"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."