TOPOGRAPEY. The surface of Idaho is elevated and mostly mountainous. Lying between the main axis of the Rocky Mountains on the east and the Cascades on the west, the State embraces a por tion of the Great Basin, a plateau lying 2000 to 5000 feet above the sea, while the northern and eastern parts are traversed by mountain ranges whose loftier summits rise above the snow-line. The principal ranges. the Salmon River and Bitter Root, attain their maximum development near the eastern border, but they send out spurs which extend nearly across the whole width of the State. Northward from the Bitter Root Mountains the system of elevations is continued by the Cceur d'AI('-ne and Cabinet ranges to the Canadian frontier. In the extreme southeast are the Blackfoot, and Snake River ranges, offshoots from the main Rocky Mountain system in Wyoming. Nearly the whole area of Idaho is drained into the Columbia by the Kootenai, Clark Fork, Spokane, and Snake rivers. The
Snake, or Lewis Fork, is much the largest, its basin within the State covering more than 60, 000 square miles, and its course being about S50 miles. It receives important tributaries in the Boise, Payette, Weiser, Owyhee, Salmon, and Clearwater, but its waters are usually shallow. In its course from east to west it passes over three falls, the American, the Shoshone, and the Salmon. The Shoshone Falls have a perpendicu lar descent of nearly 200 feet. Below the Salmon Falls the river is navigable for light-draught boats to the mouth of the Powder River. In the northern part of the State there are several lake basins, including Pend Oreille, Kaniksu, and Caur d'Alene, and in the southeast on the Utah boundary, Bear Lake drains through the Bear River into Great Salt Lake.