"Ahaggars very strange," said Fekmah to the Americans, as they rode in a group at the back of their pack camels. "There are high cliffs, tall needle-like peaks, deep caves. There are canyons, ravines, underground passageways. We see much, and we too be in great danger." "Danger?" Joe looked up in some surprise. "Yes. Very great danger. Wild Tuaregs roam about, and when on a raid, think only of robbing travelers. Then, too, we be in region where the two thieves who stole my map are. They perhaps be waiting for us and shoot us quick without giving warning. Many other dangers we might see." Fekmah sobered the Americans a little. They had not anticipated any great peril, although they knew the two thieves might, should they have arrived at the hidden riches first, give them trouble. "But we'll come out all right," predicted Bob, again becoming cheerful. "We'll show those fellows that we're capable of attending to any crisis." A little farther on they reached the wall of rock that had previously shut out the view of the mountains. It stretched many miles to their right and left, but there were numerous breaks that afforded openings into the country beyond. They had barely reached the other side of the wall-like formation when Joe caught sight of a group of tents quite a distance to the east. He motioned for his friends to look in that direction. "Probably Arabs," pronounced Fekmah, after Tishmak had chattered rapidly for a moment. "They nomads, who wander about the desert taking their flock of goats with them." "Suppose we go over and see them," suggested Mr. Holton. "Perhaps they can give us a description of the country ahead of us. There may be many more wells than we think, and it will do us no harm to know of them." The others were in favor of carrying out Mr. Holton's move. But Fekmah warned them to be on the lookout for treachery. "They probably not do us harm, but can never tell," he said, as the dromedaries were turned in the direction of the tents. They reached the encampment in a very short time and were about to look up some of the Arabs when a savage growl made them wheel around in surprise and fear. "Look!" cried Joe, laying his hand on his rifle. Two large, savage dogs were making toward them with all fury, showing their terrible teeth in anger. The enraged creatures were probably owned by the Arabs in the tents and were acting as guards against all marauders. The foremost dog was almost upon Mr. Lewis's camel. In another moment the beast would sink its teeth in the dromedary's throat. Displaying the quickness of a cat, the naturalist unslung his rifle, took hasty aim, and fired. The report of the gun was followed by a longdrawn howl from the huge dog. "Quick!" cried Bob. "The other dog!" The second beast was rushing forward angrily. Mr. Lewis again took aim. The others, trusting in his marksmanship, made no move to get their rifles. Click! There was no report this time. His magazine was empty!