MECHANICS AND USEFUL ARTS. 65 



head of which a powerful air-pump can be connected. The pile is 

 placed in the proper position, the air from the interior exhausted, and, 

 a stream of water, sand, shingle and gravel, rushing up from below, 

 the pile sinks gradually into the displacement made to any required 

 depth. It is, therefore, a kind of sub-aquatic excavation, the lower end 

 of the hollow pile being converted into a kind of scoop worked by the 

 air-pump on the platform above. In this way, hollow iron piles, three 

 feet in diameter, have been sunk to the depth of 78 feet, through a 

 material that would not admit the penetration of a screw, or of a wooden 

 pile, to a greater depth than 20 feet. After the piles have been sunk 

 any required distance, they may be exhausted of their contents, and 

 filled with concrete, which, before the decay of the exterior iron shell, 

 will form an artificial stone pile of great strength and durability. 



In the recent construction of a bridge across the Shannon, for the 

 Midland Great Western Railway, cylinders ten feet in diameter were 

 used successfully, in the place of hollow piles, by the method described. 

 Hitherto the piles employed for Potts' process for sea-beacons and 

 other structures, have been of very small diameter, so that the pro- 

 ceedings we have just described are of the greatest importance. A 

 cylinder of ten feet diameter gives a large bearing, and four such cyl- 

 inders will carry a large tablier or platform for a pier, and which can 

 be put down without coffer-dams or other preparatory works, thereby 

 greatly reducing the expense of submarine foundations. Here neither 

 cofferdams, caissons, steam engine pump, nor diving-bells are wanted, 

 only an air-pump of adequate power, which can be easily carried about 

 and rigged anywhere. It will be obvious that unless sunk from the 

 inside, (when there would be as much trouble for pumping as by 

 the pneumatic process, and very much labor and expenditure of time,) 

 any external application of power would, if it could be employed, exer- 

 cise a very unfavorable effect upon the material of the cylinder. Indeed, 

 a force of much less than 13 Ibs. to the square inch would smash a 

 hollow iron cylinder to pieces. Then, again, it is to be observed, that 

 ten feet is by no means the limit of the diameter to which the cylin- 

 ders can be carried, so that it is open to engineers to design works ia 

 situations and under economical conditions, where hitherto the 

 resources of art were insufficient to meet the emergency. 



NOVEL METHOD FOR SINKING PILES. 



THE following is an abstract of a paper recently read before the Brit- 

 ish Institution of Civil Engineers, by Mr. G. Hughes, C. E., on a novel 

 method of sinking piles. It was proposed to construct the piers of a 

 bridge over the Medway, on hollow cylindrical iron piles, seven feet in 

 diameter, each composed of two, three, or more cylinders, nine feet in 

 length, bolted together through stout flanges ; the bottom length of 

 each pile being also bevelled, to facilitate the cutting through the 

 ground. The bed of the river was originally presumed to consist of 

 soft clay, sand, and gravel, overlaying the chalk, and, accordingly, the 

 application of Dr. Potts' pneumatic method for forcing the cylinder piles 

 into the ground, which had been successfully carried out in similar 



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