162 TOPOGRAPHY OF ROUTE FROM THE MISSISSIPPI TO THE COLUMBIA. 
the small detached parties, though without having this circumstance especially in view; and it 
is impossible to suppose that such an insignificant water-course should have a length and volume 
necessary to penetrate the formidable plateau of the Missouri. 
This misconception is stated at length to show the uncertain character of information supplied 
by guides, who, however well acquainted with the country in which they hunt and live, are rarely 
capable of expressing themselves with reference to any subject foreign to their own pursuits, 
besides being always liable to be misunderstood from the confusion of tongues which is usually 
heard on the outskirts of civilization. It is but justice here to say that a signal exception to 
these remarks was ever presented in the intelligent and exact description of our French guide, Mr. 
La Bombard, who accompanied the main train to Fort Benton. 
Mouse river presents a new river character in the deep and ramified coulées which intersect 
the valley in every direction, in other respects closely resembling the Shayenne, having a narrow 
but dense fringe of oak, ash, maple, and other timber, filling the intervale, and extending some 
way up the intricate coulées ; in some of which are found small streams in sandy beds, and massive 
sandstone rocks. Many of them reach to the edge of the Missouri plateau, which is here well 
defined ; and in the examination for a good passage for the wagon train, secluded spots were found 
where beetling crag and winding stream, venerable trees and greenest sward, combined in scenes 
of much picturesque beauty. 
The main route strikes Mouse river at its most southerly bend, about one hundred and twenty- 
five miles from Lake Jessie, from which point the river turns abruptly northward towards its 
confluence with the Assiniboin. In the same general course of northwest the route runs nearly 
parallel to the course of Mouse river, heading the coulées for thirty miles, when the river is 
found coming down from the north, being joined at this turning point by the Riviére des Lacs, 
which flows southeast from the most northern edge of the great plateau, of which it may be 
assumed asa boundary. From Dog House hill to the junction of the Riviére des Lacs the 
coteau decreases in elevation, until blended insensibly with the rolling prairies rising from that 
river. On the approach to these high prairies from the more open country the swelling outline 
assumes the appearance of a distant coast, which seems to rise in a direction parallel to the 
route of the traveller, and suggests the idea of a plateau or bench of table-land beyond; hence the 
use of the word ‘‘coteau.”’ But this appearance has proved so frequently deceptive with reference 
to the extent of tracts exhibiting it, that only a thorough exploration can be relied upon: thus the 
preliminary sketches in the neighborhood of Fort Union represented this phantom coteau running 
in whatever direction the line of examination was conducted; so that it will be only when all the 
detached surveys are combined that the exact extent of these plateaux can be determined. 
The plateau between Missouri and Mouse rivers cannot be called simply a rolling prairie, 
though in detailresembling the hilly prairies noticed, but in a very exaggerated degree: a general 
similarity of outlines; the absence of wood and rocks in place; boulders plentiful; ponds and 
marshes if possible more frequent; but the elevations so much greater as to be almost considered 
mountainous, and becoming still more rugged on the approach to Fort Union, where it ends 
abruptly on the level intervale of the Missouri. It is intersected by numerous water-courses, 
which run dry in summer, showing the same character of sandy and clayey soil in the bottoms, 
which is also seen in the rain-worn sections of the most elevated points. The principal of these 
is the White Earth river, its character being partly indicated by its name, heading in several 
marshy lakes within the limits of the plateau, and flowing in a winding southerly course to the 
Missouri about fifty miles east of Fort Union. Vegetation is generally scanty on this plateau; 
grass is rank in the bottoms, but mostly thin and inferior for grazing; the prickly pear, the most 
common kind of cactus, begins to appear; and the wild turnip is found in comparative abundance, 
being the only useful production, and probably the only vegetable food of the wandering Indians, 
by whom it is regularly gathered. ; 
North of the plateau an admirable reconnaissance by Mr. Lander develops a low, marshy 
