"Great Cæsar!"
Before him were a number of letters, cut in smooth rock, which was apparently quite soft. The letters read:
Barnaby Winthrop's Mine.
Allen stared at the letters on the rock as if he had not spelled out the words aright. But there was no mistake. They really read "Barnaby Winthrop's Mine."
"Well, if this isn't the most wonderful discovery ever made!" ejaculated the young man, finally. "So this is the place that Uncle Barnaby talked of as being the richest claim in Idaho. I wonder how he ever found it?"
While Allen stood close to the rocky wall he reached the conclusion that his uncle must have come there by the river, but whether a voluntary or involuntary passenger he could not decide. He knew Uncle Barnaby was exceedingly fearless, but was there any human being who would take the awful risk of a journey on that underground river, not knowing to where it led?
"He must have been caught, just as I was," said Allen to himself, at last. "And that
