304 A. P. COLEMAN 



According to this view, after the Scarboro' beds were deposited 

 the water sank to a level below that of the present lake and 

 remained there long enough to cut back the mass of delta 

 deposits to about the position of the present cliff. Although the 

 first explanation seems the more simple, the one given by Pro- 

 fessor Penck deserves careful consideration. At present there 

 is not evidence enough to settle positively which is correct. 



Toward the west of the Scarboro' exposure the stratified sand 

 gradually thins and disappears beneath the bowlder clay and the 

 same is afterwards true of the peaty clay, which sinks below the 

 lake at Victoria park at the east end of Toronto. Here probably 

 another wide valley was cut, though its western shore is not 

 seen distinctly. The upper stretch of the Don Valley, which 

 turns to the east after emptying into Toronto Bay, discloses only 

 till and the overlying unfossiliferous beds in its ravines, though 

 peaty clay rises to 152 feet near Mount Pleasant cemetery toward 

 the west, and to nearly 100 feet at Price's brickyard to'the south- 

 east, suggesting an old river valley between, perhaps of an inter- 

 glacial Don. The form of this valley is not so well worked out, 

 however, as in the case of the other two. 



As no interglacial deposits have been found clearly belong- 

 ing to this later low water stage, there is no evidence as to the 

 climate during the latter part of the interglacial time ; but we 

 may suppose that it grew colder until the region was once more 

 covered with an ice sheet, probably corresponding to the Wis- 

 consin till of the states to the southwest. 



LATER GLACIAL DEPOSITS 



The earlier (Iowan) ice advance found little obstruction in 

 the region of Toronto and passed over leaving only a compara- 

 tively thin sheet of bowlder clay, not greatly modifying the gen- 

 eral form of the surface; but the later glacial invasion took place 

 under changed conditions. The broad Georgian Bay — Scar- 

 boro' Valley through which the Laurentian river had flowed, 

 was now largely blocked with the great interglacial delta depos- 

 its, which no doubt stretched, as a tongue some miles in length 



