Roman arms had penetrated, and the capital of these oases still possesses 2 Roman castle, whose inhabitants have replaced the roof by a layer of earth supporting a few date-palms. The palm groves of the Northern Zab yield the finest dates in the country; but the cultivated tracts do not suffice for the support of the inhabitants, although fresh oases have recently been created by the French settlers.
The capital of the archipelago is Tolga, a great religious centre, with some fifteen mosques and a zawya even more powerful than that of Sidi Okba, attracting to its school of Arab jurisprudence as many as one thousand students. Its political influence also, always conciliatory towards the French, makes itself felt as far as the Tunisian frontier. In the Lishana oasis, north-west of Tolga, a few ruins mark
the site of Zaacha, which after its heroic defence and destruction by the French in 1849, has never been rebuilt.
South of Biskra, the Tugurt route, which will soon be accompanied by a railway. traverses the newly created oasis of Um-el-Thiur, and after skirting the northern bank of the Jeddi, follows the west side of the Shott Melghigh and its southern prolongation, the Shott Merwan. Here the oases run north and south in the plain of the Wed Righ, beneath which the underground waters are tapped at intervals by old and modern artesian wells. Thanks to the recent borings of the French engineers, the palm groves of Mghaier now contain some fifty thousand trees, while extensive tracts have been brought under cultivation in the Ughlana and Tamerna districts. Since the middle of the century the supply of water has increased fourfold, changing the whole aspect of the Wed Righ, and causing new oases and villages to spring up in all directions.
