TOM SWIFT
IN THE CAVES OF NUCLEAR FIRE
By VICTOR APPLETON II
No. 8 in the Tom Swift Jr. series.

From the inside cover:
"Tom, that strange gas is fantastic-disintegrates everything it touches! What do you think it is?"
Fascinated by the amazing report from a pilot who crash-landed in the African jungle, Tom Swift Jr.'s eyes glow with curiosity as he replies: "Sounds like anti-protons rampaging. Such a phenomenon is unknown on earth. This may be the greatest discovery of the century. It could revolutionize the whole science of atomic energy. Let's investigate that taboo mountain."
Although several of the young inventor's associates view his latest expedition with skepticism, Tom sets off in the Flying Lab for the Dark Continent to fathom the secret of the mysterious mountain. The deadly vapors which have terrified the natives for generations challenge even the scientific genius of Tom and his companions.
When their atomic drill inexplicably is sucked into a forbidding peak, a series o£ startling events threaten the Swift expedition. How Tom, with his new invention the Terrasphere, conquers a heretofore unknown, violent quirk of nature brings this breath-taking story to a spectacular finish.

GROSSET & DUNLAP
new york 10. N. Y.

THE NEW TOM SWIFT JR. ADVENTURES
TOM SWIFT IN THE CAVES OF NUCLEAR FIRE
BY VICTOR APPLETON II

The Tom Swift Jr. series:
1 Tom Swift and his Flying Lab (1954) 
2 Tom Swift and his Jetmarine (1954) 
3 Tom Swift and his Rocket Ship (1954) 
4 Tom Swift and his Giant Robot (1954) 
5 Tom Swift and his Atomic Earth Blaster (1954) 
6 Tom Swift and his Outpost in Space (1955) 
7 Tom Swift and his Diving Seacopter (1956) 
8 Tom Swift in the Caves of Nuclear Fire (1956) 
9 Tom Swift on the Phantom Satellite (1956) 
10 Tom Swift and his Ultrasonic Cycloplane (1957) 
11 Tom Swift and his Deep-Sea Hydrodome (1958) 
12 Tom Swift in the Race to the Moon (1958) 
13 Tom Swift and his Space Solartron (1958) 
14 Tom Swift and his Electronic Retroscope (1959) 
15 Tom Swift and his Spectromarine Selector (1960) 
16 Tom Swift and the Cosmic Astronauts (1960) 
17 Tom Swift and the Visitor from Planet X (1961) 
18 Tom Swift and the Electronic Hydrolung (1961) 
19 Tom Swift and his Triphibian Atomicar (1962) 
20 Tom Swift and his Megascope Space Prober (1962) 
21 Tom Swift and the Asteroid Pirates (1963) 
22 Tom Swift and his Repelatron Skyway (1963) 
23 Tom Swift and his Aquatomic Tracker (1964) 
24 Tom Swift and his 3D Telejector (1964) 
25 Tom Swift and his Polar-Ray Dynasphere (1965) 
26 Tom Swift and his Sonic Boom Trap (1965) 
27 Tom Swift and his Subocean Geotron (1966) 
28 Tom Swift and the Mystery Comet (1966) 
29 Tom Swift and the Captive Planetoid (1967) 
30 Tom Swift and his G-Force Inverter (1968) 
31 Tom Swift and his Dyna-4 Capsule (1969) 
32 Tom Swift and his Cosmotron Express (1970) 
33 Tom Swift and the Galaxy Ghosts (1971)

ILLUSTRATED BY GRAHAM KAYE
GROSSET & DUNLAP
©BY GROSSET & DUNLAP, INC., 1956 ALL RIGHTS RESERVED
PRINTED IN THE UNITED STATES OF AMERICA

CONTENTS
1 An Eerie Light
2 Jungle Phenomenon
3 A Crash
4 The Forgery
5 A Wild Chase
6 Questioned by Police
7 Mysterious Escape
8 An Unexpected Plunge
9 Farewell Surprise
10 Six Hours Lost
11 A Defensive Move
12 Black Magic
13 An Angry Leopard
14 An Enemy Returns
15 "Grab Your Helmets!"
16 Tense Moments
17 A Lion Interferes
18 Phosphorescent Rocks
19 An Inventor's Dream
20 A Terrifying Fall
21 Missing Explorers
22 A Signal for Help
23 The Natives Attack
24 At Nature's Mercy
25 A Surprise Victory

TOM SWIFT IN THE CAVES OF NUCLEAR FIRE

CHAPTER 1
AN EERIE LIGHT

"What’s wrong, Bud? You look worried."
"I am worried, Tom. Here you are experimenting with something you know absolutely nothing about-something from another world!"
Tom Swift, tall and blond, smiled at his husky dark-haired friend, Bud Barclay. "That makes it all the more interesting!" he replied.
The two eighteen-year-old boys were in Tom's special laboratory at Swift Enterprises, the sprawling research and development firm headed by the young inventor's famous father.
"Suppose the thing blows up," said Bud, staring doubtfully at an opaque tube which rested on a small table near the center of the well-equipped laboratory.
The strange tube had been taken from a rocket ship sent by space beings with whom Tom had established communication. Above the tube was a large complicated camera and alongside o£ it a black spherical machine.
2 THE CAVES OF NUCLEAR FIRE
"What's that gadget?" Bud inquired curiously.
"Dad developed it," Tom replied. "It's a high-energy-wave generator he calls Genero X. Remember when we found the space rocket? This Eye-Spy camera could penetrate every part of it except the opaque tubes."
"How could I forget?" Bud chuckled. "What an adventure that was! And since we came back you've talked about nothing else but working on this tube."
Tom laughed. "Okay, chum, I plead guilty. Now I want to find out if the radiation from Genero X will affect the tube in such a way that the camera can penetrate it."
"Now you've got me curious," Bud said enthusiastically. "Let's get started."
The young inventor walked over to a metal locker, withdrew two antiradiation suits, and gave one to Bud. The boys put them on, then each donned a helmet with a heavy lead-glass visor. Tom moved toward the table.
"Ready?" he called.
"Fire away!"
Tom switched on the special apparatus and a buzzing sound replaced the quiet of the laboratory. Then he set the frequency control to half power and the two experimenters watched the tube closely.
It began to glow-first yellow, then blue, then white-until it reached such intensity that Tom
AN EERIE LIGHT 3
and Bud had to turn away to keep from being blinded. Gradually the glare faded, leaving the laboratory bathed in a cold light. Then, the next moment, a strange iridescence covered everything in the room.
To the boys' amazement, various objects in the room began to change shape. Metal implements and glass flasks seemed to be melting!
"Jumping jets!" Bud exclaimed. "Wh-what's happening?"
"I don't know," Tom replied. "Never saw anything like it before." At that moment he noticed that his visor was turning black! "We'd better get out of here!" he warned.
"I can't see!" Bud yelled, fear clutching him.
Briefly Tom assured him that he thought they would be all right if they left the laboratory immediately.
"But I-I feel-so drowsy," Bud said slowly.
"Don't give in to it!" Tom urged, beginning to feel sleepy also. "We're in trouble, Bud. Head for the door! These suits aren't giving us enough protection! Get out of here fast!"
Groping ahead, unable to see, Tom stumbled into a workbench and crashed to the floor. Desperately he crawled along until his hand touched the leg of the table holding the tube and generator. Fighting to stay awake, he pulled himself up, fumbled frantically for the power switch, and turned it to off.
4 THE CAVES OF NUCLEAR FIRE
Meanwhile, Bud had managed to make his way to the door. "Here's-the-exit, Tom!" he called. "Follow-my-voice!"
"I'm right behind you. Go on out!" Tom commanded.
He himself reached the door and staggered

AN EERIE LIGHT 5
into the corridor. Tearing off his helmet, Tom
hurried over to Bud who was leaning against a
wall, visor in hand.
"Quick!" he ordered. "Come with me!"
His eyes smarting, Bud followed Tom to a
smaller laboratory located near the end of the

6 THE CAVES OF NUCLEAR FIRE
long corridor. Here Tom had set up one of his recent inventions-a device to detect in a few moments the amount of radiation absorbed by human tissues.
To Bud's arms Tom quickly attached four wires which were connected to an intricate panel. He snapped on the device, adjusted a dial, and watched the pointer of the radiation indicator flicker to life.
"What's the verdict?" Bud asked, almost afraid to hear the answer. Had he been fatally exposed to radiation?
Tom smiled in relief. "Luckily you're okay. You've only absorbed 150 milliroentgens and it takes about 450 before a fellow's in trouble."
Tom then tested his own body. Although he showed a slightly higher indication, it was still within the safe limit. "It's fortunate we got out when we did."
Bud, heaving a thankful sigh, turned to his friend with a grin. "You mean we won't glow in the dark after all? Well, what's next?"
"I'm going back to that lab, Bud."
"What!" his friend exploded. "Have you lost your senses?"
"The radiation's down by now," replied Tom. "I must make certain the room isn't dangerously contaminated, though."
Bud groaned. "Well, genius boy, you're the boss. But you're not going alone. Lead on!"
AN EERIE LIGHT 7
Tom extracted two fresh antiradiation suits from an equipment locker. The boys donned them and Bud picked up a Geiger counter.
"We'd better take some lead-glass light bulbs with us," Tom said. "You can bet that radiation has burned out the filaments in the regular bulbs."
Looking like space men in the protective suits, the boys walked down the corridor and entered the laboratory. They paused to replace a few bulbs with the lead-glass ones, then looked around.
"Hey!" Bud cried. "This place is still mighty 'hot'! Listen to the Geiger counter! Don't you think we should get out?"
"We'll be safe in these suits for a while," Tom assured him. "The rays are considerably weaker than they were, but later we must wash this room down with a cadmium salts solution."
Tom picked up a few samples of the metal objects and glass pieces which had changed shape under the radiation. "Let's take a look at this stuff in the lab next door," he said. "And, Bud, bring the opaque tube, will you?"
Switching off the lights, Tom followed his friend from the room. In the laboratory he made a careful examination of the misshapen samples and discovered that they were extremely hard. "This whole thing is baffling," he said. "I'm going to call in the radiation boys."
8 THE CAVES OF NUCLEAR FIRE
He summoned Enterprises' staff of radiation technicians, who helped him to determine the atomic structure of the opaque tube. They found that the material contained a new isotope of silicon.
"I can't believe it!" Tom exclaimed. "This isotope is unheard of here on earth!"
Bud raised an eyebrow. "Naturally. The tube wasn't made on this earth."
Tom chuckled, recognizing his friend's logic. "It's still fantastic," he insisted. "Silicon has an atomic weight of 28 and has three known isotopes; the first with a weight of 28, the others 29 and 30. The isotope in this tube has a weight of 33!"
"Is this what almost turned us into a couple of human neon signs?" Bud asked, grinning.
Tom shrugged. "I don't know yet. It'll take a lot more research to find out."
At that moment the phone rang and the young inventor picked up the receiver. "Tom," said Miss Trent, private secretary to Tom and his father, "Craig Benson is on the line."
"Craig Benson!" Tom repeated, his jaw sagging in disbelief. Craig was a pilot who had crashed two years before in Africa and had not been heard from since.
A deep, pleasant voice said, "Hello, Tom? Surprised to hear from me? . . . I'm calling from your home. Just got here. I want to talk to you and your father."
AN EERIE LIGHT 9
"Craig! It's really you!" Tom exclaimed. "Bud and I will be there in less than half an hour. This is wonderful news."
Craig, a former flier for Enterprises, had been lent to a foreign government to open up a cargo air route. It was during a flight in connection with this project that the pilot had crashed. An intensive search for the missing plane had proved fruitless. Since that time, the air route had been fully developed.
Tom put the phone in its cradle and turned to give Bud the astounding information. He was as amazed as Tom. "Craig sure will have a whale of a story to tell," he remarked.
The sun was setting as the two friends set off for the Swift home in Bud's convertible. A few minutes later they parked the car in the garage and strode across the lawn and through the magnetic-alarm field which surrounded the house. Special coils built into their wrist watches allowed Tom and Bud to pass through without setting off the alarm system.
Inside the large, comfortable home, the boys were met by Tom's father. The tall, distinguished-looking man, with twinkling blue eyes, was an older edition of the young inventor. Mr. Swift led the way into the library where Craig Benson was waiting. Craig, a tall, husky man of twenty-four, had light-brown hair and blue eyes which were accented by his deep tan.
10 THE CAVES OF NUCLEAR FIRE
"I'm really here in the flesh," he said, grinning, then added soberly, "I came to see you as soon as I got to this country because I have a story that I think will astound you. I found something in the jungle you'll certainly want to investigate."
Before Tom could reply, his mother entered the library and announced that dinner was ready. She was a slim, attractive woman with sparkling eyes and a charming smile. "I'm sorry to interrupt you," she added, "but would you mind continuing your discussion at dinner?"
She led them to the dining room where Tom's pretty seventeen-year-old sister, Sandy, who was greatly admired by Bud, was waiting. Phyllis Newton, Tom's frequent date, was another guest. The pert, dark-haired girl was the daughter of Ned Newton, Mr. Swift's long-time friend, who was now head of the famous Swift Construction Company.
As soon as everyone had been seated and grace had been said, Tom asked eagerly, "Now let's hear your story, Craig!"
The pilot smiled. "Well, it concerns the greatest and strangest disappearing act in the history of the world!"
CHAPTER 2
JUNGLE PHENOMENON
"IT ALL began," Craig continued, as his listeners sat spellbound at the dinner table, "when I crash-landed in Central Africa. I was rescued from the wreck by some friendly natives of the Mabawiki tribe who took me to their village and nursed me very eEectively.
"When I recovered," Craig went on, "the natives wouldn't let me leave. It seems that since I was still alive after falling from the sky they considered me to be some sort of minor god!"
The Swifts and their guests smiled and Tom said, "I suppose that you received special attention."
"Yes, indeed. And they told me many tribal secrets. One concerned a nearby mountain that was taboo."
The pilot described a religious ceremony he had attended one night near a huge mountain in
11
12 THE CAVES OF NUCLEAR FIRE
the area. Noticing that all the natives were bowing toward it in awe, Craig had looked up just in time to see a strange sight. "Some sort of gas was issuing from a crevice in the slope," he said. "It glowed-literally glowed-with a bright greenish light!"
Tom was leaning forward, intrigued by the story. Everyone had stopped eating.
"The natives could tell me nothing about the gas," said Craig, "except that it was a signal of anger from the fire god who lived under the mountain. I decided to try finding out what the phenomenon was, so one night I managed to slip away and explore the mountain."
"Did you find out what the gas was?" Tom asked.
"No. That's the job I thought you'd take over. But it will be the most difficult thing you ever attempted."
"Why?"
Craig said he had salvaged the oxygen container from his wrecked plane to capture some of the gas for analysis. "And since it was a long hike, I took my water flask and an earthen jar containing some food."
Craig told how he had waited hours for the gas to erupt, then had left all the containers at the crevice, and gone off to a sheltered spot to sleep.
"In the morning I returned, but there was no sign of the containers," the pilot said. "They
JUNGLE PHENOMENON 13
couldn't have been stolen, since the mountain was taboo, so I figured that they must have been disintegrated by the gas."
"African black magic!" Sandy said excitedly.
Craig chuckled. "Seemed that way, I'll admit. To make sure, I got other containers and tried the experiment again. This time I watched until the glowing gas did appear. Sure enough, the containers vanished-in an intense burst of white light."
"Sounds fantastic," commented Mr. Swift.
Tom and Bud exchanged glances. Both were thinking of their experience in the laboratory. The objects there had begun to change shape. Would they have disappeared completely if the experiment had continued? And, Tom wondered, was an unusual phenomenon taking place under the mountain in Africa which produced an element like the composition of the tube he had received from another planet?
At this point in the story, the whole group adjourned to the library where Craig recounted the story of his forced leave-taking from the native village-because he had ignored the taboo-and the long, terrible ordeal of his trek back to civilization. Eventually he had boarded an ocean liner and returned to America.
"An amazing story," Mr. Swift remarked, and Phyllis asked, "What does the mountain look like?"
14 THE CAVES OF NUCLEAR FIRE
"I have some pictures of it," Craig replied, explaining that he had managed to save his camera from the plane wreck.
Eagerly the others glanced through the pictures he took from his wallet. Tom and his father noticed that the area around the mountain was totally without plant life and that all the closer shots were badly fogged. The two exchanged meaningful and worried glances.
"The gas you describe must be caused by some type of nuclear reaction," Mr. Swift said slowly. "Everything points to that-the vanishing containers, lack of plant life, and the fogged pictures."
"Yes," said Tom. His face grim, he turned to Craig and asked, "How long did you stay in the area of the glowing gas?"
The pilot seemed startled by the question. He frowned for a moment, then answered, "I must have been around there for a total of ten hours. Why?"
"We don't want to alarm you," Mr. Swift said, putting a hand on Craig's shoulder, "but Tom and I have reason to think that you may have been exposed to some powerful radiation from that gas."
He suggested that the young man go with Tom to the laboratory and submit to a test with the radiation detector. Craig readily agreed.
While he and Tom rushed to Enterprises, Mr.
JUNGLE PHENOMENON 15
Swift phoned the company physician, Dr. Simp son, and asked him to meet the two there. The doctor arrived just as Tom finished attaching the wires of the detector to Craig's arms.
Tom introduced the two men, then adjusted a control dial. The indicator flickered to life and the three stared at the pointer as it climbed to over 200 milliroentgens.
"You seem to have absorbed more than a moderate amount of radiation," Dr. Simpson declared.
Craig paled and turned questioning eyes to the physician. "A fatal amount?" he asked.
"Not that, son," the doctor said, smiling. "It's not so serious as I may have made it sound. A few days' rest, together with sodium chloride and potassium chloride treatments, should put you back in healthy shape."
"Whew!" Craig swallowed hard. "You had me scared for a minute!"
After Dr. Simpson had administered a treatment of chlorides to Craig in the company's infirmary, he instructed Tom to see that his friend had plenty of rest and fresh air for at least a week.
Tom telephoned his mother to inquire if Craig might use the guest room at their home. "Of course," she said warmly, "and how wonderful that he's going to be all right!"
When Tom and Craig returned to the Swift
16 THE CAVES OF NUCLEAR FIRE
home, they learned from Sandy that Bud, after hearing the good report about Craig's condition, had left to take Phyllis home. But the Swifts were eager to hear more of Craig's story.
"I must admit that I'm intrigued by it," said the older inventor, as Tom and Craig sank deep into comfortable chairs.
After Craig had filled in a few details, Tom described the strange experience he and Bud had had that afternoon and their suspicions there might be a similarity between the mountain phenomenon and the contents of the opaque tube.
"This is amazing, Tom!" exclaimed Mr. Swift. "If Enterprises could locate the source of a silicon isotope not yet discovered on this earth, it would be a great boon to mankind."
"And to the manufacture of rockets for interplanetary travel," Tom added. He looked straight at his father. "If it wouldn't interfere with our experiments here, I'd like to go to Africa at once, Dad."
"I knew this would be coming." Mr. Swift chuckled. "Go ahead, Tom!"
"Great!" Craig exclaimed. "I was hoping you would go there with me."
"But what about the natives?" Mrs. Swift asked, concern in her voice. "They banished you, Craig."
The pilot smiled. "If I show up a second tim»
JUNGLE PHENOMENON 17
alive, they'll really think I'm some kind of little god. I'm sure that we won't have any trouble with the Mabawikis-my rescuers. But we might have a little opposition from a neighboring tribe known as the Onaris. I wouldn't want any of them for playmates!"
"Well, we'll lick that problem when we get to Africa," Tom commented. "The first step is to plan the expedition."
Next morning the two young men ate a hearty breakfast, then walked to Swift Enterprises. Tom ushered Craig into the office he shared with his father. The pilot wandered around the spacious room, admiring the models of inventions by Tom and Mr. Swift that he had not seen before. He asked about the Sky Queen, Tom's giant plane which could ascend vertically by jet lifters.
"It's really a Flying Lab," said Tom. "It's what we'll use for the trip to Africa."
"And what kind of a submarine is this?" asked Craig. "It has an open part in the center with rotor blades in it."
Tom smiled. "It took me down to ocean depths deeper than anyone had been before. While in it, I found the rocket from another planet, but nearly lost my life doing it. You know, Craig, every time I start a new project, I can't help wondering what adventures I'll run into. Now take this African expedition-"
18 THE CAVES OF NUCLEAR FIRE
Craig interrupted. "There's one thing I haven't mentioned about that, Tom. It may not be important, but it has me puzzled."
"Okay, let's hear it."
Tom perched on a corner of his desk while Craig relaxed in an easy chair. "Ever since I left Africa, I've had a feeling that I'm being followed," the pilot began. "Nothing I can put my finger on, but a few unexplained incidents."
"Like what?" Tom prompted.
"Well, just as I was about to board the liner to return to the States, I was detained by the local police. Something about an anonymous phone call warning them that I was smuggling diamonds out of the country. Luckily I managed to prove my innocence before sailing time.
"Then on shipboard two men seemed to go out of their way to make friends with me. They called themselves Karl Taylor and Eric Cameron. They kept pumping me about my business in Africa-subtly, of course, but they were persistent enough to make me uneasy. Then, one evening after dinner, I returned to my cabin to find Taylor tampering with the latch on the door!"
"What happened?" Tom asked.
"Naturally I asked Taylor what he wanted," Craig replied. "Tom, he's a smooth operator! He gave me such a convincing line about thinking I was asleep in the cabin and trying to rouse me for a chess game that I almost believed him,
JUNGLE PHENOMENON 19
despite the fact I'd suspected him of trying to break into my cabin."
"Did you see much of the men after that?" Tom queried.
"No. They didn't exactly avoid me, but they didn't seek me out, either. Then, after we landed, I didn't see them again until yesterday when I arrived at Shopton. I'm positive I spotted Cameron in the railroad station, but he vanished before I could hail him."
Tom picked up a Shopton directory. Neither man was listed. "Of course, Cameron's being here may not mean a thing, but just the same we'd better be on guard. I'll alert our security chief, Harlan Ames. He'll want you to describe these men."
"Taylor is about five feet nine, black hair-" The pilot reached for a pencil and paper. "Maybe I can sketch a picture of him."
"I didn't know that you were an artist," Tom commented.
"I'm not really," Craig answered modestly. "But it's fun for a hobby."
The pilot had finished one sketch and had begun work on another when there was a heavy knock on the door.
"Come in!" Tom called.
A short, roly-poly man, bronzed from the sun, strode into the office. Polished western boots flashed beneath the cuffs of his blue jeans and a
20 THE CAVES OF NUCLEAR FIRE
garish plaid sport shirt completed his outfit. Formerly a Texas chuck-wagon cook, Chow Winkler was now in charge of food on Tom's expeditions.
"Howdy!" he shouted. "Oops! Didn't know you had company- No, oh no! It can't be! But it sure is I Well, brand my lil lost palomino! Where'n creation did you come from, Craig Benson?"
"Chow, it's good to see you again. I finally escaped from that jungle cooking-crocodile stew with a few humans mixed in-"
"You mean you been livin' with cannibals?" the cook cried out. But Craig could not keep his face straight and Chow said, "At your ole jokin' again, eh? Well, I sure am glad you're back an* don't fly over none of them jungles any more."
Tom laughed. "Why, Chow, that wouldn't worry you, would it?" he asked. "Craig and I are planning a trip to the African jungle and thought you'd like to come along."
Chow scratched his balding head. "Are you kiddin', too, Tom?"
"No, I'm serious."
The cook sighed. "Where you go gallivantin', I go too. But it sounds mighty risky. By the way, I jest rambled in to see if you wanted lunch brought in, so I could start fixin' it."
As Tom nodded, Chow's eyes suddenly fell on the first sketch Craig had made. "Well, I'll be hog-tied!" he blurted out. "Who drew these?"
JUNGLE PHENOMENON 21
"Craig," Tom said.
"Mighty nice. Say, either of these hombres from Texas?"
"Why do you ask?" Tom queried.
"Jest thought I'd seen one of 'em before. This one here."
"That's Taylor," Craig said. "Karl Taylor."
"Don't savvy the name." The cook ran a ham-like hand through his sparse hair. "Not real sure where I saw him," he murmured. "Might 'a' been Texas. Let me ponder it a bit. If I saw him, you kin bet I'll remember." Chow left to prepare lunch.
The remainder of the day was spent in preliminary preparations for the coming expedition. Tom and Craig studied charts of Central Africa provided by Enterprises' geographical department and made a few tentative lists of equipment and supplies.
It was almost dark when they started on foot for the Swift home, glad of a walk in the fresh air.
"Since it's so late," Tom said, "let's take the short cut I use through the lane in the woods."
The two were striding briskly along the deserted dirt road when they heard the roar of a motor directly behind them. Tom and Craig whirled to see a car, without lights, approaching at terrific speed. The driver evidently did not see them.
"Look out!" Tom cried out.
CHAPTER 3
A CRASH
SUDDENLY the car's headlights blazed on, blinding Tom and Craig. For a split second the young men stared in horror as the vehicle careened madly toward them on the narrow road.
Then Tom pushed Craig into a ditch and jumped for it himself. The car sped by, grazing Tom and hurling him to the ground. Dirt and stones thrown up by the car's wheels showered down on the boys.
Dazed, Tom arose, brushed off the debris, and hobbled onto the road. "Craig!" he called. "You okay?"
"I-I guess so," responded the pilot shakily. He stumbled from the ditch, muttering, "Whoever was driving that car meant to kill us!"
Tom nodded grimly. "You're right. I think there were two men in it. Did you spot the license number?"
Craig shook his head regretfully. "All I know is, it was a black sedan. Tom, I feel that it's be-
22
A CRASH 23
cause of me you nearly lost your life a few minutes ago."
"Not necessarily, Craig. This sort of thing has happened to me before. Well, let's get to the house. I want to phone Harlan Ames. I have a hunch that there's more to this African business than we thought."
From his home Tom contacted the security chief and briefed him on the attempt to run down Craig and himself. "It was a deliberate attack," Tom emphasized, and told him about Craig's suspicions. He mentioned the sketches that the pilot had made of Taylor and Cameron, and Chow's belief that he had seen Taylor before.
"I'd like some copies of those sketches," Ames stated. "Maybe I can dig up something on the suspects."
Just as Tom replaced the receiver, Mrs. Swift called her family and Craig to dinner. Sandy, who had expected Bud to join them, asked where he was, then blushed as Tom winked at her.
"Bud left this morning in one of the cargo planes, Sis. He's going to pick up some equipment for our expedition."
Other news of the day was exchanged, with the exception of the near-tragic car episode, then Mr. Swift asked, "How is that expedition of yours coming along, son?"
"We've made some tentative plans," Tom re-
24 THE CAVES OF NUCLEAR FIRE
plied. "I hope to start actual preparations in a couple of days."
The following morning it was decided that Craig should remain at the Swift home for a day of complete rest. Tom went off alone to his private laboratory, where he was soon joined by Bud, who had returned to Shopton late the night before.
"Good trip?" Tom asked.
"Got everything I went for." Bud grinned. "Even those white helmets you wanted, jungle boy. But after you've made the discovery of the ages, yours probably won't fit," he gibed.
Tom pretended to throw a glass flask at him, then continued his work. Bud watched his friend sort an array of ten-inch, capsule-shaped objects which had just been delivered from Enterprises' metallurgical department.
"They're containers I had made up to get samples of that African gas," Tom explained. "According to Craig, it disintegrated his crockery and metal bottles, but I'm hoping one of these more refractory capsules will hold the gas."
He picked up a sheaf of papers from the workbench and handed them to Bud. "These are the 'specs' on each of the containers-what material was used to make them and how. Read them off to me, please, and I'll stamp the symbols on each one."
"Right," Bud began reading: "Heavy glass,
A CRASH 25
lead, asbestalon- That plastic asbestos of yours ought to do it." He went on reading, "Tomasite -Pal, I'd bet on that one any day." Bud knew that this plastic, transparent paint, which Tom had invented, was heat-resistant and radiation-proof, and a three-inch thickness of it would protect the engine of an atomic power plant!
Just then a buzzer sounded. "Somebody's at the door," Bud said. "I'll get it."
Reaching under the workbench, he pushed a switch that operated the locking device on the laboratory door. Hank Sterling, head engineer of Enterprises' patternmaking division, and Arvid Hanson, chief modelmaker, entered.
"Hi, Tom, Bud! Sorry to disturb you," said Hanson. The tall, big-boned man had a genial smile. "Hank and I have a few questions to ask about the Terrasphere."
The craftsman was referring to Tom's new invention, a vehicle specially designed for the exploration of cave systems and areas of very rough terrain. It was a low-slung, streamlined tank eighteen feet long, powered by nuclear-activated steam turbines. These would drive a set of caterpillar treads.
The driver's cabin was located in the rear and a hoisting crane rested along the top, nearly the length of the roof. The unique feature of the invention was its main cabin which nestled on the forepart of the chassis.
26 THE CAVES OF NUCLEAR FIRE
Spherical-shaped, with two wide windows, the cabin was removable. When the crane was in operation, cables hanging from it were attached to the cabin to swing it away from the chassis, and raise or lower it. Occupants of the cabin could safely explore and study deep chasms or caves which other vehicles could not penetrate.
"I'm taking a Terrasphere to Africa," Tom explained to Bud. Then, turning to the men, he asked, "What seems to be the trouble?"
"Arv's miniature working model ran perfectly," said blond-haired, square-jawed Hank Sterling. "But we're not satisfied with the test model of the Terrasphere that was built. I'm worried that the locking device on the crane isn't adequate."
"I'll go over to the test shop and take a look at it," Tom said at once. "Come on, Bud. I'll need your help."
The boys accompanied the two men to a large building which housed an elaborate array of testing equipment.
In the center of the high-ceilinged main room stood the shiny gray Terrasphere, firmly anchored to the floor with giant expansion bolts. After Tom had thoroughly inspected the whole Terrasphere, he announced that every part seemed to be in perfect working order.
"I want to give Terry a test, Bud," he said. "I'll climb into the sphere. You get into the con-
A CRASH 27
trol cabin, and swing me back and forth. I want to put maximum stress on these cables and watch the signaling system."
The two boys took their places, then Bud moved a dial which lifted the crane from a prone position on the Terrasphere. Its dangling cables reached down for the locking device on the roof of the cabin and Bud moved a control lever to clinch the electronic connection.
"Ready for your ride?" he called to Tom over the intercom.
"Swing away!"
Tom watched the gauges on the panel in front of him, which indicated the amount of strain on each cable. As Bud swung the crane from side to side, the young inventor felt as if he were being rocked.
"This is smooth and working in perfect rhythm," he said to himself.
Elated, the young inventor grinned and waved to Hanson and Sterling. But as he turned back to look at the gauges, the grin faded. One of the dials was flashing a red signal. There was too much stress on cable number three!
"Bud, hoist me back to the Terrasphere!" Tom yelled into the intercom.
At the same instant every light on the panel blinked red. This was followed by a loud twang as the cables parted just above the locking device. The cabin broke loose and was hurtled into
28 THE CAVES OF NUCLEAR FIRE
the air, then somersaulted to a crash landing against one wall of the building!
Bud dashed from the control cabin, fear gripping him.
Sterling and Hanson had already reached the sphere. Through a window they could see Tom lying unconscious against the panel board. Blood streamed from a gash in his head.
Working quickly, the men opened the door and carefully lifted Tom out and laid him on the floor. Bud leaned over him. When he realized that his friend was still alive, he raced to an adjoining room for a first-aid kit and administered a restorative. Five minutes later the young inventor opened his eyes.
"Take it easy," Sterling cautioned him. "You had a nasty crack-up."
Tom lay still for a minute. Then, as his memory returned, he smiled ruefully. "I goofed that time," he confessed. "Swinging so violently must have crystallized the cables and they gave way." Starting to rise, he said, "I've got to get busy and make cables which will be less subject to metal fatigue."
"Not today," Bud told him firmly. "You're going home and relax, old man."
He drove Tom to the Swift residence where Sandy and her mother took charge. Both gave sighs of relief when they learned he had escaped serious injury.

