1898-99. | THE GEOLOGICAL HISTORY OF LAKE SUPERIOR. 53 
A great part of the work of excavating the lake basins was therefore 
completed before the glacial period and at its close, the land, which had 
stood at a considerably higher level than at the present day, had been 
depressed somewhat below its present position, and the relative eleva- 
tions of different parts had been slightly but sufficiently altered to check 
the flow of the waters as continuous river-courses, and to flood extensive 
tracts and form lakes much greater than even the present ones. 
The wide river-valley forming the bottom of Lake Ontario, about 700 
feet below the present surface of the lake, was not continuous with its 
present outlet by the St. Lawrence, but turned southward opposite to 
Oswego, and was continued in the valley of the Mohawk and Hudson. 
The rivers, whose branching valleys now form Lakes Huron and Erie, 
probably discharged from the west end of the latter into the old Missis- 
sippi, as these lakes are known to have done by the Wabash at the close 
of the glacial period. The ancient river of the valley of Lake Michigan 
probably flowed south into the old Mississippi, as the lake itself did, at 
the close of the glacial period, and as it will do again very soon. Lake 
Superior appears to cover two valleys of ancient erosion, one lying under 
the western part and the other under the main body of the lake. The 
bottom or deeper part of the former runs from Duluth, at the head of 
the lake in a very direct course to Black Bay, keeping quite close to the 
northwest side. The land along this side of the lake is high and bold, 
so that with the portion under water added, the total depth of the valley 
is 2,000 feet. The other valley has several main branches spreading 
over the remainder of the lake, but all apparently leading also to Black 
Bay. The pre-glacial discharge of the valleys which now hold Lake 
Superior was most probably by way of Black Bay, the valley of Black 
Sturgeon River, Lake Nipigon, and thence northeastward directly into 
the sea, or by way of an ancient river which traversed the site of 
Hudson’s Bay when the continent stood at a higher level. In 
considering this question, it must be borne in mind that during the 
period referred to the relative levels of the land to the north and 
south were reversed, as compared with the present day. 
There is a possibility that the ancient drainage of what is now the 
basin of Lake Superior was southward, perhaps by way of Train River, 
near Grand Island. We have thus seen that the advent of the glacial 
epoch found all the eastern part of the continent standing perhaps 3,000 
feet higher than at present, with a very old eroded surface totally unlike 
the present one, and with an entirely different topography. There was 
a general scarcity of lakes and few or no waterfalls or rapids in the 
larger rivers, as all would be worn down to base levels. 
