p. Bless my life insurance policy! but I
never was in such a state as this."

"We may soon be in a worse one," was the answer of the gloomy
scientist.

"What do you mean?" asked Mr. Damon, but he hurried on without
waiting for a reply.

Suddenly, from without the cave came a series of fierce yells. It
was the battle-cry of the Indians. At the same moment there sounded
a fusillade of guns.

"The battle is beginning!" cried Tom Swift, grimly. He held his
electric gun, though he had not used it very much in the previous
attack, preferring to save it for a time of more need.

As the defenders of the cave reached the entrance they saw the body
of natives rushing forward. They were almost at the gold hole, with
Andy Foger and his father discreetly behind the first row of
Eskimos, when, with a suddenness that was startling, there sounded
throughout the whole valley a weird sound!

It was like the wailing of some giant--the sighing of some mighty
wind. At the same time the air suddenly became dark, and then there
came a violent snow squall, shutting out instantly the sight of the
advancing natives. Tom and the others could not see five feet beyond
the cave.

"This will delay the attack," murmured Ned, "They can't see to come
at us."

Mr. Parker came running up from the interior of the cave. On his
face there was a look of alarm.

"We must leave here at once!" he cried.

"Leave here?" repeated Tom. "Why must we? The enemy are out there!
We'd run right into them!"

"It must be done!" insisted the scientist. "We must leave the cave
at once!"

"What for?" cried Mr. Damon.

"Because the movement of the ice that I predicted, has begun. It is
much more rapid than I supposed it would be. In a short time this
cave and all the others will be crushed flat!"

"Crushed flat!" gasped Tom.

"Yes, the caves of ice are being destroyed! Hark! You can hear them
snapping!"

They all listened. Above the roar of the storm could be made out the
noise of crushing, grinding ice-sounds like cannon being fired, as
the great masses of frozen crystal snapped like frail planks.

"The ice caves are being destroyed by an upheaval of nature!" went
on Mr. Parker. "This one will soon go! The walls are bulging now! We
must get out!"

"But the natives! They will kill us!" cried Mr. Damon. "Bless my
soul! what a trying position to be in."

"I guess the natives are as bad off as we are," suggested Ned.
"They're not firing, and I can hear