She was still a long way off, only her canvas and the upper portions of her hull showing above the sky line. At that distance it was impossible, without the aid of a telescope or binoculars (neither of which was on the boat), to distinguish her rig or in which direction she was heading. As she was a sailing craft, and, taking for granted that she carried the same wind as the boat, the chances were that she would soon disappear from sight. Nevertheless Mostyn meant to leave nothing undone that might attract the stranger's attention. Rockets were fired in the hope that the loud detonation might be audible at that distance. The light they gave out would be unseen in the terrific glare of the sun. At Preston's suggestion strips of canvas were soaked in lamp oil and set alight at the end of the boat-hook. These flares gave out a dense smoke that rose to an immense height in the now still and sultry air. For the best part of half an hour these signals were repeated at frequent intervals. Then, to everyone's disappointment, the strange sail faded from view. "It's not to be wondered at," remarked Preston. "You know what a look-out at sea is like; and, in any case, they don't keep a fellow on watch to see what's coming up astern." "They ought to," declared Olive. The Acting Chief was sitting up, his back supported by some spare oilskins folded over the after thwart. At the girl's retort he winked solemnly with the eye that was not covered with bandages. "Do we?" he asked. "Look astern now." To the surprise of everyone else in the boat a large sailing craft was bowling along dead in their wake. She was now a little less than a mile away, and had evidently been attracted by the signals made to the craft that had so recently been sighted in vain. "A rum sort of packet, by Jove!" exclaimed Peter. "A dhow, my sweet youth," explained Preston. "'Tisn't often you find 'em so far south, but you'll see shoals of them up along the coast from Mozambique and Zanzibar right up to the Red Sea and Persian Gulf. Clumsy-looking hookers, but they can shift." It was Mostyn's first sight of an Arab dhow. He had seen plenty of Chinese junks in Shanghai whilst he was on the Pacific trade. This craft reminded him of them, only its rig was more in accord with Western ideas. End-on it was impossible to see that the masts raked at different angles, but the well-drawing lateen sails and the "bone in her teeth" indicated that she was a swift craft ably managed. Even in the light air she was moving at about six knots. The Wireless Officer leant forward and whispered in Preston's ear. "S'pose she's all jonnick, old man?" he asked. "Sure," replied the Acting Chief. "The slave-dhow and the gun-runner are as dead as the dodo in these parts. Probably she's a trader from Reunion, blown out of her course by the late hurricane. Nothing to worry about, old son."