russell.] ARTESIAN WELLS. 181 
containing some -too square miles, having- Shoshone, Bliss, and Sho- 
shone Falls at its corners, will, I think, agree with me in the conclu- 
sion that they are sufficiently favorable to the hope of obtaining flow- 
ing water to be deserving of a thorough test. The rise of the water 
in a hole drilled in the covering layer of an artesian slope depends on 
the friction of flow in the water-bearing layer below the site chosen. 
The less pervious the layer, down to a certain indefinite limit, the 
higher the water will rise with a given slope. In the case of the per- 
vious beds beneath the "Shoshone triangle" there is a remarkably 
free passage for the water. On the other hand, the volume of water is 
great, and this perhaps more than counterbalances the adverse condi- 
tion resulting from freedom of natural escape, and favors the hope 
that water would rise to the surface if drill holes properly cased were 
put down. There is the same necessity for an impervious cover to 
the water-bearing stratum in an artesian slope that there is for an 
impervious layer above the pervious bed in an artesian basin. In the 
"Shoshone triangle" the covering bed, as indicated in Snake River 
Canyon, is basalt, but above the lowest known water-bearing bed 
there are at least three strata of lava, and sedimentary beds may occur 
between these. The presence of such beds has not been proved from 
observation, but the fact that the water forming the springs along 
Snake River comes from three separate pervious beds is sufficient 
evidence that practically impervious rocks occur between them. 
I have dwelt on these probahilities at some length in order to place 
the reader who is familiar with the "Shoshone triangle" in a position 
to judge for himself whether the chances of obtaining flowing water 
are sufficiently good to warrant making a test. In my judgment it 
would be worth while to put down a pioneer well to a depth of 700 or 
1,000 feet, at a distance over miles from the brink of Snake River 
Canyon, anywhere in the triangular area referred to where broad tracts 
of fine land occur. The locality chosen should be at as great a distance 
as possible from elevations like Flat Top and Notched buttes, which 
indicate the position of old volcanic vents. 
POSSIBILITY OF OBTAINING FLOWING WELLS IN ALLUVIAL DEPOSITS. 
As has already been stated, the border of the Snake River Plains 
is covered in part by alluvium brought down by streams from the 
adjacent mountains. There is reason for believing also that similar 
deposits were formed from time to time between the successive erup- 
tions that furnished the Snake River lava. In such alluvial deposits 
generally an alternation of pervious and impervious beds occurs. 
The pervious beds have in a general way the shape and associations 
described on a previous page under the term "artesian wedges." 
The conditions here referred to may be expected to occur at any of 
the localities where streams flowing from valleys in the mountains 
