MECHANICS AND USEFUL ARTS. 35 



XAYAL DKY DOCK AXD RAILWAY AT PHILADELPHIA. 



THE Journal of the Franklin Institute gives the following description 

 of the U. S. Dry Dock and Railway, recently completed at Philadel- 

 phia ; the dock and its appendages being the largest in the world. 



The lifting power consists of nine sections, six of which are 105 feet 

 long inside, and 148 feet over all, by 32 feet wide, and 11 feet 

 deep ; three of them are of the same length and depth as the others, 

 but two feet less in width ; the gross displacement of the nine sections 

 is 10,037 tons, gross weight 4,1-15 tons, leaving a lifting power of 5,892 

 tons, which far exceeds the weight of any vessel yet contemplated. 

 The machinery for pumping out the sections consists of two engines 

 of 20, and two of 12 horse power. In connection with the sections 

 (which form the lifting power of the dock.) is a large stone basin, 350 

 feet long, 226 feet wide, and 12 feet 9 inches deep, with a depth of 

 water of 10 feet 9 inches at mean high tide. At the head of this basin 

 are two sets of ways, each being 350 feet long, and 26 feet wide. 

 These ways are level, and consist of the bed pieces, which are three 

 in number, and firmly secured to a stone foundation ; the central way 

 supports the keel, while the side ways receive the weight of the bilge ; 

 these ways are of oak, and are finished off to a smooth surface. On 

 the top of the bed pieces or fixed ways, comes the sliding ways or 

 cradle, which are also 350 feet long and 26 feet wide, so constructed 

 as to admit of being adjusted to the length of any vessel. The opera- 

 tion of the dock is as follows : The sections are sunk so as to allow 

 the vessel to be floated in ; as soon as she is secured in the proper 

 position, the pumps are put in operation, when the sections begin to 

 rise, and as soon as they come to a bearing on the keel, the bilge 

 blocks are run in until they fit the ship. When all is secure, the sec- 

 tions are pumped out until the keel is some two or three feet above 

 the water. If repairs that will only require a short time are contem- 

 plated, the vessel is kept on the sections, and no other portions of the 

 dock used. When this is accomplished, the sections are filled with 

 water, and rest on the bottom of the basin, which is of stone. Bed 

 ways are now laid on the sections in line with those before mentioned. 

 When they are secured they are greased, and the cradle is now slid 

 under the ship, and she is blocked up on the cradle, and the blocks on 

 the sections are removed. At this point of the operation a new instru- 

 ment of power is brought forward for the purpose of hauling the ship 

 from the sections to the bed ways in the Navy Yard. It consists of a 

 large hydraulic cylinder, having a ram of 15 inches diameter and 8 

 feet stroke, and a power of 800 tons. On the top of this cylinder, 

 and attached to it, are two vertical direct acting engines, with cylin- 

 ders 16 inches in diameter and 16 inches stroke, connected at right 

 angles to one shaft, on which are four eccentrics for working four 

 hydraulic pumps of H inches bore, and 6 inches stroke ; the tank 

 which carries the water for the press is also on the top of the cylinder, 

 and forms the bed on which the pumps are secured. The boiler 

 which supplies these engines with steam, is on a sliding cast iron bed 

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