It was left for Speke and Grant, in 1862, on a journey from the east coast, to discover that the great lake, now known as the Victoria Nyanza, was the main source of the White Nile. Sir Samuel Baker, in March, 1863, working up stream, discovered the Albert Nyanza; but it was not till some time afterwards that the actual course of that portion of the river, now known as the Bahr El Jebel, was mapped and traversed, Lieutenants Watson and Chippendall, R.E., being the first, under Gordon in 1874, to lay down the actual course. During the ensuing years, this, the upper portion of the river, was several times blocked with sudd, and at the re-conquest of the Sudan from the Dervishes in 1898, it was permanently blocked. An expedition under Major Peake, however, succeeded in clearing a channel in 1899-1900, and there is no likelihood of the clear channel now existing being, except quite temporarily, blocked again. 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 Famaka (Abyssinian-Sudan border) has never been accurately laid down. The course of the Atbara, as far up as 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 the 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[19] or El Homr, have not yet been even roughly determined. 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. (ii.)—GENERAL DESCRIPTION (DOWN STREAM). [Sidenote: Albert Nyanza to Khartoum, Bahr el Jebel.]