The man took off his hat and approached Tom, genuflecting as he might have done in church.

"She say you save baby from condor," the man said in his halting English. "She t'ank you—me, I t'ank you. Bird see babe in deer skin—t'ink um dead animal. Maybe so bird carry baby off, drop um on sharp stone, baby smile no more. You have our lives, senor! We do anyt'ing we can for you."

"Thanks," said Tom, easily. "I'm glad I happened to be around. I supposed condors only went for things dead, but I reckon, as you say, it mistook the baby in the deer skin for a dead animal. And I guess it might have carried your little one off, or at least lifted it up, and then it might have dropped it far enough to have killed it. It sure is a big bird," and Tom strolled over to look at what he had bagged.

The condor of the Andes is the largest bird of prey in existence. One in the Bronx Zoo, in New York, with his wings spread out, measured a little short of ten feet from tip to tip. Measure ten feet out on the ground and then imagine a bird with that wing stretch.

This same condor in the park was made angry by a boy throwing a feather boa up into the air outside the cage. The condor raised himself from the ground, and hurled himself against the heavy wire netting so that the whole, big cage shook. And the breeze caused by the flapping wings blew off the hats of several spectators. So powerful was the air force from the condor's wings that it reminded one of the current caused when standing behind the propellers of an aeroplane in motion. The condor rarely attacks living persons or animals, though it has been known to carry off big sheep when driven by hunger.

It was one of these animals Tom Swift had shot with his electric rifle.

"We do anyt'ing you want," the man gratefully repeated.

"Well, I've got about all I want," Tom said. "But if you could tell me where those ten missing men are, and how they got out of the tunnel, I'd be obliged to you."

The woman did not seem to comprehend Tom's talk, but the man did. He started, and fear seemed to come over him.

"Me—I—I can not tell," he murmured.

"No, I don't suppose you can," said Tom, musingly. "Well, it doesn't matter, I guess I'll have to cross it off my books. I'll never find out."

Again the Indian and his wife expressed their gratitude, and Tom, after letting the little brown baby cling to his finger, and patting its chubby cheek, went on his way with Koku.

"Well, that was some excitement," mused Tom, who made little of the shot itself, for the condor was such a mark that he would have had to aim very badly indeed to miss it. And perhaps only the electric rifle could have killed quickly enough to prevent the baby's being injured in some way by the big bird, even though it was dying.

"Master heap good shot!" exclaimed Koku, admiringly.

The tunnel work went on, though not so well as when Tom's explosive was first used. The rock was indeed getting harder and was not so easily shattered. Tom made tests of the pieces he had obtained from the outcropping ledge on the mountain where he had shot the condor, and decided to make a change in the powder.

Shipments were regularly received from Shopton, Mr. Swift keeping things in progress there. Mr. Damon's business was going on satisfactorily, and he lent what aid he could to Tom. As for Professor Bumper he kept on with his search for the lost city of Pelone, but with no success.

The scientist wanted Tom and Mr. Damon to go on another trip with him, this time to a distant sierra, or fertile valley, where it was reported a race of Indians lived, different from others in that region.

"It may be that they are descendants from the Pelonians," suggested the professor. Tom was too busy to go, but Mr. Damon went. The expedition had all sorts of trouble, losing its way and getting into a swamp from which escape was not easy. Then, too, the strange Indians proved hostile, and the professor and his party could not get nearer than the boundaries of the valley.

"But the difficulties and the hostile attitude of these natives only makes me surer that I am on the right track," said Mr. Bumper. "I shall try again."

Tom was busy over a problem in explosives one day when he saw Tim Sullivan hurrying into the office of the two brothers. The Irishman seemed excited.

"I hope there hasn't been another premature blast," mused Tom. "But if there had been I think I'd have heard it."

He hastened out to see Job and Walter Titus in excited conversation with Tim.

"They didn't come out, an' thot's all there is to it," the foreman was saying. "I sint thim in mesilf, and they worked until it was time t' set off th' blast. I wint t' get th' fuse, an' I was goin' t' send th' black imps out of danger, whin—whist—they was gone whin I got back—fifteen of 'em this time!"

"Do you mean that fifteen more of our men have vanished as the first ten did?" asked Job Titus.

"That's what I mean," asserted the Irishman.

"It can't be!" declared Walter.

"Look for yersilf!" returned Tim. "They're not in th' tunnel!"

"And they didn't come out?"

"Ask th' time-keeper," and Tim motioned to a young Englishman who, since the other disappearance, had been stationed at the mouth of the tunnel to keep a record of who went in and came out.

"No, sir! Nobody kime hout, sir!" the Englishman declared. "Hi 'aven't been away frim 'ere, sir, not since hi wint on duty, sir. An' no one kime out, no, sir!"

"We've got to stop this!" declared Job Titus.

"I should say so!" agreed his brother.

With Tom and Tim the Titus brothers went into the tunnel. It was deserted, and not a trace of the men could be found. Their tools were where they had been dropped, but of the men not a sign.

"There must be some secret way out," declared Tom.

"Then we'll find it," asserted the brothers.

Work on the tunnel was stopped for a day, and, keeping out all natives, the contractors, with Tom and such white men as they had in their employ, went over every foot of roof, sides and floor in the big shaft. But not a crack or fissure, large enough to permit the passage of a child, much less a man, could be found.

"Well, I give up!" cried Walter Titus in despair. "There must be witchcraft at work here!"

"Nonsense!" exclaimed his brother. "It's more likely the craft of Blakeson & Grinder, with Waddington helping them."

"Well, if a human agency made these twenty-five men disappear, prove it!" insisted Walter.

His brother did not know what to say.

"Well, go on with the work," was Job's final conclusion. "We'll have one of the white men constantly in the tunnel after this whenever a gang is working. We won't leave the natives alone even long enough to go to get a fuse. They'll be under constant supervision."

The tunnel was opened for work, but there were no workers. The morning after the investigation, when the starting whistle blew there was no line of Indians ready to file into the big, black hole. The huts where they slept were deserted. A strange silence brooded over the tunnel camp.

"Where are the men, Serato?" asked Tom of the Indian foreman.

"Men um gone. No work any more. What you call a hit."

"You mean a strike?" asked Tom.

"Sure—strike—hit—all um same. No more work—um 'fraid!"



Chapter XIX

A Woman Tells

"Well, if this isn't the limit!" cried Torn Swift. "As if we didn't have trouble enough without a strike on our hands!"

"I should say yes!" chimed in Job Titus.

"Do you mean that the men won't work any more?" asked his brother of the native foreman.

"Sure, no more work—um much 'fraid big devil in tunnel carry um off an' eat um."

"Well, I don't know that I blame 'em for being a bit frightened," commented Job. "It is a queer proceeding how twenty-five men can disappear like that. Where have the men gone, Serato?"

"Gone home. No more work. Go on hit—strike—same like white men."

"They waited until pay day to go on strike," commented the bookkeeper, a youth about Tom's age.

This was true. The men had been paid off the day before, and usually on such occasions many of them remained away, celebrating in the nearest village. But this time all had left, and evidently did not intend to come back.

"We'll have to get a new gang," said Job. "And it's going to delay us just at the wrong time. Well, there's no help for it. Get busy, Serato. You and Tim go and see how many men you can gather. Tell them we'll give them a sol a week more if they do good work. (A sol is the standard silver coin of Peru, and is worth in United States gold about fifty cents.)

"Half a dollar a day more will look mighty big to them," went on the contractor. "Get the men, Serato, and we'll raise your wages two sols a week."

The eyes of the Indian gleamed, and he went off, saying.

