HYDKOSTATIC PRESS. 207 



hung upon stout hinges, and is opened for the removal of 

 the bale when the pressing is completed. 



To estimate the power of this machine, divide the 

 square of the diameter of the piston, F, by the square of 

 the diameter of the piston of the forcing-pump, and multi- 

 ply the quotient by the power of the lever, B. For ex- 

 ample, suppose the piston, F, is 16 inches in diameter, and 

 the piston of the forcing-pump is 2 inches in diameter. 

 The square of 16 is 256 ; divide this by 4, the square 

 of 2, and the resuU will be 64. If the lever, B, increases 

 the power five times, the whole power of the machine will 

 be 320 ; that is, a force of one pound applied to the lever 

 will raise the large piston with a force equal to 320 pounds ; 

 or, if a force of 100 pounds be given to the lever, the 

 power will be 32,000 pounds, or 16 tons. Reducing the 

 diameter of the smaller piston to half an inch, and in- 

 creasing the force of the lever to twenty times, the whole 

 power exerted will be thirty-two times as great, or equal 

 to 960 tons. In ordinary practice, it is more convenient 

 and economical to reduce the diameter of the larger piston 

 to a few inches only, making the forcing-pump correspond- 

 ingly small, the power depending entirely on the dispro- 

 portion between them. Such presses may be worked rap- 

 idly by horse, water, or steam power. 



One great advantage which the hydrostatic press pos- 

 sesses over those worked by screws results from the little 

 friction among liquids, nearly the only friction existing in 

 the whole machine being that of the two pistons, which is 

 comparatively small. Another is the smallness of the 

 compass within which the whole is comprised ; for a man 

 might, with one not larger than a tea-pot, standing before 

 him on a table, cut through a thick bar of iron with as 

 much ease as he could chip pasteboard with a pair of 

 shears. 



