WA1^ER-SUP1>LY. 53 



more economic, and that a greater area of the world is 

 irrigated by the storage of storm waters than is irri- 

 gated by well waters. Storm waters are very rich, 

 carrying with them many elements of fertilization, and 

 are very valuable. 



Underflow, Phreatic and Artesian.— These are 

 all definitions of subterranean waters. Underflow 

 waters may consist of either the phreatic — those waters 

 underneath that have come from the surface — or the 

 artesian, which are almost invariably deep- founded, 

 and owe their depth to the earth's stratifications, 

 through which they have percolated from higher 

 sources, either open or hidden, and generally in either 

 case at great distances from the artesian channel proper. 

 These waters are necessarily not nearly so available as 

 the more readily attained surface supplies, and are to 

 be developed only in urgent cases and in the places 

 where a surface supply is not accessible. Underflow 

 waters are sometimes brought to the surface by the 

 gravity process. This is possible in the sandy beds of 

 many western streams a greater portion of the year. 

 Phreatic waters usually abound within loo feet of the 

 surface and are raised chiefly by pumps, while the deep 

 artesians have an invisible power, which forces the 

 water to the top in ever-flowing streams. I^ater chap- 

 ters in this work will bear upon these subterranean 

 waters more fully. 



Tunneling for Water. — In California where fruit 

 crops form the main agricultural pursuits, the rather 

 expensive plan of tunneling the high mountains for 

 water supply has been successfully carried out in many 

 places. The work has been done mostly by organized 



