13. =The Albert Nile.=--The Albert Nile, or the Bahr-el-Gebel, has a length of 1280 kilometres from Lake Albert to the mouth of the Sobat river. For 218 kilometres, past Wadelai to Dufile, it has a broad stream with a sluggish current as a rule, and covered with islands and papyrus marshes. This reach of the Nile is navigable. The fall here must be very little, and it may be considered as 8 metres. In high floods enormous quantities of pistea weeds float down this reach of the Nile. Papyrus and ambatch are very common along the shores and on the islands. At Dufile begin the Fola rapids followed by numerous cataracts up to Fort Berkeley. In this reach of 155 kilometres the river falls 223 metres. Sir William Garstin states that some of the falls have a width of only 12 metres. The depth must be extraordinary, while the velocity is terrific. The green water of the upper reaches is purified in its passage through these cataracts. The rock is granite. If the regulator for Lake Albert were constructed near Dufile, it should contemplate development of electricity for working a railway along these 155 kilometres. South of Dufile the principal tributaries of the Albert Nile are on the right bank viz: the Achua and Umi. In the dry season they are dry, but after rains they may add some 50 cubic metres per second to the river. Between Dufile and Fort Berkeley many rivers flow into the Albert Nile. The Asua, the Atappi, the Umi, the Karpetu, the Kweh and many others from the right bank bring down water in flood well laden with sand. In the dry season all but the Asua are dry. The left bank tributaries are numerous but insignificant. The volume discharged by these streams in the rainy season is very considerable, as will be seen if the discharges at Gondokoro north of Fort Berkeley are compared with those at Wadelai. They are between them capable of increasing the discharge of the Albert Nile for short intervals of time by 1500 cubic metres per second. All these streams are torrential. They rise and fall quickly. From Fort Berkeley to Khartoum, the Albert and White Niles are navigable.