CHAPTER VIII.
TUNISIA.
ITHIN its present limits, Tunis does not form a geographical unit distinct from the rest of Mauritania. Its highlands belong to the Algerian orographic system, while its chief rivers take their rise beyond the frontiers, which are themselves frequently displaced, and which, since the French occupation, have acquired a purely conventional value. Hence it becomes impossible to study the main physical features of Tunisia apart from the rest of the Atlas regions, of which it forms little more than a special geographical division. Nevertheless, certain natural limits may be traced along a line of rugged and almost uninhabited hills; its historic evolution also differs in several respects from that of Algeria, while its inhabitants are still grouped under a distinct political administration.
Taken in its broader sense, and not in its more restricted historic acceptation, Mauritania forms one of the best defined natural regions in the world. It comprises the portion of North Africa which enbraces the whole of Tunisia, Algeria, and Marocco, and which was designated by the Arabs under the general appellation of Gharb, or Maghreb, that is, the "West," in a pre-enminent sense, and even Jeziratel-Maghreb, or the "Western Island." Belonging, like Spain, the south of France, and Italy, to the Mediterranean zone, it is far more compact than those south European lands, presenting a surprising simplicity of outline instead of a contour broken by deep bights, headlands, and peninsulas. Its general form is that of a regular quadrilateral, limited northwards by the Mediterranean, cast and west by the Gulf of Cabes and the Atlantic, south by another ocean of sands, clays, rocks, and shingle. This very desert space, or at all events a great part of it, may itself have possibly at one time been a marine basin, as Bourguignat has endeavoured to show, and as has since been asserted by many writers. But this Saharian sea, dry land at all events since the early Miocene period, has left no fossils to attest its former existence, and it is now known that the proposed attempts to restore the inland basin could result in nothing more than a chain of lakes flooding the shotts standing at a lower level than the Gulf of Cabes.
But however this be, Maghreb still remains, from the geographical standpoint, a perfectly isolated upland region, connected by no rivers or great natural or arti-
