
228 B. N. A. BOUNDARY COMMISSION. 
Lignite Tertiary, and characterized by gorges and large vallies 
draining toward the Missour%. 
The second region can, perhzps, scarcely be said to cross the Line, but 
appears immediately north of it. On the Line and southward, the streams 
flowing to the Missouri, rise near the southern edge of the first division, 
the greater part of the plateau having succumbed to denuding agencies, 
523. The Missouri Coteau is one of the most important features of the 
Western Plains, and is certainly the most remarkable monument of the 
glacial period now existing there. Though frequently mentioned in 
western reports, | cannot learn that its structure has yet been care- 
fully studied. I have had the opportunity of examining more or less 
closely, that portion of it which crosses the forty-ninth parallel, for a 
length of over 100 miles. 
524. Where cut somewhat obliquely by this parallel, the Coteau may 
be said to extend from the 290, to the 335 mile point, a distance of forty- 
five miles. Atright angles to its general course, however, its extreme 
width at this point cannot be more than about thirty miles. On ap- 
proaching it from the east, on the trail from Wood End, which as already 
stated, is somewhat more elevated than the prairie lying east of it, a | 
gradual ascent is made, till the edge of the Coteau is reached ; amounting 
in a distance of twenty-five miles, to about 150 feet. The country at the 
same time becomes more distinctly undulating—as on approaching Turtle 
Mountain from the east—till almost before one is aware of the change, 
the road is winding among a confusion of abruptly rounded, and tumul- 
tuous hills, which consist entirely of drift material, and in many cases 
seem to be formed almost altogether of boulders and gravel, the finer 
matter having been to a great extent washed down into the hollows. 
Where it appears, however, it is not unlike that of the drift of the lower 
prairies, being yellowish and sandy. Among the hills are basin-like 
vallies, round, or irregular in form, and without outlet ; which are some- 
times dry but generally hold swamps or small lakes, which have frequently 
been filled in with material washed from the hills so as to become flat- 
bottomed. The hills and vallies have in general no very determinate 
direction, but a slight tendency to arrangement in north and south lines 
was observable in some parts of this region. The hills culminate on the 
Line about the 305 mile point, and westward from this place, they are 
neither so steep nor so stoney. The country gradually subsides from its 
rough and broken character, to that of rather boldly undulating prairie, 
