32 THE CANADIAN NATURALIST. [Vol. 



VI. 



interveuing between the banks cast up by the Arctic currents on 

 the present American coast, and like those deep channels of the 

 Arctic current in the Atlantic recently explored by Dr. Carpenter. 

 Their arrangement geographically as well as their geological rela- 

 tions, correspond with this view. 



Another consideration with regard to the great lakes deserves 

 notice. Dr. Newberry has collected many facts to show that the 

 lake basins are connected with one another and with the sea by 

 deep channels now filled up with drift deposits. It is therefore 

 possible that much of the erosion of these basins may have oc- 

 curred before the advent of the glacial period, in the Pliocene age, 

 when the American continent was at a higher level than at pres- 

 ent. Dr. Newberry has given in the Report in the Geology of 

 Ohio a large collection of facts ascertained by boring or otherwise, 

 which go far to show that were the old channels cleared of drift 

 and the continent slightly elevated, the great lakes would be 

 drained into each other and into the ocean by the valleys of the 

 Hudson and the Mississippi, without any rock cutting, and if the 

 barrier of the Thousand Islands were then somewhat higher, the 

 St. Lawrence valley might have been cut ofi" from the basin of 

 the great lakes. 



I shall close the discussion of this subject by quoting from one 

 of the papers above referred to, my views in 1864 ; reserving, 

 however, some points respecting the present action of floating ice, 

 to which I shall refer in the sequel. 



" Our American lake-basins are cut out deeply in the softer 

 strata. Running water on the land would not have done this, 

 for it could have no outlet ; nor could this result be effected by 

 breakers. Glaciers could not have effected it ; for even if the 

 climatal conditions for these were admitted, there is no height of 

 land to give them momentum. But if we suppose the land sub- 

 merged so that the Arctic current, flowing from the northeast, 

 should pour over the Lauren tian rocks on the north side of Lake 

 Superior and Lake Huron, it would necessarily cut out of the 

 softer Silurian strata just such basins, drifting their materials to 

 the southwest. At the same time, the lower strata of the cur- 

 rent would be powerfully determined through the strait between 

 the Adirondac and Laurentide hills, and, flowing over the ridge 

 of hard rock which connects them at the Thousand Islands, would 

 cut out the long basin of Lake Ontario, heaping up at the same 

 time in the lee of the Laurentian rid^je. the s:reat mass of boulder- 



