shall be drowned! Why didn't you
speak before?"

"I wasn't sure till it began to run up so quickly; and what could we do?
If we had gone out we should have been seen directly. Perhaps it won't
rise any higher now. It never covered the seal cave."

"That was twice as high," groaned Mike. "Look at the limpets and
mussels on the roof: this must be shut right in at every tide."

CHAPTER THIRTY THREE.

RE-TRAPPED.

Misfortunes, they say, never come singly, and these words had hardly
been uttered when voices were heard, and directly after a familiar voice
said loudly, the words coming in through the low passage and quite
plainly to the boys' ears,--

"Made the oar myself, Skipper Jarks, and I ought to know it again. What
I say is as they must ha' managed somehow to ha' got in here."

The boat darkened the entrance for a few moments, and then glided by;
while the cavern kept closing like some monstrous eye whose lid was
pressed up from below, opening again fairly widely, enough almost to
suggest the possibility of their passing under; but closing again as the
tide rose and sank in slow, regular pulsations.

But as they watched they could make out that the soft wave rose higher
and higher and sank perceptibly less, while the prisoners' eyesight
became so preternaturally sharp that they could detect the gradual
opening of the sea anemones, as they spread out their starry crowns of
tentacles after the first kiss of the water had moistened them. The
many limpets, too, which had been tight up against the smooth rock, like
bosses or excrescences, were visibly raising their shells and standing
up, partly detached.

Then a new horror attracted the boys, and made them almost frantic for
the moment; for, as they crouched there in the bottom of the boat,
watching the slowly diminishing amount of light which came in through
the archway, the water softly and quickly, welled up, nearly shut the
entry, and a wave ran up the passage and passed under the boat, which
was heaved up so high that the gunwale grated against the roof, and they
had to bend themselves down to avoid being pressed against the rock.

Then, as they lay there, they heard the wave run on and on, whispering
and waking up the echoes far inside, till the whole of the interior
seemed to be alive with lapping, hissing sounds, which slowly died away
as the boat sank to nearly its old level, and the light flashed in once
more.

"That's a hint to do somethin