AFRICA MINERALS Among the minerals of Africa, salt is widely distributed, though in some districts wholly wanting. Thus in the Abyssinian high land the salt, which is brought up in small blocks from the depressed salt plain on the Red Sea coast beneath, is so valued as to be used as a money currency ; and in the native kingdoms of South Central Africa, the salt districts are royal possessions strictly guarded. Metals seem nowhere very abundant. Gold is perhaps the most generally distributed. The gold-fields of the Transvaal Republic and of the country which extends thence to the Zambeze, are numerous; but no yield has as yet been discovered of sufficient quantity to overcome the difficulties of working, and of transport to the distant sea-ports, to which no navigable rivers lead from this region. Copper is known to exist in large quantities in the mountains of native kingdoms of the centre of South Africa ; and one of the objects of Dr Livingstone's present journey is to visit the famed copper country of Katanga south-west of the Tanganyika Lake. The diamond-fields in the districts of the Vaal and Orange rivers north of the Cape Colony are now steadily worked, and give good returns.

Africa is the only one of the continents of the globe which lies equally to north and south of the equator, and the portions of it which extend beyond the tropics do not advance far into the temperate zones. From this it results that Africa, besides being the warmest of all the continents, has also the most equal distribution of the sun's heat during the seasons over the parts which lie north and south of the central line. Winds and rain, depending on the distribution of heat, are also correspondingly developed in these two great divisions of the continent, and the broad landscape zones, passing from humid forest to arid sandy desert, also agree exactly with one another north and south of Equatorial Africa.

Between 10° N. and 10° S. of the equator, but especially in that portion of it the outskirts of which have only as yet bean reached by travellers, Africa appears to be a land of dense tropical forest. -Wherever it has been penetrated, travellers speak of an excessively rank vegetation; passage has to be forced through thick underwood and creeping plants, between giant trees, whose foliage shuts out the sun's rays; and the land teems with animal and insect life of every form and colour. Describing the forests of Manyuema country, west of the Tanganyika Lake, Livingstone says - " Into these [primaeval forests] the sun, though vertical, cannot penetrate, 'excepting by sending down at midday thin pencils of rays into the gloom. The rain water stands for months in stagnant pools made by the feet of elephants. The climbing plants, from the size of a whipcord to that of a man-of-war's hawser, are so numerous, that the ancient path is the only passage. When one of the giant trees falls across the road, it forms a wall breast high to be climbed over, and the mass of tangled ropes brought down makes cutting a path round it a work of time which travellers never undertake." Here there is a double rainy season, and the rainfall is excessive. To north and south of this central belt, where the rainfall diminishes, and a dry and wet season divides the year, the forests gradually open into a park-like country, and then merge into pastoral grass-lands. In North Africa this pastoral belt is occupied by the native states of the Soudan, from Abyssinia westward, in the parallel of Lake Chad, to the Gambia on the Atlantic coast; and corresponding to this in the south, are the grass-lands stretching across the continent from the Zambeze to southern Angola and Benguela. The pastoral belts again gradually pass into the dry, almost rainless desert zones of the Sahara in the north, and the Kalahari desert in the south, which present many features of similarity.

The extremities of the continent, to which moisture is carried from the neighbouring oceans, again pass into a second belt of pastoral or agricultural land, in the northward slopes of the plateaus of Barbary, Marocco, Algeria, and Tunis, corresponding with the seaward terraces of cultivated land in the Cape Colony in the south.

Taking a broad view of the hydrography of Africa, there are two great areas of continental drainage, one in .the north, the other in the south, from which no water escapes directly to the ocean. These correspond almost exactly with the two desert belts of the Sahara and the Kalahari above described. The whole of the remaining portions of the continent, its forests and pastoral districts, in which the greater rainfall gives greater power to the rivers, are drained by streams which find their way to the ocean on one side or other, generally forcing a passage through soms natural or waterworn gorge in the higher circle of mountains which run round the outer edges of the great plateau.

By far the larger portion of the oceanic drainage of the continent is to the Atlantic and its branch the Mediterranean, to which the Nile, Niger, Ogowai, Congo, and Orange rivers flow. The great rivers which drain on the opposite side, to the Indian Ocean, are the Juba, Zambeze, and Limpopo ; whilst the northern continental basin, by far more extensive than the southern, has only one great river, the Shari, which supplies Lake Chad.

