ar of the next wave as it came bursting in, splashing them
from head to foot where they sat, was a wonderful quickener to their
movements, and away they scrambled through the pitchy blackness,
clinging like limpets to the rough side of the cavern as they felt their
feet slide upon the treacherous rocks, and thought of the unseen gulf
below.

Onward, onward still, deeper and deeper into the heart of the cold,
silent rock, fearing at every moment to feel their way barred by a solid
wall, and find themselves cut off from escape, and doomed to be drowned
by inches. But, no; the strange tunnel went on and on as if it would
never end, their only consolation being that they were unmistakably
tending _upward_, and already (as they calculated) beyond the reach of
the flood-tide.

Suddenly Jack uttered a shout of joy:

"Hurrah, Pierre! here's one of the lantern candles in my inner pocket,
and I know I've got my matches somewhere. We'll be able to see where we
are at last, my boy!"

The matches (luckily still dry) were produced, the candle was lighted,
and our heroes took a survey of their surroundings.

They were in a long narrow passage, rising to a considerable height
overhead, and with another ledge on its opposite side, steeper and more
broken than the one on which they were. In the centre lay the chasm
already mentioned; but instead of the frightful depth which they had
imagined, it was only six or seven feet deep at the most, and more than
half full of water.

"There's our terrible precipice," laughed Jack, stooping over it. "I
don't think _that_ would hurt us much. But--holloa! I say, Pierre, this
isn't sea-brine; it's _fresh-water_, running water! It's a stream that's
tunnelled its way through the rock; and if we follow it far enough,
we'll get out. Hurrah!"

"Hurrah!" echoed Pierre, brightening up. "We sha'n't run short of water,
anyhow; and as for food, we may as well have a bite of that loaf before
starting again."

The under-ground breakfast was soon finished, and the adventurous lads
started once more.

But the pain of Pierre's bruises, which he had manfully concealed
hitherto, began to master him at last. His tired limbs began to drag
more and more heavily; his feet slipped again and again, and only the
strong hand of his comrade saved him from more than one serious fall.

"Better sit down and rest a bit, old fellow," said Jack, kindly;
"there's no hurry, for this candle will burn a long while yet. I kn