As the result of several favourable meteorological combinations, there exists in these loftier elevations a more luxuriant development of vegetation than in any of the neighbouring mountain districts of South Nubia, which have a lower altitude. This is illustrated very plainly by the clusters of beard-moss (_Usnea_) which hang on every twig and branch, by the abundance of sulphur-coloured lichens on every mass of rock, and likewise by the formation of numerous luxuriant beds of moss. Mosses are generally deficient alike in Egypt proper and in Nubia, and are scarcely seen in the trenches and clefts of the Nile valley; their existence is dependent on a minimum of moisture throughout the year, which is there but rarely reached. At Erkoweet I found again the wild olive tree, which I had already discovered some years previously on the mountains by the Elbe. I noticed that it assumes the same low bushy shape here, and bears the same box-like foliage, as it does on the coast ridges of the Mediterranean; when the two are compared they exhibit a general identity, so that I conclude the African and European are of the same family. The olive tree, it is well known, is reckoned, like the fig tree, as originally a product of the frontiers of Asia; in remote antiquity, it was reverenced by Semitic nations, and cultivated until it bore a rich produce. This type of vegetation fails completely in the interior of the continent. In the time of Homer the olive grew wild on the islands of the Grecian Archipelago, and it is still to be met with, though in an altered condition, on the coasts of Syria; but here on the Red Sea it has remained unchanged for thousands of years, and the famous classical tree of myth and song is still undisturbed in the dreams of its youth. [Sidenote: WATER-COURSES.] A bare boulder-flat of black hornblende stones, extending several miles, divides the mountains of Erkoweet from those which bound the valley of Singat on the east. The broad water-courses which run between, show what must be the prodigious volume and violence of the currents which occasionally rush downwards to the sea. These deep water-courses are, however, only periodically filled, and then only for a few hours, in the course of the year, so that for some months they are adapted for the cultivation of corn. Notwithstanding, there was here but a very limited cultivation of sorghum, the Arabian durra, since there is a difficulty in securing labour. The idle nomads have no disposition for agricultural employment, although famine in dry seasons, when the flocks can nowhere find sufficient pasture, brings back its recurring calamity. In the year before my last visit, in the valleys about Singat alone, seventy men had died literally of hunger, after vainly endeavouring for weeks to subsist upon wild purslane.