Geology of Lincoln Co., S. D. — Bcndrat. 85 
Glacial times — the "Dakota" glacier, liut while during this 
epoch the moraine seems to have been continuous also along the 
western bank of the Big Sioux between Beloit and Sioux Falls, 
thus connecting the northern and the southern members with 
each other, there exists now, as will be noted from the map, a 
gap of about 20 miles, where only here and there isolated hills, 
composed cf drift-material, speak of the former presence of the 
lateral moraine. They show more or less flattened tops and 
rise in the knobs, whicH are occasionally developed, a little 
N.N.E. of Canton, to a hight of 1360 feet, farther N.E., about 
2 miles from Canton in the most prominent of these hills, to a 
hight of about 1440 feet, near Klondike in sec. 17 of Dayton 
township to 1380 feet, and in the S. W. corner of T.iooN., 
R.48\\'. to nearly 1440 feet above sea-level, i.e. in the average 
to a hight of 53 feet above the axis of the trough. From these 
data it appears that this portion of the lateral moraine was less 
developed than the now detached northern and southern mem- 
bers, and the reason for this seems to be the existence of a 
swift current at that time, which flooded a channel, now occu- 
pied by recent deposits and the waters of the Big Sioux, and 
which, rushing along the eastern flank of the ice-sheet, removed 
at least a part of the detritus of the glacier as soon as it became 
deposited. There is also some reason for supposing that at the 
time of the invasion of the region by the glacier the base of 
the glacier was inclined towards the axis of the trough and had 
also subsided towards the east along the axis so that much of 
the sub-glacial drainage was forced to seek an outlet in that 
direction, digging large channels into the soft deposits of the 
base which are now occupied by Xine Mile creek and Xortli 
and South Beaver creeks, and pouring mighty floods, especially 
during the time of the melting of the ice, upon this feebly de- 
veloped portion of the Altamont moraine, thus removing it al- 
most entirely. 
The northern and southern members of the moraine are far 
better developed, the till with its sand "pockets" and the un- 
derlying sands and gravels forming the bulk of both ridges. 
The loess, as already mentioned, occupies the flat back of the 
northern ridge, while in the "Canton ridge" it is more restrict- 
ed to the southern slope. 
What caused the glacier to spread laterally to the east as 
soon as it reached the latitude of 43"^ 30' X., was evidently the 
