ong, very
picturesque in outline, and surrounded by lesser islands, as well as
isolated rocks, which are the terror of all who know them. The lads
found a great deal to interest them in the Stack; but their main object
was to find the caves which tradition said had been the abode of
lawless men in olden times.

There was one large cavern in a cliff easily found and well known; but
that was not the Wrecker's Den, for the sea came into it, and in stormy
weather filled its vast solitudes with the body and voice of many
waters. This cave, however, was supposed to communicate with one
inland, as many helyers[1] do, and our boys were determined to discover
the hidden abode.

For a long time the search was a vain one; but at last an idea was
suggested to Harry, who had halted by a small cairn.

"Boys," he said, "I should not wonder if we are on a wrong tack looking
for a natural cave. It is more likely that the wreckers' den was a
place dug out of the earth by themselves."

"That was a common dodge long ago," quoth Yaspard; and Tom added, "We
got a good illustration of that sort of thing in the old Broch of Burra
Isle."

"And you are thinking, Harry," Yaspard exclaimed, "that this cairn may
cover some portion of the den--perhaps be the entrance to it?"

Harry nodded, and after a careful inspection of the rougue, remarked,
"I think we shall find something here; but we must not come to grief in
a ruin, as Garth Halsen did when he dug into the old Broch."

They went to work with a will, and soon removed the cairn and laid bare
what was evidently the entrance to a vault of some sort. The mouth of
the pit was covered by two enormous stones, and it took a long time to
remove these; but so interested were the adventurers in their
investigations, that they forgot the warning of the sea and the rising
of the wind.

"It is curious," said Harry, peering into the dark pit at their feet,
"that there seems no foul air to speak of down there, and yet I don't
see any speck of light that would indicate a passage to the outer
world."

"Might the way not be curved, or sufficiently blocked to exclude
light?" Yaspard suggested; and Harry frankly answered, "Of course. You
are wiser than I. Has any one got a match in his pocket?"

Matches were produced, and a piece of paper was lighted; but such a
meagre illumination revealed nothing beyond the fact that the vault
seemed a large one, and roughly built round with a rude kind of mas