We left the valley, by a pass to the southward, and entered an extensive plain, named Ambulum: in this we travelled the whole day. The surface, in some places, a firm sand, with here and there rocky eminences, and patches of gravel: the latter was fine, and mixed with fragments of shells. Often, for a considerable extent, not the least vestige of vegetation; and in no place was the ground completely covered, except in a few small oases, where there was a species of grass, of the genus festuca. The feniculum duter, and a beautiful genista, which extends all the way from the coast, were common. The butum occurred in abundance, and its shade was a defence to us at times. We found some beautiful fragments of striped jasper, and some small pieces of cornelian. Bonjem.—We had no opportunity of examining any of these; but from the strewed masses they appear to be limestone. The wadey of Bonjem has characters different from any of the other valleys we have passed through. This valley is strewed over with gypsum in different states, with numerous shells, of the genus pecten, and several terebrellæ. There are here and there sand, and many incrustations of the carbonate, mixed with crystals of the sulphate, of lime, that gives to the surface a shining white appearance, which, in place of being pleasing, is disagreeable, by the power of the reflected light. There are small ranges of low hills, composed of soft white chalk (whiting), covered with a crust of gypsum. In this structure we found one large pit, about forty feet deep, and nearly as much in diameter. These low hills are bounded by much higher, and of a dark brown colour: the low hills are numerous, some are separate, but in general they are in short ridges, and have, at a distance, very much the appearance of fortifications. A small senecio, a geranium, and a statice, were the principal beings of the vegetable creation. Barometer 30.020. temperature 72. Near the wells, the _arundo phragmites_ grows in abundance; it has long creeping roots, the first true roots of that kind I have seen in North Africa. Plants of this kind would soon make considerable encroachments on the desert, and render habitable where it is difficult even to travel over. This quarter is poor in the grasses, for I think I have not seen above eight different kinds. Our course was among sand-hills, and over a gravelly road, strewed with masses of common opal, with small portions of botroidal iron ore, and thick layers of gypsum, with their edges appearing above ground. The low hills presented the same features as those near which we remained in the wadey: one, detached on the road, had a curious appearance, and was called, by the natives, “The Bowl of Bazeen.” It is about forty feet high, and formed above of a calcareous crust, with sulphate of lime, and below of soft chalk.