A line of rocks of volcanic origin skirts the Red sea coast, along which there is also a fringe of coral, embracing Massowa and the neighboring islands. The precipitous gorges through which so many of the Abyssinian rivers flow have probably been worn down through the solid rock to their present depth by the ceaseless action of water exerted through enormous periods of time. The ravine of the Tacazze. one of the streams which unite to form the Blue Nile, is 3,000 ft. deep. A firm clay underlies the deserts of N. Africa. On the W. boundary of Egypt limestones occur, and granite, sandstone, and argillaceous slates are found in Nubia. The deltas of all the great rivers are alluvial deposits. The geological structure of the S. African tableland, according to Murchison, is unique in having maintained the same terrestrial and lacustrine conditions since the secondary epoch. No fossil bones have been found in this territory except such as belong to species of animals which still inhabit it. There are tertiary rocks at the Mombas mission in Zanzibar, near the mouth of the Zambesi, and at the Cape; but these are coast formations distinct from those of the interior, in which marine fossils have been sought in vain.

Every known fact connected with the geology or palaeontology of this region indicates that it has remained practically unchanged through ages which have witnessed the rise and fall of other continents. Within its borders all traces of glacial drift are absent; and there are no volcanic mountains except the Cameroons near the W. coast, and Mt. Kilimanjaro, which has probably been inactive since prehistoric times. The precious metals do not seem to be very generally distributed throughout Africa, and, so far as at present known, the mineral productions are neither abundant nor varied. Until the discovery of gold in Australia and California, however, the gold fields of Guinea, in the Kong mountains, were esteemed as among the most important sources of the world's supply. Iron and copper occur in many parts of intertropical Africa, and Livingstone found seams of coal cropping out along the banks of the Zambesi. Salt is said to be plentiful in almost every country on the continent. Extensive diamond fields, producing many stones of fine quality and great size, were discovered in 1867 in the districts N. of the Orange river and near its contluence with the Vaal. Some controversy arose between the authorities of Cape Colony and the government of the neighboring Orange Free State as to which was entitled to exercise jurisdiction over this territory, and was finally settled in favor of the British claim.

The diamond called " the Star of South Africa," which was found shortly after the opening of the diggings, was sold in its rough state for £11,500 sterling. - Among the distinguishing features of the fauna of Africa may be noted the numerical preponderance of terrestrial over aquatic species of mammals; the large proportion of quadrupeds exclusively African in their origin or habitat; and the number of gigantic pachyderms. Considered with reference to the geographical distribution of animals, Africa is partially included in each of two great provinces recognized by naturalists: the palaeo-arctic region, which comprises nearly all northern Asia and the African continent N. of the Sahara, and the Ethiopian region, containing the remainder of Africa and the whole of Madagascar. The affinities between the existing and fossil animals of S. Africa and India strongly indicate that these now widely sundered countries must once have been connected with each other more intimately than at present. Two of the three known genera of anthropoid apes, the chimpanzee and the gorilla, are found only in Africa. The habitat of the chimpanzee comprehends the whole western region between the Sahara and the Congo river, but that of the gorilla is limited to the tropical delta districts on the Atlantic seaboard near the equator.

Baboons, with one or two exceptions about which there is some doubt, are also confined to Africa.

Everywhere in Abyssinia is found the great dog-faced baboon (cynocephalus hamadryas), remarkable for its long hair. These monkeys traverse the country in bands numbering from 200 to 300, with a venerable male at the head of the line of march. The galagos of Senegal, Gambia, S. Africa, and Sennaar are the continental representatives of the lemurs of Madagascar. Of the rhinoceros there are five African species, all with two horns, and all restricted to the region S. of the Great Desert, the two white species never having been encountered N. of the equator. The range of the elephant (elephas Africanus), which differs from its Asiatic congener, and has never been domesticated like him, is similarly limited. Multitudes of hippopotami are met with on the Nile, the Niger, the Senegal, and in nearly all the equatorial rivers and lakes, the animal being peculiar to the continent. Sir Samuel Baker saw immense herds of them in the Albert N'yanza. Among the pachydermata are also the hyrax and the wart hog. In Bornoo, Abyssinia, and the Galla country, the ox is remarkable for the extraordinary size and length of his horns. Buffaloes are numerous, and the Cape variety is quite fierce and formidable.

The giraffe or camelopard, perhaps the most singular of African ruminants, and found in no other land on the globe except as a fossil, is a timorous creature of gregarious habits, which roams over the interior beyond the Orange river, in flocks seldom amounting to 100 in number. The zebra and quagga abound in S.

Africa. Five sixths of the known species of antelopes are said to be natives of Africa; of these, the most noteworthy are the eland, the springbok, the klipspringer, and the Abyssinian Beni Israel (A. salt/ana), one of the smallest of antelopes, a specimen measured by Blan-ford being only 1 ft. 4 in. high at the shoulder. The more ferocious carnivora abound. The lion, although somewhat circumscribed in his range, is still found in the Atlas mountains on the north, and throughout a great portion of the table land. According to Dr. Kirk, every tribe has a name for him. The tiger is not found in any part of Africa, but leopards, panthers, and the smaller cats are common, as also are hyenas, jackals, and foxes, ft is worthy of note that the domestic cat is exceedingly rare in Africa. The single-humped camel is the most useful of the domesticated animals, being almost indispensable for the performance of the long desert journeys to which it is so perfectly adapted. Tame goats and several varieties of coarse-wooled sheep are numerous in certain districts. The birds of X. Africa are almost identical with those of Europe, but the ornithology of the ton-id section is represented by some forms of uncommon interest, such as the ostrich, the guinea fowl, and the serpent-slaying secretary bird.