COMMON THIXGS PUMPS. 



of flat circular plates, one above the other, by which the water is 

 lifted. These saucers lift the water and press it up through a 

 vertical pipe placed near the ascending side of the chain. The 

 water, rising through this pipe, is discharged into a cistern on the 

 deck, from which it flows off into the sea through a waste pipe 

 called the pump-dale. 



There are two hollow vertical barrels, or cases, through one of 

 which the chain ascends, and through the other it descends. The 

 chain is worked by means of a winch attached to the upper roller, 

 over which it passes. This winch receives a continual motion of 

 rotation, by the power of men applied to its handles, which are 

 so formed that several men can work them simultaneously. 



In large vessels these pumps are constructed upon a scale suffi- 

 cient to enable them to raise a ton of water, or about 250 gallons 

 per minute. 



22. The purpose to which pumps are applied on the most vast 

 scale is in the drainage of mines. In that case the power required 

 far exceeds the limit to which animal power is practically available, 

 and even steam-power, by which such pumps are worked, requires 

 to be applied on a scale far exceeding every other form in which 

 it has been applied in the industrial arts. 



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