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.
In the Wadi _El Sheikh_, meaning the "Valley of the Elder," or "Chief," which is one of the principal valleys in the Peninsula, before coming to "Moses' seat" (_Mokad Seidna Mousa_), occurs a range of low hills of a substance called _Taffal_, chiefly a detritus of the _felspar_ of _granite_, like pipe clay. The easiest approach to the present Sinaic district is by the east side of this Wadi, which leads into the wider Wadi, or plain _El Raha_, _i.e._, a "plain surrounded by hills." The view of Gebels _El Deir_ ("The Convent"), the now-termed _Horeb_, _Humer_ (red), and others, from thence is very striking. The lower granitic mountains of the present _Sinai_ are more regularly shaped than the upper; being less rugged, they have _no_ insulated _peaks_; and their summits terminate in smooth _curves_. Whilst in the ascent to the higher mountains, _peaks on peaks arise_, of the form of sharp cones, and of various altitudes. _Gebel Mousa_, or "Moses' Mount," is of _red granite_ for about half-way up; all the rest being a _yellowish granite_, with small _black_ grains, and from _Wadi Leja_ ("asylum"), these colours appear most distinct. The height of the apex of G. _Mousa_ peak, which does not exceed fifty yards in width, was ascertained by Lieutenant Wellsted, from the _mean_ of observations, to be 7505 feet above the sea of Akaba; and that late, able, and lamented officer, who was upon that summit in _January_, and "enjoyed the advantage of a clear serene atmosphere," which, in a more advanced season of the year, would have been hazy, with a blue mist, arising from the powerful sun, "was thereby enabled, by means of angles taken to the hills on the Arabian coast, ninety miles distant, to correctly fix the geographical position of the mountain." He has also well described the most extensive view from that peak, as follows:--