"Um try, but men much 'fraid."

Whether Serato used his best arguments could not, of course, be learned, but he came back at the close of the day, unaccompanied by any workers, and he shook his head despondently.

"Indians no come for one sol, mebby not for two," he said. "I no can git."

"Then I'll try!" cried Job. "I'll get the workers. I'll make our old ones come back, for they'll be the best."

Accompanied by his brother and Tom he went to the various Indian villages, including the one whence most of the men now on strike had come. The fifteen missing ones were not found, though, as before, their relatives, and, in some cases, their families, did not seem alarmed. But the men who had gone on strike were found lolling about their cabins and huts, smoking and taking their ease, and no amount of persuasion could induce them to return.

Some of them said they had worked long enough and were tired, needing a rest. Others declared they had money enough and did not want more. Even two more sols a week would not induce them to return.

And many were frankly afraid. They said so, declaring that if they went back to the tunnel some unknown devil might carry them off under the earth.

Job Titus and his brother, who could speak the language fairly well, tried to argue against this. They declared the tunnel was perfectly safe. But one native worker, who had been the best in the gang, asked:

"Where um men go?"

The contractors could not answer.

"It's a trick," declared Walter. "Our rivals have induced the men to go on strike in order to hamper us with the work so they'll get the job."

But the closest inquiry failed to prove this statement. If Blakeson & Grinder, or any of their agents, had a hand in the strike they covered their operations well. Though diligent inquiry was made, no trace of Waddington, or any other tool, could be found.

Tom, who had some sort of suspicion of the bearded man on the steamer, tried to find him, even taking a trip in to Lima, but without avail.

The tunnel work was at a standstill, for there was little use in setting off blasts if there were no men to remove the resulting piles of debris. So, though Tom was ready with some specially powerful explosive, he could not use it.

Efforts were made to get laborers from another section of the country, but without effect. The contractors heard of a big force of Italians who had finished work on a railroad about a hundred miles away, and they were offered places in the tunnel. But they would not come.

"Well, we may as well give up," said Walter, despondently, to his brother one day. "We'll never get the tunnel done on time now."

"We still have a margin of safety," declared job. "If we could get the men inside of a couple of weeks, and if Tom's new powder rips out more rock, we'll finish in time."

"Yes, but there are too many ifs. We may as well admit we've failed."

"I'll never do that!"

"What will you do?"

But Job did not know.

"If we could git a gang of min from the ould sod—th' kind I used t' work wit in N'Yark," said Tim Sullivan, "I'd show yez whot could be done! We'd make th' rock fly!"

But that efficient labor was out of the question now. The tunnel camp was a deserted place.

"Come on, Koku, we'll go hunting," said Tom one day. "There's no use hanging around here, and some venison wouldn't go bad on the table."

"I'll come, too," said Mr. Damon. "I haven't anything to do."

The Titus brothers had gone to a distant village, on the forlorn hope of getting laborers, so Tom was left to his own devices, and he decided to go hunting with his electric rifle.

The taruco, or native deer, had been plentiful in the vicinity of the tunnel until the presence of so many men and the frequent blasts had driven them farther off, and it was not until after a tramp of several miles that Tom saw one. Then, after stalking it a little way, he managed to kill it with the electric rifle.

Koku hoisted the animal to his big shoulders, and, as this would provide meat enough for some time, Tom started back for camp.

As he and Mr. Damon, with Koku in the rear, passed through a little clearing, they saw, on the far side, a native hut. And from it rushed a woman, who approached Tom, casting herself on her knees, while she pressed his free hand to her head.

"Bless my scarf pin!" exclaimed Mr. Damon. "What does this mean, Tom?"

"Oh, this is the mother of the child I saved from the condor," said Tom. "Every time she sees me she thanks me all over again. How is the baby?" he asked in the Indian tongue, for he was a fair master of it by now.

"The baby is well. Will the mighty hunter permit himself to enter my miserable hovel and partake of some milk and cakes?"

"What do you say, Mr. Damon?" Tom asked. "She's clean and neat, and she makes a drink of goat's milk that isn't bad. She bakes some kind of meal cakes that are good, too. I'm hungry."

"All right, Tom, I'll do as you say."

A little later they were partaking of a rude, but none the less welcome, lunch in the woman's hut, while the baby whose life Tom had saved cooed in the rough log cradle.

"Say, Masni," asked Tom, addressing the woman by name, "don't you know where we can get some men to work the tunnel?" Of course Tom spoke the Indian language, and he had to adapt himself to the comprehension of Masni.

"Men no work tunnel?" she inquired.

"No, they've all skipped out—vamoosed. Afraid of some spirit."

The woman looked around, as though in fear. Then she approached Tom closely and whispered:

"No spirit in tunnel—bad man!"

"What!" cried Tom, almost jumping off his stool. "What do you mean, Masni?"

"Me tell mighty hunter," she went on, lowering her voice still more. "My man he no want to tell, he 'fraid, but I tell. Mighty hunter save Vashni," and she looked toward the baby. "Me help friends of mighty hunter. Bad man in tunnel—no spirit!

"Men go. Spirit no take um—bad man take um."

"Where are they now?" asked Tom. "Jove, if I could find them the secret would be solved!"

The woman looked fearfully around the hut and then whispered:

"You come—me show!"

"Bless my toothbrush!" cried Mr. Damon. "What is going to happen, Tom Swift?"

"I don't know," was the answer, "but something sure is in the wind. I guess I shot better than I knew when I killed that condor."



Chapter XX

Despair

Calling to a girl of about thirteen years to look after her baby, Masni slipped along up a rough mountain trail, motioning to Tom, Mr. Damon and Koku to follow. Or rather, the woman gave the sign to Tom, ignoring the others, who, naturally, would not be left behind. Masni seemed to have eyes for no one but the young inventor, and the manner in which she looked at him showed the deep gratitude she felt toward him for having saved her baby from the great condor.

"Come," she said, in her strange Indian tongue, which Tom could interpret well enough for himself now.

"But where are we going, Masni?" he asked. "This isn't the way to the tunnel."

"Me know. Not go to tunnel now," was her answer. "Me show you men."

"But which men do you mean, Masni?" inquired Tom. "The lost men, or the bad ones, who are making trouble for us? Which men do you mean?"

Masni only shook her head, and murmured: "Me show."

Probably Tom's attempt to talk her language was not sufficiently clear to her.

"My man—he good man," she said, coming to a pause on the rough trail after a climb which was not easy.

"Yes, I know he is," Tom said. "But he went on a strike with the others, Masni. He no work. He go on a 'hit,' as Serato calls it," and Tom laughed.

"My man he good man—but he 'fraid," said the wife. "He want to tell you of bad mans, but he 'fraid. You save my baby, I no 'fraid. I tell."

"Oh, I see," said Tom. "Your husband would have given away the secret, only he's afraid of the bad men. He likes me, too?"

"Sure!" Masni exclaimed. "He want tell, but 'fraid. He go 'way, I tell."

Tom was not quite sure what it all meant, but it seemed that after his slaying of the condor both parents were so filled with gratitude that they wanted to reveal some secret about the tunnel, only Masni's husband was afraid. She, however, had been braver.

"Something is going to happen," said Tom Swift. "I feel it in my bones!"

"Bless my porous plaster!" cried Mr. Damon. "I hope it isn't anything serious."

"We'll see," Tom went on.

They resumed their journey up the mountain trail. It wound in and out in a region none of them had before visited. Though it could not be far from the tunnel, it was almost a strange country to Tom.

