"Forward! cried Tom Swift.

"Where?" asked Mr Damon, hanging back for an instant. "Bless my compass, Tom! do you know where you're going?"

"I haven't the least idea, but it must lead to something, or the ancients who made this revolving stone door wouldn't have taken such care to block the passage."

"Ask Goosal if he knows anything about it," suggested Mr. Damon to the professor.

"He says he never was here before," translated the savant, "but years ago, when he went into the hidden city by the cave we left yesterday, he saw doors like this which opened this way."

"Then we're on the right track!" cried Tom. "If this is the same kind of door, it must lead to the same place. Ho for Kurzon and the idol of gold!"

As they passed through the stone door, Tom and Professor Bumper tried to get some idea of the mechanism by which it worked. But they found this impossible, it being hidden within the stone itself or in the adjoining walls. But, in order that it might not close of itself and entomb them, the portal was blocked open with stones found in the passage.

"It's always well to have a line of retreat open," said Tom. "There's no telling what may lie beyond us."

For a time there seemed to be nothing more than the same passage along which they had come. Then the passage suddenly widened, like the large end of a square funnel. Upward and outward the stone walls swept, and they saw dimly before them, in the light of their torches, a vast cavern, seemingly formed by the falling in of mountains, which, in toppling over, had met overhead in a sort of rough arch, thus protecting, in a great measure, that which lay beneath them.

Goosal, who had brought with him some of the fiber bark torches, set a bundle of them aflame. As they flared up, a wondrous sight was revealed to Tom Swift and his friends.

Stretching out before them, as though they stood at the end of an elevated street and gazed down on it, was a city--a large city, with streets, houses, open squares, temples, statues, fountains, dry for centuries--a buried and forgotten city-- a city in ruins--a city of the dead, now dry as dust, but still a city, or, rather, the strangely preserved remains of one.

"Look!" whispered Tom. A louder voice just then, would have seemed a sacrilege. "Look!"

"Is it what we are looking for?" asked Ned in a low voice.

"I believe it is," replied the professor. "It is the lost city of Kurzon, or one just like it. And now if we can find the idol of gold our search will be ended--at least the major part of it."

"Where did you expect to find the idol?" asked Tom.

"It should be in the main temple. Come, we will walk in the ancient streets--streets where no feet but ours have trod in many centuries. Come!"

In eager silence they pressed on through this newly discovered wonderland. For it was a wonderful city, or had been. Though much of it was in ruins, probably caused by an earthquake or an eruption from a volcano, the central portion, covered as it was by the overtoppling mountains that formed the arching roof, was well preserved.

There were rude but beautiful stone buildings. There were archways; temples; public squares; and images, not at all beautiful, for they seemed to be of man-monsters--doubtless ancient gods. There were smoothly paved streets; wondrously carved fountains, some in ruins, all now as dry as bone, but which must have been places of beauty where youths and maidens gathered in the ancient days.

Of the ancient population there was not a trace left. Tom and his friends penetrated some of the houses, but not so much as a bone or a heap of mouldering dust showed where the remains of the people were. Either they had fled at the approaching doom of the city and were buried elsewhere, or some strange fire or other force of nature had consumed and obliterated them.

"What a wealth of historic information I shall find here!" murmured Professor Bumper, as he caught sight of many inscriptions in strange characters on the walls and buildings. "I shall never get to the end of them."

"But what about the idol of gold?" asked Mr. Damon, "Do you think you'll find that?"

"We must hurry on to the temple over there," said the scientist, indicating a building further along.

"And then we must see about rescuing your rivals, Professor," put in Tom.

"Yes, Tom. But fortunately we are on the ground here before them," agreed the professor.

Undoubtedly it was the chief temple, or place of worship, of the long-dead race which the explorers now entered. It was a building beautiful in its barbaric style, and yet simple. There were massive walls, and a great inner court, at the end of which seemed to be some sort of altar. And then, as they lighted fresh torches, and pressed forward with them and their electric lights, they saw that which caused a cry of satisfaction to burst from all of them.

"The idol of gold!"

Yes, there it squatted, an ugly, misshapen, figure, a cross between a toad and a gila monster, half man, half beast, with big red eyes--rubies probably--that gleamed in the repulsive golden face. And the whole figure, weighing many pounds, seemed to be of solid gold!

Eagerly the others followed Professor Bumper up the altar steps to the very throne of the golden idol. The scientist touched it, tried to raise it and make sure of its solidity and material.

"This is it!" he cried. "It is the idol of gold! I have found We have found it, for it belongs to all of us!"

