But little is known with certainty about the geological relations of the ore deposits of Arizona, no systematic geological studies yet having been made of the Territory as a whole, nor of any of its rich mining districts. As its name indicates it is a generally arid region, the aridity increasing from the east, westward and southward, the western part of the Territory, though traversed by the Colorado river, having the desert features that characterize the greater part of Nevada.
The northeastern portion forms part of the Colorado plateau, about one-third of which is included within the boundaries of Arizona. It is an elevated region supporting some forest growth, and as contrasted with the rest of the Territory is fairly well watered. To the southwest of the plateau region are a series of narrow isolated ranges separated by broad arid valleys, similar to the basin ranges of Nevada, with which, by their general north westerly trend, they are connected. They are made up generally of Paleozoic strata resting on a basement of crystalline rocks, and traversed to a greater or less extent by eruptives. The intervening valleys in general increase in width to the southwest, approach more and more to sea level, and Paleozoic strata disappear, the rocks being mainly granites and schists. Coal-bearing rocks appeal to be entirely wanting. Under such physical .conditions mining and pastoral pursuits are the only self-supporting industries. Two trans-