36 Southern Affluents 120 yards broad 300 miles above its month, and has at that point been crossed in boats (Felkin). .Natives state it is navigable from above Taimo (330 miles,) down to the Bahr el Ghazal,* bnt it appears to pass through marshydepressions on its course.

(/) Southern Affluents of the Bahr el Ghazal and Bahr el Arab.

The characteristic of all these affluents is that in their upper reaches, coming* from the hilly Nile-Congo watershed, they keep to their own beds at all seasons, while on. the middle and lower reaches they overflow during the rainy season. On these reaches the rivers during the dry season serpentine in their narrow beds along the bottom of broad, sharply defined, trough-like depressions, which they fill to the banks in times of inundation. These depressions, 1 to 4 miles broad, lie 10 to 20 feet below the level of the surrounding country, and are mostly covered with reeds and grass. The rainy season begins about July in these parts and lasts for about two months. After a particularly heavy downpour the rivers become impassable, but as the water runs off quickly, the troughs empty in a fewr days, and the rivers resume their ordinary channels, and may, even during the rains, become fordable in parts.

The chief rivers, supplied by numberless streams and tributaries, are the Rohl, the Jau, the Tonj, and the Sueh ; the latter becomes the Jur about the seventh, parallel, and flows into the Wau. These all flow into the Bahr el Ghazal.

The chief affluents of the Bahr el Arab are the Dembo and the Bili.

None of these rivers have been traversed in their entirety, and it is probable that none of them are navigable throughout the year. The natives do not appear to use them for transit, and for trade purposes navigation from the Bahr el Ghazal has always stopped at Meshra er Rek, whence goods have been transported by land.

* Statement to De la Kethulle (Belgian) in 1894.