362 
Culver—The Erosive Action of Ice. 
fjords had a similar origin both in the matter of time and also 
of the excavating agent. 
But such reasoning is no mor§ conclusive than that of Dr. 
Hansen. Although it is far too commonly indulged in by 
geologists when discussing regions which they have never 
studied, the writer wishes to avoid the fault, and so while he 
doubts very much the capacity of even such very industrious 
ice as that of Scandinavia is said by Helland to have been, to 
excavate such deep passages as the Norwegian fjords in such 
hard rocks as their walls are said to show, yet he must con¬ 
fess that he really knows very little about it, and perhaps Dr. 
Hansen is right after all. 
CONCLUSIONS. 
From such study as he has been able to make of this subject 
the writer has been led to the conclusion that the efficiency of 
ice as an eroding agent has been very greatly exaggerated in 
the past. 
The claims made for the erosive power of ice have been based 
on many observations. The chief of these claims are here speci¬ 
fied: 
1. The fact is undisputed that the lakes of the globe are 
practically confined to the regions that have been glaciated. 
Some of these lakes were apparently found to occupy rock basins. 
The conclusion was thus reached that the lakes for the most part 
had been furnished with beds by glacial erosion. It has since 
keen shown that in this country a very large majority of the 
lakes lie in drift hollows, still others lie in drift obstructed 
valleys, others have been formed by differential uplift. A few 
lie in folds in the rock and a very few lie in what seem to be 
true rock basins the origin of which still remains in doubt. 
2. Lakes have been observed to discharge their waters over a 
rocky rim the lowest visible point of which was many feet above 
the deeper portions of the lake bottom. 
The assumption has usually been in such cases that the lake 
occupies a true rock basin which could not have been made by 
water and hence must have been made by ice. 
