partly from the
excitement, and because he felt a touch of alarm.

But he could not help noticing the actions of his chum. When the
thunderous roar was about at its height Frank had thrown himself flat
on the ground. Bob could not see what he was doing, but his groping
hand came in contact with the head of his comrade; and he discovered
that it rested on the ground, with one ear pressed to the rock.

Frank was listening!

He knew how the ground carried sounds more distinctly than the air, and
evidently he hoped to discover something concerning the thunder by this
method of wireless telegraphy.

Then, as the volume of sound gradually decreased, just as a lion's roar
dies away, Bob discovered that Peg and Nick were undoubtedly moving
off. He supposed that Nick had made up his mind to hunt for an
outcropping ledge, or some friendly opening, where he could be
sheltered from the storm; and as Peg dared not stay alone, he was
compelled to accompany his guide. The complaining voice of the rich
man's son could be heard for a minute or so. Then even that ceased.

"They're gone, Frank!" exclaimed Bob.

"Yes, I know it," replied the other, as he arose from his position flat
on the rocks. "And Peg is badly rattled, too. Say, I always told you
he lacked real grit, and this proves it. He's scared at that noise.
Think of him wanting to fly down to the plain! I reckon he's had about
all of the exploring he wants. It's 'take me back to my daddy!' now
with Peg."

"Well," remarked Bob, with a sigh, "I don't blame him so very much,
Frank. I tell you what, that noise is enough to give anybody fits.
I'm all of a tremble myself, and I'm honest enough to admit it."

"That's all right, Bob," replied his chum, quickly; "but are you ready
to give the game up here and now?"

"Who, me?" answered the Kentucky boy, instantly; "well, I should say
not--not by a long sight! No matter what comes, I'm ready to stick it
out on this line if it takes all summer!"

"Just what I thought," chuckled Frank. "That's what makes all the
difference between a brave fellow and a coward. Why, to tell you the
truth, Bob, I'm shaking all over right now myself; but it isn't with
fear. I'm excited, curious, and worked up; so are you. When you say
you don't want to back out it tells the story that you're not afraid."

"But it wouldn't make any difference, Frank, seeing that we couldn't
get away from here, even if we wanted to just now," remarked