  purposes  of  traffic,  has  been  overcome 
by  the  introduction  of  a  lowering  platform.  The  platform,  which  consti- 
tutes the  roadway,  is  supported  on  a  series  of  hinged  verticals,  in  a  manner 
more  fully  described  in  Chapter  x.  A  caisson  designed  in  this  manner,  by 
the  late  Mr.  W.  R.  Kinipple,  closes  the  entrance  to  the  Garvel  Graving 
Dock,  at  Greenock.**     It  is  a  rolling  caisson,  with  the  rollers  attached  to 

*  Macalister  on  "  Caissonfi  for  Dock  Entrances,"  if  in.  Proc.  Inst.  C.E.,  vol.  Ixv. 


[?•  fact  pagt  360, 


y 


tttm 


fmna/t'fiitmif 


'Sm¥tt^ 


Transverse  SecUsn. 


Plan 
at  Liverpool. 


LOWERING   PLATFORMS.  36 1 

the  underside  of  the  caisson,  ui<)  mnning  upon  plate  rails  let  into  the  fioor. 
A  section  showing  the  general  arrangement  is  given  in  fig.  348.  "The 
doable-fianged  cast-iron  rollers  are  18  inches  diameter,  and  are  spaced 
9  feet  apurt.  The  breadth  of  the  caisson  over  the  greenheart  meeting 
faces  is  19  feet  10  inches,  and  the  width  between  the  granite  faces  20  feet, 
giving  a  clearance  of  2  inches.  A  difierence  of  head  of  from  3  to  4  inches 
is  sufficient  to  move  the  caisson  from  one  face  to  the  other."* 


Tables  are  appended,  with  statistics  of  size  and  expenditure,  relating  to 
typical  caissons  constructed  in  various  parts  of  the  world. 

REFERENCES. 

On  the  subject  of  Btresses  in  dock  gates,  the  reader  who  dosirea  further  informs. 
tioD  is  referred  to  the  following  papers  in  the  Proceedings  q/*  Ihe  Itutitalion  0/  CivU 
EnginteTa  .-— 

"Strain  to  which  Lock  Gates  are  inbjecled. "    By  P.  W.  Barlow.     Vol.  i. 

"  Strains  OD  Lock  Gat«8."    By  W.  J,  Kingsbury.     Vol.  zviii. 

"Strength  of  Lock  Gates."    By  W,  R.  Browne.     Vol.  ixxi. 

"  Dock  Gates."    By  A.  F.  Blandy.     Vol.  Iviii. 

"  Design  and  Coostruotion  of  Dock  Galea  of  Iron  and  .Steel."    By  J.  M.  MoucrieS 
Vol.  cxvii. 
Also,  to  a  paper  in  the  Procetdingi  qflht  Lhtr/iool  Engijieeritig  Society: — 

"  Dock  Gates."    By  \V.  Brodie.     Vol.  iviii. 

•  Kinippte  on  "Greenock  Harbour,"  J/iw.  Froc.  Itiel.  C.E.,  voL  cxxx. 


362 


DOCK  ENGINEERING. 


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364 


CHAPTER  IX. 

TBANSIT   SHEDS   AND  WABEHOUSES. 

ExTBNT  OF  Accommodation  Required — Pbopobtion  of  Goods  to  Quayage — Statistics 
OF  Sample  Cargoes— AocEssiBiLiTy  of  Sheds— Proximity  to  Edge  of  Quay — 
Level  of  Floor — General  Diversity  of  Practice— Features  of  Construction — 
Doors  and  Doorways — Compartments— Lighting — Materials  for  Floors— 
Fire-resisting  Construction — Monier,  Hennebique,  and  C0TTAN91N  Systems — 
Pressure  Sustained  by  Floors— Columns  and  Piers— Strength  of  Columns — 
Roof  Coverings— Weight  of  Shed  Roofs  —  Examples  of  Sheds  and  Ware- 
houses AT  'I'lLBURY,  Liverpool,  Dundee,  Greenock,  Glasgow,  Manchester, 
Antwerp,  Rotterdam,  Havre,  Marseilles,  Calais,  Dunkirk,  Dieppe,  Rouen, 
Bremen,  Hamburg,  Calcutta,  and  Buenos  Ayrbs. 

Few  articles  of  commerce  are  altogether  unaffected  by  exposure  to  climatic 
conditions,  and  for  by  far  the  greater  quantity  of  goods  deposited  on  dock 
quays,  some  protection  from  the  vicissitudes  of  the  weather  is  absolutely 
essential.  This  is  provided,  in  most  cases,  in  the  form  of  transit  sheds  and 
warehouses.  The  former  class  are  for  the  temporary  accommodation  of 
discharged  cargoes,  or  of  freights  on  the  eve  of  shipment.  The  latter  class 
are  for  the  reception  of  goods  which,  having  reached  their  destination,  are 
to  be  stored  for  periods  of  longer,  and  probably  indefinite,  duration.  In 
bonded  sheds  and  warehouses,  dutiable  articles  may  remain  under  customs' 
seal  until  such  time  as  the  consignee  has  need  of  them,  the  imposts  mean- 
while remaining  in  abeyance. 

Extent  of  Shed  Accommodation. — The  area  of  quay  space  allocated  to 
storage  purposes  will  necessarily  depend  upon  several  considerations.  It 
is  not  always  practicable  to  provide  shed  accommodation  commensurate 
with  the  cubic  capacity  of  vessels  frequenting  the  berths,  neither  is  it,  in 
other  instances,  essential  or  advisable  to  do  so.  Under  certain  circum- 
stances, goods  may  be  removed  from  the  quays  almost,  if  not  quite,  as 
rapidly  as  they  are  discharged  from  the  ship's  hold.  This  happens  when 
a  cargo,  even  if  not  entirely  homogeneous,  is  fairly  uniform  in  character, 
and  is  consigned  to  but  few  individuals.  When,  on  the  other  hand,  goods 
have  to  be  broken  up  and  sorted  into  numerous  lots,  it  becomes,  even  with 
the  utmost  expedition,  a  matter  of  several  days  before  they  can  all  be 
despatched  to  their  several  destinations.  Accordingly,  it  is  not  unreason- 
able nor  unusual,  in  such  cases,  to  allow  consignees  a  period  of  seventy-two 
to  ninety-six  hours  in  which  to  claim  and  remove  their  property. 

A  further  complication  arises  from  the  necessity  of  dealing,  practically 
simultaneously,  with  outgoing  goods.     Deposited  on  the  site  ready  for  the 


SHED  ACCOMMOnATION. 


365 


reloading  of  a  discharging  vessel,  they  serve  to  decrease  the  amount  of 
available  quay  space,  and  thus  interfere  with  freedom  and  rapidity  of 
movement.  It  is  a  good  plan,  where  feasible,  for  a  ship  to  discharge  her 
inward  freight  at  one  berth,  and  then  proceed  to  another  to  receive  her  out- 
ward consignments. 

Mr.  Hay  ter  *  has  laid  it  down  as  his  opinion  that  350  or,  at  the  most,. 
400  tons  of  goods  per  lineal  yard  of  quay  can  be  dealt  with  per  annum. 
But  in  the  case  of  Liverpool,  of  British  ports  at  any  rate,  this  quantity 
has  been  largely  exceeded,  upwards  of  800  tons  of  goods  per  lineal  yard  of 
quay  having  passed  through  the  double-storey  sheds  at  that  port  in  one 
year.  At  Marseilles,  500  tons  has  been  stated  as  the  limit ;  but,  on  the 
other  hand,  1,000  tons  is  no  unusual  allowance  at  Russian  ports,  and  as 
much  as  2,000  tons  per  lineal  yard  have  been  accommodated  on  certain 
quays  at  Antwerp!  and  Liverpool.  The  ensuing  table  gives  detailed 
instances  of  the  ratio  of  the  registered  tonnage  of  vessels  to  the  length 
and  area  of  the  berths  occupied. 


TABLE  XXVI IL — Comparison  op  Number  and  Nbtt  Reoisteked 
Tonnage  of  Vessels  Discharged  and  Loaded  during  One  Ykar  at 
CERTAIN  Appropriated  Berths  in  Liverpool  Docks,  with  Length 
OP  Quay  Space  and  Area  op  Shed  Accommodation  involved. 


Berth. 

Quay 

Space  in 

Lineal 

Shed  Area 
in 

VeaaelB  Worked. 

Days  Occupied 

Proportion  of  Tonnage. 

Feet. 

Sq.  Yardfl. 

No. 

Tonnage. 

Dis- 
charging. 

Loading. 

Per  Liu.  Ft. 
of  Quay. 

PerSq.Yd. 
of  Shed. 

A 

2000 

16,727 

114 

428,729 

309^ 

247 

214-36 

25  03 

B 

1408 

12,594 

102 

310,818 

316 

229 

220-75 

24-68 

C 

900 

7,970 

58 

180,548 

132 

153 

200-5 

22-65 

D 

800 

8,048 

63 

141,236 

188 

171 

176-54 

17-67 

£ 

900 

9,108 

67 

179,402 

144 

158^ 

199-33 

19-69 

F 

438 

3,467 

41 

68,264 

19 

178 

164-98 

19-68 

G 

566 

6,639 

37 

89,995 

147i 

88i 

15918 

13-55 

H 

1400 

13,187 

91 

278,639 

267i 

189 

199  02 

2113 

I 

1103 

10,088 

80 

210,886 

152i 

239 

19119 

20-9 

J 

708 

7.120 

26 

51,157 

58i 

38 

72-25 

7-18 

K 

716 

7,249 

43 

;     119,279 

166 

153 

166-57 

16-45 

L 

703 

9,637 

63 

169,097 

152^ 

78i 

226-31 

16-5 

M 

200 

714 

70 

19,384 

59i 

2 

96-92 

27-28 

The  sheds  in  every  instance  were  single-storey  sheds. 

Where  the  nature  of  the  traffic  is  variable,  it  is  evident  that  no  correla- 
tion whatever  between  its  amount  and  the  area  or  length  of  quay  space  is 
possible.  A  shed  may  be  used  at  one  time  for  the  reception  of  grain  in  bulk, 
at  another  for  cotton  in  bales,  at  another  for  provisions  in  boxes.     The 

•  Afin.  Proc.  Inst,  C.E.,  vol.  c.,  p.  44. 

t  Proceedings,  Seventh  Inter.  Nav.  Gong.,  Brussels,  1898. 


366 


DOCK  ENGINEERING. 


width  of  sheds  will,  accordingly,  be  regalated  almost  entirely  by  the  land 
available  for  the  purpose,  and  no  other  limit,  apparently,  can  be  suggested. 
From  the  smallest  dimension  consistent  with  practical  utility,  sheds  have 
been  constructed  to  such  great  widths  as  150  feet  at  Liverpool,  190  feet  at 
Manchester,  and  196  feet  at  Havre.  In  the  case  of  Manchester,  however,  it 
should  be  pointed  out  that  the  shed  is  traversed  at  its  centre  by  a  roadway, 
included,  therefore,  within  the  roof. 

As  indicative  of  the  extremely  heterogeneous  character  of  some  cargoes 
the  following  analyses  of  representative  cases  will  be  interesting  and  not 
inappropriate : — 

List  of  cargo  discharged  in  London,  Sept.,  1897,  from  8.8.  "Milwaukee," 
470  feet  by  56  feet  by  34  feet  9|  inches*  :— 


514  head  of  cattle. 

132  horses. 

640  sheep. 
18,412  bushels  of  oats. 
1,209  bales  of  hay. 
13,149  sacks  of  flour. 
51,629  pieces  of  deal. 
16,328  boards. 
4,398  pieces  of  lumber. 

195  tierces  of  lard. 


200  bags  of  starch. 
189,200  bushels  of  com. 
20,025  boxes  of  cheese. 
399  cases  of  apples. 
11  cases  of  machinery. 
16,737  deal  ends. 
5,723  pieces  of  birch  plank. 
134  radiators. 
830  pails  of  lard. 
5,730  bags  of  grape  sugar. 


This  is  said  to  be  the  largest  cargo  discharged  iu  London  up  to  that  date. 
In  this  condition  the  ship  had  11,100  tons  dead  weight.  It  is  reported  she 
was  discharged  in  66  working  hours. 

This  may  be  compared  with  the  list  of  cargo  carried  by  the  8.8.  "Oevic" 
on  her  maiden  voyage  in  1894  : — 


500  head  of  cattle. 
2,330  sheep. 
9,061  bales  of  cotton. 
14,778  pails,  tierces,  barrels,  and 

firkins  of  lard. 
3,006  boxes  of  bacon  and  ham. 
1,000  bundles  of  shooks. 

175  boxes  of  meats. 
11,642  bags  of  copper  matte. 
6,532  pieces  of  oak. 
885  Imrrels  of  oil. 
5  barrels  of  bladders. 
3  coops  of  fowls. 
100  barrels  of  glucose. 
803  cases  of  canned  meat. 
100  tierces  of  beef. 


10  cases  of  varnish. 
27  cases  of  axes. 
33  cases  of  woodware. 
20  barrels  of  metal  polish. 
13  cases  of  agricultural  imple- 
ments. 
120  barrels  of  grease  and  oiL 
250  barrels  of  scale. 
1,800  sacks  of  oilcake. 
2,352  pigs  of  lead. 

160  boxes  of  cheese. 
1,250  sacks  of  flour. 
1,000  barrels  of  resin. 

5  barrels  of  rope  covering. 
5,000  bags  of  grape  sugar. 
4,897  oak  staves. 


•  De  Russett  on  "Recent  Improvements  in  Cargo  Steamers,*'  Eng,  Conf,,  London, 
1899,— Vide  Engineering,  June  16,  1899. 


ACCESSIBILITY  OF   SHEDS. 


367 


The  following  are  the  records  of  actual  dead- weight  cargoes  discharged  at 
Liverpool  at  the  dates  named : — 


"Georgic," 
July,  1889. 

"Cymric,'* 
August,  1899. 

"Cymric." 
October,  1900. 

General  cargo,    . 
Bulk  grain,  . 
Fresh  meat, 

Live  stock,  . 

Tons.        Tons. 
4,617 
5,118 
611 

10,246 

696 

Tons.        Tons. 
5,084 
4,665 
612 

10,361 
575 

Tons.       Tons. 
3,504 
6,193 
567 

10,264 
687 

10,942 

10,936 

10,951 

The  diversity  between  weight  and  capacity  is  illustrated  by  the  sample 
cargoes  given  below  : — 


Ksme  of  Ship. 

Length. 

Gross  Begis- 
tered  Tonnage. 

Cargo. 

Area  of 

Shed 
Occupied. 

Tons 
Weight. 

Tons 
Measurement. 

Cubic 
Feet. 

"  Horace," 
"Cymric,"      . 
"Georgic,"     . 
"Celtic,"  .     . 

Feet. 

350 

585^ 

558i 

681 

3,335 
12.647 
10.077 

20,880 

2,959 
9,749 
9,209 
6,102 

13^390 
11,112 
15,644 

5,436 
535,600 
444,480 
625,760 

Sq.Yaids. 

18,'647 
18,647 
18,647 

One  ton  measurement  is  equivalent  to  40  cubic  feet  of  the  ship's  hold  occupied  by 
actual  cargo.  The  ship's  gross  registered  tonnage  is  based  on  her  total  content,  calculated 
by  certain  rules  and  divided  by  100. 

The  cargoes  have  been  purposely  chosen  to  exhibit  a  wide  range  and 
contrast. 

Accessibility  of  Sheds. — Under  all  these  mutable  conditions  one  thing, 
at  any  rate,  is  perfectly  clear — viz.,  that  the  means  of  access  to  a  shed,  and 
the  facilities  for  the  transference  and  removal  of  its  contents  are  points  of 
vital  importance.  It  will  be  well  then  to  briefly  consider  what  steps  may 
be  taken  to  achieve  the  ideal  result. 

Considerable  divergency  of  opinion  will  be  found  to  exist  in  regard  to 
this  question  at  various  ports,  due  mainly  to  conditions  peculiarly  local. 
For  there  are  no  less  than  four  ways  in  which  oversea  goods  may  be 
despatched  to  their  final  destinations,  and  each  of  these  obtains  to  a  greater 
extent  than  the  others  at  some  locality  and  demands  special  measures. 
They  are  as  follows : — 

1.  By  direct  transfer  to  coasting  vessels,  barges,  lighters,  and  other 
river  and  canal  craft. 

2.  By  direct  transfer  to  railway  trucks  and  waggons. 


368  DOCK   ENGINEERING. 

3.  By  direct  transfer  to  lorries  and  vehicles.  In  this  case  the  distance 
the  goods  are  to  be  taken  will  not  be  great. 

4.  By  temporary  discharge  upon  the  quay  and  subsequent  t»*ansference 
by  canal,  rail,  or  road,  as  the  case  may  be. 

These  methods  may  be  found  both  singly  and  in  combination  at  the 
same  port.  With  the  first,  however,  we  need  not  concern  ourselves  as  it 
is  outside  the  scope  of  the  present  section.  The  second  and  third  methods 
may  be  considered  conjointly  as  representative  of  direct  transfer  in  contra- 
distinction to  the  fourth  method  which  we  will  term  indirect  transfer.  It 
is  not  difficult  then  to  understand  that  based  upon  these  methods  there  have 
arisen  two  separate  and  distinct  systems  of  transit  sheds,  viz. : — (1)  Those 
in  which  the  shed  fronts  are  brought  very  close  to  the  face  of  the  quay 
wall,  leaving  only  a  narrow  margin  of  from  5  to  10  feet  for  foot  traffic; 
and  (2)  those  in  which  the  sheds  are  situated  at  a  distance  back  from  the 
edge  of  the  quay,  sufficiently  great  to  admit  of  two  or  more  lines  of  railway 
running  parallel  to  the  quay  within  the  space  intervening  between  the 
shed  and  the  dock. 

The  latter  type  of  shed  is  in  vogue  at  Marseilles,  Hamburg,  Bremen, 
and  most  Continental  ports,  which  may  be  called  ports  of  transit.  It 
is  eminently  suited  to  those  cases  in  which  a  ship's  freight  is  trans- 
ferable without  the  necessity  of  selecting  and  sorting.  The  former  system 
is  practised  at  Liverpool,  the  older  docks  at  London,  and  in  other  places 
where  reverse  conditions  obtain  and  goods  require  subdivision  before 
removal.  Such  ports  may  be  distinguished  as  ports  of  destination. 
Sometimes  the  two  classes  of  shed  are  exemplified  at  the  same  place, 
as  at  Manchester. 

Of  the  two  lines  of  rails  at  the  dock  side,  that  nearest  the  water  will 
generally  be  used  for  the  loading-off  cranes.  The  second  will  accommodate 
the  trucks  to  be  loaded,  and  a  third  line  may  advantageously  be  added  as 
a  siding.  Quay  cranes,  however,  of  broader  gauge  than  the  regulation 
4  feet  8^-inch  track,  if  placed  on  pedestal  platforms,  as  is  frequently  the 
ease,  admit  of  a  line  of  trucks  passing  beneath  and  between  them,  thereby 
producing  a  considerable  saving  in  quay  space.  The  drawback  to  the 
arrangement  is  a  lessening  of  the  stability  of  the  crane.  Occasionally, 
cranes  may  be  found  located,  so  that  the  outer  end  of  the  pedestal  runs 
upon  a  rail  at  the  quay  level,  while  the  inner  end  is  carried  on  a  rail 
fixed  to  some  part  of  the  shed  structure,  as  in  fig.  393. 

When  the  shed  is  close  to  the  quay  the  discharging  cranes  must  neces- 
sarily be  situated  entirely  upon  the  shed,  either  at  the  roof  or  some 
intermediate  fioor  level. 

The  two  arrangements  of  quay  sheds  are  illustrated  in  figs.  349  and 
350,  which  are  ground  plans  respectively  of  sheds  at  Bremen  and  Liverpool. 

A  considerable  portion  of  a  ship's  cargo  may  be  raised  from  the  hatches 
by  the  ship's  own  appliances,  and  trucked  ashore  on  gangways,  or  even, 
when  the  vessel's  sides  are  at  some  height  above  the  quay,  discharged  by 


PLAN  OF  SHED  AND  WAREHOUSE. 


369 


24 


370  DOCK  ENGINEERING. 

means  of  slides.  Where  there  are  no  cranes  these  methods  must  obviously 
be  adopted ;  but  the  question  of  unloading  appliances  is  more  suitable  for 
discussion  under  the  section  of  Working  Equipment. 

On  the  landward  side  of  the  shed,  will  generally  be  found  a  roadway 
for  cart  traffic,  often  in  conjunction  with  additional  lines  of  railway. 

The  level  of  the  shed  floor  is  another  point  concerning  which  opinion 
is  divided.  At  some  ports  it  coincides  with  the  quay  level ;  at  others  it 
is  raised  3  feet  or  more  above  the  quay,  the  object  in  the  latter  case  being 
to  bring  it  on  a  plane  with  the  floors  of  waggons  and  carts  so  as  to 
facilitate  trucking.  This  method  forbids,  while  the  alternative  method 
allows,  carts  and  vehicles  to  enter  the  shed,  and  so  to  a  certain  extent 
to  obviate  trucking.  Local  practice,  again,  influences  the  decision  as  to 
which  method  in  preferable. 

Dock 


\ 
^ 


Customs  w  lock  -  ups 


:es\ 
Tnfnr 


Convenimces 

m        ■'         ■ 1 u ■ 1 i. %—m ■  _        ■ II        t         .        F 

Roadymv 
Fig.  350. — ^Plan  of  Shed  Compartment  at  liverpool. 

As  illustrating  the  diversity  of  opinion  prevailing  in  regard  to  the 
general  disposition  of  sheds  and  warehouses,  and  the  utter  impossibility 
of  formulating  any  definite  or  systematic  regulations  thereon,  the  following 
conclusion,  unanimously  adopted  after  a  long  discussion  of  the  subject 
by  the  members  of  the  Seventh  International  Maritime  Congress  {Fourik 
Section — Seaports)  sitting  at  Brussels  in  1898,  may  be  quoted : — 

^^  Question, — Warehouses  and  sheds:  accommodation,  size,  mode  of 
construction,  means  of  access. 

'*  Conclusion, — Considering  the  preponderating  influence  which  variable 
elements  in  the  different  ports,  especially  the  nature  of  the  traffic  and  the 
commercial  customs,  must  have  on  the  conditions  of  the  establishment  of 
quays  and  warehouses,  the  Fourth  Section  is  of  opinion  that  there  is  no 
occasion  to  draw  up  general  rules  with  regard  to  these  conditions  of  estab- 
lishment, as  the  arrangements  adopted  in  each  particular  case  are  of  interest 
solely  by  way  of  indication  for  analogous  cases." 

Features  of  Construction. — Methods  of  shed  construction  fall  largely 
under  those  of  building  generally,  and  it  is  not  proposed  here  to  discuss 
details  which  are  common  to  ordinary  structures,  and  for  which  reference 
may  be  made  to  any  suitable  text-book  on  building  construction.     Those 


DOORWAYS.  371 

features  alone  will  be  dealt  with  which  are  essential  and  promiDent  from 
the  point  of  view  of  a  dock  engineer. 

It  is  manifestl}'  desirable  tliat  sheds  (and  warehonses)  should  be,  as 
far  as  possible,  of  thoroughly  fireproof  construction  throughout.  From 
motives  of  economy,  however,  the  former  are  often  constructed  of  in- 
flammable material,  sncb  as  timber  and  zinc.  Single-storey  sheds  are  most 
noticeable  in  this  respect. 

Doorvjayg. — The  openings  in  the  sides  of  a  shed,  both  at  the  dock  front 
and  along  the  roadway,  should  be  as  numerous  as  possible,  more  particularly 
in  the  first  case,  so  as  to  be  adapted  for  receiving  the  discharge  from  several 
hatchways  simultaneously.  It  is  a  good  plan  to  have  continuous  doors,  on 
account  of  the  difficulty  of  getting  several  ship's  hatchways  to  coincide  with 


Plan 
FigB.  361  and  3fi2,-Woodet)  Shed  Door. 

isolated  door  openings.  With  this  arrangement,  the  sides  of  the  shed  will  con- 
sist of  a  series  of  columns  with  intervening  spaces,  generally  closed  by  doors, 
but  sometimes,  as  at  Havre,  without  tbera.  At  the  same  time,  it  must 
be  remarked  that  the  absence  of  longitudinal  walls  causes  a  shed  to  lose 
much  of  its  stiffness  as  a  structure,  and  deprives  it  of  the  means  of  affording 
lateral  support  to  its  contenta.  Grain  discharged  in  bulk  is  often  prevented 
from  spreading,  on  one  side  at  least,  by  an  external  wall  or  partition,  with 
a  consequent  saving  in  space,  and  similar  assistance  is  rendered  in  the  case 
of  many  other  classes  of  goods.  This  fact  emphasises  the  necessity  for  sub- 
stantial sides  to  a  shed.  The  advantages  of  continuous  doorways,  moreover, 
on  the  roadside  are  more  imaginary  than  real.     Not  more  than  onelialf 


372 


DOCK  ENGINEERING. 


the  entire  length  can  be  available  open  space,  and  the  only  benefit  con- 
ferred is  that  of  exercising  some  restricted  choice  as  to  its  disposition. 

Doors  are  of  two  varieties — rolling  (or  sliding)  and  folding. 

Rolling  or  sliding  doors  consist  of  frames  of  timber  or  iron,  with  a  facing 
of  the  same  material.  Movement  is  made  with  wheels,  which  run  either  on 
a  ground  rail  or  upon  a  rail  above  the  door.  The  grooves  in  a  ground  rail 
are  liable  to  become  choked  with  dirt  and  grain,  and  need  frequent  cleaning. 


a'.s'. 


r-—/- 


^JT  3**/ia  rj. 


*lf34  ■»/»  L.K 


•rima't^tt^ 


- 


K 


4 


Bar  sirik*  f^'/curf 

Figs.  353  and  354.— Iron  Shed  Door— Elevation  and  Vertical  Section. 

They  hold  water,  which  in  winter  freezes  and  causes  inconvenience.  The 
use  of  lower  wheels  further  necessitates  an  upper  guide  rail  for  the  top  of 
the  door.  Usually  two  rows  of  slide  rails  are  provided,  the  doors  being 
arranged  in  pairs  to  overlap  slightly.  Fastenings  are  made  in  the  usual 
way  by  drop-bolts,  hasps,  kc.  Fig.  351  is  an  elevation  of  a  wooden,  and 
fig.  353  of  an  iron,  door  constructed  in  this  manner  at  Liverpool. 


COMPARTMENTS.  3  73 

Folding  doora  are  flexible  sheetings  of  wood  or  inetHl,  so  oontriTed  as 
to  be  wound  round  a  roller  at  the  top  of  the  doorway.  Details  of  one  in 
ase  At  Dundee  are  given  in  figs.  355  to  360.  It  is  constructed  of  pitch- 
pine  laths  threaded  on  steel  wire,  and  fastened  to  an  iron  drum,  12  inches 
in  diameter.  By  means  of  balance  weights  and  simple  gearing,  one  man 
can,  with  ease,  lift  and  lower  the  sashes.*  Folding  doors  are  lighter  and 
take  up  less  space  than  sliding  doors.  At  the  same  time,  sliding  doom  are 
stouter  and  offer  a  greater  obstacle  to  the  passage  of  fire. 


BACK     ELKVATION.  CHB     ILIV* 

FigB.  355  and  356.— Folding  Door  at  Dundee. 

The  effect  of  fire  on  iron  (or  steel)  doors  is  somewhat  curious.  Under 
the  influence  of  intense  heat  they  curl  up  and  twiat  like  a  piece  of  burning 
paper.  This  erratic  beliavionr  constitutes  a  source  of  peril,  and  some  have 
even  gone  so  far  as  to  advocate  the  adoption  of  wooden  doors  oa  the  ground 
that  they  burn  away  in  comparative  harmlessness. 

Compartmvnla. — When  a  shed  is  of  considerable  length,  it  is  advisable  to 
divide  it  into  a  series  of  compartments,  within  any  one  of  which  an  out- 
break of  fire  can  be  completely  confined.  Division  walls  between  adjoining 
compartments  should  then  be  carried  some  5  or  6  feet  above  the  roof  line, 
in  order  to  cut  off  all  connection.  For  the  same  reason,  any  door  openings 
in  such  walls  should  be  fitted  with  doable  doors.  The  system  of  detached 
compartments,  with  intervening  alley  ways,  is  a  greater  safeguard,  but  it 
involves  less  economy  in  space  and  greater  expenditure  in  construction. 

•G.  C.  Buchanan  on  "The  Port  of  Dundee,"  ^I'lt.  Proe.  Intl.  C.E.,  vol.  oilii. 


DOCK  ENGINEERING. 


Sheds   for  the  reception  of  dutinble    goods 'should  |be  provided   with 
t  small  office,  or   lock-up,  in   the   interior  for  the  use  of  the   Customs' 


SHED   FLOORS.  375 

Authorities.     Public  conveniences,  including  urinals  and  w.c,  are  useful 
adjuncts. 

Lighting, — Single  storey  sheds  are  best  lighted  from  the  roof,  either  by 
glass  tiles,  skylights,  or  lanterns.  Artificial  light  is  also  necessary  for  night 
time,  and  during  the  short  days  of  winter.  Qas  may  be  burnt  in  the  form 
of  sunlights,  as  shown  in  fig.  372,  suspended  from  the  roof  by  chains,  by 
means  of  which  the  frame  can  be  lowered  for  cleaning  purposes.  Electricity 
is  a  common  illuminant,  and  there  are  other  systems,  such  as  the  Kitson 
light  (burning  petroleum  vapour),  the  Lncigen  light,  acetylene,  and  others, 
into  the  relative  merits  of  which  it  is  unnecessary  to  enter  here.  The 
lower  floors  of  sheds  more  than  one  storey  in  height,  will  necessarily  derive 
their  natural  light  from  the  sides,  either  through  windows  or  glazed  panels 
ill  the  doors. 

Shed  Floors. — The  nature  of  the  material  employed  for  the  formation  of 
shed  floors  is  of  some  importance.  The  area  may  be  paved,  flagged, 
asphalted,  tiled,  concreted,  or  timbered,  but  it  roust  be  borne  in  mind  that 
the  dust  arising  from'  the  wear  of  a  stone  surface  is  exceedingly  detrimental 
to  cargoes  consisting  of  cereals.  On  the  other  hand,  timber  platforms  are 
hardly  suitable  where  there  is  vehicular  traffic  within  the  shed,  and,  from 
the  point  of  view  of  fire  prevention,  their  introduction  is  not  to  be 
commended.  So-called  asphalt  floors,  consisting  of  macadam  bedded  in 
tar,  are  flexible,  and  do  not  crack  or  fracture  under  concentrated  moving 
loads,  as  sometimes  occurs  with  floors  of  more  rigid  materials  laid  upon  a 
yielding  foundation,  but  their  very  plasticity  is  an  objectionable  feature  in 
warm  climates  and  in  situations  exposed  to  the  direct  heat  of  the  sun's 
rays.  Natural  asphalt  forms  a  smooth,  hard,  and  durable  surface.  This 
and  a  granolithic  surface,  composed  of  equal  parts  of  Portland  cement  and 
crushed  granite,  will  be  found  to  yield  the  least  amount  of  dust  from 
attrition.  But  the  former  is  expensive,  and  the  latter  is  only  adapted  to 
the  conditions  of  ordinary  trucking.  Where  vehicular  traffic  is  heavy,  a 
pavement  of  granite  or  whinstone  setts,  laid  in  cement  on  a  bed  of  rock 
rubble  and  concrete,  will  generally  be  found  the  most  serviceable. 

Sheds  of  more  than  one  storey  should  have  upper  floors  of  fireproof,  or, 
at  any  rate,  of  fire-resisting  material.  For  this  purpose  combinations  of 
iron  or  steel  and  concrete  are  generally  employed.  And  as  this  department 
of  shed  construction  is  of  a  very  important  character,  some  of  the  more 
prominent  forms  will  be  briefly  noticed. 

The  first  and  earliest  type  was  that  formed  of  a  series  of  iron  girders 
connected  by  brick  arches,  the  upper  surface  being  levelled  with  concrete. 

A  later  example  (fig.  361)  is  that  of  a  floor,  formed  by  buckled  iron 
plates,  rivetted  to  the  upper  flanges  of  plate  girders.  A  concrete  covering 
forms  a  bed  for  Staffordshire  blue  tiles,  1^  inches  thick.  In  the  instance 
selected  for  illustration  the  iron  plates  are  52  inches  square. 

A  third  form  of  floor,  shown  in  tig.  362,  consists  of  a  series  of  rolled 
steel  joists,  6  by  3  inches,  bedded  in  concrete  at  a  uniform  distance  apart  of 


376 


DOCK  ENGINEERING. 


26  inches.     The  upper  surface  is  of  granolithic  concrete  to  a  depth  of 
2  inches.     The  main  joists  are  12  feet  apart. 

The  foregoing  examples  constitute  very  heavy  types  of  floor,  in  propor- 
tion to  their  strength.  With  a  view  of  minimising  the  amount  of  material, 
and  reducing  the  cost  of  construction,  various  systems  have  heen  proposed 
in  recent  years,  chiefly  founded  upon  the  intimate  incorporation  of  iron  or 
steel  and  concrete  in  one  mass,  and  in  such  a  way  that  each  exercises  its 
characteristic  strength  to  the  best  advantage.  One  or  two  of  the  more 
important  of  these  systems  may  advantageously  be  described,  as  there  can 
be  little  doubt  that  the  combination  of  these  two  fire-resisting  materials  is 
capable  of  effecting  a  great  and  useful  saving  in  structural  weight. 

iy4''' Staffordshire  tiles 


'/^2^^2Z^/yyyyy^y<^y^^^ 


Fig.  361.— Shed  Upper  Floor. 
. ^ranoWhic  Swface  Ftnisftina   2  to  i 

'■'■.'^.'  ■•*r*;' '.'.'■".'.'.".','.i..i.n»»v;n.ti.i.ii  ■■■■.  I. 11   iJiT,,    ,,    _ 


^vV*'- •V'-""^'^  -^..^W'tivlj 


,\Ji-  .-J^'.'^ 


.o .  9  .'I 


. •  -  ."-:•.  .Cement .  -J  ?•:;:;  Coh&ete  :V  ^ 

;•>?•*  I  °r''^fa /:*.;«. ^?:|':  :•••••..•  .^:''-  «>-•>' ••• 


STx  3'  Rolled  Steel  Joists^ 
Fig.  362.— Shed  Upper  Floor. 

Monier  System. — The  Monier  system  consists  of  a  network  of  metal 
bedded  in  a  concrete  slab,  the  network  being  formed  by  two  rows  of  bars  or 
wires  crossing  one  another  at  right  angles.  The  lower  row  are  the  stressed 
bars.  They  are  intended,  in  flat  floors,  to  relieve  the  concrete  of  its  tensile 
stress,  and  consequently  are  proportioned  in  number  and  size  to  the 
load  to  be  carried  and  the  amount  of  span.  In  arched  floors  they  assist  in 
taking  up  the  compressive  stress.  The  function  of  the  upper  row  of  bars  is 
merely  to  distribute  the  pressure  evenly,  and  they  are  generally  made 
three-fourths  of  the  diameter  of  the  lower  bars.  The  floor  is  divided  into 
bays  by  a  series  of  iron  joists,  upon  which  the  network  is  laid.  It  is  recom- 
mended that  the  width  of  the  bays  should  not  be  too  small.  "  Fairly  large 
spans  enable  the  supporting  joists  to  be  more  economically  designed,  on 
account  of  a  better  proportion  of  depth  to  length  being  obtained."*  At  the 
same  time,  the  floor  must  not  be  made  unduly  deep  or  it  will  prove  an 
arrangement  of  dubious  economy.    "  The  minimum  thickness  of  the  concrete, 

•  Beer  on  "  The  Monier  System  of  Construction,"  Miii,  Proc,  Inst,  C,E,,  voL  cxxxiii. 


MONIER  SYSTEM. 


377 


under  ordinary  conditions,  considered  exclusively  of  any  wearing  surface, 
may  be  1|  inches  for  flat  floors  and  interior  roofs  and  2  inches  for  arched 
floors  and  exterior  roofs,  while  3  and  8  feet  may  be  considered  as  minimum 
spacings  for  flat  and  arched  floors  respectively.  Arched  floors  are  generally 
constructed  with  a  rise  of  only  one- tenth  the  span;  the  thrust,  where  much 
weight  is  supported,  is  therefore  considerable.  Provision  for  the  thrust 
may  be  supplied  by  tie-rods  in  the  end  bays  of  a  floor  or  by  horizontal  end 
girders  suitably  anchored  to  the  walls — the  latter  method,  where  possible, 
being  preferable.  Further,  when  a  series  of  arches  succeed  one  another, 
care  should  be  taken  that  their  centre  lines  meet  on  the  vertical  centre  lines 
of  the  girders  which  carry  them,  for  a  very  small  divergence  will  cause  an 
appreciable  tendency  to  twist.  This  tendency  may  be  further  guarded 
against  by  embedding  the  girders  in  concrete.  It  is  customary  with  ordinary 
flooring  arches  (which  probably  partake  more  of  the  nature  of  a  girder  than 
an  arch)  to  allow  a  series  to  finish  with  its  end  member  resting  simply  on  a 
brick  corbel ;  this  should  not  be  attempted  with  Monier  arches,  but  a 
shallow,  wide  joist  should  be  used  as  a  wall -plate."'"' 


^9mtkm*m   giwfn 


l*  


-JO.  O. 

Fig.  363.— Monier  Floor. 


•! 


a— ^^M^^^^i^^iM^^i^fci 


t^m^l^m^amt^i^^^^^m 


••tnS    HSTTIHI 


!#••—••—•- 


s:  e' 


Fig.  364. —Monier  Floor. 


Examples  of  floors  constructed  on  the  Monier  system  are  reproduced  in 
figs.  363  and  364,  from  Mr.  Walter  Beer's  paper,  from  which  quotations 
have  been  already  made,  and  in  which  the  student  will  find  a  very  interest- 
ing investigation  of  the  nature  and  amount  of  the  stresses  set  up  in  the 
various  parts.  These  stresses,  which  have  engaged  the  attention  of  several 
eminent  mathematicians,  are  too  complicated  for  analysis  in  these  pages. 

Joints  are  formed  by  causing  the  ends  of  the  bars  to  overlap  by  a  certain 
amount,  which  depends  on  the  tensile  strength  of  the  bars  and  the  coeflicient 
of  adhesion  between  iron  and  concrete,  the  latter  being  about  300  lbs.  per 
square  inch  of  surface.  After  the  bars  have  been  laid  the  concrete  is 
deposited  in  layers,  not  less  than  IJ  inches  thick,  and  well  rammed.  Thin 
slabs  need  a  closer  mesh  than  thick  slabs,  owing  to  there  being  greater 
liability  to  local  failure. 

*  Beer  on  "The  Monier  System  of  Construction,"  Min,  Proc.  Inst,  C.E,,  voL  cxxxiii. 


378  DOCK  ENUINEEKING. 

The  Hghtness&nd  slendemeas  of  the  floor  c&ll  for  the  best  materials  and 
the  moat  careful  workmaoBhip.  The  coDcrete  should  be  composed  of  the 
best  Portland  cement,  with  an  aggregate  of  broken  brick  or  clean  gravel  and 
sand  or  cruflhed  granite,  in  the  proportion  of  1  to  3.  The  best  metal  for  the 
bars  is  bard  steel ;  a  soft  iron  does  not  possess  a  sufficiently  high  coefficient 
of  elasticity.  "  Expanded  metal,"  which  is  a  network  sheared  out  of  a  solid 
steel  plate,  may  he  used  instead  of  disconoected  bars. 

Heimebiqne  S7Btem.~This  system  differs  from  that  just  described  more 
in  detail  than  in  principle.  There  is  the  same  network  of  bars,  bnt  the 
mesbes  are  larger,  the  bars  thicker,  and  tbe  parts  are  generally  set  obliquely 
with  reference  to  the  supporting  beams.  These  beams  are  themselvea 
constructed  on  the  same  system  aa  the  flooring. 

Figs.  365  and  366  are  the  plan  and  section,  respectively,  of  a  bay  of 
Hennebique  flooring.*    It  will  be  seen  that  the  main  beam  is  composed  of 


SECTION  OF   FLOOR  AND  S 


Tl 


iiiiiSiliili  il 


Fige.  303  and  366. — Hennebique  Floor. 

three  vertical  rows  of  bars,  each  row  containing  two  bars,  of  whicb  the  lower 
one  is  straight  and  the  upper  curved.  These  bars  are  bedded  in  concrete  of 
a  rectangular  section,  adhesion  between  the  parts  being  assisted  by  U-shaped 
clips  of  hoop  iron,  which  enclose  the  bars  and  extend  almost  to  tbe  upper 
surface  of  the  beam.  The  model  is  that  of  a  trussed  beam.  Tbe  concrete 
takes  the  compressive  duty  ;  the  bars  are  simply  tension  rods. 

The  ends  of  the  bars  are  either  turned  up  or  split  to  a  fish-tail  to  increase 
the  hold. 

The  Soor  illustrated  has  its  beams  8  feet  4  inches  apart,  centre  to  centre. 
The  latter  are  8  inches  wide  by  14  inches  deep.  The  floor  is  5  inches  thick, 
and  was  tested  to  a  uniform  load  of  ISj  cwts.  per  square  yard. 


"Construction  in  Fortified  Concrete,"  JUin.  Proc,  L.E.S.,  vol.  ixii. 


COTTANCINS  SYSTEM.  379 

The  moat  notable  application  of  this  system  is  to  the  construotion  of 
concrete  piles,  which  are  considered  in  an  earlier  section  of  this  work. 

Cottancln's  System. — The  disconnected  b&ra  employed  ta  the  previous 
methods  are  replaced  by  a  jointleaa  wire  network  ^'^  to  j  inch  diameter,  the 
design  varying  according  to  circumstances.  Two  examplee  are  shown  in. 
figs.  367,  36!i,  and  369.  The  inventor  claims  for  his  design  a  large  increase 
in  strength  for  a  given  weight  of  metal. 

There  are  many  other  proprietary  systems  which  it  would  take  too  long 
to  enumerate  and  describe.  The  foregoing  methods  are  largely  typical  of 
the  rest. 


Figs.  367,  368,  and  369.— Cottan^in's  S}at«mB. 

Three  conditions  are  essential  to  the  stability  and  durability  of  a  floor 
compounded  of  concrete  and  metal : — 

1.  The  metal  must  be  completely  enclosed  so  as  to  be  protected  from 
atmospheric  and  corrosive  influences.  As  far  as  present  knowledge  goes, 
the  bedding  of  ironwork  in  Portland  cement  mortar  is  attended  by  none  of 
the  evil  results  characteristic  of  bedding  in  lime  mortar.  Bars  which  have 
been  completely  embedded  for  lengthy  periods  have  exhibited  not  the  least 
sign  of  deterioration  on  close  examination  after  disinterment.  Exposed  to 
the  atmosphere,  however,  gradual  corrosion  is  inevitable,  particularly  in 
maritime  situations.  Hence  the  necessity  for  a  thorough  covering  of  concrete 
over  all  parts  of  the  metal. 

2.  The  coefficients  of  expansion  must  be  the  same  for  the  two  substances, 
or  very  nearly  so,  within  the  limits  of  temperature  to  which  they  will  he 
subjected.     This  is  necessary  to  prevent  excessive  mutual  stress. 

3.  The  coefficient  of  direct  elasticity  of  the  metal  must  be  greater  than 
that  of  the  concrete,  otherwise  the  metal  is  useless.     The  ratio  of  intensity 

of  stress  in  an  elongated  prism  of  the  combination  is  ,  where  E  is  the 

coeflicient  of  elasticity  of  the  concrete,  e  that  of  the  iron,  and  A,  a,  their 
respective  sectional  areas. 

Shed  floors  should  not  be  absolutely  level.  In  order  to  get  rid  of  any 
wet  blown  into  the  shed  during  boisterous  weather,  it  is  advisable  to  give 
the  floors  a  rise  of  at  least  2  inches  in  the  first  10  feet, 


38o 


DOCK  ENGINEERING. 


TABLE  XXIX.,  GIVING  Cubic  Feet  op  Space  occupied  by 

One  Ton  op  Merchandise. 


Almonds  (bags), 
Ammonia  (drums). 
Apples  (barrels), 
Arrowroot  (casks), 
Arsenio  (kegs), 
Ash  poles, 

„    lumber, 
Asphalt  (casks), 
Bacon  (boxes), . 
Bananas  (crates), 
Barley  (bulk),  . 
Beef,  fresh  (in  refrigerator), 

,,     (tierces), . 
Beer  (barrels), . 

„    (casks),     . 
Biscuits,  . 
Bran  (bags). 
Brandy  (barrels), 
Bricks,  Fire-  (loose), 
Brimstone  (bags). 
Butter  (boxes), 
„      (tubs),  . 
Canned  fruit  (casks), 


it 


), 


meat  ( 
milk  ( 
Carbon  (barrels). 
Caustic  (drums). 
Cheese  (boxes). 
Cider  (barrels). 
Cigars  (casks), . 
Coal, 

,,  cannel,  . 
Cocoa  (bags),  . 
Coffee  (  „  ),  . 
Copper,  ingots  (casks), 

,,       pigs,    . 
Coni  (bulk). 
Cotton  (bales),  compressed, 

„      (    ,)   )i  uncompressed, 

„       Egyptian, 
Currants  (barrels), 
Divi  (bags). 
Ebony  (pieces), 
Eggs, 
Flour  (barrels), 

„     (sacks),  . 
Fur  skins  (bales). 
Glucose  (barrels). 
Hair  (bales),     . 
Hams  (boxes), . 
Hares,  Australian, 
Hay  (bales). 
Hemp  (bales),  . 
Hides  (bundles), 
Kentledge  (blocks). 
Lard  (boxes),    . 
(firkins),  . 
(pails),     . 


i* 


»» 


153 
79 

106 
70 
42 
62 
44 
57 
50 

132 
55 
82 
54 
72 
56 

245 
96 
60 
18 
32 
51 
67 
52 
50 
41 

260 
24 
54 
56 

115 
44 
54 
72 
71 
13 
7 
50 

124 

245 
62 
51 

120 
44 

112 
64 
58 

122 
45 

172 
50 
76 

170 
95 
38 
6 
51 
68 
89 


Lea^l  (pigs),      . 

6 

Leather  (bales). 

.     148 

Lignum  vitie  (pieces). 
Lime  acetate  (ockgs). 

58 
.     110 

Linseed  (bulk). 

50 

Meal  (sacks),    . 

62 

Mineral  wool  (bags), 

.     266 

Molasses  (hogsheads), 

45 

Mutton,  Australian, 

.     113 

Nails  (kegs),     . 

28 

Nickel  (barrels). 

.       18 

Nuts,  Brazil  (bulk), 

61 

,,     cocoa  (bags),  . 

.     103 

Oak  (planks),   . 

34 

Oatmeal  (bags). 

62 

Oats  (bags), 
„    (bulk),      . 

66 

59 

Ochre  (barrels). 

.      47 

Oil  (barrels),    . 

.      67 

„   (casks). 

51 

,,   cake  (bags). 

42 

Oranges  (boxes). 

68 

Ore  (bags), 

21 

Oysters  (barrels). 

61 

Palm  oil  (casks), 

58 

Paper  (bundles), 

81 

„      (rolls),    . 

.       74 

Paraffin  wax  (barrels). 

77 

,,          (casks), 

59 

Poultry,  Australian, 

62 

Quicksilver  (bottles), 

12 

Rabbits,  Australian, 

60 

Resin  (barrels). 

57 

Rice  (bags), 
„     (casks),     . 

47 

58 

Rubber  (cases), 

.       51 

Salt  (bulk),       . 

48 

Soap  (barrels). 
Spelter  (plates), 

62 

6 

Sponges,  .         .         ... 
Starch  (bags),  . 

.     201 
65 

Staves  (hogsheads), . 

78 

Stearine  (       „       ), . 

64 

Steel  blooms,    . 

5 

Sugar,  crape  (bags). 
Syrup  (barrels), 

57 

43 

Tallow  (hogsheads). 
Tea  (half-chests),     . 

61 

96 

Tobacco  (barrels),     . 

166 

„        (hogsheads), 

109 

,,        (manufactured). 

60 

Walnut  (logs). 

28 

Wheat  (bags),  . 
„       (bulk),. 

54 

44 

Wool,  Australian  (bales). 

107 

,,               (without  hoops),  . 

150 

Zinc  oxide  (barrels). 

• 

■ 

67 

Weight  of  Animate. 


Riding  horse,   8  to  10  cwts. 
Cart  horse,  .  12  to  14 


I ) 


Ox, 
Pig, 


0  to  8  cwts. 


*f 


Sheep, 


^  cwt. 


COLUMNS  AND   PIERS.  38? 

In  calculating  the  strength  of  a  floor,  due  regard  must  be  paid  to  the 
weight  which  is  likely  to  be  placed  upon  it.  This  may  be  estimated  from 
the  weights  of  the  various  items  of  which  an  average  cargo  is  composed. 
Table  xxix.  gives  a  series  of  values  obtained  from  actual  observation, 
but  it  is  necessary  to  point  out  that  the  figures  can  only  be  regarded  as 
approximately  exact,  there  being  frequently  a  considerable  divergence  in 
the  extremes  from  which  the  average  has  been  computed.  It  will  probably 
be  found  suflicient  in  ordinary  cases  to  provide  for  an  average  pressure  of 
3  tons  to  the  square  yard  on  a  quay  floor,  and  of  30  cwts.  to  the  square 
yard  on  an  upper  floor,  exclusive  of  the  weight  of  the  shed  structure  itself. 
Care  should  be  taken  to  see,  by  official  inspection,  that  wharfingers  and 
others  do  not  stack  or  pile  goods  to  a  height  inconsistent  with  the  weight 
allowed  for.  This  is  more  important  in  the  case  of  heavy  ores,  kentledge,, 
and  metal  goods,  which  exert  a  vastly  augmented  pressure  per  unit  volume^ 
compared  with  bulkier  articles. 

Golumns  and  Piers. — ^To  avoid  roofs  of  excessive  span  in  single  storey 
sheds,  and  upper  floors  of  undue  weight  in  sheds  of  more  than  one  storey, 
intermediate  supports  are  generally  introduced  in  both  cases.  These  usually 
take  the  form  of  metal  columns  or  brick  piers  connected  longitudinally  by 
girders.  Brick  piers  are  bulky ;  they  occupy  a  good  deal  of  valuable  space 
and  obstruct  light  to  a  considerable  extent.  Columns,  either  of  cast  iron 
or  steel,  are  better  adapted  to  the  conditions  obtaining  in  dock  sheds. 
Cast-iron  columns  are  commonly  circular  in  section  and  in  one  piece  with 
planed  bearing  surfaces  for  the  seats  of  the  upper  connecting  girders.  The 
bases  may,  however,  be  cast  separately.  Steel  columns  are  usually  built  by 
rivetting  together  marketable  forms  into  a  rectangular  or  I  section,  bases 
and  bearings  being  formed  by  plates  with  gusset  stays.  Hollow  columns 
have  the  advantage  of  forming  suitable  ducts  for  rain  water  from  the  roof 
to  the  ground  drain. 

All  columns,  piers,  doorway  jambs,  and  the  like  should  have  their  bases 
protected  by  metal  bumpers  or  (granite)  guard  stones  to  a  height  of  about 
2  feet  above  the  floor.  These  are  designed  to  ward  off  concussions  with 
passing  vehicles.  For  columns,  hollow  castings  of  an  approximately  ellip- 
soidal or  spherical  form,  bolted  together  in  two  segments  and  filled  with 
concrete,  will  be  found  most  suitable.  Occasionally,  wisps  of  straw  have 
been  wound  round  the  column  prior  to  the  insertion  of  the  concrete,  in 
order  to  still  further  diminish  the  shock,  but  the  precaution  is  of  dubious 
value. 

On  account  of  the  unsatisfactory  behaviour  of  ironwork  under  the  heat 
of  a  conflagration,  columns  of  concrete  strengthened  by  a  hearting  of  metal 
have  been  proposed  as  a  substitute  for  the  ordinary  type  of  iron  and  steel 
columns.  It  will  certainly  be  found  expedient  to  leave  no  metal  surface 
exposed,  and  one  valuable  safeguard  is  to  encase  metal  columns  with 
external  fireclay  cylinders.  These  may  be  obtained  in  lengths  of  2  feet 
or  less;  they  are  generally  about  1  inch  thick  and  exceed  the  diameter 


382  DOCK   ENGINEERING. 

•of  the  column  by  2  inches,  the  1  inch  annular  space  being  grouted  with 
cement.  Another  proposed  expedient  is  to  adapt  the  interior  of  the 
columns  to  the  circulation  and  distribution  of  water. 

Strength  of  Columns. — The  strength  of  long  columns  or  struts  constitutes 
a  very  intricate  problem.  Such  columns,  though  nominally  in  compression, 
rarely  fail  from  a  simple  compressive  stress ;  they  succumb,  when  loaded  to 
collapse,  to  a  bending  stress  induced  by  the  unsymmetric  application  of  the 
load.  Theoretically,  the  load  should  be  applied  so  that  the  stress  passes 
absolutely  through  the  centre  of  every  transverse  section  of  the  column, 
and,  in  that  case,  there  would  be  no  tendency  to  bind;  but  this  ideal 
condition  is  unattainable  in  practice. 

Let  us  briefly  investigate  the  case  of  a  column  deflected  by  a  load,  W, 
acting  at  a  distance,  x,  from  the  axis  of  symmetry.  If  5  be  the  amount  of 
deflection  produced,  the  bending  moment  at  the  foot  will  be  W  (x  +  3). 
Assuming  for  the  moment  that  the  deflection  curve  is  circular,  as  in  the 
case  of  a  beam  of  uniform  strength,  we  have  by  Euclid  III.,  35, 

a  X  2  R  =  Z2, (70) 

where  I  is  the  length  of  the  column  and  B  the  (very  considerable)  radius 
of  curvature. 

Now,  the  moment  of  resistance, 

M  =  ^  =  23^  •        •        •     (^^) 

Equating  the  two  moments  : — 


W  («  +  «)  =  "2  3  ^p^, 


whence 


^  =  ^   .    1   •   "tT'      ....     (72) 


and 


^  =  0..-^ ....     (73) 


2EI 

WZ2 


-   1 


From  a  consideration  of  (73),  if  a;  =  0,  3  will  also  be  zero,  unless 

W  =  ^, (74) 

and  this  is  the  critical  value  for  W,  when  the  column  is  in  a  state  of  neutral 
equilibrium ;  so  that  the  least  increase  in  the  load  will  cause  indefinite 
bending  and  consequent  fracture. 

If  the  column  be  of  uniform  transverse  section,  instead  of  uniform 
strength,  as  assumed  above,  the  curve  will  be  one  of  sines,  and  the  equation 
becomes 

W  =  ^  .  5^ (76) 


STRENGTH    OF   COLUMNS.  383 

The  equivalent  length  of  a  column  fixed  at  both  ends  is  one-fourth  of 

that  described  above,  and  if  we  substitute  for  I,  its  value  -j-,  and  reduce  to 

unit  area,  we  obtain  the  following  ultimate  strength  per  square  inch  for  a 
<;olumn  of  circular  section,  with  radius  r : 

;>  =  E^~ (76) 

This  formula  (75),  having  onginated  with  Euler,  is  known  by  his  name. 
Its  efficacy  depends  on  three  conditions,  two  of  which,  at  least,  cannot  be 
guaranteed  in  practice,  viz. : — 

(a)  The  uniformity  of  the  modulus  of  elasticity  (E)  for  all  fibres 
throughout  the  section; 

(iS)  The  absence  of  any  initial  deflection  ; 

(y)  The  axial  position  of  the  load. 

Furthermore,  it  will  be  noticed  that  no  allowance  is  made  in  the 
equation  for  the  possible  failure  of  the  material  by  direct  crushing,  so 
that  for  short  columns  the  calculated  strength  is  greatly  in  excess  of  the 
compressive  limit. 

Professor  Claxton  Fidler  shows'^  that  if  the  opposite  sides  of  a  pillar 
whose  moduli  of  elasticity  are  Ej  and  E^  respectively,  be  subjected  to  the 
same  amount  of  compressive  stress,  one  side  will  be  shortened  more  than  the 

other  in  the  proportion  of  —  to  =->  and,  consequently,  of  the  total  deflection 

produced  by  a  given  load,  one  portion  causes  no  difference  of  stress  and, 
therefore,   no  moment   of  resistance,    while  the   remainder  alone  is   the 
measure  of  the  real  moment  of  resistance. 
The  total  deflection  is  found  to  be 

11  f  r\ 

where  e^  and  e^  represent  =r  and  ^    respectively;    ^  f  =flr2E^)   is  the 

resilient  force  of  the  ideal  column  in  pounds  per  square  inch;  r,  in  this 
case,  is  the  radius  of  gyration,  and  p  is  the  actual  load-intensity. 

The  bending  moment  M  =  P  3,  and  the  extreme  stress  in  the  fibres  at  a 
distance,  y,  from  the  neutral  axis  due  thereto,  is 

-A  -  ^p  -    ^2  •  •         •         •         ('°) 

^    y    «i  -  ^2 


Inserting  the  equivalent  for  6  from  (77)  and  giving  to  ^r  .  -  .    ^ 

2      f      e^ 


«,  +  Cj 


its  approximate  value  '4,  the  maximum  compressive  stress  on  the  concave 
side  of  the  column, 

f=P+f-p{^+J~)>       '        ■        ■        (79) 

*  •*  Bridge  Construction,"  chap,  x.;  vide  also  Min,  Proc.  Inst.  C.E.,  vol.  Ixxxvi. 


384 


DOCK   ENGINEERING. 


which  involves  a  quadratic  in  p.  This  formula  expresses  the  relationship 
existing  between  the  apparent  stress,  p,  due  to  the  load  and  the  maximum 
stress,  /,  on  the  concave  side.  If,  then,  we  insert  the  ultimate  compressive 
stress  of  the  material  in  place  of  /,  and  solve  the  equation,  we  find  the 
breaking  stress,  p,  of  the  column. 

It  has  been  assumed  that  the  ends  of  the  column  are  free  to  move. 
In  dealing  with  a  column  in  which  both  ends  are  fixed,  the  length  of  an 
equivalent  round-ended  column  may  be  taken  at  three-fifths  of  the  actual 
length. 

The  ultimate  compressive  stress  in  various  materials  may  be  taken  as 
follows : — 

Timber,   .  .         .         2  to  4  tons  per  square  inch. 

Wrought  iron,  .         .         16  tons  per  square  inch. 

Mild  steel,        ...         30 
Cast  iron,         ...         40 

A  formula  very  commonly  used  for  the  determination  of  the  compressive 
strength  of  long  struts,  is  that  devised  by  Professor  Lewis  Gordon,  which,, 
using  the  same  rotation  as  before,  may  be  expressed  thus — 


ty 


99 


i> 


n 


P  = 


1  ^* 


(80) 


I 


The  fraction  -7  expresses  the  ratio  of  the  length  of  the  column  to  its 

diameter,  or  its  least  dimension  in  cross-section.     The  values  of  a  are  given 
in  the  annexed  table. 

Results  obtained  by  this  formula  agree  fairly  closely  with  those  given  by 
Prof.  Fidler's  method. 

TABLE  XXX. 


Material. 

Cross  Section. 

Values  of  a. 

Both  Ends 
Rounded. 

Both  Ends 
Fixed. 

One  End 

Bounded. 

One  Fixed. 

Timber,    . 

Rectangular  or  circular, 

9^0 

tlv 

ilxf 

Wrought  iron, 

Rectangular,         .        .         .  i 
Circular  (solid  or  hollow),     .  / 

4 

iTinr 

TTmr 

>f 

^TFTT 

1) 

LT  +  D  Qx  LJ    .         . 

V^IF 

nin 

tItt 

Caat  iron, 

Circular  (solid),    . 

riiy 

T^<r 

IT^' 

f  1 

,,        (hollow), 

fiiF 

iVff 

vio 

tt               • 

Rectangular, 

tSit 

TrtW 

^ 

»i 

Cross-shaped, 

tin 

niv 

TVO 

Mild  steel, 

Circular  (solid),    . 

Tib  17 

l«*OtJ 

shf 

»i                • 

Rectangular  (solid), 

uU 

14^80 

»io 

ROOF   COVERINGS.  385 

As  an  example,  take  the  case  of  a  solid,  cylindrical,  cast-iron  column,  12 
inches  diameter  and  20  feet  long,  fixed  at  both  ends.  Then,  by  the  fore- 
going formula —  ^ 

p  =  = = — —  =  20  tons  per  sq.  in. 

Fidler's  formula  gives  19"4  tons  under  the  same  conditions. 

Roof  Coverings. — The  roof  coverings  usually  employed  for  sheds  are 
slate,  lead,  zinc,  galvanised  iron,  felt,  and  roofing  paper.  The  last-named 
material  is  inferior  to  the  others,  and  should  only  be  used  for  temporary  and 
unimportant  purposes. 

SUUe  is  the  best  roofing  material,  being  unalterable  in  nature  and  exempt 
from  decay.  It  has  the  drawback  of  being  heavy,  but  this  disadvantage  is 
more  than  compensated  for  by  its  durable  qualities.  Large  sized  slates  form 
the  best  kind  for  use,  as  with  fewer  joints  there  is  less  •  opportunity  for 
leakage,  and  with  greater  weight  there  is  less  chance  of  the  slates  being 
lifted  by  the  wind.  For  the  latter  reason  slates  should  be  centre-nailed,  and 
in  very  exposed  situations  they  may  be  additionally  secured  by  lead  or 
copper  tingles. 

Lead  is  a  durable  roof  covering,  but  both  heavy  and  expensive.  More- 
over, it  is  not  a  suitable  material  for  steep-pitched  roofs  (though,  perhaps, 
this  drawback  is  of  little  importance  in  the  case  of  sheds,  where  the  roofs  are 
generally  low-pitched),  owing  to  its  tendency  to  creep  under  the  influence 
of  expansion  and  gravitation. 

Zinc  has  the  advantage  of  lightness  combined  with  economy,  but  it  is 
very  subject  to  corrosion  and  decay,  and  is  highly  inflammable  at  a  red  heat. 
Contact  with  iron,  copper,  or  lead,  in  the  presence  of  moisture,  produces 
destructive  voltaic  action.  Lime  is  another  deteriorating  agent,  as  also  is 
oak,  ow^ing  to  an  acid  which  it  contains. 

From  an  exhaustive  examination  of  a  great  number  of  zinc-covered  shed 
roofs  at  Liverpool,  the  following  valuable  observations  were  deduced  : — 

1.  That  when  zinc  is  in  free  contact  with  the  (sea)  atmosphere,  a  slow 
and  gradual  wasting  away  of  the  zinc  takes  place.  The  metal  throws  off  a 
fine  flour-like  substance,  which  forms  a  deposit  on  its  surface  and  is  washed, 
or  blown,  away  or  cemented  by  sooty  matter,  as  the  case  may  be. 

2.  That  in  exposed  situations  the  wasting  away  is  intensified,  and  the 
surface  of  the  zinc  soon  presents  a  roughened  appearance  due  to  close  and 
minute  pitting.  Especially  does  this  occur  at  the  more  prominent  points, 
such  as  step  flashings,  at  weather  faces,  at  ridges  and  rolls,  and  at  cappings 
over  joints. 

3.  That  wherever  a  leak  occurs,  and,  to  a  greater  degree,  where  moisture, 
in  passing  down  the  underside  or  covered  upper  surface  of  a  sheet,  is  checked 
and  forms  into  beads,  as  is  frequently  the  case  at  the  top  edge  of  laps  and 
joints,  or  where  water  is  driven  by  the  wind  between  the  overlapping  por- 
tions of  sheets,  the  efflorescence  lying  there  becomes  encrusted  and  gradually 

hardens,  biting  into  the  zinc,  and,  in  course  of  time,  perforating  it. 

25 


386  DOCK   ENGINEERING. 

4.  That  where  water  lodges  to  the  exclusion  of  air,  as  frequently  occurs 
at  the  back  of  ridge  laps  or  the  lower  end  of  bottom  sheets,  or  under  sky- 
light aprons,  the  white  efflorescence  is  transformed  into  a  light  umber  paste 
which  attacks  the  zinc  in  annular  forms,  and  speedily  rots  it. 

5.  That  where  steam  power  is  largely  used  under  a  roof,  and  the  dis- 
charge from  the  furnace  chimney  is  delivered  within  the  shed,  the  zinc 
covering  in  the  immediate  neighbourhood,  and  especially  at  the  openings 
through  which  the  smoke  makes  its  exit,  shows  signs  of  wear  corresponding 
to  the  effect  produced  by  a  fine  sand  blast.  The  zinc  also  becomes  soft 
and  loses  its  elasticity. 

GcUvanised  ctnd  Corrugated  Iron  Sheets  are  open  to  all  the  objections 
enumerated  with  regard  to  zinc,  with  the  additional  drawback  that,  as  soon 
as  the  thin  coating  of  zinc  is  perforated,  the  galvanic  action  set  up  between 
the  two  metals  enormously  increases  the  rate  of  decay.  This  is  particularly 
in  evidence  at  bolt-holes  and  fastenings,  where  the  leather  washers  usually 
employed  afford  but  imperfect  protection  from  the  access  of  moisture.  In 
many  instances,  sheds  constructed  with  galvanised  sheets  have  had  to  be 
coated  with  tar  or  black  varnish  to  preserve  them  from  further  ravages. 

Weight  of  Shed  Roofs. — In  order  to  afford  a  rough  estimate  of  the 
weight  to  be  carried  by  columns  and  side  walls,  the  following  approximate 
data  will  be  found  useful.  The  weights  are  given  in  lbs.  per  square  foot 
of  horizontal  area,  covered  by  roofs  of  from  20  to  60  feet  span  : — 

TABLE  XXXI. 

Timber  trusses,  inclading  purlins, 3^  to    7i 

Iron            „             „               „ 54  »f     8i 

Common  rafters, 3^ 

Battens, 2 

Boards,  |  to  1^  inches  thick, 2}  to    4} 

Slates, 5     „   14 

Tiles, 13     „  20 

Lead  covering, 6     „     9 

Zinc        „ IJ  „     2 

Ck>rrugated  iron  covering, 2J  , ,     3 J       - 

Allowance  for  snow, 5 

„          ,,  wind, 20     „  40 

From  a  brief  but  detailed  consideration  of  some  of  the  more  salient 
features  of  shed  construction,  we  now  pass  to  a  succinct  review  of  the  types 
to  be  met  with  at  various  ports. 

Tilbury  Dock  Sheds,  liOndon.^ 

"  The  twenty-four  berths  in  the  branch  docks  are  each  provided  with  a 
quay  shed  301   feet  long  and  120  feet  wide,  giving  a  floor  area  of  over 
I  acre,  the   roofs   being  constructed  with  timber  storey-posts,  iron   roof- 
*  Scott  on  "Construction  of  Tilbury  Docks,"  Min,  Proc*  Inst.  C,E.,  vol.  cxx. 


LIVERPOOL  SHEDS.  387 

principals,  and  boarded  and  slated  roofs.  The  front  and  the  back  of  each 
shed,  for  240  feet  of  its  length,  are  entirely  open,  but  can  be  closed  at  will 
by  steel  self-coiling  revolving  shutters,  working  between  the  storey-posts 
supporting  the  roof.  When  these  shutters  are  open,  free  access  is  afforded 
between  the  quay  and  the  railway  in  the  rear  of  the  sheds,  and  when  they 
are  closed,  the  requirements  of  the  custom-house  for  the  safe  custody  of 
bonded  goods  are  complied  with.  The  ends  of  each  shed,  and  the  small 
portions  of  the  front  and  back  not  closed  by  the  shutters,  are  covered  with 
corrugated  iron  supported  upon  timber  framing.  Well  distributed  light 
for  the  interior  is  obtained  through  480  lar^e  glass  slates  in  the  roof  of  each 
shed.  The  floors  of  the  sheds  are  of  pitchpine  planking,  laid  upon  sleepers 
bedded  upon  a  layer  of  ballast  12  inches  thick.  Quay  sheds,  generally 
similar  to  those  for  the  branch  docks,  but  of  one  60-foot  span,  are  provided 
for  the  berths  in  the  tidal  basin." 

Liverpool  Sheds. 

At  Liverpool  the  sheds  are  continuous,  and  their  length  practically 
coincides  with  the  length  of  the  quays  upon  which  they  stand.  They  are, 
however,  for  working  purposes  divided  up  into  compartments,  of  which  the 
average  length  in  the  more  modem  examples  is  rather  less  than  300  feet. 
In  width  they  vary  considerably,  but  the  roof  spans  range  generally  from 
30  to  80  feet,  with  a  few  extreme  cases  approaching  100  feet. 

Fig.  370  shows  a  section  of  a  single-storey  shed,  150  feet  wide,  roofed  in 
two  spans.  The  walls  are  of  brickwork,  with  doorways  20  feet  wide  by 
16  feet  and  17  feet  6  inches  high.  The  roof  trusses  are  a  combination 
of  wood  and  iron,  the  compression  members  being  of  wood  and  the  tension 
members  of  iron.  The  intermediate  supporting  columns  are  of  cast  iron, 
and  the  roof  covering  of  Vieille-Montagne  zinc.     The  floor  is  asphalted. 

Fig.  371  is  a  section  of  a  double-storey  shed,  95  feet  wide,  roofed  in 
three  spans.  The  upper  floor  is  supported  on  brick  piers,  3  feet  square  and 
26  feet  apart  longitudinally.  It  is  formed  by  main  and  subsidiary  girders, 
the  enclosed  spaces  being  covered  by  buckled  plates,  upon  which  is  laid  a 
bed  of  concrete  to  form  a  level  surface  for  a  layer  of  1  J-inch  blue  Stafford- 
shire tiles.  The  roof  trusses  are  entirely  constructed  in  angle-  and  bar- 
iron,  with  riveted  joints.  The  roof  covering  is  Velinheli  slates  nailed  on 
boarding.  Continuous  skylights  run  along  each  side  of  the  ridge.  The 
lower  floor  is  lighted  by  windows  in  the  walls  and  by  glazed  panels  in  the 
upper  portion  of  the  sheet-iron  doors.  In  later  examples  of  this  type  of 
shed,  the  width  has  been  divided  into  two  equal  spans  by  means  of  a 
central  row  of  cast-iron  columns.  Upon  made  ground  the  column  bases 
are  supported  by  concrete  beds,  7  feet  square,  surrounding  and  covering 
the  heads  of  two  pitchpine  piles,  14  inches  square  and  about  38  feet  long, 
driven  to  a  firm  substratum  of  boulder  clay.  The  fronts  of  the  shed,  both 
to  the  quay  and  the  roadway,  consist  of  a  series  of  doors  closing  openings. 


388  DOCK   ENGINEERING. 

26  feet  wide,  between  steel  cxtlumna,  except  at  the  roadside  of  the  upper 
floor,  where  bays  of  brickwork  alternate  with  doorways.  The  ground  floor 
is  paved  with  4-inob  granite  cubes,  bedded  in  gravel  on  an  8-inch  fotmda- 


SECTION    OF  SINGLE    STOREY    SHED    ISO  FEET    WIDE. 
Fir.  370.— Shed  at  Liverpool, 


SECTION    OF    DOUBLE     STOREY    SNED    BS    FEET    WIDE  . 
Fig.  871.— Shed  at  Liverpool. 


tion  of  concrete,  well  packed  with  rubble.  The  upper  floor  has  main  girders 
of  47  feet  span,  spaced  32  feet  apart,  and  longitudinal  girders  connecting 
these    at    about    12    feet    intervals.      Upon    this   framework,  and   bolted 


LIVERPOOL  SHEDS. 


389 


to  it,  lie  rows  of  rolled  joists,  6  by  3  inches  by  16  lbs.,  spaced  26  inches 
centie  to  centre,  forming  a  core  for  a  body  of  concrete  8  inches  in  depth, 
which  covers  the  top  of  the  joists  by  2  inches.  The  surface  coating  is  of 
crushed  granite  passed  through  a  sieve  of  16  meshes,  and  retained  by  a 
sieve  of  64  meshes,  to  the  square  inch,  mixed  with  an  equal  quantity  of 
cement.  For  the  bulk  of  the  concrete,  6  parts  of  broken  brick  and  gravel 
to  1  of  cement  are  employed.  The  ironwork  throughout  is  of  mild  steel. 
Three-storey  sheds  are  now  being  constructed  on  identical  lines. 

Fig.  372  is  a  cross-section  of  a  single-storey  shed  of  a  less  permanent 
and  more  economical  type.  The  sides  and  end  walls  are  of  timber  framing, 
covered  with  IJ-inch  Norway  planking.     The  main  uprights  are  of  pitch- 


11 1 1 


1  '■  I  H  I  I  H  I  I  ^  I   I   1    I   1   T  11  f 


S3'- 1 


8   9' 


!t«-- 


n 


i^M^ 


1 ' '  I 


TT- 


r^tri 


"TT 


'  .  ,     // M    '   >    '  M 

rfTT-TTTT--y^rr 

I  ' 


I  /  y  I      I  I  1  V,  \ 


[ y . .  \  \  I .  i -1 1 1 1 > ' 


I     I 


.M. j..J./:.<'°^.qd,'yr!??i?f^,,MtMl.^:;k;;m^.^T!:^S 


e'coruTTtP^  bed 


Concrete  SiU 


Fig.  372.— Shed  at  Liverpool. 


pine,  12  inches  squai*e,  13  feet  apart,  with  intermediates  12  by  6  inches, 
all  having  their  bases  bedded  in  concrete.  The  division  walls  alone 
are  of  brickwork,  and  this  with  the  design  of  curtailing  the  ravages  of 
a  possible  fire.  The  roof  has  combined  timber  and  iron  trusses,  covered 
with  boarding  whereon  is  laid  Graves'  Patent  Boofing  No.  2,  the  laps  and 
joints  of  which  are  coated  with  mastic  before  being  nailed  to  the  boarding. 


DOCK   ENGINEERING. 
\ 
A  coat  of  warm  maatic  has  then  been 
laid  over  the  whole  of  the  roof  sur- 
face, and  covered  immediately  with 
warm,  sharp  Band. 

Sheds  at  Dundee.* 
"  Around  the  docks  and  river 
quays  there  are  aingle-atorey  transit- 
sheds  covering  an  area  of  45,000 
square  yards.  A  cross-section  of  one 
recently  erected  is  shown  in  fig.  373. 
It  is  300  feet  in  length  hy  120  feet  in 
breadth,  in  two  roof  spans  of  60  feet, 
and  the  height  from  ground  level  to 
the  eaves  is  13   feet   9  inches.     The 

0  walls  are  of  brick,  with  ashlar  quoins 
g  and  tabling,  and  there  is  a  row  of 
3  cast-iron  columns  along  the  centre 
3    of   the  shed  supporting  the  roof,  and 

1  a  similar  row  on  the  river  front,  which 
e  is  closed  in  with  wooden  sliding  doors. 
s    The  roof  covering  is  of  slate,  and  the 

principals   and    girders    are   of   mild 
g    steel.     The  shed  is  floored  with  grano- 
g    lithic  pavement,  consisting  of  a  4-inch 
c    layer  of  broken  stone,  upon  which  is 
'.    laid  4  inches  of  Port)  and -cement  con- 
^    Crete,  covered  with  2  inches  of  grano- 
cp    lithic,  composed  of  clean  granite  chijis 
"     and  Portland  cement,  gauged  1  to  1. 
The  cost  is  5s.  per  square  yard,  and 
this  flooring  is  found  very  satisfactory 
for  both  light  and  heavy  traffic.    The 
total  cost   of    the  buildings  averages 
3s.  per  square  foot  of  ground  covered. 
A  row  of  single- storey  warehouses  has 
been  built  opposite  the  transit-sheds, 
constructed  of  iron  with  party  walls 
of  rubble  masonry.     They  cost  0'97d. 
per  cubic  foot  of  contents,  or  2a.  per 
square  foot  of   ground    covered.      In 
addition,    there  is  a    five-floor   ware- 
house   at     Victoria     Dock,     with    a 


WAREHOUSES  AT  GREENOCK.  39 1 

capacity  of  270,000  cubic  feet,  which  cost  £16,147  to  build."  The  trade  at 
Dundee  is  largely  in  Indian  jute,  a  bale  of  which  measures  4  feet  by  1  foot 
6  inches  by  1  foot  9  inches,  and  weighs  400  lbs. 


Warehouses  at  Greenock.^ 

"  On  the  south  side  of  the  James  Watt  Dock,  at  the  east  end,  a  block  of 
warehouses,  676  feet  in  length,  has  been  erected,  one  warehouse  being  275 
feet  long  and  one  223  feet  long,  106  feet  wide  and  47  feet  high,  and  two 
warehouses  89  feet  long,  106  feet  wide  and  57  feet  high  to  eaves  and  97  feet 
to  ridges  of  roofs.  The  fronts  of  the  warehouses  are  constructed  of  cast-iron 
columns  and  girders,  with  wrought-iron  sliding  doors,  and  the  back,  end, 
and  division  walls  are  of  brickwork.  The  two  longer  warehouses  are 
arranged  with  two  floors  above  quay  level.  The  two  shorter  warehouses 
have  four  floors  above  the  quay  level ;  and  the  insertion  of  an  intermediate 
floor  between  the  ground  and  first  floors  has  been  provided  for.  The  first 
floor  is  made  fireproof  with  10  by  6  inches  rolled  beams,  spaced  4 J-  feet 
apart,  carrying  brick  arches  4J  inches  deep  at  the  crown,  on  top  of 
which  the  floor  is  rendered  with  1  to  1  Portland  cement  granolithic  com- 
position 1  inch  thick.  The  upper  floors  and  roofs  are  of  timber.  A 
well-hole  in  the  centre  of  each  of  these  warehouses,  24  feet  long  by  16  feet 
wide,  enables  cranes  placed  on  the  top  floors  to  load  or  unload  goods  from 
any  floor  into  or  out  of  railway  waggons  on  the  ground  floor.  The  ware- 
houses are  intended  for  general  merchandise,  but  the  columns  carrying  the 
floors  have  been  cast  with  openings  fitted  with  valve-flaps,  in  order  that 
they  may  be  utilised  as  ducts  for  distributing  grain  over  any  portion  of  any 
floor,  and  also  for  transferring  it  from  a  higher  to  a  lower  floor,  or  for 
loading  railway  waggons  inside  the  warehouses.  In  each  floor  there  are 
openings,  with  branch  pipes  connected  to  the  vertical  columns,  for  receiving 
the  spouts  of  portable  hoppers  when  it  is  desired  to  transfer  grain  to  a  lower 
level,  but  cover-plates  ordinarily  close  the  openings  in  the  floors. 

"  There  are  doorways  on  the  ground  floor  through  the  brick  party  walls 
separating  the  warehouses,  for  railway  waggons  to  pass,  closed  by  double 
iron  doors,  separated  by  an  air-space  of  9|  feet.  In  front  of  the  warehouses 
there  is  a  covered  way,  27|  feet  wide,  half  outside  and  half  inside  the 
warehouses,  enabling  loading  and  unloading  to  be  carried  on  under  cover. 
This  corridor  outside  the  line  of  warehouses  is  covered  with  a  fireproof  floor 
similar  to  that  of  the  warehouses  and  at  the  same  level,  forming  a  con- 
tinuous platform,  13  feet  wide,  in  front  of  the  warehouses,  on  which  goods 
are  landed  and  conveyed  into  any  of  the  warehouses,  thereby  enabling 
imports  to  be  dealt  with  on  the  ground  floor  and  exports  on  the  upper  floor, 
and  thus  admitting  of  the  loading  or  unloading  of  the  vessels  to  be  largely 
done  by  gravitation." 

*Kinipple  on  **  Greenock  Harbour,"  Min.  Proc,  InsL  C.E.,  vol.  cxxx. 


392  DOCK   ENGINEERING. 

Sheds  at  Glasgow.* 
"  Except  where  open  quaj's  are  necessary,  all  the  quays  are  lined  with 
excellent  modem  sheds.  These  sheds  are  generally  single-storeyed  and  60 
feet  in  width,  but  at  the  Prince's  Dock  two-storeyed  sheds  have  been 
provided,  one  1,664  feet  long  by  70  feet  wide,  and  four  of  an  t^gregate 
length  of  5,312  by  75  feet  wide.  The  sheds  are  placed  usuaUy  15  or  20  feet 
back  from  the  face  of  the  quay.  The  total  floor  area  provided  by  the  single- 
storeyed  sheds  amounts  to  111,432  square  yards,  and  by  the  two-storeyed 
she<)s,  to  113,292  square  yards,  or  about  4CJ  acres  in  all." 

Warehoofies  at  Uanchester.t 
Two  blocks  of  seven-storey  warehouses,  situated  on  the  north  side  of  No. 
8  Dock,  cover  an  area  of  about  6,000  square  yards.  Their  concrete  founda^ 
tions  rest  on  hard  gravel  at  depths  varying  from  12  to  19  feet  below  quay 
level.  Each  warehouse  measures  about  60  feet  by  54  feet,  and  is  divided 
from  its  neighbour  by  a  strong  party  wall.  The  walls  are  3  feet  thick  at 
the  ground  level  and  1  foot  10|  inches  at  the  summit.     They  are  carried 


Fig.  374— ShedaiMancheater. 


6  feet  above  the  roof  line.  The  columns  are  cast  iron  throughout,  and  range 
from  12  inches  diameter  and  IJ-inch  metal,  with  bases  3  feet  square  at  the 
basement  level,  to  7  inches  diameter  and  1-inch  metol  at  the  top  floor, 
carrying  the  roof  65  feet  above  ground  level.  All  floors  are  framed  with 
14  by  12  inches  pitchpine  beams,  spruce  pine  joists,  and  double  boarding. 
The  doors  and  door  frames  throughout  are  of  iron. 

A  section  of  a  recently-constructed  transit-shed  with  five  floors  is  .shown 
in  fig.  374.     The  columns  and  girders  are  of  iron  and  the  floors  of  concrete. 

■Alston  on  "The  River  Clyde  and  Harbour  of  Glasgow," /«(.  £ng.  Con/.,  1»U1. 

+  Engineer,  July  30,  1897. 


SHEDS   AT   MANCHESTEIt   AND  ANTWERP.  393 


394  DOCK   ENGINEERING. 

The  balconies  on  the  dockside  and  roadside  are  hinged  so  as  to  be  tamed  up 
or  let  down  at  will.  The  topmost  floor  is  unsheltered  and  is  used  as  an 
open  quay  space,  upon  which  goods  unaffected  by  the  weather  are  deposited. 
Tlie  section  through  a  similar  shed  is  given  in  fig.  375. 

Antwerp  Sheds. 

The  older  sheds  at  this  port  are  mainly  constructed  in  timber,  having 
uprights,  framing,  and^roof  trusses  of  red  pine  with  a  covering  of  corrugated 
iron.     One  of  these  sheds  is  shown  in  section  in  fig.  376. 

The  later  sheds  along  the  quays  of  the  Scheldt  are  entirely  constructed 
in  iron.  Tlie  struts  and  chairs  for  roof  trusses  and  the  column  guards  are 
cast ;  all  the  remainder  is  wrought.  The  sheds  are  disposed  in  groups  of 
several  spans,  each  of  a  uniform  width  of  40  feet,  with  their  gable  ends 
facing  tlie  river  bank.  The  spaces  between  the  groups  range  between  40 
and  80  feet  in  width,  and  are  occupied  by  one  or  more  lines  of  rails  con- 
nected with  the  quay  service  by  means  of  turn-tables.  The  depth  of  the 
sheds  varies  from  100  to  160  feet,  and  they  cover  an  area  of  nearly  17  acres. 

The  type  of  shed  is  uniform  throughout  and  is  illustrated  in  fig.  377. 
The  roof  trusses  are  situated  at  11  feet  4  inches  centres,  bearing  on  longi- 
tudinal plate  girders,  20  inches  deep,  which  span  the  distance,  34  feet, 
between  consecutive  columns.  These  last  are  built  of  two  channel  irons 
connected  by  plates,  so  as  to  form  a  hollow  rectangular  interior,  which  is 
utilised  to  accommodate  the  rain-water  spouts.  The  column  bases  are 
bolted  down  to  a  masonry  foundation.  The  principal  rafters  are  of  joist 
iron ;  the  struts  of  cast  iron,  cruciform  section ;  the  ties  of  round  iron,  and 
the  purlins  of  angle  iron.  Along  the  ridge  on  the  north  slope  of  the  roof 
runs  a  continuous  skylight,  7  feet  in  width. 

Warehouses  and  Sheds  at  Botterdam. 

The  oldest  type  of  warehouse,  constructed  in  the  seventies  of  last 
century,  has  a  length  of  656  feet  and  a  width  of  120  feet.  It  is  divided 
into  five  compartments  by  fireproof  partitions,  which  project  beyond  the 
face  and  above  the  roof  of  the  building  by  6  feet  6  inches.  The  ground 
floor  and  its  exterior  platform  are  3  feet  6  inches  higher  than  the  quay 
levt4.  There  are  fireproof  cellars  with  an  area  of  5,330  square  yards,  and, 
in  addition  to  this,  there  are  three  floors.  Along  the  first  of  these  runs 
a  balcony  23  feet  wide ;  above  there  is  a  narrow  gangway  of  6  feet  6  inches 
in  width. 

Contemporaneously  with  this  warehouse  were  constructed  eight  sheds, 
entirely  in  wood,  with  an  internal  width  of  59  feet.  .  The  floor  rests  upon 
piles,  spaced  8  feet  apart,  which,  however,  are  a  cause  of  inconvenience 
from  their  continuous  settlement  and  the  consequent  necessity  for  raising 
the  floor.     The  roof  covering  is  bituminous  paper  (papier-bitume)  laid  on 


SHEDS   AT   HAVRE   AND   MARSEILLES.  395 

boarding.  It  is  worthy  of  mention  that,  with  a  single  coat  of  tar  per 
annum,  this  covering  has  remained  intact  for  more  than  twenty-five  years. 
It  is,  however,  very  inflammable,  and,  taken  in  conjunction  with  the  fact 
that  there  is  an  open  void  of  some  10  feet  between  the  shed  floor  and 
the  ground,  these  sheds  must  be  considered  constructed  in  such  a  manner 
as  to  be  highly  combustible.  In  fact,  one  of  them  was  totally  burnt  in 
1889.     The  reconstruction  was  carried  out  entirely  in  brickwork  and  iron. 

The  latest  sheds  at  this  port  have  a  width  of  131  feet  and  a  length  of 
367  feet  6  inches.  The  gable  walls  and  the  division  wall  between  the  two 
compartments  into  which  the  sheds  are  divided  are  of  brick,  but  the 
remaining  sides  and  the  roof  are  of  corrugated  iron.  The  wood  floor 
rests  directly  on  the  sand.  There  are  platforms  13  feet  in  width  at  the 
front  and  4  feet  in  width  at  the  back.  The  roof  truss  is  of  the  bow- 
string type,  in  three  spans  supported  by  columns  in  lattice-work. 

