My sketch being finished, I was still attracted to a greater distance up the valley by something which seemed at first to be another monument; but it was only a mark fixed by the Arabs, and served but to lengthen my march back, which was more slow, as the heat had set in. But I was well satisfied with my morning’s work; and my companions were greatly astonished when they saw the sketch. In the afternoon I made with Overweg another excursion in the opposite direction, when after an hour’s march we ascended a height and obtained a most interesting view over this singular tract, which seems to be the fragmentary border of a plateau torn and severed by ravines and precipices, so that only wall- like cliffs, rising like so many islands out of a sea of desolation, indicate its height. A high craggy ridge towards the west, with precipitous pinnacled walls, looked like a castle of the demons. Just in a ravine on the border of this wild scene of natural revolutions, my companion had the good luck to find some very interesting fossils, particularly that beautiful specimen which after him has been called Exogyra Overwegi; but our zeal had carried us too far, and it grew dark as we commenced our return, so that we had some difficulty in groping our way back to our encampment, where we arrived weary and fatigued, after having caused our people a good deal of apprehension. [Sidenote: April 14th.] We were roused from our refreshing sleep as early as two o’clock after midnight; but this was a mere sham of our camel-drivers, who feigned making up for the loss of yesterday, and after all we did not get off early. Our road carried us from wadi to wadi, which were generally separated from each other by a defile, occasionally presenting some difficulty of passage. We left a castle of Roman workmanship, as it seemed, in the distance to the left, and further on to the right a slight stone wall called Hakl el Urínsa, dating from the petty wars between the Arab tribes. We had already passed a few small ethel-bushes; but now we came to a most venerable-looking old tree called Athelet Si Mohammed fi Useát, spreading out its weatherbeaten branches to a considerable distance: under this I sat down quietly for a while, waiting for our people, who were still behind. The caravan at length came up; and continuing our march, we soon passed on our right hand the chapel of a great Merábet of the Welád Bu-Séf, called Si Rashedán. The Welád Bu-Séf in general enjoy great authority with the other tribes for their sanctity of life and purity of manners; they allow no stranger to come near their villages, but pitch a tent for him at a distance, and treat him well. The person at present most distinguished among them for learning seems to be an old man named Sidi Bubakr, who exercises great influence, and is able to grant serviceable protection to travellers in time of war.