The caravan of the Tawáti having passed by our encampment at an early hour, we followed betimes, having an interesting day’s march before us. For the first three miles we still kept along the large valley, into which masses of sand had been driven down from the plateau by the strong east winds; further on it became dry and bare. To this succeeded an irregular knot of hollows and plains between the sides of the plateau, which in some places formed imposing promontories and detached buttresses, all on one and the same level. We then began to ascend along a sort of broad valley, which gradually assumed a regular shape, and bore the name of Tísi. The slope of the plateau was shaped into regular strata, the uppermost of which form steep precipices like the wall of a castle; the lower ones slope, down more gradually. Here we discovered ahead of us, at the foot of the southern slope, the encampment of the pilgrim-caravan, who were resting during the heat of the day. We continued our march, always ascending, till a little after noon we reached the edge of the pass, a perfect watershed, of more than 2,000 feet elevation, descending more gradually towards the east as far as the well of Sháraba, while towards the west is formed a steep precipice, passable only along a most interesting gully cut into it by the water towards the Valley of Ghát. The higher level, which rises above the pass about 300 feet, seems to be considerably depressed in this place, where it collects large floods of water, such as could alone cut the remarkably wild passage through the sandstone cliffs which we were about to descend: it is called Rálle. The first part of it was more rough than wild, and the cliffs of the sandstone rather rugged and split than precipitous and grand; but after half an hour’s descent it bore evident traces of the waters that descend from the heights, and which being here collected into one mighty stream, with enormous power, force their way down through a narrow channel. The defile was here encompassed by rocky walls about a hundred feet high, half of which consisted of sandstone, while the other half was formed by a thick deposit of marl; and a little further down it was not more than six feet wide, and the floor and the walls were as smooth as if they had been cut by the hand of man; but the course of the defile was rather winding and not at all in a straight line, forming altogether a pass easily to be defended by a very small power, and affording the Tuarek a stronghold against any designs of conquest on the side of the Turks, although it does not form the frontier, but is regarded as entirely belonging to Fezzán. At the narrowest point Tuarek as well as Arab travellers had recorded their names.