﻿1851.] 



BIGSBY ON CANADIAN ERRATICS. 



215 



I shall merely add that the United States' geologists have shown, 

 that, as we ascend the eastern slope of the continent, the superficial 

 formations are more recent. We pass from the Silurian strata of 

 Lake Ontario, to the Carboniferous series south of Lake Erie and in 

 the peninsula of Lake Huron ; and when we come to the prairie lands 

 along the Missouri and Arkansas, Chalk fossils occur in abundance 

 to nearly three thousand feet above the sea-level. Higher than this 

 by some thousands of feet, at various localities along the base of the 

 Rocky Mountain chain, Tertiary lignite formations occur, containing 

 dicotyledonous leaves. It would appear that the country bordering 

 on the Rocky Mountains was the latest deposited, and that that chain 

 is the most recently elevated of the mountain ranges in the continent. 



3. On the Erratics of Canada. By John J. Bigsby, M.D., 



F.G.S. 



The following notes on the Drift and other superficial detritus of the 

 Great Canadian Lakes and of certain portions of South Hudson's 

 Bay are laid before the Society with the intention of extending north- 

 ward and westward the observations made on these points by Messrs. 

 Hitchcock, Hall, Mather, and others in the northern parts of the 

 United States. 



An essay is not intended ; the author merely offers his own per- 

 sonal notices, as written down on the spot. At the end of the Paper 

 a few remarks will be offered. 



It will not be necessary to describe these countries topographically, 

 as the accompanying Map, PI. XIV., will deliver us from anything so 

 tedious. 



I shall begin with the Lake of the Woods, and, proceeding east- 

 wardly, successively note down my observations on Lakes Superior, 

 Huron, Erie, and Lake Ontario. 



Lake of the Woods. — The lake of the Woods lies 360 miles north 

 of Lake Superior, and about 1 70 miles south of Lake Winnepeg, with 

 which it communicates by the great river of that name. It is 400 

 miles round ; and is severed into two unequal parts by a great pro- 

 montory. 



The rocks of the northern portion of the lake, called " Kaminitic," 

 are wholly metamorphic. Granite and gneiss occupy its west shore 

 and neighbouring crowds of islands, while syenite and greenstone pre- 

 vail on its eastern and southern shores. 



The larger and southern division has few islands, except on the 

 north and east, where they consist of primitive rocks. The rest of 

 the lake-shores, with little exception, are buried in fine sand, and 

 hence its Indian name " The Lake of the Sand Hills." On the 

 southern and western shores of Sand Hill Lake, where the sand has 

 been removed, we have a few low mounds of gneiss and a large quan- 

 tity of yellow limestone debris, either in small angular grits, or in 

 sharp-edged blocks, some of which are several tons in weight ; but 

 in no instance could I be sure that they were fixed ; nevertheless my 

 Relief is that these masses are in place ; but split and shaken by thaws 



