Review and Comment. 
841 
Notwithstanding the abundant evidence of pre-glacial erosion 
in the region of Lake Constance, which is fifty miles long and 
fifteen miles wide, and lies in Miocene strata, he concludes that 
since the falls of the Rhine are more than 800 feet above the 
bottom of the lake, the lake must lie in a rock basin which was 
excavated by the Rhine glacier. 
He considers the great depth of the Italian lakes, Maggiore, 
Lugarno and Como, as sufficient evidence that they lie in rock- 
basins which were excavated by ice. As confirmatory evidence, 
he notes the fact that the deepest part of Lake Maggiore is at 
the place where the enormous glacier of the Val de Ossola 
joined the great ice-stream that was formed by the united glac¬ 
ier drainage of the valleys above Bellinzona and Locarno. Where 
these glaciers united there the lake begins; and where the ice 
was on the largest scale, there the lake is deepest. 
That he may have taken cause for effect here does not seem 
to have occurred to him, at least he does not hint at such a pos¬ 
sibility. Yet it is quite certain that if the valleys had been 
formed before the advent of the ice, the disposition of the ice- 
flow would have been the same as described, i. e., where the val¬ 
ley was deepest the ice would have been thickest. 
In all these cases of alpine lakes he does not believe in 
the possibility of buried outlets; nor does he seek to combine 
the single causes which are considered by him as separately in¬ 
adequate. 
The North American and Scandinavian lakes are similarly dis¬ 
posed of, but with less discrimination, as the writer had of 
course not had opportunity for personal observation of the 
North American lakes. He quotes Sir William Logan, then di¬ 
rector of the Canadian Geological survey, as fully agreeing with 
him and as even thinking that the Great Lakes, Michigan, Huron, 
etc., may be accounted for in the same way. 
A remarkable change seems to have come over his views within 
the two following years. His theory had been much discussed 
and sharply criticised. In reply he published in November, 
1862, the following: 
“No better proof could be required that in great part the val¬ 
leys of the Alps were approximately as deep before the glacial 
epoch as they are at present (italics mine); and I believe, with 
