106 E. Desor on the Drift of Lake Superior. 
times deflected either to the east or to the west. ‘These deflec- 
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with the effects produced by glaciers upon the walls and bottoms 
of the valleys through which they move, it cannot be deni 
that they exhibit the closest analogy to the phenomena which 
we have been describing. The appearance of the rocks, as well 
as the form and size of the strie, is the same; yet it must be I 
‘ceive how they could exist and move in a wide and level cowl 
try, like the northern parts of the United States and Canada. I= 
order to avoid this difficulty, it has been assumed that the whole 
northern hemisphere, as far as erratic phenomena reach, W% 
once covered with a general cap of ice, similar to that of the 
ishing of the surface rocks However inclined I 
: 8. | may be, from 
oY cle of the glacial phenomena both in Switzerland 
an ndinavia, to refer the groovings to this agency, accords 
ed by 
I have shown elsewhere that the glacie | 
: f the Alps are as much de 
upon the orographical features of the Paka Bui anne jie 
es Sciences, ee i See ae 
y arising from the climate, I would remark that it has bee 
ever existed in these latitudes, it was poss ay ek oe i : peal glaciers ; ae 
