DRIVE PUMPS. 



221 



for tlie ingress of vrater thus obviating entirely tlie cost 

 and labor of digging wells. If driven through a subter- 

 ranean spring, a stratum of water, or a wet layer of sand or 

 gravel, it is obvious that the Avater will immediately flow 

 through the perforations into the pipe ; and, by attaching a 

 good pump to the pipe and pumping for a time, all the par- 

 ticles of sand and fine gravel will be drawn out ; and the 

 cavity thus formed around the perforations will remain filled 

 with pure water. These tubes and pumps are admirably 

 adapted to localities where large beds of wet gravel exist 

 fifteen or twenty-five feet below ; and, in fact, to all soils 

 where large stones are not abundant. ^Yhero these occur, 

 the pipe must be withdrawn, and tried in a new place, 

 until success is attained. 



In the Chain Pump^ a i')artial cross-section of which is 



Fig. 247. 



Fig. 248. 



Section. Eotary Pump, for Barrels, etc. 



here shown, (fig. 247), the chain is made to revolve rapid- 

 ly on the angidar wheel by means of a winch attached to 



