338 DRY-FARMING 



Available subteiranean water 



Where surface waters are not readily available, the 

 subterranean water is of first importance. It is gen- 

 erall)' known that, underlying the earth's surface at 

 various depths, there is a large quantity of free water. 

 Those living in humid climates often overestimate 

 the amount of water so held in the earth's crust, 

 and it is jjrobably true that those living in arid regions 

 underestimate the quantity of water so found. 

 The fact of the matter seems to be that free water 

 is found ever}^vhere under the earth's surface. 

 Those familiar with the arid West have frequently 

 been suri)rised by the frequency with which water 

 has been f(juntl at comparatively shallow depths in 

 the most desert locations. \'arious estimates have 

 been made as to the quantit}' of underlying water. 

 The latest calculation and jjerhaps the most reliable 

 is that made by Fuller, who, after a careful analysis 

 of the factors involved, concludes that the total 

 free water held in the earth's crust is equivalent to a 

 uniform sheet of water over the entire surface of the 

 earth ninety-six feet in dc])th. A quantity of water 

 thus held would be equivalent to about one hun- 

 dredth ])art of the whole volume of the ocean. Even 

 though the thickness of the water sheet under arid 

 soils is only half this figure tliere is an amount, if 

 it could be reached, that would make possible the 

 establishment of homesteads over the whole dry- 



