506 THE ICE AGE IN NORTH AMERICA. 



this author infers two periods of glaciation, separated by an 

 interglacial epoch, in which the land was submerged from one 

 to two hundred feet.* Again, in the northeast part of the 

 Queen Charlotte Islands Dr. Dawson finds evidence of sub- 

 mergence to the amount of two or three hundred feet, while 

 the glacial conditions still endured, f 



In Europe the glaciated area stood at a greater height be- 

 fore the Ice age, as is shown by fiords ; it was similarly de- 

 pressed while loaded with the ice-sheet ; and since then it has 

 been partially re-elevated. Its maximum post-glacial uplift 

 known in the British Isles, so far as it has not been counter- 

 acted by subsequent depression, is five hundred and ten feet, 

 near Airdrie, in Lanarkshire, Scotland;]; and in Scandinavia 

 it is about six hundred feet. # As in all the North American 

 districts noted, these upward movements seem attributable to 

 the rise of the earth's crust, upborne by inflow of a molten 

 magma beneath. 



But the derivation of the floras of the Faroe Islands, Ice- 

 land, and even Greenland from the flora of Europe, demon- 

 strates, according to Professor James Geikie, that the portion 

 of the earth's crust extending from Britain and Scandinavia 

 to Greeuland was uplifted in early post-glacial times about 



* " Geological and Natural History Survey of Canada, Annual Report," vol. 

 ii, p. 105 B. 



f " Geological and Natural History Survey of Canada, Report of Progress 

 for 1878-79," p. 95 B. Further important notes of recent changes in level of 

 .the coast of British Columbia, and of Washington Territory and Alaska, are 

 given by Dr. Dawson in the "Canadian Naturalist," new series, vol. viii, pp. 241 

 -248, April, 1877. He concludes that this area had a preglacial elevation at 

 least about nine hundred feet above the present sea-level, during part or the 

 whole of the Pliocene period, this being indicated by the fiords ; that it was 

 much depressed in the Glacial period ; and that in post-glacial time it has been 

 re-elevated to a height probably two or three hundred feet greater than now, 

 followed by subsidence to the present level, the latest part of this oscillation 

 being a somewhat rapid depression of perhaps ten or fifteen feet during the 

 latter part of last century — a movement which may still be slowly going on. 



% " Quarterly Journal of the Geological Society," vol. vi, 1850, pp. 386-388, 

 and vol. xxi, 1865, pp. 219-221 ; "American Geologist," vol. ii, pp. 371-379, 

 December, 1888. 



*" Geological Magazine," I, vol. ix, 1872, p. 309; and II, vol. ii, 1876, 

 p. 390. 