Suddenly Masni stopped in a narrow gorge where the walls of rock rose high on either hand. She seemed looking for something. Her sharp, black eyes scanned the cliff and then with an exclamation of satisfaction she approached a certain place. With a quick motion she pulled aside a mass of tangled vines, and disclosed a path leading down through a V shaped crack in the cliff.

"Mans down there," she said. "You go look."

For a moment Tom hesitated. Was this a trap? If he and his friends entered this narrow and dark opening might not the Indian woman roll down some rock back of them, cutting off forever the way of escape?

Tom turned and looked at Masni. Then he was ashamed of his suspicion, for the honest black face, smiling at him, showed no trace of guile.

"You go—you see lost men," the woman urged.

"Come on!" cried Tom. "I believe we're on the track of the mystery!"

He led the way, followed by Mr. Damon, while Koku came next and then Masni. It could be no trap since she entered it herself.

The path widened, but not much. There was only room for one to walk at a time. The trail twisted and turned, and Tom was wondering how far it led, when, from behind him, came the cry of the woman:

"Watch now—no fall down."

Tom halted around a sharp turn, and stood transfixed at the sight which met his gaze. He found himself looking out through a crack in the face of a sheer stone cliff that went straight down for a hundred feet or more to a green-carpeted valley.

Tom was standing in a narrow cleft of rock—the same rock through which they had made their way. And at the foot of the cliff was a little encampment of Indians. There were a dozen huts, and wandering about them, or sitting in the shade, were a score or more of Indians.

"There men from tunnel," said Masni, and, as he looked, wondering, Tom saw some of the workers he knew. One especially, was a laborer who walked with a peculiar limp.

"The missing men!" gasped the young inventor.

"Bless my almanac!" cried Mr. Damon. "Where?"

"Here," answered Tom. "If you squeeze past me you can see them."

Mr. Damon did so.

"How did they get here?" asked the odd man, as he looked down in the little valley where the missing ones were sequestered.

"That's what we've got to find out," Tom said. "At any rate here they are, and they seem to be enjoying life while we've been worrying as to what had become of them. How did they get here, Masni?"

"Me show you. Come."

"Wait until I take another look," said Tom.

"Be careful they don't see you," cautioned Mr. Damon.

"They can't very well. The cleft is screened by bushes."

Tom looked down once more on the group of men who had so mysteriously disappeared. The little valley stretched out away from the face of the cliff, through which, by means of the crack, or cleft in it, Tom and the others had come. Tom looked down the wall of rock. It was as smooth as the side of a building, and offered no means of getting down or up. Doubtless there was an easier entrance to the valley on the other side. It was like looking down into some vast hall through an upper window or from a balcony.

"And those men have been in hiding, or been hidden here, ever since they disappeared from the tunnel," said Mr. Damon.

"It doesn't look as though they were detained by force," Tom remarked. "I think they are being paid to stay away. How did they get here, Masni?"

"Me show you. Come!"

They went back along the trail that led through the split in the rock, until they had come to the place where the natural curtain of vines concealed the entrance. Tom took particular notice of this place so he would know it again.

Then Masni led them over the mountain, and this time Tom saw that they were approaching the tunnel. He recognized some places where he had taken samples of rock from the outcropping to test the strength of his explosive.

Reaching a certain wild and desolate place, Masni made a signal of caution. She seemed to be listening intently. Then, as if satisfied there was no danger, she parted some bushes and glided in, motioning the others to follow.

"Now I wonder what's up," Tom mused.

He and the others were soon informed.

Masni stopped in front of a pile of brush. With a few vigorous motions of her arms she swept it aside and revealed a smooth slab of rock. In the centre was what seemed to be a block of metal Masni placed her foot on this and pressed heavily.

And those watching saw a strange thing.

The slab of rock tilted to one side, as if on a pivot, revealing a square opening which seemed to lead through solid stone. And at the far end of the opening Tom Swift saw a glimmer of light.

Stooping down, he looked through the hole thus strangely opened and what he saw caused him to cry out in wonder.

"It's the tunnel!" he cried. "I can look right down into the tunnel. It's the incandescent lights I see. I can look right at the ledge of rock where I kept watch that day, and where I saw—where I saw the face of Waddington!" he cried. "It wasn't a dream after all. This is a shaft connecting with the tunnel. We didn't discover it because this rock fits right in the opening in the roof. It must have been there all the while, and some blast brought it to light. Is this how the men got out, or were taken out of the tunnel, Masni?" Tom asked.

"This how," said the Indian woman. "See, here rope!"

She pawed aside a mound of earth, and disclosed a rope buried there, a rope knotted at intervals. This, let down through the hole in the roof of the tunnel, provided a means of escape, and in such a manner that the disappearance of the men was most mysterious.

"I see how it is!" cried Tom. "Some one interested, Waddington probably, who knew about this old secret shaft going down into the earth, used it as soon as our blasting was opened that far. They got the men out this way, and hid them in the secret valley."

"But what for?" cried Mr. Damon.

"To cripple us! To cause the strike by making our other workers afraid of some evil spirit! The men were taken away secretly, and, doubtless, have been kept in idleness ever since—paid to stay away so the mystery would be all the deeper. Our rivals finding they couldn't stop us in any other way have taken our laborers away from us."

"Bless my meal ticket! It does look like that!" cried Mr. Damon.

"Of course that's the secret!" cried Tom. "Blakeson & Grinder, or some of their tools—probably the bearded man or Waddington—found out about this shaft which led down into our tunnel. They induced the first ten men to quit, and when Tim went to get the fuse the rope was let down, and the men climbed up here, one after the other. Those Indians can climb like cats. Once the ten were out the shaft was closed with the rock, and the ten men taken off to the valley to be secreted there.

"The same was done with the next fifteen, and, I suppose, if the strike hadn't come, more of our workers would have been induced to leave in this way. They're probably being better paid than when earning their wages; and their relatives must know where they are, and also be given a bonus to keep still. No wonder they didn't make a fuss.

"And no wonder we couldn't find any opening in the tunnel roof. This rock must fit in as smoothly as a secret drawer in the kind of old desk where missing wills are found in stories."

"You say you saw Waddington, or the bearded man?" asked Mr. Damon.

"At the time," replied Tom, "I thought it was a dream. Now I know it wasn't. He must have opened the shaft just as I awakened from a doze. He saw me and closed it again. He may have been getting ready then to take off more of our men, so as to scare the others. Well, we've found out the trick."

"And what are you going to do next?" asked Mr. Damon.

"Get those missing men back. That will break the hoodoo, and the others will come back to work. Then we'll get on the trail of Waddington, or Blakeson & Grinder, and put a stop to this business. We know their secret now."

"You mean to get the men out of the secret valley, Tom?"

"Yes. There must be some other way into it than down the rock where we were. How about it, Masni?" and he inquired as to the valley. The Indian woman gave Tom to understand that there was another entrance.

"Well, close up this shaft now before some one sees us at it—the bearded man, for example," Tom suggested. He took another look down into the tunnel, which was now deserted on account of the strike, and then Masni pressed on the mechanism that worked the stone. She showed Tom how to do it.

"Just a counter-balanced rock operating on the same principle as does a window," Tom explained, after a brief examination. "Probably some of the old Indian tribes made this shaft for ceremonial purposes. They never dreamed we would drive a tunnel along at the bottom of it. The shaft probably opened into a cave, and one of our blasts made it part of the tunnel. Well, this is part of the secret, anyhow. Much obliged to you, Masni!"

The Indian woman had indeed revealed valuable information. They covered the secret rock with brush, as it had been, hid the rope and came away. But Tom knew how to find the place again.

