Geology and Mineralogy. 63 
ward over Minnesota, and thence, as N. H. Winchell has shown, 
south to Iowa, where it was connected with the ice over northern 
Tilinois. 
The independence of the glacier-mass of the Michigan Bay de- 
— and that of the long Green Bay valley is well proved by 
of. 
of ponds and pools over its surface. It is one to ten miles wide, 
west outlines of the Green Bay valley glacier. It consists of gravel, 
bowlders, sand and clay, unstratified, but with portions here and 
h 
glacial scratches made by the Michigan and Green Bay ice- 
c 
Bay side and a southeast on that of the Green River Valley, thus 
pointing to the range as a moraine ridge between the two ice- 
masses or along their blending borders. Again, on the west side 
of the Green Bay Valley the glacial scratches run southwest- 
ward (while southeastward on the east side) and terminate in the 
edly have an undermining action and may have produced part of 
the depressions, Over the regions of Wisconsin between the Green 
gion was left iceless and driftless. He states that the surface is 
not higher than that of Wisconsin to the east, and is lower than that 
of Minnesota to the west; and hence that no argument can be 
rawn in favor of its escape from the ice by its altitude or by an 
elevation of the land. The explanation, though different, is closely 
