f about 250,000 sq.
m., of which 38,395 are in British Columbia; some 105,000 sq. m. belong
to the valley of the Snake and 11,700 to that of the Willamette. The
source of the river is partly in the Yellowstone country, partly near
the Titon peaks, and partly in the pine-clad mountains of British
Columbia. Some American geographers regard the head as that of the Clark
Fork, but it is most generally taken to be in British Columbia about 80
m. north of the United States line. From this point it runs some 150 m.
to the north-west to the "Big Bend," and then in a great curve
southward, enclosing the superb ranges of the Selkirks, crossing the
international line near the boundary of Washington and Idaho, where it
is joined by the Pend Oreille river, or Clark Fork, already referred to.
This latter river rises in the Rocky Mountains west of Helena, Montana,
falls with a heavy slope (1323 ft. in 167 m.) to its confluence with the
Flathead, flows through Lake Pend Oreille (27 m.) in northern Idaho, and
runs in deep canyons (falling 900 ft. in 200 m.) to its junction with
the Columbia, which from this point continues almost due south for more
than 106 m. Here the Columbia is joined by the Spokane, a large river
with heavy fall, and enters the "Great Plain of the Columbia," an area
of some 22,000 sq. m., resembling the "parks" of Colorado, shut in on
all sides by mountains: the Moses range to the north, the Bitter Root
and Coeur d'Alene on the east, the Blue on the south, and the Cascades
on the west. The soil is rich, yielding great harvests of grain, and the
mountains rich in minerals as yet only slightly prospected. After
breaking into this basin the river turns sharply to the west and skirts
the northern mountain barrier for about 105 m. Where it strikes the
confines of the Cascades, it is joined by the Okanogan, turns due south
in the second Big Bend, and flows about 200 m. to its junction with the
Snake near Wallula.

After the confluence of the Snake with the Columbia the greater river
turns west toward the Pacific. Throughout its course to this point it
may be said that the Columbia has no flood plain; everywhere it is
cutting its bed; almost everywhere it is characterized by canyons,
although above the Spokane the valley is much broken down and there is
considerable timbered and fertile bench land. Below the Spokane the
canyon becomes more steep and rugged. From the mouth of the Okanogan to
Priests Rapids extends a superb