"Wait!" cried the colonel; "lend me the hammer. Let us try first to remove this smaller stone, then we can better get at the larger one."
He took the sledge-hammer, raised it over his shoulder, and brought it down with a well-directed blow upon the smaller stone, splitting it. A second blow broke it into splinters. These he removed. Beneath them he discovered the end of a rusty bar of iron that was shot like a bolt through an iron ring. The bar seemed to extend under the larger flagstone, supporting it through its centre of gravity. For many minutes he hammered at the rusty iron, and with each blow the flagstone trembled on its axle and a shower of loosened stones and gravel fell into the depths below. With each development the old soldier's energy increased, while Colin looked on absorbed in boyish expectation.
At last the corroded bar broke. The flagstone collapsed and slipped a few inches into the void, where it was arrested by some obstacle. Its removal revealed an irregular opening, some two feet in diameter.
"You were right, boy," remarked the colonel; "there is indeed a secret chamber here, and this is, or once was, its entrance. See! the flagstone has formed a sort of trap-door. It may have been opened by a spring set under the smaller stone at the side. Look down there; you can see the edge of one of the stone stairs."
"Can we get down?" asked Colin.
"It is possible, I think," returned the old soldier. "But we should require a lighted lantern. Could you fetch one?"
Colin ran off. He was absent some ten minutes. During that interval Colonel Ossington contrived so to force back the broken flagstone that it left an opening sufficiently wide to admit his body. He went upon his knees and thrust his feet into the cavity, descending step by step until his eyes were on a level with the paved floor. There he waited, resting with his hands on the second step. The fingers of his right hand touched something that was softer than the cold stone. He gripped it and drew it forth into the fuller light. It was a fragment of mouldy cloth or felt. Attached to it was a disc of tarnished metal upon which the figure "4" was embossed.
"God!" he exclaimed, "it's the badge of the Fourth Foot."
He tore off the badge and thrust it into his pocket. At this moment Colin Leslie appeared with the lighted lantern, and accompanied by his grandfather.