TII£ LIBYAN DESEBT. 820 the wildcrnoss were a Bpcciul favour of heaven. Ncvertheleaa the sovereigns of Egypt, and after them the Roman and Byzantine emperors, were well aware that these oases were not the happy abodes sung by the poets, for thither they banished their enemies to perish of weariness and inanition. Thousands of Christians, exiled by their fellow-Christians of different theological opinions, yielded to home-sickneas in these dreary " convict stations." Some of the oases, amongst others that of Dakhel, possess the romantic beauty imparted by a superb rampart of cliffs, with their fantastic towers and embattlements rising from 800 to 1,000 feet above the hamlets and pulm-groves. But the traveller's admiration is, even here, due mainly to the impression of contrast presented by the patches of verdure to the dismal waste of bare rocks and sand encircling them. lie is naturally enraptured when, after traversing the waterless desert, the constant sport of the mirage, he at last comes upon real streams of water, flowing beneath the shade of leafy groves. But then comes the inevitable feeling of oppression produced by the narrow limits of these garden-plots, everywhere surrounded by boundless wastes, stretching in all directions beyond the horizon. The Libyan Desert. The sands of the desert form shifting dunes like those on the Mediterranean and Atlantic coasts. Between the Nile Valley and the chain of oases several ranges of these dunes are disposed, nearly all in the direction from the south-east to the north- west, parallel with the course of the river between Assuan and Miuich. The sand- hills do not attain an elevation comparable to those of the French landes ; doubtless the laboratory where rocks are weathered into minute particles are more remote, while the winds are less powerful. A few stunted shrubs, especially the tamarisk plant, are the chief instruments employed by nature in binding the sand in compact masses. Behind these obstacles a little heap is formed, the horns of its crescent curving forward with the wind. Soon the plant is enveloped, and would in a short time be entirely swallowed up, if its gro^-th did not keep pace with the rising sands. Thus are formed hillocks, whose mean height scarcely exceed 12 or 14 feet, and on the crest of which is visible the foliage of a tamarisk or some other shrub. A peculiar physiognomy is imparted to the Libyan desert by these low eminences, which in form and colour resemble eroded cliffs, but all of which bear a plant of some kind on their summits or slopes. The sands do not pass beyond any rocky heights exceeding the mean elevation of the plateau ; they are also arrested before the Pyramids on the edge of the limestone rocks skirting the valley of the Nile. Hence arose the otherwise groundless and absurd hypothesis that the huge tombs of the Pharaohs were erected to protect Egj'pt from the invading sands of the desert. When the west wind prevails, thousands of small streams of red or golden sands overflow from the rocky battlements of the plateau, fonning long ridges which here and there encroach on the cultivated lands. In this way the course of tho
