es 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