a plateau, crossed indeed by mountains and somewhat rough in surface, but of a uniform general elevation. It constitutes a sort of debatable region between the two great slopes, one from the Rocky summits to the lakes and the other from the lakes to tide-water. On those slopes the white waters of cataract and rapid are found; on the plateau, the deep, still lakes. A glance at the map reveals the fact that the larger of these lakes are long and narrow, and lie on north and south lines. A journey on them reveals the fact that they are deep and clear and cold. Join these facts with the additional one that they are surrounded by snowy mountains, and you have no difficulty in deciding their origin. They are glacial. At some time in the glacial ages, stupendous ploughshares of ice descending from Rockies, Selkirks, Gold Range, Cascades, and Bitter Roots, gouged out profound cañons in the rents already wrought by earthquakes, and these became the lake beds.
Each one of the branches of the River in this plateau region has one or more of these expansions. On the Columbia itself are the Arrow Lakes. Kootenai Lake is an enlargement of the River of the same name. Okanogan Lake is likewise an expansion of its river. Christina Lake is the source of Kettle River. The Slocan River derives its icy torrents from Slocan Lake. Flathead, Kaniksu, and Pend Oreille lakes feed Clark's Fork, now more commonly known in its lower section as Pend Oreille River. Cœur d'Alene Lake supplies the Spokane River. Chelan pours its cold flood into the Columbia through a river of the same sweet sounding name. Wenatchee Lake gives life to the Wenatchee River.
