BULLETIN OF THE UNITED STATES FISH COMMISSION. 
tlie mouth of the Yellowstone to the summit of the Bitter Boot Mountains, about two- 
fifths belong to the mountain region, the remaining three fifths consisting of broad, 
open plains lying east of the Bocky Mountain range. The mountain belt, which 
forms a broad margin along the western end, has probably an average width of 175 
miles, running northwest parallel to the western boundary. Besides these two lead- 
ing ranges and their interlocking spurs on the west slope, there are some minor ranges 
on the eastern side, which, though comparatively small in extent, are important in 
respect to the influence they have upon the course of the water drainage and the form 
and direction of the principal valleys. 
In and about the Yellowstone National Park appears to be the great mountain 
nucleus of this region. Here the Bighorn, Yellowstone, Gallatin, Madison, Jefferson, 
Snake, and Green rivers have their origin. From this mountain center a number 
of short ranges run northward, giving direction to a number of streams. Along the 
southern border the Snow Mountains penetrate Montana for a short distance, com- 
pelling the Yellowstone Biver to make a grand detour in order to sweep around the 
northern flank. In the central portion are the Belt, Judith, and High wood mountains, 
forming an irregular group of short and broken ranges, around which the Missouri 
sweeps to the northward before entering upon its long eastward stretch. These also 
have a nucleus where the Musselshell, Judith, Deep, and Shields rivers take their rise. 
The mountains of this region, as a rule, are less rugged than those of Colorado. 
There are some very rough, rocky groups, such as the Grand Tetons, portions of the 
Main Divide southeast of Flathead Lake, and a number of peaks east of Yellowstone 
Lake. Instead of the rocky, jagged sides and serrated crests, we usually see here 
smooth slopes and rounded outlines. 
According to Dr. Hayden, the elevation of both mountains and valleys of Montana 
is less than that of the great mountain belt of Colorado, Wyoming, Utah, Nevada, and 
New Mexico. The average altitude of the entire State is given as being 2,260 feet 
lower than that of the other States named, a difference regarded as the equivalent 
of seven degrees in latitude. 
Climate . — Western Montana and northwestern Wyoming are among the most 
fortunate regions of America as regards rain and snow 7 . According to Prof. Arnold 
Hague, “snow falls early in October [in the National Park region] and rarely disap- 
pears before June, and throughout the winter it is said to lie 0 feet in depth over the 
plateaus and higher regions of the Park.” 
A discussion of the forests and other vegetation will be given in detail in connec- 
tion with the description of each stream or particular locality examined. It may be 
said here, however, that western Montana and Wyoming constitute a vast region 
which is for the most part covered with immense coniferous forests on the mountains, 
while here and there are a few large tracts with little or no timber, such as the plain 
at the south end of Flathead Lake, constituting the greater part of the Flathead 
Indian Beservation, and such valleys as those of the Prickly Pear and Deer Lodge. 
On the mountains the timber line is not far from 9,000 feet above sea level. At this 
height the dwarfed, scraggy spruce trees are mere bushes, not over a yard in length, 
and lie pressed flat upon the ground by the heavy snows. The forests are extremely 
heavy on the Big Blackfoot, Biver, about Swan Lake, below Dempsey Lakes, and the 
region south and east of the Yellowstone National Park which has recently been 
added to the Park as a timber preserve by proclamation of President Harrison. 
