
GENERAL PHYSICAL GEOGRAPHY. 9 

undulating with some small lakes and swamps, while the hills are 
flat-topped and dry, and in some piaces coalesce to form a high-level 
plateau. 
14. This southern transverse watershed is throughout characterized 
by diffuseness, and is indeterminate in direction. It has, in all proba- 
bility, been outlined at first by some very gentle flexure of the strata on 
a large scale, produced during the elevation of the Cretaceous and 
Tertiary beds to their present position; but has been subsequently 
shaped by the denudation of these soft formations on all sides. Such an 
elevation would very likely be accompanied by corresponding parallel 
depressions, like it, slight in amount but extensive in area, which would 
indieate the valleys of the Saskatchewan and Missouri. The eastern 
extension of the northern of these synclinals might also account for the 
passage of the Nelson and Churchill Rivers through the otherwise 
continuous barrier of metamorphic rocks there. 
15. The Tertiary plain of the third prairie steppe must first have been 
scored by rivers flowing from west to east, and then by their numerous 
branches flowing to the north and south to the precursors of the 
Saskatchewan and Missouri. By these the strata have been gradually 
cut down and back, till an extensive table-land separated the valleys of 
the two streams. Waste still continuing, has reduced this in many 
places to a mere dividing ridge, or has almost altogether removed it. 
The quantity of material carried away has been vast, and by far the 
greater part of this denudation appears to have been accomplished 
before the glacial period. 
16. Of the second great transverse watershed but little is known. 
It separates the waters of the Saskatchewan system of rivers from those 
which pass directly into the Arctic Ocean by the Mackenzie River. 
Where crossed by the canoe route at Methy Portage, near its eastern 
junction with the Laurentian, Sir J. Richardson gives it an elevation of 
1,560 feet. According to Dr. Hector’s observations, its western end 
would appear to have an altitude of about 2,400 feet. The intermediate 
portion is probably less elevated than either of the extremities. 
17. Of the area as at first defined, extending from the Rocky Moun- 
tains to the base of the Laurentian country, and lying between the 
fifty-fourth and forty-ninth parallels, the great Saskatchewan River and 
its tributaries drains by far the largest part, av area of about 139,000 
square miles. The Red River and its great tributary the Assineboine, 
drain 70,500 square miles; the vallies of numerous small streams flow- 


