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 water surface. Its extreme length, N. and S., is 484 m., and its extreme width, E. and W., is 321 m. (For map, see .)

Physiography.—With the exception of its N.E. and S.E. corners, the state lies wholly within the Great Basin, the floor of which is really a vast table-land between 4000 and 5000 ft. above the sea. This plateau, however, is not a plain, but contains many buttes and mesas and isolated mountain ranges rising from 1000 to 8000 ft. above its surface. In the N.E. an unnamed range of highlands, with an E. and W. trend, forms the water-parting between the streams tributary to the Humboldt river in Nevada and those that flow into the Snake river through Idaho and Oregon and thence to the Pacific Ocean. This range is very broken and ill-defined, with peaks often reaching altitudes of from 9000 to 12,000 ft., and with numerous spurs diverging N. and S. from the main divide. Between this ridge and the valley of the Colorado river lies all that portion of the Great Basin included within the state. The surface of this table-land is very rugged, and frequently broken by mountain ranges running N. and S. and from 5 to 20 m. wide at their bases. Intersecting the mountains are numerous ravines and passes. Between the ranges lie valleys of about the same width as the bases of the mountains. These valleys are generally level-floored, but at their borders gradually slope upward, and are filled, often to a depth of several thousand feet, with the detritus of gravel, sand and silt from the neighbouring hills. This is a region of innumerable faulted crust blocks, the elevated ones creating the N. and S. mountain ranges, and the depressed ones the valleys that lie between. It is for this reason that the mountain slopes are generally more abrupt on one side than on the other. Several valleys often unite into a large elevated plain, broken only by scattered buttes and spurs. The combined areas of the valleys and the area occupied by the mountains are about equal.

The mean elevation of the state is 5500 ft. There are 5400 sq. m. between 2000 and 3000 ft. above the sea; 11,100 sq. m. between 3000 and 4000 ft.; 23,700 sq. m. between 4000 and 5000 ft.; 29,800 sq. m. between 5000 and 6000 ft.; 30,100 sq. m. between 6000 and 7000 ft.; 7800 sq. m. between 7000 and 8000 ft.; and 2800 sq. m. between 8000 and 9000 ft. The highest point within the state is Wheeler Peak, near the centre of the eastern boundary, with an elevation of 13,058 ft.; the lowest points are along the Colorado river, where the altitudes range from 700 to 800 ft. With the exception of this dip in the S.E. corner, the entire state lies above the 2000 ft. line.

The Sierra Nevada range, which forms the western rim of the Basin, sends into the state a single lofty spur, the Washoe Mountains. At the foot of this range there is, relatively speaking, a depression, with an altitude of about 3850 ft. above the sea, which receives the drainage of the eastern slopes of the Sierra and what little drainage there is in the northern half of Nevada. From this depression eastward the general level of the plateau gradually rises to an elevation of 6000 ft. near the eastern borders of the state. The mountains also increase in height and importance as far as the East Humboldt range, a lofty mass about 60 m. W. of the Utah boundary. This range is the water-parting for nearly all the westward-flowing streams of the state, and is by far the steepest and most rugged within Nevada, a number of its peaks attaining a height of 11,000 or 12,000 ft. On its eastern slope the waters soon disappear within the bed of narrow canyons, but break out again at the foot in ice-cold springs that form the source of the Ruby and Franklin lakes; on its western side the descent is more gentle, and the waters form the South Fork of the Humboldt river. Somewhat S. of the centre of the state lie the Toyabe Mountains, with several peaks from 10,000 to 12,000 ft. in height. The waters on the eastern slopes flow into the Smoky Valley; those on the other side assist the neighbouring Shoshone Mountains in feeding the Reese river, which flows N. toward the Humboldt, but seldom has sufficient volume to enable it to reach that stream. About 100 m. E. of the California boundary lies a third important range, the Humboldt Mountains, whose highest point (Star Peak) is 9925 ft. above the sea. Owing to their great height these three ranges receive heavier rainfall than the surrounding country and are feeders to the northern valleys, which constitute the chief agricultural region of the state. Many of the block mountains of the Great Basin are of complicated internal structure, showing rocks of all ages—slate, limestone, quartzites, granite, multi-coloured volcanic rocks, and large areas of lava overflow.

From the valley of the Humboldt river southward the plateau gradually rises until the divide between this stream and the Colorado

river, in the vicinity of the White Pine Mountains, is reached. From this point there is a fall, which is gradual as far S. as the 38th parallel, and then more abrupt. Thus at Pioche the altitude is 6100 ft., at Hiko 3881 ft., at St Thomas 1600 ft., and at the Eldorado Canyon 828 ft. The region of the Colorado river is largely desert, with occasional buttes and spurs.

