called also, but not so generally, Chippewagan Mountains, the principal range in North America, extending from the shore of the Arctic Ocean, near Mackenzie Bay, about 70° N. Lat., in a S.S.E. direction, through the continent. The name is sometimes applied to the whole range of mountains so far S. as 19° N. Lat., where they are interrupted by the low lands in Nicaragua and the isthmus of Panama; but, properly speaking, the Cordilleras of Mexico do not form part of the Rocky Mountains, nor are they indeed immediately connected with that chain. In its stricter application, the term designates only the mountains which traverse the British possessions and the United States, and terminate a few miles S.E. of Santa Fe in the territory of New Mexico. They form a part of the great mountain chain, which, with a few interruptions and under various names, traverses the whole of the Western Continent from very nearly its extreme northern to its extreme southern point, forming the watershed between the Atlantic and Pacific oceans, though much nearer the latter than the former. The northern range, however, does not approach so near to the sea as the southern range does at almost all parts of its course. Near the southern extremity of the Rocky Mountains, and not far from the source of the Arkansas River, is a knot of mountains from which various chains diverge in different directions,—the Sierra de San Juan, stretching S.W. towards the Sierra Madre; the Rocky Mountains, on the one hand N.W., and on the other S.E.; and the Medicine Bow Hills towards the N.E. The main ridge continues in a single almost unbroken line as far northwards as Mount Brown, about 53° N. Lat., where a lower ridge diverges and runs nearly parallel to the principal chain, a short distance to the W. This second chain is known by the name of the Peak Mountains, and sends off another range, also parallel to the two former, and still nearer the coast. The loftiest summits of the Rocky Mountains throughout the greater part of their length rise from 10,000 to 14,000 feet; but N. of Mount Brown, where the divergence takes place, they begin to diminish in altitude, and towards the extremity their average height is not more than 2000 feet. The highest elevation in the southern part of the range is Fremont's Peak, 13,570 feet above the sea. Farther N., between Lat. 46° and 48°, there is a considerable depression; but beyond this there is another elevated portion, where Mount Hooper (15,690 feet) and Mount Brown (about 16,000 feet) rise. Some peaks are said to attain the height of 18,000 feet above the sea. The mountains are traversed by several passes. Among these are South Pass, immediately south of Fremont's Peak, forming the principal route to the Mormonite settlements in the W.; Lewis and Clark's Pass, near the head waters of the Missouri, 6323 feet high; and Athabasca Portage, between Mounts Hooper and Brown, about 7300 feet. The two former of these have been proposed as railway routes across the North American continent. Very recently several additional passes have been discovered by Captain Palliser, some account of which will be found in the Proceedings of the Royal Geographical Society for Feb. 1859.

As the range has been but imperfectly explored, little is known of its geological character. There seems, however, no reason to doubt that its structure is primitive. The upper portions consist of granite and gneiss, rising up in bare, rugged, and precipitous peaks. This formation is overlaid in the higher slopes with limestone, and in the lower with sandstone. Volcanic rocks exist in some places; and there is said to be a volcanic region, 100 miles in length, near Fremont's Peak, containing several burning mountains now in activity. Hot springs are found not only here, but in several other places on both slopes of the range; one of the most remarkable being that called the Steamboat Spring, sending up the water to the height of 3 feet. The eastern declivity of the mountains is in general much more precipitous than the western, which in some places rises to a series of terraces and inferior ridges. Many of the summits are covered with perpetual snow. They are seen like a vast rampart rising from the grassy plains, stretching from north to south. Sometimes their aspect is that of continued ranges of a greyish colour, rising into the blue of the atmosphere above the region of the clouds. A great number are black, ragged, and precipitous; and their bases are strewn with immense boulders and fragments of rock, detached by earthquakes and the elements. From this iron-bound and precipitous character they probably received the appellation of Rocky Mountains. They are for the most part but thinly covered with vegetation, a few scrub pines and other trees being all that clothes the lower slopes; but in some places there are magnificent forests. The rivers that take their rise in the Rocky Mountains fall into three great divisions: those which flow into the Arctic Ocean or Hudson's Bay, of which the Athabasca and the Saskatchewan are the chief; those which flow into the Gulf of Mexico, of which the Missouri is the largest; and those which join the Pacific or the Gulf of California, especially the Columbia and Colorado.