But his search was vain. Fully half an hour was spent thus, and to no effect. The pavement over that whole part of the chapel was as intact, as firm and solid as though it had been a single mass, without break or flaw. Where could it be? He examined the altar itself. Certainly there was no possible opening in any part of that. It was a single block of stone, without flaw or blemish. The explorer looked around at the open windows. Not by any one of them could the seeming monk have gone. That was decided at once. Where then? Had the whole thing been a wild, fantastical hallucination? Only a dream? Could it be possible that they had seen nothing? Could it be that the very excursion itself, together with what he had deemed the most rapturous event of his life--could that have been but a baseless vision of his distempered brain? He looked down, and his eyes rested upon his poor staff--its beautiful, evenly spotted and highly polished surface, erstwhile so smooth and fair, now marred and cut, and bruised and hacked by its rough contact with the edge of Lord Oakleigh’s sword. Ah! that had been real at all events, and he very soon told himself that all that had gone before had been real. Yes--the gray friar had certainly vanished from sight at that altar. There had been no deception; no hallucination--the departure had been a fact; and that was the end. He had given up, and had turned, in deep dejection, toward the vestibule for the purpose of departing, when suddenly a new thought came to him, under the influence of which he stopped, and presently went back to the altar. Was it cemented to the pavement? Was it secured in its place in any way? Again he went down on his knees, with his pocket-knife in his hand. He commenced at the rear wall, at the end of the huge block where the specter had stood, and examined the point of connection between it and the pavement. Ah! he found places where he could insert the knife-blade. He arose, and went outside and cut a small twig from a bush near by, the wood of which was tough and elastic. This he shaved down to a long, thin strip, and returned to his work. He commenced again at the rear wall, brushing away the accumulated dust, and probed with the new implement. And so he went entirely around the altar; and at no point had it any further connection with the pavement than simply to rest upon it. He was gazing upon the line, between the lower edge of the block and the floor, when something caught his eye that caused him to start. It was a series of marks--abrasions--extending out from the edge of the altar, with a circular sweep, entirely across one of the broad stone flags. What did it mean? What could have done it? A critical examination, with a little calculation, showed him that exactly such an abrasion as that would have been made by the swinging outward of the altar, away from the wall.