Geological Society. 375 
In the first part of this paper, the author describes the ge- 
neral form of the country, in which are placed the great lakes 
of Superior, Huron, Erie, and Ontario, with a sketch of some 
of the rocks occurring in their vicinity. 
He then examines the question of the present level of their 
waters, as compared with their ancient level, and enumerates 
many circumstances to prove that no recent alteration has taken 
place. He then endeavours to establish, that the Canadian 
lakes are monuments of the last flood, by the features of the 
country, the abrasion of its rocks, and the nature of the trans- 
ported matter. He ascribes the shape of the Islands of Lake 
Superior, and of the Promontory of Keweewoonan to diluvial 
denudation. ‘The Manitouline gaps are adduced as effects of 
one simultaneous deluge. 
Dr. Bigsby divides the debris of the St. Lawrence Valley 
into four classes :—1. Diluvial; 2. Messalluvial: 3. Alluvial; 
4, Native. 
1. The Diluvium lies usually in extensive flattened heaps. 
Cape Tourment, 1800 feet above the level of the sea, is covered 
with it. Marine shells, of the genus Sazicava, are found in the 
Ottawa, 300 miles N.N. W. of Montreal. 
The actual position of numerous primitive bowlders on the 
plains, being south and south-east of their original sites, indi- 
cates that the flood proceeded from the north and north-west, 
or, ina direction contrary to the present course of the St. Law- 
rence. The trap of Montreal is found at Lake Champlain, and 
bowlders of tabular spar (one of which weighs 600 pounds) are 
traced to the west end of Ontario, where the Ophicalcic rock 
is also seen in broken masses. ‘The chalcedonies from Lake 
Superior have been transported south-west to Lake Pepin. 
The south and west shores of the Lake of the Woods are load- 
ed with bowlders, whilst the opposite shore is destitute of them. 
These evidences of denudation are given, as coinciding with the 
views of Saussure, De Luc, and Buckland. 
2. The Messalluvion is presumed to have been formed in the 
intermediate state of the earth, which it assumed between its 
total submergence and its present form. At that period, cen- 
_tral North America is imagined to have been occupied by one 
great lake; and the author’s evidences to prove this, consist of, 
1. The series of embankments, and 2. their being composed of 
adjacent rocks, and even of fresh-water materials. 3. Rolled 
masses of neighbouring lakes being reciprocally found in 
each other. 4. The peculiar nature of the sand and gravel, 
beneath the mould of the Valley of the St. Lawrence. 5. The 
mountain-barriers broken through for the passage of rivers and 
lakes. 6. The analogy of this supposed reservoir to og 
which 
