PERHAPS TEN THOUSAND YEARS OLD

"By Jove!" gasped Dave, also bending back a bush and glaring down,
his eyes wide open with interest.

"That's where our man went," Dick whispered.

"Not a doubt of it," Dave assented.  "We'll signal the other fellows,
and then get him at our leisure."

"Unless there are other openings to this cave," Dick hinted.

"That's so!  The fellow may be a quarter of a mile away from here
already," Darrin quivered.  "Let's not lose any time.  I'll go
in there first."

Dave was on his knees, quivering with eagerness, dominated by
purpose, when Dick grabbed him, hauling him back.

"Let me alone," growled Dave.  "Don't interfere with me!"

"But you don't know what you might run into in there, Darry,"
Prescott insisted firmly.  "For one thing, you have no idea how
many villains may have their secret home in there."

"Then, what are you going to do?" Darry demanded, looking up.

"I'm going to watch, right here, while you go forward and find
Tom and Dan.  Bring them here, and then we'll decide what ought
to be done."

"That's rather slow," hot-headed Darry objected.

"It is, and a heap safer," Dick contended.  "Hot-foot it after
Tom and Dan.  I'll stay right here and see to it that the mouth
of the cave doesn't run away.  Start---at once, Darry, please!
Don't let us waste time."

Knowing how stubborn Dick could be when he knew that he was wholly
right, Dave lost no time in argument.  He sprinted away, and presently
Dick heard faint echoes of Darry's signaling, "hoo-hoo!"

A few minutes later the trio came up at a dog trot.

Not one of them spoke, as all had lost their breath in their haste.
Tom, now in the lead, dashed up to where Dick stood on guard
a few yards away from the bushes.

"Over there," nodded Dick, pointing to the bushes.

Tom and Dan pulled the bushes aside curiously.

"If we're going into that cave we may as well cut the bushes down,"
murmured Reade, producing a pocket knife.  "Any objections, Chief?"

"No," smiled Dick, "and I'm not the Big Chief, either.  Cut the
bushes down, if you want.  Move over, and I'll give you some help."

Within a short time the bushes had been cut down close to the
ground, revealing an irregular shaped opening in the cave.  This
aperture was about three feet high and some five feet in width.

"Did you bring that pocket flash lamp, Tom?" asked Dick suddenly.

"Thank goodness, I did," replied Reade, producing the lamp.

Dick took it and crawled a few feet into the hole.

"There's water all along on the floor here," he called, "but just
a dribble.  Come in here and you'll find that you can stand up."

It needed no urging to induce the other boys to follow.  Then
they stood up, in almost complete darkness, save when the flashlight
showed them their surroundings.

Some parts of the cave rose to a height of perhaps sixteen feet.
Twelve feet was about the average height.  From what the boys
could see as they moved along, the cave extended for some sixty
feet.

"I don't believe there's anyone in here except ourselves," muttered
Darry in disgust, peering all around him.  "In that case, we are
wasting our time in this cave.  Phew!  How cold it is in here!"

"And well it might be," laughed Dick.  "Do you see that mass just
ahead of us?"

"What is it?" asked Dan.  "Flash the light on it."

"Come over and look at it," Dick went on.  "No one could live
in this cold place.  It is chilling me to the bone, just to stand
here.  And now you see why that little trickle of water keeps
moving out through the mouth of the cave.  Fellows, we're in one
of nature's icehouses."

"But we're not after ice," Dave protested.

"We won't turn down ice in the wilderness, when we can find it
in July," Dick rejoined.

"Not much!" answered practical Tom Reade. "Why, fellows, ice is
just what we need at the camp.  Let's get a closer look at it
and make plans for an ice-box over at the camp."

"But I want to follow that man of mystery," protested Dave.

"Go ahead, David, little giant," Dick laughed.  "We won't stop
you.  But we've lost our man of mystery, anyway, and this cave
contains something that we really do want.  Tom, you're the
mathematician of the party.  How much ice is there here?"

"If I could see better I could tell you better," sniffed Reade.
"Hundreds of tons of it, anyway."

"How did the stuff get here?" asked Dan wonderingly.

Dick was now at the edge of the ice pile, and flashed the light
at the roof of the cavern.

"See the rifts in the rock up there?" he asked.  "Water must have
leaked in here during the heavy winter rains.  It was cold water,
too.  Then, in extra cold spells, such as this country experiences,
the water must have frozen.  As heat doesn't get in here in warm
weather the ice may have been here for generations.  Fellows,
we may be looking upon ice that was here when George Washington
was a boy."

