Toronto Interglacial Period.—Coleman. 79 
ter of the Labradorean ice sheet. During those centuries of 
warm, dry climate the ice must have shrunk to the vanishing 
point. There is no more reason to suppose that glacier ice ex- 
isted then in central Labrador than there is to suppose it now; 
and there is much more probability of finding glaciers at pres- 
ent around Mt. Washington, which cannot be more than 2,000 
or 3,000 feet below snow level, than of finding glacier ice on 
the low lands a few hundred miles northeast of Toronto in 
- interglacial times, when the isotherms of Pennsylvania were 
shifted 150 miles to the northward. 
My own opinion is that in the interglacial period repre- 
sented by the Toronto formation the ice completely vanished 
from eastern America, not to return for thousands of years; 
and that it is quite possible that we are now living in an inter- 
glacial period, though not so mild a one as the last. 
In concluding this rejoinder to Mr. Upham’s article it may 
be stated that a brief study of the facts on the ground has 
convinced several geologists, both European and American, 
who were formerly skeptical regarding interglacial periods, 
that here we have undoubted proof of one, and of too great a 
magnitude to be accounted for merely by a short recession of 
the ice field. Probably so able a field geologist as Mr. Upham 
would in a day or two along the Don and Scarboro’ Hights 
convince himself as others have done. 
Interglacial time has also been discussed by Dr. T. C. 
Chamberlin, in the Bulletin of the Geological Society of 
America. Vol. 1, p. 469, 1890, and by Professor N. H. 
Winchell in the American Geologist, 1892, p. 69, and No- 
vember, 1892, p. 302. The former refers to certain § an- 
cient valleys or trenches which are presumed to have 
been excavated by streams in interglacial time. This 
would require several hundred feet of perpendicular 
rock-erosion by the various streams in interglacial time. 
The latter discusses the interglacial recession of the falls of St. 
Anthony, along a gorge, now buried under the drift, on the 
west side of the Mississippi, at Minneapolis, reaching the con- 
clusion that about 15,000 years were needed for the recession of 
the falls in interglacial time. 
