“After about three hours of level route we began to descend, not rapidly, but by degrees, and at noon we reached a singular depression, a huge natural basin, hollowed out in the limestone rock, with tracks resembling deep trenches leading to it from every side. At the bottom of this crater-like valley were a dozen or more wells, so abundant in their supply that they not unfrequently overflow the whole space, and form a small lake; the water is clear and good, but no other is to be met with on the entire line hence to Hasa. “For the rest of the day we continued steadily to descend the broad even slope, whose extreme barrenness and inanimate monotony reminded me of the pebbly uplands near Ma’an on the opposite side of the peninsula, traversed by us exactly seven months before. The sun set, night came on, and many of the travellers would gladly have halted, but Aboo-’Eysa insisted on continuing the march. We were now many hundred feet lower than the crest behind us, and the air felt warm and heavy, when we noticed that the ground, hitherto hard beneath our feet, was changing step by step into a light sand, that seemed to encroach on the rocky soil. It was at first a shallow ripple, then deepened, and before long presented the well-known ridges and undulations characteristic of the land ocean when several fathoms in depth. Our beasts ploughed laboriously on through the yielding surface; the night was dark, but starry, and we could just discern amid the shade a white glimmer of spectral sand-hills, rising around us on every side, but no track or indication of a route. “It was the great Dahna, or ‘Red Desert,’ the bugbear of even the wandering Bedouin, and never traversed by ordinary wayfarers without an apprehension which has too often been justified by fatal incidents. So light are the sands, so capricious the breezes that shape and reshape them daily into unstable hills and valleys, that no traces of preceding travellers remain to those who follow; while intense heat and glaring light reflected on all sides combine with drought and weariness to confuse and bewilder the adventurer, till he loses his compass and wanders up and down at random amid a waste solitude which soon becomes his grave. Many have thus perished; even whole caravans have been known to disappear in the Dahna without a vestige, till the wild Arab tales of demons carrying off wanderers, or ghouls devouring them, obtain a half credit among many accustomed elsewhere to laugh at such fictions.