FLUID FORCES. 



G, as it had upon the one barrel B. Pour 

 water into A ; it will find its level in all, the 

 atmospheric pressure as well as that of the 

 water itself being transmitted in all directions 

 so as to procure a perfect balance. Fit them 

 all with pistons, and the whole five will re- 

 spond to an exactly equal extent, just as the 

 one did. And if we put a one-pound weight 

 additional on each piston, the whole five will 

 remain exactly balanced at the same level 

 by universally transmitted pressures. 



Here we come upon the key to the ex- 

 planation of the hydraulic press. The pressure 

 transmitted is equal for equal areas of pressure- 

 surface. Any weight on the one square inch 

 of water in A balances an equal weight on each 

 of the square inches in B, D, E, F, and G. 

 Therefore one pound on the water in A can 

 balance five pounds distributed over the other 

 five water-surfaces. And so a pound and a 

 half at A would more than balance, would 

 actually raise, five pounds at B, D, E, F, 

 and G. 



But it is clear that we should not change 

 the relation between the one barrel and the 

 other five if we combined these latter all in one 

 larger barrel, whose section area was five square 

 inches like theirs added together, and whose 

 weight of air-pressure on the top would there- 

 fore be equal to theirs, as well as its weight 

 of water for the same height of column. 



G 8l 



