156 SNAKE EIVER PLAINS OF IDAHO. [bull. 199. 
is at present, and much of it would be practically impassable to 
travelers. 
DEVELOPMENT OF SPRINGS. 
The conditions on which the several varieties of springs described 
above depend at once suggests methods by which their now may be 
increased, or new springs produced. This matter will be considered 
later in more detail, but I may call attention briefly to the self-evident! 
fact that to increase the flow of a hillside or canyon spring the proper 
method would be to imitate nature and excavate tunnels or horizontal, 
wells. As fissure springs rise through more or less vertical openings, 
it is obvious that in order to obtain water from subterranean sources 
where it exists under pressure vertical wells must be put down. Such 
artificial fissm\ springs are termed artesian wells. 
ARTESIAN WELLS. 
REQUISITE CONDITIONS. 
The governing and qualifying conditions pertaining to artesian wells 
have been described by many writers, and are noted in a previous 
report relating to Idaho," and need not be repeated here except in a 
very general way, to serve as an introduction to what follows. 
The presence of water in a pervious stratum is usually dependent 
on the exposure of a portion of the bed at the surface, so that it may 
receive the direct precipitation from the atmosphere or be charged by 
percolation from surface rock waste, seepage from streams, etc. A 
pervious bed may also become water charged by leakage from other; 
beds, as has been explained by Chamberlin. 6 The geological condi- : 
tions which lead to the filling of pervious beds so inclosed that the 
water can not escape from them, at least not freely, are various. The 
conditions most frequently occurring are illustrated by what are known 
as artesian basins and artesian slopes. 
In an artesian basin the strata containing one or more pervious beds — 
we will assume, for simplicity, that but one is present, with a water- 
tight bed above and below — have the form of a basin, at some portion 
of the rim of which the pervious bed comes to the surface and receives 
sufficient water to saturate it. An illustration of this structure may 
be had hy spreading a layer of sand over the interior of a saucer and 
placing another saucer within it, both vessels being in an upright 
position. If water is poured into the lower saucer until the spaces 
between the sand grains are filled and a hole is drilled in the bottom 
a I. C Russell, Water-Supply and Irrigation Papers U. S. Geol. Survey No. 54, 1891. Bibliography 
on p. 130-131. 
5T. C. Chamberlin, The requisite and qualifying conditions of artesian wells: Fifth Ann. Kept. V. S. 
Geol. Survey, 1885, pp. 125-173. 
