"First of all, let us clear the wall and take a general view of it.

Guessing won't help us; but I have the strongest hopes that behind one of these stones lies a cavern. By the way, Dias, take a torch and go into the next chamber and see if the stones are solid there."

"They are just the same as those here," Dias said when he returned.

"I would rather that it had been the other way," Harry said, "for then I should have been more sure that there was some special reason for their building them in this way here."

It took them all half an hour's work to move the spears and arrows to the other side.

"Do you think, Harry, if we were to tap the stones we should be able to find whether there is a hollow behind any of them?"

Harry shook his head.

"Not in the least. I have no doubt these stones are two or three feet thick, and there could be no difference in the sound they would make if struck, whether they were filled in solid behind or had no backing. To begin with, we will make a careful examination of the walls. Possibly we shall see some signs of a stone having been moved. It would be very much more difficult to take one of the great blocks out and put it in again than it would be to get up one of the paving-stones."

When they had gone about half-way along, examining each stone with the greatest care, Bertie, who was ahead of the rest, and pa.s.sing the candle he held along the edge of every joint, said, "Look here! this stone projects nearly half an inch beyond the rest."

The others gathered round him. The stone was of unusual size, being fully two and a half feet wide and four feet long, the bottom joint being two feet above the floor.

Bertie moved along to let the others look at the edge. He was keeping his finger on the joint, and they had scarcely come up when he said, "The other end of the stone's sunk in about as much as this end projects."

"Something certainly occurred to shift this stone a little," Harry said, examining it carefully. "It is curious. If others had been displaced, one would have put it down to the shock of an earthquake--a common enough occurrence here--but both above and below it the stones are level with the others, and nowhere about the house have we seen such another displacement. Look! there is a heap of rubbish along the foot of the wall here. Stir it up, Dias, and let us see what it is."

"It is sand and small stones, and some chips that look like chips of rock."

"Yes, these bits look, as you say, as if they had been chipped off a rock, not like water-worn stones. Though how they got here, where everywhere else things are perfectly tidy, I cannot say. However, we can think that over afterwards. Now for the stone! Let us all put our weight against this projecting end. I don't in the least expect that we can move it, but at any rate we can try."

They all pushed together.

"I think it moved a little," Harry said, and looked at the edge.

"Yes, it is not above half as far out now as it was."

"That is curious, for if it is as thick as we took it to be, it would weigh at least a couple of tons. We won't try to push it in any farther. I am sorry we pushed it at all. Now, give me that heavy sledge, Jose, possibly there may be a hollow sound to it. I will hit at the other end, for I don't want this to go in any farther."

He went to the stone beyond it first and struck two or three blows with all his strength. Then he did the same with the stone that they were examining.

"I don't think it gives such a dead sound," he said.

The others were all of the same opinion.

"Good! This is another piece of luck," he said. "We have certainly hit on something out of the way."

"Your hammering has brought this end out again, Harry," Bertie said.

"So it has, and it has pushed this end in a little. Let us try again."

But although all took turns with the sledges, they could make no further impression on the stone.

"Well, we will try the drills," Harry said. "In the first place, we will find out how thick it is."

They at once set to work with the drill. Progress was slower than it had been before, because, instead of striking down on the head of the drill, they had now to swing the hammer sideways and lost the advantage of its weight; and they were obliged to work very carefully, as a miss would have seriously damaged the one holding the drill. It took them four hours' steady work to get the hole in three inches. Ten minutes later, to their astonishment, the drill suddenly disappeared. Dias, who was striking, nearly fell, for instead of the resistance he had expected, the drill shot forward; the hammer hit Jose, who had this time been holding the drill, a heavy blow on the arm, causing him to utter a shout of pain.

Harry, who was sitting down having breakfast, having just handed his hammer to Bertie, jumped to his feet.

"How did you manage that, Dias? I suppose it slipped off the head. You must have hit Jose a very heavy blow."

"I have hit him a heavy blow, senor, and nearly tumbled down myself; but I struck the drill fairly enough, and it has gone."

"Gone where, Dias?"

"I think it must have gone right through the hole, senor."

"Then there is an empty s.p.a.ce behind!" Harry shouted joyfully.

"However," he went on in changed tones, "we must see to Jose first.

That blow may have fractured his arm. Let me look, Jose. No, I don't think anything is broken, but there is a nasty cut on the wrist. It is fortunate that you were not striking straight down, Dias, for I am sure we have not put anything approaching the strength into our blows, now we are hitting sideways, that we exerted before. You had better go up to Maria, Jose, and get her to bathe your wrist with cold water, and put on a bandage."

"Now, senor, what shall we do next?"

"Well, now that we know that its weight cannot be anything very great, and that certainly to some extent it can be moved, we will try hammering again at that end. Do you stand three or four feet beyond it, so as to be able to bring your sledge down with all your strength just on the lower corner. I will face you and strike six or eight inches above where you hit. Of course we must both bring our hammers down at the same instant. We shall be able to do that after two or three trials. Stand at the other end of the stone, Bertie, and tell us if it moves at all."

After one or two attempts the two men got to swing their hammers so as to strike precisely at the same moment, and when half a dozen blows had fallen, Bertie said: "It comes out a little at each blow. It is not much, but it comes."

Three or four minutes later he reported, "It is an inch and a half out now, and there is room to get the end of a crowbar in here."

"That is curious," Harry said as he lowered his sledgehammer, and, taking up the candle, examined the end where he had been striking.

"This is sunk about the same distance, Bertie. The stone must work somehow on a pivot."

They now put a crowbar into the end Bertie had been watching, and all three threw their weight on the lever. Slowly the stone yielded to the pressure, and moved farther and farther out. It was pushed open until the crowbar could act no longer as a lever, but they could now get a hold of the inside edge. It was only very slowly and with repeated efforts that they could turn the stone round, and at last it stood fairly at right angles to the wall, dividing the opening into equal parts about two feet four each.

"There is a pivot under it; that is quite evident. It may be a copper ball in the stone below, or it may be that a k.n.o.b of the upper stone projects into a hole in the lower. However, it does not matter how it works. Here is an opening into something. Dias, will you go upstairs and tell your wife and Jose to come down? They had better bring half a dozen more torches. Our stock here is getting low, and we shall want as much light as possible. It is only fair that we should all share in the discovery."

Dias went off.

"Now, Bertie, we must not let our hopes grow too high. I think it is more likely than not that we shall find nothing here."

"Why do you think so, Harry? I made sure we had as good as got the treasure."

"I think, if there had been treasure," Harry went on, "that this stone would have been closed with the greatest care. They would hardly have left it so carelessly closed that anyone who examined the wall would have noticed it, just as we did. We found the other places most carefully closed, though there was nothing in them."

"Perhaps there was something that prevented them from shutting--a little stone or something."

"But we know that that wasn't so, Bertie, because the stone yielded to our weight; and if it did so now, it could have been shut with the greatest ease originally, when no doubt the pivot was kept oiled, and the whole worked perfectly smoothly. It is almost certain that they were able in some way to fasten it securely when it was shut. What is that piece of square stone lying there?"

"It fell down from above just as the slab opened."

Harry took it up. It was about six inches long by two inches square.

"It is a very hard stone," he said--"granite, I should say. I expect you will find that it fits into a hole in the stone above."