PHYSICAL AND CLIMATAL CONDITIONS. 75 



At this period the valley of the St. Lawrence and the 

 eastern coast, as far west as lake Champlain and the east 

 end of lake Ontario, as well as the borders of the arctic 

 basin and of the Pacific, were under the waters of the 

 ocean and inhabited by a rich boreal fauna, nearly all the 

 species of which, in its eastern development, I have 

 myself dredged alive in the waters of the estuary of the 

 St. Lawrence. On the other hand, the western plains 

 were covered with waters w^hich have not afforded marine 

 animals in their deposits, but hold remains of land plants. 

 Farther, these land plants were of species not arctic, but 

 merely boreal or north temperate,* while the proper 

 arctic flora must have been still farther north. 



(3) This mid-glacial period was followed by the second 

 boulder-deposit, in which still farther subsidence occurred, 

 and boulders were carried by floating ice to the summit 

 of the higher hills in eastern Canada and New England, 

 up to the height of 4,200 feet, and in the Eocky Moun- 

 tains even to the great elevation of 5,289 feet.f This 

 second period of boulder-drift and its deposits must not 

 be confounded with the earlier till. 



(4) From this depression the continent arose gradually 

 or by intermittent throes, leaving the terraces of the hills 

 and the sand and gravel beds (Saxicava sand) of the 

 plains as evidences of the recession of the waters. This 

 elevation proceeded so far as to inaugurate the second 

 continental period, when the land was more extensive 

 than at present, and a southern fauna penetrated far 

 north along our coasts, while great mammals, now extinct, 

 overspread the land. Since that time there have been 



* See Chapter V. 



t G. M. Dawson, Report on Superficial Deposit, Bow river, 1884. 