Sheds  at  Havre.* 

On  the  north  quay  of  the  Bellot  Basin  there  are  three  sheds,  each  147 
feet  6  inches  wide,  exclusive  of  overhang,  with  lengths  of  255  feet,  457  feet, 
and  306  feet  respectively.  On  the  south  quay  of  the  same  dock  the  sheds 
(fig.   378)  are  180  feet  wide  and  262  feet,  525  feet,  and  590  feet  long 


-r^ 


Fig.  378.— Shed  at  Havre. 

respectively.  In  each  case  they  are  separated  by  open  spaces  of  130  feet. 
These  spaces  are  intended  not  only  for  the  purpose  of  isolating  conflagra- 
tions, but  also  in  order  to  accommodate  cumbersome  merchandise,  and  to 
permit  of  trucking  from  the  dock  quays  without  the  necessity  of  passing 
through  the  sheds.  These  last  have  metallic  frames,  roof  coverings  of  zinc 
sheets,  and  external  walls  of  brickwork. 

The  roofs  are  in  two  spans  e€u;h,  of  73  feet  9  inches  and  90  feet 
respectively.  The  total  height  of  the  north  sheds  is  38  feet  and  of  the 
south  sheds  41  feet.  There  are  continuous  doors  along  the  quay  front  of  a 
uniform  height  of  15  feet  6  inches  in  both  cases. 

Sheds  at  Marseilles,  t 

The  double-storey  shed  illustrated  in  fig.  379  has  a  roof  in  one  span  of 
78  feet  9  inches,  the  ridge  of  which  is  43  feet  above  ground-floor  level.     The 

*  Despres  on  "  The  Plant  of  Maritime  Commercial  Porta  of  France,"  Proc.  Am,  &oc, 
C.E.f  vol.  XXX. 


396  DOCK  ENGINEERING. 

upper  floor,  aupported  on  cast-iron  columns  20  feet  apart,  is  placed  at  a 
height  of  16  feet,  and  is  extended  so  as  to  form  an  exterior  gallery,  11  feet 
9  inches  in  width.     Examples  of  single-storey  sheds  are  given  in  fig.  380. 


Fig.  379.— Shed  at  Marseilles. 


Fig.  380.— Sheds  at  Marseilles. 

The  following  are  stated  to  be  the  dispositions  found  to  be  most  .suitable 
for  sheds  at  this  port : — 

The  abed  to  be  enclosed  on  three  sides ;  on  the  fourth,  or  dock,  side  to 
have  doorways  alternating  with  solid  panels.  Sliding  doors  in  two  leaves, 
with  angle-iron  frames,  ii'on  sheeting,  and  wood  border.  Roofs,  in  spans 
not  exceeding  100  feet  in  width,  carried  on  cast-iron  columns,  serving  aa 
downspouts.  Trusses,  16  feet  apart,  with  framed  iron  principals  and  wood 
purbns.  Koof  covering  of  tiles,  with  a  double  lantern,  12  feet  wide,  on  each 
slope,  astride  riilge. 


Other  Frenoh  Forts. 

The  sheds  at  Calais  (fig.  381)  are  in  two  equal  spans  of  6 
vith  overhangs  of  13  feet  on  each  side. 


■  feet  6  inches, 


SHEDS  AT   DUNKIRK,   ETC. 


397 


The  sheds  at  Dunkirk  (fig.  382)  are  in  one  span  of  98  feet  6  inches,  with 
a  short  overhang  on  the  roadside. 


^^^s^w  v-^   ;    ;;'    w .V  \ .... 


^     vS'*-    .^  .\\» 


Fig.  382.— Shed  at  Dunkirk. 

At  Dieppe  (fig.  383)  and  at  Rouen  (fig.  384)  the  spans  are  78  feet  9 
inches  and  82  feet  6  inches,  and  the  overhangs  11  feet  and  14  feet  9  inches 
respectively.     At  Bordeaux  the  span  is  65  feet. 


^^IW*«^l'^^^»«W!i'f^ 


Fig.  383.— Shed  at  Dieppe. 


Fig.  384.— Shed  at  Rouen. 


At  French  ports  the  practice  is  generally  to  locate  the  sheds,  so  that  a 
distance  of  30  to  40  feet  separates  them  from  the  edge  of  the  quay. 


Sheds  and  Warehouses  at  Bremen.^ 

"The  fronts  of  the  quay  sheds,  which  are  for  the  most  part  131  feet 
wide,  are  entirely  closed  by  galvanised  corrugated  iron  sliding  doors,  so  that 
several  hydraulic  cranes  can  be  worked  together,  and  the  vessel  can  be 
unloaded  from  several  holds  at  the  same  time.  A  shed  can,  therefore,  be 
entirely  closed  or  opened  on  the  water  side,  and  on  the  land  side,  access  is 
given  by  doors,  between  each  two  of  which  a  crane  is  placed.  These  sheds 
are  surrounded  by  loading  stages,  and,  in  order  that  the  cart  traffic  may  be 
kept  separate  from  the  railway  traffic,  they  are  arranged  so  that  vehicles 

*  Franzius  and  De  Thierry  on  "  River,  Harbour,  and  Canal  Works  in  Germany," 
Min,  Proc.  Inst.  CE,,  vol.  exxxv. 


398  DOCK  ENGINEERING. 


SHEDS   AT   BREMEN   AKD   HAMBURG. 


400  DOCK   ENGINEERING. 

may  drive  in  under  them  from  the  street,  and  nine  may  at  one  time  be 
conveniently  loaded  from  the  floor  level,  which  is  the  same  as  that  of  the 
loading  stages.  Besides  this,  the  warehouse  fronts  serve  the  vehicular 
tratiic.  On  the  rebuilding  of  one  of  these  sheds,  which  had  been  completely 
destroyed  by  fire  in  a  short  time,  it  was  divided  up  by  two  fireproof  walls. 
The  total  length  of  sheds  already  built  (in  1898)  amounts  to  5,052  feet,  and 
they  have  a  total  area  of  724,800  square  yards.  For  unloading  and  storing 
cargoes  of  cotton,  there  is  a  shed  on  the  north  side  of  the  dock,  the  floor  of 
which  is  at  street  level  on  the  water  side,  and  rises  gradually  to  the  level 
of  the  loading  platforms  on  the  land  side.  This  shed,  built  of  wood  and 
corrugated  iron,  and  roofed  with  roofing  paper,  differs  from  the  others, 
which  are  built  of  iron.  Behind  this  shed  is  a  storage  warehouse,  which 
is  built  in  a  similar  manner. 

"Two  giuin  warehouses  were  erected  in  1896-97.  One  warehouse,  on 
the  quay,  558  feet  long  and  135  feet  wide,  has  only  one  storey  for  the  first 
third  of  its  width  towards  the  water  side,  while  the  remaining  two-thirds 
are  two  storeys  high.  At  the  back  of  this  warehouse,  and  separated  by  a 
street  66  feet  wide,  down  which  lines  of  railway  pass,  is  a  two-storey  ware- 
house 886  feet  long  and  98  feet  wide.  The  upper  floors  of  both  warehouses 
are  intended  chiefly  for  grain  in  bulk.  The  warehouse  on  the  quay  covers 
an  area  of  7,940  square  yards,  and  the  storage  warehouse  6,110  square 
yards.  They  can  store  18,000  tons  in  a  manner  usual  for  a  lengthy 
period,  and  12,000  tons  for  the  time  usually  adopted  for  grain  in  towns. 
The  total  cost  amounted  to  about  £56,100." 

A  section  across  Bremen  Quays  is  given  in  figs.  385  and  386. 

Sheds  at  Hamburg. 

The  sheds  on  the  quays  (figs.  387  and  388),  where  the  sorting  of  the 
unloaded  goods  is  generally  done,  are  one  storey  high  throughout;  they 
are  closed  on  the  land  side  and  open  to  the  water.  On  the  land  side  there 
are  four  or  five  lines  of  railway,  on  the  two  first  of  which  trucks  stand  to 
be  loaded.  The  goods  unloaded  from  the  sea-going  ships,  which  are  to  be 
forwarded  by  rail,  are  dealt  with  on  the  land  side  of  the  sheds,  while  those 
to  be  sent  to  warehouses  in  the  town  by  barge  are  dealt  with  by  cranes  on 
the  water  side.  The  water  side  is  paved  throughout,  forming  a  roadway  for 
vehicles.  With  the  exception  of  those  on  the  Sandthor  Quay,  all  sheds  are 
built  of  wood  and  roofed  with  roofing  paper.  The  Sandthor  Quay  sheds 
have  stone  walls  on  the  land  side  and  are  roofed  with  iron.  The  breadth 
of  the  sheds  varies  between  48  feet,  on  the  Sandthor  Quay,  and  110  feet,  on 
the  Asia  Quay. 

Kidderpur  Book  Sheds,  Calcutta.^ 

"Cargo  sheds  have  been  constructed  on  both  sides  of  the  dock,  each 
shed  being  300  feet  long  by  120  feet  wide.     They  are  constructed  in  two 

♦Bruce  on  "The  Kidderpur  Dock  Sheds,  Calcutta,"  Min.  Proc.  Inst,  C.E., 
vol.  cxxi. 


SHEDS  AND  WAREHOUSES  AT  BUENOS  AYRES,  ETC.   4OI 

bays  of  .60  feet  each,  carried  on  cast-iron  columns  of  H  section,  and  are  roofed 
with  corrugated  iron,  and  are  enclosed  by  15-inch  brick  walls  built  between 
the  H  columns,  and  fitted  with  sliding  doors,  one  in  each  15-foot  bay.  To 
avoid  down  pipes  passing  through  the  sheds  to  drainage  channels  under 
the  floors,  the  centre  gutters  are  made  large  enough  to  carry  the  rain- 
water to  the  ends  of  the  buildings,  the  necessary  fall  being  obtained  by 
raising  the  bases  of  the  middle  columns.  All  the  gutters  are  of  ^inch 
galvanised  steel  plates.  The  floors  are  laid  with  a  slope  of  1  in  60,  and, 
on  the  quay  side,  are  raised  1  foot  above  the  coping  level.  The  height 
above  ground  level  at  the  back  of  the  shed  is  3  feet  6  inches,  and  along 
this  inner  face  a  platform,  8  feet  wide,  has  been  constructed  for  the  con- 
venience of  the  railway  traffic.  The  total  shed  area  provided  is  432,000 
square  feet.  The  sheds  are  lighted  by  electricity.  Each  of  the  sheds  has 
forty  16-candle-power  incandescent  lamps,  hung  from  the  tie-beams  of  the 
piincipals.  In  addition  to  these,  and  to  arc  lamps  upon  the  quays,  a 
terminal  box  is  provided  in  each  shed,  to  which  a  portable  lamp  may  be 
connected,  in  case  of  more  light  being  required  in  any  part  of  the  shed, 
or  outside,  when  loading  or  unloading  has  to  be  carried  on  at  night." 

Sheds  and  Warehouses  at  Buenos  Ayres.* 

The  total  capacity  of  the  sheds  and  warehouses  amounts  to  687,378  cubic 
yards,  and  the  total  floor  area  to  230,595  square  yards.  The  sheds  are  of 
iron,  with  corrugated  iron  roofs.  They  are  mainly  built  on  piles  in  made 
ground.  Each  shed  has  a  platform,  31  feet  wide,  on  the  dock  side,  covered 
by  a  verandah.     . 

Four  of  the  thirteen  warehouses  have  wooden  roof-trusses,  with  tiles 
laid  on  planking.  The  remainder  have  iron  roof-trusses,  with  a  zinc 
covering,  as  well  as  iron  partition  doors  and  iron  window  frames.  These 
latter  warehouses  have  an  extra  floor,  making  five  in  all,  and  have  longi- 
tudinal platforms  running  the  whole  length  of  the  front  of  the  warehouses, 
so  that  goods  can  be  deposited  on  any  part  of  the  platforms  in  order  to 
be  removed  into  the  warehouses  afterwards.  The  warehouses  are  built-  of 
rubble  masonry  up  to  the  level  of  the  quays,  and  from  that  level  to  the 
top,  of  brickwork.  All  the  floors  are  of  timber,  with  the  exception  of  the 
ground  floors  over  the  bonds,  which  are  of  concrete  in  the  proportion  of 
1  cement,  4  sand,  and  6  stone,  with  a  rendering  of  1  inch  of  1  cement  and 
1  sand. 

Figs.  389  to  391  illustrate  the  practice  at  this  port. 

Various  other  instances  of  shed  and  warehouse  construction,  sufficiently 
intelligible  without  description,  will  be  found  in  figs.  392,  393,  and  394, 
which  illustrate  sheds  at  Zeebmgge  and  Emden,  and  a  warehouse  at 
Amsterdam. 

*  Dobson  on  "Buenos  AjTes  Harbour  Works,"  Min.  Proc.  Inst,  C,  E.,  vol. 
cxxxviii. 

26 


DOCK  ENGINEERING. 


WAREHOUSE. 
—Sheds  and  Warehouse  al 


SHEDS  AT  ZEEBRUGGB  AND  EMDBN. 


DOCK   ENGINEERING. 


405 


CHAPTER   X. 

DOCK    BBIDGBS. 

CLASsmcATiON — FLOATING  Bridobs — Trayebsing  Bbidou — Drawbridoks — Basculks 
—  Lifting  Bridges  —  Swing  Bridges  —  Single-leaf  versus  Double  •  leaf 
Bridges— Stresses  in  Movable  Bridges — Case  of  the  Double  Cantilever — 
Case  of  the  Cantilever  and  Beam — Case  of  the  Arch — Case  of  the  Con- 
tinuous Beam — The  Theorem  of  Three  Moments— Effect  of  Counterpoise — 
Loads  imposed  on  Movable  Bridges — ^Weight  of  Structure — ^Weights  of 
Ttpical  Locomotives — Equivalent  Live  Loads — Weight  of  Vehicles  and 
Men  —  Practical  Example  of  the  Calculations  for  a  Swing  Bridge  — 
Distinctive  Features  of  Movable  Bridges— The  Pivot— Balanced  Rollers 
AND  Wheels— The  Counterpoise — Setting  Apparatus — Interlocking  Appar- 
atus— Notes  on  Design — Illustrations  of  Movable  Bridges  at  Greenock, 
Antwerp,  Rotterdam,  Chicago,  Marseilles,  Liverpool,  Leith,  and 
Ridderfur. 

Narrow  waterways  and  locks,  linking  together  the  various  parts  of  a 
dock  system,  are  generally  spanned  at  convenient  points  by  bridges,  in 
order  that  vehicular  and  foot  traffic  may  be  transmitted  across  them  and 
access  provided,  as  uninterruptedly  as  possible,  tojedl  quarters.  On  account, 
moreover,  of  the  necessity  of  maintaining  the  navigation  of  these  passages, 
it  is  essential  that  bridges  crossing  them  should  be  of  a  movable  nature  and 
characterised  by  great  rapidity  of  action,  so  as  to  avoid  lengthy  stoppages 
and  interference  with  the  use  of  either  road  or  waterway. 

Such  bridges  are,  of  course,  used  in  a  variety  of  situations  and  in 
branches  of  engineering  not  necessarily  connected  with  docks.  Their 
importance,  however,  to  the  dock  engineer  is  indisputable. 

Classification. — For  the  purpose  of  this  treatise,  movable  bridges  may  be 
divided  into  five  classes  : — 

Floating  bridges. 
Traversing  bridges. 
Drawbridges. 
Lifting  bridges. 
Swing  bridges. 

Floating  Bridges,  as  the  name  implies,  are  water-borne,  either  con- 
tinuously  and  wholly,  or  partially  and  during  such  times  as  they  are 
being  moved.  The  former  variety,  which  are  generally  formed  of  pontoons, 
•either  singly  or  in  combination,  are  rarely  used  otherwise  than  for  purposes 
of  a  purely  temporary  nature,  such  as  the  crossing  of  rivers  and  streams 
during  military  operations.      A  striking  instance  of  their  application  to 


406  DOCK  ENGINEERING. 

more  permanent  ends  is  afforded  by  the  Liverpool  and  Birkenhead  landing- 
stages  on  the  River  Mersey,  which,  themselves  constructed  on  the  same 
principle,  are  connected  with  the  shore  by  floating  bridges,  consisting  of  a 
series  of  pontoons,  flexibly  linked  together  so  that  they  are  able  to  adapt 
themselves  to  the  fluctuations  of  tidal  level.  The  length  of  the  Liverpool 
bridge  is  550  feet  and  its  width  35  feet.  The  Birkenhead  bridge  is  678  feet 
in  length  by  30  feet  in  width.  Neither  of  these  bridges  is,  however,  a 
movable  bridge  in  the  sense  intended  in  this  section. 

There  is  a  pontoon  bridge,  which  is  movable  in  the  true  sense  of  the 
word,  over  the  Kaiser  William  Canal  at  Holtenau.  It  consists  of  two  main 
or  turning  pontoons,  meeting  at  the  centre  of  the  canal,  united  to  two- 
bearing  pontoons  at  their  shore  ends.  The  bridge,  which  carries  a  15-foot 
roadway  and  two  2  feet  6-inch  footpaths,  is  opened  by  turning  the  pontoons 
round  their  shoreward  ends,  and  this  is  accomplished  by  having  a  chain,  one 
end  of  which  is  attached  to  a  mushroom  anchor  in  the  bed  of  the  canal,  and 
the  other  to  a  bollard  on  the  bank,  wound  round  the  barrel  of  a  winch,, 
which  is  on  a  small  pontoon  alongside  of,  and  fixed  to  the  main  pontoon. 

The  second  kind  of  floating  bridge  is  represented  by  caissons,  which,, 
however,  only  act  incidentally  as  bridges,  their  primary  function  being 
that  of  closing  a  waterway.  It  has  already  been  noted  that  one  of  the 
advantages  appertaining  to  a  caisson,  in  comparison  with  a  pair  of  gates, 
ia  this  capacity  to  discharge  dual  duties,  whereby  the  additional  expenditure 
for  a  bridge  is  avoided.  Caissons  as  a  class  have  already  been  dealt  with  in 
Chap,  viii.,  so  that  there  is  no  need  to  pursue  this  branch  of  the  subject 
further. 

Traversing  Bridges  are  supported  by  the  quay  at  or  about  the  coping 
level  and  are  projected  forward  or  withdrawn  in  a  straight  line — ^in  other 
words,  their  motion  is  rectilinear  and  approximately  horizontal,  or  with 
just  sufficient  inclination  to  enable  them  to  clear  the  edge  of  the  roadway 
abutting  on  their  recesses;  for,  except  in  the  case  of  footbridges,  which 
may  be  provided  with  approach  steps  at  each  end  of  the  bridge,  forming 
part  of  the  moving  structure,  the  wheel  track  of  a  traversing  bridge  must 
lie  somewhat  below  the  quay  level  in  order  that  its  floor  may  form  a 
continuous  horizontal  plane  with  the  roadways.  Consequently,  for  the 
purpose  of  removal,  the  tail  or  inner  end  of  the  bridge  must  be  raised  to 
the  height  of  the  roadway  before  it  can  be  drawn  backwards. 

Several  arrangements  have  been  devised  for  the  working  of  traversing 
bridges,  of  which  the  following  are  a  few  typical  instances : — 

(a)  The  nose  or  forward  end  of  the  bridge  rests  upon  rollers  driven  in 
between  the  bridge  girders  and  the  wall-bearing  plate.  In  order  to  open 
the  passage  these  rollers  are  withdrawn,  and,  at  the  same  time,  the  tail  end 
is  lifted.  The  bridge  tilts  about  intermediate  wheels,  fixed  at  the  quay  edge, 
and  upon  these  and  the  tail-end  wheels  the  structure  is  supported  during 
withdrawal. 

(b)  The  same  effect  of  tilting  the  bridge  is  obtained  by  making  the  tail 


DRAWBRIDGES.  407 

end  lighter  than  the  overhanging  portion.  The  nose  end  is  then  provided 
with  movable  supports,  and  when  these  are  lowered,  the  bridge  naturally 
inclines  into  a  position  suitable  for  removal. 

(c)  The  intermediate  support  is  formed  by  a  pair  of  wheels  surmounting 
hydraulic  rams  which  lift  the  bridge  bodily.  The  nose  end  of  the  bridge  is 
the  lighter  end,  and  is  checked  in  its  tendency  to  rise  by  a  bracket  which 
engages  in  the  abutment.  This  allows  the  tail  end  to  clear  the  roadway 
prior  to  being  drawn  over  fixed  wheels  at  its  edge. 

(d)  The  main  girders  of  the  bridge  have  prolongations  in  the  form  of 
bent  levers,  inclined  upwards  and  counterweighted,  so  that,  with  a  slight 
additional  pressure,  the  inclined  tail  is  brought  down  to  the  level  of  the 
roadway,  and  the  bridge,  with  its  nose  end  now  tilted,  moves  backwards 
over  wheel  tracks  provided  for  it. 

Traversing  bridges  are  much  inferior  to  swing  bridges,  in  that  the 
working  friction  on  the  axles  is  considerably  greater  than  that  on  a  pivot, 
but  they  afford  decided  advantages  where  it  is  desirable  not  to  curtail  the 
length  of  the  quayage,  since  they  only  occupy  a  frontage  equal  to  their 
width.  They  share  this  feature  in  common  with  the  class  of  bridges  next  to 
be  considered. 

Drawbridges  are  the  most  ancient  of  iJl  movable  bridges,  dating  back  to 
mediaeval  times,  when  a  militant  nobility  were  in  the  habit  of  girdling  their 
residences  with  moats  or  ditches,  spanned  by  bridges  which  could  be  raised 
for  defence  or  lowered  for  sortie,  as  occasion  might  require.  Such  a  bridge 
consisted  of  a  single  flap.  It  was  raised  by  chains  attached  to  the  nose  end ; 
these  passed  over  pulleys  at  the  summit  of  uprights  fixed  near  the  hinged 
end. 

The  later  development  of  this  type  of  bridge  is  known  as  a  Bascule 
Bridge.  Like  its  prototype,  it  revolves  about  a  horizontal  axis,  but  it  is  also 
provided  with  a  counterpoise  in  the  form  of  a  weighted  prolongation  of  the 
bridge,  whereby  the  power  required  for  working  the  bridge  is  reduced  to  a 
minimum.  An  alternative  method  of  counterbalancing  is  by  means  of  over- 
head beams,  set  a  little  back  from  the  axis  of  rotation.  The  first  method 
needs  a  deep  pit  to  receive  the  tail  end  of  the  bridge  when  in  the  vertical 
position,  and  this  is  not  always  easy  to  provide  without  some  portion  of  the 
counterpoise  becoming  submerged.  Hence  the  second  method,  which  is 
much  in  vogue  in  Holland,  where  the  quays  are  very  little  above  water  level. 

A  third  method  of  counterbalancing  the  structure  is  by  means  of  weights 
attached  to  chains  connected  with  the  bridge  and  passing  over  pulleys 
carried  by  independent  posts.  This  method  has  the  objection  that,  the 
moment  of  the  bridge  about  its  axis  being  variable  at  different  stages  of  the 
lift,  while  the  moment  of  the  counterpoise  remains  constant,  the  bridge 
cannot  be  maintained  in  even  approximate  equilibrium  throughout. 

A  compound  arrangement  of  self-contained  and  extraneous  balancing  is 
afforded  by  the  design  in  fig.  396,  due  to  Mr.  W.  R.  Browne.  The  axis  of 
rotation  is  fixed  some  little  distance  away  from  the  centre  of  gravity  of  the 


408  DOCK  ENGINEEBING. 

bridge,  being  both  horizontally  behind  and  vertically  below  it.  At  the 
instant  of  commencing  to  open  the  bridge,  the  moment  of  the  counterbalance 
is  slightly  in  excess  of  the 
moment  of  the  bridge,  thus 
assisting  it  to  rise.  The  excess 
continues  until  the  centre  of 
gravity  of  the  bridge  comes 
rerticalJy  over  the  axis,  at 
which  stage  the  line  of  chain 
also  intersects  it,  producing 
equilibrium.  As  the  bridge 
continues  its  rotation  the  con- 
trary effect  is  set  up,  the 
J  moment  of  the  bridge  tend- 

I  ing  to  increase  its  travel,  while 

^  the  moment  of   the  counter- 

J  poise    acts    aa    a    check.     In 

I  closing  the  bridge  the  action 

is  the  same,   but  in  reversed 
^     order. 

,§  Bascule  bridges  are  usually 

■|     in  two  leaves,  meeting  at  the 

I     centre    of    span.     The   under 

■^      side  of  each  leaf  is  then  per- 

1(5     fectly  curved  in   form,  or  is 

"     provided  with  raking  struts, 

£      fitting  into  pockets  or  recesses 

in    the  side   walls   when   the 

bridge  is  lowered.     This  type 

of  bridge  forms  an  arch,  and, 

accordingly,   it    derives   very 

considerable  support  from  the 

t  mutual  abutments  at  its  centre 

and     the    skewbacka    at    the    - 
^  sides.      These    parts    can    be 

I  adjusted  to  a  nicety  which  is 

I  not  realisable  in  the  case  of 

i  other  types. 

I  The  main  objections  to  the 

i  employment  of    bascules   are 

a  their  liability  to  come  in  con- 

tact with  the  yards  and  spars 
of  passing  vessels,  tuid  also  the 
very  large  surface  which  they 
The    leverage  exerted  by  the  wind  materially 


expose  to  wind  pressure. 


SWING   BRIDGES.  409 

increases  the  labour  of  raising  the  bridge,  and  from  the  nature  of  its  office 
no  perforations  are  allowable  in  the  bridge  platform.  The  former  draw- 
back can  be  remedied  to'  some  extent  by  setting  back  the  axis  from  the 
&kce  line  of  the  quay,  but  this  step  considerably  augments  the  length  and 
cost  of  the  bridge. 

It  has  been  proposed*^  as  an  antidote  to  both  evils  that  the  bridge, 
instead  of  being  raised,  should  be  lowered  into  its  vertical  position  and  at  the 
same  time  recessed  within  the  side  walls.  The  author  is  unaware  of  any 
instance  in  which  the  suggestion  has  been  carried  out.  Except  in  the  case 
of  very  high  quays  the  project  would  evidently  entail  the  submersion  of  a 
part  of  each  leaf ;  but,  though  this  might  be  detrimental  to  the  durability 
and  appearance  of  the  structure,  from  an  operative  point  of  view  it  would 
<5onfer  a  benefit  rather  than  otherwise.  There  are  one  or  two  obvious 
difficulties  to  be  overcome,  but  the  author  of  the  scheme  (Mr.  C.  J.  Findlay) 
does  not  consider  them  insuperable. 

All  bascules  do  not  rotate  about  a  fixed  axis.  There  is  a  variety,  known 
as  the  rolling  bascule^  in  which  the  tail-end  of  the  bridge  takes  the  form  of  a 
circular  segment,  upon  which  the  bridge  rolls  in  a  manner  similar  to  the 
action  of  a  rocking  chair  (fig.  435). 

Lifting  Bridges  are  horizontal  platforms  raised  vertically  in  such  a  way  as 
to  maintain  a  level  surface  throughout  the  process.  Instances  of  their  use 
are  rare,  and  are  apparently  confined  to  rivers  and  canals.  Indeed,  their 
eligibility  for  dock  work,  except,  conceivably,  in  connection  with  canal 
basins,  is  dubious,  owing  to  the  great  height  to  which  they  would  have  to  be 
raised  in  order  to  clear  the  masts  of  vessels  passing  beneath  them.  Further- 
more, it  would  be  a  difficult  matter  to  secure  equable  movement  of  the 
platform,  lifted,  as  it  would  be,  from  two  opposite  sides  of  the  waterway, 
unless  the  action  were  controlled  from  one  centre — an  arrangement  which  is 
scarcely  feasible  in  the  majority  of  cases.  The  advantages  attached  to  the 
system  are  limited  to  a  minimum  appropriation  of  quay  space.  There  is  a 
lifting  bridge  over  a  channel  100  feet  wide  at  Chicago. 

Swing  Bridges. — These  constitute  by  far  the  most  numerous  and  the  most 
important  class  for  dock  work.  It  includes  all  movable  bridges  in  which  the 
axis  of  rotation  is  vertical.  The  merits  of  the  principle  are  a  comparatively 
slight  expenditure  of  motive  power,  ease  of  movement,  and  less  wear  of  the 
bearing  surfaces,  the  absence  of  deep  pits  for  counterbalancing  purpases,  and 
of  appreciable  change  in  level.  On  the  other  hand,  two  important  drawbacks 
must  not  be  overlooked  : — 

1.  Swing  bridges  are  necessarily  longer  than  bascules  or  traversing  bridges. 
Bascules  may  rotate  about  an  axis  as  close  to  the  edge  of  the  coping  as  is 
considered  desirable.  The  pivot  of  a  swing  bridge  must,  however,  be  set 
back  a  distance  not  less  than' half  the  width  of  the  bridge,  in  order  that  the 
latter  may  be  entirely  housed  within  the  quay  line  when  the  passage  is  open. 
Since  the  counterbalance  must  lie  behind  the  pivot,  it  necessarily  follows  that, 
•  Findlay  on  "The  Design  of  Movable  Bridges,"  Min.  Proc,  L.E.S.,  vol.  ii. 


4IO  DOCK   ENGINEERING. 

in  the  second  case,  both  the  effectiye  span  and  the  Length  of  tail  are  increased. 
This  consideration  is  not  without  importance  on  grounds  of  economy  alone. 
In  traversing  bridges  the  effective  length  is  measured  between  the  bearings^ 
and  these  may  be  practically  at  the  edge  of  the  coping. 

2.  The  side  recesses  of  swing  bridges  occupy  a  large  extent  of  valuable 
quay  frontage — ^much  more  than  other  kinds  of  bridge — and  in  the  case  of 
wide  passages  this  leads  to  the  necessity  for  side  walls  of  considerable  lengthy 
with  a  corresponding  increase  in  cost  of  construction,  apart  from  any  question 
of  intrenching  upon  the  area  of  dock  accommodation. 

On  the  whole,  the  balance  of  technical  opinion,  as  evidenced  by  practice, 
inclines  toward  the  employment  of  swing  bridges  in  preference  to  other  types, 
in  so  far  as  heavy  traffic,  at  any  rate,  is  concerned.  There  is  one  case  in 
which  a  swing  bridge  offers  signal  advantages.  When  two  waterways  of 
about  equal  width  lie  side  by  side  with  an  island  between,  as  in  fig.  456,  a 
swing  bridge  may  be  arranged  symmetrically  upon  a  central  pivot,  so  that 
each  wing  acts  as  a  counterbalance  to  the  other.  In  this  way  the  length  of 
bridge  necessary  for  closing  the  opening  is  reduced  to  a  minimum,  and  the 
rotation  of  the  wings  neutralises  the  effect  of  the  wind  pressure  upon  the 
surface  of  the  bridge.  This  last  statement,  though  theoretically  convincing, 
is  only  partially  true  in  practice,  for,  as  has  already  been  pointed  out,  the 
wind  does  not  exert  a  uniform  pressure  over  large  areas.  On  the  contrary, 
it  is  given  to  surging  and  eddying ;  consequently  it  is  quite  possible  that, 
however  symmetrically  disposed  the  wings  of  a  bridge  may  be,  the  pressure 
on  one  will  exceed  that  on  the  other.  Such  was  proved  to  be  the  case  by  an 
incident  at  Goole,  whei'e  a  bridge  over  the  River  Ouse  spanning  two  openings, 
each  100  feet  wide,  broke  loose  in  a  severe  gale  and  swung  violently  back' 
wards  and  forwards,  describing  about  one-third  of  a  circle  each  time. 

The  converse  of  a  single  bridge  spanning  two  openings  is  that  of  a  bridge 
in  two  leaves  spanning  a  single  opening,  and  we  now  enter  into  the  merits  of 
single-leaf  and  double-leaved  bridges  respectively. 

Single-leaf  versus  Double-leaf  Bridges.  — The  relative  advantages  and  dis- 
advantages of  single  and  double  leaves,  in  the  cases  of  traversing,  bascule, 
and  swing  bridges,  may  be  summed  up  as  follows : — 

1.  The  depth  of  a  single-leaf  bridge  is  necessarily  greater  than  that  of  & 

double-leaf  bridge  for  the  same  span.     If  «  be  the  span,  w  the  weight  per  foot 

run,  t  the  maximum  permissive  tension  in  the  top  flange — all  fixed  values — 

we  have,  by  taking  moments  about  the  bottom  of  the  bridge  at  the  ^ide  of 
span — 


(a)  in  the  case  of  a  single  leaf,    d^  =  -^ 


W8^ 


W8 


t 
2 


(6)  in  the  case  of  double  leaves,  rfj  =  -^ — , 

so  that  the  depth  {d)  of  the  bridge,  treated  while  in  motion  entirely  as  & 
cantilever,  needs  to  be  four  times  as  great  in  the  first  case  as  in  the  second* 


STRESSES  IN   MOVABLE  BRIDGES.  41I 

If  we  consider  the  support  afforded  by  the  further  abutment  in  the  single- 
leaf  bridge  when  at  rest,  the  ratio  is,  of  course,  considerably  reduced. 

2.  On  the  other  hand,  the  length  of  a  single-leaf  swing  bridge  is  less 
than  the  combined  lengths  of  two  leaves  for  the  same  opening.  The  reason 
for  this  has  already  been  given — viz.,  that  the  pivot  has  to  be  placed 
sufficiently  far  back  from  the  face  of  the  coping  to  accommodate  the  whole 
width  of  the  bridge  upon  the  quay.  When  there  are  two  pivots,  the  excess 
of  length  thus  involved  is  doubled. 

3.  A  single-leaf  bridge  only  requires  a  single  set  of  actuating  machinery. 
For  a  given  opening,  the  set  will  have  to  be  at  least  twice  as  powerful  as  the 
two  sets  combined,  but  the  cost  of  construction,  of  repairs,  and  of  general 
maintenance  will  certainly  not  be  doubled  for  a  single  set. 

4.  The  control  of  the  machinery  of  a  single-leaf  bridge  is  in  the  hands 
of  one  man.  Two  sets  of  machinery  necessitate  two  attendants  at  least, 
whose  co-operation  can  only  be  secured  by  imperfect  signals  or  by  shouted 
instructions,  which,  in  windy  weather,  are  liable  to  be  unheard  or  mis- 
understood. 

5.  Additional  apparatus  for  interlocking  is  required  in  the  case  of 
double-leaved  bridges. 

6.  The  adjustment  of  the  levels  of  two  leaves  at  their  junction  is  a 
matter  of  some  delicacy.  Any  irregularity  (however  slight)  in  the  joints  of 
a  locomotive  track  leads  to  percussive  action  and  the  gradual  destruction  of 
the  rail.  The  absolutely  necessary  clearance  between  the  two  sets  of  rails 
is  sufficient  to  cause  this,  and  repairs  or  renewal  involve  inconvenience 
and  delay. 

7.  A  double-leaf  swing  bridge  necessitates  less  length  of  passage  than  a 
single-leaf  bridge,  the  whole  of  whose  length  has  to  be  accommodated  on 
one  side. 

Stresses  in  Movable  Bridges. — It  would  manifestly  be  impracticable, 
within  the  limits  of  a  single  chapter,  to  attempt  to  treat  with  the  least 
degree  of  precision  and  finality  the  very  numerous  and  important  considera- 
tions peculiarly  involved  in  the  design  of  movable  bridges.  Still  less  would 
it  be  possible  to  investigate,  with  that  thoroughness  which  the  question 
demands,  the  nature  and  amount  of  the  stresses  set  up  in  the  framework  of 
such  bridges,  generally,  under  the  varying  conditions  of  load  and  support  to 
which  they  are  subjected.  These  latter  problems  form  the  basis  of  distinct 
treatises,  to  which  the  reader  is  referred  for  information  more  complete, 
more  detailed,  and  more  comprehensive  than  could  be  included  here. 

At  the  same  time,  in  view  of  the  identification  of  movable  bridges  with 
dockwork  and  the  unique  features  which  they  possess  in  that  connection,  it 
would  evidently  be  equally  injudicious  and  inappropriate  to  abstain  alto- 
gether from  presenting  some  account  of  the  principles,  upon  the  basis  of 
which  such  structures  are  adapted  to  the  particular  kind  of  work  which  they 
are  called  upon  to  perform. 

Accordingly,  we  will  endeavour  to  compromise  the  matter  by  investiga- 


412  DOCK   ENGINEERING. 

ting,  in  the  first  instance  in  general  terms,  and  then,  as  far  as  practicable,  in 
some  brief  detail,  the  fundamental  problems  which  present  themselves  to  the 
engineer  in  designing  movable  bridges,  in  so  far  as  they  are  connected 
with  the  equipment  of  docks. 

Excluding  floating  and  lifting  bridges  as  too  remotely  related  to  the 
subject  for  general  application,  we  may  divide  our  consideration  of  the 
stresses  in  the  remaining  kinds  of  bridge  into  four  cases,  representing  the 
different  conditions  in  which  any  of  them  may  be  found. 

(1)  A  double  cantilever  resting  upon  a  central  support. 

(2)  A  single  cantilever  supported  at  two  points,  or  a  cantilever  and 

beam  combined. 

(3)  An  arch. 

(4)  A  continuous  girder  resting  upon  three  supports. 

The  first  case  represents  a  single  swinging  bridge  with  two  equal  wings. 
The  second  embraces  generally  all  cases  of  bridges  in  one  or  two  leaves 
projecting  over  an  opening,  with  certain  exceptions,  as  under.  The  third 
applies  to  those  double-leaved  bridges  which  afford  one  another  mutual 
support  at  their  meeting  faces ;  and  the  fourth  is  the  normal  condition  of  a 
single-leaf  bridge  in  a  state  of  rest. 

Case  /.  A  double  cantilever  resting  upon  a  central  suppoH  (fig.  396). 

%^  0  w  This  is  an  extremely  simple  case  and 


-,  .     need   not  be   the   cause    of    more  than  a 

g  moment's   detention    in    passing.      If    the 

Fig.  396.  imposed    load    be    w    per  foot   run,   and, 

assuming  that  the  bridge  is  symmetrical,  the  central  reaction  is  obviously — 

Rj  =  2wa, (81) 

and  the  shearing  stress  increases  from  zero  at  each  extremity  to  one-half  of 
the  above  amount  on  each  side  of  the  support. 
The  bending  moment  at  O  is — 

Mo  =  "'/, (82) 

and  at  each  end  it  is  zero.  The  curve  of  moments  for  each  half  of  the 
bridge  is  parabolic,  with  its  origin  at  the  extremity  and  its  axis  vei-tical. 
Where  the  arms  are  of  unequal  length,  the  stresses  are  clearly  those  due  to 
the  longer  arm,  a  counterpoise  being  added  to  the  shorter  arm  to  produce  an 
equal  effect. 

Ca^e  If.  A  single  cantilever  in  combination  with  a  beam  (fig.  397). 
.  ».../•  I^et  A  C  be  a  girder  of  total  length 

♦ a + 6---*| 

Id  1 


^B  ^C 


{a  +  b)  supported  at  two  points,  B  and 
C,   of    which    only    one    is    at   an   ex- 
tremity. 
^'       '  The  reactions,  Kb  &z^d  Bo,  at  B  and 

C  may   be   determined   by  taking   moments  about  the  points   C  and  B, 

respectively,  thus— 


A  SINGLE   CANTILEVER,  415 

I  +   6 j  +  t/72  5-    .  .  .  .     (83) 

O  *  Q 

Ro  being  measured  downwards.     The  amount  of  counterpoise  required  to- 
prevent  the  cantilever  end  overbalancing  is,  accordingly,  the  positive  term 


w.  or 


in  the  value  of  Re  in  (84) — viz.,  -kr-' 

At  any  point  distant  x  to  the  left  of  6,  the  shearing  stress  is — 

Si  =  ti;^  (a  -  a;), (85) 

and  the  bending  moment — 

M,»t«x^^-=^ (86) 

These  become  tc^j  a  and  — W— ,  respectively,  at  B. 

At  any  point  distant  x  to  the  right  of  B,  the  shearing  stress  is — 

Sg  =  m;2  (6  -  «)  +  Ro 

=  u;^  (*  -  a?)  +  w'l  |j  -  «^2  2 '        •         •         •     (^7> 
and  the  bending  moment — 


h  -  X 
b  -  X 


tOj  -T-  -  Wgic  I (88) 


At  B,  these  become  w^^  +  ^1  oa  ^^^  "o — >  respectively. 

The  same  equations  necessarily  hold  good  whether  a  closed  cantilever 
bridge  be  supported  at  one  point  by  the  pivot,  or  by  bearing  blocks  located 
nearer  the  edge  of  the  quay,  the  only  difference  being  in  the  respective 
lengths  of  the  two  portions  of  the  bridge.  The  general  practice  is  to  raise 
the  tail  end  of  the  bridge  with  wedges,  screws,  rams,  or  other  contrivances,, 
so  as  to  throw  the  forward  pressure  on  to  bearing  blocks  and  relieve  the 
pivot  and  rollers  of  unnecessary  stress.  In  this  way  the  length  of  the 
overhanging  or  cantilever  portion  of  the  bridge  is  reduced,  and  it  is  even 
possible  that  the  reduction  in  length  of  the  closed  bridge  may  more  than 
compensate  for  the  increased  load  which  it  incurs  in  that  position. 

When  the  bridge  is  swinging  the  pressure  on  the  pivot  is  that  due  to 
the  ordinary  weight  of  the  structure  plus  the  counterpoise,  which,  computed 
to  balance  the  bridge  under  the  condition  of  maximum  load,  generally 
throws  some  excess  of  pressure  upon  the  rollers. 


414 


DOCK  ENGINEERING. 


To  find  the  amount  of  the  respective  pressures  on  the  rollers  and  the 
pivot,  let  P  (fig.  398)  be  the  position  of  the  pivot  and  C  that  of  the  rollers. 


<  — 


-  o  - 


B     P 


b-' 


C 


R. 


/?. 


Fig.  398. 


Then  taking  moments  about  P — 


whence, 


And 


w(a  +  z)^       w(b  -  zy       w^  a*  (6  -  «)       _^ 
2 2~~  ""  26 ^^* 

w  (  (b  -  z)*  -  (a  +  g)«  1    ^  w,  a« 


-«). 


Rp  =  W  +  C  -  Rg, 

where  W  =  m;  (a  +  b)  and  C  =    ^-,-* 


(89) 


26 


Case  III, — An  Arch  (fig,  399). — In  the  preceding  investigation  each 
wing  of  the  closed  bridge  has  been  treated  separately.  If  it  be  desired  to 
take  advantage  of  the  support  afforded  by  the  mutual  abutment  of  the  two 
meeting  faces  of  the  bridge,  it  is  evident  that  the  tail  end  must  be  lifted  in 
order  to  develop  the  full  thrust  due  to  the  dead  weight.  Assuming  (as 
would  essentially  be  the  case)  that  the  underside  of  the  cantilevers  constitute 
a  real  or  virtual  arc  of  rise  r  and  span  2  a,  we  have  by  the  conditions  of 
equilibrium  for  three  forces  and  by  similar  triangles, 


or,  approximately, 


whence, 


T 

a 

W 

2r' 

T 

a 

^E 

«,    > 

wa 

2r 

T 

toa^ 

(90) 


which   gives   us  an   expression  for  the  amount   of    mutual  thrust.      The 

upward  force,  Fc  ,  at  C,  required  to  develop  this  thrust  is  found  by  taking 

moments  about  B — 

T  r  =  F,.  h, 
so  that. 


wa' 


(91) 


h  being  the  distance,  B  C.  This  force,  the  value  of  which  is  identical  with 
that  of  the  counterpoise,  is  additional  to  the  reaction  at  C,  due  to  the  load 
onBC. 


A  CONTINUOUS  BEAM. 


415 


The  pressure  on  the  abutment  B  is 


Rb  =  w  a  J 


1  + 


a 


2 


4r2' 


(92) 


from  which  it  is  apparent  that  it  may  be  considerable  and  that  carefully 
adjusted  and  solid  bearings  are  essential.  It  is  a  matter  of  some  difficulty 
to  secure  these  in  the  case  of  swing  bridges,  and  accordingly  it  is  not  usual 
for  the  central  reaction  to  be  much,  if  at  all,  relied  upon.  In  bascule 
bridges,  on  the  other  hand,  it  is  comparatively  easy  to  provide  accurate 
bearing  surfaces. 

C<ise  IV, — A  contintMus  beam  supported  at  three  points  (fig.  400). — Let 


Fig.  400. 

A  B  C  be  a  girder  continuous  over  three  points  of  support — A,  B,  and  C  all 
on  the  same  level.  Take  the  intermediate  support,  B,  as  the  origin  of 
co-ordinates,  and  let  y  represent  the  deflection  of  the  beam  at  the  point  X 
due  to  a  uniform  load,  t^,  per  unit  length.  Let  S  be  the  shearing  stress  and 
M  the  bending  moment  at  the  same  point. 

By  a  well-known  formula  establishing  the  connection  between  the  bending 
moment  (M)  the  modulus  of  elasticity  (E)  the  moment  of  inertia  (I)  and 
the  radius  of  curvature  (R),  we  have  at  any  point  X — 

EI 

R' 

Now,  when  the  curvature  is  very  small,  as  is  assumed  to  be  the  case  in 

the  foregoing  relationship,  we  may  find  a  very  close  approximation  for  the 

1  .  .  • 

value  of  ^  from  the  principles  of  the  Calculus,  viz. : — 
R 


M 


1^ 
R 


dx^' 


where  x  and  y  are  the  co-ordinates  of  the  deflection  curve.     Hence  we  may 

write — 

d^y 


M  =  -  EI 


dx^' 


Again,  let  us  consider  the  conditions  of  equilibrium  at  the  point  X.  If 
P  be  a  point  indefinitely  near  to  B,  where  the  shearing  stress  is  S^  and  the 
bending  moment  Mj,  it  is  clear  that  for  equilibrium  of  the  portion  P  X,  we 
have — 

.2 


M  =  -  Mj  +  Sj  a  + 


WX' 


(93) 


41 6  DOCK   ENGINEERING. 

Equating  the  two  values  of  M,  we  obtain 

whence,  integrating, 

EI^^  =  C,  +  M,,,-?l^-«'*'.   .        .        .    (94) 
ax         *  *  2  o 

To  find  what  value  to  attach  to  the  constant  (C|)  in  this  expression,  we 
have  the  following  consideration : — Let  fi  be  the  slope  of  the  beam  at  the 
origin,  B — or,  in  other  words,  the  inclination  of  the  tangent  of  the  curve  to 

the  horizontal.     Then  tan  /8  =  -^  and,  in  the  limit,  tan  fi  =  fi.     When  thia 

ax 

is  the  case  x  is  so  small  as  to  become  negligible,  and  so  we  can  write 

C  =  EIiS, 
and,  by  substitution, 

dx  *  ^  2  6 

Integrating  again. 

The  constant  is  omitted  in  this  case  because  y  =  0  when  x  =  0.  Again, 
since  y  =  0  when  a:  =  6,  we  have — 

0  =  EI^  +  M,|-Si|-^.         .        .    (95) 

Now,  at  a  point  Q,  equally  indefinitely  near  to  but  on  the  opposite  side 
of  B,  we  shall  find  the  bending  moment  identical  in  value  with  that  at  the 
point  P.  We  can  therefore  write  a  similar  equation  in  this  case,  noting 
that  a  has  a  negative  value.     Thus — 

a       ^   a^       wa^ 


0  =  E  I  3  -  M,-^  -  So  --  + 


Subtract,  and  for  both  M^  and  M2  write  M^  or  the  bending  moment  at 
the  point  B,  to  which  they  both  approximate  so  closely  as  to  be  practically 
identical  with  it  and  each  other.     Accordingly, 

^»(^)-^S^T-Sx?-£(»"'  +  *'')  =  0.-        •    (96) 
Again,  taking  moments  about  A  for  the  portion  A  B — 

M^  =  Mb  +  S2  a  -  ^  a2 


and,  similarly,  about  C  for  the  portion  B  C — 


w 


Mo  =  Mb  -  Si  6  -  ^  b^. 


2 


A  CONTINUOUS   BEAM.  417 

Multiply  the  first  equation  throughout  by  -  o,  the  second  by  6,  and 
re-arrange — 

Sg  a*  =  -  Mb  a  +  M^  a  -{■  ^  a^ 
Si  62  =      Mb6-Mc6-^68. 


Subtract 

!  -  S_  W  =  -  M_  ^/.  4.  M  J.  M .  /»  -L  M  .  A  4.  . 


S2  a2  -  Si  62  =  -  Mb  (a  +  6)  +  M^  a  +  Mc.  6  +  -^  (a»  +  68). 


Divide  by  6,  and  substitute  in  equation  (96)  above — 

Mb    -2" -Mb     g     +M^-+Mog  +  j2(a3  +  6S) -24(«'  +  ^*)  =  ^» 
which  reduces  to 

M^  a  +  IVIc  6  +  2  Mb  (a  +  6)  +  j  (a»  +  6»)  =  0.  .     (97) 

This  equation  is  known  as  the  Theorem  of  Three  Momenta^  and  its  first 
enunciation  is  attributed  to  Clapeyron.  By  means  of  the  relationship  thus 
established,  if  the  bending  moments  at  two  of  the  points  of  support  of  a 
uniformly  loaded  beam  are  known,  the  third  can  be  deduced.  The  bending 
moments  at  the  end  supports  are  sufficiently  obvious.     If  the  beam  project  a 

distance,  c,  beyond  the  outer  support,  C,  the  moment  at  C  is  -jr-.    If  the  beam 

do  not  project,  the  moment  at  the  point  of  support  is  zero. 

The  shearing  stresses  can  then  be  obtained  from  the  formula  already 
given,  viz.  : — 


Mb      Mc       wh 


g    ^  Mb      M^       wa 
^        a  a  2  ' 

The  shear  at  any  point,  X,  is  Sj  -  to  x.  Accordingly,  at  A  and  C  it  is 
Sa  =  -  S.2  +  w?a  and  S©  =  Sj  -  W7  6  respectively. 

From  these,  the  reactions  at  the  points  of  support  are  readily  forthcoming, 
for  "Rj^  =  S^  and  Re  =  ^c ,  if  there  be  no  overhang.  If  there  be  an  over- 
hanging portion,  as  c  at  C,  "Rq  =  Sq.  +  w  c. 

Also 

R3  =  S, -Si  =  -^  +  -j5-M,(^-^j  +  2(«  +  6).     .    (98) 

Assuming  that  there  is  no  overhang  this  equation  simplifies  into 
T>        «^/        TV   fa^+  3a6  +  62) 

^^s^^^^M — rb — r 

Equation  (98)  may  be  confirmed  by  an  independent  investigation  which 

is  worthy  of  notice,  for  it  gives  an  expression  for  the  current  moment  in 

terms  of  the  moments  at  the  points  of  support. 

27 


4i8 


DOCK  ENGINEERING. 


If  AB  (fig.  401)  be  a  portion  of  a  weightless  beam  between  any  two 
supports,  P  Q,  with  bending  moments,  y,  and  y^  at  A  and  B  respectively, 

due  to  some  external  system  of  loading,  it  is 
clear  that  the  line  of  moments  between  A  and 
B  will  be  right,  and  by  a  simple  application  of 
geometrical  principles 

If,  however,  the   beam    be  not   weightless, 
Fig.  401.  or  be  loaded  with  a  weight  of  w  lbs.  per  foot 

run,  the  curve  of  moments  is  parabolic  and  the  equation  becomes — 


.f 


4       X     B 


I 


w 


y  («i  +  ^2)  =  yi  ^2  +  2/2  «i  +  9  ^1  ^2  («i  +  ^2)- 


.  (100) 


The  foregoing  relationship  is,  of  course,  conditional  upon  there  being  no 
point  of  support  between  A  and  B.  When  such  is  not  the  case,  and  there 
is  an  upward  reaction,  R,  at  the  point,  X,  we  must  expand  the  expression 

still  further  into 

w 

y  (^1  +  ^2)  =  Vi  ^1  +  2^2  »i  +  2  ^  ^2  (^1  +  ^2)  -  R  ^1  ^2-    (101) 

Re-arrange,  and  divide  throughout  by  a?i  ajg, 


•      (102) 


an  equation  which  is  identical  with  the  value  of  Rb  given  above,  when  the 
notation  has  been  adapted  thereto. 

The  second  equation  (100)  in  the  preceding  group  yields  us  an  expres- 
sion for  the  current  bending  moment  at  any  point,  X,  intermediate  between 
the  points  of  support. 

w  h  it 

Mx6  =  Mbo:  +  Mo(6  -  a)  +  '-^{f>  -  «:).       .        (103) 

If  we  revert  to  the  case  in  which  there  are  no  moments  at  the  end 
supports,  we  may  derive  the  amounts  of  reaction  at  these  points  very 
readily,  as  follows  : — 

From  equation  (97)  we  have 

w 


2MB(a  +  6)=    -  ^(a»  +  h% 


or. 


w 


-  Mb  =  ^  (a*  -  a  6  +  6').        .         .         .        (104) 
Also,  from  a  consideration  of  the  conditions  of  equilibrium  to  the  left  of  B, 


Mb  =  R^a  - 


wa 


A   CONTINUOUS   BEAM. 


419 


Combining, 


R*  a  = 


R. 


w 
8a 


(3  a«  +  a  6  -  6»), 


and  a  similar  expression  may  be  written  for  Re- 

In  the  preceding  investigation,  for  the  sake  of  simplicity,  it  has  been 
assumed  that  the  three  points  of  support  are  on  a  level.  If  this  is  not  so, 
and  the  supports,  A  and  C,  are  respectively  heights  of  y^  and  yg  above  B 
(the  heights  being  small),  it  is  not  difficult  to  establish,  in  the  same  manner, 
that 

M^a  +  Mc6  +  2MB(a  +  b)  +  |(a»  +  0*)  =  6EI  (^  +  ^).      (105) 

And  it  is  also  clear  that,  if  the  lengths  a  and  b  be  subjected  to  different 
loads,  as  w^  and  Wg  per  foot  run  respectively,  the  equation  will  then 
become 


M. 


a  ^  Me6  -^  2Mb(«  -H  6)  4-  ^  -,  1^^'  =  6  EI  (^  -.  'f). 


It  would  take  too  long,  and  it  is  unnecessary,  to  elaborate  the  formulsB 
for  these  cases  in  detail.  The  preceding  method  may  be  followed,  and  it 
will  be  found  that  where  a  level  girder,  without  overhangs,  is  subjected  to 
different  intensities  of  load  upon  its  two  sections,  the  reactions  are  given  by 


8" 


(106) 


Ra  a  (a  4-  6)  =  «?!  a^  ^_^  +  ^J  -  t 

Re  6  (a  +  ^)  =  w,  b'  (?g^  +  I)  -  w,^.     .         .     (107) 

Rb  =  w?!  a  +  tt?2*  -  (Ra  +  Re).  .         •     (108) 

We  now  come  to  the  question  of  counterpoise.  No  notice  has  hitherto 
been  taken  of  the  effect  exercised  by  the  ballast  at  the  tail  end  of  the  bridge, 
because  it  is  much  more  convenient  to  consider  this  question  separately  from 
that  of  the  uniform  load  of  the  structure  generally,  and  afterwards  to  com- 
bine the  results  obtained  in  the  two  investigations. 

To  arrive  at  the  stresses  due  to  a  sectional  load,  we  must  first  consider 
those  due  to  a  concentrated  load.     As  before,  let  ABC  (fig.  402)  be  a 


6 "' 

Fig.  402. 

girder  continuous  over  three  points  of  support,  A,  B,  and  C,  and  let  Wj  and 
W2  be  concentrated  loads  at  distances,  dj  and  (igj  from  the  central  support. 


420  DOCK   ENGINEERING. 

Take  any  point,  P,  between  B  and  W,  at  a  distance,  a;,  from  B,  the 
origin  of  oo-ordinates. 

Then,  as  already  established,  for  the  equilibrium  of  the  portion  B  P, 


Integrate 


EI^?^  =  C  +  Mb;p-SiJ 

dx  *■  2 


and  as  -~-  =  tan  )8  when  x  is  indefinitely  small,  so  in  the  limit, 

U  X 

C  =  EI/3, 
and 

EI^  =  EI/3  +  MBa;-S  •^'.         .        .    (109) 
dx  '2 

Integrating  again, 

EIy  =  EI)8«  +  MBj-SiJ.      .        .     (110) 

There  is  no  constant,  since  x  and  y  vanish  together. 

These  equations  hold  good  for  all  values  of  x  between  x  =  0  and  x  ^  dy. 
Next,  let  the  point,  P,  lie  between  W^  and  C,  and  remove  the  origin  of 
co-ordinates  to  C.     Then 

d^ 
da^ 


E I  ^  =  -  Sc  ic. 


Integrating  and  determining  the  constant  as  before, 

EI^=  Ela- Sc^",      ....     (Ill) 
dx  2  ^       ' 

and  again, 

Ely  =  Elaaj-  Scf (112) 

6 

Now,  these  two   pairs   of  equations,    though   possessing  different  co- 
ordinates, have  two  conditions  in  common,  viz. : — 

(1)  At  the  point,  W^,  the  value  for  y  must  be  the  same  in  each  case. 

(2)  At  the  same  point  the  slope  or  gradient  is  the  same,  but  measured  in 
opposite  directions — i.e., 


\d  x/^      \dxJ2 


Hence,  substituting  di  for  x  in  equation  (110)  and  (b  -  d^)  for  x  in  equation 
(112),  we  deduce  from  the  first  condition, 

EI)8rfi+  MB'^^'-S,^=EIa(6-rfi)-Sc^^-^^'.    .     (113) 

Also,  substituting  likewise  in  equations   (109)  and  (111),  and  using  the^ 
second  relation, 

Ela  +  MB^i -Si?^i%-  EIa-Sc^-*-"^  =  0.         .    (lU) 


A  CONTINUOUS  BEAM.  42 1 

Next,  let  us  consider  the  span,  5,  as  a  whole,  and  take  moments  about 
the  points  B  and  C  respectively.     In  the  first  case,  we  have 

Soft- Wc^i  +  Mb  -  0, (115) 

and  in  the  second, 

S16  -  W(6  -  cfi)  -  Mb  =  0 (116) 

Substitute  the  values  for  S^  and  So  given  by  these  equations  in  (113) 
and  (114),  re-arranging  as  below — 

El[0d^-a(b  -  c/j)]  =Mb^(6-3c;i)- W^(6-(ii)(6-2(/i). 
EI(/J  +  a)  = -MbJ  + W^(6-rfi).  .     (117) 

Multiply  the  latter  equation  by  (b  -  d^)  and  eliminate  a  by  addition — 

EI)86=-Mb^'+ W^(6-rfi)(26-rfi).     .    (118) 

Now,  let  us  deal  in  a  similar  manner  with  the  span,  a,  to  the  left  of  the 
point,  B.  It  is  only  necessary  to  re-write  the  previous  equation,  making  the 
requisite  changes  in  sign — 

-  EIi3a=  -  Ms  J  +  W'h(a-d^)(2a-'d^),      (119) 

Whence,  eliminating  fi  between  the  two  equations,  we  get 

M,^ 1       f^rd,(b-d,){2b^d,)     W,d,(a-d,)(2a^d^\     .^gO) 

^       2(a  +  b)\  b  a  r  ^       ^ 

an  expression  which  furnishes  us  with  the  value  of  the  bending  moment  at 
the  intermediate  support,  B,  The  bending  moment  at  each  end  is,  of 
course,  zero. 

It  is  sufficiently  obvious  that,  when  there  is  a  load  on  only  one  of  the 
spans  (as  W^  on  the  span,  b)  the  bending  moment  at  the  intermediate 
support  is  given  by 

^B=,,^         Jw.li^^-^y^'^i)},      ....     (121) 
2  (a  +  6)  I      *  b  ) 

and  that,  for  any  system  of  concentrated  loads  on  a  single  span,  the 
general  equation  may  be  written — 

^'  °  26(i+  6)^^^*^^^  -  rf)(26  -  d)) (122) 

The  reactions  at  the  point  of  supports  will  be  easily  determined  from  a 
consideration  of  the  conditions  of  equilibrium  in  each  span.  Assuming  one 
span  to  be  loaded  as  above — 

Mb  =  —  Ra***    ....••.■••     (l2o) 
Mb  =  Reft- SWc^. (124) 


422 


DOCK  ENGINEERING. 


Substituting  these  values  for  Mb  in  (122),  we  find — 

R^=  1_      2{W<f(6-(/)(26-rf)}.         .        .        .     (125) 

2ao{a  +  b) 

I^=__i_^^  .        .     (126) 

Rb  =  2W-(Ra  + R«) (127) 

Having  obtained  the  equations  corresponding  to  a  concentrated  load,  we 
now  proceed  a  step  further  to  obtain  an  expression  for  the  bending  moment 
due  to  a  uniform  load,  w,  of  length,  /,  less  than  one  span,  b  (see  fig.  403). 


Fig.  403. 

The  weight  on  an  infinitesimal  length,  cfa;,  at  a  distance,  x,  from  Bis  w  ,dxy. 
and,  taking  the  sum  between  the  limits,  x  =  {b-l)  and  a;  =  6, 

Vr  26(a  +  6)  86(o  +  6)  •     V^  °/ 

The  reactions  at  the  points  of  support  will  therefore  be — 

R.  =  -  «;^2  _?^-lZ_ /129) 

^  8a6(a  +  6)  ^     ^ 

T)            //  1       ^(6^^  +  4a6  -  l^)  I  ,,«^v 

R,  =  ../jl.  J  ______  ^^ (13^) 

Rb  =  «;/ -  (Ra  +  R«) (131) 

These  results  afford  us  all  the  data  for  dealing  not  only  with  the  stresses 
due  to  the  counterpoise,  but  also  with  those  due  to  a  moving  load  covering 
the  span  to  any  desired  extent.  Having  taken  in  detail  the  dead  load,  the 
counterpoise,  and  the  moving  load,  it  is  only  necessary  to  compute  their 
algebraical  sum  in  order  to  find  the  stresses  due  to  the  combined  systems. 

It  would  be  possible  to  pursue  the  subject  much  further,  but  we  have 
now  reached  the  boundary  which  divides  movable  bridges  from  stationary 
bridges.  The  remaining  calculations  are  common  to  both  forms  of  structure, 
and  the  student  is  accordingly  referred,  for  further  information,  to  treatises 
dealing  with  the  latter  subject,  in  a  more  complete  and  efficient  manner  than 
is  possible  within  the  limits  of  the  present  volume. 

Loads  imposed  on  Movable  Bridges. — Before  designing  the  framework  of 
a  movable  bridge,  and  in  order  that  the  stresses  in  the  proposed  members 
may  be  calculated,  an  estimate  has  to  be  made  of  the  loads  which  the  bridge 
will  be  called  upon  to  bear.     These  loads  may  be  classified  as  follows : — 

1.  Dead   Load,  —  («)  Weight  of  main  girders  and  bracing. 

(/8  )  Weight  of  roadway  or  railway. 

2.  Moving  Load, — (y)  Weight  of  trains,  vehicles,  &c. 


DEAD  LOAD.  423 

Dectd  Load. — ^The  weight  of  the  main  framework  can  be  calculated  in 
detail  from  the  following  data : — ^The  weights  of  a  square  foot  of  cast  iron, 
wrought  iron,  and  steel,  1  inch  in  thickness,  are  37*5,  40,  and  40*8  lbs. 
respectively.  But  the  process  would  necessitate  a  design  too  detailed  for 
merely  tentative  purposes,  and  the  calculations  would  be  too  lengthy  for  a 
preliminary  estimate.  A  sufficiently  accurate  approximation,  for  practical 
purposes,  can  be  obtained  by  the  use  of  some  empirical  formula,  based  on 
existing  examples.     Trautwine  *  gives  the  following : — 

For  lengths  not  exceeding  75  feet,  the  weight  in  lbs.  per  foot  run  of  two 
trusses  or  main  girders,  with  lateral  bracing  for  a  single  track, 


W  =  *5  X  span  in  feet  +  60  J  span  in  feet. 
For  spans  between  75  and  250  feet. 


W  =  4*5  X  span  in  feet  +  22  ^  span  in  feet. 

For  double-track  bridges,  add  80  per  cent,  to  the  above  values,  and  for 
narrow-gauge  tracks,  take  75  per  cent,  of  the  standard  (4  feet  8^  inches) 
gauge. 

The  foregoing  formulsB  do  not  include  any  provision  for  the  weight  of 
cross  girders,  flooring,  or  rails. 

The  weight  per  foot  run  of  iron  floor  systems,  comprising  a  longitudinal 
stringer  under  each  rail,  is  given  by  the  same  authority,  as  follows  : — 

Span.  Single  Track.  Double  Track. 

20  to  100  feet.  200  to  275  lbs.  550  to  700  lbs. 

100  „  250    „  250  „  350    „  700  „  800   „ 

Exclusive  of  the  main  girders  of  a  bridge,  the  dead  load,  consisting  of 
iron  or  timber  flooring  slightly  covered  with  ballast,  the  permanent  way, 
cross  girders  with  gusset  attachments  to  main  girders,  and  the  horizontal 
bracing,  of  a  double  line  of  railway  carried  upon  two  main  girders,  may  be 
estimated,  according  to  Sir  Benjamin  Baker,  as  follows  ; — 

10  to  100  feet  span,        ....         14  cwts. 
100  „  150    „        „  ....         15    „ 

150  „  200    „        „  ....         16    „ 

Where  the  two  lines  of  railway  are  supported  upon  three  main  girders, 
the  above  loads  may  be  reduced  by  2  cwts.  per  foot,  and  where  upon  four 
girders,  by  4  cwts.  per  foot.t 

"The  weight  of  the  cross  girders  and  bracing  for  a  railway  bridge,  to 
carry  two  lines  of  railway  between  main  girders,  may  be  taken  on  an  aver- 
age to  vary  from  6*7  cwts.  for  a  20-foot  span  to  9  cwts.  for  a  275-foot  span ; 
but  it  will  be  understood  that  considerable  modification  in  these  weights, 
both  of  a  plus  and  minus  nature,  may  be  effected  by  a  variation  in  the 
depth  or  arrangement  of  the  cross  girders."  J 

*  The  Civil  Engineer's  Pocket  Book,  17th  ed.,  p.  604. 

t  Baker  on  "  Short  Span  Railway  Bridges."  t  I^id, 


424 


DOCK  ENGINEERING. 


The  following  tabular  values  for  the  weight,  in  cwts.  per  foot  run,  of 
the  main  girders  and  of  the  entire  bridge  are  condensed  from  an  extensive 
compilation  of  data,  from  existing  railway  bridges,  by  Sir  Benjamin  Baker. "^ 


TABLE  XXXII. 


Flats  Oirdebs. 

Lattice  Giri>rrs. 

Two  Kaln  Oirders 

Two  l£ain  Girders 

Four  Midu  Girders 

Two  Main  Girders 

Three  Main  Girders 

with 

with 

under  Kails 

with 

with 

Feet 

Lower 

Upper 

without 

Lower 

Lower 

CroM  Girders. 

Cross  Girders. 

Cross  Girders. 

Cross  Girders. 

Cross  Girders. 

Main 
Girders. 

Total 
Iron- 
work. 

Main 
Girders. 

Total 
Iron- 
work. 

llafn 
Girders. 

Total 
Iron- 
work. 

Main 
Girders. 

Total 
Iron- 
work. 

Main 
Girders. 

Total 
Iron* 
work. 

Cwtfc 

Cwts. 

Cwts. 

Cwts. 

Cwts. 

Cwts. 

Cwts. 

Cwts. 

Cwts. 

Cwts. 

20 

3-4 

10*1 

3*4 

8-2 

4*7 

6*2 

3  1 

9*8 

3*7 

8*3 

25 

3*9 

10*6 

3*9 

8*7 

6*6 

7*1 

3*6 

10*3 

4*2 

8*9 

30 

4*4 

11*1 

4*4 

9*2 

6*2 

7*8 

41 

10*8 

4*7 

9*4 

35 

60 

11*8 

6*0 

9*9 

7*0 

8*6 

4*6 

11*3 

6-3 

10*0 

40 

6-6 

12-3 

6*6 

10*4 

7*8 

9*5 

5*0 

11*8 

6*8 

10*6 

45 

61 

12*9 

61 

11-0 

8*6 

10*3 

5*4 

12*2 

6-3 

111 

60 

6-6 

13*6 

6-6 

11*6 

9*3 

111 

6*9 

12*8 

6-9 

11-8 

60 

VI 

14*7 

7*7 

12*8 

11*0 

12*8 

6*8 

13*8 

7*9 

12*8 

70 

8*8 

16*9 

8*8 

14*0 

12*4 

14*3. 

7*7 

14*8 

90 

14*0 

80 

9*9 

17-2 

9*9 

161 

14*1 

16*0 

8*6 

.15*8 

10-1 

151 

90 

11*0 

18*3 

11*0 

16*3 

16*8 

17*8 

9*5 

16-8 

111 

16*2 

100 

121 

19-5 

121 

17*6 

17*7 

19*8 

10*4 

17*8 

12*2 

17*4 

120 

14*3 

21*9 

14*3 

19*8 

•  ■  • 

•  •  • 

12*2 

19*8 

•  ■  • 

•  •  • 

140 

16*6 

24-3 

16-5 

221 

■  •  • 

•  •  • 

140 

21*8 

•  •  • 

•  «• 

160 

18*7 

26-7 

18*7 

24*4 

•  ■  • 

•  •  t 

15*9 

23*9 

•  ■  • 

•  •  • 

180 

20*9 

291 

20-9 

26-8 

■  •  • 

•  •  • 

17*7 

25*9 

•  %  m 

«  ■  • 

200 

23*1 

31*6 

23  1 

29*1 

•  •  • 

•  ■  • 

19*5 

27*9 

... 

•  •• 

The  preceding  formulae  and  data  are  only  relatively  applicable  to 
movable  bridges  under  certain  modifications  and  restrictions.  The  structure 
of  a  swing  bridge  has  necessarily  to  be  more  substantial  than  that  of  a  fixed 
bridge  for  the  same  span,  on  account  of  the  more  exacting  nature  of  its 
functions  and  also  because  it  has  to  be  provided  with  a  heavy  pivot  girder 
with  other  fittings.  From  a  comparison  of  the  lengths  and  weights  of  a 
number  of  existing  bridges,  the  writer  has  found  the  total  structural  weight 
per  foot  run  (exclusive  of  counterpoise)  to  range,  generally  speaking,  from 
about  1  ton  for  small  spans  to  2  tons  for  large  spans ;  there  being,  of 
course,  instances  in  which  these  limits  are  not  maintained.  For  moderate 
spans,  say  openings  of  from  50  to  125  feet,  the  dead  load  might  fairly  be 
estimated  at  30  cwts.  per  foot  run  of  the  extreme  length  of  the  bridge, 
allowing  for  the  accommodation  of  a  double  railroad  track  and  a  double 
footway. 

Live  Load. — While  in  a  long  bridge  the  weight  of  the  locomotive  and  its 
tender  may  form  a  comparatively  small  proportion  of  the  loaded  length 

•  Baker  on  "  Short  Span  Railway  Bridges." 


UVE  LOAD. 


425 


due  to  a  long  train,  in  a  swing  bridge,  the  span  of  which  is  small,  the 
contingency  of  a  continuous  line  of  engines  upon  the  bridge  should  be 
provided  for. 

The  following  table  gives  a  statement  of  the  weight  of  some  recent 
locomotives  and  their  tenders  : — 


TABLE  XXXIII. — Weight  op  Modern  Locomotives.* 


Name  of  Ballway. 


Midland,' 

London  and  North- 
Western,' 

Lancashire  and  York- 
shire,' . 

NorLh-Eastem,' 

Great  Western,' 

Belgian  State,' 
Prussian  State,^ 
Swedish  State,' 
Union  Pacific,  U.S  A-,'** 
Chicago  and  North- 
western, U.S.A.,2 

Pennsylvania, 


}> 


Passenger  engine 
Goods  engine, 
Tank  engine. 
Passenger  engine 
Goods  engine, 
Tank  engine, 
Passenger  engine 
Goods  engine, 
Tank  engine, 
Passenger  engine 
Goods  engine. 
Tank  engine. 
Passenger  engine. 
Goods  engine. 
Tank  engine. 
Passenger  engine. 
Goods  engine. 
Tank  engine. 
Passenger  engine 


Passenger  engine 
and  tender, 


Length 

Wheel 

Total 

Over  All. 

Baae. 

Weight. 

Feet 

Feet. 

Tons. 

63-2 

441 

85-48 

497 

37  0 

76-46 

33-4 

220 

51-02 

61-7 

44-0 

80-50 

51-8 

39*8 

75-85 

33-7 

22-4 

52-30 

50-0 

40-9 

70-92 

48-7 

36-0 

68-25 

38-7 

24-3 

59  15 

56-5 

46*5 

91-90 

601 

47-9 

75-65 

36-9 

22-5 

55-22 

67-5 

47-6 

84-65 

67-9 

48-9 

93-00 

30*4 

15-5 

47-00 

67-3 

490 

104-21 

32-6 

«  ■  • 

56-40 

•  •  ■ 

130 

57-00 

« ■  • 

260 

82-25 

•  •  • 

27  0 

7150 

}... 

47-5 

77-25 

Weight 
per  Foot 

Rail 
Over  All. 


Tons. 
1-61 
1-54 
1-58 
1-56 
46 
56 
40 
1-40 
1-53 
1-62 
1-51 
1-54 
1-47 
1-61 
1-55 
1-82 
1-73 


1 
1 
1 


Weiffht 

per  Foot 

Run  of 

Wheel 

Baae. 


Tons. 
1-95 
2-03 
2-32 
1-83 
1-91 
2-35 
1-72 
1-90 
2-43 
1-97 
2  00 
2-45 
1-78 
1-91 
303 
2-12 

4-40 
3-16' 

2-65 
1-63 


From  the  preceding  table  it  will  be  seen  that  the  ordinary  concentrated 
rolling  load  incurred  by  bridges  in  the  United  Kingdom  at  the  present  time 
may  be  taken  at  from  30  to  35  cwts.  per  foot  run  for  each  line  of  rails.  In 
view  of  the  likelihood  of  heavier  developments,  however,  in  the  future, 
2  tons  or  even  2J  tons  would  be  by  no  means  an  excessive  allowance. 
Even  these  figures  are  exceeded  in  certain  cases,  as  is  evident  from  a  table  f 
prepared  by  Mr.  Alexander  Ross,  the  engineer  to  the  Great  Northern 
Railway  Co.,  of  which  an  abridgement  is  given  below.  The  table  shows 
the  equivalent  uniformly  distributed  live  loads  derived  from  the  maximum 

*  Note. — These  statistics  are  derived  from  the  following  sources  : — 
^  Fair  on  "  Moving  Loads  on  Railway  Underbridges,"  Min.  Proc,  Irist,  C.J?.,  voL  cxli. 
^  Leigh  on  "  American  Passenger  Locomotives,"  Min,  Proc.  Inst,  C.E.y  vol.  cxlvi. 
'  Trautwine's  Civil  Engineers^  Pocket-Booh, 

^  Von  Borries  on  "Prussian  State  Railways,"  Min.  Proc.  Inst,  C.E.,  vol.  cxxii. 
*  Teknish  Tedskrijt,  Stockholm,  Oct.  31, 1901,  and  Min.  Proc.  Inst.  C.E.,  vol.  cxliv.,  p.  340. 

t  Ross,  on  **  Railway  Bridges,"  Eng.  Conf.,  1903,  vide  Engineerijtg,  June  19,  1903. 


426 


DOCK  ENGINEERING. 


bending  moment  caused  by  representative  heavy  engines  running  on  British 
railways,  with  an  addition  of  2 J  per  cent,  for  possible  future  increase. 


TABLE  XXXIV. — Equivalent  Distributed  Live  Loads  Derived  from 
Maximum  Bending  Moments  for  a  Single  Line  of  Way. 


Feet. 

Srlkctbd  Engines 

» 

1 

1 

Single  Driver. 

4-A\lieel  Coupled. 

6-Wheel  Coupled. 
Ton*         Tons 

8- Wheel  Coupled. 

10- Wheel  ( 

[Coupled. 
Tons 

Tons 

Tons 

Toufl 

Tons 

Tons     ■ 

Tons 

Tons 

Distri- 

per Ft. 

Distri- 

per Ft. 

Distri- 

per Ft. 

Distri- 

pern. 

DUtri- 

per  Ft. 

10 

buted. 

Run. 

buted. 

Run. 

buted. 

Run. 

buted. 

Run. 

buted. 

Run. 

36-9 

3-69 

36-9 

3-69 

36*9 

3*69 

34*6 

3-46 

39*9    ' 

3*99 

15 

381 

2-54 

46-6 

3*11 

48-8 

3*25 

50-28 

3*35 

56*8    i 

3  72 

20 

44-0 

2  20 

57-6 

2*88 

56-2 

2*81 

63-5 

3*18 

68*9   , 

3-44 

25 

51-5 

2  06 

65-4 

2-61 

66*3 

2*65 

73-8 

2*95 

83*7 

3*36 

30 

61-2 

204 

73-6 

2*45 

74-7 

2*49 

83*2 

2*77 

98*5 

3*28 

35 

711 

2-03 

82-6 

2*36 

84  0 

2*40 

91-4 

2*61 

106*9   , 

3*06 

40 

80-4 

2-01 

89*0 

2*22 

92*4 

2*31 

98-8 

2*47 

115*3 

2*88 

45 

90  0 

2-00 

95-6 

2*12 

99-0 

2*20 

105-6 

2*34 

120*2 

2*67 

50 

990 

1-98 

105-3 

210 

104*0 

2*08 

112-3 

2*24 

125*0 

2*50 

60 

116  0 

1-93 

124-8 

2-08 

117*6 

1*96 

126*0 

2*10 

136*3 

2-27 

70 

135-3 

1-93 

142-8 

2  04 

132*3 

1*89 

140-5 

2-01 

168-9 

2*27 

80 

152-7 

1-91 

160-4 

2-00 

150*4 

1*88 

159*2 

1*99 

180-8 

2*26 

90 

1720 

191 

176-4 

1-96 

168*3 

1*87 

176*4 

1*96 

202-5 

2*25 

100 

188-6 

1-88 

193-3 

1-93 

186*0 

1*86 

192*0 

1*92 

223*7 

2-24 

125 

233-8 

1-87 

240-0 

1*92 

232*5 

1-86 

240-0 

1*92 

278-7 

2-23 

150 

277-5 

1-85 

288  0 

1-92 

279-0 

1-86 

286-5 

1-91 

333-0 

2*22 

175 

316-8 

1-81 

336*0 

1*92 

325*6 

1-86 

332-5 

1*90 

385*0 

2*20 

200 

352-3 

1-76 

383*2 

1*92 

370-0 

1-85 

378  0 

1*89 

436*3 

2*18 

For  cartways  and  vehicular  tracks,  a  rolling  load  of  10  to  15  cwts.  per 
foot  run  should  be  a  sufficient  estimate  in  ordinary  cases.  Special  vehicles 
may,  however,  carry  loads  equivalent  to  a  ton  per  foot  run.  Floats  or 
lorries  for  heavy  goods  vary  in  size  between  about  14  feet  9  inches  by  6  feet 
9  inches  to  17  feet  6  inches  by  7  feet  6  inches.  The  former  generally  carry 
loads  up  to  7  or  8  tons  and  the  latter  up  to  1 0  or  1 1  tons,  though  1 2,  and 
even  15,  tons  maybe  reached  under  certain  circumstances.  Traction  engines 
will  exert  a  pressure  of  300  to  600  lbs.  per  square  foot  over  the  area  of  their 
wheel-bases. 

The  weight  of  a  crowd  of  men  is  generally  taken  at  80  to  84  lbs.  per 
scjuare  foot.  Dr.  Stoney  records  an  experiment  in  which  he  succeeded  in 
packing  a  number  of  labourers  in  an  enclosure,  so  closely  as  to  produce  a 
pressure  of  147  lbs.  per  square  foot.  It  would  not  be  injudicious,  therefore, 
to  assume  100  lbs.,  or  even  1  cwt.,  as  the  possible  amount  of  concentrated 
load  upon  footways. 

Practical  Application. — By  way  of  illustration  of  the  theoretical  methods 
involved  in  designing  a  movable  bridge,  an  outline  of  the  calculations  for 
finding  the  reactions  at  the  points  of  support  in  a  specific  instance  is  appended. 


PRACTICAL  APPLICATION. 


427 


Fig.  404  is  the  skeleton  diagram  of  a  swing  bridge  over  a  passage  100  feet 
wide.  P  is  the  position  of  the  pivot  upon  which  the  bridge  turns,  and 
A,  B,  and  C  are  the  blocks  which  support  the  bridge  in  the  closed  position. 
Their  respective  distances  apart  are  shown  in  the  figure. 

It  is,  first  of  all,  necessary  to  assume  a  value  for  the  anticipated  dead  and 
live  loads.  Let  us  take  the  former  at  30  cwts.  and  the  latter  at  70  cwts.  per 
foot  run. 


7 


B 


=T 


^---50' A  !> 100'-- 

^ 7/'  -  -J ^ 104'  -  •  - 

U- 1 4--     /75' 

I  '  ' 

"* Span  b ^ Span  a  - 

Fig.  404. 


-d 


1.  To  find  the  amotmt  of  baUast  required. — Suppose  the  ballast  box  to 
occupy  a  length  of  16  feet  at  the  tail-end  of  the  bridge.  Then  the  centre  of 
gravity  of  the  counterpoise  will  be  42  feet  from  the  pivot,  and,  by  taking 
moments  about  P, 

42  B  +  50  X  IJ  X  4r=  125  X  1|  X  -. 

,\     B  =  234  tons, 

where  B  is  the  quantity  in  tons  of  ballast  required, 
stability  it  will  be  as  well  to  say  250  tons. 

2.  To  find  the  pivot  reaction — 

Bridge  structure,  175  x  H, 

Ballast, 


To  afford  a  marginJ^of 


=  262|  tons. 
=  250"^ 


Rp  =  512^ 


» 


» 


3.  To  find  tlie  reactions  of  the  bearing  blocks, — It  will  be  convenient  to 
consider  the  dead  and  live  loads  in  combinations,  adding  the  ballast  later. 
This  admits  of  the  taking  of  four  cases  to  cover  the  principal  dispositions  of 
the  load : — 

Case  /. — Dead  load  throughout. 

Case  II. — Dead  load  on  span  a ;  dead  plus  live  load  on  span  b. 
Case  III. — Dead  plus  live  load  on  span  a ;  dead  load  on  span  b. 
Case  IV. — Live  load  throughout. 

For  the  purpose  in  view  it  is  only  necessary  to  deal  with  one  of  these 
cases.     Accordingly,  we  will  select  Case  II.  as  typical  of  the  group. 
From  formula  (106) — 

■D        /        j.\  o  /3  a      6\  b^ 

R^  a  (a  4-  6)  =  w^  a-  ^—  +  2/       ^2  g^ 


R^  (104  X  175)  =  1|  X  1042  ^-^- 
R^  =    54*1  tons. 


3  X  104       71\       ^7P 

8— ■♦■yj-^T 


428  DOCK  ENGINEERING. 

Similarly,  from  (107),  Re  =  142-4  tons, 
and,  by  residue,  Rg  =  314*5     „ 

Now  take  the  ballast.     From  formulas  (129),  (130)— 

Tj  »     26^  -  ^»  _.     _  /      2  X  71»  -  W      \ 

R^  =   -    WP^ =-; ri    =  -    250  X  16    Is — TT-r --^  ) 

^  Sab  (a  •\-  b)  \8  X  71  X  104  X  175/ 

=  -  3-7  tons ; 

and,  by  residue, 

Rb  =  37-7  tons. 
Hence,  the  nett  reactions  for  the  whole  bridge  under  the  conditions 

stated  are — 

R^  =    54-1  -      3-7  =    60-4  tons. 

Rb  =  314-5  +    37-7  =  3522    „ 

Re  =  142-4  +  2160  =  358-4    „ 

7610    „ 

The  sum  is  the  total  weight  of  bridge  structure,  imposed  load,  and  ballast. 

Having  determined  the  reactions  at  the  points  of  support  by  calculation 
as  above,  it  will  be  found  most  convenient  to  obtain  the  bending  moment 
and  shearing  stress  throughout  the  bridge  by  graphical  methods.  The 
diagrams  admit  of  superposition,  from  which  the  points  of  maximum  stress 
may  be  determined  under  any  variation  of  loading.  At  this  stage,  however, 
the  procedure  is  common  to  bridge  design  generally  and  need  not  be  fui-ther 
investigated. 

Distinctiye  Features  of  Movable  Bridges. — The  following  essential  and 
distinctive  features  of  swing  bridges  claim  some  brief  attention : — 

7'he  Pivot, — There  are  two  main  systems,  or  methods,  in  which  a  swing 
bridge  is  united  with  the  pivot  upon  which  it  revolves — viz.,  the  method  of 
suspension  and  the  method  of  superposition.  In  the  latter  instance,  the 
body  of  the  bridge  rests  directly  upon  the  pivot  in  a  manner  analogous  to 
the  ordinary  balancing  of  a  bar  upon  any  vertical.  In  the  former  system, 
the  bridge  structure  is  suspended  from  the  pivot  by  means  of  stout  bolts, 
which  pass  up  from  the  underside  of  the  pivot  girders  to  the  extremities  of 
a  crosshead,  or  saddle-piece,  carried  by  the  pivot. 

The  structure  of  the  pivot  itself  follows  an  almost  numberless  variety 
of  individual  designs,  dependent  on  one  or  other  of  the  two  principles 
adopted.     We  will  accord  a  passing  notice  to  a  few  typical  cases. 

(a)  A  long,  narrow  pivot  passing  through  the  bridge,  nearly  to  the 
surface  of  the  roadway,  as  at  Velsen  (fig.  405).  Such  a  pivot  requires  a 
firm   and   unyielding  foundation,   for  any  inequality  of   settlement   will 


BRIDGE  PIVOT  AT  VEL8EN.  429 

materially  interfere  with  the  working  of  the  bridge.  Further,  owing  to 
ita  slender  proportions,  it  is  very  liable  to  fracture  from  shocks  or  impact 
due  to  abrupt  stoppages  and  passing  vessels.  Accordingly,  it  must  be  well 
protected.  The  advantage  of  the  design  lies  in  the  fact  that  a  high  pivot 
identifies  the  point  of  support  more  nearly  with  the  centre  of  gravity  of  the 
bridge,  or  even  places  the  support  above  it,  and  so  conduces  to  steodinesa 


'^.L.Z t £ i 1 1 i Z f       t  .    f"^ 

Fig.  406.— Bridge  Pivot  at  Volaen. 
of  movement  and  absence  of  surging.  This  type  of  pjvot  can,  of  course, 
only  be  adopted  when  the  plane  of  the  roadway  is  some  distance  above  the 
lower  flanges  of  the  bridge  girders.  Sometimes  the  conical  form  of  the 
pivot  is  more  accentuated,  as  in  fig.  406,  which  is  the  pivot  of  a  bridge  at 
Botterdanl.  A  is  the  socket  on  which  the  pivot  rests  after  passing  through 
the  cast-iron  bearing  girder,  B. 


DOCK  ENGINEERING. 


(6)  A  abort,  stout  pivot  with  a  hemispherical  head,  as  in  flg.  407,  taken 
from  a  bridge  at  Liverpool.    This  type  naturally  offers  great  resistance  to 


Fig.  406.— Bridge  Pivot  at  RotterdsDi. 


Fig.  407.— Bridfje  Pivot. 


