230 B. N. A. BOUNDARY COMMISSION. 

the hilly country of the Coteau itself, is always from a distance well 
defined. To the northward and eastward, boundless, level, treeless plains 
stretch to the horizon. The Traders’ Road to Wood Mountain, after pass- 
ing along the base of the Coteau, for the distance above indicated, turns 
westward, and crosses it, taking advantage of a deep bay in its edge, in | 
which also rises a main tributary of the Souris River. The road 
then passes for about fifty miles through the Coteau belt, which must 
here be about thirty miles wide, and repeats almost exactly the physical 
features already described, though in this particular locality neither quite 
so tumultuous nor so stoney as on the Line. 
530. Following the Traders’ Road westward, for about twenty-five 
miles, toward Wood Mountain, it passes for the most part between the 
southern edge of the Coteau proper, and the northern margin of the Ter- 
tiary plateau. Wherever, from any hill, a view over the Coteau to the 
north can be obtained, it is seen to stretch away to the horizon in a 
succession of wave-like mounds and ridges, which do not differ much in 
average altitude. 
531. The intervening region, followed by the road on account of its 
facility, has characters of its own. Wide and deep vallies, often flat-bot- 
tomed, with systems of tributary coulées, are found everywhere cut in the 
soft rocks of the foot of the Tertiary plateau. Some have small streams 
still flowing in them, fed by the drainage of the plateau ; but for the most 
part these old vallies are dry or occupied by chains of small saline lakes, 
the waters of many of which disappear early in the summer. The lakes 
usually have the long river-like forms of the vallies which contain them, 
and receive the waters of the brooks which still flow. One of the most 
important, probably nine miles in length, forms the drainage-basin for the 
streams of Wood Mountain ; its sides are abrupt, and the water appears 
to be deep. These old vallies are evidently of pre-glacial age, and have 
formed a part of the original sculpture of the country. The heaping up 
of the great drift deposits of the Coteau along the foot of the Tertiary 
plateau, has blocked them up, and prevented the drainage finding its way 
northward as before. Since the elevation succeeding the glacial subsi- 
dence, the rainfall of the district has never been sufficiently great in 
proportion to the evaporation, to enable the streams to cut through the 
barrier thus formed. The existence of these vallies, and the arrange- 
ment of the drift deposits in this region, have important bearings on 
several problems connected with its general history, which will be again 
referred to, 
