can be raised annually on the same land. In the selection of lands, as governed by these conditions, the higher lands will be avoided on the one hand because of the rigor of the climate; if these conditions alone governed, no settlement should be made in Utah above 6,500 feet above the level of the sea, and in general still lower lands should be used; on the other hand the irrigable lands should not be selected at such a distance from the source of the stream as to be the occasion of a great loss of water by direct and indirect evaporation. For general climatic reasons, the lands should be selected as low as possible; for economy of water as high as possible; and these conditions in the main will cause the selections to be made along the middle courses of the streams. But this general rule will be modified by minor physical conditions relating to soil and slope--soils that will best conserve the water will be selected, and land with the gentlest slopes will be taken. In general, the descent of the streams in the arid land is very great; for this reason the flood plains are small, that is, the extent of the lands adjacent to the streams which are subject to overflow at high water is limited. In general, these flood-plain lands should not be chosen for irrigation, from the fact that the irrigating canals are liable to be destroyed during flood seasons. Where the plan of irrigation includes the storage of the water of the non-growing season, by which all the waters of the year are held under control, the flood-plain lands can be used to advantage, from the fact that they lie in such a way as to be easily irrigated and their soils possess elements and conditions of great fertility. Other locally controlling conditions are found in selecting the most advantageous sites for the necessary water works. These are the chief physical factors which enter into the problem, and in general it will be solved by considering these factors only; but occasionally artificial conditions will control. The mining industries of the Arid Region are proportionately greater than in the more humid country. Where valuable mines are discovered towns spring up in their immediate vicinity, and they must be served with water for domestic purposes and for garden culture. When possible, agriculture will be practiced in the immediate vicinity for the purpose of taking advantage of the local market. In like manner towns spring up along the railroads, and agriculture will be carried on in their vicinity. For this and like reasons the streams of the Arid Region will often be used on lands where they cannot be made the most available under physical conditions, and yet under such circumstances artificial conditions must prevail.