r came close to the edge of the Cascade Range. The ancient
canon of Lake Chelan had been dammed up by the lava, and a lake
occupied a portion of the former bed of the river. The Columbia
could not cut its channel deep enough to drain the lake, and there
it remained.

[Illustration: FIG. 60.--LOOKING DOWN LAKE CHELAN FROM THE UPPER
END]

Then another change came: the climate grew cold and heavy snows
gathered upon the Cascade Range. The snow did not all melt during
the summers, but went on increasing from year to year. The masses
of snow moved gradually down the mountain slopes, growing more
and more icy until they became true glaciers.

In this manner it came about that a river of ice occupied the canon
in which the old lake lay, and, displacing its waters, scraped
and ground out the bottom and sides. The moving ice deposited the
waste material at the lower end of the canon, where it joined the
Columbia River, the canon of which was also occupied by a glacier
coming from farther north. When the glacier began to retreat up the
Chelan canon, it left a great mass of rock debris, forming a dam
between its basin and the Columbia. After the ice had disappeared,
water collected in the canon above the dam, and the narrow, deep
lake was formed, enclosed within granite walls.

As the snows melted, forests spread over the mountains, the bear,
deer, and mountain goats came back again, while the streams, bringing
down earth and rocks, began their work of filling up the lake. This
task they will succeed in accomplishing some day unless something
unforeseen happens to prevent. A valley, composed partly of meadow
and partly of boulder-covered slopes, will then have taken the
place of the lake.

THE NATIVE INHABITANTS OF THE PACIFIC SLOPE

The explorers and early settlers found a native race occupying nearly
every portion of our continent. These people had many characteristics
in common and were all called Indians. It is believed that they came
originally from Asia, but their migration and scattering occurred
so long ago that they have become divided into many groups, each
having its own language and customs.

In the western portion of the country, where the surface is broken
by numerous barriers, such as mountains and deserts, almost every
valley was found to be occupied by a distinct group of Indians
called a "tribe." The language of each tribe differed so much from
the languages of adjoining tribes that they could wit