The War Department Cross-Channel Train Ferry.” by FREDERICKOWEX STAKFORD,O.B.E., Assoc

(Paper No. 4326.)

“ The War Department Cross-Channel Train Ferry.” By FREDERICKOWEX STAKFORD,O.B.E., Assoc. M. Inst. C.E. TEIE TrainFerry Service between England and France was established in 1917 by the War Department as a “war service,” to meet the demands and requirements of military transport, which had become acute under the conditions which then existed. There was, at that time, both a serious shortage of shipping a,nd a great congestion atthe ports,particularly on the French side, which delayed the turn-round of the ships employed on this traffic. An appreciable proportion of the traffic consisted of locomotives, wagons, ambulance coaches, tanks, heavy ordnance, motor transport, and other bulky material, equally inconvenient to stow, occupying an undue amount of space in the holds of vessels, requiring much man-power, crane-power and time toload and unload, and frequently necessitatingthe dismantling and subsequent re-erection of the machinery. The first reason for establishing the ferry service was therefore to relieve the shipping of this class of trafic ; the second was to provide the ferry steamers with their own berths, without taking up any of the already over-taxed existing quay space ; thirdly, to effect a valuable saving of handling at a timewhen man-power was of vital importance and crane-power a serious consideration; and fourthly, to afford means of meeting urgent demands for any special war material, such as guns or ammunition, by delivery, in case of possible emergency, straight from the factory to the theatre of war by rail without any transhipment, when time might mean everything. There were other points also to be considered, such as the initial cost of the scheme, andthe disadvantage of requiringtime ancl

labour for its installation, and to some extent interfering with the provisionof ordinary shipping, which was aquestion of great importance. It was decided, however, that as a war measure the advantages far outweighed thedisadvantages, and in January, 1917, the Cabinet decided that the scheme should be proceeded with, on the basis of providingthree ferry steamers and terminal berths at Richborough (near Sandwich) and on the Solent, in England, and at correspondingpoints in France. The latter were ultimately selected, in conjunction with the French authorities, as Dunkirk, Calais and Dieppe. The authority of the French Government for the establishment of the installations for the ferry-boats in these ports was given on 12th February, ‘1917. There are thus two ferry routes, namely, the northern from Rich- borough to Dunkirk or Calais, on which two vessels are engaged, andthe southern between Southampton and Dieppe with one vessel.’ This arrangement anticipated a military contingency which was afterwards seriously threatened, but fortunately averted, namely, the necessitythrough enemy action, of suspendingthe northern routetemporarily, and falling back on the southern. Although this never occurred, the use of Dunkirk was restricted for a considerable period, when the advantage of an alternative terminal at Calais was realized (Fig. 1, Plate 5). Although the earliest installations of train ferries of which any published accountcan be traced, namely, across the river Nile in2 1857 and across the Forth and the Tay in 1861, had been established by Britishengineers, and had been followed in 1885 by theIsle of Wight Train Ferry, the system had not been further developed in the British Isles. Schemes for a Channel Ferry had been suggested as far back as 1871, and though revived in 1905-1907, and again in 1913, the outbreak of war found the project still unaccomplished. In other parts of the world, however, under different geographical conditions, the system had been widely adopted :-in Canada, the United States, Denmark, Sweden, (3ermany and elsewhere. When the War Department had the question under consideration, therefore, they obtained the assistance of a very comprehensive review of the published accounts of existing ferries, prepared through the courtesy of The Institution by Mr. W. E. Simnett, M.B.E., formerly a member of the Secretary’s staff,to whom the Author is indebted. While this reportis too extJensiveto be quoted at length, it contains . ~- . . * This Paper was written in December, 1919. 2 Minutes of Proceedings Inst. C.E., vols. xvii and XI. [THE INST. C.&. VOL. CCX.] P

Downloaded by [ University of Ottawa Library System] on [14/09/16]. Copyright © ICE Publishing, all rights reserved. 210 6TASFORD ON THE WAR DRPACT>lKST [Minutes of so much collected information of interest to thoseconcerned with the subject that it is to be hoped that it may be printed and issued separately. From the consideration of the particulars of existing systems the following main features suggestthemselves. A trainferry, as a means of connectingtwo railwny systems which are divided by water, may be regarded as an alternative for R tunnel or bridge, or as a temporary substitute until suchcon- tinuousconnection is provided. Theferry, of course,involves interruption in the journey of the train. It is usually necessary to break up the train into lengths before it can be loaded on to the vessel, and tojoin up again after beingunloaded. One of the firstconsiderations is thatthe gauge of thetwo railway systems thus connected should be the same, or sufficiently alike to enable rolling stock to run on both systems. This question TVKS dealtwith by SirJohn A. F. Aspinall inhis Presidential Address (5th November, 1018), and is referred to in more detail in connection with this undertaking later on. The field of utility occurswhere a bridge or tunnel is nota practicalproposition, on account of the physical difficulties and great cost, in proportion to thetraffic to be dealt with ; where, as in the present instance, the time taken to install the communication is of importmce; and where the distance is suDicient!y short,as compared with a voyage by ordinary shipping, that the saving in double handling, breaking bulk and time is in such a proportion to the total cost of the voyage as to result in economy. The train ferry, of course, carries the same proportion of tare as both theordinary cargo-ship and the railway, with the general exception of the locomotive and tender in the latter case. The ferryvessels may be eitherself-propelled, or dumb floats towed by tugs. The type and details of those in use vary widely under different conditions, but it is of importance that the vessels on any one ferry system should be so far identical as regards their hulls, shore connections and landing arrangements as to be available at any terminal berth of the system. The terminal arrangements in use also vary according to local conditions.Those for overcoming the differences in water-level maybe broadly classified underfour types, (U) communicating bridges or Brozos hinged at the shore end and suspended near the outerend, with counterbalance weights ; (B) similar brozcs, but supported at the outer end by pontoons ; (c) lifts, either hydraulic or electric on shore; and (d) a liftingwdjustable deck on the vessel. In each case some form of flexible apron is usually employed tq

effect the actual connection between the rails on the shore and those onthe vessel. As inthe case of the vessels, whichever type is adopted, all the terminals of a ferry system should be so far identical in their arrangements as to fit anyof the vessels. The general arrangements for berthing the vessels, and the lay out of the railway sidings at the terminal stations, havenecessarily to be varied to suit the local conditions of the site, both on shore and afloat in each case. The selection of suitable termina.1 ports for a train ferry service involves theconsideration of the access byland, including the railway connections and facilities for adequate sidings, and of the access by sea, including the tides and berthingaccommodation.

ROUTNES. Table I gives theapproximate distances between the terminal ports : TABLEI.

, Southampton.Richborough.

Dunkirk ...... 69 I 60 ~ 180 ~ 157

Calais ...... 44 35 1 155 135

At Richborough, Southa,mpton and Dieppe, the train ferry berths are in tidal water, and the times of arrival and departure of the vessels ancl the working of traffic on and off the vessels is dependent on the state of the tide. At Dunkirk and Calais the berths are in closed basins, so that the working of the traffic can proceed at any time. The arrival and departure of the vessels is, however, partly restricted by the working of the t,iclal entrances to these ports, so thatthe ferry service tl~roughoutis a tidal one. Therailway connection at Richborough is made by a junction with the South Eastern and Cha.tham Railway near Minster. Theconnection at Southamptcm ismade by a linealong the westernforeshore to a junctionwith the London and South- Western Railway at Sout'hampton. West. Atthe three French ports the connection is made with the existing dock sidings and thus with the French railway system, P2

GAUGES. The gauge adopted for the train ferry was the English standard, 4 feet S$ inches, and for the maximum loading-gauge, the profile whichhad already been chosen by the War Departmentfor the construction of locomotives, cranes and rolling-stock for over-seas. This profile is that adoptedby the Berne International Con- ference with two slight modifications, namely, the exclusion of two smalltriangles at thebottom corners and the provision of a minimum of 7 inches instead of 54 inches clearance above rail level, Fig. 2. These modifications were introduced to enable the rolling- stock, which was being provided by the War Department, to clear

Fig. 2.

