1882 .] 
365 
[Davis. 
would be entirely drained if the drift were cleaned out from 
the old channel leading to Green Bay 1 ; and Winnepeg and its 
neighbors are described as preglacial valleys obstructed by drift . 2 
The irregular forms and many islands of the latter can be due 
only to overflow of an uneven surface, and never to erosion 
by a broadly acting ice-sheet. 
The large lakes of Northwestern Russia are in several ways like 
the series of lakes in our country that stretches around from the 
St. Lawrence valley to the Arctic Ocean ; behind them is an old 
worn-out mountainous country of crystalline rocks, with uneven 
surface though of no great height, out from which crept the ice 
of early quaternary times; in front of them is a broad flat region 
of old sedimentary strata, scarcely disturbed from their original 
horizontal position, and never yet subjected to rapid erosion at a 
considerable height above sea-level ; on the former small lakes 
are extremely numerous, on the latter they are comparatively rare ; 
and separating these two areas stand the large lakes, Onega and 
Ladoga, and their salt homologues the White Sea and the Gulf of 
Finland. Without asserting that local disturbance may not 
have had something to do with these larger depressions, I believe 
it will be found that they are like our great lakes in origin as in 
position; that they are essentially old valleys of erosion, shaped 
during a greater elevation of the old mountainous region, slightly 
modified by glacial action, and now obstructed by drift. 
The very numerous lakes of Finland seem to be mostly of 
this character, though it is difficult to find any full description of 
them . 3 
We may here again refer to the presence of drift and alluvial 
barriers below the Swiss lakes, which so far as effective, obviate 
the necessity of both orographic and glacial erosion basins. 
All the larger lakes on the Italian slope of the Alps (except Lago 
dTdro) are thus aided to an unknown extent ; even the two 
1 T. C. Chamberlain, Geol. Wise., ii, 1877, 137. 
2 G. M. Dawson, Geol. Mag., v. 1878, 211. Maps of Lake of the Woods and Rainy 
Lake are given by Bigsby, Geol. Soc. Journ., vm, 1852; x, 1854; and of the former 
by Dawson, Resources of the 49th Parallel, 1875, 204. 
8 G. Bohtlingk, Ein Blick auf die Diluvial-und Alluvialgebilde in siidlichen Finnland. 
St. Petersbourg, Acad. Bull., v, 1839, 273. N. Nordenskiold, Beitragzur Ivenntniss der 
Schrammen in Finnland, Helsingfors, 1860. 
