818 NORTH-EAST AFEICA. along the Egyptian coast, produced either by the vertical rising of the land or by the subsidence of the surrounding waters. Altogether the west coast is more healthy and less obstructed by coral reefs than the opposite side. The sea is also deeper near the shore, and good harbours are consequently more numerous. West of the granites, schists and porphyries of the border range, the rocks over- lying the crystalline nucleus consist of sandstones and limestones. In the southern district rises an isolated sandstone mass resembling those of Nubia, Kordof&n, and Senar. This rock, especially at the Jebel-Silsileh between Assuan and Esneh, is very close-grained and disposed in regular layers, rendering it peculiarly suitable for the erection of large buildings. Hence from this source have been obtained the materials for the construction of thousands of temples and other structures. The breaches made by the ancient quarrymen in the rocks on the right side inspire a sort of awe by their prodigious dimensions. According to Charles Blanc, these mountains supplied the building stone for at least half of the old Egyptian monu- ments. The quarries on the west side, although less extensive, are more remarkable from the artistic point of view, for they contain several temples excavated in the live rock, as well as sepulchral caves and statues. Scarcely had the quarries been opened when they appear to have been, converted into tombs. In the northern section of the Arabian range the sandstones are replaced by limestones of various dates, some belonging to the cretaceous, others to the eocene epochs. To these chalk formations chiefly belong the cliffs stretching along the right bank of the Nile, which present the most varied and picturesque forms of monumental aspect, separated by mere fissures or by gloomy ravines, and often crowned with fantastic towers and pyramids. In the extreme north the last hills, terminating at Cairo itself with the Jebel- Mokattam, or " Inscribed Moimtain," are composed almost entirely of nummulites — osti*aBa, cerithium, and other shells massed together in a limestone conglomerate. Owing to the abundance of their fossils, they have become a sort of Eldorado for geologists. These nummulitic strata include in some places transparent alabasters of the choicest quality. Such are, west of Beni-Suef, those of the Jebel-Urakam, whence have been derived the materials employed in the construction of Mohammed Ali's mosque in the citadel of Cairo. Such are, also, farther south the alabasters, which take their name from the city of Alabastron, whose site was not far removed from the spot now occupied by the town of Minieh. But more important than these costly marbles are the quarries of building- stone skirting the Nile, especially those of Turah and Masarah. From the vast pyramids erected on the opposite side of the river some idea may be formed of the excavations begun six thousand years ago in these nummulitic limestone quarries, which also supplied the building materials for the cities of Memphis and Cairo.