PROFILESSHOWING STANDARDLOADING GAUGES.

certain fixtures on the Belgian railways and the Chemin de fer du Nord (France),which had not yet been modified in accordance with the Berne Conference. For structures, a minimum clearance of 5 inches outside the top and sides of this profile was providedon the ferry, and the rail tracks, both on the vessels and on the sidings on shore, are spaced at 11 feet 6 inches centre to centre, providing 16 inches clearance between these profiles. The profile adopted is considerably larger than that of English railways. This was necessary in order to permit of full-sizeloads for over-seas being made up at the two English terminal ports, or brought back to these ports as required. 'Subject to the modificn- tions of the Berne gauge.. mentioned, and to the fact t!mt t'lle flanges

Downloaded by [ University of Ottawa Library System] on [14/09/16]. Copyright © ICE Publishing, all rights reserved. Plocc-ediugh.1 CRO~S-C~I.AS,\’E;L:mm FERRY. 2 13 of wheels of stock made for the continental track, 4 feet 9 inches (1 * 45 metre), are somewhat tight cm English rails, the continental stock could be brought, if required, as far as these ports either for loading and unloading or repair. OrdinaryEnglish wagons, withfew exceptions, will clear the French structural gauge, and thus all which can be consigned over- seas can be carried by the ferry. For return traffic from France, a composite profile of the variousEnglish companies (except the Metropolitan) was adopted, as agreed with the Railway Executive Committee, in order to allow through consignments to travel over any lines to their destination. Thus two loadinggauges, ‘‘ Overseas ” and “ English Composite ” were provided for each terminal port. The advantage of the larger continental profile is only obtainable as far as the English terminal ports ; it is, of course, impossible for continental wagons made to this profile to travel inland over the Englishrailways; consequently all through traffic bythe train ferry must be in English gauge wagons. This limitation, of course, applies equally to a tunnel or bridge in such circumstances.

TYPEOF FERRY,LOADING AND CAPACITY. Although a considerable amount of cross-channeltraffic was being carried on by the Royal Engineers at the time by means of barges and tugs, and the first suggestion for a train ferry for this purpase, so far as the Author is aware, was for the adaptation of barges as truck carriers, the type of vessel ultimately adopted was a self-propelled steamer, with four lines of track. The method of communication between ship and shore selected for each terminal was a double track bridge, hinged at the shore end, and suspended near the outer end by wire ropes,, with lifting gear and counter- weightscarried on an over-headsteel structure. Subsequently an extra vessel of thelifting decktype was purchased, and special berths were provided for her, but this formed no part of the original scheme here described. The scheme comprised three vessels, all built to the same specifi- cation and drawings, andfive communication bridges, differing only in regardto their length and the details of their electrical equipment. The hulls of the vessels and the bridges were designed to comply with the following conditions of loading : (U) On each track simultaneou:dy, a train of loadedrailway wagons, each 28 feet 2 inches over buffers, 12 feet 3 inches wheel base, and weighing 30 tons, headed by a six-wheel coupled shunting

locomotive, 6 feetcentres of axles, 12 feet wheel-base, w-eighing 48 tons, distributed equally on a11 three axles. (b) On one track only, a locomotive and tender of the Chemin de fer du N'ord, " Decapod " type, weighing 123 tons light, G2 feet 3 inches over buffers. (c) On one track only, a twelve-inch gun on railway mounting. Wind pressure of 300 lbs. per lineal foot was allowed for on the loaded bridge. Theunit stresses and allowance forimpact were calculated fortunately on a somewhat conservative basis, as the exigencies of thewar soon afterthe ferry came intooperation demanded the transport of weightsmuch in excess of whathad beenforeseen, involving axle loads 16-97' tons and a distributed load of 4-87 tons per foot run, and resulting in a total deck load of 926 tons. The car deck of the vessel provides an available length of track of about 310 feet on each of the two centre tracks, and 240 feet on each of thetwo sidetracks, whichwill accommodate fifty-four ordinary 10-ton wagons 20 feet over buffers. The vessels are designed to carry a deckload of 850 tons cars andfreight, equivalent approximately, to twenty-eight 30-ton wagons, in addition to 80 tons of oil and 30 tons of water, stores and spare gear, making a total dead-weight of about 960 tons. Theferry beingoriginally intended to carry railway vehicles only, the vessels and bridgeswere designed for this purpose, but before they were completed it was decided that one of the vessels should be fitted so as to enable it to carry road vehicles on their own wheels. Thiswas eEected by providing timber tracks, flush with the surface of the rails, on the vessels, and decking the bridges with timber to correspond. The extra weight of. this addition slightly decreased the dead- weightcarrying capacity of the vessels, andadded tothe dead-load on the bridges, though not sufficiently to affect practical working. It enabled theferry to transport about fiftyto sixty motor vehicles at a time, without any delay for hoisting, stowingor packing, and proved so useful thatthe two other vessels were subsequently fitted in the same way.

VESSELS. Thethree ferry vessels are twin-screwsteamers of the single- deck type with forecastle and side erections, and arranged so that a roof may be added later if required for covering in the cars, Figs. 3, Plate 5.

Four lines of rails are laid on the deck, running into two lines at the after end to enable cars to beshipped or discharged at that end only. Thetwo centre tracks are straight, and the two side tracks branch off from them with reverse curves of 160 feet radius. Bufferstops are placed at the forwardend of each track.Long bogie stock, locomotives and special loads, are placed on the centre tracks, the side tracks being used for ordinary 4-wheeled vehicles. The deck is formed of steel plates and is specially framed to support the weight of the loaded cars and locomotives. Beams are fitted to everyfmme, and four lattice girders formed of steelangles and plates are provided under the deck, extending as far forward and aft as possible, and connected at the bottom to the side keelsons, and at the top to thedeck beams and plsting. The rails are 75 lbs. per yard flat-bottomed rails, riveted direct to the deck, the outer rail of each track being levelled up to the inner.The timber tracks for road vehicles are 2 feet 7 inches wide, following the line of the rails and packed up flush with their surface. Anangle-iron along eachside, projectingabove the surface of the track serves as a kerb or guard line. Eye-plates for the attachment of chains for securing the wagons are fixed tothe deck at intervalsalong each track.After the wagons have been pushed home agninst the buffer stops, they are secured by chains, looped over the buffers of the wagons, hooked to the eyebolt and tightened up with union screws. The wheels of the wagons are chocked with rail clamps, secured to the rails by tightening wedges. Bottlejacks are alsoprovided to relieve the springs and prevent oscillation of the wagons, but, except in the roughest weather, it is not generally found necessary to ,use these. Twosteam capstans are providedforward for hauling wagons, if necessary, and two aft for mooring the vessel. Thehull of the vessel is as plainas possible, onlyone deck extendingthe whole length of the vessel. The bridgedeck and flying bridge, the harbour deck, forecastle and docking bridges are arranged above. Thecaptain’s cabin, chart-room, and wireless cabin are arranged on the bridge, and the wheel-house on the flying bridge.Side-houses are constructed on eachside of the car deck. Thesegive side protection tothe wagonson this deck, andare so constructed that a roof over the deck can be added if desired. The hull is divided into ten water-tight compartments, the two amidshipsbeing occupied by theengines and boilers. Thenine water-tighttransverse bulkheads are carried from the keel to the car deck, and no water-tight doors are fitted, except one in the bulkhead between the engine and ‘boiler compartments.

