INDIAN TRIBES OF THE MISSOURI VALLEY. 393 
ranges of mountains may be divided into three different zones. The first third, from the 
base up, is well covered with tall pines, poplars, and other trees of large growth. ‘The 
second portion is composed of gigantic masses of rock, overhanging in such a manner as 
to present a frightful appearance to the traveller below. Among these, a few stinted 
cedars and pines, with some other shrubs struggle for an existence, sometimes taking root 
where there is apparently no earth. In the last zone, the vegetation has ceased, and the 
snow commences, which continues to the summit. This snow is perpetual, though ‘a por- 
tion of it melts annually, which loss is supplied the ensuing winter, yet it is presumed 
that no thaw takes place on the summit, but on the sides some distance down. When 
the snow accumulates on the projections so as to lose its balance, it is precipitated below 
in the form of avalanches, something like those of the Alps. Taking in their way large 
rocks, and increasing in size as they descend,-trees give way before them, until they find 
rest in some portion of the lower zone, where they melt away, and aid in forming the 
sources of rivers. Snow-slides are also common, by which piles of snow miles in extent 
are detached, and force their way into the valleys, or at least as far as the thickly tim- 
bered section. Some of the springs near the sources of the Yellowstone are bituminous, 
sending forth an inflammable substance like tar; others are sulphurous, and a few are 
hot, or boiling. ‘The water of the last is hot enough to cook meat readily. Most of the 
tributaries of the Yellowstone are well fringed with timber, though the river itself is 
wooded only about half the way from its mouth to the base of the mountains, that is, many 
portions of it for considerable distances are destitute of trees. The lower portion of the 
valley contains wide belts of cottonwood, and the soil is moderately good for agricultural 
purposes. Considering the Crow district as a whole, it can never become thickly settled, 
and all the land that can ever be rendered useful for cultivation, is found only in the valleys 
of the streams, and along the base of the mountains. 
The Yellowstone, like the Missouri, rises to the top of its banks every spring, owing to 
the melting of the snow along the sides of the mountains. ‘This rise usually commences 
about the middle of May and continues until the middle of June, when it begins to fall, 
unless kept up by heavy rains. During this high stage of water steamers of light draught 
might navigate it to the first rapids, which are about one hundred and fifty miles from its 
mouth. ‘The ice commonly yields about the first of April, and when broken up suddenly, 
by pressure of water from the mountains, it forms dams quite across the valley, raising the 
water fifty or sixty feet, and inundating the neighboring country. The Crow Indians are 
greatly in fear of the water on these occasions, and suffer severely when taken unawares. 
One of these breakings up occurred a few years ago, early in the month of February. 
About one hundred and thirty lodges of the Crows were encamped in the valley of the 
Yellowstone, where the distance from bluff to bluff is more than three miles. The water 
