Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/551

Rh NILE 507 probably of Lake Cliad and the Congo. Flowing in many cases for 400 or 500 miles, these streams in the upper part of their course are of considerable volume and of much importance in the economy of the countries which they traverse. About 95 miles below the junction of the Kir, and 30 below that of the Bahr al-Zeraf, the White Nile receives its first great affluent from the east. The Sobat, as it is called, has its headwaters (largely unexplored) distributed over a wide area the southmost rising possibly as far south as 4 N. lat. in the hilly country of Atuka, the eastmost in Kaffa, and the northmost about 9 in the Berta mountains. 1 On one of them there is probably a consider able lake : first inserted as Baro Lake on our maps by Petermann on the report of a slave dealer, it was expunged by Matteucci ; but Schuver claims to have seen it from the mountains to the north, and proposes to call it Haarlem Lake. The Sobat proper is navigable from June to November as far as Nasser (180 miles), an Egyptian port established by Gordon in 1874, and even, it is said, for three days farther, though it divides into four branches a short distance above this point. Junker, who visited Nasser 2 in 1876, found the river 15 to 20 feet deep, flow ing at the rate of 80 paces per minute between banks high enough to prevent any general inundation. At the mouth of the Sobat there is an Egyptian post of the same name (see Zeitschr. der Ges. f. Erdk., Berlin, 1877). The northward progress of the White Nile for the next 300 miles is through a great plain stretching from the spurs of the Abyssinian highlands in the east to the hilly districts of Takalla and Kordofan in the west, and con sisting almost exclusively of red and other sandstone, often flat as a pavement. Escaping from the swampy region, the river again forms a well-marked channel, with regular and sometimes high banks. Throughout the whole dis tance indicated a striking confirmation of Baer s law is afforded, the fairway or deeper side of the stream gene rally keeping to the eastern shore. About 60 miles below the Sobat mouth lies (on the right bank) Fashoda, an Egyptain town founded in 1867 on the site of Denab, the old &quot; capital &quot; of the Shilluks. In the neighbourhood of Mahadat Abu Zaid (about 13 5 N. lat.) begin the Sunt Islands, so called from the Arab name for the Acacia nilotica, a tree characteristic of the White Nile. At Khartoum (Khartum), in 15 37 N. lat., the White Nile is joined by its greatest eastern confluent the Blue Nile 3 (Bahr el-Azrak). This river has its head reservoir in Lake Tana (Tsana), which is so situated that the lines of 12 N. lat. and 37 2 E. long, cut it into four nearly equal portions. 4 The height of the lake is 5658 feet (Rohlfs). From east to west the breadth is about 40 miles, and the area is estimated at 2980 square miles. Between Dega and Zegi a depth of 236 feet has been found, and between Korata and Zegi 219. The Blue Nile, or Abai as it is called in Abyssinia, rises on the northward slopes of a cluster of mountains (Mount Gesh, &c.) about 11 N. lat., and flowing northwards enters Lake Tana near the south west corner, to issue again at no great distance. Of the multitudinous ramifications by which the Abai and its tributaries drain a large part of the Abyssinian plateau, a better idea will be obtained from the map than from any description. From east and south and north the mountain 1 The connexion of the Godjeb or Orno with the Sobat, first sug gested by Beke in 1841, and strongly opposed by Von Kloden, is still matter of doubt. 2 Naser, locus ubi torrentes fiuunt in alveum. 3 At Khartoum the water of the one river has a milky-limy appear ance, that of the other is clear and blue, except when in flood, when it gains a reddish-yellow from its alluvial burden. 4 Lake Tana has been explored by Bruce, Blanc, DeCosson, Piaggia, Stecker, &c streams pour down into the river, its eastmost tributary probably rising east of Magdala, and its southmost between 8 and 9 N. lat. At Fazokl or Famaka, 11 17 N. lat., it begins to escape from the mountains ; about 1 30 miles farther down, after passing Rosaires and Karkoj on the right and Sennaar on the left, it is joined by the Binder ; and 35 miles more bring it to the confluence of the Rahad (Ra ad) and the town of Abu Haraz. Beyond this point it flows through the most fertile portion of the Egyptian Soudan, the plain on the left hand more especially being a great grain-growing district. The total length of the Abai or Blue Nile may be estimated at 960 miles. On the north-west side of the mountains which enclose Atbara. Lake Tana are some of the headwaters of the Atbara, another important tributary of the Nile ; but it does not reach the main stream till about 17 41 N. lat., or 200 miles below Khartoum. Its principal branch, the Settit or Takazze, has a course of about 420 miles through the Abyssinian plateau before it joins or (more strictly) is joined by the river which gives its name to the united stream. The Khor-el-Gash, or Mareb, though a consider able river in its upper regions, reaches the Atbara (and thus the Nile, of which it is the northmost affluent) only during a heavy rainy season (see James, Wild Tribes of the Soudan, 1883). A large number of these eastern tributaries are mountain torrents, of enormous volume and impetuosity during the rains, and for a short time afterwards, but rapidly dwindling again into mere threads of water or chains of pools, and leaving the rocks and sand of their deep-cut channels as dry and parched as the surrounding desert. No one who has read it will easily forget Sir Samuel Baker s graphic account of the deep pool in the bed of the Atbara into which the fishes, tortoises, crocodiles, and hippopo tami from a long reach of the river had gradually been crowded as the water disappeared, and of the sudden release effected by the return of the rainy season. 5 A more recent traveller, Herr Schuver, had a similar experience on the Tumat, the southern tributary of the Blue Nile. 6 After receiving the Atbara the Nile continues for 650 miles through the Nubian desert, where the volume of the river suffers continual diminution from the ex treme dryness of the air, without being recruited by a single drop of water. Between Berber (an important town on the right bank 30 miles below the Atbara) and Wady Haifa (about 600 miles) rapids and cataracts follow at intervals. The highest of these, the fifth cataract of the Nile, is situated about 40 miles below Berber, the fourth, 170 miles farther down, below Shitab, the third, 230 miles farther, at Hannek, and the second just above Wady Haifa. At Assuan (200 miles lower) are the first cataracts. Beyond that point the river flows through the wonderful valley which has already been described in the article EGYPT. Reduced to its simplest expression, the Nile system may be said to consist of a great steady flowing river fed by the rains of the tropics, controlled by the existence of a vast head reservoir and several areas of repose, and annually flooded by the accession of a great body of water with which its eastern tributaries are flushed. The following details will enable the reader to estimate the hydro- graphic value of the different portions: 7 Victoria Nynnza lies in a zone where rain falls all the year round. At Kagei (south shore) the lake was seen by Mr Wilson in 1877 to be slowly rising in the middle of February, and it had attained its maximum (2 feet) about the middle of May, ten days after the rain had ceased. The total rainfall of this zone is not excessive. Speke s estimate of 49 inches is confirmed by Mr Wilson s much longer experience. In Uganda there are two maximum periods March to May, and September to November. The Assua is important from 15th April to 15th November. The Bahr al-Jcbel, at Gomlokoro, begins to rise in April, and 8 Baker, Abyssinian Tributaries of the Nile. 6 See Petermann s Mittheilungen, 1883 ; Erg. -Heft, No. 72.
 * Of. Keith Johnston, Africa, Appendix.