Harry and his brother went to the edge of the pool, where they undressed and waded out. They found that the bottom of the passage sloped more gradually at the edge of the water than it did higher up, and they were able to walk out till they came to the point where the roof dipped into the water. They dived, and in a few strokes came up beyond the roof.  
"This is glorious!" Bertie said. "We have often bathed in pools, but this is a different thing altogether. It is more than a year since we had our last dip in the sea, the day we arrived at Callao."
 
Although there was little or no wind, the rollers were breaking on the line of rocks outside, pouring over the lower points in volumes of foam, and coming in broken waves up the passage.
 
"We mustn't go beyond the point, Bertie, or we may be dashed against the foot of the cliff. We will climb up that rock to the left; it is not too steep, and I think we can manage it. From there we shall get a good view of this side of the house and of the situation in general."
 
It required considerable care to climb the rocks, and more than once they hurt their feet on sharp projections. The top of the rock, however, was smooth by the action of time and sea, and they were able to sit down on it in comfort.
 
"The castle is just as you described it, Bertie; and certainly no one sailing past, however close he came outside these rocks, would be able to detect it. No doubt the stone of which it is built is the same as that of the cliffs. Most likely it was taken from the ravine where the passage now is, and had fallen from the arch above. It might have been more noticeable at first, but now it is weathered into exactly the same tint as the cliffs. The openings are very dodgily placed, and a stranger would not dream that they went many inches in. Now, from where we stand we can look up into that curious opening on the top story. I have been puzzling over that ever since I saw it, but can't think of any possible reason for its having been cut like that, except to enable them to throw stones on to any boat that came into this passage behind the rocks; and yet that can hardly have been the case, for, as I remarked, there are no stones piled up there. Certainly they had a very large number of arrows, but stones would be very much more useful than arrows against a boat almost under their feet. However, that does not concern us now. This line of rocks must greatly aid in hiding the house from the sea. They are higher than you thought they were, looking down at them from above. We are quite thirty feet above the water, and at two or three points they are at least ten or twelve feet higher. Of course a short way out no one would be able to see that they were detached from the cliff, or that there was any passage whatever behind them.
 
"Besides, they break the force of the waves. If it was not for them it would be impossible for any boat to come up close to the face of the house, and a heavy storm might even break down the wall altogether. A tremendous sea would roll in here in a westerly gale; and if it hadn't been for these rocks it would have been necessary to build the lower part of the house absolutely solid to resist the sea. It is possible that the rocks were higher than they now are when the place was first constructed, in which case the house might have been almost entirely hidden from sight. Well, we may as well go back again, Bertie; we know all there is to be known about this side."
 
They swam back into the tunnel, dressed, and went out.
 
"We have come out, Maria," Bertie called. "The coast is clear for you. The water is not so deep as we thought it was, and you can walk out to the point where the roof comes down on to the water without getting out of your depth."
 
It did not take them long to cut a number of switches to serve as brooms, and a couple of handles. They carried them up into the house, and lashed the switches firmly on to the handles. The work was rough, but the brooms when completed were large, and, although not strong enough for heavy work, would do well to sweep aside the thin layer of almost impalpable dust on the floor below.
 
"Shall we take wood down there, Harry?"
 
"No; I think a fire would be a drawback rather than an assistance. It would be very valuable if we were working at one spot, but it could give no general light in a place a hundred feet long. We will take a torch down, and hold it and sweep by turns. We shall only want, to begin with, to make a clear path a couple of feet wide down the middle. Of course later on we shall clear it all. That will be sufficient to enable us to see how the floor is constructed, whether with big blocks or small ones, how closely they are fitted together, and so on. It is certainly unlikely that we shall find any indication as to where chambers exist."
 
It took but a very short time to clear the path; the dust was so light that one sweep of the broom cleared it away. When they got to the farther end they returned to examine the floor. For four or five feet from the cistern the rock had been evidently untouched, except to cut off any projecting points. Then there was a clear line running across the path. Bertie held the torch down close to it. Harry knelt down and examined it.
 
"This is a clean cut, Bertie. It is evidently solid above this, but the stone is not quite the same colour on each side of it, and it looks as if they had cut away the rock here and begun to build so as to keep the floor level. The cut may be six inches deep and it may be a foot, that doesn't matter. The face of this stone is very smooth, but it is not cut; it is, I think, the face of the natural fracture. Move the torch along and let us see where the next join is. Ah, here it is!"
 
The slab was four feet across.
 
"You had better sweep the dust off both ways, Bertie, so that we may see what size it is."
 