"I've read, somewhere," declared Tom soberly, "that icebergs that
float down from the polar regions in spring often represent ice
that is at least ten thousand years old.  Fellows, some of this
very ice may have been here in this cave long, long before Julius
Caesar went into the soldiering business!"

That thought had somewhat of an awesome effect upon Dick & Co.
The four high school boys felt as though they were in the presence
of great antiquity.

"But the practical side of it," declared Tom, "is that we must
devise the best way of cutting some of this ice and getting it
across the lake to the camp."

"Oh, you can break off enough for making ice water," replied Dave
Darrin impatiently, "and take it over in the canoe, though the
spring water is cold enough for anybody."

"All of Dave's thoughts are still on the man of mystery," Dick
declared, with a chuckle.

"It's much more interesting than standing here figuring on how
to get ice that we don't need," retorted Darry.

"Now, as to moving this stuff to the camp," Tom went on, "it seems
to me-----"

"Of course," laughed Dick.  "It has already struck you that we
can fell a few small trees and build a raft on which we can tow
a few hundred pounds of ice at a time."

"Oh, pshaw!" fidgeted Dave.  "I am anxious to find the man of
mystery."

"That isn't anything practical," scoffed Tom Reade, "while in
hot weather a good supply of ice is eminently practical."

"You'll think there's a practical side to the man of mystery and
his cronies when to-night comes, and there's so much noise about
the camp that we miss another night's rest," hinted Darry sagely.

"Humph!" was Tom's greeting to that assertion.  "I don't know
but you're right."

"Well, we know where the ice is," remarked Dick.  "We can get
it at our convenience.  Darry, we'll follow you in pursuit of
your man of mystery.  Come out of here, fellows."

Dick led the way out of the cave, flashing the light as he walked.
All four blinked when they found themselves out in the sunlight.

"Now, which way are we going, David, little giant?" demanded Tom
good-humoredly.

Now that he was put to it, Dave had to confess that he didn't
know.

"Let's make a swift, thorough search all around here, and see
if we can find any footprints not made by ourselves," Dave suggested
rather weakly, at last.

This was done, and faithfully, for, now that they were out in
the sunlight again, the interest in the mystery began to return.
It grew stronger as they searched.  At last, however, after more
than an hour of fruitless effort that offered not an atom of promise,
even Darry was willing to give it up for the time, at any rate.

"Let's keep on walking along the slope, then," Dick suggested,
"until we come in sight of the canoe."

As they walked along they came to a brook that, at this point,
was nearly the width of a creek.  The water ran noisily down over
the stones, save here and there where there were deep pools.

"It's narrow enough, at one point below here, to jump over," Dave
volunteered.

"Thank you," replied Dick, "but just at present I'm not for jumping
over this brook."

"Well, then, what on earth does interest you?" Dan asked.  "This
isn't the first time you've seen this stream.  You passed it
down by the lake, though down there it runs more smoothly."

"I know," Dick nodded.  "I remember the fallen tree we used for
a bridge, and I'm simply ashamed of myself that I didn't think
more about this stream at the time---but my head was then too
full of the lake mystery and the chap with the haunting face.
But now-----"

"Well?" demanded Tom impatiently.

"Reade, old fellow," Dick answered solemnly, turning back from
peering at one of the quiet pools in the creek, "you're a wonder
at black bass fishing, no doubt.  My tastes ran to another form
of sport.  Mr. Morton taught me trout fishing; he lent me his
tackle before we started, and I have it over at the camp now.
Fellows, I believe, from the looks of things, that this stream
is well stocked with trout.  At all events, I mean to have a try
at it."

"To-morrow?" asked Dave.

"No, siree!  This afternoon----just as soon as possible!  A little
while ago we were talking about ferrying ice over to the camp.
Instead, we'll ferry the camp over here, and keep the cave just
as it is for our ice-house.  Do you fellows know that brook trout
make the most delicious eating to be had when the cook knows his
business?  I do, for Mr. Morton has cooked trout for me in the
woods.  Besides, brook trout are growing scarce these days.  If
we can make a good haul, we can get a pretty big price per pound
for them!  We have ice, now, and we could carry a lot of trout
to market on our push cart, on top of enough ice to keep them.
Come on!  Back to camp!  We'll shift it to this side of the lake
at once.  This crowd can't do better than to work out this trout
stream.  I know the trout are there!  I can smell 'em!  Tom, I've
got an important job for you!"