THE BEGINNINGS OF EXPERIMENTATION 59 



itself is pushing equally in every direction, for if it 

 did not react on the adjacent particle with an equal 

 force there would be an unbalance of force which would 

 cause motion. In other words, Pascal's Law means 

 that in a liquid at rest any two adjacent particles of 

 the liquid are acting on each other with equal and 

 opposite forces. Consider now two adjacent particles 

 in the horizontal portion of the tube of Fig. 5. Since 

 the liquid is at rest the pressure transmitted from the 

 right must be equal to that from the left. The pres- 

 sure exerted by the fluid in the long tube is then equal 

 and opposite to that of the fluid in the short tube. 



The total downward force exerted by the liquid in 

 the right-hand tube is as many times greater than that 

 of the left-hand as the area of the right tube is greater 

 than the area of the left tube. A mechanical advan- 

 tage may therefore be obtained by utilizing this prop- 

 erty of a liquid. This is illustrated by the hydraulic 

 press in which a small force acting on a piston of small 

 area produces the same pressure as does a larger force 

 applied to a correspondingly larger piston. As a con- 

 sequence of the incompressibility of liquids, the dis- 

 tances through which the acting and resisting forces 

 are exerted are inversely as the forces, as the "work 

 principle" requires. 