30 THE CAVES OF NUCLEAR FIRE
Craig, looking on, finally broke the tense atmosphere by remarking, "You can't keep a good man down!"
Late that afternoon a telephone call came to Tom from Harlan Ames. Tom took it on the extension in his bedroom. After the security chief had made sure Tom was recovering nicely from his shock, he said, "The local police have just recovered a stolen car-a black sedan. It could be the one that almost ran you and Craig down."
"Any clue to the thief?"
"None," Ames replied. "They forced open the door of the car and probably used a jumper wire to get it started. No fingerprints except the owner's."
"Have you done any checking on those men Craig described-Taylor and Cameron?" Tom asked.
"I sent copies of the sketches to the FBI in Washington," Ames reported. "I'll let you know the minute I get a report."
After the security chief had hung up, Tom sat on his bed for a moment in deep thought. If Taylor and Cameron had been the attackers, what was their motive? And why would they be shadowing Craig?
Heavy footsteps pounded on the stairs and Chow rushed into Tom's room excitedly. "Brand my cowhide boots!" he cried out. "I got it!"
Tom gazed at the cook in astonishment.
A CRASH 31
"Steady, old man. Tell me slowly what you've
got."
"Remember the picture you showed me of that feller Taylor? He's from my own ranch country in Texas!"
"Are you sure?" Tom demanded.
"Sure as I am o' tamin' a mustang!" Chow insisted. "I recall the very newspaper back home showin' his picture. Seems he got in bad with the folks 'round there. Shady doings o' some kind."
"Is his name really Taylor?" Tom asked.
Chow shook his head. "I don't reckon 'tis, but I cain't remember what he was called."
"What newspaper was his picture in?"
"The Comanche Daily."
"Perfect!" said Tom. "We can check with their office."
"Don't think you kin," the Texan murmured. "The Daily's whole place burned down 'bout a week later!"
"That's bad." Tom sighed. "Any idea where Taylor might have gone?"
"Well, some folks say they knew where he lit out to."
"Where was that?"
"Africa!"
CHAPTER 4
THE FORGERY
AT CHOW'S amazing announcement Tom whistled in surprise and thumped the Texan on the back. "Good work, Chow! This ties in with Craig's suspicion that Taylor and Cameron had more than a passing interest in his African adventures."
"I'm sure glad I remembered 'bout that hom-bre," said the cook proudly.
Later, when Tom and Craig were lounging in the Swifts' guest room, Tom told the pilot of Chow's verdict.
"Then I was right about Taylor all the time!" Craig exclaimed.
"Has it occurred to you that he may be trying to keep us from going to Africa?" Tom injected.
"No. But I believe you're right. Why don't we have Taylor picked up?"
"On what charge?" Tom pointed out. "We
32
THE FORGERY 33
haven't a shred of proof that he was in that automobile. In fact, we can't even say for sure he's here in Shopton."
"But I'm certain that I saw Cameron in Shop-ton, so it's likely Taylor's here too," the pilot protested. "Anyway, if Taylor was involved in something shady and skipped the country, he must be wanted by the authorities."
"Yes, but the name Taylor is probably an alias," observed Tom. "If it weren't for your sketches, we wouldn't know whom to look for. We'll have to be patient. If Taylor and Cameron are trying to cause us trouble, they'll show their hands sooner or later."
The next few days passed without any indication that their suspected enemies still were in the vicinity. Tom pushed construction of the Terrasphere he would take to Africa. He personally supervised the making of cables of great tensile strength. As a further precaution, these were X-rayed for flaws before being installed.
Early one morning Tom said to Craig, "We'll be ready to take off in the Sky Queen pretty soon. Want to help me inspect her?"
"Sure thing, if there's no charge for admission," he replied jokingly.
The two went to the underground hangar where the Flying Lab was berthed. Craig gazed in admiration at the three-decker plane. "It's beautiful, Tom. Almost overwhelming!"
34 THE CAVES OF NUCLEAR FIRE
Tom led the way on the tour of inspection, which began with the laboratory section. This was on the second deck. Partitions divided the spacious enclosure into separate compartments. Each was a laboratory completely equipped for some branch of research.
"This is a world all its own," Craig remarked.
"The Sky Queen," commented the young inventor as they walked along, "is like an old and loyal friend. It has carried Bud and me safely through many a tough adventure."
Craig congratulated Tom on the new and sleek Skeeter, a midget helicopter housed in a hangar on the lowest deck of the Sky Queen. He was equally impressed when he saw the Kangaroo Kub, a small delta-winged craft, powered by a single jet engine, which stood nearby.
As the inspection ended and the boys were about to leave the building, they were met by Mr. Swift. After greeting them, he said, "Tom, I'd like to discuss with you that experiment we conducted together. Project XA-107. We'll get out the file and go over it."
Tom looked at his father curiously. "Do you mean the one on the antiproton phenomena, Dad?"
"That's right. I'd like to review our findings."
"Any particular reason?" asked the young scientist.
"Just a hunch, son. From what Craig has told us
THE FORGERY 35
about that glowing gas in Africa, I was wonder-
ing-"
"If it might have something to do with the existence of antiproton matter under the mountain?" Tom finished the sentence.
"Yes. If such a thing exists there, our locating it would be one of the greatest discoveries of all time."
Craig, who had been listening quietly to the discussion, displayed a puzzled expression. "Is this a family secret?" he asked, smiling, "or may I join in with a question?"
"Sorry," Tom apologized. "Fire away."
"First of all," said Craig, "what's antiproton matter?"
"To explain that," said Mr. Swift, "you'd need a basic idea of how atoms are constructed."
"I took some science in school," Craig replied. "I know that the popular concept of an atom is that it looks like a miniature solar system. In the center is a nucleus. Moving around it are particles called electrons. The whole thing is similar to our own planets moving around the sun."
"That's basically it." Mr. Swift nodded. "An electron has a negative charge. A proton is the positive charge of the nucleus. Then we have the neutron, which is the uncharged constituent of an atomic nucleus."
"That much I understand," said Craig.
"Now in antiproton matter," Tom took up the
36 THE CAVES OF NUCLEAR FIRE
story, "the atoms have the same 'solar system' setup you mentioned, but there's one difference. The charges on the particles are reversed. What was the electron is now a positron and what was the proton is now an antiproton."
"I suppose," Craig said, "there's a completely different reaction if they come into contact with foreign substances."
"Definitely!" Mr. Swift broke in. "If enough antiproton matter reacted with substances here on earth, the heat produced could start a chain reaction. The world could blow itself into oblivion!"
"Wow!" exclaimed Craig. "That stuff wouldn't be anything to play with!"
"No," Tom agreed, "but actually it could be put to good use."
When the group reached the office building, Craig said good-by and Tom followed his father inside. They went directly to their private office where the young inventor slid open a wooden panel in the wall. Behind it was a small but sturdy safe. He flicked the combination lock rapidly and opened the door.
Tom reached inside and withdrew a stack of leather-bound manuscripts. After going completely through the pile, he stared at the stack curiously.
Mr. Swift sensed that something was wrong. "What's the matter, son?"
THE FORGERY 37
"It's gone!" Tom cried out. "The file on an-tiprotons is gone!"
"Great Scott!" exclaimed the elder inventor, stunned. "This is serious."
"I can't imagine how it disappeared," Tom mused. "The only other person who has access to this safe is Alvy Tompkin."
"Tompkin wouldn't be interested in our treatise," said Mr. Swift. "Besides, he's one of our most trusted employees. He's been with us Swifts since the day Enterprises was formed."
Tompkin had been transferred from the Swift Construction Company and made special guardian of the office a few months before.
"Just the same," said Tom, "it won't do any harm to ask him if he knows anything about the manuscript."
Tom summoned Alvy Tompkin to the office over the intercommunication system. A few minutes later a thin, elderly man came in. His strong face and direct gaze reflected his integrity.
"Tom and I are hunting for something we can't find," Mr. Swift said. "We thought we left an important file, Project XA-107, in the safe. Do you remember seeing it there?"
"Yes," replied Tompkin, but with a puzzled look. "It was only yesterday, Tom, that I took it from the safe. I was only following your orders."
"Orders!" Tom exclaimed. "What orders?"
"Your note." From a pocket Tompkin pro-
38 THE CAVES OF NUCLEAR FIRE
duced a short typewritten letter signed Tom Jr. It instructed Tompkin to procure the file on antiprotons and deliver it to Craig Benson at the north gate of Swift Enterprises. He was to say "Hoptoad" as a password. Benson would reply "Orion."
"Who gave you this note?" Tom asked. "I never wrote it."
Tompkin turned ash white. "Harry, the guard at the north gate, gave it to me."
Tom asked for a description of the man who received the file.
Tompkin thought for a moment, then said, "He was about six feet tall, had black hair, a thin face, and very dark eyes. He was driving a light-blue sedan."
Tom extracted copies of the two sketches Craig Benson had made. "Was he either of these two men?" he asked.
Tompkin studied the drawings, then pointed. "Yes," he muttered, "it was this man."
"That's a fellow named Cameron!" Tom cried out.
Realizing the gravity of the situation, Tompkin was extremely remorseful. He severely reprimanded himself for falling prey to the hoax.
"Don't blame yourself too hard," Tom said gently. "This forged signature could fool even me at first glance."
He contacted Harlan Ames at once and the
THE FORGERY 39
security chief came to the office immediately. He sat down and Tom briefed him on what had happened, then showed Ames the fake note. After the detective had scrutinized the signature closely, he commented, "The forgery of this signature is one of the cleverest I've ever seen. At least we know a little more about Taylor and Cameron. Probably one of them is an expert forger."
"The note was a simple ruse," Tom said an-grily, "but it worked."
"Yes," Ames answered, "and we'll need police help on this. I'll start working with them at once." He arose. "See you all later."
That evening little was said at the Swifts' dinner table. Bud and Phyl were there, but everyone was unusually quiet. As Tom sat pondering the loss of the important manuscript, Sandy looked at her brother. "How valuable are those papers?" she asked.
"In the wrong hands," he replied, "the information could affect the welfare of the entire world. Dad's and my experiments were not complete by any means, but the file revealed an important start. I'm inclined to think Cameron suspects that there is an antiproton gas in Africa."
"What gets me," Craig spoke up, "is why that crook used my name."
"Taylor and Cameron found out that you're a
40 THE CAVES OF NUCLEAR FIRE
trusted member of our organization," said Mr. Swift. "And that your face wasn't known to Tompkin."
At that moment the telephone began to ring. Tom excused himself and answered it.
Chow's voice came booming out of the receiver. "Toml" he shouted. "That you?"
"Yes."
"Stay put!" commanded the cook. "I'll be over as fast as my gas buggy'll fetch me there." Before Tom could reply, Chow hung up.
Several minutes later a small jeep came bounding up the Swifts' driveway and skidded to an abrupt halt. Chow leaped out and rushed up the front steps.
"Tom," he boomed, as he came into the living room where the others had assembled, "Tompkin jest told me 'bout that forgery!"
"Yes?"
"I jest recollected about that feller-the one who calls himself Taylor. Only his brand ain't Taylor. It's Harry Hoplin!"
"You mean it?"
"Brand my prairie dog, I sure never was more certain. Listen, folks. That sneakin' critter was wanted back in Texas fer forgery!"
CHAPTER 5
A WILD CHASE
WITHOUT a moment's hesitation Tom went to telephone Harlan Ames. The security chief should be apprised of the fact that Taylor's real name was Hoplin and that he was a wanted forger! But Tom learned that Ames was not at home-he was out searching for the suspect.
Tom sat thinking for several moments. As soon as the thief realized that the local police were looking for him, he probably would skip out. "If he could only be caught before he learns the authorities are after him-" Tom reflected.
Jumping up suddenly from the telephone chair, he rushed back to the living room and told the others his thoughts. "I believe that the more people who join the search, the better," he concluded. "Come on, Bud. Let's go on a hunt for Hoplin ourselves!"
"I'll go too," Mr. Swift decided, and went fof his car keys.
41
42 THE CAVES OF NUCLEAR FIRE
Chow, who said he had to meet a friend from Texas at the train, wished them all luck and went on his way.
"You can't leave me out of this hunt," said Craig, starting after the others.
"Wait!" Mrs. Swift protested. "You'd better stay here."
"Why?" asked the flier. "Doc Simpson told me I was all right."
"I realize that," she replied, "but he also advised you not to exert yourself for another week."
Craig, disappointed, watched Mr. Swift, Bud, and Tom hurry from the house. After making a thorough investigation of the grounds, they climbed into Mr. Swift's sedan. The car had the latest short-wave equipment, with the special Enterprises' band. A high-powered searchlight was mounted on its roof.
As Tom took the wheel, Bud said, "Where do we start?"
Mr. Swift surmised that all the surrounding areas, except the locale of the Swift home, would be covered by the police. "So our best bet," he said, "would be to search right here, close to home."
"Yes," Tom nodded. "I have an idea those men are watching every move we make. Let's smoke 'em out!"
They cruised around the roads near the house,
A WILD CHASE 43
the research center, and the Swift Construction Company. Tom operated the swivel searchlight as the eyes of the others alertly followed the beam which pierced the darkness. Nothing suspicious was revealed. Minutes stretched into an hour. Soon the group found themselves back in the vicinity of the house.
"One more road," said Tom as he turned the car into a woods lane. "We'll drive through here," he announced. "If we don't find anybody, I suggest we go back to the house and check to see if there's any report from the police."
"Good idea," said Mr. Swift. "We've covered about every inch of our area."
Bud, in the rear seat, slumped back for a moment to rest. Then, suddenly, he sat upright. "Tom!" he called. "Swing that light around to nine o'clock low!"
Tom spun the narrow shaft of light to the left side of the lane and angled it downward. Its glare revealed a man running across a small clearing. No longer hidden by the night, he bolted toward a heavy cluster of trees and brush.
"He looks like Hoplin!" Tom cried out.
Turning off the ignition, he leaped from the car, with Bud following. They lost sight of the suspect when he got out of range of the searchlight, but they could hear him crashing through the thickets just ahead.
44 THE CAVES OF NUCLEAR FIRE
The boys whipped out flashlights and raced after the man. The woods became more dense the farther they went.
Bud tripped and tumbled down a shallow ravine. Stunned but unhurt, he scrambled to his feet. Tom stopped to make sure that his friend was all right.
"Never mind me!" Bud shouted. "Keep after that fellow!"
But the slight delay had been costly. Now the flashlights no longer picked up the fugitive. The boys forged ahead for some distance, but Hoplin had disappeared.
"It's no use looking any more," Tom admitted in disgust. "I'm afraid that we lost this round, Bud. But it proves one thing. Hoplin is still in the neighborhood."
Fatigued by the wild chase, he and Bud trudged out of the woods and back toward the car. Reaching it, they were startled to find Mr. Swift gone.
"Dad!" Tom shouted. "Dad, where are you?"
"Look!" Bud exclaimed. "Someone has wrecked the car's radio."
Tom examined the special transmitting and receiving set Mr. Swift had installed. All the tubes were smashed. Bud, noticing that the hood of the vehicle was not fully closed, raised it and peered at the engine connections. The distributor cap was missing.
A WILD CHASE 45
"Dad was attacked!" Tom cried out in a choked voice.
Worried, Bud began sweeping the ground with his flashlight. "I see footprints!"
Tom examined them. "There was a struggle involving three men!" he said excitedly. "Dad must have been trying to fight off two thugs!"
The boys followed the footprints for a short distance around a bend. Then the three sets of tracks became only two.
"Your dad must have been carried from here," Bud said.
He and Tom continued to follow the tracks. They led along the road a short distance, then were replaced by the prints of automobile tires.
"The kidnapers got away by car! No telling how far they'll take Dad!"
"Maybe we'd better get back to your house and report this," Bud suggested.
"Yes," said Tom. "But it's a good two miles. Suppose you go and I'll try to fix the radio. 1 may be able to get a message through to Enterprises."
As they reached Mr. Swift's car and Bud was about to start off, an automobile came around the bend. In the glare of its headlights the boys froze. Was the driver someone friendly who would give Bud a lift? Or was he an enemy bent on attacking them?
Tom and Bud jumped well to the side of the
46 THE CAVES OF NUCLEAR FIRE
road and waited tensely. A few moments later the car stopped. Its lone occupant leaned out and grinned at them.
"Harlan Ames!" Bud exclaimed.
"You two look as if you thought I was Taylor or Cameron," the security chief said. "Craig told me you were searching for them."
Tom quickly told him all that had happened, including the fact that Taylor was really Harry Hoplin, a wanted forger.
Ames frowned. "It was a brazen move on the part of your enemies," he commented. "But a big mistake! Now we'll turn the whole countryside upside down, if need be, to find your father."
"Did you get any clue as to where the kidnapers are living?" Tom asked.
"No. Enterprises and the police have had every available man out. We checked hotels, motels, and trailer camps within a radius of fifteen miles. And road blocks have been set up on all highways leading out of Shopton. There hasn't been a sign of either Hoplin or Cameron."
Bud mentioned that he was just about to set off for the Swift home. "We thought Tom's father might have returned or at least sent some message," he said.
"I can tell you that the answer to that is no," said Ames. "I've just come from the Swifts'." The security chief went on to say that he could not figure out why Mr. Swift had been kidnaped.
A WILD CHASE 47
Tom had an answer. "They're using him as a hostage to prevent my going to Africa."
"Then you don't think they'll harm him?" Bud asked anxiously. "I suppose there would be no point in that."
Tom was not so sure of this. "They may try to force Dad to tell them of our plans. But he'd never do that, of course."
As Bud opened the trunk compartment of Mr. Swift's car to look for tools and spare tubes for the radio, Tom glanced at his wrist watch. "It has been almost an hour since we left Dad," he thought. Suddenly his eyes widened with excitement. "Wrist watch!" he exclaimed. "How could I forget?"
"Forget what?" asked Bud.
"Dad's wrist watch," Tom replied. "The one with the built-in miniature transmitter. It can broadcast a message for a radius of several miles. Unless Dad is beyond its range, he'll try to send a message on Enterprises' wave band."
"Are you certain your father was wearing the watch?" Ames questioned.
"He's never without it," Tom replied.
Ames and Bud instantly knew what was going through Tom's mind: that even though Mr. Swift was being held, he might take a chance on broadcasting a message. They must start as soon as possible to listen for one!
"We'll do a triangulation," said Tom. "Har-
48 THE CAVES OF NUCLEAR FIRE
Ian, will you drive to our house? Notify the police and alert Sandy and Craig. They can get one direction on our home set. Then phone Billing at Enterprises to get a fix from there. Bud and I will try to repair this radio. If a message does come through, we'll get the direction here, and then all meet at my house to work out the spot where Dad is being held."
"That's the best thing to do," Ames agreed. "I'll be off."
The two boys replaced the smashed tubes and soon had the radio working. They listened intently, but there was only a low hum. Nevertheless, Tom kept his eyes glued to the compass connected to the direction finder, ready to operate the finder instantly, should an incoming message be a short one.
Ten minutes went by! Twenty minutes! Not a sound came over the short wave. The boys did not dare talk, for fear of missing any word that might come. Thirty minutes passed!
Suddenly Tom and Bud jumped. A strange voice crackled over the radio.
"You'll be here a long time, Mr. Swift! We won't tolerate any interference either from you or your son! The plans of our group will be carried out and the Swifts are not going to stop us!"
CHAPTER 6
QUESTIONED BY POLICE
HOLDING their breaths, Tom and Bud listened intently as the strange voice on the Swift shortwave band concluded:
"One more thing, Mr. Swift. Don't count on having your son or others rescue you. The life of any man who tries it will be in danger!" After that there was silence.
Tom and Bud, sitting tensely in the car, kept hoping that Mr. Swift himself would speak and give a clue to his whereabouts. On previous occasions father and son had communicated in code without their listeners being aware of the real meaning of the conversation.
But after a few moments of complete silence Tom spoke. "Bud, this is worse than I thought. 1 believe one of us should go back to the house and find out what Dilling, Sandy, and Craig learned from their direction finders. We must
49
50 THE CAVES OF NUCLEAR FIRE
pinpoint where Dad is and go after him right away. I got a bearing of about twenty degrees. That voice was coming from northeast of Shop-ton."
Tom decided that perhaps he should go, since his mother probably was very much worried. "I'd better try to reassure her," he said, and started off on a short cut through the woods.
Tom covered the two miles to his house in record time. As he hurried through the front door, his mother and Craig greeted him. Mrs. Swift threw her arms about her son.
"Oh, Tom, isn't this dreadful!" she cried. "And now to make matters worse, Sandy and Phyl have gone off!"
"Gone!" Tom exclaimed in amazement.
"Yes," his mother answered. "We were all listening to the short wave when suddenly that dreadful man spoke. Did you hear him too?"
Tom nodded, then mentioned his theory about the kidnapers not harming his father.
"Oh, I hope you're right, Tom," Mrs. Swift replied. "But you can never trust people like that. Your father is so daring-just like you. He might anger his captors."
Her son smiled. "Try not to worry, Mother. When Dilling gets here with his findings for the triangulation, we'll pinpoint the spot where Dad is being held and rescue him."
QUESTIONED BY POLICE 51
Mrs. Swift looked slightly relieved, but a moment later she mentioned the girls again. "I do wish they hadn't started out alone."
"Why did they go?" Tom asked.
His mother said that Sandy, knowing Tom had no means of getting to the house, had hoped to bring him back quickly. She wanted to begin as soon as possible using the short-wave findings to plot the location where her father was being held prisoner. So she had gone with Phyl to pick up Tom.
"But they've been gone long enough to have driven there and back twice," Mrs. Swift added nervously.
Tom had to admit that his mother's alarm was justified. Fear seized him that the girls, as well as Mr. Swift, might be in the hands of the kidnapers!
"I'll go after them at once!" Tom decided. He dashed from the house and hopped into his convertible.
Tom did not know which way to go to look for the girls, but he sped up one road and down another until he spotted Sandy's car. As he came alongside, she stopped.
"Tom!" his sister cried out. "We've been looking everywhere for you!"
"We were worried," said Phyl.
Sandy's brother gave a grin of relief. "You two
52 THE CAVES OF NUCLEAR FIRE
girls gave us all an awful scare. Do you realize that you've been gone from home almost an hour?"
"No," said Sandy. "We were so busy hunting for you that we didn't even turn on the radio and hear about everyone being ordered off the roads."
"What's that?" Tom asked, puzzled.
"So you didn't hear it either?" his sister replied, and told him about a motorcycle policeman who had stopped the girls a few minutes before and told them the police were clearing the roads because they were hunting some criminals.
"That's strange," said Tom. "Mother didn't say anything about it, or Craig either. Both of them had the radio tuned in to the local station."
By special arrangement Tom's car contained the local police short-wave band. He now tuned the radio to it, flicked on his microphone, and asked headquarters about motorists being ordered off the roads. To his complete amazement, the sergeant on duty said no such orders had gone out.
At once Tom relayed the story which his sister had told him. "Who was the officer who stopped them?" he asked.
"I'll look at my records," the sergeant replied. "Hold on!"
Within ten seconds he was back with the information that for the past half hour no motor-
QUESTIONED BY POLICE 53
cycle policeman had been covering Old Pine Road where Sandy and Phyl had been stopped.
Tom whistled. "If that's true," he said, "then that man was a fake! Thank you for checking, sergeant."
Turning off the radio, he asked the girls for a description of the impostor. Listening, he nodded grimly. "I'll bet that so-called cop was Cameron!"
CHAPTER 7
MYSTERIOUS ESCAPE
AS THE full import of the incident with the policeman dawned upon Phyl Newton, she wailed, "I've done a dreadful thing! Tom, I told that man everything about your father's kidnap-ing!"
Tom was worried but tried to console Phyl. "That phony cop was probably Hoplin or Cameron or one of their gang, and knows the whole story anyway."
"But I told him about your father's wrist watch!" Phyl explained. "Now they'll take it away from him, so he can't possibly send you a message telling where he is."
Both Sandy and Tom endeavored to comfort Phyl by saying that Mr. Swift probably was gagged, so he could not send a message. It was fortunate that he had been able to turn on the transmitter and have one of his abductors unknowingly broadcast as much as he had.
"But there's no time to lose!" said Tom.
54
MYSTERIOUS ESCAPE 55
"You girls follow me home. I'm sure that Billing will be there with a fix from Enterprises' direction finder on the place where Dad is being held. The thing for us to do now is to get there and rescue him before that phony cop and his pals have a chance to move him!"
Quickly he turned his car in the road and drove off. Sandy followed at a good clip. When they reached the Swifts' residence they found Billing there, also Bud Barclay and Ames. The security chief, feeling that Bud might be in danger if left alone, had gone to pick him up and pushed Mr. Swift's car home.
"So that's why I couldn't find it!" said Sandy, then told her story.
Ames frowned and remarked, "Those men are getting desperate!"
Tom went for a map of the local area and laid it on a table. Then the three sets of directional lines, which had been made for the triangula-tion, were compared. They converged on a position about five miles northeast of Shopton, not far from Old Pine Road.
"It's in a woods," said Tom. "I suggest that Bud, Billing, and I head for the spot. Ames, contact the police and have your men and theirs surround the area in case Bad's kidnapers make a run for it."
"It probably will be dangerous for you," Ames warned.
56 THE CAVES OF NUCLEAR FIRE
"I know," said Tom, "and maybe the others should remain here. But it's my father those kidnapers are holding. There's no talking me out of going unless Mother-"
He turned to Mrs. Swift, who was as pale as a ghost. "Son," she said, "I'm dreadfully worried, of course. But I know how you feel. Go and rescue Dad!"
"And count me in!" said Bud.
As plans were made, Ames said, "You won't dare search with lights or you'll be spotted. I suggest that you start at dawn. That's not far off."
As the first streaks of light came over the horizon, Tom and his two companions drove off. When they reached the woods where they suspected the hide-out was, they spoke to a policeman patroling the road, then went on. The road became a narrow, winding trail. When this dwindled to a footpath, Tom stopped the car.
"We're less than quarter of a mile from the fix," he stated. "From this point we'll travel on foot."
Tom led the way, his eyes straining for signs of a camp or cabin. A few minutes later he halted abruptly. Just ahead, nestled in a cluster of pine trees, was a log cabin. This could be the spot they sought! Tom gestured to his companions to crouch down.
MYSTERIOUS ESCAPE 57
"That building," he said, pointing, "is in the position our fix shows. Let's get as close to it as we can without making any noise."
The young scientist crawled, Indian fashion, in the direction of the cabin. Bud and Billing followed. The three pushed their way quietly to the edge of a clearing which fronted the log structure, and listened. Everything was still.
"Shall we rush the place?" Bud whispered.
"We'd get caught if there are guards watching from the woods," Billing murmured.
"Right," Tom agreed. "Let's try smoking out anybody who's watching for us."
"How?" the radio chief asked.
Tom suggested that they each find a small rock and heave it, Billing to the left, Bud to the right, and Tom straight at the cabin. After locating round, good-sized stones and tossing them, the trio waited alertly, but there was no response to their strategy.
"Guess there's no one inside except possibly your father," said Bud. "And he's no doubt tied up. If there were anyone else, he'd have come out. Let's investigate!"
Although Tom was fearful that his father had been moved, he led the way to the cabin and peered through a window. His heart gave an exultant leap. Seated in a chair in the center of the room, his back to the outside, was Mr. Swift!
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THE CAVES OF NUCLEAR FIRE
MYSTERIOUS ESCAPE
59
He was bound to the chair and still wore his sports jacket and his hat which was tilted on the back of his head.
"Dad!" Tom cried out, making a beeline for the door.
The others followed, but as they reached the door, two objects whizzed through the air from the woods and fell almost directly at their feet. Tom recognized the objects as bombs and started to yell, "Run!"
But the words died in his throat. There was a terrific explosion. Tom, Bud, and Billing were thrown violently to the ground and blacked out!
Tom, the first to revive minutes later, saw a
frightening sight. His friends lay unconscious on the ground and flames from burning grass were licking their way toward the trio. The cabin was already ablaze.
With superhuman effort Tom got to his feet and dragged his companions away from the danger. Then he staggered into the cabin to rescue his father.
"Dad! I'm here!" he shouted, then stopped short.
The figure strapped to the chair was a dummy!
"But the hat and coat are Dad's," he thought, puzzled. "Why were they left here? To trap us?"
There was a sudden blast of intense heat and

