HYDROSTATIC PRESS. 205 



water in the tube as the surface of the upper board ex- 

 ceeds the cross-section of the tube. Thus, if a pound of 

 water fills a tube half an inch in diameter, and the bellows 

 are two feet in diameter, then this pound will raise more 

 than two thousand pounds on the bellows (if it be strong 

 enough), because the surface of the bellows is more than 

 two thousand times greater. 



In the same way, a strong, iron-bound hogshead may- 

 be burst with the weight of a single gallon of water by 

 pouring it into a long and narrow tube set upright in 

 the bung of the filled hogshead. If, for instance, the inner 

 surface of the hogshead be 20 square feet, or 2,880 square 

 inches, a tube of water 23 feet high will press with a force 

 of 10 pounds on every square inch, or equal to a force of 

 28,800 pounds, or 14 tons, on the whole surface. 



HYDROSTATIC PRESS. 



The Hydrostatic Press owes its extraordinary power to 

 a similar principle ; but, instead of a bellows, there is a 

 moving piston in a strong metallic cylinder; and instead 

 of being worked by the mere weight of the water, it is 

 driven into the cylinder by means of the lever of a pow- 

 erful forcing-pump. An instrument of this sort, possess- 

 ing enormous power, was used to elevate the great tubular 

 iron bridge in England. It was found necessary to make 

 the sides of the cylinder into which the water was driven 

 no less than eleven inches thick, of solid iron ; and so 

 great w^as the pressure given to the confined water, as 

 to have forced it up through a tube higher than the 

 summit of Mont Blanc. I*n the port of New York, ves- 

 sels of a thousand tons' burden have been lifted by the 

 liydrostatic press. 



This machine has been applied in compressing hay, cot- 

 ton, and other bulky substances into a compact form, so 

 that they may occupy but little space, for conveyance to 



