down in the earth, and the wise men tell us that inside the earth are raging fires. I don't know about that, but I do know my medical spring will cure rheumatism. And I guess now, everything is explained."
"No, not everything," said Sammy quickly.
"Eh?" asked the old man.
"We found a secret room in the old mansion," went on Sammy, "and it's a counterfeiters' den, I'm sure. We thought you were going there, Mr. Addison, that's why we followed you.
"And while we were in there," Sammy went on, "there was an explosion. We thought someone was shooting at us, and we ran out. That has to be explained yet."
"That's so! " exclaimed Mr. Jessup. "I've got to look into that."
Mr. Houghton laughed.
"It won't take much of an explanation to do away with that mystery," he said. "If you'll come with me I'll show you all about it. I fancy you stumbled across one of my fads. Will you come. Uncle Frank?"
"No, I'll go back to my cabin," was the hermit's answer. "I'm going to pack up and go back to the mainland to live, now that my medical spring is safe."
"Then the rest of us will go," suggested the young man.
They left the little glade where the hot spring made grass grow in the middle of Winter, and soon reached the hermit's cabin again. He went in there, while Sammy and his chums, with Mr. Jessup and Mr. Houghton, kept on to the deserted mansion, telling the hermit they would soon be back to look after him. The doctor, whom Mr. Jessup had brought, had gone back to the mainland in his cutter.
"Shall we go right in?" asked Sammy, when Mr. Hough-
