Page:Africa by Élisée Reclus, Volume 4.djvu/469

 the ravines by which they are broken at irregular intervals give access to shingly steppes where the gravel is in many places covered by a blackish silicious layer, interspersed with ferruginous nodules. These elevated plains reminded the French explorer, M. Révoil, of the appearance of the Crau formations in the south of France. A zone of upheaved coral reefs some miles in breadth, which here skirts the F present shore-line for some distance, seems to indicate a general upheaval of the

land, or else a corresponding subsidence of the sea-level in these waters. The chain of sandy dunes which still marks the line of the old beach lies some distance

Of all the fluvial systems in Somali Land the most important, both as regards the length of its course and the volume of its waters, is that which, under the