"We wouldn't be able to breathe if we didn't discover an air of mystery every fifteen minutes," George declared.
Half way back to the shaft the boys, who were walking very softly in their stockinged feet, heard a rattle as of a moving stone or piece of coal in the passage, and at once drew up against the side wall.
While they stood there, scarcely daring to breathe, they sensed that some one was passing them in the darkness. The tread was light and brisk, and they thought they heard a soft chuckle as the unseen figure breezed by them.
"I'll bet the lad who was listening near our door never came down the shaft until after we did!" George whispered after the figure had passed by.
"That's very likely!" agreed Will.
"Then he may have been poking around our quarters while we have been gone."
"That's very likely, too."
Believing the way to be clear now, the boys hastened on toward the shaft. Just as they reached the foot of the ladder they heard a sound which sent the blood throbbing to their checks.
"He's making fun of us!" exclaimed George.
"It looks like it," admitted Will.