284 THE CANADIAN NATURALIST. [Vol. X. 



greater part of the unstratified drift, as stated by Prof. Dana, 

 was deposited in the Lower Chaniplaiu epoch. 



The boulder clay of the St. Lawrence was deposited in both 

 the Glacial Drift and Lower Champlain epochs (of Dana), and 

 a portion of the Erie clay of the region of the great lakes in the 

 latter epoch, if not in that of the Glacial Drift of the present 

 classification. But as the Erie clay is stratified, it could not 

 have been deposited in the epoch of the Glacial Drift according 

 to the theory of an elevated continent. After the Diluvian or 

 Lower Champlain epoch, the waters continued to be deep, but 

 with much floating; ice, bearing; erratics. This constitutes Dana's 

 AUuvian or " Upper Champlain era " of stratified clays and 

 gravels. 



At the same time the Leda clay (stratified by water and of 

 marine origin) and the upper portion of the Erie clay (stratified 

 and of fresh water origin) were deposited. Then the seas became 

 shallow from the elevation of the continent; and, finally, in 

 some places a forest growth appeared on the uplifted land 

 Again, there was a subsidence on the production of a glacial lake, 

 and there were then deposited the upper beds of Dana's " AUu- 

 vian era," corresponding to the Saxicava marine sands of the 

 St. Lawrence, and the Saugeen clays of Ontario. There was 

 still boulder-laden floating ice. As the continent was again rising, 

 or the waters of the glacial lake subsiding, the elevated terraces 

 or beaches were made at heights from 1700 feet to the sea level 

 in ihe region of the lower lakes. These terraces will be described 

 in succeeding pages. This elevating process continued until the 

 continent stood at perhaps 200 feet above the present altitude, 

 marking an epoch known in Europe as the Reindeer or Second 

 Glacial period. Then came the subsidence which brought the 

 continent to the present general level with the modern deposits. 



The Icehtrg Theory. — The Iceberg Theory difi"ers essenti:illy 

 ill the beginning and early days of the " Great Ice Age." 



According to this theory the old channels now buried were 

 produced in days before the advent of the Glacial period, by 

 the erosive action of the atmosphere, and pre-existing rivers, 

 when the continent was at a higher elevation, and date back to 

 very ancient geological times. At the commencement of the 

 Ice Age the continents were subsiding; until depressed much be- 

 low the present sea-level. At the same time glaciers were 

 accumulating; in the northern highlands, and even farther south- 



