COMMON HOUSE PUMP. 



in the cistern falls. When the piston rises, water is raised, and 

 the quantity in the cistern is increased faster than it flows from 

 the spout, consequently the level of the water in the cistern rises, 

 and thus this level alternately rises and falls with the piston. 

 But if the magnitude of the cistern be much greater than the 

 section of the pump-barrel, then this variation in the surface will 

 be proportionally small, for the quantity of water which fills a 

 part of the barrel, equal to the play of the piston, will produce 

 a very slight change in the surface of the water in the cistern. 

 The flow, therefore, from the spout will be uniform, or nearly so. 

 The action of this sort of pump will be rendered still more easily 

 intelligible by fig. 13, which represents the working model of a 



Fig. 13. 



suction-pump usually provided for demonstrations in popular 

 lectures. The pump-handle H H' raises and lowers the piston 

 rod a. The pump-barrel is formed of glass, so as to show the 



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