ROCKY MOUNTAINS 381 than 20,000 tons a month are mined at Evans- ton, Rock Springs, and Carbon, in Wyoming territory, for the use of this road alone. From Coalville, Utah, E. of Salt Lake City, no re- markable beds of coal are found along the im- mediate vicinity of the Pacific railroad to San Francisco. The scarcity of tree vegetation in the Rocky mountain area renders this coal of vital importance to the present and future in- dustries of the great west. The timber line or highest limit of tree vegetation does not vary much in the main chain of the Rocky moun- tains. In Colorado and Utah it is from 11,000 to 12,000 ft. ; in northern Wyoming and Mon- tana, from 8,000 to 11,000 ft. ; on Mt. Shasta, California, 8,000 ft. ; while as far south as San Francisco mountain, Arizona, between lat. 35 and 36, it is 11,547 ft. According to the observations made up to this time (1875), the timber line is lower to the far north. Between lat. 45 and 46 in Montana, it varies from 8,800 to 9,600 ft., while from lat. 40 to 35 it is quite uniformly from 11,000 to 12,000 ft. These statements may be regarded as approx- imately accurate, though more observations ought to be made. The mean elevation along several parallels of latitude has been ascertained approximately. For instance', along the 32d parallel, between Ion. 95 and 96, the mean elevation is 500 ft. ; the highest mean between 108 and 110, in the Sierra Madre plateau, is 6,000 ft. ; 35th parallel, first mean 650 ft, highest mean, between Ion. 107 and 109, at Zufii mountains, 7,000 ft. ; 39th parallel, first mean 1,000 ft., highest mean, between Ion. 105 and 107, in the Colorado, Sahwatch, and Elk ranges, 11,000 ft. ; 41st parallel, first mean 1,000 ft., highest mean, between Ion. 105 and 107, Laramie range and South park, 8,000 ft. ; 45th parallel, first mean 1,000 ft., highest mean, between Ion. 108 and 110, Big Horn moun- tains and Yellowstone range, 7,000 ft. ; 48th parallel, first mean 1,500 ft., highest mean, between Ion. 113 and 114, the main Rocky chain, 4,000 ft. The mean elevation of Arizona is 4,200 ft. ; of California, 2,800 ft. ; of Colora- do, 6,600 ft. ; of Idaho, 3,800 ft. ; of Montana, 3,950 ft. ; of Nevada, 4,900 ft. ; of New Mexi- co, 5,400 ft. ; of Oregon, 2,700 ft. ; of Washing- ton territory, 1,800 ft.; of Wyoming, 6,450 ft. In almost every state and territory W. of the Mississippi old lake basins exist, and from the sediments that were deposited in the bottoms of these lakes have been obtained the remains of a great variety of extinct animals, including camels, rhinoceroses, elephants, mammoths, crocodiles, huge saurians, turtles, birds, &c. In the vicinity of the Black hills of Dakota is a large area marked on the maps as Mauvaises Terres, or Bad Lands, so called on account of its ruggedness, in which thousands of extinct vertebrate animals were entombed. It was formerly a vast fresh-water lake, probably dating back at least to the beginning of the miocene period, and continuing through the pliocene nearly to the present time. During this time at least two distinct faunal groups appeared on the earth, lived out the period of their existence, and perished. The first group, which lived during the miocene period, left not a single species to the pliocene, and the fauna of the latter furnished no species for our pres- ent period. In the Sweetwater valley, near the three forks of the Missouri, in Oregon, California, Texas, New Mexico, and Colorado, are similar lake basins filled with the remains of these extinct animals. On the Laramie plains, about Fort Bridger, and far S. on Green river, are lake basins of older date, referred to the lower miocene or upper eocene, in the de- posits of which have been discovered the abun- dant remains of hundreds of extinct forms of vertebrate animals, entirely distinct from those just mentioned as of more recent age. Great quantities of fossil insects, fishes, and plants are found in these lake beds. Over 500 species of extinct forms of plants have been found, mostly in connection with the coal, indicating that at a comparatively modern period, geologi- cally speaking, this great region, occupied with mountains and barren plains, was covered with forests as luxuriant as those of the gulf states. These plants belong mostly to the early ter- tiary period. The present scarcity of timber in the eastern and central portions of the con- tinent is well known. The principal winds come from the west and northwest, and, as they pass over the summits of the different ranges of mountains from the Pacific coast eastward, laden with moisture, discharge a por- tion of it from summit to summit, until on the eastern slope the air is almost dry. The ab- sence of timber is due to the absence of moist- ure, and the inference from the fact of the luxuriant forests existing in the Rocky region during the early tertiary period is that these high summits did not then exist. The drainage areas of the west are well marked out. The Missouri river and its great branches, the Yel- lowstone and Platte, have their sources in the eastern portion of the Rocky range, and, gath- ering their waters from myriads of branches, flow at first E. across the dry plains, and gradu- ally turn S. E. and join the Mississippi ; the average rainfall in the upper Missouri drainage is 18 inches. The second drainage is that of the Arkansas further S., which rises in the Sahwatch and Park ranges of Colorado, flows S. to lat. 38 80' and Ion. 106, then bends E. and flows across the plains to unite with the Mississippi ; the average rainfall is 28 inches. The third system of drainage is still further S., that of the Rio Grande, which rises in the San Juan mountains of southern Colorado, flows S. through New Mexico and between Texas and Mexico, and empties into the gulf of Mexico; average rainfall, 16 inches. West of the last is the drainage of the great Colo- rado of the West, which, rising far north (in its branches the Green and Grand rivers), near the Yellowstone national park, flows S. and S. W. across Wyoming, Utah, and Arizona, and
