11 - 



very far removed, generally rises to a height of from 

 fifty to one hundred and fifty feet, and from this 

 level very gradually ascends to the base of the hills 

 which bound the region. 



Unlike the two regions already described, these 

 great plains are underlaid by beds of unaltered Silu- 

 rian and Devonian rocks, consisting of sandstones, 

 limestones, and shales. These are but little disturbed, 

 and are generally nearly horizontal ; but over by far 

 the greater part of the region they are overlaid by 

 beds of clay, occasionally interstratified with or over- 

 laid by sand and gravel. These superficial strata, 

 which are in some parts several hundred feet in 

 thickness, are throughout the eastern division, in great 

 part of marine origin, and date from a time when 

 this champaign region was covered by the waters of 

 the ocean ; while throughout the western division 

 the clays are more probably of fresh-water origin. 

 It results from the distribution of these superficial 

 post-tertiary strata, that the soil over the greater part 

 of the region consists of strong and heavy clays, 

 which in the newly cleared portions are overlaid by 

 a considerable thickness of vegetable mould. In the 

 eastern division, a line drawn from Quebec to Ottawa, 

 and two others from these points, converging at the 

 outlet of Lake Ghamplain, will enclose a triangular 

 area of about 9000 square miles, which is very nearly 

 that occupied by the marine clays. These are over- 

 laid, chiefly around the borders of this space, by more 

 sandy deposits, which are well seen near Three Ri- 

 vers, and about Sorel. They form a warm but light 

 soil, which yields good crops when well manured, but 

 is not of lasting fertility. The greater part of this 

 area however is covered by a tenacious blue clay, 

 often more or less calcareous, and of great depth, 

 which constitutes a strong and rich soil bearing in 



