A little above Rabba the river makes a loop south-west, at the head of the loop being (right bank) Jebba. Here there is an island in midstream, taken advan tage of in the bridging of the river by the railway from Lagos. Sixty miles lower down is the mouth of the (left hand) tributary the Kaduna, a river of some magnitude whose head waters are not far from Kano. In 7° 50' N.
45' E. the Niger is joined by its great tributary the Benue. At their confluence the Niger is about a m. broad and the Benue rather more than a mile. The united stream forms a lake-like expansion about 2 m. in width, dotted with islands and sandbanks; the peninsula at the junction is low, swampy and intersected by numerous channels. The stream, as far south as Iddah (Ida), a town on the east bank, rushes through a valley cut between the hills, the sandstone cliffs at some places rising 15o ft. high. Between Iddah and Onitsha, 8o m., the banks are lower and the country flatter, and to the south of Onitsha the whole land is laid under water during the annual floods. Here may be said to begin the great delta of the Niger, which, extending along the coast for about 120 m., and 14o or 150 m. inland, forms one of the most remarkable of all the swampy regions of Africa. The river breaks up into an intricate network of channels, dividing and subdividing, and intercrossing not only with each other but with the branches of other streams, so that it is exceedingly difficult to say where the Niger delta ends and another river system begins. The Rio Nun is a direct continuation of the line of the undivided river, and is thus the main mouth of the Niger. From the sea the only indication of a river mouth is a break in the dark green man groves which here universally fringe the coast. The crossing of the bar—where the depth of water is but 12 or 13 ft.—requires considerable care, and as other branches of the Niger
better access the Nun mouth is now little used. East of the Nun the estuaries known as the Brass, Sombrero, New Calabar, Bonny, Opobo (or Imo), etc. (with the exception, perhaps, of the first-named), seem to derive most of their water from inde pendent streams. West of the Nun all the estuaries up to the Forcados seem to be true mouths of the great river. The For cados has supplanted the Nun river as the chief channel of com munication by water with the interior. The mouth of the For cados is 2 m. wide, the bar, formerly but a m. across, had by 1927 grown to 21 m. across, but the depth of water allowed vessels of 18 ft. draught to enter the river; within the bar is a deep water natural harbour of 3 to 4 square miles. Five miles up stream is the port of Burutu. From the mouth of the Forcados to the main stream is 105 m., with a minimum depth in the dry season of seven feet. The other western mouths of the Niger have as a rule shallow and difficult bars. The delta is the largest in Africa and covers 14,000 square miles, a larger area than the more famous Nile delta.
The Benue is by far the most important of the affluents of the Niger. The name signifies in the Batta tongue "Mother of Waters." The river rises in Adamawa in about 7° 40' N. and 13° 15' E., at a height of over 3,00o f t., being sep arated by a narrow water parting from one of the head-streams of the Logone, whose waters flow to Lake Chad. In its upper course the Benue is a mountain torrent falling over 2,000 ft. in some 150 miles. With the Chad system it is connected by the Kebbi or Mayo Kebbi, a river which issues from the south-west end of the Tuburi marshes, and eventually joins the Benue. The Tuburi marshes occupy an extensive depression in the plateau east of the Mandara hills, and are cut by io° N., 15° E. The central part of the marshes forms a deep lake, whence there is a channel going northward to the Logone.
Below the Kebbi confluence the Benue, now a considerable river, turns from a northerly to a westerly direction and is navigable all the year round by boats drawing not more than 21 feet. At Yola, a town some 85o m. by river from the sea and at an altitude of 600 ft., the width of the stream at flood time reaches to i,000 or 1,50o yd., and though it narrows at the somewhat dangerous rapids of Runde Gilla to 150 or 180 yd.,
it soon expands again. About 5o m. above Yola the Benue is joined by the Faro, a river rising in the Adamawa hills, and some so m. below Yola the Benue receives, on the right bank, the Gongola, which rises in the Bauchi highlands and after a great curve north-east turns southward. It is over 30o m. long, and at flood time is navigable for about half of its course. In its lower course the Benue is joined by several other streams; its valley is bordered by ranges of hills.
As the Niger and the Benue have different gathering grounds, they are not in flood at the same time. The upper Niger rises in June and decreases in December. The middle Niger, however, reaches its maximum near Timbuktu only in January and April– July is the low water season. The Benue reaches its greatest height in August or September, begins to fall in October, falls rapidly in November and slowly in the next three months, and reaches its lowest in March and April. The flood rises with great rapidity, and reaches 50, 6o or even 75 ft. above the low-water mark.
Below the Benue confluence the Niger is at its lowest in April and May; in June it is subject to great fluctuations; about the middle of August it usually begins to rise; and its maximum is reached in September. In October it sinks, often rapidly. A slight rise in January, known as the yangbe, is occasioned by water from the upper Niger. Between high and low-water mark the difference is as much as 35 ft.
Vague ideas of the existence of the river were possessed by the ancients. The great river flow ing eastward reached by the Nasamonians as reported by Herod otus can be no other than the Niger. Pliny mentions a river Nigris, of the same nature with the Nile, separating Africa and Ethiopia, and forming the boundary of Gaetulia; and it is not improbable that this is the modern Niger. In Ptolemy, too, ap pears along with Gir (possibly the Shari) a certain Nigir (NI-yap) as one of the largest rivers of the interior; but so vague is his description that it is impossible definitely to identify it with the Niger. Arabian geographers, such as Ibn Batuta, who were ac quainted with the middle course of the river, called it the Nile of the Negroes. At the same time contradictory opinions were held as to the course of the stream. It was supposed by some geographers to run west, an opinion probably first stated by Idrisi in the 12th century. Idrisi gave the Nile of Egypt and the Nile of the Negroes a common source in the Mountain of the Moon. Fountains from the mountain formed two lakes, whence issued streams which united in a very large lake. From this third lake issued two rivers—the Nile of Egypt flowing north, and that of the Negroes flowing west (see R. Dozy and M. J. de Goeje's Edrisi, Leiden, 1866: Premier Climat, i st four sections). From Idrisi's description it would appear that he regarded the Shari, Lake Chad, the Benue, Niger and Senegal as one great river which emptied into the Atlantic. From 1405 to 1413 a French man, Anselme d'Isalguier, lived at Gao, a city on the Niger 400 m. below Timbuktu; the account of his travels was never printed and is lost. Knowledge of his adventures, never widely known, was completely forgotten until brought to light by Ch. de la Ron ciere (see his Decouverte de l'Afrique au Moyen Age, vol. iii., Cairo, 1927). Leo Africanus visited the Niger regions in 1513– I 5 without settling the question as to the direction of the river. The belief that a western branch of the Nile emptied itself into the Atlantic was held by Prince Henry of Portugal, who in structed the navigators he despatched to Guinea to look for the mouth of the river, and when in 1445 they entered the estuary of the Senegal, the Portuguese were convinced that they had discovered the Nile of the Negroes (see Azurara's Discovery and Conquest of Guinea, Beazley and Prestage's translation, vol. ii., London, 1899, chap. lx. and lxi., and introduction and notes). The Senegal being proved an independent river and the east ward flow of the Niger assumed, the theory that it ran into the Nile was revived.