PHYSICAL PARADOXES. 



of fifteen pounds to the square inch. On the 

 rest of the water, at C C, the air continues to 

 exercise that pressure, and the water, being a 

 fluid, transmits it equally in all directions, in- 

 cluding the upward direction at B. The water 



at B is therefore pushed 

 upwards by this pres- 

 sure, as the counter- 

 balancing pressure 

 downwards has been 

 removed by the bucket. 

 Thus the water rises at 

 B by repulsion from 

 below, not by pulling 

 from above. 



Here is a case, then, 

 where the action which 

 appears to us to be 

 pulling, drawing, suc- 

 tion, or attraction, and 

 which we so name, is 

 in reality an indirect or 

 circuitous process of 



pushing or repulsion. The water is pushed up 

 the pipe of the suction-pump by atmospheric 

 pressure just as truly as it is pushed up the 

 pipe of a force-pump by muscular pressure. 



All other so-called suctions that by a 

 boy's wet leather and string, that by a fly's 

 foot-cushions, the drawing of smoke through 

 a pipe-stem, the drawing of cider-cup through 



188 



FIG. 41. SUCTION BY A PUMP 

 REALLY REPULSION BY AIR. 



