456 NOETH-WEST AFEICA. escarpment of the cretaceous plateau, along the depression of the Wed Meguiden, occupied by the Quaternary alluvia of the Saharian formations. Even along the direct route across the plateaux from El-Golea to Tidikelt he meets wells, planta- tions, and pasturages at stated intervals. No dunes occur on the first day's march south of El-Golea, except for a short distance of 2| miles, and the tracks across the hamadas and other wastes destitute of vegetation are all carefully indicated by a regular system of landmarks. For a great part of the way, the Mejebel, that is, the main caravan routes, are kept clear of stones and other obstructions for a normal width of from 20 to 30 feet. All the pebbles, shingle, and boulders that formerly strewed the ground have been carefully removed and disposed in rough walls right and left of the highway. This great work, which must have required a vast amount of labour, dates from an unknown epoch. By the Shaanba tribe it is attributed to a mythicaj being named Ben Buur, who is supposed to have flourished at a time when Twat was still uninhabited. Flora, Fauna, and Inhabitants of Twat. The products of Twat differ in no respect from those of the other districts in the Central Sahara lying at the same altitude and under the same climatic condi- tions. In all these oases, as in those of Marocco and Eastern Mauritania, the date- palm is the characteristic plant ; but with the exception of a few choice varieties, it yields a fruit of inferior quality to that of the Suf and Tafilelt districts. But although the palms of Twat are generally of small size, the wood is better and more durable than that of the western plantations. In the shade of their tufted foliage the natives cultivate wheat, barley, and beshna, the latter yielding two crops in the year. In the orchards are also grown pomegranates and some grapes, but in small quantity, these fruits being generally dried up by the sun before arriving at maturity. The inhabitants of Twat also raise various kinds of vegetables in their well- watered gardens. But the yearly produce is insufficient for the local wants, so that the natives have to supplement their stores with supplies of various kinds from the Algerian agricultural districts. A part of the land is also reserved for the culti- vation of industrial plants, such as cotton, henna {^Lawsoniji inennis), and korunka (^calotropis procera^, a shrub, the wood of which supplies the charcoal employed in the manufacture of gunpowder. Opium, which the natives of Twat smoke with avidity, is cultivated especially in the northern districts, while tobacco is one of the chief products in those of the south. The domestic animals are the same as in the other oases, but less numerous. In Twat the camel is man's chief associate, both as a pack-animal and for riding. Horses, fed like the asses, on damaged dates, are very rare, while horned cattle are completely absent. The sheep, covered like the goats with a coat of hair, resemble those of Tibesti, and full-grown poultry are no bigger than the chickens of Western Europe. According to Rohlfs, the first inhabitants of Twat would appear to have been
