In the low country to the west of Zergat Naam, between the Wadi Garara and the Rod el Kharuf, the most conspicuous hills are =Erf el Dubeis=, a ridge twenty-six kilometres due west of the beacon, =Gebel el Nikeiba=, a granite hill marked by a triangulation cairn, 570 metres above sea-level and thirty-four kilometres west-north-west of Zergat Naam; =Gebel Felieiti=, a sandstone hill, also marked by a triangulation cairn, 500 metres above sea and sixteen kilometres south-west of Gebel Nikeiba; =Erf Abu Homur=, a ridge at the head of Wadi Abu Homur (a tributary of Garara), about seven kilometres north of Gebel Felieiti; =Erf el Mohaib=, marked by a triangulation cairn 465 metres above sea-level, about nine kilometres north-west of the last-named hill; and =Gebel el Ghar=, a hill on the south side of Wadi el Kharit, close to the point where the Rod el Kharuf enters it. =The Abu Dahr — Orga — Um Tenedba Group.= The mountains of this group occupy the tract between the Wadi Naam and Gebel Faraid, and are limited on the south by the Wadi Hodein. =Gebel Abu Dahr=, the highest mountain of the group, is a great mass of serpentine, situated in latitude 23° 35′ and about forty kilometres from the coast. Its summit, marked by a triangulation beacon in latitude 23° 36′ 8″, longitude 35° 5′ 46″, is 1,131 metres above sea-level. Its western face is drained by the heads of Wadi Betan, its north-east flanks by those of Wadi Khoda, and its south-east parts by feeders of Wadi Rahaba. Abu Dahr is surrounded by high hills except on the west, where there is low hilly country containing the wells of Betan and the old mining ruins of Um Eleiga (_see_ Plate IV, p. 30). The mountain can be most easily reached either by following up the Wadi Betan to its head, or by ascending the Wadi Salib el Azrak (a tributary of Wadi Khoda) and its feeder the Wadi Um Karaba. There is an easy pass 1,800 metres north of the beacon, between the central mass of Abu Dahr and the high hills north of it, connecting the heads of Wadi Betan and Wadi Um Karaba. A short distance to the south-west of this pass there is a galt in a spur of the mountain which holds water for some time after rain, and which furnished supplies during my stay at the place in 1907. In occupying the triangulation station, I fixed my camp in a small stony wadi draining from the north of the mountain, on the east side of the pass just referred to; the camp was 600 metres above sea-level and 1,200 metres north-north-east of the beacon. The ascent, which occupied three hours, was rather difficult and dangerous, the mountain being not only steep[110] but composed of rotten highly crushed rock which came away in tons at a mere touch. There is a very extensive view from the summit, the striking peaks of Faraid being a marked feature to the east and south-east, while to the south are the great masses of Mishbih, Niqrub and Gerf, with the sandstone plateaux of