Rivers and Lakes.—There are three drainage systems within the state. North of the Humboldt Valley an area of about 5000 sq. m. is drained by the Owyhee, the Little Owyhee, the Salmon and Bruneau rivers, whose waters eventually reach the Pacific Ocean. Below this region flow the streams of the Great Basin, none of which reach the sea, but either terminate in lakes having no outlet or else vanish in sloughs or “sinks.” Small streams often sink from sight in their beds of gravel, and after flowing some distance underground, reappear farther on. Of the basin streams the Humboldt is the most important. Rising in the N.E., it flows in a tortuous channel in a general S.W. direction for 300 m. and drains 7000 or 8000 sq. m. This stream empties into the Humboldt lake, the overflow from which goes into the so-called Carson Sink. At no part of its course is it a large river, and near its mouth its waters are sub-alkaline. The Truckee river flows with more vigour, having its source in Lake Tahoe, in California, at an altitude of 6225 ft., and entering the Carson river through an irrigation canal completed in 1905; before this date it flowed into Pyramid Lake and Lake Winnemucca in the depression at the foot of the Sierra Nevada. A short distance to the S. two other streams, the Carson and the Walker rivers, receive their waters from the eastern slope of this range and empty into lakes bearing their names. Of this group of lakes in the western depression, Pyramid Lake is the largest, being 33 m. long and 14 m. wide. Fed by the same stream is its western neighbour, Lake Winnemucca, a much smaller body. The waters of these two lakes are only moderately saline and may be used for live-stock but not for human beings. Next in importance is Walker lake, 33 m. long and 6 or 7 m. wide, whose waters are strongly saline. On the western boundary, and partly included within the limits of Nevada, is Lake Tahoe, 20 m. long and 10 m. wide, which is 1645 ft. deep at its centre and whose waters have never been known to freeze, notwithstanding the lake’s elevation. The topography and the climate of Nevada have led to the formation of two kinds of lakes, the ephemeral and the perennial. The perennial lakes, such as those just described, hold their waters for years and perhaps centuries; but the ephemeral lakes usually evaporate in the course of the summer. The latter class is formed by waters that fall on the barren mountain-sides and rush down in torrents, forming in the valleys shallow bodies of water yellow with the mud held in suspension. The largest of these occurs in the Black Rock Desert, in the N.W., and at times is from 450 to 500 m. in length and only a few inches deep. Such bodies often become nothing but vast sheets of liquid mud, and are called “mud lakes,” a term most frequently applied to the sloughs fed by Quinn’s river. When the waters evaporate in the summer they leave a clay bed of remarkable hardness, which is sometimes encrusted with saline matter of a snowy whiteness and dazzles the eyes of the traveller. When such is the case the beds are called “alkali flats.” During the glacial period many of the Nevada lakes attained a great size, several of them uniting to form the ancient “Lake Lahontan,” in north-western Nevada. As these lakes shrank after the return of an arid climate, they left elevated beaches and deposits of various minerals, which mark their former extent. Both hot and cold springs are numerous, with temperatures ranging from 50° to 204° F.

In the S.E. corner of the state is the third drainage system. Here the Virgin river enters the state after crossing the N.W. corner of Arizona and flows S.W. for 60 m. until it joins the Colorado river. The latter stream flows for 150 m. along the S.E. boundary towards the Gulf of California.

Fauna and Flora.—Of native animals the varieties are few and the numbers of individuals small. In the arid valleys Coyotes (prairie wolves), rabbits and badgers are found. Large animals, such as the black and the grizzly bear, and deer are found on the slopes of the Sierra Mountains, and antelope, deer and elk visit the northernmost valleys in the winter. At rare intervals antelope appear in the southern deserts. Here also are found the sage thrasher, Le Conte’s thrasher, the Texas nighthawk, Baird’s woodpecker, and the mourning dove. Certain species of grouse are common high in the timbered mountains. Several varieties of water-fowl, especially curlews, pelicans, gulls, ducks, terns, geese and snipe, are found in the vicinity of the lakes. The Truckee river and the western lakes abound in trout and black bass. Of the reptiles the leopard lizard and gridiron-tailed lizard, the “chuck-walla” (Sauromalus ater), the rattle-snake, and the horned toad are the most numerous. The “black mouse” or Carson field mouse (Microtus montanus) is found throughout Nevada, as well as in Utah, north-eastern California, and eastern Oregon; it multiplies rapidly under favourable conditions, and at times causes serious injury to crops.

The flora of Nevada, although scanty, varies greatly according to its location. With the exception of the alkali flats, no portion of the desert is devoid of vegetation, even in the driest seasons. In the Washoe Mountains, as in the rest of the Sierra Nevada range, there is a heavy growth of conifers, extending down to the very valleys; but in many places these mountains have been almost