It was, they found, about eight feet long.
 
"It has straight edges, Harry, almost as straight as if it had been sawn."
 
"Very likely it was sawn, Bertie; They could have had no tools that would cut a hard stone like this regularly, but as they were certainly clever builders they must have employed some means to do it. Possibly they used a saw without teeth, for however much they might have hardened the copper, the teeth could not have stood, but if they had a hard copper band fixed like the saw some masons use, and kept the stone moistened with fine sand, they might have cut into it. Of course it would have been a slow process; but they would not have needed to go far into the stone, for when they got down two or three inches they might have broken it through by dropping a heavy weight on the end. It would not have mattered if the fracture had not been straight below the cut, for only on the surface would they have wanted to fit accurately to the next stone. In another way they might have got a straight edge, that is, by driving very dry wedges into the cut made by the saw, and then moistening them. I know that great stones can be split in that way. They may have used both methods. However, it doesn't matter to us much how they did it. It is clear that they could in some way or other cut stones. As they took the trouble to do so here, we may conclude that they were anxious to have a smooth floor that would be extremely difficult to get up.
 
"They would never have taken all this trouble if they had merely been making a floor for a cellar. For that purpose it would only have been necessary to throw rocks and stones of all sizes into the vacant space below, and when it was nearly full, to level it with small stones and sand. That they chose to undertake such tremendous labour as the making of so regular a floor as this must have been, shows that they had some very strong motive for doing so."
 
Going carefully along the track they had cleared, they found that the stones were of different sizes; some were but two feet wide, others as much as ten, but all fitted so closely together that it was difficult to see the joints.
 
"It is going to be a hard job to get these out, Bertie," Harry said, when they had completed their examination, "and it is lucky for us that the room gradually narrows from sixteen feet wide to two at the other end, and when we stepped it we made it eighty feet long. We need not take up the stones near the rock wall, for the ravine would naturally narrow as it went lower, and the depth would be greatest by the side of the wall of the tunnel."
 
"Well, we shall soon blow up the stones when we have got the powder."
 
"I hope so, Bertie; but I see that we shall have difficulty unless these top stones are extraordinarily thick."
 
Bertie looked surprised. "Why, I should have thought the thicker they were the more difficult to break up."
 
"Beyond a certain point that would be so. But suppose they are six inches thick, you may take it for granted that underneath there will be rubble, loose stuff, except where any chambers may be built. If we were to bore a hole through this top layer the powder, instead of splitting the stones up, would expend its force among the loose stuff beneath it; and besides, instead of remaining in its place, it might get scattered, and we would then get no explosion at all."
 
"Then we should only have to make the hole four inches deep, Harry?"
 
"As a result of which there would only be two inches of tamping over the powder, and this would blow right out, as if from a little mortar, and would have no effect whatever upon the stone. I have no doubt that we shall find some way to get over these difficulties, but it is evident that the work will not be all clear sailing."
 
"Of course we shall manage it somehow, Harry, even if we have to smash up all the stones with the sledge-hammers Dias will bring us."
 
"Is breakfast nearly ready, se?ora? That swim in the sea has given us a prodigious appetite. Did you enjoy it?"
 
Maria nodded.
 
"It is very nice, se?or; but I should have liked it better if the water had not been so blue. It seems so strange bathing in blue water."
 
"You will soon get accustomed to it," Bertie laughed. "There are no pools except that one two miles up the valley. Besides, it is much nicer to have a great bathing chamber all to yourself. Here comes José!"
 
"Well, José, are the mules all right?" he shouted.
 
"Yes, but I had difficulty in catching them. They had evidently been frightened by something, and were three miles up the valley with their coats all staring. It must have been either a puma or a jaguar. Of course they must have got wind of him in time; but as, fortunately, they were not tethered, they were able to get away from him."
 
"I should think he must be up somewhere among the bushes, José," Harry said. "We had better go down tonight and see if he returns again. We shall be losing some of the mules if we don't put a stop to his marauding. Besides, it will be very dangerous for you, José, cutting the wood up there, if he is lurking somewhere. It is fortunate that you escaped yesterday."
 
"I expect he was on the other side of the ravine, se?or; and even if he had not been, the sound of the chopping would have scared him. They will not often attack in the daytime."
 
When they had finished their breakfast José asked what he should do next.
 
"There is nothing else to do, so it would be as well to take our pickaxes and get some of those brackets out of the walls. We will begin with the other rooms of this floor and leave these here till the last."
 
