all this totally covered up the lake so that nobody would know it was here. And then they built that valve apparatus, which was also submerged, so that they could let out the water when they wanted to get at this stone thing, whatever it is. What a scheme to hide anything! Even if anybody discovered the lake, which would not be likely until some part of the cave fell in, they would not know it was anything but a lake when they did see it. And as for letting off the water, nobody but the people who knew about it could possibly do that, unless somebody was fool enough to take the cold bath I was obliged to take, and even then it would have been one chance in a hundred that he found the lever, and would know how to turn it when he did find it. This whole thing is the work of the ancient South Americans, and I imagine that this stone mound is the tomb of one of their kings."
At this moment the captain heard something, and turned to listen. It was a voice—the voice of a boy. It was Ralph calling to him. Instantly the captain turned and hurried away, and as he went he extinguished his lantern. When he reached his pail of water he picked it up, and was very soon joined by Ralph, who was coming to meet him over the bottom of the lake.
"I have been looking for you everywhere, captain," said he. "What have you been after? More water? And you took a lantern to find it, eh? And you have been ever so far into the cave. Why didn't you call me? Let me have the lantern. I want to go to explore."
But the captain did not give him the lantern, nor did he allow him to go to explore.
"No, sir," said he. "What we've got to do is to hurry outside and help get supper. We must wait on ourselves to-night."
When supper was over, that evening, and the little party was sitting out on the plateau, gazing over the ocean at the sunlit sky, Mrs. Cliff declared that she wished they could bring their bedding and spread it on the ground out there, and sleep.
"It is dry enough," she said, "and warm enough, and if there is really nothing to fear from animals or men, I don't want ever to go inside of those caves again. I had such horrible fears and ideas when I was sitting trembling in those dismal vaults, expecting a horde of human devils to burst in upon us at any moment, that the whole place is horrible to me. Anyway, if I knew that I had to be killed, I would rather be killed out here."
The captain smiled. "I don't think we will give up the caves just yet. I, for one, most certainly want to go in there again." And then he told the story of the stone mound which he had discovered.
"And you believe," cried Mrs. Cliff, leaning forward, "that it is really the tomb of an ancient king?"
"If it isn't that, I don't know what it can be," said the captain.
"The grave of a king!" cried Ralph. "A mummy! With inscriptions and paintings! Oh, captain, let's go open it this minute, before those blackies get back."
The captain shook his head. "Don't be in such a hurry," he said. "It will not be an easy job to open that mound, and we shall need the help of the blackies, as you call them, if we do it at all."
"Do it at all!" cried Ralph. "I'll never leave this place until I do it myself, if there is nobody else to help."
Miss Markham sat silent. She was the only one of the company who had studied the history of South America, and she did not believe that the ancient inhabitants of that country buried their kings in stone tombs, or felt it necessary to preserve their remains in phenomenal secrecy and security. She had read things, however, about the ancient peoples of this country which now made her eyes sparkle and her heart beat quickly. But she did not say anything. This was a case in which it would be better to wait to see what would happen.
"Captain!" cried Ralph, "let's go to see the thing. What is the use of waiting? Edna and Mrs. Cliff won't mind staying here while you take me to see it. We can go in ten minutes."
"No," said Mrs. Cliff, "there may be no danger, but I am not going to be left here with the sun almost down, and you two out of sight and hearing."
"Let us all go," said Edna.
The captain considered for a moment. "Yes," said he, "let us all go. As we shall have to take a lantern anyway, this is as good a time as another."
It was not an easy thing for the two ladies to get over the wall at the end of the passage, and to make their way over the rough and slippery bottom of the lake basin, now lighted only by the lantern which the captain carried. But in the course of time, with a good deal of help from their companions, they reached the turning of the cave and stood before the stone mound.
"Hurrah!" cried Ralph. "Why, captain, you are like Columbus! You have discovered a new hemisphere."
"It is like one of the great ant-hills of Africa," said Mrs. Cliff, "but, of course, this was not built by ants I wonder if it is possible that it can be the abode of water-snakes."
Edna stood silent for a few moments, and then she said, "Captain, do you suppose that this dome was entirely covered by water when the lake was full?"
"I think so," said he. "Judging from what I know of the depth of the lake, I am almost sure of it."
"Ralph!" suddenly cried Mrs. Cliff, "don't try to do that. The thing may break under you, and nobody knows what you would fall into. Come down."
But Ralph paid no attention to her words. He was half-way up the side of the mound when she began to speak, and on its top when she had finished.
"Captain," he cried, "hand me up the lantern. I want to see if there is a trap-door into this affair. Don't be afraid, Mrs. Cliff. It's as solid as a rock."
The captain did not hand up the lantern, but holding it carefully in one hand, he ascended the dome by means of the row of protuberances on the other side, and crouched down beside Ralph on the top of it.
"Oh, ho!" said he, as he moved the lantern this way and that, "here is a square slab fitted into the very top."
"Yes," said Ralph, "and it's got different mortar around the edges."
"That is not mortar," said the captain. "I believe it is some sort of resin. Here, hold the lantern, and be careful of it." The captain took his jack-knife out of his pocket, and with the large blade began to dig into the substance which filled the joint around the slab, which was about eighteen inches square. "It is resin," said he, "or something like it, and it comes out very easily. This slab is intended to be moved."
"Indeed it is!" exclaimed Ralph, "and we're intended to move it. Here, captain, I'll help you. I've got a knife. Let's dig out that stuff and lift up the lid before the darkies come back. If we find any dead bodies inside this tomb, they will frighten those fellows to death, if they catch sight of them."
"Very good," said the captain. "I shall be only too glad to get this slab up, if I can, but I am afraid we shall want a crowbar and more help. It's a heavy piece of stone, and I see no way of getting at it."
"This isn't stone in the middle of the slab," said Ralph. "It's a lot more resinous stuff. I had the lantern over it and did not see it. Let's take it out."
There was a circular space in the centre of the stone, about eight inches in diameter, which seemed to be covered with resin. After a few minutes' work with the jack-knives this substance was loosened and came out in two parts, showing a bowl-like depression in the slab, which had been so cut as to leave a little bar running from side to side of it.
"A handle!" cried Ralph.
"That
