2 THE ICE AGE IN CANADA. 



by facts to insist on the following great leading principles 

 as to the glacial period and its causes : — 



1. The phenomena are not to be explained by any one 

 cause or by any one great all-embracing hypothesis, but 

 by a more active and extensive operation of many of the 

 ordinary causes still existing in the more northern regions. 



2. The astronomical changes which have been invoked 

 to account for cold climate, not excepting those advocated 

 by Croll and Ball, are incapable of fully explaining the 

 facts as now actually ascertained. 



3. There has not been at any time a polar ice cap, and 

 the theory of great continental ice sheets covering the 

 northern parts of the two great continents is also baseless. 



4. The phenomena indicate the action of local mountain 

 glaciers of great volume, along with that of floating ice 

 in various forms, and this more especially in periods of 

 subsidence of the land. 



5. The cold climate of the glacial period was mainly a 

 result of peculiar geographical conditions and a different 

 distribution of ocean currents, and was not so much 

 characterised by general low temperature as by the local 

 occurrence of extreme evaporation and condensation. 



6. The close of the glacial period is not very remote, 

 and cannot have antedated by many centuries or mil- 

 lenniums the first appearance of man, as known to us in 

 history. 



These theses I have maintained in papers whose dates 

 reach back to 1855, and in addresses delivered to the 

 British ^and American Associations and to the Natural 

 History Society of Montreal, and in popular works on 

 geology. They still appear to me to be true, notwith- 

 standing the wave of extreme glacial ideas that has been 

 passing over the world. But I am glad to see that a 



