128 
IOWA ACADEMY OP SCIENCES. 
Conclusions and Suggestions . — From the data given, we seem 
justified in concluding that there had been considerable deposi- 
tion of till over the region of the Big Sioux valley, previous to 
the occupation of the Altamont moraine of the Wisconsin 
epoch. The readiest explanation, no doubt, is that the ice 
sheet spread, at least, over the region mentioned, although it 
seems not impossible that the comparatively pebbleless till 
which has been observed at Sioux Falls and east of Canton, 
may have been deposited by marginal waters, and while 
occasional bowlders are found they are by no means as numer- 
ous nor as large as in the Wisconsin till. From the compara- 
tively driftless region ab )ut Garretson and the direction of the 
stria© west of Palisades, we can scarcely doubt that the valley 
of the Big Sioux was occupied by a lobe of ice but that there 
were patches east which were comparatively stationary. 
We have not given the subject sufficient study to speak with 
confidence and yet it seems permissible, at least, to offer a few 
suggestions which are little more than speculations. 
If we examine the map of the region, we shall find that the 
valley of the James river in South Dakota is separated by a 
high table land rising over considerable of its surface, to a 
height of 2,000 feet above the sea. Immediately north of the 
South Dakota line, the James river makes its nearest approach 
to the Red River of the North, the distance being about seventy 
miles. At that point the divide between the streams is very 
low and close to the former stream. A cut of twenty to twenty- 
five feet would probably turn the James river into the Wild 
Rice and Red rivers. From that point northward, although 
the divide is about 150 feet above the James, there is no we 1 
defined ridge, as further south. This brings us to a serious 
objection to the view that the course of the Missouri was down 
the James river valley, especially while the mass of ice was 
moving up the Red river valley. Moreover, some have thought 
that the ancient drainage was once northeast through the 
valley of the Wild Rice. If such were the case, the difficulties 
of keeping the James river valley open for passage of the 
wmter while the Red river valley w^as occupied by ice, would 
be still more difficult to explain, if not inconceivable. It seems, 
therefore, more probable that the dividing ridge, which is now 
so well defined in South Dakota, previous to the Wisconsin 
epoch, extended further north, possibly as far north as Devil’s 
Lake; though it was narrower and probably lower there than 
