_Friday, August 16._—We started early. Gravelly and pebbly grounds succeeded each other, the principal formation being granite; but when, after a march of about thirteen miles, we passed the narrow sandy spur of a considerable ridge approaching our left, a fine species of white marble became visible. We then passed a rugged district, of peculiar and desolate appearance, called Ibéllakang, and crossed a ridge of gneiss covered with gravel. Here, while a thunder-storm was rising in the east, our caravan, to our great regret, divided, the Tinylkum turning off towards the east, in order, as we were told, to look for a little herbage among the sand-hills. Meanwhile thick, heavy clouds, which had been discharging a great quantity of rain towards the east, broke over us at a quarter past four o’clock in the afternoon, when we were just in the act of crossing another rocky crest covered with gravel. A violent sand-storm, followed by heavy rain, which was driven along by a furious gale, soon threw the caravan into the utmost confusion, and made all observation impossible; but fortunately it did not last long. It was on descending from this crest, while the weather cleared up, that the Háusa slaves, with a feeling of pride and joy, pointed out in the far distance “dútsi-n-Absen” (Mount Absen). Here the granite formation had been gradually succeeded by sandstone and slate. This district, indeed, seems to be the line of demarcation between two different zones. At twenty minutes past six o’clock we at length encamped, but were again in the saddle at eleven o’clock at night, and in pale moonlight, sleepy and worn out as we were, began a dreadful night’s march. But altogether it proved to be a wise measure taken by the Kél-owí, who had reason to be afraid lest the Hogár, of whom they appeared to have trustworthy news, might overtake us before we reached the wells of Asïu, and then treat us as they pleased. Our companions, who were of course themselves not quite insensible to fatigue, as night advanced, became very uncertain in their direction, and kept much too far to the south. When day dawned our road lay over a flat, rocky, sandstone surface, while we passed on our left a locality remarkable for nothing but its name, Efínagha. We then descended from the rocky ground into the extremely shallow valley of Asïu, overgrown with scanty herbage of a kind not much liked by the camels. Here we encamped, near a group of four wells, which still belong to the Azkár, while a little further on there are others which the Kél-owí regard as their own property. How it was that we did not encamp near the latter I cannot say. But the people were glad to have got so far. The wells, or at least two of them, afforded an abundant supply of water; but it was not of a good quality, and had a peculiar taste, I think on account of the iron ore with which it was impregnated.