TEE APPLICATIONS OF PHYSICAL FORCES. [BOOK i. 



whither it is brought by suction to the place where it is required. The 

 pump is then both a suction and force-pump. In Fig. 31 is shown 

 the kind generally adopted for deep wells. 'It is simply a force- 

 pump, the pump-barrel of which is fixed in the interior of the well 

 at a sufficient depth for the water to be sucked into it in the manner 

 just described. Thence it is forced up at each upward movement 

 of the piston into a reservoir, also placed in the interior of the well, 

 and into a pipe which connects this reservoir with the exterior part 

 of the pump. When the piston descends, the weight of the water 

 closes the upper lateral suction-valve ; this prevents the return of the 

 water into the pump-barrel. In this manner, after a certain number 

 of strokes of the piston, which are necessary to fill the machine, the 

 water is poured out intermittently by the tap. It is clear that this 

 arrangement will enable water to be forced to any height to raise 

 it, for instance, to the different floors of a house. 



Numerous and various forms and arrangements are given to pumps 

 and the different parts which compose them, the detailed description 



FIG. 32. Double aotio'n pump 

 (section). 



FIG. 33. Another form (Owen's) of double action- 

 pump (section). 



of which would occupy volumes ; but these details, which are all 

 based upon the physical principle to which we have referred, would 



