248 B. N. A. BOUNDARY COMMISSION. 

centage of Laurentian, must not be supposed to show that erratics of that 
origin are equally frequent over the second and third steppes, for the 
total quantity of drift on the latter is comparatively small. 
The Red River Valley. 
572. The valley of the Red River, is a continuation of the trough, in 
the northern part of which Lakes Winnipeg, Winnipegosis, and Manitoba 
lie. On the east, it is bounded by the plateau of drift materials, already 
described, which stretches southward from the Laurentian region. On 
the west, the nearly straight line of the Cretaceous escarpment, with the 
terraced front of Pembina Mountain form its limit. The part of this 
valley lying north of the Boundary-line, and between it and the southern 
shore of Lake Winnipeg, is ninety miles in length; while from the Line 
southward to Traverse Lake, itis 225 miles, giving a total length of 315 
miles. On the forty-ninth parallel, its width is forty-six miles, and for a 
long way south of the Line, it preserves an average breadth of about 
thirty miles, though finally narrowing near Traverse Lake. The general 
course of the valley is exactly north and south, to which the river con- 
forms, but not very precisely ; for at Grand Forks, seventy miles south of 
the Line, the Red Lake River—a stream of magnitude, equal to, or greater 
than, the southern branch which continues to bear the name of Red 
River—comes in at right angles without producing any corresponding 
bifurcation or change in the valley. The valley appears to have been 
adopted by the river, not formed by it. 
573. The slope of the valley northward from the Line, probably does 
not exceed six inches in the mile. From Morehead in Minnesota, 150 
miles south of the Line; the average fall ofthe river is a little less than 
one foot per mile, by railway levels, and that of the valley must be even 
less. The inclination of the sides of the valley, east and west of the 
central depression, probably seldom exceeds ten or twelve feet in the 
mile, and frequently falls much below this. Its general aspect is that of 
a perfectly level plain, bounded only by the horizon, or by a belt of trees 
fringing some stream. | 
574. The whole of this valley, has at a time geologically recent, 
been occupied by a great lake, with the fine silty deposit of which, it is 
now floored. The alluvial deposit is uniform and of great depth. I 
have never observed any organic remains in it, but leaves and fragments 
of wood appear to have been found in some places. The lake must have 
been a fresh-water one, but the remains of molluscs are not found. The 
