FLUID FORCES. 



into a machine, Nature takes toll of it by con- 

 verting a portion into friction, which is lost 

 to you as power. That is the banker's com- 

 mission. So that the total which comes out 

 of a machine as power is always less than that 

 which was put into it. 



If, then, by using a pressure of sixty pounds 

 a man can get a machine to lift sixteen tons, 

 we may be sure that there is some compensating 

 circumstance to be looked out for which will 

 reduce the apparently magical gain to a balance 

 of powers. This compensation is in the dis- 

 tance through which the weight is lifted as 

 compared with the distance through which 

 the power is exerted. When a man develops 

 with the hydraulic press six hundred times the 

 pressure that he exerts on its handle, the lift 

 will be through only the six-hundredth part of 

 the distance. If the stroke of his pump-handle 

 be two feet six inches, the weight of sixteen tons 

 will only rise one-twentieth of an inch per stroke. 

 It will take twenty strokes to raise it one inch, 

 and six hundred strokes to raise it the height 

 of the stroke itself. Also the operator will 

 have to press each time with a force a little 

 greater than sixty pounds, to make up for what 

 is lost in friction. 



How the necessity for this compensation arises 

 can easily be seen from another glance at Fig. 20. 



When a piston forces the water down below 

 H in the barrel A, and so forces it up in the 



83 



