Geology of Lincoln Co., S. D. — Bend rat. 87 
into an amphitheatre-like basin, within the outer slope of the 
moraine. In the northwestern corner of the area another out- 
let has' bet-n met with, which is, however, not so deep and also 
narrower, its width amounting- to only about half a mile. All 
these outlets are during the rainy season to a greater or less 
extent occupied by freshets, the last mentioned by the waters of 
Beaver creek. 
Also the southern member of the Altamont moraine, within 
the limits of the area, exhibits this feature. Its surface, in 
which the character of a ridge is better pronounced than in that 
of the northern member, in so far as it is rendered more un- 
even by erosion, carrying a number of knolls, which testify to 
the original hight of the ridge, rising from 200 to 220 feet 
above the axis of the trough, is more or less cut up by shallow, 
flat-bottomed and also by deeper outlets, which have assumed 
in the course of time the form of V-shaped valleys, all of them 
being now temporarily claimed by the head-waters and tribu- 
taries of West Brule creek as well as by the head-waters of 
a creeklet tributary to the Big Sioux. One sag is met with near 
the eastern end of the ridge, a little west of the point where the 
road, coming from the north and ascending the slope, enters 
upon the back of the terrace-like most eastern end of the ridge, 
now detached from the latter to some extent by said sag, which, 
although having attained a breadth of one mile, has become 
extremely shortened through the agency of Pattee creek as 
well as of the tributary of the Big Sioux. The waters, dis- 
charged by the glacier through this outlet, probably occupied 
during that time the channel which is now drained by Pattee 
creek and its tributaries. Three other outlets are to be found 
within T.96N.. R.49W. The middle one, now claimed by the 
upper course of West Brule creek, is a rather \'-shaped valley, 
the narrow bottom of which lies over 80 feet below the detached 
portions of the ridge east and west, while the sag, about three 
c[uarters of a mile east, is now unoccupied, and the other, a 
little deeper, which is met with about one mile N.E. of Beres- 
ford, is at the present time during the rainy season flooded by 
a western tributary of West Brule creek. Its width amounts 
to about three quarters of a mile, while its flat floor lies about 
25 to 30 feet below the summit of the Beresford portion of the 
moraine. The reason whv not only the back, but also the south- 