Fig.  408.'-Baritai)  Bridge  Pivot, 
pi-essure  and  concussions,  and  affords  a  broad  base  for  the  distribution  of 
stress.  It  allows  of  ihs  bridge  tilting  slightly,  but 
any  decided  movement  in  this  direction  may  be 
checked  by  a  ring  of  rollers,  or  by  wheels  at  suitable 
points.  In  some  instances  a  more  pointed  bearing 
surface  will  be  found,  as  in  fig.  408,  showing  the 
arrangement  in  the  Baritan  bridge.  The  rollers 
are  here  called  upon  to  exercise  considerable  steadying 
effort, 

(c)  A  long,  cylindrical  pivot  with  a  concave 
Fig.  409.  Bridge  Pivot.  seating  or  bearing— strictiy  speaking,  a  socket-as 
in   fig,  409,  exemplified    in   several    forms.      In  one  case,    at   Hawarden 


BRIDGE  PIVOT  AT  HAWARDEN.  ^ 

(figs.  410  and  411),  the  method  of  suapeosioii  has  been  adopted,  but  i 
kindred      example      at  ciiaMHMD 

Liverpool  (figs.  412  and  l.  _.  «.m~    ^ 

413)    the    bridge    waa  ^T^^" 

superimposed.      Tilting  f       Jf-         ^" 

is  very  possible,  and 
there  is  even  a  ten- 
dency to  disturb  the 
bridge  to  a  dangerous 
extent  in  the  absence 
of  proper  precautions. 
A  bridge  of  this  de- 
scription was  invaded 
one  dinner  hour,  by  a 
dense  crowd  of  im- 
patient working  men 
before  it  had  ceased 
swinging,  with  the  re- 
-sult  that  it  canted  over 
forward,  and  a  disaster 
was  only  averted  by 
the  nose -end  coming 
into  contact  with,  and 
resting  upon,  the  pas- 
sage gates.    Consequent 

upon    this  mishap,  the  '       j  ' 

intermediate     bearing  ' 

blocks  were  made  con-  ■ 

tinuoua  throughout  the 
arc  of  travel,  so  that 
excessive  tilting  at  any 
stage  of  the  rotation 
was  rendered  impos 
sible    on     any     future 


(d)  A  dwarf,  cyhn 
•Jrical  pivot,  also  with 
a  concave  seat,  as  at 
the  Fleetwood  bridge 
(figs.  414  and  415). 
Any  overturning  lever- 
age exerted  upon  the 
support  is  reduced  to  a 
minimum,  but  the 
steadiness  of  the  bridge  i 


1 

•^[^ 

T  TPTT  T 

Jliajl 

u 

J   J 

FigB.  410  and  411.— Bridge  Pivot  at  Hawardon. 
thereby  lessened.     A  peculiar  feature  about  the 


432 


DOCK  EKGIKGERING. 


^^^^^^^^^^^^^^^^^^ 


o 


, 

o  o  o  o  O  <  I 

O    <>^  <tri:a)    O   O   O/r. 

O  O   O  O  ,  I  I 

o  O  O  O  I  I  \ 


I 


I 


0000,1 

y   • 


pivot  illustrated  is  that  it  is  provided  with  keys  or  wedges,  whereby  the 
bridge  can  be  more  accurately  balanced. 

All  the  foregoing  examples  are  instances  of  what  may  be  termed  the 

solid  pivot,  in  contradistinc- 
tion to  the  hydraulic  pivot, 
n  exemplified  in  the  two  f oUow- 

'^  ing  cases. 

(e)  A  cylindrical  pivot  of 

medium  height  (figs.  416  and 

417),  with  a  perfectly  plane 

,   top  so  disposed  as  to  receive 

J   only  the  vertical  pressure  due 

-«   to  the  weight  of  the  bridge, 

-2   the  axis  of  the  pivot  passing 

g   through  the  centre  of  gravity 

^  of  the  bridge.     Any  lateral 

jS  action  due  to  surging  or  vibra- 

J   tion  is  taken  by  a  horizontal 

J,   ring  of  small  rollers  encircling 

g^  the  lower  part  of  the  bridge 

«   seating.    The  pivot  is  essenti- 

^   ally  a  ram  or  piston  raised 

««   into    position    by    hydraulic 

g   pressure    against    its    under 

^   surface,    and  allowed  to  fall 

J^  after  the  completion   of  the 

)§   rotative  work.     This  system 

I.   is    practised    at     Marseilles. 


0000''      ' 

o  o  o   O  I  ,     ' 

O   O  O    O  }  I  I  

Woo.  ^^6°,^^ 
^  ^  -.  ^  I  I 


00000 


^ 


^■^^ 


v^w 


[I 


^  With  a  slight  modification  it 
'^  has  been  also  practised  at 
Q^  Liverpool.  The  modification 
55  consists  in  a  concavity  in  the 
S,  upper  surface  of  the  ram,  to 
-  ^  receive  the  hemispherical 
seating  of  the  bridge,  so 
that  the  latter  may  revolve 
about  the  pivot  instead  of  the 
pivot  turning  in  the  cylinder 
with  a  tendency  to  wear  the 
sides.  As  a  matter  of  fact, 
it  is  difiicult  to  enaure  the 
immobility  of  the  pivot,  so 
that  the  object  aimed  at  cannot  be  said  to  be  achieved.  It  is  important 
to  note  that  there  is  a  grave  risk  attaching  to  the  apparently  simple  and 
effective  contrivance  just  described.     Should  the  hydraulic  pressure  not  be 


BRIDGE  PIVOT  AT  FLEETWOOD.  433 

cut  off,  through  any  failure  of  the  automatic  apparatus,  there  ia  nothing  to 
prevent  the  pivot  being  driven  completely  out  of  the  cylinder,  with  disastrous 
ooUBequences  to  the  bridge.  This  has  actually  occurred  in  two  instances  to 
tfie  author's  knowledge.  A  solid  pivot  is,  therefore,  to  be  preferred  on 
this  account  Any  accident  to  a  bridge  over  an  important  waterway  entails 
loss  and  inconvenience  far  exceeding  the  damage  to  the  structure  iteelf. 


view  tnuTBTH  to  the  Brldc>- 


Vlew  IcmKliadlim  wltb  Um  BMgt. 
Figa.  414  and  415.— Bridge  Pivot  at  Fleetwood. 

(/)  A  water-borne  carriage,  consisting  of  a  buoy  continuously  immersed, 
with  a  very  small  central  pivot  beneath  it,  taking  about  5  per  cent  only  of 
tike  dead  weight  of  the  bridge.  The  carriage  is  steadied  by  a  horizontal  ring 
d  wheels.  Fig.  418  is  an  illustration  of  a  pivot  thus  constructed  at  the 
Spencer  Bock,  Dnblin. 

A  practical  point  worthy  of  notice  is  the  very  decided  tendency  exhibited 


434  ^^^^  issGiSBEmso. 

by  swing  bridges  to  wear  their  pivots  unevenly.  Owing  to  the  pull  exercised 
by  the  turning  rams  behind  the  pivot,  the  bridge  bears  more  heavily  against 
the  forward  side,  and  in  process  of  time  creeps  gradually  backward  from  its 
true  centre,  so  as  eventually  to  cause  the  tail  of  the  bridge  to  jamb  against 
the  masonry  of  the  bridge  pit.  This  movement  has  been  known  to  take 
place  to  the  extent  of  an  inch  or  more.  A  remedy  might  perhaps  be  found 
in  B,  movable  pivot  provided  with  a  base  fitting  into  a.  fixed  sole-plate,  where 
it  could  be  adjusted  at  intervals  by  means  of  cotters  or  wedges. 


Figa.  116  and  417.— Bridge  Pivot  at  MarseiUas. 

Balaneing  Rollers  and  Wheels. — For  a  swing  bridge  whose  centre  of 
gravity  does  not  lie  upon  the  axis  of  rotation,  some  additional  supporting 
power  is  rendered  necessary,  and  this  is  supplied  by  balancing  wheels  or 
rollers.     In  some  cases  (fig.  431)  the  weight  is  brought  to  bear  upon  the  top 


SWING  BRIDGE  AT  DUBLIN. 


436 


DOCK  ENGINEERING. 


L^ 


!b 


- — .gj — _,    jjj 


CO 


of  a  ring  of  rollers,  which  are  either  free  to  travel  with  the  bridge  or  which 
simply  revolve  upon  their  own  axes  without  progression.     In  other  instances 

(figs.  419,  420,  and  421)  a  series 
of  two  or  more  wheels  is 
attached  to  the  under  side  of 
the  bridge  and  travel  over  a 
circular  roller  path.  The  weight 
is  transmitted  through  the  wheel 
axles,  and  the  turning  friction  is 
considerably  greater  than  with 
live  rollers.  Wheels  do  not 
always  run  upon  the  floor  of 
the  bridge  pit.  In  some  in- 
stances, the  ballasting  of  the 
bridge  is  reduced  to  a  minimum, 
and  the  centre  of  gravity  liea 
forward  of  the  pivot.  The  wheels 
are  then  placed  at  the  extremity 
of  the  tail  end  and  bear  upwards 
against  the  under  side  of  a 
corbel  course  or  projection  in 
the  circumference  of  the  bridge 
pit,  which  must  necessarily  be 
constructed  in  heavy  blocks  of 
masonry. 

For  bridges  accurately  bal- 
anced over  their  centre  of 
gravity,  no  additional  support 
is  required  except  for  steadying 
purposes,  and  that  only  in  the 
case  of  very  light  bridges,  but 
it  is  nearly  always  provided, 
more  perhaps  as  a  precaution 
than  as  a  necessity.  The  force 
required  to  disturb  the  stability 
of  balanced  heavy  bridges  is 
extremely  great.  M.  Barret* 
alludes  to  a  bridge  at  Marseilles 
which,  with  a  length  of  247  feet 
and  a  weight  of  500  tons,  would 
allow  a  two-wheel  dray  carrying 
6  tons  to  mount  one  end  of  it 
at  the  moment  of  swinging 
without  disturbing  the  longitudinal  equilibrium,  while  a  force  of  no  less 

*  Min,  Proc,  Inst,  C,E,,  vol.  Ivii 


I  " 


. .C3---i 


CO 


•'II! 


THE  COUNTERPOISE. 


437 


than  89  tons  would  haye  to  be  applied  at  its  axis  in  order  to  affect  the 
transverse  equilibrium. 

The  great  majority  of  swing  bridges,  however,  have  their  weights  distri- 
buted between  the  pivot  aod  the  wheels  oi-  rollers  in  varying  proportions, 
capable  of  adjustment  bj  mechanical  contrivances.  The  revolving  members 
must  have  conical  surfaces  with  axes  radiating  to  the  centre  of  rotation. 
Their  diameters  in  existing  examples  vary  from  about  8  inches  to  5  feet;  but 
such  extremes  are  injudicious  owing,  in  the  first  case,  to  the  difficulty  of 
obtaining  a  satisfactory  adjustment  and,  in  the  second,  to  the  great  depth  of 
the  roller  path.  Between  18  inches  and  3  feet  will  be  found  a  suitable  range 
for  practical  purposes.  I^rge  rollers,  on  account  of  the  correspondingly 
obtuse  angles  which  they  subtend,  have  a  tendency  to  work  out  of  position 
under  pressure.  They  are  restrained  by  their  inner  flanges  or  by  axial  rods 
to  the  pivot,  but  in  either  case  the  friction  is  augmented. 


Fig.  4^— Balancing  Lever. 

Sometimes  a  double  wheel  track  is  provided,  or  there  is  an  intermediate 
row  of  friction  rollers  near  the  centre.  In  order  to  secure  a  proportionate 
pressure  upon  these  intermediate  supports,  the  bearing  is  communicated 
through  a  volute  or  other  spring  or  by  means  of  counter- weigh  ting.  This 
latter  method  is  achieved  by  placing  the  wheel  journals  in  a  loose  cast-iron 
frame  connected  with  a  balancing  lever  as  shown  in  fig.  422. 

Some  bridges  move  entirely  upon  a  turntable  of  rallers,  leaving  scarcely 
any  appreciable  weight  to  be  borne  by  the  pivot.  A  footbridge  has  been 
constructed  which  revolved  upon  a  row  of  cannon  halls  between  two  grooved 
cast-iron  plates. 

The  CounterpoUe. — Masonry,  gravel  or  rubble  ballast,  Eind  cast-iron 
kentledge  have  all  been  utilised  for  the  purpose  of  counter  weighting 
movable  bridges.  The  last-named  material,  being  heavier  and  easy  to 
mould  in  blocks  of  suitable  shape  and  size,  is  most  generally  used,  a  very 
inferior  quality  of  iron  being  employed. 


438  DOCK  ENGINEERING. 

The  kentledge  is  deposited  in  a  special  compartment  called  the  ballast 
box,  arranged  at  the  extremity  of  the  tail  end  of  the  bridge,  commonly 
below  the  floor  level,  though  the  space  between  the  webs  of  box  girders  is 
also  available  for  the  purpose.  The  interior  surfaces  of  the  ballast  box 
should  be  washed  over  with  liquid  Portland  cement,  and  the  interstices 
between  the  blocks  run  with  grout,  to  prevent  corrosion. 

The  counterpoise  has  occasionally  been  disposed  as  an  ornamental 
feature,  and  a  massive  balustrade  or  an  entrance  arch  in  cast  iron  may  be 
cited  as  illustrations.  Such  artistic  pretensions  are,  however,  in  question- 
able taste  in  situations  where  the  functions  of  a  bridge  are  strictly 
utilitarian. 

The  amount  of  ballast  required  to  give  the  requisite  stability  depends 
upon  the  ratio  which  the  length  of  the  tail  bears  to  the  length  of  the  bridge 
forward  of  the  pivot  or  point  of  support.  A  bridge  with  the  pivot  exactly 
at  its  centre,  as  is  generally  the  case  where  two  parallel  openings  have  ta 
be  spanned,  and  also  for  some  single  openings,  as  at  Naburn  on  the  Ouse, 
near  York,  needs  no  counterweight.  In  the  majority  of  cases  a  shorter  tail 
is  the  rule  for  two  reasons — ^first,  on  the  ground  of  expense,  for  the  structure 
of  a  bridge  is  far  costlier  than  even  a  much  greater  dead  weight  of  ballast ; 
and  secondly,  there  is  less  occupation  of  valuable  quay  space  by  a  counter- 
balanced tail.  In  fact,  at  some  sites,  a  short  tail  is  absolutely  unavoidable. 
The  Whitehaven  swing  bridge  has  a  tail  only  one-fourth  of  the  total  length, 
or  one-third  of  the  length  of  the  forward  portion.  In  a  number  of  cases  the 
proportion  is  one-half  of  the  forward  portion,  while  at  Marseilles  it  is 
three-fifths.  In  an  interesting  paper  on  the  subject,  Mr.  C.  F.  Find  lay  "^ 
demonstrates,  by  an  application  of  the  calculus,  that  if  the  cost  per  ton  of  the 
bridge  structure  be  Ave  times  the  cost  of  the  kentledge,  for  any  bridge  not 
of  extremely  minute  span,  the  length  of  tail  should  be  approximately  one- 
third  of  the  length  of  the  other  section,  if  the  most  economical  proportion 
is  to  be  observed. 

Bridges  which  depend  for  their  stability  upon  the  downward  reaction 
of  an  inverted  roller  path  do  not  of  necessity  require  ballasting,  if  the  path 
itself  be  secure. 

BaUast  being  an  unremunerative  form  of  weight,  an  attempt  has  been 
made,  in  one  case  at  least,  to  balance  a  bridge  by  placing  the  hydraulic 
rams,  which  work  it,  within  the  ballast  box.  This  method  necessitates  a 
hollow  pivot  for  the  transmission  of  the  water  pressure.  In  the  case  of  a 
small  bridge,  the  paving  of  the  short  end  with  stone  setts,  and  the  long  end 
with  wood  blocks,  has  been  found  an  adequate  solution  of  the  difficulty. 

Settiiig  Apparatus, — For  obvious  reasons  it  is  not  advisable  to  allow  a 
bridge  to  rest  upon  its  pivot  longer  than  is  required  for  the  operation 
of  turning.  While  undergoing  the  stress  due  to  moving  loads,  the  structure 
is  preferably  supported  on  some  independent  base.  Before  the  introduction 
of  hydraulic  power,  when  the  usual  practice  was  to  carry  the  bulk  of  the 
*  Findlay  on  **  The  Design  of  Movable  Bridges,"  Min.  Proc.  L.E,S,,  vol.  ii. 


SETTING  APPARATUS.  439 

weight  on  a  ring  of  live  rollers,  a  single  bridge  was  wedged  up  at  each  end 
until  such  time  as  it  was  necessary  to  put  it  in  motion,  when  the  wedges 
were  withdrawn.  A  bridge  with  double  leaves  was  also  wedged  up  at  the 
tail  ends,  so  that  each  leaf  tilted  forward  on  to  bearing  blocks  proyided  at 
the  edge  of  the  coping.  The  wedges  were  actuated  by  mechanical  means, 
such  as  the  screw  and  the  lever. 

With  the  advent  of  hydraulic  power  came  the  water  pivot,  which  raised 
the  bridge  off  its  fixed  bearings  during  the  process  of  rotation,  and  after- 
wards allowed  it  to  return  to  them.  The  advaatages  of  a  solid  pivot  have 
caused  the  transference  of  the  hydraulic  lifting  rams  to  the  extreme  rear, 
where  the  wedging- up  process  has  been  followed,  but  with  this  modifica- 
tion, that  when  the  rams  have  lifted  the  bridge  clear  off  the  pivot,  a 
pair  of  sliding  bearing  blocks  are  inserted,  and  the  lifting  power  is 
withdrawn  until  it  is  required  once  more  to  raise  the  bridge  for  the 
removal  of  the  bearing  blocks  and  the  resumption  of  the  pivot  seating  (see 
fig.  441). 

Another  form  of  lifting  apparatus  is  the  knuckle  or  toggle  gear,  which 
consists  essentially  of  two  short  bars  linked  together,  and  fiexibly  con- 
nected with  an  upper  frame,  constructed  to  move  vertically,  and  a  base 
which  is  fixed.  When  the  two  bars  are  in  one  vertical  line,  the  upper  plate 
is  at  its  highest  elevation,  and  any  movement  in  the  bars  produces  a  depres- 
sion in  the  level  of  the  plate.  The  thrust  of  a  hydraulic  ram  straightens  the 
knuckle,  so  that  a  bearing  block  may  be  inserted  as  before,  but  in  some  cases 
the  weight  of  the  bridge  continues  to  be  borne  by  the  gear,  the  links  being 
driven  slightly  past  the  vertical  position  in  order  to  preclude  any  tendency 
to  a  backward  movement  of  the  ram.  The  opposite  motion  is  effected  by 
another  hydraulic  cylinder.  As  a  mechanical  means,  the  toggle  joint  is  very 
powerful.  Eccentrics  and  cams  on  shafting  and  bent  levers  have  also  been 
employed  to  accomplish  the  necessary  lift. 

An  ingenious  arrangement  adopted  for  a  double-leaved  swing  bridge, 
each  leaf  weighing  116  tons,  over  an  80  feet  passage  at  Barrow,  consists 
in  allowing  the  bridge  to  remain  continuously  upon  the  pivot  through  the 
medium  of  a  very  shallow  and  flexible  girder.  During  the  passage  of  a 
load  over  the  bridge,  this  girder  deflects  sufficiently  to  admit  of  the 
structure  coming  in  contact  with  specially  arranged  fixed  blocks,  which 
themselves  take  up  the  actual  weight.  After  the  transit  of  the  load  the 
resilience  of  the  girder  causes  it  to  spring  back  to  its  original  position 
and  the  bridge  resumes  the  swinging  condition.  By  this  contrivance  all 
apparatus  for  lifting  and  setting  is  dispensed  with. 

Examples  of  blocks  provided  for  the  centre  bearing  and  the  nose  end  of 
a  bridge  at  Liverpool  are  given  in  figs.  423  to  428.  The  blocks  for  the  tail 
end  are  similar  to  the  centre  bearing  blocks,  with  the  addition  that  their 
undersides,  instead  of  being  fixed,  are  arranged  to  slide  in  grooves  in  sole- 
plates,  as  shown  in  fig.  441.  The  upper  members  in  figs.  426  and  427  are 
attached  to  the  underside  of  the  bridge  structure. 


440  DOCK  ENQINBERING. 

/ntoWocttn^  Apparatus.— -The  two  leaves  of  a  double  swing  bridge  &re 
often  locked  together,  not  so  much  with  the  idea  of  formitig  a  continuous 
structure,  as  for  the  purpose  of  equalising  the  deflection  of  the  nose  ends 


, ;„ , 


i        p  O  O 

I  O  ;— 1       O 

'    j  "  i 

!      o  o  o 


11 


Iff 


under  a   load   approaching   from   one  side  only.      Without   some   sacli 
arrangement  there  would  be  a  perceptible  difference  in  level  between  the 


GENERAL  NOTES  ON  DESIGN.  44 1 

extremities  of  the  loaded  and  unloaded  leaves  and  a  sharp  recoil  of  one  of 
them  when  the  pressure  had  been  transferred  to  the  other. 

This  connection  may  take  the  form  of  a  projection  on  one  of  the 
meeting  faces  with  a  corresponding  groove  in  the  other  face,  engagement 
being  made  in  the  ordinary  process  of  rotation.  Or,  again,  where  the 
leaves  tilt  slightly  after  turning,  so  that  a  tongue-and-groove  joint  is  not 
feasible,  long  bolts  have  been  shot  home  through  the  faces  of  the  leaves. 
The  motive  power  in  such  cases  may  be  a  hand  lever,  a  screw,  or  a 
hydraulic  ram. 

In  a  number  of  instances  horizontal  interlocking  is  omitted  entirely, 
partly  on  account  of  the  necessary  clearance  required  for  expansion  and 
partly  to  avoid  the  inconveniences  of  a  complicated  adjustment.  A  simple 
plug  dropped  into  a  vertical  dovetailed  groove  serves  to  unite  the  leaves 
and  keep  them  in  position. 

General  Notes  on  Design, 

Having  regard  to  the  maximum  resistance  of  the  material  to  stress  and 
the  minimum  thickness  consistent  with  stiffness,  one-ninth  or  one-tenth  of 
the  unsupported  length  will  generally  be  found  the  most  effective  ratio 
for  the  depth  of  iron  or  steel  girders  at  the  point  of  support.  Towards 
the  nose  end  of  the  bridge  a  reduction  is  advisable,  both  on  account  of 
economy  and  headroom. 

Except  for  very  short  spans,  lattice  girders  are  preferable  to  plate 
girders.  The  latter  make  a  heavier  bridge  and  expose  a  larger  sur£ftce  to 
wind  pressure. 

In  bridges  carrying  a  railway  track,  the  cross  girders  must  be  designed 
to  take  at  least  the  full  concentrated  load  of  a  pair  of  engine  driving 
wheels,  say  16  to  19  tons,  and  in  order  that  this  intensity  of  pressure  may 
not  be  exceeded,  it  is  necessary  that  their  distances  apart  should  not  be 
greater  than  the  distance  between  two  consecutive  pairs  of  wheels,  say 
6  or  7  feet,  while  it  cannot  economically  be  much  less  than  that  amount. 
But  in  ordinary  cases,  9  to  12  feet  is  considered  a  generally  advantageous 
range,  in  which  case  the  load  on  the  cross  girders  is  32  tons  for  each  track, 
exclusive  of  structural  load.  It  will  be  found  economical  to  give  the  cross 
girders  a  larger  proportion  of  depth  than  the  main  girders,  say  one-seventh 
or  one-eighth  of  their  span.  Wind  bracing  should  be  provided  to  withstand 
the  authorised  (but  excessive)  estimate  of  56  lbs.  per  square  foot. 

An  alternative  to  the  cross  girder  system  is  to  carry  the  rails  on  the 
main  girders  themselves,  which  accordingly  must  lie  below  the  platform. 
This  method,  while  diminishing  the  headroom  of  the  closed  passage, 
increases  the  effective  breadth  of  the  bridge  by  the  flange  width  of  two 
or  more  girders,  which  otherwise  would  protrude  above  the  roadway  level, 
and  at  the  same  time  provides  a  clear  deck,  flush  with  the  coping,  when 
the  bridge  is  swung  back  into  its  recess.      On  the  other  hand,  a  deeper 


442  DOCK  ENGINEERING. 

bridge  pit  is  required  and  the  system  cannot  be  adopted  in  the  case  of 
low  quays. 

From  an  investigation  made  by  Mr.  Find  lay,  it  appears  that  for  a 
rolling  load  of  10  cwts.  per  foot  per  girder,  a  single-leaf  swing  bridge  is 
more  economical  than  a  double-leaf  bridge  up  to  150  feet  span.  If  the 
rolling  load  be  increased  to  1  ton  per  foot  run  per  girder,  the  economical 
limit  of  single-leaf  bridges  is  raised  to  180  feet. 

Folding  or  Ijowering  Bridge  at  Greenock.'^ 

This  forms  the  superstructure  to  a  caisson  closing  the  entrance  to  the 
Gary  el  Graving  Dock  at  Greenock,  and  already  alluded  to  in  Chap.  viii.  It 
is  only  necessary  to  supplement  the  account  there  given  of  the  whole 
structure  with  some  particulars  relating  exclusively  to  the  bridge  portion, 
which  is  the  design  of  the  late  Mr.  W.  R.  Kinipple  (figs.  429  and  430). 

The  bridge  roadway  is  carried  by  a  series  of  parallel  axles  in  pairs, 
placed  vertical  over  one  another,  transversely  to  the  bridge,  at  a  distance  of 
30  inches,  each  pair  being  connected  by  four  parallel  rocking  bars  working 
freely  on  both  axles.  The  outer  bars  are  prolonged  above  the  roadway 
level  to  form  standards  for  handrailing.  Two  pairs  of  the  inner  bars  are 
extended  downwards  into  a  watertight  chamber  of  the  caisson,  where  they 
are  attached  to  boxes  of  ballast  which  act  as  counterweights.  The  raising 
or  lowering  of  the  bridge  platform  is  effected  by  rollers  fixed  on  each  end, 
which  work  against  curved  plates  in  the  abutment  and  the  curved  girder  or 
lowering  plate  across  the  entrance  to  the  recess.  The  process  of  hauling 
the  caisson  into  its  chamber  brings  the  inner  roller  in  contact  with  a  convex 
plate,  causing  the  handrail  and  platform  automatically  to  fall  to  a  lower 
level.  The  opening  of  the  bridge  consists  of  the  reverse  process.  The 
outer  rollers  of  the  platform  come  in  contact  with  a  concave  plate  which 
causes  the  platform  to  rise  to  the  quay  level.  When  the  bridge  is  in 
position  it  is  locked  between  the  abutments  so  that  it  cannot  fall,  and  in 
such  a  way  that  it  does  not  vibrate  under  the  heaviest  traffic.  The 
plummer  blocks  carrying  the  rocking  bars  are  9  feet  9  inches  apart,  and  are 
supported  on  plated  columns  extending  to  the  bottom  of  the  caisson. 

Traversing  Bridge  at  Antwerp,  t 

The  bridges  at  Antwerp  docks  are  generally  swing  bridges,  one  of  which 
is  exemplified  in  fig.  431,  but  there  is  a  traversing  bridge  over  the  entrance 
lock  to  the  Kattendyk  Dock,  which  is  constructed  according  to  the  type 
shown  in  figs.  432  and  433.  The  structure  consists  of  two  main  plate 
girders  of  a  uniform  height  of  9  feet,  one  on  e€u;h  side  of  the  roadway, 
connected  at  intervals  of  12  feet  by  cross  joists,  between  which  are  ri vetted 

*  Kinipple  on  "Greenock  Harbour,"  Min.  Proc,  Inst.  C,E,,  vol.  cxxx. ;  Macalister 
on  "Caissons  for  Dock  Entrances,"  Min,  Proc,  Inst.,  C.E.,  vol.  Ixv. 
t  Vide  **  AnverSy  Port  de  Mer." 


TRAVERSING  BRIDGE  AT  ANTWERP.  443 

two  series  of  longitudinal  joists.  A  footwalk,  4  feet  6  inches  wide,  is 
carried  on  brackets  outside  the  main  girders.  The  width  of  the  passage 
opening  is  90  feet,  and  the  total  length  of  the  bridge  is  158  feet  6  inches. 
The  roadway  is  paved  with  blocks  of  creosoted  pine,  laid  upon  a  ^inch  bed 
of  asphalt,  which  in  its  turn  covers  a  floor  of  jointed  oak.  At  the  tail  end 
of  the  bridge  there  is  a  counterbalance  of  106  tons.  The  total  weight  of  the 
movable  platform  is  370  tons. 

To  open  the  passage,  it  is  necessary  to  lift  the  bridge  to  such  a  height  as 
will  enable  the  tail  rollers  to  run  back  on  the  level  of  the  roadway  by  which 
the  bridge  is  approached,  and  this  is  eflected  by  placing  under  each  girder  a 
hydraulic  press  with  a  large  roller  fixed  on  the  head  of  the  ram.  The  ram 
is  2  feet  7  inches  in  diameter  and  the  roller  3  feet  7  inches ;  the  latter  is 
mounted  on  a  9-inch  axle.  The  amount  of  lift  is  3  feet.  When  the  water 
enters  the  presses  the  bridge  is  lifted,  but  the  tail  end,  which  preponderates, 
does  not  begin  to  rise  until  the  horn,  or  projection,  at  the  nose  end  of  the 
bridge  comes  in  contact  with  a  small  inverted  roller  just  below  the  surface 
of  the  coping.  The  tail  end  then  ascends  until  the  bridge  becomes  hori- 
zontal at  its  full  elevation,  as  shown  on  the  diagram  by  the  dotted  lines. 


wy/v/A 


g<- - Ml.  A' 

Fig.  431. — Swing  Bridge  at  Antwerp. 

It  is  then  drawn  back  upon  the  press  rollers  and  the  tail  rollers  by  the 
action  of  a  horizontal  cylinder  and  ram,  with  chains  and  multiplying 
sheaves,  situated  beneath  the  bridge.  The  ram  is  20  inches  diameter  with 
a  stroke  of  12  feet,  and  there  are  four  sheaves  at  each  end,  multiplying  the 
power  eightfold.  The  chain  is  1^  inches  diameter.  An  iron  pathway,  to 
bear  upon  each  press  roller,  is  fixed  to  the  underside  of  each  girder.  The 
process  of  closing  is  the  same  as  that  just  described,  but  in  the  inverse 
order. 

The  bridge  was  constructed  by  Messrs.  Sir  W.  G.  Armstrong  &  Co.,  of 
Newcastle,  to  the  late  senior  partner  of  which  firm  the  engineering  profession 
is  mainly  indebted  for  the  many  present  valuable  applications  of  hydraulic 
power.  Several  bridges  have  been  designed  upon  the  same  principle,  and 
are  reported  to  work  very  well,  notwithstanding  the  excessive  weight  which 
is  necessarily  carried  on  the  main  rollers.  In  one  case,  where  the  arrange- 
ment is  a  little  different  from  that  described  above,  the  load  on  each  roller 
amounted  to  nearly  100  tons,  and  yet  it  was  at  work  for  more  than  20  years 
without  any  important  renewals  of  the  working  apparatus.  In  this  instance 
both  the  rollers  and  the  roller  paths  were  of  cast  iron,  9  inches  broad,  the 
diameter  of  the  roller  being  3  feet. 


DOCK  ENOINEEBINO. 


BASCULE  BMDGES  AT  ROTTERDAM.  445 

Automatic  cut-offs  and  other  precautions  are  adopted  to  prevent  any 
tendency  to  accident  during  the  movement  of  the  bridge. 

The  swing  bridge  shown  in  fig.  431  is  notable  for  a  lowering  arm  or 
strut  designed  to  turn  the  bridge  structure  into  an  arch  when  in  the  closed 
position.  The  efficacy  of  the  strut,  however,  as  a  compression  member,  is 
rendered  dubious  by  the  necessity  for  an  accurate  bearing,  which  cannot  in 
all  cases  be  ensured. 


Bascule  Bridges  at  Botterdam.* 

Between  the  years  1881  and  1894,  a  series  of  seven  bascule  bridges  were 
constructed  at  Rotterdam,  all  upon  the  same  principle,  which  is  illustrated 
by  the  typical  bridge  (the  Scheluwebrug)  in  fig.  434.  Former  bascules  had 
been  provided  with  a  very  considerable  rise  towards  the  centre  of  the  span, 
in  order  to  obtain  as  nearly  as  possible  all  the  advantages  of  the  arched 
system.  This  rise,  however,  proved  very  inconvenient  for  heavily-loaded 
vehicles,  and  in  the  later  type  the  platform  was  made  almost  horizontal. 
In  one  instance  only  was  this  arrangement  departed  from,  and  in  that 
instance  the  form  of  the  bridge  was  parabolic  at  the  haunches,  with  a  very 
fiat  connecting  curve  in  the  centre  of  the  span. 

In  the  class  of  bridge  under  notice,  the  two  leaves  of  which  each  bridge 
is  composed,  do  not  abut  against  one  another  at  their  junction.  They  are 
only  connected  in  the  closed  condition  by  locking  bolts,  for  the  purpose  of 
securing  uniformity  of  pressure  and  deflection.  The  tail  ends,  however, 
derive  considerable  support  from  their  abutment,  when  horizontal,  against 
an  iron  structure  placed  above  the  watertight  pits  in  which  the  tails 
revolve,  and  strongly  anchored  to  the  foundation.  Each  leaf,  accordingly, 
is  capable  of  acting  as  a  self-sustained  cantilever.  The  bridges  are  calcu- 
lated to  support  a  load  of  about  10  cwts.  per  square  foot.  The  platforms 
are  of  oak,  with  a  pavement  of  blocks  of  "  djati,''  or  teak. 

Nearly  all  these  bridges  are  moved  by  hydraulic  power.  The  machines 
consist  of  oscillating  cylinders  receiving  pressure  from  the  town's  ordinary 
water  main  by  means  of  a  hollow  trunnion.  The  piston  actuates  a  cranky 
which  is  in  connection  with  the  turning  axis  of  the  bridge. 

An  ingenious  arrangement  causes  the  withdrawal  of  the  interlocking 
bolts  to  depend  upon  the  closing  of  the  two  ends  of  the  bridge  to  traffic  by 
an  iron  grating,  so  that  it  is  not  possible  to  raise  the  bridge  until  this 
grating  has  been  moved  into  position. 

Appended  is  a  list  of  the  seven  bridges  with  the  principal  particulars  of 
their  design  attached :  — 

*  YsseUteyn  on  Le  Port  de  Rotterdam. 


446  I>OCE  ENGINEBRmG. 


s  ,2 
«•  s 
a  8, 


BASCULE  BRIDGES  AT  CHICAGO. 


447 


1 
2 
3 
4 
5 
6 
7 


Kune  of  Bridge. 


Keizersbnig, 
Stokkenbrug, 
Nieuwe  Ooetbrug, 
Jan  Kuitenbrug,  . 
Spangaardsbrug,  . 
Nieuwe  Leu  vebrug, 
Scheluwebrug, 


Width 

Width 

Weight  of 

of  Plat- 

of Pass- 

Super- 

form. 

age- 

structure. 

Feet 

Feet. 

Tons. 

23 

33 

135 

28 

44 

210 

25J 

32i 

146 

29 

45 

275 

29 

45 

249 

32 

47 

322 

32 

46 

276 

Remarks. 


Manual  movement  only. 
Movement  by  hand  or  hydraulic  power. 
Manual  movement  exclusively. 
Hydraulic  or  hand  power. 

I)  >i 

Hydraulic  power  only. 


*t 


It 


In  addition  to  the  foregoing,  there  is  a  bascule  bridge  across  the  entrance 
to  the  Binnenhaven,  the  span  of  which  is  75  feet  and  the  width  of  platform 
34  feet.  The  upper  surface  is  perfectly  horizontal,  but  the  four  girders,  of 
which  each  leaf  is  composed,  are  curved  in  form,  and  find  a  lower  bearing 
8  feet  below  the  roadway  level.  The  arched  structure,  however,  has  not  been 
realised  as  designed.  The  union  of  the  two  extremities,  in  spite  of  several 
different  devices  successively  tried,  is  not  sufficiently  perfect  and  each  leaf 
remains  a  cantilever,  exercising  considerable  force  upon  its  axis,  and  causing 
a  large  annual  expenditure  for  maintenance  and  repairs. 

The  bridge  is  twin,  comprising  two  separate  structures  side  by  side,  each 
capable  of  acting  without  the  other  in  case  of  repairs,  but  under  normal 
conditions  coupled  together. 

The  weight  of  each  leaf  is  121  tons,  and  gas  engines  supply  the  motive 
power. 

Bascule  Bridges  at  Chioago.^ 

These  are  of  the  type  described  as  rolling  bascules — one  of  the  latest 
examples  of  which,  near  Taylor  Street,  Chicago,  is  illustrated  in  figs.  435 
and  436 — a  design  due  to  the  late  Mr.  William  Scherzer.  The  heels  or 
shore  ends  are  fitted  with  curved  and  counterweighted  girders,  which  roll 
on  a  path  on  the  bridge  abutment,  the  girders  having  holes  fitting  over  the 
teeth  of  a  horizontal  rack,  which  serves  to  guide  the  motion  of  the  bridge. 
Each  bridge  has  two  leaves. 

The  Van  Buren  Street  bridge  has  a  span  of  115  feet  between  centres  of 
bearings,  and  covers  a  waterway  109  feet  wide.  The  structure  is  formed 
of  three  parallel  trusses  covered  by  a  platform,  comprising  a  roadway, 
41  feet  wide,  and  two  footwalks,  each  8  feet  wide.  The  roadway  accommo- 
dates a  double  track  for  electric  trams. 

The  North  Halsted  Street  bridge  has  a  span  of  127  feet  and  covers  a 
waterway  121  feet  wide.  There  are  only  two  trusses  in  this  case,  the 
roadway  being  only  34  feet  wide,  with  two  footwalks,  7  feet  3  inches  wide. 
Provision  is  made  for  an  electric  railway. 

The  railway  bridge,  between  the  two  bridges  just  described,  is  con- 
structed on  the  same  lines.  The  span  is  114  feet,  and  the  channel  width 
108  feet.    The  bridge  is  composed  of  two  similar  or  duplicate  pairs  of  leaves 

*  Vide  Engineer,  November  26,  1897. 


448 


DOCK  ENOINEERINO. 


nj 


SWING  BRIDGE  AT  MARSEILLES.  449 

placed  side  by  side,  each  pair  forming  a  complete  span,  and  carrying  a 
double  railway  track.  Under  normal  conditions  they  are  coupled  together, 
but  in  case  of  repairs  they  can  be  disconnected,  and  each  pair  then  acts 
independently  of  the  other.  Each  leaf  is  so  counterweighted  that  on 
drawing  the  centre  and  end  locks,  it  rises  to  an  angle  of  about  30**,  rolling 
back  on  the  abutment,  and  the  application  of  power  is  only  required  to 
completely  open  the  bridge  or  to  close  it.  The  weight  of  each  double  track 
is  about  135  tons.  The  bridge  can  be  opened  or  closed  in  thirty  seconds, 
each  leaf  being  operated  by  two  horizontal  struts  connected  to  the  ends  of 
the  trusses.  The  struts  are  run  in  and  out  by  gearing,  operated  by  a  25 
H.P.  electric  motor.  When  the  bridge  is  closed,  each  leaf  acts  as  a 
cantilever,  anchored  by  the  tail  end,  which  takes  a  bearing  against  the 
underside  of  the  approach  viaduct,  the  approach  being  firmly  anchored  to 
the  masonry  of  the  abutment.  The  end  lock  holds  the  tail  firmly  home 
against  its  bearing. 

The  following  are  the  general  dimensions  of  the  bridge  : — 

Length  between  ends  of  approaches,    ....  276  feet. 

Span  between  bearings 114    „ 

Width  of  channel, 108    „ 

Headway  at  centre 35    „ 

Depth  of  truss  at  shore  end, 26 

Depth  of  truss  at  free  end, 6    ,,     6  inches. 

Width  between  trusses, 21     „    2 

Total  width  of  bridge,  .  .  51     „  10 

Radius  of  heel  of  truss, 26 

Weight  of  each  double  track  leaf,        ....  135  tons. 

Total  weight  of  bridge, 540 

Counterbalanced  weight  on  each  side,         ...  28 


6in( 
o 

If 
)i 


ft 


Swing  Bridge  at  Marseilles.'^ 

The  bridge  (figs.  437,  438,  and  439)  over  the  entrance  to  the  Marseilles 
repairing  docks  has  a  total  length  of  203  feet  5  inches  and  a  width  of 
46  feet.  The  framework  consists  of  three  parallel  trellissed  girders,  each 
11  feet  6  inches  deep,  with  carved  upper  flanges.  Between  one  pair  of 
girders  is  a  single  line  of  railway;  between  the  other  pair  a  roadway,  with  a 
footpath,  6  feet  6  inches  wide,  carried  on  brackets  outside  the  outer  girder. 
The  width  of  the  waterway  is  91  feet  10  inches,  and  the  swinging  bridge 
consists  of  two  cantilevers,  126  feet  and  77  feet  5  inches  long  respectively. 
The  total  weight  of  the  structure  is  700  tons,  of  which  125  tons  is  due  to 
counterpoise.  The  bridge  is  raised  and  turned  upon  a  hydraulic  pivot  of 
only  22*8  inches  diameter,  which  necessitates  a  pressure  of  over  4,000  lbs. 
per  square  inch,  obtained  by  means  of  a  double-acting  force  pump  and  an 
accumulator.  Each  girder  carries  a  roller  under  it  near  the  extremity  of  its 
tail  end ;  the  three  rollers  are  in  a  line  parallel  to  the  bearing  girder,  so  that 

*Gaudard  on  "Swing  Bridges,"  Min.  Proc,  Inst,  C,E,f  vol.  xlvii. ;  Price  on 
"Movable  Bridges,"  Min.  Proc.  Inst.  C.E.,  vol.  Ivii. ;  and  Barret  on  '*The  Swing 
Bridge  at  Marseilles,"  Min.  Proc.  Inst.  C.E.,  vol.  xlii. 

29 


DOCK  ENGINEERING. 


SWING  BRIDGE  AT   MARSEILLES.  45 1 

the  bridge  may  rest  evenly  on  all  three  when  slightly  raised.  This  arrange- 
ment necessitates  two  circular  roller  paths  of  radii,  64  feet  and  67  feet  7 
inches,  respectively.  The  bridge  is  turned  by  a  chain  passing  round  a  cast- 
iron  slewing  drum,  46  feet  in  diameter,  the  motive  power  being  supplied  by 
two  hydraulic  cylinders,  with  rams,  each  11*8  inches  diameter,  and  9  feet  2^ 
inches  stroke,  one  of  which  serves  to  open  and  the  other  to  close  the  bridge. 

The  operation  of  turning  consists  in  first  releasing  the  wedges  at  the 
tail  end,  by  which  means  the  rollers  at  that  part  are  lowered  on  to  their 
tracks.  The  pivot  press  then  lifts  the  bridge  until  the  nose  end  is  raised 
from  its  supports,  and  everything  is  ready  for  rotation.  A  hydraulic 
cylinder,  13'8  inches  in  diameter,  actuates  the  wedging  apparatus  under  a 
pressure  of  700  lbs.  per  square  inch,  which  is  the  same  as  that  obtaining  in 
the  slewing  cylinders.  The  kentledge  is  arranged  to  throw  a  weight  of 
1 5  tons  on  the  guiding  rollers  while  the  bridge  is  being  swung. 

The  pivot  is  enclosed  in  a  press,  6*3  inches  thick,  which  is  secured  by 
keys  to  a  cast-iron  base,  from  which  it  can  be  withdrawn  for  repairs.  The 
prismatic  top  of  the  pivot  inserts  itself  into  a  bearing  plate  fixed  to  the 
underside  of  the  pivot  girder.  The  surface  of  contact  is  made  slightly 
convex,  so  that  the  bridge  may  always  have  a  good  bearing  on  its  axis, 
despite  any  slight  displacements  during  the  process  of  lifting.  A  leather 
lining  makes  a  watertight  joint  between  piston  and  cylinder,  but  in  order 
to  prevent  a  tendency  to  tear  from  the  turning  stress  imparted  by  the 
adherence  of  the  rotating  pivot,  the  interstice  between  the  edges  has  been 
fitted  with  a  band  of  india-rubber,  which,  by  the  interior  adhesion  it  gives 
to  the  opposite  edges  of  the  leather,  causes  its  exterior  surface  to  slide  on 
the  metal.  A  horizontal  sector  is  fastened  to  the  head  of  the  piston,  which 
rests  against  two  rollers  with  light  movable  axles,  supported  by  a  cast-iron 
bracket  to  counteract  the  lateral  strain  caused  by  the  chains  in  turning 
the  bridge. 

Commenting  in  the  A  finales  des  Fonts  et  Chauss^y  May,  1875,  on  the 
arrangements  described  above,  M.  Barret,  then  engineer  to  the  Marseilles 
Dock  Company,  adds  : — "  If  a  similar  bridge  had  to  be  constructed  for  an 
important  line  of  railway,  and  over  a  channel  through  which  there  was  a 
considerable  traffic,  it  would  be  desirable  to  substitute  a  double  line  for  the 
single  tramway,  and  to  make  a  footway  on  each  side  of  the  cart-road  within 
the  girders,  which,  though  increasing  the  width  to  59  feet,  would  make  the 
bridge  more  symmetrical  and  easier  to  balance.  The  raising  and  lowering 
of  the  ends  might  be  regulated  by  making  the  rollers  at  the  tail  end  fall 
and  rise  in  the  roller  boxes,  keeping  them  always  in  contact  with  the  roller 
paths  by  means  of  a  counterpoise.  The  diameter  of  the  pbton  (pivot)  of 
the  press  might  be  increased  to  4-9  feet,  so  that  the  bridge  could  be  raised 
with  the  ordinary  water  pressure.  The  guide  rollers  might  be  increased  in 
number,  and  placed  higher  up,  so  as  to  act  all  round  the  bearing  plate. 
Also,  if  the  webs  of  the  girders  were  made  of  plate  iron,  the  strains  would 
be  more  evenly  distributed,  and  the  construction  simplified  with  a  slight 


452  DOCK  ENGINEERING. 

increase  in  the  weight  of  the  girders.  With  these  modifications,  it  would 
be  possible  to  construct  swing  bridges,  weighing  about  2,500  tons,  which 
could  be  safely  and  easily  worked." 

Tilting  Bridge  at  MarBeilles. 

At  the  Passage  de  La  Joliette,  70  feet  wide,  at  Marseilles,*  there  is  a 
large  traffic  of  un  mas  ted  timber  lighters  and  but  few  sea-going  ships.  As 
it  is  therefore  advisable  to  open  the  passage  as  seldom  as  possible  for  any 
considerable  time,  owing  to  the  roadway  traffic,  a  form  of  bridge  (fig.  440) 
has  been  devised,  combining  the  swinging  principle  with  that  of  the 
bascule.     For  un  masted  barges,  the  bridge  is  tilted  by  means  of  a  piston 


Fig.  440. —Tilting  Bridge  at  Marseilles. 

pivot,  and  it  is  only  rotated  for  large  vessels.  When  in  the  tilted  position 
the  gradient  of  the  floor  is  1  in  14  and  a  headway  of  10  feet  3  inches  is 
afforded.  The  time  occupied  in  tilting  is,  of  course,  much  less  than  in 
swinging. 

Single  Swing  Bridge  at  Liverpool. 

This  bridge  (figs.  441,  442,  and  443)  constitutes  a  design  used  in  three 
or  four  instances  for  spanning  passages,  90  feet  in  width.  The  structure, 
which  is  of  mild  steel,  consists  of  two  main  girders,  each  159  feet  long  and 
11  feet  deep  generally,  but  reduced  to  6  feet  in  depth  at  the  nose  end. 
These  girders  are  connected  at  intervals  of  8  feet  6  inches  by  cross  girders, 
2  feet  deep,  supporting  intermediate  longitudinal  joists,  12  inches  by 
6  inches.  The  pivot  girder  consists  of  two  box  girders,  each  4  feet  deep 
at  the  centre  and  2  feet  9  inches  deep  at  the  ends,  joined  by  ^-inch 
diaphragms  and  a  covering  plate,  the  pivot  casting  being  bolted  to  and 
between  the  box  girders. 

The  main  girders  are  22  feet  apart,  centres,  providing  a  double  road- 
way, 17  feet  wide,  separated  by  a  central  cast-iron  curb.  A  narrow  space, 
for  carters  and  others,  adjoining  each  girder  is  also  protected  by  a  curb. 
The  foot  walks  proper  are  two  in  number,  each  6  feet  4  inches  wide,  and 
carried  outside  the  main  girders  by  brackets  which  are  prolongations  of  the 
cross  girders. 

Although  rails   have  not  actually  been   laid   down  upon  the  bridge, 
provision  has  been  made  for  their  accommodation,  by  spacing  the  longi- 
tudinals to  suit  a  double  railway  track,  and  the  bridge  has  been  calculated 
to  sustain  the  heaviest  type  of  locomotive  as  a  continuous  load. 
•Price  on  "Movable  Bridges,'*  Min,  Proc.  Inst.  CE,,  vol.  Ivii. 


453 


454  I>OCK  ENGINEERING. 

The  decking  is  of  greenheart,  laid  upon  a  4-inch  platform  of  creosoted 
pine.  Under  the  wheel  tracks,  which  are  iron-plated,  the  greenheart  is 
laid  in  longitudinal  planks,  4  inches  thick.  The  horse  tracks,  3  feet  wide, 
are  of  blocks,  9  inches  by  5  inches  by  3^  inches,  set  in  Portland  cement. 
The  footpaths  are  of  3-inch  greenheart  planks,  laid  longitudinally  across 
4^-inch  by  4^-inch  bearers.  There  are  elm  rubbers,  9^  inches  by  5^  inches, 
at  each  side  of  the  bridge.  The  handrail,  which  adjoins  the  waterway  when 
the  passage  is  open,  is  arranged  to  fall,  so  as  to  offer  no  obstruction  to 
warps  and  lines. 

While  the  passage  is  in  use  the  bridge  remains  upon  its  pivot,  but, 
having  been  rotated  across  to  the  closed  position,  a  couple  of  vertical  cast- 
iron  rams,  working  in  a  25-inch  diameter  hydraulic  cylinder,  with  a  7  inches 
stroke,  lift  the  extreme  tail  end  of  the  bridge,  so  that  the  latter  leaves  the 
pivot  and  tilts  forward  on  to  bearing  blocks  at  the  edge  of  the  coping  on 
both  sides  of  the  passage.  At  the  same  time  a  pair  of  sliding  blocks  are 
brought  under  the  tail  end,  and  a  very  slight  subsidence  of  the  rams 
causes  the  bearing  to  be  transferred  to  the  blocks. 

The  slewing  machinery  consists  of  a  pair  of  hydraulic  rams,  each  14 
inches  diameter,  9  feet  10  inches  stroke,  and  furnished  with  sheaves  giving 
a  power  of  2  to  1.  The  roller  path  is  43  feet  radius  and  the  wheels  are  of 
cast  steel,  17  inches  diameter,  turned,  bored,  and  coned.  The  slewing  chain 
is  If  inches  diameter.     The  radius  of  the  slewing  drum  is  11  feet  9  inches. 

The  Victoria  Swing  Bridge  at  Leith.^ 

This  bridge  (fig.  444)  constructed  in  1874  has  a  clear  span  of  120  feet 
and  was,  at  the  time  of  its  construction,  the  largest  in  the  kingdom.  The 
total  length  is  214  feet  3  inches,  and  the  width  over  all,  39  feet  3  inches. 
The  platform  comprises  two  lines  of  railway  and  roadway,  with  a  footpath 
on  each  side.  The  weight  of  the  whole  bridge  is  upwards  of  600  tons, 
including  a  counterpoise  of  240  tons.  There  are  two  main  girders,  each 
27  feet  in  depth.  The  pivot  or  lifting  press  has  a  diameter  of  5  feet 
9  inches,  and  divides  the  bridge  into  a  long  arm  of  147  feet  and  a  short  arm 
of  67  feet  3  inches. 

The  principle  upon  which  the  bridge  is  manoeuvred  is  the  same  as  that 
described  in  connection  with  the  Marseilles  bridge,  with  the  exception  that 
the  ordinary  hydraulic  pressure  of  750  lbs.  per  square  inch  serves  to  work 
the  pivot  without  the  intervention  of  a  force  pump.  The  turning  gear  is 
illustrated  in  fig.  445. 

Swing  Bridge  at  Stanley  Dock,  Ijiyerpool.t 

This  bridge  carries  an  overhead  electric  railway  across  the  50-foot 
entrance  to  the  Stanley  Dock.     It  is  a  combination  of  a  swing  bridge  and  a 

*  Whjrte,  "  Notes  on  Leith  Docks  and  New  Works  in  Progress,"  1901. 
tGreathead  and  Fox  on  "Liverpool  Overhead  Railway,"  Min.  Proc.  InH,  CE., 
vol.  cxvii. 


456  DOCK  ENGINEERING. 

dravbridge.     It  is  ia  two  leaves  and  haa  two  decks.     The  apper  carries  the 
electric  railway,  the  lower  carries  a  doable  line  of  rails  provided  for  the 
dock  traffic.     The  lower  level  is  arranged  with  bascule  leavee,  so  that  barges 
and  small  craft  can  use  the 
passage  without  the  neces- 
sity of  swinging  the  whole 
structure  and  interrupting 
the  railway  service  which 
is    a    very   frequent  one. 
The  bridge  is,  in  its  normal 
condition,  a    fixed    struc- 
*  ture,  resting  upon  bearing 

p  blocks  at  the  tail  end  and 

>  upon  two  legs  at  the  front 

^  of    each     abutment.      To 

enable   the   bridge   to    be 


^  j     §    completely  opened  the  fol- 
S  5     I  1 


lowing    movements    have 
:3   to  be  made.     The  tail  end 
'i    of    each    leaf   is    slightly 
^  lifted  to  allow  the  bearing 
^   blocks  to   be  withdrawn, 
B   and   then   it   is    lowered 
J   until    it    rests  upon    the 
I    roller    path.     In    acoom- 
^    pliahing  this,  the  pivot  of 
i       "^    the  bridge  comes  in  con- 
r-   tact  with   its  socket,  the 
*   girders  are  canted  upward 
1  ^   J>  at  the  nose  end,  the  inter- 
•  mediate   supporting    legs 

are  Ufted  off  their  bear- 
ings, and  the  bridge  is 
ready  for  swinging.  The 
load  on  the  pivot  is  270 
tons.  The  length  of  the 
bridge  between  pivot  cen- 
tres is  80  feet  6  inches, 
and  114  feet  6  inches  is 
the  extreme  length.  The 
width  of  way  between  the 
longitudinal  girders  is  21 
feet.  The  slewing  drum 
has  a  diameter  nf  12  feet,  and  is  turned  by  a  l|-inoh  chain.  The  weight 
of  the  combined  structure  is  600  tons. 


FOOTBRIDGES   AT   LIVERPOOL. 


457 


Detailed  drawings  of  the  bridge  are  exhibited  in  figs.  446,  447,  and 


448. 


Footbridges  at   Iiiverpool. 


Illustrations  are  given  of  two  types  of  footbridge— the  first  constructed 
in  wood,  and  the  second  in  iron.  The  wooden  bridge  (figs.  449,  450,  and 
451)  which  has  a  total  length  of  73  feet  6  inches,  spans  an  opening  of  50 


0' 


rq- 


Figs.  449  and  450. — Footbridge  at  Liverpool.     Scale — 16  feet  =  I  inch. 


Bair  Section 
at  A. 


HOT  Section 
atB. 


Fig.  451. — Footbridge  at  Liverpool.     Scale — 4  feet  =  I  inch. 


feet.  The  width  of  the  footway  is  4  feet,  and  in  order  to  accommodate  the 
ballast  the  bridge  is  widened  at  the  tail  end  to  8  feet  2  inches  over  alL 
The  ballast  is  composed  of  concrete  laid  in  the  floor  and  in  the  side  panels. 
Movement  is  made  entirely  by  hand.  The  iron  bridge  (figs.  452,  453,  and 
454)  has  a  length  of  96  feet,  and  covers  an  opening  of  60  feet.  It  is 
propelled  by  hydraulic  power,  by  means  of  rack  and  pinion  gearing  on  the 
underside  of  the  bridge  floor.  The  bridge  was  tested  as  a  cantilever  with  a 
uniformly -distributed  load  of  7^  tons. 


!  \ 


1 
1 
I* 

ft 


'ft 


41 


If 


\% 


DOUBLE  SWING  BRIDGE  AT  CALCUTTA. 


459 


Double  Bving  Bridge  at  Eldderpur.  * 

A  double  swing  bridge,  over  passagei  60  &nd  80  feet  wide,  baa  been 
tuBtrooted  at  the  Kidderpur  Docks,  Calcutta,  and  is  sbovD  in  figs.  465, 


1 


456,  and  457. 


Tbe  example  is  all  the  more  interesting  in  tbat  the  axis  of 
*Kid<terpDr  Docks,  Calcutta,"  J/iJt.  Proc.  lti$t.  C.E.,  vol.  csii. 


460 


DOCK  ENGINEERING. 


the  roadway,  and  therefore  of  the  bridge,  is  not  rectangular  with  the  axis 
of  the  passages.  This  fact  entails  a  greater  length  of  bridge  than  would 
otherwise  be  necessary.  The  various  details  of  construction  will  be  readily 
understood  from  the  diagrams. 


kHM^ 


SCCTI  ON   AT    B   B 


Fig.  457. — Swing  Bridge  at  Calcutta. 


Boiling  Bridge  at  Qreenook.* 

A  travelling  bridge  (fig.  458)  on  the  same  principle  as  a  rolling 
caisson,  connects  the  two  sides  of  the  entrance  to  the  West  Harbour 
at  Greenock.  The  bridge  has  this  difference,  however,  that  it  is  con- 
structed in  openwork  so  as  to  allow  the  tide  to  pass  freely  in  and  out 
of  the  harbour. 

The  entrance  is  103.^  feet  wide,  and  a  bridge  of  this  type  was  deemed 
most  suitable  for  the  site,  owing  to  the  great  depth  (60  feet  below  H.W.) 
to  which  it  would  have  been  necessary  to  go  for  a  firm  foundation  for  a 
swing  bridge,  apart  from  the  inconvenience  attaching  to  the  accommodation 
of  such  a  bridge  upon  a  narrow  quay.  A  timber  gridiron,  resting  upon 
piles  driven  into  the  hard  clay,  and  having  their  heads  encased  in  plastic 
concrete,  carries  the  rails  (9  inches  by  4  inches,  solid  section),  which  are  laid 
to  a  16- foot  gauge  upon  greenheart  runners  at  a  depth  of  26  feet  below  H.W. 
The  bridge  structure  consists  of  three  pierd  forming  watertight  tanks,  each 
18  feet  by  18  feet,  connected  top  and  bottom  by  girders,  23  feet  span. 
On  the  underside  of  the  lower  girders,  six  rollers  are  fixed  at  each  pier. 
The  bridge  has  a  lowering  deck  similar  to  that  already  described  (p.  360, 
ante).     The  total  cost,  including  the  hauling  machinery,  was  jB9,700v 

* Kinipple  on  "Greenock  Harbour,"  J/tn.  Proc,  Inst,  CJS,,  vol.  cxxx. 


ROLLING  BRIDGE   AT  GREENOCK.  46 1 


462 


CHAPTER  XI. 

GRAVINQ  AND  BEPAIBINQ   DOCKS. 

Various  Methods  op  EFFEcrriNG  Repairs  to  Ships— Careening — Beaching — The 
Gridiron  — The  Slipway  — The  Hydraxtlic  Lift  — The  Graving  Dock  — The 
Floating  Dock— Essential  Requiremsnts  of  a  Repairing  Dep6t  ^Comparison 

OF    THE     various     TyPES     IN     REGARD     TO     ACCESSIBILITY,    VENTILATION,    LiGHT, 

Capacity,  Initial  Cost,  Maintenance  and  Repairs,  Working  Expenses,  Dura- 
bility AND  General  Adaptability — ^Design  and  Construction  of  Slipways — 
Foundation — ^Permanent  Way — Cradle — Sliding  Slipways — Broadside  Slip- 
ways— Stresses  in  Slipways — Design  and  Construction  of  Graving  Docks — 
Types  of  Floating  Docks— Process  of  Overhauling— Equipment  of  Rbpaib- 
iNQ  Docks — Distribution  of  Pressure  on  E^eel  Blocks — Description  of 
Gridirons  at  Liverpool,  Hydraulic  Lift  at  London,  Slipway  at  Dover, 
Graving  Docks  at  Bremerhaven,  Liverpool,  Glasgow,  Barry,  and  London, 
AND  Floating  Docks  at  Cartagena  and  Bermuda. 

The  necessity  of  providing  at  every  port  sites,  suitable  in  situation  and 
•equipment,  where  vessels  can  from  time  to  time  undergo  examination, 
painting,  and  repair,  is  self-evident.  There  would  be  danger,  to  say  nothing 
of  loss  of  time  and  inconvenience,  in  transferring  a  disabled  vessel  from  one 
port  to  another,  however  short  the  distance  might  be ;  and,  apart  from  this, 
any  lack  of  facilities  for  repair  must  inevitably  react  upon  the  prestige  of  a 
port  and  prejudice  its  development. 

But,  if  the  desirability  of  such  a  site  be  generally  admitted,  opinion  upon 
the  form  it  should  take  is  not  so  unanimous.  There  are  strong  advocates 
for  several  very  different  types  of  repairing  dep6t.  When  we  have  examined 
the  claims  put  forward  in  favour  of  each  of  these,  we  may  possibly  be  able  to 
assign  some  order  to  their  respective  merits. 

Apart  from  the  operation  of  careODing,  in  which  a  water-borne  vessel 
was  temporarily  given  a  pronounced  list,  the  earliest  means  of  obtaining 
access  to  the  under  side  of  a  ship  was  that  of  dragging  it  by  hand  out  of  the 
water  on  to  some  moderately  sloping  strand  of  firm  sand  or  gravel.  If  too 
heavy  for  manual  haulage,  the  vessel  was  caused  to  take  ground  at  high 
water,  so  that  the  receding  tide  left  her  high  and  dry.  Such  was  the 
method  of  beaching  as  practised  by  the  Phoenicians,  the  Egyptians,  and  other 
nations  during  the  infancy  of  the  mercantile  marine.  For  light  vessels  of 
shallow  draught  the  method  is,  no  doubt,  quite  satisfactory  and  sufficient^ 
and,  despite  its  primitive  nature,  it  is  still  in  use  at  the  commencement  of 
the  20th  century.  Its  modern  prototype  is  the  Gridiron,  located  in  a  tidal 
basin,  and  consisting  of  an  extended  series  of  parallel  beams  or  logs  laid  at 
regular  intervals  upon  a  firm  masonry  foundation.     The  operation  is  simply 


HYDRAULIC   LIFT.  463 

to  float  the  vessel  into  position  and  leave  her  suitably  moored  ;  the  tide  does 
the  rest. 

This  system,  though  simple  and  effective  in  its  way,  has  many  defects. 
In  the  first  place,  it  is  only  practicable  in  localities  where  there  is  sufficient 
range  of  tide  for  the  purpose.  Then  repairing  operations  are  intermittent 
and  have  to  be  suspended  with  each  recurring  period  of  high  water,  occasion- 
ing delay  and  the  repetition  of  manoeuvres.  And  lastly,  the  floor,  in  the 
absence  of  any  means  of  adjustment  to  the  keel  of  the  superimposed  vessel, 
does  not  lend  itself  to  any  but  the  rudest  kind  of  support. 

The  Carthaginians  seem  to  have  discovered  an  improved  method  of 
dealing  with  the  problem  by  the  introduction  of  Artificial  Slipways,  in  which 
smooth  timber  slides  formed  a  less  frictional  surface  for  the  haulage  of  ships 
than  the  rough  and  irregular  contour  of  a  natural  beach.  Furthermore, 
they  had  the  decided  advantage  of  being  utilisable  in  almost  any  situation. 
This  was  the  origin  of  the  modern  slipway  and  slip-dock.  The  design  has 
naturally  undergone  many  modifications  and  improvements  since  the  days 
of  triremes  and  galleys,  and  it  now  exists  in  several  distinct  forms,  but  it  is 
still  essentially  the  same  design.  It  would,  of  course,  be  superfluous  to  trace 
the  various  stages  of  its  development,  and  we  need  only  coDcern  ourselves 
with  the  features  displayed  by  its  representative  of  the  present  day.  Long 
timber  ways,  carrying  iron  rails,  are  laid  at  a  uniform  slope,  ranging  in 
different  cases  from  about  1  in  15  to  about  1  in  25,  from  some  distance  under 
water  to  a  point  at  which  the  longest  vessel  to  be  accommodated  is  com- 
pletely out  of  the  range  of  the  tide.  A  cradle  or  travelling  frame  is  passed 
down  the  ways  and  under  the  oncoming  vessel's  keel.  The  latter  takes  a 
bearing  upon  the  cradle,  which  is  then  drawn  up  to  the  highest  point  by 
suitable  hauling  gear.  Despite  its  advantages,  the  drawbacks  to  the  system 
are  sufficient  to  prevent  its  general  adoption.  The  length  of  a  slipway  is 
necessarily  great,  on  account  of  its  prolongation  under  water  to  a  depth 
equal  to  the  draught  of  vessels  using  it.  This  entails  the  appropriation  of 
valuable  water  space  and  offers  obstruction  to  navigation.  To  obviate  these 
ill  effects  to  some  degree,  the  cradle  has  been  made  telescopic  or  collapsible, 
80  that  it  consists  of  sections  attached  to  one  another  by  sliding  bars. 
These  sections,  compressed  at  the  foot  of  the  slipway,  are  drawn  out  to  their 
full  extent  by  the  hauling  apparatus  as  each  portion  receives  its  propor- 
tionate load.  The  percentage  of  length,  however,  saved  by  this  device  is 
small.  The  appropriation  of  land  space  in  congested  districts  is  also  an 
expensive  matter,  and  recognition  of  this  fact  has  led  to  the  introduction  of 
side  walls  and  a  pair  of  watertight  gates  at  low-water  level.  The  ship  has 
then  only  to  be  withdrawn  within  the  gates  which  shut  out  the  tide.  In 
this  respect  the  slipway  trenches  upon  the  province  of  the  graving  dock  and 
becomes  a  Slip-dock. 

To  do  away  with  the  excessive  length  of  a  slipway,  the  Hydraulic  Lift  was 
devised,  towards  the  middle  of  last  century,  by  the  late  Edwin  Clark.  In 
some  respects  it  is  akin  to  the  gridiron,  consisting  of  a  horizontal  platform 


464  DOCK   ENGINEERING, 

upon  which  a  vessel  can  be  floated.  Here,  however,  the  resemblance  ceases, 
for  in  this  case  the  platform  is  formed  of  pontoons,  the  whole  of  which  are 
raised  by  hydraulic  pressure  until  the  vessel  is  entirely  above  water.  The 
operation,  in  fact,  produces  the  efiPect  of  a  falling  tide  and  avoids  the  incon- 
venience of  a  rising  one.  The  whole  structure  remains  afloat  until  the  time 
comes  for  the  vessel  to  be  re-launched. 

We  now  come  to  the  Dry  or  Graving  Dock,  the  principle  of  which  is  the 
reverse  of  those  already  described ;  instead  of  withdrawing  the  ship  from  the 
water,  the  water  is  withdrawn  from  the  ship.  In  its  earlier  stages,  it  is  but 
the  natural  and  logical  development  of  the  beaching  process.  Finding  the 
inconveniences  of  only  having  access  to  their  vessels  during  short  periods  at 
low  water,  the  obvious  advantage  of  enclosing  them  within  temporary 
mounds  or  banks  of  earth  would  suggest  itself  to  enterprising  shipwrights 
of  ancient  times.  Then,  in  order  to  reduce  the  labour  of  constructing  a 
continuous  dam,  the  selection  of  a  natural  creek  or  inlet  would  occur, 
involving  a  dam  across  only  one  end.  From  a  natural  creek  to  an  artificial 
chamber  is  but  a  single  step,  though,  no  doubt,  some  time  would  intervene 
between  the  two  stages. 

A  modern  graving  dock  is  an  excavated  chamber,  three  sides  and  the 
floor  of  which  are  lined,  either  naturally  or  artificially,  with  watertight 
material.  The  fourth  side,  or  end,  is  the  entrance,  and  is  provided  with  a 
pair  of  gates  or  a  caisson.  After  the  entry  of  a  ship,  the  entrance  is  closed 
and  the  water  is  pumped  from  within  the  dock,  though  in  certain  cases  the 
operation  may  be  partially  efiected  or,  at  any  rate,  assisted  by  the  fall  of 
the  tide. 

Lastly,  we  have  the  Floating  Dock — a  hollow  structure,  formerly  of  wood 
but  now  universally  of  iron  or  steel,  generally  similar  to  a  graving  dock  in 
outline,  but  gradually  diverging  therefrom  in  process  of  evolution,  and 
entirely  dissimilar  in  action,  in  that  it  reverts  to  the  former  principle  of 
withdrawing  the  vessel  from  the  water.  It  is,  in  fact,  an  outcome  of  the 
hydraulic  lift.  To  receive  its  charge  the  floating  dock  is  sunk  to  the  requisite 
depth  by  allowing  its  air  chambers  to  fill  with  water,  which  is  afterwards 
removed  by  pumping  when  the  vessel  has  been  berthed.  This  process 
causes  the  dock  to  rise  bodily  and,  in  so  doing,  to  lift  the  vessel  above  the 
water  line. 

Thus  far  we  have  very  briefly  reviewed  the  rise  and  progress  of  various 
repairing  systems.  We  will  now  proceed  to  consider  them  more  closely 
with  reference  to  their  construction  and  equipment.  But,  before  doing  so, 
it  will  be  well  to  lay  down  three  general  essential  requirements  of  any 
system  : — 

1.  Accessibility. — All  parts  of  a  vessel's  keel  and  under  side  must  be 
readily  accessible.  Beaching  is  deficient  in  this  respect,  unless  the  position 
of  the  vessel  be  changed,  and  this  is  not  always  feasible. 

2.  Ventilation. — If  a  vessel  has  to  be  painted,  it  is  essential  that  her 
sides  should  dry  as  quickly  as  possible,  and  this  result  is  best  achieved  in 


CAPACITY.  465 

the  open.  Hence  gridirons,  slipways,  and  lifts  have  a  certain  advantage 
over  docks,  and,  of  the  latter,  the  floating  dock  is  more  open  than  the 
graving  dock. 

3.  Light. — Artificial  light  can,  of  course,  be  provided,  but  natural  light 
is  always  better  and  more  economical.  The  same  comparison  holds  good  as 
in  the  case  of  ventilation. 

Apart  from  these  general  requirements,  there  are  various  points  of  view 
from  which  the  advantages  of  the  systems  may  be  estimated,  and,  accordingly, 
we  will  deal  with  these  in  order.  Setting  aside  the  gridiron  as  too  primitive 
and  the  hydraulic  lift  as  now  superseded  by  its  development,  the  floating 
dock,  we  may  usefully  confine  our  comparison  to  the  remaining  three  types. 

4.  Capacity. — Although  no  apparent  limitation  attaches  to  the  size  of 
slipways,  yet  it  will  be  found  that  they  have  only  been  constructed  for 
a  comparatively  small  class  of  vessel — those  with  lengths  not  exceeding 
350  feet  and  dead  weights  of  not  more  than  5,000  tons.  This  arises  from 
three  causes  :  first,  the  excessive  length  of  slipway,  both  above  and  below 
water,  required  for  the  reception  of  larger  ships ;  secondly,  the  liability  of 
such  ships  to  undergo  strain  during  the  process  of  getting  them  on  to  the 
cradle  ;  and,  thirdly,  the  difficulty  of  keeping  a  very  large  slipway  remunera- 
tively engaged.  Theoretically,  there  is  no  reason  why  a  ship  of  any  length 
and  weight  should  not  be  supported  upon  a  slipway  of  sufficient  size  and 
stability,  and  to  economical  reasons  alone  must  be  attributed  the  main 
objection  to  its  more  extended  utility. 

Judging  from  existing  examples,  the  size  of  graving  and  floating  docks  is 
restricted  by  no  such  consideration,  and  their  maximum  capacity  has  yet  to 
be  determined.  Every  succeeding  year  witnesses  an  increase  in  dimensions. 
As  regards  their  relative  capacities  there  is  some  difficulty  in  instituting  a 
comparison,  for  that  of  a  graving  dock  is  based  upon  its  linear  dimensions, 
the  weight  of  any  incoming  vessel  not  entering  into  account,  while  a  floating 
dock,  open  at  each  end,  is  gauged  by  the  weight  which  it  can  lift,  and  is 
practically  independent  of  size.  The  largest  vessels,  designed  or  in  existence 
at  the  present  time,  are  nearing  or  have  reached  a  length  of  760  feet,  a  beam 
of  78  feet,  a  loaded  draught  of  36  feet,  and  a  displacement  of  upwards  of 
38,000  tons.  The  largest  graving  docks  have  lengths  of  over  850  feet, 
entrances  more  than  85  feet  wide,  and  a  draught  of  water  on  sill  at  high 
water  of  ordinary  spring  tides  somewhat  exceeding  32  feet.  While  the 
superficial  area  of  such  graving  docks  is  largely  in  excess  of  all  present 
requirements,  it  will  be  noticed  that  there  is  an  apparent  insufficiency  in 
draught,  and  this  fact  is  often  alleged  as  a  disqualification.  But  in  the 
great  majority  of  cases,  a  vessel  will  discharge  the  whole  or  the  larger  part 
of  her  cargo  before  entering  the  dock  and  so  reduce  her  draught  by  several 
feet.  At  the  same  time,  it  must  be  admitted  that  the  margin  thus  obtained 
is  by  no  means  a  large  one,  and  it  frequently  disappears  at  neap  tides,  while 
there  is  always  the  remote  contingency  of  a  seriously  damaged  vessel  having 
to  be  docked  fully  loaded  immediately  upon  its  arrival  at  a  port.     It  is  an 

30 


466 


DOCK   ENGINEERING. 


unfortunate  feature  of  grating  dock  oonstruction  that  an  extra  foot  in  depth 
adds  most  disproportionately  to  the  cost. 

The  largest  floating  dock  at  present  in  existence  has  a  lifting  power  of 
18,000  tons,  or  about  one-half  of  maximum  requirements.  The  increase 
in  size  of  late  years  has,  however,  been  so  rapid  that  there  is  every  proba- 
bility of  the  disparity  being  cancelled  in  a  very  short  time.  It  has,  moreover, 
been  justifiably  pointed  out  that,  whereas  a  graving  dock  is  unable  to 
accommodate  a  vessel  any  one  of  whose  dimensions  exceeds  a  certain  limit, 
a  floating  dock,  on  the  other  hand,  is  quite  capable  of  partially  raising  a 
heavier  vessel  than  she  has  been  designed  to  lift  entirely  above  water.  A 
floating  dock  at  Barrow,  with  a  lifting  power  of  little  more  than  3,000  tons 
and  a  length  of  242  feet,  raised  the  s.s.  "  Empress  of  China,"  485  feet  long 
and  4,500  tons  displacement^  sufficiently  high  to  allow  her  propellers  to  be 
removed  and  replaced.  Any  excessive  overhang,  however,  is  liable  to  cause 
severe  strain  both  in  the  ship  and  the  dock,  and  it  is  inadvisable  to  risk 
carrying  such  an  experiment  too  far. 

The  following  table  affords  some  particulars  of  the  largest  existing 
ships : — 

TABLE  XXXY. — Particulars  of  Some  of  the  Largest  Modern  Vessels. 


VeBBel. 

Line. 

Date  of  Con- 
struction. 

Extreme 
Length. 

4 
Feet. 

Moulded 
Depth. 

1 

QroBB 
Tonnage. 

Displace- 
ments 

Jfeet. 

Feet. 

Feet. 

Tons. 

Tons. 

Baltic,      .... 

White  Star,     . 

1903 

725-7 

75 

49 

•   B  •• 

23,000 

40,000 

Cedric,     .... 

>»             •        • 

1902 

700 

75 

49-3 

3t5-5 

21,000 

38,200 

Kaiser  Wilhelm  XL, 

North  Grerman  Lloyd, 

1902 

706-6 

72 

52-6 

29 

20,000 

26,000 

Kronprinz  Wilhelm, 

)) 

1901 

663 

66 

43 

29 

15,000 

21,300 

Celtic,      .... 

White  Star,     . 

1901 

700 

76 

49 

36 

20,880 

37,700 

DeutBchland,    . 

Hambure  American, 
French  l^ansatlantiCf 

1900 

684 

67 

44 

29 

16,502 

23,620 

La  Lorraine,  La  Savoie,  . 

1900 

582-4 

60-6 

39-4 

25-6 

11,869 

15,400 

Ooeanic,   .... 

White  Star,     . 

1899 

704 

68-3 

49 

32-5 

17,274 

28,500 

Kaiser  Wilhelm  der  Grosse, 

North  German  Lloyd, 

1898 

648-7 

66 

43 

28 

14,349 

20,880 

St.  Paul,  St.  Louis, 

American, 

1895 

554-2 

63 

42 

26 

11,629 

16.000 

Campania,  Lucania, 

Cunard,    . 

1893 

622 

65-3 

41-6 

25 

12,500 '  18,000 

5.  Initial  Cost. — The  factor  of  locality  enters  so  largely  into  the  question 
of  cost  of  construction  of  slipways,  that  it  is  impossible  to  fix  any  absolute 
standard  of  comparison.  For  example,  a  slipway  at  Penarth,  built  in  1879, 
and  capable  of  accommodating  a  vessel  of  2,500  tons  deadweight,  cost 
£25,000  or  £10  per  ton.  On  the  same  basis,  a  slipway  at  Belfast, 
constructed  in  1847,  for  vessels  of  1,000  tons,  should  only  have  cost 
£10,000,  whereas  it  cost  £17,000  or  nearly  double  that  amount,  of  which 
£12,000  was  spent  on  foundations  alone.  Mr.  Walter  Beer*  estimates  the 
cost  of  slipways  for  small  boats  of  600  tons  at  £9,000  or  £15  per  ton — an 
intermediate  value  to  the  previous  cases.     Not  much  reliance,  therefore, 

♦Beer  on  "  Ship  Slipways,"  Min.  Proc.  Inst.  CE,^  vol.  oxviii. 


INITIAL  COST,  467 

oould  be  placed  upon  an  estimate  for  a  slipway  to  accommodate  modern 
ships  of  from  20,000  to  30,000  tons,  with  lengths  of  600  to  700  feet, 
especially  when  the  largest  slipway  in  existence  is  one  with  a  cradle  of 
only  330  feet  and  a  power  of  5,000  tons. 

So,  too,  with  graving  docks.  One  at  Newport  (Mon.),  built  in  1890,  cost 
£70  per  lineal  foot,  or  10s.  per  square  yard  of  internal  cross-section  below 
high  water;  another  at  Biloela,  New  South  Wales,  completed  about  the 
same  date,  cost  £440  10s.  per  lineal  foot,  or  26s.  per  square  yard  of  section ; 
for  a  third  at  Halifax,  finished  in  1889,  the  figures  were  £233  and  158.  6d. 
respectively.  No  useful  purpose,  accordingly,  can  be  served  by  attempting 
to  fix  the  unit  of  expenditure.  The  kind  of  material  (whether  concrete, 
timber,  brickwork,  or  masonry),  the  mode  of  construction,  the  nature  of  the 
foundation,  the  state  of  the  labour  market,  and  the  cost  of  transport — all 
these  conflicting  conditions  combine  to  render  nugatory  calculations  based 
on  existing  data. 

The  fluctuation  in  the  price  of  iron  and  steel,  more  than  anything  else, 
influences  the  cost  of  a  floating  dock,  but  there  are  often  special  features 
to  be  taken  into  account.  Not  infrequently  a  site  has  to  be  specially 
prepared  by  dredging  for  its  reception.  Shore  connections  and  approaches 
are  required,  more  particularly  for  the  type  known  as  the  *'  ofl'-shore  dock." 
Also  for  docks  built  in  this  country,  to  be  located  at  Colonial  or  Conti- 
nental ports,  there  is  the  cost  of  freight  or  of  towage  and  insurance. 

Herr  Howaldt*  of  Kiel,  estimates  the  cost  of  composite  floating  docks 
of  wood  and  iron,  designed  on  his  system,  at  llOs.  to  120s.  per  ton  of 
lifting  power,  if  built  in  the  west  of  Europe,  and  at  170s.  to  200s.  per  ton 
if  built  in  the  east  of  Europe. 

For  docks  altogether  of  iron,  he  estimates  the  cost  at  180s.  to  200s.  and 
230s.  to  270s.  per  ton  of  lifting  power,  in  the  west  and  east  of  Europe 
respectively.  Messrs.  Clark  and  Standfield  state  "an  all-round  figure  of 
£10  per  ton  of  lifting  power  for  floating  docks  of  medium  size.'' 

At  first  sight  it  may  appear  that  the  cost  of  a  light,  hollow  iron 
structure,  built  amid  the  conveniences  of  the  shipbuilding  yard,  must 
inevitably  be  less  than  that  of  a  masonry  or  concrete  dock,  involving  a  deep 
•excavation,  with  expensive  gates  and  other  appurtenances.  Such,  however, 
is  not  necessarily  the  case.  Undoubtedly,  there  are  circumstances  of  site 
and  foundation  which  would  render  the  construction  of  a  graving  dock  an 
inadvisable,  if  not  an  impossible,  proceeding,  but  it  is  not  improbable 
that  the  same  conditions  would  equally  preclude  the  construction  of  such 
essential  adjuncts  to  a  floating  dock  as  a  jetty  and  a  shipbuilding  yard. 
These  circumstances  are  generally  abnormal  and,  in  the  main,  local  con- 
ditions are  favourable  to  either  type. 

Speaking  roughly,  but  upon  a  basis  of  experience,  the  cost  of  a  graving 
dock  constructed  in  this  country,  under  normal  conditions,  to  accommodate 
a  vessel  700  feet  in  length,  should  not  greatly  exceed  £200,000.      The 
♦  Howaldt  on  "Floating  Docks,"  IrU.  Nov.  Cong.^  DuBseldorf,  1902. 


468  DOCK   ENGINEERING. 

displacement  of  a  vessel  of  this  size  would  be  at  least  25,000  tons,  and^ 
according  to  Herr  Howaldt  and  Messrs.  Olark  and  Standfield  alike,  the 
cost  of  a  floating  dock  to  receive  her  would  lie  between  £225,000  and 
£250,000.  Or,  looking  at  the  matter  another  way,  the  proportion  of 
deadweight  of  a  floating  dock  to  lifting  power,  from  a  number  of  examples, 
averaging  about  45  to  100,  the  deadweight  of  a  floating  dock  as  above 
would  be  11,250  tons,  which  at,  say,  £20  per  ton  (to  include  all  fittings  and 
pumping  machinery),  comes  to  £225,000  as  before.  This  is  without  taking 
into  consideration  any  ancillary  works,  such  as  shore  connections,  site 
dredging,  <fec.  So  that,  as  regards  the  cost  of  the  largest  docks,  the  balance 
inclines  in  favour  of  the  graving  dock.  This  opinion  receives  confirmation 
Id  the  report  of  the  engineer  (Mr.  Wm.  Ferguson)  to  the  Port  of  Wellington, 
N.Z.,  who  after  a  tour  of  inspection  of  the  repairing  docks  in  Great  Britain, 
Australia,  and  the  United  States,  recommends  the  adoption  of  a  concrete 
graving  dock  for  that  port  as  less  expensive  than  a  floating  dock  of  similar 
capacity.* 

6.  Maintenance  and  Repairs. — ^The  structures  of  slipways  and  graving 
docks,  if  solidly  built  in  the  first  instance,  require  very  little  attention 
afterwards,  whereas  owing  to  the  destructive  action  of  salt  water  on 
ironwork,  floating  docks  call  for  regular  inspection  and  frequent  painting. 
In  slipways  the  cradle  wheels  occasionally  get  broken,  but  this  item  should 
equitably  be  included  in  repairs  to  machinery,  which  are  common  to  all 
three  types,  though  possibly  a  more  pronounced  item  in  floating  docks. 
The  structural  repairs  of  a  concrete  or  masonry  graving  dock,  with 
greenheart  gates,  are  infinitesimal.  If  iron  gates  are  used,  they  will 
necessitate  some  expense  of  upkeep,  as  against  a  reduction  in  their  cost 
of  construction  compared  with  wooden  gates.  No  doubt,  the  timber 
graving  docks  prevalent  in  the  United  States  require  extensive  repairs 
from  time  to  time,  but  in  this  case  also,  the  capitalised  amount  is  balanced 
by  a  corresponding  economy  in  initial  expenditure,  and  they  represent^ 
moreover,  a  very  limited  class. 

According  to  some  statistics,  supplied  by  Messrs.  Clark  and  Standfield, 
the  average  annual  cost  of  upkeep  of  iron  floating  docks  ranges  between 
'75  and  1*5  per  cent,  of  the  invested  capital.  The  former  figure  represents 
exceptional  care  in  primary  preparation,  the  outside  surfaces  being  par- 
ticularly well  painted  and  '*  the  whole  of  the  mill-scale  having  sweated  off 
before  launching,  so  that  the  paint  was  fairly  on  the  iron." 

7.  Working  Expenses. — In  this  respect  the  floating  dock  exhibits  an 
economy  far  beyond  that  of  the  graving  dock,  because,  in  the  former  case, 
the  quantity  of  water  to  be  removed  by  pumping  is  little  more  than  the 
actual  displacement  of  the  vessel  which  is  being  docked,  while  in  the  latter 
case,  unless  any  assistance  can  be  rendered  by  a  falling  tide,  the  volume 
of  water  to  be  pumped  out  is  the  cubic  contents  of  the  graving  dock,  less 
the  displacement  of  the  ship.     Furthermore,  while  for  a  graving  dock  the 

*  Report  on  Docking  Facilities  for  the  Port  of  Wellington,  1901. 


DURABILITY.  469 

amount  of  pumping  increases  with  a  decrease  in  the  size  of  the  vessel,  for 
a  floating  dock  the  reverse  is  the  case,  since  it  need  only  be  sunk  to  a  depth 
sufficient  to  take  the  vessel's  keel.  There  is  only  one  point  which  slightly 
reduces  the  overwhelming  advantage  of  the  floating  dock,  and  that  is  in 
reference  to  the  head  pumped  against.  In  the  case  of  the  graving  dock, 
the  head  varies  from  zero  to  the  depth  of  the  fldor  below* free  water  level, 
and  the  mean  head  may  be  approximately  stated  at  one-half  this  depth. 
In  the  case  of  the  floating  dock,  the  initial  head  is  the  draught  of  the 
vessel  plus  the  depth  of  the  floor  pontoon,  and  the  final  head  is  the  latter 
of  these  two  amounts.  Hence,  supposing  two  vessels  of  equal  draught 
taken,  the  one  on  to  a  floating  dock  and  the  other  into  a  graving  dock, 
the  depth  of  water  in  the  docks  being  likewise  the  same,  then  the  mean 
head  of  pumping  in  the  former  instance  would  exceed  that  in  the  latter 
by  one-half  the  depth  of  the  floor  pontoons.  But  this  advantage  is  more 
apparent  than  real,  for  it  only  occurs  in  the  isolated  case  of  a  vessel  of 
maximum  draught  using  the  graving  dock.  In  the  majority  of  cases  the 
clearance  between  keel  and  floor  is  much  greater  than  the  semi-depth  of 
■a  floating  pontoon. 