It must be noticed that the capabilities of the African rivers, as highways of approach to the interior of the continent, are exceedingly small in comparison with those of the other great continents of the globe, most of them. being either barred at their mouths, or by rapids at no great distance from the coast. It is owing to this physical cause mainly that the African continent has remained for so many centuries a sealed book to the civilised world. On the other hand, it must be observed, that when these outer barriers have been passed, the great interior of the land, in its most productive regions, possesses a network of vast rivers and lakes, unsurpassed in extent. by those of any country of the world, by means of which the resources of Central Africa may in future be thoroughly developed.

The Nile is the oldest of historical rivers, and afforded the only means of subsistence to the earliest civilised people on earth, and yet the origin of this river remained an enigma almost to the present day. Though it drains a larger area than any other river of Africa, upwards of 1,000,000 square miles, and in this respect is one of the largest rivers of the globe, the Nile, passing for a great portion of its lower course through the desert belt of North Africa, and receiving no tributaries there, loses much of its volume by evaporation, and is far surpassed in the quantity of water conveyed to the ocean by the Congo, in the moist equatorial zone. The great labours of Dr Livingstone, in the lake region of Central Africa, have so narrowed the space within which the sources of the Nile can exist, that, though no traveller has yet reached the ultimate feeders of the great river, their position can now be predicated almost with certainty. The limit of the Nile basin on the south is formed by the high mountains which rise to westward of the Albert Lake, and which divide between this great reservoir and the Tanganyika, extending eastward to the plateau of Unyamuezi, on the northern side of winch the Victoria Nyanza lies. The ultimate sources must then be the feeders of these great equatorial lakes, the Victoria and Albert.. The river issuing from the former lake, at the Ripon Falls, 3300 feet above the sea, to join the northern end of the Albert Nyanza, may be considered as the first 'appearance of the Nile as a river. At the Ripon Falls the overflow is from 400 to 500 feet in breadth, and the descent of 12 feet is broken in three places by rocks. Further down, where the river turns westward to join the Albert Lake, it forms the Karuma and Murchison Falls, the latter being 120 feet in height. From the Albert Lake, the Nile, called the Kir in this part, begins its almost due northward course to the Mediterranean, and has no further lake expansion. Between the Albert and Gondokoro, in 5° N. lat., which lies at 2000 feet above the sea, the Nile descends at Feast 500 feet in a series of rapids and cataracts. Beyond Gondokoro, up to which point it is navigable, it enters the northern lower land of Africa, which is here a region of swamps and forests, and several tributaries join it from the west. The largest of these, named the Bahr-el-Ghazal, unites with the main stream below the 10th parallel; and, not much further on, a main tributary, the Sobat river, joins the Nile from the unknown region which lies to the southeast. Hence, onward, the Nile is known as the Bahr-elA biad or White River. The two remaining great tributary rivers descend from the high land of Abyssinia on the cast. The first of these, the Bahr-el-Azrek or Blue River, its waters being pure in comparison with those of the Nile, has its source near Lake Dembea or Tzana, through which it flows, in the western side of the Abyssinian plateau, 6000 feet above the sea ; forming a semicircular curve in the plateau, the Blue Nile runs north-westward to the confluence at Khartum, 1345 feet above the sea. Between this point and the union of the next tributary, the Nile forms the cataract which is known as the sixth from its mouth. In about 18° N. it is joined by the Atbara or Black River, the head stream of winch is the Takkazze, flowing in a deep cut valley of the high land. This tributary is named from the dark mud which it carries from the high land, brought down to it by streams which swell into rushing torrents in the rainy season. It is to these rivers that the fertility of Lower Egypt is mainly due, for each year a vast quantity of Abyssinian mud is borne down to be spread over the delta. Hence the Nile pursues its way in a single line through the dry belt of desert to the Mediterranean without a single tributary, descending by five cataracts, at considerable distances apart. The delta of the Nile, in which the river divides into two main branches, from which a multitude of canals are drawn off, is a wide low plain, occupying an area of about 9000 square miles. The most remarkable circumstance connected with the data is the annual rise and overflow of the river, which takes place with the greatest regularity in time and equality in amount, beginning at the end of June, and subsiding completely before the end of November, leaving over the whole delta a layer of rich fertilising slime.

The Sheliff in Algeria, and the Muluya in Eastern Marocco, are the chief streams flowing to the Mediterranean from the high land of Barbary.