Events moved rapidly from then on. The Titus brothers were more than astonished when Tom told them what he had learned. Masni had told him how to get into the secret valley by a round about, but easy trail, and thither Tom, the contractors, Mr. Damon and some of the white tunnel workers went the next day.

The sequestered men, taken completely by surprise, tried to bolt when they saw that they were discovered, and then, shamefacedly enough, admitted their part in the trick.

They would not, however, reveal who had helped them escape from the tunnel. Threats and promises of rewards were alike unavailing, but Tom and his employers knew well enough who it was. The tunnel workers seemed rather tired of living in comparative luxury and idleness, and agreed to come back to their labors.

They packed up their few belongings, mostly cooking pots and pans, and marched out of the valley to the village at Rimac.

And so the strike was broken.

The reappearance of the missing men, in better health and spirits than when they went away, acted like magic. The other men, who had missed their wages, crowded back into the shaft, and the sounds of picks and shovels were heard again in the tunnel.

Whether the missing ones told the real story, or whether they made up some tale to account for their absence, Tom and his friends could not learn. Nor did the bearded man (if he it were who had helped in the plot), nor any representative of Blakeson & Grinder appear. The work on the tunnel was resumed as if nothing had happened. But Tom arranged a bright light so it would reflect on the spot in the roof where the moving rock was, so that if the evil face of the bearded man, or of Waddington, appeared there again, it would quickly be seen. A search of the neighborhood, and diligent inquiries, failed to disclose the presence of any of the plotters.

And then, as if Fate was not making it hard enough for the tunnel contractors, they encountered more trouble. It was after Tom had set off a big blast that Tim Sullivan, after inspecting what had happened, came out to ask.

"I soy, Mr. Swift, why didn't yez use more powder?"

"More powder!" cried Tom. "Why, this is the most I have ever set off."

"Then somethin's wrong, sor. Fer there's only a little rock down. Come an' see fer yersilf."

Tom hastened in. As the foreman had said, the effect of the blast was small indeed. Only a little rock had been shaled off. Tom picked up some of this and took it outside for examination.

"Why, it's harder than the hardest flint we've found yet," he said. "The powder didn't make any impression on it at all. I'll have to use terrific charges."

This was done, but with little better effect. The explosive, powerful as it was, ate only a little way into the rock. Blast after blast had the same poor effect.

"This won't do," said Job Titus, despairingly, one day. "We aren't making any progress at all. There's a half mile of this rock, according to my calculations, and at this rate we'll be six months getting through it. By that time our limit will be up, and we'll be forced to give up the contract What can we do, Tom Swift?"



Chapter XXI

A New Explosive

The young inventor was idly handling some pieces of the very hard rock that had cropped out in the tunnel cut Tom had tested it, he had pulverized it (as well as he was able), he had examined it under the microscope, and he had taken great slabs of it and set off under it, or on top of it, charges of explosive of various power to note the effect. But the results had not been at all what he had hoped for.

"What's to be done, Tom?" repeated the contractor.

"Well, Mr. Titus," was the answer, "the only thing I see to do is to make a new explosive."

"Can you do it, Tom?"

The reply was characteristic.

"I can try."

And in the days that followed, Tom began work on a new line. He had brought from Shopton with him much of the needful apparatus, and he found he could obtain in Lima what he lacked.

A message to his father brought the reply that the new ingredients Tom needed would be shipped.

"The kind of explosive we need to rend that very hard rock," the young inventor explained to the Titus brothers, "is one that works slowly."

"I thought all explosions had to be as quick as a flash," said Walter.

"Well, in a sense, they do. Yet we have quick burning and slow-burning powders, the same as we have fuses. A quick-burning explosive is all right in soft rock, or in soil with rock and earth mingled. But in rock that is harder than flint if you use a quick explosive, only the outer surface of the rock will be scaled off.

"If you take a hammer and bring it down with all your force on a hard rock you may chip off a lot of little pieces, or you may crack the rock, but you won't, under ordinary circumstances, pulverize it as we want to do in the tunnel.

"On the other hand, if you take a smaller hammer, and keep tapping the rock with comparatively gentle blows, you will set up a series of vibrations, that, in time, will cause the hard rock to break up into any number of small pieces.

"Now that is the kind of explosive I want one that will deal a succession of constant blows at the hard rock instead of one great big blast."

"Can you make it, Tom?"

"Well, I don't know. I'll do the best I can."

From then on Tom was busy with his experiments.

Work on the tunnel did not cease while he was searching for a new explosive. There was plenty of the old explosive left and charges of this were set off as fast as holes could be drilled to receive it. But comparatively little was accomplished. Sometimes more rock would be loosed than at others, and the native laborers, now seemingly perfectly contented, would be kept busy. Again, when a heavy blast would be set off hardly a dozen dump cars could be filled.

But the work must go on. Already the time limit was getting perilously close, and the contractors did not doubt that their rivals were only waiting for a chance to step in and take their places.

Nothing more had been seen or heard of the bearded man, Waddington, or Blakeson & Grinder. But that the rival firm had not given up was evidenced by the efforts made in New York to cripple, financially, the firm in which Tom was interested. In fact, at one time the Titus brothers were so tied up that they could not get money enough to pay their men. But Tom cabled his father, who was quite wealthy, and Mr. Swift loaned the contractors enough to proceed with until they could dispose of some securities.

It might be mentioned that Tom was to get a large sum if the tunnel were completed on time, so it was to his interest and his father's, to bring this about if he could.

Tom kept on with his powder experiments. Mr. Damon helped him, for that gentleman had succeeded in putting the affairs of the wholesale drug business on a firm foundation, and there was no more trouble about getting the supplies of cinchona bark to market. The natives seemed to have taken kindly to the eccentric man, or perhaps it was the reputation of Tom Swift and his electric rifle that induced them to work hard.

It must not be supposed that Professor Bumper was idle all this while.

He came and went at odd times, accompanied by his little retinue of Indians, a guide and a native cook. He would come back to the tunnel camp, where he made his headquarters, travel stained, worn and weary, with disappointment showing on his face.

"No luck," he would report. "The hidden city of Pelone is still lost."

Then he would retire to his tent, to pour over his note-books, and make a new translation of the inscription on the golden plates. In a day or so, refreshed and rested, he would prepare for another start.

"I'll find it this time, surely!" he would exclaim, as he marched off up the mountain trail. "I have heard of a new valley, never before visited by a white man, in which there are some old ruins. I'm sure they must be those of Pelone."

But in a week or so he would come back, worn out and discouraged again.

"The ruins were only those of a native village," he would say. "No trace of an ancient civilization there."

The professor took little or no interest in the tunnel, though he expressed the hope that Tom and his friends would be successful. But industrial pursuits had no charm for the scientist. He only lived to find the hidden city which was to make him famous.

He heard the story of the queer shaft leading down into the bore under the mountain, and, for a time, hoped that might be some clue to the lost Pelone. But, after an examination, he decided it was but the shaft to some ancient mine which had not panned out, and so had been abandoned after having been fitted with a balanced rocky door, perhaps for some heathen religious rite.

There seemed to be no further trouble among the Indian tunnel workers. Those who had disappeared—who had, seemingly, gone willingly up the knotted rope to hide themselves in the valley—kept on with their work. If they told their fellows why and where they had gone, the others gave no sign. The evil spirits of the tunnel had been exorcised, and there was now peace, save for the blasts that were set off every so often.

Tom tried combination after combination, testing them inside and outside the tunnel, always seeking for an explosive that would give a slow, rending effect instead of a quick blow, the power of which was soon lost. And at last he announced:

"I think I have it!"

"Have you? Good!" cried Job Titus.

