Africa

lowlands under 660 ft. above the sea are also narrow, and represent only about 15 per cent. of the surface (cf. Europe, 57 per cent.). The greater part of the land between 660 and 1,650 ft. in elevation lies in the N., and is 34 per cent. of the whole; but much of the land between 3,300 and 6,600 ft.-viz., 19 per cent. of the whole-lies in the s. Only 24 per cent. of Africa is over 6,600 ft., and this is mostly in Abyssinia and the Atlas region. The average elevation of the continent is 2.130 ft.

Natural Regions.-Except for the folded chain of (1) the Atlas, which is sharply distinguished

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over 3,000 ft. high. In the w., the Great Atlas of Morocco has an average height of 10,000 ft.its lowest pass, Tel Remt, being 7,000 ft., and its highest summit over 14,000 ft. South of and parallel to it rise the plateaus of the Little or Anti-Atlas (9,500 to 11,000 ft.).

The Northern Plateau has an area of between four and five million sq. m., and an average elevation of 1,500 ft. The lowlands are in the w. and N. The band of Tarso (Tibesti highlands), rising from 6,000 to 8.000 ft. high, crosses this region diagonally from N.W. to S.E., and the Upper Guinea Plateau bounds it

Africa

East Africa is bounded on the w. by the Nile and the great lakes -Albert, Albert Edward, Tanganyika, and Nyassa. It is characterized by two lines of rift valleys-the w., that of the lakes just mentioned; and the E., that passing from the N. of Nyasa, by Lakes Naivasha, Rudolf, and Margherita, to the s. and E. escarpments of Abyssinia. The Red Sea trough and the Jordan valley are regarded by many authorities as a continuation of this E. rift. Much of the plateau s. of Abyssinia lies about 4,000 ft. above the Indian Ocean, to which it descends by a series of terraces. The lowest terrace forms the low

Africa-Native Races.

from the rest of the continent, the natural divisions are not well marked. A line from the mouth of the Nile to that of the Zambezi separates (2) East Africa from the rct of the table-land, which may be subdivided into (3) the Northern Plateau, N. of 5° N.; (4) the Central Plateau, or Congo basin; and (5) the Southern Plateau, s. of 10° s. The (6) Eastern Islands and (7) the Western Islands must also be considered as separate natural divisions.

The Atlas Mountains, which lie to the N. of a line drawn from the Wadi Draa to the Gulf of Gabes, are a continuation of the folded mountain system of Southern Europe. In the E., two parallel ranges, the Mediterranean and Saharan ranges, are separated by the Algerian Plateau, which is

in the s. The N. and centre of this region form the Sahara, a land of barren stony plateaus and shifting sand-dunes, crossed by a few dry valleys. In the s. the land becomes less arid, and the Niger and its tributary the Benue flow across it to the Gulf of Guinea, the Shari to Lake Chad, and the Bahr-el-Ghazal to the Nile.

The Congo basin is a hollow in the Central Plateau formerly occupied by a great lake. This depression is almost circular in shape, and is about 1,000 ft. above the sea at its floor, rising to from 4,000 to 5,000 ft. round its rim, but rarely higher. The divide with the Shari is less than 1,500 ft. high, and the river forces its way to the w. over a still lower lip by a series of rapids to a great estuary.

coastal plain, which attains a considerable width only in the s. near the Zambezi delta, and in the N. in the Somali peninsula. Between the two rifts the Victoria Nyanza fills the lowest basin, and in the E. the land rises to an average height of 7,000 ft. in the Nandi plateau. Near the w. rift active volcanoes, such as Mt. Kirunga, are found near Lake Kivu, between Lakes Tanganyika and Albert Edward. Farther N. is the great igneous mass of Ruwenzori (variously estimated at from 16,000 to 20,000 ft.). This and the extinct volcanic peaks of Kilima-Njaro (19,200 ft.) and Kenya (17,300 ft.), which rise near the E. rift, are the culminating points of Africa. Abyssinia is also mainly composed of young volcanic accumulations, rising in Ras Dashan to 15,000 ft. Here

Africa

Jurassic rock is found beneath the loose volcanic deposits, in which the rivers have excavated gorges some thousand feet deep. In the heart of the plateau is Lake Tsana or Dembea, the source of the Blue Nile. North of Abyssinia the plateau is both narrower and lower, although it attains 9,000 ft. at the highest point. It is composed of crystalline rocks

much older than the sedimentary ones of Nubia. A depression, probably an old Nile course, runs from the first turn of the great s. bend of the Nile to the Red Sea, and the towns of Berber and Suakin have arisen at its extremities.

and

The South African Plateau has also a high average elevation, between 3,000 and 4,000 ft.; but no great heights rise above it, except in the S.E., where the massive tables of the Drakenberg or Kwathlamba Mountains reach over 11,000 ft. This plateau is divided into four regions, each over 4,000 ft., by the valleys of the Zambezi, Limpopo, Orange-the Congo-Zambezi plateau in the N., the Matabele plateau in the E., the High Veldt in the s.E., and the Damara plateau in the w. Across these most of the rivers flow in gorges, and the undulating landscape is diversified by flat-topped hills (the tables or mesas locally known as kopjes), which are often steepsided. The descent to the coast is by a series of terraces, those in the E. being cut up into more rounded hilly regions, which gradually sink to the sea-line. In the s. the terrace flats widen, and from the Great and Little Karroos, each bounded on its s. side by a parapet of older folded mountains, the Zwarte and Lange Bergen chains.

Coastal Belt and Islands.-The coast-line is very regular. Islands are few, and the coast is either steep, or a flat, sandy plain of varying width, leading to the steep terraces of the inland plateau. The N.W. coast is steep from the Wadi Draa to Cape Bon, and from the Barka peninsula to the Nile. Between the Atlas and Barka a low coast curves s., and forms the Gulf of Gabes in the w. and the Gulf of Sidra in the E. The E. coast along the Red Sea and to beyond Cape Guardafui, is straight, regular, and steep. The island of Sokotra is an outlier of the Somali peninsula, which protrudes eastwards s. of the Gulf of Aden like a horn, and is bordered on the E. by a low plain. From the equator to Delagoa Bay the coastal plain is narrow, with hills which here and there approach the sea. this coast lie the little islands of Pemba, Zanzibar, and Mafia, and Madagascar, the last of which is separated from the mainland by

Off

coast

formed where the W. changes from a N.S. to an E.W. direction, and is divided by the Niger delta into two bays-the Bight of Biafra in the E., and the Bight of Benin in the w. A line of volcanic islands, including Fernando Po., Prince's I., St. Thomas, and Annobon, rises above the Bight of Biafra. The N. Guinea coast, trending E. and w., is known by various names-e.g. the Slave Coast (immediately w. of the Niger delta), the Gold Coast, the Ivory Coast, the Grain or Pepper Coast, each succeeding the other to the w. Off Cape Verde lie the Cape Verde Is., and

Climate-Three-quarters of Africa lies between the tropics, and here the days are of nearly uniform length, with almost twelve hours of light every day. At sealevel the mean temperature of the coldest month is over 70° F., except near the extremities of the continent, where it falls to 55° F. Round the tropics the daily and seasonal ranges of temperature are great-over 30° F. between the warmest and coldest month; but in equatorial regions. and towards the N. and s. of the continent, where it is bordered by seas, the range is small. A narrow strip of the s.w. coast is