604 G. M. DAWSON ON THE SUPERFICIAL GEOLOGY OE 



composed, not of a single upheaved ridge, but of a number of more 

 or less nearly parallel ranges, which have a general direction a little 

 west of north, and a breadth of over 60 miles, extending from the 

 margin of the great plains to the valleys of the Kootanie and Colum- 

 bia rivers. In the vicinity of the forty-ninth parallel, the geological 

 continuity of the country is as sharply broken by the line of their 

 eastern base as its physical character, and we pass suddenly from 

 the little-altered or disturbed strata of Cretaceous and Tertiary age 

 to scarped mountain-sides of palaeozoic rocks, metamorphosed and 

 crumpled. The higher peaks of the mountains north of the boun- 

 dary do not seem often to surpass 10,000 feet. The plains may 

 therefore be considered broadly as a trough intervening between the 

 two great longitudinal watersheds of the northern part of the con- 

 tinent. The lowest portion of this trough, however, is several hun- 

 dred feet above the sea-level; and much of its western part is actually 

 higher than its eastern Laurentian rim (see Section, PL XXXII. 



fi s- 2 > . . . 



Besides the main longitudinal watersheds, there are also two very 

 important transverse ones (see map), which are not marked by any 

 grand physical features, but appear to be merely caused by low gentle 

 rolls in the strata. Of these, one in a general way follows the political 

 boundary of the forty-ninth parallel. It separates the waters of the 

 Bed, the Assineboin and Saskatchewan rivers (which find their way 

 through Winnipeg Lake to Hudson's Bay) from those of the Missis- 

 sippi and Missouri and their various tributaries. Beginning in that 

 region of swamp and lake in Northern Minnesota which feeds the 

 variously destined head-waters of the "Winnipeg, St. Lawrence, Mis- 

 sissippi, and Bed rivers, it dips southward between the tributaries 

 of the latter two streams, and passes between Lake Traverse and Big- 

 Stone Lake, with an altitude of only 970 feet, about 200 miles south - 

 of the boundary-line. Thence it pursues a general north-westerly 

 course along the high lands formed by the southern extensions of 

 Pembina Escarpment and the Missouri Coteau, and, becoming iden- 

 tified with the latter, crosses the boundary-line near the 104th meri- 

 dian, 300 miles west of Bed Biver. Then falling south of the drift 

 ridge of the Missouri Coteau, it follows the summit of the plateau of 

 the Lignite Tertiary for about 300 miles to the Cypres Hills, where 

 it is only 40 miles north of the line, in longitude 110° 30'. Thence 

 it trends southward and crosses the forty-ninth parallel for the last 

 time about 30 miles east of the base of the Bocky Mountains. The 

 average altitude of this watershed region east of the Bed Biver is 

 1400 feet. In Northern Dakota it may be estimated at 2000 feet ; 

 and from this it rises till near the mountains it has attained an ele- 

 vation of about 4000 feet. 



The second transverse watershed crosses from the Bocky Moun- 

 tains to the Laurentian region, near the fifty-fourth parallel ; and 

 not much is known about it. It separates the rivers which reach 

 the Arctic Sea directly, from those of the Saskatchewan system, which 

 flow into Hudson's Bay. Where crossed by the canoe-route to 

 Mackenzie Biver at Methay Portage, near its eastern extremity, its 



