"You're right," agreed George. "We must get to work on it at once."

"We've been at work on it ever since we struck this island," said Fred warmly. "Where have you been all this time?"

"Well, when I get down to business we'll soon solve the riddle," said George pompously. "I'll soon get an idea."

"Hit him, Grant," cried John. "You're nearest to him and we ought not to let such things live."

George burst out laughing. "Forget those old numbers for a while," he advised. "So far no one has been able to do anything with them, but if we let them alone for a few days we can go back to them with our minds fresh. Who knows, somebody might get an idea all of a sudden that would solve the whole business."

"I wish somebody would," sighed Fred.

"Think of this, though," exclaimed Grant. "Suppose we do forget it all for a few days, as Pop suggests. In the meantime a boat might come along and take us away and our chance of ever finding the treasure would be gone."

"That's right, Grant," cried John. "We don't want to lose an opportunity like this."

"Can't we take the code home with us?" said George. "We have all the rest of our lives to find out what it means and if it is worth while we can always come back."

"How can we tell whether it is worth while or not until we see it?"

asked Fred.

"Probably that code contains a description of what it is."

"Perhaps it does," said Grant. "We'll know better when we find out just what it does say. I'm in favor of keeping right at it."

"So am I, Grant," exclaimed John. "Don't let it rest for a second."

"Dat's de boy!" cried Sam heartily. "Ah get dat diamon' ho'shoe yet."

"Yes, and I hope you get a big automobile to go with it, Sam," said Grant.

"Ah hopes so mahself," grinned Sam. "Say, wouldn't dat be gran'?"

"We'll all have them," said John. "We'll have motor-boats and yachts, too, and maybe flying-machines."

"Stick a pin in that fellow, Fred," urged George. "He's asleep."

"Is that so?" exclaimed John. "At any rate, it's cheap enough to dream."

"That's true," laughed George. "Go ahead and dream if you like."

"Some one of us ought to be able to read that code," said Grant. "Why should a lot of figures get the better of us? We ought not to let them."

"Maybe the numbers mean letters," George suggested.

"We've all thought that ourselves," said Grant grimly. "Just what letters, though?"

"Let me see the thing," exclaimed George. "What number occurs oftenest?"

"I don't know," mused Grant, looking over his shoulder. "I guess five does."

"All right then," said George quickly; "now what is the commonest letter in the alphabet?"

"I thought of that, too," said Grant. "The trouble is that none of us know."

"That might be an idea, though."

"Yes," admitted John, "but if we don't know those things I don't see how we can get very far."

"Nor I," said George. "We might try some experiments, though."

"Go ahead," urged Grant. "Try everything you can think of. We've nothing to lose and everything to gain. No matter how silly an idea may seem to you, try it. That's the only way we can ever get anywhere."

"Right you are, Grant!" exclaimed Fred. "That's the way to talk. If we stick to it, I know we'll find out all about it some day."

"Perhaps we will 'some day,'" said George mournfully.

CHAPTER XVII

UNDERGROUND WORK

One day John was standing at the back of the cave looking up through the opening which was there. Here it was that the billy goat had given him such a fright a few weeks before. This time, however, he did not see any "white bearded old man" as he gazed up into the aperture, but he did spy something almost equally interesting.

"Hey, Fred!" he called. "Come here a minute."

Fred hastened to respond to his friend's summons and soon reached the spot where John was standing.

"What do you want, String?" he inquired.

"Look up through that opening."

"All right," said Fred, doing as he had been directed. "I'm looking."

"Don't you see anything?"

"Sure I do. I see the sky."

"Don't be silly, Fred," exclaimed John. "In the opening, I mean."

"I see dirt."

"Is that all?"

"Absolutely. What are you trying to do, anyway?"