fell on the stone floor with a crash that
aroused a multitude of echoes in the dark interior. At the same moment
something like a faint shriek or wail was heard within, causing the
hearts of the three listeners to beat faster.

"Did you hear that, Hockins?"

"Ay, I heard it sure enough. What is it, think 'ee, lad!" said the
seaman to the negro.

Ebony, who was gazing into the dark cavern with glaring eyeballs and
distended nostrils, replied--

"My advice to you is, let's go back de way we come. Dis no place for
'spectable Christians."

"Do you fear ghosts?" asked Mark, smiling, yet at the same time bringing
his gun into a convenient position, with his finger ready on the
trigger.

"I fears nuffin," returned the negro with a proud look, while beads of
perspiration stood on his brow.

"Then ye're a braver man than I am, Ebony, for I fear that climbin'
plant worse than a ghost; so here goes to find out what it is."

Although the sailor spoke thus boldly, and tried to look cool, it is
certain that he also was afflicted with sensations of an unusual
description, which, of course, he would have scorned to admit were the
result of fear! His power of will, however, was stronger than his
fears. Drawing his cutlass, he was about to enter the cavern, when Mark
laid a hand on his shoulder.

"Come, Hockins, you have accepted my lead hitherto. It is not fair to
take it out of my hands at this critical point."

So saying he glided past his comrade, and was almost lost to sight
immediately in the deep gloom.

"Softly, softly, doctor," whispered the seaman, as he followed, "there
may be holes or pits within--"

"All right; I'm feeling my way carefully. Keep close."

As he spoke a slight, indescribable sound was heard--almost like a sigh.

"Hist! Did 'ee hear that?" said Hockins in the lowest possible whisper.

"Oh! massa, let's go back de way we come," urged Ebony, in the same low
but earnest tone.

Mark Breezy did not reply, but the click of his gun as he cocked it
showed that he was on the alert.

For nearly a minute the three men stood in absolute silence, listening
for a repetition of the mysterious sound, and, though it did not recur,
there was an indescribable feeling in the heart of each that they were
not alone in that cavern.

"Have you not flint and steel?" asked Mark.

"Yes; but to strike a light would only show our whereabouts if there
_is_ any one here."

The seaman accidentally touched Eb