340 
Culver—The Erosive Action of Ice. 
would probably be now named as first in the list of authorities 
on all glacial questions. 
Perhaps the majority of geologists regard the presence of 
such great numbers of lakes in the glaciated districts of the 
world as strong evidence of the power of ice to excavate rock. 
Particular mention is often made of the Alpine lakes, as well as 
of those of Scotland, Scandinavia and northern North America. 
Indeed it seems to be on this point — the origin of lake basins — 
that the question of glacial erosion chiefly turns. 
The one party confidently refers to these lake basins as of un¬ 
doubted glacial origin; and the other party as strenuously as¬ 
serts the utter incapacity of the ice to do any such work. 
The English geologist, Ramsay, 1 was among the first if not 
the first, to take the ground that the lakes above referred to are 
of glacial origin, i. e. lie in rock basins which were excavated by ice. 
He believed that the greater number of the Scottish tarns lie in 
rock basins, formed by the grinding of glacier ice, whether in 
valleys, on rough table lands, or on the water-sheds of passes. 
Some basins were formed by reason of local softness of the rock, 
but more generally he supposed them to be due to the greater 
thickness of the ice on particular areas. 
“ The theory of the glacial origin of many rock-basins, must, 
I feel convinced, be extended much beyond such mountainous 
districts as Switzerland, Wales and the Highlands of Scotland 
where they first attracted my attention. ” 
In regard to the great alpine lakes he says of Lake Geneva 
that (1) it does not lie in a simple synclinal basin; (2) it is not 
due to special subsidence; (3) it is not due to a fracture of the 
rock; (4) it is not the result of water erosion, since water can¬ 
not possibly scoop out a hollow nearly a thousand feet deep. 
The only other agency to which he can appeal is ice, and the 
Rhone glacier is the agent which he believes excavated the basin 
of Lake Geneva. 
In a similar manner he accounts for Lakes Neuchatel, Thun, 
Brienz, Zug, Lucerne, Constance, Zurich and Wallen. 
Lake Zurich has its waters held at their present level by a 
moraine, but he thinks the main basin is excavated in the rock. 
Quart. Jour. Geol., Aug., 1862. 
