AFRICA, which has an estimated area of 11,500,000 square miles, is remarkable alike for the regularity of its coast line and the comparative simplicity of its topographical features. Its general appearance is that of a plateau, the walls of which rise in some places steeply from the sea, and in others are separated from it by plains of no great breadth. To the south of the equator this plateau has an average elevation of about 3,000 feet, but to the north it generally falls to about 1,000 feet, except in certain regions which may be regarded as extensions of the southern plateau. The first of these lies in the east, where it forms the highlands of Abyssinia and is continued northwards along the coast of the Red Sea ; the second runs from south-east to north-west across the centre of Africa, north of the equator, and appears in the Darfur plateau, the Tibesti hills, and the Tasili plateau ; the third bends round the Gulf of Guinea, and gives rise to the Upper Guinea plateau and the Futa Jallon mountains. Between the first and second of these extensions of the southern plateau lies the lowland basin of the Bahr-el-Ghazal, while between the second and third lies that of the Middle Congo. The mountains which appear on the plateau itself owe their existence, as a rule, either to volcanic action or to the denudation of surrounding land ; and, as they generally occur near the rim, they give to the continent something of the appearance of an inverted saucer. Another feature of importance in the plateau region is the continuation of that great rift valley in which the Jordan, the Dead Sea, and the Red Sea all lie. From the southern extremity of the Red Sea it makes its way southwards, and is occupied by a long line of lakes, of which Rudolf and Nyasa are the most important ; while a western branch, which runs from the northern end of Nyasa; contains Lake Tanganyika, Albert Nyanza, and Edward Nyanza. In the north-west of Africa is the Atlas region, which differs in many respects from the remainder of the continent, and belongs physically to the mountain system of Europe.
-The position of Africa within the parallels of 37° N.
and 35° S., and the relative simplicity of its structural features, render a general description of its climatic conditions compara tively simple. A large area, extending roughly from about lat. N.
to about lat. 10° S., excluding the Abyssinian and East African Highlands, but including the east coast as far south as the Zambesi, is hot at all seasons of the year. Of the remainder of the continent, the greater part has hot summers and warm winters ; but there are notable exceptions in the Atlas region in the north, and in the High Veld in the south, in both of winters are cool. Along the south-wc.,t coast there is a comparatively narrow strip of land, which, owing to the proximity of cold currents, does not get hot in summer, but remains warm at all seasons of the year. The rainfall varies greatly from one region to another. During the northern summer, when the Sahara becomes an area of low pressure, the equatorial belt of constant precipitation moves northwards, and; in July, extends from just south of the equator to a line which runs from the mouth of the Senegal inland to the north of Timbuktu, and, after curving round the Tibesti hills, goes by way of Khartum almost to the Red Sea. In the northern part of the area covered by this belt, the rainfall is a summer one ; but in the south there are two periods of maximum precipitation, one when the sun is going north and the other when it is returning to the south. Monsoonal influences make themselves felt in two regions during the northern summer : in Abyssinia, where great heating on the uplands draws in part of the monsoon current from the Indian Ocean ; and on the west coast, south of the Senegal, where the trade winds of the South Atlantic are pulled across the equator and blow as south-west winds. In other parts of Africa comparatively little rain falls at this period of the year. The Mediterranean States lie under the influence of the tropic belt of high pressure, while the winds drawn into the Sahara from that high pressure belt have but little moisture to deposit. To the south of the equator the land mass is, on the whole, a region of high pressure and outflowing winds ; and it is only in the extreme south of Cape Colony, where westerly winds prevail during the southern winter, that much precipitation occurs.