60 THE CAVES OF NUCLEAR FIRE
flickering light. Quickly Tom glanced around the room. One wall was a glaring sheet of flame.
Tom hoisted the dummy to his shoulder. Using it as a shield against the blistering heat, he hurried out of the building, made a flying leap over the crackling strip of grass, and rushed to his friends. They were just reviving.
"Wh-what happened?" stammered Billing.
Tom explained. "A hand grenade and an incendiary bomb were thrown at us."
"Who threw them?" Bud asked.
"I wish I knew," said Tom grimly. "And now, let's put out this fire."
"With what?" Billing asked.
Tom reached into a hidden recess of his belt. From it he withdrew a handful of capsules and handed several of them to his companions.
"What are these?" asked Billing.
"Extinguisher capsules," replied Bud. "Tom invented them."
"Start throwing the capsules into the fire," Tom ordered. "Spread them around."
As the tiny extinguishers landed in the flames, each exploded in a thick, white cloud of smoke. Miraculously the fierce flames began to vanish. Soon they had all been quenched.
"These capsules are remarkable," said Billing, as the trio started back toward the car, carrying the dummy with them.
Suddenly Bud stretched and heaved a great
MYSTERIOUS ESCAPE 61
sigh. "I'm sure glad to be alive," he remarked. "That grenade was meant to stun or kill us, then our bodies were supposed to burn to cover any evidence."
The others agreed and Billing added, "I suppose whoever threw those bombs figured we were done for and hurried off. Well, I hope our security men or the police have captured him!"
"This whole adventure netted us nothing but blisters and bruises," Tom said ruefully. "We don't know any more about where Dad is than we did before."
Glumly, he and his friends plodded back to the automobile. They got in and Bud took the wheel. Tom sat beside him with the dummy on his lap. After a while he said:
"Wonder if there could be some other significance to this dummy. I'm going to investigate it."
Billing looked dubious. "There may be a bomb inside!" he cautioned.
Tom said he doubted it. Methodically he began to examine the clothes on the stuffed figure. There was nothing in the coat. Next, he lifted the hatband. Still nothing. Turning the hat over, Tom pulled down the inside band. A scrap of paper fell out.
"This may be important," he said hopefully.
"What is it?" Bud asked.
Tom gazed at the small white scrap he had
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found. On it was scribbled a line of numbers. "This looks like a numeral code Dad and I worked out," he replied. "Yes, it is!"
Quickly Tom decoded the message. "It is from Dad! He escaped from his captors!"
Bud began to whistle happily, then stopped to remark, "That's a load off my mind. I can't wait to hear what your father has to say."
When they reached the end of the woods road, they were stopped by a police officer. Quickly Tom told him the good news. "I'll send in a report at once," the policeman said. "We'll close in on that bomb thrower. He hasn't left the woods."
Bud drove on and a short time later brought the car to a halt in front of the Swift home. Tom leaped out and bounded into the house.
"Hello!" he shouted.
Sandy and Craig emerged from the living room, their faces expectant. "Any luck in finding your father?" Craig asked eagerly.
Tom's feeling of jubilation ebbed away. "You mean," he groaned, "that Dad hasn't shown up here? And you haven't even heard from him?"
"No," Sandy answered. She looked puzzled.
Tom gazed at the fragment of paper still clutched in his hand. "Dad escaped," he said, "but I'm afraid that he has been captured again!"
CHAPTER 8
AN UNEXPECTED PLUNGE
A PERIOD of shocked silence followed Tom's words. Mr. Swift had escaped, only to be recaptured!
"Oh, we must do something to stop those men!" Tom's mother said fearfully.
Craig stepped forward. "Let's not lose heart," he said. "Your husband is a clever man. He'll outwit those kidnapers somehow."
But as the morning dragged on, with no word from Mr. Swift, hope faded. Three radios were kept on: the Enterprises' wave band, the local station, and the police band. Only routine broadcasts were heard.
Tom telephoned Harlan Ames at the plant every hour for a progress report. So far, the organized search had proved fruitless.
Mrs. Swift and the girls prepared meals but they were hardly touched. Sandy and Phyl merely picked at their food between glances out
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the window. To please his mother, Tom forced himself to eat a little, then went to sit near one of the radios.
"I can't stand this inactivity any longer," he declared when midafternoon came and there still was no word. "Bud, let's go over to the plant and work."
For the next few hours the two boys concentrated on transportation problems in connection with their proposed expedition. But not once did they give up the hopeful thought that Mr. Swift would break away from his abductors.
Finally, unable to concentrate on work, they returned to the Swift home. Again there was a pretense of eating, then more waiting. No one went to bed, but from sheer nervous exhaustion the various members of the party dozed off in their chairs.
About midnight, as Tom was desperately fighting sleep, Sandy shook him violently. "Tom!" she said in a low voice. "Tom!"
He snapped awake. "What is it?"
"Someone's at the back door! The alarm didn't go off. One of those kidnapers must have stolen Dad's keys and is trying to get in!"
Her brother awoke Bud and told him. Stepping lightly, the boys walked to the rear of the house. Sandy was right-the lock was being tampered with!
Tom decided to use the element of surprise.
AN UNEXPECTED PLUNGE 65
Placing one hand on the knob of the door, he eased off the lock with the other. Then, with lightning speed, he pulled the door open to reveal a startled figure.
"Dad!" exclaimed Tom.
"Hello, son," Mr. Swift responded with a quizzical grin and walked in. "In the dark I couldn't tell one key from another."
When Tom recovered from his surprise, he asked, "Where? How? Dad, you got away!"
The commotion roused the household. Everyone rushed to greet the elder inventor. Mrs. Swift and Sandy hugged him. The others wrung his hand fervently.
The welcoming soon developed into a chaotic confusion of questions and laughter, in the midst of which Tom reported to Ames and the police that Mr. Swift had returned.
"Great!" Ames exclaimed. "I'm certainly glad your father got away from that gang. Congratulate him for me!"
The security chief told Tom that the bomb thrower had been captured as he fled from the woods. The man, who declared this was his first offense, had talked freely. "But we suspect that the names he gave us of the principals involved in the kidnaping are more aliases of Hoplin and Cameron," Ames said. "This fellow Calder declares he doesn't know where they live. But we're still looking for them."
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When Tom went to the living room where the others had gathered, his father, fatigued by his ordeal, was just lowering himself into a comfortable chair.
"Sandy, bring me a bite of supper," he saia, "and I'll tell all of you what happened. I haven't eaten since last night."
As she hurried off, Tom said, "You certainly had us worried. We thought you had been captured a second time."
"Then you did find the log cabin where I was being held," said Mr. Swift.
"Yes," Tom responded, "and also the coded message you hid in the dummy."
"Oh, yes, the dummy." The elder inventor smiled. "I'm surprised that little deception worked so well." When Sandy came back with a tray of food, he continued his story. "After I escaped, I watched the guard from among the trees. He looked through the window several times but didn't know he was gazing at a figure I'd made out of a large sack stuffed with old newspaper I found in the cabin."
"Who kidnaped you?" Craig asked.
"Two members of a gang headed by Hoplin and Cameron, who were already at the cabin. When Tom and Bud dashed off in pursuit of that man in the woods, two others were hiding nearby. I was taken completely by surprise."
AN UNEXPECTED PLUNGE 67
"How did you escape?" Tom put in.
"While I was being held in the cabin," related Mr. Swift, "one of the gang dressed up in a stolen uniform to pose as a policeman. He was told to send home any snoopers that came along Old Pine Road. The trail they were using came out there."
"He's the phony officer Phyl and I met!" Sandy exclaimed, and told her father of the incident.
"Thanks to you two," Mr. Swift said, smiling, "I was given an opportunity to escape."
"Who? Phyl and I?" Tom's pretty sister asked in amazement.
"Yes. The fake policeman you met sent some kind of a message over a walkie-talkie system they had. I heard them say that they'd better get away from the cabin fast, but they wouldn't dare take me along."
"What happened then?" Tom prodded as his father paused.
"They decided to tie me to the heavy chair and leave me in the cabin," Mr. Swift explained. "Then, if you came to rescue me, they'd trap you too. I didn't hear the instructions they gave the guard outside, but they certainly weren't concerned about the possibility of his being captured."
Mr. Swift said he had been unaware that his wrist-watch transmitter was turned on for a few
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seconds. He himself had been bound and gagged. Directly after the threat which Tom had heard, Mr. Swift had been thrown on the floor and the transmitter had smashed.
"I found this out later when I tried to get in touch with you," Mr. Swift remarked ruefully. "I didn't have much hope that you would pinpoint the cabin, but I left the note in case you did."
"Tell us how you got away," pleaded Sandy, her eyes wide with excitement.
"While they were tying me up," her father resumed, "I employed an old trick taught me by your grandfather. I took a deep breath and tensed all my muscles. When the men finished binding me, I simply relaxed. This slackens the rope enough to let you work free."
"They must have been amateurs," Craig spoke up, smiling.
"Lucky for me they were!" commented Mr. Swift. "After I got loose, I set up the dummy. Then I climbed out a back window.
"Not knowing where the others were-and they were armed-I decided to stay in a cave I knew about until dark. It's on the far side of the woods and across the road at the back of a farm. Then I did a foolish thing."
"Foolish?" Mrs. Swift queried.
"Yes." Her husband grinned boyishly. "I fell asleep. When I awoke, I banged the back of my head on the top of the cave and blacked out for
AN UNEXPECTED PLUNGE 69
a while. Between feeling groggy and being hungry, I didn't make very good time getting home. Sandy, these chicken sandwiches are mighty good."
"I'll make some for everybody," Phyl offered, and went to the kitchen.
As they munched the chicken sandwiches, their spirits rose. With the safe return of Mr. Swift, plans could now be resumed for the African expedition.
"We can't risk losing a single second," Tom pointed out. "Now that Dad's no longer a hostage, Hoplin and Cameron may plan something else to keep us from heading for Africa. We must get underway before they can create more mischief."
The following day Tom and the other members of the expedition, including Sterling, Hanson, and two crewmen, reported to the medical department for special inoculations. When il came time for Chow to be jabbed, he yelled:
"Ow! Brand my cow pony's sore hoofs, when: in tarnation did you rake up a crowbar fer a needle, Doc?"
"Well, I tell you, Chow," replied Dr. Simpson with a wink at Tom and Bud, "I keep this for specially tough hides."
The boys roared with laughter and Chow finally grinned as a patch was put over the prick. in his skin. He left the room immediatelv. how-
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ever, to attend to supplies for the galley of the Sky Queen.
Tom turned to Bud. "I want to give the Terra-sphere a final road test," the young inventor said. "How about you taking over?"
"Okay, pal. I'll put the caterpillars through their paces."
Bud went to the hangar where the Terra-sphere was housed. The crane and sphere had been detached. Bud climbed into the driver's cabin and took the vehicle outside.
For fifteen minutes Bud tried the motor at various speeds and tested the treads backward, forward, and turning. He beamed in satisfaction.
"Tom sure knows how to put machinery together to get maximum performance," Bud said to himself. "I'll run down to the edge of that pond, then put Terry away." Bud was referring to the deep, artificial testing pond on Swift Enterprises grounds.
The futuristic tank zoomed along at fifty miles an hour. Bud, instead of braking it, decided to let the vehicle coast the last ten feet. A few feet from the pond it was on the verge of stopping, when, without warning, the Terrasphere picked up speed and raced forward. Quickly Bud jammed on the brake but he was too late.
The tank and its occupant plummeted to the bottom of the pond!
With lightning speed Bud shoved back the