The various compartments of the ship have a suction pipe from the bilge pnmpin the engine-room, and a. Domntonhand-pump, connected up to thebilge suction box, is fitted on deck. The forward and after peaks are arranged as ballast tanks for trimming purposes, of 160 tons and210 tonscapacity respectively, and are each connected by a pipe to special ballast pumps in the engine- room, having a capacity of G00 tons per hour. There are also two wing tanks, each about 45 tons capacity. The stern of the vessel is cnt away for a length of B0 feet, SO that the twin screws andlarge balanced ruddershave an ample manceuvring power. At the stern tl~ecar deck is cut away square across, and seatings are provided for the ends of the girders of the hinged communicating bridge to rest upon, while the stern of the vessel isstepped down 2 feet,in order to provide clearnnce for the cross-girder of the bridge. A fender of oak, about 16 inches by 12 inches, is fittedall round the vessel, securedbetween steelangles, and having short vertical fenders of wedge shape to prevent the top fender from over-lapping a quay wall. On the centre line of the vessel at the stern is provided a 7-inch diameter forged steel pin, fitting ingrooved castings and projecting above the deck, on to which a slotted eye, in the locking casting on the end of the communicating bridge, engages when the vessel is berthedand the bridge lowered into position. Thisensures true alignment between the railson the bridge and those on thevessel. The propelling machinery consists of two sets of vertical triple- expansionengines, with cylinders 18 inch, 29 inch,and 47 inch diameter,and 27 inchstroke, driving twin screws. Steam is supplied at 180 lbs. pressure from four single-ended boilers, 12 feet G inches diameter, and 11 feet 6 inches long, fitted with oil firing appliances. The boilers are in pairs on each side of the vessel, with oil-fuel tanks between them, which have a total capacity of about 80tons at 38 cubic feetper ton. The funnels nre csrriedup on each side of the vessel. Each vessel is fitted with a complete installation of electric light, two searchlights, wireless installation ; with two high-angle, and two 12-pounderguns, magazines andammunition hoists, a Kelvin CompTss, four life-boats, steam stearing gear with telemotor control from the wheel-house, and full equipment of anchors, mooring bitts, windlass and all usual fittings. The general arrangements, bothof the vessel and of the machinery, were designed to meet two principalconditions, namely, the carrying capacity required, and the limited draught, which could not exceed

10 feet, on account of the tidal conditions at the shallowest of the selected terminal ports. The speed specified was 12 knots continuously, under ordinary working conditions, on a mean draught of 9 feet 6 inches and with the full dead-weight load of 960 tons on board. On trial with 940 tons dead-weight on board the mean draught was 9 feet 3 inches andthe displacementwas 3,654 tons.The power developed was 3,220 HP. and the speed was 13 knots.

COMXUNICATIONBRIDaEs (Figs. 4, Plate 5). Thecommunication bridges at all five portswere built upon the same principle; differing only in regard to their length which wasgoverned by thetidal conditions, and in respect of their electrical equipment which was varied to suit the electric current available. Thevarious spans measured from centre to centre of bearings were :- Span. Southampton and Dieppe . . . , . . . 120 feet. Richborough and Calais ...... 100 ,, Dunkirk . . ’ ...... 80 ,,

Each bridge consists of two main girders of N type with raking ends.These are connectedby cross-girders, which arefastened to thevertical members of themain girders by pin joints, and carry the rail bearers and decking. Thepin joints were introduced in order to render the bridge flexible and to allow it to adapt itself to the heel of the vessel, upon which the outer ends of the main girders rest when the bridge is in use.The extent of heelallowed for, was 5 degrees ineither direction, so as to provide, not only for the motion of the ship while loading and unloading, but also for a damaged vessel having to be unloaded with a list to that extent. The shore end of the bridge is carried by means of two hinged bearings on the shore foundations, and the outer or .ship end is suspended 20 feet from the centre of the ship bearings by means of a pin-jointed bridle and wire ropes from the overhead structure. This structure, restingon concrete or timber foundations, consists of two steel towers connected at the topby overhead girders which carry the operating machinery and sheaves. The wire ropes from the bridle pass round the winding-drum and over guide sheaves to the counterbalance-weights suspended inside each pillar. The main girders are 13 feet 3 inchesdeep over channels, the

booms being of trough section composed of two channels 15 inches by 4 inches connectedby flange-plates. Thevertical bracings are spaced 10 feetcentre to centre, and are composed of two web-plates spaced 9f inchesapart, and each is stiffened by two angleson its outer face. The inclined bracings consist of two channels connected by batten-plates.The bracings are connected to the booms by means of gusset-plates. The main girders are spaced 25 feet 11 inches apart, centre to centre. The cross-girders are built of steel joists 24 inches by 74 inches and flange-plates, except thatat the outer end, which is composed of angles and plates. The ends of the cross-girders arehoused between the web-plates of the vertical members of the main girders, and are hung from steel pins, the centres of which are at rail level to allow the necessaryflexibility and play. Provisionis made for lubricating all pin joints. The longitudinal rail-bearers consist of 12 inches by G inches H beams, and are connected together at the top by the tie-bolts. The rails consist of steel bars 4 inches by 23 inches attached to the rail bearers by countersunkbolts. Sufficient lateral stiffness, without interfering with the necessary flexibility of thebridge, is provided for by a longitudinalplate T5G-inchthick, riveted to the two centre rail bearers, and bracing anglesbetween the two outer ones. In addition,the horizontal portion of thebottom booms are connectedby fourlattice type struts, attached by pin joints at alternate vertical members of the main girders, and cross braced. Bearings.-At theland end the two hinges for securingthe bridge to the land foundations consist of a double-eyed cast steel bracket, seated on the foundation, and tied back by anchor-bolts to take horizontal stresses. This carries a steel pin 7 inches diameter at the ends, and 8 inches diameter at the centre, on which rests a cast steel bearing fixed to the underside of ithe main girder. The line of the pin is at the level of thesurface of the rails of the bridge at this point. At the ship end of the bridge a ball-bearing is provided on each maingirder. This consists of a cupbracket fixed tothe girder, carrying a hemispherical pivot with a square base, which rests on theseating provided for the purpose on the stern of the vessel. The ball is held loosely in the cup by two pins through slots in the upper casting. These bearings transmit to the stern of the vessel so much of the dead load of the bridge as is not counterbalanced (about 10 tons), and a proportion of the live load on the bridge.

LoCl~illgCasting.-At the ship end of the bridge a steel casting is bolted to the end cross-girder, and in the projecting portion of this casting is a slotted hole which, when the bridge is lowered into position,engages with the 7-inch diameter forged steel centring pin at the stern of the vessel. The slot allows a longitudinal travel of 7 inchesbetween the vessel and the bridge. Though provision is made for mooring the vessel independently, andit is not intended that she should hangon to the bridge, this connection and the hinges at theshore end are designed totake a pull of 25 t,ons horizontally in case of emergency. A sliding connection between the rails on the bridge and those on the vessel is provided by means of rail-flaps of hard forged steel, fixed to the end cross-girders of the bridge by hinge brackets. The sliding portion of the flap is about 16 inches long, taper in section, and hollowed on the under side to allow clearance. The groove in which it slides is formed. by a guide casting bolted to the deck on the outer side of the rail, the end of which is scarfed, the head and flange being partly cut away, so that the inner edge of the sliding portion of the flap, falls in line with the centreof the rail, and the shouldered portion at the hinge is in line with the running face. Hinged plate-flaps are provided toform the connection forroad vehicles. The tower, from which the outer end of the bridge is suspended, is formed of two steel legs of box t,ype about 5 feet 6 inches square, connected together at the top by double plate girders, 4 feet deep, upon which thehoisting machinery is erected. Thevertical legs are built up of steel plates and angles, and are stiffened in a longitudinal direction by raking struts, which are tied back to the main towers by horizontaland diagond bracing. Lateral stiffness is obtained by splaying the feet of the towers with triangular gussets, to increasethe spread of thefoundation bolts; and by corner brackets at thetop, connected to themachinery girders. Tlm foundation level of the steel towers is in each case 4 feet below the rail level at the hinge of the bridge, and the height is 43 feet from this level to the undersideof the machinery girder. Thevertical legs are spaced 36 feet 6 inchesapart, centre to centre.The inner faces arefitted with vertical guides forthe cross-heads of thelifting bridle, and also with timber rubbing pieces 29 feet 2 inches clear between the faces, allowing sufficient playfor the free movement of thebridge-girders which are also fitted with timber rubbers on the outside. Theestimated dead-weight of thebridge, including flooring is about 1.5 tons per lineal foot. For the longest bridge this gives

