160 
Culver—The Erosive Action of Ice. 
In this volume Prof. Forel rejects the hypothesis so long ago 
put forth by Ramsay, that the basin of Lake Geneva was exca¬ 
vated by the old Rhone glacier. He finds instead that the lake 
basin is an extension of the old Rhone valley. This valley was 
defined at a very early period in the uprising of the Alps. Its 
excavation progressed with their growth. It was practically com¬ 
pleted at a time when they were higher by 1,000 meters than 
they are at present. Then followed a subsidence of the mountain 
region, the lowland being comparatively unaffected. 
This formed the lake. The movement in the disturbed region 
may have been differential, but Prof. Forel does not consider this 
supposition necessary to account for the facts. 
It is by such work as that o f Prof. Forel, of which this brief 
mention gives but a glimpse, that the question of glacial erosion 
will be settled. 
Prof. C. W. Hall says 37 : 
“The lakes of Minnesota are conveniently divided into three 
classes: first, rock bound lakes; second, silted river lakes; third, 
glacial lakes. 
“The first class occur chiefly in the northeastern part of the 
state. They occupy the troughs in the crustal folds that have 
contorted the surface, or the depressions where excessive faults 
have broken and considerably tilted the strata. These as a 
rule are long, uarrow and deep. By far the greater number of 
lakes in Minnesota are those occupying the depressions in the 
unevenly .distributed morainic matter deposited during glacial 
times. 
“They were all evidently formed in the same general manner, 
by the washing down of fine silt from the highlands into the 
bottom, thus gradually filling the interstices in the gravels and 
sands beneath them, making water tight bottoms to hold the 
water. ’’ 
There is here no reference to glacial erosion to account for 
any of the 10,000 lakes accredited to Minnesota. 
The observations of the writer on the lakes of north-east¬ 
ern Minnesota are quite in accord with the views here express¬ 
ed by Prof. Hall. 
The same statements may be made with reference to the 
lakes of Wisconsin and of the Dakotas. In none of these states 
has a lake been found which can be shown to owe its origin di- 
37 On the formation and deformation of Minnesota lakes, Science, 
vol. 21, pp. 314-315. 
