1898-99. | THE IROQUOIS BEACH. 43 
of Toronto at present, the evidence available suggests that it was by no 
means Arctic, probably only cold temperate, in spite of the immense 
glacier generally supposed to have dammed its waters near the 
Thousand Islands. There are some interesting problems connected 
with this ice dam which held the water of Lake Iroquois for at least 
2,500 years at a constant level in a climate apparently not Arctic. 
During the whole time its front seems to have retreated not more than 
fifty miles in a north-northeasterly direction, since the ice must have 
occupied the region near Kingston until the Iroquois water was drained 
to a lower level. If the Iroquois beach at Toronto réquired 2,500 years 
to form, the ice must have retreated in the direction N 17° E at the 
rate of about one mile in fifty years. If the time allowed for its 
formation is 15,000 years, the glacier retreated at the rate of one mile in 
300 years. How many years were required for the ice to withdraw 
from its most southern point to Toronto, and how many more were 
needed for the retreat from the point where the Iroquois water was 
drained to the vanishing point in Labrador? 
It is, of course, very improbable that the ice withdrew in a uniform 
manner. The great moraine of the Oak Ridges stretching across south- 
ern Ontario represents, no doubt, a prolonged halt in the retreat and 
is perhaps connected with the damming of the Iroquois water, since the 
moraine reaches Lake Ontario at about the point where the dam must 
have stood. Why should the ice have halted so long in a climate which 
seems not to have been Arctic? The Alaskan glaciers, it is true, present 
somewhat similar features, but they are Piedmont glaciers with an 
immense range of snowy mountains behind them as a source of supply, 
while the waning ice sheet of Northeastern Canada rested on a 
comparatively level plain. 
Another point that has presented itself with considerable distinctness 
in the study of the lroquois beach deposits is that their formation seems 
to have been preceded by a considerable period of low water. Under 
the thirty feet of Iroquois gravel at the Hunter street tunnel in 
Hamilton, the boulder clay has been weathered brown for a depth of 
two feet, and the time of low water was long enough for large tamaracks 
and spruces to grow. At that time the water must have stood at least 
thirty-five feet lower than the Iroquois level at Hamilton. 
Near Toronto there is evidence not easily set aside suggesting that 
the till-covered surface was eroded into valleys and cliffs before the 
Iroquois water occupied its basin to the full depth. At the British 
Association shaft near the Don, stratified sand, probably of Iroquois 
age, is found resting on a brown, evidently weathered, surface of inter- 