From  a  specific  comparison  between  two  docks  of  equal  capacity,  it  has 
been  found  that  the  pumping  power  required  for  the  graving  dock  was 
nearly  four  times  that  required  for  the  floating  dock,  the  duration  of 
pumping  being  the  same  in  both  cases.  If  the  power  had  been  equalised 
by  difiPerentiating  the  time,  the  excess  consumption  of  fuel  and  oil  would 
fltill  have  been  retained.  Again,  apart  from  the  primary  emptying  of  a 
graving  dock,  an  auxiliary  drainage  pump  is  required  to  deal  with  leakages. 
In  a  floating  dock  there  is  no  leakage,  and,  therefore,  no  necessity  for  a 
drainage  pump. 

On  the  other  hand,  it  must  not  be  overlooked  that,  the  main  pumps 
being  only  intermittently  employed,  it  is  quite  feasible  for  a  single  pumping 
station  to  serve  two  or  more  graving  docks,  whereas  each  floating  dock 
requires  its  own  pumping  plant,  and  this  is  often  subdivided  and  dis- 
tributed throughout  the  dock.  Again,  on  account  of  the  necessity  of 
maintaining  equilibrium  in  the  floating  dock,  great  care  has  to  be  exercised 
and  attention  paid  to  numerous  valves.     This  entails  a  large  working  stafi^ 

8.  Durability. — Here  the  balance  of  merit  reverts  to  the  granite,  brick- 
work, or  concrete  graving  dock,  which  is  practically  indestructible. 

The  life  of  an  iron  or  steel  floating  dock  depends  naturally  on  the  care 
which  is  devoted  to  its  maintenance,  and  upon  the  locality  in  which  it  is 
placed.  In  Ohap.  viii.,  it  has  been  stated  that  a  pair  of  iron  gates,  under 
average  conditions,  may  be  expected  to  last  thirty  years,  but  as  overhauling 
and  repairing  can  be  carried  out  much  more  effectively,  and  with  greater 
facility  in  the  case  of  a  self-docking  floating  dock,  these  more  favourable 
•conditions  warrant  the  expectation  of  somewhat  greater  longevity — ^say 
forty  or  forty-five  years. 

The  Bermuda  Dock,  launched  in  1868,   was  found  to  have  suffered 


470  DOCK  ENGINEERING. 

considerably  by  the  end  of  the  century,  and  other  docks  of  the  non-self- 
docking  type  have  undergone  equally  rapid  deterioration ;  but,  on  the  other 
hand,  the  Oartagena  Dock,  built  in  1859,  is  still  in  good  repair,  as  also  are 
the  pontoons  of  the  Victoria  Dock,  constructed  in  1857. 

A  timber  graving  dock  must  necessarily  be  very  liable  to  decay  owing 
to  its  alternate  exposure  to  the  wet  and  the  dry  condition. 

It  has  been  pertinently  pointed  out  that  a  dock  may  outlast  its  period 
of  usefulness ;  that,  with  the  rapid  increase  in  size  and  alteration  in  shape 
of  modern  ships,  a  repairing  dock  ultimately  becomes  incapable  of  receiving 
any  but  those  which  are  obsolete.  This  may  be  true  to  some  extent,  but  it 
is  no  less  true  that  both  graving  and  floating  docks  are  capable  of  being 
altered  within  certain  limits,  so  as  to  adapt  themselves  to  new  conditions. 
They  have  been  lengthened  in  more  than  one  instance.  Any  increment  in 
width  and  depth,  however,  can  only  be  obtained  at  practically  prohibitive 
expense,  and  the  author  is  only  aware  of  a  very  few  instances  in  which  such 
alterations  have  been  carried  out.  The  cutting  away,  in  some  cases,  of  the 
lowermost  altar-courses  of  masonry  docks  has  produced  an  additional  few 
feet  of  bottom-width  at  a  moderate  cost. 

9.  General  Adaptability. — There  are  several  detached  points  of  practical 
importance  which  may  be  grouped  under  the  above  heading. 

(1)  A  floating  dock  has  the  advantage  of  mobility.  It  may  be  towed  to 
another  port.     Per  contra  it  may  founder  or  sufiPer  shipwreck. 

(2)  A  floating  dock  may  conceivably  be  trimmed  by  water  ballasting  to 
take  a  ship  with  a  list  so  pronounced  that  it  could  not  pass  through  the 
vertical  profile  of  a  graving  dock  entrance.  Practically,  such  a  step  would 
be  attended  with  serious  risk  of  capsizing. 

(3)  Accidents  are  more  rare  in  graving  docks.  Floating  docks  have  sunk 
under  ships  of  heavy  tonnage,  though  not,  it  must  be  admitted,  in  recent 
times  or  with  docks  of  the  latest  type. 

(4)  A  floating  dock  takes  comparatively  little  time  to  construct — say, 
from  seven  to  nine  months  with  expedition.  An  average  graving  dock 
could  hardly,  under  the  most  favourable  circumstances,  be  built  in  less 
than  two  years. 

(5)  Where  land  is  dear,  or  the  site  restricted,  a  floating  dock  either 
renders  its  purchase  needless  or  allows  of  its  allocation  to  other  purposes. 

Design  and  Construotion  of  Slipways. 

The  essential  parts  of  a  slipway  are: — (1)  The  foundation,  (2)  the 
permanent  way,  (3)  the  cradle,  and  (4)  the  hauling  machinery. 

The  Foundation  should,  if  possible,  be  absolutely  incompressible;  but, 
failing  that  ideal,  a  very  slight  settlement  is  permissible,  provided  it  be 
uniform  throughout.  Any  transition  from  an  elastic  to  a  rigid  base,  or 
wee  versdf  throws  considerable  local  strain  upon  the  cradle,  often  resulting 
in  broken  rollers.     The  intensity  of  pressure  on  slipways  is  not  great,  the 


SLIPWAY  FOUNDATIONS. 


471 


superimposed  weight  being  spread  over  a  large  area.  In  the  largest  slip- 
ways at  present  in  existence,  the  weight  of  vessel  and  cradle  does  not  exceed 
10  tons  per  foot  run,  and  in  smaller  slipways,  it  may  be  taken  at  one-fourth 
less.  Accordingly,  where  the  ground  is  naturally  very  firm,  little  more  than 
mere  surface  dressing  will  be  requisite,  with  perhaps  a  shallow  bed  of 
concrete.  In  other  instances,  the  site  may  require  some  dredging  and 
subsequent  levelling  with  rubble  filling  to  the  under  side  of  a  concrete  bed, 
but  in  all  cases  of  uncertain  strata,  bearing  piles  should  be  resorted  to. 

A  very  considerable  portion  of  a  slipway  is  necessarily  under  water,  and 
the  construction  of  this  section  often  presents  some  difficulty.  At  places 
where  there  is  a  great  range  of  tide,  opportunities  are  afforded  at  low  water 
for  getting  the  bulk  of  the  work  done  without  serious  inconvenience.     On 


^•Oatdt^pOm 


^ya^ccr 


Figs.  459  and  460. — Slipway  Gonstniotion. 

the  other  hand,  where  the  tidal  range  is  small,  a  temporary  dam  for  the 
exclusion  of  water  from  the  site  becomes  a  desideratum,  if  not  a  necessity. 
The  expense  attending  this  mode  of  procedure  is  a  deterrent  to  its  ready 
adoption.  Under  favourable  circumstances,  the  work  may  be  economically 
carried  out  by  divers  in  a  sufficiently  satisfactory  manner.  The  following  is 
an  account  of  the  system  as  practised  by  Mr.  John  Thompson  : — "^ 

'*  When  the  portion  of  the  site  below  low  water  had  been  dredged  out  to 
the  desired  depth,  the  foundation  was  made  by  filling  in  broken  stone  of 

*  Lightfoot  and  Thompson  on  "  Slipways  for  Ships,"  Min,  Proc.  Inst.  C,E,,  vol.  Ixxii. 


472  DOCK  ENGINEERING. 

convenient  size  to  near  the  level  of  the  intended  platform.  Upon  this  a 
layer  of  macadam  was  placed,  bringing  the  foundation  up  to  the  required 
height.  As  a  guide  for  the  accurate  execution  of  this  work,  a  line  of  piles, 
A  (fig.  459),  was  driven  on  each  side  of  the  foundation,  clear  of  the  sides  of 
the  timber  platform,  and  to  these  piles,  guide  timbers,  B,  were  affixed  at  the 
required  inclination  of  the  slipway  and  at  the  depth  of  the  ends  of  the 
straight-edge  above  it.  The  foundation  was  now  ready  to  be  dressed  off  true 
by  divers,  who,  as  they  frequently  had  to  work  in  the  dark,  were  provided 
with  iron-faced  straight-edges,  0,  made  about  the  weight  of  a  similar  volume 
of  water  so  as  to  be  easily  moved.  These  were  long  enough  to  reach  across 
the  entire  foundation  and  to  slide  underneath  the  guide  timbers.  With 
these  straight-edges,  the  divers  were  able  to  dress  the  macadam  face  so  truly 
that,  in  one  case  of  a  foundation,  360  feet  long,  it  was  found,  after  the 
platform  was  finished,  there  was  only  one  error  of  ^j^  inch." 

In  the  construction  of  a  slipway  for  Earle*s  Shipbuilding  Co.,  at  Hull, 
by  Mr.  Godfrey,  in  1882,  the  method  of  piling  the  foundation  was  adopted. 
"Whole  timber  piles,  cross  sleepers,  and  longitudinal  bearers  were  used 
throughout.  In  the  centre  way,  two  rows  of  piles  were  driven,  18  inches 
apart  from  centre  to  centre,  transversely  and  3  feet  from  centre  to  centre, 
longitudinally.  For  the  side  ways  single  piles  were  driven,  6  feet  from 
centre  to  centre,  these  coming  opposite  every  second  row  of  piles  in  the 
centre  way,  thus  giving  one  pile  for  each  lineal  foot,  or  a  supporting  power 
of  10  or  12  tons  per  lineal  foot.  A  sleeper,  30  feet  long,  was  placed 
transversely  on  the  four  piles  and  one,  6  feet  long,  on  the  two  intermediate 
piles.  Upon  these  sleepers  were  fixed  the  longitudinal  timbers  or  rail 
bearers,  securely  fastened  with  oak  trenails.  The  centre  timbers  were 
4  feet  6  inches  wide  to  take  a  plate  of  the  same  dimensions.  The  ground 
for  4  feet  below  the  cross  sleepers  was  excavated  and  filled  with  rough  chalk 
for  a  width  of  15  feet  on  both  sides  of  the  slipway  ;  the  whole  was  planked 
over  with  3-inch  redwood  deals."  The  piling  was  effected  as  follows : — ^A 
cofferdam  could  not  be  thought  of,  the  situation  being  too  exposed  and  the 
method  too  costly.  The  width  of  the  slipway  being  30  feet,  a  traveller 
35  feet  wide  was  constructed  to  span  it  transversely  and  placed  upon  a  line 
of  rails,  the  diameter  of  the  wheels  being  made  to  suit  the  inclination  of  the 
slipway.  Upon  this  traveller  was  placed  a  Sissons  &  White's  steam  pile- 
driver,  with  40  feet  leaders,  and  a  ram  weighing  21  cwts.  As  the  tide  ebbed 
the  pile-driver  was  allowed  to  go  down  upon  the  traveller  by  gravitation, 
and  the  piles  were  driven  in  successive  rows  of  two  and  four  alternately,  the 
machine  being  worked  across  the  traveller  from  side  to  side.  When  the  tide 
rose,  the  traveller  was  withdrawn  to  the  higher  portion  of  the  work. 

The  Permajient  Way  is  usually  laid  at  some  gradient  between  1  in  15  and 
1  in  25.  There  is  a  slipway  at  Palermo  with  a  gradient  of  1  in  13*3,  but 
this  is  exceptionally  steep,  the  average  being  1  in  20.  Any  flatter  slope 
than  1  in  25  causes  an  unnecessarily  great  length  of  slipway.  Occasionally 
curved  slipways  may  be  found  with  a  steep  inclination  below  the  water-line, 


CRADLE.  473 

gradually  becoming  flatter  as  the  summit  is  reached.  The  permanent  way 
generally  consists  of  three  or  four  main  lines  of  rails,  arranged  in  pairs  close 
together,  the  rails  being  of  a  shallow  type,  with  3  to  6  inches  flat  bearing 
surface.  Between  the  centre  pair  is  a  strong  cast-iron  rack  to  receive  the 
pawls  of  the  cradle.  The  rails  are  spiked  to  longitudinal  sleepers  which,  in 
their  turn,  are  carried  by  cross  sleepers  laid  upon  or  bedded  in  the  prepared 
foundation.  For  the  immersed  portion  of  the  way,  it  has  been  found 
convenient  to  construct  short  lengths  of  a  timber  platform  upon  which  the 
rails  are  laid,  and  to  float  these  out  successively  into  position  between  guide 
piles,  D  (fig:  460).  The  platform  has  then  been  lowered  into  position  by 
means  of  a  winch,  the  necessary  weight  for  effecting  this  being  supplied  by 
the  ballast.'^ 

Great  care  is  requisite  in  laying  the  rails  to  see  that  there  are  no 
inaccuracies  in  the  joints.  In  order  to  ensure  an  even  bearing,  it  is  advis- 
able to  bed  the  rails  upon  a  layer  of  tarred  felt. 

The  Cradle  is  a  framework  of  timber  or  iron,  usually  consisting  of  three 
main  longitudinals,  of  which  the  centre  one,  carrying  the  keel  blocks,  is 
much  stronger  than  the  other  two.  All  three  longitudinals  are  connected 
by  transverse  pieces  of  iron  or  wood.  The  latter  also  serve  to  carry  the 
sliding  bilge  blocks.  The  whole  structure  is  mounted  over  numerous  cast- 
iron  rollers,  working  in  carriages  of  the  same  metal.  Pawls  are  attached  to 
the  centre  longitudinal  of  the  cradle,  at  intervals  of  about  20  feet,  and 
these  engage  in  the  rack  in  the  permanent  way  and  prevent  any  back  slip. 
It  will  generally  be  found  useful  to  provide  short  supplementary  lengths  of 
cradle  to  attach  to  the  main  one,  in  case  a  very  large  vessel  has  to  be 
accommodated.  A  wrought-iron  plough,  for  the  removal  of  silt  accumula- 
tions upon  the  rails,  is  a  serviceable  adjunct  to  each  longitudinal. 

With  the  object  of  utilising  a  slipway  to  its  fullest  extent,  various 
contrivances  have  been  adopted  for  releasing  the  cradle  from  its  first  load, 
in  order  that  it  may  return  for  a  second.  One  method  of  achieving  this 
result  IB  that  of  pivoting  the  cross  pieces  to  the  side  longitudinals,  so 
that  they  may  be  swung  round  to  rest  upon  the  latter.  After  the  vessel 
has  been  drawn  up  to  its  assigned  position,  it  is  wedged  up  on  fresh  blocks 
placed  upon  the  ways  between  the  longitudinals,  the  cross  pieces  are 
swung  round,  the  bilge  blocks  and  keel  blocks  released,  and  the  cradle  is 
available  for  a  second  journey.  Another  method  (Thompson  and  Cooper's) 
is  to  employ  two  cradles  with  ways  constructed  at  different  inclinations. 
When  the  vessel  has  reached  a  certain  point,  it  is  transferred  from  the  first 
cradle  to  the  second  by  means  of  fresh  bilge  blocks  on  the  latter.  The 
cradles  move  simultaneously,  and  the  steeper  slope  of  the  second  causes  it 
to  gradually  raise  the  vessel  off  its  previous  bearings.  In  this  case  also 
the  cross  pieces  are  pivotted  for  removal. 

Hauling  Machinery. — The  subject  of  hauling  machinery  will  be  more  ap- 
propriately considered  under  the  head  of  Working  Equipment  in  Chap.  xii. 

*  Mill.  Proc,  Inst,  C.E.,  vol.  Ixxii.,  p.  168. 


474  DOCK  ENGINEERING. 

Sliding  Slipways. — A  distinct  system  of  slipway  from  the  foregoing  is  the- 
sliding  slipway,  in  which  a  sledge  takes  the  place  of  a  cradle.  The  waya 
are  necessarily  well  greased,  but  in  any  case,  the  friction  is  greater  and 
tiie  wear  of  the  structure  much  more  considerable.  The  system  is  only 
adopted  in  isolated  instances  and  under  special  circumstances,  notably  at 
Palermo,'^  where  the  configuration  of  the  ground  is  precipitous.  The  space 
available  was  enough  to  admit  of  a  slide,  but  not  of  a  line  of  rails,  the 
incline  of  which  would  have  to  be  far  less  steep  and  therefore  propor- 
tionately longer.  The  way  is  formed  of  a  large  number  of  cross  sleepers 
on  which  four  strong  beams  are  placed  longitudinally.  Above  the  water 
level  these  are  fixed,  but  the  lower  part  is  connected  by  hinges,  and  floats 
as  soon  as  the  weight  is  taken  off. 

Broadside  Slipway. — ABailtuaydes  transatlantiqiies  at  Lormont,  Bordeaux,, 
has  the  peculiarity  of  withdrawing  vessels  from  the  water  broadside-on,  as 
against  the  general  practice  of  taking  them  end-on.  The  slipway  is  400  feet 
long,  the  length  of  cradle  being  393  feet.  Either  one  vessel  of  410  feet 
length  can  be  accommodated,  or  two  single  vessels,  203  and  180  feet  long 
respectively.  The  lifting  power  is  3,000  tons.  The  extreme  width  is 
46  feet. 

The  slipways  at  the  shipbuilding  yard  of  the  Imperial  and  Royal  Danube 
Steam  Navigation  Co.,  at  Alt-Ofen,  in  Hungary,  have  been  constructed  on 
the  same  plan.  They  have  a  riverside  length  of  650  feet,  and  a  breadth 
inland  of  280  feet,  of  which  only  180  feet  is  permanent  way.  The  largest 
vessels  accommodated  are  250  feet  long  and  460  tons  light  displacement. 

Stresses  in  Slipways. — The  power  required  to  raise  a  ship  upon  a  slip- 
way is  divisible  into  two  portions — viz.  (1)  that  for  lifting  the  dead  weight 
of  the  vessel  and  its  cradle,  and  (2)  that  for  overcoming  friction. 
Theoretically,  the  force  necessary  to  draw  a  given  load,  W,  up  a  smooth 
incline  is  something  in  excess  of  W  sin  6,  where  6  is  the  angle  which  the 
incline  makes  with  the  horizontal.  But  as  ^  is  very  small  in  slipways,  and 
tan  ^  is  a  much  simpler  quantity  to  deal  with,  the  expression  may  be 
written  W  tan  ^,  without  sensible  error.  Now,  W  is  compounded  of  three 
items — the  weight  of  the  vessel  (w^),  the  weight  of  the  cradle  (tv^),  and  the 
weight  of  the  hauling  chain  and  rods  (w^).  Of  these,  at  least  two,  and 
sometimes  all  three,  contribute  some  frictional  resistance  to  movement,  in 
addition  to  their  own  weight.  There  is  the  friction  of  the  cradle  rollers, 
and  possibly  that  of  the  rods,  upon  the  ways ;  and  furthermore,  there  will 
be  a  certain  amount  of  friction  in  the  hauling  apparatus  itself.  Calling  the 
former  amount  /^,  and  the  latter  ^,  and  assuming  a  rigid  base,  we  have  the 
following  general  expression  for  the  pull  on  the  hauling  chain  : — 

P  =  (w  +  w?!  +  W.2)  tan  ^  +yi  +  /2.  .         .     (132) 

In  an  experiment  made  at  the  Dover  slipway,  where  the  gradient  is 
1  in  18,  with  a  total  load  of  242  tons,  it  was  found  that  the  effective  pull 

*  Min,  Proc,  LuU,  CE,,  voL  xlviii.,  p.  297. 


THE  DESIGN  OF  GRAVING  DOCKS.  475 

on  the  draw-chain  amounted  to  22*88  tons.     The  pover  absorbed  in  lifting: 

242 
was  -yo   ~  13*44  tons,  leaving  9*44  tons  for  the  power  absorbed  in  over- 

ooming  friction.     This  is  equivalent  to  3*9  per  cent,  of  the  weight  lifted. 

In  another  experiment^  made  at  a  slipway  on  the  River  Hooghlj,  with 
a  gradient  of  1  in  24,  the  weight  of  the  vessel  and  cradle  amounted  to- 
602  tons,  and  the  effective  haulage  to  45*2  tons.     The  power  absorbed  in 

lifting  being  -^j-  =  25*1  tons,  this  left  20*1  tons  as  the  power  absorbed 

by  friction,  or  3*33  per  cent,  of  the  weight  lifted. 

At  Palermo  the  friction  of  a  sliding  slip  on  a  gradient  of  1  in  13*3  ha» 
been  determined  to  be  about  7}  per  cent.,  and  the  power  required,  20  per 
cent,  of  the  whole  load. 

In  Messrs.  Lightfoot  and  Thomson's  system,  a  ram  for  the  return  stroke- 
has  to  be  pushed  home  simultaneously  with  the  lifting  of  the  cradle. 
Indicating  the  pressure  on  this  ram  by  the  letter  9,  the  inventors  have 
deduced  the  following  empirical  formula  from  a  number  of  actual  experi- 
ments, and  it  has  been  found  to  answer  with  fair  accuracy  for  slipwaya 
of  about  1  in  20 — 

p  = ,  +  !fL±^jL^.         .        .        .    (133) 

A  great  deal  depends  upon  the  efficiency  and  condition  of  the  ways. 
Unless  kept  clean,  silt  and  other  accumulations  will  cause  a  large  increase 
in  the  amount  of  resistance  to  movement.  The  fact  also  must  not  be 
overlooked  that  some  additional  force  will  be  required  to  overcome  the 
initial  inertia  of  the  load. 

The  Design  of  Graying  Dooks. 

■  » 

The  principles  affecting  the  design  of  graving  docks  do  not  materially 
differ  from  those  enunciated  in  Ohap.  vi.  for  the  design  of  entrance  locks. 
The  one  exception  is  in  regard  to  the  floor.  Locks,  although  the  water 
they  contain  is  constantly  undergoing  changes  of  level,  rarely  have  their 
floors  uncovered,  and  then  only  for  purposes  of  repair.  On  the  other  hand, 
the  very  function  of  a  graving  dock  demands  that,  for  the  greater  portion 
of  its  useful  time,  it  should  be  entirely  free  from  water.  With  a  natural 
foundation  of  hard  and  impervious  rock,  this  fact  entails  no  difference  in 
the  construction  of  the  two  chambers,  but  where  the  substrata  are  water- 
bearing, it  is  obvious  that  the  floor  of  a  graving  dock  must  be  made 
sufficiently  strong  to  resist  a  hydrostatic  pressure  on  the  underside, 
equivalent  to  the  greatest  head  of  water  in  the  immediate  neighbourhood. 

At  first  sight  it  may  appear  that,  under  these  conditions,  the  graving 
dock  floor  is  a  beam,  supported  at  each  end  by  the  side  walls  and  loaded 
uniformly.  That  such  is  not  the  case  is  evident  from  the  fact  that  few 
docks  (if  any)  in  the  world  would  be  capable  of  sustaining  the  estimated 


476  DOCK   ENGINEERING. 

load.  For  example,  the  coefficient  of  the  breaking  weight  of  8  to  1 
concrete,  uniformly  loaded,  may  be  taken  at  10  tons  for  a  unit  beam  (1  foot 
Bquare  section  and  1  foot  between  supports).  The  intensity  of  water 
pressure  due  to  a  moderate  head  of,  say,  35  feet  is  1  ton  per  square  foot. 
This  means  for  a  graving  dock  with  only  60  feet  width  at  floor  level,  a 
uniformly  distributed  load  of  60  tons  on  the  underside  of  the  floor.  To 
adequately  sustain  such  a  load  in  this  way,  the  floor  would  need  to  be 
38  feet  thick. 

For,  the  breaking  weight  of  the  beam  is  calculable  from  the  following 
formula : — 

B  W  =  -r=—  X  constant, 
and  substituting  the  known  values,  with  unit  breadth, 

60  =  ^l  X  10, 

whence  c?  =  19, 

and  taking  a  factor  of  safety  of  4,  which  is  equivalent  to  twice  (  ^4)  the 
depth,  the  thickness  of  the  floor  becomes  38  feet.  And  this  is  for  docks  of 
the  smallest  class.  For  docks  80  feet  and  upwards  in  width,  the  thickness 
would  be  even  more  absurdly  excessive. 

One  simple  consideration  will  dispose  of  the  beam  theory.  There  is 
hydrostatic  pressure  against  the  vertical  faces  of  each  extremity  of  the 
floor  amply  sufficient  to  neutralise  any  tension  in  the  latter,  and  subject 
it  entirely  to  a  compressive  stress.  In  other  words,  the  floor  must  be 
treated  as  an  arch,  either  actual  or,  in  the  case  of  flat  floors,  virtual. 

If  we  take  a  permissible  compressive  stress  for  concrete  of  20  tons  per 
square  foot,  and  consider  the  real  or  imaginary  arch  to  have  a  depth  or 
thickness  of  5  feet,  the  rise  of  the  invert  between  the  centre  and  sides  of 
the  dock  is  given  by  a  slight  modification  of  formula  (90),  explained  in 
Ohap.  X. 

where  r  is  the  rise,  I  is  the  span,  W  (  =  tvl)  the  total  weight,  and  t  the 

horizontal  thrust  at  the  centre.  With  unit  breadth  £  =  20x5=100  tons, 
and 

6C^60  _ 

"^       8  X  100  "  **  '^*' 
and  as  this  is  to  be  measured  to  the  centre  line  of  the  thickness  of  the  arch, 
a  flat  floor  only  requires  a  maximum  depth  of  7  feet  or  so,  which  is  a  much 
more  reasonable   figure,  and   one  which  accords  with  results  gained   by 
•experience. 

One  practical  observation  is  deducible  from  this  conclusion — viz.,  that 
the  joints  in  masonry  floors,  if  flat,  should  radiate  towards  the  imaginary 
centre  of  the  invert  It  is  assumed  that  concrete  floors  will  be  constructed 
in  a  homogeneous  mass,  without  joints. 


THE  CONSTRUCTION  OF  GRAVING  DOCKS.        477 

It  has  already  been  remarked  that,  where  the  natural  foundation  i& 
sound  hard  rock,  the  necessity  for  an  artificial  floor  to  withstand  hydrostatic 
pressure  disappears.  At  the  same  time,  care  must  be  taken  to  see  that 
there  is  no  possible  infiltration  of  water  under  the  sill.  The  slightest  film 
can  transmit  all  the  pressure  of  the  external  head.  To  prevent  any  such 
contingency — one  inevitably  producing  disaster — it  will  be  well  to  havo 
numerous  ground  drains  communicating  with  the  surface  of  the  floor,  so 
that  the  water  may  have  free  vent,  and  the  worst  effect  of  infiltration  will 
be  some  leakage  or  a  possible  flooding. 

There  is  yet  another  side  to  the  question.  When  a  ship  is  dry-docked, 
her  weight  is  transmitted  through  the  keel-blocks  to  the  floor,  the  centre 
line  of  which  consequently  undergoes  a  shear  on  each  side  of  the  blocks- 
equivalent  to  this  weight.  And,  as  the  imposed  stress  due  to  the  vessel  is 
best  taken  in  the  form  of  compression,  it  will  be  advisable  to  design  the 
floor  so  that  it  may  possess  a  second  real  or  virtual  arch,  in  this  case  upright,, 
not  inverted.  A  slight  camber  in  the  upper  surface  is  useful  for  draining 
the  water  to  the  side  channels. 

The  Construotion  of  Graving  Books. 

Masonry  at  one  time  constituted  the  material  most  in  favour  for  the 
construction  of  graving  docks,  but  of  late  years  Portland-cement  concrete 
has  superseded  it  to  a  very  large  extent.  Either  material  is  extremely 
durable,*  but  concrete  has  the  advantage  of  greater  economy  in  most  cases* 
Timber  has  been,  and  is,  largely  used  in  the  United  States.  It  is,  however, 
much  inferior  to  stone  or  concrete  in  durability,  and  there  are  indications 
that  the  desirability  of  a  more  permanent  form  of  construction  is  becoming 
recognised.  One  advantage  of  wood  is  stated  to  be  that  it  is  safer  than 
stone  to  work  upon  in  frosty  weather,  ice  being  less  likely  to  form  and 
remain  upon  its  surface.  The  claim  is  of  dubious  validity.  Another 
contention,  that  timber-work  is  injured  less  than  masonry  by  the  severity 
of  North  American  winters,  strikes  one  as  being  untenable  and  even 
absurd,  if  any  analogy  exist  in  the  behaviour  of  the  two  materials  in  this 
country.  Timber  docks  are  certainly  much  cheaper  to  construct,  and 
herein,  apparently,  lies  their  most  effective  recommendation. 

The  methods  adopted  in  building  stone  or  concrete  docks  are  identical 
with  those  in  building  locks,  and  the  general  features  of  these  having 
already  been  discussed  in  Chapter  vL,  the  subject  need  not  be  further 
considered. 

In  the  construction  of  timber  docks,  the  most  prevalent  practice  is  as 
follows  : — The  site  of  the  floor  is  first  enclosed  within  continuous  sheet 
piling,  formed  of  half-timbers  having  tongued  and  grooved  joints,  and  the 
whole  area  is  then  studded  with  bearing  piles  of  whole  timber,  driven  at 

*  The  deterioration  of  concrete  work  in  certain  graving  docksi  as  at  Belfast  and 
Aberdeen,  has  been  the  subject  of  an  inquiry  in  the  Chapter  on  *'  Materials,"  to  which 
the  reader  is  referred  for  an  explanation  of  the  phenomena. 


47  S  DOCK  ENGINEERING. 

intervalB  of  3  feet  or  more.  Under  the  keel-blocks,  the  piling  is  still  more 
concentrated.  Their  heads  having  been  cut  off  to  a  uniform  level,  the  piles 
are  connected  by  longitudinal  and  transverse  beams  some  12  inches  square, 
upon  which  is  laid  the  3-inch  planking  forming  the  floor  surface.  The  pile- 
tops  and  the  longitudinals  are  bedded  in  concrete  provided  with  a  smooth 
sloping  surface  to  drain  off  the  water. 

Square  balks,  set  at  an  angle  of  about  40  degrees,  form  an  inclined 
foundation  for  the  altar  courses  at  the  sides  of  the  dock.  The  courses  have 
vertical  and  horizontal  faces  and  splayed  undersides.  The  supporting 
timbers  are  carried  on  rows  of  piles,  pitched  about  a  yard  apart.  Above 
the  concrete  under  floor  level,  the  sides  are  backed  with  clay-puddle, 
confined  within  a  second  and  outer  row  of  sheet-piling  driven  well  down 
below  the  floor  level. 

A  combination  of  timber,  stone,  and  concrete  construction  is  exemplified 
at  a  graving  dock  (fig.  461)  at  Halifax,  Nova  Scotia.*  The  substratum  of 
the  dock  is  rock,  and  it  was  proposed  to  form  a  floor  of  concrete  upon  this 


€trd/ 


I 

Fig.  461. — Section  of  Graving  Dock  at  Halifax,  Nova  Scotia. 

Scale,  50  feet  =  1  inch. 

foundation,  2  feet  thick,  but,  to  meet  the  wishes  of  the  Oity  Oorporation,  a 
pitchpine  floor  was  substituted,  laid  on  sleepers  bolted  to  the  concrete, 
which  was  reduced  to  a  minimum  thickness  of  12  inches.  "The  flooring 
has  proved  a  great  convenience,  as,  when  the  dock  is  pumped  out,  the  water 
drains  away  from  the  surface  immediately."  Above  the  rock  level  the 
walls  consist  of  rubble-in-cement  backing,  and  they  are  faced  with  concrete, 
3  feet  thick,  from  top  to  bottom,  the  altars  being  capped  with  granite, 
12  inches  thick. 

Mud  docks  of  a  very  primitive  description  are  apparently  still  in  use  at 
some  insignificant  oriental  ports,  but  they  do  not  call  for  any  serious  notice. 

Tsrpes  of  Floating  Books. 

The  earliest  floating  docks  were  of  wood,  with  a  sectional  profile 
resembling  that  of  a  ship.  They  were  fitted  with  a  pair  of  gates  at  one 
end,  which  were  closed  after  the  entrance  of  a  vessel,  and  the  impounded 
water  was  then  pumped  out. 

Wooden  docks  of  a  later  type  are  known  as  the  "  Sectional  Dock  "  and 
the  "  Balance  Dock." 

♦  Parsona  on  "  Halifax  Graving  Dock,  N.S.,"  iftn.  Proc  IneU  CM,  voL  cxi. 


THE  SECTIONAL  AND  BALANCE   DOCKS.  479 

"The  Sectional  Dock,  as  its  name  implies,  is  divided  into  as  many 
sections  as  are  required  for  the  particular  vessel  to  be  docked.  Each 
Bectinn  consists  of  a  rectangular  wooden  box  made  watertight,  and  in  the 
ends  of  these  there  is  an  open  wooden  framework  of  a  height  somewhat 
greater  than  the  depth  to  which  it  is  proposed  to  sink  the  dock.  Within 
this  frame  a  wooden  watertight  box  slides  up  and  down,  which  can  be  fixed 
by  means  of  a  rack  and  pall  to  any  required  position.  These  boxes  or 
tanks  serve  the  purpose  of  keeping  the  base  or  lower  part  of  the  dock 
steady,  water  not  being  allowed  to  enter  therein.  Thus,  a  complete  dock 
consists  of  a  series  of  eight  or  ten  independent  compartments  below,  with 
two  movable  air  chambers  to  each  ;  and,  although  there  are  certain  timbers 
connecting  the  different  boxes,  they  are  not  constructed  so  oa  to  enable  any 
box  to  support  the  adjoining  ones."  * 

A  disaster  occurred  to  one  of  these  docks  at  Oallao,  involving  the 
sinking  of  a  ship,  by  reason  of  the  disconnected  compartments  yielding  to 
unequal  stress. 


TRIKSVESSC    SECTION. 

Pig.  462.— Cartagena  Floating  Dock. 

The  Balance  Dock  is  an  attempt  at  improving  the  sectional  dock. 
There  is  only  one  compartment,  subdivided  internally  into  a  series  of 
separate  chambers.  Bocks  constructed  on  this  principle  have  generally 
been  successful,  and  have  had  considerable  vogue  in  the  United  States. 

Iron  docks  came  in  about  the  year  1859.  They  were  introduced  by 
Mr.  Kennie  at  the  naval  arsenal  at  Oartagena,  and  based  on  the  principle 
of  the  balance  dock  of  Mr.  Gilbert.  A  transverse  section  of  the  Oartagena 
Dock  is  shown  in  flg.  462.  It  had  a  length  of  324  feet,  a  breadth  of 
105  feet,  and  a  lifting  power  of  11,500  tons. 

In  18C0,  the  elliptical,  or  U  section,  which  had  disappeared  with  the 

earliest  timl>er  types,  was  reproduced  in  the  Bermuda  Dock,  and  continued 

to  be  adopted  at  intervals.     At  the  present  time,  the  rectangular  shape  is 

almost  the  invariable  rule.     The  U  section  was  generally  fitted  with  gates 

*  Beanie  on  "Floating  Docks,"  Min.  Pnx.  Inet.  O.E,,  voL  izxi. 


4So  DOCK  ENQINEERING. 


to  increase  its  stability  ;  gates  and  caissons  ^re  quite  unnecessary  and  are 
rarely  used  in  connection  with  the  rectangular  section. 

Herr  Howaldt^  of  Kiel,  advocatea  a  system  of  composite  docks  which 
ho  has  devised,  the  frames  being  of  iron  or  steel  and  the  deck  and  bottom 
sides  of  wood.  He  states,  as  the  result  of  his  experience,  that  while  with 
metal  plating,  the  girders  must  not  be  more  than  2  feet  apart,  with  planks 
of  pitchpine  or  beech,  4  inches  thick,  the  frsmes  can  be  placed  4  feet 
apart,  without  the  least  deflection  in  the  panels.  The  advantages  claimed 
for  the  system  are  economy  in  construction  and  maintenance  (wood  requiring 
less  atteDtion  than  iron),  and  a  certain  amount  of  natural  flotation,  which 
reduces  the  pumping  power  required.  This  last  contention  is  of  doubtful 
value :  the  bulk  of  a  wooden  ship  largely  discounta  its  natural  flotation. 


Fig.  463.  —  DepoBitiDg  Dock. 


Fig,  46*.— Off-shore  Dock. 

The  restriction  in  beam-accommodation  imposed  upon  a  double-sided 
dock  led  Messrs.  Clark  and  StandGeld,  about  the  year  1S77,  to  design  the 
depositing  dock,  in  which  one  of  the  vertical  sides  is  suppressed.  This  has 
given  rise  to  two  varieties,  according  to  the  means  adopted  for  maintaining 
equilibrium.  The  term  Depositing  Cock  (fig.  463)  is  applied  to  a  dock 
freely  floating  and  balanced  by  an  outrigger.  A  similar  dock  connected 
with  the  shore  by  means  of  hinged  arms  attached  to  strong  columns,  is 
known  as  the  Off-shoie  Dock  (fig.  464).    The  off-shore  dock  is  much  more 


DESIGN   OF  FLOATING   DOCKS.  48 1 

stable  than  the  depositing  doc^,  though  the  latter  is,  of  course,  well  within 
the  limits  of  practical  safety.  Another  difference  between  the  two  types 
is  that  the  off-shore  dock  is  constructed  in  one  continuous  pontoon,  which 
is  a  lighter  form  of  construction  than  the  separate  caissons  of  the  depositing 
dock. 

Design  of  Floating  Docks. 

The  design  of  floating  structures  being  the  particular  province  of  the 
naval  architect,  it  is  manifestly  outside  the  range  of  the  present  work  to 
enter  into  a  discussion  of  any  of  the  specific  problems  or  details  connected 
with  the  disposition  and  arrangement  of  floating  docks.  The  broad  prin- 
ciples of  the  equilibrium  of  floating  bodies  have  already  been  enunciated, 
in  connection  with  the  subject  of  dock  caissons,  in  Chapter  viii.,  and  it 
would  certainly  be  inadvisable  to  do  more  than  supplement  the  information 
therein  contained  by  a  few  remarks  of  a  general  nature,  relating  to  the 
subject  at  present  under  consideration. 

In  the  first  place,  then,  with  a  given  length  and  displacement,  an  increase 
in  breadth  means  an  increase  in  stability,  hence  a  broad  beam  is  an  advan- 
tage to  a  floating  dock.  The  usual  proportion  of  beam  to  draught  lies 
between  8  and  10  to  1. 


Fig.  465.  Fig.  466. 

Secondly,  a  rectangular  transverse  section  has  a  lower  centre  of  gravity 
than  a  curved  section,  and  therefore  is  more  stable.  It  has  already  been 
pointed  out  that  docks  with  elliptical  or  U-shaped  profiles  were  fitted  with 
gates  j  the  object  of  these  is  to  lower  the  centre  of  gravity. 

Thirdly,  the  less  the  height  of  the  sides,  consistent  with  the  require- 
ments of  shoring,  the  less  tendency  there  will  be  to  top-heaviness,  with 
the  concurrent  advantages  of  greater  light  and  ventilation  in  dealing  with 
vessels  to  be  repaired. 

Lastly,  the  more  compartments  in  a  cross-section,  the  greater  the  stability 

under  water  ballast.     This  is  evident  from  figs.  465  and  466,  which  repre- 

sent  two  fioating  tanks  containing  water,  and  slightly  displaced.      The 

distribution  of  the   water  after  displacement  is  much  more  uniform  in 

the  subdivided  tank   than  in  the  other,  and  there  is  also  less  surging 

motion. 

31 


482 


DOCK  ENGINEERING. 


Frooess  of  OTerhauling  a  Self-Dooking  Floating  Dock. 

The  manner  in  wiiich  a  modem  floating  dock,  constructed  on  Messrs. 
Clark  and  Standfield's  system,  undergoes  a  thorough  overhauling  is  hoth 
ingenious  and  interesting.  It  will  he  readily  understood  from  an  inspection 
of  figs.  467  to  474. 

In  the  first  operation  the  vertical  sides  are  dealt  with.  The  whole 
structure  is  sunk,  to  the  extent  shown  in  fig.  467,  hj  admitting  water  to 
the  side  and  floor  compartments  alike.      The  dock  is   then  raised  hy 


Pig.  467. 


Fig.  469. 


Fig.  471. 


R^ 


W 


Fig.  473. 


Fig.  468. 


\ 


K 


Fig.  470. 


Fig.  472. 


\ 


^ 


^r 


/: 


Fig.  474. 


pumping  out  the  floor  pontoons  alone.  This  hrings  it  into  the  position 
shown  in  fig.  468.  Next,  the  water  is  allowed  to  escape  from  one  of  the 
sides,  and  the  dock  takes  a  list  sufficient  to  raise  that  side  well  out  of 
the  water  (fig.  469).  Each  side  is  dealt  with  in  this  manner.  The  dock 
is  then  restored  to  level  trim,  with  all  its  compartments  empty  {^g,  470). 

The  dock  floor  is  next  undertaken.     It  is  formed  of  a  series  of  pontoons 
extending  the  whole  internal  width  of  the  dock,  and  capahle  of  being 


KEEL-BLOCKS. 


483 


entirely  disconnected  from  each  other  and  the  sides.  Usually  one  pontoon 
is  dealt  with  at  a  time,  and  the  operation  consists  in  raising  it  above  the 
rest.  The  pontoon  is  separated  from  the  sides  by  an  open  space  of  2  feet, 
to  which  water  has  free  access.  Attachment  is  made  by  means  of  "  fish- 
plate "  joints,  consisting  of  steel  lugs,  secnred  together  by  steel  taper  pins. 
The  drainage  junction-pipes  between  the  pontoon  chambers,  and  the  pumps 
in  the  side  walls,  are  first  of  all  disconnected.  Then  the  taper  pins  are 
withdrawn.  To  complete  this  step,  it  is  necessary  to  tilt  the  dock  slightly, 
as  in  fig.  471,  even  trim  being  afterwards  restored  (fig.  472).  One  pontoon 
is  now  floating  clear  of  the  remainder  of  the  structure.  The  dock  is  next 
sunk  by  the  re-admission  of  water  into  its  compartments  until  the  relative 
positions  are  as  shown  in  fig.  473.  At  this  stage  the  floating  pontoon  is 
re-connected  to  the  sides,  at  a  higher  level,  by  means  of  similar  lugs  and 
pins.  The  dock  is  raised  bodily  by  pumping,  the  single  pontoon  leaves  the 
water,  and  the  operation  is  complete  (fig.  474). 

Docks  of  L  section  have  their  component  pontoons  berthed  upon  one 
another,  in  the  ordinary  manner  of  docking  a  vessel. 


Equipment  of  Bepairing  Books. 

The  various  items  for  the  equipment  of  a  repairing  dock  include  keel- 
blocks,  bilge-blocks,  side-shores,  lifting  cranes,  capstans,  snatch  blocks, 
bollards,  hooks,  dbc. 


910c    HL&VATlOfl 

Scde,  ,^o^* 


HAI^    tMV 
CLSVATIOM 


Fig.  475.— Keel-block,  Belfast. 

1.  Keel-blocks. — These  are  for  the  purpose  of  affording  a  uniform  and 
level  base  for  a  ship's  keel,  and  in  order  to  give  ready  access  thereto,  they 
stand  a  few  feet  above  the  dock  floor.  The  height  usually  ranges  between 
2  feet  6  inches  and  4  feet.  The  greater  height  involves  a  corresponding 
additional  depth  of  dock  to  accommodate  the  same  class  of  vessel,  but  owing 
to  the  headroom  it  affords,  the  cost  of  repairs  is  reduced.  The  best  material 
for  keel-blocks  is  a  matter  of  dispute.  Cast  iron  was  very  largely  employed, 
with  timber  caps,  until  the  accident  to  the  "  Fulda"  threw  casMron  blocks 
into  disrepute;  most  unjustifiably,  because  accidents  have  occurred  with 


484  DOCK   ENGINEERING. 

other  kinds  of  blocks.  Many  engineers  prefer  wooden  blocks — oak  for 
preference,  pitchpine  often  on  account  of  its  cheapness.  In  the  latest  and 
largest  graving  dock  at  Liverpool  the  blocks  are  of  cast  iron  surmounted  by 
a  12-inch  birch  log,  capped  with  3  inches  of  soft  wood.  Similar  blocks, 
capped  with  greenheart,  are  used  at  Belfast  (fig.  475).  On  account  of  the 
flotation,  wood  blocks  must  be  anchored.  Curved  cast-iron  caps  have  been 
used  at  Amsterdam,  the  object  being  self-adjustment  between  block  and 
ship.  With  the  same  object  in  view,  hydraulic  blocks  have  been  proposed, 
but  the  consequent  uniformity  of  pressure  produced  all  the  effects  of  rigidity, 
and  the  method  was  abandoned  after  trial.  Steel,  greenheart,  elm,  and  teak 
have  also  been  employed  for  blocks. 

The  distance  apart  of  the  block  centres  varies  from  2  to  5  feet,  being 
governed  by  the  load  to  be  carried.  Wide  intervals,  where  possible,  are 
convenient.  On  the  other  hand,  it  is  often  necessary  to  support  a  large  ship 
by  inserting  temporary  intermediate  blocks  between  the  permanent  ones. 
The  large  Atlantic  liners  are  continuous-blocked  in  this  fashion  for  a  great 
portion  of  their  lengths. 

As  regards  shape,  wedge-shaped  blocks  have  been  found  most  convenient 
for  adjustment.  The  wedges  should  be  readily  removable  and  portable. 
Wooden  blocks,  however,  are  generally  rectangular  and  bound  at  the  ends 
with  iron  bands. 

Bilge-blocks  or  Side  Cradles  are  not  so  commonly  employed  in  graving  as 
in  floating  docks,  though  they  form  useful  adjuncts  to  keel-blocks.  Their 
drawback  is  that  they  rather  interfere  with  freedom  of  movement,  and 
consequently  they  are  arranged  at  greater  intervals — say,  about  50  feet. 
Their  upper  surfaces  have  to  be  adjusted  to  the  level  of  the  ship's  bilge. 
Sometimes  props  under  the  bilge  keels  are  substituted  for  them. 

Side-shores. — These  form  a  series  of  lateral  supports  to  a  vessel  upon  the 
blocks.  They  are  of  wood,  about  9  or  10  inches  square  at  the  centre, 
tapering  slightly  each  way  to  the  ends,  which  are  bound  with  iron.  They 
are  lowered  into  position  as  the  pumping  proceeds,  in  somewhat  primitive 
fashion  by  means  of  ropes,  and  are  tightened  up  with  wedges,  so  that  one 
end  bears  firmly  against  the  vessel's  side  and  the  other  against  an  altar 
course.  It  has  been  suggested  that  a  series  of  horizontal  steel  shores, 
worked  in  and  out  of  the  sides  of  the  dock  by  mechanical  means,  would  be  a 
great  improvement.  No  doubt  the  method  would  be  more  scientific,  but  it 
has  certain  obvious  difficulties  attached  to  it  in  the  way  of  regulating  the 
level  of  the  shores  so  as  to  suit  ships  of  all  sizes.  Moreover,  since  pumping 
is  a  process  involving  some  time,  ample  opportunity  is  afforded  for  setting 
shores  by  hand  without  causing  extra  or  undue  delay. 

Hooks,  fixed  to  the  quay  at  coping  level  with  rope  moorings,  are  some- 
times employed  for  securing  a  vessel  in  position,  more  especially  when  she 
is  only  shored  on  one  side,  as  in  the  case  of  a  graving  dock  capable  of 
accommodating  two  ships  side  by  side.  The  vessel  is  then  given  a  slight  list 
towards  the  nearer  quay.  Bollards  and  mooring  posts  serve  the  same  purpose. 


DISTRIBUTION   OF   PRESSURE   ON   KEEL-BLOCKS,  485 

Timber  Slides,  of  smooth  granite,  in  the  side  walls  are  handy  for  the 
purpose  of  lowering  shores  and  other  timber,  but  their  use  is  not  universal, 
as  in  many  cases  the  logs  and  planks  required  are  thrown  into  the  water 
while  pumping  is  still  proceeding. 

A  Rudder  Pit  is  a  useful  feature  in  the  event  of  the  removal  of  a  ship's 
rudder,  though  many  graving  docks  are  without  them,  and  they  are  only 
required  on  rare  occasions.  There  are  two  such  pits  at  the  Canada  Graving 
Dock,  Liverpool,  each  50  feet  long,  6  feet  wide,  and  16  feet  6  inches  below 
iioor  level.  When  they  are  not  in  use  for  this  particular  purpose,  the 
keel-blocks  are  continued  over  them,  being  supported  on  stout  girders. 

A  Travelling  Crane  of  large  power  and  wide  range,  for  lifting  heavy 
machinery  in  and  out  of  a  vessel,  is  essential.  A  propeller  may  have  to  be 
lifted  from  the  dock  bottom  or  even  from  the  ship's  hold,  and  in  the  latter 
case  it  would  have  to  clear  the  hatchway  coaming  and  the  bulwark,  both  of 
which  will  in  most  cases  be  above  the  coping  level.  A  lifting  power  of  not 
less  than  25  tons  and  up  to  50  tons  should  be  provided,  with  a  clear  outreach 
beyond  the  centre  line  of  dock  floor,  and  a  height  of  30  feet  from  coping 
level  to  under  side  of  jib.  The  great  amount  of  outreach  is  more  particularly 
requisite  in  the  case  of  vessels  with  twin  screw  propellers. 

In  addition  to  hydraulic  mains  for  gate  machinery  and  cranes,  it  is  an 
advantage  to  utilise  the  pipe  trenches  for  the  conveyance  of  electric  or 
pneumatic  power  to  drilling  machines,  which  are  very  commonly  needed  to 
remove  plates  from  the  hulls  of  ships.  Portable  electric  lights  are  extremely 
serviceable  beneath  a  ship's  hull. 

Distribution  of  Pressure  on  Keel-blocks. 

The  distribution  of  the  pressure  of  a  ship's  keel  over  the  blocks  in  a 
graving  dock  is  a  very  difficult  and  complex  problem,  and  one  to  which  no 
satisfactory  solution  has  yet  been  propounded,  despite  the  attention  which 
it  has  received  from  many  eminent  scientists  and  technical  experts.  Yet  the 
question  cannot  be  ignored,  for  it  has  been  the  cause  of  several  accidents  of 
a  very  serious  nature.  A  recent  disaster  which  has  attracted  widespread 
notice  and  caused  much  misgiving,  if  not  dismay,  is  that  which  occurred  to 
the  North  German  Lloyd  s.s.  **Fulda*'  while  in  No.  2  Graving  Dock,  Birken- 
head, on  2nd  February,  1899.  Not  more  than  15  or  20  minutes  elapsed,  from 
the  time  she  was  left  dry  upon  the  blocks  till  she  crashed  through  them  to  the 
dock  floor  and  received  such  injuries  as  to  become  a  total  loss,  constructively. 

The  data  involved  are  these  : — The  "  Fulda "  was  a  vessel  430  feet  in 
length  between  perpendiculars,  45  feet  9  inches  in  breadth,  moulded,  and 
36  feet  6  inches  in  depth,  moulded.  Her  displacement,  as  laden  at  the  time 
of  the  accident,  was  about  6,600  tons ;  she  had  a  bar  keel  12  inches  deep 
and  3^  inches  wide ;  the  blocks  upon  which  she  was  docked  were  of  cast 
iron,  with  6-inch  greenheart  caps  and  3  inches  soft  wood  on  top  of  the 
greenheart  (flgs.  476  to  479).     These  blocks  were  2  feet  6  inches  high  and 


486 


DOCK  ENGINEERING. 


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DISTRIBUTION  OF  PRESSURE  ON   KEEL-BLOCKS.  487 

4  feet  6  inches  apart  from  centre  to  centre.  The  amount  of  overhang 
forward  was  very  great.  At  one-fourth  of  the  Tessel's  length,  measured 
from  the  stem,  the  keel  rose  f  inch,  and  continued  to  rise  as  it  proceeded 
forward.  The  condition  of  things  is  shown  in  fig.  479,  the  black  blocks 
indicating  the  extent  of  the  supported  part  of  the  keel. 

The  exact  sequence  of  the  occurrence  was  never  clearly  ascertained,  the 
evidence  being  somewhat  conflicting,  bat  the  most  competent  witness  stated 
that  he  found  the  blocks  flying  out  at  the  after  end  of  the  ship  first,  and  then 
the  forward  blocks  came  down.  On  the  other  hand,  Dr.  Elgar,  who  was 
called  in  as  a  consulting  expert  by  the  Mersey  Docks  and  Harbour  Board, 
inclined  to  the  opinion  that  the  catastrophe  was  due  to  the  great  pressure 
imposed  on  the  forward  blocks  by  the  excessive  overhang  of  the  vessel's 
stem,  and,  therefore,  that  disruption  began  in  that  quarter. 

In  a  paper*  read  before  the  Institution  of  Naval  Architects  the  same 
year,  Dr.  Elgar  gave  the  reasons  for  his  decision,  and  entered  very  minutely 
into  the  question  of  the  probable  amount  of  stress  produced  in  the  foremost 
loaded  block,  deducing  a  pressure  of  178^|  tons.  Without  desiring  in  the 
least  to  depreciate  the  care  and  skill  with  which  the  mathematical  calcula- 
tions were  carried  to  their  conclusion,  it  cannot  but  be  felt  that  the  postulates 
were  too  hypothetical  to  justify  any  definite  numerical  result.  It  is,  in  fisust, 
only  possible  to  approach  the  question  by  means  of  certain  assumptions, 
none  of  which  may  be  accurately,  or  even  approximately,  true.  For 
example,  it  has  to  be  taken  for  granted,  either  that  the  blocks  were  elastic 
or  that  they  were  rigid,  the  keel  flexible  or  inflexible,  and  the  probability  is 
that  no  one  of  these  conditions  prevailed  throughout. 

It  is  useless  to  go  into  the  matter  again  in  so  far  as  the  '^Fulda"  is 
concerned.  Whether  the  blocks  were  sheared  at  the  forefoot  or  abaft  the 
middle  (and  it  is  a  strange  complication  of  the  whole  aflair  that  the  blocks 
had  been  in  use  for  40  years  and  the  '*  Fulda "  docked  several  times  before 
without  mishap),  the  fact  remains  that  the  pressure  upon  the  keel-blocks 
is  very  unevenly  distributed,  and  is  certainly  very  great  on  the  forward 
blocks  under  any  ship  of  ordinary  design. 

About  the  time  of  the  ''Fulda"  disaster,  the  author  made  a  number  of 
careful  observations  of  the  actual  profile  assumed  by  the  keels  of  various 
vessels  in  graving  dock.  In  all  cases  he  found  two  regions  of  great  de- 
pression— one  immediately  abaft  the  forefoot  and  the  other  amidships  under 
the  machinery.  In  these  localities,  the  keels  had  crushed  the  soft  wood 
caps  to  a  much  greater  extent  than  elsewhere,  there  being  a  maximum 
diflerence  of  level  in  some  cases  of  as  much  as  1^  inches. 

The  intricacies  of  the  problem  are  too  numerous  for  any  exact  solution, 
but  if  we  choose  to  conflne  our  investigation  within  certain  limits,  we  may 
arrive  at  a  result  which  will  have  some  relative  value.  We  will  therefore 
briefly  deal  with  the  general  case  of  the  distribution  of  stress  under  a  system 
of  irregular  loading,  making  the  following  assumptions : — 

*  Elgar  on  **The  Supporting  of  Ships  in  Dry  Docks,"  Afin.  Proc.  Inst.  \.A,,  1899. 


488 


DOCK  ENGINEERING. 


1.  That  the  vessel  is  a  rigid  structure — i,e.y  there  is  no  bending  or 
yielding  in  any  part  of  the  keel. 

2.  That  the  blocks  are  perfectly  elastic — i,e,,  the  amount  of  compression 
is  proportional  to  the  load. 

3.  That  the  line  of  keel  coincides  with  the  line  of  blocks — i,e.,  there  is 
no  initial  stress  due  to  a  cambered  keel. 

The  converse  of  all  these  postulates  is  equally  likely  to  hold  good  in 
practice. 

Let  A  B  =  ^,  represent  the  total  length  of  a  ship  (fig.  480),  and  O  R,  the 
vertical  line  through  its  centre  of  gravity,  taken  for  simplicity  through  the 
centre  of  the  ship.     Let  W  be  the  total  weight. 

If  now  the  vessel  be  supported  uniformly  throughout  its  entire  length, 
the  pressure  diagram  will  be  the  rectangle  A  B  C  D,  in  which  if  A  D  =  a, 
and  A  B  =  Z,  then  al^W. 


Z    Y 


I  I 


I'' 


,''  I 


I .' 


Fig.  480. 


Secondly,  suppose  the  vessel  to  have  an  overhang  equivalent  to  one-fourth 
of  her  length,  so  that  the  supported  portion  of  her  keel  is  K  B  =  f  Z.  If 
the  load  were  distributed  over  the  supported  portion  only,  so  that  the 
centre  of  pressure  coincided  with  the  middle  point,  Y,  of  that  length,  there 
would  be  a  uniform  intensity,  a^,  determined  by  the  consideration, 

aj  X  f  Z  =  W (134) 

But  this  is  not  the  case,  for  the  centre  of  pressure   is   still   at   O,  while 

the  centre  of  support   is   at  Y,  giving  an   eccentricity  O  Y  =  —^  ;  i.e., 

one-sixth  of  the  supported  length.  Now,  we  have  already  determined  in 
connection  with  stresses  in  wall  joints  (Chap,  v.)  that  when  the  eccen- 
tricity of  pressure  is  one-sixth  of  the  length  of  the  base,  the  intensity  is 
zero  at  the  inner,  or  further,  edge,  and  a  maximum  of  twice  the  mean 
uniform  stress  at  the  outer  edge.     Hence,  if  we  draw  K  L  =  2ap  and  join 


DISTRIBUTION   OF   PRESSURE   ON   KEEL-BLOCKS.  489 

L  B,  we  have  K  L  B  as  the  pressure  diagram  for  an  overhang  of  one-fourth 

the  vesseFs  length. 

For  overhangs  greater  than  this,  we  may  proceed  by  analogy  thus: — Take 

the  point  M  as  the  limit  of  the  supported  length,  and  make  O  T  =  2  O  M. 

M  T 
Then  the  eccentricity  of  the  point  O  is  O  Z  =  — ^.     Hence,  make 

9  W 

where  L2  is  the  length  of  effective  base  M  T.     Join  N  T,  and  M  N  T  is  the 

pressure  diagram.     Although  the  vessel  apparently  receives  support  from 

T  to  B,  such,  as  a  matter  of  fact,  is  not  the  case,  the  compressive  stress 

passing  through  zero  value  at  T  to  a  negative  value  beyond  that  point.     In 

other  words,  there  would  be  a  gradually  increasing  tensile  stress  from  T  to 

B,  if  the  vessel  were  fastened  down  to  the  blocks. 

Similarly,   if   the   forefoot   extend   to   P,   take   O  S  =  2  O  P.      Draw 

P  Q  =  2  Og,  where 

flg  l^  =  Wj  as  before. 

Join  Q  S^,  and  P  Q  S  is  the  pressure  diagram  under  those  conditions. 
Any  number  of  points  may  be  found  in  this  way,  and  since 

LKxKB  =  NMxMT  =  QPxPS  =  2W, 
we  may  write  down  the  general  equation — 

X  y  =  constant, (1^^) 

so  that  the  curve  L  N  Q  is  a  rectangular  hyperbola,  with  its  origin  at  O, 
and  the  lines  O  A  and  O  R  as  its  asymptotes. 

This  equation  is  only  applicable  to  values  of  x  not  exceeding  K  O. 
When  the  overhang  of  the  vessel  is  less  than  one-fourth  of  the  total  length, 
the  compression  does  not  vanish  at  B,  but  gradually  increases  as  the  forefoot 
decreases,  until  it  attains  a  maximum  value  of  B  0,  with  the  disappearance 
of  all  overhang  at  the  stem. 

Consequently,  we  must  substitute  for  (135)  another  equation  conforming 
to  the  altered  conditions.  We  obtain  this  readily  from  the  investigation  in 
Ohap.  V.  already  alluded  to.  There  it  was  seen  that  when  the  eccentricity 
was  less  than  one-sixth  of  the  base,  the  value  of  the  greatest  intensity 
of  pressure  at  the  outer,  or  nearer,  edge  of  the  joint  was 

Y  =  a  +  y, 

where  a  =  the  uniform  intensity  due  to  zero  eccentricity  under  similar 
conditions  of  load,  and 

Q  a  X 

y  =  -J-, 

X  being  the  eccentricity. 

Apply  this  to  the  case  where  the  rise  of  the  vessel's  stem  begins  at  the 
point  I.     Then  the  length  of  base  is  I O  =  Z^,  and 

W 


490 


DOCK  ENGINEERING. 


l.k= 


The  ecoentricUy  is^  -  ^=  jp^  which  is  accordingly  known.     Make 


and 


TT         ^ 

IJ  =  -y-    + 

^4 


6  Wa?^ 


6W 


X, 


11^ 


Join  J  IT,  and  IJ  U  B  is  the  pressure  diagram. 
Similarly  at  G  we  have 

W 

a^  =  -V-,  where  Zg  is  the  length  G  B; 


6Wa;g 


and 


CV  = 


W       6Wa;, 


L 


IL 


x^  being,  of  course,  -r  —  4- 


Joining    H  V,    we 


\smM    § 


have   the  pressure   diagram    G  H  V  B   for   these 
particular  conditions. 

In  this  way,  we  have  found  a  series  of  points, 
D  F  H  J  L  N  Q.  Joined  together,  they  form  a 
curve  which  may  be  termed  the  curve  of  maximum 
pressures,  since  any  ordinate,  £F,  GH,  I  J,  kc.j 
is  a  measure  of  the  intensity  of  pressure  at  the 
outermost  keel-block,  corresponding  to  an  over- 
hang from  that  point. 

With  the  limited  space  at  disposal,  it  is  not 
possible  to  enter  into  a  discussion  of  the  modifi- 
cations caused  in  the  above  equations  by  a  depar- 
ture from  any  of  the  conditions  upon  which  they 
are  based.  It  must  be  stated  that  such  modifi- 
cations will  often  entail  values  largely  exceeding 
those  given,  but  as  they,  too,  are  founded  upon  a 
series  of  hypotheses,  no  practical  advantage  would 
accrue  from  the  very  complicated  investigation  of 
their  influence.  The  point  to  be  really  emphasised 
is  the  absolute  necessity  for  a  large  margin  of 
safety. 

The  diagram  (fig.  481)  shows,  in  the  case  of 
the  Onnard  s.s.  '^Etruria"  and  her  sister  ship  the 
^'Umbria,''  the   relative    distribution    of   weight 
throughout  the  length  of  each  vessel.     The  dotted 
line  indicates   to   scale   the    intensity  of  pressure   upon  the  keel-blocks. 


GRIDIRONS  AT  LIVERPOOL. 


491 


supposing   each  vessel  to  be  uniformly  supported  throughout  her  entire 
length. 

The  following  table  illustrates  the  amount  of  overhang  in  typical  ships 
of  the  present  day : — 

TABLE   XXXVI. 


Overhang. 

KeeL 

Name  of  Vegsel. 

Extreme 
Length. 

Nett 

Registered 

Tonnage. 

Forward. 

Aft. 

Kind. 

Size. 
Inches. 

Feet. 

Feet. 

Feet 

Cevic,    . 

520 

52 

41 

Plate, 

10    X 

3 

5,402 

Georgic, 

670 

52 

36i 

>i 

10    X 

3 

6,570 

Tauric,  . 

476 

52 

8 

** 

10    X 

3 

3,670 

Lake  Superior, 

415 

26 

•  •  • 

Bar, 

5i  X 

9 

2,897 

Manchester  City,  . 

461 

55 

45 

... 

•  •  • 

3,727 

Cymric, 

600 

52 

33^ 

Plate, 

12    X 

3 

8,508 

Etruria, 

520 

95 

•  •  • 

Bar, 

6    X 

10 

3,690 

Teutonic, 

580 

78J 

35 

PUte, 

17    X 

3 

4,269 

Campania,     . 

6-20 

95 

... 

•  •  ■ 

•  •  • 

4,973 

Cufic,     . 

444 

42i 

10 

Bar, 

5i  X 

9 

3,122 

Parisian, 

455 

27i 

*•• 

•  •  « 

•  •  • 

3,385 

Aurania, 

488 

50 

10 

Bar, 

7    X 

10 

4,029 

Oceanic, 

705 

87i 

40 

Plate, 

18^  X 

34 

■     6,916 

Winefredian, 

570 

55 

... 

ft 

11       X 

3 

6,816 

New  England, 

570 

55 

15 

tf 

12    X 

3 

7,416 

Norseman,     . 

510 

42^ 

12 

i} 

10    X 

3 

6,129 

Afric,    . 

670 

45 

13 

i> 

12    X 

3 

7,804 

Ivemia, 

600 

80 

30 

... 

•  •• 

9,052 

Celtic,   . 

704 

m 

32A 

Plate, 

ISi  X 

H 

13,448 

Gridirons  at  Iiiverpool. 

There  are  two  gridirons  existing  at  Liverpool.  One,  in  a  recess  at  the 
Clarence  Graving  Dock  Basin,  has  a  length  of  313  feet  6  inches  and  a  breadth 
of  25  feet  6  inches.     The  logs  or  blocks  (fig.  482)  are  11  inches  wide  by 


-  4'  7--. 


p  ff 


/■y'^       ''<y'  ,-yi 


Fig.  482. — Gridiron  at  Liverpool. 

14  inches  deep,  laid  4^  feet  apart,  centre  to  centre,  ui>oq  masonry  blocks  on 
a  concrete  foundation.  There  is  a  fall  of  2  feet  5  inches  in  the  length  of  the 
gridiron,  the  lower  end  of  which  is  20  feet  below  high  water  of  ordinary 
spring  tides.  The  other  gridiron  is  at  the  King's  Pier,  and  has  a  kngth  of 
509  feet  and  a  breadth  of  26  feet.  The  blocks  in  this  case  are  level 
throughout. 


DOCK   ENGINEERING. 


Hydraulic  Ziift  at  London. 


The  following  accouat  of  Clark's  hydraulic  lift  at  the  Victoria  Docka, 
London,  is  extracted  from  an  article  by  Mr.  G.  B.  Reonie  in  the  Praeticai 
Meohanic's  Journal  Record  o/tlte  Great  Exhibilion  of  1862 : — 

"  The  lift,  (fig.  483)  oonaists  of  an  excavated  cbaanel,  of  about  300  feet 
long  and  about  60  feet  broad,  on  each  eide  of  which  16  caat-iron  columns, 
6  feet  in  diameter,  are  sank  about  12  feet  into  the  ground,  20  feet  from 
centre  to  centre.  At  the  bottom  of  the  column  there  is  a  hydraulic  preaa  or 
lift.  The  diameter  of  the  ram  is  10  iocheB,  with  a  travel  of  about  25  feet. 
Oa  the  top  of  the  piston  or  ram  a  wrought-iron  croashead  is  fitted,  from 
which  iron  links  are  suspended  and  connected  with  a  cBsC^iron  girder,  one 
on  each  aide  of  the  colnnin,  ao  that  there  are  16  coupled  girders  of  about 
60  feet  length  and  20  feet  apart,  each  couple  being  suspended  and  lifted  by 


Fig.  483.— Hydraulic  Lift. 

two  hydraulic  rams  or  pumpa.  On  the  top  of  theae  girders  a  pontoon  is 
placed  at  the  requisite  length.  These  pontoons  vary  from  150  to  320  feet 
in  length,  and  are  59  feet  broad.  The  smaller  are  placed  on  S  sets  of  coupled 
girders  and  the  Urger  on  the  whole  16.  They  are  made  of  sufficient  depth 
for  stilTness  and  in  order  to  give  the  required  displacement,  bo  that  when 
empty  they  hsve  buoyancy  enough  to  keep  the  vessel  welt  out  of  the  water. 
The  pistons  or  rams  are  worked  by  a  pair  of  horizontal  engines  made  by 
Messrs.  Easton  &  Amoa  These  engines  are  on  the  expansive  condensing 
principle,  with  one  high-pressure  cylinder  of  23  inches  diameter  and  2  feet 
stroke,  and  two  expansive  cylinders  of  33J  inches  diameter  with  the  same 
stroke.  The  steam  expands  from  the  small  cylinder  into  the  two  larger 
ones ;  pressure  of  steam  per  square  inch,  50  lbs. ;  iodicated  horse-power,  120. 
The  engines  work  12  hydraulic  force  pumpa  of  196  inches  diameter  and 
3  feet  stroke  in  three  groups — viz.,  two  groups  of  3  and  one  of  6  pumps. 


SLIPWAY  AT  DOVER.  495 

The  amount  of  pressure  obtained  is  28  cwts.  per  circular  inch,  equal  to  about 
4,000  lbs.  per  square  inch.  From  these  pumps  the  water  is  discharged 
through  wrought-iron  pipes,  ^  inch  internal  diameter  and  1  inch  external, 
and  above  10,000  feet  in  length. 

"  The  following  is  the  manner  of  docking  a  vessel : — The  girders  with 
the  pontoon  upon  them  are  allowed  to  sink  to  the  depth  required  for  the 
particular  vessel  to  be  docked.  She  is  then  hauled  over  the  pontoon  and  on 
to  the  blocks  and  shored,  or  rather  wedged  up  by  movable  bilge  blocka 
instead  of  breast  shorea  The  pontoon  and  vessel  are  lifted  out  of  the  water 
and  the  water  in  the  pontoon  allowed  to  escape  by  valves.  When  empty 
the  valves  are  closed,  the  girders  lowered,  and  the  pontoon  left  to  bear  the 
whole  weight  of  the  vessel  and  to  be  moved  into  any  suitable  position.  To 
give  greater  accommodation  Mr.  Edwin  Clark  arranged  a  system  of  shallow 
docks,  eight  in  number,  communicating  with  a  shallow  basin  of  about 
500  feet  square,  into  one  of  which  the  pontoon  has  to  be  floated.  The  space 
occupied  by  the  docks  and  basin  is  about  25  acres.  Many  vessels  have  been 
already  lifted  and  repaired  in  this  manner,  the  largest  of  which,  the 
*  Calcutta,'  is  of  1,800  tons  burthen." 

Slipway  at  Dover.* 

Originally  constructed  in  1849,  the  Dover  slipway  underwent  an  enlarge- 
ment in  1888,  being  lengthened  to  556  feet,  with  a  capacity  for  vessels  up 
to  850  tons  deadweight.  The  gradient  is  1  in  18,  and  the  width  at  quay 
level,  52  feet  (see  figs.  484  to  491). 

'*  The  upper  part  of  the  slipway  is  in  made  ground  for  a  length  of  about 
370  feet,  and  the  remaining  portion  is  upon  the  chalk.  In  the  made  ground, 
a  layer  of  cement  concrete,  3  feet  6  inches  thick,  with  an  additional  foot 
under  the  centre  pair  of  rails,  is  laid  at  the  required  inclination.  Embedded 
in  this  are  fir  cross-sleepers,  1 2  inches  by  6  inches,  32  feet  long  and  about 
11  feet  pitch,  carrying  the  longitudinals  to  which  the  cast-iron  rails  are 
trenailed.  In  the  lower  portion  of  the  slip,  the  cross-sleepers  are  laid 
directly  upon  the  chalk,  with  only  enough  concrete  to  bed  them  evenly,  and 
are  held  down  by  six  bars,  about  2  feet  long,  driven  into  the  rock.  The 
upper  part  of  the  slip,  for  a  length  of  about  260  feet  above  low  water  mark, 
is  paved  with  Kentish  rag,  flush  with  the  tops  of  the  longitudinals,  and  the 
lower  portions  with  bricks  on  end." 

There  are  three  pairs  of  cast-iron  rails,  in  lO-foot  lengths,  and  weighing 
69  lbs.  per  lineal  yard,  the  centre  pair  and  rack  plate  being  in  one.  The 
single  rails  are  bossed  out  at  the  ends  and  centre,  and  secured  to  the 
longitudinals  by  six  trenails,  the  double  rail  being  secured  by  trenails  on 
each  side  of  the  rack  plate. 

The  cradle  is  in  four  sections — two  of  them,  forming  the  main  cradle, 
are  together  133  feet  long,  the  remaining  two  being  auxiliary  pieces,  25  feet 
*  Beer  on  "  Ship  Slipways,"  Min.  Proc.  Inst,  C.E,,  vol.  cxviii. 


494 


DOCK   ENGINEERING, 


and  15  feet  long  respectively.  The  main  cradle  consists  of  three  lines  of 
longitudinals,  supported  upon  rollers,  travelling  on  six  lines  of  rails, 
carrying  seven  pairs  of  cross  pieces  or  bilge-cods.  The  centre  longitudinal 
is  made  up  of  two  10-inch  by  6-inch  pitchpine  timbers,  bolted  together  with 
a  5-inch  by  l{-inch  flat  iron  bar  between  them,  and  5-inch  by  l^inch  banr 
on  each  side.  The  central  iron  bar  runs  the  whole  length  of  the  main  and 
auxiliary  cradles,  and  is  increased  to  2^  inches  thickness  above  the  first 
section  of  the  main  cradle.     The  side  bars  run  through  to  within  26  feet  of 


lii+44- 


'lt$fm.  Oriflitml  Slipwty....'.\l 


CtmUNCCTO 
AIVCR  DOUR 


I  i  rrVl  [  i  -  n  Tl  f  -  ]  ^  ^^fl  T  -  TT  ]  f  III  i  I  \  f  f  TiTI  t  SI  l\ 

■  1  ffl:   T  !  I         jtmt  MTtm 


UONGmiDINAL  CLCVATION^ 

Figs.  484  and  485. — Plan  and  Elevation  of  Slipway  at  Dover. 


q(/o>    L*vi    t 


H?  6  Flat-  iron  bars  Jrivmn  into  tho  Rock 


SECTION     C.  O. 


Figs.  486  and  487.— Dover  Slipway. 

the  bottom  of  the  cradle.  The  centre  longitudinal  is  supported  by  83  pairs  of 
rollers,  placed  directly  underneath  the  main  cradle,  and  the  auxiliary  cradles, 
by  rollers  about  3  feet  apart.  At  the  centre  portion  of  the  main  cradle,  the 
side  supports  are  formed  of  12-inch  by  5-inch  longitudinals,  carried  by  two 
pairs  of  rollers  under  each  bilge-cod  at  the  upper  and  lower  ends ;  the 
longitudinals  are  jointed  on  the  inside,  so  as  to  bring  them  directly  over 
the  inner  rails  of  the  outer  pairs,  and  they  are  carried  by  two  single  rollers 
on  each  side,  under  the  bilge-cods. 


SLIPWAY   AT   DOVER, 


495 


The  cross-pieces,  or  bilge-oods,  are  of  oak,  the  four  central  pairs  being 
37  feet  long  and  the  remaining  three,  33  feet  long.  They  are  secured  to  the 
centre  longitudinal  by  placing  the  ends  of  a  pair  of  cods  together,  and 
wedging  out  againsfc  two  cast-iron  knee-pieces  with  small  teeth  on  their 
faces,  these  fit  into  holes  in  the  cods.  The  bilge-cods  are  shaped  on  the 
upper  face  to  a  slope  of  about  1  in  14,  and  for  the  greater  part  of  their 
length,  strips  of  iron,  3  inches  wide,  are  let  into  them  and  upon  these  run 
the  sliding  bilge-blocks.  The  longitudinals  at  the  bottom  of  the  cradle  are 
framed  into  oak  cross-pieces,  and  are  stiffened  by  four  cast-iron  brackets. 


Figs.  488  and  489.— Plan  and  Elevation  of  Cradle. 


:^X&^-^ 


o  !G  v&%ar  i±^Ai^  ^A 


Figs.  490  and  491.— Details  of  Cradle. 

At  about  every  20  feet  in  length  of  the  main  and  auxiliary  cradles,  a 
pawl  is  fixed  under  the  centre  beam,  working  in  the  rack  between  the  rails. 
When  not  in  use,  it  may  be  lifted  up  into  a  horizontal  position.  The 
auxiliary  cradles  have  no  bilge-cods  or  blocks.  Chains  are  fixed  to  the 
sides  of  the  main  cradle  and  attached  to  the  auxiliary  lengths  near  the 
centre.  They  have  a  sectional  area  of  1  square  inch  and  are  provided  with 
adjusting  screws.  The  rollers  are  8  inches  in  diameter,  3^  inches  wide  on 
the  face,  with  a  flange  |  inch  deep.  They  are  of  iron,  cast  round  a  If -inch 
Bessemer  steel  shaft,  bossed  out  and  roughened  in  the  centre.   The  wrought- 


496  DOCK   ENGINEERING. 

iron  draw-rods  are  double  and  have  a  minimum  sectional  area  of  16  square 
inches,  a  length  between  centres  of  12  feet  6  inches,  and  a  total  length  of 
312  feet  6  inches.  There  is  also  a  draw-chain,  49  feet  long,  with  the  same 
sectional  area. 

The  Kaiser  Graving  Dock  at  Bremerhayen.''^ 

This  dock  was  built  by  the  State  of  Bremen,  between  1896  and  1899, 
to  accommodate  the  large  new  ships  of  the  North  German  Lloyd,  to  which 
Company  it  has  been  let.  It  is  entered  from  the  "  Kaiserhafen,"  which  itself 
is  connected  by  locks  with  the  estuary  of  the  River  Weser.  It  is  illustrated 
in  figs.  492  to  499. 

The  maximum  available  nett  length  of  the  dock,  measured  at  the  level 
of  the  keel-blocks,  is,  in  round  figures,  741  feet.  The  dock  in  this  case  is 
closed  by  a  floating  caisson,  placed  outside  and  bearing  against  the  square 
quoins  of  the  pierhead  of  the  entrance.  In  its  normal  position,  however, 
*  the  caisson  is  berthed  13  feet  further  inwards  at  grooves  provided  midway 
in  the  entrance,  and,  when  in  this  position,  the  nett  length  of  the  dock  is 
only  728  feet.  There  is  yet  a  third  sill,  with  corresponding  grooves  for  the 
caisson,  within  the  dock  and  enclosiog  a  length  of  545  feet. 

The  side  walls  of  the  main  entrance  have  a  batter  of  1  in  4,  and  the  . 
mean  width  of  the  entrance  is  about  92  feet.  The  sill  of  the  dock  is  laid 
8  inches  below  the  sill  of  the  entrance  lock  between  the  river  and  the 
Kaiserhafen,  and  is  23  feet  6  inches  belo  w  the  local  zero.  Ordinary  high  water 
is  11  feet  9  inches  above  zero,  giving  a  draught  over  the  sill  of  35  feet  3 
inches ;  on  extremely  rare  occasions,  however,  the  water  in  the  wet  dock 
may  fall  to  6  feet  6  inches  above  zero,  and  the  available  draught  then 
becomes  30  feet. 

The  width  of  the  dock  bottom  has  been  arranged  so  as  to  leave  a 
clearance  of  6  feet  for  workmen  on  each  side  of  the  hull  of  a  vessel,  82  feet 
wide.  The  central  strip  upon  which  the  keel-blocks  rest  has,  like  these,  a 
fall  of  1  in  600,  at  the  side  there  is  a  fall  of  1  in  450  towards  the  inlet 
channels  of  the  pumping  station  well,  which  are  placed  in  the  western  side 
wall  of  the  dock  behind  the  inner  sill.  The  floor  was  subsequently  raised 
for  a  length  of  98  feet  at  its  inner  end,  so  that  workmen  who  are  engaged 
in  repairing  a  ship's  screws,  can  start  upon  their  work  without  waiting  for 
all  the  water  to  be  pumped  out.  The  height  of  the  keel-blocks  is  3  feet 
6  inches,  and  this  also  represents  the  depth  of  the  dock  below  the  sill. 

The  dock  is  closed  by  a  floating  caisson,  which  only  diflers  from  those  of 
ordinary  construction  in  that  it  carries  a  20-ton  crane.  The  dock  can  be 
closed  in  twenty  minutes. 

The  keel-blocks  are  entirely  of  timber,  spaced  at  4  feet  6  inches  centres, 
and  have  a  base  area  of  6  feet  by  20  inches.  The  upper  portion  consists 
of  oak  logs,  bolted  together,  and  the  lower  portion  of  pitchpine  timbers, 

♦Rudloflf  on  "Docks,"  Int,  Nav,  Cong,,  Dusseldorf,  1902. 


[To  AUM  pag4  m. 


ir  Oraviag  Dock  at  BremerhaveD. 


GRAVING  DOCK  AT  BREMERHAVEN.  497 

secured  in  the  same  waj.  The  bilge-blocks,  for  supporting  the  bottom  of 
a  ship  on  both  sides  of  the  keel,  consist  of  strong  pitchpine  timbers, 
arranged  scaffold  fashion,  resting  upon  cradles,  which  are  drawn  under  the 
ship  and  adjusted  by  wire  ropes,  passing  through  rollers.  The  cradles 
move  on  special  slides  bordered  with  iron,  and  are  spaced  27  feet  apart. 

The  graving  dock  is  constructed  parallel  to  and  adjoining  a  large 
sea-lock,  which,  generally  speaking,  was  built  under  the  same  conditions 
as  the  dock.  The  experience,  gained  during  the  former  undertaking, 
proved  very  useful  in  carrying  out  the  second  without  any  serious  inter- 
ruption.    The  work  proceeded  in  the  following  manner  : — 

Preliminary  operations  consisted  in  digging  out  trenches  to  a  depth  of 
3  feet  3  inches  below  zero  or  about  14  feet  9  inches  below  ground  level,  by 
means  of  a  land  dredger,  and  the  excavated  material  (soft  clay)  was  carried 
off  in  tipping  waggons  and  utilised  for  raising  the  ground  all  over  the 
harbour  site.  In  the  trenches  thus  formed,  1 2-inch  sheet  piling  was  driven, 
averaging  55  feet  in  depth,  to  enclose  the  dock  foundation  proper.  A 
second  row  of  piles  was  driven  at  the  same  time  to  serve  as  anchorage 
to  the  sheet  piling.  When  this  had  been  done,  water  was  admitted  into 
the  trenches  from  the  harbour,  and  excavation  was  continued  down  to  the 
bottom  of  the  foundation  by  means  of  a  floating  bucket-dredger.  But  as 
the  latter  was  incapable  of  working  at  a  depth  of  58}  feet,  and  as  grabs  did 
not  work  satisfactorily,  the  trenches  had  to  be  closed  again  by  dams  and 
pumped  out  for  the  concluding  portion  of  this  work. 

After  the  trenches  had  been  carried  down  to  the  required  depth,  water 
was  admitted  to  them  a  second  time,  and  the  bottom  layer  of  concrete, 
composed  of  I  part  of  lime,  1  of  trass,  and  1  of  sand  to  4  parts  coarse  river 
gravel  from  the  Weser,  deposited  in  skips.  The  whole  of  the  foundations 
were  completed  in  15  weeks  at  the  rate  of  800  cubic  yards  a  day,  the 
maximum  output  being  930  cubic  yards  in  twenty  hours.  The  average 
thickness  of  the  foundation  was  19  feet  6  inches. 

The  layer  of  concrete  was  left  undisturbed  for  a  period  of  three  months, 
after  which  it  was  pumped  dry  and  levelled  to  an  even  surface,  being 
further  strengthened  with  strong  iron  bands,  to  prevent  its  breaking  up. 
The  building  of  the  walls  was  then  proceeded  with.  They  were  mainly 
constructed  in  concrete,  with  a  hard  clinker  facing  and  granite  copings, 
quoins,  and  bedstones.  No  leakage  occurred  through  the  concrete  founda- 
tion, but  a  strong  flow  through  a  gap  in  the  sheet  piling  was  conducted 
into  the  pump  well  without  giving  further  difficulty. 

The   pumping    plant  consists   of   two   49-inch   centrifugal    pumps  for 

emptying  the  dock,  and  two  10-inch  centrifugal  pumps  for  dealing  with 

the  leakage  water.     The  former  set  are  driven  by  special,  direct-coupled, 

triple-expansion  engines.     Each  pump  can  lift  on  an  average  150  cubic  feet 

a  second,  and  as  the  dock  holds  2,700,000  cubic  feet,  it  can  be  emptied  in 

2J  hours.     The  drainage  pumps  are  driven  by  30  H.P.  compound  engines. 

Only  one  drainage  pump  is  needed,  as  a  rule,  and  that  intermittently. 

32 


498  IX)CK  ENGINEERING. 

There  are  two  culverts  for  filling  the  dock,  one  in  each  side  wall,  with 
a  sectional  area  of  87  square  feet,  closed  with  vertical  paddles  of  the 
ordinary  type,  working  in  granite  grooves.  Each  paddle  consists  of  a 
built-up  mild  steel  frame,  covered  with  tongued  and  grooved  oak  planks 
and  provided  with  greenheart  rubbing  fillets. 

Canada  Graving  Book  at  Iiiverpool. 

The  extreme  length  of  the  dock  (figs.  500  and  501)  from  point  of  sill  to 
head  of  dock  is  925  feet  6  inches.  It  has  an  entrance  width  of  94  feet  and 
a  depth  of  water  of  32  feet  at  high  water  of  ordinary  spring  tides.  The 
height  of  the  pierheads  is  41  feet  above  sill  level.  In  the  interior  of  the 
dock  the  bottom  width  is  94  feet,  whence  the  side  walls  recede  in  a  series  of 
thirteen  offsets,  or  altar  courses,  of  irregular  height,  to  a  width  of  124  feet 
2  inches  at  coping  level.  The  coping  level  is  35  feet  8  inches  and  36  feet 
1  inch  above  sill  level  on  the  north  and  south  sides  of  the  dock  respectively. 
Communication  with  the  bottom  is  made  by  means  of  six  sets  of  stone  steps 
and  slides,  three  at  each  side,  and  there  are  also  two  stairways  at  the  head 
of  the  dock. 

The  fioor  of  the  dock  has  a  fall  of  9  inches  from  the  centre  to  the  sides, 
where  drainage  channels  communicate  through  18-inch  drain  pipes  with  the 
two  central  culverts.  These  are  parallel  to  each  other,  and  to  the  longi- 
tudinal axis  of  the  dock,  commencing  with  a  section,  4  feet  by  3  feet,  of 
which  the  sides  are  vertical  and  the  roof  and  fioor  curved,  passing  through 
the  circular  form  with  5  feet  6  inches  diameter,  and  finally  assuming  an 
egg-shape,  8  feet  deep.  A  rectangular  pit,  12  feet  by  35  feet  open  save  for 
an  iron  grating,  receives  the  water  from  the  dock  at  its  north-west  corner, 
whence  it  is  transmitted  by  two  large  rectangular  culverts,  each  10  feet 
9  inches  by  9  feet,  to  the  pumping  well  at  a  level  of  18  feet  below  the  sill. 