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window and climbed through. Holding his breath, he swam to the surface. Moments later, he was standing on the bank ruefully trying to figure out what had happened.
A few seconds later several workmen joined him and Tom was summoned.
"Golly, I'm sorry," Bud said to his friend. "I can't understand what went wrong. And besides, Terry's probably ruined and our trip will be delayed."
After hearing the full story, Tom put an arm around Bud's shoulder. Smiling, he said, "I'll take all the blame. There's an automatic electric cut-in device on the Terrasphere for emergency use in case the main power is cut off. It should have been disconnected but apparently wasn't."
Tom called for a small wrecking crew and the sunken vehicle was brought to the surface. Upon inspection it was found that the young inventor's surmise had been right. The device was now disconnected. To Bud's relief, the motor was in running order, but water spewed from the exhaust and every seam and crevice of the vehicle. It was taken to the drying room of the paint shop and in a short time the Terrasphere was in perfect working condition again.
Late that afternoon Tom, Bud, and Craig gathered in Tom's office to talk over plans for leaving.
"How soon will it be?" Craig asked.
AN UNEXPECTED PLUNGE 73
"In a couple of days," Tom replied. "We have to wait for proper clearances for Sterling, Hanson, and the two crewmen."
Tom's office phone buzzed. He picked up the receiver and after a moment said, "Bring it in, please, Miss Trent."
The secretary opened the door and handed him a cablegram. As Tom quickly scanned the message, his face turned pale.
Bud noticed his friend's worried expression. "What is it?" he asked.
"This cable," murmured Tom, "is from the authorities in the Belgian Congo."
"Bad news?" Craig asked quickly.
"It's tragic!" Tom replied. "We're being refused the right to conduct an expedition into that country!"
CHAPTER 9
FAREWELL SURPRISE
TOM and his companions were stunned by the message in the cablegram. The planning, the effort, the time-all seemed hopelessly lost.
"Why didn't those people in Africa tell us this before?" growled Bud.
Tom continued to stare at the cablegram. Presently he said, "I'm beginning to wonder if perhaps there isn't something fishy about this deal. It seems to me that such a message would have been sent to our government first and relayed to me."
"I believe you're right," said Craig.
"Then you mean," Bud put in, "that maybe Hoplin or Cameron are in cahoots with some official over there and sold him the idea of sending this cable?"
"Could be," Tom replied. "In any case, I want to talk to Dad about this before I make another move."
The upshot of the conference between father
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FAREWELL SURPRISE 75
and son was that Mr. Swift agreed the cable should be investigated and set the wheels in motion to do this. Hours later he summoned his son to their private office.
"Tom," he said, "you can proceed with your trip as planned. That cablegram was a fraud. The Belgian Congo officials know of no order, such as you received, being issued by their government."
"What a relief!" said Tom, grinning with anticipation of carrying out his plans for the African expedition.
"In fact," Mr. Swift continued, "they're eager to have you come. However, they sent a warning about some natives causing trouble in the area where the Mabawiki tribe is."
Tom smiled. "With luck and a little diplomacy, our group ought to be able to make friends with the natives."
"You're right in that respect," said Tom's father, "but sometimes it's difficult to win the friendship of primitive people. They instinctively distrust strangers. Be certain to use every precaution. Supply yourself and your crew with adequate protection against possible attacks."
"I will," Tom promised.
He immediately sent word to the other members of the expedition. There was a sigh of relief from all of them and a whoop of excitement from Bud. "I've got jungle jitters already," he joked.
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As an extra safety precaution Tom decided to take one of the Swift Construction Company's regular small tanks to use in the jungle. It would be impervious to attack. Also, being air conditioned, it would make safaris pleasanter when the temperature rose to 120 degrees.
Last-minute preparations went forward at a feverish pace and finally the explorers were ready to depart. "We leave at five tomorrow morning," Tom announced to his friends.
That evening Sandy and Phyl gave a surprise farewell party for Tom, Bud, and Craig. Twenty young people were there and the Swifts' living room was alive with excited chatter.
"That's quite a place you're going to," said a youth named Will Brown. "I hear one of the tribal kings weighs two hundred and fifty pounds and has as many wives!"
"Stay away from him, Tom," ordered blond Jane Denton. "He may try to give you one of them!"
"There's an old chief in that country who has nothing the matter with him," said Will, "but he's too sacred to touch the dirty old ground, so he's carried everywhere he goes-from bed to bath to table."
"Wow! What a life!" Bud exclaimed. "I think I'll hunt up that old fellow and offer to pinch-hit for a while."
FAREWELL SURPRISE 77
At the height of the gaiety, supper was announced by Sandy and the guests filed into the dining room where refreshments, buffet style, were awaiting them. As the young people heaped their plates with food, Bud remarked with a grin:
"This is swell! We ought to go to Africa every day!" Then his expression turned to one of complete astonishment. Pointing to the hall doorway, he exclaimed, "Ugh! Who let that in?"
Standing there was a grotesque figure. Upon second glance everyone recognized him as Chow who had been asked to help with refreshments. Now he was attired in his own idea of what a well-dressed African native would wear. He had colored his skin with brown make-up to the shade of a tribesman's. The headdress he wore was adorned with long feathers that drooped in his face like banana peelings.
A short, red, sarong-type garment reached almost to his knees. Because the make-up had been applied sparsely, his legs looked like two badly rusted rain pipes.
Howls of laughter issued from the young people but Chow had not meant his entrance to be at all humorous. Loud grumbling could be heard from behind the cluster of feathers. Indignant, the Texan went to the kitchen, but returned in a few minutes with a huge tray, on which was a steaming mass of green plants.
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"What's that?" Tom asked.
"I bought these here at one o' them tropical fish an' plant places," the cook replied. "An' brand my burnin' sagebrush, it's good!"
To avoid hurting Chow's feelings again, everyone took a portion of his tropical concoction. Bud was first to put his fork in the greens and swallow a small mouthful. From his pained expression one would have thought that he had swallowed the fork instead!
"Are you sure it wasn't the wrappings you cooked," Bud blurted out, "instead of what came in them?"
Tom took a deep breath, closed his eyes, and placed some of the unusual food in his mouth. "It tastes like decayed spinach with horse-radish sauce," he murmured to Bud.
"How do you like it?" Chow asked, grinning broadly. Then, without waiting for an answer, he added, "I made this here dish up myself. But I got me a whole book full o' jungle receipts I want to try out in Africa."
Tom made no response to Chow's comment, deciding to deal with this threat when the time came!
The party broke up at midnight and everyone in the Swift household went to bed immediately to catch a few hours' sleep. But they all were on hand at the Enterprises' airstrip for the take-off, and so was Phyl Newton.
FAREWELL SURPRISE 79
"Please be careful, Tom," Phyl begged as the giant Flying Lab arose from its underground hangar.
Tom put his arm around her shoulder. "I'll be back soon," he assured Phyl.
Sandy and Bud, meanwhile, exchanged farewells. Tom kissed his mother and Sandy, and gave his father a firm handshake. Then he climbed into the mammoth plane and went to the pilot's seat. Bud, as copilot, sat next to him, and Craig just behind.
Checkoffs were made with military precision and soon the giant plane was ready to take off. Tom had been pleased that eleventh-hour clearances had made it possible for Doc Simpson to accompany the expedition. Besides acting as ship's doctor, the youthful physician also wanted to do some research on cures accomplished by African medicine men.
As Tom checked his instruments, his thoughts turned to Hoplin and Cameron. No word had been heard from them since the kidnaping. Where were they now? If they had been responsible for the cable which had failed to keep Tom home, were they preparing a trap in Africa?
"It will pay us to keep our eyes open," Tom decided, as he touched a switch and the thundering roar of the jet lifters responded. Amid waves of farewell from the members of the expedition and the group on the runway, the giant craft rose
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straight into the air, slowly at first, then rapidly picked up speed.
Altitude attained, Tom applied forward thrust and pulled back on the yoke. The Sky Queen shot ahead and zoomed off into the blue.
"This is a remarkable ship!" Craig said, still marveling at the facile operation of Tom's Flying Lab, as Chow brought in breakfast.
Soon the East Coast was left far behind, with the green water changing to blue. The craft hummed along at twelve hundred miles an hour while the boys enjoyed the ham and eggs.
"Tell us something about the language of the Congo," Bud asked Craig.
The navigator smiled. "It's hard to believe but there are thirty-eight different native languages -and two hundred tribes in that area. But the population is small compared to the territory. It's the size of the United States east of the Mississippi River, but has only one-fourteenth the number of people."
"That leaves more room for the wild animals," Bud remarked. "Anybody ever take a census of them?"
Craig laughed. "There are plenty. But I guess the white people who go to the Congo are too busy exploiting the natural resources to worry about that. The country is fabulously rich in uranium and copper, and it produces seventy per cent of the world's industrial diamonds."
FAREWELL SURPRISE 81
"Hm," said Bud with a wink at Craig. "What about the fancy ones? Could be that Tom might buy one cheap and put it away for a certain young lady back in Shopton!"
Tom smiled, then suddenly he frowned and leaped forward in his seat.
"What's wrong?" Craig asked.
"We're losing power on all engines!" Tom said, and worked the throttles frantically.
Bud noticed that the RPM showed an alarming decrease.
Tom commanded, "Cut in the fuel-pump boosters, Bud!"
His friend threw the switch. No change! Tom scanned the instruments again. "Altitude's going -fast!" he declared. "If we don't get power back in a couple of minutes, we'll have to ditch!"
CHAPTER 10
SIX HOURS LOST
AS THE Sky Queen continued to sink earthward, Tom turned on the jet lifters to compensate for the loss of altitude. But he would not dare risk limping along for thousands of miles.
Frantically, the young inventor scrutinized his instruments for some sign of the cause of the mechanical failure. Nothing new showed up.
To ease the strain on the lifters, Tom put the huge craft into a shallow, gliding attitude. But the power for forward cruising speed was almost nil.
"We're down to fifteen thousand feet!" Bud cried out. "How low are we going?"
Tom did not reply. He worked the throttles again, but the rate of forward thrust was decreasing more and more rapidly. Suddenly Bud, glancing out the window, cried out:
"Tom, it looks as if we've picked up ice in our engine air inlets!"
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SIX HOURS LOST 83
The pilot peered at the gaping orifices near the root of the wings. "You're right!" he exclaimed. "Ice is choking off the air to our engines!"
"Ice!" Craig exclaimed. "The sky is clearf Where did all that moisture come from?"
Tom clapped a hand to his forehead. "I must have been daydreaming!" he said. "A little while ago I pulled the Sky Queen up through a layer of cirro-stratus clouds. But the thought of moisture freezing on the inlets never entered my mind!"
"I'll switch on the inlet deicers!" Bud offered.
He dashed to the flight engineer's control panel, situated just to the rear of Craig's seat, and threw a series of switches. Nothing happened!
"The ice is so thick," Bud yelled, "it won't break off!"
"We're down to ten thousand feet!" declared Craig, as he caught a glimpse of the altimeter.
Setting his jaw, Tom cut off the jet lifters and shoved the control wheel forward. The Sky Queen pitched into a steep dive. His companions stared out the front windshield as they approached the ocean at an alarming rate.
"Thundering rockets!" Bud screamed. "Are you trying to drown us?"
Tom shook his head and held the craft in its diving position. Then, when a crash seemed inevitable, he hauled back carefully on the control
84 THE CAVES OF NUCLEAR FIRE
wheel, pulling the nose of the plane up. The fast recovery from the dive caused the occupants to feel as if they weighed tons. Tom's vision became obscured by a veil of gray.
"Can't black out now!" he thought grimly. A slight forward motion on the wheel decreased the angle of ascent and relieved the threat of unconsciousness.
Craig, gripping his seat, was amazed to discover that they were flying only a few feet above the surface of the ocean. Bud and Craig, though they knew the reason, were uneasy.
But the others in the plane were badly frightened. When the craft did not hit the water, however, Hank Sterling called out over the intercom, "Why the acrobatics, Tom?"
"Getting rid of the ice in the engine inlet," the pilot replied.
His daring maneuver was accomplishing this. The ice began to flake away, shooting out like tracer bullets as the high-speed air stream carried them rearward. Gradually the power returned and the RPM indicators revealed a welcome increase.
From the galley came Chow's highly excited voice. "Brand my no good skillet, ain't had a ride like that since I lost a saddle one day on a wild bronc!"
"I'm glad it's over," said Tom, wiping perspiration from his forehead.
SIX HOURS LOST 85
He explained his unusual action to the other passengers. "Hope I didn't scare you out of ten years' growth," he added. "But I was pretty sure we'd be able to shake off the ice that way. At this time of year," he explained, "water is comparatively warmer than the air over it. Therefore, by conduction, air within about fifty feet of the water is heated."
They regained altitude and the rest of the trip above the clouds progressed smoothly. Six hours after take-off-it was now five o'clock in the afternoon in Leopoldville-Tom started downward. With their destination only minutes away, the occupants of the Sky Queen became excited.
"I see the city up ahead!" Bud exclaimed.
Everyone gazed in surprise at the sprawling city below them. The modern-looking capital of the Belgian Congo jutted out of the green jungle like a point of light in a dark sky.
Tom banked his huge craft and headed east of the city toward the modern airport. Receiving clearance from the control tower, he guided the Flying Lab down to a skillful landing.
Several small automobiles came out to greet the Americans. After officials of the local government had welcomed Tom and his group, they invited them to go into town. All accepted but the two crewmen who would stay aboard the Sky Queen and guard it.
During the drive to the center of Leopoldville,
86 THE CAVES OF NUCLEAR FIRE
the explorers admired the attractive city. Fine houses and schools had been built along the outlying streets and the center of the city was filled with modern buildings that speared skyward. The vehicles soon reached the Boulevard Albert ler. Luxurious, modern cars rolled along the wide ribbon of road that cut through the African metropolis. Well-dressed men and women strolled the streets.
"It's funny," Chow remarked to Craig, "but I figgered this lil ole Congo country was jest a lot o' mud huts an' people wearin' only a few duds."
"Africa is changing all right." Craig smiled. "But it still has its wild regions, Chow. Only a fifteen-minute ride from the center of this city will take you into a dense jungle."
When the travelers arrived at their hotel, courteous porters showed Tom and his companions to neat, modern rooms. The escorting officials made certain everything was satisfactory, then left.
Ten minutes later there was a knock on the door of the room Tom was sharing with Bud. "Come in!" he called.
A tall, deeply tanned Belgian in a white uniform entered.
"Mr. Tom Swift, Jr.?" he inquired.
"That's correct," responded Tom, and then introduced Bud.
"My name is Frederick Shopfer," the caller an-
SIX HOURS LOST 87
nounced. "I am from the local police headquarters."
"How do you do, sir," Tom answered.
"I received a cablegram from one of your security men," the officer stated. "A Mr. Ames, I believe."
"Oh, yes." The young inventor smiled. "I told Harlan that I wanted to make contact with the local authorities."
"My facilities are at your disposal," declared the caller.
"Thank you," replied Tom. "I must say you were very prompt."
He told the officer of his suspicions concerning Hoplin and Cameron, and produced the sketches Craig had drawn.
"My men will be on the lookout for them," the officer stated. "We do not wish any undesirable characters in this country." He stood pondering a few moments, then continued, "I do not know if there is any significance to this, but an unidentified plane was spotted flying high over Leopold-ville this morning. It was thought to be of Ameri-ican manufacture and heading northeast across the jungle. It may have no connection with your expedition, but I felt you should be informed."
Tom nodded thoughtfully. "I appreciate it, sir. Thank you for your co-operation."
That evening he and his friends strolled along the main boulevard with no desire to retire when
88 THE CAVES OF NUCLEAR FIRE
bedtime came. They had not adjusted themselves to the change in time.
"Purty near like gettin' up an' go in' right back to bed again," Chow remarked.
The following day the visitors made a trip to the African section of the divided city. Here an intertribal convention was being held. Representatives from the various tribes were meeting to discuss tribal laws and practices. The meetings were concluded with a gala celebration which the explorers witnessed in fascination.
Around a large fire danced medicine men wearing grotesque masks and shaking weird rattles. Doc Simpson tried to learn the significance of the ritual, but the chiefs would reveal none of their secrets.
Other natives, attired in loincloths, sarongs, and simple, togalike garments, watched the proceedings with solemn faces. Bud was intrigued by some women whose lower lips were fantastically stretched. "They must be of the Ubangi tribe," he commented.
"Look!" Chow exclaimed excitedly, as he glanced at a group of very small natives. "Dwarfs!"
"They're Pygmies," Craig explained. "I might add that it's a rare sight you're seeing, for Pygmies seldom leave the jungle."
Next morning, the stillness of the Congo dawn was broken by the roar of the Sky Queen's powerful jets as Tom took off for the final stage of their
SIX HOURS LOST 89
journey-the mysterious mountain near the Ma-bawiki village. Below them the gleaming green forest, much of it containing rubber-producing trees, was occasionally broken by grassy plains. These immense veldts served as grazing lands for buffalo and antelope.
"Some of this jungle is almost inaccessible even by surface travel," Craig pointed out. "It takes days to go a short distance." He kept watching the terrain keenly and finally said excitedly. "Quick! Tom! Bank sharp to the right!"
The young inventor maneuvered the craft into a turn. Craig searched the ground below.
"That's where I crashed!" he declared suddenly. "And look over there! It's misty, but you can make out the lines of that magic mountain we're headed for."
Tom and Bud gazed in awe. "Craig," said Tom, "you sure were lucky to come out of this place alive!"
"I know it," the cargo pilot agreed, then said, "The Mabawiki village is approximately three miles northeast of here."
The Sky Queen covered the distance in a matter of seconds and Craig pointed to a cluster of mud huts with grass roofs almost hidden by towering trees.
"That's the village!"
Native men, women, and children rushed outside and stared upward.
90 THE CAVES OF NUCLEAR FIRE
"We'll set down in that clearing to the west of the village," Tom announced.
He circled, then brought the Flying Lab down to the chosen landing spot. The huge ship settled with a roar.
The members of the expedition stepped out of the plane and gazed at their surroundings. How still and sweet-smelling the jungle was! But how hot! Fascinated, the party stood for a minute taking in the strange exotic beauty around them. Vines, bearing orchids of every hue and shape, trailed from the trees. Masses of tremendous ferns, with leaves twelve feet long, bordered the tropical forest.
Craig pointed to the birds of numerous breeds and varicolored plumage. Startled by the Sky Queen's descent, they were crying shrilly as they flitted among the trees. Many of these, he said, belonged to the parrot family.
He had barely spoken when about twenty native men, carrying spears, emerged from the trees. Before Craig could call to them in the Bantu dialect which the Mabawikis spoke, the natives dropped to their knees and began bowing in great humility.
Tom, walking toward the group, said happily, "It looks as if they're going to be friendly."
But suddenly the natives, at a signal from their leader, stopped bowing. As one, they arose and hurled their spears at the Americans 1
CHAPTER 1 1
A DEFENSIVE MOVb
CAUGHT off guard, the visitors flattened themselves to the ground and the first volley of spears miraculously missed them.
"Into the plane!" Tom yelled.
His companions needed no urging. They made a dash for the Sky Queen, but as they reached it, the wildly yelling natives launched a second volley of spears. Some of the weapons crashed against the fuselage of the craft, but the shaft of one struck Sterling a glancing blow on the shoulder. He slumped to the ground. Then Hanson let out a yell of pain and fell, clutching his right leg.
With the others already inside the plane, Bud helped Sterling up the ladder and through the hatch. Tom had run to Hanson, who was wincing with pain but trying to stand up.
"Quick! I'll help you," Tom offered. "Lean on me!"
Assisted by the young inventor, Kanson man-si
92
THE CAVES OF NUCLEAR FIRE
aged to pull himself up the ladder to safety. Tom crawled into the plane after him and slammed the hatch shut. They were just in time. A third volley of spears crashed against the side of the Sky Queen!
Frustrated, the warriors ran forward, screaming, and beat the wheels of the Flying Lab with their fists. "Those guys will ruin our gear!" Bud growled. "Let's fight back!"
A DEFENSIVE MOVE
93
At that moment Craig rushed up to Tom. "Those men aren't the Mabawikis! They're the warring Onaris I told you about. We'd better get out of here before they do any more damage!"
"We'll leave, but not for good," Tom stated, his jaw set in determination. "I'm going to give 'em the scare of their lives with the lifters!"
On previous occasions Tom had used the jet lifters to ward off enemies. He decided to try it again.

