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HISTORY OF ENGINEERING.
Book J.
iron columns, and paved with slabs of granite, except at the water’s edge, where there areiron plates for the more easily working of the trucks, which are drawn by two men, wliotransport the various casks to the entrance of the large warehouses.
Along the southern quay is a shed with an iron roof covered with slate, and also sup-ported by iron columns ; this shed is 443 yards in length. To counteract the effects of ex-pansion and contraction, of which the metal is susceptible, the iron tie-beams which rest onthe columns are not closely united, but a sufficient interval is allowed to admit of somepky.
Under the sheds are spacious cellars, with octagonal pillars of stone, supporting flatbrick arches ; they are lighted by vertical openings taken from the interior of the sheds abovethem. Where two vaults intersect, a cylindrical well is built up, through which the lightdescends from a lantern. On a level with the floor of the sheds, plates of cast-iron coverthese wells, and in them are fixed five lens or glass illuminators. Reflectors have also beenmost ingeniously introduced to distribute light in various parts.
Iron railways are not used on the quays, but in their stead large slabs nicely fitted toge-ther, upon which the friction of the wheels is inconsiderable. In the middle of the pave-ment there are two rows, running parallel with the quays and warehouses, and opposite toeach crane a double row conducts to the warehouse doors, or the sloping passage to thevault.
East of the docks is the mahogany shed, which is remarkable for the machine used inpiling up the vast logs imported from the West Indies ; five men, by the aid of thismachine, move logs weighing as many tons with facility.
William Jessop furnished the plans for the West India docks, and superintended theirexecution, as did Mr. Gwilt those for the warehouses.
Deptford is situated on the southern bank of the Thames , not far from the mouth of thelittle river Itavensbourne, which rises at Keston, in Kent, near the remains of the Romancamp.
Henry VIII . established there a royal dock, or king’s yard, which has been considerablyimproved since that time; at present it comprises upwards of 31 acres, contains wet docks,slips for men-of-war, basin, mast ponds, and several storehouses. The old storehouse is aquadrangular pile, and was built in 1543. The roofing,'which covers some of the slips, isa fine example of carpentry. At a short distance on the north is the victualling yard, withsteam mills for grinding corn, ovens for baking biscuits, cattle-sheds, slaughter-houses, acooperage, and packing-rooms. There are houses for the residence of all the officers be-longing to this most important establishment.
Woolwich, on the same bank, farther down the river, has a much more extensive dockyard,which was established at a very early period. The ship Harry Grace de Dieu< of 1000tons, w’as built here in 1512. 'The dockyard has been enlarged from time to time; at pre-sent it is about 5 furlongs in length and l in breadth. Within this area are dry docks,mast ponds, slips, smithery, anchor manufactory, model lofts, storehouses of various descrip-tions, mast houses, sheds for timber, and dwellings for the superior officers. Several of thelargest vessels in the British navy have been built there.
The dry dock, erected under the superintendence of Mr. Walker, is one of the most com-modious lately built. After the site was excavated, a foot of brickwork was laid over thewhole, then a course of granite 3 feet 6 inches in thickness. The base is 230 feet in length,and of a proportional breadth; the dock will contain vessels of 300 feet in length, owing tothe excellent manner in which it is arranged.
Another dock, similarly constructed, 360 feet at the base, will admit vessels of 400 feetin length on the upper deck.
Many timber piers have been carried out from the banks of the Thames within the lastfew years, for the convenience of the steamboat passengers, some of which are between 300and 400 feet in length ; the most important of these are at Erith , Greenhithe, and Grays ;it is difficult to say how long the timbers may remain uninjured by the Teredo navalis ,which does great injury below Gravesend.
Gravesend, which contains a population of nearly 20,000 persons, being much resorted toduring the summer months, has grown into considerable importance : steamboats are con-stantly arriving and departing. In 1833 an act was obtained to construct a new landing-pier, and thirteen months afterwards the present town pier was opened to the public ;W. T. Clark, Esq. was the engineer employed by the corporation, and Mr. William Woodcontracted to perform the work for 8700/. It extends 127 feet from the front of the townquay, and is 140 feet wide, being built upon cast-iron arches of that span, with a rise of 6feet; the land arch springing from the stone wall of the quay, and all the others fromcolumns. The transverse arches and framing, also of cast-iron, are supported by eightcolumns on foundations of Bramley fall-stone.
At the extremity of the platform is a T head 76 feet in length, and 30 feet wdde, underwhich are contrived the steps which communicate with a floating vessel, which rises and fallswith the tide, and is always level with the packets alongside.