GLACIAL PERIOD. 113 



a paper read before the Royal Geographical Society,^ discusses this ques- 

 tion in detail and arrives at the same conclusion which I stated in 1866, 

 namely, that glaciers are " agents of abrasion rather than erosion," and 

 that in the latter their power is much inferior to that of fluviatile action. 

 Nor are glaciers agents in the excavation of lake-basins, which are to be 

 accounted for in other waj^s ; and the great gorges and fiords which have 

 been ascribed to them are due to aqueous erosion when the continents 

 were at a higher level, before the glacial age. 



'Lastly, on this subject, very important facts have been ascertained bj^ 

 the Geological Survey of Canada and by United States observers in 

 Alaska, indicating that during the height of the Glacial period there 

 was an open arctic basin in the north. This coincides with the fact stated 

 by Professor Penhallowf and myself in a previous volume of the Bulletin 

 of this Society, that in the Pleistocene period the flora of Canada w^as 

 boreal rather than arctic ; consequently the arctic flora must have main- 

 tained its ground farther north. In northern Europe, Nathorst and 

 others have shown a southward movement of the Scandinavian flora, 

 but this does not seem to have been general, and the recent work of 

 Lange and Warming on the flora of Greenland proves that the' persistence 

 of the arctic flora in the north applies even to that country, whose con- 

 dition as to climate does not seem in the Pleistocene to have diflered 

 much from that of the present time. It is not impossible that, as Howorth 

 has suggested, the north Polar regions are colder now than in the Pleis- 

 tocene, that the cold of that period was thus more local than has been 

 supposed, and that we may find that even the mammoth was able to 

 hold his ground in the north throughout the great Ice-age. 



Allow me further to say that these facts tend to confirm the conclusions 

 already stated in this address, that we are to look, for causes of change of 

 climate, rather to movements of elevation and subsidence of the conti- 

 nents than to any extra-mundane influences. 



Post-Pleistocene continental ^Iovements. 



We come now to the last great vicissitude of our continents, one that 

 is beginning to connect itself with the history of man himself. No geo- 

 logic fact is more certain than the occurrence of a period of continental 

 elevation after the great Pleistocene submergence, and that this period 

 coincided with the spread of postglacial or palanthropic man over the 

 continents of the northern hemisphere. It is equally certain that within 



* Geographical Journal, July, 1893. See also J. W. Spencer: Quart. Jour. Geol. Soc. of London, 



1890, p. 523. 

 t On the Pleistocene Flora of Canada. Bull. Geol. Soc. of Am., vol. i, pp. 311-344. 



