184 HYDRODYNAMICS. 



raise more than two thousand pounds on the bellows 

 (if it is strong enough), because the surface of the bel- 

 lows 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 

 into the bung of the hogshead. If, for instance, the 

 inner surface of the hogshead be 20 square feet, or 

 2880 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 powerful forcing-pump. An instrument of 

 this sort, possessing enormous power, was used to ele- 

 vate 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 was the pressure giv- 

 en to the confined water, that it would have forced it 

 up through a tube higher than the summit of Mont 

 Blanc. In the port of New York, vessels of a thousand 

 tons burden have been lifted by the hydrostatic press. 



This machine is applied in compressing hay, cotton, 

 and other bulky substances into a compact form, so 

 that they may occupy but little space for conveyance 



