For some days past, Captain Bonneville had been made sensible of the great elevation of country into which he was gradually ascending by the effect of the dryness and rarefaction of the atmosphere upon his wagons.  The wood-work shrunk; the paint boxes of the wheels were continually working out, and it was necessary to support the spokes by stout props to prevent their falling asunder.  The travellers were now entering one of those great steppes of the Far West, where the prevalent aridity of the atmosphere renders the country unfit for cultivation.  In these regions there is a fresh sweet growth of grass in the spring, but it is scanty and short, and parches up in the course of the summer, so that there is none for the hunters to set fire to in the autumn.  It is a common observation that “above the forks of the Platte the grass does not burn.”  All attempts at agriculture and gardening in the neighborhood of Fort William have been attended with very little success.  The grain and vegetables raised there have been scanty in quantity and poor in quality.  The great elevation of these plains, and the dryness of the atmosphere, will tend to retain these immense regions in a state of pristine wildness.

In the course of a day or two more, the travellers entered that wild and broken tract of the Crow country called the Black Hills, and here their journey became toilsome in the extreme.  Rugged steeps and deep ravines incessantly obstructed their progress, so that a great part of the day was spent in the painful toil of digging through banks, filling up ravines, forcing the wagons up the most forbidding ascents, or swinging them with ropes down the face of dangerous precipices.  The shoes of their horses were worn out, and their feet injured by the rugged and stony roads.  The travellers were annoyed also by frequent but brief storms, which would come hurrying over the hills, or through the mountain defiles, rage with great fury for a short time, and then pass off, leaving everything calm and serene again.

For several nights the camp had been infested by vagabond Indian dogs, prowling about in quest of food.  They were about the size of a large pointer; with ears short and erect, and a long bushy tail—­altogether, they bore a striking resemblance to a wolf.  These skulking visitors would keep about the purlieus of the camp until daylight; when, on the first stir of life among the sleepers, they would scamper off until they reached some rising ground, where they would take their seats, and keep a sharp and hungry watch upon every movement.  The moment the travellers were fairly on the march, and the camp was abandoned, these starving hangers-on would hasten to the deserted fires, to seize upon the half-picked bones, the offal and garbage that lay about; and, having made a hasty meal, with many a snap and snarl and growl, would follow leisurely on the trail of the caravan.  Many attempts were made to coax or catch them, but in vain.