194 



PUMPS AND THEIR VALUE TO MA AT 



for agricultural purposes unless artificially watered. In the 

 West, several large irrigating systems have been built by the 



federal government, 

 and at present about 

 ten million acres of 

 land have been con- 

 verted from worthless 

 farms into fields rich 

 in crops. Public irri- 

 gating systems make 

 use, for the most part, 



FIG. 136. Centrifugal pump with part of the casing 



cut away to show the wheel. OI the modem pumps 



to force water over 



long distances and to supply it in quantities sufficient for vast 

 agricultural needs. In many regions, the success of a farm or 

 ranch depends upon the irrigation furnished in dry seasons, or 



FIG. 137. Agriculture made possible by irrigation. 



upon man's ability to drive water from a region of abundance 

 to a remote region of scarcity. 



The draining of land is also a matter of considerable im- 

 portance; swamps and marshes which were atone time con- 

 sidered useless have been reclaimed and converted into good 

 farming land. The drainage is usually done by centrifugal 



