teaus, and valleys, with a general slope to the westward.
Of the many mountain passes, 13 are over 10,000 feet in altitude, the Argentine reaching 13,100 feet. The great valleys or parks above mentioned inclosed by mountains are a distinguishing feature of the scenery. San Luis Park contains 8000 square miles (the most level land in the State, though elevated 7500 feet). Other important valleys are the Arkansas (q.v.), Rio Grande (q.v.), White Grande, and Gunnison. There are over 39,964 square miles of park and valley lands. The North Platte and South Platte unite to form the Platte of Nebraska. The source of the South Platte is 11,176 feet above tide, and its fall in the short distance to Denver is 6000 feet. The Arkansas rises 10,176 feet above the sea in the west central part of the State, rapidly falling to 7877 feet, and flows southeast and east into Kansas, passing through the ‘Royal Gorge’ cañon, 3000 feet deep. The Rio Grande rises in the Saguache Range and flows through San Luis Park into New Mexico. The largest streams on the west are the Yampah and White, tributaries of the Green River, Utah; the Grand, one of the main affluents of the Colorado; and its tributaries, the Gunnison, Dolores, and San Miguel. None of these streams is navigable. No other State contains the headwaters of so large a number of rivers. From near the centre of the Commonwealth rivers flow outward in many directions, and the waters are distributed in almost equal proportions to the Atlantic and to the Pacific Ocean. The only lake of consequence, San Luis, about 60 miles long and a quarter of a mile wide, lies in San Luis Park, and receives several small streams, but has no visible outlet. The lofty peaks and deep-lying parks are equaled in grandeur by the river cañons; those of the Arkansas, Grand, Black Cañon of the Gunnison, Little Colorado, and Uncompahgre, varying in depth from 1000 to 3000 feet. ‘The Garden of the Gods’ and ‘Monument Park’ are filled with castellated buttes that rise out of green meadows, or with grotesquely shaped pillars and towers of red sandstone, carved by erosion. A large area in Saguache County has been reserved as a State park.
Climate and Soil. The high altitude of the State premises a cool temperature; but, save on the higher elevations, extremes are rare, the climate being generally mild and remarkably salubrious. The days are sometimes hot, but the nights are cool and free of humidity. The yearly mean temperature at Denver (5182 feet) in January is 28.2° F.; July, 71.7° F.; Pueblo (4675 feet), January, 28.7° F.; July, 74° F. Frosts do not occur until late in the autumn and disappear early in the spring; but snows are heavy and lasting on the mountains, yet in the low levels are seldom deep, and very soon melt away.
The mean annual rainfall for the State is 14.8 inches. This fall, although light, is well distributed, and in many sections of the ‘Great Divide’ cereals are grown without irrigation. The heaviest rainfall is in the mountains. At Pike's Peak the mean precipitation is 29.7 inches; at Climax (10,304 feet), 34.8 inches. On the plains it is much less. At Denver the mean fall is 14.3 inches; at Colorado Springs (6032 feet), 14.5 inches; at Las Animas (3899 feet), 11.0 inches.
The atmosphere is so dry and pure that fresh meats are preserved by the simple process of drying. The late summer is almost rainless. The climate and air of Colorado are considered of great benefit to asthmatic and pulmonary sufferers, and the charming parks are likely to become the great natural sanatoriums of North America. Thousands of people flock to Denver, Colorado Springs, and other sections of the State to regain their health. The various mineral springs are also adjuncts to the remedial nature of the climate. The hot sulphur springs of Middle Park and Wagon-Wheel Gap, and the hot iron and soda springs of Manitou, Cañon City, Glenwood Springs, and Idaho Springs are famous.
The soil along the river-bottoms is largely alluvial. In the eastern part of the State it is a light loam. In some places siliceous and micaceous substances abound, while here and there clay formations crop out. The forests of the State cover about 10,500,000 acres of land, and are restricted mainly to the mountains.
For flora and fauna, see the paragraphs under Rocky Mountains and United States.
Geology. The geological structure of Colorado is extremely varied. In the less elevated region east of the Rocky Mountains, Cretaceous and Tertiary strata are exposed in nearly horizontal position and in great thickness. On the eastern flank of the Rocky Mountains these strata are succeeded by older sediments, including Silurian, Carboniferous, and Jura-Trias, which are upturned and in places intensely folded. The axis of the mountain system is formed by granites and other igneous rocks, more or less metamorphosed, of Archæan age, with a great variety of later volcanic rocks. On the western edge of the system Paleozoic strata again appear, and are overlaid in the extreme western part of the State by Cretaceous, Jura-Trias, and Tertiary beds. The Carboniferous rocks, unlike those along the Appalachian Mountains, inclose no coal-seams. Coal occurs, however, in great abundance in the Laramie group of the Cretaceous. The great upheavals accompanied by volcanic activity along the Rocky Mountains have favored the formation of ore deposits, some of which are of great economic importance. Cripple Creek on the slopes of Pike's Peak. Leadville, Boulder, Ouray, Rosita, Silverton, Gilpin, Lake City, and Gunnison are important centres of gold, silver, and lead mining. Copper, zinc, manganese, and iron ores also occur in extensive deposits.
Mining. Colorado is best known as a mining State, ranking first in the mining of precious metals, and surpassed only by Pennsylvania in the total mineral output. This is due largely to the State's great productivity of gold and silver ores. Colorado produces twice as much of these two metals as any other State, and more than one-third of the total output of the United States. The production of gold increased in value from $4,150,000 in 1889 to $28,760,000 in 1900. In 1897, for the first time, the gold product exceeded that of California, while the output for 1900 was twice that of the rival State. Silver-mining reached its maximum output in 1892, and then decreased until 1895: since which time it has slightly increased. The com-
