154 KANSAS ACADEMY OF SCIENCE. 
popular rather than scientific, and in this connection will be so used. In the 
Tertiary deposits of western Kansas, or the glacial material of eastern Ne- 
braska, the so-called sheet water is usually found at the base of these surface 
formations, near the top of the underlying strata. The Cenozoic deposits, being 
for the most part composed of more or less porous clay, sand, and gravel, readily 
absorb large quantities of water, which gradually settles to the base of the 
formation till it finds a lodgment in a sand-and-gravel bed above an impervious 
stratum, the latter most often occurring at the line of unconformity with the 
subjacent formation. This, of course, means thatthe wells, in order to strike 
sheet water, must in most cases penetrate the entire thickness of the surface de- 
posit. 
Now it is very evident that the Dakota sandstone does not form a good floor 
for holding water. For this reason, if the subjacent strata be Dakota, the 
water, instead of remaining at the bottom of the Tertiary or Glacial, will readily 
enter the sandstone, which is ordinarily even more porous than the overlying 
rocks. It is to this sheet water, then, that many geologists look for the greater 
part of the water of the Dakota group. 
There is little doubt that a considerable portion of the water-supply of the 
Dakota may be accounted for by the theories just discussed. It is difficult, not 
to say impossible, however, to believe that all the water in the group comes from 
either the Rocky Mountain region or from the sheet water of the Tertiary and 
Glacial. Mr. Logan recognized this fact and discussed the question at some 
length. Among other things he says: ‘‘It is not impossible that the source of a 
large part of the water is much nearer at hand than even the Tertiary formation. 
The Dakota sandstone is capable of storing a great quantity of water and of re- 
taining it for a long time.’’™ 
Two examples are given, illustrated by figures, showing that a comparatively 
small area of sandstone is capable of storing a sufficient quantity of water to sup- 
ply a perennial spring. The most conspicuous example given by Mr. Logan is 
that of Terra Cotta mound, in the eastern part of Ellsworth county, Kansas. 
This mound is a solitary butte, consisting of 100 or more feet of shale and clay 
capped with a forty-foot ledge of sandstone. Although the sandstone is but a 
few acres in extent, a spring which flows from its base near the top of the shale 
is so strong that the water is carried through a pipe to a tank in a farmyard at 
the foot of the mound, where it furnishes sufficient stock water for the farm. It 
is evident that the water that supplies this spring either comes from the rainfall 
on the sandstone or else it is drawn up through the shale. Whichever solution 
is adopted the problem is not an easy one. It appears vastly improbable that 
capillarity or any other known physical force can draw this amount of water 
through such a thickness of shale; while, on the other hand, it would seem that 
the rainfall on a rocky point of not to exceed three acres, in a region where the 
annual rainfall is but twenty-six inches, is not sufficient to supply a never-failing 
spring. 
One point on which the writer has attempted to inform himself, but with in- 
different success, is that of the relative flow of springs in wet and dry seasons. 
Inquiries have been made concerning hundreds of springs with regard to the 
steadiness of flow. Many persons will assert that certain springs show no differ- 
ence in amount from year to year, while others with equal opportunities for ob- 
servation will declare that a marked difference in flow may be observed in wet 
and dry seasons. As far as my observation goes, some of the springs appear to 
53. Univ. Geol. Surv. of Kansas, 2: 213. 