The  pumping  plant  consists  of  three  51-inch  centrifugal  pumps,  each 
driven  by  a  condensing  engine  of  700  H.P.,  with  two  high-pressure 
cylinders,  25  inches  diameter  and  2  feet  stroke.  Steam  at  110  lbs.  pressure 
is  supplied  from  six  sets  of  Babcock  and  Wilcox  patent  water- tube  boilers, 
having  3,1 16  square  feet  of  heating  surface  and  59^  square  feet  of  grate  area 
to  each  boiler.  The  pumps  are  capable  of  lifting  1,000  tons  per  minute,  and 
of  emptying  the  dock,  whose  capacity  is  3,226,648  cubic  feet,  in  an  hour  and 
a-half.  There  is  also  a  small  14-inch  drainage  pump  for  dealing  with  leak- 
age, which  is  very  slight. 

The  bulk  of  the  walls  and  floor  are  of  concrete,  composed  of  1  part  of 
Portland  cement  to  6  and  8  of  Harrington  gravel,  faced  with  2  to  1  concrete, 
and  having  granite  coping,  quoins,  sills,  steps,  and  slides.  The  keel-blocks 
are  of  cast-iron  wedges,  surmounted  by  a  birch  cap  12  inches  thick.  The  top 
of  the  blocks  is  4  feet  above  the  fioor  level.  The  entrance  is  closed  by  green- 
heart  gates,  and  the  clough  paddles  are  also  of  greenlieart  Behind  the  gate 
heel-posts  are  two  culverts  for  filling  the  dock. 


[To  tatt  ptff*  iss. 


U         W         too  Fret 


GRAVING  DOCK,  GLASGOW.  499 

The  equipment  consists  of  the  usual  mooring  posts,  shores,  capstans,  and 
mushrooms,  together  with  a  40-ton  hydraulic  crane  erected  by  Messrs.  Geo. 
Russell  &  Co.,  of  Motherwell. 

No  difficulties  of  any  serious  importance  were  encountered  during  the 
construction  of  the  dock.  The  site  lay  to  the  eastwards  of  the  Canada  Dock, 
a  short  distance  behind  the  east  wall  of  which,  the  main  bulk  of  the  excava- 
tion, principally  clay,  interspersed  with  beds  of  sand,  was  done  under 
normal  conditions  with  a  steam  navvy  and  grabs.  When  this  operation  had 
been  completed  as  far  as  possible,  and  the  walls,  floor,  and  sill  put  in,  a  dam 
of  12-inch  sheeting  piles  was  driven  across  the  front  of  the  entrance  and  was 
shored  in  the  first  instance  to  the  masonry  of  the  east  wall.  The  water 
having  been  pumped  out  between  the  dam  and  the  wall,  the  pierheads  were 
put  in.  Then  the  old  east  wall  was  gradually  demolished,  the  bearings 
of  the  shores  being  transferred  to  the  pierheads  and  the  sill.  Finally, 
water  was  let  into  the  dock,  the  dam  removed,  and  then  some  little  dredging 
at  the  entrance  completed  the  undertaking. 

No.  8  Graving  Dock,  Q-lasgow.* 

This  dock  (fig.  502)  opened  in  1898,  has  the  following  general 
dimensions : — 

Ft.    Ins. 
Length  of  floor,  from  inside  of  caisson  at  outer  entrance  to  heeul 

of  dock, 880  0 

Width  at  bottom, 81  8 

Width  at  top, 115  0 

Width  of  outer  entrance  at  bottom  and  top, 83  0 

Width  of  inner  entrance  at  bottom  and  top, 83  0 

Depth  on  centre  of  sill  of  outer  entrance  at  M.W.O.S.T.,    ...  26  6 

Depth  on  centre  of  sill  of  inner  entrance  at  H.W.O.S.T.,     ...  27  0 

Levelof  floor  of  dock  below  H.W.O.S.T., 28  6 

(except  at  gate  chamber,  where  it  is  6  inches  deeper. ) 

The  dock  is  divided,  by  a  pair  of  steel  gates,  into  two  lengths  of  460  and 
420  feet 

The  strata  underlying  the  site  of  the  dock  consisted  mainly  of  fine  sand 
and  gravel  with  occasional  pockets  of  clay.  The  structure  rests  upon 
moving  sand,  and  the  wing  walls  and  apron  are  founded  on  triple-concrete 
cylinders,  in  the  manner  described  in  Chap.  v.  Two  of  the  cylinders  of  the 
apron  remained  unfilled  till  the  dock  was  nearly  completed,  being  used  as 
sumps  for  pumping  purposes.  Into  these  wells  9-inch  pipes,  bedded  in 
clean-riddled  gravel,  were  led,  in  order  to  drain  the  dock  area  which  was 
excavated  to  low-water  level  with  side  slopes,  but  below  that  level  excava- 
tion was  carried  on  within  sheet  piling,  44  feet  long  by  12  inches  thick, 
driven  along  the  sides  and  round  the  upper  end  of  the  dock. 

*  Alston  on  «  Glasgow  No.  3  Graving  Dock,"  Int.  Eng.  C(mf,y  Glasgow,  1901 ;  also 
Tht  Bngmur,  May  20,  1898. 


500  DOCK  ENGINEERING. 

The  floor  foundatioa  consists  of  a  bed  of  concrete,  li  inches  thick  at  the 
centre  and  4  feet  6  inches  thick  at  the  sides.  On  this  was  laid  the  brick 
invert,  6  feet  10  inches  thick,  with  a  radius  of  177  feet,  snrmonnted  by  a 
bed  of  concrete  6  feet  6  inches  thick  at  the  centre,  diminishing  to  12  inches 
at  each  side,  with  a  cross-sectional  camber  of  6  inches  on  the  upper  surface. 
The  surface  finishing  consists  of  a  6-inch  granite  causeway,  with  the  excep- 
tion of  a  length  of  103  feet  at  the  head  of  the  dock,  which  was  paved  with 
granite  blocks. 

The  side  walls  of  the  outer  and  inner  entrances  and  the  head  of  the  dock 
are  of  brick  and  concrete.  The  walls  of  the  outer  entrance  were  &ced  with 
granite  and  those  of  the  inner  entrance  and  the  head  of  the  dock,  with 
moulded  granolithic-faced  ashlar,  all  coped  with  granite. 


Fig.  602.— No,  3  Graving  Dock,  GUagow. 

The  side  walls  of  the  dock  proper  are  of  concrete,  put  in  between  movable 
frames,  roughly  stepped  to  receive  the  granolithic  altar  courses,  fourteen  itt 
number,  ranging  in  dimensions  from  46  by  20  inches  to  18  by  14  inches. 
The  altar  courses,  with  the  exception  of  the  bottom  course,  were  made  in 
moulds  on  a  platform  and  then  built  in  position  like  ashlar;  the  bottom 
course  was  made  in  situ.  The  side  walls  are  i  feet  6  inches  lower  than  the 
pierheads  of  entrance.  Four  double  stairs  of  granite,  with  granite  timber 
slides,  are  arranged  in  each  of  the  two  divisions  of  the  dock. 

Near  the  outer  entrance  there  is  a  rudder  well,  10  feet  long  by  7  feet 
wide  by  8  feet  deep. 

The  apron  for  the  sill  of  gates  of  inner  entrance  is  6  inches  below  the 
floor  of  dock  at  the  centre.  The  sill  is  18  inches  above  the  floor  at  its  centre. 
The  meeting  faces  and  inner  side  of  the  sill  are  of  granite.  The  upper 
surfaces  of  sill  and  apron  are  paved  with  granite,  and  in  the  apron  are  bedded 


COMMERCIAL  ORAVINO  DOCK  AT  BARRY. 


501 


radiated  granite  stones  to  carry  the  cast  steel  roller  paths,  9  inches  wide,  for 
the  gates. 

The  outer  division  is  filled  hy  two  culverts,  7  feet  4  inches  high  by  4  feet 
wide,  one  of  them  passing  round  the  caisson  chamber.  The  inner  division 
is  filled  from  the  outer  division  by  two  similar  culverts.  A  loop  culvert, 
6  feet  by  3  feet  6  inches,  is  also  provided,  leading  from  the  main  discharge 
<;ulvert  into  a  sump  to  increase  the  rapidity  of  filling. 

For  emptying  the  dock,  a  sump  or  well,  61  feet  long  by  12  feet  broad  by 
11  feet  deep,  is  constructed  under  the  engine-house,  and  the  water  is 
discharged  therefrom  into  Princes  Dock  through  a  main  discharge  culvert, 
11. feet  6  inches  high  by  8  feet  wide.  The  pumping  installation  consists  of 
two  60-inch  centrifugal  pumps,  each  driven  by  a  pair  of  vertical  direct- 
acting  engines,  with  cylinders  28  inches  diameter  and  24  inches  stroke,  the 
steam  pressure  being  110  lbs.  per  square  inch.  An  auxiliary  15-inch  pump 
deals  with  leakage  water.  Steam  is  supplied  from  four  boilers  of  the  return 
tubular  marine  type,  with  assisted  draught,  each  12  feet  6  inches  diameter 
and  10  feet  long,  giving  a  working  pressure  of  130  lbs.  per  square  inch. 

The  capacity  of  the  dock  when  no  vessels  are  in,  is  about  2,202,000  cubic 
feet  or  13,762,500  gallons  at  high  water.  This  quantity  can  be  discharged 
in  1  hour  40  minutes. 

The  equipment  consists  of  a  25-ton  steam  travelling  crane  on  the  north 
eide,  with  sweep  to  centre  of  dock ;  five  5-ton  direct-acting  hydraulic  capstans 
and  12  hand  capstans,  together  with  31  mooring  posts.  The  sets  of  portable 
keel-blocks,  620  in  number,  are  laid  down  in  three  lines.  Their  general 
sizes  are  5  feet  long,  16  inches  broad,  and  30  inches  high. 

The  Portland  cement  concrete  was  of  the  following  proportions : — For 
the  foundation  cylinders,  5  to  1  ;  for  floor  and  sides  of  dock,  6  to  1 ;  for 
pockets  in  brickwork  of  entrance  and  end  walls,  9  to  1 ;  for  moulded 
granolithic- faced  ashlar,  6  to  1  ;  and  the  granolithic  facing,  3  to  1. 


Gommeroial  Graving  Dock  at  Barry.* 

The  general  dimensions  of  this  dock,  completed  in  1893,  are  as  follows 
'{vide  figs  503  and  504)  :— 


Extreme  length, 

Outer  compartment, 

Inner  compartment, 

Width  of  outer  entrance  at  coping  level, 
Width  of  inner  entrance  at  coping  level, 
Depth  of  water  on  outer  sill  at  H.W.O.S.T., 
Depth  of  water  on  inner  sill  at  H.W.O.S.T., 
Width  of  dock  chambers  at  coping, 
Width  of  dock  chambers  at  floor, . 


Ft. 

lUB. 

747 

6 

384 

6 

363 

0 

60 

3 

59 

44 

26 

8i 

27 

2i 

113 

6 

100 

0 

The  earthwork  consisted  chiefly  of  red  marl.     Magnesian  limestone  was 
;also  found,  and  was  used  in  the  dry  rubble  drains  behind  the  walls  and  for 
•  Robinson  on  "  The  Barry  Graving  Docks,"  Min,  Proc,  Inst,  C.JS,,  vol.  cxvi. 


502  DOCK  ENGINEERING. 

backing.  Numerous  joints  and  fissures  were  exposed  by  the  excavations  in 
the  hard  marl  and  limestone,  and  from  some  of  these  salt  water  issued. 
Under  the  foundations  of  the  west  wall  of  the  inner  dock  a  cavern,  27  by 
23  feet  and  14  feet  deep,  was  discovered  in  the  marl,  through  a  hole  in 
which,  sea  water  burst  forth  and  continued  to  flow  at  each  tide,  but  ceased 
at  low  water  of  spring  tides.  A  brick  wall  in  cement  mortar  was  built 
round  the  hole  at  the  top  of  the  cavern  to  keep  in  the  water.  Bubble 
stones  were  then  deposited  in  the  cavern,  and  a  Portland  cement  concrete 
floor,  6  feet  thick,  was  laid  on  them,  and  on  this  the  wall  is  founded. 

The  floor  is  of  Portland  cement  concrete,  6  to  1,  and  2  feet  in  thickness,, 
with  stone  drains.  Across  the  floor,  in  and  under  the  concrete,  4-inch  land 
drains  are  laid,  20  feet  apart,  to  convey  any  rising  water  to  the  open  drains. 
The  walls  are  built  of  mountain  limestone,  weighing  169  lbs.  per  cubic  foot, 
from  the  Alps  quarry,  about  5  miles  away.  The  roughly -dressed  face- 
stones  are  squared  but  not  laid  in  courses,  and  have  close  beds  and  jointa 
for  6  inches,  lipped  with  cement  for  3  inches  inwards  at  the  time  of  building. 
The  remaining  portions  of  the  walls  are  built  in  blue  lias  lime  mortar. 
Headers,  not  less  than  3^  feet  long,  pass  through  from  front  to  back  and 
overlap  each  other.  The  altars,  2  feet  by  9  inches,  and  the  coping  are  of 
granite.  The  depth  of  the  dock  from  coping  level  to  floor  is  32  feet  6  inches. 
The  walls  have  not  been  designed  to  resist  wat^r  pressure  from  the  back,, 
and  cast-iron  pipes  are  inserted  in  them  to  allow  the  water  to  escape.  Any 
reflex  action  is  prevented  by  brass  clack-valves.  There  are  wrought-iron 
ladders  connecting  the  altar  courses  and  flights  of  wooden  steps  in  the 
corners  for  access  to  the  floor. 

The  walls  of  the  entrance  have  a  batter  of  1  in  8.  The  sill  stones  and 
caisson  quoins  are  of  granite,  fine-axed  on  the  meeting  face.  The  bearing 
blocks  for  the  bottom  of  the  caisson  are  limestone,  2  feet  by  15  inches, 
standing  1^  inches  above  the  concrete  floor,  6  feet  apart  centre  to  centre,  and 
level  throughout.  Hydraulic  pipes  and  electric  light  mains  are  carried  in  a 
recess,  8  feet  wide  and  18  inches  deep,  in  the  walls  and  across  the  invert. 
The  last-named  is  built  in  brickwork  with  cement  mortar,  faced  with  two* 
courses  of  Staffordshire  blue  bricks. 

Beneath  the  engine  and  boiler  house  (fig.  505)  are  the  suction  and' 
discharge  chambers,  10  feet  wide  and  11  feet  high,  with  floors  3  feet  6  inches 
lower  than  that  of  the  graving  dock.  Two  culverts,  6  feet  6  inches  in 
width  and  height,  conduct  the  water  to  the  suction  chamber  and  a  similar 
sized  barrel-culvert  conveys  the  water  from  the  suction  chamber  to  the  sea. 
There  are  three  suction  |)ipes  in  the  pumping  chamber,  33  inches  diameter,, 
and  three  similar  discharge  pipes  in  the  discharge  chamber.  In  addition, 
there  are  two  suction  pipes  and  one  discharge  pipe,  12  inches  diameter, 
connected  with  the  two  drainage  pumps.  The  pumps  consist  of  three  33-ihch 
horizontal,  high-pressure  condensing,  centrifugal  pumping  engines  and  two- 
12-inch  drainage,  centrifugal  pumping  engines,  supplied  with  steam  from 
three  Lancashire  boilers  and  one   auxiliary  Oornish   boiler.      The  main. 


tf 


(To  faet  IKV«  SOt. 


COMMERCIAL  GRAVING  DOCK  AT  BARRY.  503 

pnmpiag  engines  have  diacB,  5J  feet  in  diameter,  and  18-isch  cylinders  of 
16  inches  stroke,  sjid  thej  are  fitted  with  rariable  expansion  gear  and  steam 
stop-Talves.  Each  pump  can  make  )60  revolations  a  minute,  dischai^ng 
17,000  gallons  of  water  or  about  1,000,000  per  hour.  The  dock  lias  been 
completely  emptied  ia  three  hours  against  a  head  increasing  to  32  feet,  but 
both  divisions  can  also  be  emptied  in  an  hour  and  a  half,  by  letting  the'water 
flow  into  the  sea  and  in  forty  minutes  when  the  tide  permits. 


Fig.  G05. — Pumping  Station,  Bbitj  Graving  Dock. 

The  equipment  consists  of  three  hydraulic  capstans,  six  bollards,  and  a 
number  of  snatch  heads  and  books.  The  last-named  are  for  giving  a  slight 
list  to  vessels  after  they  have  settled  on  the  keel-blocks.  The  blocks  are  of 
cast  iron  with  elm  caps,  i  feet  long,  3  feet  high,  and  12  inches  wide.  They 
are  spaced  at  4  feet  6  inches  centres  and  are  in  two  parallel  Lines,  each 
division  of  the  dock  being  able  to  accommodate  two  vessels  side  by  side. 
Vessels  are  supported  by  timber  props  from  the  altars  of  one  side  only. 
They  are  so  arranged  that  those  whose  repairs  are  first  completed  can  leave 
the  dock  with  the  least  possible  interference  to  the  others.  The  dock  ia 
lighted  by  electricity. 

The  entrance  and  passage  are  closed  by  a  pair  of  interchangeable 
caissons,  17  feet  wide  and  34  feet  6  inches  deep,  the  top  decks  of  which 
are  planked.  A  line  of  railway  runs  over  the  dock  for  locomotives  and 
waggons. 


504  I>OOK  ENGINEERING. 

Tilbury  Graying  Dooks,  London. 

There  are  two  graving  docks  lying  parallel  to  one  another  at  the 
entrance 'to  the  Tilhury  Docks,  London  *  (fig.  506).  They  are  also  capable 
of  acting  as  entrance  locks,  and  for  this  purpose  they  are  provided  with 
caissons  at  both  ends.  In  addition  to  this,  there  are  three  central  positions 
in  each  dock  fitted  for  the  reception  of  a  caisson.  The  result  of  this 
arrangement  is  that,  apart  from  the  use  of  each  graving  dock  in  its  entirety 
of  875  feet,  there  are  virtually  four  graving  docks,  each  complete  in  itself, 
two  being  entered  from  the  tidal  basin  and  two  from  the  main  dock.  And, 
by  means  of  a  variation  in  the  position  of  the  central  caisson,  each  pair  can 
be  adjusted  to  any  of  the  following  lengths  in  the  clear — viz.,  450  and  400 
feet,  350  and  500  feet,  and  300  and  550  feet. 

The  large  graving  docks  have  a  width  of  70  feet  across  the  bottom  and  a 
depth  of  35  feet  below  Trinity  high-water  mark  on  the  sills.  The  width  of 
the  small  graving  docks  is  60  feet,  and  the  depth  on  sills  30  feet  (figs.  507 
to  50S). 

The  walls  of  the  large  graving  docks  have  a  thickness  of  16  feet  3  inches 
at  fioor  level  and  of  5  feet  at  the  coping.  The  backs  of  the  walls  are  verti- 
cal, except  where  it  was  necessary  to  increase  the  width  for  culverts,  and 
the  internal  faces  of  the  walls  have  a  batter  of  1  in  20  for  a  height  of 
22  feet  6  inches.  The  upper  part  of  the  walls  is  stepped  to  form  six  altars. 
The  thickness  of  the  invert  varies  with  the  depth  to  which  it  was 
required  to  excavate  to  reach  the  gravel  foundation,  but  the  normal 
thickness  is  15  feet.  The  walls  of  the  small  graving  docks  are  13  feet  6 
inches  thick  at  the  base,  and  their  other  dimensions  are,  in  general,  smaller 
than  those  of  the  walls  of  the  large  graving  docks  in  the  same  proportion. 
The  invert  is,  however,  relatively  thicker,  on  account  of  the  necessity  of 
excavating  the  foundations  to  the  same  depth  in  both  cases.  A  portion  of 
the  invert  of  the  small  docks  is,  owing  to  a  dip  towards  an  old  channel, 
carried  upon  short  whole-timber  bearing  piles,  spaced  at  4  feet  centres,  in 
each  direction.  The  invert  is  entirely  of  9  to  1  concrete,  with  a  stop- 
water  course,  3  inches  thick,  of  fine  3  to  1  concrete.  Upnor  clay-puddle, 
1  foot  6  inches  thick,  is  carried  down  the  backs  of  both  graving  dock 
walls  from  Trinity  high-water  level  to  below  the  stop-water  course.  The 
floors  are  of  pitchpine  planking,  4  inches  thick,  spiked  down  to  pitchpine 
sleepers,  14  inches  square,  which  are  bedded  in  concrete.  Teak  keel-blocks 
are  laid  along  the  whole  length  of  the  docks,  and  are  fixed  down  to  the 
floors  by  dogs.  The  altars  are  paved  with  6-inch  hard  York  stone,  the 
copings  being  of  teak,  12  inches  square,  furnished  with  eye-bolts  and 
secured  to  teak  cross-timbers,  3  feet  6  inches  long,  bedded  in  brickwork 
at  the  tops  of  the  walls. 

The  docks  are  provided  with  five  hydraulic  capstans  of  2^-ton  and  5-ton 
power  and  cast-iron  bollards,  the  latter  having  perforated  capd  and  being 

•  Scott  on  **  The  Ck>n8tniction  of  Tilbury  Docks,"  Min,  Proc,  Inat.  C,S.,  vol.  CX3C 


0 . 


^o A  Cmvin^Jtodu  oh  daf*Uti  fry  cmt 


FLOATING  DOCK  AT  BERMUDA.  505 

connected  with  the  various  culverts,  so  as  to  serve  as  air-shafts.  Each  of 
the  four  sections  of  the  graving  docks  has  a  distinct  set  of  culverts  for 
running  out  and  filling  in  the  water,  and  the  pumping  arrangements  allow 
of  pumping  the  water  out  of  any  one  section  into  any  other  section,  or, 
through  the  discharge  pit.  in  the  rear  of  the  engine-house,  into  either  the 
main  dock  or  the  tidal  basin. 

The  machinery  at  the  pumping  station  consists  of  four  centrifugal 
pumps,  two  with  fans  5  feet  in  diameter,  and  two  with  fans  4  feet  6 
inches  in  diameter.  These  are  driven  by  four  sets  of  engines  of  inverted, 
direct-acting,  high-pressure  type,  two  with  cylinders  22  inches  diameter 
and  16|  inches  stroke,  and  two  with  cylinders  17 J  inches  diameter  and  16| 
inches  stroke,  for  the  large  and  small  pumps  respectively.  The  pumps  are, 
together,  capable  of  discharging  650  tons  of  water  per  minute  into  the 
diHcharge  pit,  and,  therefore,  of  pumping  out  the  large  pair  of  docks  in 
about  one  hour.  Two  distinct  sets  of  double-acting  plunger-and-bucket 
pumps  for  drainage,  each  capable  of  raising  1,000  gallons  per  minute  into 
the  main  dock,  are  provided.  The  engines  driving  them,  through  gearing, 
are  of  the  horizontal  type.  Steam  is  raised  from  five  boilers,  one  being 
spare,  of  modified  marine  tubular  type,  7  feet  6  inches  diameter  and  20 
feet  long,  with  two  flues,  3  feet  diameter.  The  flues  lead  to  wrought-iron 
chimneys,  one  for  each  boiler,  and  thus  an  ordinary  shaft  is  dispensed 
with.  Forced  draught  is  driven  through  the  stokeholds  by  five  fans,  each 
with  a  small  independent  engine.  A  cast-iron  tank  of  250,000  gallons* 
capacity,  into  which  water  from  the  drainage  culverts  is  pumped  by  an 
auxiliary  engine,  covers  the  boiler-house. 

Floating  Dock  at  Bermuda.* 

The  new  dock  at  Bermuda  (figs.  510  and  511)  launched  in  1902,  to 
replace  the  former  dock  of  1868,  is  from  designs  by  Messrs.  Clark  and 
Standfield.  It  is  545  feet  long,  with  a  clear  width  of  100  feet  between 
the  rubbing  fenders.  The  side  walls  are  13  feet  in  width,  which  gives 
a  total  width  to  the  structure  of  about  126  feet.  The  lifting  power,  up  to 
the  pontoon  deck  level,  is  15,500  tons,  but,  by  using  the  shallow  pound,  this 
can  be  increased  to  17,500  tons.  The  weight  of  the  hull  is  6,500  tons. 
The  sides  are  high  enough  to  enable  a  vessel  of  32  feet  draught  to  be 
berthed  on  the  keel-blocks,  the  latter  being  3  feet  6  inches  high.  The 
whole  structure  consists  mainly  of  five  parts — three  floor  pontoons  and  two 
side  walls.  The  pontoons  supply  the  chief  part  of  the  lifting  power,  and 
though  the  side  walls  may  be  used  to  some  extent  for  the  same  purpose, 
their  primary  object  is  to  give  the  structure  stability  and  to  afford  control 
over  the  dock  in  sinking  it  to  take  the  ship  on  board.  The  end  pontoons 
are  each  120  feet  long  and  are  bevelled  in  such  a  way  as  to  facilitate 
towing.     The  centre  pontoon  is  300  feet  long.     The  sides  of  the  pontoons 

•  Vide  Engineering,  February  14,  1902. 


506  DOCK  ENGINEERING. 

are  built  up  above  the  deck  level  to  a  triangular  profile  so  as  to  form  three 
altar  courses. 

The  side  walls  are  each  435  feet  long  and  53  feet  3  inches  high,  and, 
in  order  to  give  sufficient  space  for  the  boilers,  they  are  sponsoned  out, 
forming  an  upper  chamber,  12  feet  6  inches  wide.  There  are  four  large 
openings  in  the  walls  for  the  purpose  of  affording  light  and  ventilation 
under  the  bottom  of  a  docked  vessel. 

The  three  pontoons  are  subdivided  into  40  pumping  compartments,  and 
of  these  32  are  watertight.  There  are  also  eight  watertight  compartments 
in  each  side  wall.  All  these  divisions  are  provided  with  a  separate  pipe  and 
valve,  the  pipes  leading  directly  into  the  two  main  side  drains.  The  drains 
are  continuous  throughout  the  length  of  the  walls,  and  as  the  four  18-inch 
centrifugal  pumps  are  seated  directly  on  them,  any  one  pump  can  empty 
all  the  compartments  of  its  half  of  the  dock.  There  is  a  central  bulkhead, 
dividing  the  dock  into  two  halves,  but  this  is  not  quite  watertight,  small 
leakage  holes  being  purposely  left.  If,  therefore,  the  whole  of  the  pumping 
machinery  on  one  side  were  to  break  down,  the  other  half  could  still  empty 
the  dock,  though  at  a  somewhat  slow  rate.  The  pumps  are  driven  each 
by  a  separate  compound  condensing  engine  directly  attached.  A  return- 
tube  boiler  supplies  each  pair  of  pumping  engines  with  steam ;  but  tba 
connections  are  so  made  that  the  supply  of  steam  from  any  boiler  is 
interchangeable. 

The  working  of  the  whole  dock  is  done  from  two  central  positions  on 
the  top  of  the  dock  towers,  where  the  valve  wheels  and  connections  are 
placed,  with  indicators  to  show  the  condition  of  the  valves,  whether  open 
or  shut.  There  are  six  capstans  for  warping  ships  into  position,  with  the 
usual  bollards,  fairleads,  &c.  Lighting  at  night  is  done  by  electricity  with 
12  arc  lamps,  beside  smaller  services.  Two  5-ton  travelling  jib  cranes  are 
worked  by  the  same  motive  power  from  separate  generating  plants  placed 
in  the  dock  towers,  the  leads  being  mutually  interchangeable. 

The  underside  of  the  dock  is  protected  by  a  series  of  greenheart  keels^ 
as  it  is  possible  the  dock  may  ground  at  low  water,  and  the  bottom  of  the 
harbour  at  Bermuda  is  of  coral.     The  top  decks  are  planked  with  teak. 

Figs.  512  to  515  are  views  of  the  dock  in  its  various  positions. 


FLOATING  DOCK  AT  BERMUDA. 


;.  312.— Dock  Heeled  to  remove  Starboard  Connection. 


Fig.  613. — Centre  Pontoon  Floating  Free.     Rest  of  Dock  being  Sunk. 


508  DOCK  ENGINEERING. 


Fig.  514. — Dock  Sunk,  bringing  Centre  Pontoon  Connection  into  Upticr  Pu< 


509 


CHAPTER   XII. 

WORKING    EQUIPMENT    OF    DOCKS. 

Sources  of  Power — Compressed  Air— Steam — Water  under  Pressure— Elec- 
tricity—Comparative  Expenditure  op  Energy- Crane  Tests- Cost  op  Power 
—Hydraulic  Machinery — Systems  of  Electrical  Distribution- Applications 
TO  Dock  Equipment — Gate  Machinery— Power  of  Gate  Machines — Sluicin& 
Machinery — Capstans— Quay  and  Floating  Cranes — Jiggers  and  Trans- 
porters— Coal  Tips  and  Lifts  — Grain  Elevators — Slipway  Haulage— 
Pumping  Instatjations— Petroi^um  Storage — General  Equipment — List 
OF  Appliances  in  Use  at  Hamburg,  Havre,  and  Liverpool. 

The  subject  of  dock  equipment  is  scarcely  less  extensive,  and  certainly  no 
less  important,  than  that  of  dock  construction,  strictly  so-called.  Indeed, 
the  two  departments  are  so  intimately  associated  in  aim  and  development,, 
that  they  cannot  well  be  separated,  and  a  technical  work  which  pretends 
to  any  completeness  of  treatment,  must  inevitably  include  not  only  an 
outline  of  the  nature  and  functions  of  the  various  appliances  included 
in  the  working  equipment  of  a  dock  system,  but  also  some  description,^ 
however  succinct,  of  their  essential  parts.  Any  elaborate  investigation 
appertains,  of  course,  more  appropriately  to  the  domain  of  the  mechanical, 
and,  often  in  these  later  days,  the  electrical  specialist ;  but,  without  some 
general  knowledge  of  the  subject,  a  dock  engineer  would  be  manifestly 
imperfectly  fitted  to  discharge  the  duties  and  responsibilities  of  his  position. 

Before  proceeding  to  a  categorical  analysis  of  the  machinery  in  question, 
it  will  be  well  to  devote  a  few  preliminary  remarks  to  the  broad  question  of 
sources  of  power — their  availability,  utility,  and  economy,  for  the  respective 
purposes  held  in  view. 

Power. — The  power  employed  for  actuating  dock  machinery  is  derived 

from  four  sources  : — 

1.  Compressed  air. 

2.  Steam. 

3.  Water  under  pressure. 

4.  Electricity. 

Strictly  speaking,  all  but  the  second  of  these  agencies  are  mere  trans- 
mitters of  power  already  in  existence.  As  a  matter  of  fact,  all  present 
forms  of  power  have  their  practical  origin  in  the  steam  engine,*^  by  which 

*  The  waterfall  and  wiDdmill  are  ignored  as  too  limited  in  application  and  as 
unlikely  to  be  resorted  to  in  connection  with  dockwork.  Internal  combustion  engines, 
such  as  the  gas  engine,  despite  their  great  potentialities  and  rapidly  increasing  use,  have 
not  yet  acquired  sufficient  importance  as  prime  movers  to  bring  them  into  active 
competition  with  the  steam  engine.  The  day,  however,  is  not  far  distant  when  they 
will  gain  a  very  prominent  position  in  this  respect. 


5IO  DOCK  ENGINEERING. 

-electricity  is  generated,  and  air  and  water  are  pumped  under  pressure.  This 
distinction,  however,  is  not  of  sufficient  moment  to  call  for  more  than  a 
passing  remark,  and  need  not  invalidate  the  tabular  arrangement  adopted 
Above,  of  which  it  will  be  convenient  to  take  each  item  in  detail,  sericUim, 

Compressed  Air. — Air,  like  steam,  is  an  elastic  fluid,  and,  consequently, 
in  its  capacity  as  a  transmissive  medium,  has  the  advantage  of  accommo- 
dating its  volume  to  the  resistance  of  the  load — in  other  words,  the  work 
done  is  commensurate  with  the  power  employed.  But  this  alteration  of 
volume  entails  corresponding  disabilities.  Compressed  air  never  effectively 
reproduces  all  the  work  which  is  done  upon  it ;  partly,  because  it  is  not 
capable  of  expansion  to  the  same  extent  as  its  previous  compression  and, 
also,  because  some  of  the  energy  imparted  to  it  is  dissipated  in  the  form  of 
heat.  Then,  again,  leakages  are  rapid  and  difficult  to  detect,  so  that  in 
long  lines  of  communication  there  is  inevitably  much  loss. 

Apart,  however,  from  these  drawbacks  to  its  use  on  a  large  scale, 
•compressed  air  has  many  advantages  to  offer  for  the  working  of  small 
portable  appliances,  such  as  those  employed  in  connection  with  ship  repairs 
in  graving  docks,  and  the  fact  that  sufficient  power  for  the  purpose  can 
igenerally  be  obtained  from  a  small  air-pump  renders  it  desirable,  in  the 
absence  of  more  important  installations,  to  equip  such  docks,  especially 
if  in  isolated  situations,  with  a  pump,  pipe  lines,  and  branch  couplings, 
AO  that  the  pressure  may  be  transmitted  readily  to  any  desired  point. 
This,  however,  apparently  marks  the  limit  of  utility  of  compressed  air  in 
•connection  with  dockwork. 

Steam. — The  most  useful  characteristic  of  steam  power  is  the  con- 
venience with  which  it  can  be  adapted  to  detached  locomotive  machinery. 
It  necessitates  no  central  generating  station,  although  such  can  be 
•employed  in  cases  where  the  circumstances  render  it  permissible.  The 
general  practice  is  for  each  machine  to  be  entirely  independent  and  self- 
supplied.  In  this  way  the  loss  of  energy  arising  from  long  lines  of 
•communication  and  multiple  connections  is  entirely  obviated.  Steam  has 
the  further  advantage  of  supplying  each  machine  with  its  own  means  of 
mobility,  whereas  in  the  case  of  other  systems  conforming  to  the  exigencies 
of  dockwork,  *  transportive  power  has  generally  to  be  obtained  from 
•extraneous  sources.  On  the  other  hand,  for  intermittent  operations,  unless 
carried  out  in  connection  with  a  central  station,  steam  power  is  not 
always  readily  available,  nor  indeed  without  due  preparation.  A  boiler 
has  to  be  heated,  and  some  delay  is  inevitable  before  the  requisite  pressure 
is  obtained  ;  furthermore,  there  is  considerable  waste  of  heat  in  the  cooling 
down  of  the  boiler  after  the  allotted  duty  has  been  performed. 

A  central  generating  station  certainly  does  away  with  these  defects, 

but  the  loss  of  heat  from  the  steam  supply  due  to  its  transmission  through 

pipes  to  outlying  positions  is  excessive,  so  much  so  that  in  no  case  will  any 

*  Trolley  wires  and  underground  cables  are  considered  inapplicable  to  these  special 
.conditions. 


WATER  UNDER  PRESSURE.  5  1 1 

advantage  be  derived  if  the  point  of  application  be  situated  more  than 
350  to  400  yards  from  the  point  of  generation.  Even  at  less  distances,  a 
machine  will  be  but  indifferently  served. 

These  considerations  all  point  to  the  conclusion  that  steam  is  an  admir- 
able motive  agency  for  locomotive  cranes  and  other  appliances  in  which,  in 
addition  to  local  action,  movement  through  an  extensive  range  of  position 
is  ess<^ntial,  but  that  in  order  to  be  economical  such  machines  must  be  at 
work  continuously  for  long  periods.  It  has  advantages,  also,  for  small 
detached  installations,  where  the  cost  of  a  centralised  generating  plant,  with 
extensive  ramifications,  would  be  out  of  proportion  to  the  duty  required. 
In  all  other  cases,  a  system  of  hydraulic  or  electrical  energy  will  be  found 
preferable. 

Water  under  Pressure. — In  contradistinction  to  the  previous  elements, 
water  is  an  incompressible  medium  ;  but  its  very  inelasticity,  while  freeing 
it  from  loss  of  power  in  one  direction,  only  exposes  it  to  loss  in  another, 
and  not  improbably  to  an  equal  extent.  The  motive  effort  of  water-power 
is  obviously  invariable,  whatever  resistance  may  be  opposed  to  it,  and, 
consequently,  the  same  expenditure  of  energy  is  necessary  whether  the 
work  done  be  considerable  or  insignificant. 

On  the  other  hand,  hydraulic  machinery,  when  working  at  full  power, 
is  characterised  by  a  high  efficiency ;  the  loss  due  to  the  friction  of  the 
working  parts  then  rarely  exceeds  8  or  10  per  cent.*  Furthermore,  there 
is  great  smoothness  and  regularity  of  movement,  and  the  appliances  are 
capable  of  being  manipulated  with  extreme  precision,  while  they  do  not  call 
for  specially  trained  or  skilled  operators. 

As  against  this,  must  be  set  the  trouble  and  inconvenience  caused  by 
frost  Apart  from  the  freezing  of  water  in  the  conduits,  which  in  many 
cases  are  unavoidably  exposed  to  atmospheric  influence,  there  is  the  con- 
sideration that  the  neighbourhood  of  hydraulic  machinery  is  invariably 
wet  and  sloppy,  and  this  leads  to  the  formation  of  ice  there,  which  is 
manifestly  dangerous  to  those  working  at  a  quay  side.  The  evils  have 
to  a  certain  extent  been  mitigated  by  the  provision  of  gas  jets  in  machinery 
pits,  or  by  bringing  all  the  service  pipes  and  valves  into  a  closed  cabin 
which  can  be  artificially  warmed  when  necessary.  But  such  arrangements, 
whilst  more  or  less  effective  in  themselves,  are  undoubted  evidence  of  the 
difficulties  attending  the  use  of  water-pressure  machinery  in  the  winter 

*  Mr.  Robinson  gives  the  following  coefficients  for  hydraulic  rams  with  ordinary 
hemp  packing : — 

Direct-acting, '93  efficiency. 

2  to  1, -8  „ 

4  „  1, -76         „ 

-      6  „  1, -72 

8  „  1, -67 

10  „  1 -63         „ 

"  Tranamiesion  of  Power,"  Min.  Proc.  Inst.  C,t!,,  voL  xUx. 


512  DOCK  ENGINEERING. 

time;  and  in   countries  where   the  thermometer  is  often  below  zero,  it 
would  be  difficult  to  secure  perfect  immunity  from  interruption  of  working. 

To  this  drawback  must  be  added  the  great  cost  of  laying  mains  and 
forming  culverts  for  their  reception.  Water  pressure  is  also  very  materially 
affected  by  bends  and  changes  of  direction,  so  that  where  these  are  inevitable 
there  will  be  a  corresponding  loss  of  power. 

Electricity. — As  a  distributive  agent,  electricity  has  very  largely  come 
into  favour  during  the  last  ten  to  fifteen  years.  Its  principal  merits  are 
the  extreme  cleanliness  and  compactness  of  its  working  parts,  and  the 
tenuity  and  flexibility  of  its  supply  mains,  both  of  which  features  stand 
out  in  prominent  juxtaposition  to  the  soot  and  smoke  of  the  steam  engine 
and  the  bulky  and  awkward  canalisation  of  hydraulic  power.  Moreover, 
the  first  cost  of  wire  mains  is  much  less  than  that  of  any  corresponding 
pipe  system. 

As  a  motive  force,  electricity  is  able  to  discharge  all  the  functions  of 
steam  for  actuating  mechanism  identical  in  character.  The  main  shaft  of 
a  machine  may  be  driven  indifferently  by  a  steam  engine  or  an  electric 
motor.  But  whereas  steam  power  is  rarely  capable  of  centralisation, 
electricity  is  most  admirably  adapted  to  systematic  distribution  from  a 
common  centre.  Since  steam  is  most  commonly  employed  for  the  genera- 
tion of  the  electric  current  itself,  it  is  not  contended  that  the  latter  system 
is  as  economical  as  the  former ;  but  it  may  be  pointed  out  that  one  large 
electrical  generating  station,  worked  by  steam  power,  will  probably  involve 
less  expenditure  in  fuel,  repairs,  maintenance,  and  attendance  than  a 
number  of  separate  steam  engines,  each  with  its  own  special  outfit  and 
upkeep.  Moreover,  the  generating  plant  may  find  an  additional  use  at 
night-time  for  lighting  purposes,  and  this  at  a  period  when,  lifting  appliances 
being  more  or  less  idle,  there  would  be  little  or  no  interference  with  the 
discharge  of  its  primary  functions.  There  must  inevitably  be  considerable 
saving  arising  from  the  adaptation  of  a  single  installation  to  the  supply  of 
both  power  aud  light.  The  advantages  arising  from  the  combination  are, 
however,  largely  discounted  during  the  winter,  when  the  shortness  of  the 
days  necessitates  early  lighting. 

The  amount  of  electrical  energy  consumed  is  sensibly  proportional  to 
the  work  done,  and  in  this  respect  electric  power  differs  advantageously  from 
hydraulic  power. 

Electric  distributors,  however,  are  more  complicated  than  the  working 
parts  of  the  other  two  systems;  they  are,  therefore,  less  easily  kept  in 
repair,  and  they  necessitate  the  attendance  of  skilled  workmen.  Moreover, 
they  do  not  act  with  the  smoothness  and  precision  of  hydraulic  machines, 
nor  with  the  independence  and  directness  of  the  steam  engine. 

Comparative  Expenditure  of  Energy — In  order  to  institute  a  comparison 
between  the  several  systems  in  regard  to  their  expenditure  of  energy  and 
the  cost  of  its  production,  it  is  necessary  to  establish  the  relationship  existing 
between  their  respective  units  of  power.     The  primary  unit  of  work  is  the 


COMPABATIVE  EXPENDITURE  OF  ENERGY. 


513 


foot-pound,  and  33,000  foot-pounds  per  minute  constitute  1  horse-power,  the 
basis  upon  which  steam-engine  power  is  estimated.  Hydraulic  power  is 
specified  in  terms  of  the  supply  of  gallons  of  water  per  hour  at  a  definite 
pressure,  and  electric  power  in  Board  of  Trade  units.  To  trace  the  connec- 
tion between  the  various  standards  we  proceed  as  follows  : — 

If  H  be  the  head  iu  feet  of  a  column  of  water  and  P  its  pressure  per 

square  foot, 

P  =  wH, 

where  w  is  the  weight  of  a  cubic  foot  of  water. 
CoDsequently  the  pressure  per  square  inch  is 

wH. 
^=144' 
and,  taking  w  at  62-5  lbs.,  H  =  2-307  p. 

Hydraulic  pressure  of  x  lbs.  per  square  inch  is  therefore  that  due  to  a 
head  of  2-307  x  feet,  and  the  potential  energy  of,  say,  1,000  gallons  at  this 
head  is 

1,000  gallons  x  10  lbs.  per  gallon  x  2-307  a;  feet  =  23,070  x  foot-lbs. 

Assuming  this  to  be  the  hourly  rate  of  supply,  and  noting  that  1  horse- 
power hour  is  equivalent  to  33,000  x  60  =  1,980,000  foot-lbs.,  we  conclude 
that  1,000  gallons  of  water  at  x  lbs.  pressure  possess  energy  to  the  extent  of 

1  noAAitA  =  '01165  a;  horse-power  hours. 

The  Board  of  Trade  unit  of  electricity  is  1,000  watts  per  hour.  The 
watt  is  the  product  of  1  volt  (the  unit  of  head  or  pressure)  into  1  ampere 
(the  unit  of  current),  and  corresponds  in  electrical  terminology  to  the  foot- 
pound of  mechanics ;  746  watts  are  equivalent  to  1  electrical  horse-power. 

Therefore,  at  the  same  rate  of  supply,  the  Board  of  Trade  unit=  1.^  =  1*34 


horse-power  hours. 

From  the  foregoing  data  the  following  table  is  deducible  : — 


746 


TABLE  XXXVIL— Comparison  of  Power  Supply. 


One  Thousand  GalloiiB  of  Water  under 
the  Following  Pressures  :— 

Equivalent  to  Energy  In 

Horse-Power 
Units. 

Board  of  Trade 
Electrical  Units. 

700  lbs.  per  square  inch, 

750    „ 

800    „ 

860    „ 

900    „ 

950    „ 
1000    „ 
1250    ,. 
1600    ,, 

8-16 

8-74 

9-32 

9-90 

10-48 

1107 

11-65 

14-66 

17-48 

6-09 
6-62 
6-96 
7-39 
7-82 
8-25 
8-69 
10-86 
13  04 

33 


514 


DOCK  ENGINEERING. 


Crane  Tests. — Tests  with  cranes  afford  a  convenient  and  the  most 
practicable  criterion  of  power  expenditure,*^  and  somei  very  interesting 
experiments  have  been  made  in  this  connection  by  M.  Delachanal,  the 
engineer  to  the  Havre  Chamber  of  Commerce,  the  results  of  which  are 
tabulated  below.  The  operations,  which  were  carried  out  at  the  port  of 
Havre,  consisted  in  the  lifting  of  loads  of  29-5  cwts.  (1,500  kilogrammes)  and 
7*88  cwts.  (400  kilogrammes),  respectively,  by  each  crane  to  a  height  of 
29'5  feet  (9  metres),  at  which  point  the  crane  was  slewed  through  an  angle 
of  180°  and  the  load  lowered  and  deposited.  The  empty  hook  was  then 
raised  to  the  same  height,  steered  through  a  semicircle  in  the  inverse 
direction,  and  lowered  for  a  fresh  load.  In  the  case  of  electrical  power, 
variation  in  speed  was  effected  by  a  rheostat  in  series  with  the  motor. 

The  actual  working  expenditure  per  hour  is  given  by  multiplying  the 
tabular  figures  by  30,  40,  or  50,  according  to  the  rate  of  working. 


TABLE  XXXYIIL — Expenditubb  of  Energy  by  Cranes  in 

Foot-lbs.  per  Operation. 


Speed  in 

Feet 
per  Sec. 

Duration 
of  Lift 
in  Sees. 

Hydraulic  Crane. 
Load. 

steam  Crane. 
Load. 

Electric  Crane. 
Load. 

29-6  Cwts. 

7-88  Cwta. 

29-6  Cwte. 

7-88  Cwts. 

29-6  Cwte. 

7-88  Cwts. 

•492 
1-312 
2132 

60 

22-6 

13-85 

318,975 
318,975 
318,976 

190,589 
190,589 
190,589 

458,543 
496,053 
566,054 

359,263 
380,860 
392,525 

913,3.32 
411,868 
295,656 

564,600 
278,998 
212,049 

The  work  effectively  performed  in  each  case  was  97,645  ft.-lbs.  and 
26,038  ft.-lb8.  respectively. 

The  figures  demonstrate  the  disadvantage  of  making  steam  cranes  wurk 
too  quickly  and  electric  cranes  (with  series  wound  motors)  too  slowly.  At 
the  higher  and  more  usual  speeds,  steam  cranes  are  shown  to  be  much 
inferior  to  hydraulic  and  electric  cranes. 

Equally  interesting  experiments  have  been  restricted  to  a  comparison 
of  these  last  two  agencies.  Thus,  Mr.  Philip  Dawson  f  has  recorded  the 
following  expenditure  of  power  in  watt-hours  for  hydraulic  and  electric 
cranes  under  similar  conditions  of  working.  The  cycle  of  operations 
consisted  of  a  lift  of  36*1  feet,  a  slew  of  HO"*,  and  a  lower  of  13  feet,  all 
under  load,  with  the  inverse  movements  unloaded.  The  hydraulic  crane 
had  three  powers. 

*  It  is  difficult  in  the  case  of  other  apparatus  to  obtain  identical  conditions  for  the 
purpose  of  experiment. 

t  Traction  and  Transmiaaion^  May,  1903. 


COST  OF  POWER. 


515 


TABLE  XXXIX. — Expenditure  op  Power  in  Watt-hours  per  Otcle. 


Load. 

i  Tod. 

iTon. 

ITon. 

li  Tou. 

H  Ton. 

Hydraulic  crane, 
Electric          ,, 

820 
48-5 

127-2 
58-5 

127-2 
73-5 

172-4 
80-6 

172-4 
105-6 

A  test  with  two  cranes  at  Glasgow,  carried  out  by  Mr.  Baxter  of  the 
Clyde  Navigation,  was  analysed  by  Mr.  Walter  Pitt*  in  the  same  units. 
The  lift  in  this  case  was  30  feet,  the  slew  100*',  and  the  lower  10  feet  The 
hydraulic  crane  had  only  one  power,  and  consequently  was  at  a  great 
disadvantage  in  regard  to  the  lighter  loads.  At  its  full  load  it  exhibited 
a  superiority  to  the  electric  crane. 


TABLE  XL. — Expenditure  op  Power  in  Watt-hours  per  Cycle. 


Load. 

ITou. 

2  Tons. 

2^  Tons. 

3  Tons. 

1 

Hydraulic  crane, .                            '236*7 
Electric          „     .        .        .              83-3 

236-7 
160-4 

236-7 
197-9 

236-7 
241-9 

Cost  of  Power. — Greater  expenditure  of  energy  does  not  necessarily 
involve  a  correspondingly  greater  cost  of  working.  This,  of  course, 
depends  on  the  relative  rates  at  which  power  can  be  supplied,  and  will 
vary  with  different  localities.  Equal  conditions  prevail  when  the  cost  of 
water  under  pressure  bears  to  the  cost  of  electricity  the  ratios  given  in 
Table  xxxvii.  Thus,  electricity  at  3d.  per  Board  of  Trade  unit  is  the 
equivalent  of  water  under  750  lbs.  pressure  at  3  x  6*52  —  Is.  TJd.  per 
1,000  gallons. 

A  comparison  of  the  cost  of  hydraulic  power  and  electric  supply  as 
compiled  by  Mr.  Ellington  f  from  the  B.eports  of  the  London  Hydraulic 
Power  Supply  Company  (L.H.P.),  and  the  Westminster  Electric  Supply 
Corporation  (W.E.S.),  for  the  year  1894,  yielded  the  following  results  : — 


*Pitt  on  "The  Modem  Equipment  of  Docks,"  Efig.  Con/,,  London,  1903. 
t Ellington,    "Notes    on    Hydraulic    Supply    in    Towns,"    Froc.    I,    Meek, 
July,  1895. 


£J,f 


5i6 


DOCK  ENGINEERING. 


TABLE  XLI. 


18M. 

Total  Amounts. 

Comparison  in  OallODB 

at  750  Lbs.  Pressure  per 

Square  Inch. 

Comparison  in  Board 

of  Trade  Electrical 

Units. 

L.  H.  p. 

W.  B.  8. 

L.  H.  p. 

W .  IS.  5. 

L.H.  P. 

W.  B.  8. 

j 

Capital  outlay, 
Output, . 
Quantity  sold, 
Received  for  supply. 
Average  price  ob- 
tained, 

£ 
471,552 

•  •  • 

49,237 

£ 
411,018 

•  •  • 

66,'729 

•■■{ 

Oals. 

400,3i3,000 
332,390,000 

35'55d.  per 
1,000  gals. 

Equivalent 
Gals.      . 

396,256,000 
333,430,000 

■  •  • 

36*51d.  per 
1,000  gals. 

Equivalent 
Elec.  Units. 

2,609,240 
2,166,520 

5*45d. 
per  unit. 

1 
Elec.  Units.  I 

2,582,801 

2,173,298 

1 

5-6d. 

per  unit. 

The  actual  cost  of  production,  or  station  cost,  was  5*17d.  per  1,000 
gallons  of  water  and  l*38d.  per  electrical  unit.  Both  power  supplies  can 
now  be  obtained  at  a  much  cheaper  r^te.  At  the  present  time  the  total 
cost  of  electricity  at  the  switchboard,  amounts  to  *9d.  per  unit  at  Liverpool 
Hud  to  only  *35d.  per  unit  at  Newcastle,  the  cost  of  coal  being,  no  doubt, 
responsible  for  the  difference.  The  station  cost  of  hydraulic  power  at 
London,  in  1900,  was  given  as  3*03d.  Electric  power  is  furnished  to 
consumers  at  Id.  per  unit  at  Wigan  and  at  l^d.  per  unit  at  several  other 
towns,  including  Liverpool,  at  which  last  named  place  the  price  of  hydraulic 
power  (750  lbs.  pressure)  ranges  from  15d.  upward. 

Conclusions. — Reviewing  the  systems  as  a  whole,  the  precedence  will  be 
generally  accorded  to  electrical  energy  for  convenience  and  adaptability, 
and  to  hydraulic  energy  for  simplicity  and  control.  Where  a  hydraulic 
installation  is  already  in  existence,  a  change  to  an  electrical  regime  could 
scarcely  be  justified  in  this  country  on  other  than  the  most  exceptional 
grounds;  but  where  the  question  is  an  open  one  and  unfettered  by 
conditions,  there  is  a  slight  preponderance  of  evidence  in  favour  of  the 
adoption  of  electricity  for  the  transmission  of  power. 

At  all  events  the  two  systems  are  in  such  general  vogue — either  singly 
or  in  combination — ^at  nearly  all  ports  as  to  merit  some  discussion  in  regard 
to  the  lines  of  their  application  and  their  suitability  for  particular  classes 
of  work. 

Hydraulic  Machinery. — The  development  of  hydraulic  power  constitutes 
one  of  the  most  remarkable  features  of  the  past  century.  From  a  compara- 
tively insignificant  position,  as  a  source  of  energy,  water  pressure  suddenly 
and  rapidly  rose  to  a  foremost  place  in  engineering  operations.  Any 
attempt  at  tracing  the  inception  and  expansion  of  water-pressure  machinery 
would,  however,  necessitate  a  lengthy  retrogression  into  history,  and  this  we 
cannot  afford  here.  But  it  will  be  generally  admitted  that,  apart  from  the 
Bramah  press,  the  present  wide  range  of  useful  applications  for  water  power 
is  mainly  due  to  the  ingenuity  and  the  exertions  of  the  late  Lord 
Armstrong.     The  student  who  is  interested  in  the   historical  aspect  of 


HYDRAULIC  MACHINERY.  5  17 

the  subject  will  fiad  much  entertaining  and  Tkluftble  information  contained 
in  a  paper  read  hj  him  before  the  Institution  of  Civil  Engineers  in  1877.* 

The  modem  hydraulic  m&chine  (for  dock  work)  takes  the  form  either  of 
a  direot^cting  rau),  working  backwards  end  forwards  in  a  cylinder  with 
suitable  multiplying  gear  for  increasing  the  effective  length  of  its  stroke,  or 
of  a  bent  crank  with  rotary  motion  imparted  by  two  or  more  pistons  niao 
working  in  cylinders.  The  former  system  is  most  commonly  applied  to  gate 
and  slaicing  machines,  and  to  cranes ;  the  latter,  generally,  to  capstans,  and 
occasionally  to  gate  machines. 

We  will  deal,  first  of  a11,  with  the  ram  apparatus.  Primarily,  this  con- 
sisted of  a  ram  fitting  into  the  bore  of  a  cylinder,  the  pressure  being  Hpplied 
at  one  end  of  the  ram,  so  that  it  was,  accordingly,  capable  of  acting  io  a 
forward  direction  only.  The  return  stroke,  being  unopposed,  was  effected 
either  by  gravitatioo,  if  the  ram  were  vertical,  or  by  a  small  auxiliary  ram, 
if  the  main  ram  were  horizontal.  One  imjiortaDt  drawback  of  this  contriv- 
ance was  that  it  admitted  of  no  variation  in  the  power  applied.  Whether 
th*^  load  moved  were  great  or  small,  the  same  expenditure  of  energy  was 
necessary.     When  the  load  was  fairly  uniform,  as  in  the  working  of  dock 


Fig.  6ie. — Combined  Pieton  and  Bam. 

gates  aud  sluices,  the  objection  was  of  little  importAnce,  and  this  type  of 
machine  is  still  largely  used  for  that  purpose.  But  in  the  case  of  cranes  and 
other  lifting  apparatus,  where  loads  are  irregular,  economy  demands  some 
modification  so  as  to  make  the  expenditure  of  water  correspond  approsi- 
mately  to  the  actual  load.  This  has  been  contrived  by  the  use  of  two  or 
three  cylinders,  able  to  act  either  independently  or  collectively.  Three 
power  values  have,  however,  been  found  superfluous,  or,  at  anyrate,  unduly 
cumbersome  in  practice,  and  it  is  now  customary  to  be  satisfied  with  two 
powers  at  the  most,  and  these  are  obtained  with  a  single  cylinder  in  one  of 
two  different  ways  ; — 

First,  by  the  use  of  a  combined  piston  and  ram  (fig.  516),  water  being 
admitted  to  both  sides  of  the  piston  for  the  lower  power,  and  to  the  larger 
side  only  for  the  higher  power.  This  arrangement  is  now  very  rarely  used, 
one  of  the  reasons  being  that  a  bored  cylinder  is  required,  the  machined 
surface  of  which  becomes  corroded  while  out  of  action,  with  the  result  that 
the  packii^  on  the  piston  is  cut. 

Secondly,  by  the  use  of  two  concentric  rams  (fig.  517),  one  contained 
within  the  other,  in  the  same  cylinder.  For  the  lower  power,  the  smaller 
'Armstrong  on  "Water-pressure  Machinerf,"  Mm,  Prac.  Imt.,  O.B.,  vol.  1. 


5l8  DOCK  ENGINEERING. 

ram  only  is  put  in  motion  ;  for  the  higher  power,  the  larger  ram  ie  liberated 
and  moves  aimultaneously  with  it. 

la  Bome  iDstunces,  a  combination  of  both  the  preceding  methods  has 
been  utilised  to  obtain  three  powers  from  one  cylinder.  The  outer  or 
larger  ram  is  fitted  with  a  piston  so  as  to  give  two  powers  hj  the  first 
tDPthod,  while  the  internal  ram  supplies  the  lowest  power.  The  arrange- 
ment is,  however,  so  complicated  as  to  be  of  doubtful  utility,  and,  except  in 
extreme  cases,  it  will  be  found  preferable  in  this  respect  to  sacrifice  economy 
to  efficiency.  The  uniform  expenditure  of  water  upon  work  of  the  most 
variable  nature  cannot  be  considered  excessive  when  it  is  borne  in  mind 
that  simplicity  in  construction  and  manipulation  has  advantages  to  offer 
nearly,  if  not  quite  equivalent,  to  economy  in  power. 

The  second  system  is  based  on  the  principle  of  the  reciprocating  action 
of  the  connecting-rod  and  crankshaft  of  the  ordinary  steam  engine,  and  one 
type  of  the  apparatus  consists  of  three  small  cylinders  with  plungers,  each 
acting  upon  a  three-throw  crank  and  having  mitre  valves,  worked  by  cama 
upon  a  revolving  abaft. 


Fig.  617.— Two  Concentric  Rams. 

Another  type  (fig.  634),  until  recently  much  in  vogue,  had  only  two  cylin- 
ders. These  oscillated  U[ion  trunnion  bearings,  and  were  fitted  with  com- 
bined rams  and  pistons  working  on  over-end  cranks  set  at  right  angles  to 
each  other.  The  areas  exposed  to  pressure  in  the  cylinder  were  as  two  to  one. 
One  face  of  the  piston  had  the  exact  moiety  of  the  area  of  the  other  face, 
the  difilerence  being  due  to  the  displacement  of  the  ram.  The  pressure 
on  the  smaller  face  was  maintained  constant,  there  being  continuous  com- 
munication with  the  supply  pipe.  The  pressure  on  the  larger  face  was 
intermittent,  and  alternately  full  and  nil,  according  as  the  cylinder  on 
that  side  was  open  to  supply  or  exhaust.  The  piston,  accordingly,  was 
actuated  by  the  difilerence  of  pressure  on  its  two  faces,  the  stroke  in  one 
direction  being  pfiected  by  unopposed  pressure  on  the  smaller  face,  and  in 
the  other  direction  by  the  balance  of  pressure  on  the  larger  face,  which,  by 
the  adjustment  of  areas,  resulted  in  regularity  of  effort. 

The  three-crank  system  is  adapted  for  large  engines  in  situations  where 
there  is  ample  space  at  disposal.  The  two-crank  system,  on  the  other  hand, 
is  more  compact  and  also  less  expensive  in  construction,  in  that  a  middle 
crank  is  obviated,  but  it  lacks  the  uniformity  of  movement,  characteristic  of 


HYDRAULIC  ACCUMULATORS.  519 

the  former  arrangement.  Furthermore,  the  saving  effected  by  omitting  one 
cylinder  and  ram  is  largely  discounted  by  the  cost  of  making  the  other  two 
cylinders  double-acting,  and  almost  necessarily  of  brass.  The  maintenance 
charges  also  are  greater.  Except,  therefore,  in  the  case  of  restricted  space, 
the  three-cylinder  system  with  plain  rams  is  generally  adopted. 

We  now  turn  our  attention  for  a  moment  to  the  production  of  hydraulic 
power. 

Hydranlic  Accnmolators. — In  the  first  instance  the  requisite  pressure  for 
driving  hydraulic  machinery  was  obtained  by  means  of  a  natural  head  of 
water,  but  this  system,  in  the  majority  of  cases,  the  locality  being  flat, 
involved  the  erection  of  a  lofty  water  tower  and  reservoir.  The  impossi- 
bility of  economically  erecting  such  a  tower  at  New  Holland  on  the 
Humber,  where  the  foundation  consists  of  silt  to  a  considerable  depth, 
led  Armstrong,  in  1850,  to  substitute  an  arrangement,  since  generally 
adopted  and  known  as  an  ''accumulator,"  by  which  water  was  pumped  into 
a  large  cylinder  against  the  weight  of  a  heavily  loaded  ram  or  plunger. 
As  long  as  the  ram  is  kept  off  its  seat  at  the  bottom  of  the  cylinder  the 
water  is  maintained  at  a  high  and  constant  pressure — at  a  much  higher 
pressure,  in  fact,  than  could  be  obtained  by  natural  means ;  for,  whereas 
before  the  introduction  of  the  accumulator,  in  no  instance  had  a  greater 
pressure  than  90  lbs.  per  square  inch  been  used,  at  the  present  time 
pressures  as  great  as  700  and  750  lbs.  per  square  inch  are  quite  common, 
and  1,000  and  1,250  lbs.  pressures  are  also  in  use.  The  advantages  arising 
from  this  increment  are  apparent.  The  sizes  of  the  distributing  mains  and 
of  the  pressure  cylinders  have  been  greatly  reduced,  while  at  the  same  time 
the  capacity  for  work  has  been  materially  augmented.  The  accumulator 
has  one  drawback :  it  does  not  afford  much  storage  room,  consequently 
pumping  is  necessarily  continuous,  and  the  joints  and  pipes  in  the  mains 
must  be  rendered  pressure  proof.  These  considerations,  however,  are  of 
minor  importance  compared  with  the  advantages  accruing  to  the  system 
as  a  whole. 

It  is  essential  that  the  water  used  in  connection  with  hydraulic 
apparatus  should  be  both  fresh  and  clean.  Salt  or  acidulated  water  will 
corrode  the  mains  and  cylinders ;  grit  and  sediment  will  wear  and  choke 
the  valves.  Consequently,  where  the  source  is  at  all  liable  to  contamina- 
tion there  should  be  a  settling  tank,  and  supplies  should  be  taken  from 
the  top  in  such  a  way  as  to  ensure  purity.  There  is  no  objection  to  the 
repeated  use  of  the  same  water;  in  fact,  this  arrangement  is  generally 
adopted,  the  water  being  returned  to  the  pumping  well  through  an 
additional  main,  the  diameter  of  which  is  rather  greater  than  that  of  the 
pressure  main. 

Slide  valves  are  more  liable  to  injury  from  grit  than  mitre  valves,  but 
if  the  settling  tank  be  adopted  and  ordinary  precautions  observed,  there 
is  no  reason  why  extensive  repairs  should  be  necessary  in  either  case. 

Air  vessels  have  been  tried  in  place  of  weighted  accumulators,  but  they 


520 


DOCK  ENGINEERING. 


are  open  to  the  objections  that  the  pressure  is  by  no  means  constant,  that 
the  storage  is  generally  insufficient,  and  that,  in  some  instances,  there  is  loss 
arising  from  the  absorption  of  air  by  the  water,  which  has  to  be  replaced 
by  an  auxiliary  feed-pump.  There  are  situations,  however,  such  as  on 
board  ship,  where  accumulators  are  inadmissible  and  where  air  vessels  have 
the  advantage  of  lightness. 

Fluctuations  in  Pressure. — Hydraulic  power  in  application  to  dock- work 
is  liable  to  extreme  changes  in  amount.  The  constantly  varying  number 
of  machines  under  action,  while  the  area  of  the  supply  main  is  always 
the  same,  causes  the  intensity  of  pressure  to  fluctuate  considerably.  It 
frequently  falls  much  below  the  nominal  value,  and  sometimes,  under  the 
influence  of  surging,  it  may  rise  above  it.  The  following  readings,  recently 
taken  in  connection  with  the  working  of  the  entrance  gates  to  a  dock  at 
Liverpool,  illustrate  this  irregularity  very  forcibly  : — 

TABLE  XLIL 


Time. 

Locality. 

Draught  of 
Water  on  SiU. 

« 

MaTlmnm 

Pressure  Prior 

to  MoTement 

of  Bam. 

Working 

Pressure  fairly 

Constant 

throogtaout 

Stroke. 

A.M. 

Feet  Ills. 

Lbs. 

Lbs. 

6.50 

80  feet  entrance, 

30    0 

730 

680 

6.68 

40 

25    0 

730 

730 

7.0 

100 

29    0 

730 

530 

9.0 

80           „ 

21     0 

730 

690 

9.10 

40 

16    3 

760 

350 

9.15 

100 

20    6 

760 

660 

11.0 

80 

15    6 

750 

720 

11.5 

40 

11    0 

760 

300 

11.10 

100           „ 

15    0 

760 

600 

P.M. 

1.0 

80 

16    6 

740 

720 

1.10 

40 

12    0 

760 

260 

1.20 

100 

17    6 

760 

680 

The  normal  pressure  was  760  lbs.  at  the  accumulator.  The  areas  of  the  rams  were 
as  foUuws: — 80-feet  entrance,  227  square  inches;  40-feet  entrance,  113  square  inches; 
100-feet  entrance,  283*5  square  inches. 


Electrical  Distribution  of  Energy. — Electricity,  as  a  practical  science,  is 
much  the  junior  of  hydraulics,  and,  in  reference  to  dockwork,  it  has  only 
been  adopted  to  any  noticeable  extent  within  the  last  decade.  Hamburg 
and  the  German  ports  of  the  Baltic  introduced  it  about  the  year  1892.  It 
was  speedily  taken  up  by  Rotterdam,  Amsterdam,  Bordeaux,  Havre,  and 
Copenhagen.  Southampton  is  apparently  the  first  port  at  which  it  appeared 
in  this  country,  but  the  use  of  electricity  is  now  rapidly  becoming  general 
and,  where  the  question  is  not  complicated  by  the  prior  existence  of  a 
hydraulic  installation,  its  claims  for  selection  are  admittedly  pre-eminent. 

The  electric  current  is  either  continuous  or  alternating,  and  this  latter 
case  either  single  or  multiphase. 


ELECTRICAL  DISTRIBUTION  OF  ENERGY.  52 1 

The  continuous  current  flows  uninterruptedly  in  one  direction,  being  the 
reverse  of  the  alternating  current  which  flows  alternately  in  opposite 
directions.  Mulliphase  currents  are  a  group  of  the  latter  type  which  difier 
from  each  other  by  their  relative  difference  in  phase. 

The  continuous  current  has  hitherto  proved  to  be  the  most  satisfactory 
for  dealing  with  operations  so  variable  in  nature  as  those  which  prevail  in 
connection  with  dockwork.  Alternating  single-phase  currents  only  give 
good  results  when  utilised  at  a  fairly  uniform  speed,  and  without  the 
necessity  of  overcoming  the  inertia  of  heavy  bodies  at  starting.  Continuous 
currents,  on  the  other  hand,  on  account  of  insulation  difficulties  with  regard 
to  the  construction  of  both  armatures  and  commutators  of  the  generators, 
and  the  fact  that  it  is  necessary  to  use  rotating  transformers  for  reducing 
the  pressure,  are  not  so  well  adapted  for  the  transmission  of  power  to  very 
long  distances,  though  within  the  ordinary  limits  of  most  dock  systems,  they 
ivill  be  found  perfectly  effective  and  sufficient. 

The  dynamos  and  motors  generally  utilised  may  be  enumerated  as 

(1)  Series  wound, 

(2)  Shunt  wound,  and 

(3)  Compound  wound. 

In  the  first  case,  the  armature,  the  field  winding,  and  the  external 
-circuit  are  all  in  series.  In  the  event  of  short  circuiting,  the  field  current 
is  intensified  and  the  winding  may  be  injured  by  the  heating  of  the  wire. 

In  the  second  case,  the  field  winding  is  distinct  from  the  outer  circuit, 
and  there  is,  consequently,  a  separate  current  to  excite  the  field  magnets. 
Short  circuiting  can,  therefore,  produce  no  heating  effect. 

The  compound  machine  has  two  coils  on  its  field  magnet.  One  winding 
is  in  series  with  the  external  circuit  and  the  armature,  the  other  is  in  shunt. 
This  machine,  from  the  counter  action  of  its  coils,  is  more  regular  under  the 
influence  of  varying  currents  than  either  of  the  other  two,  but  it  is  only 
completely  regular  and  automatic  at  one  particular  speed. 

A  series-wound  motor  is  suitable  for  use  in  positions  where  great 
starting  power  is  required,  such  as  in  cranes,  haulage  gear,  &c.,  and  also  in 
the  case  of  single  motors,  driving  pumps,  and  heavy  machinery  where  the 
load  is  constant  after  being  once  applied.  When  run  off  constant  pressure 
circuits,  the  motors  are  controlled  by  a  variable  resistance  placed  in  series 
with  them  and  regulated  by  hand,  as  required.  In  the  series-wound  motor 
the  speed  decreases  as  the  current  increases.  The  torque  is  greatest  at 
starting  when  the  current  is  a  maximum,  being  about  six  times  the  normal 
amount,  and,  as  it  is  proportional  to  the  latter,  it  varies  inversely  as  the 
«peed.     When  the  load  varies  the  speed  is  not  constant. 

The  shunt-wound  motor  is  not  so  well  adapted  for  starting  against  a 
heavy  torque  as  the  series- wound  motor.  It  will,  however,  run  at  nearly 
constant  speed  under  a  varying  load  when  supplied  with  current  at  constant 
pressure.     With  the  shunt  motor,  also,  considerable  variation  in  speed  can 


522  DOCK  ENGINEERING. 

be  obtained  by  varying  the  resistance  in  the  shunt  circuit,  and  so  affecting 

the  exciting  current.     The  starting  torque  is  about  three  times  the  normal 
amount. 

Compound-wound  motors  may  have  their  field  coils  wound  either 
differentially,  with  the  series  coils  in  opposition  to  the  shunt  coils,  or 
cumulatively,  with  the  series  coils  assisting  the  shunt  coils.  Where  great 
regularity  of  speed  is  required  the  differentially-wound  motor  is  probably 
the  better^  but  it  has  not  met  with  any  great  measure  of  success.  One 
objection  to  it  is  the  liability  to  start  in  the  wrong  direction,  owing  to  the 
reversed  series  winding.  The  most  important  feature  of  the  cumulatively- 
wound  motor  is  the  increased  torque  at  starting,  due  to  the  series  coil.  It 
combines,  in  fact,  to  a  certain  extent,  the  starting  power  of  the  series  motor 
with  the  speed  regulation  of  the  shunt  motor.  In  this  last  respect,  how- 
ever, it  is  not  so  good  as  the  shunt  motor.  This  type  of  motor  is  sometimes 
fitted  to  cranes  where  the  motor  is  allowed  to  run  constantly,  and  in  such 
situations  has  given  good  results. 

Applioations  of  Power. 

The  various  types  of  appliances,  which  it  is  proposed  to  briefly  describe^ 
may  be  classified  under  the  following  heads  : — 

Gate  machinery, 

Sluice  machinery. 

Capstans, 

Wharf  and  floating  cranes, 

Jiggers  and  transporters. 

Slipway  machinery. 

Coal  tips  and  hoists, 

Grain  elevators, 

Pumps, 

Miscellaneous  apparatus,  such  as  moorings,  &jc. 

Dock  Gate  Machinery. — Dock  gates  may  be  worked  by  means  of  chains- 
or  of  arms  or  struts. 

The  chains  may  be  wound  on  barrels  or  drums  in  gear  with  rotary 
shafts  driven  by  steam,  hydraulic  or  electric  power,  or  they  may  pass  over 
sheaves  at  the  ends  of  the  cylinder  and  ram  respectively  of  a  hydraulic 
machine.  An  example  of  the  former  class  is  that  given  in  figs.  518  and  519, 
which  show  the  plan  and  section  of  a  gate  crab  or  winch  worked  by 
hydraulic  power.  The  ram  system  has  already  been  exemplified  in 
figs.  516  and  517.  Where  space  is  restricted  and  long  chains  are  necessary, 
a  cupped  drum  grasping  the  links  of  the  chain  will  be  used  in  preference 
to  a  barrel,  which  is  less  compact.  There  are  drawbacks,  however,  to  this 
arrangement,  in  that  special  links  are  required,  and  that  u  corresponding 
adjustment  must  be  made  whenever  stretching  occurs. 

Chains,  in  fact,  call  for  constant  attention.     They  must  be  frequently 


DOCK  GATE  MACHINERY.  525 

overhauled  and  examined,  and  should  be  annealed  in  a  wood  fire  at  least 
once  a  year.  This  involves  the  provision  of  spare  chains,  and  these  should 
be  ready  for  instant  substitution,  in  case  of  breakage  or  other  serious 
accident.  The  advisability  of  the  chain  connections  being  simple  and 
accessible  is  therefore  apparent.  For  gate  attachments  below  water  level 
a  riug  at  the  end  of  the  chain,  of  larger  diameter  than  the  staple  through 
which  the  chain  passes,  will  be  found  a  suitable  arrangement. 

The  expansive  system  01  the  hydraulic  ram  with  multiplying  sheaves 
seems,  on  the  whole,  preferable  to  the  rotary  engine,  owing  to  the  greater 
risk  of  damage  to  the  gearing  of  the  latter.  Damage  to  chains  and 
mechanism  arises  principally  from  such  causes  as  irregularity  of  movement, 
with  abrupt  jerks  and  stoppages,  which  induce  momentary  stresses  of 
unexpected  magnitude.  Fracture  or  strain  may  easily  result  from  an 
attempt  to  force  a  gate  home  in  the  face  of  some  submerged  obstruction, 
and  as  it  is  preferable  for  a  gate  to  be  brought  to,  rather  than  for  a 
breakage  to  occur,  it  is  by  no  means  judicious  to  provide  machinery  of 
excessive  power,  unless  it  be  carefully  regulated. 

Gate  chains  are  arranged  on  the  two  systems  indicated  in  figs.  520 
and  521.  In  the  first  case,  chains  are  attached  to  the  back  and  front  of 
the  gate  respectively,  near  the  bottom  and,  being  led  horizontally  to 
sheaves  set  in  the  walls,  at  opposite  sides  of  the  passage,  they  pass 
vertically  upwards  to  other  sheaves  near  the  coping  level,  whence  they 
are  conducted  to  their  respective  machines.  In  the  second  system,  known 
as  the  ^'overgate  system''  (Rg,  521),  chains  (A  and  B)  are  fixed  to  the 
opposite  walls  of  the  passage  and  led  horizontally  to  sheaves  at  the  foot  (C) 
of  the  gate,  thence  vertically  upward  to  sheaves  at  the  top  of  the  gate,  and, 
tinally,  in  a  parallel  course,  over  a  third  pair  of  sheaves  near  the  heel-post 
to  the  actuating  gear.  By  this  latter  arrangement,  each  leaf  of  the  gate  is 
opened  and  closed  from  the  same  side  of  the  passage  and  from  one  spot. 
Thus,  the  cost  and  inconvenience  of  two  separate  chain-ways  through  the 
walls  to  the  machine  pits  are  avoided. 

Struts  or  direct-acting  rams  were  introduced  by  Sir  J.  W.  Barry  for 
working  the  gates  at  the  Barry  Docks  in  1894.  They  have  the  possible 
advantage  over  chains  of  being  able  to  hold  the  gate  up  against  external 
pressure,  and  thus  discharge  the  functions  of  a  strut  gate  in  minimising  the 
effect  of  waves  at  high  water.  This  advantage,  however,  is  more  apparent 
than  real,  as  the  power  of  gate  machines,  unless  unduly  great,  is  inadequate 
to  do  more  than  work  gates  under  ordinary  circumstances.  The  earliest 
examples  of  direct-acting  rams  worked  in  cylinders  oscillating  upon  trunnions, 
but  this  type  has  not  been  repeated,  at  all  events  in  this  country.  Recent 
practice  has  entirely  favoured  a  fixed  cylinder,  with  ram  and  connecting-rod, 
which  latter,  by  means  of  a  crosshead  and  vertical  and  horizontal  pivot  pins, 
is  free  to  turn  in  any  direction.  The  gates  at  Leith,  illustrated  in  figs. 
526  and  527,  are  worked  in  this  manner,  as  also  are  the  West  India  Dock 
gates  at  London,  and  many  others. 


524  DOCK  ENQIKEEHINO. 

The  ram  or  the  connecting-rod,  as  the  case  may  be,  is  nsually  attached 
to  the  gate  through  the  niedinm  of  a  girder  or  radius  arm,  one  end  of  which 
is  fixed  to  the  heel-post  and  the  other  to  a  point  somewhere  about  one-third 
of  the  length  of  the  leaf  from  the  mitre-post.  In  this  way  the  pressure  of 
the  ram  is  more  effectively  applied  to  the  gate,  but  the  faot  that  tlie  applica- 
tion  of  pressure  is  necessarily  above  the  water  line  militates  against  any  com- 


Fig.  520. — Arrangement  of  Gate  Chains — Direct  System. 


Fig.  521.— Overgate  System. 

pletely  satisfactory  arrangement.  Tlie  objection  has  possibly  not  bo  much 
weight  in  regard  to  iron  and  steel  gates,  which  can  be  suitably  stiffened,  but 
is  of  90  great  importance  to  wooden  gates  as  to  have  rendered  the  system 
practically  inapplioable  to  such  gates,  owing  to  the  difficulty  of  making  them 
sufficiently  rigid.  In  some  cases  attachment  is  made  at  a  point  more 
distant  from  the  heel-ftostj  and  the  stroke  of  the  ram  is  oorrespondiagly 


I 


To  face  page  691^ 


Coping  Level    \ 


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Gale  Platform 


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jt  Lock. 


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7 


POWER  OP  GATE  MACHINES.  525 

increased.  The  chain  system  is  preferable  to  the  ram  in  this  respect,  for  it 
is  quite  feasible  to  attach  the  chains  at  the  centre  of  gravity  of  the  displaced 
fluid,  which  is  the  ideal  position. 

One  advantage  which  the  rotary  engine  possesses  over  the  ram  is  that  in 
certain  cases  of  breakdown — viz.,  those  not  involving  the  gearing,  barrel  or 
chain — the  former  can  still  be  worked  by  hand,  whereas  it  is  never  possible 
to  work  a  ram  in  this  way.  The  expedient  then  generally  resorted  to  is  to 
attach  a  i*ope  to  the  head  of  the  mitre-post  of  the  gate  and  lead  it  to  the 
nearest  capstan.  This  is  by  no  means  a  desirable  or  convenient  arrange- 
ment, but  it  should  nevertheless  be  looked  upon  as  a  likely  contingency  and 
provided  for  accordingly. 

A  point  which  must  not  be  overlooked  is  that  chains  reduce  the  effective 
draught  of  water  over  dock  sills,  and  that,  in  order  to  allow  the  former  to 
lie  perfectly  flat,  so  that  vessels  passing  over  them  may  not  foul,  it  ia 
necessary  to  provide  a  large  amount  of  slack  chain.  Chases  have  been 
cut  in  the  sill  to  receive  the  chain,  but  it  is  by  no  means  certain  that  the 
latter  will  lie  in  them. 

The  accompanying  illustrations  (figs.  522  to  527),  showing  the  applica- 
tion of  hydraulic  power,  by  means  of  both  chains  and  rams,  to  recently 
constructed  gates  at  Leith,  are  reproduced  from  drawings  kindly  furnished 
by  Messrs.  Sir  W.  Q.  Armstrong,  Whitworth  k  Co.,  with  the  courteous 
sanction  of  Mr.  Peter  Whyte,  the  harbour  engineer  of  that  port. 

Power  of  Gate  Machines. — While  the  determination  of  the  amount  of 
{)ower  necessary  to  work  cranes,  capstans,  and  other  dock  appliances  is  a 
matter  of  comparatively  simple  calculation,  the  paucity  of  existing  data  in 
reference  to  the  forces  at  work  upon  dock  gates  renders  the  problem  in  this 
last  instance  apparently  incapable  of  an  exact  or,  at  any  rate,  a  general 
solution.  There  can  be  little  doubt  that,  in  the  majority  of  cases,  a  large 
margin  of  power  has  to  be  provided  to  cover  unknown  contingencies. 

The  resistances  to  be  overcome  are  three  in  number.  At  the  moment  of 
starting  there  is  the  inertia  of  the  gate,  and  during  movement  there  are  the 
friction  of  pintles,  collars,  wheels,  rollers,  <fec.,  as  the  case  may  be,  and  the 
resistance  of  the  water  to  disturbance  by  the  motion  of  the  gate. 

The  force  required  to  overcome  the  first  of  these  may  be  estimated  as 
follows : — Calculate  the  moment  of  inertia  of  the  gate  about  its  axis  of 
rotation;  for  the  purpose  it  may  be  treated,  without  serious  error,  as  a 
weighted  rectangle  revolving  about  one  edge.     Then 

1  =  JMZ«, 

where  M  is  the  mass  of  the  leaf  and  I  its  length.  From  this  we  find  the 
radius  of  gyration,  which  is 


jk-  y^*="7^, 


and  the  mass  of  the  leaf  may  accordingly  be  considered  concentrated  at  a 
point  distant  *577 1  from  the  axis  of  rotation. 


526  DOCK  ENGINEERING. 

If  the  gate  chain  be  attached  at  a  distance,  x,  from  the  same  origin,  the 
equivalent  mass  on  the  line  of  pull  is 

M  X  -577 

— — =  m,  say. 

Now,  if  it  be  desired  to  impart  to  such  a  mass  a  velocity '  of  v  feet  per 

second  in,  say,  t  seconds,  the  acceleration  will  be  -,  and  the  force,^^,  required 
to  produce  it 

/i  =  ^xp.  .        .        .        .        (136) 

The  second  force,  /^j  which  is  required  to  overcome  friction,  may  be 
estimated  with  the  aid  of  a  suitable  coefficient,  c,  at  some  fraction  of  the 
weight  (W)  to  be  moved. 

/2  =  cW (137) 

Lastly,  the  resistance  of  the  water  to  displacement  during  movement  is 
theoretically  determined  by  the  consideration  that  the  pressure  on  the  plane 
of  the  gate  is  some  factor  of  the  pressure  which  would  be  produced  by  a 
body  of  water  falling  upon  the  gate  with  a  velocity  equal  to  the  velocity  of 
movement  of  the  latter. 

If  ^  be  the  distance  through  which  the  water  is  supposed  to  fall,  we 

have,  in  lbs., 

/^  =  A  .  toh  ,  k 

=  A  .  .  A;  .        (138) 

where,  for  fresh  water,  w  =  62^  lbs.  and  k  '■=^  1*8  ;  and  for  salt  water, 
i&  =  64  lbs.  and  k  ==  1*85.  A  is,  of  course,  the  area  in  feet  of  one  surface  of 
the  leaf. 

As  an  example  let  us  take  the  case  of  a  greenheart  gate,  55  feet  long  by 
40  feet  deep,  with  the  possibility  of  the  full  extent  of  head,  and  suppose  it 
to  be  worked  by  a  chain  attached  at  a  point  10  feet  from  the  outer  extremity 
of  the  leaf.     Assume  the  weight  of  the  gate  to  be  150  tons.     Then 

150  X  -577  X  55       ,^^  o  . 

m  = j^ =  lOO'o  tons  : 

45 

iind  if  it  be  deemed  desirable  to  obtain  a  speed  of  1  foot  per  second,  in  ten 

seconds, 

.      105-8        .  „^. 

/=  -3IP  X  Tiy  =  -33  ton. 

This  is  on  the  supposition  that  the  pull  is  horizontal ;  any  deviation 
therefrom  would  necessitate  a  suitable  modification. 

The  frictional  coefficient  is  most  difficult  to  estimate  in  the  case  of  a  dock 
gate,  there  being  so  many  modifying  influences  at  work.  For  a  railway 
train  travelling  at  normal  speed  about  10  lbs.  per  ton  would  be  considered  a 
fair  allowance,  but  this  coefficient  is  manifestly  too  low  for  a  cumbersome 


POWER  OF  GATE  MACHINES. 


527 


greenheart  gate,  moving  at  a  much  slower  rate  with  conical  rollers  over 

splayed  tracks,  and  it  will  still  further  be  augmented  by  a  certain  amount 

of  friction  at  the  heel-post.     On  the  other  hand,  there  is  the  diminution  of 

the  load  on  the  rollers  due  to  flotation,  which  will,  of  course,  vary  with  the 

depth  of  water  at  the  time  of  working.     Further,  there  is  the  ratio  of 

the  diameter  of  the  roller  to  that  of  its  axle,  and  the  proportion  of  weight 

which  the  roller  carries.     With  a  ratio  of  4  to  1  and  a  coefficient  of  '15, 

the  friction  due  to  that  portion  of  the  gate  borne  by  the  roller  would  be 

2  240  X  '15 
-  — -r =  84  lbs.  per  ton.     Allowing  for  flotation  and  dealing  with  the 

question,  as  is  inevitable,  in  a  somewhat  rough  and  ready  way,  it  will  pro- 
bably not  prove  an  excessive  estimate  if  we  take  the  frictional  resistance  of 
the  gate  at  20  lbs.  per  ton  on  its  gross  weight,  in  which  case 

.       150x20       -  _  ^^ 

For  the  resistance  offered  by  salt  water  to  displacement  we  have 

65  X  40  X  64  X  1-85 


/3  = 


=  1-81  tons. 


64  X  2,240 

Hence  the  maximum  tension  in  the  chain,  exerted  at  the  moment  of 
starting  the  movement  of  the  gate,  will  be 

T=/i  +/2  + /3  =  3-47  tons. 

This  figure  will  need  some  additional  margin  to  cover  uncertainties  in 
the  frictional  resistance.  Under  circumstances  only  too  common  in  con- 
nection with  the  working  of  dock  gates,  the  resistance  may  easily  be 
increased  to  double  the  amount  calculated  above,  for  which  fair  conditions 
of  track  have  been  assumed. 

The  following  table  exhibits  data  relating  to  several  existing  examples  of 
machinery  for  greenheart  gates.  For  metal  gates  with  buoyancy  chambers 
the  friction  of  movement  will  be  much  less,  and  the  amount  of  power  to  be 
applied  will  accordingly  be  considerably  reduced. 

TABLE   XLIII.— Gate  Machines. 


Width  of 
Entranoe. 


Greatest 

Least 

Working 

Working 

Head. 

Head. 

