186 HYDRODYNAMICS. 



thrown into a square box or chamber of strong plank, 

 of the size of the intended bundle. One side is hung 

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

 hay 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 

 multiply the quotient by the power of the lever, B. 

 For example, suppose the piston, F, is 16 inches in di- 

 ameter, and the piston of the forcing-pump is 2 inches 

 in diameter ; then the square of 16 is 256. Divide 

 this by 4, the square of 2, and the result 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 di- 

 ameter 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 correspondingly small, the power depend- 

 ing entirely on the disproportion between them. Such 

 presses may be worked rapidly by horse, water, or steam 

 power. 



One great advantage which the hydrostatic press 

 possesses over those worked by screws results from 

 the little friction among liquids, nearly the only fric- 

 tion existing: in the whole machine being that of the 



