Once we halted and began to feel that a great depression lay in front of us; but not till two in the afternoon after we had crossed a basalt outcrop did we look out over a trough fifteen miles across, which was Wadi Hamdh, escaped from the hills. On the northwest spread the great delta through which Hamdh spilled itself by twenty mouths; and we saw the dark lines, which were thickets of scrub in the flood channels of the dried beds, twisting in and out across the flat from the hill-edge beneath us, till they were lost in the sun-haze thirty miles away beyond us to our left, near the invisible sea. Behind Hamdh rose sheer from the plain a double hill, Jebel Raal: hog-backed but for a gash which split it in the middle. To our eyes, sated with small things, it was a fair sight, this end of a dry river longer than the Tigris; the greatest valley in Arabia, first understood by Doughty, and as yet unexplored; while Raal was a fine hill, sharp and distinctive, which did honour to the Hamdh.