diamonds?" cried Mr. Damon, as he raced along
behind Tom. "Now's our chance. Those fellows have all gone!" The odd man
made a grab for something as he ran.

"It's as much as our lives are worth," declared the young inventor. "We
dare not stop! Come on!"

"I'd like to investigate some of the machinery," spoke Mr. Jenks, "but I
wouldn't stop, even for that."

"The storm is too dangerous," called Bill Renshaw. "I can show you a
shorter way out than the one those fellows have taken. Follow me."

"No way can be too short," said Mr. Parker, solemnly. "This mountain
will go to pieces shortly, I think!"

Tom shuddered. He remembered how narrow had been their escape when
Earthquake Island sank into the sea. And that some terrific upheaval was
now imminent might be judged from the awful reports that sounded more
plainly as the adventurers raced toward the opening of the cave. It was
like the bombardment of some doomed city.

Mr. Jenks and Tom cast one longing look behind at the complicated and
expensive machinery that had been installed in the cave by the diamond
makers. They had abandoned it, and in it lay the secret of making
precious gems. But there was no time to stop now, and investigate.

"This way," urged Bill Renshaw. "We'll soon be out."

"But won't it be dangerous to go outside?" asked Mr. Damon. "Shan't we
be struck by lightning? There is some protection in here."

"None at all," said Mr. Parker, quickly. "This mountain is a natural
lightning rod. To stay here in this cave will be sure death when the
storm gets directly over it. And that will be very soon. We must get
on insulated ground. Is there any part of this mountain that does not
contain iron ore?" the scientist asked of the former spirit.

"Yes; the way out by which we are going lands on a dirt hill."

"That's good; then we may be saved."

On they ran. They had no lanterns, but the blue light of the
electricity, as it leaped from point to point inside the cave, where
there were outcroppings of iron ore, made the place bright enough to
see.

"Here we are!" cried Bill Renshaw at length. "Here's the way out!"

Making a sudden turn in the winding passage he showed the adventurers
a small opening in the side of the crag. In an instant they had passed
through, and found themselves in daylight once more. The sudden glare
almost blinded them, for, though the sky was overcast by clouds, from
which jagged tongues of lightning played, the outside was much