TUE ATI*.VS H1(H1I^ND8. 851 to the south of the hills which skirt the northern fuce of the Aiashin on the route from Fez to Tuiilelt. liut further on towards the south-west, occur several braachai jiffording connuunicution between the Um-er-llbia and Drau ImMns. Of thettc the most iini>ortunt ure the three Tizi n'Gluwi pusses between the Jebcl Anienier and the Jebel Tidili, which are practicable throughout the yeur. South-west of this depression rises the imposing mass of the snowy Jebel Sirwu, which is probably the culminatiug point of the Atlas system. Standing somewhat beyond the main axis, it forms u connecting link between the Great and Little Atlas, and separates the two basins of the Sus and Draa. The Mount Miltsin, surveyed in 1829 by Washington, no subsequent traveller has been able to identify by that name, which appears to be unknown to the natives. According to Ball and Hooker, it refers perhaps to a mountain '36 miles south-east of Marrakesh, whose highest peak may be about 13,200 feet. Seen from the capital, the chain of the Atlas presents the aspect of an almost unbroken rampart covered with snow till the early summer. According to Maw, the mean altitude in this section is about 1. 3,000 feet, the highest peaks rising scarcely more than 600 feet above this median line. Thus the Atlas is much inferior in extreme elevation to the Alps, although for a space of at least 100 miles it maintains a mean height greater than that of any of the Alpine ranges. The Tagherut Pass, about the meridian of Marrakesh, leading southwards to the Upper Siis Valley, stands at a height of perhaps 11,600 feet, and is approached by rugged gorges presenting great difficulties to pack animals. But 18 miles further west a large breach presents an easy passage to caravans. From the summit of the pyramidal Jebel Tiza, which attains an altitude of over 11,000 feet, a view is commanded of this narrow defile, above which it towers to a height of 4,000 feet. West of this point the main range, here running perpendicularly to the coast, still maintains an average altitude of 10,000 feet, as far as another deep gorge known as the " Tizi " or " Pass," ia a pre-eminent sense, which is crossed at an elevation of 4,000 feet by the route leading from Marocco to Tarudant in the Sus Valley. This pass, which also takes the name of Bibuw&n and Bib&n, or the " Gates," has been traversed by Lempriere, Jackson and other explorers. Beyond it the maritime Atlas still presents a superb aspect, with peaks exceeding 8,000 feet. As far as is known of its geological constitution, the Atlas consists largely of sandstones, together with old schists, limestones, and marbles, while porphyries seem to prevail in the central parts of the Deren range. Diorites and basalts occur in several places, and the Jebel Tiza, ascended by Ball and Hooker, forms a porphyry dome, which has cropped out through the mica schists. The character of the rocks in the main range is revealed chiefly by the debris scattered along its slopes, and which, according to Maw, are of glacial origin. At elevations of from 6,000 to 8,000 feet, the valleys sloping towards the Atlantic art» filled with lateral, median, and terminal moraines, apparently differing in no respect from those of the Alps. A series of hills composed entirely of glacial debris also occurs at the foot of the mountains, where they occupy a broad zone interrupted at intervals by the luteral valleys.