94 THE CAVES OF NUCLEAR FIRE
Without further hesitation, Tom pushed his way forward to the pilot's compartment and seated himself behind the controls. He quickly engaged the ignition switches and a low hum filled the cabin.
A few seconds later there was a deafening roar and tongues of flame began shooting from beneath the Flying Lab. Smoke and waves of hot gases filled the immediate area and a deafening roar echoed through the jungle as the ship shot upward.
The Onaris had jumped back in alarm. But now smiles of satisfaction spread over their faces because the unwanted strangers were leaving.
"We're going to have the last laugh," Bud chortled, as Tom lowered the craft and gave the warriors another blast.
The natives waited no longer. Screaming with fear they fled for the protection of the trees, leaving the ground covered with spears. Tom followed them for half a mile, then turned back. "I guess we won't hear from those fellows in a hurry," he commented, and brought the ship down in the clearing.
Meanwhile, Doc Simpson had been treating Sterling and Hanson in the plane's small but well-equipped infirmary. Sterling's shoulder was only bruised. Hanson's injury was more serious, but fortunately the spear head was blunt and had not penetrated the flesh very deeply.
A DEFENSIVE MOVE 95
"But your leg will be sore for a while and you'll have to stay off it a couple of days," the doctor said.
Tom expressed his relief that the battle had had no worse results. Then, just as he was about to discuss plans for a trip to the mountain, Bud's worried voice came over the loud-speaker from the lounge.
"Those warriors are returning!" he shouted.
Tom rushed off to join his friends. Craig was standing beside Bud, staring out a window. Suddenly he heaved a great sigh.
"They're not the same natives," he said. "These men are Mabawikis!"
"But will they be friendly?" Bud asked.
"I don't know!" Craig replied. "But I recognize that tall, muscular man leading them. He's Makua, their chief."
Craig hastened to one of the hatches and flung it open. "Makua!" he shouted. "Makua!"
The chief halted in his tracks, evidently startled to hear his name being called.
"N'JambU- It's I-Craig."
The leader cautiously stepped closer and stared at the figure framed in the hatchway. His expression showed amazement.
"It is you!" he declared in English. "You come back to Mabawiki."
Makua then noticed Tom and Bud. "You bring friends!" he concluded.
96 THE CAVES OF NUCLEAR FIRE
The chief turned and faced his people. He began to speak to them in the Bantu dialect.
"What's he saying?" Tom asked Craig.
"He's telling the others that I must be a god, after all," Craig replied. "The fact that I survived being so near the mountain proves it. At least, that's what Makua believes and I'm kind of sacred around here again. They won't harm us."
Bud chuckled. "That kind of makes angels of the rest of us. First time anybody thought of me that way."
Craig told Makua how many were in the party, how they had been attacked, and that Hanson was laid up.
"I'm very sorry about man," said Makua in English. "But rest of party come with me."
"We can't refuse," Craig informed Tom and Bud. "It would be an insult."
The other explorers were informed of the invitation, but Sterling insisted upon staying with Hanson.
Makua led the visitors toward his village. As they neared it, the group could hear a monotonous chanting. It was accompanied by the beating of tom-toms. At the native settlement, men, women, and children of various ages awaited the Americans with a smile. Some wore few clothes while others were adorned in bright colored handmade skirts and a dozen necklaces made of animals' teeth or birds' feathers.
A DEFENSIVE MOVE 97
One little boy insisted upon walking beside Tom, who finally lifted the lad to his shoulders. The rider, as well as other children in the village, giggled and screamed with pleasure.
"American father do this?" Makua asked. "No play this game in Mabawiki."
Tom had to give each small child a turn, and by the time he finished, the young inventor was a hero to the children in the village. Makua was pleased, but presently when Craig made an announcement the chief looked grave.
"You come to work at taboo mountain?" he asked incredulously.
"Yes," said Craig.
Makua frowned. "No come to village any more. Taboo."
"But we're taking every precaution," Tom tried to reassure him. "There would be no harm in it and we may need your help."
"No, no!" the chief stated emphatically. "But today you are friend of Mabawiki. We have big feast and dance for mad god of fire in mountain."
"Thank you," said Tom, realizing that there was no hope of persuading the chief to change his mind.
Craig turned to Tom. "I've seen only one such great feast," he said. "But I can tell you that it's an experience you'll never forget."
CHAPTER 12
BLACK MAGIC
WITH the coming of night, the sound of tomtoms filled the Mabawiki village. Natives preparing the great feast hurried to finish their individual tasks. Small fish, caught in nearby streams, had to be cleaned. Roasting corn needed attention. Edible cassava leaves were being boiled by the Congo chefs.
Tom and his companions re-entered the village shortly after sunset. At once a medicine man, called a mfumu by the natives, danced at a frenzied pace around the explorers and scattered an array of colored powders over them.
"That medicine man," said Craig, "is just making sure we're free of daua."
"Dauaf What's that?" Bud asked.
"Daua means evil eye," replied the flier. "The natives believe that a man can be the bearer of ill omens, and want to ward them off."
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BLACK MAGIC 99
"I ain't carryin' nothin'!" Chow exclaimed.
"That's not what I mean." Craig smiled. "Daua isn't a material thing. It's simply bad luck -black magic. Perhaps it fails to rain when th<2 crops need moisture. Maybe a member of the tribe becomes ill. These Mabawikis don't know about science. They just blame it all on daua."
The Mabawikis began congregating in the village square, seating themselves in a wide circle. The tom-toms increased to a wild tempo.
"One thing a visitor to Africa never forgets," remarked Craig, "is the drum. Its beat is haunting. I sometimes hear it in my sleep."
"Wai, I'll be a Texas bullfighter!" Chow boomed, pointing to the arena formed by the seated natives. "There's a couple o' hombres tryin' to kill each other!"
The explorers turned to watch. Two Mabawikis in their early twenties were clutching each other in combat.
"They aren't really fighting," Craig explained. "They're wrestling. It's a favorite sport of the Congo tribes."
"But they don't fight like our fellers," Chow stated.
"The African style allows only one fall," said Craig. "If either contestant touches the ground with any part of his body, except the hands or feet, he loses."
At that instant one of the wrestlers obtained a
100 THE CAVES OF NUCLEAR FIRE
firm hold on his opponent. With a violent, twisting motion he threw him to the ground. The spectators roared with delight.
"Guess they know their business at that," said Chow, nodding in approval.
"Where's Makua?" Tom asked Craig.
"In his hut. It is the custom for the tribal chief to remain there until the feast is well under way."
After several wrestling matches, young women served the first course to the visitors. Heaped on huge wooden platters was a steaming concoction of stuffed palm leaves.
"Vittles!" Chow yelled. "An" about time! I'm hungrier than a starved coyote!"
The Texan reached out eagerly and grasped several of the green morsels. "What's this?" he asked Craig.
"Cassava bread."
Chow bit deeply and munched vigorously as the others took one apiece. "Ain't bad," he declared. "A little tough!"
"Glad you like it." Craig grinned and winked at the others.
"What's this here cassava bread made out of?" Chow asked.
"Well," Craig began, "first they boil cassava leaves. Then they're beaten into heavy cakes. Added to this is a little rice, some corn, and occasionally-a rotten egg."
BLACK MAGIC 101
Chow's face suddenly lost color. His jaws ceased to chew. The Texan stared ahead with a blank expression.
Craig could not resist the urge to tell more of the jungle recipe. "Sometimes," he continued, as he watched the wincing face of Chow, "meat is added in the form of bats, Npeke birds, snakes, and caterpillars."
This was more than the cook could stand. He began choking. "I been pizened!" he howled.
With this, Chow leaped up and made a frantic dash through the jungle for the Sky Queen.
Tom and the others, with the exception of Craig, were hysterical with laughter. "I didn't mean to cheat Chow out of his supper," he said.
Suddenly the drums and chanting subsided. Silence fell over the village.
"What now?" whispered Bud, who sat next to Craig.
"Makua will make his entrance."
All eyes were fixed on the chief's hut. The animal hide which served as a door was flung back. From the small opening stepped the chief. A heavy leopard skin was draped from his wide shoulders and his neck was adorned with strings of the animal's teeth.
The native leader walked to a large, vine-draped rock which served as a throne. With a sweep of his hand, he gestured for the tom-toms and the chanting to be resumed.
102 THE CAVES OF NUCLEAR FIRE
Men dancers, adorned with cassava leaves and wooden necklaces and bracelets, leaped into the clearing. 1 hey were followed by another dancer wearing a hideous black-and-white mask. This man carried a bow and arrowr, and swinging from his waist was a string of bells and wooden clappers.
"This is a ceremonial dance," explained Craig. "That dancer represents Mabungu, the hunter. The black and white paint on his mask is symbolic. The black stands for the death he brings to his prey; the white, for the life he brings to the tribe, in the form of game."
"Native dances tell a story, don't they?" asked one of the crewmen.
"That's right. The dancer who portrays Mabungu will go through the actions of the hunt. When he finishes, another dancer representing Kituga, the warrior, acts out a battle. Then comes N'ganda, the doctor, Maluba, the merchant, and so forth."
"It's fascinating!" remarked Tom.
"Since we're guests," said Craig, "and mustn't cause any ill feeling, we'd better eat some of this food that's coming."
"No, thanks!" exclaimed Bud sternly.
"Don't worry," said Craig, as a native girl handed small wooden bowls to Tom and the others. Into each she poured a tinted liquid.
BLACK MAGIC 103
"What is it?" Bud asked, sniffing at the contents.
"It's called banganju," replied the pilot. "The women grind palm nuts and extract the oil with hot water. This mixture of oil and water is seasoned with finely pounded cassava leaves."
"Are you sure the bats and snakes are left out of *'f?" questioned Bud.
Craig laughed. "I'm sure!"
The explorers drank the liquid. Surprisingly, the mixture proved to be a tolerable beverage. It was followed by fish and corn meal cooked in palm oil.
"This is good," Bud conceded.
But as the celebration continued, the visitors felt stuffed and uncomfortable.
"We'd better leave before we fall asleep," Tom advised with a chuckle. "Besides, we have a lot of work ahead of us tomorrow."
Craig approached Makua and spoke for the group. He expressed their regret at having to leave the sumptuous feast and interesting entertainment, and thanked the chief. Then the explorers returned to the Sky Queen and were soon sound asleep.
The next morning Tom was shaken awake by Sterling. "Tom!" he called. "Tom!"
The young scientist sat up in his bunk. "What is it?"
104 THE CAVES OF NUCLEAR FIRE
"We've been invaded by insects! Someone left a small hatch open."
By this time Bud, who shared Tom's cabin, had awakened. Quickly they pulled on some clothes and followed Sterling into the corridor. The place was alive with inch-long insects batting themselves against the walls and ceiling. They winged into the boys' faces, stinging their skin.
Covering his mouth to avoid one of the insects getting between his lips, Tom asked, "Did anyone close the hatch?"
"I did," Sterling replied.
"Then we'll use the exterminators," said Tom. "But first I want to examine these bugs." He caught one and looked at it. "Never saw an insect like this." He grinned. "I'd say it's a locust that isn't a locust."
Several of them were put into a large wire-mesh cage, to be taken back to Shopton. Sterling carried it to the biological laboratory, while Tom ordered the exterminating spray used. A few minutes later hundreds of the insects were swept up and put in the incinerator.
"Our troubles aren't over yet," Sterling reported. "Look outdoors."
Tom gazed through a window. Filling the air and clinging to the surfaces of the huge plane were thousands of the giant insects.
"How can we get rid of them?" Sterling asked.
"I'll fix those pests!" said Tom. "A short flying
BLACK MAGIC 105
trip will shake 'em off and I'll use the gas from the jet lifters to exterminate the whole bunch!"
Tom ran to the pilot's seat and started the jets. As the Sky Queen lifted off the ground, the insects dropped from the craft. Attaining a height of about five hundred feet, Tom came down, the jets throwing out flame and gas. After landing, the occupants of the Flying Lab were delighted to find that the menace was wiped out.
Chow came to Tom with a suggestion. "Brand my ole horseflies, but that sure was a slick one. Mebbe you ought to hang out your shingle: 'En-terprisin' Exterminatin' Company-no bugs too large to handle.' "
Tom was in the midst of an uproarious laugh when Doc Simpson called for him on the intercom. "Please come to the infirmary immediately. Hanson's suddenly become very ill."
Sobered at once, Tom sped to the infirmary, followed by Chow. To their dismay, Hanson was unconscious and breathing heavily.
"What's wrong?" Tom asked. "Arv was all right an hour ago!"
"I know," the physician replied. "My guess is that the tip of the spear which hit Hanson had been dipped in a slow-acting poison."
"Don't we have any antidote?" Tom asked in alarm.
"Since we don't know what the poison was," Doc Simpson answered, "all I could give was a
106 THE CAVES OF NUCLEAR FIRE
general antidote. But it doesn't seem to be working. I'll keep track of his pulse and respiration. If they don't improve within an hour, we'd better fly back to Leopoldville and get some help."
So concerned were Tom and the physician that they did not notice when Chow left the infirmary. A few minutes later Tom turned to speak to the cook but he had vanished.
"Where could he have gone?" Tom asked himself.
Within thirty minutes the Texan was back. He was accompanied by the head medicine man of the Mabawiki tribe.
"Jumping jets!" exclaimed Bud as the two approached the sickroom. "You're not going to allow that hocus-pocus character to work on Hanson!"
"Wait a minute!" Doc Simpson intervened as Bud barred the way. "These native African doctors understand more about jungle illnesses than we appreciate. Let him diagnose Hanson's case."
Craig spoke to the medicine man in the Bantu dialect. He told him about the Onari spear which had punctured Hanson's leg.
"Ikumu!" the tall native exclaimed and Craig said this meant "spear." He walked over to Hanson's cot. After a brief examination, the medicine man said a few words to Craig, then left the infirmary.
"What happens now?" Tom asked.
BLACK MAGIC 107
"He'll be back shortly," Craig replied. "He's going to pick up a certain herb. Doc was right about the poison on the spear."
"Did he explain the nature of the poison?" Doc Simpson questioned.
"No," the flier answered. "The only one I know of is a kind used by the Pygmies. They extract a juice from the white flowers of the Madura plant. Dipping their arrows into this liquid makes them deadly."
The medicine man soon returned with a handful of herbs, which he crushed in a wooden mortar. Presently he had a small amount of green liquid. Nervously the explorers stood aside while the native mixed a few drops of it with water and forced it down Hanson's throat.
"I hope that we're doing the right thing," Tom murmured.
"It's a chance we'll have to take," replied Doc Simpson. "Hanson is sinking fast."
The medicine man sat on the edge of the cot, muttering incantations. In a few minutes Hanson started to writhe on his cot. Unintelligible phrases came from his lips. The medicine man, however, seemed unmoved and merely continued to chant.
Tom and his companions watched fearfully, wondering if this primitive treatment would work!
CHAPTER 13
AN ANGRY LEOPARD
THE morning dragged on. In the infirmary the medicine man continued his muttering and at intervals gave Hanson more of the potion.
"How is Arv?" Tom asked Doc Simpson at noontime.
There was little change and Tom was heartsick. "If anything happens to Arv I'll never forgive myself. I feel responsible for his condition. If it hadn't been for my expedition, he'd be safe in Shopton."
Late in the afternoon, the tension was lifted somewhat when Doc Simpson reported that Hanson was no longer delirious, but was sleeping soundly. "That's a good sign," he said.
From the Mabawiki village came the steady beat of tom-toms accompanied by chanting. Craig explained that the friendly natives believed Hanson's illness had been instigated by the fire god
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AN ANGRY LEOPARD 109
in the mountain who wanted no interference. They were trying to appease him with their prayers.
Tom felt a lump in his throat at this show of camaraderie. No matter what religious beliefs a more educated person might have, he could not show more sincerity or faith than these simple tribesmen.
Outside the Sky Queen groups of awed natives stood, waiting patiently for news of Hanson. At six o'clock Doc Simpson suddenly stood up and leaned over his patient. "I think Arv's coming out of it!" he whispered hopefully.
Word spread through the ship. Everyone on board rushed to Hanson's bedside. The stricken man moved, lifting one hand to his face. A moment later he opened his eyelids part way, then closed them again.
"Arv!" Simpson called softly. "Glad you're awake."
"Doc? Doc Simpson? Wh-what happened?" Hanson asked, opening his eyes wide.
"You were poisoned, but you're all right now. How do you feel?"
Hanson managed a wry smile. "Like I just swam the Atlantic Ocean underwater," he said.
"You'll be as good as new in a few days, thanks to this man here," said the doctor.
For the first time Hanson noticed the native who had risen from the side of the cot and was
110 THE CAVES OF NUCLEAR FIRE
edging toward the door. When Doc Simpson announced that he had saved Arv Hanson's life, Tom wrung the medicine man's hand fervently and Craig thanked him profusely in the Bantu dialect.
"Wait!" Hanson called as the healer started out the door.
But the man moved off without a word, a solemn expression on his face as if he were in a trance. When he reached the ground, he stalked off, his tribesmen following.
With the tension gone, everyone relaxed. Chow's jovial spirits returned. "I'll rustle up one o' my specialty meals fer Hanson," he declared.
Bud grinned. "Give the poor guy a chance to recover first. We don't want him to have a relapse!"
Chow gave Bud a dark look and stamped out of the infirmary so vigorously that the giant plane seemed to rattle. "I'll cook you some caterpillars fer your breakfast!" he threatened.
But when that mealtime arrived the next day, he served orange juice, bacon, waffles, and tall glasses of iced cocoa in preparation for Tom's journey with Bud and Craig to the mysterious mountain. He also packed a kit of food to last for a couple of days if they should decide to stay away.
"Thanks, Chow," said Tom, and grinned. "In
AN ANGRY LEOPARD HI
return I'll bring you back some containers of gas."
"Some of that stuff what blows things up?" the cook gasped. Then, seeing the twinkle in Tom's eyes, he added, "Brand my rusty spurs, if you ain't as bad as that Barclay feller!"
The small tank which had been brought along for cutting through the dense jungle was taken down the ramp from the Flying Lab's hangar. The boys climbed in and checked the equipment.
"Let's go!" Tom urged, and a few moments later the great treads began to eat their way through the bush.
"There's a lot of rough terrain between us and the mountain," Craig warned.
The vehicle surged ahead. Ravines, rocky surfaces, deep mud, forest, bush failed to halt their advance. After a while the explorers came to a region of dense jungle. Tom shifted to a lower gear. Small trees and thick vines snapped out of their path.
Eventually they came to what appeared to be an almost perpendicular slope. Its real steepness was obscured by heavy vegetation. Tom brought the tank to a stop.
"I don't know whether to try that incline or not," he said, peering out the forward window.
Tom climbed from the vehicle. "Watch out for snakes and wild animals!" Craig warned.
112 THE CAVES OF NUCLEAR FIRE
"Okay." Tom's eyes quickly swept the area in every direction and he kept his right hand on the holster of the pistol he carried for emergency.
After forcing his way through the dense brush, he reached the incline. Making a careful survey of it, Tom felt that the tank could negotiate the ascent.
The young scientist turned to rejoin his friends, then froze in his tracks. Two yellow gleaming eyes glared at him from a tree ahead. Crouched on a low limb was a black female leopard! The large cat was ready to spring!
There was no chance for him to escape and Tom's first impulse was to whip out his gun. But instead he remained motionless, thinking, "I hate to shoot that beautiful specimen if I can avoid it."
