G. K. Warren— Valley of the Minnesota and Mississippi. 423 
If we follow the Mississippi down we find similar conditions 
produced by the Wisconsin River as by the Chippewa; that is, 
a great increase of the slope and shoaling of the river below the 
junction, with gentler slopes, deep water, and Jake-like aspect 
above. There would probably have been a large lake here, if 
the affluents above had not silted it up. 
Another instance is afforded by the damming-back effect of 
the Mississippi deposit at the mouth of the Illinois River, mak- 
ing it at low water almost like a lake up to La Salle. : 
ke Pepin must therefore be regarded as due to the deposit 
by the Chippewa of heavy coarse sediment into the valley of 
an ancient and larger river. This view may be strengthened 
further by the following considerations: It lies immediately in 
the course of the main valley above an important tributary. In 
this respect it agrees with Lac-qui-parle, on the Minnesota, just 
above the Lac-qui-parle River; with another lake on the same 
valley just above Yellow Earth River; with Big Stone Lake 
In the same valley, just above Whetstone River; with Lake 
Traverse, which is formed by deposits from a stream at each 
end, and thus empties sometimes in both directions. It agrees 
In this relation with the lakes on the Qu’Appelle, which all 
le just above a considerable tributary, and with like lakes on 
the Upper Fox of Lake Winnebago. This constant relation 
Seems unmistakably one of cause and effect. 
ake Winnipeg southward.— As I have 
stated in previous reports, I regard the ancient river draining 
Valiey formed since the glaciers began to retire.—It also seems 
Most probable that the ancient valley itself, as a whole, was 
formed in the region of glacial deposits, part! y during the period 
this great field of ice was receding, and partly since it left the 
ancient Mississippi basin, for the following reasons: When this 
1cé-period was on the increase, its southern margin must have 
been gradually advancing in this region, crushing down and 
planing off the ridges and filling the ravines and water-courses 
with the débris not only of the neighboring rocks, but with 