"Yes," Tom went on, "I've got a mixture here that seems to give just the effect I want. I tried it on some small pieces of rock, and now I want to test it on some large chunks. Have you brought any down lately?"

"Yes, we have some big slabs in there."

Some large pieces of the hard rock, which had been brought down in a recent blast, were taken outside the tunnel, and in them one afternoon Tom placed, in holes drilled to receive it, some of his new explosive. The rocks were set some distance away from the tunnel camp, and Tom attached the electric wires that were to detonate the charge.

"Well, I guess we're ready," announced the young inventor, as he looked about him.

The tunnel workers had been allowed to go for the day, and in a log shack, where they would be safe from flying pieces of rock, were Tom, Mr. Damon and the two Titus brothers.

Tom held the electric switch in his hand, and was about to press it.

"This explosive works differently from any other," he explained. "When the charge is fired there is not instantly a detonation and a bursting. The powder burns slowly and generates an immense amount of gas. It is this gas, accumulating in the cracks and crevices of the rock, that I hope will burst and disintegrate it. Of course, an explosion eventually follows, as you will see. Here she goes!"

Tom pressed the switch and, as he did so, there was a cry of alarm from Mr. Damon.

"Bless my safety match, Tom!" cried the old man. "Look! Koku!"

For, as the charge was fired, the giant emerged from the woods and calmly took a seat on the rock that was about to be broken up into fragments by Tom's new explosive.



Chapter XXII

The Fight

"Get off there, Koku!"

"Stand up!"

"Run!"

"Get out uf the way! That's going up!"

Thus cried Tom and his friends to the big, good-natured, but somewhat stupid, giant who had sat down in the dangerous spot. Koku looked toward the hut, in front of which the young inventor and the others stood, waving their hands to him and shouting.

"Get up! Get up!" cried Tom, frantically. The powder is going off, Koku!"

"Can't you stop it?" asked Job Titus.

"No!" answered Tom. "The electric current has already ignited the charge. Only that it's slow-burning it would have been fired long ago. Get up, Koku!"

But the giant did not seem to understand. He waved his hand in friendly greeting to Tom and the others, who dared not approach closer to warn him, for the explosion would occur any second now.

Then Mr. Damon had an inspiration.

"Call him to come to you, Tom!" shouted the odd man. "He always comes to you in a hurry, you know. Call him!"

Tom acted on the suggestion at once.

"Here, Koku!" he cried. "Come here, I want you! Kelos!"

This last was a word in the giant's own language, meaning "hurry." And Koku knew when Tom used that word that there was need of haste. So, though he had sat down, evidently to take his ease after a long tramp through the woods, Koku sprang up to obey his master's bidding.

And, as he did so, something happened. The first spark from the fuse, ignited by the electric current, had reached the slow-burning powder. There was a crackle of flame, and a dull rumble. Koku sprang up from the big stone as though shot. What he saw and heard must have alarmed him, for he gave a mighty jump and started to run, at the same time shouting:

"Me come, Master!"

"You'd better!" cried the young inventor.

Koku got away only just in time, for when he was half way between the group of his friends and the big rock, the utmost force of the explosion was felt. It was not so very loud, but the power of it made the earth tremble.

The rock seemed to heave itself into the air, and when it settled back it was seen to be broken up into many pieces. Koku looked back over his shoulder and gave another tremendous leap, which carried him out of the way of the flying fragments, some of which rattled on the roof of the log hut.

"There!" cried Tom. "I guess something happened that time! The rock is broken up finer than any like it we tried to shatter before. I think I've got the mixture just right!"

"Bless my handkerchief!" cried Mr. Damon. "Think of what might have happened to Koku if he had been sitting there."

"Well," said Tom, "he might not have been killed, for he would probably have been tossed well out of the way at the first slow explosion, but afterward—well, he might have been pretty well shaken up. He got away just in time."

The giant looked thoughtfully back toward the place of the experimental blast.

"Master, him do that?" he asked.

"I did," Tom replied. "But I didn't think you'd walk out of the woods, just at the wrong time, and sit down on that rock."

"Um," murmured the giant. "Koku—he—he—Oh, by golly!" he yelled. And then, as if realizing what he had escaped, and being incapable of expressing it, the giant with a yell ran into the tunnel and stayed there for some time.

The experiment was pronounced a great success and, now that Tom had discovered the right kind of explosive to rend the very hard rock, he proceeded to have it made in sufficiently large quantities to be used in the tunnel.

"We'll have to hustle," said Job Titus. "We haven't much of our contract time left, and I have reason to believe the Peruvian government will not give any extension. It is to their interest to have us fail, for they will profit by all the work we have done, even if they have to pay our rivals a higher price than we contracted for. It is our firm that will pocket the loss."

"Well, we'll try not to have that happen," said Tom, with a smile.

"If you're going to use bigger charges of this new explosive, Tom, won't more rock be brought down?" asked Walter Titus.

"That's what I hope."

"Then we'll need more laborers to bring it out of the tunnel."

"Yes, we could use more I guess. The faster the blasted rock is removed, the quicker I can put in new charges."

"I'll get more men," decided the contractor. "There won't be any trouble now that the hoodoo of the missing workers is solved. I'll tell Serato to scare up all his dusky brethren he can find, and we'll offer a bonus for good work."

The Indian foreman readily agreed to get more laborers.

"And get some big ones, Serato," urged Job Titus. "Get some fellows like Koku," for the giant did the work of three men in the tunnel, not because he was obliged to, but because his enormous strength must find an outlet in action.

"Um want mans like him?" asked the Indian, nodding toward the giant. He and Koku were not on good terms, for once, when Koku was a hurry, he had picked up the Indian (no mean sized man himself) and had calmly set him to one side. Serato never forgave that.

"Sure, get all the giants you can," Tom said. "But I guess there aren't any in Peru."

Where Serato found his man, no one knew, and the foreman would not tell; but a day or so later he appeared at the tunnel camp with an Indian so large in size that he made the others look like pygmies, and many of them were above the average in height, too.

"Say, he's a whopper all right!" exclaimed Tom. "But he isn't as big or as strong as Koku."

"He comes pretty near it," said Job Titus. "With a dozen like him we'd finish the tunnel on time, thanks to your explosive."

Lamos, the Indian giant, was not quite as large as Koku. That is, he was not as tall, but he was broader of shoulder. And as to the strength of the two, well, it was destined to be tried out in a startling fashion.

In about a week Tom was ready with his first charges of the new explosive. The extra Indians were on hand, including Lamos, and great hopes of fast progress were held by the contractors.

The charge was fired and a great mass of broken rock brought down inside the tunnel.

"That's tearing it up!" cried Job Titus, when the fumes had blown away, the secret shaft having been opened to facilitate this. "A few more shots like that and we'll be through the strata of hard rock."

The Indians, Koku and Lamos doing their share of the work, were rushed in to clear away the debris, so another charge might be fired as soon as possible. This would be in a day or so. The contract time was getting uncomfortably close.

Blast after blast was set off, and good progress was made. But instead of half a mile of the extra hard rock the contractors found it would be nearer three quarters.

"It's going to be touch and go, whether or not we finish on time," said Mr. Job Titus one afternoon, when a clearance had been made and the men had filed out to give the drillers a chance to make holes for a new blast.

Tom was about to make a remark when Tim Sullivan came running out of the tunnel, his face showing fright and wonder.

"What's up now, I wonder," said Mr. Titus. "More men missing?"

"Quick! Come quick!" cried the Irishman. "Thim two giants is fightin' in there, an' they'll tear th' tunnel apart if we don't stop 'em. It's an awful fight! Awful!"



