PART I.—TOPOGRAPHICAL.

CHAPTER I.

THE WHITE NILE FROM OMDURMAN TO THE

ALBERT NYANZA.

General Description (Downstream). After leaving the Albert Nyanza, the White Nile (or, as

it is called up there, the Bahr el Jebel) flows for 135 miles

in a deep broad arm with scarcely any slope or velocity to Dufile, and then, after a short and troubled course, tosses over the Fola Falls in a channel only 50 yards broad. From here it continues as a torrent to about Regaf.

Here the river is 7 feet deep at low Nile and 15 feet in flood time, discharging

1 between 500 and 1,600 tons

(18,000 to 60,000 cubic feet) per second. The regulating effects of the great lakes are well felt here. It is here at its lowest in winter, begins to rise about the 15th April, with a maximum about the end of August.

From Regaf to Bor, 112 miles, the river is in one

channel, with a rapid fall.

From Bor to the junction of the Bahr el Ghazal, 316 miles, the river meanders in numerous marshy channels, with a very feeble slope. The main channel, always used, is the Bahr el Jebel. In this reach are the

sudds, dams of living vegetation, at times capable of

barring the surface and completely blocking navigation

(v. p. 3 and Appendix I for details of the sudd). At the junction of the Bahr el Ghazal and the Nile is a lake called No, or Mogren el Buhur, varying in size

according to the season, but in the summer about 60 square miles. At that time of year the lake and swampy sur- roundings act as an evaporating basin, and the loss of

(386) B