CHARACTERISTICS OF THE MOUNTAIN AREA. 
287 
The principal parts of the courses of the branches of the river which 
enter it in this valley are in heavily-timbered, mountainous country. 
The Teton Eange is heavily timbered. 
Below Jackson's Hole the Snake flows through a close canon, passing 
through a gieat mass of mountains in seeking an exit to the Snake Eiver 
Plains. In this part of its course it receives three large branches from 
the left. The upper of these, Hoback's Eiver, heads in a partially open 
valley just north of the Green Eiver Basin, in the angle between the 
Wyoming and Gros Ventre Eauges. The surface of this valley is con- 
siderably broken. It is well grassed, but on the minor ridges which 
•diversify its surface are many groves of aspens and coniferae. This 
valley can be burned over, but fires would require constant attention to 
prevent them from destroying the timber. Below this valley the stream 
flows in a canon, by which it cuts its way across the Wyoming Eange. 
The eutire course of John Day's Eiver, the next branch of the Snake, 
is in a canon valley between two high timbered ranges, known as the Wy- 
oming and the Salt Eiver Eauges. It is heavily timbered throughout 
with coniterae. 
Next we pass to Salt Eiver, the third large branch of the Snake. 
Heading mainly in the Salt Eiver Eange, we find its main stream through 
its whole course in a broad valley, mainly of gravelly soil and covered 
with a sparse growth of sage and grass. It is probably burnable, though 
with some difficulty. 
Continuing our examination of the country tributary to the Snake on 
the left-hand side, we find the region lying between the valleys of the 
Salt and Blackfoot Eivers to consist of a mass of hills, rising one above 
another toward the west to a crest, and thence falling somewhat abruptly 
to the Blackfoot. About its crest line these hills are well timbered with 
coniferee and aspens, but the slopes and lower summits are covered with 
bunch-grass, varied by occasional small groves of, aspens, a country 
easily burned over. 
The region drained by the Blackfoot, the next left-hand branch of the 
Snake of note, is characterized by an almost total absence of timber, 
eitlier in the valleys or on the hills. Most of the valley portion is over- 
laid by a floor of basalt, on which Artemisia grows luxuriantly. The 
hills are covered with bunch-grass. That portion of the drainage area 
of this stream which lies in and among the hills and low mountains can 
easily be burned over. The country about its lower course, which forms 
a part of the Great Snake Eiver Plains, is not as combustible, as will be 
shown further on. 
Next we turn to the Portneuf and its tributaries. Like the Bear and 
the Blackfoot, this stream has a very circuitous course through and 
around the lava fields which obstruct it. Starting with a southerly 
course it suddenly turns to the westward, declining the apparently easy 
route southward to the Bear, and cuts its way doggedly through the 
Portneuf Eange. Its upper valley is well grassed, as are also the hills 
