ATLAS MOUNTAINS, the name for the mountain chains more or less parallel to the coast of north-west Africa. They ex tend from Cape Nun (west) to the Gulf of Gabes (east), a dis tance of 1,5oom., traversing Morocco, Algeria and Tunisia. They are bounded on the north by the Mediterranean sea and on the south by the Sahara desert. They can be roughly divided into two main chains: (I) the Maritime Atlas from Ceuta to Cape Bon; (2) the inner and more elevated ranges, which, starting from Cape Ghir, run south of the coast ranges and are separated from them by high plateaux. The western inner ranges, described here as the Moroccan ranges, are the most important of the whole system. The Maritime Atlas and the inner ranges in Algeria and Tunisia are treated under the heading Eastern Ranges.
I. The main range (the Great Atlas) occupies a central posi tion and is by far the longest and loftiest chain. It has an average height of over i I,000ft. The slopes are precipitous toward the Atlantic but long and gradual toward the Dahra district of the north-east. Only one or two peaks reach the line of perpetual snow, but several summits are snowclad during most of the year. The northern sides and tops of the lower peaks are often cov ered with dense forests of oak, cork, pine, cedar and other trees, with walnuts up to the limit of irrigation. Their slopes enclose well-watered valleys of great fertility, in which the Berber tribes cultivate tiny irrigated fields, their houses clinging to the hill sides. The southern flanks, being exposed to the hot dry winds of the Sahara, are generally destitute of vegetation.
At several points the crest of the range has been deeply eroded, thus forming devious passes. The central section, culminating in Tizi n 'Tagharat or Tinzar, a peak estimated at 15,000f t. high, maintains a mean altitude of ii,600ft., and from this great mass of schists and sandstones a number of secondary ridges radiate in all directions.
For a distance of loom. the central section nowhere presents any passes accessible to caravans, but in the south-west two gaps afford communication between the Tensift and Sus basins, those respectively of Gindafi and Bibawan. A few summits in the ex treme south-west in the neighbourhood of Cape Ghir still exceed and although less majestic, the average height of this district is greater than that of the Alps. The most imposing view is to be obtained from the plain of Marrakesh, immediately north of the highest peaks. Besides huge masses of old schists and sand stones, the range contains extensive limestone, marble, diorite, ba salt and porphyry formations, while granite prevails on its south em slopes. The presence of enormous glaciers in the ice age is attested by the moraines at the Atlantic end, and by other indica tions farther east. The best-known passes are : The Bibawan in the upper Wad Sous basin (4, I 5of t.) ; (2) the Gindafi, giving access from Marrakesh to Taroudant, rugged and difficult, but low; (3) the Tagharat, difficult and little used, leading to the Dra'a valley (11,484ft.); (4) the Glawi (7,600ft.) ; (5) Tilghemt (7,25oft.), leading to Tafilelt.
2. The lower portion of the Moroccan Atlas (the Middle At las), lying north of the Great Atlas, is crossed by the pass from Fez to Tafilelt. Both slopes are wooded, and here only in Morocco does the lion still survive. From the north this range, which is only partly explored, presents a regular series of snowy crests.
3. The Anti-Atlas (Jebel Sarro or Lesser Atlas) runs parallel to and south of the central range, and has a mean altitude of 5,000ft., although some peaks and even passes exceed 6,000ft. The relation of the Anti-Atlas to the Atlas proper at its western end is not clear. Two more or less parallel ranges of less im portance complete the western system: 4. The Jebel Bani, south of the Anti-Atlas, a low, narrow rocky ridge with a height of 3,000f t. in its central parts ; and 5. The mountains of Ghaiata, north of the Middle Atlas, a series of broken mountain masses from 3,00o to 3,5ooft. high, to the south of Fez, Taza and Tlemsen.
The southern or main range of the eastern division, the Sa haran Atlas, is linked by secondary ranges to the mountains of Morocco. The Saharan Atlas is essentially one chain, though known under different names : Jebel K'Sour and Jebel Amour on the west, and Jebel Aures on the east. The central part, the Zab mountains, is of lower elevation, the Saharan Atlas reaching its culminating point, Jebel Chelia (7,61 I f t. above the sea) , in the Aures. This range sends a branch northward which joins the Mejerda range of the Maritime Atlas, and another branch runs south by Gafsa to the Gulf of Gabes. Here Mt. Sidi Ali bu Musin reaches a height of 5,70oft., the highest point in Tunisia. In the Saharan Atlas the passes leading to or from the desert are numerous, and in most instances easy. Both in the east (at Batna) and the west (at Ain Sefra) the mountains are traversed by railways, which, starting from Mediterranean seaports, take the traveller into the Sahara.
