A Treatise On The Principles And Practice Of Dock Engineering

38 DOCK ENGINEERING. state, from entering thé 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 look-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 IV«.—Dimensions of the Madero Docks, Buenos Ayres. Length. Breadth. Area. Quayage. Depth below Zero. Yards. Yards. Acres. Yards. Feet. Dock No. 1, . . 623 175 23 1,553 237 Dock No. 2, . 623 175 23 1,553 237 Dock No. 3, . 755 175 27 1,815 237 Dock No. 4, . . 689 175 25 1,679 237 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^ 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. Tilbury 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 intermediate 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 beruh in the branch docks is provided with a shed, 301 feet long and 120 -feet wide, and has direct