e seemed to be coming directly
from the spot where his comrade had pointed out as the opening of a
cave.

There was not the faintest trace of lightning accompanying the
manifestation; and this proved, beyond all question of dispute, that
the mystery connected with Thunder Mountain had nothing to do with an
electrical storm. Possibly the observing Indians had many years ago
discovered this same thing; and it had strengthened their belief that
the great Manitou spoke to his red children through the voice of the
wonderful mountain.

It took longer, this time, for the noise to die away; just as though,
whatever its cause, there was increasing reluctance to subside again.

"That was a screamer, sure enough!" said Frank, when he could make
himself heard above the declining roar.

"And Bob, you noticed, didn't you, that it seemed to come right out of
that hole? All right, it begins to look now as if we were Johnny on
the spot, if we've got the nerve to push things. Somewhere in there,
Bob, lies the explanation of the mystery. Do we take the dare; or stay
out here and wait till the fuss is over before entering?"

Bob possibly swallowed hard before replying. It was no easy thing for
him to say the words that would thrust them up against so terrible a
thing as this unknown peril awaiting them in the gloom of that crack of
the great mountain. But his hesitation was brief. In fact, he only
wanted to catch his breath, shut his teeth hard together, and summon
his Kentucky blood.

"It's a go, Frank!" he said, with determination in his voice; "the
chance may never come to us again. Let's go in, and discover for
ourselves the secrets of the Indian god they say is guarding Thunder
Mountain. I'm ready, so lead on!"

CHAPTER XVII

FRANK HOLDS THE HOT STICK

"No hurry," said Frank, who realized that his comrade was worked up to
a high pitch of excitement, and thought it the part of wisdom to do
something in order to quiet Bob's nerves.

"But if we've got to try it, Frank, what's the use of waiting?"
demanded the impetuous one.

"Well, for one thing, we don't want to be carrying these candles
without making use of one, you see," replied Frank, who was again
getting out his handy matchsafe.

"What a silly I am, to be sure," laughed Bob; "why of course we want a
light, if we're going to invade that den of the demon Joe told us
about. What do you think about that yarn, Frank; did he meet up with
anything; or was