The ancient caravan route from Mauretania to the western Sudan crossed the lower Moroccan Atlas by the Pass of Tilghemt and passed through the Oasis of Tafilelt, formerly known as Sajil masa, on the east side of the Anti-Atlas. The Moroccan system was visited, and in some instances crossed, by various European travellers carried into slavery by the Salli rovers, and was tra versed by Rene Caine in 1828 on his journey from Timbuktu, but the first detailed exploration was made by Gerhard Rohlfs in 1861-62. Previous to that almost the only special report was the misleading one of Lieut. Washington, in 1837.
In 1871 the first scientific expedition, consisting of Dr. (after wards Sir) J. D. Hooker, John Ball and G. Maw, explored the central part of the Great Atlas. They ascended by the Ait Mizan valley to the Tagharat pass (11,484f t.), and by the Amsmiz val ley to the summit of Jebel Tezah (11,9 7 2 f t. ). Dr. Oskar Lenz in 1879-80 surveyed a part of the Great Atlas north of Tarudant, determined a pass south of Iligh in the Anti-Atlas, and penetrated thence across the Sahara to Timbuktu. He was followed in 1883 84 by Vicomte Ch. de Foucauld, whose itineraries included parts of the first and middle ranges; three routes over the Great Atlas, which was, moreover, followed along both flanks for nearly its whole length;' and six journeys across the Anti-Atlas, with a general survey of the foot of this range and several passages over the Jebel Bani. Then came Joseph Thomson, who explored some of the central parts, and made the ascent of Mt. Likimt, 13,15of t. (1888) ; and Walter B. Harris, who explored some of the south ern slopes and crossed the Atlas at two points during his expedi tion to Tafilelt in 1894. In and again in 1905 the marquis de Segonzac, a Frenchman, made extensive journeys in the Mo roccan ranges. A member of his expeditions, de Flotte Rocque vaire, made a triangulation of part of the western portion of the main Atlas. Since that time numerous travellers and scientists have visited and explored the mountains. (See also MOROCCO, ALGERIA, TUNISIA and SAHARA.) Ch. de Foucauld, Reconnaissance an Maroc 1883-84 (Paris, i888) ; Hooker, Ball and Maw, Morocco and the Great Atlas (London, 1879), these two books are still very useful; W. B. Harris, Tafilelt, a Journey of Exploration in the Atlas Mountains, etc. (London, 1895) ; B. Meakin, The Land of the Moors (London, 1901) ; M. W. Hilton Simpson, Among the Hill Folk of Algeria (1921) ; V. C. S. O'Connor, A Vision of Morocco (1923) ; C. E. Andrews, Old Morocco and the Forbidden Atlas (1924) ; N. Slouschz, Travels in North Africa (1927) ; E. A. Powell, In Barbary (1927) ; and for the geology see Louis Gentil, Mission to Segonzac, etc. (Paris, 1906), and Le Maroc Physic. (Paris, 1912).
(J. I. P.) ATLAS PORTLAND CEMENT COMPANY had its origin in the Mathey Cement company which was incorporated in New York State in 1885. This company underwent various corporate changes that in 1889 developed in embryo the present organization. In 1888 property at Coplay, Lehigh county, Pa., was acquired, and in 1889 a beginning for Atlas cement was made with a mill turning out 200 barrels a day. In 1896 a sec ond mill, in Northampton county, Pa., began operations with a capacity of 3,00o barrels a day. In 1900 a third mill started opera tion with a capacity of io,000 barrels a day, and in 1905 a fourth mill, with a like capacity got under way at Northampton, Pa., 1905. The Company in 1905 opened two additional mills with a combined capacity of about I 2,000 bbls. a day. Other acquisitions followed until, in 1930, it had plants producing 20,000,000 bbls. annually. On January 9, 1930 the Atlas Portland Cement Com pany was united with the Universal Portland Cement Company, under the name of the Universal Atlas Cement Company, a sub sidiary of the United States Steel Corporation. The Universal Port land Cement Company had its beginning in 1896 as the Cement Department of the Illinois Steel Company, its original plant in Chicago producing Soo bbls. of cement daily. The Company con tinued to grow until in 1930, its total producing capacity was 15, 000,000 bbls. annually. The capacity of the Universal Atlas Cement Company is in excess of 35,000,000 bbls., being the larg est cement producer in the world. It manufactures Atlas and Uni versal (gray) Portland cements, Atlas White and Atlas Water proofed White Portland cement and Atlas Lumnite cement.
(B. F. A.)