214 THE CANADIAN NATURALIST. [Vol. ix. 



Newberry has however expressed his entire dissent from the 

 writer's views in the following words (Geol. of Ohio, Vol, III.. 

 p. 46) : " The considerations which oppose this theory" (that 

 the beds of these lakes are only portions of the valleys of 

 pre-glacial rivers blocked up in the ice period by beds of drift) 

 " are so apparent and formidable that it never could have been 

 proposed or accepted by any one who had carefully studied the 

 problem." While yielding to none in due respect for Dr. New- 

 berry's labours and his contributions to the geology of the 

 Western and Midland States, without which the very materials 

 for the paper in question would not have been attainable, the 

 writer must maintain that his theory was not hastily put forward 

 and that in his opinion, for reasons hereinafter given, the objec- 

 tions urged by Dr. Newberry are not valid, and further that Dr. 

 Newberry's own position is not tenable. These objections are 

 as follows : 



1st. '' The lakes occupy a series of boat-shaped rock-hasina 

 which have almost nothing in common with river- valleys. The 

 notion that the valley of a river could be beaded in this way by 

 the broad excavation of such portions as lay in soft rock and the 

 formation of canons through hard strata, has no warrant in any 

 facts yet observed on the earth's surface." 



It may be quite correct technically to speak of the beds of the 

 great lakes as basins, but the impression generally produced by 

 this use of the term is far from accurate. As was pointed out 

 in the paper referred to, if the water were drained away their 

 beds would appear not as deep valleys nor to the eye as valleys 

 at all, but as wide almost level plains. The bed of Lake Erie 

 would show a slope from its north and south shores to its middle 

 averaging about ten feet to the mile. Lake Michigan, with a 

 depth of 900 feet and breadth of 90 miles, would become a vast 

 plain sloping only 20 feet in the mile. Such slopes would be 

 utterly undiscoverable by the eye, and consequently the lake- 

 beds would appear as immense prairies rather than basins. Now 

 such broad slightly sloping vales are precisely what large rivers 

 form when flowing for long ages through a region of the softer 

 rocks. If at any spot cliffs of such material are ever formed, 

 the weather ere long destroys them and reduces all to a smooth 

 outline. It is for this very reason that a practised eye can to a 

 great extent read the geology of a country by observing its sur- 

 face. One portion consists of smooth, rounded hills, sloping 



