As it was, when we encamped in the afternoon, we had still a long day’s march before us, and therefore the next day, from general impulse, in order to make sure of our arrival at the well, we started at an early hour, keeping the caravan together by repeated shouting. After a march of about twelve miles, we reached the first passage leading down from the Hammáda and called Tníe[50] Twennín; but it was too steep and precipitous for our rather heavily laden caravan, and we had to continue till we reached the Tníe el ʿArdha, a little after eleven o’clock, when we began to descend from the plateau along a rough winding pass. The sandstone of which it is formed presented to us a surface so completely blackened, not only in the unbroken walls of the ravine, but also in the immense blocks which had been detached from the cliffs, and were lying about in great confusion, that at first sight anybody would have taken it for basalt; but when the stones were broken, their real nature became apparent. Over this broad layer of sandstone, which in some places covered a bed of clay mixed with gypsum, there was a layer of marl, and over this, forming the upper crust, limestone and flints. After a winding course for an hour, the narrow ravine, shut in by steep, gloomy-looking cliffs, began to widen, and our direction varied less; but still the whole district retained a gloomy aspect, and the bottom of the valley was strewn with masses of black sandstone, while the country ahead of us lay concealed in a hazy atmosphere, which did not admit of an extensive view. Eager to reach the well, the caravan being scattered over a great extent of ground, we three travellers, with one of the shoushes, pushed on in advance, the south wind driving the sand, which lay in narrow strips along the pebbly ground, into our faces. We cherished the hope of finding a cool little grove, or at least some shade, where we might recline at ease after our fatiguing march; but, to our great disappointment, the sand became deeper, and nothing was to be seen but small stunted palm-bushes. But even these ceased near the well, which was dug in the midst of the sandy waste, and had once been protected by an oval-shaped building, of which nothing but crumbling ruins remained.