764 ZAIRE menon. Tlie very fact that, in the short space of time during which the Tanganyika has been observed by Europeans, its level lias undergone such considerable alteration seems to suggest that a series of unusually rainy seasons may have been the source of all the inundation that was requisite. 1 Below Lake Lanji there is another portion of the stream still unexplored ; but from the junction of the Luama, a river 400 yards wide at its mouth (about 5 S. lat.), the whole course of the Congo down to the Atlantic (1800 iniles) is known. At Nyangwe the channel is about a mile wide, with (according to Stanley) a volume of 230,000 cubic feet per second. As it flows northward it receives the Elila, the Ulinde, the Lowa, and the Munduku Lilu, all of moderate importance. The first point of much interest is the series of cataracts known as the Stanley Falls, situated at the equator. The first cataract occurs just after the Congo has received the Black river and the Leopold river ; about 6 miles farther down follow in somewhat rapid succession the second, third, fourth, and fifth ; and then the river is divided into two by the large inhabited island of Asama. The sixth cataract, caused by a broad dyke of greenish shale, does not occur for upwards of 20 miles, and between the sixth and seventh there is a distance of 25 miles. At the last of these the Congo is about 1300 yards broad, of which width 40 yards is occupied by the right branch, 760 yards by the island of Wemya, and 500 yards by the main river. The fall is only about 1 feet ; but the enormous mass of water, and the narrow limits to which it is suddenly contracted, make it much more imposing than many a far loftier cataract. After passing the falls the first great left-hand affluent is the Lubilash or Boloko, first ascended by Grenfell in 1884 to the neighbourhood of 1 30 . Next we come to an important right-hand affluent, the Aruwimi, Arawhimi, or Biyerre, which is now recognized as identical with the Nepoko, discovered by Junker in the south of the Monbuttu territory. About 24 30 E. lat. this stream, which discharges 158,850 cubic feet per second, is interrupted by the Yam- buga Falls ; but above the falls Stanley in 1887 found it navigable for his steel boat. Another right-hand affluent of similar rank is the Itimbiri or Loika, ascended in 1884 by Grenfell for 100 miles, as far as the Lubi Falls. No other tributary of equal importance is known to exist till we come to the Lulongo, about 45 miles north of the equator, formed by the junction of the Lopuri and the Masinga, which drain the country to the south of the great bend of the river. The Lopuri is 500 yards wide at the confluence and has a depth of from 7 to 8 feet. The Lulongo is 500 yards wide at its mouth and higher up occupies a channel from one-half to three-quarters of a mile in width. According to Von Francois, it discharges 494,200 cubic feet per second. It was ascended in 1885 by Grenfell, who describes it as commercially the most im portant affluent of the Congo, on account of the value of its ivory and slave trade. Just to the north of the equator is the junction of the Juapa or Chuapa, which Grenfell has followed as far east as 23 E. long., a distance of 400 miles. This is Stanley s Black river. An unusual amount of geographical interest attaches to the next Congo tribu tary the Ubangi or Mobangi ; if the latest reports are to be trusted, it is the recipient of the waters of the Welle- Makua, the river discovered by Schweinfurth in 1870, which has ever since been one of the hydrographic prob lems of the time. 2 Grenfell ascended the Ubangi in 1885 for some distance above the rapids of Zongo, which are formed by the river striking athwart a line of hills running north-west and south-east, with peaks from 600
- See null. Soc. Roy. Beige de Geoy., 1886, or Scot. Geog. Mag., 1886.
2 For the discussion of the Welle problem, see Mouvement Geoyra- phique, 1886, Janko s resume of theories in Scot. Geoyr. May., 1888, and Wills s criticism of the same. to 700 feet above the level of the stream. At this point the breadth is reduced to about 800 yards. In 1886 M. van Gele failed in his attempt to surmount the Zongo rapids; but in 1888, according to the latest reports, he succeeded in advancing sufficiently far up the river (which turns eastward at the rapids) to prove its identity with the Welle-Makua. By this discovery the limits of the Congo basin are carried eastward as far as within 40 miles of the Nile at Wadelai the Welle being mainly formed of the Kibali, a stream about 80 yards wide, whose head-waters rise in that neighbourhood. 3 Quite a multitude of second ary streams join the upper course of the Ubangi, and it continues to receive accessories from the north and west till it merges in the longer river, into which it is calculated to pour about 529,500 cubic feet per second. Its last right- hand tributary probably drains the Tukki swamp in 13 E. long. The Nghiri Muinda or Loij, a comparatively small river draining the peninsula between the Ubangi and the Congo, joins the former about 30 N. lat. , with a current 100 yards wide and from 15 to 20 feet deep. It was ascended by the " Henry Beed" in 1886 as far as Mikutu (1 20 N. lat.), where the stream, still 9 feet deep, was found to be formed of a number of small channels issu ing from a swampy forest. The Ibangi, a right-hand tributary of the Ubangi, was also navigated for 60 miles, to a spot where the depth was still 10 feet; but the passage was obstructed by a barrier of tree trunks. The ascent of the Lobay, which is about 200 yards wide and 13 feet deep at its junction with the Ubangi in 3 50 N. lat., was interrupted at a distance of 40 miles by a three-foot fall. A short distance below the confluence of the Ubangi and Congo there enters from the left the emissary of Mantumba Lake, a considerable basin discovered by Stanley in 1883 and since examined by W. H. Bentley in the missionary ship " Peace." When the Congo is in flood there is a back-flow into the lake, and, as the whole country is very flat, it is quite possible that there is a connexion both with the Uruki and Bussera, on the one hand, and with Lake Leopold II., on the other. This latter lake is much larger, and is certainly connected southward with the Lukinje or Lukatta, a tributary of the Kassai. In its further course the Congo is joined by a number of moderate-sized streams from the west. Below Lukolela it spreads out into a kind of river lake 20 to 25 kil. (12J to 15J miles) wide, and along its left bank extends a swampy region, the chain of low wood-covered hills which has hitherto confined the valley retiring for a mile or two. In 3 15 S. lat. it receives its last great affluent the Kassai or Kwa, which has recently been proved to be the most important of the southern or left-hand, as the Ubangi is the most important of the northern or right-hand, tribu taries. The Kassai rises to the south of 12 S. lat. and flows north through Muata Yamvo s kingdom. In its upper course it possibly receives an emissary from Lake Dilolo, which also sends a branch south to the Zambesi. As it advances northwards it is joined by a large number of streams, all generally flowing northward. The Kassai enters the Congo in 3 10 S. lat., with a depth of 25 to 80 feet and a breadth of 600 yards, at a height of 942 feet above the sea. The exploration of the system was carried out by Wissmann, Wolf, Von Francois, and Mueller in 1883-85. The Kassai itself has been ascended as far as the Wissmann Fall in 5 40 S. lat., and its course has been struck at Digundu in 10 S. lat. The Lulua, which joins it from the right, is known as high up as Kangombe Fall ; it is there about 200 yards wide ; but it does not become truly navigable till it is joined by the Luebo. The San- kuru, at one time supposed to flow directly into the Congo, 3 See map illustrating the journeys of Dr W. Junker, Proc. Roy.
Geojr. Soc., 1887.
