=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