The animal was as immobile as an ebony statue, yet poised for the kill. Tom's position was the same, but his heartbeat was fast. Would he regret having waited to make the first move?
The two continued to glare at each other. Tom almost felt as if he were being hypnotized. "I mustn't let that happen!" he cautioned himself grimly.
Suddenly he realized that the situation had changed. It seemed that he had hypnotized the leopard! A moment later the big cat turned her back on him, jumped down from the tree, and loped off through the bush!
AN ANGRY LEOPARD 113
"Whew!" said Tom, not only relieved but amazed. He hurried back to the tank.
When the young inventor told what had happened, Craig rebuked him. "Boy, you took an awful chance!"
"Oh no he didn't," Bud countered. "Tom is an old hand at hypnotizing the girls-even lady leopards!" Tom picked up an extra radiation helmet and pitched it playfully at his pal.
The explorers resumed their journey. The slope was ascended with remarkable ease and the tank negotiated the downgrade equally well. Tom was pleased with their progress.
Occasionally they caught fleeting glimpses of chattering monkeys and once they stared in wary fascination at a huge python coiled about a low-hanging limb. At one point an elephant came crashing through the jungle.
Shortly after eleven that morning the brush thinned out, then the vegetation vanished completely. A short distance beyond towered their destination-the mysterious "mountain of the fire god." Its snow-capped peak soared up through a ring of cumulus clouds.
"What a sight!" Tom exclaimed.
"Snow above, fire below," said Bud. "By the way, where are the crevices?"
"About a mile from here," answered Craig. "They're near the base of the mountain."
Tom recommended that they put on their
114 THE CAVES OF NUCLEAR FIRE
antiradiation suits before driving closer. The three boys climbed into them and adjusted the helmets. Then Tom drove forward.
"There's the biggest crevice!" Craig pointed to the right.
Tom brought the vehicle to a halt. The various types of self-sealing containers to collect the gas were unpacked. He divided the supply among himself and his two companions.
The boys climbed out of the tank and Craig led the way to the narrow opening.
"So this is the crack we traveled halfway around the world to see," Bud remarked, unimpressed. "It sure doesn't look important."
"Maybe not," Craig responded. "But what's going on underneath is mighty important."
"Let's get started with our job so we can find out," Tom urged impatiently.
One by one the various bottles were positioned over the crevice. The vacuum-sealed containers had automatic valves. At the first sign of the gas a release would open them. The higher air pressure existing outside the containers would force samples of the gas inside, then the automatic device would reseal the vessels.
When the task was completed, Tom gazed at the row of glass, lead, and Tomasite-covered containers that bridged the crevice. "That should do it!" he declared. "I wonder how long we'll have to wait."
AN ANGRY LEOPARD 115
The group returned to the tank and removed the headpieces of their antiradiation suits.
"You don't know how often the gas appears?" Bud queried Craig, gazing at the mountain.
"No," he replied. "I was never able to establish a definite timetable."
"It's possible we'll have to wait for days," said Tom.
Morning merged into afternoon. Then the sun began to sink. Nothing had happened at the mountain.
"We'd better return to the Sky Queen," said Tom. "I'm a little anxious about Hanson. I want to make sure the medicine man's cure was permanent. We'll come back in the morning."
The containers were left in position while the three boys backtracked along the swath they had cut through the bush and jungle.
Sterling ran from the plane to meet them. At the same instant Tom asked, "How's Hanson?" and Sterling said, "How did you make out?"
"Arv's fine."
"No luck yet on our side."
The following morning Tom, Bud, and Craig returned to the mountain, arriving about ten. "It really isn't far when you don't have to hack your way through," Bud remarked. As the tank approached the crevice, he shouted, "The containers have disappeared!"
CHAPTER 14
AN ENEMY RETURNS
THE mysterious mountain had played her strange trick again! The containers for capturing the gas had vanished!
"Is this the same crevice where we left those bottles?" Bud asked practically.
"It has to be," Craig declared. "Don't you fellows remember that big rock near the edge?"
Both boys nodded.
Tom, disappointed, put on his antiradiation suit and got out of the tank. The others, similarly garbed, followed and they all walked closer to the narrow opening.
"This certainly is an enigma," murmured the young inventor. "You're absolutely sure, Craig, that the natives wouldn't steal the containers?"
"Out of the question!" Craig replied. "As I told you, the mountain is strictly taboo and no native would dare come this close or he'd be banished from the tribe."
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AN ENEMY RETURNS 117
As Tom pondered the strange phenomenon of the mountain, Craig asked, "Could the bottles have blown up under outside pressure?"
"If they had," Tom replied, "we'd see fragments lying around. But there's not a scrap." He stepped closer to the edge of the crevice and peered down into the black abyss. "My guess is that when the gas escaped during the night not one of my containers was proof against it."
"Good night!" Craig exclaimed. "Then nothing will store that stuff!"
"I have another idea I'd like to try," said Tom. "But I'll need some things from the Flying Lab."
As the trio walked back to the tank, a massive shadow swept across their path. They looked up to see a small twin-engine plane swooping low. The craft then turned steeply and flew out of sight without dipping its wings in salute.
"Who could that have been?" Craig asked. "The pilot acted as if he was spying on us!"
"You're right," Bud agreed. "The plane looked like an American-built one. I'll bet it's the same one the police chief told us about."
"There certainly was something fishy about that flier's maneuvers," murmured Tom. "Why would he fly so low over this particular spot? I'm going to notify the police."
"How will you do that from this wilderness?" Craig asked.
Tom smiled. "Talk to Dad over our short wave
118 THE CAVES OF NUCLEAR FIRE
and have him relay the message to the authorities in Leopoldville." Then he said wistfully, "I wish I had brought my camera with the telephoto lens and taken a picture of the plane. But I'll remember it next time."
Tom and his friends climbed into the tank and drove back to the Sky Queen as fast as possible. When they arrived, Hanson was strolling beneath a giant baobab tree. In one hand was Tom's telephoto camera.
As the three explorers descended from the tank, Hanson flashed them a wide smile. "I hope you don't mind my using your camera, Tom, but when a queer-acting plane buzzed us here I decided to snap a few pictures. I suppose the pilot wanted to find out what we're doing here."
Tom was overjoyed. "You've done us a big favor, Arv. I suspect that plane was doing some snooping. I'll develop the film, then contact Dad, so he can pass along the information to the authorities in Leopoldville."
Tom took the camera and went directly to the darkroom of the Sky Queen where his combination developing-printing machine was. He flicked on a dim green light, then removed the film from the camera and turned on the developer. Tom began feeding the film into a slot at the left end of the elaborate device which Bud had dubbed a magic radiator cover. It stood three feet high, was eighteen inches wide, and
AN ENEMY RETURNS 119
extended six feet along the far wall of the darkroom.
Inside the machine were electronic controls which dropped the film into high-speed developers, fixed, washed and dried the negatives and automatically made eight-by-ten prints.
Switching on the bright overhead lights, Tom waited tensely as the necessary sixty seconds ticked off. Then click! Glossy prints began to slip from the ejector chute on the other end of the machine.
Tom was stunned when he first looked at the pictures, then ran excitedly from the darkroom. "Craig! Bud!" he shouted. "Sterling! Hanson!"
The group gathered outside and peered at the pictures. "Great Scott!" exclaimed Craig. "The man in the cockpit of the plane is Hoplin!"
"Right!" said Tom grimly. "So our enemies are here!"
"I can't make out the face of the fellow next to Hoplin," Bud said, "but I'm willing to bet it's his partner, Cameron!"
"This is serious," Hanson commented. "I wonder what they're doing here in Africa."
"They certainly didn't follow us for the fun of it," Tom replied, "and I'm sure they'll try to make trouble."
"How did they ever get clearance from the U. S.?" Sterling asked.
"Forged passports is my guess," Tom an-
120 THE CAVES OF NUCLEAR FIKE
swered. "And furthermore, I'm sure that they haven't reported to the authorities here."
"If their plane is the mysterious one the police officer told us about," Bud spoke up, "it may be hidden in this wild country. I think I'll do a little scouting in the Kangaroo Kub and see what I can find out."
Bud took the little plane aloft and flew around for an hour but saw no sign of the mystery craft or any encampment that indicated Hoplin had a hide-out in the bush.
Tom got in touch with his father, giving him all this information and asking him to notify the Leopoldville authorities. Tom also told about his disappointing lack of progress so far on the capture of any of the gas. Then he asked for detailed news from home.
When the conversation was concluded, Bud, who had been standing by, asked eagerly, "What's the latest from Shopton?"
His chum smiled. "Sandy's bloodhounds have tonsilitis and can't bay!"
Both boys laughed heartily, then Tom reported that everyone at home was in good health, as well as Bud's family in California. When the explorers gathered for lunch, they speculated on why Hoplin was in the area.
"Perhaps he and Cameron are also interested in the sacred mountain," Craig suggested. "They could have been collaborating with some scien-
AN ENEMY RETURNS 121
tist on this same project and that's why they stole your antiproton manuscript."
"It's possible," Tom replied. "But somehow that explanation doesn't fit exactly. If they're interested in the sacred mountain, why should they be so mysterious about it? They have as much right to investigate the phenomenon as we have."
"You don't suppose Hoplin removed your containers?" Bud suggested.
"That could be," Tom answered. "In any case, I'll make new containers and put them in place over the crevice. One of two things will happen: We'll either catch a thief, or, if the gas emits, prove to ourselves that it disintegrates the bottles."
Tom spent the balance of the day and evening in the metallurgical laboratory of the Sky Queen with his friends, fashioning new containers.
"This time," Tom declared, "we'll stay at the mountain until the phenomenon takes place."
"What if the thief or the gas shows up in the middle of night?" Bud asked. "Will we go on guard duty?"
"None of us need lose any sleep on that score," the young inventor replied, smiling. "I'm attaching a miniature radio transmitter to the automatic valve of each container. When the valves open or are tampered with in any way, a signal will be sent out. This signal, in turn, will set off an alarm inside our vehicle."
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"Very ingenious, inventor boy!" Bud commented. "So if the alarm goes off, we'll get some kind of answer to this mystery."
"Right. By the way, we'll use the Terrasphere, without the crane section, this time. It's larger than the tank and I want to see how she travels in the jungle. And I'll take a small earth blaster along. I may do a little digging with the atomic drill to see what the mountain is made of."
The next morning he, Bud, and Craig prepared for their trip to the mystery mountain.
"All the vittles are loaded," Chow announced. "Enough fer a week, five meals a day. Mebbe you all won't have nothin' else to do but eat fer a while."
"Thanks," said Tom, then added, "All aboard!"
At that moment a terrifying roar came from the direction of the nearby trees. "A lion!" Bud yelled.
"I thought I heard a man's voice too!" said Tom. "Maybe he's in trouble!"
Tom ran to the edge of the clearing and peered into the dense jungle bush. A second roar was followed by the crack of a rifle and the whine of a bullet. The missile tore through the sleeve of Tom's jacket! As he dodged behind the trunk of a tree, another shot ricocheted off the bark.
A third bullet came whistling toward Tom!
CHAPTER 15
'GRAB YOUR HELMETS!"
IN THE nick of time, Tom had thrown himself to the ground. Still more shots rang out. Chunks of bark were ripped from a tree just behind the young inventor, then all was quiet.
Tom heard worried shouts from the Sky Queen, but remained in his prone position, listening. He could detect the faint sound of snapping twigs. As the noise grew louder, Tom watched intently. Some of the brush began to swish violently. Someone, or something, was approaching their camp!
A few seconds later a tall, husky man, wearing the clothes of a big-game hunter, stepped from the brush into the clearing. He held a rifle in readiness.
Tom, deciding the man was only hunting, rose to his feet. "What's the idea of shooting at me?" he yelled.
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124 THE CAVES OF NUCLEAR FIRE
"Do you mean one of my shots nearly hit you?" the hunter gasped.
"More than one. What were you trying to do?" Tom pointed to the holes in his shirt sleeve and the shattered bark of the trees.
"I must apologize!" the stranger replied. "I wasn't aware there was a camp here. When that lion came toward me, I just kept shooting! Guess I scared him off. But this settles it! From now on I'll leave big-game hunting to the experts. Why, I might have killed you!"
Bud, unable to remain quiet any longer, retorted, "You sure might have. You'd better leave that rifle here, mister."
The burly stranger glared at Bud. "The name is Lloyd Burgess."
"I'm Tom Swift," said the young inventor, then introduced his friends. "Are you in Africa for sport?" he asked the hunter.
"No," the man replied. "I accepted a position with a small company here that transported cacao down the Congo River for export. I was one of their steamer pilots. After a year, the firm went bankrupt."
Burgess scanned the explorers' camp. He marveled at the Sky Queen and the Terrasphere. "You have quite an operation here. Maybe you could use an extra man?"
"I'm afraid not," Tom answered.
"In that case I'll be shoving off," Burgess said.
"GRAB YOUR HELMETS!" 125
He slung his rifle over his shoulder and was soon lost among the trees.
Tom went to change his shirt. When he returned, Bud said, "Maybe the heat has got me, Tom, but I don't trust that guy. Too snoopy."
"Frankly," admitted Tom, "I feel the same way. His story sounded fishy to me. I can't imagine anybody going on an African hunt without a guide. And his rifle! It was a Model 270. That's a poor choice of caliber for brush country."
The young scientist instructed Sterling and the other men not to give out any information concerning their expedition if the stranger should return. Then the journey in the Terra-sphere to the sacred mountain was finally begun.
With the route flattened, Tom made the trip in record time, arriving about twelve-thirty. Craig and Bud aided him in placing over the crevice a few of the containers he had brought. Then they returned to the air-conditioned Ter-rasphere.
"Make yourselves comfortable," Tom advised, picking up a science magazine he had brought. "It might be a long wait. But we'd better keep on our antiradiation gear, except the helmets."
The afternoon drifted by, then night shrouded the area in darkness. Still there was no sign of the mysterious gas. One by one, the explorers fell asleep.
Two hours later Tom was awakened by the
126 THE CAVES OF NUCLEAR FIRE
loud buzzing of the alarm inside the Terrasphere. He opened his eyes in time to witness an eerie green glow at the crevice in the mountain.
"Quick!" he shouted to Bud and Craig. "It's the gas! Put on your helmets!"
They hurriedly slapped them on and dashed outside. Impatiently they waited for the glow to disappear, so that they could venture near the crevice. To their amazement, an hour went by before the area was in darkness. Tom now switched on a powerful flashlight and they walked forward.
The containers had again vanished!
"Amazing!" cried Bud. "Now we know it's the gas and not a thief that's responsible for the disappearance of those bottles."
Tom was looking into space, thinking, as Bud went on, "We're still getting absolutely nowhere in capturing the stuff."
"He's right!" Craig agreed. "We're up against a stone wall."
"We aren't beaten yet," Tom stated. "A thought occurred to me just now. It's simple, yet it might be the answer to our problem."
"What is it?" the others chorused.
"Notice the walls of the crevice." Tom pointed. "The gas doesn't affect them. The composition of the rock must be immune to the gas."
"Yes. But how does that solve our problem?" Bud questioned.
"GRAB YOUR HELMETS!" 127
Tom answered quickly, "I'll obtain specimens of the crevice walls and construct containers out of the same material."
"To get those specimens," said Craig nervously, "means we'll have to work inside the crevice."
"I'm not that foolish," said Tom. "I'm positive that the emissions of the gas follow some sort of schedule. They're not haphazard. If we can only find the key I can work out a timetable."
"How do you propose to do that?" Craig asked.
"By setting up another container," explained the young scientist. "I know it will disintegrate like all the others. However, the alarm will tell us when it happens. By recording the time, we'll have a rough schedule, since we know the alarm went off tonight about eleven-fifty and we have an approximate time for the eruption of gas yesterday."
The experimental container was put firmly into place, then the trio returned to the comfort of the Terrasphere. Tom jotted down notes and made a list of figures. Only when the first streak of dawn spread across the sky did he interrupt his work. The young inventor lay down and fell asleep almost instantly.
The alarm remained silent, and when the explorers awoke, they found the morning sky growing formidably dark. Strong winds began to raise huge whirlpools of dust across the open spaces.
128 THE CAVES OF NUCLEAR FIRE
Menacing black clouds boiled overhead in the savage churning of the turbulent air. Drops of rain spattered against the cabin windows.
"Maybe we ought to get out of this area!" Bud suggested. "No telling what may happen when rain gets into that crevice."
Tom drove the Terrasphere a good distance from the mountain but felt it best not to travel among the trees in the tropical storm. Within seconds, visibility outside the cabin was reduced to zero as the torrential rain descended. The wind exceeded gale force.
"Look at that lightning!" Bud cried out.
Suddenly, like a sinking ship, the Terrasphere began to list heavily to one side.
"Good night!" Craig cried. "We're going to turn over!"
The occupants clung to their seats. The angle of the tilt became increasingly greater.
"There must be a soft spot under our right treads," said Tom.
"Start up this contraption!" Bud demanded. "Let's pull out of here!"
"Trying to move her now," declared Tom, "might mire us deeper."
The words were hardly out of his mouth when the entire vehicle shuddered and the cabin glowed with an eerie light.
"We've been struck!" yelled Bud. "We're on fire!"
CHAPTER 16
TENSE MOMENTS
IN A moment Bud's fears were allayed. Though the bolt of lightning had been very close to the Terrasphere, the vehicle was not on fire. A nearby tree, however, had been seared from top to bottom.
"Whew!" Bud exclaimed. "I don't want any more of those!"
Tom gave his friend a quizzical look. "Have you forgotten, chum, that this bus is impervious to fire-even lightning?"
Bud looked sheepish. "I sure had. Say, I wonder what the lightning and wind are doing to that container you set at the crevice?"
The young scientist wondered too. Was the bottle still there or had the storm blown it away?
To the intense relief of the occupants of the Terrasphere, the storm showed signs of subsiding. The wind dwindled in velocity and the rain
129
130 THE CAVES OF NUCLEAR FIRE
diminished to a mere shower. Finally the sun broke through a blanket of clouds, its hot rays spreading across the area.
The Terrasphere still leaned precariously. "Do you think we can pull ourselves out of here?" Craig asked Tom.
"Before we try it, I'd better look the situation over."
Tom flung open the door and climbed out of the vehicle. A careful inspection of the ground convinced him that the caterpillar tracks would take hold.
"I think I can pull her free without too much trouble," Tom called, "but you fellows get out. No sense in all of us taking a chance."
Although they objected, Tom insisted, so Bud and Craig jumped down and stood by.
Tom seated himself behind the wheel and started the nuclear-powered turbines. The engaging of a gear set the giant treads in motion and the Terrasphere jerked ahead. But as it advanced, the treads sank deeper in the mire and the next instant the vehicle seemed about to capsize!
But Tom quickly gunned the motor, roared forward, and skillfully maneuvered the Terra-sphere to level ground ahead. There were groans of relief from the onlookers, who praised his quick thinking when he got out. The three walked back toward the crevice.

