Location of the city of Spokane] The city of Spokane, in eastern Washington, clearly illustrates the control which physical features exert upon the settlements and industries of men. The Spokane River, soon after issuing from Coeur d'Alene Lake, flows out over the volcanic plains of Washington. In the course of a few miles it descends into a shallow canon by a series of cascades and waterfalls. The water-power furnished by these falls has determined the position and growth of Spokane. The falls brought sawmills and manufacturing plants, and these in turn brought people and railroads. The city has become a great commercial centre for all the region round about. The extensive and rich mineral district upon the north, extending even into British Columbia, finds its most convenient source of supplies at Spokane. East of the city is the Coeur d'Alene mining region, while south and west are large areas devoted to the cultivation of fruit and grain. [Illustration: FIG. 120.--VIRGINIA CITY, NEVADA Supported entirely by mining] The city of Great Falls, Montana, in the Missouri River basin, is destined to become a great industrial centre, because of the presence of unlimited water-power afforded by the Great Falls of the Missouri River. No other reason would lead to the growth of a settlement at this particular spot, for boundless plains extend about it in every direction. [Illustration: FIG. 121.--BUTTE, MONTANA A city of smelters] The mining cities of the West, such as Butte, Virginia City, and Leadville, illustrate the growth of important centres of population in the vicinity of large deposits of minerals. In the case of these cities, as well as many others, there are no agricultural resources in the surrounding country to support the people gathered together here. Nearly all their food has to be shipped hundreds of miles. Cities supported by mining are less likely to be permanent than those supported by an agricultural community, by commerce, or by manufacturing. THE FOREST BELT OF THE SIERRA NEVADA MOUNTAINS No other coniferous forests in the world can compare with those covering the western slope of the Sierra Nevada and Cascade ranges. They are remarkable both for the number of species and for the size of the trees. The moderate temperature and the moist winds from the Pacific seem to offer the conditions which are best suited to the growth of cone-bearing trees. As we go northward along the coast, or ascend the mountain slopes, we find the climate growing cooler and cooler. With this changing climate the species of conifers change, for each has become accustomed to certain conditions of temperature and moisture, which it must have in order to thrive.