130 J. W. SPENCER ON 



all of which movement belonged equally to the whole basin of Ontario ; therefore it is 

 certain that Ontario was at sea-level. Then, the Iroquois Beach enclosed a lake with a 

 very broad outlet, "700 or 800 feet deep in places. 



At Smith's Falls, about seventy-five miles north of Adam's Centre, the remains of a 

 whale (belonging to a species that is now sometimes seen in the Lower St. Lawrence 

 Eiver) were found in a gravel bed, at a height of 450 feet above the sea.' Its occurrence 

 indicates that to this point there was free communication from the sea, to which level 

 it was depressed, when the region was 450 feet lower than now — an amount of change 

 that equally affected the Iroquois Beach, about the eastern end of Lake Ontario, although 

 the effects diminished towards the west. Yet, westward of the present outlet of Ontario, 

 no marine shells have been discovered ; and there is no proof that the beaches belonged 

 to brackish water. Nor have fresh-water shells been found in them. The waters, which 

 admitted the whales, extended far up the Ontario basin, without leaving anything to 

 enable us to trace to what extent they were freshened, as they were distant from the sea. 



The outlet of Iroquois Lake was deep — seven or eight hundred feet below sea-level. 

 If any barrier existed between the Ontario basin and the Grulf of St. Lawrence, it cer- 

 tainly was neither rock or dirt. 



(10.) G-LACIAL Daws Theory. — This has been posited by Mr. G-ilbert and others 

 owing to the supposed necessity of barriers to keep out the sea-water. Now, if anywhere 

 upon the American Continent such existed, it was here, between Lake Ontario and the 

 sea, for there were mountains on either side of the St. Lawrence valley, between which, 

 glaciers, if such existed, could form dams. Furthermore, the Iroquois Beach was at 

 sea-level, so that there would be no hydrostatic pressure to force the water out beneath 

 the glacier. Yet the glacial dam is not established, for I have found the beaches, where 

 the supposed glacier was located ; and our knowledge of the old shores, down the St. 

 Lawrence valley, is still too imperfect to necessitate the existence of a dam. Nor does the 

 absence of the discovery of marine shells tell anything in favor of a glacier holding back 

 the waters, of what we call Lake Iroquois, any more than their absence, when the level 

 of the region was 450 feet lower than now, proves the existence of an ice barrier west of 

 the gravel bed, which contained the whale remains referred to in the last paragraph. 



The Grulf of Obi is to-day the counterpart of old Lake Iroquois. The Grulfof Obi 

 is from 40 to 60 miles wide, and 650 to 700 miles long. Its waters are fresh, and the 

 discharge from it so sweetens the Arctic Ocean that the water 60 miles beyond its mouth, 

 in the open sea, is almost potable." The old Grulf of St. Lawrence and Lake Iroquois — its 

 continuation — had once similar dimensions. 



The foundation of the glacial dam hypothesis is the occurrence in the Alps of some 

 small glacial lakes. These are of two kinds : — One, where the glaciers, carrying lateral 

 morains, cross river-valleys and form permanent lakes, on account of the earth-dams thus 

 made ; the other, where glaciers unite at the foot of hills, between which and the ice, 

 lakelets are formed, or where the glaciers pass the mouths of ravines, in which there are 

 no considerable streams. The latter class of glacial dams is always evanescent. "When 

 glaciers, not bearing lateral moraines, cross considerable streams, the rivers simply flow 



' Sir Win. Dawson in Canadian Naturalist, vol. x, no. 7, p. 385. 



■' Nordenekjold's, Voyage of the Vega around the North of Europe and Asia, i>. 140. 