132 THE CAVES OF NUCLEAR FIRE
"The container still is there and in place," said Craig, who was in the lead.
"Good!" Tom replied. "My supply is getting low. And by the way, I was doing a little figuring last night. I'm making a prediction that there'll be an eruption of the gas about noontime."
"How come?" asked Bud.
Tom smiled. "If my guess is right, I'll tell you the theory. In the meantime, let's eat, and then clean up the Terrasphere. This baby looks like a mud-wallowing hippo."
During the rest of the morning, the boys worked hard at their task, although greatly hampered by their antiradiation suits. As noontime approached, they moved the vehicle nearer the mountain and waited. Twelve o'clock came and went. Bud and Craig looked at Tom, whose face was immobile but his eyes betrayed the excitement he felt.
Twelve-two! Twelve-three! Twelve- The alarm began to buzz! The boys stared out the window. No eerie glow was evident at the crevice, but the container melted to nothingness in a few seconds.
"You were right, Tom!" exclaimed Bud. "How did you guess when the gas would show itself again?"
"According to my calculations," Tom answered, "the eruption of gas could be related to tidal movement."
TENSE MOMENTS 133
"Tides? How can that be?" Craig asked. "The nearest ocean is hundreds of miles away. There isn't even a river close by!"
"It's possible," Tom told him, "that there's a subterranean river beneath the mountain. If so, it probably empties into the ocean. That means it would be affected by tides."
"Clever deduction," said Craig, "but even if your theory is correct, what would the rise and fall of the tide have to do with the gas?"
Tom explained that at high tide the underground river must reach a mineral deposit in the mountain. "A reaction is set up," he said.
"Sounds logical." Bud nodded. "You figure that since high tide occurs twice every twenty-four hours and some minutes, we can expect the gas to appear twice a day at a certain time."
"Correct," Tom replied. "And from my charts I figure twenty-four hours and twenty-one minutes. There shouldn't be another flare-up for twelve hours, so I suggest we take this opportunity to get specimens of rock from the crevice wall-Torn and his friends extracted the small earth blaster from the equipment locker and wheeled it to the crevice. The atomic drill was put to work.
"I hope you're right about your tide table," Bud said. "I'd hate to vanish in a puff of smoke."
Over the noise of the drill, Tom failed to hear
134 THE CAVES OF NUCLEAR FIRE
his friend's comment. As he guided the bit deep into the crevice wall, geysers of fine soil streamed behind him. Presently the drill broke through the initial layer of rock. Under it was a stratum of white granular stone.
The earth blaster stopped abruptly. When Tom attempted to restart it, his efforts proved fruitless. The boys lifted the drill out of the rock wall and examined it.
The digging point was completely gone! Further examination showed that the power unit also was ruined.
"This is extraordinary!" Tom exclaimed. "Something in that stone has put the earth blaster out of commission."
"Couldn't it just be an ordinary mechanical breakdown?" Craig suggested.
"No. Not when the digging point has vanished!"
"What now?" Bud asked.
"Let's collect as many samples of the rock as we can," Tom proposed. "The drill cut enough away before it hit that white stone for me to try some experiments."
They quickly gathered the fragments and carried them to the Terrasphere. After storing the samples in a shielded compartment, Tom headed back through the jungle for the Sky Queen.
Tom's mind was crowded with thoughts about the mountain. Where did the mysterious gas
TENSE MOMENTS 135
originate? Could he construct new containers from the rock that would not disintegrate? What was the nature of the white stone that damaged his earth blaster?
Craig also appeared to be meditating. Finally he said, "I've been thinking about Hoplin and his partner. It seems to me they wouldn't give up so easily. I expect more trouble from them."
"There's been no sign of their plane since they first flew over the camp," Bud said. "But I have a feeling they haven't left here. What I can't figure out is where they base it. Certainly not at a public airfield. They wouldn't dare."
"No," Tom agreed. "Bud, maybe you couldn't spot the plane because it has been camouflaged. But it may be nearby."
"Never thought of that," said Bud. "Well, if those men buzz us again, I'm going to follow them!"
When the Terrasphere arrived at the camp, the three boys found it bustling with activity.
"What's going on?" Tom wondered aloud.
In a perturbed voice Sterling asked, "Did you see Chow on your way back?"
"No," Tom replied. "Is he gone?"
"Chow left camp soon after you did and has been missing ever since!"
CHAPTER 17
A LION INTERFERES
"CHOW left yesterday?" Tom repeated anxiously. "Why?"
Sterling explained that Chow had become friendly with one of the Mabawiki natives who spoke a little English. Since the cook had not been near the mountain, he had been allowed to enter the village any time he desired.
"Chow said he wanted to get some herbs and was going to ask his friend to help him," Sterling .explained. "When Chow didn't return late in the afternoon, I went over to the Mabawikis to find out what had happened."
"Yes. Go on," Tom urged.
The patternmaker said that when Chow had arrived he found that a group of natives was about to set off on a lion hunt. "So Chow joined them."
Tom relaxed a little. "Those hunts sometimes take days," he remarked. "I'm sure that Chow will be all right."
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A LION INTERFERES 137
"But you don't understand," Sterling said. "About an hour ago Chief Makua sent Chow's friend over here to see if he'd gotten back safely. The lion hunters had returned to the village without him."
"You mean Chow left them?" Bud asked anxiously.
"Yes. Somewhere deep in the jungle, too. It seems Chow didn't like stalking a lion and decided to come back to the Sky Queen."
"We must look for him at once!" Tom urged.
The young inventor then asked what route the hunters had taken. Since no one knew, Hank Sterling offered to go to the Mabawiki village and find out. But just then Chow's native friend ran up to the group. Apparently he did not feel that the taboo against the Americans visiting the village applied to his calling at the Sky Queen.
"Chow come?" he asked.
"No."
The native rolled his eyes in fear. "Chow maybe dead. Lion kill. Sorry."
At Tom's request Craig asked the runner in his native language for detailed directions to the route the hunters had followed.
"An hour's journey east on foot, then two hours north from three baobab trees by a stream," Craig translated.
Tom turned and ran toward the small tank which stood nearby. Bud and Craig followed.
138 THE CAVES OF NUCLEAR FIRE
Soon they were moving eastward through the jungle. The occupants, silent and worried, kept their eyes and ears alert for any sign of Chow.
Tom switched on a sensitive microphone, fitted on the outside roof of the vehicle. The device was capable of picking up even the faintest noises within a radius of several hundred yards.
Tom guided the tank slowly along the route taken by the hunters. Under ordinary circumstances the boys would have been intrigued by the flaming array of the jungle flowers. But now their thoughts were centered only on Chow.
When the searchers reached the point where the hunters had started their trek north, Tom swung the vehicle to the left. Suddenly a frantic cry bellowed over the loud-speaker. "Help!" howled the voice. "Help!"
"It's Chow!" Bud exclaimed.
"But where is he?" questioned Craig, straining his eyes. "I don't see him anywhere in that grass and bramble."
Tom, gazing in another direction toward a baobab tree, gasped. At the base of the tree a huge lioness was springing repeatedly at a plump figure huddled on a low branch.
"Chow!" Tom cried out in horror.
There was no time to spare-the hungry beast might succeed at any moment in reaching the Texan with her deadly claws.
"I'll try scaring her off," Tom said tersely.
A LION INTERFERES 139
With that, he gunned the tank ahead full speed at the lioness, who was crouched for another leap. At the vehicle's approach, the tawny beast wheeled and, for a moment, stood her ground, eyes blazing. But as the tank hurtled nearer, she turned tail and slunk away into the bush.
Tom came to a sudden halt beneath the baobab tree and Bud threw open the hatch. "Quick, Chow!" he cried. "Get in!"
The Texan released his grip on the branch and plummeted down. The tank shuddered as his heavy body made contact. Bud caught the cook by one leg to drag him inside, pulled him through the hatch, and slammed it shut.
As Tom headed the tank back toward the Sky Queen, he said, "Chow, why did you leave those natives and take a chance in this wilderness alone?"
"My spine was gettin' prickly too often," the cook replied. "I want no part o' lion meat, dead or on the hoof. No sirree. So I decided to get back to the Sky Queen. I was doin' all right, too, 'til that lady lion come along an' put me up a tree."
"You had our whole expedition worried, and the Mabawikis too," said Tom.
"I'm sure sorry," said Chow contritely. Then he brightened. "Mebbe I kin make up to you fer my bad behavior. Listen! I was talkin' to that Ma-bawiki friend o' mine what savvies English. He
140 THE CAVES OF NUCLEAR FIRE
told me somethin' interestin' about that mountain you been goin' to."
"Yes?" said Tom curiously.
"Yup!" answered the Texan. "He said a white man told him there's a cave goin' into that mountain."
"Cave!" Tom exclaimed.
The existence of a cave could mean finding the source of the mysterious gas!
"Where is it, Chow?"
"I don't know, but mebbe I kin find out."
Back at the Flying Lab, Sterling and the others were relieved to see Chow and thumped him affectionately on the back. Meanwhile, Tom decided to check the Texan's information about a cave first thing in the morning. As a special precautionary measure he sprayed the tank and their antiradiation suits with a fresh coat of Tomasite.
At nine a.m. he set out in the tank with Bud and Craig. Soon they were at the base of the sacred mountain, and started a circular tour of it.
"Keep your eyes open, boys," Tom requested.
He maneuvered the vehicle in and out of the uneven juttings that formed the face of the mountain. After completing the circle at the base and finding no sign of a cave, Tom started a search on the mountainside, spiraling up it as far as he dared go. Hours of intensive exploring disclosed no cave.
A LION INTERFERES 141
"That native must have told Chow a tall story," Bud commented.
"It looks that way." Tom sighed. "We may as well head back to camp."
When they reached it, Tom confronted Chow with their failure. The Texan said nothing. Turning, he walked off toward the Mabawiki village. In less than an hour he returned, his eyes gleaming with excitement.
"I jest talked to my friend over there again," Chow stated. "Look! He made me a map!"
Tom studied the markings impressed on a dried piece of bark.
Bud peered over the young inventor's shoulder. "But, Tom," he said, "we went over that area very carefully. It's right at the foot of the mountain. We couldn't have missed."
"I know it, Bud, but the cave entrance is probably so well hidden we overlooked the spot. At least it's worth another try!"
For the second time that day the tank rolled toward the mysterious mountain. Tom checked the position of the cave on the rough map, and when they reached the spot at two o'clock, he stopped. They saw no sign of an opening.
"Let's take a look on foot," he said.
The three explorers, wearing their radiation-proof suits, made their way along the rocky terrain fronting the sacred mountain. Wearily they searched and searched, but in vain.
142 THE CAVES OF NUCLEAR FIRE
"We'd accomplish more by just going on a picnic!" Bud joked.
Suddenly Craig halted and cried excitedly, "Look! About a hundred feet up the side of the mountain!"
Tom and Bud followed his gaze to a slight depression in the slope. The area appeared to be unusually heavily littered with dead branches and bulky stones.
"Let's take a look," said Tom.
When they had climbed the steep grade, he asked them to help him clear away the branches and rocks. They set to work with a will, heaving tree limbs and stones aside. Suddenly the three paused, staring ahead excitedly. Partially revealed was an opening into the mountain's stony face.
"This is a cave entrance, all right," said Tom. "And someone has deliberately covered it up- someone who wasn't afraid of the mountain!"
The explorers resumed work feverishly to finish clearing the entrance of the boulders and brush that blocked it. Perspiration streamed from their foreheads and their visors became fogged.
As they yanked at a huge rock, there was a sudden, violent upheaval of the ground.
Tom, Bud, and Craig were flung into the air!
CHAPTER 18
PHOSPHORESCENT ROCKS
THE explorers landed, stunned, amid a deluge of rock and dirt. Then all was quiet.
Minutes later, Tom regained consciousness and struggled to his feet. Bud and Craig were still lying half-dazed on the ground. Tom pushed aside the debris and helped them to their feet.
"That must have been the gas exploding!" Bud muttered. "Let's get out of here fast!"
Tom was looking toward the cave entrance. "I don't think that the explosion was due to natural causes," he said grimly. "It was man-made!"
"You mean somebody rigged a booby trap?" Craig exclaimed.
"Exactly!"
"What makes you so sure?" Bud asked.
"To begin with," Tom began, "don't you detect a distinct odor in the air?"
Bud and Craig sniffed curiously. "You're its
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right!" Craig cried out. "That odor is familiar, but I can't place it."
"Dynamite!" Tom asserted.
"Who would have planted that?" Bud asked angrily.
"Certainly not the natives," Craig answered. "Not one of them would come within a mile of this mountain. Anyway, the Mabawikis know nothing about handling modern explosives."
Tom nodded and began searching the area near the entrance to the cave. "Perhaps we can find some sort of clue," he said.
The trio proceeded to scan the ground carefully. Presently Craig spotted something shiny and bent down to pick it up. He beckoned the others. "Take a look at this!"
Tom and Bud hurried over and stared at a small metal object in Craig's hand. It was as thick as a lead pencil and about four inches long.
"This is a blasting cap for dynamite!" Tom disclosed grimly. "From its appearance, I'd say it wasn't dropped here more than a day or two ago."
The hunt went on. Suddenly Bud shouted from a point higher up the slope, then came bounding down to his friends, carrying a rifle. "I found this underneath that overhanging rock formation!"
Tom examined the weapon. "This rifle is the same type Burgess was carrying!"
PHOSPHORESCENT ROCKS 145
"Do you think he set the explosive?" Bud asked.
"We can't say for sure he's the one," Tom replied. "But if Burgess is involved, my guess is that he's working for Hoplin and Cameron. In fact, a lot of the puzzle begins to fall into place. Burgess could have sent that phony cablegram. He could have been pretending to be a big-game hunter when he came to our camp."
"But," said Craig, "he was really spying to find out what we're doing. That's why he wanted a job with us."
"No doubt about it," Bud injected. "Burgess may be more dangerous than we think. He may not have been shooting at a lion at all. I'll bet that he was aiming at Tom!"
This new turn of events worried the group tremendously. Would there be more attacks?
"Tom, what do you figure set off the explosion?" Bud asked.
"Probably some form of spring device. When we cleared away some of the rocks, it automatically released the spring."
"Actually," said Craig, "the dynamite setter did us a favor. He opened the rest of the entrance for us."
Tom and his companions peered into the yawning cavern. Bud ran for a flashlight and beamed it into the blackness. A long tunnel lay ahead. "It's more than large enough for us to take the tank in," he said excitedly. "And the
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whole secret of the mysterious gas might be in that cave."
Craig objected. "What if Hoplin and his partner are hiding near here?" he warned. "They could seal the entrance after we went in!"
"Why not post one of us as a guard?" Bud suggested. "I'll stay here," he offered.
"One man wouldn't be enough against Hop-lin's gang," Tom reminded his friend. "We'd better go back to the Sky Queen and get help."
The explorers climbed into the tank and in a short while were back at their camp. When Tom told the group of the latest developments, everyone was eager to return to the mountain. Since the Flying Lab had to be guarded, the young inventor selected only three to go: Hanson, now fully recovered, Chow, and a crewman named Howard.
"Brand my fryin' pans," Chow growled, "I been itchin' to git my hands on that skunk Hoplin! Now's my chance!"
The three guards procured antiradiation suits, then the expanded unit set off in the tank. Tom drove to within a few yards of the cavern entrance. Chow, Hanson, and Howard took suitable positions outside the cave.
As the tank eased into the cave, Tom, Bud, and Craig tingled with anticipation. Soon the bright sunlight was left behind. The vehicle's searchlight stabbed the inky darkness.
PHOSPHORESCENT ROCKS 147
"The floor of this cave is reasonably level," Tom remarked.
"Let's hope it stays that way," said Craig, "and that the tunnel stays big enough for us to get through."
Minutes passed as the tank penetrated deeper and deeper into the mysterious corridor. Eventually the explorers arrived at a sharp bend. Tom, about to make the turn, brought the vehicle to an abrupt stop.
"What's up?" Bud asked.
For answer, Tom snapped off the spotlight. A ghostly light was shining from around the bend.
"Jumping jets!" Bud exclaimed. "That glow! It must be from the gas!"
Tom did not agree. "High tide isn't due for several hours!" he said.
As the explorers stared at the weird glow ahead, Craig suggested fearfully that there might be other people in the cave.
"Not Hoplin and Cameron," remarked Tom. "They'd greet us in darkness and pull a fast one."
Tom was inclined to think that the ghostly light was a natural phenomenon of the mysterious mountain. With this thought in mind, he sent the vehicle forward and rounded the turn.
"Wow!" exclaimed Bud. "What a sight!"
The cavern walls were glowing phosphores-cently. Every bit of rock surface seemed to be aflame with a cold, green-white light.
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"Remarkable!" said Craig, "but it's sure eerie. What do you think is causing the cave to glow, Tom?"
"It must be a secondary reaction of the gas," the young scientist theorized. "The atomic structure of the rock is being excited. That would produce such an emission."
Greatly intrigued by the phenomenon, Tom continued ahead. The corridor of glowing rock stretched for a considerable distance, then stopped abruptly. Beyond was a solid barrier of rock.
"End of the trail," Bud muttered somberly.
"Maybe not," Tom retorted optimistically. "I'm convinced we're getting near the source of the mysterious gas. Perhaps it's originating from a subterranean pit on the other side of that wall."
"Surely you don't intend trying to dig through this wall?" Bud asked in amazement.
"Not yet," Tom replied. "First, I want to check the location of the crevice where we put the containers in relation to this wall. It may help me pinpoint the source of the gas."
"Let's go!" said Bud.
"Just a minute," Tom replied. He checked his suit and helmet. "I want to collect some specimens of this rock. It must be inert to the glowing gas. I want to find out why it isn't affected."
He climbed out of the tank, carrying a pick.

