42 THE GLACIAL LAKE AGASSIZ. 



Ill Maiiitolja this escarpment extends with a north-northwest course 

 by Mountain City and Thornhill to G miles east-southeast of Treherne, a 

 distance of about 50 miles With its extent in North Dakota, the whole 

 length of Pemliina ^Mountain is approximately 80 miles. Its crest north of 

 the international boundary averages al)out 400 feet aljove its liase, or 1,400 

 feet above the sea; but within a few miles farther west tlie rolling surface 

 of the highland rises 100 to 200 feet higher. 



Northwestward from Treherne the plateau of which Pembina Moun- 

 tain forms the eastern edge is interrupted across a distance of 65 miles to 

 Riding Mountain. This broad depression is occupied by the Assiniboine 

 River and its tributaries, and by small streams on the northeast which send 

 their waters to Lake jVIanitoba. The plateau, indeed, loses its regularity of 

 surface upon the country farther north and west, because it has been eroded 

 to the depth of several hundred feet <;»n the greater part of the Assiniboine 

 basin. 



Tiger Hills. — The border of the plateau south of the Assiniboine, 

 reachhig from close south of Treherne westei'ly 50 miles to the elbow of 

 the Souris River, is called the Tiger Hills.^ It is irregularly sculptured in 

 steep, rounded, massive hills, and is overspread by drift deposits, consisting 

 partly of morainic accumulations. For a distance of 40 miles west from 

 the Pembina Mountain this belt occupies a width of 5 to 8 miles, upon 

 which the surface falls from south to north 300 to 400 feet. The country on 

 the south has an average elevation nearly the same as the summits of the 

 hills, which yet rise very prominently as seen from the lower region on the 

 north. The western part of the Tiger Hills, extending 10 or 12 miles east 

 and an equal distance west from the gorge that is cut through the range by 

 the Souris, rises considerably above the adjoining- nearly flat surface on each 

 side. The foot of the belt of hills there is 100 to 150 feet lower on the 

 north than on the south, and the 8ouris flows through it in a gorge 350 feet 

 deep. From this vicinit}' Hind applied the name Blue Hills of the Souris 

 to this belt, but that name is not used by the people of the district. 



Biding and Duck motmtains. — North of the Assiniboine River the eastern 

 outline of the continuation of this plateau is preserved in the prominent 



' From the aboriginal name, which doiibtless refers to the cougar or American panther {Fella 

 concolor L.). 



