HYDRAULICS. 20.5 



However, by filling the whole void between the 

 piston and the clack at first with water, this last 

 objection might be removed. 



In some cases, the pump cannot be placed con- 

 veniently perpendicular to the well : for example, 

 being to raise water out of the well at A, by means 

 of a pump at B (Fig. 1 1.), the best way will be to 

 carry the barrel as low as the spring is, communi- 

 cating therewith by means of the pipe at C. The 

 bucket then playing in the barrel B C, will have 

 the same effect as if the well were made perpen- 

 dicular to the pump ; because the water, by its 

 proper weight, will always replenish B C. 



And if it should happen, from some considerable 

 impediment, that the barrel cannot get down to 

 the well directly, it may be led about any other 

 way for sake of convenience. And then making 

 the pipe of conveyance E, less in diameter than 

 the barrel, it will sooner be exhausted of air, by 

 moving the piston ; and the water will follow very 

 briskly, as by the leaden pump at B, 



It will, however, always be more easy to draw 

 water with pipes that are large, and of an equal 

 bore throughout, because the water will have a less 

 velocity in them, and the friction will be in pro- 

 portion less. Upon this account, the common 

 pumps made by plumbers frequently do not work 

 easy, because, by making the pipe that brings up 

 water from the spring much less than the bucket, 

 they, as it were, wire-draw the water raised. 



Archimedes' screw, (Plate 9- %. 12.) deserves 

 consideration, not only for its antiquity, but its 

 usefulness in raising water. It consists of a long 

 cylinder, with a hollow pipe-tube, or groove, coiled 

 about it, as represented in the figure. It is placed 

 in a position oblique to the horizon, with the lower 



