To most Americans the southwest means the desert, and it is true that most of Arizona, New Mexico, and Utah, and portions of Colorado and southern California, are arid or semiarid lands, relieved, however, by regions of fertility and agricultural prosperity. In popular conception the desert has been the negative of all that means beauty, richness, and sublimity; it has been the synonym of poverty and death. Gradually but surely the American public is learning that again popular conception is wrong, that the desert is as positive a factor in scenery as the mountain, that it has its own glowing beauty, its own intense personality, and occasionally, in its own amazing way, a sublimity as gorgeous, as compelling, and as emotion-provoking as the most stupendous snow-capped range. The American desert region includes some of the world's greatest scenery. The Grand Canyon of the Colorado River is sunk in a plateau which, while sprinkled with scant pine, is nearly rainless. Zion Canyon is a palette of brilliant color lying among golden sands. A score of national monuments conserve large natural bridges, forests of petrified trees, interesting volcanic or other phenomena of prehistoric times, areas of strange cactus growths, deposits of the bones of monstrous reptiles, and remains of a civilization which preceded the discovery of America; and, in addition to these, innumerable places of remarkable magnificence as yet unknown except to the geologist, the topographer, the miner, the Indian, and the adventurer in unfrequented lands. This arid country consists of rolling sandy plains as broad as seas, dotted with gray sage-brush and relieved by bare craggy monadnocks and naked ranges which the rising and the setting sun paints unbelievable colors. Here and there thin growths of cottonwood outline thin ribbons of rivers, few and far between. Here and there alkali whitens the edges of stained hollows where water lies awhile after spring cloudbursts. Here and there are salt ponds with no outlet. Yet even in the desolation of its tawny monotony it has a fascination which is insistent and cumulative. But the southwest is not all desert. There are great areas of thin grazing ranges and lands where dry farming yields fair crops. There are valleys which produce fruits and grains in abundance. There are hamlets and villages and cities which are among the oldest in America, centres of fertile tracts surrounded by deserts which need only water to become the richest lands on the continent. There are regions reclaimed by irrigation where farming has brought prosperity. In other places the plateau covers itself for hundreds of square miles with scrubby pine and cedar. All in all, it is a land of rare charm and infinite variety. To appreciate a region which more and more will enter into American consciousness and divide travel with the mountains, the reader should know something of its structural history.