Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/272

Rh 250 AFRICA [PHYSICAL 1869 by the traveller Rohlfs, were found to be everywhere from 100 to 150 feet beneath the level of the Mediterranean; and M. de Lesscps, in conducting a survey from the Egyptian side, found the eastern part to be much beneath the level of the Nile. Here then must be one of the greatest areas of depression in the land of the globe, com parable with that which surrounds the Caspian Sea. This depressed region is again followed by a table-land of con siderable extent and width, extending from the Gulf of Kabes in a southerly direction, along the Tripoline shores, and probably traversing, in the same direction, the Libyan Desert, and reaching as far as the Nile, near the first cataract. Its north-western part, as far as Sokna, consists of the Hamadah, a stony, dreary, and extensive table-land, of from 1500 to 2000 feet high, &quot; which seems to be like a broad belt intercepting the progress of commerce, civili sation, and conquest, from the shores of the Mediterranean to Central Africa.&quot; Near Sokna this plateau breaks up and forms what are called the Jebel-es-Soda, or Black Mountains, a most picturesque group of cliffs ; and again, on the route from Murzuk to Egypt, it also breaks into huge cliffs, and bears the name of El-Harouj. The whole of the central portion of the Northern Sahara, as far south as the plateau of Air or Asben, is occupied by similar bare table-lands, with lower areas of sand dunes between. Numerous wadys, the only inhabited parts of the country, intersect the slopes of these plateaux. The country of Ahaggar, between 23 and 29 N. lat., and 5 E. long., appears to form the central elevation from which the greater of these dry water-courses radiate ; from it a series of long wadys one of them, the wady Rharis or Igharghar, being about 600 miles in length run northward towards a depressed country which lies inland from the Gulf of Cabes, and contains several salt lagoons, covered with a few feet of water in winter, but dried up in summer, and lying considerably below the Mediterranean level. Other wadys radiate west and south-west from Ahaggar to the unknown region of the Sahara, which lies between this and the northern bend of the Niger. The most truly desert region of the Sahara is an irregular belt of shifting sand dunes, the &quot;Erg&quot; or &quot; Areg,&quot; which stretches from the lagoons above referred to near the Mediterranean coast south-westward to near the river Senegal and the Atlantic, in an unbroken chain for upwards of 2000 miles, and hav ing an average width of perhaps 200 miles. In this sand belt the wadys of the inward slope of the plateau of Barbary terminate, excepting the Wady Saura, which crosses the Erg to the important oasis of Tuat, near the centre of its southern border, and the Wady Draa, which turns to the Atlantic coast. From Wady Draa a great plain extends along the western shore as far as the river Senegal, and probably continues as such to the east towards Timbuktu, and thence to Lake Chad. Thus it appears that the western half of the Sahara is surrounded by a broad belt of plains and depressions, the central parts being formed by extensive table-lands, with occasional mountain knots, such as that which forms the fertile kingdom of Air and Asben, the culminating points of which are from 4000 to 5000 feet high. The eastern portion of the Sahara appears to have nearly the same general elevation as the western half, and near its centre several fertile mountain regions, comparable with that of Asben, are known. Such is the mountainous country of Borgu, north-east of the kingdoms which surround Lake Chad, and Tibesti, north of it, in the centre of the Tibbu district, recently explored by Dr Nachtigal, who found rich vegetation and abundant animal life in the valleys of this mountain group. To the south and east of the region just described Africa may be considered as one connected mass of elevated land, comprising the most extensive table-lands, as well as high mountain groups ;md chains. The great mass of the African plateau land is to south ward of the 10th parallel of N. latitude, but it is pro longed on the eastern side almost to the north coast of the continent by the wedge-shaped table-land of Abys sinia, the highest surface in Africa, and by the moun tains which extend from it between the lower course of the Nile and the Red Sea. The terminal point of the high land in this direction may be said to be Jebel Attaka, which rises immediately west of Suez to a height of 20 40 feet. From this point to the southern extremity of the Eastern continent the eastern, and generally higher edge, of the ei S e of great plateau runs in an almost unbroken line. Passing r 1:;teau southwards along its margin, the most prominent heights before the table-laud of Abyssinia is reached are Mounts Elba, 6900, and Soturba, 6000 feet in elevation, near the middle of the African coast of the Red Sea. There may, however, be greater heights in the little known region of Nubia, which lies between these mountains and the Nile. The eastern slope of the Abyssinian plateau begins im mediately south of the port of Massowah, and is a uni form line of steep descent, unbroken by any river, falling abruptly from an average height of 7000 feet to the depressed plain winch here skirts the coast of the Red Sea. This edge, which extends southward for at least 800 miles, forms the water-parting of the rivers which have furrowed deeply into the opposite slopes of the plateau, and appears to be higher than the general surface of the country; yet several lofty groups of mountains rising from the level of the high land attain a much greater elevation, and Mount Abba Jared, the highest known point, is esti mated at 15,000 feet above the sea. Between the most southern part of Abyssinia which is known and the equator, where the edge of the plateau has again been partly explored, a long space of unknown country inter venes; but there is every reason to believe that the slope is continuous. Mount Keuia, 18,000 feet, and Kilima njaro, 18,715 feet, the highest points in all Africa, mark the eastern edge under the equator; further south on tho inland route from Zanzibar to the Tanganyika, the edge is known as the Rubeho Mountains, with a height of 5700 feet at the pass by which they are crossed on the caravan route. Still further, the edge is again known where it forms a rampart, called the Njesa, walling in the Nyassa Lake. From this point Mount Zomba, 7000 feet high, near Lake Shirwa, Mount Milauje, 8000 feet, and Mount Clarendon, GOOO feet, carry it south to where the Zambezc river makes the first break in its uniform line. The narrows and rapids of Lupata, below the town of Tete, mark the point at which the river breaks through the plateau land to the coast slope beneath it. Passing the river, the eastern edge is again followed in the Mashona and Matoppo Mountains (7200 feet) of Mosilikatse s kingdom, from which heights the chief tributaries of the Limpopo river flow. At the head waters of that river the plateau edge forms the Hooge Veldt of the Transvaal Republic which joins with the Kathlamba or Drakenberg. The portion of the edge which bears this name is specially prominent : it runs southward in a huge wall of rocky crags which support the table-land behind for 500 miles, almost parallel with the coast, and at a dis tance of 150 miles from it, having Zulu Land, Natal, and Caffraria on the slopes of the spurs which it throws down to the coast. In the Transvaal Republic, where the Drakenberg joins the Hooge Veldt, the edge attains a height of 8725 feet in the summit named after the explorer Mauch, but it is highest where it forms the interior limit of Natal, and where Cathkin Peak rises to 10,357 feet above the sea. As in Abyssinia, so here, this part of tLe eastern plateau