200 THE ICE AGE IX CANADA. 



at an elevation of about 560 feet above the sea. Lauren- 

 tian boulders, probably drifted on ice in the later glacial 

 age, are found at a still higher level. 



The site of the Peter Eedpath Museum presents 

 another interesting example of the special features of the 

 drift-deposits on the south side of Montreal mountain. 

 The first floor of the museum is 160 feet above the level 

 of the sea, which is about the height to which intense 

 glaciation and boulder-clay extend on the mountain,* the 

 terraces above this level being of sand and gravel, and 

 the limestone and trap of the mountain weathered and 

 deeply decomposed and not covered with the boulder-clay. 

 Thus the foundations of the building were excavated into 

 a slope at the exact junction of the glaciated and non- 

 glaciated surface. The excavation for the front of the 

 building was made in tough boulder-clay, with large 

 Laurentian and limestone boulders, and this rested on an 

 intensely glaciated rock surface of limestone, with striae 

 bearing S. 33 W. The rear of the building was cut into 

 the same limestone, not glaciated, and decomposed to a 

 depth of 20 feet or more into an earthy, crumbling 

 mass, still showing the stratification and fossils of the 

 formation. 



There could not be a finer illustration of the " ice-foot " 

 of the margin of the old Pleistocene sea ; and any idea 

 of glacier action was excluded by the directions of the 

 striae, and by the absence of any lateral moraine. 



The most strongly marked terraces on the Montreal 

 mountain are at heights of 470, 440, 386, and 220 feet 

 above the sea, but there are less important intermediate 



* The heavy glaciation on the plateau north-east of the mountain 

 extends up to about 180 feet. 



