LAKES AND WADIES. 71 of about 60 miles ; but its surface is broken hero and there by small verdant depressions, mostly inhabited, and by some narrow wadiea. Amongst these is the Wady Zelaf, a remarkable fissure in the ground overgrown with a forest of palms, whose delicious fruit is the common property of all wayfarers. Custom, however, forbids them to carry away any supplies, and what is not consumed on the spot by passing caravans is gathered by the inhabitants of the Esh-Shiati. The western part of the plateau intersected by the wooded Zelaf watercourse is occupied by the so-called cdeyen, that is, in the Temahaq dialect of the eastern Tuaregs, *' sandhills." According to M, Duveyrier, who traverse<l it at two points, this sea of sands stretches for a distance of 480 miles in the direction from west to east, with a mean breadth of 50 miles. Towards the part of the plateau crossed by the main caravan route between Tripoli and Murzuk, the hitherto uninterrupted sandy surface becomes decomposed into a number of low eminences and distinct archipelagoes of sandhills, which are nowhere disposed in regular ranges, but rise in some places in completely isolated heights. North of Jerma, Earth's caravan found the winding lines of dunes so difficult to cross, that the men were obliged to level the crests with their hands before the camels could gain a footing. But the sandhills attain a still greater elevation farther west, where by trigonometrical measurement Vogel found one eminence rising 540 feet above a small lake occupying a depression in the plateau. Lakes and Wadies. The explorer is often surprised to meet in this almost rainless region permanent or intermittent lakes in the midst of the dunes. In a single group north of the Murzuk hamada there are as many as ten, nearly all, however, of difficult access, owing to the hillocks of fine sand encircling them, in which the foot sinks at every step. Two of these basins contain chloride of sodium and carbonate of soda, like the natron lakes of the Egyptian desert; hence the designation of Bahr-el-Trunia, or ** Sea of Xatron," applied to one of the Fezzan lakes. Several other lacustrine basins are inhabited by a peculiar species of worm, highly appreciated by the epicures of the district. The lake yielding the most abundant supplies of this delicacy is specially known as the Bahr-el-Dud, or " Sea of Worms," and the local fishermen take the name of duwada, or " worm- grubbers." This sheet of water, fringed by palms and almost circular in form, has a circumference of about 600 miles, with a depth in the lowest part, measured by Vogel, of 26 feet. But owing to the almost viscous consistency of the excessively saline water, it appears far deeper to the natives, who regard it as fathomless. Invalids from all parts of Fezzan frequent it in crowds, first bathing in this basin, and then plunging in some neighbouring freshwater pool, in which is dissolved the incrustation of salt covering their bodies. The worm, known to naturalists by the name of artcmia Oadncyi, is the larva of a diptera, whose serpentine body, one-third of an inch long, and of a gold-red colour lik^jLa^f the cyprinus of China, flits about like a flash of fire, with surpris-
