Charley knew well enough that Mr. Morton was trying to mislead him. He saw at once that the kind-hearted ranger had intended to spend the night in camp. But not knowing what to say, he turned in silence to the pup, which evidently smelled the wildcat, and tried to quiet him. "You can be glad that you've got that dog," said the ranger. "I don't think that cat will come any closer, for it can smell the dog as well as the meat. Take care of him and make him useful. Now we'd better turn in, for we must pull foot early in the morning." "Let's first see if our clay is baked," suggested Charley. Charley scattered the embers and rolled the clay ball out of the ashes with a stick. It was baked as hard as a brick. The ranger folded up the newspaper which he had used as an outer wrapper for the meat, and picked up the ball with the paper. Lew held the candle lantern close while the ranger examined the clay. Slowly he turned the ball around, picking at it with his knife blade. "Who made this ball?" he asked suddenly. "I did," said Charley. "Did Lew touch it at all?" "I can't recall that he did." "No; I never laid a finger on it," said Lew. "Charley rolled it and carried it here himself." "Let me see your thumbs, Charley," said the ranger. Charley, puzzled, held them up for inspection. The ranger examined them closely. "Now let me have that little microscope of yours," he continued. Charley handed it to the ranger, who studied the clay ball intently through the glass, then as carefully looked at Charley's thumb. Then he chuckled. "We've taken another king in this little checker game," he said. "Look at that." While Mr. Morton held the lantern for them, the two boys studied the burned ball of clay. On it were a number of distinct thumb-prints, now turned into solid brick by the action of the fire. The boys looked at each other questioningly and then at Mr. Morton. "It's a clever rogue who doesn't trip himself up somewhere," chuckled the ranger. "What happened is as clear as daylight. Collins and his companion found this clay while they were inspecting your camp. They must have suspected that it was fire-clay and that you had found a deposit of value. They took some along to test, and rolled what was left into a ball again, thinking you would never notice the difference. But they forgot that clay would take finger-prints so readily, and they have left their calling cards behind them." The ranger carefully wrapped the clay ball in his handkerchief, and then in a newspaper. "Let me have this," he said. "The police may have some duplicate prints somewhere. We don't know what Collins and his pal are up to, but we have something here that we may find very useful. It isn't every crook that is so considerate as to leave his thumb-prints behind him." Chapter XVI Good News For the Fire Patrol