252 GEOGRAPHICAL MEMOIR. 
the mouth of the Koos-koos-kia, in latitude 46° 30’. It then turns westward and joins the 
Columbia in about latitude 46° 15’, longitude 118° 49’, about forty-eight miles below Priest’s 
Rapids. It is probably navigable for steamers at certain stages of the water as far as the 
mouth of the Peluse, a distance of sixty miles, and probably to its junction with the Clearwater, 
or Koos-koos-kia. 
Lewis and Clark took canoes on the Koos-koos-kia 59 miles above its mouth, and descended 
to the Snake, and thence to the Columbia, from the Tth to the 10th of October, 1805, the river 
being at its lowest stage. "Their course on the Koos-koos-kia was 59 miles and on the Snake 
1393 miles. Comparing the difficulties they met with on the Snake with those they encountered 
on the Columbia, from the mouth of the Snake to the Dalles, they seem to be all of the same 
general character, leaving but little doubt of the navigability of the Snake for steamers to the 
mouth of the Koos-koos-kia, or, perhaps, for even sixty miles further. The other streams which 
flow into the main Columbia from the east, worthy of being referred to in this connexion, are 
the Spokane, which has its confluence with the main Columbia at the point where it turns 
from the south to make the great bend to the west; Clark’s Fork, and the Koutenay river, which 
have been already referred to in the description of the mountain region. "The Snake river itself 
has-considerable tributaries: first, the Peluse, which consists of several branches, one coming 
from the north, having its rise in the central portion of the Great Plain of the Columbia; but 
the main branch comes from the main divide of the Bitter Root mountains, flows nearly due 
west for 130 miles, and joins the other branch of the Peluse twelve miles above its mouth. 
In the narrative a circumstantial account is given of the great fall of the Peluse, which is an 
extraordinary place for salmon, and therefore a great resort for the Indians. The most con- 
siderable tributary of Snake river, however, is the Clearwater or Koos-koos-kia river, which 
flows into the Snake at a point where, running nearly due north, it turns suddenly to the 
west. This Koos-koos-kia has several branches which, with the main stream, flow through 
a country densely wooded with fir and larch, spruce and cedar. These tributaries of the 
Koos-koos-kia coming from the north are not navigable, but are excellent for rafting; and the 
pineries and forest trees on their banks will furnish an inexhaustible supply for settlements in 
the lower portion of the Clearwater and Snake river valleys, пож, destitute of wood. The 
Salmon river flows into the Snake fifty miles above the mouth of the Clearwater, and it also passes 
through a very rich and arable country. At the crossing of Salmon river, a landmark well 
known to Indians and voyageurs, the Mormons had last year a flourishing settlement. The 
Snake river forms a great re-entering {rom the Clearwater to its junction with the Columbia, 
which re-entering, being bounded on the south by the Blue mountains, has been named the 
Walla-Walla valley, although that term properly applies to the immediate system of valleys 
whose streams connect with the Walla- Walla river itself, That portion of the Great Plain lying 
east of the main Columbia, and which may be regarded as bounded on the north by the Spokane, 
and on the east by the foot-hills of the Bitter Root mountains, is, for the most part, well watered 
and well grassed. The eastern half of this portion is exceedingly well adapted to agricultural 
purposes. The various streams—the Peluse, the Kamas Prairie creek of the Coeur 4 Aléne, 
the Spokane and Cœur 4” Aléne rivers—are well timbered with pine, and numerous rivulets and 
springs are found through that portion of the country, facilitating the progress of settlements, 
and rendering the whole at once available to the agriculturist. Indeed, the whole of the 
western slopes of the Bitter Root mountains are densely timbered with pine, spruce, larch, 
cedar, and other trees. These spurs have, in most cases, a gradual slope to the west, and the 