Chapter XXIII

A Great Blast

Hardly comprehending what the Irish foreman had said, Tom Swift, the Titus brothers and Mr. Damon followed Tim Sullivan back into the tunnel. They had not gone far before they heard the murmur of many voices, and mingled with that were roarings like those of wild beasts.

"That's thim!" cried Tim. "They're chawin' each other up!"

"Koku and that Indian giant fighting!" cried Tom. "What's it all about?"

"Don't ask me!" shouted Tim. "They've been on bad terms iver since they met." This was true enough, for one giant was jealous of the other's power, and they were continually trying feats of strength against one another. Probably this had culminated in a fight, Tom concluded.

"And it will be some fight!" mused the young inventor.

Hurrying on, Tom and his companions came upon a strange and not altogether pleasant sight. In an open place in the tunnel, where the lights were brightest, and in front of the rocky wall which offered a bar to further progress and which was soon to be blasted away, struggled the two giants.

With their arms locked about one another, they swayed this way and that—a struggle between two Titans. Of nearly the same height and bigness, it was a wrestling match such as had never been seen before. Had it been merely a friendly test of strength it would have been good to look upon. But it needed only a glance into the faces of either giant to show that it was a struggle in deadly earnest.

Back and forth they reeled over the rocky floor of the tunnel, bones and sinews cracking. One sought to throw the other, and first, as Koku would gain a slight advantage, his friends would call encouragement, while, when Lamos seemed about to triumph, the Indians favoring him would let out a yell of triumph.

For a few minutes Tom and his friends watched, fascinated. Then they saw Koku slip, while Lamos bent him farther toward the earth. The Indian giant raised his big fist, and Tom saw in it a rock, which the big man was about to bring down on Koku's head.

"Look out, Koku!" yelled Tom.

Tom's giant slid to one side only just in time, for the blow descended, catching him on his muscular shoulder where it only raised a bruise. And then Koku gathered himself for a mighty effort. His face flamed with rage at the unfair trick.

"Bless my bath sponge!" cried Mr. Damon. "This is awful!"

"They must stop!" said Job Titus. "We can't have them fighting like this. It is bad for the others. If it were in fun it would be all right, but they are in deadly earnest. They must stop!"

"Koku, stop!" called Tom. "You must not fight any more!"

"No fight more!" gasped the giant, through his clenched teeth. "This end fight!"

With a mighty effort he broke the hold of Lamos' arms. Then stooping suddenly he seized his rival about the middle, and with a tremendous heave, in which his muscles stood out in great bunches while his very bones seemed to crack, Koku raised Lamos high in the air. Up over his head he raised that mass of muscle, bone and flesh, squirming and wriggling, trying in vain to save itself.

Up and up Koku raised Lamos as the murmur of those watching grew to a shout of amazement and terror. Never had the like been seen in that land for generations. Up and up one giant raised the other. Then calling out something in his native tongue Koku hurled the other from him, clear across the tunnel and up against the opposite rocky wall. The murmuring died to frightened whispers as Lamos fell in a shapeless heap on the floor.

"Ah!" breathed Koku, stretching himself, and extending his brawny arms. "Fight all over, Master."

"Yes, so it seems, Koku," said Tom, solemnly, "but you have killed him. Shame on you!" and he spoke bitterly.

Job Titus had hurried over to the fallen giant.

"He isn't dead," he called, "but I guess he won't wrestle or fight any more. He's badly crippled."

"And him no more try to blow up tunnel, either," said Koku in his hoarse voice. "Me fix: him! No more him take powder, and make tunnel all bust."

"What do you mean, Koku?" asked Tom. "Is that why you fought him? Did he try to wreck the tunnel?"

"So him done, Master. But Koku see—Koku stop. Then um fight."

"Be jabbers an' I wouldn't wonder but what he was right!" cried Tim Sullivan, excitedly. "I did see that beggar." and he pointed to Lamos, who was slowly crawling away, "at the chist where I kape th' powder, but I thought nothin' of it at th' time. What did he try t' do, Koku?"

Then the giant explained in his own language, Tom Swift translating, for Koku spoke English but indifferently well.

"Koku says," rendered Torn, "that he saw Lamos trying to put a big charge of powder up in the place where the balanced rock fits in the secret opening of the tunnel roof. The charge was all ready to fire, and if the giant had set it off he might have brought down the roof of the tunnel and so choked it up that we'd have been months cleaning it out. Koku saw him and stopped him, and then the fight began. We only saw the end."

"Bless my shoe string!" gasped Mr. Damon. "And a terrible end it was. Will Lamos die?"

"I don't think so," answered Job Titus. "But he will be a cripple for life. Not only would he have wrecked the tunnel, but he would have killed many of our men had he set off that blast. Koku saved them, though it seems too bad he had to fight to do it."

An investigation showed that Koku spoke truly. The charge, all ready to set off, was found where he had knocked it from the hand of Lamos. And so Tom's giant saved the day. Lamos was sent back to his own village, a broken and humbled giant. And to this day, in that part of Peru, the great struggle between Koku and Lamos is spoken of with awe where Indians gather about their council fires, and they tell their children of the Titanic fight.

"It was part of the plot," said Job Titus when the usual blast had been set off that day, with not very good results. "This giant was sent to us by our rivals. They wanted him to hamper our work, for they see we have a chance to finish on time. I think that foreman, Serato, is in the plot. He brought Lamos here. We'll fire him!"

This was done, though the Indian protested his innocence. But he could not be trusted.

"We can't take any chances," said Job Titus. "Our time is too nearly up. In fact I'm afraid we won't finish on time as it is. There is too much of that hard rock to cut through."

"There's only one thing to do," said Tom, after an investigation. "As you say, there is more of that hard rock than we calculated on. To try to blast and take it out in the ordinary way will be useless. We must try desperate means."

"What is that?" asked Walter Titus.

"We must set off the biggest blast we can with safety. We'll bore a lot of extra holes, and put in double charges of the explosive. I'll add some ingredients to it that will make it stronger. It's our last chance. Either we'll blow the tunnel all to pieces, or we'll loosen enough rock to make sufficient progress so we can finish on time. What do you say? Shall we take the chance?"

The Titus brothers looked at one another. Failure stared them in the face. Unless they completed the tunnel very soon they would lose all the money they had sunk in it.

"Take the chance!" exclaimed Job. "It's sink or swim anyhow. Set off the big blast, Tom."

"All right. We'll get ready for it as soon as we can."

That day preparations were made for setting off a great charge of the powerful explosive. The work was hurried as fast as was consistent with safety, but even then progress was rather slow. Precautions had to be taken, and the guards about the tunnel were doubled. For it was feared that some word of what was about to be done would reach the rival firm, who might try desperate means to prevent the completion of the work.

There was plenty of the explosive on hand, for Mr. Swift had sent Tom a large shipment. All this while no word had come from Mr. Nestor, and Tom was beginning to think that his prospective father-in-law was very angry with him. Nor had Mary written.

Professor Bumper came and went as he pleased, but his quest was regarded as hopeless now. Tom and his friends had little time for the bald-headed scientist, for they were too much interested in the success of the big blast.

"Well, we'll set her off to-morrow," Tom said one night, after a hard day's work. "The rocky wall is honeycombed with explosive. If all goes well we ought to bring down enough rock to keep the gangs busy night and day."

Everything was in readiness. What would the morrow bring—success or failure?



Chapter XXIV

The Hidden City

Gathered beyond the mouth of the tunnel, far enough away so that the wind of the great blast would not bowl them over like ten pins, stood Tom Swift and his friends. In his hand Tom held the battery box, the setting of the switch in which would complete the electrical circuit and set off the hundreds of pounds of explosive buried deep in the hard rock.

