Canfield stepped out and closed the door behind him. Then he came back and looked in again with a half-smile on his face.
"Do you boys know anything about mines?" he asked.
"Not a thing!" replied Tommy.
"Then don't you go climbing down the ladders and wandering around in the gangways tonight!" the caretaker warned.
"Say, there's an idea!" Tommy said to Sandy, with a wink, as Canfield went out. "How do you think one of these mammoth coal mines looks, anyway?"
"Cut that out, boys!" exclaimed Will. "If I catch one of you attempting the ladders tonight, I'll tie you up!"
"Who said anything about going down the ladders tonight?" demanded Tommy.