1898-99. | THE GEOLOGICAL HISTORY OF LAKE SUPERIOR. 59 
the driftless area to the south of Lake Superior in Wisconsin. The 
great extent and depth of the basin of Lake Superior, which, as we have 
seen, was in existence before the advent of the glacial period, lying 
across the course of the on-coming land ice, must have had an important 
. ~ ~ o.* 
~ CANVPHO)U.ENG BU. 
View near Ashland, South Shore, showing gradual submergence. 
effect in checking its progress. This influence of a great depression 
would be much enhanced by the very considerable height of the land on 
the south side of the greater part of the lake. 
