ROCKY Mountains, a great mountain chain which traverses the western part of North America, extending from about latitude 70° north to Mexico where it is continued by the Cordilleras of the Andes. These ranges are considered as forming part of one vast chain, which in South America, near the equator, attains its greatest elevation. At the Isthmus of Panama it is so low as nearly to disappear; but this is in conformity with the narrowness of the land in that quarter, and but for a short space. This slight interruption is not sufficient to entitle us to consider the continuity as broken, so that we have in the western hemisphere one great mountain range extending along both continents, from the Polar Sea on the north, to Cape Horn on the south, a distance of more than one hundred and twenty degrees of latitude, without including the windings. The eastern side of North America is traversed by a similar range of mountains called the Alleghanies, which stretch along in continued and parallel lines; but the extent, breadth, and height of the Rocky Mountains are much greater than those of the former. It is however supposed that the Rocky Mountains extend along the western part of the continent, at about the same distance from the Pacific Ocean that the Alleghanies on the eastern side extend from the Atlantic Ocean. Although but partially explored, the primitive character of the Rocky Mountains is clearly established. Their eastern sides are covered to the height of two hundred or three hundred feet, with a sandstone consisting of the ruins of the granitic rocks upon which it reposes, where disintegration was apparently effected by the gradual agency of an ancient ocean, once occupying the immense plain or basin now extending eastward from the base of these mountains to the chain of the Alleghanies. They have not however been sufficiently explored to admit our advancing any scientific details in regard to them. Many of the detached mountains and prominent peaks have not yet been either named, classified, or described. It does not appear that many of them rise above the region of perpetual refrigeration. But we have the concurrent testimony of Lewis and Clarke, as well as others, that in latitude 47° north, immense quantities of snow are on their summits, between the Missouri and Columbia, in the months of June and July. 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 grayish 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. Some of the peaks are supposed to be twelve or thirteen thousand feet in height; and the general range is considerably higher than any other in North America, with the exception of the [7:19:309]Cordilleras. It is not certainly known whether any of them are volcanic. Pumice stones are often seen floating on the Mississippi, and still oftener on the Missouri. These are generally of a reddish yellow, or flame colour, and are amongst the largest and finest specimens of this substance to be met with. Some assert that they proceed from hills of burning coal, but we never heard of hills of burning coal ever yielding such a product. They are entirely a volcanic production, and beyond doubt are either discharged from craters at present active, or are washed away by the mountain torrents, from places which were formerly the scene of such phenomena. Mica is also abundantly carried along by the waters which flow from the Rocky Mountains. The great rivers that are discharged from their eastern and western declivities wind among the mountains, the Arkansas on the east, and the Oregon or Columbia on the west, more than a hundred leagues before they issue into the plains. In following the beds of such streams, travellers pass through the range without much difficulty, so that the reports of the early travellers that they presented a high, continuous, and almost impassable barrier, are incorrect. Various leaders of expeditions have passed them at different points, and affirm that they found no such formidable and insurmountable barriers, the mention of which was wont to deter traders from attempting to cross from east to west or from west to east by this route. Following the river Platt, which is one of the principal southern branches of the Missouri, the traveller finds a road even to Lake Buenaventura, on the Pacific plains, that needs little labour to adapt it to the passage of horses and waggons. The acclivity is nowhere so great as to exceed an ascent of three degrees.

This vast range has been divided into the Rocky, Chepy-wan, and Masserne Mountains, on what ground is not exactly kno¼ r n. The ranges on the south, at the sources of the Arkansas, and running thence towards the Gulf of Mexico are called the Masserne Mountains. A single peak of this ridge, seen as a landmark for immense distances over the subjacent plains, is called Mount Pike, a very appropriate name. It is described as of incomparable grandeur in appearance, and has been differently estimated at from seven to ten thousand feet in height. On the ridges of the Rocky Mountains, the Colorado of the Pacific, the Rio del Norte of Mexico the Roche-jaune or Yellow-stone of the Missouri, and the Arkansas and Red River of the Mississippi, streams which have outlets at such immense distances apart, all have their origin. Many accounts have been given of the appearance of silver and other metals in the Rocky Mountains, but they have been too partially explored to entitle us to pronounce on the extent or value of the veins. (r. r. r.)