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ice rose up the inclined plane, and after meeting the walls of the 
building, fell back, and formed, in a few minutes,an enormous but pro- 
tecting rampart, In some years the ice accumulated nearly as high 
as the roof of the warehouse. 
Several of these grand glacial movements take place, sometimes 
at intervals of many days, but occasionally of only a few hours, the 
permanent setting being indicated by a longitudinal opening of con- 
siderable extent in some part of St. Mary’s current. This opening, 
which is never afterwards frozen over, even when the temperature is 
30° below zero of Fahrenheit, is due to the water having formed a free 
subglacial as well as superficial passage, in consequence of its own 
action and the cessation in the supply of drifting ice. From this 
period the waters gradually subside, but seldom or never to their 
summer level; and when they have attained their minimum, the trough 
of the St. Lawrence exhibits, Mr. Logan states, a glacial landscape 
of undulating hills and valleys. 
Qn the banks of the river, near Montreal, is an immense accumu- 
lation of boulders, chiefly of igneous rocks, the most abundant con- 
sisting of syenite ; and multitudes of them are stated to be “ tons in 
weight.’’ As they appear also above the surface in the shallow parts 
of the river, Mr. Logan is of opinion that the bed of it likewise teems 
with them. Their position has been frequently observed to be 
changed, both in the St. Lawrence and on its banks, at the breaking 
up of the ice in the spring. Mr. Logan examined, in the autumn of 
1841, the boulders between Montreal and Lachine, a distance of nine 
miles, and again in the spring of the present year (1842), when he 
missed some which had particularly attracted his attention ; but he 
adds, he may, from not having mapped their position, have imad- 
vertently passed them over. The author then offers some remarks 
on the power of ice in moving or transporting boulders along the 
river, and furrowing the surface of the fixed rocks, as well as along 
the shores ; but he is of opinion that the distance is limited to which 
they may in the latter position be conveyed annually. 
It is not only on the immediate banks of the St. Lawrence that 
boulders abound, as they are spread more or less over the whole island 
of Montreal, and the plains on the opposite side of the river. Mr, 
Logan states that he had not examined their position with sufficient 
accuracy to offer an opinion respecting the causes of their distribu- 
tion, but they appeared to him to be more abundant in the upper than 
the lower part of the island, and they are stated to cease altogether 
not many miles below it; but their size is not less at the limit of 
their range than elsewhere. 
2. Landslip.—The country for a considerable distance on both 
sides of the St. Lawrence, between Montreal and Quebec, is very 
level, and is generally covered to some depth by a highly levigated 
deposit composed of clay, sand, and calcareous matter resting on 
black shale and black and grey limestone belonging to the Silurian 
system. ‘This flat region or trough is bounded on the north-west by 
granitic and syenitic hills about 500 feet in ‘altitude; and on the 
south-east by an undulating picturesque tract, composed of a hard 
