into the cave.

"Okay. Now let's pick out the spot for embedding the unit," Tom said.

The men had no sooner begun to look around the huge underground chamber
when a fearsome growl rumbled through the cave. Everyone whirled about
and the next instant froze in horror.

A huge bear reared up in the mouth of the cave! The monster snarled and
blinked its yellow eyes in the glare of lights.

"We're trapped!" Hank cried out.

The enormous bruin was now waving his huge head from side to side, as if
daring the intruders to step up and fight.

Several of the government men had brought rifles and shotguns. But in
spite of their peril, no one wanted to shoot the handsome old fellow.

"I'll send out an SOS," Tom said. "If help arrives before the bear
attacks, we won't use guns."

He radioed the local Forest Ranger post. After a nerve-racking wait,
with the group expecting a charge from the beast at any minute, two
rangers appeared and captured the bear with a net. One man of the
government work crew knocked together a stout wooden cage. The beast,
outraged, was loaded aboard the heliplane to be released in an area
remote from the cave.

[Illustration (Tom and Hank meet a bear in the cave)]

Now the grueling job of installing the Quakelizor began. First the cave
was cleared of debris, bats, and other small living creatures. Then a
site was marked out on the cave floor. Tom had brought along a midget
model of his great atomic earth blaster, which he had invented to drill
for iron at the South Pole.

With the blaster, Tom quickly drilled a pit of exact size into the
bedrock. Then the Quakelizor was assembled and lowered into place by a
portable crane. A power plant and radio antenna were set up and the
installation was finally completed.

"I must return to Shopton now," Tom said. "Art here will stick around
and help you operate the setup," he told the government engineers after
radio contact had been made with Washington. "If anything goes wrong,
just flash word to Enterprises."

The _Sky Queen_ and the heliplane sped back across the continent. As Tom
landed at Enterprises he was greeted by Bud, who came speeding out on
the airfield by jeep.

"Just got back from the space wheel about an hour ago," Bud said. "Your
dad's really worried about those exploding radio sets, Tom. He has no
clues, but he's sure the scientists working for the Brungarian rebel
setup are responsible. He thinks they may try to ruin all of
Ente