THE GLACIAL HYPOTHESIS 3*7 



Canadian geologists. Singularly enough, the views are, if anything, 



less original than those of the workers on this side of the line. The 



establishment of a geological survey of Canada under Logan led to the 



publication of the now well-known volume of 1863. The views here 



expressed may be accepted as a summary of the knowledge relating to 



the glaciation on Canadian territory, as it then existed. 



Concerning the region of the lake basins of western Canada, Logan 



wrote : 



These great lake basins are depressions, not of geological structure, but of 

 denudation, and the grooves of the surface rocks which descend under their 

 waters appear to point to glacial action as one of the great causes which have 

 produced these depressions. This hypothesis points to a glacial period when 

 the whole region was elevated far above its present level and when the Lauren- 

 tides, the Adirondacks, and the Green Mountains were lofty Alpine ranges 

 covered with perpetual snow from which great frozen rivers or glaciers ex- 

 tended over the plains below, producing by their movements the glacial drift 

 and scooping out the river valleys and the basins of the great lakes. 



In his address before the Natural History Society of Montreal in 

 1864 J. W. Dawson took occasion to combat vigorously these ideas of 

 Logan, and this on the ground that ' it requires a series of supposi- 

 tions unlikely in themselves and not warranted by facts ' ; that it 

 seems physically impossible for a sheet of ice to move over an even 

 surface striating it in uniform directions over vast areas; that glaciers 

 could not have transported the large boulders and left them in the 

 positions found, having no source of supply; that the peat deposits, 

 fossils, etc., show that the sea at that period had much the same tem- 

 perature as the present arctic currents, and that the land was not cov- 

 ered by ice. 



In describing the course of the rock stria? he announced that he had 

 no hesitation in asserting that the force which produced those having 

 a westerly direction was from the ocean into the interior against the 

 slope of the St. Lawrence Valley, and as he could not conceive of a 

 glacier moving from the Atlantic up into the interior, he considered 

 this as at once disposing of the glacial theory. He conceived, rather, 

 that a subsidence took place sufficient to convert all the plains of 

 Canada, New York, and New England into seas. This, he felt, would 

 determine the direction of the Arctic current which moved up the slope. 

 He would account for the excavations of the basins of the Great Lakes 

 by supposing the land so far submerged that an Arctic current from 

 the northeast would pour over the Laurentian rocks on the northern 

 side of Lake Superior and Lake Huron, cutting out the softer strata 

 and at the same time transporting the debris in the form of drift to 

 the southwest. Glaciers were not wholly dispensed with, but limited 

 to regions of mountainous elevation. 



J. S. Newberry, while director of the geological survey of Ohio 

 (1869-78) had frequent occasion to discuss glacial phenomena, and a 



