Anything more unlike the Atlas than this parallel range could scarcely be imagined, for in place of the long line of limestone cliffs there presents itself a chain of peaks of no very great altitude and of every colour and shape, the whole torn and twisted by volcanic action, and of an alternately deep red, purple, and black hue. Probably none of the peaks of the range that I saw are above 2000 to 3000 feet above the level of the plain, which would give an altitude of from 6000 to 7000 feet above the sea-level, for I found that we at Aït Yahia were at an elevation of 4700 feet. In one respect only was any resemblance noticeable between the two ranges—namely, the utter absence of vegetation on each; and anything more dismal than the intervening strip of desert, shut in by grey limestone and snow-capped mountains on the north, and dreary black hills on the south, it would be difficult to imagine. We crossed the Wad Imguna before daylight on the morning of November 9, and ascending the cliff to the level of the plain which we had left the evening before, turned slightly to the north, and for two or three hours travelled over the dreary barren plain. It was most curious to note the suddenness with which one comes into sight of, and loses again, the settlements in the wide valleys of this part of the country; for no sooner had we reached the summit of the cliff than Aït Yahia was entirely lost to view, the plain seeming to be one with the gradual slope of Jibel Saghru, on the farther side of the river. Ten minutes later not a habitation was to be seen, the _äudin_, or watch-towers, along the line of the valley being the only signs of any inhabitants in the dreary surroundings. Except for these we might have been in the centre of the Sahara, and even the half-ruined towers seemed the work of a long-departed people.