g suits and tennis shoes.

[Illustration: With the lighted lanterns they could get a better idea of
their surroundings. Page 211]

"We don't mind the rain," Apple announced. "We are going out. Look for
us when you see us."

They had already cached a couple of lanterns, a pick and two spades near
the Ice Box and it was no trick at all to get them into the cave. With
the lighted lanterns they could get a better idea of their surroundings.
The floor of the cave was waist deep in water which seemed to rush on in
a swift current and escape again into the creek through a counter
opening a few feet away. The cave was quite long. It did not, as they
supposed, have its beginning at the opening where they entered, but
extended some distance back into the gloom, and as the current was quite
swift back there it was evident that there were other hidden openings.
The vault of the cave was high, so high that they could not see the top
by the feeble light of their lanterns. But the thing that they could see
and that thrust from their minds every other subject was a solid arch of
masonry.

"I was right!" shouted Apple. "I was right! That's no natural formation.
That has been built up by men's hands years ago. It's sure to be the
hiding place of the treasure. What else could it be?"

"It couldn't be anything else," agreed Glen. "We'll mighty soon see. Get
up to the top and I'll hand you the things."

"I'm up," said Apple. "Are you coming too?"

"Sure thing. The way to tear this down is a stone at a time beginning
at the top."

"Let me have the pick, then."

"No, you hold the lantern and let me use the pick. I'm the biggest."

Splash! The first big stone disappeared in the water. Another splash and
the second followed. But prying them loose was no easy job and they did
not follow one after the other in the rapid succession the boys would
have liked. In less than half an hour they decided that an enormous lot
of work had been done in the effort to bury the treasure.

"We think this is pretty hard work getting these stones loose and
pitching 'em down in the water," said Apple, reflectively, "but think of
carrying all of 'em in from outside to build this."

"Perhaps there were more than two to do it," said Glen.

"Of course there were," said the more romantic Apple, his imagination
stirred by the picture. "There was a small army of them. I can imagine I
see them coming in here in a long procession each carrying his load,
givi