338 DRY-FARMING 
Available subterranean water 
Where surface waters are not readily available, the 
subterranean water is of first importance. It is gen- 
erally 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 probably 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 everywhere under the earth’s surface. 
Those familiar with the arid West have frequently 
been surprised by the frequency with which water 
has been found at comparatively shallow depths in 
the most desert locations. Various estimates have 
been made as to the quantity of underlying water. 
The latest calculation and perhaps 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.depth. A quantity of water 
thus held would be equivalent to about one hun- 
dredth part of the whole volume of the ocean. Even 
though the thickness of the water sheet under arid 
soils is only half this figure there is an amount, if 
it could be reached, that would make possible the 
establishment of homesteads over the whole dry- 
