240 The American Geologist. October, i»oa 
Soil. 
The soil on the Oligocene formation and on a great 
part of the Cretaceous is very poor ; hut in the valleys and 
in the Loup Fork districts it is good, producing excellent 
crops whenever there is a sufficient amount of rainfall. 
Water. 
The water of the Cretaceous country is bitter to the 
taste and usually contains alkali, sometimes in such quanti- 
ties that it kills stock or "alkalies" them, that is, causes 
them to loose their hoofs. The water of the sand districts 
has a good taste and is usually wholesome. Here the water 
for ordinary drinking purposes is furnished by comparatively 
shallow wells. 
Throughout the entire region mapped if the water is 
running slow or is in a standing condition, it has a color 
similar to that of the water in a drain from a barnyard. 
Sink Holes, Ponds and Lakes. 
Dry sink-holes, ponds, and lakes of considerable size 
are scattered over the entire country. The sink-holes are 
due to underground drainage. In many places the last 
twenty to forty feet of the Oligocene, except the very last 
stratum, is often a very porous limestone ; the same is also 
true of the lower strata of the Arikaree formation, except 
that the porous rock is sandstone. Consequently sink-holes 
are readily formed when the less porous rock is removed. 
In these holes after a big rain the water quickly seeps away 
and comes out below in springs. The ponds and lakes re- 
main partly filled with water most of the year, though their 
dimensions are small compared with what they were for- 
merly as is indicated by the old beach lines, especially in 
the case of the larger lakes. Some of the lakes have water 
in them throughout the year. The ponds and lakes are 
usually due to the unequal piling of the surface debris of 
the formation in which they occur. The most of them are 
on the Loup Fork formation. 
Springs. 
Most of the springs are located at the heads of the sev- 
eral streams along the contact lines between the Loup Fork 
and the Oligocene and the Oligocene and the Cretaceous. 
The springs of the former group are good drinking water, 
