GEOGRAPHICAL MEMOIR. 243 
well-watered and most arable region, whose southern portion has also been described by Lewis 
and Clark as fertile and beautiful. 
It will thus be seen that the mountain system lying between the plains of the Missouri and 
the great plain of the Columbia is denominated by Lewis and Clark as the Rocky mountains, 
but which, in my narrative, has been spoken of as the Rocky mountains and as the Bitter Root 
and Coeur d’ Aléne mountains. Indeed, this mountain system consists of two backbones. The 
Rocky mountain chain, passing north from the sources of Snake river, branches off in about 
latitude 45° 30' and longitude 113° 45’. One branch moves to the east and northeast, about 
ninety miles on the parallel. The other branch moves to the west and northwest about forty- 
five miles, also on the parallel. Тһе two branches then continue in about the same general 
direction, north 40° west, and at a distance apart of about one hundred and thirty-five miles 
on the parallel. The western backbone, or the Bitter Root and Cœur d'Aléne mountains, 
decline somewhat in their northern course, so that on reaching Clark's Fork the chain becomes 
much broken and the system confused. It may be said to cross Clark's Fork at about the 
Cabinet mountain, and then it changes its course more to the west, forming the divide between 
Clark's Fork and the Koutenay river. The main range of the Rocky mountains, which, 
between the source of Snake river and the three forks of the Missouri, has a high altitude, and 
continues to be elevated along the region whence the Jefferson Fork has its source, begins to 
fall soon after it branches to the east. The divide has a singular course from this point: it 
makes a great bend to the east and a return again to the west, making nearly a semicircle, from 
which flow streams to the Clark's Fork of the Columbia. The semicircle commences at the 
Big Hole prairie, where you pass from the Bitter Root river to the upper tributaries of Wisdom 
river, and may be said to end at the Gates of Sun river. Its radius is eighty miles, and its 
periphery one hundred miles, the centre being near the junction of the Hell-Gate and Bitter Root 
rivers. "Through this entire distance the whole chain is broken down, affording great numbers 
of passes, all of them having an altitude not far from 6,000 feet above the sea. Going north 
from the Gate of Sun river the mountains rise in elevation, so that when we come to our 
parallel the height of the passes exceeds 7,000 feet above the sea; and when we go further 
north to the 52d or 53d parallel of latitude, the divide exceeds 10,000 feet above the sea. It 
is the country, therefore, between these two great backbones of-the Rocky mountains which 
I wish now to describe, and especially will I first call attention to that beautiful region whose 
streams, flowing from the great semicircle of the Rocky mountains before referred to, pass 
through a delightful grazing and arable country, and find their confluence in the Bitter Root 
river opposite Hell-Gate. 3 i 
From the Big Hole prairie, on the south, flows the Bitter Root river, which has also a branch 
from the southwest, up which is a trail much used by Indians and Voyageurs passing to the 
Nez Percés country and Walla-Walla. This trail was used in the exploration by Lientenaat 
Macfeely and Mr. Tinkham, and has since been used very much by my expressmen and trains. 
The Bitter Root valley, above Hell-Gate river, is about eighty miles long and from three to ми 
in width, having a direction north and south from the sources of the Bitter Root river to its 
junction with the Hell-Gate. Besides the outlet above mentioned towards ы Kooskooskia, 
which is the most difficult, it bas an excellent natural wagon d communication at its head, 
by the Big Hole Pass to Jefferson Fork, Fort Hall, and other points southward, as well " d 
the Hell-Gate routes to the eastward. From its lower end, at the junction of the Hell-Gate, it is 
believed that the Bitter Root river is, or can be made, navigable for small steamers for long 
