270 Canadian Record of Science. 
diately surrounding the lake being but slightly elevated 
above its waters. Ata very recent period these waters ex- 
tended in shallows over the prairie country, giving it a 
marshy character. Parts of the land are still so low lying 
and wet as to be chiefly suited for grazing purposes. All 
of the level black-loam prairies of Northern Illinois and In- 
diana have at one time been of this marshy character, but 
by the annual growth and decay of the grasses, sedges and 
aquatic plants generally, the black loam soil has in the long 
lapse of time accumulated and the land has gradually ap- 
peared above the water. This extreme southern section of 
Lake Michigan has thus had its boundaries defined in their 
present outline within a period probably as recent as exist- 
ing times. 
Like Lake Huron the main portion of the lake is pre- 
glacial. The Wisconsin geologists, especially Winchell, 
Chamberlain and Salisbury, have strongly insisted not only 
on a continental ice-sheet covering Northeastern and Central 
North America in the glacial times, but on a great glacier 
having, during what they denominate the later glacial period, 
occupied among others, the Lake Michigan basin, whilst a 
separate smaller glacier overspread Green Bay and its sur- 
rounding country. Chamberlain thinks that Lake Michigan, 
in its regular outline and great depth and breadth, is due to 
glacial action, though it might have been deeply channelled 
by running waters in pre-glacial times. Like others of these 
geologists, he points to the so-called moraines running 
through Wisconsin, Illinois, Indiana and Michigan, some 
distance from but irregularly uniform with the coast line of 
the lake, as proof of the existence of the glacier. Now, it 
seems to me that the small extent of these moraines, if their, 
in general more or less, stratified appearance allows them to 
be called such, is ample evidence thatif a glacier did occupy, 
for an immense period of time, the basin of the lake, its 
eroding power was small. Ifthe great superficial area and 
depth of Lake Michigan had been excavated by the glacier, 
the accumulated debris forced to its edges would have been 
vastly greater than the moraines indicate, more especially 
