Across the brown of the hard, pebbly desert there had been visible for some time a single long, thin, yellow streak, extending north and south as far as they could see. It was a band of sand not more than a few hundred yards across, and rising at the highest to eight or ten feet. But the prisoners were astonished to observe that the Arabs pointed at this with an air of the utmost concern, and they halted when they came to the edge of it like men upon the brink of an unfordable river. It was very light, dusty sand, and every wandering breath of wind sent it dancing into the air like a whirl of midges. The Emir Abderrahman tried to force his camel into it, but the creature, after a step or two, stood still and shivered with terror. [Illustration: The creature, stood still p171] The two chiefs talked for a little, and then the whole caravan trailed off with their heads for the north, and the streak of sand upon their left. “What is it?” asked Belmont, who found the dragoman riding at his elbow. “Why are we going out of our course?” “Drift sand,” Mansoor answered. “Every sometimes the wind bring it all in one long place like that. To-morrow, if a wind comes, perhaps there will not be one grain left, but all will be carried up into the air again. An Arab will sometimes have to go fifty or a hundred miles to go round a drift. Suppose he tries to cross, his camel breaks its legs, and he himself is sucked in and swallowed.” “How long will this be?” “No one can say.” “Well, Cochrane, it's all in our favour. The longer the chase the better chance for the fresh camels!” and for the hundredth time he looked back at the long, hard skyline behind them. There was the great, empty, dun-coloured desert, but where the glint of steel or the twinkle of white helmet for which he yearned? And soon they cleared the obstacle in their front. It spindled away into nothing, as a streak of dust would which has been blown across an empty room. It was curious to see that when it was so narrow that one could almost jump it, the Arabs would still go for many hundreds of yards rather than risk the crossing. Then, with good, hard country before them once more, the tired beasts were whipped up, and they ambled on with a double-jointed jog-trot, which set the prisoners nodding and bowing in grotesque and ludicrous misery. It was fun at first, and they smiled at each other, but soon the fun had become tragedy as the terrible camel-ache seized them by spine and waist, with its deep, dull throb, which rises gradually to a splitting agony. “I can't stand it, Sadie,” cried Miss Adams, suddenly. “I've done my best. I'm going to fall.” “No, no, Auntie, you'll break your limbs if you do. Hold up, just a little, and maybe they'll stop.”