ATLAS, a celebrated but little known mountain chain of Northern Africa, between the great desert of Sahara and the Mediterranean. Geographers differ as to the extent of this range, some considering it to extend from Cape Ghir on the Atlantic to Cape Bon, the north-east point of Tunis; while others, under that name, include the whole mountain system between Cape Nun and the greater Syrtis. In this latter sense it forms the mountain-land of the countries of Morocco, Algeria, Tunis, and Tripoli. It is composed of ranges and groups of mountains, inclosing well-watered and fertile valleys and plains, and having a general direction from W. to E. The highest peaks are supposed to attain an elevation of nearly 15,000 feet; and although none of them reach the height of perpetual snow, some of their loftiest summits are covered with snow during the greatest part of the year. Mount Miltin, 27 miles S.E. of the city of Morocco, was ascertained by Captain Washington to be 11,400 feet high. The greatest heights are in Morocco, from which point they appear to diminish in elevation as they extend towards the E. These mountains, except the loftiest summits, are, for the most part, covered with thick forests of pine, oak, cork, white poplar, wild olive, and other trees. The inferior ranges seem to be principally composed of secondary limestone, which, at a greater elevation, is succeeded by micaceous schist and quartz-rock; and the higher chains are said to consist of granite, gneiss, mica-slate and clay-slate. The secondary and tertiary formations are frequently disturbed and upraised by trap-rocks of comparatively modern date. Lead, iron, copper, antimony, and sulphur, occur frequently here; and in the Morocco portion of the range, mines of gold and silver are said to exist. In the Algerian division are mines of copper, lead, silver, and antimony.