"Does seem strange," Bob agreed. "But I suppose he's been over the route so much that he knows all the landmarks by heart, though it looks like a sandstorm or something else would change the surface of the land." Mention of the Ahaggars brought to mind the possibilities of finding the hidden riches. Bob and Joe wondered if the two thieves who had caused the explorers so much trouble would, with the aid of the stolen map, locate the treasure first. Perhaps they had already found the place and were gloating over the success of their wicked scheming. The youths said nothing, but the expression on their faces told what they would do to the men if given the opportunity. "We'll finally have a chance to square things," thought Bob, gritting his teeth. "And oh, how those fellows will look when we're through with them!" A little later they came to a deep valley between the mounds of sand. In order for the camels to cross it they would find it necessary to climb the steep sides of the dune. Mr. Lewis rode back to the boys. "Have to be careful here," he warned. "It's rather steep near the top. Don't let your mounts get out of control." The next instant he was on his way back to the front of the caravan. The climb was hard and not a little dangerous, but the sure-footed dromedaries did not even threaten to slip. They had barely reached the top when a cry of delight from Joe mingled with the scarcely less emotional exclamations of the others at sight of a small oasis not far away down the opposite slope. A number of tall date palms towered above the green grassy area, an indication that water was to be had for the taking. "Hurrah!" cried Bob. "Water at last!" "And if I'm not mistaken, we'll find dates there, too," put in Joe. "You're right," affirmed Mr. Lewis, coming up from the side. "And this seems to be a good spot to stop for the noon meal. We'll have it shady this afternoon when we take our midday rest." Nearer and nearer they were coming to the oasis, when suddenly, from behind a low dune of sand, appeared a small caravan of Arabs--possibly bandits. CHAPTER XI Fighting Heavy Odds "Keep your hands on your guns," called Dr. Kirshner, as he gazed at the approaching party of Arabs. There were ten of them, and each armed with a short range rifle, which, although inferior to the guns of the Americans, could do a great deal of damage. In addition to the mounts of the Arabs, there were six or seven pack camels that trailed. As the caravan came nearer, Tishmak waved and shouted a friendly greeting, but he did not receive the same in return. Evidently the men had no friendly intentions. Tishmak chattered a moment to Fekmah, who then turned to the Americans. "They are probably nomad bandits," Fekmah said excitedly. "Tishmak says we might have fight." "A fight!" cried Joe. "Why? Are they going to try to rob us?" Fekmah nodded. "Worse, perhaps," he replied.