LAKES FORMED BY GLACIAL ACTION. 297 



The Formation of Lake Basins. — Some geologists seem to hesitate to admit 

 that the basins of the great lakes mentioned above could be formed in this 

 way, on account of their extensive areas and the great depth of some of 

 them. At the same time, they would probably not deny the glacial origin 

 of thousands of smaller lake basins, which can be pointed out in Canada, 

 where the whole evidence is presented to the eye in a very limited compass. 

 There we can see 'simultaneously glacial strise descending into the water on 

 one side of the lake-basin and emerging on the other, while more or less 

 drift material is deposited all around. Here we have no difficulty in realizing 

 the whole process of the formation of these small lakes. We have only to 

 enlarge our conceptions of nature to picture the formation of greater lakes 

 by the same process, which is equally easy on any scale, no matter how large, 

 if we can admit the forces to have been equal to the requirements ; and why 

 should we not? Why should we seek to limit the operations of Nature by 

 bounds set through our own narrow conceptions ? 



Some lakes in the glaciated area, however, occupy sites of depressions 

 which existed loug before the drift period, and which may date far back in 

 geological time. These may have been greatly enlarged or partly re- 

 excavated by the action of the ice. Lakes Superior, Nipigon, Temiscaming 

 (on the Ottawa), and St. John (on the Saguenay) are examples of such ancient 

 geological depressions; but the grandest of all is Hudson's bay. The orig- 

 inal basins of all these bodies of water have existed since Cambrian and 

 Silurian or even earlier times. But there is abundant evidence of their 

 having been enlarged by glacial action. The site of Lake Superior appears 

 to have acted as a reservoir for the accumulation of ice, which again forced 

 itself out in different directions. Reference has already been made to the 

 fact that it moved westward from the northwest shore ; and it had a general 

 southward course for some distance from the south side. But the most 

 curious feature in this connection is the fact that it moved eastward, and 

 even northeastward, up the steep and rocky shores on the east side. Evi- 

 dence of this may be seen on mauy parts of the coast, all the way from 

 Michipicoten to Batchewana bay. 



The wide but shallow basin of Hudson's bay is situated in the centre of 

 the greatest area of glaciation in North America, and it offers the most inter- 

 esting field for the study of the phenomena of the drift period, on account 

 of both the grandeur of the scale on which the forces operated and the 

 distinctness with which their records may be read at the present day. This 

 great central basin of the continent stretches from the interior of the Labra- 

 dor peninsula on the east to the Rocky Mountains on the west, and from 

 Baffinland on the north to Minnesota and Dakota on the south ; and it 

 has, therefore, a diameter of two thousand miles each way. As already 

 stated, the site of the present bay acted on a stupendous scale as a reservoir 