"Are all the men out?" asked the young inventor of Tim Sullivan, who had charge of this important matter. Tim was in sole charge as foreman now, having picked up enough of the Indian language to get along without an interpreter.

"All out, sor," Tim responded. "Yez kin fire whin ready, Mr. Swift."

It was a portentous moment. No wonder Tom Swift hesitated. In a sense he and his friends, the contractors, had staked their all on a single throw. If this blast failed it was not likely that another would succeed, even if there should be time to prepare one.

The time limit had almost expired, and there was still a half mile of hard rock between the last heading and the farther end of the big tunnel. If the blast succeeded enough rock might be brought down to enable the work to go on, by using a night and day shift of men. Then, too, there was the chance that the hard strata of rock would come to an end and softer stone, or easily-dug dirt, be encountered.

"Well, we may as well have it over with," said Tom in a low voice. Every one was very quiet—tensely quiet.

The young inventor looked up to see Professor Bumper observing him.

"Why, Professor!" Tom exclaimed, "I thought you had gone off to the mountains again, looking for the lost city."

"I am going, Tom, very soon. I thought I would stop and see the effect of your big blast. This is my last trip. If I do not find the hidden city of Pelone this time, I am going to give up."

"Give up!" cried Mr. Damon. "Bless my fountain pen!"

"Oh, not altogether," went on the bald-headed scientist. "I mean I will give up searching in this part of Peru, and go elsewhere. But I will never completely give up the search, for I am sure the hidden city exists somewhere under these mountains," and he looked off toward the snow-covered peaks of the Andes.

Tom looked at the battery box. He drew a long breath, and said:

"Here she goes!"

There was a contraction of his hand as he pressed the switch over, and then, for perhaps a half second, nothing happened. Just for an instant Tom feared something had gone wrong that the electric current had failed, or that the wires had become disconnected—perhaps through some action of the plotting rivals.

And then, gently at first, but with increasing intensity, the solid ground on which they were all standing seemed to rock and sway, to heave itself up, and then sink down.

"Bless my—" began Mr. Damon, but he got no further, for a mighty gust of wind swept out of the tunnel, and blew off his hat. That gust was but a gentle breeze, though, compared to what followed. For there came such a rush of air that it almost blew over those standing near the opening of the great shaft driven under the mountain. There was a roar as of Niagara, a howling as in the Cave of the Winds, and they all bent to the blast.

Then followed a dull, rumbling roar, not as loud as might have been expected, but awful in its intensity. Deep down under the very foundations of the earth it seemed to rumble.

"Run! Run back!" cried Tom Swift. "There's a back-draft and the powder gas is poisonous. Stoop down and run back!"

They understood what he meant. The vapor from the powder was deadly if breathed in a confined space. Even in the open it gave one a terrible headache. And Tom could see floating out of the tunnel the first wisps of smoke from the fired explosive. It was lighter than air, and would rise. Hence the necessity, as in a smoke-filled room, of keeping low down where the air is purer.

They all rushed back, stooping low. Mr. Damon stumbled and fell, but Koku picked him up and, tucking him under one arm, as he might have done a child, the giant followed Tom to a place of safety.

"Well, Tom, it went off all right," said Mr. Job Titus, as they stood among the shacks of the workmen and watched the smoke pouring out of the tunnel mouth.

"Yes, it went off. But did it do the work? That's what we've got to find out."

They waited impatiently for the deadly vapor to clear out of the tunnel. It was more than an hour before they dared venture in, and then it was with smarting eyes and puckered throats. But the atmosphere was quickly clearing.

"Switch on the lights," cried Tom to Tim, for the illuminating current had been cut off when the blast was fired. "Let's see what we've brought down."

Following the eager young inventor came the contractors, some of the white workers, Mr. Damon and Professor Bumper. The little scientist said he would like to see the effect of the big blast.

Along they stumbled over pieces of rock, large and small.

"Some force to it," observed Job Titus, as he observed pieces of rock close to the mouth of the tunnel. "If it only exerted the force the other way, against the face of the rock, as well as back this way, we'll be all right."

"The greater force was in the opposite direction," Tom said.

A big search-light had been got ready to flash on the place where the blast had been set off. This was to enable them to see how much rock had been torn away. And, as they reached the place where the flint-like wall had been, they saw a strange sight.

"Bless my strawberry short-cake!" gasped Mr. Damon. "What a hole!"

"It is a hole," admitted Tom, in a low voice. "A bigger hole than I dared hope for."

For a great cave, seemingly, had been blown in the face of the rock wall that had hindered the progress of the tunnel. A great black void confronted them.

"Shift the light over this way," called Tom to Walter Titus, who was operating it. "I can't see anything."

The great beam of light flashed into the void, and then a murmur of awe came from every throat.

For there, revealed in the powerful electrical rays, was what seemed to be a long tunnel, high and wide, as smooth as a paved street. And on either side of it were what appeared to be buildings, some low, others taller. And, branching off from the main tunnel, or street, were other passages, also lined with buildings, some of which had crumbled to ruins.

"Bless my dictionary!" cried Mr. Damon. "What is it?"

Professor Bumper had crawled forward over the mass of broken rock. He gazed as if fascinated at what the searchlight showed, and then he cried:

"I have found it! I have found it! The hidden city of Pelone!"



Chapter XXV

Success

Had it not been for Tom Swift, the excited professor would have rushed pellmell over the jagged pile of rocks into the great cave which had been opened by the blast, the cave in which the scientist declared was the lost city for which he had been searching. But the young inventor grasped Mr. Bumper by the arm.

"Better wait a bit," Tom suggested. "There may be powder gas in there. Some of it must have blown forward."

"I don't care!" excitedly cried the professor. "That is the hidden city! I'm sure of it! I have found it at last! I must go in and examine it!"

"There'll be plenty of time," said Tom. "It isn't going to run away. Wait until I make a test Tim, hand me one of those torches."

Some torches of a very inflammable wood were used to test for the presence of the deadly smoke-gas. Lighting one of these, Tom tossed it into the big excavation.

It fell to the stone floor—to the stone street to be more exact—and, flaring up brightly, further revealed the rows of houses as they stood, silent and uninhabited.

"It's all right," Tom announced. "There's no danger so long as the torch burns. You can go on, Professor."

And Professor Bumper rushed forward, scrambling over the pile of blasted rock, followed by Tom and the others. Some of the debris from the explosion had fallen into the cave, and was scattered for some distance along the main street of what had been Pelone. But beyond that the way was clear.

"Yes, it is Pelone," cried Professor Bumper. "See!"

He pointed to inscriptions in queer characters over the doorway of some of the houses, but he alone could read them.

"I have found Pelone!" he kept repeating over and over again.

And that is just what had happened. That last great blast Tom Swift had set off had broken down the rock wall that hid the lost city from view. There it was, buried deep down under the mountain, where it had been covered from sight ages ago by some mighty earthquake or landslide; perhaps both. And the earth and rocks had fallen over the main portion of the city of Pelone in such a way—in such an arch formation—that the greater part of it was preserved from the pressure of the mountain above it.

The outlying portions were crushed into dust by the awful pressure of the mountain—millions of tons of stone—but where the natural arch had formed the weight was kept off the buildings, most of which were as perfect as they had been before the cataclysm came.

The buildings were of stone block construction, mostly only one story in height, though some were two. They were simply made, somewhat after the fashion of the Aztecs. A look into some of them by the light of portable electric lamps showed that the houses were furnished with some degree of taste and luxury. There were traces of an ancient civilization.

