36 ANNUAL OF SCIENTIFIC DISCOVERY. 



way, some 12 or 15 feet ahead of the hydraulic cylinder, and connected 

 to it by two cast iron rods. This boiler is of the usual locomotive 

 form, and has 85 tubes of 2 inches diameter, and 9 feet long. To get 

 ready for operation, the hydraulic cylinder is slid down to the edge 

 of the basin, its ram is run in, and a connection made by means of two 

 side rods of wrought iron from the cross head of the ram to the sliding 

 cradle which carries the ship. The central bed way has key holes 

 mortised through it horizontally, every 8 feet, and there are projec- 

 tions from the hydraulic cylinder, which have corresponding key holes 

 in them. Two cast iron keys, 24 inches wide, and 6 inches thick, 

 are slid throuo-h the key holes on small wheels : these keys secure the 



" ** - 



cylinder to the central bed way ; the engines and pumps being now 

 put in operation, a pressure is brought on the 1 5 inch rani, and as 

 soon as the pressure overcomes the resistance, the vessel must move. 

 As soon as the vessel has been moved 8 feet, the keys which hold the 

 cylinder to the central way arc withdrawn, and by means of a screAv 

 which is attached to the head block of the ram, and driven from the 

 engine, the cylinder and boiler are in their turn rapidly slid ahead, 

 (the water in the cylinder being allowed to escape into the tank,) 

 when the cast iron keys are again slid in place, and the vessel moved 

 another 8 feet. To push the vessel off, the cylinder and appendages 

 are moved to the head of the ways, put on a turn-table and reversed, 

 when it is a^ain brought down to the cradle, and the cylinder being 



O o *> c* 



secured as before, the head of the ram is applied directly to the cradle, 

 and the vessel shoved back on to the sections, which requires the same 

 time and power as to haul them off. The capacity of this dock ex- 

 ceeds that of the stone, docks at New York, Boston, and Norfolk, 

 combined, for united they can take but three vessels, while here, two 

 of our longest war steamers may be hauled out on the ways, and two 

 frigates lifted on the sections. The advantages that must result from 

 the facilities of repairing a vessel elevated into light and air over one 

 sunk in a stone dock, are very great, and have only to be seen to be 

 appreciated. 



BEACON ON KOMEK SHOALS. 



A NEW beacon, having some peculiarities of structure, has recently 

 been erected on the Romer Shoals, at the entrance of New York 

 Harbor, under the direction of Mr. J. W. Lewis, C. E. The Beacon 

 is built on the southeast crest of the Eomer Shoal, about two miles 

 from Sandy Hook Light, in lo feet water, and is in plan an octagon 

 20 feet in diameter and 50 feet in height. The principle of its con- 

 struction consists in screwing into the sand of the shoal, at each angle 

 of the octagon, and in the centre, one of Mitchell's screw piles ; the 

 blade of each screw being 2 feet in diameter, and entering the sand 

 to a depth of 10 feet; attached to the screw are nine wrought-iron 

 shafts or piles, each G inches in diameter and 32-J- feet in length, 

 extending to a height of 8J- feet above high water mark; on the 

 top of these piles, heavy cast iron sockets are keyed, to which aro 



