Review of Recent Geological Literature. 59 
water. No successful wells have been obtained from it. Above the 
Dakota sandstone the remaining members of the Cretaceous are almost 
entirely impervious shales. A map is given of an elongated region cor- 
responding in a general way to the Arkansas valley in which flowing 
wells may be obtained. Along the south and west sides of this area 
wells may be obtained at a depth less than a thousand feet, but along 
the northern side throughout a narrower strip they cannot be obtained 
without going to a greater depth. The former area is estimated to 
be about 4,000 square miles, and the latter 1,500. Some valuable state- 
ments are given concerning the areas in which the water is collected. 
The average width of the exposure of the Dakota formation along the 
foot hills is estimated to be not more than one mile. "Where it is nar- 
row the slopes are so steep that a large share of the storm water runs 
off and the sand can imbibe but little. But the broader parts of the 
belt have gentle slopes more or less covered by a blanket of sand, in 
which the rain water is stored for a time and from which it may be 
slowly absorbed by the sandstone." 
He outlines several areas of this sort, one having an area of tifty or 
sixty square miles, another of five hundred, and a third of not less than 
a thousand. The author remarks, " It is impossible to say what share 
of these areas contributes water to the sandstone. In part they are oc- 
cupied by the upper layers of sandstone, which are of so fine texture as 
to receive little water. The irregularity of the sandstone beds is so great 
as to raise the question whether all the porous beds exposed to the rain 
are of such horizontal extent as to carry water to the deeply buried por- 
tions of the formation. Such considerations make it impossible to es- 
timate the amount of water which may annually be imbibed, and for 
the present at least it is useless to discuss the annual rainfall with 
reference to the extent of the gathering grounds." 
The artesian waters are found to vary much according to locality. In 
general they are rich in chlorides, sulphates, carbonates of sodium, cal- 
cium, magnesium, with freqvient occurrence of silica and lithia, in pro- 
portions varying from .0008-. 0036. 
The ground water of the region is derived mainly from the Upland 
Sand and Gravel. Considerable attention was given to circulation of 
water in the sand occupying the stream beds, as well as those of the 
terraces and upland. In the Arkansas river, as in most rivers of the 
plains, a large portion of the water is flowing beneath the surface of a 
vast amount of sand filling its channel. Upon the upland the water 
contributed by rainfall is found here, as in other regions, to have a very 
irregular surface, corresponding sometimes to the surface of the under- 
lying rock, sometimes to the surface of the soil and at other times ap- 
parently without relation to either. 
Some interesting experiments were made to determine the absorptive 
power of sands. The experiments were performed by filling a vessel 
with sand thoroughly dried, then pouring into it water until it was sat- 
urated, then by puncturing the bottom of the vessel so as to permit the 
water to drain away, and after a lapse of several days determining the 
