ught," 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?"

"Nothing," gasped Aleck. "I can't--can't whistle now."

But he made another effort to control his quivering tips, mastered them
into a state of rigidity, and produced a repetition of the same low,
plaintive note that had reached their ears.

Directly after, the whistle was repeated from outside, and, as Aleck
produced it once more in trembling tones, the lads leaped to their feet,
for, coming as it were right along the surface of the water, as if
through some invisible opening, there came the welcome sound:

"Ship ahoy! Master Aleck--a--" _suck--suck--flop--flop_--a whisper, and
then something like a sigh.

"It is Tom Bodger!" cried Aleck, in a voice he did not know for his own,
and something seemed to clutch him about the throat, and he knelt there
muttering something inaudible to himself.

CHAPTER THIRTY.

_Phee-ew! Phee-ew_! The peculiar gull-like whistle once more, to run
in a softened series of echoes right up into the farthest part of the
cavern. Then there came the peculiar sucking, ploshing sound as of
water filling up an opening. A minute later "Ship ahoy!" from outside.

"Tom! Ahoy!" yelled Aleck, wildly.

"Ahoy, my lad! Ahoy!" and something else was cut off by the soft
sucking splash of water again, while to make the lads' position more
painful in their efforts to reply, twice over they were conscious of the
fact that when they replied with a shout their cries did not pass
through the orifice, which the water had closed.

But the tide was ebbing steadily, and the tiny arc of the rocks which
showed the way in was growing more open, so that at the end of a few
minutes they heard plainly:

"Where'bouts are yer, my lad?"

"In here!" shouted Aleck, but only in face of a dull _plosh_.