"I reckon we've come quite two miles," said Baker, "and in a fairly straight direction according to my compass. If I had known——"
The remark was suddenly cut short by a low warning whistle from Atherton. The rest of the patrol closed upon their Leader, who had come to a standstill before a blank wall. Right and left were short passages terminating in spiral flights of steps.
Once more Atherton and his two chosen comrades began their subsidiary investigations, while the remaining members of the "Otters" remained at the junction of the two cross-ways.
It was not long before the Leader returned.
"No go," he announced. "There are only eleven stairs and then a bricked-up wall. By the undisturbed state of the dust on the steps we know that no one has been there for months at the very least. Come on, all of you, we'll try our luck with this branch."
Round and round, up and up, went the Scouts. They realised that they were on the eve of an important discovery, for here there were undoubted traces of human footsteps. At the fifty-fourth step, Atherton found farther progress barred by a stone wall, each block being roughly fifteen inches wide and twelve high, and set in hard, black cement.
The Scouts looked at each other with feelings akin to dismay. It seemed hard lines, after traversing the whole length of the subterranean passage, to find a blank wall.
"I'll tell you what, Atherton," said Green. "It's my opinion that Tassh, or whoever it is, discovered the tunnel at the Seal Island end, and, like us, explored it as far as it went. He then had to retrace his footsteps, and that accounts for the complicated nature of the trail."
"Yes, that's all very well," replied Atherton. "But how do you account for the finding of the silver stuff in the underground chamber?"
"Perhaps Tassh meant to hide it there, or it was too heavy for him to carry any farther," suggested Mayne, as he rested on the edge of a step his end of the staff from which the bowl was slung. As he did so the end of the pole touched the stonework at the side of the staircase. The slab of granite trembled visibly.