Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/92

 tion, as I have not sufficient time at command to describe them in the present paper.

General Outline. — As regards its physical outline, the western side of the peninsula of Arabia Petraea, or that part of it under immediate consideration, between Suez on the north and Tur on the south, along the coast of the Red Sea, together with the high ground behind, up to the culminating point of the country on the ridge of Sinai, may be best described as forming a series of comparatively level masses, arranged in steps or table-lands varying in height according to their distance from the coast. Through these steps have been cut a number of valleys, comparatively deep and of tortuous course, the general level of the plains being broken by numerous peaks, formed either by outlying masses of sedimentary strata or the undenuded edges of dykes of intrusive rocks, which have resisted the action of the atmosphere more than the softer granite and crystalline schists containing them.

Desert near Suez. — The country from Suez southward to the mouth of Wady Gharandel, a distance of 40 miles, as a rule, slopes gently down to the sea, though in some places an old raised beach forms a cliff from 10 to 25 feet in height. At Moses's Wells (Ain Mousa), about seven miles below Suez, the beach is very flat, so that boats cannot come within a considerable distance of the shore. The surface of the ground is strewed with marine shells and corals, often cemented into a kind of shelly oolite (miliolite). This recently formed rock is common along both sides of the Gulf of Suez, and often contains full- sized specimens of Tridacna gigantea with the nacre still fresh. At Suez, just opposite the hotel at the landing-place for boats, on the Arabian side, so much of it is found that the excavations for the Suez Canal are made by boring and blasting with gunpowder.

Raised Beach. — Immediately on getting above the level of high- water-mark, a change is seen in the shells, which are decidedly less fresh in lustre and appearance, although not sensibly worn or broken, and occurring in large quantities. The worn and broken appearance becomes more marked on receding from the beach; and at the same time the character of the sand changes. The proportion of foraminiferal shells and rolled grains of shell-sand diminish by the admixture of grains of quartz and other comminuted rocks derived from the waste of the interior cliff, until at about two miles from the shore, and about 40 or 50 feet above high-water-mark, the former have almost entirely disappeared. The subsoil at Moses's Wells consists of soft shales and gypseous marls, which extend across the bay to Suez. They are of marine origin, or at any rate have been below water, as in a section on the Suez and Cairo Railway, about half a mile from the town, they are seen to be covered by the raised shell-beach before mentioned.

Desert at Moses's Wells. — The general relation of the superficial deposits near the head of the Gulf of Suez is shown in Pl. I. fig. 1 : a is the escarpment of the Tertiary rocks, probably some part of the Nummulitic series. Prom the foot of the cliff to c the ground is covered with small table-topped hills and ridges, formed of a limestone- gravel cemented into a conglomerate by means of gypsum, and about