Feet 

Feet 

36-5 

26-6 

41 

31 

40 

30 

41 

31 

34 

24 

41 

31 

40 

30 

39 

29 

Area  of 

Surface  of 

I^af. 


Square  Feet 
766-6 
1722 
1680 
2091 
1768 
2316-6 
2260 
2203-5 


Diameter 

of  Bam  of 

Diameter 

Gate 

of  Chain. 

Machine. 

Inches. 

Inches. 

12 

1 

17 

ItV 

17 

lA 

18 

IS 

18 

If 

19 

H 

19 

H 

20 

H 

Gear. 


6  to   I 


6 
8 
6 
6 
6 
6 
6 


1 
1 
1 
1 
1 
1 
1 


Accumu- 

lator 
Pressure. 


SaS 


DOCK   ENGINEERING. 


Figs.  628  ftnd  529.— Electric  Clough  at  YmnideD  Looks. 


SLUICING  MACHINERY. 


529 


Sluicing  Machinery. — The  penstocks  or  doughs  which  regulate  levelling 
and  sluicing  culverts  may  be  worked  either  by  the  chain  or  the  ram.  The 
former  method  is  more  usual  with  electrical,  the  latter  with  hydraulic, 
power. 

The  doughs  and  their  electrical  connections  at  Ymuiden  Locks  are 
illustrated  in  figs.  528  to  530.  Each  frame  (which  is  built  of  timber  and 
sheet  metal)  is  suspended  by  two  endless  chains  fixed  to  the  ends  of  a 
pivoted  yoke  at  the  top  of  the  frame,  and  resting  on  a  horizontal  shaft 
above,  through  which  they  receive  their  motion  before  being  carried  round 
a  secondary  winding  shaft  half-way  down  the  pit.  The  shaft  is  actuated 
by  an  electric  motor  situated  in  a  separate  chamber  behind  a  partition 


Fig.  530. — Diagram  of  Electric  Comiections  to  Gates  and  Sluices  at  Ymuiden  Locks. 

wall  through  which  the  shaft  is  carried.  The  motor  is  capable  of  developing 
17  H.P.  when  running  at  270  revolutions.  The  weight  of  the  sluice  is 
partly  balanced  by  a  counterweight,  which  is  attached  to  the  chain  end 
and  which  glides  on  two  rods  provided  with  collars  bearing  against  strong 
helical  springs.*^ 

In  the  hydraulic  dough  the  frame  terminates  in  a  piston,  which  passes 
into  a  cylinder  and  is  worked  by  differential  pressure.  Vertical  guides 
are  added  to  keep  the  frame  in  position  during  its  ascent  or  descent. 

In  case  of  failure  of  any  part  of  the  mechanical  apparatus,  it  is  advisable 
to  provide  a  separate  dough  which  can  be  worked  by  manual  power.  This 
is  usually  effected  by  a  cross-bar  at  the  summit  of  a  spindle,  with  screw 
thread,  passing  through  a  fixed  bracket. 

*  Articles  on  ''The  Electrical  Gear  at  the  Ymuiden  Locks'*  appeared  in  Engineering  y 
Feb.  7,  1902,  and  subsequent  issues. 

34 


530  DOCK  ENGINEERING. 

Power  of  Sluice  MachinOB. — In  eatimatiDg  the  power  required  for  working 
clongh  paddles,  there  are  two  factors  to  be  taken  into  consideration — viz., 
(1)  the  weight  of  the  paddle  itself,  and  (2)  the  working  friction  against  the 
facet)  of  the  clongh  jambs.  This  latter  is  greatest  at  starting  and  will 
diminish  as  the  paddle  rises.  The  maximum  effect  can  be  found  hj  calcn- 
l&ting  the  presanre  against  the  face  of  the  paddle,  due  to  the  initial  bead 
of  water,  and  multiplying  hj  a  coefficient  of  friction. 


The  following  a 
wet  or  dry  : — 


Figs.  683  and  534.— HjdrauUo  CapBlan. 
for  the  latter  wheo  the  surfaces  in  contact  are 


CAPSTANS.  531 

Capstans. — Capstans  betong  to  the  same  claas  of  appliances  as  winches, 
the  onlj  difference  being  that  their  axes  are  vertical  instead  of  horizontal. 
This  arrangement  favonrs  the  working  of  them  by  baud  when  necessary. 
Accordingly  the  capstan  head  should  be  designed  at  a  convenient  height  and 
apertures  for  poles  arranged  in  it,  so  that,  in  case  of  any  breakdown  in  the 
usual  motive  power,  the  machinery  may  be  actuated  by  hand.     A  pawl  and 

ratchet  gear  along  the  lower  circum-  

ference  will  prevent  backslip. 

Capstans  of  from  3  to  12  tons 
power  are  generally  found  sufficient 
for  dock  work.  Excessive  power  would 
only  result  in  the  fracture  of  cables. 

One  capstan,  at  least,  should  be 
located  at  each  side  of  an  entrance, 
and  if  there  be  a  long  lock,  two  or 
four  others  will  certainly  be  advisable 
at  equal  intervals.  The  position  of  a 
capstan  should  be  such  that,  if  there 
be  a  pair  of  gates  in  the  vicinity,  a 


I  VERTICAL     SECTION 

Fig.  635.  Fig.  636.— Electric  CapBtan. 

convenient  lead  may  be  obtained  for  opening  or  closing  the  gates  in  the 
event  of  an  accident  to  the  gate  machinery. 

Capstans  are  obviously  most,  if  not  solely,  adapted  for  working  by  means 
of  rotary  engines.  In  the  case  of  hydraulic  power,  an  illustration  of  the 
mechanism  as  devised  by  Lord  Armstrong  for  a  two-cylinder  machine  is 
afforded  in  figs.  531  to  534.     The  method  of  admitting  the  pressure  water  to 


532  IX>CK  ENGINEERING. 

alternate  faces  of  the  piston-ram  will  be  perceived  from  an  inspection  of 
fig.  535,  which  is  a  section  showing  the  valve  of  the  cylinder.  A.  is  the 
supply  passage ;  B,  the  constant  pressure  port,  always  open  to  the  upper 
side  of  the  piston ;  C,  the  pressure  port  to  the  under  side  of  the  piston ;  D, 
the  exhaust  therefrom  ;  and  E,  the  discharge  passage  from  the  engine.  E  is 
a  ring  of  hard  metal  forming  the  fixed  working  fJEkce,  the  upper  segment  of 
which,  marked  G  G,  is  free  to  press  up  against  the  rubbing  surface  as  it 
wears  down,  and  is  kept  in  contact  by  the  pressure  of  the  water.  H  is  the 
trunnion  in  section,  showing  the  pressure  port  on  the  upper  side  and 
the  exhaust  port  on  the  lower;  and  I  is  the  relief  valve,  the  port  to 
which  is  always  open  at  the  moment  when  the  relief  valve  is  required 
to  act. 

A  vertical  section  of  an  electrically  worked  capstan  at  the  Ymuiden 
Locks  is  given  in  fig.  536. 

Quay  Cranes. — Quay  cranes  are  of  all  capacities,  from  half  a  ton  or  less 
to  150  tons  or  more. 

Types  are  innumerable,  and  it  is  quite  beyond  the  province  of  this  work 
to  attempt  to  deal  with  them  except  on  very  restricted  lines.  For  dock 
work,  cranes  may  be  concisely  divided  into  two  classes — viz.,  fixed  cranes 
and  movable  cranes.  The  smaller  class  of  cranes,  dealing  with  the  loading 
and  unloading  of  vessels  with  cargo^  are  generally  of  the  latter  type,  from 
the  necessity  of  adapting  them  to  the  variable  positions  of  the  hatchways. 
They  are  subdivisible  as  follows  : — 

1.  Cranes  which  travel  upon  rails  all  of  which  are  at  coping  level.  To 
accommodate  the  track,  and  also  to  ensure  stability,  this  arrangement 
involves  a  clear  space  of  some  width — say,  10  feet — for  the  crane  alone,  and 
as  additional  tracks  will  generally  be  required  for  trucks,  both  while  loading 
and  in  reserve,  the  width  may  easily  be  extended  to  30  or  even  50  feet.  To 
reduce  this  large  allowance,  often  inconvenient  when  space  is  limited, 
pedestal  cranes  have  been  devised,  such  that  one  or  more  lines  of  waggons 
can  pass  beneath  the  crane  platform. 

A  hydraulic  crane  of  the  former  type  is  shown  in  figs.  537  and  538  and 
a  pedestal  crane  in  figs.  539  to  541.  In  both  cases  the  lifting  is  performed 
by  a  ram  and  cylinder  with  six  sheaves. 

The  pedestal  crane  is  the  copy  of  one  in  vogue  at  Havre,  Dunkirk, 
Bordeaux,  and  other  French  ports.  It  is  adapted  to  two  lifting  capacities 
of  15  and  35  cwts.  respectively.  The  different  powers  are  obtained  by 
concentric  cylinders.  A  slewing  motion  is  imparted  by  two  hydraulic  rams 
placed  vertically  behind  the  pivot.  A  single  chain,  common  to  both  presses, 
is  attached  to  the  turning  drum,  so  that  the  motion  of  one  ram  causes  it  to 
revolve  in  one  direction  while  the  motion  of  the  other  ram  produces 
revolution  in  the  other  direction. 

2.  Cranes  (fig.  393)  which  travel  upon  one  rail  at  the  coping  level  and 
upon  another  carried  by  a  balcony  or  corbel  on  a  transit  shed  at  some  height 
above  the  quay,  generally  at  first  floor  level.     This  is  obviously  a  device  for 


t 

I 


TC* 


/id 


Figs.  538,  540,  and 


! 


QUAY  CRANES. 


Fig.  542.— IdO-ToD  Crane  at 


Fig.  343.— ISO-Ton  Revolving  Cnne  at  Kiel. 


Fig.  544 — lOO'ToD  Derrick  Crane  at  Hamburg. 


Fig.  fi40.— 100-Ton  Revolving  Crane  at  Bremen.  Fig.  546.— 120-Ton  Crane  at  Barrow. 


534 


DOCK  ENOIKEERING. 


gaining  space  on  narrow  quays.  It  embodies  all  the  features  of  a  pedestal 
crane  miaua  the  back  legs. 

3.  Cranes  (fig.  374)  which  are  carried  entirely  upon  the  shed  structure, 
either  at  some  floor  level  or  upon  the  roof  This  arraagement  is  inevitable 
when  there  is  not  sufficient  spsce  to  accommodate  the  crane  upon  the  quay, 
and,  in  other  cases,  it  avoids  the  obstruction  caused  by  the  front  legs  of  the 
semi-pedestal  crane,  but  it  involves  a  corresponding  increase  in  the  amount 
of  outreach. 

The  hydraulic  roof-crane  at  Liverpool,  shown  in  fig.  371,  lias  luffing  gear 
capable  of  altering  the  outreach  or  rake  from  18  to  33  feet  beyond  the  line 
of  coping.  The  total  height  of  lift  is  76  feet,  and  the  rate  of  lifting  the  full 
load  of  30  cwts.  is  150  feet  per  minute. 

Fixed  cranes  have  the  advantage  of  greater  stability,  and  are  employed 
for  lifting  heavy  loads.  One  at  Malta,  capable  of  raising  a  weight  of 
160  tons,  is  described  at  p.  S36,  potl.  Others,  of  various  types,  are  illua- 
trated  in  figs.  542  to  546. 

The  difficulty  of  employing  large  cranes  with  long  outreach  is  the 
revolution  of  the  jib  amid  the  intricacies  of  masts,  yards,  stays,  &c,  of 
shipping.  In  many  cases  a  pair  of  sheer  legs,  or  oscillating  derriok  crane,  ia 
to  be  preferred.  In  form,  the  apparatus  is  a  tripod  with  two  legs  pivoted 
horizootally  at  the  edge  of  the  quay  and  the  third  adjustable  to  the  amount 
of  outward  projection.  The  movement  of  the  load  is  entirely  in  one  plane, 
at  right  angles  to  the  direction  of  the  quay,  by  which  arrangement  any 
iuterference  with  objects  on  either  side  is  avoided. 

Floating  Cranes. — A  floating  crane,  or  sheers,  is  a  valuable  adjunct  to 
the  equipment  of  a  dock  system,  as  apart  from  its  availability  for  shipping 


Fig.  547.— Floating  Crane.     Elevation, 
and  commercial  purposes,  it  is  of  great  utility  in  lifting  dock  gates  for 
repairs,  in  berthing  temporary  dams,  and  in  many  other  cases.   Such  cranes 
are  constructed  up  to  100  tons  lifting  power.     One  of  25  tons  is  shown  in 

figs.  547  and  548. 


VWA.TmQ  CBANE  AND  JIOQER. 


Figs.  C49  and  660.— Hydraulic  Jigger. 


536  DOCK  ENGINEERING. 

Jiggers. — Closely  akin  to  cranes  are  jiggers  (figs.  549  and  550)  actuated 
commonly  by  hydraulic  power.  The  apparatus  is  so  light  as  to  not  require 
a  rail  track.  There  is  no  jib,  and  goods  are  simply  hoisted  out  of  a  ship's 
hold  by  means  of  a  chain,  or  rope,  passing  oyer  a  sheaye  suspended  to 
the  rigging.  It  may  be  used  as  a  useful  auxiliary  to  quay  cranes,  and 
it  has  certain  advantages  in  rapidly  lifting  light  articles  out  of  the  holds. 
It  has  a  close  competitor  in  this  respect  in  the  winches  with  which 
steamships  are  usually  furnished. 

Hydraulic  Crane  at  Malta.* — This  crane,  the  elevation  of  which  is 
shown  in  fig.  551,  has  a  maximum  working  load  of  160  tons.  This  weight 
can  be  lifted  through  a  height  of  50  feet  at  a  radius  of  70  feet.  Loads  up 
to  35  tons  can  be  lifted  through  a  height  of  90  feet  at  a  radius  of  75  feet. 
The  larger  loads  are  raised  by  means  of  a  direct-acting  hydraulic  cylinder 
suspended  in  gymbals  from  the  jib ;  the  smaller  loads  by  a  chain  purchase, 
worked  by  a  rotary  hydraulic  engine. 

The  structure,  which  was  constructed  and  erected  by  Messrs.  Sir  W.  G. 
Armstrong  &  Oo.,  of  Newcastle,  is  carried  by  and  revolves  upon  96 
bevelled  live  rollers,  15  inches  mean  diameter  and  16  inches  wide,  working 
on  a  lower  roller  path  of  cast  iron,  planed  on  the  top  and  bottom,  the  top 
being  bevelled  to  suit  the  rollers.  The  rollers  are  connected  on  the  outside 
by  links,  5  inches  by  j-inch,  passing  over  the  ends  of  the  axles,  each  link 
taking  two  rollers ;  and  on  the  inside,  the  end  of  the  axle  is  clipped  in  a 
w rough t-iron  circular  frame,  connected  by  bracing  (figs.  652  and  553)  to  a 
collar,  working  on  rollers  round  the  centre  column  of  masonry.  The 
centre  pivot  is  fixed  to  the  masonry  by  four  bolts,  15  feet  long,  extending 
into  the  centre  chamber,  and  is  made  hollow  to  admit  the  hydraulic  pipes. 
These  pipes  are  concentric  through  the  pivot,  the  internal  one  being  for 
pressure  and  the  other  for  exhaust.  The  foundation  consists  of  a  solid 
mass  of  Portland  cement  concrete,  composed  of  6  parts  of  hard  limestone 
and  3  of  sand  to  1  of  cement,  faced  above  ground  with  limestone 
masonry. 

The  main  lifting  cylinder  is  of  cast  iron,  in  three  lengths,  connected  by 
fourteen  3^inch  bolts.  Its  internal  diameter  is  29  inches,  and  the  thick- 
ness of  the  metal  3^  inches.  The  piston  is  of  cast  iron  and  arranged  for 
hemp  packing.  The  piston-rod  is  of  wrought  iron,  8  inches  in  diameter,  and 
fitted  at  the  lower  end  with  swivel  eye  and  shackle.  A  platform  is 
suspended  from  the  cylinder,  from  which  the  inlet  and  outlet  valves  are 
controlled ;  it  is  reached  by  a  light  iron  bridge  hinged  to  it,  and  resting 
upon  the  framework  of  the  jib.  The  cylinder  is  carried  in  a  wrought-iron 
trunnion  ring,  suspended  from  the  jib  by  four  forged  iron  links,  so  that  it 
can  be  swung  in  towards  the  jib  when  the  30-ton  purchase  is  in  use. 

The  rotary  hydraulic  engine  for  working  the  30-ton  purchase,  the 
slewing  machinery,  and  the  swinging-in  gear,  has  three  oscillating  cylinders, 

*  C.  and  C.  H.  Colson  on  <'The  160-Toq  Hydrauho  Crane  at  MalU  Dockyard 
Extension  Works,"  Min,  Proc,  Inst,  CE.^  vol.  cxiv. 


TBANSPORTERS. 


537 


with  gun-metal  plungers,  3^^  inches  in  diameter  and  14  inches  stroke.  All 
the  levers  for  actuating  the  starting  and  stopping  valves  and  gearing 
generally  are  arranged  so  as  to  be  worked  by  one  man  standing  upon  a 
platform,  raised  above  the  lower  framework  of  the  crane.  Turning  motion 
is  effected  through  spur  and  bevel  gearing,  acting  on  a  toothed  rack  on  the 
outer  edge  of  the  lower  roller  track. 

All  the  machinery  pipes  and  valves,  subjected  to  a  working  pressure  of 
700  lbs.  per  square  inch,  were  tested  to  1,400  lbs.,  and  the  cylinder,  piston- 
rod  and  piston,  links,  d^c,  were  tested  to  320  tons,  or  double  the  working 
load. 

Transporters. — A  transporter  consists  essentially  of  a  long  arm  or  track, 
placed  horizontally  or  very  nearly  so,  along  which  travels  a  carriage  with  a 
hook  for  the  attachment  of  loads.  There  are  several  types  of  transporter ; 
two  will  be  briefly  described. 


Fig.  554. — Temperley  Transporter. 

The  Temperley  Tra/nsporter  consists  of  an  iron  beam  of  H  section, 
supported  by  a  special  tower,  by  the  mast  of  a  vessel,  or  by  the  underside 
of  a  shed  floor  or  roof.  The  traveller,  or  truck,  is  provided  with  an 
arrangement  for  throwing  itself  automatically  out  of  gear  at  fixed  positions 
vertically  over  the  points  of  loading  and  discharge.  It  is  actuated  by  a 
steel  wire  cable,  which  can  be  set  in  motion  by  steam,  hydraulic,  or  electric 
power,  and  also  by  gas  engines  for  lower  speeds.  These  transporters  are 
applicable  to  loads  of  from  5  to  60  cwts.,  and  to  distances  up  to  1,000  feet, 
with  travelling  speeds  ranging  from  500  to  1,500  feet  per  minute. 

A  view  of  the  transporter  is  shown  in  fig.  554.  The  traveller,  at  the 
left  end,  contains  automatic  mechanism  which  secures  it  to  the  beam  during 
the  lifting  of  the  load,  and  which  sustains  the  load  during  the  movement  of 
the  traveller.  The  load  having  been  attached  to  the  hook  in  its  lowest 
position,  the  latter  is  hoisted  by  a  hydraulic  or  other  engine  until  the 
fall  block  enters  the  bell  of  the  traveller,  when  two  hooks  automatically 
engage  the  block  and  sustain  the  load,  while,  at  the  same  time,  the  traveller 
is  released  from  the  notch  in  the  beam  and  commences  to  travel  into  the 
building. 


538  DOCK  ENGINEERING. 

These  notches,  which  fix  the  stoppages  of  the  traveller,  are  arranged  at 
intervals  of  about  5  feet.  On  arriving  at  the  position  at  which  it  is  desired 
to  lower  the  load,  the  engine  is  stopped,  the  hoisting  drum  thrown  out  of 
gear,  and  the  traveller  with  its  load  commences  to  run  backward  iinder  the 
action  of  a  tail  rope  or  overhauling  gear  until  it  comes  to  a  notch,  in  which 
it  engages  automatically,  and,  at  the  same  time,  releases  the  fall  block,  so 
that  the  load  can  be  lowered  with  the  brake  in  the  usual  manner. 

The  outer  projecting  ends  of  the  beams  may  be  hinged,  so  that  they  can 
be  drawn  into  a  vertical  position  when  out  of  use. 

The  Trofuporter  shown  in  figs.  565  and  556  is  of  a  type  used  in  France, 
and  manufactured  by  Messrs.  Dayd^  and  Fill^,  of  CreiL  It  is  formed  of  a 
vertical  framework  in  the  shape  of  the  letter  A,  at  right  angles  to  which 
the  transporting  beam  is  set.  The  frame  is  free  to  travel  along  the  quay 
on  a  line  of  rails,  and  is  steadied  by  a  second  line  of  rails  placed  along  the 
shed  front,  at  some  distance  above  the  quay  level,  so  as  to  prevent  over- 
turning. 

The  travelling  beam  can  be  set  to  any  required  inclination.  The 
apparatus  is  worked  by  two  independent  winches,  one  of  which  controls  the 
hoisting  of  the  load  and  the  other  the  travelling  movement.  Both  these 
winches  are  driven  by  steam  power  from  machinery  at  the  foot  of  the  frame, 
movement  being  communicated  by  means  of  shafts  and  bevelled  wheels. 

The  apparatus  in  question  is  adapted  to  loads  of  30  cwts. 

Coal  Tips  and  Lifts. — ^The  process  of  loading  a  vessel  with  a  cargo  of 
coal  is  attended  by  some  difficulty,  owing  to  the  brittleness  of  the  material, 
which  is  such  that,  unless  extreme  care  be  taken,  its  value  may  be  very 
seriously  depreciated  by  breakage  into  minute  fragments  and  dust. 

Goal  is  usually  conveyed  to  port  from  the  collieries  in  waggons,  either 
end-tipping  or  with  drop-bottoms.  Waggons  of  the  latter  class  are  simply 
lifted  and  slewed  bodily  by  a  quay  crane,  and  suspended  over  the  hold 
while  the  coal  is  discharged.  End-tipping  waggons  are  tilted  so  that  their 
contents  are  emptied  into  a  shoot  which  directs  them  into  the  hatchway. 
Until  a  conical  heap  of  sufficient  height  is  formed,  the  operations  in  both 
cases  are  accompanied  by  considerable  breakage  of  coal,  owing  to  the  great 
depth  of  the  hold  into  which  it  has  to  fall.  This  can,  to  some  extent,  be 
remedied  by  the  assistance  of  an  anti-breakage  crane,  which  forms  an 
auxiliary  feature  of  most  coaling  tips.  For  the  first  few  waggon  loads,  the 
coal,  after  passing  down  the  shoot,  enters  a  skip  placed  to  receive  it,  the 
skip  being  suspended  from  the  crane,  by  which  it  is  lowered  carefully  to 
the  bottom  and  its  contents  there  deposited.  Even  after  the  cone  has 
attained  a  good  height,  it  will  be  necessary  to  control  the  'discharge  from 
the  shoot  with  the  aid  of  flaps,  or  doors,  as  a  rapid  rush  of  material  will 
frequently  produce  nearly  as  much  damage  as  a  long  fall. 

If  the  railway  tracks  are  at  a  sufficiently  high  level,  the  waggons  may 
be  discharged  direct  from  that  level,  but,  in  the  case  of  a  low-level  approach, 
it  will  be  necessary  to  first  lift  the  waggons  to  such  a  height  as  will  clear 


[To  190^  P^^ 


5S8. 


N. 


\ 


\ 


\ 


\ 


\ 


X 


\ 


\ 


G 


^^  Boiler. 

C    Speed  Regulator. 

B,  OeoiUating  Beam, 

If   Traveller. 

G   Hoisting  G^**- 

H   Travelling  <^^- 
i;  Upper  Track. 

K.  l»wer  TracJ. 


GRAIN  ELEVATORS.  539 

the  bulwarks  and  hatchway  coamings,  and,  at  the  same  time,  give  the 
requisite  inclination  to  the  tip. 

Figs.  557  to  559  are  illustrations  of  a  hydraulic  coal  hoist  and  tip 
recently  constructed  at  Dundee.* 

The  hoist  is  designed  to  lift  a  20-ton  waggon  through  a  height  of  50  feet 
above  the  level  of  the  jetty  rails,  and  at  the  summit  to  tip  it  through  an 
angle  of  45  degrees.  Owing  to  the  difficulty  of  providing  suitable  founda- 
tions at  a  moderate  cost,  the  structure  having  to  stand  in  the  river  120  feet 
beyond  the  line  of  quay,  a  suspended  form  of  hoist  has  been  adopted, 
instead  of  that  in  which  the  cradle  is  raised  by  direct-acting  cylinders 
placed  in  a  well  below  the  surface  of  the  quay.  The  hoist  framing  is  of 
steel,  braced  and  strutted,  and  securely  bolted  to  the  timber-work  of  the 
jetty.  The  cradle  and  tipping  frame  are  lifted  and  lowered  by  four  chains, 
two  of  which  are  for  lifting  and  two  for  tipping.  The  lifting  cylinder  is 
fixed  vertically  against  one  side  of  the  framing,  and  the  tipping  cylinder 
is  fixed  on  the  upper  end  of  the  lifting  cylinder.  Each  cylinder  is  fitted 
with  a  plunger,  multiplying  sheaves,  guide  bars,  &c  The  hoist  is  also 
furnished  with  a  2^ton  anti-breakage  ^crane,  having  a  lift  of  55  feet.  The 
structure  is  said  to  be  the  largest  of  its  type. 

Owing  to  the  dust  arising  from  the  shipment  of  coal,  it  is  essential  to 
locate  tips  at  a  safe  distance  from  quays  for  the  reception  of  cargo  of  a 
nature  likely  to  be  affected  by  it. 

Grain  Elevators. — Appliances  for  dealing  with  cargoes  of  grain  in  bulk 
are  necessarily  very  different  from  those  employed  in  lifting  packages  and 
portable  objects  generally.  In  the  case  of  a  granular  substance  it  is  clearly 
advantageous  to  provide  some  method  of  uninterrupted  transmission,  such 
as  that  afforded  horizontally  by  endless  bands  in  revolution,  and  vertically 
by  a  succession  of  buckets  on  a  continuous  chain.  Pneumatic  power,  in 
the  form  of  either  suction  or  pressure  through  tubes,  can  also  be  employed 
to  achieve  the  same  result.  When  the  quantity  dealt  with  is  small,  or 
when  it  forms  part  of  a  miscellaneous  cargo,  intermittent  discharge  by 
meana  of  grabs,  worked  by  cranes,  may  suffice. 

The  bucket  system  is  in  vogue  at  Liverpool  and  other  places,  and  the 
rate  of  travelling  reaches  100  feet  per  minute.  An  important  drawback  of 
the  system  is  the  limited  range  of  self-feed  for  the  buckets.  They  are  only 
able  to  deal  directly  with  the  grain  in  the  immediate  vicinity  of  the  hatch- 
way. That  portion  of  it  which  lies  under  cover,  it  may  be  to  the  extent 
of  a  hundred  feet  or  more,  fore  or  aft,  has  to  be  trimmed  in  the  direction  of 
the  buckets,  generally  by  manual  labour. 

The  pneumatic  system  adopted  at  the  Millwall  Docks,  London,  and 
elsewhere,  whilst  entailing  a  greater  consumption  of  coal  than  the  bucket 
system,  offers  some  advantages  in  other  directions.  The  pneumatic  tubes, 
being  flexible,  can  be  applied  in  any  required  position,  and  the  cost  of 
trimming  is  thereby  saved,  though  at  the  same  time  the  shifting  of  the 
*  Buchanan  on  "The  Port  of  Dundee,"  Min.  Proc,  Inst,  C,E,,  vol.  oxlix. 


540  DOCK  ENOINBBRINQ. 

tubes  necBBsitates  attention,  bat  not  to  the  same  extent.  No  matter  how 
tortuous  the  route,  the  grain  can  be  sucked  out  of  bunkers  and  other  con- 
fined spaces,  which  would  be  otherwise  inaccessible.  Forthermore,  there  is 
much  less  exposure  to  the  weather,  and  pneumatic  elevators  can  be  worked 
under  almost  any  atmospheric  conditions. 


Figs.  660  and  661. — Pneumatic  Or&in  Apparatus. 

The  MJllwall  apparatus,*  illustrated  in  figs.  560  and  661,  is  located  in 
a  hull  about  80  feet  long  by  24  feet  wide  by  10  feet  deep.  It  is  driven  by 
a  compound  engine  connected  direct  with  ur^exhausting  pumps,  capable 
of  producing  and  mainteining  a  partial  vacuum  of  15  inches  of  mercury,  in 
a  tenk  into  which  some  0,000  feet  of  air,  under  atmospheric  conditions,  is 
being  admitted  per  minute.     The  tank,  which  acte  as  a  grain-receiver,  is 

*  Duckham  on  "  Pneumatic  Machinery  for  Loading  and  Dischai^ing  Grain  Cargoes," 
The  Enginetr,  April  8,  1898. 


SLIPWAY  HAULAGE.  54 1 

supported  from  the  deck  by  a  tower,  and  has  a  diameter  of  10  feet  with  a 
height  of  16  feet.  It  is  coned  at  the  bottom,  and  furnished  with  connec- 
tions for  two  or  three  pipes,  through  which  the  grain  is  drawn  with  the 
current  of  air  from  the  hold  of  the  ship.  An  automatic  air-lock  is  attached, 
and  through  it  the  grain  discharges  itself  into  the  hopper  of  the  weighing 
machine,  whence,  after  weighing,  it  is  directed  into  a  barge  in  bulk  or  is 
filled  into  sacks.  This  type  of  machine  is  also  in  use  at  Bemerhaven  and 
Hamburg. 

In  a  pneumatic  apparatus  employed  at  Limerick,  the  grain,  instead  of 
flowing  away  in  bulk,  finds  its  way  through  a  second  air-lock  into  a 
chamber  below  the  deck  into  which  air  is  forced  at  a  pressure  of  from 
6  to  8  lbs.  per  square  inch.  From  this  a  pipe  passes  upwards,  bends  over 
the  elevator's  side,  and  is  there  connected,  by  a  piece  of  flexible  hose,  with 
an  underground  pipe  passing  up  into  and  along  the  roof  of  a  warehouse. 
By  means  of  outlets  provided  at  convenient  intervals  the  grain  is  discharged 
into  the  required  bins. 

Slipway  Haulage. — As  originally  devised  by  the  late  Thomas  Morton, 
the  inventor  of  the  slip  dock,  the  machinery  for  hauling  vessels  up  the 
ways  consisted  of  spur  gearing  worked  by  manual  power,  horses,  or  the 
steam  engine.  Hydraulic  apparatus  was  introduced  about  the  year  1850^ 
and  has  since  existed  through  various  stages  of  development  in  competition 
with  a  form  of  winding  apparatus  originated  about  the  year  1879. 

The  hydraulic  apparatus  in  its  later  form,  as  contrived  by  Messrs. 
Lightfoot  and  Thomson,"^  consists  of  three  main  hauling  rams  (figs.  662 
and  563),  connected  by  means  of  an  upper  crosshead  with  a  single  reversing 
ram  under  constant  pressure,  and  by  means  of  a  lower  crosshead  with  a 
double  set  of  hauling  links  which  extend  nearly  to  the  extremity  of  the 
ways,  resting  upon  wings  cast  upon  I  the  centre  rails  and  being  guided 
thereby.  The  action  is  as  follows : — By  the  admission  of  water  to  one  or 
more  of  the  main  cylinders,  according  to  the  size  of  the  vessel  being  dealt 
with,  a  forward  stroke  of  10  feet  is  made  against  the  constant  pressure  of 
the  reversing  ram.  The  main  cylinders  are  then  opened  to  exhaust,  and 
the  backward  stroke  is  made  under  the  action  of  the  reversing  ram.  There 
is  a  dual  system  of  pawls  on  the  cradle,  so  arranged  that  one  of  them 
engages  in  the  rack  of  the  permanent  way  at  the  end  of  each  forward 
stroke,  while  the  other  engages  in  the  joint  plates  of  the  hauling  links  at 
the  completion  of  each  backward  stroke.  During  the  backward  stroke, 
therefore,  the  cradle  remains  stationary  upon  the  ways,  while  the  hauling 
links  are  passing  downwards  to  take  up  a  new  position  10  feet  behind  the 
pawls  in  which  they  were  previously  engaged.  With  this  system,  no 
disconnection  or  removal  of  links,  such  as  obtained  in  earlier  types,  is 
required.  The  return  stroke  is  made  much  more  rapidly  than  the  forward 
stroke  on  account  of  the  much  smaller  area  of  the  ram. 

♦Lightfoot  and  Thompson  on  "Slipways  for  Ships,"  Min.  Proc,  Tnat.  C,E,, 
vol.  Ixxii. 


DOCK  ENGINEEMNG. 


i  I 


544  ^^^^  ENGINEERING. 

A  double  set  of  cylinders  and  rams  is  the  system  adopted  by  Messrs. 
Hay  ward,  Tyler  &  Co.,  and  the  apparatus  is  so  arranged  that  one  set  is  in 
forward  motion  while  the  second  is  returning.  By  attaching  the  links  alter- 
nately to  each  set,  the  cradle  is  maintained  in  almost  continuous  motion. 

The  hauling  gear  of  Messrs.  Day  and  Summers  consists  of  a  wire  rope, 
12  inches  in  circumference,  used  either  in  single  tension  or  with  multiply- 
ing sheaves,  coiled  upon  a  drum,  some  9  or  10  feet  in  diameter,  which  is 
actuated  by  steam  or  other  convenient  power 

The  smoothness  and  regularity  of  the  hydraulic  ram  commend  it  for 
the  purpose  of  slipway  haulage,  particularly  in  dealing  with  vessels  of  large 
size.  Steel  wire  rope,  on  the  other  hand,  is  light  and  flexible.  Its 
durability  has  been  contested,  but  appears  to  be  satis&ctory. 

Pumping  Machinery. — Permanent  pumping  power,  as  distinguished  from 
that  of  a  temporary  nature,  dealt  with  in  a  previous  chapter,  is  required 
in  connection  with  docks  for  two  important  objects  : — (1)  For  emptying 
graving  docks,  and  (2)  for  arti6cially  raising  the  level  of  the  water  in  wet 
docks.  This  latter  expedient  is  adopted  in  cases  where,  greater  draught 
being  required  for  vessels,  the  deepening  of  a  dock  is  deemed  inadvisable 
on  constructive  or  economical  grounds.  The  use  of  pumping  plant  in 
connection  with  hydraulic  accumulators  is,  of  course,  obviously  necessary 
where  such  power  is  adopted. 

The  type  of  pump  most  commonly  employed  for  the  first  named  objects 
is  that  known  as  the  centrifugal,  in  which  the  rapid  rotation  of  a  series  of 
blades  or  fans  causes  the  water  within  the  pump  chamber  to  be  whirled 
round  and  propelled  in  an  upward  direction.  Valvular  pumps  are  unsuit- 
able for  dealing  with  dock  water,  on  account  of  the  great  quantity  of  refuse 
matter  to  be  found  in  it ;  corks,  straw,  chips,  and  ship  scrapings  are  a  few 
examples  only  of  the  multitudinous  small  objects  which  suffice  to  obstruct 
the  action  of  valves.  Centrifugal  pumps  themselves  have  to  be  protected 
by  entrance  gratings  from  the  risk  of  entanglement  with  ropes  and  canvas, 
to  say  nothing  of  more  serious  damage  by  log-ends,  pieces  of  planking,  and 
wedges.  It  is  no  uncommon  experience  for  a  pump  to  have  its  intake  pipe 
choked  by  eels  and  small  fish,  and  the  writer  knows  of  one  instance  in 
which  the  pump  blades  were  smashed  by  a  piece  of  timber  which  had 
mysteriously  intruded  itself  into  the  well.  The  following  incident,  narrated 
by  Mr.  John  Hayes,  is  likewise  instructive : — 

Two  large  centrifugal  pumps  and  engines,  at  Demerara,  had  been  fitted 
up  and  set  to  work  in  connection  with  drainage  operations  on  a  somewhat 
extensive  scale.  One  day,  after  they  had  been  some  considerable  time  in 
operation,  the  Resident  Engineer  observed  that  the  engine  and  pump 
suddenly  pulled  up  and  then  went  on  again  immediately  afterwards.  For 
a  long  time  the  cause  was  undiscovered,  but  eventually  the  remains  of  an 
alligator,  14  feet  long,  were  found  in  the  outlet  of  the  pump.  The  reptile 
had  passed  through  the  pump,  and  had  been  cut  into  three  pieces,  which  the 
Resident  Engineer  caused  to  be  stuffed,  as  a  specimen  of  what  centrifugal 


PETROLEUM  STORAGE.  545 

pumps  would  do  in  the  way  of  getting  rid  of  obstructive  debris.      The 
alligator  was  undamaged  except  where  it  had  been  severed.'^ 

Centrifugal  pumps  are  of  two  types — the  vertical  and  the  horizontal. 
The  latter  is  perhaps  more  generally  known  as  the  turbine.  The  turbine 
has  an  advantage  over  the  centrifugal  proper,  in  that  the  machinery  for 
driving  it  can  be  placed  at  or  about  the  quay  level,  whereas  the  other 
has  its  motive  power  applied  near  the  middle  of  its  lift,  about  half  of 
which  is  done  by  suction,  and  the  other  half  by  propulsion.  This  involves 
an  expensive  watertight  chamber  below  the  level  of  the  surface  of  the 
dock.  On  the  other  hand,  the  centrifugal  pump  is  simpler  in  construc- 
tion, being  driven  by  the  main  shaft  direct,  while  the  turbine  pump 
necessitates  the  interposition  of  gearing.  The  maintenance  of  a  centri- 
fugal pump  is  therefore  less  expensive,  and  on  this  ground  it  commends 
itself  to  the  favour  of  engineers. 

It  is  not  proposed  to  enter  here  into  details  of  pumping  machinery. 
The  subject  is  so  extensive  as  to  call  for  separate  and  specialised  treatment, 
which  may  be  found  elsewhere.  Some  brief  particulars  relating  to 
installations  at  several  graving  docks  are  given  in  Chap.  xi. 

Petroleam  Storage. — Petroleum  is  imported  into  this  country  either  in 
barrels  or  in  bulk — the  latter  by  means  of  specially  constructed  tank 
steamers.  The  barrel  system  is  the  less  economical  of  the  two,  owing  to 
the  depreciation  in  the  value  of  the  imported  barrels,  which  may  amount  to 
as  much  as  20  or  30  per  cent. 

An  ordinary  barrel  is  some  33  inches  long  and  25  inches  middle 
diameter;  it  weighs  about  64  lbs.  when  empty,  400  lbs.  when  full,  and 
contains  42  imperial  gallons.  Barrels  can  be  most  conveniently  and 
effectively  landed  or  shipped  by  means  of  parallel  tracks  of  angle  iron,  set 
up  on  trestles,  where  necessary,  to  give  the  requisite  inclination.  It  is 
found  that  there  is  no  disposition  on  the  part  of  the  barrels  to  leave  the 
tracks,  however  great  the  speed. 

Petroleum  in  bulk  from  a  tank  steamer  is  usually  pumped  through 
conduit  pipes  into  a  storage  tank  or  tanks  ashore.  These  tanks  are 
cylindrical  in  form,  built  of  plates  of  wrought  iron,  or  steel,  and  suitably 
stiffened.  A  settling  tank  of  similar  construction  is  often  included  in  the 
equipment. 

The  following  particulars  relate  to  the  petroleum  storage  dep6t  at 
Barrow  Docks  : — 

There  are  two  installations.  The  smaller  consists  of  two  tanks,  with  a 
capacity  of  2,500  tons  each.  In  the  other  installation  there  are  six  large 
tanks,  two  small  tanks,  and  a  settling  tank,  with  a  total  capacity  of  16,360 
tons. 

The  tanks  are  of  wrought  iron,  cylindrical  in  shape,  64  feet  in  diameter 
and  33  feet  high,  with  flat  bottoms  and  low-pitched  conical  roo&  of  iron 
plates,  supported  by  iron  principals  resting  on  an  angle-iron  ring,  2  feet 

*  Jftn.  Proc,  Inst,  C.E.,  vol.  xcii.,  p.  178. 

35 


546 


DOCK  ENGINEERING. 


below  tKe  top  of  the  cylinder.  There  are  two  other  angle-iron  rings,  one 
at  the  top  and  the  other  at  the  bottom  of  the  cylinder,  and  between  these 
three  rings  of  tee-iron. 

The  roof-plating  is  about  ^  inch  thick,  and  the  side-plating  ranges  from 
^  inch  thick  at  the  top  to  ^^  inch  at  the  bottom.  The  tanks  are  set  on  a 
bed  of  sand  and  stand  their  full  height  above  the  ground. 

A  vent-hole  is  provided  at  the  apex  of  the  roof,  with  a  screw-down 
cover,  and  there  are  manholes,  with  covers  bolted  on,  in  the  roof  and  also 
in  the  bottom  side-plates. 

The  wrought-iron  settling  tank  is  36  feet  in  diameter  and  5  feet  deep. 
It  is  open  at  the  top,  and  contained  within  a  brick  house  octagonal  in  plan. 

There  are  also  large  barrelling  sheds  and  a  cooperage. 


Fig.  664. — Buoy  with  Anchorage. 

Ordinary  Russian  petroleum  weighs  8^  lbs.  per  gallon,  American  petro- 
leum 8  lbs.  per  gallon.  Petroleum  increases  in  bulk  1  in  200  with  an 
increase  in  temperature  of  10°  F. 

Moorings  may  be  classified  as  water  moorings  and  quay  moorings. 

The  former  class,  the  object  of  which  is  to  afford  means  of  berthing 
ships  while  discharging  cargoes  into  lighters  in  mid-stream  or  in  creeks, 
includes  anchored  buoys  and  piled  stagings.  The  buoys  (fig.  564)  are  secured 
by  chains  to  screw  piles  or  to  heavy  blocks  of  masonry  bedded  in  the  ground. 
The  stagings  (figs.  565  and  566)  consist  of  clusters  of  piles  suitably  braced 
and  stiffened. 


Quay  mooringg  include  tings,  hooka,  bollards,  and  poato.    Ringa  and 
books,  if  placed  in  the  vertical  fcce  of  the  quay,  should  be  recessed  ao  as  to 


Figs.  666  and  666.— Mooring  Strings. 


fFig.  667.— Mooring  Poat.        Fig,  66S.— Mooring  Poet.       Fig.  669.— Mushroom, 
avoid  receiving  or  causing  damage.     Placed  upon  the  quay  surface,  they  are 
•conveoieiit  for  dealing  with  ahips  whose  aides  rise  to  a  considerable  height 


548 


DOCK  ENGINEERING. 


above  the  quay.  Hooked  mooring  posts  and  bollards,  however,  are  the 
more  general  and  satisfactory  arrangement.  These  posts  (figs.  567  and  568) 
are  either  of  cast  iron  or  steel,  and,  occasionally,  of  stone  or  wood.  Hollow 
castings  are  undoubtedly  the  best,  being  strongest,  most  durable  and  com- 
pact, and  comparatively  light. 

Mushrooms  (fig.  569)  are  small,  horizontal,  single  sheaves,  placed  so  a& 
to  act  as  convenient  leads  for  ropes  and  warps  to  capstans. 

Book  Applianoes  at  Hamburg. 

The  following  is  a  list  of  various  lifting  apparatus  in  use  at  the  port  of 
Hamburg  in  November,  1901  : — 

A.  Quay  Crcmes  (all  fixed) — 

1  steam  and  hand  crane,      .         .  12,500  kilogrammes.'"' 

1  electrical  crane,        ....       30,000 

1  steam  crane, 50,000 

1  „  150,000 

B.  Shed  Cranes  (some  fixed  and  some  movable) — 


» 


a 


278  steam  cranes,  .         .         .         . 

.  1,500 

to  2,500  kilogrammes. 

155  hand  cranes,     . 

.  1,000  to  2,000 

Ji 

101  electrical  cranes. 

.  2,500  to  3,000 

if 

27  hydraulic  cranes, 

•                 • 

2,000 

it 

0.  Miscellaneoios  Appliances — 

73  hydraulic  winches  or  jiggers,    . 

750  ^ilogi 

rammes. 

36  hydraulic  winches,   . 

600 

25  hand  winches, .         .         .         . 

500 

75           „            ... 

1                 t 

750 

u           „           ... 

t 

600 

39  hydraulic  lifts, 

* 

1,200 

3  hand  lifts. 

»                          i 

500 

2  steam  winches. 

■ 

1,000 

Equipment  of  the  Fort  of  Havre. 

The  following   is  a  list  of  the   various  appliances  belonging   to    the 
respective  authorities  in  November,  1901  : — 

A.  Ths  Docks- Warehoicses  Company — 
4  fixed  hydraulic  winches,  . 
10  movable  hydraulic  winches, 
1         „       electric  winch,    . 
8         „  „       winches, 

1  fixed  hand  crane, 

2  electric  grain  elevators. 
8       ,.        capstans. 

*  A  kilogramme  is  2*205  lbs.  avoir. 


400 

kilog] 

rammes. 

400  to  900 

» 

150 

n 

500 

9t 

.       10,000 

>* 

ft 


EQUIPMENT  OF  THE  PORT  OF  HAVRE. 


549 


B.  The  Chamber  of  Commerce — 

30  movable  hydraulic  cranes, 

1,250  to  3,000  kUogrammes. 

2        „               „        winches. 

200            „ 

^            i>                     )i                   n 

750  and  1,000            „ 

5         „        steam  cranes, 

1,500 

25         „        electric  cranes,  . 

1,500            „ 

1  steam  floating  crane. 

4  tonnes.* 

*         >>                 j>                 • 

.        .            10      „ 

1  tripod  shears,  . 

.        .            120      „ 

0.  Private  Companies — 

3  floating  shears,         .         2  of  30  tonnes,  1  of  7  tonnes. 

8  electric  winches. 

400  kilogrammes 

6  floating  steam  cranes. 

1,500             „ 

5  fixed  hand  cranes,  respectively, 

5, 10, 12,  15,  25  tonnes. 

7  movable  steam  cranes. 

1  to  2       „ 

2  fixed  steam  cranes,  . 

*2       " 

4     „     hand  cranes,    . 

1          „ 

A  more  detailed  statement  of  the  appliances  used  in  connection  with 
the  working  of  a  single  dock  at  Liverpool  will  be  found  on  the  following 
page.  The  Canada  Dock  is  one  of  the  most  important  on  the  Mersey 
Dock  Estate,  and  it  accommodates  the  largest  vessels  of  the  White  Star 
and  Cunard  Lines.  The  shipping  companies,  however,  themselves  provide 
the  major  portion  of  the  appliances  for  dealing  with  cargo.  These,  and 
various  manual  appliances  provided  by  the  Dock  Board,  are  not  included 
in  the  list. 


A  tonne  is  1,000  kilogrammes  =  2,205  lbs. 


S50 


DOCK  ENGINEERING. 


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INDEX. 


Aberdeen  breakwater,  277. 

,,  Concrete  deterioration  at,  124. 

Accessibility  of  repairing  depots,  464. 

„  of  sheds,  367. 

Accommodation,  Shed,  364. 
Accumulators,  Hydraulic,  619. 
Acid  process,  137. 
Administration,  Dock,  6. 
Africa  Dock  (Antwerp),  13. 
Agents,  Blasting,  86. 
A|;gregate,  117,  130. 
Air,  Compressed,  510. 
Albert  Dock  (Hull),  247. 

,,  (London),  8,  48. 

Albert  Edward  Dock  (Newcastle),  15. 
Alexandra  Dock  (Hull),  42,  265. 
■  ,,  (Liverpool),  10. 

Algiers,  Jetty  at,  281. 
Alk)ys  of  iron,  135. 
Alt-ofen,  Slipway  at,  474. 
Altona,  Quay  wall  at,  214. 
America  Dock  (Antwerp),  13. 
Amsterdam,  Warehouse  at,  404. 
Analyses  of  cement,  119,  125. 
Anchorage,  Buoy,  546. 
„  Gate,  341. 

Angle  of  repose,  157. 
Angus-Smith  process,  146. 
Animals,  Weight  of,  380. 
Antimony,  Enect  on  steel,  135. 
Antwerp,  Port  of,  13. 

Quay  wall  at,  205. 

Sheds  at,  394. 

Swing  bridge  at,  443. 

Traversing  bridge  at,  442. 
Appliances,  Block-setting,  74. 
Apron«  182. 

Arched  bridge.  Stresses  in,  414. 
Ardrossan  Dock,  Entrance  at,  264. 

Dock  walls  at,  184,  218. 

Quay  wall  at,  200. 
Arenc  Basin  (Marseilles),  14. 
Avonmouth,  Gates  at,  303. 

B 

Backing,  Earth,  181. 
Bas  work,  276,  277. 
Baker's  formula,  174. 
Balance  dock,  479. 
Balancing  lever,  437. 

,,         rollers  and  wheels,  434. 


)( 


)i 


»♦ 


»* 


f } 


i> 


II 


II 
i> 
II 
II 
II 
>i 
II 


Ballast  (see  Counterpoise),  427»  438. 

„      box,  438. 
Barcelona,  Port  of,  3. 
Barrow,  Floating  dock  at,  466. 

,,        Petroleum  storage  depot  at,  545. 
,,        Port  of,  3. 
Barry,  Dock  entrances,  263. 
docks,  34. 

Graving  dock  at,  501. 
Port  of,  3. 
Basic  process,  137. 
Basin,  see  also  Dock. 
Half-tide,  237. 
Joliette  (Marseilles),  14. 
Leuve  (Rotterdam),  14. 
Sandthor  (Hamburg),  12. 
Sluicing,  244. 
Tidal,  1,  227. 
Vestibule,  227. 
Basins,  Representative,  55. 
Batter,  18L 
Beaching,  462. 

Beacon  Basin  (Hamburg),  12. 
Beam,  Continuous,  415. 
Beech,  149. 
Belfast,  Caisson  at,  357. 

„      Jetties  and  wharfs  at,  292. 
,,       Quay  wall  at,  199. 
Bermuda,  Floating  dock  at,  505. 
Bessemer  steel,  136. 
Bilge  blocks,  473. 

,,     cods,  495. 
Birkenhead  docks,  9,  29. 

„  Gates  at,  308,  310. 

Blackwall,  Caisson  at,  356. 
Blasting  agents,  86. 
Blocks,  Bearing,  439. 
,,      Bilge,  473,  484. 
„      Keel,  473,  483. 
Block-settinff  appliances,  74. 
Block  work  for  jetties,  276,  277. 
,,  for  quay  walls,  208. 

Blue  gum,  148. 
Blyth,  Dock  gates  at,  334. 

,,    Jetties  at,  284. 
Bollard,  547. 
Bordeaux,  Shed  at,  397. 
Bougie,  Quay  wall  at,  211. 
Boussinesq's  formula,  166. 
Breakwater,  269. 

at  Aberdeen,  277. 
„  Peterhead,  273. 
„  Wick,  273. 
Bremen,  Shed  at,  369,  397. 


19 


II 


11 


Bremen,  Warehouses  at,  369, 397. 

Calcutta,  Swing  bridge  at,  459. 

Bremerhaven,  Gates  at,  144,  306. 

Callao,  Floating  dock  at,  479. 

,,            Graving  dock  at,  496. 

Canada,  Basin  (Liverpool),  243. 

„            Lock,  266. 

Dock  (        „        ),  10,  560. 

Bridge,  Bascule,  407. 

„       Lock   (        „        ),  234,  248. 258. 

^,            ,,        at  Chicago,  447. 

Cantilever  Bridge,  Stresses  in,  412. 

,,            ,,         ,,  Rotterdam,  446. 

Capacity  of  floating  docks,  466. 

„      Double-leaf,  410. 

„        „  graving      „      465. 

„      Folding,  at  Greenock,  442. 

,,        „  slipways,  465. 

,,      Lifting,  409. 

Capstans,  531. 

„       Single-leaf,  410. 

Cardiff,  Caisson  at,  357. 

,,       Stresses  in  movable,  411. 

„       Port  of,  3.  14. 

,,      Swing,  at  Antwerp,  443. 

Careening,  462. 

,,           „        ,,  Calcutta,  459. 

Carey-Latham  concrete  mixer,  69. 

,,           ,,        ,,  Leith,  454. 

Cargoes,  Sample,  366. 

,,           ,,        ,,  Liverpool,  452,  454. 

Cartagena,  Floating  dock  at,  479. 

,,           ,,        ,,  Marseilles,  449. 

Carthage,  Port  of,  2. 

„       Tilting,  at  Marseilles,  452. 
,,      Travelling,  at  Greenock,  460. 

Cast  iron,  133. 

Castings,  Defects  in,  137. 

„      Traversing,  at  Antwerp,  442. 

„        Specification  for,  138. 

„               ,,           ,,  Liverpool,  457. 

Cattle,  25,  380. 

Bridges,  Floating,  405. 

Cement,  Portland,  119. 

„        Swing,  409. 

,,        Roman,  119. 

,,        Traversing,  406. 

Centre  of  buoyancy,  350. 

Bristol,  Port  of,  3,  17. 

gravity,  177,  350. 

Bruges,  Caisson  at,  355. 

,,        pressure,  316. 

Brooming,  60. 

Centrifugal  pumps,  113,  544. 

Brunswick  Dock  (London),  8. 

Chain  pumps,  113. 

Buenos  Ayres  Docks,  36. 

Chains,  Gate,  522. 

„            Gates  at,  303,  345. 

Chaudy's  theorem,  168. 

„            Lock  at,  262. 

Check  chains,  342. 

„            Sheds  at,  401. 

Chelura  ierthrana^  151. 

,,            Warehouses  at,  401. 

Chicago,  Bascules  at,  447. 

Bullet  tree,  148. 

,,        Oibwork  at,  287. 

Buoyancy,  Centre  of,  350. 

Chilled  iron,  136. 

Buoys,  564. 

Chromium,  Effect  on  steel,  135. 

Burrs,  Stone,  130. 

Clapping  sills,  338. 

Bute  Docks  (Cardiflf),  15. 

Clarence  Dock  (Liverpool),  10. 

• 

Clay  foundation,  185. 

C 

Clips,  115. 

Clough,  255,  529. 

Cadiz,  Port  of,  3. 

Clyde,  River,  11. 

Caisson,  301. 

Clydebank  Dock  (Glasgow),  12. 

„       at  Belfast,  357. 

CoaX  tips  and  lifts,  538. 

„        ,,  Bruges,  355. 

Coalinff  ports,  25. 
Coffenmms,  105. 

,,        „  Calcutta,  357. 

„         „  Cardiff,  357. 

Columns  and  piers.  Shed,  381. 

,,        .,  Dundee,  352. 

Strength  of,  382. 

,,        ,,  Greenock,  360. 

Compartments,  Shed,  373. 

,,        „  Liverpool,  360. 

Compound  gates,  309. 

,,        ,,  London,  357. 

0)m  pressed  air,  510. 

„        „  Malta,  354. 

Concrete,  117. 

„       Box,  354. 

,,        Action  of  sea  water  on,  123. 

„        Floating,  356. 

) 

bags,  130. 

,,        Rolling,  355. 

,,        blocks,  130. 

„       Ship,  357. 

Sliding,  354. 
„       Swinging,  351. 

,,        mixers,  66. 

1 

„        moulds,  73. 

,,        Notes  on  mixing,  130. 

„       Traversing.  352. 

1 

,        Sample  compositions,  132. 

Caissons,  Pneumatic,  201. 

1 

„        Strength  of,  131. 

„        Stresses  in,  350. 

Conjugate  pressures.  Theory  of,  159. 

Calais,  Sheds  at,  396. 

Connecting-pieces,  328. 

Calculations,  Gate,  332. 

O)nstruction,  Methods  of  wall,  197. 

Calcutta,  Ba.sin  waU  at,  182. 

Continuous  Beam,  Theory  of  the,  416. 

,,        Docks,  40. 

Copper,  Effect  on  steel,  135. 

,,         see  also  Kidderptir, 

Cork 

,  Quay  wall  at,  191,  210. 

INDUX. 


553 


)» 


it 


t) 


>t 


1} 


It 


Corrosion  of  iron  and  steel,  140. 
Corrugated  iron,  386. 
Cost  of  caissons,  362. 

dock  gates,  304. 

floating  docks,  467,  468. 

graving  docks,  467,  468. 

power  supply,  615. 

slipways,  466. 

wet  docks,  26. 
Cottangin  system,  379. 
Coulomb's  theorem,  167. 
Counterforts,  172,  182. 
Counterpoise  (see  Ballast),  412, 413, 419, 437. 
Crab  engine  (pile  driver),  57. 
Cradle,  463,  473,  484,  495. 
Cram  pile  driver,  60. 
Crane  tests,  514. 
Cranes,  114,  485,  514,  532. 
Creosote,  152. 
Cribwork,  286. 
Crowds,  Weight  of,  426. 
Culverts,  Friction  in,  240. 

,,        Levelling,  255. 
Curb,  188,  195. 
Current,  231. 
Currents,  Electric,  620. 
Cylinder  foundations,  Brick,  188. 

Concrete,  190. 
Iron,  189. 


>» 


it 


>» 


)> 


It 


it 


tt 


tt 


ti 


Dams,  103. 

„      Coffer-,  105,  259. 
,,      Concrete,  109,  259. 
„       Construction  within,  199. 
Earth,  104,  260. 
Iron,  110. 
Skin,  104. 
Stone,  109. 
Timber,  104,  200. 
Dayde  and  Pill^  transporter,  538. 
Deal,  149. 

Decay  of  timber,  161. 
Dedemsvaart,  Canal  gates,  306. 
Defects  in  castings,  137. 

„         rolled  plates  and  bars,  138. 
Definitions,  1. 
Deodar,  148. 
Depositing  dock,  480. 
Design,  Bridge,  441. 

,,       Graving  docks,  475. 
,,       Jetty  and  pier,  274. 
Destruction  of  timber,  151. 
Dhu  Heartach  Lighthouse,  273. 
Dieppe,  Shed  at,  397. 
Dimensions  of  entrances,  233. 
Direction  of  entrances,  233. 
Discharge  of  culverts,  241. 
Dock,  see  also  Basin  and  under   Special 
Names, 
administration,  6. 
Balance,  479. 
Depositing,  480. 
Dry  or  graving,  1,  464. 


tt 


tt 


tt 


tt 


It 


Dock,  Floating,  1,  464. 

,,      Greenland  (London),  4,  8. 
,,      Howland  (London),  4,  8. 
„      Off-shore,  480. 
„      Old  (Liverpool),  3,  10. 
,,      Sectional,  479. 
Slip,  1,  463. 
system.  Model,  22. 
Wet,  1 ,  3. 
Docking  of  ships,  225. 
Docks,  Kepresentative,  54. 
Doors,  Folding,  373. 
„      Rolling.  372. 
„      Shed,  372. 
„      Sliding,  372. 
Doorways,  Shed,  371. 
Dover,  Jetty  at,  280. 
,,      Port  of,  3. 
„      Slipway  at,  475,  493. 
Drainage,  181. 
Drawbridges,  407. 
Dredgers,  88. 

Clam-shell,  100. 
Dipper,  98. 
Grao  or  grapple,  100. 
Hopper,  88. 
Ladder,  94. 
Land,  76. 
Suction,  >9. 
Dredging,  Cost  of,  103. 

,,         Maintenance,  246. 
Drilling  appliances,  85. 
Dublin,  Gates  at,  303. 
,,       Quay  wall  at,  208. 
,,       Swing  bridge  at,  436. 
Dundee,  Caisson  at,  .352. 
,,        Coal  tip  at,  539. 
,,        Sheds  at,  390. 
„        Wharf  at,  293. 
Dunkirk,  Bason  of,  5. 

Gates  at,  .303,  345. 
Jetty  at,  294. 
Lock  at,  260. 
Sheds  at,  .397. 
Durability  of  dock  gates,  306. 

,,  floating  docks,  469. 

,,  graving  docks,  469. 

Duration  of  levelling  operations,  257. 
Dynamos,  521. 


>» 
tt 
tt 

I* 


I) 

)* 

tt 


tt 


Eastuam  entrance  locks,  263. 

Efficiency  of  hydraulic  power,  511. 

Eglinton  Dock  entramce  (Ardrossan),  264. 

Ejector,  111. 

Electric  pile  driver,  61. 

Electrical  distribution  of  energy,  520. 

Electricity,  512. 

Elevators,  Grain,  539. 

Elm,  149. 

Emden,  Shed  at,  403. 

Empirical  formulae  for  retaining  walls,  174. 

Empress  Dock,  Southampton,  21,  216. 

Energy,  Comparative  expenditures  of,  612. 


554 


INDEX. 


Entrance  at  Ardrossan,  264. 

,,        channels,  227. 
Entrances,  225,  235. 

„         at  Barry.  263. 
„         at  Calcutta,  263. 
Equipment  of  repairing  docks,  483,  510. 

„  wet  docks,  5()9. 

Euler*8  formula,  383. 
Excavators,  76. 


Failures  in  c^uay  walls,  213. 
Fairway,  Maintenance  of,  237. 
Fan  door,  256,  260. 
Fanshawe's  formula,  174. 
Fascine  work,  282. 
Felspar,  153. 
Fetch,  229. 
Fidler's  formula,  383. 
FilUng  behind  walls,  181. 
Fineness  of  cement,  122. 
Fir,  149. 

First  wet  dock,  3. 
Fittings  for  gates,  337. 
Float,  East  (Birkenhead),  10. 
„      West,  „  10. 

Floating  cranes,  534. 

,,        dock  at  Bermuda,  505. 
„  „       Cartagena,  479. 

Floors,  Shed,  370,  375. 
Flour,  25. 

Footbridges  at  Liverpool,  457. 
Footsteps,  Gate,  341. 
Foreign  trade,  15. 
Formula  for  columns,  Euler's,  383. 

Fidler's,  383. 
Gordon's,  384. 
,,      for  retaining  walls.  Baker's,  174. 

„     Boussinesq's, 

166. 
,,     Chaudy's,  169, 

170. 
,,      Coulomb's, 

167. 
,,     Fanshawe's, 

174. 
,,      Rankine's, 
163,  165. 
„      Reilly's.  166. 
, ,      Scheffler's, 
165. 
,,      Kutter's  hydraulic,  242. 
Foundations,  183,  247,  261,  263,  265,  470, 

477,  497,  500. 
Framework,  Weight  of  bridge,  423. 
French  steam  excavator,  77. 
Friction,  177,  239. 

,,        in  culverts,  240. 

,,        in  slipways,  474. 

**Fulda,"  Mishap  to  s.8.,  485. 

6 

Galvanised  iron,  386. 
Galvanising,  146. 


»» 

I  9 


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«» 


>  » 


tf 


f  » 


it 


it 

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Gantries,  114. 

Gate  calculations,  332. 

Gates  at  Blyth,  334. 

Bremerhaven,  144,  306. 
Buenos  Ayres,  303,  345. 
Calcutta,  345. 
Dunkirk,  345. 
Goestemunde,  143. 
Gluckstadt,  143. 
Harburg,  144. 
HuU,  344. 
Liverpool,  342. 
Manchester,  342. 
Corrosion  of,  143. 
Dock,  301,  349. 
Double-leaf,  312. 
Single-loaf,  310. 
Storm,  313. 
Strut,  314. 
Geestemunde,  Floodgates  at,  143» 
Generating  stations,  510,  512. 
Genoa,  Port  of,  3. 
George's  Dock  (Liverpool),  10. 
German  steam  excavator,  79. 
Girders,  Weight  of  bridge,  423. 
Glasgow  docks,  40. 

Gravine  dock  at,  499. 
Port  of,  3,  11. 
Quay  wall  at,  192. 
,,        Sheds  at,  392. 
Gluckstadt,  Gates  at,  306. 
,,  Sheds  at,  143. 

"  Goliath,"  74. 
Gordon's  formula,  384. 
Grabs,  84. 
Grain,  25. 

,,      elevators,  539. 
Granite,  153. 

Grasbrook  Basin  (Hamburg),  12. 
Graving  dock  at  Barry,  501. 

Bremerhaven,  49^ 
Glasgow,  499. 
Liverpool,  498. 
London,  504. 
Gravity,  CJentres  of,  177,  350. 
,,        concrete  mixer,  71. 
Greenheart,  147,  303,  304. 
Greenland  Dock  (London),  4,  8. 
Greenock,  Dock  walls  at,  222. 

Folding  bridge  at,  442. 
Rolling  bridge  at,  460. 
Warehouses  at,  391. 
„         Wharfs  at,  299. 
Gridiron,  462,  491. 

„        at  Liverpool,  491. 
Grouped  docks,  24. 
Guncotton,  87. 
Gunpowder,  87. 


H 


Half-tide  basins,  237. 

Hamburg,  Dock  appliances  at,  548. 

docks,  43. 

Port  of,  12. 


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f » 


i> 


»> 


INDEX. 


555 


Hamburg,  Sheds  at,  400. 
Hansa  Basin  (Hamburg),  12. 
Harbour,  Old  (Marseilles),  14. 
Harbours,  2. 

Harburg,  Lock  gates  at^  144. 
Haulage,  87. 

,,        Slipway,  641. 
Havre,  Dock  appliances  at,  549. 
„      Pier  at,  280. 
„      Port  of,  62. 
„      Sheds  at,  396. 
Heel-post,  313. 
Hemlock,  160. 

Hennebique  construction,  291,  378. 
Herring  Basin  (Rotterdam),  14. 
Hoists,  Coal,  638. 
Hooghly,  Slipway  on  the,  476. 
Hook  of  Holland,  Jetty  at,  283. 
Hooks,  48^1,  647. 
Hopper  barge,  8S. 

„       dredger,  88. 
Howland  Great  Wet  Dock  (London),  4,  8. 
Hull,  Dock  walls  at,  220,  222. 
,,     docks,  42. 
,,     Gates  at,  346. 
,,     Lock  at,  266. 
,,     Port  of,  3. 
•   ,,     Slipway  at,  472. 
„     Wharfs  at,  300. 
Huskisson  Dock  (Liverpool),  10,  217. 
Hydraulic  accumulators,  519. 
lift,  463. 

,,    at  London,  492. 
machinery,  511,  616. 
navvy,  81. 
pile  driving,  61. 


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it 


II 


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if 


ft 


tt 


I 


India  Basin  (Hamburg),  13. 
„     Dock,  East  (London),  8,  47. 

„      South-West  (London),  8,  47, 

216. 
,,      West  (London),  8,  47. 
Inner  Basin  (Rotterdam),  14. 
Interlocking  apparatus,  440. 
Internal  dispositions,  26. 
Iron  alloys,  136. 
„    and  steel,  133,  306. 
,,    Galvanised  and  corrugated,  386. 
„    piers,  287. 
Ironbark,  148. 


Jabrau,  148. 
Jetty,  268. 

at  Algiers,  281. 

„  Belfast,  292. 

„  Blyth,  284. 

„  Dover,  213. 

,,  Dunkirk,  294. 

,,  Liverpool,  285. 

„  Tilbury,  296. 


I) 
It 

tt 
tt 
ft 
t» 


Jetty  at  Touaps6,  289. 

,,     „  Zeebrugge,  289. 
Jigs^ers,  636. 
Joliette  Basin  (Marseilles),  14. 


K 

Kakaballi,  148. 

Karri,  148. 

Katendrecht  Basin  (Rotterdam),  14. 

Kattendyke  Dock  (Antwerp),  13. 

Keel  blocks,  473,  483. 

Keyaki,  148. 

Keyham,  Constructive  plant  at,  116. 

Kiaderpur  (Calcutta),  Caisson  at,  367. 

(      ,,       ),  Dock  entrances,  263. 

(       „       ),  Docks,  40,  216. 

(      ,,       ),  Gates  at,  346. 

(       „       ),  Sheds  at,  400. 
King's  Basin  (Rotterdam),  14. 

,,      Dock  (Liverpool),  10. 
Kingston  Dock  (Glasgow),  12. 
Knuckle  gear,  439. 
Kurrachee,  Block  work  at,  211. 
Kutter's  formula,  242. 


II 
»i 
II 
II 


Lairaobs,  25. 

Land  dredgers,  76. 

Langton  Dock  (Liverpool),  10. 

Lazaret  Basin  (Marseilles),  14. 

Lead,  385. 

Leaf  of  gates,  310. 

Leith,  lA>ck  wall  at,  181. 

„      Gate  machinery  at,  625. 
,,     Port  of,  3. 
„     Swing  bridge  at,  454. 
Leuve  Basin  (Rotterdam),  14. 
Lewis  bars,  116. 
Uft,  Hydraulic,  463. 
Lifts,  Coal,  538. 
Light  for  repairing  depots,  465. 
Lighting  of  sheds,  375. 
Limerick,  Dock  wall  at,  187. 

Gates  at,  303,  309. 

Pneumatic  grain  apparatus  at, 
641. 

Limestone,  154. 
Limits  of  stress  in  gates,  326. 
Limnoria  terebrans,  151,  307. 
Liverpool,  Caisson  at,  360. 

Dock  equipment  at,  649. 

Dock    walls  at,   184,  198,  218, 
220,  223. 

Docks  29. 

Gates  at,  303,  306,  308,  332,  342. 

Graving  dock  at,  498. 

Gridirons  at,  491. 

Jetties  at,  286. 

Lock  at,  268. 

Port  of,  3,  9. 

Sheds  at,  370,  387. 

Swing  bridge  at,  452,  454. 

Traversing  bridge  at,  457. 


II 
II 


II 


II 


II 


II 


II 
II 
•I 
II 
II 
II 
It 
II 


556 


INDEX. 


»» 


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»» 


Load,  Dead,  423. 

,,     Movine  or  live,  424. 
Loads  on  brioges,  422. 
Lock  at  Barry,  263. 

Bremerhaven,  266. 

Buenos  A3rre8,  262. 

Dunkirk,  260. 

HuU,  265. 

Liverpool,  258. 
Lockage,  236. 
Locks,  225,  235. 

„      Eastham,  263. 
Locomotives,  Weight  of,  425. 
London  Docks  (London),  S,  46. 

Graving  docks  at,  504. 

Hydraulic  lift  at,  492. 

(Limekiln),  Caisson  at,  357. 

Pneumatic  grain  apparatus  at,  540. 

Port  of,  3,  8. 

see  also  Tilbury, 
Lormont,  Slipway  at,  474. 


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If 


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Machinery,  Dock  gate,  522. 

,,  Hydraulic,  511,  516. 

„  Sluicing,  529. 

Madero  Docks  (Buenos  Ay  res),  38. 
Madras,  Pierheiad  at,  295. 
Maintenance  of  repairing  depots,  468. 
Malta,  Caisson  at,  354. 

„      Hydraulic  crane  at,  536. 
Manchester,  Dock  wall  at,  223. 
Gates  at,  342. 
Port  of,  3. 
Warehouses  at,  392. 
Manganese,  Influence  on  steel,  134. 

„  steel,  134. 

Maritime  engineering.  Development  of,  2. 
Marseilles,  Dock  walls  at,  201. 
Port  of,  13,  53. 
Sheds  at,  395. 
Swing  bridge  at,  449. 
Tilting  bridge  at,  452. 
Masonry  piers,  279. 
Mass  work,  275,  277. 
Matrix,  117. 

Men,  Weight  of  a  crowd  of,  426. 
Merchandise,  Weight  of,  380. 
Mersey  Docks  and  Harbour  Board,  29. 

„      River,  29. 
Messent  concrete  mixer,  66. 
Metacentre,  351. 
Meuse  Basin  (Rotterdam),  14. 
Mica,  153. 

Middlesbrough,  Port  of,  3. 
Middlehead,  313. 
Millwall  Docks  (London),  8,  45. 
Mitre-post,  313. 
Mixers,  Concrete,  66. 
Model  dock  system,  22. 
Moldau  Basin  (Hamburg),  3. 
Mole,  269 

,,      at  Hook  of  Holland,  283. 
„      at  Zeebrugge,  278. 
Monier  construction,  290,  376. 


Monolithic  construction,  208. 
Mooring  post,  547. 
Moorings,  546. 
Mora,  147, 
Motors,  521. 
Moulds,  Concrete,  73. 
Mud  Docks,  478. 
Mushroom,  547. 


N 


Nasmyth  hammer  pile  driver,  60. 
National  Basin  (Marseilles),  14. 
Navvies,  Hydraulic,  84. 

,,        Steam,  81. 
Necessity  for  docks,  17. 
Newcastle,  Coaling  staiths  at,  284. 

, ,         Port  of,  3. 

„         Quay  walls  at,  190,  196. 
New  York,  Port  of,  10. 
Nickel  steel,  134. 
Nitro-glycerine,  87. 
North  Lock  at  Buenos  Ay  res,  262. 

„  ,,  Dunkirk,  260. 

Northumberland  Dock  (Newcastle),  15. 


Oak,  149,  304. 

Offsets  in  walls,  181. 

Offshore  dock,  480. 

Old  dock  sill,  3. 

Open  construction  of  walls,  197. 

Overhang  of  vessels,  491. 

OverhauUng  a  floating  dock,  482. 


Painting,  145. 

Palermo,  Slipway  at,  474,  475. 

Panels,  Stresses  in,  331. 

,,      Thickness  of  gate,  332. 
Park  Basin  (Rotterdam),  14. 
Passages,  Dock,  225. 
Pedestrians,  Weight  of,  426. 
Penstock,  255. 
Periphery  of  docks,  24. 
Permanent  way,  472. 
Peterhead  Breakwater,  273. 
Petroleum,  25,  545. 

,,         Basin  (Hamburg),  13. 
Phosphorus,  Effect  on  iron  and  steel,  135. 
Pholaa  dactyltis,  151,  154,  155. 
Pier,  268. 

,,    at  Havre,  280. 

,,     „  Kinffstown,  280. 

,,      ,,  Soukhoum,  287. 
Pierhead  at  Madras,  295. 
Piers  at  Sunderland,  297. 
Pig-iron,  136. 
Pile  drivinff,  56. 
Piled  foundations,  186. 
Piling  machines,  57. 


INDEX. 


557 


») 


»> 


II 


»» 


>» 


»» 


n 


»» 


ti 


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»> 


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j» 


»> 


> » 


Piles,  Timber,  61,  261. 
,,      Hemiebique,  63,  291. 
, ,      Limit  of  driving,  64. 
,,      Supporting  power  of,  64. 
Pine,  149,  304. 

Pin^e  Basin  (Marseilles),  14. 
Pipe  trench,  183. 
Pit,  Rudder,  485. 
Pitchpine,  149,  304. 
Pivot,  Bridge,  428. 

at  Dublin,  433. 
„  Fleetwood,  431. 
,,  Ha  warden,  431. 
„  Liverpool,  430,  432. 
,,  Marseilles,  432. 
„   Karitan,  430. 
,,  Rotterdam,  429. 
,,  Velsen,  428. 
Hydraulic  or  water,  432,  439. 
Plant,  List  of,  at  Keyham,  llo. 
Plates  and  bars.  Iron,  139. 
Plating,  Thickness  «jf ,  332. 
Platform,  Caisson,  360. 

Gate,  341. 
Platforms,  252. 
Plough,  473. 
Plums,  Stone,  130. 
Plymouth,  Port  of,  3. 
Pneumatic  appliances,  485,  510,  540. 

f,  chambers,  Construction  within, 

210. 
Port  trusts,  7,  9,  10. 

,,    -Glasgow,  11. 
Porte,  Functions  of,  2. 
Position  of  docks,  19. 
Posts,  Mooring,  547. 
Power,  Comparison  of  supply,  513. 
Cost  of,  515. 
of  gate  machines,  525. 
,,  sluice  machines,  530. 
„       Sources  of,  509. 
Preservation  of  iron  and  steel,  145. 

,,  „  timber,  152. 

Pressure,  Fluctuations  in  hydraulic,  520. 
„        on  keel  blocks,  485. 
,,        Resultant,  315. 
Pressures,  Theory  of  conjugate,  159. 
Prince's  Dock  (Glasgow),  10,  40. 

„  (Liverpool),  10. 

Progress,  Recent,  in  dock  construction,  5. 
Pulsometer,  111. 
Pumping,  469. 
Pumps,  111,  544. 

„       Centrifugal,  113,  497, 498,  501,  602, 

505,  544. 
„       Chain,  113. 
„       Hand,  112. 
,,       Turbine,  545. 
Valve,  111,  544. 
Purpleheart,  147. 


»« 


ti 


ii 


Q 


Quartz,  153. 
Quay  moorings,  547. 


Quay  space,  23. 

Queen's  Dock  (Glasgow),  10,  40. 

,,  (Liverpool),  10. 

Quiescence,  63. 
Quoin,  Hollow,  253. 


Rails,  473. 

Railway  basin  (Marseilles),  14. 
,,  ,,     (Rotterdam),  14. 

Ram  and  fall  for  driving  piles,  63. 
Rams,  Hydraulic,  523. 
Rankine's  theorem,  160. 
Recesses,  253. 
Red  gum,  148. 
Reilly's  theory,  165. 
Repairing  depots,  462. 
Repose,  Angle  of,  157. 
Resultant  pressure  on  dock  gate,  318,  324. 
Rhine  basin  (Rotterdam),  14. 
Ringing  piling  machine,  57. 
Rise  of  gates,  323. 
Rivets,  140. 

Roath  Dock  (Cardiff),  15. 
Rock  foundation,  184. 
Roof  coverings,  385. 
Roofs,  Weight  of,  386. 
Rollers,  Gate,  337. 
Roman  Engineering,  2. 
Rot,  Wet  and  dry,  151. 
Rotherhithe,  Dock  at,  3. 
Rotterdam,  Bascule  bridges  at,  445. 

Port  of,  14. 

Quay  wall  at,  186. 

Sheds  at,  394. 

Warehouses  at,  394. 
Rouen,  Quay  wall  at,  187. 

,,       Shed  at,  397. 
Rudder  pit,  485. 
Ruston  steam  navvy,  81. 


»» 


») 


}» 


1* 


Saale  Basin  (Hamburg),  13. 

Sai  or  Saul,  149. 

Salmon  Basin  (Rotterdam),  14. 

Salthouse  ]>)ck  (Liverpool),  10. 

Sand,  119,  121,  127. 

Sand  and  gravel  foundations,  185. 

Sandstone,  154. 

Sandthor  Basin  (Hamburg),  12. 

Saxicavay  155. 

Scheffler's  theory,  165. 

Scraping,  246. 

Scuttling,  246. 

Sea  water.  Action  of,  on  concrete,  123. 

„         Composition  of,  125,  145. 
Sectional  dock,  479. 
Sediment,  232. 
Selection  of  timber,  150. 
Setting  apparatus,  438. 
,,       of  cement,  121. 
Sfax,  Quay  wall  at,  213. 


558 


INDEX. 


if 
>» 
if 
l» 

a 
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If 

)» 
»i 

»» 
»» 


Shape  of  docks,  20. 
.Sheds  at  Antwerp,  394. 
Bremen,  397. 
Buenos  Ay  res,  401. 
Calais,  396. 
Calcutta,  400. 
Dieppe,  397. 
Dundee,  390. 
Dunkirk,  397. 
Emden,  403. 
Glasgow,  392. 
Hamourg,  400. 
Havre,  395. 
Liverpool,  387. 
London,  386. 
Marseilles,  395. 
Rotterdam,  394. 
Rouen,  397. 
Zeebrugge,  403. 
fiheds.  Transit,  364. 
Sheemess,  Quay  wall  at,  18L 
Ship  design,  27. 

Shipbuilders'  basin  (Rotterdam),  14. 
Shoe,  Cylinder,  193. 
Siemens- Martin  steel,  137. 
Silicon,  Effect  of,  on  iron  and  steel,  135. 
Sill,  Old  dock,  3. 
Sills  of  entrances,  2.34,  251. 
Simpson  and  Porter  excavator,  81. 
■Sissons  and  White  pile  driver,  57. 
Skips,  114. 
Slate,  .385. 
Slides,  484. 
Slip-docks,  463. 
Site  of  entrances,  226. 
5lipway  at  Dover,  493. 
Broadside,  474. 
Haulage,  541. 
Sliding,  474. 
Slipways,  463. 

,,  Stresses  in,  474. 

Sluice,  Stoney,  256. 
Sluices,  Gate,  341. 
Sluicing,  237. 

,,       basins  at  Ostend,  244. 
,,        machinery,  529. 
Shores,  484. 
Sidon,  Port  of,  2. 
Smyrna,  Quay  wall  at,  213. 
Soukhoum,  Pier  at,  287. 
Soundness  of  cement,  122. 
Southampton  Docks,  21. 
Specification  for  castings,  138. 

,,  plates  and  bars,  139. 

Spree  Basin  (Hamburg),  13. 
Spruce,  149. 

St.  Katharine's  Dock  (London),  8,  46. 
Stability  of  loose  rubble,  281. 

retaining  walls,  174. 
shingle,  281. 
, ,  vessels  under  water-ballast,  481. 

StAith,  270. 

Staiths  at  Newcastle,  284. 
Steam,  510. 
Steam  navvies,  8L 
Steel,  133. 


>) 


»i 


ft 


ft 


«i 


Steel,  Manganese,  134. 
„     Nickel,  135. 
.  Steining,  189. 
Stock-ramming,  250. 
Stone,  153. 

,,      Compressive  strength  of,  154. 
'  Storm  gates,  313. 
„      of  1703,  4. 
Stratified  foundations,  185. 
Strength  of  cement,  120. 
concrete,  131. 
dock  gates,  308. 
iron  and  steel,  139. 
timber,  150. 
Stresses  in  bridges,  411. 
gates,  314. 
graving  docks,  475. 
piers  and  jetties,  270. 
Stringy  bark,  148. 
Strut  gates,  314. 
Struts  or  rams,  523. 
Suez,  Block  work  at,  211. 
Sulphur,  Effect  of,  on  iron  and  steel,  135. 
Sunderland  Docks,  50. 
„  Gates  at,  307. 

,,  Piers  at,  297. 

Surcharge,  171. 

Surrey  Commercial  Docks,  3,  9,  49. 
Sutchffe  concrete  mixer,  71. 
Swansea  Docks,  51. 
Swing  bridge  at  Dublin,  435. 
Swinging  caissons,  351. 
System,  Model  dock,  22. 


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If 
If 


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If 


If 


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ft 
fi 


Taylor  concrete  mixer,  69. 

Teak,  149. 

Temperley  transporter,  537. 

Teredo  navcUis,  151,  307. 

TermeSf  151. 

Tests  for  cement,  120. 

„      ,.  iron  and  steel,  139. 
Temeuzen,  Gates  at,  3()6. 
Theorem,  Chaudy's,  168. 
Clapeyron's  417. 
Coulomb's,  167. 
Rankine's,  159. 
of  three  moments,  417. 
Tide,  Range  of,  18. 
Tie-rods  and  bars,  173. 
Tilbury  (London),  Dock  wall  at,  223. 

(      „      ),  Docks,  9,  38. 

(      If      )f  graving  docks,  504. 

(      ,,      ),  Jetty  at,  295. 

(      „      ),  Sheds  at,  386. 
Timber,  25. 

Decay  and  destruction  of,  151. 

Durability  of,  147. 

for  various  purposes,  146. 

graving  docks,  477. 

piers,  2S2. 

Preservation  of,  153. 

Selection  of,  150. 

Weight  and  strength  of,  150l 


f  f 
ff 
tf 
ff 


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f  f 
i> 
If 


f  I 


INDEX. 


559 


Tips,  Coal,  638. 

Titan,  74. 

Titanium,  Effect  on  steel,  135. 

Toe,  182. 

Toggle  gear,  439. 

Traction,  87. 

Trafalgar  Dock  (Liverpool),  10. 

Transporters,  537. 

Travellers,  Overhead,  114. 

Traversing  caissons,  352. 

Trench  construction  of  walls,  198. 

Trusts,  Port,  7,  9,  10. 

Tungsten,  Efiect  on  steel,  135. 

Turbine  pumps,  545. 

Tyne  Dock  (Newcastle),  15. 

„    Gates  on  the,  345. 

,,    ports,  15. 
Tyre,  Fort  of,  2. 
Tongue,  270. 
Touaps^,  Jetty  at,  289. 


U 


Undebfinninq  or  underbuilding,  218. 


Vkhicles,  Weight  of,  426. 
Venice,  Port  of,  3. 
Ventilation,  465. 
Vessels,  Largest  modem,  466. 
Victoria  Dock  (London),  8,  48. 
,,  (Liverpool),  10. 

Voussoirs,  Gate,  313,  329. 


W 

Waggons,  88. 

Wall,  Dock,  at  Greenock,  220. 

Hull,  221,  223. 


>» 

it 

19 
»> 
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»» 
If 
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It 
»» 


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Liverpool,  198,  217,  223. 

London,  216. 

Manchester,  223. 

Marseilles,  201. 

Southampton,  216. 
Lock,  254. 
Quay,  at  Altona,  214. 

Ardrossan,  200,  218. 

Belfast,  199. 

Bougie,  211. 

Cork,  190,  210. 

Dublin,  208. 

Glasgow,  191. 

Newcastle,  190,  195. 

Rotterdam,  207. 

Sfax,  213. 
Walls,  Dock  and  quay,  156. 

Retaining  or  revetment,  156. 


>> 
»> 
if 

99 


»f 
» 
I) 
)l 
II 
11 


)> 


II 
If 
11 
II 
II 
l> 


Walls,  Stresses  in,  157. 
Warehouse  at  Amsterdam,  404. 
„  Bremen,  397. 
,,  Buenos  Ay  res,  401. 
,,  Greenock,  391. 
„  Manchester,  392. 
,,  Rotterdam,  394. 
Basin  (Rotterdam),  14. 
Warehouses,  364. 
Water  area,  23. 

ballast,  481. 

for  concrete  mixing,  122. 
moorings,  546. 
Pressure  of,  315. 
supply,  26. 
under  pressure,  51 1. 
Waterloo  Dock  (Liverpool),  10. 
Wave  action,  Listances  of,  273,  281. 
Waves,  229,  270,  281. 
Weaver,  Gates  on  the,  307. 
Weight  of  animals,  380. 

bridge  structures,  423. 
dock  gates,  303. 
earthwork,  170. 
iron  and  steel,  140. 
locomotives,  425. 
pedestrians,  426. 
timber,  150. 
vehicles,  426. 
walls,  173. 
Well  foundations,  186. 
Wharf,  269. 

at  Belfast,  292. 
,,  Dundee,  293. 
,,  Greenock,  299. 
„  Hull,  300. 
Whitaker  steam  excavator,  84. 

„  ,,      hammer  pile  driver,  58. 

Wick  breakwater,  273. 
Wind,  227. 

,,      screens,  130. 
Winding  engines,  87. 
Wine  Basin  (Rotteidam),  14. 
Wrought  iron,  133. 


IS 

II 
>> 
II 
II 
II 
11 
>» 
♦» 


>l 

19 

II 
II 


Ymuiden  breakwater,  274. 

Electric  dough  at,  528. 

„       connections  at,  529. 
Gates  at,  306,  307. 


i> 

II 
II 


Zeebbugge,  Jetty  at,  279,  289. 

„  Shed  at,  403. 

Zinc,  385. 

,,    roofs  at  Liverpool,  385. 
Zones  of  equal  water  pressure,  322. 


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Working  Drawings  and  280  lUnsferationfl  in  ike  Text.     21a. 

