THE PRAIRIE PLATEAU OF RUPERT'S LAND. 243 



precipitous escarpments of the Biding, Duck, and Por- 

 cupine Mountains, with the detached outliers, Turtle, 

 Thunder, and Pasquia Mountains. This is the great 

 Prairie Plateau of Bupert's Land ; it is bounded towards 

 the south-west and west, by the Grand Coteau de Mis- 

 souri, which forms the north-eastern limit of the Plains* 

 of the north-west. The area of the Prairie Plateau, in 

 the basin of Lake Winnipeg, is about 120,000 square 

 miles ; it possesses a mean elevation of 1100 feet above 

 the sea, and is approximately represented on the geolo- 

 gical map by the Cretaceous Series, coloured green, north- 

 east of the Grand Coteau. The following table shows the 

 relation of these successive levels : — 



Mean Elevation Approximate Area 



above the Ocean. in Square Miles. 



Low Country (1st Plateau) . 700 . 70,000 



Terraces of Pembina Mountain . . 900—1100 . 1,500 



Great Prairie Plateau (2nd Plateau) . 1100 . . 120 ; 000 



Great Plain Plateau (3rd Plateau) . 1600 



The Eiding and Duck Mountains, with their southern 

 and northern prolongations, probably once formed part 

 of an unbroken level to the Grand Coteau ; the in- 

 tervening depression having been the result of denu- 

 dation. The isolated ranges of hills, such as the Touch- 

 wood Hills, the File Hill, the Pheasant Hill, the Birch 

 Hills, the Lumpy Hill, &c, are parts of this former 

 elevated table-land, and would assume the character of 

 islands in a sea washing the base of the Grand Coteau de 

 Missouri. 



On the east side of Lake Winnipeg the primary un- 

 fossiliferous rocks along the canoe routes present a broken 

 and extremely irregular surface to the mouth of Eainy 

 Eiver, where the fossiliferous formations are touched. 

 From Eainy Lake to Superior the routes pass through a 



* The difference between " Prairies " and " Plains " is stated in Chap. XVI. 



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