i82 Transactions of the Canadian Institute. [Vol. VII. 



been definitely determined. A river flowing westerly through this 

 outlet would be a normal consequent stream, and tributary streams 

 from both sides would occupy the position of normally developed sub- 

 sequents. The attitude of the broadly open valleys along the Georgian 

 Bay suggest that there may have been a second master stream with an 

 outlet southwestward from the bay. At present our knowledge is so 

 imperfect that the direction of flow of these master streams, and their 

 relations to these different valleys, which may be members of a 

 normally developed system, have not been determined. 



The probability that there were streams on the Central Ontario 

 lowland, to which the streams in the preglacial valleys, already 

 described, were tributary, makes it equally probable that similar features 

 were developed to the southeast along the basin of the present lake. 

 At present we know neither the depth to the rock floor of the basin, nor 

 the amount of drift filling. The relation of the basin to the ice lobes is 

 also unknown. Hence differential deepening, which has not operated 

 on the unsubmerged lowland, may perhaps have been in effective 

 operation in the portion of the basin east of the Niagara river, and 

 west of Stony Point. 



Pleistocene History — A Summary. — The Pleistocene deposits 

 of Central Ontario present a complex which has not yet been studied in 

 sufficient detail to warrant more than a brief reference to certain salient 

 features. The best known locality is that in the vicinity of Toronto, 

 where the order of succession of the deposits has been established. 

 The probable relations of these deposits to similar beds elsewhere in the 

 area have already been noted. Mention has also been made of certain 

 sands and gravels which overlie the third till sheet in some parts of the 

 area. The fossils of the lowest group of interglacial beds at Toronto 

 indicate that the climate of that part of the region was, for a time, warm 

 and temperate, perhaps like that of Ohio. During this period the lake 

 was connected with the Mississippi drainage, a connection which may 

 have been an inheritance from the cycle preceding the first ice advance. 

 Whether the ice sheet at this time had withdrawn wholly from the 

 region, or only part way, must at present be a matter of conjecture. 

 The fossils of the upper beds of the first interglacial deposits indicate 

 climatic conditions approaching those of the lower Gulf of St. Lawrence 

 and the Labrador coast at the present day. The close of the inter- 

 glacial period was followed by an interval during which there was a 

 considerable amount of erosion, just how extensive is not determined. 

 The interglacial beds of the latter epochs have, as yet, been little 

 investigated. 



