250 THE CANADIAN NATURALIST. [Vol. vi. 



surface of the clay in places where it has not been denuded 

 before the deposition of the overlying sand, there are 

 many species of marine shells. A few large boulders are 

 scattered through the Leda clay. 



3. Boulder-clay. — Stiff gray stony clay or till, with large boulders 

 and many glaciated stones, often 'of the same Trenton 

 rocks which occur on the flanks of the Mountain. It is 

 of great thickness, though it has been much denuded in 

 places, and has not been observed to contain fossils. It 

 is especially thick at the south and south-west sides of 

 the Montreal Mountain. 



The Montreal Mountain, like other isolated trappean hills in 

 the great plain of the Lower St. Lawrence, presents a steep 

 craggy front to the north-east, and a long slope or tail to the 

 south-west ; and in front of its north-east side is a bare rocky 

 plateau of great extent, and at a height of rather more than 100 

 feet above the river. This plateau must have been produced by 

 marine denudation of the solid mass of the Mountain in the Post- 

 pliocene period, and proves an astonishing amount of this kind of 

 erosive action in hard limestones interleaved with trap dykes, 

 and which have been ground and polished with ice at the same 

 time that the plateau was cut into the hill. By ice also must 

 the debris produced by this enormous erosion have been removed, 

 and piled along the more sheltered sides of the hill in the Boulder- 

 clay. 



With re2:ard to the cra";-and-tail attitude of Montreal Moun- 

 tain, I have to observe that in large masses of this kind reaching 

 to a considerable height, and rising above the Post-pliocene, sea, 

 the north-east or exposed side has been cut into steep cliffs, but 

 in smaller projections of the surface over which the ice could 

 grind, the exposed side is smoothed or '• moutonnee," and the 

 sheltered side is ang-ular. A little reflection must show that this 

 must be the necessary action of a sea burdened with heavy floating 

 ice. 



The most strongly marked terraces on the Montreal Mountain, 

 are at heights of 4T0, 440, 386, and 220 fact above the sea, but 

 there are less important intermediate terraces. On the highest 

 of these, on the west side of the Mountain, over Cote des Neiges 

 villaofe. there is a beach with marine shells, and on the summit of 

 the Mountain, at a height of about 700 feet, there are rounded 



