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THE UPPER MARINE LIMIT AT MONTREAL. 
BY 
J. W. GOLDTHWaIT. 
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The question of the upper limit of marine submergence 
at Montreal has long been a disputed one. Unusual interest 
is attached to the locality because of contradictory opinions 
of such experts as Sir Charles Lyell, Sir William Dawson, 
and Baron Gerard deGeer. 
Mount Royal is one of several volcanic mountains 
which rise above the St. Lawrence lowland. The St. 
Lawrence lowland, which surrounds the mountain on 
every side, is a plain of subaerial denudation base-leveled 
during the Tertiary, covered by the North American ice 
sheet during the Glacial period, and upon its withdrawal 
deeply submerged by the sea. Marine sediments extend 
far and wide over it. Exposed at many places are shells 
of marine species similar to those now living in polar 
regions. Since the withdrawal of the ice the region has 
emerged from the sea, in this locality to a height of nearly 
600 feet (182 m.). Although the exposed position of 
the mountain which, during the great submergence, was an 
island in the sea, was highly favorable for wave work, 
the side slopes of the mountain were in most places too 
steep for such action, particularly at higher levels. 
The discovery of marine shells on the grounds of 
McGill University and at higher places on the mountain 
long ago raised the question as to how deeply the mountain 
had been submerged. Sir Charles Lyell reported a beach 
which contained Saxicava shells at 470 feet (143-25 m.) 
on the south-west side of the mountain above Céte des 
Neiges village. His description of this locality given in 
his ‘Travels in North America’’ makes it seem probable 
that the shell-bearing deposit lies beneath boulder clay 
rather than above it, and hence is to be interpreted as 
an inter-glacial marine deposit instead of a deposit formed 
during the last submergence. In any case it is now known 
that the recent submergence reached to higher altitudes than 
this. Sir William Dawson, an ardent follower of Lyell, ac- 
cepted in full his ‘drift theory’’ which accounted for all 
