By the month of October, the conditions resulting from the movement of the sun back to the equator have asserted themselves. The belt of equatorial rainfall is practically confined within the parallels of ten degrees north and south of the equator, and does not extend eastward beyond the fortieth meridian ; the Mediter ranean States and Cape Colony both lie within the west-wind belts ; while along the east coast, from the Zambesi southwards, the trade winds are beginning to make their influence felt.
In January, when the land mass south of the equator is at its hottest, the belt of constant rainfall does not extend for more than a few degrees north of the equator, but, to the south of it, it covers a great part of the Congo basin. At the same time, the south-east trade winds are sucked into the land by the low pressure area which lies over it ; and, as these winds are moisture-bearing (unlike those which blow over the Sahara), there is rainfall over the greater part of Africa, south of the equator, at this season of the year, the principal exceptions being the south-west coast and part of Cape Colony. On the other hand, there is a comparatively heavy precipitation in the Mediterranean States, and even the coast lands of Tripoli and Egypt receive some rain.
The annual precipitation of Africa is, therefore, distributed somewhat as follows : on both sides of the equator, and especially in the basin of the Congo, on the Guinea coast, and in the high lands of Abyssinia, there is a heavy rainfall. To the north, pre cipitation rapidly diminishes, and beyond the latitude of Khartum very little moisture is received until the Mediterranean States are reached. To the south of the equator, conditions are somewhat different owing to the influence of the south-east winds, and beyond the twentieth parallel the rainfall decreases from east to west.
-The north-west part of Africa, with its winter rainfall and hot dry summers, is characterised by a hard-leaved evergreen vegetation, which soon passes, with decreasing precipita tion, into poor steppe and scrub-land. These, in turn, give place to the deserts of the Sahara where vegetation is almost entirely wanting, except in the oases scattered here and there over its vast extent, and in the lands which owe their fertility to the waters of the Nile. Further south, where there is a light summer rainfall, a transitional belt of semi-desert, in which acacia forests and occasional grasslands are found, leads to the rich savanna lands of the well-watered Sudan. In Abyssinia, where there is also a summer rainfall, the vegetation is somewhat different, and woodlands, grasslands, and deserts all occur. In the belt of heavy equatorial rainfall along the coasts of the Gulf of Guinea and in the greater part of the Congo basin, dense forests cover the land, and a some what similar forest is found in a gradually narrowing strip along the east coast of the continent from Zanzibar southwards. The savanna lands of the Sudan are continued to the east and south of the equatorial forests, and extend over the greater part of the African plateau as far south as the twentieth parallel, but beyond that they are confined to the eastern part of the sub-continent. On the west and south they pass into steppe-land which in turn gives place to scrub (a strip of which makes its way along the west coast from the mouth of the Cunene almost to that of the Congo), and in the rainless west to desert. The region of winter rains in the south west of the continent has a vegetation similar to that of the Mediterranean States.