"Hurray!" cried Tom Swift, and Ned and Mr. Damon joined in the cry.

There was no need for silence or caution now; and yet, as they stood about the squat and ugly figure, which, in spite of its hideousness, was worth a fortune intrinsically and as an antique, they heard from the direction of the stone passage a noise.

"What is it?" asked Tom Swift.

There was a murmur of voices.

"Indians!" cried Professor Bumper, recognizing the language--a mixture of Spanish and Indian.

The cave was illuminated by the glare of other torches which seemed to rush forward. A moment later it was seen that they were being carried by a number of Indians.

"Friends," murmured Goosal, using the Spanish term, "Amigos."

"They are our own Indians!" cried Tom Swift. "I see Tolpec!" and he pointed to the native who had deserted from Jacinto's force to help them.

"How did they get here?" asked Professor Bumper.

This was quickly told. In their camp, where, under the leadership of Tolpec they had been left to do the excavating, the natives had heard, seen and felt the effects of the storm and the earthquake, though it did little damage in their vicinity. But they became alarmed for the safety of the professor and his party and, at Tolpec's suggestion, set off in search of them.

The Indians had seen, passing along the trail, the uprooted trees, and had noted the footsteps of the explorers going down to the stone passage. It was easy for them to determine that Tom and his friends had gone in, since the marks of their boots were plainly in evidence in the soft soil.

None of the Indians was as much wrought up over the discovery of Kurzon and the idol as were the white adventurers. The gold, of course, meant something to the natives, but they were indifferent to the wonders of the underground city. Perhaps they had heard too many legends concerning such things to be impressed.

"That statue is yours--all yours," said old Goosal when he had talked with his relatives and friends among the natives. "They all say what you find you keep, and we will help you keep it."

"That's good," murmured Professor Bumper. "There was some doubt in my mind as to our right to this, but after all, the natives who live in this land are the original owners, and if they pass title to us it is clear. That settles the last difficulty."

"Except that of getting the idol out," said Mr. Damon.

"Oh, we'll accomplish that!" cried Tom.

"I can hardly believe my good luck," declared Professor Bumper. "I shall write a whole book on this idol alone and then----"

Once more came an interruption. This time it was from another direction, but it was of the same character--an approaching band of torch- bearers. They were Indians, too, but leading them were a number of whites.

And at their head was no less personage than Professor Beecher himself.

For a moment, as the three parties stood together in the ancient temple, in the glare of many torches, no one spoke. Then Professor Bumper found his voice.

"We are glad to see you," he said to his rival. "That is glad to see you alive, for we saw the landslide bury you. And we were coming to dig you out. We thought this cave--the cave of the buried city--would lead us to you easier than by digging through the slide. We have just discovered this idol," and he put his hand on the grim golden image.

"Oh, you have discovered it, have you?" asked Professor Beecher, and his voice was bitter.

"Yes, not ten minutes ago. The natives have kindly acknowledged my right to it under the law of priority. I am sorry but----"

With a look of disgust and chagrined disappointment on his face, Professor Beecher turned to the other scientists and said:

"Let us go. We are too late. He has what I came after."

"Well, it is the fortune of war--and discovery," put in Mr. Hardy, one of the party who seemed the least ill-natured. "Your luck might have been ours, Professor Bumper. I congratulate you."

"Thank you! Are you sure your party is all right--not in need of assistance? How did you get out of the place you were buried?"

"Thank you! We do not require any help. It was good of you to think of us. But we got out the way we came in. We did not enter the tunnel as you did, but came in through another entrance which was not closed by the landslide. Then we made a turn through a gateway in a tunnel connecting with ours--a gateway which seems to have been opened by the earthquake-- and we came here, just now.

"Too late, I see, to claim the discovery of the idol of gold," went on Mr. Hardy. "But I trust you will be generous, and allow us to make observations of the buildings and other relics."

"As much as you please, and with the greatest pleasure in the world," was the prompt answer of Professor Bumper. "All I lay sole claim to is the golden idol. You are at liberty to take whatever else you find in Kurzon and to make what observations you like."

"That is generous of you, and quite in contrast to--er--to the conduct of our leader. I trust he may awaken to a sense of the injustice he did you."

But Professor Beecher was not there to hear this. He had stalked away in anger.

"Humph!" grunted Tom. Then he continued: "That story about a government concession was all a fake, Professor, else he'd have put up a fight now. Contemptible sneak!"

In fact the story of Tom Swift's trip to the underground land of wonders is ended, for with the discovery of the idol of gold the main object of the expedition was accomplished. But their adventures were not over by any means, though there is not room in this volume to record them.