a reaction of 73 tons at the shore end, on two-hinged bearings, and 108 tons at the point of suspension. Allowing for impact and the weight of the suspending bridle and sheave, the total load on the suspension ropes is about 124 tons. The bridle is formed with a triangular head constructed of two horizontal steel channels, braced together, and two pairs of inclined tension bars riveted to a gusset-plate at the apex, and connected to the channels by pinjoints, from which also hang the vertical links which are connected to brackets on the main girders. These links have a gimbal arrangement at each end. Thesuspension ropes used are 5-inchcircumference steel wire ropea, having a breakingstrength of 121 tons. Four ropes are used, each in two parts, giving a factor of safety of approximately eight. One end of each rope is attached to an equalizing yoke piece mounted on a long screw, the thrust of which is taken upon the end of themachinery girder by ball bearings. This screwcan be rotated by means of bevel gearing driven by a chain drive from a small winch in the machinery cabin, easily operated by two men. The four ropes are led, from the yoke piece, over a guide drum, 3 feet in diameter,down to the four-sheavepulley carrying the suspension bridle, and thence uv to the winding drum of the lifting winch. Two of the ropes taking 2$ turns round this drum are led, from the top over guide sheayes, 4 feet 5 inches diameter, to the counter-weight inside one vertical leg of the tower, and the other two ropes taking 23 turns round the winding drum are led in the opposite direction from the bottom of the drum over similar guide sheaves to thecounter-weight on the other side. Thesheaves of the pulley are 3 feet 10 inchesdiameter. The winding drum is 4 feet 5; inches diameter, grooved right and left from the centre. The ends of, the roped are secured by balancing yokes to the tension pin through the centreof each counter-weight. The lower end of this pin isscrewed and has a large nut andwasher which allows of some adjustment of length. From the under-side of the girders supporting the machinery, is hung a pair of suspensionlinks for the purpose of housing the bridge in its highest position, either when out of use or when it is required to adjust orchange the ropes. The ends of these links are forked, and engage by meansof sliding pins with lugs provided for the purposeon the bridle. A platformis provided on each vertical leg of the tower for manipulating these pins. When the bridge is thus housed the counter-weights can be lowered on to stops in the bottom of the towers,by means of thehand winch and screw release gear mentioned above, and the ropes can then be detached.

The travel of the counter-weights is, of course, twice the vertical motion of the bridge at the point of suspension, and stops are provided both at top and bottom. The weight of each is 28 tons for the 120 foot bridges, and less in proportion for the shorter bridges, leaving an unbalanced weight in each case of about 10 tons, which is carried either by the lifting winch when the bridge is hoisted, or by the stern of the vessel when the bridge is lowered on to it. The contract for the bridge-work provided that each bridge should be fully assembled at the makers works before dispatch. This was carried out in the case of three of thebridges and presented no difficulty, it was therefore dispensed with in the case of those for Southampton and Dieppe owing to pressureof time. Lifting Machinery.-The machinery for operating the bridge is

' placed in, and operated from, a cabin on the top of the tower. It is electrically driven,and hand-gear is also provided, in case of a breakdown or stoppage of the electric current. The supply at the several terminal ports is :- Volts. Southampton ...... 400 directcurrent. Dieppe ...... 200 ,, ,, Richborough ...... 220 ,, ,, Calais ...... 200 three-phase, 50 cycles. Dunkirk ...... 500 directcurrent. The machinery, generally, consists of a 20 B.HP. motor, running at 500 revolutionsper minute, and driving, through worm and spur-gearing, a cast-iron grooved rope-drum. Pawl gear is provided forholding the drum and sustaining the bridge when not in operation. The electrical equipment is generally similar in each case, with the necessary modifications where a,lternating currentis used. The motor is of the totally enclosed compound-wound reversing type, rated to carry its full load out-put continuously for half an hour, with a temperature rise not exceeding 50" C., and capable of exerting 25 per cent. over-load for 5 minutes and a considerably greater over-load for shorter periods without injury. The controller, fixed in a convenient position in the cabin, is of the drum reversing type, with single crank handle and two-minute rated,protected type resistances. It is arrangedto give special slow speeds in either direction on two of the notches. The main switch, also fixed in the cabin, consists of a double-poleloose handle 'type, totally enclosed circuit-breaker, with over-load time element and no-volt releases. All the connectionsbetween themain switch, controller, resistancesand motor, consist of 2,500 megohm C.H.A. quality

rubberinsulated cables, ‘inheavy gauge-screwed conduit.The worm gearing is enclosed, and runs in an oil bath. The worm is of forgedsteel and provided withball thrust bearings and the worm-wheelhas a phosphor-bronzerim. The spur-gearing is of steel. Two brakes are provided, namely, a solenoid operated brake, in- corporated on the motor, capable of sustaining the full load, and so arrangedthat if thecurrent fails, or is cut off, thebrake is automatically applied ; and a hand-brake of the barrel type on the hand-gear, which is disengaged when the bridge is being operated by electric power. Two clutches are provided,one to disengage the worm gearing while working by hand, and the other to enable the drum to run freeimmediately the bridge is in positionon thesteamer. The latter is operated either by hand or automatically. In order to avoid any blow against the end of the bridge, due to possible movements of the ship while placing the bridge inposition, it is necessary that the drum should be free and that the bridge should “ float ” immediately it has taken its bearing on the vessel. This is effectedby means of an automatic release gear, actuated bythe cup and ballbearings on theend of the bridge. A spindle, carrying a powerful spring of india-rubber and vulcanite plates, is taken through each upper casting, and adjusted so that, when the bearings have made contact with the deck of the steamer and are transmitting a load of about 2 tons each, the spindle is pressed up and an electrical trip gear comes into operation. This completes thecircuit of a solenoid onthe winch, which instan- taneouslywithdraws the clutchand sets the bridge drum and counterweightsfree to “float” with the vessel. A bell and a lamp in the cabin indicate the withdrawal of the clutch when this operationtakes place. To lift the bridge thecurrent is cut off and the clutch is inserted by the hand lever, while the current is held off the solenoid byan auxiliary switch until the bridge bearings are clear of the vessel. The control platform is conveniently placed EO that the operator can see the stern of the vessel, and the whole operation is safely and simply performed by one man in thecabin.

RAILWAYSIDINGS AND SIGNALS. In order to enable thevessels to be rapidly unloaded and reloaded with wagons, it was necessary to provide adequate siding accommodation, both to receive the in-coming boat-load, and to enable

the traffic,delivered from themain lines for shipment, to be marshalled so that, every time the steamer is berthed, a complete boat-load is ready to be run on board, sortedin " sets " to correspond with the lengthsof the four tracks on thevessel. At Southampton, as at Richborough, a double track was laid from the berth to t.he nearest point on the foreshore reclama.tion, where a group of sidings could be provided. From these the double track was continued towards the junction with the main line, and two loops were provided, each to take :a full train of fifty wagons and locomotive. The provision of these double tracks enables two " sets " to be drawn off the vesselsimultaneously. The usual practice at these ports is to dram two tracks and re-load them, and then draw and re-load the other two. The whole operation of unloading all four tracks usually takes about 20 to 25 minutes. At the French ports, however, owing to the existing conditions, the siding accomodation is considerably restricted, and there is only a single line between the sidings and the berth; only one track of the vessel can therefore be unloadeld or loaded at a time. In the interests of safety in traffic working, catch-points, with buffer-stops and sand-traps, are pllaced on each approach track to the bridge, and these are interlocked .with a system of signalling andelectrical control, designed as acomplete system depending upon the working of the communication bridge and the vessel. Adjacent to the catch-points on the land side of the bridge, a signalcabin and a gantry were constructed,on whichis alarge double-faced disk signal, forming a visual indicator for all traffic on and off the vessel. Signalsare also provided for controlling the traffic up to the disk signal, and the signals and points have the usual interlocking. The sequence of operations is as fohvs :- Coritrolapparatus for the use of theman in chargeon the ship is fixed onthe end of one of themain girders of the bridge. As soon as the bridge hamsbeen lowered on to the vessel, andthe automatic release gear previously described comes into action, withdrawing the clutch of the hoisting winch, and leaving the ship end of the bridge free to float with the vessel, the man incharge on theship exchangesbell signals with thebridge operator. This indicates that the bridge is in its correct position, allready for the movement of traffic. Hethen pulls outthe electrically controlled handle in his apparatus, which thereby completes the release of the control lever in the bridge cabin and itself becomes back-locked.

