On the following morning work was resumed in the cutting. The loose earth having been cleared away, a reasonably solid roof was put up, and once more the tunneling operations were pushed forward vigorously.
All hands were on the alert for a repetition of the mysterious cries, but nothing was heard save the noise of the picks and shovels, with now and then a muffled crash as fragments of the vein were detached by blasts.
During the "nooning" lunch was eaten in the cutting, and while they were sitting quiet a singular vibration of the earth could be felt.
"It seems as if some one was digging directly beneath us," Fred said, when the little party ceased eating to gaze at each other in surprise.
"Most likely there's a line of slate just under our feet, an' brings the sound from the other drift," Joe replied promptly.
"That's about the size of it," Bill added; but the boys noticed that both the men listened from time to time as if in great perplexity.
The peculiar tapping continued without interruption, and before the time of rest had more than half expired Joe said, as he arose to his feet:
"Come on, lads. We're close to the old drift, an' after that's been opened we'll have another look around, for I want to find out what these queer noises mean."
Each one worked with the utmost rapidity, and when another hour had been spent Bill's pick broke through the barrier of earth.
"That ends the job, an' now to see how the air is."