The two explorers were much alarmed.
But the sound died out, and all was again tranquil.
“Och, hone, I thought the berg was afther goin’ to smash!” cried Barney. “Shure, sor, I reckon we’d better get out av here at wanst, sor!”
“Oh, no, I reckon it’s all safe enough now,” said Frank, lightly. “It was only the breaking off of some distant part of the berg. Let us go on once more.”
With this the young inventor took a step forward.
But in that instant he felt something giving way beneath his feet, and heard a warning cry from Barney.
It was an awful cry of terror, and the young inventor made a desperate spring forward.
This was just in time.
He gained a firm footing and turned about with a thrill of horror to witness an awful sight.
A tremendous hole yawned at his feet.