Wadi Anfeib, which enters Wadi Hodein from the south-west eight kilometres below the point of influx of Wadi Dif, is formed by the union of three main heads, called Wadi Anfeib el Tawayib, Wadi Atalab, and Wadi Mitatib, draining respectively the northern, central, and southern parts of the great sandstone plateau of Gebel Anfeib. Mitatib is joined half-way down its course by Wadi Unfagalan, which likewise heads in the plateau. Below the junction of its three main heads, Wadi Anfeib has a course of only about seven kilometres to run, through low hill country, before it joins Wadi Hodein.
Wadi Madi, the next great tributary of Wadi Hodein from the south, heads in the western side of the complex group of mountains called Gebel Gerf, and courses in a northerly direction for over seventy kilometres before joining Wadi Hodein in longitude 35° 7′, five kilometres lower down Wadi Hodein than the mouth of Wadi Anfeib. The heads of Wadi Madi are extremely complex, consisting of a multitude of branching drainage lines, and some of them divide their drainage with the Wadi Gemal, which enters Wadi Hodein by way of Wadis Feqoh and Dif. The most southerly head is the Wadi Difoteb, draining from the west side of Gebel Gerf in latitude 22° 39′; but only a part of the drainage from this gets into Wadi Madi, the rest going into Wadi Sherefa el Gharbi. A similar fate is shared by Wadi Eirahimib, which heads in a slightly difficult pass, leading into Wadi Um Reddam, about three kilometres west of the highest point of Gebel Gerf in latitude 22° 42′; this wadi courses in a direction a little south of west, falling very rapidly, past the hill mass of Gebel Tueiwi, where it divides, part of its drainage going northwards as Wadi Madi, and part crossing the plain as Wadi Buyet and joining the Wadi Seyet. The next head of Wadi Madi to the north is formed by Wadi Faditiai, which drains the high hills east of Gebel Tueiwi, and captures a part of the drainage brought down by the above-mentioned Wadi Eirahimib. Exactly where the name Madi commences to be applied to the drainage is uncertain, as Arabs differ on the point, but it is probably most correct to consider Madi as commencing just south of Gebel Tueiwi, where the drainage of Wadi Eirahimib, with part of that from Wadi Difoteb, divides into two parts, the lesser going down Wadi Buyet to join Wadi Seyet, while the greater forms Wadi Madi itself. On this basis, Wadi Faditiai is a tributary of Wadi Madi, joining it by several openings between latitudes 22° 44′ and 22° 46′. There are numerous feeders from the low hill country both to Wadi Faditiai and to Wadi Madi proper. After receiving Wadi Faditiai, Madi flows in a well-defined trench, with many trees, north-west for a few kilometres to latitude 22° 47′, where it turns sharply, almost at a right angle, to the north-east. A kilometre and a half beyond the bend where there is a high granite hill on the west side of the wadi, is Bir Madi. This is a well sunk in the alluvium of the wadi floor, having its mouth lined with stone slabs; in December 1907, when I visited it, the water was four and a half metres deep, with its surface three and a half metres below the wadi floor, and the water was good. The wadi floor here is 476 metres above sea-level. A beacon on the granite hill overlooking the well has the position latitude 22° 47′ 46″ N., longitude 35° 1′ 38″ E., altitude 556 metres above sea. Below the well, Wadi Madi follows a rather winding course among moderately high hills to a little north of latitude 22° 50′, where it gets into more open country and continues as a broad sandy valley, curving gently in a northerly direction, to latitude 23° 5′. Beyond this point, where it receives the Rod Mukrayib and the Wadi Kolaiqo from the west and east respectively, Wadi Madi becomes narrower, and winds about, though still keeping a general northerly direction, among low hill country to its junction with Wadi Hodein. Wadi Madi has many tributaries, the chief being the Wadis Shellal el Gharbi, Tugudbaia, Sinatib, Atluk and Kolaiqo, and the Rod Mukrayib, which will be treated separately further on. The upper parts of Wadi Madi and many of its tributaries are well stocked with trees, but its central parts, where it is wide and sandy, are more barren. Its principal head, the Wadi Eirahimib, falls at an average rate of sixteen metres per kilometre; from near Gebel Tueiwi to Bir Madi the average slope is nine metres per kilometre; while in the final fifty-four kilometres of its course from Bir Madi to Wadi Hodein, the average gradient is rather less than six metres per kilometre.
Wadi Shellal el Gharbi, a tributary of Wadi Madi, originates in the mountains about six kilometres north of the highest peak of Gebel Gerf, where a pass connects it with Wadi Shellal el Sharqi, a tributary of the eastward draining Wadi Radad. Flowing at first nearly due west, Wadi Shellal el Gharbi receives the Wadi Um Reddam, which collects the drainage from the north faces of the highest peaks of Gebel Gerf. Two of the heads of Um Reddam lead to passes; one eastward to Wadi Shellal el Sharqi, and one westward into the head of Wadi Eirahimib. Entering a lower hill country from which it receives numerous feeders, Wadi Shellal el Gharbi turns north-west to join Wadi Madi about eight kilometres below Bir Madi. It has a rather rapid fall, and contains a fair quantity of trees and bushes. Its total length along its main channel is twenty-one kilometres.
Wadi Sinatib, which enters Wadi Madi about six kilometres below Shellal el Gharbi, is a small wadi coursing north-west through the low hill country north of Wadi Shellal.
Wadi Tugudbaia conveys to Wadi Madi the drainage from the dyke country south-east of Gebel Niqrub el Foqani. It is only a short wadi, and enters Wadi Madi nearly opposite Sinatib.
Wadi Berendiyeb, which joins Wadi Madi from the west about latitude 22° 54′, drains the western flanks of Gebel Niqrub el Foqani. It is a many headed wadi, coursing at first among the low foot-hills of the mountain, and then crossing almost a sandy plain to join Wadi Madi. Its length along its main channel is about twelve kilometres. North of Berendiyeb, there are two other feeders of Wadi Madi coming from the low hills north-east of Gebel Niqrub el Foqani; they have no special names, being broad and sandy and without much vegetation in consequence of their draining only low country.
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.