THE WHITE NILE. 45 



down very little water, and none at all for the rest of the year. Unique in this 

 respect among the great rivers of the globe, the Nile seems for the greater part 

 of its course to be a river destitute of tributary basins. On its west bank nothing 

 occurs for 2,200 miles from its mouth except some wadies flushed during the 

 rains. 



But then follows a sudden and remarkable contrast, due to the changed climatic 

 conditions. All the triangular region comprised between the Bahr-el-Jebel, the 

 Nile, and Congo water-parting, and the Dar-For uplands, is intersected by 

 numerous perennial streams nearly converging in the direction of the old 

 lacustrine basin now filled with alluvia and vegetable refuse. With their minor 

 headstreams and affluents they form a vast and intricate hydrographie system, 

 extremely difficult accurately to survey, especially owing to the varied and shifting 

 nomenclature. Like the Nile itself, every secondary branch bears as many names 

 as there are tribes in its valley or neighbourhood. The most important appear to 

 be the Yei, which is lost in the swamps bordering the left bank of the Nile ; the 

 Rol, flowing to the Bahr-el-Ghazal ; the Roa and Tonj, whose united waters form 

 the Apabu ; the Diur, which reaches the Bahr-el-Ghazal near Meshra-er-Rek, and 

 which is the most copious of its many affluents ; the Pango, a branch of the Diur ; 

 lastly the Famikam, better known as the Bahr-el-Arab, which forms the northern 

 limit of the whole region, and which, after its junction with the Ghazal, deflects 

 the Nile eastwards. 



Most of these streams have a very gentle incline, the most rapid being those 

 that take their rise in the mountains near lake Albert Nyanza. Some have their 

 source altogether in the plains, offering an almost imperceptible transition to the 

 basin of the Congo. In their lower course the E-ol, Diur, and some others have 

 too slight a fall to scour their beds of the vegetation constantly accumulating. 

 The consequence is that, like the Nile, they overflow their banks, during the 

 floods converting the whole country for some thousands of square miles into an 

 impassable morass. A large portion of the rainfall in this part of the Nile basin 

 evaporates before reaching the main stream. Here the annual rains represent a 

 volume greater than the whole discharge of the Nile at Cairo. 



At the point where it resumes its normal northerly course beyond the region 

 of sedd, the Nile is joined on its east bank by the Sobat, which is also known by a 

 great variety of names.* The Sobat, which drains a very large area, and which 



* Nomenclature of the Upper Nile and its afflui'nts : — 



Nile: Kivira, Somerset (between lakes Victoria and Albert) ; Meri (intlieMadi country); Karré (by 

 the Bari people) ; Kir (by the Denkas) ; Yer (by the Xuer) ; Bahr-el-Jebel (by the Arabs between Lakes 

 Albert and No) ; Bahr-el-Abiad, or " White River" (by the Arabs below the Sobat). 



Yei: Ayi, Doghurguvu, Jemid, Rodi, Bahr-Lau. 



Rol: Nam-Pol, Ferial, Welli, Yabo, Nam-Gel. 



Roa: Meriddi. Bahr-jan. 



Tovj : Tondy, Lessi, Dnggoru, Kuan. 



Diur: Here, Nyenam, Bahr-Wau, Ugul, Relaba. 



Pango : Ji, Dishi, Ugakaer, Bahr-el-Homr. 



Famikam : Balir-el-Arab, Lialui, Loi, Lollo, Komkom. 



Sobat : Bahr-el-Mogalé, Walk, Telfiu, Wah, or Tah (by the Shiluks). Pinyin, or Tilfi (by the Nuer), 

 Biel, Kieti, Kidi, or Kiradid (by the Dinkas). 



