As he ceased speaking, and his voice was no longer reverberating and whispering about overhead, a peculiar fluttering, whirring sound, as of many wheels in rapid motion, struck upon the boys’ ears, a sound which added strangely to the mysterious air of the place. It was evident, too, that the roof was now far above their heads, giving room for the strange dwellers in darkness to wheel and swoop about, often so close that the wind raised by their pinions beat upon the explorers’ cheeks.
“Lucky I’d got the lantern door shut,” said John Manning, in a strange whisper, “or they’d have blown it out a dozen times over.—Shall I go any farther, sir?”
“No; it is of no use. But what a hiding-place! There’s room, Manning, for quite a brigade.—What’s that?”
A sharp crash fell upon their ears, as of a stone dislodged somewhere high up in the distance; and this was evidently the case, for they heard it rattle down, loosening others, and sending a reverberating echo along the cavern, which told of its vastness being greater than they had before imagined.
“One of the birds loosened a stone, sir,” said John Manning. “Look out: here they come.”
For, evidently alarmed by the falling stones, there was now the rush as of a mighty wind, and the little party could feel that a great flock of birds was passing overhead toward the entrance, hurriedly making their escape out into the open air.
“Let’s follow their example,” said the colonel; “we are only wasting time. But this would make a capital retreat if we were attacked; and we could defend it against hundreds.”
“Till we were starved, or burned out,” grumbled John Manning.
“It would take a forest on fire to burn us out of this, sir,” said the colonel. “What! make difficulties? We have plenty to encounter without. Now then, forward with the light.”
John Manning faced round, and led on at once, while, as he held up the lantern, the dark mass of birds in a regular train could be seen passing on toward the entrance, which was reached directly after, both boys uttering a sigh of relief on finding themselves once more in the outer darkness, where they could breathe freely, and feel as if a great danger had been escaped.