436 NOETH-WEST AFEICA. The inhabitants of Kawar are also subject to other masters, the redoubtable Aulad-Sliman Arabs, who after long sojourning on the steppes of the Tripolitana coast, have sought other pastures and other fields of plunder in the neighbourhood of Lake Tsad. Hereditary foes of the Tibbus, they often suddenly sweep down on the Kawar oases, slaying the men, carrying off women and children, and retiring laden with booty. The villages remain unpeopled for a time, but a short period of peace suffices for fresh immigrants to come and occupy the empty houses. At the time of Nachtigal's visit the dwellings scattered over various parts of the oasis would have afforded homes for a population of six thousand ; but all the inhabitants numbered no more than two thousand three hundred. The Bilma Salt Pans. It cannot be said that immigrants are attracted to the oasis by its fertile soil or abundant crops. The dates of its palm groves are of poor quality, and the inhabi- tants scarcely venture to occupy themselves with field operations. But the advantages derived from the transit trade through this important station, midway between Murzuk and Kuka, are sufficient inducement to settlers, notwithstanding the dangers they run from Arab marauders. Kawar also possesses a local treasure, which secures it customers from a large part of the Sudan. These are its saline lakes, many of which surround the capital towards the centre of the oasis and one of which swarms with "worms" {^arteinia adneyi^XiikQ the Bahr-el-Daud in Fezzan. But the most productive salines are those situated in the Bilma district, that is, the northern part of the oases, in which is situated the town of Garu. Here the salt basins are very shallow, and divided into compartments by clay walls, like the '* bosses " in the French saline lagoons. Through the effect of evaporation, crystals are formed on the surface of the water, which mingling with the sand and dust brought by the winds, soon constitute a greyish incrustation differing Httle in appear- ance from the surrounding soil. On the bottom is precipitated another layer of salt, which is collected and divided into lots according to its quality, for the use of men and animals. Afterwards it is fashioned into blocks of various forms, a camel-load of which is bartered for about four shillings' worth of corn. In the Sudan markets this price is increased at least thirtyfold. No doubt, in the various regions of Sudan salt can be procured by the combustion of certain plants and by several other processes. But they are all so tedious and difficult, and the yield is of such a poor quality, that the chief supply naturally comes from the desert. No region of the Sahara contains larger deposits of excellent salt than the Bilma district, which accordingly attracts buyers from far and wide. In order to welcome the strangers, the native women receive them by throwing handfuls of salt over their clothes, as if to say, " The best of the land for you ! " According to Nachtigal, seventy thousand camels come every year for their load of salt at the Bilma salines, and some of the salt caravans, such a^ those of the Tuareg traders with Haussa, comprise as many as three thousand pack animals. The Tedas have a monopoly of the transport between the Kawar oasis
