222 THE CANADIAN NATURALIST. [Vol. ix. 



ice tongue 200 miles long and 40 miles wide occupying for ages 

 the place of Lake Ontario and only connected with the ice sheet 

 at its eastern end. The same is true of the glacier supposed to 

 have excavated the bed of Lake Erie. Yet more incredible is 

 the theory that would require us to accept the existence of a 

 glacier tongue 350 miles long by 80 miles wide occupying the 

 site of Lake Michigan and employed in scooping out that lake- 

 bed. For be it remembered these are not Alpine glaciers lying 

 in deep narrow valleys hemmed in by rocky walls which pre- 

 vent all escape and bar all progress except downward. These 

 glaciers must have lain upon the level or nearly level surface of 

 the continent, and towered above it for hundreds of feet in order 

 to possess the weight necessary to grind or scoop out the lake- 

 beds as the theory of Dr. Newberry requires. Such a phenome- 

 non, so far as the writer knows, is without parallel on earth, and 

 moreover its existence is opposed to what we know of the physics 

 of ice. Such a mass must move either by its own weight or by 

 a propelling force behind it. The former is excluded, because a 

 glacier tongue thus extended would lie not in the zone of accu- 

 mulation but ;in the zone of waste, and must be maintained by 

 supplies of ice from behind it. But ice thus supplied from be- 

 hind would find much less resistance at the sides of the mass and 

 would consequently spread out laterally instead of urging forward 

 the ice in front, and would thus form a wide semicircular sheet 

 rather than a long and narrow tongue. To suppose such a gla- 

 cier occupying the site of Lake Michigan for so long a time as 

 to scoop it out to the depth of 900 feet is therefore contrary to 

 the principle of dynamics, which maintains that when a glacier 

 moves it moves in the line of least resistance. 



If however we admit the existence of the lake beds to nearly 

 their present depth and width before the ice age, we may without 

 difficulty admit that as the continental glacier was retreating, a 

 short projecting tongue would be found occupying each of them 

 in part and extending a small distance southward or westward 

 from the main body of the ice. This would not necessitate the 

 persistence of such glaciers long enough to fill the whole valleys 

 at once or to scoop them out to their present depth, but only long 

 enough to produce those superficial east-west scratches which 

 Dr. Newberry admits have not always efiaced the earlier north- 

 south grooves made by the great continental ice sheet. On this 

 view we have a reason for the deflection of the ice, ample depth 



