When breakfast was ended no time was lost in starting for a tour round Swarta Stack, which is a lofty island about a mile long, 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?"