54 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. VI. 
In whole districts the general course of the streams was in the opposite 
direction from the present. Several great rivers, which existed then, are 
now entirely wiped out, and the whole topography is so changed that, 
looking at the map of the present day, their courses would not be sus- 
pected. Take, for example, that of the old St. Lawrence as mapped by 
Dr. Spencer, starting from the middle of Lake Michigan, crossing the 
land to Lake Huron, thence through Georgian Bay, then across country 
to Lake Ontario, from which it again crossed country to the Mohawk 
and on down the Hudson to the Atlantic coast, which was then far to 
the east of.its present position. About the same time, as I have stated, 
Lake Superior may have discharged through Black Bay and Lake 
Nipigon into the sea to the north. The present round-about arrange- 
ment of the discharge of the great lakes, which however is only 
temporary, has a very unusual appearance from a topographical point 
of view. The pre-glacial drainage of the valleys which now form the 
bottoms of three lakes, running in the various directions I have 
indicated, would be more in accordance with what we might expect 
from the general contour of the country, so that it is not at all extra- 
ordinary that it followed these lines. In a paper read to the Royal 
Society of Canada a few years ago, I sketched the hypothetical course 
and the branching of a great pre-glacial stream which finally flowed 
into the north Atlantic along the bottom of what is now Hudson’s 
Strait. and which was probably larger than any of the existing rivers of 
the world. 
The glacial epoch was of long duration and in these latitudes it was 
broken by interglacial periods, each of which probably lasted for a 
great length of time, and during them the vegetation, which had been 
driven south, partially returned and must have given the country 
something of the appearance of the present day. Although the glacial 
conditions have finally retreated as far as Baffinland and Greenland, 
many of the trees of North America are still in the process of returning 
as far as possible towards their original home in the north. But we 
have not the time this evening to pursue this interesting topic. Ina 
general way the climate of these latitudes since the disappearance of 
the continental glacier has never been better than at the present day, 
but in certain deposits of more recent date on the north side of Lake 
Superior, I have found evidence of a milder interval which may never: 
theless have been some thousands of years ago. 
As the very existence of our great lakes, as well as their former 
extensions, their successive relations to each other and their drainage 
