136 THE ICE AGE IN CANADA. 



already made in my first chapter are, I think, sufficient to 

 illustrate these views, and I may therefore here merely 

 introduce a few remarks respecting variations of climate 

 in the glacial age, referring to the map of the North 

 American continent in the Pleistocene period at p. 77. 



In the early glacial period, if we judge from the great 

 accumulation of snow on the Cordillera of the west and 

 the Laurentian highlands, the temperature must have 

 been low. Similar evidence is afforded by the few species 

 of shells found in the boulder-clay, which are of species 

 now occurring in the cold waters of the Arctic regions 

 loaded all summer with ice.* It would seem that to 

 reduce the mean temperature of the sea to this extent it 

 would be necessary that geographical changes should 

 occur which would direct most of the warm equatorial 

 water both from the North Atlantic and the North 

 Pacific. 



In the time of the lower Leda clay the temperature of 

 the sea seems scarcely to have increased ; but in the 

 upper Leda clay we have a marine fauna identical with 

 that of the colder waters of the present gulf and river St. 

 Lawrence. One can to-day dredge in a living state off 

 Metis in the river St. Lawrence all the species found in 

 the upper Leda clay of the neighbouring coast. In like 

 manner the vegetable remains of the upper Leda clay and 

 its equivalent in the west are not arctic but boreal plants, 

 and we should have to go near to the arctic circle, then 

 as now, to find the true arctic flora. These facts, while 

 they imply a mean temperature somewhat lower than 

 that of the present day, show that the climate of the 

 mid-Pleistocene was not an arctic one. It may have 



* See list of fossils, infra. 