But of the inhabitants, there was not a trace: either they had fled before the earthquake or the volcanic eruption had engulfed the city, or the countless centuries had turned their very bones to dust.

"Oh, what a find! What a find!" murmured Professor Bumper. "I shall be famous! And so will you, Tom Swift. For it was your blast that revealed the lost city of Pelone. Your name will be honored by every archeological society in the world, and all will be eager to make you an honorary member."

"That's all very nice," said Tom, "but what pleases me better is that this tunnel is a success."

"Success!" cried Mr. Damon. "I should call it a failure, Tom Swift. Why, you've run smack into an old city, and you'll have either to curve the tunnel to one side, or start a new one."

"Nothing of the sort!" laughed Tom. "Don't you see? The tunnel comes right up to the main street of Pelone. And the street is as straight as a die, and just the width and height of the tunnel. All we will have to do will be to keep on blasting away, where the main street comes to an end, and our tunnel will be finished. The street is over half a mile long, I should judge, and we'll save all that blasting. The tunnel will be finished in time!"

"So it will!" cried Job Titus. "We can use the main street of the hidden city as part of the tunnel."

"Use the street all you like," said Mr. Bumper, "but leave the houses to me. They are a perfect mine of ancient lore and information. At last I have found it! The ancient, hidden city of Pelone, spoken of on the Peruvian tablets, of gold."

The story of the discoveries the scientist made in Pelone is an enthralling one. But this is a story of Tom Swift and his big tunnel, and no place for telling of the archeological discoveries.

Suffice it to say that Professor Bumper, though he found no gold, for which the contractors hoped, made many curious finds in the ancient houses. He came upon traces of a strange civilization, though he could find no record of what had caused the burial of Pelone beneath the mountains. He wrote many books about his discovery, giving Tom Swift due credit for uncovering the place with the mighty blast. Other scientists came in flocks, and for a time Pelone was almost as busy a place as it had been originally.

Even when the tunnel was completed and trains ran through it, the scientists kept on with their work of classifying what they found. An underground station was built on the main street of the old city, and visitors often wandered through the ancient houses, wherein was the bone-dust of the dead and gone people.

But to go back to the story of Tom Swift. Tom's surmise was right. He and the contractors were able to use the main street of Pelone as part of their tunnel, and a good half mile of blasting through solid rock was saved. The flint came to an end at the extremity of Pelone, and the last part of the tunnel had only to be dug through sand-stone and soft dirt, an easy undertaking.

So the big bore was finished on time—ahead of time in fact, and Titus Brothers received from Senor Belasdo, the Peruvian representative, a large bonus of money, in which Tom Swift shared.

"So our rivals didn't balk us after all," said Walter Titus, "though they tried mighty hard."

The big tunnel was finished—at least Tom Swift's work on it. All that remained to do was to clear away the debris and lay the connecting rails. Tom and Mr. Damon prepared to go back home. The latter's work was done. As for Professor Bumper, nothing could take him from Pelone. He said he was going to live there, and, practically, he did.

Tom, Koku and Mr. Damon returned to Lima, thence to go to Callao to take the steamer for San Francisco. One day the manager of the hotel spoke to them.

"You are Americans, are you not?" he asked.

"Yes," answered Tom. "Why?"

"Because there is another American here. He is friendless and alone, and he is dying. He has no friends, he says. Perhaps—"

"Of course we'll do what we can for him," said Tom, impulsively. "Where is he?"

With Mr. Damon he entered the room where the dying man lay. He had caught a fever, the hotel manager said, and could not recover. Tom, catching sight of the sufferer, cried:

"The bearded man! Waddington!"

He had recognized the mysterious person who had been on the Bellaconda, and the man whose face had stared at him through the secret shaft of the tunnel.

"Yes, the 'bearded man' now," said the sufferer in a hoarse voice, "and some one else too. You are right. I am Waddington!"

And so it proved. He had grown a beard to disguise himself so he might better follow Tom Swift and Mr. Titus. And he had followed them, seeking to prevent the completion of the tunnel. But he had not been successful.

Waddington it was who had thrown the bomb, though he declared he only hoped to disable Tom and Mr. Titus, and not to injure them. He was fighting for delay. And it was Waddington, working in conjunction with the rascally foreman Serato, who had induced the tunnel workers to desert so mysteriously, hoping to scare the other Indians away. He nearly succeeded too, had it not been for the gratitude of the woman whose baby Tom had saved from the condor.

Waddington had been an actor before he became involved with the rival contractors. He was smooth shaven when first he went to Shopton, to spy on Mr. Titus, whose movements he had been commanded to follow by Blakeson & Grinder. Then he disappeared after Mr. Titus chased him, only to reappear, in disguise, on board the Bellaconda, as Senor Pinto.

Waddington, meanwhile, had grown a beard and this, with his knowledge of theatrical makeup, enabled him to deceive even Mr. Titus. Of course it was comparatively easy to deceive Tom, who had not known him. Waddington had really been ill when he called for help on the ship, and he had not noticed that it was Tom and Mr. Titus who came into his stateroom to his aid. When he did recognize them, he relied on his disguise to screen him from recognition, and he was successful. He had only pretended to be ill, though, the time he slipped out and threw the bomb.

Reaching Peru he at once began his plotting. Serato told him about the secret shaft leading into the tunnel, and with the knotted rope, and with the aid of the faithless foreman, the men were got out of the tunnel and paid to hide away. Waddington was planning further disappearances when Tom saw him, but thought it a dream.

Masni, the Indian woman, out herb-hunting one day, had seen Waddington, 'the bearded man' as he then was—working the secret stone. Hidden, she observed him and told her husband, who was afraid to reveal what he knew. But when Tom saved the baby the woman rewarded him in the only way possible. And it was Serato, who, at Waddington's suggestion, caused the "hit" among the men by working on their superstitious fears.

Waddington, knowing that he was dying, confessed everything, and begged forgiveness from Tom and his friends, which was granted, in as much as no real harm had been done. Waddington was but a tool in the hands of the rival contractors, who deserted him in his hour of need. His last hours, however, were made as comfortable as possible by the generosity of Tom and Mr. Damon.

No effort was made to bring Blakeson & Grinder to justice, as there was no evidence against them after Waddington died. And, as the tunnel was finished, the Titus brothers had no further cause for worry.

"But if it had not been for Tom's big blast, and the discovery of the hidden city of Pelone just in the right place, we might be digging at that tunnel yet," said Job Titus.

The day before the steamer was to sail, Tom Swift received a cable message. Its receipt seemed to fill him with delight, so that Mr. Damon asked:

"Is it from your father, Tom?"

"No it's from Mary Nestor. She says her father has forgiven me. They have been away, and Mary has been ill, which accounts for no letters up to now. But everything is all right now, and they feel that the dynamite trick wasn't my fault. But, all the same, I'm going to teach Eradicate to read," concluded Tom.

"I think it would be a good idea," agreed Mr. Damon.

Tom, Mr. Damon and Koku, bidding farewell to the friends they had made in Peru, went aboard the steamer, Job Titus and his brother coming to see them off.

"Give us an option on all that explosive you make, Tom Swift!" begged Walter Titus. "We were so successful with this tunnel, thanks to you, that the government is going to have us dig another. Will you come down and help?"

"Maybe," said Tom, with a smile. "But I'm going home first," and once more he read the message from Mary Nestor.

And as Tom, on the deck of the steamer, waved his hands to Professor Bumper and his other friends whom he was leaving in Peru, we also, will say farewell.

THE END