Page:Africa by Élisée Reclus, Volume 1.djvu/359



To the west of the border chain which skirts the Red Sea, the mountainous ridges run transversely either from the east to the west, or from the north-east to the south-west, in the same direction as the portion of the Nile comprised between Abû-Hamed and Dabbeh. Some of these ridges are continuous; such, for instance, os that of the "Cataracts," which forms the natural barrier between Nubia and

Egypt, west of Assuan; such also is the range whose culminating point is the Jebel-Shikr, north-east of Abû-Hamed.

Other ridges are intersected at intervals by broad breaches, and from a distance present the appearance of walls partially crumbling away. Like the mountains of the border chain, those of the highest transversal chains consist of crystalline rocks, granites, gneiss, porphyries, syenites, diorites, and volcanic formations. In many parts of the desert occur metamorphic sandstones, which have overflowed into the crevasses in the soil. But between the mountains, which form the backbone of Eastern Nubia, are other projections of less height, nearly all isolated, although