IDENTICAL CHANGES 



But if the tube B is filled with air only the pres- 

 sure on the little rod will not be multiplied a 

 hundredfold onto the larger rod. 



Then it is evident that the comparative incom- 

 pressibility of the water is a factor in the result. 

 Considering the molecules of water as spheres of 

 like diameter, if 10 spheres are in contact with the 

 end of the little rod 1,000 are in contact with the 

 larger rod. And all these 1,010 spheres and every 

 other one in the tube are as close together as the 

 intervening void matter will admit. 



That the increase of pressure can be the result of 

 one sphere slipping in between two others is out 

 of the question, for that would mean an increase 

 of volume. 



Neither can the converging of the rows of 

 spheres, from the lesser to the larger rod, act as a 

 knuckle joint lever, for then the pressure would 

 increase after the square, whereas it is equivalent 

 to the simple increase of the larger rod over the 

 smaller. 



It is then evident that the pressure exerted on 

 any one sphere, within the tube, is imparted, un- 

 divided and undiminished, to every other sphere. 



And as long as the pressure remains a pressure 

 only, it makes no difference how many spheres are 

 involved in the whole pressure, for each transmits 

 as a whole what it receives as a whole. 



And the little rod of Figure A received and 

 transmitted the pressure upon it as one whole to 

 all the several spheres in contact with its end. But 

 103 



