The Wadi Ghudhagidh, and the more southern tributaries of the Jerafah, flow to the NE. to the Dead Sea, as already explained; and they, with some smaller winter torrents that unite with them, are the only water-courses in this part of _Arabia Petræa_ which supply that sea. On the SE. of the upper Jerafah, some low _limestone_ ridges present themselves; but, on the other side is the _sandy_ plain _El Adhbeh_: beyond this, northwards, follows a level plain covered with pebbles and black _flints_. The high West Desert, called by the Arabs El Tyh, the "wandering," and so named in Edrisi and Abul-feda, near its centre at _Nakhl_, signifying "date trees" (at which station there exists a grove of those trees), at an elevation of near 1500 feet above the sea, consists of vast plains, or _plateaux_ of varying, mostly higher, altitudes, a sandy, flinty, or gravelly soil, and limestone hills of the _cretaceous_ or secondary formation, having very irregular ridges disposed in different directions. The numerous _Wadis_, or water-courses, and winter torrents of this enormous desert, all run to the N. or NW., and pour their waters into the Mediterranean Sea; while those _Wadis_ that lie on the other side of the Great Mountain range, which bounds the desert in its western and southern extremities--_Gebel-el-Rahah_ and _Gebel-el-Tyh_--divide their waters, and so supply, in part, the Gulf of _Suez_, and in part the Gulf of _Akaba_. Of the former _Wadis_, two are the principal; namely, _Wadi-el-Agaba_, which rises somewhat to the east of the line of 34° E. long.; and _Wadi-el-Arish_, which Russegger and later authors affirm as springing to the _west_ of it, and of _Gebels_ Heiyalah, Yelak, and Mishea, and of which _Wadi Nesil_ seems to me to be only a tributary. The chain called _Gebel-el-Egmeh_, or _El Odjme_ by Burckhardt, appears, as he says, _chalky_; and such, also, is the soil of the plain, and frequently covered with _black_ pebbles (_flints_); it unites with the higher chain of the Gebel-el-Tyh, about the centre of the Peninsula,--that is to say, of the _Peninsular Triangle_, and where the branches North-el-Tyh and South-el-Tyh separate. There the height of the summit of _El Tyh_ is given by Russegger as 4322 Paris feet, or 4615 English feet, above the sea; descending thence by the pass of Mureikhi, into the sandy plain of _Debbet-el-Ramleh_, the elevation of that plateau, just about the middle of it, and about half way to the head of _Wadi-el-Sheikh_, is near 4000 feet above the sea level; Alahadar being a little to the east.