A     MANUAL     OF 

LOCOMOTIVE    ENGINEERING: 

A  Praetieal  Text-Book  for  the  Use  of  Engine  Builders, 

Designers  and  Draagfatsmen,  Rulway 

Engineers,  and  Students. 

By  WILLIAM  FRANK  PETTIGREW,  M.Inot.CE. 

With  a  Section  on  American  and  Continental  Engines. 

By  albert  F.   RAVENSHBAR,    B.Sc, 

Of  Hb  Ifisjesty't  Pfttent  Office. 

CInUeiiM.  ' Historical  Introdaction,  1768-1868.^ Modern  Looomottvee :  Simple.— 
Uodem  LocomoUvea :  Compound.  Primary  Conalderation  in  LooomotiTe  Deaign.— 
Cylinders,  Steam  Cheats,  and  Staffing  Boxes.— Pistons,  Piston  Rods,  Croaataeads,  and 
SUde  Bars.— Oonneoting  and  ConpUng  Bods.— Wheels  and  Axles,  Axle  Boxes,  Hornbloeka, 
and  BearinjK  Springs.— Balancing.— Valve  Gear.- Slide  ValTCs  and  Valve  Qear  Details.— 
Framing,  Bogies  and  Axle  Tracks,  Radial  Axle  Boxes.— Boilers.—Smokebox.  Blast  Pipe, 
nreboz  Fittings.— Boiler  Monntings.— Tenders.  -  Railway  Braken.—  Lubrication. ->00D- 
fomptloii  of  FaeU  Evaporation  and  Engine  Lffidency.— American  Locomotives —Oon- 
tinental  Looomotivea.— Repairs,  Running^  Inspection,  and  Renewals.— Three  Appendieea. 
— Indez. 

**Tlie  work  ooHTAura  all  that  cah  bb  lxabxt  fkx>m  a  book  apon  sach  a  sabjeot  It 
will  at  onoe  rank  as  thb  stabdabd  wobk  upoh  tbis  importaht  sCBJacr.*'— Aatiwoy  Magaximt. 


At  Press.     In  Large  8vo.     Fully  Illustrated. 

LOCOMOTIVE  COMPOUNDING  AND  SUPERHEATINa 

By    J.    F.    GAIBNS. 

Contents.— Introductory.— Compounding  and  Superheating  for  Locomotives.— A 
Classiflcation  of  Compound  Systems  lor  Locomotives.— The  History  and  Development  of 
the  Compound  Locomotive.  —  Two-Cylinder  Non-Automatic  Systems.  —  Two^ylinder 
Automatic  Systems.— Other  Two-Cylinder  Systems.- Three-Cylinder  Systems.— Four- 
Cylinder  Tandem  Systems.— Four-Cylinder  Two-Crank  Systems  (other  than  Tandem). — 
Four-Cylinder  Balanced  Systems.- Four-Cylinder  Divided  ana  Balanced  Systems. — 
Articulated  Compound  Engines.— Triple-Expansion  Locomotives.— Compound  Rack 
Locomotives.— Concluding  Remarks  Concerning  Compound  Locomotives.— The  Use  of 
Superheated  Steam  for  Locomotives.— Index. 


In  Large  8vo.     Handaome  Cloth.     With  Plates  and  lUustratioM.     16%. 

LIOHT       R  A  I  ILi  "BIT  A  ir  S 

AT  HOME  AND  ABROAD. 

Br  WILLIAM   HENRY  OGLE,   M.Inst.O.E., 

Late  Deputy-Manager,  North-Western  Railway,  India. 

Contend.— DiflcuBsion  of  the  Term  "Li^ht  RulwayB.''— English  Railwm, 
Rates,  and  Farmers.  —  Lijght  Railways  m  Belgium,  France,  Italy,  other 
European  Countries,  America  and  the  Colonies,  India,  Ireland.— Roaa  Trana- 
port  as  an  alternative.— The  Light  Railways  Act,  1896.— The  Question  of 
Gauge.— Construction  and  Working. — Locomotives  and  BU)lliiig-Stock. — Li^^t 
Railways  in  England,  Scotland,  and  Wales.— Appendices  and  Index. 

"  Will  remain,  for  some  time  yet  a  Btandabd  Work  in  everything  relating  to  Light 
Rail  wave.  "^  Knginnr. 

*'  Ilie  whole  subject  Is  bxhadstivblt  and  pbaoticallt  considered.  The  work  oao  be 
cordially  recommended  as  ibdibpbvsablb  to  those  whose  duty  it  is  to  become  aoqnaint^l 
with  one  of  the  prime  necessities  of  the  immediate  fntara"— fiatfisay  OjgHcial  GauUt, 

LONDON :  CHARLES  BRIFFIN  &  CO..  LIMITED.  EXETER  STREET.  STRA^C 


BNQINEBRINO  AND  MBOHANIGS,  31 

Fourth  Edition,  Thoroughly  Hevised  and  Greatly  Enlarged. 
With  Nvmfherous  lilvstrations.     Price  IDs,  6cL 

VALVES  AHD  VALVE-GEARING: 

A   PRACTICAL  TEXT-BOOK  FOR    THE    USE   OF 
ENGINEERS,  DRAUGHTSMEN,  AND  STUDENTS. 

By   CHARLES   HURST,    Practical    Draughtsman. 


Part  I.— Steam  Engine  Valves. 
Part  n.— Gas   Eni^ne  Valves    and 
Gears. 


Part  III.— Air  Compressor  Valves  and 

Gearing. 
Part  IV.— Pump  Valves. 


**  Mb.  Hubst  b  valvbs  and  TALV»«iAEiiie  win  prove  a  very  valoable  aid,  and  tend  to  the 
prodoction  of  Engines  of  sciairaiFio  DBSiaN  and  lOOHOiiiCAibwoaKiKO.  .  .  .  WlUbelaisaly 
■onght  after  by  Students  and  Desivners."— ilf  ariM  Xnffineer. 

"  As  a  practical  treatise  on  the  sabject.  the  book  stands  without  a  rival"—  Mechanical 
World. 

Hints   on   Steam   Engine  Desigrn  and  Construotlon.    By  Charles 

Hurst,  "Author  of  Valves  and  Valve  Gearing."    Second  Edition, 

Revised.      In  Paper  Boards,  8vo.,  Cloth  Back.     Illustrated.     Price 

Is.  6d.  net. 

CosTBHW.— I.  Steam  Pipes.— IL  Valves. —HI.  Cylinders.— IV.  Air  Pumps  and  Con- 
densers.-V.  Motion  Work.— VI.  Crank  Shafts  and  Pedestals.— VII.  Valve  Gear.  ~ VIII. 
Lnbrication.— IX.  Miscellaneous  Details  — Iitdbx. 

*'  A  handy  volume  which  every  practical  young  engineer  should  posiess.'*— 77k«  Model 
Engineer.  

Sixth  Edition.     Folio,  strongly  half-bound,  ais. 

rrRAVSRSS     TABI^SS: 

Computed  to  Four  Places  of  Decimals  for  every  Minute  of  Angle 

up  to  100  of  Distance. 

For  the  Use  of  Surveyors  and  Engineers. 
By    RICHARD    LLOYD    GURDEN, 

Authorised  Surveyor  for  the  Govenmients  of  New  South  Wales  ano  Victoria. 

*  *  Published  with  the  Cona 

WaUs  and  Vktaria, 

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enable  the  user  to  ascertain  the  sines  and  cosines  for  a  distance  of  twelve  miles  to  within 
half  an  inch,  and  this  by  RKniRKNCB  to  but  Onb  Tablb.  in  place  ot  the  usual  Fifteen 
Bunute  computations  required.  This  alone  is  evidence  of  the  assistance  which  the  Tables 
ensure  to  every  user,  and  as  every  Surveyor  in  active  practice  has  feU  the  want  of  such 
a«istance    fbw    knowing    or    thbir    PUBbicATiON    will   rbmain    without   thsm." 

—Engineer, 


,    Pubiished  with  the  Concurrma  oj  the  Sutveyors-GemertU  tor  New  Soutk 


Strongly  Bound  in  Super  Royal  8vo.      Cloth  Boards.      78.  6d.  net. 


For  Calculating  Wages  on  the  Bonus  or  Premium  Systems. 

for  Engineering^  TechnicaJ  cmd  Allied  Trades, 
By  HENRY   A.    GOLDING,    A.M.Inst.M.E., 

Technical  Assistant  to  Messrs.  Bryan  Donkin  and  Clench,  Ltd.,  and  Assistant  Lecturer 
in  Mechanical  Engineering  at  the  Northampton  Institute,  London,  KG. 

"Cannot  fail  to  prove  practically  serviceable  to  those  for  whom  they  have  been 
designed."— iSeo  toman. 

lONDON :  CHARLES  GRIFFIN  ft  CO..  LIMITED,  EXETER  STREET.  STRAND. 


32  CHARLBS  QRIFFIN  S  00.*8  PUBLI0ATI0N8. 

Just  RxADT.    SiooND  EDITION.    Large  Svo,  Ti»nA^nfn^  doth.    Witli 

Dliutratioiifl,  iSkbles,  &o. 

Lubrication  &  Lubricants: 

A  TREATISE   ON   THE 
THEORY  AND  PRACTICE  OF  LUBRICATION 

AND  ON  THB 

NATURE,   PROPERTIES,  AND  TESTING  OF  LUBRICANTS. 
By  LEONARD  ARCHBXJTT,  F.I.O.,  F.O.S., 

Chemist  to  the  MldUiid  Ballwaj  Oompany, 
AND 

R.    MOUNTFORD   DEELEY,   M.I.Mech.E.,   F.G.S., 

Ohlaf  LooomotiYe  Saperintendent,  lOdland  Ballwftj  OomiNuu. 

Cosmns.— L  IMctloii  of  Solids.— n.  Liquid  Friction  or  yiMOiit¥|  and  Flastlo 
fHotion.— IIL  BnperfloUl  Teneion.— lY.  The  Theory  of  Labrioatloo.— v.  Labiioanti, 
tbslr  Sooroes,  Preparation,  and  Propertlet.— YI.  Plunical  Propertiet  and  Method*  of 
■zaminafcion  of  Lnbricanta.— YII.  Chemical  Propertiet  and  Methoda  of  K¥am1natlon 
of  Lnbrloanta.— Yin.  The  Syatamatio  Teating  of  Lnbrioanta  by  Phnlcal  and  Chemioal 
Methods.— IX.  The  Mechanical  Tettine  of  Lubricanta.— X.  The  Design  and  Labrioatifln 
of  Bearings.— XL  The  Lubrication  of  Maohlnery.— Indiz. 

'*  Destined  to  become  a  olabbio  on  the  subject."— Jfwiialriet  and  Inn, 
**  Contains  practically  all  that  is  known  on  the  subject    Desenres  the  oacetul 
attention  of  all  iBngineers."— itofiioay  OJMal  OauUe. 


Fourth  Edition.     Verjf  fully  lUtutnUed,    C^oih^  4b,  fUL 

STEAM  -  BOILERS: 

THBIB   DOFBOTS,    MANAGSMSNT,    AND    OONSTBUOTION, 

By    R    D.    MTJNRO, 

CM^  Bnqinmr  of  OU  SeottiA  Bo&er  Intwranee  and  Engine  Jfupeotfon  Compmnf 

Gbnbkal  Contents.— I.  Explosions  caused  (x)  by  Overheating  of  Plates— (»)  By 
Defective  and  Overloaded  Safety  Valves— (3)  By  Corrosion,  Internal  or  External— ^4)  By 
Defective  Desi^  and  Construction  (Unsupported  Flue  Tubes ;  Unstrengthened  Manholes ; 
Defective  Staying ;  Strength  of  Rivetted  Joints :  Factor  of  Safety)— II.  Constkuction  or 
VsnTiCAL  BoiLSRS:  SheUsr-Crown  Plates  and  Uptake  Tubes— Man-Holes,  Mud-Holes, 
and  Fire-Holes — Fireboxes  —  Mountings  —  Management  —  Cleaning — Table  of  Bncstlng 
Pressures  of  Steel  Boilers — ^Table  of  Kivetted  Joints — Soecificauons  and  Drawings  of 
Lancsshire  Boiler  for  Wwldng  Pressures  (a)  80  lbs. ;  (6)  soo  lbs.  per  square  inch  respectively. 

"  A  valuable  companion  for  workmen  and  engineers  engaged  about  Steam  Bmleis,  ooglit 
to  be  carefully  studied,  and  always  at  hand."— C«//.  GnanUaM^ 

"  The  book  is  vaav  usbfvl,  especially  to  steam  users,  artisans,  and  young  Engineers."— 

Bt  the  same  Author. 

KITCHEN    BOILER    EXPLOSIONS:    Why 

they  Occur,  and  How  to  Frerent  their  Occurrence.  A  PractiaLl  Hmnd- 
book  based  on  Actual  Experiment.  With  Diagram  and  Coloured  Plate. 
Price  3s. 

LONDON:  CHARLES  GRIFFIN  «  CO.,  LIMITED,   EXETER  STREET,  STRAND. 


BNQINEERINO  AND  MBOHANIOa.  33 

In  Crown  8zv,   CiotA,    Fully  Illustrated,     5^.  net, 

EMERY   GRINDING    MACHINERY. 

A  Text-Book  of  Workshop  Ppaetlee  in  General  Tool  6rtndinfir,|and  the 
Deslffn*  ConstPuetlon,  and  AppUeatlon  of  the  Machines  Employed. 

By  R.  B.  HODGSON,  A.M.Inst.Mech.E. 

Introduction. — ^Tool  Grinding. — Emery  Wheels. — Momiting  Emenr  Wheels. 
— ^Bmery  Rings  and  Cylinders.  —  Conditions  to  Ensure  EfiScient  Working. — 
Leading  Types  of  Machines.— Concave  and  Convex  Grinding.— Cup  and  Cone 
Machines.  —  Multiple  Grinding.  —  "Guest"  Universal  and  Cutter  Grinding 
Machines. — Ward  Universal  Cutter  Grinder. —  Press. — Tool  Grinding. — Lathe 
Centre  Grinder.— Polishing.— Index. 

"  Eminently  practical    .    .    .    cannot  fail  to  attract  the  notice  of  the  users  of  this  dass  of 
isachinery,  ana  to  meet  with  careful  perusal." — CJkem.  TratUIoumal. 


In  Three  Parts.    Crown  8vo,  Handsome  Cloth.    Very  Fully  Illustrated. 

MOTOR-CAR  MECHANISM  AND  MANAGEMENT. 

By  W.  POYNTER  ADAMS,  M.Inst.KE. 


Part  I.— The  Petrol  Car.    Part  II.— The  Eleetrieal  Car. 

Part  ni.— The  Steam  Car. 


PART    I.— THE  PETROL    CAR.    5s.  net. 

Contents.— Section  I.— The  Mechanism  op  the  Petrol  Car.— 
The  Engine. — The  Engine  Accessories. — Electrical  Ignition  and  Accessories. 
— Multiple  Cylinder  Engines. — ^The  Petrol. — The  Chassis  and  Driving  Gear. 
— Section  II. — The  Management  of  the  Petrol  Car. — ^The  Engine. — 
The  Engine  Accessories. — Electrical  Ignition. — The  Chassis  and  Driving 
Gear.  —General  Management — Glossary.  — Index. 

"  Should  be  carefully  studied  by  those  who  have  anything  to  do  with  motors." — Auio- 
wufbilt  etnd  Carriage  BuiUUr^  fotnnal. 


At  Press.    In  Large  8vo.    Handsome  Cloth.    Very  Fully  Illustrated. 

A     MANUAL     OF 

PETROL  MOTORS  AND  MOTOR-CARS. 

Comprising  the  Designing,  Construction,  and  Wor/dng  of  Petrol  Motors. 

By    F.    STRICKLAND. 

OiNERAL  CoNTKNTS.— Part  I. :  Engines.— HiBtorical.— Power  Itequired.— General 
Arrangement  of  Engines.— Ignition.— Carburettors.— Cylinders,  Pistons,  Valves,  Ac— 
Crank  Shafts,  Crank  Chambers,  Cams,  Banners,  Ghuides,  Ac— Pumps.— Flywheels. — 
Pipe  Arrangements.— Silencers.— Engine  Control,  Balancing.— Motor  Cycle  Engines.— 
Marine  Motors.— Two-Cycle  Motors.— Paraffin  Carburettors.— Gas  Producers.  Part 
II.:  Cabs.— General  Arrangements.— Clutches.— Transmission.  — Differential  Gears.— 
Universal  Joints.- Asles.  —  Springs.  —  Badius  Bods.  —  Brakes.  —  Wheels.  —  Frames.  — 
Steering  Gear.  —  Badiator.  —  Steps,  Mudguards,  Bonnets,  Ac.  —  Lubrication.  —  Ball 
Bearing8.—Bodies.— Factors  of  Safetv.— Calculations  of  Stresses.— Special  Change  Speed 
Gears.— Special  Cars.— Commercial  vehicles.— Badng  Cars.— INSKX. 

LONDON:  CHARLES  GRIFFIN  «  CO.,  IIMITED,  EXETER  StREET.  STRANa 


34  0HARLS8  ORIFFIN  db  00.*8  PUBU0ATI0N8. 

WOBKS     BY 

ANDREW  JAMIESON,  MJnst.CE.,  M.I.RE^  F.R.S.E., 

Formerly  Proftssor  of  EUctrieal En^isuering^  The  Glas.  emd  IV.  of  Scot.  Tech.  CoU. 

PROFESSOR  JAMIESON'S  ADVANCED  TEXT-BOOKS. 

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Vol.  I. — Comprising  568  pages,  300  Illustrations,  and  Questions: 
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BNaiNaaRiNo  and  mscbanios.  35 

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THOBOUGHLT  BKYI8XD  BT 

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A  Pnotloftl  Mid  Simple  Introdaotioii  to  the  Stady  of  Meehanioi.  ^y 
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t« ' 


Mo  more  endnriac  Memorial  of  Pkofeoor  Rankiiie  could  be  devised  than  Ae  r^Htm- 
4ioB  of  theve  paper*  in  an  accgiiriMe  fonn.  .  .  .  The  Collection  b  most  Talnihle  oa 
aflFwmt  of  the  nature  of  hit  diacoreriee,  and  the  beantjr  and  mmplcirfneii  of  hit  analfiia. 
.  .  .  Hie  Volume  excecdi  in  importance  any  work  m  the  lame  department  twiMlrtieif 
in  our  time."— iffvAxte^. 


By  W.   VINCENT    SHELTON    (Foreman  to 

the  Imperial  Ottoman  Gun  Factories,  Constantinople) : 

THE  MECHANICS  GUIDE :  A  Hand-Book  for  Engineen  and 
Artisans.  With  Copious  Tables  and  ValnaUe  Redpes  for  Piactical  Use. 
lUnstnted.    Sic^tid  EdiHoH,    Crown  8vo.    Cloth,  7/6. 

LONDON :  CHARLES  6RIFFIN  «  G0«  LIMITED.  EXETER  STREET.  STRANa 


WNQINEBRINO  AND  ME0HANI08.  37 

Third  Edition,  Thoroughly  Revised  aaid  Enlarged,     With  60  PkUet  and 
Numerous  Illustrations,    Handsome  Cloth,    ^^s. 

HYDRAULIC   POWER 


AND 


HYDRAULIC   MACHINERY. 

BT 

HENRY    ROBINSON.    M.   iNST.   CE,   F.G.S.. 

PBLLOW  OF  king's  COLLBGB,   LONDON ;  PROF.   KMESITUS  OF  dVIL  BNGINXBRING, 

king's  COLLBGB,  BTC.,  BTC 

Contents  — Dischaive  through  Orifices. — Flow  of  Water  through  Pipes. — ^Accumulators. 
— Presses  and  Lifts. — Hoists. — Raxns. — Hydraulic  Engines. — Pumping  Engines. — Capstans. 
—  Traversers.  — 'Jacks.  —  Weighing  Machines.  —  Riveters  and  Shop  Tools.  —  Punchuig, 
Shearing,  and  Flangine  Machines. — Cranes. — Coal  Discharging  Machines.-;— Drills  and 
Cutters. — Pile  Drivers,  Excavators,  &c. — Hydraulic  Machinery  applied  to  Bridges^  Dodc 
Gates,  Wheels  and  Turbines. — Shields.  —  Various  Systems  and  Power  Installations  — 
Meters,  &c— Indbx. 

"The  standard  work  on  the  application  of  water  power."— CoJvirr'f  MaganiMt. 


Second  Ediiionj  ChreaUy  Enlarged.     With  Frontiapieee,  eevertU 
Plates,  and  aver  250  lUuUratians,    21a.  net, 

THE  PRIKCIPLES  AMD  COHSTRUGTIOII  OF 

PUMPING  MACHINERY 

(STEAM  AND  WATER  PRESSURE). 

With  Praotioal  Illiutratioiui  of  Enoinbs  and  PuiiPS  applied  to  MumrGs 

Town  Water  Supply,  Dbaikaok  of  Lands,  &c.,  alio  Economy 

and  Efficiency  Trials  of  Pumping  Machinery. 

By    henry    DAVEY, 

MomlMr  of  the  Instltntioii  of  Civil  Engineers,  Member  of  fhe  Instftation  of 

Meohenioal  Engineers,  F.G.S.,  Ao. 

O0NTSMT8  —Early  History  of  Pnmcniig  En^es— Steam  Pomping  Engines- 
Pumps  and  Pmnp  Valves — Greneral  fScinciples  of  Non-Rotative  Pumping 
Engines — ^The  Gomish  Engine,  Simple  and  Compound — Types  of  MiTiing 
Engines — Pit  Work — Shaft  Sinking — Hydraulic  Transmission  of  Power  in 
Mines — Electric  Transmission  of  Power— Valve  Clears  of  Pumping  ESngines 
—  Water  Pressure  Pumping  Engines  —  Water  Works  En^es  —  Pumping 
Engine  Economy  and  Trials  of  Pumping  Machinery — Centrifugal  and  other 
Low-Lift  Pumps — Hydraulic  BamSf  Pamping  Mains,  ftc — Index. 

"By  the  *one  English  Engineer  who  probably  knows  more  about  Pumping  Usohinery 

than  AKT  OTHKB.^     ...     A  VOLUXB   RSOOSDIire  THB   BS8ULTB  OW  LOVa  KZnKOOICB  AVD 

nuvfJ'^—Tht  Sngiueer, 
**  Undoubtedly  THx  bxst  avd  most  PHAonoAL  tbxatisx  on  Pamping  Haohinery  that  has 

TKT  BUN  PUBUSHBD.**— ifintfinr  JoumoL 

LONDON:  CHARLES  GRIFFIN  «  CO..  LIMITED,  EXETER  STREET.  STRAND 


3S  OHARLBS  QRIFFIN  S  00.*8  PUBLJ0AT10N8. 

^oi/ai  Suoi  NoMlsome  OloUi.    With  numerous  /ttuatrathas  and  Tables.    25a. 

THE   STABILITY  OP   SHIPS. 

BY 

SIR  EDWARD  J.   REED,   K.C.B.,  F.R.S.,   M.P., 

rMIORT  OF   TKB    DIPBRIAL   OKDBR8    OF   ST.  STANILAUS   OF    RUSSIA;    FRANCIS    JOOFH    OF 

AUSTRIA;    ICBDJIDIB   OF    TURKBV ;    AMD    RISING    SUN    OF    JAPAN;    FICV- 

PRBSIDBNT  OF  THR  INSTITUTION  OF  NATAL  ARCKITRCTS. 

"  Sir  Kdwaro  Rxbd's  '  Stability  of  Ships  '  u  infaluablr.  The  Naval  Arlmubct 
will  find  broogfat  toget&er  and  ready  to  hu  hand,  a  mass  of  infonnation  which  he  would  ochar* 
wise  have  to  seek  in  an  ahnost  endleas  variety  of  publications,  and  some  of  which  be  would 
poaaUy  not  be  able  to  obtain  at  all  elsewhere.'*— AtetfWfAcA 


THE  DBSIOK  AND  COKSTBUCTIOK  OF  SHIPS.  By  John 
Harvard  Bilks,  M.Inst.N.  A.,  Professor  of  Naval  Architecture  in  the 
University  of  Glasgow.  [/n  Preparaiion. 


Third  Edition.     Illustrated  with  Plates,  Numerous  Diagrams,  and 

Figures  in  the  Text.     1 8s.  net 

STEEL    SHIPS! 

THEIB    CONSTBUCTION    AND    MAINTENANCE. 

A  Manual  for  Shipbuilder*,  Ship  Superintendents,  Students, 

and  Marine  Engineers, 

By  THOMAS  WALTON,   Naval  Architect, 

AUTHOR    OF    "  KNOW    YOUR    OWN    SHIP." 

GoNTENTB. — I.  Manufacture  of  Oast  Iron.  Wrought  Iron,  and  SteeL~<Som- 
poflition  of  Iron  and  Steel,  (Quality,  Strengtn,  Tests,  &c.  II.  Olassifioation  of 
oteel  Ships.  III.  Considerations  in  maidng  choice  of  Type  of  VesseL — ^Fnunine 
of  Ships.  rV.  Strains  experienced  by  ShifM.  — Metnods  of  ComputiiM:  and 
Comparing  Strengths  of  Ships.  V.  Construction  of  Ships. — Alternative  Modes 
of  Construction. — Types  of  Vessels. — Turret,  Self  Trimming,  and  Trunk 
Steamers,  &o. — Rivets  and  Bivetting,  Workmanship.  VI.  Pumping  Arrange- 
ments.    VII.   Maintenance. — Prevention  of   Deterioration  in  the  Hulls  of 

Ships. — Cement,  Paint.  A;o.— Index. 

^*  So  thorouffh  and  weii  written  is  every  chapter  In  the  book  that  it  Is  diffloolt  to  seleet 
anv  of  them  as  being  worthy  of  ezoeptionai  pnnse.  Altogether,  the  work  is  excellent,  and 
will  prove  of  ^raat  value  to  those  for  whom  It  la  intended. —7!A<  Engineer. 

At  Press.    In  Handsome  Cloth.     Very  fully  Illustrated. 

PRESENT-DAY  SHIPBUILDING. 

For  Shipyard  Students,  Ships'  Officers,  and  Engineers. 

By  THOS.  WALTON, 
Author  of  "Know  Your  Own  Ship.* 

General  Contents.— Classificatioii.— Materials  used  in  Shipbuilding. — 
Alternative  Modes  of  Construction. — Details  of  Construction. — Framing, 
Plating,  Rivetting,  Stem  Frames,  Twin-Screw  Arrangements,  Water 
Ballast  Arrangements,  Loading  and  Discharging  Gear,  &c. — Types  of 
Vessels,  including  Atlantic  Liners,  Cargo  Steamers,  Oil  carrying  Steamers, 
Turret  and  other  Self  Trimming  Steamers,  &c.— Index. 

LONDON:  CHARLES  GRIFFIN  &  CO..  LIMITED.  EXETER  STREET.  STRAND. 


NAUTWAL  WORKS.  39 


GRIFFIN'S    NAUTICAL    SERIES. 

Editbd    bt    EDW.    BLACKMORE, 
Matter  Mariner,  Fint  daas  Trinity  Home  CerUfloate,  Amoo.  Inst.  H.A. ; 

AHB  WBTRUr.  MAmLT,  by  SAIL0B8  for  SAILOB0. 


"This  admxkabli  SBitm."— Faifptey.        "A  yebt  ntnuruL  birihs."— JTaditis. 
"  Etxrt  Ship  should  bare  the  whoui  Sbrdb  at  a  RsraRKNcn  Libbabt.    Hab»- 

BOMBLT  BOnRD,  OLBARLT  PBDITBD  and  ILLU8TRATBD."— I««eflN>Oi  Jcum.  cf  CmHHOMTO^ 

The  British  Mercantile  Marine :  An  Historical  Sketch  of  its  Rise 
and  DeTelopment.    By  the  Bditor,  Capt.  Blaokx obb.    80.  6d. 
"  Captain  Blackmore  •  splbhdid  book    .    .    .    oontaina  paragraph!  on  OTeiy  point 

of  interest  to  the  Merchant  Marine.    The  243  pages  of  this  book  are  thb  most  valu. 

ABLB  to  the  sea  captain  that  have  btbb  been  ooxpilbd."— ifMisftanC  ServiM  Remsw. 

Elementary  Seamanship.     By  D.  Wilson-Barkbr,  Master  Mariner, 
F.IL.S.B.,  F.B.O.S.    With  numerous  Plates,  two  in  Colours,  and  Vrontispleoe. 
Fourth  Bditiom,  Thoroughly  BeTised.    With  additional  Illustrations,    es. 
"This  ADKIRABLB  MANUAL,  by  Capt.  Wilsob  Barkbr,  of  the  *  Worcester,'  seemi 

to  us  PBBFBOILT  DBSIQBBD."— ^tfttfTMeum. 

Know  Your  Own  Ship :  A  Simple  Explanation  of  the  Stability,  Con- 
struction, Tonnage,  and  Freeboard  of  Ships.    By  Thob.  Walton,  Naval  Architect 
With  numerous  Illustrations  and  additional  Chapters  on  Buoyancy,  Trim,  and 
Calculations.    Ninth  Bdition.    7b.  0d. 
*'  Mb.  Walton's  bock  vrill  be  found  vbrt  usbful."— 7A«  Engineer. 

Naviflration :  Theoretical  and  Practical.     By  D.  Wilson-Baskui 

and  WHiLiAH  Allinoham.   Sboond  Edition,  Bevlsed.   8s.  dd. 
■  "Prbcisblt  the  kind  of  work  required  for  the  New  Certificates  of  oompetenoy. 
Candidates  will  find  it  intaluablb.  "—Dund^  Advertiter, 

Marine    Meteorolorjr :    For    Officers    of    the   Merchant   Kayy.       Bv 
WiLUAM  Allingham,  fSxtt  Class  Honours,  Navigation,  Science  and  Art  Department. 
With  ninstrations,  Maps,  and  Diagrams,  and  Jaeaimile  reproduction  of  log  page. 
7s.  6d. 
"  Quite  the  BBSI  publication  on  this  avbiecV— Shipping  Qautte, 

Latitude  and  Longitude :  How  to  find  them.    By  W.  J.  Millab, 

C.B.    Sboond  Edition,  Bevlsed.    2s. 

"Cannot  but  prove  an  acquisition  to  those  studying  Navigation."— JfarifM  Bnginsttr. 

Practical  Mechanics  :  Applied  to  the  requirements  of  the  Sailor. 
By  TH06.  Maokbnzib,  Master  Mariner,  F.B.A.S.  Sboond  Edition,  Bevised.  8b.  6d. 
"  Wbll  WOBTH  the  money  .    .    .  bxobbdinolt  bxlpwul." —Shipping  World, 

Trifironometry :  For  the  Youns  Sailor,  A;c.     By  Rich.  G.  Buck,  of  the 
lluutnes  Nautical  Training  CoUege,  H.M.S.  "  Worcester."    Third  Edition,  Bevlsed. 
Price  8s.  6d. 
"This  bminbntlt  pbaotical  and  reliable  volume."— Sdboolnuuter. 


Practical  Algrebra.     By  Rich.  C.  Buck.     Companion  Volume  to  the 
above,  for  Sailors  and  others.    Second  Edition,  Bevised.    Price  8s.  6d. 
"  It  is  JUBT  thb  book  for  the  young  sailor  mindful  of  progress."— ^autioo^  MoQiui'M. 

The  Legal  Duties  of  Shipmasters.    By  Bbitediot  Wm.  QiNSBUBa, 

M.A.,  LL.D.,  of  the  Inner  Temple  and  Northern  Circuit:  Batrister-at-Law.    SBCOND 

Edition,  Thoroughly  Bevised  and  Enlarged.    Price  is.  6d. 

"  INVALUABLB  to  masters.    ...    We  can  fully  recommend  \X,."Shipping  QazetU. 

A  Medieal  and  Suririeal  Help  for  Shipmasters.    Including  First 

Aid  at  Sea.    By  Wm.  Johnson  Smith,  F.B.G.S.,  Principal  Medical  Officer,  Seamen's 
Hospital,  Greenwich.    Third  EDmoN,  Thoroughly  Bevised.    6b. 
"  SoxTND,  judicious,  RBALLT  hblpful."— 7A«  Lancet. 

LONDON:  CHARLES  QRIFFIN  &  CO.,  LIMITED,  EXETER  STREET,  STRAND. 

2 


^  CHARLES  QRIFFIN  S  CO.'S  PUBLICATIONS. 

GRIFFIN'S  NAUTICAL  SERIE& 

IfUrodtu:tory  Volume,     Price  Ss.  6cL 

British  Mercantile  Marine. 

By  EDWARD    BLACKMORE, 

MASTBR  MARIMBa;   ASSOCIATE  OP  THB  INSTITUTION  OP  NAVAL  AJtCHITBCTS; 

MBMBBR  OP  THB  niSII'lUHON  OP  BNGIMBBRS  AND  SHIPBUILOBRS 

IN  SCOTLAND:  BDITOR  OP  CRIPPnTS  "NAVTICAI.  SBBIBS." 

QmtEBAL  GoMTKirrB.— Historical  :  From  Early  Times  to  1486~PMrMi 
ander  Henry  VIII.— To  Death  of  Mary— During  Elizabeth's  Reign— Up  to 
the  Reign  of  William  III.— The  18th  and  19th  Centuries— Institntion  <A 
Examinations  —  Rise  and  Progress  of  Steam  Propulsion  —  Development  of 
Free  Trade— Shipping  Legislation.  1862  to  1875— "  Locksley  HaU^  Gase- 
ShiimiasterB*  Societies — ^Loading  of  Ships — Shipping  Legislation,  1884  to  1894— 
Statistios  of  Shipping;  The  Pkbsonnel  :  Shipowners— Officers-Marineri— 
Duties  and  Present  Position.  Education:  A  Seaman's  Ednoation:  what  it 
should  be— Present  Means  of  Education— Hints.  DisdPLim  and  Dutt— 
Postscript— The  Serious  Decrease  in  the  Number  of  British  Seamen,  a  Mattev 
demandmg  the  Attention  of  the  Nation. 

"  ImsBBsma  and  Invrauunvs   .    .    .    may  be  read  wim  psonr  aad  Buonanrr.'*- 
tflmutm  Btrald. 

''  KvBRT  bbauch  of  the  sabjeot  is  dealt  with  in  a  way  which  ahowB  that  the  writer 
^  knows  the  ropee*  familiarly."— Aeotmum. 

"This  ADiOBABLB  book    .    .    .    TBxxB  With  osefiil  informatloii— ttionld  be  In  tht 
hands  of  e^ery  Sailor.**— IFiMtem  Morning  New. 


Fourth  Edition,  Thoroughly  Beviaed.     With  Additional 

lUvstratione,     Price  6b. 


ELEMENTARY    SEAMANSHIP. 


D.  WILSON-BARKER,  Master  Mabiheb;  F.R.S.B.,  F.R.G.S.,&a,  fto. 

TOUMOMR  B&OTHSB  OV  THB  TBDIITT  BOUBIi 

With  Frontispieoe,  Numerous  Plates  (Two  in  Colours),  and  Hlnstratioiia 

in  the  Text. 

GsznEKAL  GoiiTisrT&— The  Building  of  a  Ship;  Parts  of  Hull  Masts^ 
Ac.- Ropes,  KnotL  Splicing,  kc  —  Gear,  Lead  and  Log,  &c  —  RuKing, 
Anchors— Sailmakmg — The  Sails,  &c.  — Handling  of  Boats  under  Saii- 
Signals  and  Signalling— Rule  of  the  Road— Keeping  and  Relieving  Watch— 
Pomts  of  Etiquette— Glossary  of  Sea  Terms  and  fhritfes— Index. 

***  The  Tolinne  oontainB  the  mew  bolss  or  thb  boaa. 

••This  AniOBABLB  KANUAi*  by  Gapt.  Wnjwv-BAXKBB  of  the  'Worcester,'  seems  to  ns 
pmsvBorLT  DSBiessD,  and  hokls  its  place  ezoellentlT  in  •  Oaiirar's  Naotioal  Ssbbs.'  .  .  . 
Although  intended  for  those  who  are  to  become  Offloen  of  the  Merchant  Nayy,  It  will  be 
foond  nsefnl  by  all  rAonixaoai.'^'^Athenmim. 

%*  For  complete  List  of  OBOVDr's  Naohcal  Snans,  see  p.  t9. 

LONDON :  CHARLES  GRIFFIN  «  CO.,  LIMITED,  EXETER  STREET,  STRAND. 


NAVTIOAL  W0RK8.  41 

GRIFFIN'S  NAUTICAL  SERIES, 

Second  Edition,  Revised  and  lUvstraUd,     Price  Ss,  6d, 

NAVIGATION: 

PJET&C'X'ICJLi:!     JLM^O      'X'SiCSSORS'X'ICJiXi. 

By  DAVID  WILSON-BARKER,  RN.R,  F.R.S.E.,  &o.,  Aa, 

WILLIAM  ALLINGHAM, 

lIBST-OLAflB  HONOUBS,  NAVIGATION,  SGIENCn  AND  ABT  DBPABTXINT. 

TRnftb  flutiiecou0  5Utt0tcatfon0  and  Bsamfnation  (ftueatfotiA 

GiNXKAL  CoNTKNTS.— Definitioiijs — Latitude  and  Longitude — Instnimentt 
•of  Navigation — Correction  of  Courses — Plane  Sailing — Traverse  Sailing— Day's 
Work  —  Parallel  Sailing  —  Middle  Latitude  SaiLing  —  Mercator's  Chart— 
Mercator  Sailing — Current  Sailing — Position  by  Bearings— Great  Circle  Sailing 
— The  Tides — Questions — Appendiz :  Compass  Error — Numerous  Useful  Hints. 
fto. — Index. 

^  PxaoisBLT  the  kind  of  work  required  for  the  New  Gerfelflcatei  of  competency  in  frades 
from  Second  Mate  to  extn  Master.  .  .  .  Candidates  will  find  it  nnr at.dabt.Bi  "—JwiKJef 
AthmiUer. 

"  A  CAPITAL  UTTLK  BOOK  .  .  .  specially  adapted  to  the  New  Examinations.  Tt9 
Avtlkors  ere  Oapt.  WnsoN-BABKSx  (Captsin-Soperintendent  of  the  Naatieal  Oollege,  H.M.B. 
'  Worcester/  who  has  had  great  experience  in  the  highest  problems  of  Navigation),  snd 
Mb.  Aluvoham,  a  well-known  writer  on  the  Science  of  Navlgaaon  and  Nautical  Astronomy  " 
—Shipping  World. 


Handsome  ClotK    Fully  IlluelroUed,     Price  78.  6d, 

MARINE    METEOROLOGY, 

FOB  OFFICERS  OF  THE  MERCHAHT  HAVT. 
By  WILLIAM  ALLINGHAM, 

Joint  Author  of  "Navigation,  Theoretical  and  Practical." 

With  numerous  Places,  Maps,  Diagrams,  and  Illustrations,  and  a  facsimile 
Reproduction  of  a  Page  from  an  actual  Meteorological  Log-Book. 

SUMMARY   OF  CONTENTS. 

IHTBODUOTORT.— Instruments  Used  at  Sea  for  Meteorological  Parposes.— Meteoro> 
logical  Log-Books-^Atmospheric  Pressure. —Air  Temperatures.— Sea  Temperatures.— 
winds.— wind  force  Scales.— History  of  the  Law  of  Storms.— Hurricanes,  Seasons,  and 
Storm  Tracks.— Solution  of  the  Cyclone  Problem.— Ocean  Currents.- Icebeivs.--S]m- 
ohronons  Charts.— Dew,  Mists,  Fogs,  and  Hase.— Clouds.— Aain,  Snow,  and  Hail.— 
Mirage,  Bainbows,  Coronas,  Halos,  and  Meteors.— Lightning,  Corposants,  and  Auroras.— 
QUBSnOHB.— APFKNDDL— IKDEX. 

**  Quite  the  bbst  publication,  asd  certainly  the  host  ixtbbxstiko,  on  this  subject  erer 
presented  to  Nautical  men."— Skipping  Oautte. 


*  * 


For  Complete  List  of  Gkiftin's  Nautioal  Series,  see  p.  30. 


iONDON:  CHARLES  GRIFFIN  ft  CO..  LIMITED.  EXETER  STREET.  STRAND. 


4*         osAgLm  efsimir  s  oo.v  publicatiomb. 
QRIFFnrS   NAUTICAL  SERIES. 

SaooND  Edition,  Rbyisbd.    With  Nameroiu  lUnstrations.    Price  3s.  6d. 

Practical  Mechanics: 

Applied  to  the  Bequirements  of  the  Sailor. 

By    THOS.    MACKENZIE, 

Matter  Marintr^  F.a.AJ^ 

GnmtAL  CoNTVNTB.— Resoltition  and  CompoBition  of  Forcefl— Work  done 
by  Machines  and  living  Agents — The  Mechanical  Powers:  The  Lever; 
Denioks  aa  Bent  Levers— The  Wheel  and  Axle :  Windlass ;  Ship's  Capstan  ; 
Crab  Winch— Tackles :  the  '*01d  Man"— The  Inclined  Plane;  the  8crew^ 
The  Centre  of  Gravity  of  a  Ship  and  Cargo  —  Kelative  -Strength  of  Rope  : 


"  Tms  XXOKLLXNT  BOOK  .  .    .   Contains  a  laboi  ahoitnt  oi  information.'' 

"  Wbll  wobth  the  money  .  .  .  will  be  fonnd  bxoibdinglt  HELPFUih**— 
Shkw^  World, 

''Ko  Ships'  Ofticbbs'  bookoabi  will  henceforth  be  complete  without 
Captain  MACKSNasu's  '  Practioal  Mbchanios.'  Notwithstanding  my  many 
years'  experience  at  sea,  it  has  told  me  how  much  more  there  it  to  acquire,** — 
(Letter  to  the  Publishers  from  a  Master  Mariner). 

"  I  must  express  my  thanks  to  you  for  the  labour  and  care  you  have  takev 
In  'PiucnoAL  Mbohanigs.'    .    .    .    It  ib  a  life's  kxperibnok.    .    . 
What  an  amount  we  frequently  see  wasted  by  rigging  purchases  without  reaaoi^ 
and  accidents  to  spars,  &q.,  &c  !    'Pjeugtioal  Mechanics'  would  save  all 
~ — (Letter  to  the  Author  from  anoUier  Master  Mariner). 


WORKS  BY  RICHARD  G.  BUCK, 

Of  the  Thunea  Naafcioal  Training  College,  H.1LS.  '  Woroester.* 

A  Manual  of  Trigonometry: 

With  Diagrams,  Examples,  and  Exercises.    Price  8s.  6d. 

Third  Edition,  Revised  and  Corrected. 

*«*  Mr.  Buck's  Text-Book  has  been  specially  prepared  with  a  view 

to  me  New  Examinations  of  the  Board  of  Trade,  in  which  Trigonometry 

is  aa  obligatory  subject. 

**Thia  SMDnuiTLT  paAoncAL  and  sbuabls  yroLxna.^'—SdiooltMuter. 

A  Manual  of  Algebra. 

Designed  to  meet  the  Requirements  of  Sailors  and  others. 
Second  Edition,  Revised.    Price  3b.  6d. 

%*  These  elementary  works  on  algebra  and  trioohomstbt  are  written  tpedally  for 
those  who  wUl  have  little  opportunity  of  consnlting  a  Teacher.  They  are  books  for  "sax^ 
■SLP.**  All  bnt  the  simpleat  explanations  have,  therefore,  bem  avoided,  and  Axawsis  ts 
the  Bxerdaes  are  given.  Any  person  may  readily,  by  caref al  itndv.  become  master  of  their 
eontents,  and  thus  lay  the  foundation  for  a  further  mathematical  course,  if  desired.  It  is 
hoped  that  to  the  younger  Officers  of  our  Mercantile  Marine  they  will  be  found  deddedly 
serviceable.  The  Examples  and  Exercises  are  taken  from  the  Examination  Papers  sat  for 
the  Oadets  of  the  "  Worcester.  *' 

"  Olearly  arranged,  and  well  got  op.        .     .    A  flnt-rate  Etomentary  Algebra.  — 
Ifautieal  Magatine. 
*»*For  complete  List  of  QairFni's  Nautical  Sbmss.  see  p.  »9. 

LONDON :  CHARLES  GRIFFIN  ft  CO.,  LIMITED,  EXETER  STREET,  STRAND. 


NAUTICAL  WORKS.  43 


GRIFFIN'S  NAUTICAL  SERIES. 

Second  Edition,  Thoroughly  Revised  and  Extended.    In  Grown  8vo. 

Handsome  Cloth.     Price  4s.  6d. 

THE  LEGAL  DUTIES  OF  SHIPMASTERS. 

BY 

BENEDICT  WM.   GINSBURG,   M.A.,   LL.D.  (Cantab.), 

Of  the  Inner  Temple  and  Northern  Circuit;  Barrister-at-Law. 

Genepal  Contents. — The  Qualification  for  the  Position  of  Shipmaster— The  Con- 
tract with  the  Shipowner— The  Master's  Duty  in  respect  of  the  Crew:  Bngafement: 
AinMrentices ;  Discipline ;  Provisions,  Accommodation,  and  Medical  Comforts ;  Payment 
of  wages  and  Discharae— The  Master's  Tmtj  In  respect  of  the  Passengers— The  Master's 
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Duty  in  Case  of  Casualty— The  Master's  Duty  to  certain  Public  Authorities— The 
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upon  Arriva]  at  the  Port  of  Discharge — ^Appendices  relatfye  to  certain  Legal  Matten : 
Board  of  Trade  Certificates,  Dietary  Scales,  Stowage  of  Grain  Cargoes,  Load  Line  Regula- 
tions, Life-saying  Appliances,  Carriage  of  Cattle  at  Sea,  Ac.,  &c.— Copious  Index. 

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Second  Edition,  Revised.     With  Diagrams.     Price  2b. 

Latitude  and  Longitude: 

EEovr    to    Fixid    tlnem. 


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to  those  studying  Navigation." — Marine  Engineer. 

**  Young  Seamen  will  find  it  hakdt  and  uskful,  biitplb  and  olbab."—  The 
Enffineer. 

FtRST  AID   AT  SEA. 

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of  Medical  Stores  on  Board  Ship.     Price  6s. 

A  MEDICAL  AND  SURGICAL  HELP 

FOR  SHIPMASTERS  AND  OFFICERS 
iN   THE  MERCHANT  NAVY. 

By     WM.      JOHNSON     SMITH,     F.RO.S., 

Principal  Medical  Officer,  Seamen's  Hospital,  Greenwich. 

%*  The  attention  of  all  interested  in  our  Merchant  Navy  is  requested  to  this  ezoeedlnglj 
useful  and  valaable  work.  It  is  needless  to  say  that  it  is  the  outcome  of  many  years 
pBAonCAL  BZpXRiBiicx  amougst  Seamen. 

'*  Sonun,  JUDICIOUS,  rballt  hblpful."— 7Vi«  Lancet. 

*«*  For  Complete  List  of  Griffin's  Nautical  Sbkies,  see  p.  39. 

LONDON:  CHARLES  GRIFFIN  &  CO.,  LIMITED,  EXETER  STREET,  STRAHO. 


44  OHARLSa  OBIFFIN  d,  OO.'S  PUBLICATIONa. 

QRirFPTS  NAUTICAL  SERIES. 

Ninth  Edition.   Revised^  wUk  Chapters  en  Trvm,  Buoyancy ^  and  CaleiUa' 
turns.  Numerous  Illustrations,  B andsome  Cloth,  Crown  8vo,  Price  7s.  6d. 

KNOW   YOUR    OWN    SHIP. 

By  THOMAS  WALTON,  Naval  Architect. 

Specialty  arranged  to  suit  the  requirements  of  Ships'  Officers,  Shipowners, 
Superintendents,  Draughtsmen,  Engineers,  and  Others, 

This  work  explains.  In  a  simple  manner,  such  important  subjects  as :— Displacement. 
—Deadweight.— Tonnage.— Freeboard. —  Moments.— Buoyancy. — Strain. —  Structure. — 
Stability.— RoUing.— Ballasting.— Loading.— Shifting  Cargoes.~Admission  of  Water.— 
Sail  Area.— dkc. 

The  little  book  will  be  found  bxcxidiholt  hakdt  by  most  officers  and  officials  connected 
with  shipping.  .  .  .  Mr.  Walton's  work  will  obtain  lasting  sncciss,  because  of  Its  unique 
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BY   THH    SAMH    AUTHOR. 

Steel  SMps:  Tbeir  Gonstniction  and  Maintenance. 

(See  page  38.) 

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A   MANUAL    OF 

MARINE   ENGINEERING: 

COMPRISIKG  THE  DESIGNING,  CONSTRUCTION,  AND 
WORKING  OF  MARINE  MACHINERT. 

By  A.  E.  SEATON,  H.LC.E.,  H.LHech.BM  HJ.N.A. 

General  Contents.  —  Part  I. — Principles  of  Marine  Propulaion. 
Pabt  II.  —  Principles  of  Steam  En^eenng.  Part  III. —  Details  of 
Marine  Engines  :  Design  and  Calculations  for  Cylinders,  Pistons,  Valves* 
Expansion  Valves,  &c.  Part  IV. —Propellers.  Part  V, — Boilers. 
Part  VI. — ^Miscellaneous. 

"The  Student,  Draughtsman,  and  Engineer  will  find  this  work  the  most  taldablb 
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Ninth  Edition,  Thoroughly  Revised.    Pocket-Size,  Leather.    8s.  6d. 

A  POCEXT-BOOK  OF 

MARINE  ENGINEERING  RULES  AND  TABLES, 

TOR  THE  USE  OF 

Marine  Engineers.  Naval  Architects,  Desisrners,  Draaghtsmen. 

Superintendents  and  Otners. 

By  A.  K  SEATON,  M.I.O.E.,  M.LMech.E.,  M.I.N.A., 

AND 

H.  M.  ROUNTHWAITB,  M.I.M©ch.E.,  Ji.LN.A. 

"  The  best  book  of  its  kind,  and  the  information  la  both  up-to-date  and  reliable."^ 
Engineer. 

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SNQINBBRINO  AND  MXOffAHIOS.  4s 


WORKS  BT  PROF.  ROBERT  H.  SMITH,  Assoe.M.I.C.EM 

M.I.ILS.,  ULSLE.,  ILLMlnJL,  Whit  Seh.,  HOnLMeljL 


THE    CALCULUS    FOR    ENGINEERS 

AND    PHYSICISTS, 

Applied  to  Teohnioal  Problems. 

WITH  IXTSN81VS 

OI1A88IFIED  BBPEBEKOS  LIST  OF  IKTEGBAIiS. 
By  PROF.  ROBERT  H.  SMITH. 


R    F.    MUIRHEAD,    M.A.,    B.Sa, 

f  onnarly  Clark  Follow  of  GImkow  Unlyenity,  and  Lootnror  on  MathenmtlM  at 

Mason  Collego. 

In  Cnn/m  8vo,  ea^o,  toith  Diagrams  and  Folding-Plate.     8b.  6<L 

**  Psor.  B.  H.  Smith's  book  will  be  Mirloeable  in  rendering  a  hard  road  as  iait  ▲■  nicno- 
▲su  for  the  non-mathematieal  Btndent  and  Bnclneer."— ^(AciMntai. 

**  Interesting  diagrams,  with  practical  lltnstrations  of  actual  occnrrenoe^  are  to  be  found  here 
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EASUREMENT    CONVERSIONS 

(English    and   French) : 
43  GRAPHIC  TABLES  OB  DIAGRAMS,  ON  28  PLATES. 

Sliowing  at  a  glanoe  the  Mxttual  Conysbsion  of  Mbabubkmxntb 

in  DmrKBBNT  Units 

Of  Lengthi,  Areas,  Volumas,  Weights,  Stresses,  Densities,  Quantities 
of  Work,  Horse  Powers,  Temperatores,  Ac. 

For  tk9  M99  of  Englnoon,  Surooyon,  AnMUoU,  nml  Contnoton. 
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THE   MECHANICAL    ENGINEER'S   REFERENCE    BOOK 

A  Handbook  of  Tablea,  FormuloB  and  Methods  for  Engineers, 

Students  and  Draughtsmen. 

By  henry  HARRISON  SUPLEE,  B.Sc,  M.E. 

"  We  feel  sure  it  wUl  be  of  great  service  to  mechanical  engineers."— J7n^ii«ertn9. 

LONDON :  CHARLES  flRIFFIN  «  CO..  LIMITED.  EXETER  STREET,  STRAlia 


46  0HARLE8  ORIFFIN  A  OO.'S  PUBLICATIONS, 

6boond  Edition.     In  Large  8to.    Handsome  Cloth.     16s. 

CHEMISTRY    FOR    ENGINEERS. 

BERTRAM  BLOUNT,      and  A.  G.  BLOXAM, 

F.LO.,  F.O.8.,  A.LC.B.  F.I.O.,  F.O.B. 

GBITBBAL  CONTBNTB.— Introdnctlon— Chemlatry  of  the  Chief  MatertalJi 
of  Ctonatractlon— Sonroeo  of  Energy— Chemistry  of  Bteam-ralslnff— Chemii- 
try  of  Labrlcatlon  and  Lnbrlcants— Metallnrgloal  ProeeBseo  need  In  tlw 
Wlnnlnif  and  Mannf aotnre  of  ICetali. 

"The  aathon  hare  iDoaEBDKD  beyond  all  expectation,  and  have  produced  a  work  whleb 
■boold  gtve  FBB8H  roirsK  to  the  lEnRlnoer  and  Mannfactnrer.**— 7%<  Timu. 

By  the  same  Aathors,  "Chemistry  for  Manufacturbrs/'  see  p.  71. 


In  Handsome  Cloth.    With  about  50  Illustrations.    3s.  6d.  net. 

THE   ELEMENTS  OF   CHEMICAL   ENGINEERING. 

By  J.  GROSSMANN,  M.A.,  Ph.D„  F.LC. 

WITH  A  PREFACE  BT 

Sir  WILLIAM   RAMSAY,    K.C.B.,    F.R.S. 

Contents.— The  Beaker  and  its  Technical  Equivalents.— Distilling  Flasks,  Liebig^a 
Condensera.— lYactionating  Tubes  and  their  Technical  Equivalents.— The  Air-Bath  and 
ts  Technical  Equivalents. — The  Blowpipe  and  Crucible  and  their  Technical  Equivalents. 
—The  Steam  Boiler  and  other  Sources  of  Power.— General  Remarks  on  the  Application 
of  Heat  in  Chemical  Engineering.— The  Funnel  and  its  Technical  Equivalents.— The 
Mortar  and  its  Technical  E(iuivalents.— Measuring  Instruments  and  their  Technical 
Equivalents.— Materials  Used  in  Chemical  Engineering  and  their  Mode  of  Application. — 
Technical  Research  and  the  Designing  of  Plant.— Conclusion.— Chemicals  and  Materials. 
—Index. 

"Excellent.    .    .    .    Every  student  of  chemistry  attending  a  technical  course  should 
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Works  by  WALTER  R.  BROWNE,  M.A.,  M.InslC.E. 

THE    STUDENT'S    MECHANICS: 

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FOUNDATIONS    OF    MECHANICS. 

Papen  reprinted  from  the  Enginter^     In  Crown  Svo,  is. 


Demy  Svo,  with  Numerous  Illustrations,  9s. 

FUEL    AND   WATER: 

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WALTER   R.   BROWNE,   M.A.,  CE. 

Gbnkkal  Contbntb.— Heat  and  Combustion— Fuel,  Varieties  of— Firing  Arrange  aenti: 
Furnace,  Flue^  Chimney —The  Boiler,  Choice  of— Varieties— Feed-water  beatcfa— 
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"The  Section  on  Heat  is  one  of  the  best  and  most  ludd  ever  written."— J 


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**  An  admirablb  digest  of  the  most  recent  state  of  knowledge.'  -^Chemical  Newi, 

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48  OBARLM8  OBIFflN  *  OO.'S  PUBLIOATIOJSS. 

ELECTRICAL   ENGINEERING. 

Second  Edition,  Revised.     In  Large  Svo.    Handsome  Cloth.     Projusefy 
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CENTRAL  ELECTRICAL  STATIONS: 

Their  Design,  Oi^^anisation,  and  Manasrement. 

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Late  Memb.  of  Coondl  InsLE.  E.,  and  Electrical  Engineer  to  the  City  of  Manchester  : 

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ABRIDQED  0ONTBNT8. 
^  Introdnctoiy. — Central  Station  Work  as  a  Profession. — As  an  InvestmenL — The  Estab- 
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llie  Transmission  of  Steam.  —  Generators.  —  Condensing  Appliaaces.  —  Switching  Gear, 
Instruments,  and  Connections. — Distributing  Mains. — Insulation,  Resistance,  and  CosL — 
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ELECTRICITY   CONTROL. 

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By    LEONARD    ANDREWS, 

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General  Principles  of  Switchgear  Design.— Constructional  Details. — Grcuit  Breakers  or 
Arc  Interrupting  Devices.— Automatically  Operated  Circuit*  Breakers. — ^Alternating  Reverse 
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General  Arrangement  of  Controlling  Apparatus  for^  High  Tension  Systems.  —  General 
Arrangement  of  Controlling  Apparatus  for  Low  Tension  Systems. — Examples  of  Complete 
Instalkitions. — Long  Distance  Transmission  Schemes. 

*'  Not  often  does  the  specialist  have  presented  to  him  so  satisfactory  a  book  as  this.  .  .  . 
We  recommend  it  without  hesitation  to  Central  Station  Engineers,  and,  in  feet,  to  anyone 
interested  in  the  subject." — Power. 


EiGHTKKNTH  EDITION.     Leather,  Pockct  Size.     8s.  6d. 

A    POCKET-BOOK 

OF 

ELECTRICAL  RULES   &  TABIJES 

FOR  THE  USE  OF  ELECTRICIANS  AND  ENGINEERS. 

By  JOHN  MUNRO,  C.E.,  &  Prof.  JAMIESON,  M.Inst.C.£.,  F.R.S.B. 

aONBRAL      0ONTBNT& 

Units  of  Measiurement.  —  Measures. — Testing.  —  Conductors.  —  Dielectrics.  —  Sufamariae 
Cables.— Telegraphy.— Electro-chemistry.— Electro-Metallurgy.— Batteries.— Dynamos  and 
Motors. — Transformers. — Electric  Lighting. — Miscellaneous. — Logarithms. — ^Appendices. 

*' WoNDBKVuixT  Pkbrct.     .    .     .     Wocthy  of  the  highnt  oommendalioo  we  can 
KiTe  iX.**— Electrician. 

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ELECTRICAL  ENQINEERINQ.  49 

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WIRELESS    TELEGRAPHY. 

By    GUSTAVB    EICHHORN,    Ph.D. 

Ck)MTEMTS. — OscillationB. — Closed  Oscillation  Systems. — Open  Oscillation 
Systems. — ^Coupled  Systems. — The  Coupling  Compensating  the  Aerial  Wire. — 
TneHeceiver. — Comparative  Measurement  m  the  Sender. — Theoretical  ResiUts 
and  Calculations  in  respect  of  Sender  and  Receiver. — Closely-Conpled  Sender 
and  Receiver. — Loose-Oonpled  Sender  and  Receiver. — Principal  Formulae. — 
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and  Methods  of  Working. — Conclusion. — Bibliography. — Index. 

"Well  written    .    .    .    and  oombines  with  a  good  deal  of  description  a  carefal 
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"  An  earnest  and  ■aooesafnl  attempt  to  deal  oomprehensiTely  with  modem  methods  of 
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"  Ttnatworthy  information.  .  .  .  We  can  confidently  recommend  the  book  to  every 
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^ . » ^^__^ 

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Unlyentty.  of  Gambridxe. 


Ihtroducjtory  Volume.      Thibd  Edition,  Revised.      Fully  Illustrated. 

lOs.  6d. 


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Volume  II.    Fourth  Edition.    Fully  Illustrated.    Prioe  8s.  Od 

S  O  XJ  M^  I>. 

GoOTKNTB.— The  Nature  of  Sound  and  its  chief  Characteristica.— The  Velocity  of  Sound 
in  Air  and  other  Media.— Reflociou  and  Befractlon  of  Sound.— Frequenov  and  Pitch  of 
Notea.— Beaonance  and  Forced  Oscillationa.— Analyaia  of  Vibrationa.— The  Tranavarae 
Vlhrationa  of  Stretched  Strings  or  Wires— Pipes  and  other  Air  Cavitiea.— Boda.— Plataa. 
—Membranes. — Vibrations  maintained  by  Heat.— Sensitive  Flames  and  Jets.— Mnaical 
Sand.— The  Superposition  of  Waves.— Indkx. 

'*  The  work    .    .    .    maybe  recommended  to  anyone  deairoaa  of  poasessing  an  rabt 
up-TO-DATB  STAin>ARD  Trratisb  ou  AcoQstlcs.*'- /.t7«raf«re. 

"  Very  clearly  written.  .  .  .  The  names  of  the  authors  are  a  guarantee  of  the 
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Volume  III.     Second  Edition,  Revised.    Fully  Illustrated.    Price  158. 

K  IB  A  rr. 

C0MTEMT8. — Temperature.  —  Expansion  of  Solids. — Liquids. — Gases.  —  Circulation 
and  Convection.— Quantity  of  Heat;  Specific  Heat.— Conductivity.— Forms  of  Energy; 
Conservation ;  Mechanical  Equivalent  of  Heat.— The  Kinetic  Theory  —Change  of  State ; 
Liquid  Vapour.  —  Critical  Points.  —  Solids  and  Liquids. — Atmospheric  Conditions. — 
Badiation. — Theory  of  Exchanges. — Radiation  and  Temperature. — Thermodynamica. — 
Isothermal  and  Adiabatlc  Changes.— Thermodynamics  of  Changes  of  State,  and  Solu- 
tions.— Thermodynamics  of  Badiation. — INDBX. 

"Well  up-to-date,  and  extremely  clear  and  exact  throughout.    ...    As  clear  as 
it^would  be  possible  to  make  such  a  text-book." — Nature. 

Remaining  Volumes  in  Preparation — 
LIGHT;  MAGNETISM  AND  ELECTRICITY. 


THE  MEAN  DENSITY  OF  THE  EARTH :  An  Essay  to  which  the 

Adams  Prize  was  adjudged  In  1893  in  the  University  of  Cambridge.     Sy  J.  H. 
POYNTINO,  Sc.D.,  F.R.S.,  Late  Fellow  of  Trinity  College,  Cambridge;  Profesaor  of 
Physics,  Birmingham  University.    In  Large  Svo,  with  Bibliography,  lUustrations  In 
the  Text,  and  Seven  Lithographed  Plates.    12s.  6d. 
"  Cannot  fail  to  be  of  QREAT  and  gene&al  interest.*'— Athenceum. 

LONDON :  CHARLES  GRIFFIN  ft  CO.,  LIMITED.  EXETER  STREET,  STRAND. 


OEOLOOr,  MININO,  AND  ItBTALLVSOT.  51 


Grlffln's  Geological,  Prospooting,  Mining,  and 

Metallurgical  Publlcatlone. 

PA02 

Geology,  Stratigraphical,        R.  £>rHBBiDOE,  F.R.S., .  52 

„    Physical,                       Pbof.  H.  G.  Sbelbt,   .  52 

9,     Practical  Aids,              Prof.  Grenyille  Oole,  53 

M    Open  Air  Studies, .              „              „  85 

Mining  Geology,    .                James  Park,  F.G.S.,    .  55 

Prospecting  for  Minerals,     S.  Herbert  Cox,  A.RS.M.,  .  55 

Food  Supply, .                        RoBT.  Bruce,        ...  54 

New  Lands,     .                         H.  R.  Mill,  D.Sc.,  F.R.S.E.,  54 

Ore  and  Stone  Mining,    .        Sir  0.  Lb  Neve  Foster,      .  56 

Elements  of  Mining,     .                 ,,          >,  56 

Coal  Mining,  .                     H.  W.  Huohes,  F.G.S.,  56 

Practical  Coal  Mining,.       G.  L.  Kerr,  M.lnst.M.£.,    .  58 

Elementary         „                       „               „  58 

Electrical  Coal  Mining,       D.  Burns,    ....  58 

Mine-Surveying,                     Benkett  H.  Brough,  A.R.S.M.,  57 

Mine  Air,  Investigration  of,   Foster  and  Haldane,  57 

Mining  Law,                           C.  J.  Alford,     ...  57 

Blasting  and  Explosives,        O.  Guttmann,  A.M.I.C.E., .  58 

Testing  Explosives, .       .       Bichel  and  Larsen,  .  58 

Mine  Accounts, .                     Prof.  J.  G.  Lawn,             .  57 

Mining  Engineers'  Pkt.-Bk.,  £.  R.  Field,  M.Inst.M.M.,  .  57 

Petroleum,  ....        Sir  Boverton  Redwood,     .  61 

A  Handbook  on  Petroleum,  Thomson  and  Redwood,  61 

Oil  Fuel,  ....        Sidney  H.  North,      .         .  2^ 

Metallurgical  Analysis,   .       Macleod  and  Walker,  60 

Microscopic  Analysis,  F.  Osmond  k  J.  £.  Stbad,F.R.S.,  60 

Metallurgy  (General),                Phillips  and  Bauerman,  60 

„          (Elementary),        Prof.  Humboldt  Sexton,      .  66 

Getting  Gold, .                        J.  C.  F.  Johnson,  F.G.S.,  59 

Gold  Seeking  in  South  Africa,  Theo  Kassner,  ...  59 

Cyanide  Process,  .              James  Park,  F.G.S.,    .  59 

Cvaniding,                                Julian  and  Smart,  59 

Electric  Smelting, .                Borohers  and  McMillan,    .  67 

Electro-Metallurg^,               W.  G.  McMillan,  F.LC,    .  67 

Assaying,                            J.  J.  <fe  0.  Beringbr,  .  66 

Metallurgical  Analysis,      J.  J.  Morgan,  F.C.S.,   .       .  66 

Metallurgy  (Introduction  to).  Sir  W.  Roberts-Austen,  K.O.B.,  63 

Gold,  Metallui^fy  of,     .        Db.  Kirke  Rose,  A.R.S.M.,  63 

Lead  and  Silver,  „                 H.  F.  Collins,  A.RS.M.,  64 

Iron,  Metallurgy  of,               Thos.  Turner,  A.R.S.M.,     .  65 

Steel,             „                           F.  W.  Harbord,    ...  65 

Iron-Founding,  .                .        Prof.  Turner,      ...  68 

Precious  Stones,                         Br.  Max  Bauer,          ,  68 

LONDON :  CHARLES  GRIFFIN  ft  CO.,  LIMITED,  EXETER  STREET,  STRAND. 


OHARLWa  ORIFFIN  S  00.*9  PUBLIOATIONB. 


Demy  Sua,   Handsome  eloth,   18s, 

Physical  Geology  and  Palsontology, 

0J^    THE   BASIS    OF  PHILLIP 8. 

BT 

HARRY    GOVIER    SEELEY,    F.R.S, 

rROFBSSOR  OF  GBOGSAPHY  IN  KING'S  COIXBGS,  LONXX>N. 

vaub  yronttspiece  in  Cbromoi^Xitbodtapbc,  an^  JUnetrattoiia* 

^  It  is  impossible  to  praise  too  highly  the  xesearch  which  Professor  Sbelbt's 
'  Physical  Geology  ^  evidences.  It  is  far  more  than  a  Text-book— it  is 
a  Directory  to  the  Student  in  prosecuting  his  researches." — PresidetUial  Ad- 
dress  to  tht  Geological  Society^  1885,4^  Rtu,  Prof,  Bcnnty.  D,Sc,^  LL,D.^  F,R.S, 

'*  Professor  Srelby  maintains  in  his  '  Physical  Geology  *  die  hi|^ 
reputation  he  already  deservedly  bears  as  a  Teacher."  —  Dr,  Henry  Wood- 
ward^ F,R.S,^  in  the  "  Geological  MagauneJ** 

**  Professor  Seelby's  work  includes  one  of  the  most  satis&ctory  Treatises 
on  Lithology  in  the  English  language." — Ametican  /oumal  0/ Engineering, 


Dem,y  Svo,  Handsome  oloth,  34sn 

StratigrapMcal  Geology  &  Paleontology, 

ox   THE   BASIS    OF  PHILLIPS. 

BY 

ROBERT    ETHERIDGE,    F.R.S., 

or  THB  NATURAL  HIST.  DBPARTMBNT.  BRmSH  MUSEUM,  LATS  PAI.430MTOLOCtST  TO  TMB 
GBOLOGICAI.  SURVBY  OP  GREAT  BRITAm,  PAST  PRESIDENT  OP  THE 

GEOLOGICAL  SOCIETY,  ETC 

THAitb  Aap,  Tlumeroua  UBblc^  anb  TTbittc-^t  plates, 

'*  No  such  oompendium  of  geological  knowledge  has  ever  been  brought  togedier  befora.**— 
Westminster  Review, 

"  If  Prop.  Srblby's  roliune  was  remailcable  for  its  originality  and  the  breadth  of  its  views, 
Mr.  Ethbridgb  fully  justifies  the  assertion  made  in  his  preCace  that  his  book  differs  in  con- 
struction and  detail  nom  any  known  manual.    .    .    .    Must  take  high  rank  among  woi 

OP  RBPBRRNCB."— .<4/AtfM««IW. 


OPEjl-AItl  STUDIES  I]l  GEOLOGY: 

An  Introduction  to  Geology  Out-of-doors. 

By  professor  GRENVILLE  COLE,   M.R.I.A.,  F.G.S. 

For  details,  see  Griffin's  Introductory  Science  Series,  p.  85. 

lONDON:  CHARLES  GRIFFIN  4  CO..  UNITED.  EXETER  STREET.  STRAND. 


METEOROLOGY  AND  QEOLOQY.  53 

Crown  8zv.     Handsome  Cloth,     2s,  6d. 

BESEABGHES  ON  THE  PAST  AND  PRESENT  HISTORY 

OF 

THE     EARTH'S    ATWIOSPHERE. 

Inoluding  the  latest  Discoueriea  and  their  Practiced  ApplicationB. 

By  dr.  THOMAS  LAMB  PHIPSON. 

PART  I. — ^The  Earth's  Atmosphere  in  Remote  Geological  Periods. 
PART  II. — The  Atmosphere  of  our  Present  Period, 

Appendices;  Index. 

*,♦  Dr.  Phipson's  work  presents,  amidst  much  which  is  of  interest  to  the 

Scientist  and  the  General  Reader  alike,  a  short  risum^  of  his  discovery  of  the 

origin  of  Atmospheric  Oxygen,  the  existence  of  which  he  attributes  wholly  to 

the  action  of  Solar  Radiation  upon  vegetable  life.     The  book  will  be  found 

replete  with  much  that  is  new,  curious,  and  interesting,  both  in  connection  with 

Weather  Lore,  and  with  Scientific  Meteorology. — Publishet^s  Note, 

"  The  book  should  prove  of  interest  to  general  readers,  as  well  as  to  meteorologists 
and  other  students  of  science.'*— ^Va^tire. 


By  GRENVILLE  A.  J.  COLE,  M.R.I.A.,  F.G.S., 

Professor  of  Geology  in  the  Royal  College  of  Science  for  Ireland,  and  £xaminer  in  the 

University  of  London. 

See  also  the  two  folloiving  pages  (54,  55),  and  page  85. 


AIDS    IN 

PRACTICAL     GEOLOGY? 

IVITH  A   SECTION  ON  PALAEONTOLOGY. 

By  professor  GRENVILLE  COLE,  M.R.LA.,  F.G.S. 

Fifth  Edition,  Thoroughly  Revised.     With  Frontispiece  and 

Illustrations.    Cloth.     los.  6d. 


aONERAL    OONTENT&— 
PART     I.— Sampling  of  the  Earth's  Crust, 

PART     II.— EXABflNATION    OF    MlITORALS. 

PART  III.— Examination  of  Rocks. 
PART  IV.— Examination  of  Fossils. 

"  Ftof.  Cole  treats  of  the  examination  of  minerals  and  rocks  in  a  way  that  has  never 
been  attempted  before  .  .  .  deserving  op  the  highest  praise.  Here  indeed  are 
'  Aids '  INNUMERABLE  and  INVALUABLE.  All  the  directions  are  given  with  the  utmost  dear* 
■ness  and  predsion." — Athgnantm. 

"That  the  work  deserves  its  title,  that  it  is  full  of  'Aids/ and  in  Ae  highest  d^ree 
'  PRACTICAL,'  will  be  the  verdict  of  all  who  use  it.'*~~Nahtre. 

"  This  EXCELLENT  MANUAL     .     .      .     Will  be  A  VERY  GREAT  HELP.      .     .     .     The  SeCtlOn 

cm  the  Examination  of  Fossils  is  probably  the  best  <^  its  kind  yet  published.  .  .  .  Full 
of  well-digested  information  from  the  newest  sources  and  from  penooal  research.** — Annais 
^fNaiJHiMtorv. 

LONDON:  CHARLES  GRIFFIN  ft  GO.  LIMITED,  EXETER  STREET,  STRAND 


54  OBARLBS  ORIFFIN  <b  CO.'S  PUBLICATIONS. 


GRIFFIN'S  "NEW  LAND"  SERIES. 

PrcboticcU  Hand-Booka  for  the   Uae  of  Prospectors,  Explorers, 

Settlers,  Colonists,  and  all  Interested  in  the  opening 

up  and  Development  of  New  Lands. 

Editkd  by  GRENVILLE  A.  J.  COLE,  M.R.LA.,  F.G.S., 
Professor  of  Geology  in  the  Royal  College  of  Science  for  Ireland,  and  Bzaminer  in 


egeois 
the  University  of  London. 

In  Orown  8vo.     Handsome  Cloth.    5$, 
With  Numerous  Maps  SpeciaUy  Drawn  and  Executed  for  this  Work. 

NEW     LANDS: 

THEIB    RESOURCES    AND    PROSPECTIVE 

ADVANTAGES. 

By  HUGH  ROBERT  MILL,  D.Sc,  LL.D.,  F.R.S.E., 

Intboduotobt. — The  Deyelopment  of  New  Lands. — The  Dominion  of 
Canada.  —  Canada,  Eastern  Provinces.  —  Canada,  Western  Provinces^  and 
Territories. — Newfoundland. —The  United  States. — Latin  America,  Mexico. — 
Latin  America,  Temperate  Brazil  and  Chili. — Latin  America,  Argentina. — 
The  Falkland  islands. — Victoria.— New  South  Wales. — Queensland. — South 
Australia. — Tasmania. — ^Western  Australia. — New  Zealand. — The  Besouroes 
of  South  Africa.— Southern  Rhodesia. — Index. 

"  PAINSTAKUffG     .     .     .     OOMPLSTB     .      .     .     Of  gfOat  PRAOTIOAL  ▲8SI8TAK0S.*'— f%C  i^teU. 

'*A  want  admirably  anppUed.  .  .  .  Has  the  advantage  of  being  written  by  a  pro- 
fessed G^eographer.'*— 6teo0TapA<ca/  Journal. 


With  many  Engravings  and  Photographs.    Handsome  Cloth,  4s.  6d. 

FOOD      STJPPIjY. 

By   ROBERT   BRUOE, 

Agriealtaral  Saperintendent  to  the  Boyal  Dablin  Society. 

With  Appendix  on  Preserved  Foods  by  C.  A.  Mitchell,  B.A,  F.LO. 

General  Contents. — Climate  and  Soil — Drainage  and  Rotation*  of 
Crops — Seeds  and  Crops — Vegetables  and  Fruits — Cattle  and  Cattle- 
Breeding — Sheep  and  Sheep  Rearing — Pigs — Poultry — Horses — The  Dairy 
— The  Farmer's  Implements — The  Settler's  Home. 

■*  Bribilrs  with  rsvOKiUiTlov/'-'FarfMrg'  OazetU. 

"  The  work  is  one  which  will  appeal  to  those  intending  to  become  farmers  at  home 
or  In  Uie  Colonies,  and  who  desire  to  obtain  a  general  idea  of  the  true  principles  of 
fanning  in  all  its  BUkvOEKS."— Journal  of  tA«  Boyal  CoUmial  Jngt. 

"  A  most  RBADABLE  and  valuable  book,  and  merits  an  extensivb  BALE."— iSeottit)^ 
Farmer. 

"  Will  prove  of  service  in  ant  part  of  the  world."-  Nature. 

LONDON :  CHARLES  GRIFFIN  ft  CO..  LIMITED.  EXETER  STREET.  STRANa 


PBOBPSOTIlfO  AND  COLONIBATION.  H 

QRIFFnrS    "NEW    LAND"    SERIES. 

Fourth  EDrnoN-^  RevUed,      With  lUvstratwM,     Handwme  Olath,  5«. 

PROSPECTING  FOR  MINERALS. 

A  Praotioaf  Handbook  for  Proapeotora,  Explorers,  Settlers,  and  €lII 
interested  In  the  Opening  up  and  Development  of  New  Lands. 

Bt  S.  HERBERT  COX,  Ab8og.B.S.M.,  M.In8t.M.M.,  F.G.S., 
Profaator  of  Mining  at  the  Boyal  Sohool  of  Mines. 

GsHBBAL  GoNTBNTB.-— Introdnctioik  and  HintB  on  (Geology— The  Detenninji- 
tion  of  Minerals :  Use  of  the  Blow-rape,  fta— Rock- forming  Minerals  and  Non- 
Metallio  Minerals  of  OommerciAL  Valne :  Rock  Salt,  BonuL  Marbles,  litho- 
graphic Stone,  Quartz  and  OnaL  &c.,  &c.— Precious  Stones  and  Gems— Stratified 
i>eposits:  Goal  and  Ores— Mmeral  Veins  and  Lodes— Irregular  Deposits— 
Dj^namios  of  Lodes:  Faults,  fto.— Alluvial  Deposit*— Noble  Metals:  Gold, 
PlatinQm,  Silver,  fta—Leaid— Mercury— Copper— Tin— Zinc— Lron— Nickel, 
Ac. — SulMiur,  Antimony,  Arsenic,  Ac. — Combustible  Minerals— Petroleum — 
General  Hints  on  Prospecting — Glossary — Index. 

'  «  This  ADIORABLI  LnTLl  WOBK     .     .     .     written  With  flOUUTUriO  AOOU&AOT  In  a 

OLBAB  and  LUdD  Style.  ...  An  dcfoetaht  .addihov  to  technifflfcl  llteratore  .  .   . 
—Uimlng  JowmaL 


IN  PREPARATION. 

BUILDING  CONSTRUCTION  ih  WOOD,  STONE,  and 
CONCBETK  By  Jambs  Ltoh,  M.A.,  Professor  of  En- 
gineering in  the  Royal  College  of  Science  for  Ireland; 
sometime  Superintendent  of  the  Engineering  Department  in 
the  University  of  Cambridge;  and  J.  Tatlob,  A.R.C.S.I. 

*•*  other  Yolomes,  dealing  with  subjects  of  PRiMAitT  Importahok  in  the  BXAnnr- 
ATION  and  Utilisaiion  of  Lands  which  have  not  as  yet  been  fully  developed,  are  in 
preparation. 


Crown  8yo.    Handsome  Cloth.    Illustrated.    6s. 

MINING    GEOLOGY. 

A  TEXT-BOOK  FOR  MINING-  STUDENTS  AND  MINBB8. 

By  PROP.  JAMES  PARK,  F.G.S.,  M.In8t,M.M., 

Frofessor  of  Mining  and  IHi  ector  of  the  Otago  Uniyersity  School  of  Mines ;  late  Director 
Thames  School  of  Mines,  and  Oeological  Surveyor  and  Mining  Geologist  to  the 

uoTemment  or  New  Zealand. 

OBmutiL  CJoirniNTB.— Introduction.-  Classification  of  Mineral  Depo6its.--Ore  Veins, 
their  Filling,  Age,  and  Structure. —The  Dynamics  uf  Lodes  and  Beds.  -Ore  Deposits 
Genetically  Considered— Ores  and  MineralB  Considered  Economically. -Mine  Sampling 
and  Ore  Valuation.- The  Examination  and  Valuation  of  Mines.— Index. 

'*  A  work  which  should  find  a  place  in  the  library  of  every  mining  engineer."— 
Uianing  World. 

LONDOH:  CHARLES  GRIFFIN  A  CO.,  LIMITED.  EXETER  STREET.  STRAW 

3 


56  OHARLES  GRIFFIN  A  OO.'S  PUBLICATIONS. 

Sixth  Edition.    With  Frontispiece  and  716  Uliutiations.    Prioe  34a. 

ORE  6c  STONE  MINING. 

By  Sir  C.  LE  NEVE  FOSTER,  D.Sc,  F.R.S., 

LATB  PROFBSSOK  OF  MIMING.  ROYAL  COIXBGB  OF  SCIBMCB. 

Revised,  and  brought  up-to-date 
By  BENNETT  H.  BROUGH,  F.GS.,  AssocR.S,M. 

GENERAL   CONTENTS. 

INTRODUCTION.  Mode  of  Oeeurrenee  of  Minerals.— Prospeetlnjr.—Borins. 
—Breaking  Ground.— Supporting  Excavations.— Exploitation.— Haulage  or 
Transport.- Hoisting  or  winding.— Drainage.— Ventilation.— Lighting.- 
Deseent  and  Ascent.— Dressing— Principles  ornnployment  of  Mining  Labour. 
—Legislation  affecting  Mines  and  Quarries.  —  Condition  of  the  Miner.— 
Accidents.- Index. 

"  We  have  seldom  bad  the  pleasure  to  review  a  work  so  thorough  and  complete  as 
the  present  one.    Both  in  manner  and  in  matter  it  is  FAB  superior  to  antthiho  oh 

nS  SPBOIAL  SUBJBOT  HITHIRTO  PUBLISHSD  IH  EHOLABD."— ^tA«n«Rim. 

"  Not  only  is  this  work  the  acknowledged  text-book  on  metal  mining  in  Great  Britain 
and  the  Colonies,  bnt  that  it  is  so  regarded  in  the  United  States  of  America  is  evidenced 
by  the  fact  that  it  is  the  book  on  that  subject  recommended  to  the  students  in  moat  of 
the  mining  schools  of  that  country."— TA«  Titnsg, 


In  Crown  8vo.    Handsome  Cloth.    With  nearly  900  Dlustrations,  many  of 
them  being  full  page  reproductions  of  views  of  great  interest.  Price  7a  6d.  net. 

THE  ELEMENTS  OF  MINING  AND  QUARRYING. 

An  Introductory  Text-Book  for  Mining  Students. 
Bt  Sir  C.  LE  NEVE  FOSTER,  D.Sc,  F.RS., 

Professor  of  Mining  at  the  Boval  CoUeoe  of  Science,  London,  with  which  Is  Incorporated 
the  Boyal  School  of  Mines ;  lately  one  of  H.M.  Inspectors  of  Mines. 

Gbnebal  Contents.  —  Introduction.  —  Occurrence  of  Minerals.  —  Pro- 
specting.— Boring. — Breaking  Ground. — Supporting  Exoavations. — Exploita- 
tion.— Haulage  or  Transport. — Hoisting  or  Wmding. — Drainage. — ^Ventilation. 
^Lighting. — Descent  and  Ascent— Dressing,  &c. — Index. 

"  A  remarkabhr  clear  survey  of  the  whole  field  of  mining  operations."— ifn^nsar. 

"  Barely  does  it  fall  to  the  lot  of  a  reviewer  to  have  to  accord  such  unqualified  prtise  as 
this  book  deserves.  .  .  .  The  profession  generally  have  evecy  reason  to  be  grateful  to 
Sir  C.  Le  Neve  Foster  for  having  enriched  Mucational  literature  with  so  admirable  an 
elementary  Text-book.**— Jftntf^r  JoumaL 


Fifth   Edition,  Revised  and  Greatly  Enlarged,      IViih  4  Plates  and 

670  Illustrations,    Price  24^.  net, 

A  TEXT-BOOK  OF  COAL-MINING: 

FOR  THE  USE  OF  COLLIERY  MANAGERS  AMD  OTHERS 
ENQAQED  IN  COAL-MININQ. 

By   HERBERT    WILLIAM    HUGHES,    F.G.S., 

Assoc  Royal  School  of  Mines,  General  Manager  of  Sandwell  Park  Colliery. 

GBNBRAL    CONTENTS. 
Geology.— .Search  for   CoaL — Breaking   Ground*— Sinking.— Preliminaiy 
Operations.  —  Methods  of  Working.  —  Haulage.  —  Winding.  —  Pumpine. — 
Ventilation. — Lighting. — ^Works  at  Surface. — Preparation  of  Coal  for  Market 
—Index. 

"Quite  THBBBST  BOOK  of  its  kind   ...   as  phactical  in  aim  as  a  book  can  be  . 
The  illustrations  are  szcbllbnt."— i4M#iMnm». 

"  We  cordially  recommend  the  work."— C^/ifirrr  GuardtoM-, 

"  Will  soon  come  to  be  regarded  as  the  stand abd  wobk  of  itt  kind-"— ^irwMif  AaM 
Dailf  GauiU, 

lOMDON :  CHARLES  GRIFFIN  ft  CO,.  LIMITED.  EXETER  STREET.  STRAND. 


WORKS  ON  MINING.  57 


Twelfth  Edition,  Revised.     With  Numerous  Diagrams. 

Cloth,  7s.  6d. 

A    TREATISE    ON    MINE-SURVEYING: 

For  the  uae  of  Managen  of  Mines  and  Co/iieriea^  Students 
at  the  RoyaJ  School  of  Mines,  do. 

By    BENNETT   H.    BROUGH,    F.G.S.,  ASSOC.R.S.M., 

Fonneriy  Instnictor  of  Mine-Surveying,  Royal  School  of  Minot. 

"Its  CL.BARNBSS  of  STYLB.  LUCIDITY  of  DBSCRIPTION,  and  PULNBSS  of  DBTAII.  have  loOflr  ago  WOO 
tor  it  a  place  unique  in  the  literature  of  tliis  branch  of  mining  engineering,  and  the  present  edition  folly 
maJntafna  the  high  standard  of  its  predecessor!.  To  the  student,  and  to  tlie  mining  engineer  alllce,  ITS 
VALUB  is  inestimable.    The  illustratioas  are  excellent."—  TAt  Mimmr  yaitrMai, 


In  Large  Crown  8vo.     Fully  Illustrated.    6s.  net 

THE  INVESTIGATION  OF  MINE  AIR: 

An  Account  by  Several  Authors  of  the  Nature,  Significance,  and  Practical 

Methods  of  Measurement  of  the  Impurities  met  with  in  the 

Air  of  Collieries  and  Metalliferous  Mines, 

EDITED  BY 

Sir  clement  LE  NEVE  FOSTER,  D.Sc,  F.R.S., 
And  J.  S.  HALDANE,  M.D.,  F.R.S. 

'*  We  know  of  nothing  essential  that  has  been  omitted.    The  book  is  liberally  supplied 
with  illustrations  of  apparatus."— Ctf/^»rfy  Guardian. 


In  Crown  8vo,  Handsome  Cloth.    8b.  6d.  net. 

MINING  LAW  OF  THE  BRITISH  EMPIRE. 

By  CHARLES  J.  ALFORD,  F.G.S.,  M.In8t.M.M. 

