Page:The American Cyclopædia (1879) Volume VI.djvu/176

 168 DOCK vidod with locks, at the principal ports, is ap- pended : PORTS. No. In acres. London 28 88 4 4 7 2 1 8 2 4 8 4 850 206 142 79 46* 51 20 32 41 107 1* 84 85 Liverpool Birkenhead Hull, exclusive of Hartlepool West llartlepool^ exclusive of timber pounds. . Leith Dundee Aberdeen The docks at Cherbourg were commenced by Napoleon I., and the first basin was opened in August, 1813. (See CHEEBOUEG; also for notices of other docks, see the articles on the places where they are situated.) The Atlantic dock at Brooklyn, technically a tidal basin, was constructed by the Atlantic dock com- pany, chartered by the state legislature in 1840. The work was commenced in 1841, and FIG. 2. Plan of Atlantic Dock. occupied several years. Over 200 acres of land were purchased at a point on the Long Island shore opposite Governor's island, and 60 acres of the low land and marsh were converted into a basin having 40 acres of water surface. The enclosure on the water side was made with cribwork piers consisting of timber filled with stone, sunk in trenches 30 ft. below high-water mark. The cribs were 25 ft. thick at the base, and were placed with their external sides 150 ft. apart, that being the width of the pier, the top of which is 10 ft. above low-water mark. The space between them was filled with sand and gravel from the excavations in the basin. Piles were driven into the filling to a sufficient depth and sawn off" 5 ft. below the surface ; and upon the heads of the piles the stone founda- tions of the warehouses were placed. The en- trance is between the north and south piers, and is 200 ft. wide. The excavation over the whole 40 acres was made principally with dredging machines working by means of an endless chain, and was carried to an average depth of 20 ft. below low-water mark, or 25 ft. below high-water mark. In the basin, reaching from either end, are wooden piers of sufficient width for the unloading of ships, built of piles covered with timber and plank- ing. Upon the cribwork piers, one of 1,070 and the other of 1,000 feet in length, there are commodious stone warehouses, 100 ft. in depth and extending the length of the piers. Upon the opposite or inland side of the basin is the commercial wharf, 2,000 ft. in length, and upon this there are three blocks of ware- houses, each 460 ft. long and 180 ft. deep, be- sides an iron yard of the same dimensions. There are several grain elevators situated upon different parts of the wharves. A plan of the dock is given in fig. 2 ; for a further descrip- tion and a perspective view, see BROOKLYN. DEY DOCKS, often called graving docks, because used for graving or cleaning the bottoms of. ships, consist, as before stated, of those which are pumped dry and those which discharge the water by being 'raised. The former are usually built of masonry, but are sometimes constructed of piling, concrete, and clay pud- dling. Two of the latter kind were construct- ed at the Erie basin, near the Atlantic dock, which are 500 ft. in length by 90 in width at top and 480 by 50 ft. at bottom, and 30 ft. deep. The dry dock at the Brooklyn navy yard is the finest structure of the kind in the United States. It was commenced in August, 1841, and completed in August, 1851. The construction of the coffer dam and the excavation which initia- ted the work are described in the article DAM. The main chamber of the dock, fig. 3, a, is 286 ft. long and 30 ft. wide at the bottom, and 307 ft. long and 98 ft. wide at the top, this being the distance between the folding gates g g and the head of the dock e. Behind the folding gates is what is called the lock chamber, c, 52 ft. long, which length may be added to the dock when it is required, a caisson, d, forming the external gate being sufficient to exclude the water. The bottom is 26 ft. below mean high tide, and 30 ft. 8 in. below the coping. The foundation had to be constructed in quicksand, and con- sisted of piling driven to great depth, covered