308 A. P. COLEMAN 



the last till was being spread over the upper interglacial beds 

 here described. Professor Fairchild places the Warren beach 

 south of Lake Ontario at 880 feet, and his next important water 

 level, Lake Dana, at about 700 feet, both far above the highest 

 interglacial stratified sand or clay at Toronto. 1 



CONCLUSIONS 



One who studies the complex set of glacial and interglacial 

 beds of the Toronto region is strongly impressed with the length 

 of time demanded for their production. There is no reason to 

 suppose that the withdrawal of the Iowan ice and the drainage 

 of the waters which it dammed were more rapid than the similar 

 series of events following the latest ice sheet. When the 

 Toronto beds began to be formed the water level in the Ontario 

 valley was probably lower than now in Lake Ontario, and some 

 erosion had already taken place in the Don valley and at other 

 points. There had been time for the warm climate plants to 

 return from exile in full force and for forest trees of a most 

 varied kind, though mainly deciduous, to grow and fall on the 

 banks of the rivers. The unios, too, had already migrated north 

 from the Mississippi stronger in species than they are now. All 

 this may imply as long a time after the Iowan ice sheet with- 

 drew as has elapsed since the last ice sheet departed, before the 

 lowest beds of the Toronto Formation were even begun. 



Then came the raising of the rocky barrier at the eastern end 

 of the Ontario basin to sixty feet above the present level, and a 

 halt at that level while the upper sands became browned and 

 cemented with limonite. The climate grew cooler and and then 

 ninety-four feet of clay and fifty-five feet of stratified sand were 

 laid down at Scarboro', the eastern barrier rising meantime to 

 152 feet above the present level. 



Then there was a halt in the elevation toward the northeast 

 and at length a reversal of the motion, the northeastern end of 

 the basin being depressed until the great Scarboro' lake was 

 drained to a level probably much lower than that of Ontario at 



'Bull. Geol. Soc. Am., 1899, p. 31 and p. 56. 



