=Wadi Atluk=, which flows into Wadi Madi from the south-east almost opposite Gebel Niqrub el Tahtani, has a rather curious origin. It arises from a splitting of the course of Wadi Korbiai, part of the drainage of which passes eastward down Wadi Kreiga, while the other part retains its northerly direction as Wadi Atluk. The total length of Wadi Atluk is about twenty-one kilometres. It has not been surveyed in detail, but for most of its course it lies in low hill country. =Rod Mukrayib= is a many-branched wadi which drains the hilly country between Gebel Niqrub el Tahtani and Gebel Anfeib. One of its heads leads by an easy pass near Gebel Butitelib into the head of Wadi Abu Hashim; another head drains the north face of Gebel Niqrub el Tahtani; while a third drains the south end of Gebel Anfeib, coursing between the sandstone plateau and the schist hills west of it. From the pass into Wadi Abu Hashim to its junction with Wadi Madi the length of its channel is fifteen kilometres, with a fall of from 405 metres to 250 metres above sea, giving an average slope of ten metres per kilometre. It joins Wadi Madi on the north side of an isolated group of hills, just where Wadi Madi begins to narrow in, about nineteen kilometres above its junction with Wadi Hodein. From the point where Rod Mukrayib joins Wadi Madi there is a good open road across the heads of Wadi Edunqul into those of Wadi Anfeib. =Wadi Kolaiqo=, which joins Madi almost opposite Rod Mukrayib, originates in the hills between Gebel Niqrub el Tahtani and Gebel Khashab, where a pass at its head leads into the heads of Wadi Khashab. It is a fairly wide wadi, shut in by rather high hills, coursing west-north-west with a length of nine kilometres and a fairly rapid fall. =Wadi Edunqul=, a small tributary entering Wadi Madi, about ten kilometres above its junction with Wadi Hodein, drains by numerous gullies the south end of Gebel Anfeib, coursing a little north of east with a length of about eleven kilometres. =Wadi Khashab=, a tributary of Wadi Hodein, drains by many branches the hilly country east of Gebel Beida. One of its heads leads to a pass six kilometres due west of the summit of Gebel Beida, whence there is a road to Bir Beida; just before reaching the pass, there is a large quartz vein with some ruins near it. Another feeder of Wadi Khashab, the =Wadi Dehaiartib=, heads in a pass leading to the head of Wadi Kolaiqo. Wadi Khashab has not been explored south of 23° 0′. From this parallel to Wadi Hodein its length is about twenty-six kilometres, but its head may be five kilometres or more further south. The country on the west side of Wadi Khashab consists of low hills, but on the east it drains very high hills, and its feeders course in trenches across the stony slopes at the feet of the hills to join the main channel. Wadi Khashab contains large numbers of trees, whence its name (Khashab = wood). Its average slope is about eight metres per kilometre.