Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/277

tween the Zambeze and the Kassabi river, and the Leeambye or Jambaji, probably the main-source stream, coming from the unknown lands south-west of the Cazembe's territory. From the union of these streams the general course of the Zambeze is in two wide curves eastward, through the plateau and over its edge to the Indian Ocean, in about 19° S. lat. From the north its main tributaries are the Kafue and Loangwa or Aruangoa rivers, and the Shire river, flowing out of Lake Nyassa. Above this point, on its middle course, where it forms the great Victoria Falls, the Zambeze receives the Chobe from the north-west; and from southward numerous minor tributaries join its lower channel. The Zambeze forms a delta with many mouths, the outmost of which are nearly 100 miles apart, and their entrances are generally barred by sand banks; but if these be passed, the main river is continuously navigable for 320 miles to the town of Teté, and its tributary the Shire may also be followed up for nearly 150 miles, to where its cataracts stop navigation. At the Victoria Falls the great river contracts stop navigation. At the Victoria Falls the great river contracts from its general width of nearly a mile, to 60 or 80 feet, and plunges over a height of 100 feet, into a remarkable zig-zag gorge rent in the hard basalt rocks.

The Rovuma, which has its chief tributaries from the plateau edge of the eastern side of Lake Nyassa, is the next great river of the drainage to the Indian Ocean. It has been navigated by Livingstone for 150 miles from the coast, and formed part of his route in entering the continent on the journey from which he has not yet returned, but its basin has not yet been explored.

Still farther north the mouths of a great river named the Rufiji are known, on the coast opposite the island of Monfia, south of Zanzibar; but no part of its course has yet been traced by any European.

The Kingani and the Wami are two streams from the plateau edge, in the country of Usagara, and reach the sea in the channel formed by Zanzibar island. The Pangani river, further north, rises in the snowy mountain Kilimanjaro. The Sabaki and Dana, which embouch on the opposite side of Formosa Bay, in 3° S., flow over the same coast plains, having their head springs in the spurs of Mount Kenia. The latter river might be navigated during the rainy season for 100 miles from the coast.

The Juba river is the most considerable on the eastern side north of the equator. It is believed to have its rise in the high lands immediately south of Abyssinia, and its general direction is south-eastward to the Indian Ocean; but nothing is known on its higher course except by report. The ill-fated expedition under Baron von der Decken explored this river for about 180 miles upwards from its mouth, but as yet no traffic is carried on by its means. The Webbe or Haines river flows down from the high lands in a direction nearly parallel to the Juba, a little farther north, but its outlet on the coast is completely barred by sand dunes of from 400 to 500 feet in height, behind which it forms a lagoon of varying extent. The desert zone is now again reached, and the water supply fails. No permanent rivers reach the Red Sea from the Abyssinian highlands or from the heights of Nubia which continue these northward; the largest water-course is that of the Barca, which is periodically filled by its tributaries in the northern part of the Abyssinian plateau.

Turning now to the great areas of continental drainage, it is observed that in North Africa there is a vast space of upwards of four millions of square miles, extending from the Nile valley westward to the Atlantic coast, and from the plateau of Barbary in the north to the extremities of the basin of Lake Chad in the south, from which no single river finds its way to the sea. The whole of this space, however, appears to be furrowed by water channels in the most varied directions. From the inner slopes of the plateau of Barbary numerous wadys take a direction towards the great sand-belt of the Erg, in which they terminate; a great series of channels appears to radiate from the higher portion of the Sahara, which lies immediately north of the tropic of Cancer and in about 5° E. of Greenwich; another cluster radiates from the Mountains of Tibesti, in the eastern Sahara.

Lake Chad, on the margin of the pastoral belt, is supplied by a large river named the Shari, coming from the moist forest country which lies nearer the equator; and the lake, which till recently was believed to have no outlet, overflows to north-eastward, fertilising a great wady, in which the waters become lost by evaporation as they are led towards the more arid country of the Sahara.

The southern area of continental drainage is of much smaller extent, and occupies the space of the desert zone which lies between the middle of the Zambeze basin and Damara Land. It centres in Lake Ngami, to which the Tioge river flows from the pastoral belt on the north-west. Several water-courses from the high Damara Land also take a direction toward this lake. The river Zuga carries off the overflow of Lake Ngami towards a series of salt lagoons which lie eastward near the edge of the plateau; but it becomes narrower and less in volume as it approaches these, and in some seasons scarcely reaches their bed.

Smaller spaces of continental drainage exist at various points near the eastern side of the continent. One of these occupies the depressed area between the base of the Abyssinian highland and the Red Sea, and is properly a continuation of the Sahara desert belt beyond the intervening plateau. In this space the Hawash river, descending from the plateau, terminates before reaching the sea. Another interior basin lies in the plateau between the edge on which mountains Kenia and Kilima-njaro rise and the country east of the Victoria Lake, and includes several salt lakes. It is probable that the great Tanganyika Lake is the centre of a third basin of no outflow on this side of the great plateau; and Lake Shirwa, south-east of the Nyassa, constitutes a fourth.

The great lakes, which form such a prominent feature in African hydrography, are found chiefly in the southern and eastern regions of the continent, but they are distributed over all the systems of drainage. The Victoria and Albert Lakes of the Nile basin are great seas of fresh water; and if their extent should ultimately prove to be nearly that which is at present believed, they rival the great American lakes for the place of the greatest expanse of fresh water on the globe. The former, the Victoria Lake, is at an elevation of about 3300 feet above the sea; and its outline, as at present sketched on our maps, occupies an area of not less than 30,000 square miles. The Albert Lake, 2500 feet above the sea, is believed to have an extent nor far short of this. Lake Baringo, north-east of the Victoria, is reported to be a great fresh lake, discharging towards the Nile by a river which is possibly the Sobat tributary. Lake Tzana or Dembea, 60 miles in length, at a level of 6000 feet above the sea, on the Abyssinian plateau, is the only remaining great lake of the Nile basin.

The great expansions of the Chambeze-Lualaba river, presumably belonging to the river Congo, are the only considerable lakes of the Atlantic drainage. The highest of them, Lake Bangweolo or Bemba, is described as being 150 miles in length from east to west, and at an elevation of 4000 feet; Lake Moero, the next, extends through 60 miles; Lakes Kamalondo or Ulenge, and the yet unvisited lakes of the same drainage, are described as of vast extent, and lie at an elevation of about 2000 feet above the sea.