“I think so,” said the middy. “We must have been. But, I say, it really is much lighter this time.”

“So I thought,” said Aleck. “And, I say, I can smell the fresh seaweed. Is the arch going to be open at last?”

Phee-ew! came a low, plaintive whistle.

“Hear that?” cried Aleck, wildly.

“Yes, I heard it in my sleep. The place is getting open then. There it goes again. It must be a gull.”

“No, no, no!” cried Aleck, wildly, his voice sounding cracked and broken from the overpowering joy that seemed to choke him. “Don’t you know what it is?”

“A seagull, I tell you.”

“No, no, no! It’s Tom Bodger’s whistle. You listen now.”

There was a dead silence in the cavern, save that both lads felt or heard the throbbing in their breasts.

“I can’t hear anything,” said the middy, at last. “What was it?”