THE CARBONIFEROUS PERIOD. 
67 
and Nova Scotia, the greater part of New Eng- 
land, the whole of New York, a narrow strip 
along the north of Ohio, a great part of Indiana 
and Illinois, and nearly the whole of Michigan 
and Wisconsin. 
Within this region lie all the Great Lakes. 
The origin of these large troughs, holding such 
immense sheets of fresh water, remains still the 
subject of discussion and investigation among 
geologists. It has been supposed that, in the 
primitive configuration of the globe, when the 
formation of those depressions at the poles in 
which the Arctic seas are accumulated gave rise 
to a corresponding protrusion at the equator, the 
curve thus produced throughout the North Tem- 
perate Zone may have forced up the Canada 
granite, and have caused, at the same time, those 
rents in the earth’s surface now filled by the 
Canada lakes ; and this view is sustained by the 
fact that there is a belt of lakes, among which, 
however, the Canada lakes are far the largest, all 
around the world in that latitude. The geologi- 
cal phenomena connected with all these lakes 
have not, however, been investigated with suffi- 
cient accuracy and detail, nor has there been any 
comparison of them extensive and comprehensive 
enough to justify the adoption of any theory re- 
specting their origin. In an excursion to Lake 
Superior, some years since, I satisfied myself that 