The lever in the bridge cabin is interlocked with the clutch, and is only released after both the clutch is out and the control of the man on board is pulled out. The bridge operator then exchanges bell signals with the ground cabin and pulls over his control lever, thereby releasing the control lever in the groundcabin and operating the disk signal. The man in the ground cabin, by pulling over his control lever, locks the bridgeoperator’s control and he is then free to move his signal and point levers. A sealed mechanical release is provided for the bridge operator’s control handle, so that in case of emergency this can be restored to normal and the clutch immediately inserted to lift the bridge clear of the ship. The disk signal, when set to “ clear ” by the bridge operator, is an indication to the man on the ground that the bridge is ready for traffic ; in an emergency either the man on the ship, by pressing aplunger switch, or the man on the bridge, by means of his mechanicallever, can atany time throw it to“danger,” thus indicating that all traffic in either direction on to the bridge must stop, and it cannot again be placed to “ clear ” until the locking has been restored to normal and permission given. The reverse sequence is begunby the man on the ground replacing hissignal and point levers and his control lever. Thebridge operator is then able to press a plunger which permits, the man in charge on the ship to restore his control lever to normal; when this is done the bridge operator can restore his control lever to normal, throw in the clutch, andlift the bridge. A galvanometer is provided on each control which gives needle indication of the movement of thecontrol proceeding. Bell and telephoniccommunication is providedbetween all the operators ; the bells beingon separate circuits and the telephones on one circuit.

WORKAT TEE TERMINALPORTS. Thework carried out at each of the five ports fallsgenerally under the following headings :- Thelaying of therailway connections and sidings, already referred to. At Richborough and Southampton and subsequently at Dieppe dredging was required. The construction of the foundations, and the erectionof the steel work and machinery of the bridges.

The construction of the jetties forming the berth to which the vessel is moored while loading. At the two first-named ports provision was made for the supply of fuel oil and water to thevessels, As the local conditions affecting the workvaried so widely, it willl beconvenient to consider the work at each port separately.

RICIIBOROCGII(Fig. 5, Plate 5). The situation and construction of the berth at ~ichborough are described in a Paper by Mr. J. K. Rohertson,l M. Inst. C.E., and need not be further referred to here, except in so far as they relate to the ferryservice as a whole. The tide levels varied in consequence of the dredging operations carriedout. The extremes provided for atthe train-ferry berth were :- Fect nlmre O.D. Highest obserred Highest H.T...... 12.42 H.W.O.S.T...... 9.50 H.W.O.N.T...... 5.70 Feet below O.D. L.W.S. ScN.T...... 2.50

The maximum working gradient adopted for the bridge was 1 in 20 up or down.Experiments made both at Richborough andin Franceindicated that trafficcould be worked withthis gradient over theapex formed at the hinge.This gives for the 100-foot bridge a range between 18.50 anti’ 8.50 feet above O.D. for the rails on the shipend of the bridge.The height of therails on the deck of the vessel averages about 8 feet above the water-line, varyingaccording to tha loading and trim of the vessel. The workingwater-level is thereforebetween 10.50 and 0-50 feet above O.D., which permits of loading operations being carried on continuouslyover high water, and they are interrupted only at lowwater, the working period being a full 6 hoursduring both spring and neap tides (Fig. 6, Plate 5).

SOGTHAUPTOS(Fig. 7, Plate 5). The selection of thesite at Southampton was decidedby con- siderations of access byland and by sea. Thejunction with the London and South Western Eailway at Southampton West gave a clearrailmny connection withthe Midlands and theSorth of

“ Ricl~boroughMilitary Transportat,ion Delmt,” unte, p. 156. [THE IKST. C.E. VOL. ccx.] Q

England, and avoided the approach to Southampton Docks, which was already congested. On the sea side, the berth had the advantage of the sheltered approach afforded by Southampton Water, and a site was selected to the west of the Royal Pier, which caused no interference whatever with existing shipping arrangements eitherat the Docks or the Town Quay. The connection between the railway junction and the berth was effected by a double track laid for a length of about 1,540 yards on reclamation along the western foreshoreof the town, and for about 210 yards on a timber viaduct across the mud flats to the berth, which was situated at a point where the necessary depth of water could be obtained with a minimum of dredging. The tide levels at Southampton are: -

Highest recorded title ....9.75 feet above O.D. 1-I.W.O.S.T...... 6.25 ,, ,, ,, H.W.O.N.T...... 2.75 ,I ,, ,, L.W.O.N.T...... 2.25 feet be!ow 0.1). L.W.O.S.T...... 6.75 ,) ,, ,, Lowest recorded tide ....9.25 ,, ,, ,,

Theberth was dredged to :L depth of 22 feet below O.D., the qumtity of mud removed being about 90,000 cubic yards. Therail level adopter1 forthe land end of the communication bridge was 11.50 feet above 0.1). The bridge being 130 feet long between centres of bexrings, a working gradient of 1 in 20 gave a. rttnge between 17.50 and 5-50 feet above 0.D. for the rails at the ship end of the bridge, and corresponding water levels of 9.50 feet above, and2.50 feet below O.D. asthe working limits. This permitted of loading operations being carried on over all but the highestrecorded tide, and :L working period of about 9f hours exh tide. The reclamation along the western foreshore wasforfried of quarry debris and stone brought by rail from the Portland quarries, about 60,000 cubic yards of fillingbeing used. Thelarger stones were selected to form the slope on the sea side, which at the outer end was packed with hand pitching, and a low parapet wall was built. Untilthis reclamation was sufficientlyadvanced, a temporary railway track was laid along the main road parallel to the foreshore, so that the work of pile-driving for the viaduct might be begun without loss of time. Thesidings originally provirlecl consisted of two loops, eacll to hold fifty TV~~OII::an11 engine, nlltl a proul) of foul. sifliugs 11olJing 140 wagons,

Downloaded by [ University of Ottawa Library System] on [14/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedinp.] CROSS-CIIANNEL TRAIN FERRY. 227 Thisarrangement of sidings was subsequently modified and extended, as shown in Fig. 7, Plat'e 5, to meet the requirements of traffic by barges from the Town Quay, which was instituted during the latter part of 1918, and also to accommodate the fourth trainferry vessel of different type already referred to,which was acquired and brought into use about the same time, Thetimber viaduct from the reclamation embankment to the communication bridge is 630 feet long and 24 feet wide, carrying two railway tracks and a footway 4 feet 9 inches on one side. The ground consisted of soft mud, the depthof which was not accurately known, and the viaduct was therefore designed so as to distribute a concentrated load on one pile on to the adjoining pilesby means of rakingstruts in both directions.There aresix piles, 12-inch square', in each row, the two outermost piles being driven with a batter of 1 in 7, and the rows are 6 feet apart. The pileswere driven to depthsvarying from 30 to 40 feet below O.D., and the penetration for the last ten blows of a 30-cwt. monkey falling 4 feet varied from 4 inch to 2 inches irrespective of the depth. Thetransverse caps restingupon the heads of the piles are 14-inch by 14-inch timber, upon which are four longitudinal steel joists,under the rails. The usual 75 lbs. flat bottomrails were used, carried on cross sleepers. When it was decided that the ferry was to carry motor vehicles as well as railway vehicles, the vi:aduct was decked flush with the top of the rails, andan approachfrom themain road was constructed. Theberth for the vesselwas also constructed of timber pile work, onlines somewhat similar to those at Richborough. The long jetty WRS placed on the starboardside of the vessel, when lying in the berth with her stern to the communication bridge, and was arranged so that a second berth could be constructed if required on the oppositeside of it. Thisjetty is 450feet long and 35 feet wide; the short jetty on the port side of the vessel being 110 feet long by 38 feet wide. Piles, 12 inchessquare, 60 to 65 feetlong, and spaced 10 feet apart,were driven to 40 feet 'below O.D. into firm sand.The tops of thejetties werebuilt to alevel of 22 feetabove O.D., to cover the highestposition of the horizontalfenders on the vessels at hightide. In orderto stiffen thejetties, where they mere shaped to receive the stern of the vessel, and were subject to blows from it, fifteen of the pileie on each side were surrounded by stone filling, enclosed in a box formed of steel sheet piling. Q2

