Wl The American Geologist. February, 1894 
spread in its shallow estuary. On the hanks of the prehis- 
toric Don grew trees such as now flourish in the same region, 
yews and cedars, maples, oaks and ashes; as well as the 
papaw, now, I believe, not occurring north of the lake. 
Judging by the flora and fauna the climate was hy no means 
subarctic, but on the contrary fully as mild as at present, if 
not a little milder. 
The length of the interglacial time was sufficient for the 
deposit of 24 feet or more of sand and clay on the Don and 
140 feet of similar materials at Scarhoro* Hights. and for tin- 
growth of large forest trees. 
It is generally supposed, from the direction of glacial stria- 
tions and of the transport of boulders, that the center from 
which the ice radiated was at the watershed between the St. 
Lawrence and Hudson bay or somewhat farther east in Lab- 
rador, at the farthest not more than TOO miles from Toronto. 
At the present time in southern British Columbia neve is 
scarcely found on mountains rising less than 8,000 feet above 
sea level, and glaciers hardly come down to 5,000 feet. It is 
probable that a depression of the highest points to 7.000 or 8,000 
feet would completely wipe out all the glaciers of southern 
British Columbia. So far as I am aware, no point reaches 
3,000 feet above sea level between Ontario and Hudson hay, 
and no point in Labrador rises much above 6,000 feet. I'nless 
the northern watershed stood very much higher above lake 
Ontario than at present, it is impossible to imagine a wide 
spread sheet of ice existing there during interglacial time, 
when oaks and maples and papaws flourished on the land and 
Mississippi Unios in the waters only 400 or 500 miles to the 
southeast. I know of no evidence proving that the glacial 
center stood at that time 3,000 or 4.000 feet higher ahove lake 
Ontario than at present, and hence conclude that the ice fields 
were completely melted during the interglacial epoch, instead 
of merely receding a comparatively short distance before ad- 
vancing again. 
After the deposit of the fossiliferous beds the lake rose to 
at least 140 feet above its present level, perhaps dammed at 
its eastern end hy the return of the ice during the second gla- 
cial period, and thick beds of clay were laid down in quiet 
water. Probably the Don at this time was a glacial stream. 
