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