of the country should be the Sahara itself, or the waterparting between the Igharghar and Niger basins, or else the Niger itself as far as Upper Senegal. But restricting it to the almost geometrical quadrilateral between the sea and the desert, Algeria has an area of about 120,000 square miles, or somewhat less than half of the territory virtually occupied by the French. Their outposts stretch far beyond the natural limits of the southern uplands, and are distributed irregularly over considerable tracts of the desert. Thus El-Golea, which now pays a regular tribute, is 420 miles in a straight line south of Algiers, and 240 from the nearest mountains of Laghwat. French expeditions have often reached the Ksurs of the Sahara, and even the Figuig district, without, however, annexing this region, out
of regard for the prior claims of Marocco. The frontier in this direction is far from clearly marked, no natural line of demarcation having been followed in determining the political confines, which by the treaty of Tangier, in 1844, were laid down at haphazard across mountains, valleys, and tribal districts.
In the western province of Oran the prevailing formations are Jurassic, which also form the chief strata throughout the plateau. In the east especially, these rocks underlie the chalk, which in its turn is overlaid in the north by Miocene and Pliocene formations. Alluvia of various epochs, and of vast depth, occupy the river valleys, and in a great part of the plateau cover both the Jurassic and cretaceous rocks. The Triassic and older schists are represented by a few isolated
