Great Lake Basins of the St. Lawrence. 273 
lake, suggest that this section of the lake is more recent 
than the main basin beyond, and that the coast at one time 
may have been between South Bay and Stony Point. The 
conformation of the shores, the line of axis of the islands 
and the direction of the strie at Kingston and of the lime- 
stone escarpment and striated Laurentian hills and gorge 
at Kingston Mills also suggest the action of a glacier from 
the north-east, whilst the whole would seem to show that 
at that time the lake outlet at Kingston did not exist. The 
absence of striz on the surface of the limestones on the 
-summit of the anticlinal at Fort Henry, near Kingston, 
though present in frequent places at the waterline, would 
indicate that the glacier here was not very thick. That 
the country around the present lake outlet has been in 
places subject to abrupt changes of level is shown by the 
heavily dipping limestones at Fort Henry and eastward, and 
the eruptions of granite through the syenitic gneiss and the 
limestone both here and farther down the river. There is 
some evidence to show that an eruption took place during 
the deposition of the Black River limestones, but the abrupt 
upheaval of these limestones at Fort Henry and Barriefield 
is conclusive that there were forces at work, operating ina 
somewhat westerly direction, subsequent to the Trenton 
and Black River, and possibly in recent, times. 
That Lake Ontario has had a pre-glacial origin seems 
beyond question. Several causes have contributed to bring 
about its present outline and depth, and it may be that one 
ov more of these causes operated after the glacial epoch. 
Towards the western and on the southern side the Medina 
sandstones and the Hudson River shales sink apparently 
north-westerly under the lake at the eastern end the Trenton 
and Black River limestones dip to the east of south, and 
the general slope of these limestones between Kingston and 
Belleville is perceptibly towards the lake. There is thus 
some ground for the assumption that the Trenton limestones, 
Utica and Hudson River shales and Medina sandstones 
descend both ways under the lake waters, forming perhaps 
originally, in at least a part of the lake, a synclinal trough 