Downloaded by [ University of Ottawa Library System] on [14/09/16]. Copyright © ICE Publishing, all rights reserved. 228 RTANFORD os THE WAR DEPAIITIIENT [Minutes of Thearrangements for mooring the vessel aresimilar to those at Richborough, namely, a bow hawser to a bollard on the end of the long jetty, and two stern hawsers through gaps, left for the purpose inthe timberwork, to a bollard on eachside of the communicationbridge. These bollards are fixed ontimber dolphins. Thefoundations for the communicationbridge, consisting of the abutment for the hinge end, and two piers for the tower,were constructed of concrete within steel sheet-piling. The area of each foundation was first piled with 12-inch square timberpiles at about 3-feet G-inches centres and driven down to about 40 feet below o.])., thepenetration being :IS previouslymentioned. The steel sheet pilingwas driven down to the same depth. The interior of the boxes for the two piers was dredged out to 19 feet below O.D. (t,he bottom being hard green sand) and the bearingpiles were cut off :Lt 6 feet below O.D. A layer of stonefilling wasplaced inthe bottom, the boxwas filled upwith concrete to O.D. level, and pierswere brought upto the level of 7.50 feet above O.D., on which the steel legs of the tower mere erected. The concrete WAS reinforced with old steel rails placed above the bearing piles, and a few lengths were also placed in the concrete under the bases of the tower legs. In thecase of the abutment: the interiorof the box was excavated to 9.33 feet below O.D., when the hard green sand was reached, and the bearing piles were cut off at 3.66 feet below O.D. A similar layer of stone filling, about 3 feet thick, was placed in the bottom, and the concrete, similarly reinforced with old rails, was carried up to the level of about 10.5 feet above O.D. to receive the base plates of the hinge bearings. It was intended to erect the bridge on temporary timber-work a5 at Richborough, and a pile staging for the purpose was provided between the piers.This was used tocarry cranes and a derrick pole for the erection of the tower and machinery. Owing, however, to delay in the delivery of the steelwork for the girders, the vessels were ready before the erection of the bridge had been begun, and in order to makeuse of theseimmediately for the delivery of wagons urgently required in France,:L change of plan was necessary. A tempor:tryapron 20 feetlong wasprovided, constructed of 15-inch by 12-inch timber balks flitched with 15-inch steel joists and bolted together. This was lifted into place by a. locomotivecrane, and the rails on the apron were bolted by fish plates to the rails on the staging and on the vessel. By this means wagons could be run over the staging on to thevessel, and a temporary ferry service

wasestablished. The wagons, however, had to be unloaded by cranes on the quay at Havre until the terminals in France were completed. This apron afforded a suflicientperiod during time of high water for a working gradient to load the vessel. In order not to interrupt this servicefor a longer time than necessary, arrangements were made to erect the bridgework on a barge andto float it into place complete.The barge used was 99 feet 6 inches long, 28 feet 6 inches wide and 9 feet deep with R tonnage of about 350 tons. It was hallastedwith 150 tons of gravel, strengthened with temporary timber shoring, and was provided with means of scuttling. During the erection of the steelwork it wasmoored alongside thetimber viaduct, where it grounded on the mud at low water. The erection was carried out by means of &ton loco-craneson theviaduct, and a floatingcrane, in the following manner, the barge being floated and turned round as the erection proceeded. The wind bracing was laid out, and the two central sections of the bottom booms were then put down and connected with it by thepin joints, the centre joints being partly riveted. The five centralstruts and diagonals were next erected, and the five corresponding cross girders were lifted over the top of the vertical struts and the pin joints connected, The four end sections of the bottomboom, which overhung the ends of the barge,were then erected and fixed with temporary strutting, the barge being swung round as each section was put in place, and the ballast trimmed so as to preserve an even keel. The three vertical struts and diagonals at each end were then erected, the corresponding cross-girders were lifted into position and securedby thepin joints. The four end portions of the top boom were next erected, followed by the two centreportions, the barge being turned round and the ballast trimmed at each operation. The sag which occurred was taken out by jacking and strutting the twoend cross-girders, and by tightening a temporary truss on the top booms till the joints in the latter came butt to butt. On completion of the erection, the barge was scuttled and allowed torest on the mud during riveting up. A fortnightbefore this wascompleted, theferry service was stopped,the temporary staging removed and the bottom of the berth under the side of the bridge dredged with a grab to 18 feet below O.D. The barge was refloated and part of the ballast removed, leaving a free-board of about 18 inches. It was then towed into position in the berth at high water. As the tide fell, the suspension links from the hoisting bridle were attached to the brackets on the main girders by the

permanent pins, and the temporary lowering girder on the hinge end of the bridge rested on packings 2 feet above the final ievel. The valves in the bargewere then opened,allowing it to sink sufficiently to be drawn from under the bridge, and the outer end of thebridge waslowered to a horizontalposition by means of the electrical hoisting gear. The hinge end was finally lowered by means of hydraulic jacks, and the hinge bed-plates were accurately set and grouted up. Vhile this was in progress the decking and rails were fitted on the bridge. Similar provision tothat at Richboroughwas made for the storage and supply of oil fuel to the vessels, and water supply and electric power and light were a160 installed. The signalling arrangements were also similar, catch-points with sand drags and buEw stops being provided on the gantry near the bridge and interlocked with the signals.

DUNKIILK(Fig. 8, Plate 5) The siteselected for the train ferry berthwas in the turningbasin of Darse No. 5, the access from the sea being gained through the entrance canal, outer port and Trystram lock to the locked basins, and then with a right-angled turn to the westward,through the passage from Darse No. 4 into No. 5, where the vessel has to turn. The approach was, therefore, somewhat awkward for. it vessel of the size of the train ferry, though therewas the advantage of stationary water level at the berth. The minimum depth of water on the lock sills is about 18 feet at L.W.O.S.T. ; it has, however, been known to fall as low as 15 feet 5 inches at intervals. The entrance channel had at one part about 4 feet 9 inches less depth, which, at the time of the construction of theferry berth, wasbeing dealtwith by dredging.The lock is 579 feet long and 83 feet wide. The datum level of the port is the level of the lowest observed tide, which is about !L$ feet below L.W.O.S.T. Y!he following are the principal levels, referred to this datmr~:- Feet above Datnm. Quay of Trystram lock ...... 29.56 Hail level attrain ferry berth ...... 25.72 Quay of docks ...... 25.17 Highest recordedHighest water hcl ...... 28’45 H.W.O.S.T. (mean) ...... 19.35 H.W.O.N.T. ,, ...... 16.07 (lowest) ...... 14.10 L.w.~’.s.T. ,, ...... 2.25 Feet below Datum. Sills and floor of Trystramlock ...... 16.40 Dock bottom ...... 19.00

The length of the bridge being em0 fect at tllis pnrt, and assuming, as previol~slymentioned, working gr:ldicnts of 1 in 20, and :m :%verageheight of 8 feet for the rails on tJhc shipabove the water- line, the working water-levels va,ry between 21 - 72, and 13* 72 feet above datum. This, though not covering the highest recorded tide, allows a fair mal-gin beyond the ordinary tide levels occurring in the dock, and in this respect provides for practically uninterrupted working of theberth. Under normal conditions the working gradient does not exceed 1 in 25. Thedepth of water in the dock is normallyabout 38 feet at springtides, which is increased or decreased by some 4 feet at exceptionally high spring or low neap tides. The side of the dock is formed by R slope of stone pitching laid upon filling which consists of fine sand, and in driving piles special precautionshad to be takento prevent the sand from running when the pitching was disturbed. Owing, therefore, to the great length of the piles, in some cases nearly 70 feet, that would have been necessary to construct a timber jetty,and to the desirability of reducingthe piling as much as possible, and also considering that the berth was in the still waterof the dock, a jetty,alongside which the vessel mightlie, was dispensed with and floating pontoons, moored to timber pile stagings constructed in the shallower water, were substituted. The abutment for the hinged end of the bridge is of concrete. Steelsheet piling was drivenalong the face andtwo ends of theabutment, to prevent the sand from running. Eighteen timber piles were driven in the foundation, nine under each main bearing, to a depth of 10 feet below datum; they were cut off at the level of 16.50feet, the ground wasexcavated to 12.50 feet above datum, and filled in with 6-to-l concrete to the Ievel of the hinge seatings. The piers for the support of the steel tower were constructed of timber piles, eighteen under each leg, the maximum load per pile beingabout 7 tons.They were driven through the pitched slope and braced with old steel rails, bolted to them below water level by divers, with timber bracings above water, and finished off at the level of 21 * 72 above datum, or 4 feet below rail level. The stone pitched slope between the piers in front of the abutment was excavated to provide a. recess for the bridge when in its lowest position, and the slope at the lower level was then covered with concrete in bags deposited by divers. A short staging on each side of the bridge, forming the curved recess for the stern of the vessel, was constructed of timber piles,

