250 GEOGRAPHICAL MEMOIR. 
numbers, 11,200 square miles of prairie land. The whole area of the mountain region (from 
divide of Rocky mountains to divide of Bitter Root, and from 45° 30’ to 49°) is about 30,000 
square miles, and it will be a small estimate to put the arable land of the prairie and the forest аф 
12,000 square miles. Thus the country in the forks of the Flathead and the Bitter Root, stretch- 
ing away east above the Blackfoot cafion, is mostly a table-land, well watered, and arable; and 
on all these tributaries—the Bitter Root, the Hell-Gate, the Big Blackfoot, the Jocko, the Maple 
river, the Hot Spring river, and the Lou-Lou Fork itself—the timber land will be found unques- 
tionably better than the prairie land. It will not be in the immediate bottom or valley of the 
river where farmers will find their best locations, but on the smaller tributaries some few miles 
above their junction with the main streams. The traveller passing up these rivers, and seeing 
a little tributary breaking out in the valley, will, in going up it invariably come into an open 
and beautiful country. The observer who has passed through this country often ; who has had 
with him intelligent men that have lived in it long; who understands intercourse with the 
Indians, and knows how to verify information which they give to him, will be astonished at the 
conclusions which he will reach in regard to the agricultural advantages of this country ; and it 
will not be many years before the progress of settlements will establish its superority as an 
agricultural region. 
BITTER ROOT MOUNTAINS TO CASCADE MOUNTAINS. 
Between the Rocky mountains and the coast are the Cascade mountains, which, in the Ter- 
ritory of Washington, have nearly a north and south course. This range, in about parallel 
47° 15’, is extremely narrow and low, but both northward and southward widens out, having 
a base on the Columbia river extending from Mount St. Helen’s to Mount Adams, and on the 
forty-ninth parallel from Mount Baker to the sources of the western tributaries of the Okina- 
kane. Тһе region between the Cascade and the Bitter Root and Coeur d’ Aléne mountains, just 
described, is remarkable for the great interior plain occupying nearly two-thirds of the country, 
and which has been denominated the Great Plain of the Columbia. This central portion of 
the Territory is watered by the main Columbia itself and its great southern branch, the Snake 
river. The Columbia, having its source in latitude 50°, pursues a northern course to latitude 
52° 10’, when it receives the Canoe tributary, whose source is in latitude 53930. It then 
turns immediately to the west and south, and continues on a course generally south until it comes 
below the boundary, then it flows through this great plain in a general direction nearly south; 
when arriving at Old Fort Walla-Walla it turns to the west and flows into the ocean in about 
latitude 469 15’, longitude 1249, In its north and south course there are remarkable bends, 
one in about latitude 47° 55', longitude 1189 10^; it turns nearly due west and it continues this 
course to the Okinakane, in longitude 1209 05’, a distance on the parallel of about eighty-five 
miles, but by the river at least one hundred and twenty miles. It then flows southwesterly 
for about fifty miles, and at the mouth of the Pisquouse, in latitude 47° 22’, again turns towards 
the southeast, which course it preserves as far as Walla-Walla, a distance by the river of 
one hundred and sixty-five miles, or one hundred and forty in a direct line. From the 
Columbia entrance up to the Cascades, a distance of one hundred and sixty-five miles, the river 
is without obstruction and can be navigated by large steamers. Sea-going steamers can ascend 
as far as Vancouver, one hundred and fifteen miles from its mouth. The Indians say that at 
the Cascades the river used to be perfectly free, but the gradual encroachments on its precipi- 
tous banks at length gave rise to a land slide, which, falling into the river, made a sort of 
natural dam, which is evidently the case from the appearance of the shore. There is а portage 
