The excited cries of the old miner brought Mr. Damon and Mr. Parker to the pilothouse on the run.

"Bless my refrigerator!" exclaimed Mr. Damon. "Are there more of those savage, shaggy creatures down there?"

"No, but we are over th' caves of ice," explained Abe. "That means we are near th' gold."

"You don't say so!" burst out the scientist. "The caves of ice! Now I can begin my real observations! I have a theory that the caves are on top of a strata of ice that is slowly moving down, and will eventually bury the whole of the North American continent. 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 get a sharpened stake he had prepared for this purpose.

"How fast do you think the ice is moving?" asked Ned.

"Oh, perhaps two or three feet a year." "Two or three feet a year?" gasped Mr. Damon. "Why, Parker, my dear fellow, at that rate it will be some time before the ice gets to New York."

"Oh, yes. I hardly expect it will reach there within two thousand years, but my theory will be proved, just the same!"

"Humph!" exclaimed Abe Abercrombie, "I ain't goin' to worry any more, if it's goin' t' take all that while. I reckoned, to hear him talk, that it was goin' t' happen next summer."

"So did I," agreed Tom, but their remarks were lost on Mr. Parker who was busy making observations. The young inventor and the others walked about among the ice caves.

"Some of these caverns would be big enough to house the Red Cloud in case of another hail storm," observed Tom. "That one over there would hold two craft the size of mine," and, in fact, probably three could have gotten in if the opening had been somewhat enlarged, for the ice cave to which our hero pointed was an immense one.

As the adventurers were walking about they were startled by a terrific crashing sound. They started in alarm, for, off to their left, the top of one of the ice caverns had crashed inward, the blocks of frozen water crushing and grinding against one another.

"It's a good thing we weren't in there," remarked Tom, and he could not repress a shudder, "There wouldn't have been much left of the Red Cloud if she had been inside."

It was a desolate place, in spite of the wild beauty of it, and beautiful it was when the sun shone on the ice caves, making them sparkle as if they were studded with diamonds. But it was cold and cheerless, and there were no signs that human beings had ever been there. Mr. Parker had completed the setting of his stake, and picked out his landmarks, and was gravely making his "observations," and jotting down some figures in a notebook.

"How fast is it moving, Parker?" called Mr. Damon.

"I can't tell yet," was the response. "It will require observations extending over several days before I will know the rate."

"Then we might as well go on," suggested Tom. "There is nothing to be gained from staying here, and I would like to get to the gold valley. Abe says we are near it."

"Right over that ridge, I take it to be," replied the miner. "An' we can't get there any too soon for me. Those Fogers may git their ship fixed up, an' arrive before we do if we wait much longer."

"Not much danger, I guess," declared Ned.

"Well, we'll go up in the air, and see what we can find," decided Tom, as he turned back toward the ship.

They found the "ridge" as Abe designated it. to be a great plateau, over a hundred miles in extent, and they were the better part of that day crossing it, for they went slowly, so as not to miss the valley which the miner was positive was close at hand. Mr. Parker disliked leaving the ice caves, but Abe said there were more in the valley where they were going, and the scientist could renew his observations.

It was getting dusk when Tom, who was peering through a powerful glass, called out:

"Well, we're at the end of the plateau, and it seems to dip down into a valley just beyond here."

"Then that's the place!" cried Abe, excitedly. "Go slow, Tom."

Our hero needed no such caution. Carefully he sent the airship forward. A few minutes later they were passing over a large Eskimo village, the fur-clad inhabitants of which rushed about wildly excited at the sight of the airship.

"There they are! Them's th' beggars!" cried the old miner. "Them's th' fellows who drove me an' my partner away. But there's th' valley of gold! I know it now! How t' fill our pockets with nuggets!"

"Are you sure this is the place?" asked Mr. Damon.

"Sartin sure of it!" declared Abe. "Put her down, Tom! Put her down!"

"All right," agreed the young inventor, as he shifted the deflection rudder. The airship began her descent into the valley. The edge of the plateau, leading down into the great depression was now black with the Eskimos and Indians, who were capering about, gesticulating wildly.

"It's quite a surprise party to 'em," observed Ned Newton.

"Yes, I hope they don't spring one on us," added Tom.

Down and down went the Red Cloud lower and lower into the valley.

"There are ice caves there!" cried Mr. Parker, pointing to the curiously rounded and hollow hummocks. "Lots of them!"

"And larger than the others!" added Mr. Damon.

The airship was now moving slowly, for Tom wanted to pick out a good landing place. He saw a smooth stretch of the ice just ahead of him, in front of an immense ice cave.

"I'll make for that," he told Ned.

A few minutes later the craft had come to rest. Tom shut off the power and hurried from the pilothouse, donning his fur coat as he rushed out. A blast of frigid air met him as he opened the outer door of the cabin. Back on the ridge of the plateau he could see the fringe of Indians.

"Well, we're here in the valley," he said, as his friends gathered about him on the icy ground.

"An' now for th' gold!" cried Abe, "for it's here that th' nuggets are--enough for all of us! Come on an' have a hunt for 'em!"