136 THE ICE AUK IN CANADA. 



already made in my first eliaptor are, 1 tliink, sutllicieiit to 

 illustrate these views, and I may therefore here merely 

 introduce a few remarks res}>ectin<^ variations of climate 

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

 American continent in the Pleistocene ])eriod at \). 77. 



In the early glacial pei'iod, if we judge from the great 

 accumulation of snow on the Cordillera of the west and 

 the Laurentian highlands, tlie temperature must have 

 been low. Similar evidence is alTorded 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 tlie mean temperature of tlie sea to this extent it 

 would be necessary that geogra})hical changes should 

 occur which would direct most of the warm ecpuitorial 

 water lx)th from the Xorth Atlantic and the Xorth 

 Pacific. 



In the time of the lower Leda clay the temperature f)f 

 the sea seems scarcely to have increased ; but in the 

 upper Leda clay we have a marine fauna identical with 

 that of tlie colder waters of the present gulf and I'iver St. 

 Lawrence. One can to-ilav dredge in a living state oil" 

 Metis in the river St. Lawrence all the s])ecies found in 

 the upper Leda clay of the neighl)ouring coast. In like 

 manner the vegetable remains of the upper Leda clay and 

 its e(piivalent in the west are not arctic but boreal j)lants, 

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

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

 they im})ly a mean temperature somewhat lower than 

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

 mid-1'leistocene was not an arctic one. It may have 



* See list of fossils, infra. 



