TOPOGRAPHY OF ROUTE FROM THE MISSISSIPPI TO THE COLUMBIA. 163 
prairie, extending with little variation of surface to the head of Mouse river, beyond the forty- 
ninth parallel; returning from which river to Fort Union, the plateau is found declining to a 
wide valley or coulée, connecting almost directly with the Missouri in a southwest direction, offer- 
ing a good chance to twrn the coteau in an engineering view, and becoming thus another im- 
portant key point on the railroad route. 
From the Shayenne to Fort Union a great many particulars are necessarily passed over, as a 
detailed notice of them would stretch to tediousness: the number of small ponds and marshes 
(the nurseries of myriads of frozs which positively rise in shoals when intruded upon) are almost 
beyond counting, and could not possibly be represented on a general map; salt marshes and 
salt-water lakes occur irregularly; around some of the small lakes the air is impregnate with the 
offensive exhalations from their waters; and, in one instance, a narrow neck but a few yards 
wide separates a lake of purest fresh water from another which is intensely salt. Further notice 
of such facts belongs more properly to the province of the mineralogist, and need not be extended 
in a topographical sketch. 
The Missouri from the Yellowstone to Milk river is a wide and turgid stream, with an ever- 
shitting channel choked with sand-bars, which are influenced by every storm; its great volume 
of water, however, insuring a navigable channel on one side or other. It flows with a very sinuous 
course through an intervale of variable width, enclosed by the tall bluffs of the plateaux on either 
side, which sometimes project upon the bank, in some places leaving an intervale of five or six 
miles; it is generally deeply fringed with the cotton-wood and its congeners, and occasionally a 
dense underbrush, affording a secure haunt to the fierce grizzly bear; good grazing occurs in spots, 
but is generally better among the bluffs and coulées than on the plain, where the soil is mostly 
hard and dusty, affording, it might be supposed, but a scanty sustenance even to the swarms 
of grasshoppers, which in certain conditions of the atmosphere take wing, and are seen drifting in 
a darkening cloud for hours before the wind. The bluffs are composed mainly of a soft, half- 
formed sandstone, which crumbles under a slight pressure, and is washed by the rains into the 
most fantastic shapes, resembling fortifications and ordinary buildings; one of these near the con- 
fluence of Big Muddy river is well known as the “Cottage Rock.” The sandstone, or rather 
sand-rock, as it washes away, discovers petrifactions and lignites of a large size, and is sometimes 
heard falling in large masses with a dull, muffled sound. These are the “ Mauvaises Terres,” or 
Bad Lands of the hunters, which occur at irregular intervals all along the Missouri, and many 
of its tributaries, and in some places are of great extent. The columnar and grotesque forms 
which are seen in great numbers in such places, are probably owing to the unequal induration 
or cohesion of what was the upper stratum of a vast alluvial deposit; the softer parts yielding 
quickly to the ‘‘scooping action of denudation,” while the harder portion of the sand-rock 
became so many fixed points—foundations, as it were—for the formation of a column, the structure 
commencing at the top. A better idea of their appearance cannot be furnished than by giving 
an extract from a most effective description by Dr. Evans, in Owen’s Geological Survey: * 
“To the surrounding country, however, the Mauvaises Terres present the most striking contrast. 
From the uniform, monotonous open prairie, the traveller suddenly descends one or two hundred 
feet, into a valley that looks as if it sunk away from the surrounding world, leaving standing all 
over it thousands of abrupt, irregular, prismatic and columnar masses, frequently capped with 
irregular pyramids, and stretching up to a height of from one to two hundred feet or more. So 
thickly are these natural towers studded over the surface of this extraordinary region, that the 
traveller threads his way through deep, confined labyrinthine passages, not unlike the narrow, 
irregular streets and lanes of some quaint old town of the European continent. Viewed in the 
distance, indeed, these rocky piles, in their endless succession, assume the appearance of massive 
artificial structures, decked out with all the accessories of buttress and turret, arched doorway, 
and clustered shaft, pinnacle, and finial and tapering spire. One might almost imagine oneself 
* Report of a Geological Survey of Wisconsin, Iowa, and Minnesota, by D. D. Owen, page 197. 
