16 White Nile": General.

The sources of the Blue Nile, which for long was considered as the main river, were, as early as 1770, discovered by Bruce to be near Lake Tsana (Abyssinia), but to this day the actual course of the Blue Nile between Lake Tsana and Faniaka (Abyssinian-Sudan border) has never been accurately laid down.

The course of the Atbara, as far upas the junction with it of the Setit, was roughly known before 1864, when Sir S. Baker made a more thorough exploration of these rivers, but the courses of the Atbara and Setit lying within the Sudan have only recently been fairly accurately laid down. The Atbara rises in the Abyssinian hills, near Chelga, where it is known as the Goang

The Sobat was explored by Marno and Junker in the " Seventies " as far as Nasser, where there was then an Egyptian post. It was left for British officers, after 1898, headed by Captain Gamble, to explore the various narrow rivers such as the Baro, Pibor, Akobo, etc., which join the main stream from South-West Abyssinia, east of Nasser. The course of U»e Upper Pibor was explored by Lieut. Comyn in September, 1904, vide p. 151.

The course of the comparatively short Bahr El Ghazal river, known to the slave-traders of old times, was laid down by Petherick, Gessi, etc., in 1864-78 ; but the courses of the western rivers which flow into it, such as the Bahr El Arab* or El Homr, have not yet been even roughly deterftiined. Those of the more southerly affluents, such as the Suei or Jur, etc., though not yet accurately fixed, have been sketched in by Junker, Marchand, etc., and the British officers in the Bahr El Ghazal since 1900.

Albert N;anza to Kbartoiiiu, Bahr el JebeL

Uke No.

Sofakt.

White Nile.

(ii.)— GENERAL DESCRIPTION (DOWN STREAM).

After leaving the Albert Nyanza, the White Nile (or as it is there called the Bahr El Jebel) flows for 1 10 miles in a deep broad arm, with scarcely any velocity or slope, past Wadelai and Dufile to Niraule, and then, after a

short and troubled coiu*se, between high mountain ranges, tosses over the Fola Rapids in a channel only 50 yards broad. From here it continues in a torrent to about Rejaf. Here the river is 7 feet deep at low Nile and 15 feet at flood time, discharging between 18,()(X) to 60,000 cubic feet per second. The regulating effects of the great lakes are well felt here. It is here at its lowest in winter ; begins to rise about 15th April, with a minimum about the end of August.

From Rejaf to Bor, 1 12 miles, the river is mainly in one channel with a rapid fall. From Bor to the junction with Lake No, ;}84 miles, the river meanders along in numerous marshy channels with a very gentle slope. The main channel

always used is known as the Bahr El Jebel. In this reach are the dams of hving vegetation, known as the " Sudd " (for description see Appendix B). On one stretch the true channel is still blocked with sudd, and a " false " channel, a Httle to the westwards, has to be used for about 20 miles.

At the junction of the Bahr El Ghazal and the Nile in north lat. 9° 29' is Lake No, or Moghren El Buhur,f a shallow expanse of water surroimded on all sides by reedy marsh and varying in size according to season, but in summer probably about 60 square miles. It forms a reservoir for the sluggish streams that drain the extensive plateau forming the water-shed between the Nile and Congo. In summer the lake and its swampy surroundings act as an evaporating basin, and the loss of water is consequently considerable. The waters here also become polluted with decaying green vegetable matter.

The Bahr El Ghazal enters Lake No at its western extremity, and the Bahr El Jebel passes through its eastern end. The Bahr El Ghazal has a feeble discharge and has no effect at any time on the volume of the White Nile.

In the stretch between Lake No and the Sobat, 81 miles, the current is slow and the channel occasionally blocked by sudd.

During flood, the Sobat has a discharge nearly equal to that of the Bahr El Jebel above the junction. In the spring the discharge from the Sobat is feeble, and the river is then unnavigable. The soil brought down by the Sobat is light and friable.

At the Sobat confluence the river changes its namej and now becomes the Bahr El Abiad or White Nile. From this point down to Omdurman, 530 miles, it receives no more perennial affluents, but several large khors join it on the east bank between Kodok and Renk — chief of which are Khor Adar and Khor Rau.

The AVhite Nile flows sluggishly along with a low velocity and gentle slope ; its course is generally straight and its section wide and shallow, banks low, supply very constant; the colour and limpidity of its water show very little change throughout the year, and the variations between the level of high and low supply are very small, being not more than 2 to 6 feet. The depth of the river in this stretch ranges from 15 feet at low Nile to 21 feet in flood. In parts, the channel in flood time is often of immense width.

The result of 94 measurements made in J une, 1 862, show the mean width of the river in flood to be 1 ,870 yards. In many places, however, the channel is more than 2 miles wide, and in its general appearance it resembles a lake rather

* An endeavour is to be made during the winter of 1904-5 to explore the Bahr El Arab from its mouth. t I.e., Meeting of the Kiver<!. I According to some the change takes place at Lake No.