Suffice it to say that means were at once taken to get the golden image out of the cave of the ancient city. It was not accomplished without hard work, for the gold was heavy, and Professor Bumper would not, naturally, consent to the shaving off of so much as an ear or part of the flat nose, to say nothing of one of the half dozen extra arms and legs with which the ugly idol was furnished.

Finally it was safely taken out of the cave, and along the stone passage to the opening formed by the overthrown trees, and thence on to camp.

And at the camp a surprise awaited Tom.

Some long-delayed mail had been forwarded from the nearest place of civilization and there were letters for all, including several for our hero. One in particular he picked out first and read eagerly.

"Well, is every little thing all right, Tom?" asked Ned, as he saw a cheerful grin spread itself over his chum's face.

"I should say it is, and then some! Look here, Ned. This is a letter from----"

"I know. Mary Nestor. Go on."

"How'd you guess?"

"Oh, I'm a mind-reader."

"Huh! Well, you know she was away when I went to call to say good-bye, and I was a little afraid Beecher had got an inside edge on me."

"Had he?"

"No, but he tried hard enough. He went to see Mary in Fayetteville, just as you heard, be- fore he came on to join his party, but he didn't pay much of a visit to her."

"No?"

"No. Mary told him he'd better hurry along to Central America, or wherever it was he intended going, as she didn't care for him as much as he flattered himself she did."

"Good!" cried Ned. "Shake, old man. I'm glad!"

They shook hands.

"Well, what's the matter? Didn't you read all of her letter?" asked Ned when he saw his chum once more perusing the epistle.

"No. There's a postscript here.

"`Sorry I couldn't see you before you left. It was a mistake, but when you come back----'

"Oh, that part isn't any of your affair!" and, blushing under his tan, Tom thrust the letter into his pocket and strode away, while Ned laughed happily.

With the idol of gold safe in their possession, Professor Bumper's party could devote their time to making other explorations in the buried city. This they did, as is testified to by a long list of books and magazine articles since turned out by the scientist, dealing strictly with archaeo- logical subjects, touching on the ancient Mayan race and its civilization, with particular reference to their system of computing time.

Professor Beecher, young and foolish, would not consent to delve into the riches of the ancient city, being too much chagrined over the loss of the idol. It seems he had really promised to give a part of it to Mary Nestor. But he never got the chance.

His colleagues, after their first disappointment at being beaten, joined forces with Professor Bumper in exploring the old city, and made many valuable discoveries.

In one point Professor Bumper had done his rival an injustice. That was in thinking Professor Beecher was responsible for the treachery of Jacinto. That was due to the plotter's own work. It was true that Professor Beecher had tentatively engaged Jacinto, and had sent word to him to keep other explorers away from the vicinity of the ancient city if possible; but Jacinto, who did not return Professor Bumper's money, as he had promised, had acted treacherously in order to enrich himself. Professor Beecher had nothing to do with that, nor had he with the taking of the map, as has been seen, the loss of which, after all, was a blessing in disguise, for Kurzon would never have been located by following the directions given there, as it was very inaccurate.

In another point it was demonstrated that the old documents were at fault. This was in reference to the golden idol having been overthrown and another set up in its place, an act which had caused the destruction of Kurzon.

It is true that the city was destroyed, or rather, buried, but this catastrophe was probably brought about by an earthquake. And another great idol, one of clay, was found, perhaps a rival of Quitzel, but it was this clay image which was thrown down and broken, and not the golden one.

Perhaps an effort had been made, just before the burying of the city, to change idols and the system of worship, but Quitzel seemed to have held his own. The old manuscripts were not very reliable, it was found, except in general.

"Well, I guess this will hold Beecher for a while," said Tom, the night of the arrival of Mary's letter, and after he had written one in answer, which was dispatched by a runner to the nearest place whence mail could be forwarded.

"Yes, luck seems to favor you," replied Ned. "You've had a hand in the discovery of the idol of gold, and----"

"Yes. And I discovered something else I wasn't quite sure of," interrupted Tom, as he felt to make sure he had a certain letter safe in his pocket.

It was several weeks later that the explorations of Kurzon came to an end--a temporary end, for the rainy season set in, when the tropics are unsuitable for white men. Tom, Professor Bumper, Ned and Mr. Damon set sail for the United States, the valuable idol of gold safe on board.

And there, with their vessel plowing the blue waters of the Caribbean Sea, we will take leave of Tom Swift and his friends.