"They aren't going far," he announced, following the Arabs' movements closely. "They've stopped behind that sand hill over there." "By George!" exclaimed Mr. Holton. "They're going to plant a battery, are they? Well, just let them waste their ammunition. We won't fire until necessary." "We may need our bullets to use on those two thieves who stole Fekmah's map," said Bob to his chum, smiling. The explorers waited ten minutes for the robbers to take the aggressive, but they did not. "Well," said Dr. Kirshner, turning about, "I'm going over and get our things packed back on the dromedaries. If nothing prevents, we want to get started in a short time now. It is much cooler, and we should cover a good distance by night." "We'll stay here and guard a few minutes longer," declared Mr. Lewis. "There's no telling what those fellows may do." Suddenly a sound from the opposite direction caused them to turn about. Then their expressions changed. Not fifty feet down the slope were the robbers, riding at full speed toward the explorers. The Arabs had their rifles in position to fire, which they were undoubtedly intending to do when slightly nearer. "Quick!" cried Bob, his voice cool but determined. "Fire at them before they get us!" A moment later he took careful aim and pulled the trigger. His rifle cracked, and the foremost camel went down, sending its rider sprawling over the ground. Bang! came the sound of Mr. Lewis's gun, and another camel fell. The eight Arabs who were still mounted wheeled about and galloped back hurriedly. As quickly as possible they formed a wide line, one beside the other, until it stretched several rods. "They're going to charge!" observed Dr. Kirshner. "Have your rifles in position, and make every shot count." When the bandits were confident of their formation, their leader gave the command, and bending low over their camels, they dashed with all speed toward the explorers. Shots rang out from the Arabs' pistols, but they were too unsteady to cause any damage. The explorers' rifles spoke out, and those of Bob and the naturalists found their marks. Again the rifles cracked. Three more camels went down simultaneously. Now only two of the animals remained on foot, but they were halted abruptly by their panic-stricken riders. "Luckily we downed the leader," remarked Mr. Lewis. "And now," he added, "suppose we get away from here at once. There will be no danger of those men starving, for this oasis will furnish them with food and drink. They can wait for another caravan to furnish them with more camels." Without hesitation the party placed the packs back on the dromedaries and rode off, Tishmak in the van. A few pistol bullets whizzed past uncomfortably close, but soon they died down as the Arabs saw the futility of their efforts. "Whew! That was some experience," remarked Bob, when they were well out of sight of the oasis. "I hope we see no more such fellows."