y2 The American Geologist. February, i904. 
level, gave rise to a flow heading 30 feet from the surface. 
Four miles N.W. of Lennox in T.99N., R.51W., the sandstone 
was found to be 210 feet below the surface, yielding water 
from that level down to 100 feet, while at Worthing, within 
sec. 9 of Lynn township the Dakota sandstone was revealed 
at a depth of 300 feet below the surface, yielding a fine flow 
of excellent drinking water. 
In the southern part of the area, in sec. 23 of Norway town- 
ship, near Linden, a very hard ("flint-like") sandstone has been 
reported to the writer, yielding a good flow. 
It will be observed, that the, Dakota formation in its posi- 
tion very closely follows the contour-line of the trough, being 
nearest the surface in the northern and the southern slopes 
and lowest near its axis. 
b : The Benton shales. 
The Benton group, which is usually found to be composed 
of dark clays along the Missouri river, is at places not readily 
distinguishable, although it is of a similar nature. It is not 
frequently exposed, and where this is the case, it sometimes 
grades imperceptably into the chalk of the Niobrara. 
Along the northern bank of Beaver creek, N.W. and S.E. of 
the 43° 20' N., a dark marly clay has been observed by the 
writer, the thickness of which could, however, not be ascer- 
tained. 
Pattee creek and its western tributaries as well as the mid- 
dle and lower courses of East and West Brule creeks seem to 
have their- beds in the dark shales of the Benton, the latter be- 
ing exposed in the banks of West Brule creek for about 10 feet 
above the level of the creek, where they are overlain by the 
Niobrara chalk and more recent deposits. As reported by Todd 
(comp. U. S. G. S., Bull. 158, opp. p. 144, sec. E-F), Brule 
creek continues to flow in the Colorado formation. 
The Big Sioux has done his share in revealing to some ex- 
tent the Benton group. In one case at least the w^riter noted 
the presence of a deposit of clays of a dark color below the 
general level of the Niobrara chalky series. 
Although hidden to a large extent by talus sloping down to 
the bottom land of the Bix Sioux, the Benton seems to lie at a 
uniform level below the chalkstone in the S.E. corner of the 
county within T.96N. and T.95N., R. 48W. 
