86 5 Culver—The Erosive Action of Ice. 
prey to it. But a solid hill of sound rock is quite another mat¬ 
ter. So is a smooth surface of undecayed rock. 
7. Finally, it seems to be a fact after all these years of dis¬ 
cussion and investigation, that not a single case of a lake basin 
which can be proven to have been made by ice action has been 
discovered. 
Perhaps as near an approach to proof as any is the case of 
Cayuga lake as reported by Prof. Tarr. But the fact of a con¬ 
siderable uplift of the region to the north of this lake, with the 
further fact of a drift filled outlet shown by borings to be at 
least 300 ft. deep, goes very far to discredit the evidence furn¬ 
ished by the lateral valleys referred to by Tarr. Like many 
that have been discussed before, it is a case not proven. 
Stevens Point , Wis. 
