igoo-i.] Physical Geology of Central Ontario. i8i 



modified, have remained to form islands or outliers in front of the 

 different escarpments, or the spurs of the intervalley ridges along the 

 valley sides. The essential features of the topography are not destroyed, 

 though they are more or less completely obscured and obstructed by 

 drift. 



The relation of the area to the fronts of the ice sheets which crossed 

 it is not y^t determined. The results of the writer's studies at present 

 suggest that the great moraine of Central Ontario is largely an inter- 

 lobate moraine between an ice lobe coming from the east of north, and 

 a lobe coming from the east ; and that the lateral spurs, on the north 

 and on the south sides of the great moraine, represent the positions 

 successively occupied by the retreating ice front.* The area seems to 

 have been almost always one receiving deposits rather than one from 

 which the soil and rock was being removed. 



The streams which produced the pre-glacial valleys throughout the 

 Central Ontario lowland, and the obsequent streams of the Niagara 

 cuesta must have been tributary to some trunk stream, or perhaps to 

 two such master subsequents. The location of these trunk streams 

 would normally be along the lines of deepest cutting. Their direction 

 of flow cannot be determined at present, though that of the tributaries 

 is known from the forms of the valleys. Those on the Black River 

 cuesta flowed southwest, those from the Niagara cuesta northeast, east, 

 and southeast. Obviously the trunk stream, though flowing parallel to 

 the escarpment, must have had some outlet from the region. Deter- 

 mining the location of this valley has been one of the chief difficulties 

 to be met by the river-erosion hypothesis for the origin of the basin of 

 Lake Ontario. The attitude with respect to the present St. Lawrence 

 valley, and certain other features of the rock valleys in the vicinity of 

 Kingston, and the immature character of the present St. Lawrence 

 channel render it extremely improbable that the waste from the lowland 

 was ever carried out through this channel. If the drainage of the 

 Ontario 'owland was that of a normally developed river lowland there 

 is but one known outlet which is at all suitable, that by the Dundas 

 valley. f The course of the valley from the vicinity of Copetown west- 

 ward is highly problematic. Spencer considers that it was towards the 

 south, while Grabau (1901) has recently advocated an extension 

 towards the west, in continuation of an initial consequent direction. 

 The direction of flow of the streams that occupied this valley has not 



*See Chamberlin, '95a, p. 768. 



tThis sug'gestion had occurred to the writer before he was aware of Dr. Grabau's opinions, referred to 

 below. 



