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farther south; and that this ridge played an important part in 
hindering the advance of the ice until it had accumulated 
sufficiently to break through into the James river valley, as it 
did during the Wisconsin epoch. This would be the more 
easily explained if the ice sheet from the north, i. e . , from the 
Keewatin center was not so vigorous in the early stages, i. e., 
in the Kansan and pre- Kansan stages. 
Prom a general consideration of the extent of the so-called 
Kansan till as compared with the Wisconsin, we may infer that 
the natural center during the former stage was further east; 
probably northeast of Lake Superior. In fact, we may con- 
ceive that some of the higher points north of Lake Huron were 
the first to receive a permanent ice cap. As the region became 
more chilled, the zone of accumulation would extend naturally 
along the more elevated surface of the ice and then the great- 
est accumulation would lie naturally near the edge of the zone 
and advance slowly outward. In this way, we may perhaps 
account for the greater vigor of the streams passing down 
Lake Michigan and Lake Superior during the Kansan stage or, 
as some would say, the latter during the Kansan stage and the 
former during the Illinoian stage. If we believe the ice to 
have here pushed forward southwest in the axis of Lake 
Superior basin, it is not difficult to conceive that its course 
would lie diagonally across the state of Minnesota, being con- 
fined in a broad shallow channel between the highlands about 
Itasca and the region of central Wisconsin, that it was directed 
to the Minnesota valley and across it against the high transverse 
ridge of the “East Coteau” the high divide separating the 
Minnesota from the James, which now has an elevation of 
1,700 to 2,000 feet. From the shape of the land and the course 
of the stream, it seems not unlikely that the highest elevations 
were along the axis of this stream. As the Des Moines valley 
to the south offered an easier slope, we may conceive the ice 
sheet to have expanded more rapidly in that direction and to 
have spread out during the Kansan stage, from that valley 
westward and south into northwestern Missouri. We may 
account for its failure to press westward over into the James 
valley by the elevation of the Coteau region and by the divert- 
ing infiuence of the Big Sioux valley, which we may suppose 
had greater effect upon the thinner edge of the ice which there 
lay in the zone of ablation. 
The failure of the ice to press equally northward may be 
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