Let me
once get down there, and I can prove what I say."

"I'd a good deal rather you wouldn't prove it, if it's going to be
anything like it was on Earthquake Island, or out among the diamond
makers." said Tom Swift. "But we will go down there, to see what
they are like. Perhaps there is a trail from among the ice caves to
the valley of gold."

"I don't think so," said Abe, shaking his head.

"I think th' gold valley lies over that high ridge," and he pointed
to one. "That's where me an' my partner was," he went on. "I
recognize th' place now."

"Well, we'll go down here, anyhow," decided Tom, and he pulled the
lever to let some gas out of the bag, and tilted the deflection
rudder to send the airship toward the odd caves.

And, curious enough did our friends find them when they had made a
landing and got out to walk about them. It was very cold, for on
every side was solid ice. They walked on ice, which was like a floor
beneath their feet, level save where the ice caves reared
themselves. As for the caverns, they, too, were hollowed out of the
solid ice. It was exactly as though there had once been a level
surface of some liquid. Then by some upheaval of nature, the surface
was blown into bubbles, some large and some small. Then the whole
thing had frozen solid, and the bubbles became hollow caves. In time
part of the sides fell in and made an opening, so that nearly all
the caves were capable of being entered.

This method of their formation was advanced as a theory by Mr.
Parker, and no one cared to dispute him. The gold-seekers walked
about, gazing on the ice caves with wonder showing on their faces.

It was almost like being in some fantastic scene from fairyland, the
big ice bubbles representing the houses, the roofs being rounded
like the igloos of the Eskimos. Some had no means of entrance, the
outer surface showing no break. Others had small openings, like a
little doorway, while of still others there remained but a small
part of the original cave, some force of nature having crumbled and
crushed it.

"Wonderful! Wonderful!" exclaimed Mr. Parker. "It bears out my
theory exactly! Now to see how fast the ice is moving."

"How are you going to tell?" asked Tom.

"By taking some mark on this field of ice, and observing a distant
peak. Then I will set up a stake, and by noting their relative
positions, I can tell just how fast the ice field is moving
southward." The scientist hurried into the ship to g