THE IROQUOIS BEACH. 131 



under the ice. Some small lakes are known in Greenland, at sea-level, where the glaciers, 

 choke out the sea-water. Upon the flank of Mount St. Elias, there are several glacial 

 lakes, the lowest at something less than 175 feet above the sea, which is fifteen miles 

 distant. There, the waters are held in the lakes, when their outlets get choked with ice- 

 bergs, for only a few hours or days, until the accumulated hydrostatic pressure breaks 

 away the barrier, whereupon the waters flow beneath eight miles of the glacier, to emerge 

 from under 500 feet of ice (Topham). ' It seems impossible to believe in the existence 

 of great glacial dams, above sea-level, sufficiently permanent to develop such regular 

 beaches and terraces as the Iroquois, which indicates a wave action of as long duration 

 as that upon the modern beaches of Lake Ontario. This last represents a time period of 

 many centuries, if not of millenniums. Of course, had morainic dams been formed, these 

 would still remain, more or less intact, across the St. Lawrence valley. 



Consequently, we have no proof, as yet, of the existence of glacial barriers closing 

 the St. Lawrence valley, nor should we assume the necessity for them, any more than in 

 the Grulf of Obi, until such is proved by future investigation into the physical structure 

 of the north-eastern portion of Lake Iroquois. 



(11.) The Climate and Life. — From the boulder pavements, associated with the 

 beach upon the northern side, the power of the ice is seen to have been no greater than 

 that of to-day either in that region, or along the lake expansions of the St. Lawrence. 



The occurrence of mollusks tells us nothing as to the temperature of the waters, as 

 they are not found in the beach. But this beach contains remains of mammoth, elk, and 

 beaver," found in the Burlington Heights at Hamilton ; and similar remains are said to 

 have been found in New York. Whether these animals came down upon the spit to 

 drink and died there, or whether their remains drifted to it from the streams of the old 

 Dundas valley we have no means of conjecture. Whilst the range of these animals is 

 wide, they are such as belong to the climate of the present day. 



I have seen fresh-water shells only in the deposits about the lake of more recent date 

 (not more than fifteen or twenty feet above its surface) associated with lagoons or former 

 swamps. 



(12.) Lower Beaches. — These are of frequent occurrence about Lake Ontario. But 

 they are all too fragmentary to form the basis of study offered by the Iroquois Beach. 

 The time occupied in their formation was too short for the old shore lines to be straight- 

 ened. From the examination of the lower beaches at the eastern end of the lake by Mr. 

 Gilbert, and that of others seen upon the northern side of the Ontario basin by the writer, 

 it appears that the elevations since they were formed have been less differentiated than 

 those first lifting the Iroquois Beach, which has also been involved in all subsequent 

 changes. The tilting of the basins has caused a submergence of the lower beaches, and 

 narrow valleys of erosion, upon the southern and western sides of the lake. Such evidence 

 is not seen upon the northern side of the lake. The effects of submergence have, however, 



' Proc. Roy. Geo. Soc. 1889, p. 424. 



'' Not only were the.se found thirty to forty feet below the top of tlio Heights, in tlie Cutting of tlie De.sjaniins 

 Canal (Geological Survey of Canaila, 1803), but remains of another maniuioth were found in an adjacent railway 

 cutting through the same beach in 1878-9, at a depth of between twenty and thirty feet. 



