It was not far distant, either, and as the young inventor listened, he heard very distinctly the ring of pickaxes and the low hum of voices.
It was an astounding discovery, and caused him to apply his ear closely to the passage wall.
CHAPTER XI.
INTO THE GREASERS’ DEN.
There was no disputing the fact.
The sounds which came to Frank’s hearing were plain and unmistakable.
The ring of pickaxes was quite audible, and could not have been twenty feet distant through the wall of earth.
The young inventor was dazed with the force of this realization.
Barney had heard the sounds also, and both sat silently gazing at each other.
What did it mean?
Startling queries and theories flashed through the minds of each.