=Wadi Erf Um Araka= heads as a series of small wadis among the low hills south of Um Bisilla, and curves round westward between the high hills of Abu Shigelat and Erf el Gimal on the north, and Erf Um Araka or Gebel Belamhandeit on the south, to join Wadi Naam about five kilometres lower down than Wadi Um Bisilla. The hill country round the heads of Wadi Erf Um Araka is fairly open, so that one can proceed freely from the head of Wadi Arais, across those of Wadi Erf Um Araka, and on into the heads of Wadi Um Bisilla. =Wadi Arais= originates by the union of many small feeders in the low hill country between Gebels Um Guruf and Hendusi, and courses for the first fourteen kilometres in a south-south-west direction. About nine kilometres below its head the =Wadi Um Guruf=, draining the hills round the conspicuous granite boss called Gebel Um Guruf, enters from the north-west. Some five kilometres further on, just beyond the place where Arais makes a sharp westward bend, =Wadi Belamhandeit=, draining the east face of the long gneiss range called Erf Um Araka or Gebel Belamhandeit, enters from the north. Wadi Arais now narrows into a winding gorge, cutting westward for about ten kilometres through the complex of high gneiss hills called Gebel Arais to join Wadi Naam. Its junction with Wadi Naam takes place in a small plain, with the sandstone plateaux of Gebel Um Sididad on the west and the gneiss hills of Gebel Arais on the east. The fall of Wadi Arais is from 464 metres above sea at the pass into Wadi Erf Um Araka, to 345 metres where it joins Wadi Naam after a course of twenty-five kilometres; so that its slope averages four and a half metres per kilometre. =Wadi Silsila=[97] heads in high sandstone hills on the meridian of 34° 40′, north of Gebel Abraq, where at least one pass, steep and sandy, leads to the Wadi Arned. Its course is almost due east, over a plain with low sandstone banks, with a great deal of blown sand. Feeders enter it from the sandstone hills which bound the plain, the principal being the =Wadi Um Sididad=, draining the high sandstone hills, called Gebel Um Sididad, on the north. About seven kilometres before it joins Naam, Wadi Silsila cuts through the range of low sandstone hills which stretches southward from Gebel Um Sididad to near Abraq springs; in proceeding to Abraq from the pass at the head of Wadi Silsila, one bears off to the south before reaching this range, entering the drainage of Wadi Abraq over an open sandy plain.