=Wadi Gerf= is the collective name given to a number of rather complicated drainage channels forming tributaries to Wadi Muelih. The principal heads are to the east and west of Gebel Nugrus. The eastern head is called =Wadi Hangalia=; it commences at about an altitude of 811 metres due east of the highest point of Gebel Nugrus, at a difficult pass leading over the main watershed to Wadi el Nom, and curves round the north spurs of Gebel Nugrus to join the western head. In the Wadi Hangalia are some old ruins of a mining camp, and also some recent prospecting workings and a well giving a poor supply of water. The Western head of Wadi Gerf commences in nearly level ground on the main divide west of Gebel Nugrus, at an altitude of 691 metres. These two main heads unite close to the east of Gebel Ras Shait, whence Wadi Gerf courses about north-west through low hills. A third head is in lat. 24° 52′, at a pass leading into Wadi Um Khariga. A fourth, called =Rod el Atut=, takes the drainage from all sides of the conspicuous black cone of Gebel Atut. A fifth, called =Rod Um el Farag=, drains from the mass of moderately high hills further west called Um el Huetat; these hills contain some old mines, chiefly in talc schists. The drainages from these various heads all eventually take a west-south-west course among low hills and over a sandy plain and enter Wadi Muelih by several openings near longitude 34°. Minor tributaries are =Wadi Abu Seyal= and =Wadi Um Seyal=, south-east of Gebel Atut, =Rod el Ligaia=, in longitude 34° 10′; and =Rod el Ligah=, in latitude 24° 50′. The principal hills of the plain over which Wadi Gerf and its tributaries run their course are some very remarkable small black peaks collectively called Khusa el Faraon, a light coloured hill called Marwot Rod el Ligah, and a ridge called Erf el Sagur; these two last rise to 514 and 523 metres above sea-level respectively. Wadi Gerf possesses a fair amount of vegetation, except where it meanders over the sandy plains; in the tributaries Wadi Um Seyal and Wadi Abu Seyal acacia trees are specially numerous. =Wadi Sibrit= is a long narrow wadi following a course somewhat south of west, originating to the west of Gebel Mudergeg and joining Wadi Muelih in longitude 33° 50′. It possesses many trees and a good well, =Bir Sibrit=. This latter is an excavation in the wadi floor, in longitude 33° 58′; it is said to yield a constant supply. In the spring of 1906 I found the water was at a depth of eight metres below the surface, and of good quality.