"I will come and hold a torch for you, se?ors," Maria said. "I like to be doing something. I will wash up first, and then I shall have nothing to do till it is time to get ready for dinner. Now I know there is a savage beast about I should not like to go down the ladder."
 
"There is very little chance of his coming down the rocks," Harry said. "He is more likely to be lying somewhere on the other side watching the mules."
 
No move was made until the woman was ready to start. Then they lit two torches. She took one and Bertie the other, while José and Harry took two picks. It was hard work, for the brackets were driven far into the pillars and walls. It was necessary to knock away the stones round them to a depth of two or three inches before they could be got out. They worked one at each side of a bracket, relieving each other by turns, and after four hours' work only eighteen brackets had been got out. As far as they could tell by lifting them, the weight was somewhat greater than they had at first supposed. Harry could hold one out in each hand for a minute and a half, Bertie and José for a little over half a minute, and they agreed that they must be about twenty pounds each.
 
By this time their shoulders ached, and it was agreed that they had done a good day's work. For the rest of the day they did nothing but sit on the sill of the window and smoke quietly. The next day's work was similar, and twenty more brackets were got out. Late in the afternoon they saw Dias coming down the steps, and at once went down the ladder to meet him.
 
"Have you got everything, Dias?"
 
"I think so, se?or, and I can tell you that the mules have had a pretty heavy load to bring back."
 
"Well, we will go with you at once, Dias, and bring some of the things up. I expect you have had nothing to eat since the morning. Before you do anything else you had better go in. Your wife has been keeping a dish hot for you, as she did not know when you might arrive."
 
"I shall not be long before I come and help you, se?or. I have unsaddled the mules and turned them out to graze."
 
"It is just as well, Dias, for there is a beast somewhere about that gave them a fright last night. We will get all the eatables up to-night, the powder and drills and hammers we can very well leave till to-morrow morning."
 
It took them four trips to bring the provisions over, for it required two of them to carry each sack of flour, and indeed all had to give their aid in getting them up the rocky slope at the foot of the wall.
 
"No one seemed to think it unusual, your taking so large a load, I hope, Dias?" Harry said as they sat down to their evening meal.
 
"No, se?or. The man I bought the powder of was a little surprised at the amount I wanted; but I said that I might be absent many weeks in the mountains, and might want to drive a level in any lode that I might discover. I led him to believe that I had seen a spot in the mountains that gave good indications, and that two of my comrades were waiting there for my return to begin work at it. I sold the llamas to a man who carries goods from Ancon up to Canta, and got the same price that you gave for them."
 
Harry then told him the work on which he had been engaged since he had been away.
 
"Of course there is no hurry about the brackets, but as we could do nothing else without the powder and drills, it was just as well to get them out, as otherwise we might have been delayed when we had done our other work. We think that they weigh twenty pounds each, so that altogether they will be worth nearly four thousand pounds. Not a bad start. I am afraid we sha'n't make such quick work down below."
 
"We shall see," Dias said cheerfully, for now that his fear of the demons had passed he was as eager as Harry himself to begin the search for the treasure.
 
"Has Maria seen any more bats?"
 
"Yes, she has seen some more bats," his wife said, "but no demons. Dias, what do you think? Don Harry suggested that we might eat the bats."
 
"I have heard of their being eaten," Dias said, "and a man who ate them raw told me that he had never enjoyed anything more. But I should not like to try it myself, unless I were driven to it as he was."
 
"How was that, Dias?"
 
"He was a muleteer, se?or, and was up in the mountains. He had a cargo of silver on his mule, and during the day he had seen some men who he doubted not were brigands on the top of the ravine he passed through. He knew of a cavern where he had once taken refuge with the animals during a storm. It lay on the hillside some twenty or thirty yards away from the road. The entrance was hidden by bushes, and he had first noticed it by seeing a bear come out as he was passing along. He had his pistols, and thought that it was better to risk meeting a bear than a brigand. He arrived opposite the cave just as it became dark, and at once led the mules up there. He first lighted a torch—the muleteers always carry these with them—and then went in with his pistols ready, but there were no signs of a bear anywhere near the entrance.
 
"He drove the mules in and put out his torch. The entrance had been only wide enough for the laden animals to pass, but it widened out a great deal inside. He took off the loads, piled them up in the narrow part to make a barricade, and then sat down at the entrance and listened. He soon heard five or six men come down the road talking. They were walking fast, and one was saying that he could not be more than half a mile ahead, and that they should soon catch him. When they had gone, he went some distance in the cave and relighted his torch. He went on and on. The cave was a very large one, and when he had gone, as he thought,............