=Wadi el Garara=, the great southern tributary of Wadi Kharit, heads on the main watershed east of Gebel Um Harba. Pursuing at first a north-westerly course over a sandy plain, it emerges between two high sandstone hills ten kilometres north of Gebel Um Harba, and turns somewhat more to the west, receiving the =Wadi el Kreim=, which drains the south-east flanks of Gebel Zergat Naam. A little further on it receives an unnamed tributary which courses north-westward from Gebel Um Harba as a great valley nearly full of blown sand. Still further on its course it is fed by another unnamed tributary which, coming from the main watershed in latitude 23° 30′, courses over a wide sandy plain north-westwards. This latter tributary is very barren, but is of some importance as forming a very easy though sandy road over the main watershed to the Wadi Arned (which leads to the springs of Abu Saafa) and as passing, about five kilometres before reaching the pass, a well known water-hole called =Galt el Aguz=. This galt is a huge sandstone basin in the hills on the east side of the road, fairly easy of access. After rain it holds an immense supply of water, but owing to the porous nature of the sandstone it becomes dry in a few months of drought; rude Greek inscriptions on the rocks, mixed with spirited drawings of animals, show that this source of water supply was known and used in Ptolemaic days. Besides the drainage from the pass, the tributary first mentioned takes that from the sandstone hills of Um Khafur situated further east. A little lower down, Wadi Garara receives feeders from the north-east, draining the hills round Gebel Nikeiba and Gebel Felieiti, and then the long Wadi Timsah coming from the south. Wadi Timsah heads among high granite hills a little north of latitude 23°, and courses in a nearly northerly direction for nearly ninety kilometres to join Wadi Garara. The prevailing character of Wadi Timsah itself is sandy and dreary, but its feeders from the eastern hills are richer in vegetation, and in years when there is rain they furnish in their upper portions good grazing ground for Arab camels. The principal of these feeders, enumerating from the south northwards, are the =Wadis Um el Rid=, =Awamtib= (with Wadi =Um Marakh=), =Shabakhit=, and =Dagalai=. All these drain the western parts of the high sandstone hills called by the same names. Water can be got from galts here after rain. Near the head of Wadi Um el Rid, there is a very easy pass over the main watershed into Wadi el Dreb, which leads to the well of Um Reit. Of the =Wadi Ghadrib=, which heads near the hills of Gebel Abu Rahia and Gebel Um Rewat, in latitude 23°, and follows a course roughly parallel to, but a few kilometres west of that of Wadi Timsah, not very much is known. Its prevailing character is sandy and arid.