spaced 10 feetapart and braced as beforewith steel rails and timber bracings. These are decked over at the level of 35.50 feet above datum, R height of 54.50 feet above the bottom of the dock. The four pontoons are rectangular, threeof them being 60 feet by 60 feet over fenders and 12 feet deep, and the fourth, 60 feet by 40 feet and the same depth. They were built with seven timber frihmed lattice girders, made of 12-inch by 12-inch main timbers, and 9-inch by 3-inch bracings ; intercostal framing is fixed between the girders, andthe planking is 2 inchesthick with caulkedjoints. Fenders were provided on all foursides, those on the frontface being vertical and carried 4 feet above the deck. Pumps were provided to remove any water from the inside, and the pontoons were ballasted to the extent necessary to keep the faces as vertical as possible. They were moored to each other by chains, and to timber staging by chains having large rings, sliding on vertical mooring-bars, fixed to the piles. The pontoons were built on slips made for the purpose on the slope of the dock side.The staging on the shore side of the pontoons, 240 feet in length, was constructed of timber piles, spced 10 feet apart longitudinally, and 15 feet apart transversely. They were driven to an average depth of 15 feet into the pitched slope. Thoseforming the face and serving as fendersfor the pontoons were finished at a level of 31 feet above datum, the remainder being finished at quay level. Theywere well bracedhorizontally, the ends of the bracings being let int.0 the pitched slope to anchor them. Great care had to be exercised in driving all the piles used in the work, as it was found that the sand filling began to run as soon :W a hole was opened in the stonepitching. To avoid this, immedi:ttely a ho\e was opened in the pitching, it was blocked with tarred bags filled withsand, through which the pileswere driven.The sand bags were afterwards removed and the spaces sealed with concrete in bags.

’ Provision is madefor mooring the vessel when in theberth to bollards or mooring-rings on the wall of the dock. The steelwork of the tower and bridge was erected by means of a 10-foot derrick crane with a 75-foot jib, which was carried on temporary piles andon the deckcoping. The bridgewas erected on temporary staging 6 feet above its find level in the manner a.lready described, andwhen riveted up waslowered by thepermanent suspension bridle and machinery at the outer end, and by jacks at the shore end. The sidings were arranged on the dockside close to the berth, andhave a totallength of 5,700 feet of track,to accommodate

140 wagons. Catch points,interlocked with signals as previously described, are provided on the single track approach to the bridge. A roadway for motor traffic to the berth was also constructed for a length of 1,764 feet and a width of 18 feet, and a standage area of 30,000 square feet was likewise provided. Electric power and light WVRSalso installed.

CALAIS(Fig. 91, Plate 5). The train ferry berth is situated at the south end of the Bassin Carnot, between the quay on the eastern side and the submarine station.The approach from the sea is throughthe entrance channel tothe outer harbsur, and thence through a lock. The Hassin Carnotis a longand somewhat narrow dock, usually crowded withshipping, which necessitatesswinging the ferry steamer inthe outer harbour, and towing the vessel sternfirst through the lock and the basin to the berth. The vessel can enter the lock at all states of the tide except for about 3 hours at low- wttter spring tides. The lock is 438 feet long and 69 feet wide, the sill being at thelevel of 8.2 feet below datum. Thedatum to which levels at t8heport are referred is, as at Dunkirk, approximately the level of the lowest observed low-water, which in this case is about 1.5 feet below the level of mean low water spring tides. The principal levels are :- Feet above Datum. Rail level at train ferry berth ...... 28.50 Quay levelQuay ,, ...... 27.60 Highest recorded water level ...... 24.60 H.W.O.S.T. (mean) ...... 23.00 H.W.O.N.T. ,, ...... 18.70 ,, (minimum) ...... 16.40 L.W.O.S.T...... 1.50 Feet I~elowDatum. Dock bottom, atberth ...... 7'50 Sills of entrance lock ...... 5.20

The depth of water at the berth during spring tidesis, therefore, about 30 to 33 feet, and the normal minimum level of impounded w;Lter in the dock is about 64 feet kdow high water spring tides. Thelength of the bridge is 100 feet, which, withthe same workinggradient of 1 in 20, gives workingwater levelsbetween 35.5 and15.5 feet above datum,and allows of uninterrupted working of the berth. In selecting the site of the berth it was stipulated that neither the berths for ordinary vessels alongside the quay, on which there

is n 40-t,on cmnc, nor tllc suhmnrine dcpot sl~o~d(lbe obst~rnctlerl, :lnd theberth W:~S t,hereforehit1 out, 1t::tving :L cle:~spncc of &out 50 feet between tllc vessel and the qu:~,y. The site of the bridge was occnpied by a long slope covered with stonepitching on concrete, of a totalthickness of about 5 feet, under which was sand. The bot,torn of tahe dockconsisted of sxnd covered with mud and silt. The design of the bridge abutment and piers, the bridge recess and the stern jetties, followed gcnerally the lines of the work at Dunkirk, but in view of the shallower water and the narrow space available, the jetty for mooring the vessel was constructed of concrete piers, fendered with timber on the berth side and connected by light gangways on timber piling. The firstwork undertaken WRS the removal of part of the pitching by means of divers, and the driving of steel sheet piling to enclose thesite of the recess forthe bridge. The pitching and material within the piling was then excavated, and the area was repitched with concrete in bags at a level, which provided for the working of the bridge in its lowest position. The abutment for the bridgewas constructed behind the steel piling, great care being exercised in the excavation of the sand so :LS not to disturb thebuildings in the vicinity. Thetower of thebridge was erected ontimber piling, as at Dtmkirk, and the jetties forming the shaped recess for the stern of. t.he vessel arealso piled structures.The pileswere drivento depths of 15 feet to 25 feet into the dock bottom, but before this could be done, holes for them had to be made by divers through the pitching and concrete. Thethree concrete piers on the west orport side of theship are each 20 feet square, and 33& feet high from dock bottom to decklevel, which is 3& feetabove H.W.O.S.T. The piers were constructed by driving twelve piles into the dock bottom on the site of each pier, the mud and silt being removed by dredging and the bottom levelledby divers. Shutters 22 feetlong by 8 feethigh, covered wit11 thinsteel sheeting, were framed round the piles and lowered to the bottom by winches. The concrete, composed of 4 parts of graveland sand to 1 part of Portlandcement was loweredthrough the water in skips with drop bottoms into the forms. As the concrete became set the forms were lifted by means of the screwed rods and nuts on the staging carried on the piles, and attached to the shutters by wire ropes nncl clips which were shortened and re-clipped as the shutters were drawn up. The fendering on the piers was carried to a height of 153 feet.

above II.W.0.S.T. in order to cover the fenders of tlle vessel at dl posai.ble conditions of loading and levels of highest tides. Mooring-ringswere provided on the piers for att:Lching breast ropes from the vessel, and stern moorings were provided on shoreon each side of the bridge. The steel towers and machinery for the bridge were erected. by means of a 10-ton derrick crane carried on temporary piling. The bridge was erectedon temporary staging about G feet above its permanent position, and was lowered by the permanent suspension machinery and by jacksat thehinge end. Rail connection between the bridge and the dock lines was made . by a shortsingle track line, with catch points and signals as alreadydescribed, Thesidings for thetrain ferry trafficwere laid out behind the dock sheds on the east side of the basin and contained accommodation for 111 wagons. The dock roads were also brought to the site of the bridge to provide for road vehicle traffic, and. electric lightWBS installed.

