296 THE ICE AGE IN CANADA. 



glaciers are " agents of abrasion rather tlian erosion," and 

 tliat in the latter their power is much inferior to that of 

 tiuviatile action. Nor are glaciers agents in the excava- 

 tion of lake basins, which are to be accounted for in other 

 ways ; and the great gorges and fiords which have been 

 ascribed to them are due to aqueous erosion when the 

 continents were at a high level, before the glacial age. 



An interesting and thoughtful paper, by Warren 

 Upham, has appeared,* in which he institutes a compari- 

 son between " Pleistocene and Present Ice-sheets." The 

 present ice-sheets are stated to be four. (1.) The Ant- 

 arctic or that which fringes the Antartic continent and 

 is probably better entitled to the name than any other ; 

 but which differs from the supposed ice-sheets of the 

 IHeistocene in fronting on the sea and discharging all its 

 produce as floating ice. In this it certainly resembles 

 many of the great local glaciers of the Pleistocene. 

 (2.) The great neve of Greenland, which, however, dis- 

 charges by local glaciers, and these open on the sea, and 

 which has margins of verdure on its borders in summer. 

 (3.) The Malaspina glacier of Alaska, evidently a local 

 glacier of no great magnitude, though presenting some 

 exceptional features and showing the possibility of the close 

 contact of glacial phenomena and flourishing woodland. 

 (4.) The Muir glacier of Alaska, also a local glacier, but 

 perhaps, like the Malaspina, showing some features illus- 

 trative of local Pleistocene glaciers, more especially in its 

 apparent want of erosive power. 



In the " conferences and comparisons," however, the 

 facts detailed in the earlier part of the paper are placed 

 in comparison with postulates respecting the Pleistocene 



* Bulletin Geol. Society of America, March 24, 1893. 



