To the west of Gebel Mishbih there is hilly country, in which many of the peaks reach considerable heights. The principal hill-masses in this part are =Gebel el Naga=, a range about four kilometres long running north-west and south-east, twenty-two kilometres west of Gebel Mishbih, with several peaks, of which the highest is 827 metres above sea; =Gebel Seiga=, a high hill (905 metres) about twenty kilometres further west, surmounted by a triangulation beacon and drained by the Wadi Seiga; =Gebel Nesheb Hasan= and =Gebel Abgeya=, two hills west and south-west of Gebel Seiga, between Wadis Seiga and Abu Had; =Gebel Um Krush=, between Wadis Abu Had and Um Ghalqa; =Gebels Ribdab=, =el Deheis=, and =Abu Brush= (810 metres), to the west of Wadi Um Ghalqa; and =Gebel Kulyeit=, a conspicuous cone about fifteen kilometres south of Gebel Seiga, rising to 724 metres above sea. Most of these hills are of schists, though Gebels Abu Brush and Ribdab are of granite. =The Gerf — Korabkansi — Abu Hodeid Group.= The central mountains of the Gerf — Korabkansi — Abu Hodeid group form a compact cluster to the east of the main watershed between the great eastward draining Wadis Hodein and Ibib. The most considerable mass in extent is Gebel Gerf, an extremely rugged mountain tract some twenty kilometres in diameter, having its highest point 1,419 metres above sea-level. The Abu Hodeid range, forming a southward extension of the Gerf mass, attains the somewhat higher level of 1,488 metres; while the detached mass of Korabkansi on the west rises to 1,230 metres. Besides these main masses, from which I have named the group, there are numerous outlying ranges of lesser height, the principal being the Beida range to the north, and the Hamra Dom range to the east. The main characteristics of the central group are its extreme ruggedness, the presence of great masses of serpentine among its constituent rocks, and a relative abundance of good water supplies. The wells and springs in the wadis draining from this group of mountains are among the best and most permanent of the water sources of the Eastern Desert of Egypt.