Fortunately for the four "stowaways" it was not the sparkle of the lens that had caused them to make that stop. A ravine or opening through the sand-ridges, much larger than that in which our adventurers were concealed, embouched upon the beach, some distance below. It was the appearance of this opening that had attracted the attention of the two mounted men; and from their gestures Colin could tell they were talking about it, as if undecided whether to go that way or keep on up the strand. It ended by the yellow man putting spurs to his horse and galloping off up the ravine, followed by the black man on the camel. From the way in which both behaved; keeping their eyes generally bent upon the ground, but at intervals gazing about over the country; it was evident they were in search of something, and this would be the she-camel, that lay tethered in the bottom of the sand-gorse, close to the spot occupied by our adventurers. "They've gone off on the wrong track," said Colin, taking his eye from the glass as soon as the switch tail of the maherry disappeared behind the slope of a sand-dune. "So much the better for us. My heart was at my mouth just a minute ago. I was sure it was all over with us." "You think they haven't seen the shine of the lens?" interrogated Harry. "Of course not; or else they'd have come on to examine it. Instead, they've left the beach altogether. They've gone inland, among the hills. They're no longer in sight." "Good!" ejaculated Terence, raising his head over the ridge, as did also the others. "Och! good yez may well say, Masther Terence. Jist look what fools we've been all four av us! We never thought av the thracks, nayther wan nor other av us." As Bill spoke he pointed down towards the beach, in the direction in which he had made his late crawling excursion. There, distinctly traceable in the half-wet sand, were the marks he had made both going and returning, as if a huge tortoise or crocodile had been dragging itself over the ground. The truth of his words was apparent to all. It was chance, and not their cunning, that had saved them from discovery. Had the owner of the camel but continued another hundred yards along the beach, he could not have failed to see the double "trail" made by the sailor; and of course would have followed it to the spot where they were hidden. As it was, the two mounted men had not come near enough to note the sign made by the old salt in his laborious flounderings; and perhaps fancying they had followed the strand far enough, they had struck off into the interior, through the opening of the sand-hills, in the belief that the she-camel might have done the same. Whatever may have been their reason, they were now gone out of sight, and the long stretch of desert shore was once more under the eyes of our adventurers, unrelieved by the appearance of anything that might be called a living creature. CHAPTER SEVENTEEN. THE "DESERT SHIP."