'376 ROCKY MOUNTAINS is related in the same way, showing that they are all the product of one uniform cause. The Black hills are in Dakota territory, ex- tending into Wyoming, E. of the Big Horn range, between lat. 43 and 45, and Ion. 103 and 105, and are quite isolated from the main chain ; they are a sort of huge puff from out of the plains, occupying an area of about 100 m. in length and 60 m. in breadth. The mass is elliptical, and the major axis trends about 20 W. of N. The base of the hills is 2,500 to 3,000 ft. above the sea, while the highest peaks are. not more than 6,000 or 7,000 ft. They are covered with a dense growth of pine, which gives them a black appearance in the distance. The two forks of the Cheyenne em- brace the Black hills, and have their origin in the plains far to the, westward ; hence they give rise to no important stream. The nucleus of the hills is composed of feldspathic granites and slates surrounded with the full series of the sedimentary strata known in this region, inclining at various angles from the central mass, as if originally their sedimentary beds had formed an unbroken communication across the entire area ; or in other words, they form a fine example of an anticlinal on a large scale. There is some good pasture and timber land in the vicinity of the Black hills, but the mineral resources have been extravagantly overrated. Like the Black hills, the Big Horn range does not give rise to any important stream. The largest river in this region, which gives name to the mountains, rises in the Wind River range, passes through the Big Horn moun- tains, and flows into the Yellowstone about 70 m. to the northward. The central mass of this range is coarse granite also, with a series of Silurian, carboniferous, Jurassic, cretaceous, and tertiary strata, inclining from the sides. The highest peak is Cloud peak, supposed to be about 7,300 ft. We may separate the nuclei of the mountain ranges roughly into three divi- sions : those with a granitic and those with an igneous nucleus, and those with a combination of the two. Usually the volcanic material has come up through the granitic mass and flowed over it, in some instances almost entirely con- cealing it. Still further W. is the Wind Riv- er chain, the loftiest peak of which Fremont, whose name it bears, found to be 18,570 ft. The central mass of the mountains is also a coarse, massive granite, overlaid by metamor- phic slates, in which the gold mines are found. This chain forms a portion of the main divide. To the north of the Wind River mountains, in the N. W. corner of Wyoming territory, is one of the most interesting and remarkable regions in the world. The Yellowstone na- tional park occupies an area of 65 m. from N. to S. and 55 m. from E. to W., or 3,575 sq. m., the whole of which is more than 6,000 ft. above the sea. The Yellowstone lake, the source of the Yellowstone river, is 22 m. long and 12 to 15 m. wide, and is 7,788 ft. above the sea. The ranges of mountains that hem it in on every side are all of volcanic origin, and are covered with snow all the year. There is frost here every month of the year, and in June, July, and August the thermometer fre- quently sinks to 25. (See WYOMING.) In a geographical point of view this park will al- ways be of the highest interest, as constituting the apex of the continent, and giving origin to three of the largest rivers in North America. On the N. side are the sources of the Yellow- stone; on the W. those of the three forks of the Missouri ; on the S. W. and S. those of Snake river, flowing into the Columbia and thence into the Pacific ocean, and those of Green river, rushing southward to join the great Colorado, and finally emptying into the gulf of Califor- nia; while on the E. side are the numerous sources of Wind river. Southward from the Wind River chain, the mountainous character of the divide is interrupted for a short dis- tance by comparatively level plateaus, while to the east are the Laramie plains, bounded by a comparatively low range, of which Laramie peak is about 10,000 ft. high, and, on account of its isolation and the insignificance of the mountains in the vicinity, is one of the great landmarks of the west. Still further S. are the remarkable mountain regions and the parka of Colorado. The Colorado or Front range rises up before the traveller on the plains like a gigantic wall, with Long's peak at the north and Pike's peak at the south, as high bastions. West of this range are three great depressions, North, Middle, and South parks. In the Front range are several peaks over 14,200 ft. high (according to the latest surveys) : Long's, 14,- 271 ft. ; Evans, 14,330 ft. ; Rosalie, or Rosa, 14,340 ft. ; and Gray's and Torrey's, twin peaks with an interval of less than a mile, 14,341 and 14,836 ft. In this range are the oldest known silver and gold mines of Colorado. On the W. side of the parks is the Park range, in which are several peaks of over 13,000 ft., and a few, as Mt. Lincoln, of over 14,000 ft. In this range are many important gold and silver mines. From Mt. Lincoln, on the W. side of the South park, one can look down into the valley of the Upper Arkansas and across to the Sahwatch range, one of the most remarkable in the west. At its N. end is the Holy Cross group, in lat. 89 30', Ion. 106 33', composed of gneiss and coarse massive granite. For 80 m. to the southward this range literally bristles with peaks, many of which rise over 14,000 ft. ; Harvard, Yale, and Princeton are respectively 14,384, 14,150, and 14,199 ft., and many others are over 18,000 ft. The rocky mass is mostly granite, intersected with igneous dikes. The general trend of this range is about 20 W. of N., and it forms one of the most gigantic anti- clinals in the entire Rocky mountain region. Vast ranges of massive granitic rock, capped with limestone and sandstone, incline from either side, with broad valleys intervening. The proofs of ancient glacial action on both sides of the range are wonderful. In the val-