Contents.— The  Principles  of  Mining  Law. — The  Mining[  Law  of  Great 
Britain. — British  India. — Ceylon.— Burma. — ^The  Malay  Penmsula. — British 
North  Borneo. — Egypt. — Cyprus. —The  Dominion  of  Canada. — British 
Guiana.— The  Grold  Coast  Colony  and  AshantL — Cape  of  Good  Hope. — 
Natal.  —  Oranee  River  Colon  v.  —  Transvaal  Colony.  —  Rhodesia.  —  The 
Commonwealth  of  Australia. — New  Zealand,  &c.— Index. 

'  Sbould  be  specially  useful  to  all  those  engaged  hi  the  direction  of  mining  enter- 
prises."—^nanefnZ  Timu. 

"  Cannot  tail  to  be  useful   ...   we  cordially  recommend  the  book."— Jfimtij^  World 


In  Large  8vo.    Fourth  Edition.    Price  10s.  M. 

Mine  Accounts  and  Mining  Bool[-Keeping. 

For  Students,  Managers,  Secretaries,  and  others. 
With  Examples  taken  from  Actual  Practice  of  Leading  Companies, 

By  JAMES  GUNSON  LAWN,  A.R.S.M.,  A.M.Imit.C.E.,  F.G.8., 

Profesaor  of  Mining  at  the  Sonth  African  School  of  Mfanes. 

Edited  bt  Sir  C.  LE  NEVE  FOSTER,  D.So.,  F.R.S. 

"It  leems  ucpossiBut  to  suggest  how  Mr.  Lawv'b  book  ooold  be  made  more  coiiFLBn  or 
more  valuablb,  csrefhl,  and  exhaaBtly9.'*—Aecovntant$'  Magasitu, 


THE  MIHINC  ENCIHEER8'  REPORT  BOOK  AND  DIRECTORS' 

AND  SHAREHOLDERS*  GUIDE  TO  MINING  REPORTS.  By 
Edwin  R.  Field,  M.Inst.M.M.  With  Notes  on  the  Valuation  of 
Mining  Property  and  Tabulating  Reports,  Useful  Tables,  Jtc.,  and 
provided  with  detachable  blank  pages  for  MS.  Notes.  Pocket  Size, 
Strongly  Bound  in  Leather.    3s.  6d. 

"An  ADMIBABLT  compiled  book  which  Mining  Engineers  and  Managers  will  find 
flXTRnoiLT  USBFUL."- Jfinif^  Journal. 

LONDON:  CHARLES  GRIFFIN  i  CO..  LIMITED,  EXETEB  STREET.  STRAND. 


58  CHARLES  ORIFFIN  A  CO.'S  PUBLICATIONS. 

Sboond  Edition.    In  Crown  8vo.     Handsome  Clath,     WW^  30  New 

Ittuatrationa.    7«.  6d  net, 

ELECTRICAL  PRACTICE  IN  COLLIERIES. 

By  D.  burns,  M.E.,  M.In8T.M.E., 

OorUflcated  Oolliery  Maiugw.  and  Lecturer  on  Mining  and  Geoloor  to  tliA  OImbow  and  Weit  of 

Sootlftnd  Technical  College. 

ITnits  of  Measnremeiit,  Condacton,  kc — ^The  Theory  of  the  Djiiamc— The 
Dynamo,  Details  of  Coostmctioii  and  Workiiig. — Motors. — I^htmg  Installa* 
tiooB  in  Clollieries.  —  Pumping  b]r  Electricity.  —  Electrical  Haulage.  —  Goal 
Catting. — Misoellaneons  Applications  of  Electricity  in  Mines. — ^.Coal  Minea 
Begnlation  Act  (Electricity).— Indkx. 

*'A  clear  and  oonciBe  introduction  to  eleotiical  practice  in  collieries."— Jfiniii^ 
JoumaL  

FouBTH  Edition,  Thoroughly  Revised  and  Greatly  Enlarged.    Ra-set 
throaghoat.     Large  &own  8yo.     Handsome  Cloth.     128.  6d. 

PRACTICAL  COAL-MINING: 

A    MANUAL     FOR     MANAQERS.     UNDER-MANAQliBS, 
COLLIERY    ENGINEERS,    AND    OTHSR& 

With  Worked'OtU  ProbUma  on  Haulage,  Pumping,  Ventilation,  Ac. 
By  GEORGE  L.   KERR,   M.K,   M.In8T.M.E. 

**Ab  lasiiiTiALLT  rmAOTiOAL  voKK,  and  can  be  oonfldantlj  reoonunended.    No  department 
of  Ooal-Mlnlng  has  been  overlooked."— JE!R(r<Mcri'  OamUt. 


ELEMENTARY  COAL-MINING :  For  the  Use  of  Students,  Miners,  and 

others  preparing  for  Examinations.    By  Gbobob  L.  Kbbr,  M.E., 

M.Inst.M.E.,  Author  of  « Practical  Goal- Mining."    In  Crown  8yo. 

Handsome  Cloth.    With  200  Illustrations.     38.  6d. 

**An  abondanoe  of  Information  eonvejed  In  a  popular  an    attraotlre  form.   .    .    .    Will  be 
of  great  nse  to  all  who  are  In  any  way  Interested  In  coal  mining."— SooMtJk  OritU, 


BLASTING :  and  the  Use  of  ExploshriBS.    A  Handbook  for 

Engineers  and  others  Engaged  in  Mining,  Tunnelling,  Quarrying,  &c 
By  OscAB  GuTTMANN,  M.Iast.C.E.,  Mem.  Soo.  of  Civil  Engs.  and 
Architects  of  Vienna  and  Budapest,  Cor.  Mem.  Imp.  Roy.  GeoL  Inst, 
of  Austria,  Jtc.  Second  Edition,  Revised.  In  Large  8vo,  with 
Illustrations  and  Folding-Plates.     10s.  6d. 

"  Should  pnyve  a  vadd-m^cnm  to  Mining  Engineers  and  all  engaged  in  practical  woxk. 
—frpm  and  Coal  Tradts  Review. 


TESTING  EXPLOSIVES.    By  C.  E.  Bichbl  and  Axel  Larsbn. 

Contents.  — Historical — Testing  Stations — Power  Gauges — Products 
of  Combustion — Heat  of  Decomposition — Rate  of  Detonation — Rate 
and  Duration  of  Flame — After  b  lame  Rates — Transmission  of  Explo- 
sion—Efficiency, &C.     In  Medium  8vo.     Fully  Illustrated.    6s.  net. 

"Its  pages  bristle  with  Bnggestions  and  actual  experimeDtal  results  to  an  exte  it 
seldom  found  in  a  Tolume  of  five  times  its  size."— Arm«  and  JSaqOotivet 


SHAFT  8INKIN6   IN   DIFFICULT  CASES.     By  J.  Beihbb. 

Translated  from   the  Oerman  by  J.   W.   BaonoH,  A.M.Inst.C  E. 
With  18  Figarea  in  the  Text,  and  19  Plates.    Large  Syo.    At  Pbws. 

LONDON:  CHARLES  GRIFFIN  ft  CO..  LIMITED.  EXETER  STREET.  STRANa  ' 


MINING  AND  METALLURGY.  59 

In  Medium  %vo.      With  Numerous  PUxUb^  Mapa^  and  lUtutnUions, 

21s.  net, 

GYANIDING  GOLD  &  SILVER  ORES. 

A   Practical  Treatise  on  the  Cyanide  Process;    its  Application, 
Methods  of  Worlcing,  Design  and  Construction  of 

Plant,  and  Costs. 

By   H.   FORBES   JULIAN, 

Mining  and  Hetellargical  Engineer ;  Specialist  in  Oold :  Late  Teclinli^  AdTiaer  of  the 
Deataclie  Gold  und  Silber  Solieide  Anstalt,  Frankfort-on-Maine. 

And  EDGAR  SMART,  A.M.I.aE., 

Giyil  and  Metallargical  Engineer. 

"A  handflome  volume  of  400  pages  which  will  be  a  valuable  book  of  reference  for  all 
aaaociated  with  the  procesa."— Jf  tnin^  Journal. 

"The  autiiora  are  to  be  congratulated  upon  the  production  of  what  should  prove  to  be 
a  standard  work."— Po^tf**  Magcuine. 

In  Large  Crown  8vo.     With  13  Plates  and  many  lUustratums  in  the  Text* 

Handsome  Cloth,     Is,  td, 

THE  GTANIDE  PROCESS  OF  GOLD  EXTRACTION. 

A  Text-Book  for  the  Use  of  Meta/lurgiata  and  Students  at 

Schools  of  Mines,  do. 

By    JAMES    PARK,   F.G.S.,  M.Inst.M.M., 

Professor  of  MinhiK  and  Director  of  the  Otago  University  School  of  Mines ;  late  Direotor 

Thames  School  of  Mines,  and  Geological  Surveyor  and  Mining  Geologist 

to  the  Government  of  New  Zealand. 

Fourth  Enqush  Edition.    Thoroughly  Revised  and  Greatly  Enlarged. 
With  additional  details  oonceming  the  Siemens-Halske  and  other 
reoent  processes. 
"  Deserves  to  be  ranked  as  amongst  the  bbst  of  vxsffmxiiTBXATiBaB,"— Mining  Journal. 


Third  Edition,  Revised.     With  PlaUs  and  lUvstrations.    Cloth,  Ss,  M. 

GETTING     GOLD! 

A   GOLD-MINING    HANDBOOK    FOR   PRACTICAL    MEN. 

By  J.    0.   F.    JOHNSON,   P.G.S.,   A.I.M.K, 

Life  Member  Australasian  Mine-Managers*  ABsoolation. 

GsNiRAL  Contents. — Introductory :  Prospecting  (Alluvial  and  General) — 
Lode  or  Reef  Prospecting — Genesiology  of  Grold — Auriferous  Lodes — Drifts — 
Gold  Extraction — Liziviation — Calcination — Motor  Power  and  its  Transmisdoii 
— Company  Formation  —  Mining  Appliances  and  Methods  —  Australasian 
Mining  Regulations. 

"  pBAOnoAL  from  beginning  to  end    .    .    .    deals  thoroughly  with  the  Prospecting, 
fittnUng,  Crushing,  and  Sztraotion  of  gold."— A^t.  Austrakutan. 


In  Crown  Svo,    lUusirated.     Fancy  Cloth  Boards.     4«.  6d, 

GOLD  SEEKING  IN  SOUTH  AFRICA: 

A  Handbook  of  Hints  for  intending  Exploreps,  PFOspectors. 

and  Settlers. 

By    THEO    KASSNER, 

Mine  Manager,  Anthor  of  the  Geological  Sketch  Map  of  the  De  Kaap  Gold  Fieloa. 

With  a  Chapter  on  the  Agricultural  Prospects  of  South  Africa. 

As  fascinating  as  anything  ever  penned  by  Jnles  Verne.**— J^^Hcan  Oommmret. 


lONDON :  CHARLES  QRIFFIN  «  CO.,  LIMITED.  EXETER  STREET.  STRAND. 


6o  CHARLES  GRIFFIN  db  C0,*8  PUBLICATIONS. 

Large  8vo.    Handsome  Cloth.     With  Illustrationa. 

128.  6d.  net. 

METALLUR6IGAL  ANALYSIS  &  ASSAYING : 

A   THRBB   YBARS'   COURSE 

FOR  STUDENTS  OF  SCHOOLS  OF  MINES. 

By  W.  a.  MACLEOD,  B.A.,  B.Sc,  A.O.S.M.  (N.Z.), 

PormerlT  Aadat-Dlrector,  Thames  School  of  Mines  iN.Z.),  and  Lecturer  in  Chemistrj,  UnlTcnitj 
of  Tasmania :  Director  of  Queensland  Government  School  of  Mines.  Charters  Towers  : 

And  CHAS.  WALKER,  F.C.S., 

konstrator  in  Chemistry,  Sydnej  UniTersitjr ;  1 
and  Metallurgy,  Charters  Towers  School  of  Mines 

Part  I.— Qnalitative  Analysis  and  Preparation  and  Properties  of  Gasea. 
Past  U.— Qualitative  and  Quantitative  Analysia.  Part  ill. — Assaying, 
l^echnical  Analysis  (Oas,  Water,  Fuels,  Oils,  &c.). 

"The  publication  of  this  volume  tends  to  prove  that  the  teaching  of  metalluiglcal 
analysis  and  assaying  in  Australia  rests  in  competent  hands."— Aottire. 


ormerly  Assist.-I>emonstrator  in  Chemistry,  JydneyJJniTersIty;  Lecturer  n  Chemistiy 

Hi 


In  Crown  8vo,  Beautifully  Illustrated  with  nearly  100 
Microphotographa  of  Steel,  &c.     78.  6d.  net. 

MICROSCOPIC  ANALYSIS  OF  METALS. 

Bt  FLOEIS  OSMOND  &  J.  E.  STEAD,  F.R.S.,  F.LC. 

CoNTXNTB.— Metallography  considered  as  a  method  of  Assay.  —  Micro- 
graphic  Analysis  of  Carbon  Steels. — Preparation  of  Specimens. — Polishing. 
—-Constituents  of  Steel;  Ferrite;  Cementite;  Pearlite;  Sorbite;  Martensite: 
Hardenite ;  Troostite ;  Austenite. — Identification  of  Constituents.— Detailed 
Examination  of  Carbon  Steels. — Conclusions,  Theoretical  and  Practical. — 
Apparatus  employed.— Appendix. 

"  There  has  been  no  work  previously  pubUsbed  in  Knglish  calculated  to  be  so  useful  to 
the  student  in  metaUographic  research/'- Iron  and  Steel  Trades'  Journal. 


Third  Edition.    With  Folding  Plates  and  Many  Illustrationa.     36a. 


A  PRACTICAL  TREATISE  ON  THE  ART  OF  EXTRACTING  METALS 

FROM  THEIR  ORES. 

By  J.  ARTHUR  PHILLIPS,  M.Inst.O.K,  F.C.S.,  F.G.S.,  to. 

And  H.  BAUERMAN,  V.P.G.S. 

Gknsbal  Contents.  —  Refractory  Materials.  —  Fire-Clays.  —  Fuels,  ^— 
Aluminium.  —  Copper.  — Tin.  —  Antimony.  —  Arsenic.  —  Zina  —  Mercury.  ^ 
Bismuth.  —Lead.— Iron.— Cobalt  —Nickel — Silver. — Gold. — Platinum. 

**  Of  the  Third  Edition,  we  are  still  able  to  say  that,  as  a  Text-book  of 
Metallurgy,  it  is  thx  bbbt  with  which  we  are  acquainted.*'— .ffn^ineer. 

"  A  work  which  is  equally  valuable  to  the  Student  as  a  Text-book,  and  to  the 
practical  Smelter  as  a  Standard  Work  of  Reference.  .  .  .  The  Illustratioiu 
are  admirable  examples  of  Wood  Engraving.** — Chemical  Newt. 

LONDON:  CHARLES  GRIFFIN  ft  CO..  LIMITED,  EXETER  STREET.  STRAND 


MBTALLURQWAL  WORKS.  61 

Second  Edition,  Revised,  Enlarged,  and  Re-aet  77ir<mghout  on  Larger  Page. 
With  ValuMe  Bibliography,  New  Maps,  lUustrtUions,  die.    45^.  net. 


A    T^RBATISE    ON 

By    sir    BOVERTON    REDWOOD, 

D.8a,  F.ti.S.E.,  Awoalsn.O.B  .  F.LO.. 

Hon.  Mam.  Am.  Phil.  8oe. :  H'W.  Mem.  Imp.  Run.  Teeh.  800. :  Advlaer  on  Peferoleum  to  the 

Admlnlt7  and  Home  Offlee :  Oonenlttng  Adylser  to  the  Oorpontlon  of  London  under 

the  Petroleum  Acta :  Adrlaer  on  Petroleum  Truuport  to  the  Thames  Conaervmncj. 

C0NTIIIT8.— SBonoN  I.:  Hiitorical  Account  of  the  Petroleum  Indaatry.— Section  XL: 
Geological  and  Oeograjdiioal  Distribution  of  Petroleum  and  Natural  Oas.— Sbotion  HI.: 
The  Qiemlcal  and  FhyBical  Properties  of  Petroleum  and  Natural  Oas. -Sbotion  IY.: 
The  Origin  of  Petroleum  and  Natural  Qas.— Section  V.:  The  Production  of  Petroleum, 
Natural  Gkw,  and  Osokerite.— Section  VI.:  The  Beflning  of  Petroleum.— Section  VII.: 
The  Shale  Oil  and  Allied  Industries.— Section  YIII.:  llie  Transport,  Storage,  and  Dis- 
tribution of  Petroleum.— Section  IX. :  The  Testing  of  Crude  Petroleum,  Petroleum  and 
Shale  Oil  Products,  Ozokerite,  and  Asphalt.— Section  X. :  The  Uses  of  Petroleum  and 
Its  Products.— Section  XI. :  Statutory,  Municipal,  and  other  Regulations  relating  to 
the  Testing,  Storage,  Transport,  and  use  of  Petroleum  and  its  Products.— Appendices. 
—BiBLioQKAPHT.— Index.       

Sboond  Edition,  Revised,     With  lUuetrations.    Price  Ss.  6d.  net. 

A     HANDBOOK     ON     PETROLEUM. 

FOR  IN8PEGT0R8  UNDER  THE  PETROLEUM  ACTS. 

And  for  those  ensaged  in  the  Stopaae,  Transpopt,  Distribution,  and  Industrial 

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suggestions  on  the  Constraetion  and  Use  of  Mineral  Oil  Lamps. 

By   captain   J.    H.    TH0M80JN, 

H.M.  Ohlef  Inspector  of  Bzploslres, 

And    sir    BOVERTON    REDWOOD, 

Author  of  **  A  Treatise  on  Petroleum. " 

Oonains.— I.  Introductorj.— IL  Sources  of  Supply.— IIL  Production.— IY.  Ohemical  Pro- 
ducts, Shale  Oil,  and  Coal  Tar.— Y.  Flash  Point  and  Fire  Test— YL  Testinga.— YIL  Existing 
Legiuatlon  relating  to  Petroleum.— YIIL  — IX.— Precautions  Necessary.— X  Petroleum  Ou 
Lraips.— XL  Oarbide  of  Oalcinm  and  Acetjlene.— Appendices.- I5J>BZ. 

"A  Tolnme  that  will  enrich  the  world's  petroleum  literature,  and  render  a  serrlee  to  the 
British  branch  of  the  induktry.  .  .  .  Reliable,  indispensable,  a  brilliant  eontribntion."— 
P§iroUum,  

In  Crown  Svo.    Fully  Illustrated.    2s.  6d.  net. 

THE  LABORATORY  BOOK  OF  MINERAL  OIL  TESTING. 

By    J.    A.    HICKS, 
Chemist  to  Sir  Boverton  Redwood. 

CoiTTBHTS.  —  Spedflc  Gravity.  —  Flashing  Point.  —  Teste.  —  Yisoosity.  —  Colour.  — 
Apparatus— Detection  of  Petroleum  Yapour.— Capillary  Teat.— Melting  Point  of  PanUOln 
Scale  and  Wax.— Oil  in  Scale.— Estimation  of  Sulphur,  of  Water.— Calorlflo  Yalue.— 
Tables.— IKDBX.  

OIL    FUBU     By  SIDNEY  H.  NORTH.    {See  page  29,) 


THB  PBTROLiBUM  LAMP:  Its  Choice  and  Use.   A  Guide 

to  the  Safe  Employment  of  the  Paraffin  Lamp.     By  Caft.  J.  H. 
Thomson  and  Sir  Boyerton  Redwood.    lUnstrated.     1  s.  net. 

**  A  work  which  will  meet  every  purpose  for  which  It  has  been  written."— Pe(roIe«m. 

LONDON:  CHARLES  GRIFFIN  H  CO..  IIMITED,  EXETER  STREET.  STRAND 


63  GBARLm  ORIPFIN  S  OO.'B  PUBLIOATIOiTB. 

STANDARD  WORKS  OF  REFERENCE 

FOR 

MetallnFgists,  Mine-Owners,  Assayers,  Manufaetnren, 

and  all  interested  in  the  development  of 

the  Metallorgieal  Industries. 

EDITED  BT 

Sir  W.  ROBERTS-AUSTEN,  K.C.B.,  D.C.L.,  F.R.S. 

In  Lairg9  8e»,  Hattdsotm  Cloth.      With  lUutiraUam, 


nrTBODUCTIOir   to   the    STUDY   of  METAIiIinBaY. 

By  the  Editor.     Fifth  Edition.     iSs.    (Seep.  63.) 

GOIiD    (The    Metallurgnr    of).      By   Thos.    Kirks    Rosk, 

D.Sc.,  Assoc  R.S.M.,  F.C.S.,  Chemist  and  Assayer  of  the  Royal 
Mint.    Fifth  Edition.    21s.    (Seep.  63.) 

IiBAD   AND   8II1VEB   (The   Metallurgy   of).      By  H.  F. 

CoLUNS,  Assoc.  R.S.M.,  M.InstM.M.  Part  I.,  Lead,  i6s;  Part 
II.,  Silver,  i6s.     (See  p.  64.) 

IBOir    (The  Metallurgy  of).    By  T.   Turner,  A.R.S.M., 
F.I.C.,  F.CS.    Third  Edition,  Revised.     i6s.    (See  p.  65.) 

8TEEI1    (The    Metallurgy    of).       By  F.   W.   Harbord, 

Assoc.  R.S.M.,  F.I.C.,  with  a  Section  on  Mechanical  Treatment  hy 
J.  W.  Hall,  A.M.Inst.C.E.  Second  Edition.  25s.  net.  (See 
p.  65.)  

Wm  bt  PubUsktd  at  Short  InUnmU. 

METAIiIiUBGICAIi  MACHIITEBY :  the  AppUcation  of 
Engineering  to  Metallurgical  Problems.  By  Henry  CharlesJenkims* 
Wh.Sc.,  Assoc  R.S.M.,  Assoc. M.  Inst. C.E.,  of  the  Royal  College  of 
Science.  (See  p.  64). 

COPPER  (The  Metallurgy  of).     By  Thos.  C.  Cloud,  Assoc. 

R.S.M. 
▲IJEjOYS.      By  Edward  T.  Law,  Assoc. R.S.M. 

*«*  Other  Volumes  in  Preparation. 

LONDON:  CHARLES  BRIFFIN  ft  CO.,  LIMITED,  EXETER  STREET.  STRAND. 


MBTALLURQIOAL  WORKS.  63 


GBIFFIir'S    METAIiIiXJBGICAIi    8EBIE8. 


Fifth  Edition,  thoroughly  Revised  and  considerably  Enlarged.     Large 

8yo,  with  numerous  Illustrations  and  Micro-Photographic 

Plates  of  different  varieties  of  Steel.     18s. 

An  Introduetion  to  the  Study  of 

BY 

Sir  W.  ROBERTS-AUSTEN,  ILC.B.,  D.C.L.,  F.R.S.,  A.R.S.M., 

Late  Chemist  and  Assayer  of  the  Royal  Mint ,  and  Profetsor  of  Metallurgy 

in  the  Royal  College  of  Science. 

Gbnbrax.  Contents.— The  RelaUon  of  Metalluxsy  to  Chemis^.— Physical  Properties 
of  Metals. — Alloys.  The  Thermal  Treatment  of  Meta^.— Fuel  and  Thermal  Measurements. 
— Materials  and  Products  of  Metallureical  Processes. — Furnaces. — Means  of  Supplying  Air 
to  Furnaces. — ^Thezmo- Chemistry. — "l^roical  Metallurgical  Processes. — ^The  Micro-Structure 
of  Metals  and  Alloys. — Economic  Considerations. 

**  No  English  text-book  at  all  approaches  this  in  the  complbtbnbss  with 
which  the  most  modem  views  on  the  subject  are  dealt  with.  Professor  Austen's 
volume  will  be  invaluablk,  not  only  to  tbe  student,  trat  also  to  those  whose 
knowledge  of  the  art  is  far  advanced."— CAmvs^o/  News, 


FiPTH  Edition,  Revised,  Considerably  Enlarged,  and  in  part  Re-written. 
With  Frontispieoe  and  numerous  Illustrations.    21b. 

THE  METALLURGY  OF  GOLD. 

BT 

T.  KIRKE  ROSE,  D.ScLond.,  Assoc.R.S.M., 

Chemiai  and  Awayer  of  the  Royal  Mini, 

GuriBAL  CONTBHIS.— The  Properties  of  Gk>ld  and  its  Alloys.— Chemistry  of  the 
OompouDdsof  Gold.— Mode  of  OccurreDce  and'  Distribution  of  Gold.— Shallow  Placer 
]>epo0itB.— Deep  Placer  Depceits. — Quarts  Crashinff  in  the  Stamp  Battery.— Amalgam- 
ation in  tiie  Stamp  Battery. — Other  Forms  of  Cmuiing  and  Amalgamating  Machinery. 
—Concentration  in  Gold  Mills.- Dzy  Cnuhing.— Be-grinding.— Roasting.- Chlorination: 
The  Plattner  Process,  The  Barrel  Process,  The  vat-Solution  Process.- The  Cyanide 
Process.— Chemistry  of  the  Cyanide  Process.— Befinine  and  Parting  of  Gold  Bullion. 
—Assay  of  Gold  Ores.— Assay  of  Gold  Bullion.- Statistics  of  Gold  Production.— Blblio- 
graphy.— IHDBX. 

**  A  ooMPRBmEirsiVB  nucncAL  tbbatisb  on  this  important  sabjeot**— 7%«  2H'mei. 

''The  HOST  ooKPLsra  desoription  of  the  GHLOBuvATioir  paoosss  whieh  has  yet  been  pnb- 
Uahed." — Mininif  Journal. 

**  Adapted  for  all  who  are  Interested  in  the  Gold  Mining  Industry,  being  free  from  teoh- 
nioalltles  as  far  as  possible,  bat  is  more  particolarly  of  value  to  those  engaged  iu  the 
Industry.  *'--C!a|)<  Tiine$. 

LONDON:  CHARLES  ORIFFIN  i  CO.,  LIMITED,  EXETER  STREET.  STRANDl 


64  OHARLES  QRIFFIN  A  CO.'S  PUBLICATIONS. 

GBIFFIIT'S   METAIiIiUBaiCAIi   8EBIE8. 

Bditm>  by  sir  W.  ROBERTS-AUSTEN,  K.O.R,  F.R.S.,  D.C.L. 
In  Large  8vo,    Ilandaome  Gloth,     With  lUustrcUions. 

In  Two  Volames,  Eaoh  Complete  in  Itself  and  Sold  Separately. 

THE  METALLUR6Y  OF  LEAD  AND  SILVER. 

By  H.  F.  COLLINS,  AssoaRS.M.,  M.In8T.M.M. 

Pa»]?t     I.— Xj  S  jHl  I>  : 

A  Complete  and  Exhanstiye  Treatise  on  the  Manu&otare  of  Lead, 
with  Sections  on  Smeltine  and  Desilyerisation,  and  Chapters  on  the 
Assay  and  Analysis  of  the  Materials  involyed.    Price  ids. 

SUMMABT  OF  CONTENTS.— SampliDff  and  Assaying  Lead  and  Silver.— Properttei  and 
Oompoonds  of  Lead.— Lead  Ores.- Lead  Smelting.- Beverberatoriet.- Lead  Smelting  in 
Hearths.— The  fioasUng  of  Lead  Ores.- Blast  Furnace  Smelting ;  Principles,  Practioe, 
and  Bxamples;  Prodncts.- Fine  Dust,  its  Composition,  GoUection  and  Treatment.— 
Costs  and  Losses,  Porchase  of  Ores.- Treatmentof  Zinc,  Lead  Sulphides,  Desilverisation. 
Softening  and  Beflning.— The  Pattinson  Process.— The  Parkes  Process.— Cnpellation  ana 
Beflning,  Ac.,  Ao, 

"A  THOBOUOHLT  SOUND  and  useful  digest.  May  with  nyeet  oonfidinob  be 
recommended."- Jfinini^  JoumuU. 


Pa.x*t     II.— SIX^VESR. 

Comprising  Details  regarding  the  Sources  and  Treatment  of  Silver 
Ores,  together  with  Descriptions  of  Plant,  Machinery,  and  Processes  of 
Manufacture,  Refining  of  Bullion,  Cost  of  Working,  &c.    Price  16s. 

SuxiEABT  OF  Contbnts.— Properties  of  Silver  and  its  Principal  Compounds.— Silver 
Ores.- The  Patio  Process.— The  I^azo,  Fondon.  Er5hnke,  and  Tina  Processes.- The  Pan 
Process.— Boast  Amalgamation.- Treatment  of  Tailings  and  Concentration.— Betortlng, 
Melting,  and  Assaying  — Chloridising-Boasting.— The  Augustin,  Claudet,  and  Ziervogel 
Processes.— The  Hypo-Sulphite  Leaching  Process.— Beflning.— Matte  Smelting.— Pyrltic 
Smelting.— Matte  Smelting  in  Beverberatories.— SUver-Copper  Smelting  and  Beflning.— 
Index. 

*'  The  author  has  focussed  A  LABoa  amount  of  talvabls  information  into  a 
convenient  form.  .  .  .  The  author  has  evidentiy  considerable  practical  es^Mrience, 
and  describes  the  various  processes  clearly  and  well.  '—Mining  Journal, 


METALLDMICAl"  MACHiNERY : 

The  Application  of  EngineerinK  to  Metalluitf  oal  Probloms. 

By  henry  CHARLES  JENKINS, 

WTlSc^  Assoc R,8.1I£.^  Assoc M,Inat,C.E. 

LONDON:  CHARLES  BRIFFIN  ft  CO.,  UNITED,  EXETER  STREET,  STRAND. 


METALLURGIOAL  WORKS.  65 


GBnvnr's  METAiiLnHaiOAii  series. 


Sicx>ND  Edition,  ReviBed.     With  Nnmerons  Blustrations.    Large  870. 

HandBome  Cloth.    25«.  net. 

With  Additional  Chapter  on  The  Eieotrio  Smelting  of  Steel, 

THE  METALLURGY  OF  STEEL. 

By  F.   W.  HARBORD,  AssocRS.M.,   RLC, 

Oontulting  Metallurgist  a/nd  Analytical  Chemist  to  the  Indian  Oovemmentf 
Royal  Indian  Engineering  College^  Ooopere  Hill. 

With  37  Platee,  280  Bliistratioiui  in  the  Text,  and  nearly  100  Micro* 

Sections  of  Steel,  and  a  Section  on 

THE   MECHANICAL   TREATMENT    OF   8TEBL. 

By    J.    W.    HALL,    A.M.Inbt.C.K 

ABBiDasD  CovTBHTS.— The  Plant,  Maohin«rv,  Method*  and  Ohemlitnr  of  the  Beeaemer 
and  of  the  Open  Hearth  ProoeeeeB  (Add  and  Baslc).~The  Meohanloal  Treatment  of  Steel 
eomprleing  Mill  Praotioe,  Plant  and  Machinery.— The  Infloenoe  of  Metalloids,  Ueat 
Treatment  Speoial  Steels,  Mloroetrootare,  Testing,  and  SpecifleationB. 

**  A  woric  whleh  we  rentore  to  commend  as  an  Invalnable  oompendimn  of  information  npon 
the  metallnigy  ofBteel."— Iron  and  Cfoal  7yade$'  Btfrtew. 

The  JBnginetr  taya,  at  the  conclusion  of  a  review  of  this  hoolc :— *'  We  cannqft  conclade  without 
eamestlr  recommending  all  who  may  he  Interested  as  makers  or  nseis  of  ateel,  which  practicallj 
means  the  whole  of  the  engiDeering  profeasion,  to  make  themselTse  acquainted  with  it  as  apeedilj 
aa  poaalhle,  and  thia  maj  he  the  more  eaallj  done  ae  the  pabliahed  price,  considering  the  alse 
of  the  book,  ia  eztremelj  moderate." 


Thibd  Edition,  Reyised.    Shobtlt. 

THE  METALLURGY  OF  IRON. 

By  THOMAS  TURNER,  Assoo.RS.M,  F.I.O., 

Profesior  of  MeiaUvrgy  in  the  UnwertUy  of  Birmingham. 

In  Labob   8vo,  Handsomb   Cloth,  With  Numbbous  Illustbationb 

(many  fbom  Photoobafhs). 

0m«rai  Cimitaiif.— Barly  History  of  Iron.— Modem  History  of  Iron.— The  Age  of  Steel. 
—Chief  Iron  Oree.— Preparation  of  Iron  Ores.— The  Blast  Fnmaoe.— The  Air  need  in  the 
Blast  Fnmaoe.— Beaetions  of  the  Blast  Fnmaoe.— The  Fuel  need  in  the  Blast  Fnmaoe.— 
Blags  and  Fnzes  of  Iron  Smelting.— Properties  of  Oast  Iron.— Foundry  Practice.— Wrought 
Iron.— Indirect  Production  of  Wrought  iron.— The  Puddling  Prooeas.— Further  Treatment 
of  Wrought  Iron.  -Corrosion  of  Iron  and  Steel. 

"  A  xoflT  YALUABLB  BUioiABT  of  knowledge  leUtang  to  every  method  and  stage 
m  the  mannfaetiiTe  of  oast  and  wrought  iron  .  .  .  rich  in  ohemieal  details.  .  .  . 
ExHAvenvB  and  thobouohlt  up-TO-DATB."~JBtt2{0tMi  of  the  American  Iron 
e/nd  Steel  AuoeicUion, 

*<  This  is  A  DBUOHTFUL  BOOK,  giving,  as  it  does,  reliable  infiMmatioQ  on  a  sabjeot 
beooming  eyeiy  day  more  elaborate.^— (7o(tterv  Ouardian. 

"A  TROBonoHiiT  nsKTUL  BOOK,  wUch  oringB  the  sabjeot  up  to  datb.  Of 
OBB4T  YALUB  to  thooe  ODgagod  in  tiie  iron  indnst^r." — Minrng  Journal, 


*«*  For  Professor  Turner's  Lectures  on  Iron- Founding,  see  page  68. 

LONDON:  CHARLES  SRIFFIN  ft  CO.,  LIMITED,  EXETER  STREET,  8TRAK& 


«6  0HARLE8  attlfFlN  *  OO.'S  PUBLI0ATI0N8. 

A    TEXT-BOOK    OF    ASSAYING: 

Fwr  the  uae  of  Students^  Mine  Managera,  Aaaayere,  do, 
By  J.  J.  BERINGER,  F.I.C.,  F.C.S., 

Public  Aoalyst  for,  and  Lectorer  to  the  Uming  Assocution  o^  ComwaO. 

And  C.  BERINGER,  F.C.S., 

Late  Chief  Aasajer  to  the  Rio  Unto  Copper  Company,  London, 

^Vtth  nwneroiis  Tables  and  Illustrations.     Crown  8vo.     Cloth,  los.  6d* 

Tenth  Edition. 

Gkmbkal  CoMTawTa.  —  Pakt  I.  —  Imtkoddctory ;    Manipulation:    Sampling; 


_ ;  Calmlafion  of  Resolts — Laboratory^booka  and  Re^orta.  Mbtmods  :  Dry 
anethc;  Wet  Granmetric— Volumetric  Asnys:  Titrometnc,  Colorimetric,  Gasoo 
Wdi^ung  and  Measurinj^-- Reagents— Formvdae,  Equations,  ftc.— Specific  Gravity. 

Pakt  II.— Mktals  :  Detection  and  Assay  of  Silver,  Gold,  Platinum,  MercuiTi  Copper, 
Lead,  Thallium,  Bismu^L  Antimonv,  Iron,  Nidcel,  Cobal^  Zinc,  Cadmium,  Tin,  Tungsten, 
Utamum,  Manganese,  Chromium,  «c.— Earths,  Aikalirs. 

Pakt  III.— Non-Mbtals :  Oxygen  and  Oxides;  The  Halogens— Sulphur  and  Sul- 
phates    Arsenic,  Phosphorus,  Nitrogen— ^licon.  Carbon,  Boron— Uselul  Tables. 

"A  axALLY  MBKiToaiODS  woKK,  that  may  be  safely  depended  upon  either  far  systemat£e 
iBStniction  or  for  reference,  ■—■iwi/iffv* 

"This  work  is  one  of  the  best  of  its  Idnd."— ^aifilPMtfr. 

FouBTH  Edition,  Revised,    Handsome  Clothe     WUk  JSumeroui 

lUiutreUionB,    68, 

A     TEXT-BOOE      OF 

ELEMENTARY   METALLURGY. 

Including  the  Author's  P&aotioal  Laboratobt  Coubbb. 
Bt    a.    HUMBOLDT    SEXTON,    F.I.C.,  P.O.S., 

ProfiBnor  of  Metaliurgy  in  the  Gkagow  and  Wert  of  SootUnd  Teohnioal  Qollege^ 

GENERAL  CONTENTS.— Introdiiotioii.^Propertie8  of  the  Metala.— Oombiistion. 
—Fuels.— Befractorj  Materials.— FnmaoeB.—Oocarrenoe  of  the  Metals  in  Nature. — 
Preparation  of  the  Ore  for  the  Smelter. — MetaUnrgical  Prooeeseo, — Iron. — SteeL— 
Oopjper. — Lead. — Zmo  and  Tin.— Silver. — Gold. — Meronry. — AUoys. — ApplioationB 
of  Blrotbioitt  to  Metallurgy. — Laboratobt  Coubsb. 

*'Jnrt   the   kind  of  work   for   Students   oommbhooio   the   study   of  MetsL 
or  fior  EiroiBBBBoro  Students.** — PraeHcal  JBnffineer. 
SxaBUJOiTLT  got-up  and  wbll-abbabobd."— CAemioaZ  Trade  Journal, 

In  Large  8yo.    Handsome  Cloth.     Prioe  48. 

tables  for 

QUANTITATIVE  METALLURGICAL  ANALYSIS. 

FOR   LABORATORY  USE. 

ON  THE  PRINCIPLE  OF  ''GROUP"  SEPARATIONS. 

By  J.  JAMES    MORGAN,  P.O.S.,  M.S.O.L 

"The  Aathor  may  be  oohobatuiatbd  on  the  way  his  work  has  been  oantod  oot**— 
f%€  Sittfiitotf 

"  WUl  oouBVD  IT8KIJ-  highly  in  Laboratory  Praotloe.  Its  or.nswMii  and  pkboisiov 
mark  the  book  out  as  a  highly  naefiil  one/^-^iUning  Journal, 

lOKDOII:  GHARLE8  QRIFFIN  «  CO..  LIMITED,  EXETER  STREET.  STRANOl 


"^i: 


ELEOTRO-METALLUROT,  ETO.  67 

Sboond  Edition,  Revised,  Enlarged,  and  in  part  Be-written. 
With  Additional  Sections  on  Modbrn  Theobubs  ot  Eleotroltsis 

Costs,  &c.     Price  10s.  6d. 

A  TREATISE   ON 

ELECTRO-METALLURGY: 

Embracing  the  Application  of  EleotrolysiB  to  the  Plating,  Depositing, 

Smelting,  ana  Refining  of  various  Metala,  and  to  the  Bepro- 

dnction  of  Printing  Sor&ces  and  Art- Work,  kc, 

BY 

WALTER   G.    M^'MILLAN,   P.LC,   F.C.S., 

Seereta/ry  to  the  Inttiiution  of  EUetrioal  Bngineen  ;  late  Leeturer  in  MetaUwrgy 

at  Matcn  CciUgef  Btrmingham, 

With   nmnerons    niiutrationB.        Large   Crown   8vo.        Cloth. 

"This  excellent  treatise,  .  .  .  one  of  the  best  and  moot  ooicpuetb 
manuals  hitherto  published  on  Electro-Metallurgy." — Electrical  Review, 

*'  This  work  will  be  a  standard.  "—Jetoe^er. 

''Any  metallurgical  process  which  rbducbs  the  oosT  of  production 
must  of  necessity  proye  of  great  commercial  importance.  .  .  .  We 
recommend  this  manual  to  all  who  are  interested  in  the  fbaotioal 
AFPUOATION  of  deotrolytic  processes." — NtUure. 


Sbookd  Edition,  Thoroughly  Revised  and  Enlarged,     bi  large  8vo. 
With  Numerous  niustrations  and  Three  Folding-Plates.    21s.  net. 

ELEOmiO  SMELTIUfr  &  REPIHIffr; 

A  Practical  Manual  of  the  Extraction  and  Treatnnent 
of  Metals  by  Electrical  Methods. 

Being  the  "  Elbktbo-Mbtaixuboie  "  of  Dr.  W.  BORCHERS. 

Translated  from  the  Latest  German  Edition  by  WALTER  G.  M*MILLAN» 

F.I.C.,  F.O.S.' 

CONTENTS. 

Part  I. — Alkalies  and  Alkalinb  Earth  Metals:  Manaesium,. 
Lithium,  Beryllium,  Sodium,  Potassium,  Calcium,  Strontium,  JBarium, 
the  Carbides  of  the  Alkaline  Earth  Metals. 

Part  IL~Thb  Earth  Metals:  Alnmininm,  Cerium,  Lanthanum, 
Didymium. 

Part  IIL — The  Heavy  Metals  :  Cop|^r,  Silver,  Gold,  Zinc  and  Cad* 
minm.  Mercury,  Tin,  Lead,  Bismuth,  Antimony,  Chromium,  Molybdenum, 
Tungsten,  Uranium,  Manganese,  Iron,  Nickel,  and  Cobalt,  the  Platinum 
Group. 

"  Comprbhenbiyb  and  aitthobitatitb  ...  not  only  full  of  yaxuable  inioe- 
XATiov,  bat  giTw  eyidenoe  of  a  thorough  nrsiOHT  into  the  technical  value  and 
rOBSlBiUTiBS  of  all  the  methodi  dlBexumed."—The  BUctrieian. 

"  Dr.  BOBOBEBS'  WELL-KHOWH   WORK     .     .     .     mnst  OF  NB0BS8ITT  BE  AOi^UIBED  hj 

eveiT  one  interested  in  the  snbject.    Bzoellentlt  put  into  EngliBh  with  additlonid 
matter  by  Mr.  McMillan."— Mature. 
"  Will  be  of  OBBAT  8BRYIOK  to  the  practical  man  and  the  Student."— JSZeetrie  SmeUing 

LONDON :  CHARU8  GRIFFIN  «  CO..  LIMITED.  EXETER  STREET.  8TRANK. 


68  CHARLB8  QRIFFIN  Jk  CO.*S  PUBLICATIONS. 

In  Large  4Ao^  Library  Style,     Beautifully  lUustraUd  with  tO  PUUe»,  VMoyy 
in  ColourSy  and  94  Figuree  in  the  Text,     £2,  28.  net, 

PRECIOUS    STONES: 

Thelp  Ppopeptles,  Ooeuppenoes,  and  Uses. 

A    Treatise  for  Dea/era,   Manufaoturers,  Jewellera,  cuid  for  a/l 
Collectora  and  others  interested  in  Gems, 

By  Dr.  MAX  BAUER, 

Profeaaor  in  the  UniTenlty  of  Marburg, 
Translatbd  bt  L.  J.  SPENCER,  M.A.  (Cantab.),  F.G.8. 

'*  The  plates  are  remarkable  for  their  beaatv,  delicacy,  and  trathfolness.  A  elance  at 
them  alone  U  a  lesson  on  precious  stones,  vhilst  the  perusal  of  the  work  itself  should 
add  a  new  interest  to  any  casket  of  Jewels  or  cabinet  of  gems,  or  even  to  a  Jewellers' 
window."— JLtAmuBum.  

In  Large  Grown  8vo,     With  Numerous  TUustratione,    8s,  6d, 

Tk  Art  of  the  Goldsmith  and  Jef  eller 

A  Manual  on  the  Manipalatlon  of  Gold  and  the  Manu- 
faetore  of  rersonal  Ornaments. 

By    THOS.    B.    WIGLEY, 

Headmaster  of  the  Jewellen  and  SilTersmiths'  Assoc.  Tech.  School,  Ktminfl^uun. 

Assisted  by  J.  H.  STANSBIE,  B.So.  (Lond.),  F.I.O., 

Lecturer  at  the  Birmingham  Municipal  Technical  SchooL 

Oknbral  CoNTBiiTS.— Introduction.— The  Ancient  Goldsmith's  Art.  ~ Metallurgy  of 
Oold.— Prices,  Ac— Alloys.— Melting,  Boiling,  and  Slitting  Gold.— The  workshop  and 
Tools.— Wire  Drawing.  —  Blngs.  —  Chains  and  Insignia. —Antique  Jewellery  and  its 
BevivaL— Etruscan  Work.— Pkboious  Stonbs.— Gutting.— Polishing  and  finishing.— 
Ghasing,  Embossing,  and  Bepouss^  Work.— Golouriug  and  Finishing.- Enamelling. — 
Engraving.- Moulduig  and  Gssting  Ornaments,  Ac.— Fluxes.  Ac.- Beoovery  of  the 
Precious  Metals.— Beflning  and  Assaying.- Gilding  and  Electro  Deposition.— HaU- 
MarUng.— Miscellaneous.— Appendix. 


Eaetra  Crown  8vo.     With  48  Illustrations,     Ss,  Qd,  net, 

LECTURES  ON  IRON-FOUNDING. 

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Professor  of  Metallurgy  in  the  Univenity  of  Birmingham* 

Contents.- Varieties  of  Iron  and  Steel.— Application  of  Cast  Iron.— History.- Pro- 
duction.—Iron  Ores.— Composition.— The  Blast  Fumaoe.— Materials.— Beaetions. — 
Grading  Pig  Iron.  —  Carbon.  Silicon,  Sulphur,  Phosphorus,  Manganese,  Aluminium, 
Arsenic,  Copper,  and  Titanium.— The  Foundry.— General  Arrangement.- Be-meltins 
Cast  Iron.  — The  Cupola.  — Fuel  Used.  —  Changes  due  to  Be-melting.— Moulds  and 
Moulding.— Foundry  Ladles.— Pouring  and  Pouring  Tempemture.— Common  Troubles. — 
Influence  of  Shape  and  Size  on  Strength  of  Castings.- Tests. 

*' Ironfounders  will  And  much  information  in  the  book."— Iron  Trade  Cireular 
iRykmd's).  

In  Medium  8vo,    Handsome  Cloth,     Fully  Illustrated. 

GENERAL   FOUNDRY  PRACTICE: 

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By  A.  C.  M°WILLIAM,  A.R.S.M.,  and  PERCY  LONGMUJR. 

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0HBM18TRT  AND  TBOHNOLOOT. 


69 


Criinn'8  Chemloal  and  Teohnologloal  Publloatlona. 


Inorgranie  Chemistry, 
Quantitative  Analysis,    . 
Qualitative  ,, 

Chemistry  for  Ensfineers, 

„        „  Maniuacturers, 
Foods  and  Poisons, . 
Tables  for  Chemists, 
Dairy  Chemistry, 
Dairy  Analysis, . 
MillL,  .... 
Flesh  Foods, 
Praetieal  Sanitation, 
Sanitary  Engineering, 
Teehnieal  Mycology, 
Ferments,  . 

Toxines  and  Antitoxines, 
Brewing,    . 

Bacteriology  of  Brewing, 
Sewage  Disposal, 
Trades'  Waste, . 
Smol^e  Abatement,  . 
Paper  Technology,  . 
Cements, 
Water  Supply,  . 
Road  Making,    . 
Gas  Manufacture,     . 
Acetylene, . 
Fire  Risks, 
Petroleum, 

(Handbook), 

Ink  Manufacture,     . 
Glue,  Gelatine,  &c., . 
Oils,  Soaps,  Candles, 
Lubrication  &  Lubricants, 
India  Rubber,  . 
Painters'  Colours,  Oils,  &c., 
Painters'  Laboratory  Guide, 
Painting  and  Decorating, 
Dyeing,      .... 
Dictionary  of  Dyes, 
The  Synthetic  Dy estuffs, . 
Spinning,  .... 
Textile  Printing, 
Textile  Fibres  of  Commerce, 
Dyeing  and  Cleaning, 
Bleaching,  Calico- Printing, 


Props.  Dupr^  aih)  Hakb, 
Prof.  Humboldt  Sbxton, 

Blount  akd  Bloxam,  . 


A.  Wyhtbb  Blyth, 
Prof.  Oastell-Evans, 

H.  D.  HiCHMOND, 
E.    P.    WiLLOUGHBT, 

0.  A.  Mitchbll, 
Dr.  G.  Rbid, 
P.  Wood,    . 
Lafar  and  Saltbb, 
C.  Oppenhbimbr, 


FA«B 

70 

70 

70 

46 

71 

73 

79 

73 

73 

73 

74 

78 

78 

74 

75 

74 

76 

75 

76 

76 

76 

81 

76 

77 

79 


Dr.  W.  J.  Sykbs, 
W.  A.  Riley,     . 
Santo  Crimp, 
W.  Naylor, 
Wm.  Nicholson, 
R.  W.  Sindall,  . 
G.  R.  Rbdgbayb, 

R    E.    MlDDLETON, 

Thos.  Aitkbn,  . 
W.  Atkinson  Buttbrfibld,  77 
Lebds  and  Buttbbfibld,  77 
Dr.  Schwartz,  .  .  77 
Sir  Boverton  Rbdwood,  61 
Thomson  and  Rbdwood,  61 
Mitchbll  and  Hbpworth,  81 
Thos.  Lambert,  .  .  81 
Wright  k  Mitchell,  71 
Archbutt  and  Deelby, 
Dr.  Carl  O.  Weber, 
G.  H.  Hurst, 


W.  J.  Pbarcb, 
EInbcht  and  Rawson, 
Rawson  and  Gardner 
Cain  and  Thorpe, 
H.  R.  Carter,     . 
Seymour  Rothwbll, 
W.  L  Hannan,    . 
G.  H.  HuBST, 
Geo.  Duerr, 


32 

81 
80 
80 
80 
82 
82 
82 
83 
83 
83 
84 
84 


LONDON :  CHARLES  BRIFFIN  ft  CO..  LIMITED.  EXETER  STREET.  STRAND. 


70  0HARLE8  ORIFFIN  ^  OO.'S  PUBLWATI0N8. 

Third  Edition,  Revised,  Enlaiged,  and  Re-issued.     Price  6s.  net. 

A  SHORT   MANUAL  OF 

INORGANIC  CHEMISTRY. 

BY 

A.    DUPRE,  Ph.D.,  F.R.S,, 

AND 

WILSON    HAKE,  Ph.D.,  F.I.O.,  F.C.S., 

Of  Um  Westmiiister  Hospital  M«dical  School 

*»  A  «<tll-fTit»<m,  rfjtttr  unA  atrsiratm  glgmantary  Manual  nf  f  nnny  wi<»  C^miMtf^      ,      .      , 

We  agree  heartily  with  the  system  adopted  by  Drs.  Duprd  and  Hake.    Will  maxb  SxntKi* 

MBMTAL  WOKK  TKBBLY  INTBRBSTIMG  BBCADSB  INTBLUGIBLB."— «S'a<l»n^  Stvinu. 

"  There  is  no  question  that,  given  the  pbrfbct  gkounding  of  the  Student  hi  his  V«i»m 
the  remainder  comes  afterwards  to  him  in  a  manner  much  more  simple  and  easily  aojiiirsd. 

Tlie  IfOric  IS  AM  BXAMPLB  OP  THE  ADVANTAQBS  OP   THX  SvBTRIfATIC  TSBATMSHT  of  a 

Science  over  the  fragmentaij  style  so  generally  fiDllowisd.    Bt  a  long  wat  trb  bbst  of  the 
CBsall  Manuals  for  Sbadaaa-^-AMoiyst. 


LABORATOBT  HANDBOOKS  BT  A.  HUMBOLDT  SEZTOM, 

Professor  of  Hetallorgy  In  the  Qlasgow  and  West  of  Sootlaad  Teohnioal  OoHege. 


OUTLINES   OF    QUANTITATIVE   ANALYSIS. 

FOR  THS  U3S  OF  STUDBNTS. 

With  niiutratioiiB.    Fottbth  Edition.    Crown  8vo^  Cloth,  8b. 

**  A  ooMPAOT  LABOBAioBT  ouiDK  for  begiiiii«n  was  wanted,  and  the  mmt  has 
been  wbll  supfubd.    ...    A  good  and  nseftil  hook,^—Lancek 


OUTLINES  OF  QUALITATIVE  ANALYSIS. 

FOR  THB  USB  OF  STUDBNTS. 

With  Ulnatrationa.   Fourth  Edition,  Revised.   Crown  8yo,  Cloth,  8b.  6d, 

**  The  work  of  a  thoronghly  practical  chemist'*— A^t«4  Medical  JawmaL 
M  Compiled  with  great  care,  and  will  supply  a  wmW^JourmU  of  EduoatioiL 


ELEMENTARY   METALLURGY: 

Including  the  Author's  Practical  Laboratory  Course.      With  many 

lUuBtrations.  [See  p.  66. 

Fourth  Edition,  Reyised.    Crown  8vo.    Cloth,   6e. 

"  Just  the  kind  of  work  for  stadents  commencing  the  study  of  metaUuij^.*— 
Practical  Bnffineer, 

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CHEMISTRY  AND  TMOBNOLOOr.  ft 

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flboold  gtra  fbhb  powaa  to  the  Bngineer  and  HanoCutorer."— Tftc  Ttmtg. 

In  Two  Vols.,  Large  8vo.     With  lUiutrationfl.    Sold  Separately. 

CHEMISTRY    FOR    ENGINEERiS 
AND    MANUFACTURERS. 

A  PRACTICAL  TEXT-BOOK. 

BY 

BERTRAM  BLOUNT,  F.I.C.,  &  A.  G.  BLOXAM,  F.I.O. 

CHEMISTRY  OF  ENGINEERING,  BUILDING,  AND 

METALLURGY. 

General  Contents.— ISTRODUOTlOK—Ch^mlBtry  of  tlie  CUef  Uaterlalt 
of  Constractlon— Sources  of  Energy— Chemistry  of  Steam-ralslng— Ohemls- 
try  of  Lubrication  and  Lubricants— Metallurgical  Processes  used  tn  the 
Winning  and  Manufacture  of  Metals. 


Second   Edition,    Thoroughly   Revised.     Illustrated.     168. 

THE    CHEMISTRY    OP   MANUFACTURING 

PROCESSES. 

Omeral  Con^enfo.— Sulphuric  Add  Manufiaoture^Alkall,  *o.— DestmctlYO 
Distillation —Artiflclal  Manure— Petroleum— Lime  and  Oement— Glay  and 
COass  — Sugar  and  Starch  —  Brewing  and  Distilling— Oils,  Resins,  and 
Varnishes— Soap  and  Candles  —  Textiles  and  Bleaching  —  Colouring 
Matters,  Dyeing,  and  Printtng  —  Paper  and  Pasteboard  —  Pigments  and 
Paints  —  Leather,  aine,  and  Sise  —  BzploslYes  and  Matdies  —  Minor 
Manufactures. 

"Oertalalj  a  good  and  dbxful  book,  oonBtitoting  a  psaonoAL  wjwm  for  stadents  hr 
affording  a  clear  oonoeption  of  the  nomeroiu  prooesees  as  a  who\t.'*^Chemieal  3Vmm 
JomrtuU.  

Second  Edition.    In  Large  8va    Handsome  Cloth.    With  Soo  pages 

and  154  lUustiations.    25s.  net. 

OILS,  FATS,  BUTTERS,  AND  WAXES : 

THEIR  PREPARATION  AND  PROPERTIES,  AND  KANUFACTURE  THERE- 
FROM OF  CANDLES,  SOAPS,  AND  OTHER  PRODUCTS. 

By  C.   R.  alder  WRIGHT,  D.Sc,  F.R.S., 

Ijtto  Lecturer  on  ChcDistry,  St  Mary's  Hospital  Medical  School ;  Brsininer 
in  "Soap"  to  the  Qty  and  Guilds  of  London  Institnte. 

Thoroughly  Revised,  Enlarged,  and  in  Part  Rewritten 

By  C.  AINSWORTH  MITCHELL,  B.A.,  F.I.C.,  F.C.S. 

"Will  he  found  absolutbly  nmjsrKKSABiM."—TJU Analytic 
"WiU  rank  as  the  Stamdaicd  English  Autmoritv  on  Oils  and  Fats  for  many 
feais  to  coma.''—Imdmtirigg  and  Iron, 

LONDON :  CHARLES  ORIFFIN  «  CO.  LIMITED.  EXETER  STREET.  STRAND. 

4 


72  QHARLMa  9BIFF1N  S  00.*8  PUBLIOATIONB. 

Futh  Edition,  Thoroughly  Revieed,  Greatly  Enlarged  and  Re- written. 
With  additioniJ  Tablea,  Plates,  and  IlliutrationB.    218. 

POODSs 

THEIR  COMPOSITION  AND  ANALYSIS. 

By  a.  WYNTER  BLYTH,  M.R.C.S.,  P.IO.,  P.O.S., 

Banister-ai-Law,  PnbUo  Analyst  for  the  Ck>Qii^  of  Deyon,  and 
Medical  Officer  of  Health  for  St.  Marylebone. 

AuD  M.  WYNTER  BLYTH,  B.A.,  B.So.,  F.C.S. 

Gkhkbal  Contents.  —  History  of  Adulteration.  —  Legislation.  — Ap- 
paratus.— "  Ash." — Sugar.  — Confectionery.  —  Honey.  —  Treacle.  — Jams 
and  Presenred  Fmits.— Starches.  —  Wheafcen-Flonr. — Bread. — Oats. — 
Barley. — Rve. — Rice.  — Maize.  — Millet. — Potatoes.  — Peas.  — Lentils.  — 
Beans. — Milk. — Cream. — Bntter.  — Oleo-Marffarine. — Cheese. — Lard.  — 
Tea.  —  Coffee.  —  Cocoa  and  Chocolate.  ~  Aleohol.  —  Brandy.  —  Rnm.  — 
Whisky.  — Gin.  — Arrack. — liqnenrs. — Absinthe. — Yeast. — ]Beer.  — Wine. 
—  Vineaar.  —  Lemon  and  Lime  Jnioe. —  Mustard. — Pepper. — Sweet  and 

Bitter  idmonds.— Annatto.— Olire  Oil.— Water  Analysts.— Appendix : 

Adulteration  Acts,  &c. 

**  Simply  Dn>i8PXB8ABiji  in  the  Analyit'a  laboratory."— 2^  Lemod. 
^  A  new  edition  of  Mr.  Wynter  Bl]rth*i  Standard  woric,  saBXCBSD  win  jxl  ms  Bsasvr 
nnooTSBixB  ukd  ocPBOYBiaanB,  win  be  accepted  as  a  boon.*'.»CA«nlec[rf  Ntm. 


FoxTBTH  Edition,  Thoroughly  RevlBed.     In  Large  Svo,  Cloth,  with 

Tables  and  Dlustrations. 

POISONS: 

THEIR  EFFECTS  AND  DETECTION. 

By  a.  WYNTER  BLYTH,  M.R.C.S.,  F.I.C.,  P.O.S., 

Barri8ter-at-Law,  Pnblic  Analyet  for  the  Conn^  of  Devon,  and 
Medical  Officer  of  Health  for  St  Marylebone. 

aSKERAI.    CONTENTS. 

I. — ^Historical  Introduction.  U. — Classification — Statistics — Connection 
between  Toxic  Action  and  Chemical  Composition — Life  Tests — General 
Method  of  Procedure — The  Spectroscope — Examination  of  Blood  and  Blood 
Stains.  III. — Poisonous  Gases.  IV. — Acids  and  Alkalies.  V. — ^More 
or  less  Volatile  Poisonous  Substances.  VI. — Alkaloids  and  Poisonoua 
Veffetable  Principles.  VII. — Poisons  derived  from  Living  or  Dead  Animal 
Substances.  VIII. — The  Oxalic  Acid  Group.  IX.— Inorganic  Poisons. 
Appendix :  Treatment,  by  Antidotes  or  otherwise,  of  Cases  of  Poisoning. 

,    "Undoabtedly  thb  xoev  coxrutri  wobx  on  Tozicology  in  oar  lansnaice.''— 2^  Amubttt  foti 
Iht  TJUrd  JCdMonJ. 

**  Ab  a  PKAonoAL  ovmi,  we  know  ho  birib  work."—!'^  Lancet  (on  the  Third  BdMonJ. 

%*  In  the  Thibd  Enmov,  Enlarged  and  partly  Re-written,  Nsw  AxALTfioAi  MiraoiM  hm9% 
bean  introdooed,  and  the  OAnATxaio  Alkaloids,  or  Ptomaihib,  bodies  playing  so  great  a  part  In 
vood-poieonlng  and  in  the  Manifestationi  of  DlaeaM^  have  reoelyed  ipedal  attention. 

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0HEMI8TRT  AND  TBOHNOLOQY.  73 

With  Numerous  Tables,  and  22  Illustrations.     i6s. 

'DAIRY   CHEMISTRY 

FOB   DAIRY   MANAGERS,    CHEMISTS,  AND   ANALYSTS 
A  Practical  Handbook  for  Dairy  Chemists  and  others 

having  Control  of  Dairies. 

By  H.   droop  RICHMOND,  F.I.C., 

CHBUIST  TO  THB  AYLBSBURY  DAIRY  COMPANY. 

Contents, — I.  Introductory.— The  Constituents  of  Milk.  II.  The  Analysis  ol 
Milk  ill.  Normsd  Milk :  its  Adulterations  and  Alterations,  and  their  Detection. 
IV  The  Chemical  Control  of  the  Dairy.  V,  Biological  and  Sanitary  Matters, 
VI.  Butter.  VII.  Other  Milk  Products.  VIII.  The  Milk  of  Mammals  other 
than  the  Cow.— Appendices.— Tables.— Index. 

"...    In  our  opinion  the  book  is  the  best  contribution  om  niB  subject  that 
MAS  YBT  APPBARBD  in  the  English  language."— Zoim://. 


Fully  Illustrated.     With  Photographs  of  Various  Breeds  of  Cattle,  &c. 

68.  net, 

MILK:  ITS  PRODUCTION  &  USES. 

With  Chapters  on  Dainf  Farming,  The  Diaeaaea  of  Cattie,  and  on  the 

Hygiene  and  Controi  of  SuppHes. 

By    EDWARD    P.    WILLOUGHBY, 

M.D.  (Lend.),  D.P.H.  (Lend,  and  Camb.), 
Late  Inspector  of  Farms  and  General  Scientific  Adviser  to  Welford  and  Sous,  Ltd. 

*'  A  good  investment  to  those  in  the  least  interested  in  dairying.  Excellently  bound : 
printed  on  good  paper,  and  well  illustrated,  running  to  259  pages,  the  purchaser  gets  ac 
the  price  01  a  novel  a  work  which  will  stand  good  as  a  work  of  reference  for  some  yean 
to  comt.*'—Agrieult.  Oazette. 

y^  We  cordially  recommend  It  to  everyone  who  has  anything  at  all  to  do  with  mUk."— 
Dairy  World.  

In  Crown  8vo,  Fully  Illustrated.      2s.  6d.  net. 
THE   LABOBATOBT   BOOS   OF 

DAIRY    ANALYSIS. 

By  H.   droop  RICHMOND,  RLC, 

Analyst  to  the  Aylesbury  Dairy  Co.,  Ltd. 

Contents. — Composition  of  Milk  and  its  Products. — Analysis  ot  Milk. — 
Analysis  of  Liquid  Products. — Application  of  Analysis  to  the  Solution  of 
Problems. — The  Analysis  of  Butter. — Analysis  of  Cheese. — Tables  for  Calcu- 
lation.— Standard  Solutions. — Index. 

''  Without  doubt  the  best  contribution  to  the  literature  of  its  subject  that  has  ever  been 
written." — Medical  Timet, 

In  Large  8vo.     Handsome  Cloth. 

A6RIGULTDRAL  GHEmSTRT  AND  ANALYSIS : 

A  PRACTICAL  HANDBOOK  FOR  THE  U8E  OF  AGRICULTURAL  STUDENTS. 
By  J.   M.   H.   MUNRO,   D.Sc,   F.I.C,   F.O.S., 

Professor  of  ChexnlBtry,  Downton  College  of  Agrionltore. 
[/n  PrtparcUion, 

LONDON :  CHARLES  KRIFFIN  &  GO.^  LIMITED,  EXETER  STREET.  8TRANCI 


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FLESH    FOODS: 

With  Mefhods  for  their  Chemical,  Microscopical,  and  Bacterio^ 

logical  Examination. 

A  Praotioal  Handbook  for  MedioaJ  Men,  AnaJyata,  Inspectors  and  others. 
By  C.  AINSWORTH    MITCHELL,  B.A.,   F.I.C.,  F.C.S., 

Member  of  Council,  Society  of  Public  Analysts. 

With  Numerow  Tables,  IlltutrcUians,  and  a  Coloured  Plate, 

Contents. — Structure  and  Chemical  Composition  of  Muscular  Fibre. — of 
Connective  Tissue,  and  Blood. — ^The  Flesh  of  Different  Animals.— The  Examina- 
tion of  Flesh. — Methods  of  Examining  Animal  Fat. — The  Preservation  of  Flesh. 
—Composition  and  Analysis  of  Sausages. — Proteids  of  Flesh. — Meat  Extracts  and 
Flesh  Peptones. — ^The  Cooking  of  Flesh. — Poisonous  Flesh. — The  Animal  Para- 
sites of  Flesh. — ^The  Bacteriological  Examination  of  Flesh. — The  Extraction  and 
Separation  of  Ptomaines. — Index. 

**  A  compOatioa  which  will  be  most  useful  for  tht  class  for  whom  it  is  intended."— ^M«»Mrwm. 
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TECHNICAL    MYCOLOGY: 

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By    Dr.    FRANZ    LAPAR, 

Prof,  of  FormentatloB-PhyBlology  and  Baeteriolosy  In  the  Technical  High  School,  Yienoa. 

With  an  Introduction  by  Dr.  EMIL  CHS.  HANSEN,  Principal  of  the  CarlBber? 

Laboratory,  Copenhagen. 

Translated  by  GHAELES  T.  C.  SALTER. 

Vol  L-SCHIZOMYCETIC  FBRMBNTATION.   168. 

Vol  IU  PaPt  I.-BUMVCBTIC  FBRMBNTATION.   78.  6cL 

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TOXINES    AND    ANTITOXINES. 

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Of  the  Phyalological  Inatitute  at  Brlangen. 
Translatkd  from  the  German  by 

0.  AINSWORTH  MITCHELL,  B.A.,  P.I.C,  RC.S. 

With  Notes,  and  AddltionB  by  the  Author,  lince  the  publication  of  the  Oemum  Edition. 

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A  M^  D     rrscExir     AcrrxoM^B. 

A  Text-book  on  the  Chemistry  and  Physics  of  Fermentative  Changes, 
By   carl    OPPENHEIMER,    Ph.D.,    M.D., 

or  the  PhysiologlMl  Ixiatltate  at  ErUngen. 

Translated  fsom  the  Qekhah  et 
C.  AINSWORTH  MITCHELL,  B.A.,  P.LC,  P.C.S. 

Abridqbd  GoNTBirT8.~lDtrodiictioii.— DefLDition.~Cbemlcal  Nature  of  FermeDti.— 
Influence  of  External  Factors.— Mode  of  Action.— Physiological  Action.— Secretion.— 
Importance  of  Ferments  to  Vital  Action.— Proteolytic  Ferments.— Trypsin.— Bacteriolytic 
and  Hemolytic  Ferments.- Vegetable  Ferments.— €!oagnlatIng  Ferments.— Saccharifying 
Ferments.  —  Diastases.  —  Polysaccharides.  —  Enzymes.  —  Ferments  which  decompose 
Olnoosides.— Hydrolytic  Ferments.— Lactic  Acid  Fermentation.— Alcoholic  Fermenta- 
tlon.— Biology  of  Alcoholic  Fermentation.— Oxydases.— Oxidising  Fermentation.— Blbll- 
ograpt^.— Index. 

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Bubjeet  "—Brwftrt  JotamtU,  


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PRINCIPLES  AND  PRACTICE  OF  BREWING. 

FOR  THE  USE  OF  STUDENTS  AND  PRACTICAL  MEN. 

By  WALTER  J.  SYKES. 
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Road  Making  and  Maintenance: 

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SUBTEYOBS,     AND     OT] 


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THE  PAINTER'S  LABORATORY  GUIDE. 

A  Student's  Handbook  of  Paints,  Colours,  and  Yamlshes. 

By  GEORGE  H.   HURST,  F.C.S.,  M.S.C.I. 

Abstract  op  Contbnts.  —  Preparation  of  Pigment  Colours.  —  Chemical  Principles 
Involved. — Oils  and  Varnishes. — Properties  of  Oils  and  Varnishes. — Tests  and  Experiments. 
—Plants,  Methods,  and  Machinery  of  the  Paint  and  Varnish  Manufactures. 

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Painters  and  Decorators. 

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UCTUSKR  AT  THB  XAHOHBSTBR  TBOmnaAL  BOBOOL  VOR  HOUas-PAnniVQ  AHD  DROORATDIO. 

GENERAL  CONTENTS. 
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Hannng— Colour  MiyiTig — Dutempering — Plain  Painting — Staining — ^Vaniisk 
and  V  amishing — Imitative  Paintmg  —  Graining — Marbling — Gilqmg-~Sigii- 
Writing  and  Lettering — Decoration:  General  Principles — Decoration  in  Jjiar 
temper — Painted  Decoration — Relievo  Decoration — Colour — Measuring  and 
Estimating — Coach-Painting — Ship-Painting. 

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MATION  in  a  CLEAB  and  concise  itobmJ**— Plumber  and  Decorator. 

*'  A  THOBOUGHLY  GOOD  AND  BELIABLE  TEXT-BOOK.      .     .      .      So  FULL  and 

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added  about  the  Painter's  craft.*' — Builder tr  Journal, 

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including  tlie  Outlines  of  a  Theory  on  Vulcanisation, 

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AND  THBnt  ALU£D  PRODUCTS, 
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CoNTKNTS. — Historical. — Gluk.— Gblatinb. — Size  and  Isinglass.— Treatment  of  Efflu- 
ents produced  in  Glue  and  Gelatine  Making. — Liquid  and  other  Glues,  Cements,  &C. — Uses 
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AprKNDix.— Indbx. 

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With  Selected  Tables  for  Stationers,  Publishers,  and  Others. 

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of  Rag  Paper,  Hand*made,  Machine-made ;  Esparto  Papers ;  Chemical  Wood  Pulp ;  Me- 
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THE   MANUFACTURE  OP  INK. 

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Writing,  and  Copying  Inks, 
By  C.  a.  MITCHELL,  B.A.,  F.I.C.,  F.C.S.,  &  T.  C  HEPWORTH. 

General  Contents.- Historical.— Inks  and  their  Manufacture.- WriUuff  Inks.— 
Carbon  and  Carbonaceous  Inks.— Tannin  Materials  for  Ink.— Nature  of  Inks.— Manufacture 
of  Iron  Gall  Ink.  —  Logwood,  Vanadium,  and  Aniline  Black  Inks.  —  Coloured  Inks. — 
Examination  of  Writing  Inks.  —  Printing  Inks.  —  Early  Methods  of  Manufacture- 
Manufacture  of  Varnish  Inks. — Preparation  and  Incorporation  of  the  PigmenL — Coloured 
Printing  Inks. — Copying  Inks.  Marking  Inks.— Natural  Vegetable  Inks.— Safety  Inks 
and  Papers.  —  Sympathetic  Inks.  —  Ink  Powders  and  Tablets.  —  Appendices.  —  Patent 
Specifications,  &c. 

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Sboond  Edition,  Thoroughly  Revised  Throughout,    In  Two  Large 

Volumes,    Handsome  Cloth, 

A    MANUAL    OP    DYEING; 

fOR  THE  USE  OF  PRACTICAL  DYERS,  MANUFACTURERS,  STUDENTS, 
AND  ALL  INTERESTED  IN  THE  ART  OF  DYEING, 

BY 

B.  KNECHT,  Ph.D.,  F.I.C.,  CHR.  RAWSON,  F.I.C.,  F.C.S., 

Head  at  th«  Obcmiitxy  and  Dyslnc  l>epartment  of         Late  Head  of  the  Ohemistzy  and  Dyeing  Departaunt 
Cbe  TMkaleel  fUhocIL,  Manehartert  Bdltor  of  "Th«        of  the  Tooluileal  OoUcne,  Btadlord  :   Member 
Jovnudof  the  Society  of  Dyen  and  Oolonziita;"  Oonnell  of  the  Sooietjr  of  Djen  and  OouMKristiCS 

And  RICHARD  LOEWENTHAL,  Ph«D. 

General  Ck>NTBNT8.~0heziiical  Technology  of  the  Textile  Fabrioe — 

Water — Washing  and  Bleaching  —  Adda,  Alkalies,  Mordants — Natural 

Colouring  Matters— Artificial  Orf^c  Colouring  Matters— Mineral  Colours 

■—Machinery  used  in  Dyeing — Tinctorial  Properties  of  Colouxing  Matters — 

Analysis  and  Valuation  of  Materials  used  in  l^eing,  &c.,  ko, 

'*  Alls  Mitborltatlya  and  exbanstiTa  work   ...    the  icon  oomflbtb  we  hSTO  yet 
on  the  sabjeot"— TfeartOe  Mmw/aetwrtr, 


In  Large  8vo,  Handsome  Cloth,     Fp,  i-xv  +  405.     16s.  net. 

THE    SYNTHETIC    DYESTUFFS, 

AND 

THE  INTERMEDIATE  PRODUCTS  FROM  WHICH  THEY  ARE  DERIVED. 

Bt  JOHN  CANNELL  CAIN,  D.Sc.  (Manchester  and  Tt^BiNOEN), 

Technical  Chemist, 

And  JOCELYN  FIELD  THORPE,  Ph.D.  (HBiDELBRao), 
Lecturer  on  Colouring  Matters  In  the  Victoria  UnlYenity  of  ICaachester. 

Part  I.  Theopetieal.    Part  II.  Fraetieal.    Part  III.  Analsrtleal. 

"  We  have  no  hesitation  in  describing  tills  treatise  as  one  of  the  most  valuable  books 
that  has  appeared.  .  .  .  Will  give  an  impetus  to  the  study  of  Organic  Chemistry 
generally.  "—Cft^mieaZ  Trade  Journal. 


Companion  Volume  to  Kneeht  d:  Rawson*s  *'  Dyeing."    In  Large  8vo. 
Handsome  Cloth,  Library  Style,    16s,  net, 

A  digtiokaby  of 

BYES,  MORDANTS,  &  OTHER  COMPOUNDS 

USED  IN  DYEING  AND  CAUCO  PRINTING. 

with  Formula,  Properties,  and  Applleatlons  of  the  uarlous  substaneos  descrthsd, 

€uui  ooneiso  directions  for  their  Commercial  Valuation, 

and  for  the  Detection  of  Adulterants. 

By  CHRISTOPHER  RAWSON,  F.I.O.,  F.C.S.. 

Consulting  Cbemist  to  the  Behar  Indigo  Planters'  Aasooisliton ;  Oo-Anthor  of  **  A  MsntuJ 

of  Dyeing;" 

WALTER  M.  GARDNER,  F.C.S., 

Head  of  the  Department  of  Chemistry  and  Dyeing,  Bradford  Municipal  Technical  College ; 
Bdltor  of  the  "  Joan.  8oc  Dyers  and  ColooristB ; " 

And  W.  F.  LAYCOOK,  Ph.D.,  F.O.S., 

Analytical  and  Consulting  Chemist 
**  Tnm  to  the  book  as  one  may  on  any  subject,  or  any  substance  in  oonnection  with  tha 
trade,  and  a  reference  is  sure  to  be  found.    The  authors  have  apparently  left  nothing  out.** 
«—  Textile  Meremrp. 

LONDON :  CHARLES  QRIFFIN  ft  CO..  LIMITED.  EXETER  STREET,  STRAND. 


TBB  TMXTILM  INDV8TE1B8.  83 

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THE  SPINNING  AND  TWISTING  OF  LONG 

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Preparing,  $  fanning,  and  Twisting  of  the  Long  Vegetable  Fibres  of  Commerce. 

Bt  HEBBERT  R.  carter,  Belfast  and  Lille. 

Gbhbbal  CoMTBiiTS.— Long  Vegetable  Fibres  of  Commerce.— Eiae  and  Growth  oC 
the  Spinning  Indostry.— Kaw  Fibre  Markets.— Purchaging  Baw  Material.— Storing  and 
Preliminary  Operations.— Hackling.— Sorting.— Preparing.-Tow  Carding  and  Mixuig.— 
Tow  Combing.- Gill  Spinning.- The  Roving  Frame.— Dry  and  Demi-aec  Spinning.— Wet 
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Cords.— Rope  Making. —The  Mechanical  Department.— Modem  Mill  Coustmctlon.— 
Steam  and  Water  Power.— Power  Transmission. 

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A  HANDBOOK  OF 

The  Oooiirrence,  Distribution,  Preparation,  and  Industrial 

Uses  of  the  Animal,  Vegetable,  and  Mineral 

Products  used  in  Spinning  and  Weaving. 

By    WILLIAM    I.    HANNAN, 

Lecturer  on  Botany  at  f  be  Ashton  Municipal  Technical  School,  Lecturer  on  Cottou 
Spinning  at  the  Chorley  Science  and  Art  School,  Ac 

With  NumerouB  Photo  SngravlngB  from  Nature. 

''  UssFUL  IiTFORXAnoK.  .  .  .  Admibablb  iLLDtTBATioHS.  .  .  .  The  information 
is  not  easily  attainable,  and  hi  its  present  oonyenient  form  will  be  yalnable.**— 7Vx<i/e 
Bteorder.  


In  Laige  Svo,  with  Illustrations  and  Printed  Patterns.    Price  ais. 

TEXTILE    PRINTING: 

▲  FBACTICAIi  UAKUAIi. 

Indnding  the  Proceaaes  Used  in  the  Piinting  of 
COTTON,   WOOLLEN,   SILK,   and  HALF- 
SILK  FABBICS. 

By  C.  F.  SEYMOUR  ROTHWELL,  F.C.S., 

if  cm.  Boc.  of  Ckemik4Ml  Induetrim;  kUe  Leetmrer  at  the  Mimieipai  TeehmktA  Sekodl^ 


Gbnxbal  Contents.  —  Introduction.  —  The  Machinery  Used  in  Textile 
Printing.— Thickeners  and  Mordants.— The  Printingrpf  Cotton  Goods.— The 
Steam  Btyla — Colours  Produced  Directly  on  the  Tibra— Dyed  Styles.— 
Padding  style. — Besist  and  Discharge  Slyles.- The  Printing  of  Compound 
Colourinn,  &a— The  Printing  of  WooUen  Goods.— The  Printing  of  Silk 
Gkxxls.— Practical  Recipes  for  Printing.— Useful  Tables.— Patterns. 

**  Bt  wam  tbx  BIST  and  moot  raAonoAL  book  on  TBxms  rsnmo  which  has  yet  been 
brought  out,  and  will  long  rematai  the  Btandard  work  on  the  enbjeot  It  ia  eaaenttally 
praettoal  in  diaraoler.*''2«ria<  Meremy. 

"  Tn  MOST  PBAcnoix KAMUAL  of  TsxTiu  PBomHO  wfaich  has  yet^ypMred.  We  have 
no  hesitation  in  reoonunending  it**— 9!te  Textile  Monm/aeturer. 

LONDON :  CHARLES  GRIFFIN  d  CO..  LIMITED.  EXETER  STREET.  STRAND. 


«4  0HABLE8  QRIFFIN  dfe  OO.'B  PUBLICATIONS. 

Large  Sva    Handsome  Cloth.    12b.  6d. 

BLEACHING  &  CALICO-PRINTING. 

A  Short  Manual  for  Students  and 

Practical  Men. 

By    QEORQE    DUERR, 

iHreetor  of  the  BleMhing,  Dyeiiigi  and  Printing  Deputmont  at  the  Aoerinston  and  Bacni^ 
Teehnlcal  Schoola ;  Ohemlat  and  Ooloorist  at  the  Irwell  Print  Woifca. 

Assisted  by  WILLIAM   TURNBULL 

(of  Tamball  ft  Stookdala,  Limited). 

With  Illustrations  and  upwards  of  One  Hundred  Dyed  and  Printed  Patterns 
designed  specially  to  show  various  Stages  of  the  Processes  described. 

GENERAL  CONTENTS.— Cotton,  Composition*  of;  BLEAcmKQ,  New 
Processes ;  Printino,  Hand-Block ;  Flat-Press  Work ;  Machine  Pzinting — 
Mordants— Styles  of  GALioo-PaiNTiNO :  The  Dyed  or  Madder  Style,  Resist 
Padded  SMe,  Discharge  and  Extract  Style,  Chromed  or  Raised  Coloois, 
Insoluble  Colours,  &c  —  Thickeners  —  Natural  Organic  Colouring  Matteia 
—Tannin  Matters— Oils,  Soaps,  Solvents— Organic  Acids— Salts — Mineral 
Colours — Coal  Tar  Colours — Dyeing— Water,  Softening  of— Theory  of  ..Colouza 
— ^Wdghts  and  Measures,  &c. 

'*  When  a  bsadt  way  oat  of  a  dillicalty  la  wanted,  it  Is  is  books  un  this  that  it  is  foand.*— 
2Vflrtfl<  Kteorder. 

"Mr.  Duima'a  woas  will  he  found  most  usstul.  .  .  .  The  Infonoiiatlon  giren  is  of  smiAy 
VALua    .    .    .    The  Recipes  are  THOBOUGHLT  rBACnOAL."— TeoBtilf  Jira»i(At6tiirer. 


Second   Edition.      Revised  and   Enlarged.     With  Numerous 

Illustrations.      43.  6d. 

GARMENT 
DYEING    AND   CLEANING. 

A  Praetieal  Book  for  Praetieal  Men, 

By     GEORGE     H.     HURST,     F.C.S., 

Memher  of  the  Society  of  Chemical  Industry. 

General  Contents.— Technology  of  the  Textile  Fibres— Garment  Cleaning 
— Dyeing  of  Textile  Fabrics — Bleaching — Finishing  of  Dyed  and  Cleaned  Fabrics — 
Scouring  and  Dyeing  of  Skin  Rugs  and  Mats — Cleaning  and  Dyeing  of  Feathers — 
Glove  Cleaning  and  Dyeing — Straw  Bleaching  and  Dyeing-Avlossary  of  Drugs 
and  Chemicals — Useful  Tables. 

"  An  UP-TO-DATB  hand  book  has  long  been  wanted,  and  Mr.  Hurst  has  done  nothinff 
more  complete  than  this.  An  important  work,  the  more  so  that  sevenl  of  the  branches  o? 
the  craft  here  treated  upon  are  almost  entirely  without  £ngUsh  Manuals  for  the  guidanos 
of  workers.    The  price  Imngs  it  within  the  readi  of  all.*' — Dyer  and  CaUco-PrinUr. 

"  Mr.  Hurst's  worx  dbcidbdly  pills  a  want  .  .  .  ought  to  be  in  ^e  hands  of 
BVBRV  GARMENT  DYBR  and  cleaner  in  the  Kingdom" — Textile  Mercury. 

LONDON:  CHARLES  GRIFFIN  ft  CO..  LIMITED,  EXETER  STREET.  STRAND. 


^ 


» 


INTRODUCTORY  SCI  SNOB  SERIES.  85 

"BogPB  OOUIJ)  HOT  HATS  A  MOB!  ALLUKniO  DITBODVOTIOir   tO  1010011110  ponillti 

tluui  tlMM  eharmlng-lookiiig  Tolnmes."— Letter  to  the  PabUahen  fkom  the  Head- 
maiter  of  one  of  oar  great  Pabllo  Sehoola. 

HandBome  Cloth,  78.  6d.    Gilt,  for  Preaeiitation,  8«.  Od. 

OPE|l-AIll  STUDIES  Ijl  BOTiqlY: 

SKETCHES    OF   BRITISH    WILD    FLOWEBS 

nr  THEIB  HOMES. 

By  R  LLOYD  PRAEGER,  B.A^,  HRLA. 

Illustrated  by  Drawings  f^m  Nature  by  S.  Rosamond  Praeger, 

and  Photographs  by  R.  Welch. 

Gbkxbai.  Contents. — A  Dujiy-Stftrred  Pasture—Under  the  Hawthorns 
— By  the  Hiver — Along  the  Shingle — A  Fragrant  Hedgerow — A  Connemara 
Bog — ^Where  the  Samphire  stows — A  Flowery  Meadow — Among  the  Com 
(a  Stndy  in  Weeds) — In  the  Home  of  the  Alpines — A  City  Rnhbish-Heap— 

Glossary. 

"A  FBBSH  AND  smnTLAiiNO  book  .  .  .  shoidd  take  a  high  plaoe  .  .  .  The 
ninstratloiiB  are  drawn  with  much  akilL"~T%«  Timu. 

"  Bbautifvllt  illusibatxd.  .  .  .  One  of  the  nofli  aooueaib  aa  well  as 
DimunTlHO  books  of  the  kind  we  hare  seen."— AtA^n^Btmi. 

"Bedolent  with  the  soent  of  woodland  and  meadow."— T%e  Standard, 


With  12  Full-Page  llluatrationa  from  Photographs.    Cloth. 
Second  Edition,  Revised.      8s.   6d. 

OPEMUl  STUDIES  III  GEOItOGY: 

An  Introduetion  to  Geology  Out-of-doors. 

By    GRENVILLE   A.  J.   COLE,   F.G.S.,  M.R.I.A., 

Professor  of  Ctoology  In  the  Soyal  College  of  Solenoe  for  Ireland, 
and  Bzaminer  In  the  University  of  London. 

Gbnebal  Contbnts. — ^The  Materials  of  the  Earth — A  Mountain  Hollow 

— Down  the  Valley— Along  the  Shore — Across  the  Plains — ^Dead  Volcanoes 

—A  Gianite  Highland— The  Annals  of  the  Earth— The  Surrey  Hills— The 

Folds  of  the  Moantains. 

'^The  VAsoDiATiHG  *Opur-AiB  Studiis'  of  pRor.  OoLs  giye  the  snbjeot  a  olow  or 
AirDfAnow    .    .    .    cannot  fall  to  aitnue  keen  interest  in  goologjJ" ^Oeologieal  MagoMvu. 
*'  A  CHARMnro  BOOK,  beantifnlly  lUastrated." —Athtnaum, 


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Specially  Drawn  Plates  by  Charles  Whymper.     7s,  6d. 

OPE]l"AItl  STUDIES  I]l  Bll{D-IiIfE: 

SKETCHES  OF  BRITISH  BIRDS  IN  THEIR  HAUNTS. 
By    CHARLES    DIXON. 

The  Spacious  Air. — The  Open  Fields  and  Downs. — In  the  Hedgerows. — On 
Open  Heath  and  Moor.— Chi  the  Mountains. — Amongst  the  Evergreens. — 
Copse  and  Woodland.— By  Stream  and  Pool.— The  Sandy  Wastes  and  Mud- 
flats.—Sea-laved  Bocks.— JBirds  of  the  Cities.- Index. 

*' Enriched  with  excellent  illustrations.  A  welcome  addition  to  all  libraries.'*— 7F/«/- 
fmruter  Rrviroi. 

"'""  ■■■■  ■^■■■■ii.   ■■^»^^».i     I  ■■  ■  ■     I  .1  ■■■  ■  ■  ■         I  ^ 

lONDON :  CHARLES  GRIFFIN  &  CO.,  LIMITED^  EXETER  STREET.  STRAMD