212 THE ICE AGE W NORTH AMERICA. 



southern extremity is near Des Moines, Iowa, and whose 

 Avestern limb is the Coteau des Prairies of eastern Dakota. 



The conclusions of Mr. Upham and President Chamber- 

 lin, concerning the movements of the ice over the region 

 west of the lakes, are intensely interesting and seem amply 

 warranted by the facts. It appears that in the northwest the 

 ice advanced in four lines of motion pointing to a center a 

 little below Dubuque, Iowa, though the columns did not all 

 reach the point of their apparent destination : 1. One line 

 of advance was down the depression of Green Bay, in Wis- 

 consin. The moraine of this lobe constitutes what is called 

 the Kettle Range of that State, and terminates a little west of 

 Madison, on the eastern edge of the driftless region. 2. A 

 second line of movement was down the valley of Kewanee 

 Bay. This movement spent its force in northern Wisconsin, 

 reaching the vicinity of Eau Claire. 3. The third move- 

 ment was along the line of the main axis of the western end 

 of Lake Superior, and extended across the Mississippi past 

 Minneapolis, as far as Lake Minnetonka, and to a line run- 

 ning northwest from this point for a hundred miles or more. 

 4. The fourth movement was from the region of Lake Win- 

 nipeg in the Red River Valley toward the south and south- 

 east, meeting and opposing the ice-current from Lake Supe- 

 rior, along a line from Stearns county, Minn., southeast by 

 Lake Minnetonka to Crystal Lake in Dakota county. This 

 is the movement which extended southward to the vicinity 

 of Des Moines, Iowa, and whose western flank is the Coteau 

 des Prairies. 



The line northwestward from Minneapolis, where these 

 last two movements met, was an interesting battle-ground of 

 the glacial forces. First, the Lake Superior Glacier pre- 

 vailed, and pushed over the ground to its extreme limit, 

 even beyond the Mississippi. This boundary-line runs from 

 Crystal Lake through Minnetonka, Wright, and Stearns 

 counties, Minn. A little later, the Red River Glacier 

 gained the ascendency, pushing the front of the Lake Supe- 

 rior Glacier back into Wisconsin, east of the Mississippi. 



