Toronto Interglacial Period.—Coleman. 77 
ably much more extensive than the field work shows, since 
they are largely buried under the drift left by the later ice 
advance. The river that formed the delta was therefore not 
glacial and was of great magnitude. The only stream that 
seems to fit the circumstances is an interglacial successor of 
the Laurentian river whose old channel from Georgian bay to 
Scarboro’ is shown by various deep wells. We have then a 
larger river draining an upper lake into the Ontario basin and 
flowing through a temperate country with no traces of the 
presence of glacial ice in its valley. On the contrary its depos- 
its suggest a derivation from an old and thoroughly weathered 
land surface. 
If the ice sheet still existed it must have been far to the 
northeast, so that no glacial waters were tributary to the 
Laurentian river. 
The changes in water level shown to have taken place in 
interglacial time, and the presence of a large river evidently 
not draining an ice sheet are sufficient to prove that the To- 
ronto formation could not have been laid down during the ex- 
istence of the great glacial lakes such as Warren and Iroquois. 
The well marked Iroquois beach, with shore cliffs 70 feet high, 
is cut in later glacial deposits overlying the interglacial beds, 
and must have been formed thousands of years afterwards. 
The whole period of time during which the interglacial river 
channels were being cut at a stage of very low water, and also 
the time required for the later ice sheet to advance and de- 
posit 200 feet of glacial material must have intervened be- 
tween the formation of the interglacial beds and the work of 
lake Iroquois. No one who has studied the field relations 
could hesitate in reaching this conclusion. 
It is necessary to consider next Mr. Upham’s opinion that a 
continental ice sheet hundreds of miles across and a mile thick 
could exist close to forests showing a climate like that of Penn- 
sylvania for a period of hundreds or even 1,000 years.* He 
supports this view by citing the proximity of cultivation 
to the tiny Swiss glaciers which reach thousands of feet below 
snow line; by the orchards of Norway, where cherries ripen, 
though heat and often barley will not, so short and chill is the 
summer, even though the relatively small Jostedal ice field is 
*Ibid., 313 and 314. 
