THE CONQUEST OF NATURE 



rises to the top of the receptacle, and beginning again 

 whenever, through use of water, the ram begins to 

 descend. Such an apparatus is called an accumulator. 

 Such water engines have come into vogue only in com- 

 paratively recent times, being suggested by the steam 

 engine. As already pointed out, their utility is re- 

 stricted, yet the total number of them in actual use to- 

 day is large, and their share in the world's work is not 

 altogether inconsiderable. 



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