Page:Popular Science Monthly Volume 86.djvu/253

Rh area are sharply marked by the abruptly rising wall of the bordering mountain ranges. The limits to the east are not so clearly marked, being considered by some to reach the eastern border of the state; by others they are held to extend less than half the distance to the Colorado River.

The elevation of the desert floor ranges from 2,000 ft. approximately to 4,000 ft. above the sea, in sharp contrast to the basin of the Salton Sea, which extends below the level of the ocean a short distance to the south. The topography of the region is characterized by great stretches of open plains many miles in extent, over which scattered mountain peaks or ranges are distributed with little suggestion of order in their arrangement.

The total rainfall of the desert amounts only to a few inches per year. Living streams are rare, and travel in all of this region is necessarily limited by accessibility of the few localities at which potable water can be obtained. Rain falls largely in the middle of the winter season, and throughout the greater part of the year there is no precipitation. The water at times comes with a rush, flows off rapidly as floods, and sometimes causes considerable damage to artificial obstacles in the path of the current. With the exception of the Mohave River, which runs a thin superficial stream for a considerable portion of the year, there are very few points at which a supply of water can be obtained on the surface. Investigation has shown that artesian water is available over certain areas, and agriculturists have operated to some extent by irrigation with water obtained from wells.

The diminished rainfall, the unhindered influence of a brilliant sun and the moderate altitude have given to the Mohave a distinctly arid climate; and with the climate go all of the accompanying characteristics of life, of erosion and deposition, and of the peculiar land forms of an arid country.

The vegetation of the Mohave area is at the present time limited mainly to desert types, the contrast with the flora beyond the ridge immediately to the west being very marked. In crossing the Tehachapi Range from the Great Valley of California to the Mohave one finds the valleys of the western side thickly studded with oak, sycamore, and willow, and the hills are carpeted with grass. On the eastern slope the whole aspect of the vegetation changes suddenly, as if one were entering a foreign land. The yuccas and the creosote bush replace oak and grass, and the oddly outstretched arms of the Joshua trees seem everywhere raised up as if to attract attention. Plants of arboreal type are rare, and, excepting a few junipers, the yuccas furnish the only trees. Creosote bushes are generally present, but are sometimes sparingly represented. Perhaps to show that under adverse conditions nature means only to be just and not unkind, the spring and early summer find the