Africa

Africa, a continent of the eastern hemisphere, forming a south-western extension of Asia, to which it has been attached since Eocene times by the narrow isthmus of Suez, now pierced by a canal 90 miles long. Africa is thus constituted an insular mass of irregular triangular shape, with base on the Mediterranean, and apex at the junction of the Indian and Atlantic waters, which bathe its eastern and western shores respectively. From Cape Blanco ($37^\{\backslash circ\}\; 19\text{'}\; 40\text{'}\text{'}$ N.) at Bizerta, Tunis, to Cape Agulhas ($34^\{\backslash circ\}\; 51\text{'}\; 15\text{'}\text{'}$ S.) in Cape Colony, it stretches across $72^\{\backslash circ\}$ of latitude, or about 5000 miles, disposed nearly equally on both sides of the equator. The extreme eastern and western points are Capes Guardafui ($51^\{\backslash circ\}\; 14\text{'}\; E.$) on the Indian Ocean, and Verd ($17^\{\backslash circ\}\; 32\text{'}\; W.$) on the Atlantic, a distance of about 4500 miles. But owing to the sudden contraction of the land at the Gulf of Guinea ($4^\{\backslash circ\}\; 30\text{'}\; N.$), whence, like both Americas, India, and other peninsular masses, it tapers continuously southwards, the total area is considerably less than would seem to be indicated by these extreme distances. Including Madagascar and all adjacent insular groups, it cannot be estimated at much more than 11,950,000 sq. m., or some 4,000,000 less than Asia or America. Of all the continents except Australia, Africa is the most uniform, heavy, and monotonous in its general outlines, unbroken by any bold projections seawards except the abortive Somali Peninsula, unrelieved by broad estuaries, bights, or inlets of any kind penetrating far inland, diversified only by the Gulfs of Cabes and Sidra (the Great and Little Syrtes) on the Mediterranean, by the Bight of Biafra at the head of the Gulf of Guinea on the Atlantic, and by the Gulf of Aden, Red Sea, and Gulf of Suez, separating it on the east side from the Asiatic mainland. Hence, although about three times larger than Europe, its coast-line scarcely exceeds 15,000 miles, as compared with the 19,000 of that more highly favoured continent.

Islands.—Geologically, Africa is nearly destitute of insular groups, almost the only islands that belong physically to the mainland being Ierba and one or two islets in the Mediterranean, and a few on the east side, such as Socotra, the 'spear-head' of the Somali Peninsula terminating at Cape Guardafui, and farther south, Pemba, Zanzibar, and Mafia, almost forming parts of the adjacent coast. Perim, Dahlak, and a few others in the Red Sea, are mere coral reefs, dominated here and there by volcanic crests. The Comoro group between Madagascar and Mozambique is also volcanic; while Madagascar itself and the outlying Mascarenhas (Mauritius, Réunion, and Rodrigues) appear to be surviving fragments of a Miocene continent, now flooded by the waters of the Indian Ocean. On the west side, the little Bissagos group alone forms a geological dependency of the mainland. Annabon, St Thomas, Prince, and Fernando Po, in the Gulf of Guinea, as well as Madeira, the Canary, and Cape Verd archipelagoes, are all of volcanic origin, the latter being separated by profound abysses of over 3000 feet from the continent. Lastly, St Helena and Ascension are mere rocks lost amid the Atlantic waters.

Relief of the Land.—Corresponding with the somewhat shapeless and uniform continental contour, is the generally monotonous character of the interior, which is relieved by no great central highlands or conspicuous water-partings at all comparable to those of the other great continental regions. Although still far from completely explored, the lie of the land is already sufficiently understood, at least in the main features of its general relief. We now know that the somewhat premature generalisation, which compared it to 'an inverted basin,' gives a very inadequate, if not absolutely misleading idea of its true conformation. The outer rim of mountain-ranges is not nearly so continuous and uniform as this comparison would imply; while the interior is disposed, not in one vast elevated plain, but in two well-marked physical regions—a great southern tableland with a mean altitude of over 3500 feet, falling northwards to a much lower but still elevated plain with a mean altitude of about 1300 feet. Owing to this generally high altitude, and to the almost total absence of extensive low-lying plains, such as the Russian steppes and Siberian tundras, Africa, notwithstanding the lack of vast alpine regions like the European Alps and Pyrenees, or the Asiatic Himalayas and Kuen-lun, has nevertheless a greater mean elevation (1900 to 2000 feet, Chavanne) than either Europe (950 to 1000), or perhaps even America (1900).

A line running from the Cameroons northwards to the Benue, and sweeping round Mount Alantika (last northern outpost of the tableland in Adamawa), eastwards to the Red Sea below Suakin, will roughly mark off the comparatively