72 How Water is Pumped. 



10. If you should suck the air from a straw 

 which has one end in a 

 cup of water, you would 

 see the effect of air pres- 

 sure in the rising of the 

 water in the straw. 



n. When a pump is 

 thus placed in a well, 

 and the air removed 

 from it, the water rises, 

 because the air which 

 rests on the water in the 

 well presses it up. 



1 2. In the first draw- 

 ing, the water in the 

 well and that in the 

 pump are on the same 

 level, because air is 



pressing down equally Rod g-oing- down-upper valve 

 . , * . i open, lower valve closed. 



on the water both in- n n 



(!N BLACKBOARD DRAWINGS, MAKE 



side and outside of the THE PuMP THIRTY INCHES IN LENGTH 



AND THREE INCHES IN DIAMETER ; 



Pump AND THE WELL TEN INCHES IN DIAM- 



ETER.) 



13. The pump is provided with two little 

 trap-doors called valves, which fit tightly. The 

 lower valve is fixed, the other is moved up and 

 down by means of an iron rod attached to the 

 handle. (See p. 49.) 



