"Well, we leave you here, then, Joe," the boy remarked, sturdily; "because we're going to find that cave, and see what lies inside it. If you want to come along, all right; if not adios!"
He turned and started to climb, Bob tagging at his heels. But Spanish Joe could not bring himself to accept the invitation. He looked after the disappearing figures of the two saddle boys, and shook his head.
"No, not for Joe," he muttered. "He knows when he has had enough. Money could not drive him to enter there again, and meet that unseen thing. Out here the danger can be understood, but Joe he takes off his hat to the young Senors; for grit they surely possess. Adios, Senor Frank; but I doubt much whether we ever meet again."
But staunch of heart, Frank was leading the way upward, determined to accept of the challenge which the cowboy's due seemed to throw at his feet.
CHAPTER XVI
THE VENT HOLE IN THE WALL
The way grew rougher with every yard they traversed. How Spanish Joe had come dashing down over this ground at headlong speed without breaking his neck was a puzzle.
Frank was feeling his way along carefully when he heard Bob call his name. The rattle of falling shale at the same time gave him a pretty strong suspicion as to what had happened.
"Hello! what's the matter Bob?" he cried.