DIErrC (Fig. 10, Plate B). The site selected for the train ferry berth is in tidal water in the ArriBre Port. The access fromthe sea is betweenpier heads tothe outer harbour, and thence through a passage to the inner port. During spring tides, it is difficult for large vessels to make the entrance to the port on the flood tide, owing to the strength and direction of thecurrent, and sailingshave to berestricted accordingly. The outer port is dredged to about 14 feet below low water, but the inner harbour hada depth of only about5 feet atlow water anda " lay-by " berth for the vessel had,therefore, to be dredged to a depth of 10 feet below datum a little distance from the berth, into which the vessel can be moved at about half tide when required to remain in the port during low tide, the bottom being soft mud. Datum level, or lowest recorded tide, at this port is about 2 feet below L.W.O.S.T., the principal levels being as follows :- Yeet shove Datum. Q uay levelQuay ferry train at htll ...... 34.45 Izail level ox1 quay ...... 34.00 H ighest recorded tide recorded Highest ...... 32.14 Ibil level at hinge of bridge ...... 31.50 H.W.O.S.T...... 30.07 H.W.O.N.T...... 23.35 L.W.O.N.T...... 7.77 L.W.O.S.T...... 2.03 Feet below Datum. Approximate bed of ArriEre port ..... 2'00 Dredged " lay-by .. berth ...... 10.00

Downloaded by [ University of Ottawa Library System] on [14/09/16]. Copyright © ICE Publishing, all rights reserved. 236 STANFORD ON THE WAR DEPARTMENT [Ifitlutes of The approach line from the quay to the bridge, which is carried on a shortviaduct, is accordingly on a gradient 1 in 26, falling towardsthe bridge, of whichthe hinge is liable to occasional submergence at exceptionally high tides. The length of the bridge being 120 feet, a working gradient of 1 in 20 and an average height of 8 feet above the water line of the rail on the vessel gave a working range of water level between 29.50 feet and 17.50 feet above datum. The difference of 0.57 feet betweenthis maximum and the level of H.W.O.S.T.increased thegradient for a shortperiod to l in 18. Owing tothe considerable range of tide, the tidal curve is comparatively steep, and the period available for loading operations, above the level of 17 *50,is about 5 hours. The period during which the vessel can lie in the berthmay, however, at times be reduced to about 3 hours, owing to the limitationsof the entrance to the Port. The site of the berth is alongside a previously existing viaduct which was adaptedto form part of theberth for the mooring of the vessel. Atthe site,the sluices andculvert also existed through which the river D’Arques discharges into the harbour. The srch of the culvert was strengthened to take the weightof the ferry traffic by building steel rods into theconcrete over the arch masonry, and the gear for operating sluices the was installed in an underground chamber beneath the rails of the railway track to the berth. Owing tothe existence of thisculvert, the abutment for the hinge end of the bridge could not be constructed of concrete on the shore as in the previous cases; and it was consequently formed of grillages of steel joists carried on timber piling. The beuings were bolted to the grillages and anchored back to the quay by long tie- rods, 2 inches diameter, with adjusting screws. The distance from the faceof the quay to this abutmentis about 60 feet, which isspanned by foursteel lattice girders (obtained second hand), supported on the quaywall at thcir inner ends andon the piled staging at their outer ends. These carry thedouble tracks providingrailway access, therails being laidon 13-inch square longitudinal sleepers, supportedby 15-inch square cross-sleepers carried on the girders. The design of the piled timber-work for carryingthe bridge tower and the jetties toreceive the sternof the vessel was generally similar to that adopted at Dunkirk and Calais, the decking of the jettiesbeing finished at 38 feetabove datum, and the fendering being carried 5 feet 6 inches higher. The piles were driven about 12 feet into the ground. The existing jetty, which formed the long arm of the berth for

mooring the vessel, consisted of masonry and concrete piers about 35 feet apart, the gaps being spanned by light steel girders. All that was necessary was to bolt timber fenders on the face of the piers. These were carried up to a height of 45 feet above datum to cover the fendersof the vessel at high water, andwere strutted back on the top of the piers. The bridge was erected on temporary staging about12 feet above its final level, and was lowered by m.eans of long screws and wire rope slings, and two 100-ton hydydraulic jacks as at Richborough. The erection of the towers and the outer end of the bridge was carried out by means of a 10-ton derrick, supported on the piling driven for one of the raking legs of the tower, and on two of Ihe existing masonry piers. The land emclof the bridge was erected by a tmvelling crane on the temporary staging and between the main girders. The riveting at all the ports was done by means of pneumatic riveters, and air-compressing plant was provided for the purpose ; about 3,000 field rivets were driven at Dunkirk, 4,000 at Calais and 6,000 at Dieppe. Thesidings for the train ferry traffic were laidon a piece of ground between the Bassin h Flot and the Eiver D'Arques to the south of the berth, and areconnected to the berthby a single track, with catch points and signals. The sidings provide accommodation for about 244 wagons. Thequay roadways were brouglht tothe head of theviaduct connecting the quay to the bridge,amd both the viaduct and bridge were decked for road vehicles.

Cop-CLULIIOS. The scheme was1 begun under the directorship of Sir Guy Granet, Director-General of Movements and1 Railways, and Brig.-Gen. A. S. Collard, C.B., Director of Inland Waterways and Docks, who were succeeded respectively by Sir Sam ]Tay and Brig.-Gen. A. S. Cooper, CB., C.M.G., to whom the Author is indebted for permission to prepare this Paper. The engineering of the scheme was entrusted in thefirst instance to Mr. H. Livesey, M. Inst. C.E. (now Sir H. Livesey, K.B.E.), as regards the vessels and bridge-work, and to Mr. JJrodie Henderson, M. Inst. C.E. (now SirBrodie Henderson, K.C.M.G., C.B.), as regards the design of the berths and accessory U-orks, the Author acting as assistant,. On thepromotion of these oflicers toother appointments in

April, 1917, the Author remained at the War Office in charge of the scheme until its completion, and wasassisted by Mr. P. Risdon, Mr. D. Anderson, M. Inst. C.E., and other officers, the supervision of the completion of the vessels being transferred to the Admiralty. On the French side the selection of the sites of the berths and the negotiations with the French authoritiesconcerned .were carried outby Mr. A.Gibb, M. Inst. C.E.(now SirAlexander Gibb, G.B.X., C.B.), in conjunctionwith Sir Brodie Henderson,. The former officer as Chief Engineer Port Construction was responsible for the design and execution of the works at thethree French ports,and wasassisted by Mr. J. A. Wickham, O.B.E.,Assoc. M. Inst. C.E., and a staff of officers, including an officer in charge of construction at each port. At Richborough the work was carriedout under theCommandant, Mr. A. J. Allen-Williams, C.M.G., M. Inst. C.E. At Southampton the officer in charge of construction was Major H. K. Foster, O.B.E., R.E., acting under direct instructions from the War Office. TheMembers of TheInstitution mentioned held temporary rank in the Royal Engineers. Allthe work except that let by contract,but including the erection of the bridges,was carried outby men enlisted inthe Royal Engineers (I. W. and D.), under officers commissioned in the same corps. At the French ports thiswas supplemented by Chinese labour. The contract for two of the vessels was let to Messrs. Sir W. G. Armstrong, Whitworth and Company, Limited., and for the third vessel to MessmPairfield Brothers, Limited; the engines andboilers for all three were suppliedby the Wallsend Slipway and Engineering Company, Limited.' Messrs. Sir W. G. Armstrong,Whitworth and Company also undertookthe contract for the manufacture of the steelwork and machinery for all five bridges, the work being sublet with the consent of the War Office tothe MotherwellBridge Company, the Cleveland Bridge Company, the Horsfall Bridge Company, and Messes. A. and W. Smith, of Glasgow.

In conclusion the Author desires to acknowledge his indebtedness to the reports furnished by various officers engaged on construction, and to the contractors, for much of the information embodied in this Paper.

The Paper is accompanied by drawings and tracings from \rl1icli Plate 5 and the Figure in the texthave been prepared,