488 NORTH-WEST AFRICA. plateau thus developed is probably the region described by the inediajval Arab writers under the name of the Jebel Tan tana. South of Rhat a narrow breach in the plateau opens a way for travellers proceeding in the direction of Air. Nowhere does nature assume a more forbidding and inhospitable aspect than in these wild mountain gorges. The absolute nakedness of these escarpments, the sombre glitter of the blackish sandstone rocks, the fantastic outlines of the heights, without a blade of grass or tuft of moss, all forms a picture of desolation producing on the wayfarer a sense of awe far more impressive than the endlass waste of sands them- selves. In the midst of these jagged cliffs, and especially in the Janet district, lying west of the breach, a few cavities are filled with water, and according te native report several of them harbour crocodiles. South of the plateau the route descends rapidly towards the plain through a series of dangerous inclines flanked at first by sandstone walls, and farther south by granite cliffs. Recent Expeditions. West of the breach, which was traversed by Earth and his associates, the mountains and plateau are scarcely known except from the reports of the natives. Nevertheless the northern outskirts of this region have been visited by Duveyrier, and since his memorable exploration of 1860, by the two peaceful expeditions commanded by Flatters. Laing also skirted the same highlands in the year 1822, at the time of his journey across the Sahara to Timbuktu. But his journal was lost, and none of his observations ever reached Europe. Rohlfs travelled over nearly the same ground as the English explorer, but from the opposite direction, between Twat and Ghadames. The unfortunate events attending the two expeditions to the Tuareg country under the direction of Flatters, which were equipped to cross the desert from north to south, are still fresh in the memory. The first, organised at Wargla in 1880, deviated from the route laid down beforehand, and ended by taking the road to Rhat, without, however, reaching that oasis. Worn out by the dilatory negotiations with the Tuareg chiefs, and finding all their supplies and money exhausted at this early stage of the journey, the members of the expedition were obliged to return. A second mission, composed partly of the same officers, started the following year in the direction of the desert. It penetrated farther south, beyond the district of North Tassili ; but it ended in disaster. The caravan, divided into detached groups, following each other at intervals of several miles, had been secretly pursued to the west by a constantly increasing horde of Tuaregs ; traitors had insinuated themselves into the presence of the leaders, offering to serve as guides, and every preliminary measure was taken for a preconcerted attack. At the fatal moment Flatters, overtaken while almost alone, is killed with one of his com- panions, the camel-drivers make off, and the whole body of Tuaregs fall upon the convoy approaching from a distance. The fifty-nine survivors of the first ' onslaught were compelled to break up the camp during the night, and begin their
