210 NORTH-WEST AFRICA. last named lies the deep gorge of Shabet-el-Akra, excavated by the waters of the "NVcd Agriun to a depth of many hundred feet, and utilised by one of two carriage routes which cross the Babor range in the direction of the coast. The hilly region fltretchino" thence northwards to Jijeli and Collo is one of the least accessible in Algeria. South of the Jurjura and Babor systems, the Jebel Dira is continued by the Biban, or " Gates," a name due to the breaks through which, during the rainy season, the surface waters of the plateau find an outlet to the plains. Amongst these breaks noteworthy are the " Iron Gates," known respectively as the Great and the Little Gate, the former of which is now traversed by the route and the railway between Algiers and Constantine. The Little Gate, lying nearly 3 miles farther east, also forms an easy roadway, and here the geologist may conveni- ently study the black limestone rocks, which assume the appearance of colossal organs, buttresses, ramparts, and other fantastic shapes. East of the Gates rises the Jelwl Sattcra, an extinct volcano, whose crater is still strewn with scorioB and pumice. The highlands lying south of the Biban range have been broken by erosive action into numerous distinct groups encircled by almost horizontal depressions. Here the loftiest summit is the Jebel Maadhid (1,630 feet), beyond which point the heights gradually fall, while the intervening depressions merge in plains extending towards Constantine. In the neighbourhood of this town the hills reappear, but SL'ldom attain an elevation of much over 3,000 feet. Towards the north-east the northern border ranges terminate in the bold headland of Edugh (3,350 feet), on whose last spur stands the citadel of Bona. Cape Garde, which encloses the road- stead, takes the normal direction from south-west to north-east, while the Cape de Fer headland projects farther west in the contrary direction. But like the Collo hills, this bluff is of volcanic origin, forming no part of the general orographic system. The ranges skirting the upland plateaux on the south begin on the Marocco frontier, some 20;) miles from the coast. North of Figuig, the highlands separating the plateaux from the Sahara form a series of small groups falling gradually towards the north-east, and collectively known as the Ksur range, from the now partly destroyed strongholds guarding their passes. But each group, called by the Arabs Kimi ("Fort"), or KeJaa ("Castle"), has its special designation, and in fact several present the appearance of fortification". The chief summits are the Maiz (0,170 feet), north-west of Figuig; Beni-Smir (0,600) north of the same oasis; Jebel Mzi (7,320) south of Ain-Sfissifa, all commanding a view of the sandy wastes of the Sahara. Beyond the Ksur groups several parallel ridges, such as the Bu-Derga, Ksel, and Tarf, form the westcu-n section of the Jebel Amur, or " Mountain " in a pre- eminent sense, both terms having the same sense, the first in Arabic, the second in Berber. Viewed as a whole, the Amur forms a plateau cut up by torrents flowing some to the Algerian shotts, others to those of the Sahara. It thus constitutes a true waterparting between the Mediterranean basin and those of the Jeddi and
