For an instant Tom and his friends paused at the entrance to the wonderful cavern, and looked at the raging storm. It seemed madness to venture out into it, yet they had been driven from the cave by those who had every right of discovery to say who, and who should not, partake of its hospitality.

"We can't go out into that blow!" cried Ned. "It's enough to loosen the very mountains!"

"Let's stay here and defy them!" murmured Tom. "If the--if what we seek--is here we have as good a right to it as they have."

"We must go out," said Professor Bumper simply. "I recognize the right of my rival to dispossess us."

"He may have the right, but it isn't human," said Mr. Damon. "Bless my overshoes! If Beecher himself were here he wouldn't have the heart to send us out in this storm."

"I would not give him the satisfaction of appealing to him," remarked Professor Bumper. "Come, we will go out. We have our ponchos, and we are not fair-weather explorers. If we can't get to the lost city one way we will another. Come my friends."

And despite the downpour, the deafening thunder and the lightning that seemed ready to sear one's eyes, he walked out of the cave entrance, followed by Tom and the others.

"Come on!" cried Tom, in a voice he tried to render confident, as they went out into the terrible storm. "We'll beat 'em yet!"

The rain fell harder than ever. Small torrents were now rushing down the trail, and it was only a question of a few minutes before the place where they stood would be a raging river, so quickly does the rain collect in the mountains and speed toward the valleys.

"We must take to the forest!" cried Tom. "There'll be some shelter there, and I don't like the way the geography of this place is behaving. There may be a landslide at any moment."

As he spoke he motioned upward through the mist of the rain to the sloping side of the mountain towering above them. Loose stones were beginning to roll down, accompanied by patches of earth loosened by the water. Some of the patches carried with them bunches of grass and small bushes.

"Yes, it will be best to move into the jungle," said the professor. "Goosal, you had better take the lead."

It was wonderful to see how well the aged Indian bore up in spite of his years, and walked on ahead. They had left their mules tethered some distance back, in a sheltering clump of trees, and they hoped the animals would be safe.

The guide found a place where they could leave the trail, though going down a dangerous slope, and take to the forest. As carefully as possible they descended this, the rain continuing to fall, the wind to blow, the lightning to sizzle all about them and the thunder to boom in their ears.

They went on until they were beneath the shelter of the thick jungle growth of trees, which kept off some of the pelting drops.

"This is better!" exclaimed Ned, shaking his poncho and getting rid of some of the water that had settled on it.

"Bless my overcoat!" cried Mr. Damon. "We seem to have gotten out of the frying pan into the fire!"

"How?" asked Tom. "We are partly sheltered here, though had we stayed in the cave in spite of----"

A deafening crash interrupted him, and following the flash one of the giant trees of the forest was seen to blaze up and then topple over.

"Struck by lightning!" yelled Ned.

"Yes; and it may happen to us!" exclaimed Mr. Damon. "We were safer from the lightning in the open. Maybe----"

Again came an interruption, but this time a different one. The very ground beneath their feet seemed to be shaking and trembling.

"What is it?" gasped Ned, while Goosal fell on his knees and began fervently to pray.

"It's an earthquake!" yelled Tom Swift.

As he spoke there came another sound--the sound of a mass of earth in motion. It came from the direction of the mountain trail they had just left. They looked toward it and their horror- stricken eyes saw the whole side of the mountain sliding down.

Slowly at first the earth slid down, but constantly gathering force and speed. In the face of this new disaster the rain seemed to have ceased and the thunder and lightning to be less severe. It was as though one force of nature gave way to the other.

"Look! Look!" gasped Ned.

In silence, which was broken now only by a low and ominous rumble, more menacing than had been the awful fury of the elements, the travelers looked.

Suddenly there was a quicker movement of seemingly one whole section of the mountain. Great rocks and trees, carried down by the appalling force of the landslide were slipping over the trail, obliterating it as though it had never existed.

"There goes the entrance to the cavern!" cried Ned, and as the others looked to where he pointed they saw the hole in the side of the mountain --the mouth of the cave that led to the lost city of Kurzon--completely covered by thousands of tons of earth and stones.

"That's the end of them!" exclaimed Tom, as the rumble of the earthquake died away.

"Of----" Ned stopped, his eyes staring.

"Of Professor Beecher's party. They're entombed alive!"