Mr. Holton tried vainly to get his rifle out in time. Something must be done at once, for the savage dog would be at the camels in but a moment. Suddenly Joe leaped from his camel directly in the path of the oncoming animal. The dog stopped for a second, then rushed at the youth with terrible ferocity. "It's now or never!" Joe thought and brought the butt of his rifle down with all his strength on the dog's head. There was a cry of pain, and the next moment the beast rolled over in a dazed condition. At last the terrible enemies had been overcome. "Great work, Joe!" praised Mr. Holton. "We weren't expecting to see you act so quickly." "I didn't know whether I could hit him at the right time or not," the youth said, wiping the perspiration from his brow. "But I thought I'd take a chance. It----" He stopped fearfully as a rifle shot rang out. Another report followed the first, and Tishmak fell from his dromedary. "Back!" cried Dr. Kirshner. "It's the Arabs shooting from the tents. Hurry or we'll all be hit!" Tishmak was rapidly picked up and placed on his camel, and then the explorers retreated behind a formation of rock near the high wall of stone that was to their right. "You look after Tishmak," said Mr. Holton to Dr. Kirshner. "Meanwhile we'll keep these Arabs away. We certainly aroused their tempers when we put those dogs out." A volley of shots came from the Arabs' tents, and the Americans at once answered with their own rifles. Wherever a shot was heard, Mr. Holton directed his friends to fire at the spot. Suddenly Mr. Lewis caught a glimpse of a large one-armed Arab who emerged into full view to send a bullet at his white enemies. Without hesitation the naturalist fired, bringing the man down with a thud. "Look!" cried Bob. "They're backing up. That fellow you shot must have been the leader." "Does seem that way," agreed Mr. Lewis. "But we must remain on guard. These are treacherous characters." Only an occasional shot rang out. Then finally there was silence. "Now we'll see how Tishmak is," said Mr. Holton, leaving his position at the end of the rocky crag. They found that Dr. Kirshner had bound and treated the wound, which was in the left arm. The Arab seemed in high spirits, despite the fact that he was evidently in pain. "It doesn't appear serious," said the archæologist. "With the right kind of attention it will probably be all right in a few days." "Lucky that he wasn't killed, or that more of us weren't hit," remarked Mr. Lewis gravely. "The Sahara is a dangerous place for explorers." They waited several minutes for any more rifle shots from the Arabs, but none came. Finally Mr. Holton mounted his dromedary. "Let's get on our way," he suggested. "I don't think there's any danger now. The Arabs have retreated to a distance beyond their tents, and I believe they'll stay there awhile." Tishmak was helped on his camel. Then, when the others had also mounted, they rode off.