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.
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.
The Sierra Nevada is the most continuous lofty range of mountains in North America. From the great valley at its western base to the crest of the range the distance is about sixty miles. Because of the great height of the mountains, there is found within these few miles every variety of climate between the sub-tropical atmosphere of the valley, where oranges ripen to perfection, and the arctic cold of the summits, where little or no vegetation can live.