282 The American Geologist. May, i9oo 
lis was deposited, the short existence of the glacial lake had 
ended, and drainage passed unobstructed along the great val- 
ley. 
Departure of the Ice- Sheet from this Area. 
In the culmination of the lowan and Wisconsin glaciation, 
the part of the ice-sheet that flowed southwestward from north- 
ern Wisconsin and the basin of lake Superior extended across 
Minneapolis to lake Minnetonka, covering the eastern parts 
of Hennepin and Wright counties, as is known by the occur- 
rence of the red northeastern drift to such limits under the 
gray northwestern drift. Along a belt traceable from lake 
Minnetonka northwest and north, the ice flow from the north- 
east was confluent with the part of the ice-sheet moving south- 
easterly from Manitoba and western Minnesota. Toward this 
belt the surface of the icefields descended from each side. But 
near the end of the Glacial period, the belt of glacial con- 
fluence, toward which the ice surface declined, was trans- 
ferred a considerable distance eastward, to the tract which in 
the progress of the glacial melting became the site of lake 
Hamline in St. Paul. 
This change of the ice currents I attribute chiefly to the 
eastwardly passing storms, which brought rain and promoted 
melting on the southwestern border of the ice-sheet, but far- 
ther upon its high and broad expanse gave only snowfall. 
While the western border of the waning ice-fields in South 
Dakota, on the latitude of Minneapolis, was melting back, nar- 
rowing the region of snow and ice to be crossed by storms be- 
fore reaching this locality, the area of their principal snowfall 
moved proportionally eastward, pushing back the belt of con- 
fluence. 
In the vicinity of these Twin Cities of Minnesota, the ice- 
sheet was first melted through at a great reentrant angle or 
sinus, occupied by lake Hamline. Thence the ice west of this 
lake area, terminating with an irregularly retreating boundary 
of general north to south course, withdrew across the site of 
Minneapolis; and the drainage from the melting ice surface, 
covered by drift which had been englacial, yielded the sand 
and gravel plains and esker hills. 
