Nile between Albert Nyanza and Gondokoro. In 1903 an Anglo German commission under Colonel Delme-Radcliffe and Captain Schlobach made a detailed survey of the Kagera from 3o° E. to its mouth. The Kioga system was surveyed in 1907-08 by Lieut. C. E. Fishbourne. A trigonometrical survey of the upper river was begun by Colonel M. G. Talbot, director of Sudan surveys, in 1900, and since then much has been done by the Sudan Survey Department and the Irrigation Service.
The sudd (see p. 452, The Region of Swamps) above the Sobat confluence seems to have stopped the Roman centurions sent by the emperor Nero to explore the Nile. When the river above the Sobat was again reached by white men (1840) the stream was clear of sudd, and so continued until 1863-1864, when both the Bahr-el-Jebel and the Bahr-el-Zeraf became blocked by floating masses of vegetation. When Baker proceeded to Gondokoro in 1870 he thus described the increase that neglect had caused in the obstruction : "The immense number of floating islands that were constantly passing down the stream of the White Nile had no exit ; thus they were sucked under the original obstruction by the force of the stream, which passed through some mysterious channel, until the subterranean passage became choked with a wondrous accumulation of vegetable matter. The entire river became a marsh, through which, by the great pressure of water, the stream oozed through innumerable small channels. In fact, the White Nile had disappeared." Baker, who had to cut through 5o m. of sudd in his passage to Gondokoro, urged the Khedive Ismail to reopen the Nile. This work was efficiently done by Ismail Ayub Pasha, and the White Nile was clear for large vessels when Gordon reached Khartoum in
The river did not long remain free, for in 1878 Emin Pasha was unable to ascend the Bahr-el-Jebel from the south on account of sudd. It was cleared in 1879-80 by officials in the Egyptian serv ice, but had again accumulated in 1884. In consequence of the Mandist movement nothing could then be done to clear the river, and the work was not taken in hand again until 1899, when, by direction of Sir William Garstin, the under secretary of state for public works in Egypt, an expedition under Major Malcolm Peake, R.A., was sent to cut through the sudd, which then extended from the Bahr-el-Ghazal confluence almost to Gondokoro. During 190o a channel was cut through the northern and heaviest portion of the sudd. The work was one of much difficulty, some of the blocks being I m. long and 20 ft. deep; the water beneath flowed with great velocity. To remove the obstruction the surface was first burnt ; then trenches were cut dividing the sudd into blocks 10 ft. square, and each of these was hauled out with wire hawsers and chains by gunboats working from below. For a distance of 172 m. north of Shambe (i.e., about midway between the Ghazal confluence and Gondokoro) the true bed of the river could not, in many places, be found, but Major Peake forced a passage to Gondokoro through a spill channel or series of shallow lakes lying west of the main stream. In 1901 Lieut. Drury, a British naval officer, removed many of the remaining blocks of sudd, opening to navigation a further 147 m. of the river. Beyond this point
for a distance of 25 m. the Bahr-el-Jebel could not be traced, so completely was the channel choked by sudd. In 1902, however, Major G. E. Matthews discovered the true bed of the river, which by 1904 was completely freed from obstructions, and freedom of navigation between Khartum and Gondokoro was permanently secured. The effect of the sudd-cutting operations on the supply of water available for irrigation purposes in the lower river was slight but it has made it available for transport, and communica tion up to Rejaf is now regularly maintained.
Explored in part by Egyptian govern ment expeditions, the upper Nile as far south as Albert Nyanza became subject, between 1840 and 1882, to Egypt. Possession of the greater part of the river above Wadi Halfa then fell to the follOwers of the Mandi. In 1896-98 an Anglo-Egyptian army re conquered the country, and from Victoria Nyanza to the Mediter ranean the main river came under British or Egyptian administra tion. The west bank of the Bahr-el-Jebel, as far north as 5° 3o' N., was in 1894 taken on lease from Great Britain by the Congo Free State during the sovereignty of Leopold II., the territory leased being known as the Lado enclave (q.v.), but the lease was terminated in 1910.
the story of exploration, see the works of Bruce, Speke, Grant, Baker and other travellers (whose books are mentioned in the biographical notices). Their achievements, and those of ancient and mediaeval explorers, are ably summarized in The Story of Africa, vols. ii. and iii., by Dr. Robert Brown (1893-94), and The Nile Quest, by Sir Harry Johnston (1903). See also J. Partsch, Des Aristotel's Buch: "Ober das Steigen des Nil" (Leipzig, 1909). For the Kagera region consult Caput Nili, by Richard Kandt (Berlin, 5904). Latest additions to geographical knowledge are recorded in the Geographical Journal (London) and the Cairo Scientific Journal. For the hydrography, geology and climate see The Physiography of the River Nile and its Basin, by Captain H. G. Lyons, director-general, survey department, Egypt (Cairo, 1906), an authoritative work, and numerous other publications of the Survey of Egypt and of the Physical Department ; "Notes on the History of the Nile and its Valley," by W. F. Hume, in Geog. Jnl. ( Jan. 1906) ; Egyptian Irrigation (2nd ed., 1899) and the Nile Reservoir Dam at Assuan and After (1900, both by Sir William Willcocks; the Annual Reports (1899 and after) of the Egyptian Public Works Department. Of special value is the Blue Book Egypt No. 2, 1904, which is a report by Sir William Garstin on the basin of the upper Nile, dealing at length with the lake area, the Nile affluents and the main river as far south as Khartum, from the topographical as well as the hydrographical aspect. Sir W. Garstin and Captain Lyons give full bibliographical notes.
The study of the zoology of the Nile valley was the special object of a Swedish scientific expedition in 190i, under the direction of Prof. L. A. jagerskiiild. The Results were published at Uppsala, pt. iii. appearing in 1909. For the botanical and other aspects of the Nile valley, see the works of Petherick, Heuglin, Schweinfurth, Junker and Emin. (F. R. C.)