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Soon the cave was filled with the sound of digging as he cut deep into one wall. Each stroke tore out big chunks of the rock.
"This should be enough," Tom said as he handed up half a dozen pieces to Bud and Craig. "Load these into the cargo bins, will you?"
Tom studied the rock wall for a few minutes, then climbed back inside the tank. Glancing at the clock on the dashboard, he noticed that it had stopped. None of the boys wore a watch.
"We don't know how long we've been here," the young inventor remarked. "High tide is still hours away, but we don't want to play it too close."
By skillful maneuvering Tom found space to turn the tank completely around and the explorers started their journey out of the cave. The young inventor sat in deep thought, wondering if the rock specimens would furnish him with a nondisintegrating material for containers. Perhaps he could concoct a special paint to use.
"We're almost out of the cave!" Bud announced, seeing a disk of sunlight ahead.
As they neared the exit, there was no sign of Chow and the other guards.
"Where could they be?" Craig exclaimed.
Panic seized Tom and his friends. There was no reason for all the men to have left their posts, unless there had been foul play!
CHAPTER 19
AN INVENTOR'S DREAM
HOPING fervently that they were wrong in their assumption, the occupants of the tank rode through the cave exit and looked about for the guards. The area was deserted.
"Hoplin must have managed to surprise them," Craig said, concern in his voice.
Just then, shouts boomed from three different directions on the hillside. For a fleeting second the three boys tensed for a raid, then smiles of relief spread over their faces. From behind a massive rock on the slope emerged the plump figure of Chow. Hanson stepped from the cover of a second boulder, and finally Howard came from still another one, higher up the slope. The men ran down to greet the others.
"You had us worried!" Tom cried out. "Thought you'd been kidnaped!"
Hanson explained that to protect themselves,
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and also to watch for intruders interested in the cave, the guards had decided to conceal themselves. "The slope gave us a bird's-eye view of the entire clearing," he said.
"It was a good idea," Tom conceded. "Did you see anyone?"
"No," Hanson replied, then asked Tom what he had learned about the cave. "Is it interest-ing?"
"Definitely!" exclaimed Tom, his eyes sparkling with enthusiasm. He told about the glowing walls of the cave and the samples of rock he had collected. "I'm hoping to discover some way to utilize the rock in making containers that won't vanish when the gas hits them."
The young inventor wasted no time in returning to the Sky Queen. He quickly unloaded the specimens of rock and had them carried to the metallurgical laboratory of the giant craft. Isolating himself, he worked feverishly to determine the contents of the material.
With barely time out to eat, Tom worked far into the night. Finally, Bud and Craig insisted that he rest for a few hours.
Smiling, he said, "To keep peace with you fellows I'll go to my bunk awhile for some s1 ut-eye."
The next morning Tom resumed work. For him the day passed quickly, as he tried experiment after experiment. Again when night came, there was another intrusion by Bud and Craig.
AN INVENTOR'S DREAM 153
"You two are like a couple of mother hens," Tom remarked, laughing. "But I suppose I owe you an explanation. Since crushing the rock, I've been trying to concoct a paint for covering containers. So far, I've had no success."
"Do you think you'll solve it?" Craig asked.
"I will!" Tom declared. "Next, I'm going to try a paint using a gelatin base. To the gelatin I'll add a portion of the finely ground rock. The combination will be a colloid. With luck, it might work!"
At eight o'clock the following morning Tom continued his work. Hours went by but he knew now that he had the right consistency of paint, although the problem of drying still confronted him. At last, however, with the addition of some Tomasite he found the answer.
Excitedly he called in all the members of the expedition. "I think I have it!" he said. "Now I'll put new containers to the test. Hank and Arv, will you help me make half a dozen of them and I'll paint the containers inside and out, then bake them to get a smooth surface. In the morning we'll go back to the mountain."
"Well, brand my empty bean cans!" exclaimed Chow. "Tom Swift, you're smarter'n a pack o' prairie wolves!"
The others added their congratulations, but Tom held up a hand. "Save your praise until the experiment has been completed," he urged.
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Three new containers were molded and carefully covered inside and out with the new paint. As Bud gazed at the gleaming bottles, he asked, "Have you thought up a name for your new concoction, Tom?"
The young inventor thought for a moment. "It may be inert to the gas. We might use that word in the name."
Bud grinned. "And the paint sticks tight. How about calling it Inertite?"
"Fine," said Tom. "Inertite it is!"
Tom rigged alarms to the containers and late the next morning he set out with Bud and Craig for the crevice. Arriving at their destination, the explorers set the bottles in place. Then Tom set up a metal pole which looked like a lightning rod. It had been covered with the special paint to which had been added grains of silicon.
"What's that for?" Bud asked.
"To show us when the gas stops pouring out of the mountain," said Tom. "The green light should reflect from this while the gas is emitting. Later, if the containers are still there, we can go get them."
"How soon will the gas appear?" Craig questioned.
"According to my tide table," Tom replied, "in approximately two hours."
The trio returned to the tank and ate their
AN INVENTOR'S DREAM T55
lunch. They talked of nothing but the experiment. The paint was being given the acid test. Would it hold up?
At exactly the scheduled time, the alarm sounded. Tom and his companions peered eagerly from the windows. The metal rod was reflecting a green glow! And every container was intact! Fifteen minutes later they still were intact.
"Well, genius boy," said Bud, slapping Tom on the back, "you've done it again!" and Craig added, "Congratulations! You're a wizard, Tom!"
The young inventor grinned. "If there's gas in those bottles, then the experiment will be a hundred per cent successful," he told his friends.
An hour later the greenish light became fitful, then disappeared altogether. Tom felt it was safe now to approach the crevice and the trio scrambled out of the tank. Bud nearly toppled from the vehicle in his eagerness to see what had happened.
They approached the containers hopefully and Tom picked one up. The valve was sealed!
At last a sample of the mysterious gas had been captured!
All the bottles proved to be tightly locked and were carefully stored in the tank. Then Tom drove back to the Sky Queen.
The camp was jubilant about his success.
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"Your dad will be thrilled to learn this," Arv Hanson remarked.
"I'll talk to him as soon as I learn a little more about the nature of the gas," Tom said.
Hanson and Sterling helped him to construct a special box-shaped chamber for this experiment. After the walls of the chamber had been heavily coated with Inertite, electronic measuring devices were attached to recesses built into the top of the chamber.
Tom carefully placed one of the containers inside the chamber and by remote control released a small quantity of the gas into the enclosure. The results of the initial test revealed some startling facts. The gas proved to give off anti-protons, as Tom had suspected, but he was amazed to learn that it had an atomic weight of 286. This value was unknown to the atomic table!
"The properties of this gas are different from anything yet known to science," Tom told his friends. "It may turn out to be the greatest discovery of our age!"
Everyone was excited, but also awed and a little worried. "That stuff is pretty dangerous!" commented Hanson. "Will it ever have any practical uses?"
"It's only a matter of learning how to harness the gas," Tom declared. "Already I see the possibility of using it to form completely new iso-
AN INVENTOR'S DREAM 157
topes. In fact, with it, I'll be able to imitate the isotopes found in the rocket from space."
"Brand my pot covers!" cried out Chow, walking into the laboratory. "What you talkin' about -icy topes from Mars?"
The others laughed and Tom informed the Texan that he had just made some amazing discoveries about the gas. "It's out of this world," he said with a wink at the other men. "Some of it's in that chamber you're standing next to."
An expression of terror came over Chow's face.
"Don't worry." Tom grinned. "The gas can't escape and the chamber is coated with Inertite."
"Inner tight?" sputtered the cook. "Oh, you mean that new paint you cooked up!"
"Yes. It's like Tomasite. The only difference is that Inertite is immune to antiprotons, whereas Tomasite is inert to gamma rays and neutrons."
Chow, completely bewildered by Tom's explanation, scratched his head. "I don't savvy nothin' 'bout them rays an' things!" he snorted. "I'd ruther take my chances ridin' one o' them convict cow ponies."
"Convict cow ponies?" Tom asked. It was his turn to be puzzled.
"Sure!" Chow answered. "Them poor black an' white critters with all the fancy stripes!"
"Oh, you mean a zebra!" Tom grinned and gave Chow an affectionate look.
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The Texan left the laboratory under a barrage of howls from all the others but Tom. The young inventor shifted his attention once again to the chamber. He rechecked several of his calculations about the half-life of the new element and the amount of energy it would emit when it decomposed.
"What are you going to call this new gas?" Craig asked.
"Exploron," Tom replied.
Satisfied with his initial experiments, Tom packed away the rest of the containers for more extensive studies with his father. He now called Mr. Swift on Enterprises' short-wave band.
The elder inventor was delighted with the report but advised that Tom and his group keep the matter entirely confidential until the Belgian government was notified. "You'll have half the scientists in the world down there if you don't keep mum!" he warned. Then he asked if Tom had seen or heard of Hoplin and Cameron.
"No," his son replied. "We suspect, though, that a fellow named Burgess who was here is in cahoots with them and set a trap of dynamite."
"Please be careful," Mr. Swift cautioned. Tom promised, then listened to news of his family. "No excitement here," his father said. "I guess you're having all of it."
That evening Tom brought out the samples of rock he had obtained from below the surface
AN INVENTOR'S DREAM 159
near the crevice. He found them to be identical to the rock in the cave.
Bud, nonplused, said, "But one disintegrated the tip of the earth blaster. The other didn't even foul up the pick."
"I think I have the answer," Tom replied. "The rock which the earth blaster hit must have had a trace of the gas in it, or perhaps still have been damp from high tide, and a slow reaction was taking place. The cave rock is dry."
Tom said that before high tide he wanted to make a few more calculations on the relative position of the rock barrier and the crevice. Then he would tackle cutting through the barrier in the cave. After repairing the earth blaster he covered it with Inertite, then announced that early the following day he would return to the mountain.
With Bud, Craig, and himself ensconced in the tank the next morning, the vehicle rolled through the jungle and into the clearing that fronted the mountain. The explorers quickly dressed in their antiradiation suits, then took the earth blaster, its cables, and instrument housing to the crevice.
"If my calculations are correct," said Tom, "the end of the tunnel is just about underneath this opening. I want to use the blaster as a scout."
Bud and Craig watched tensely as Tom began his task. From the control panel, Tom guided
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the blaster deep into the gaping crevice. This time, the earth blaster functioned without interference!
An hour passed with all the boys watching the recording instruments aboveground. All were working perfectly.
Tom carefully examined the soil and each type of rock as it spewed back from the atomic drill. Eventually the blaster unearthed a layer of white, glazed rock. According to the instruments, the crevice at this point narrowed to only a fraction of an inch in width.
Intrigued by the sudden change in rock formation, Tom drilled more rapidly. The glazed layer proved to be only two feet thick.
As the blaster bored through, an overpowering force suddenly gripped it. The cables, housing, and instruments were yanked forward into the crevice. Every instrument was crushed.
Tom rushed forward and began pulling on the cables. They came up without too much effort.
"The earth blaster is gone!" he cried. Then, as a panicky thought struck him, he ordered, "Run for your lives, fellows!"
CHAPTER 20
A TERRIFYING FALL
THE THREE explorers raced for the shelter of the tank. Once inside, they gazed toward the crevice. The rod was not reflecting the glowing green haze.
"Guess my fears were unfounded," said Tom a little sheepishly. "I thought I might have released a pocket of the gas."
Nevertheless, the three waited for half an hour before venturing outside again. As they walked toward the crevice, Craig asked what Tom thought had happened.
"I believe the earth blaster was sucked down past that layer of glazed rock," the young inventor replied.
"Sucked into the ground?" Craig asked in astonishment. "But how could that happen?"
"There's only one logical explanation," said Tom. "I must have bored into a large vacuum area. This crevice probably opens into a great
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underground pit with a river at the bottom. When I drilled a large hole into it, the outside air rushed through the opening. As a result, my earth blaster went with it."
"If there is such a central chamber," said Craig, "do you figure it adjoins the cave?"
"Yes," Tom replied. "Tomorrow we'll go into the cave with the Terrasphere fully equipped and with a fresh coat of the protective paint. If we do find a pit beyond that barrier, I want to take a ride down into it in the sphere."
They gathered up what was left of the equipment that went with the atomic drill, and the gas-detecting rod, then drove to the camp. Tom at once took inventory of his supply of spare parts for the earth blaster, and was relieved to find that he had enough to construct another drill.
"This will facilitate getting through that barrier," he told Craig, who was helping him.
Bud, together with Hanson and Sterling, worked in the Sky Queen's machine shop to assemble another small earth blaster. A heavy coating of Inertite served as the finishing touch. When tested, the new blaster functioned as well as the original one.
"We're all set now," Tom announced.
The next day the explorers embarked for the mountain. In the driver's cabin of the Terra-sphere were Tom, Bud, Craig, Hanson, Chow,
A TERRIFYING FALL 163
and Howard. The latter three had agreed to serve as guards while Tom and the others ventured into the cave.
"Remember," Tom instructed, as they reached the entrance and the three men stood up to get out, "keep your radiationproof suits on at all times. And if we're not back in four hours, get away from here. We may have drilled through the wall by that time. According to my tide table, the gas should appear about then. And this place won't be fit for man or beast."
"But what about you?" Hanson asked fearfully.
"I don't expect anything to happen, of course," Tom replied. "But if we are delayed, the Terra-sphere with its fresh coat of Inertite will protect us."
Wishing the explorers luck, Hanson, Chow, and Howard climbed down to the ground. The others waved good-by and Tom drove the Ter-rasphere into the cave. He switched on the spotlight and the vehicle moved ahead slowly.
The boys had gone only a hundred feet when Bud made a discovery. "Look! On the left-hand wall! Someone's been digging in the rock since we were here!"
Tom stopped. Bud and Craig climbed out and searched the spot. The evidence was unmistakable. Large chunks of rock had been dug from the wall. The boys stepped back into the cabin.
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"Burgess again?" Craig wondered aloud. "And what's he going to do with the rocks?"
Tom frowned and shrugged. "Maybe the same thing I've done. But we can't concern ourselves with that question now. We must hurry. However, we'd better keep alert! We may not be the only people in this cave!"
No sooner had Tom started the vehicle moving again when a strange rumbling sound was heard. It was followed by an avalanche of rocks that crashed down on the Terrasphere from the top of the cave. The impact shook the cabin vigorously.
"The cave is giving way!" Bud cried out. "Back out, Tom!"
Putting the gears into reverse, the driver did just that but in a moment he stopped. The avalanche of rocks had ended.
"I'll see how much damage was done to Terry," Bud offered. He flung open the overhead hatch and appraised the situation. "Deep dents but no holes," Bud reported.
"Dents are bad enough," said Tom. "I'll hand you a can of Inertite I brought along. Paint those dented places in a hurry, will you, Bud?" He handed up the can and a brush.
In the meantime, Craig had gotten out to investigate the barrier of fallen rocks. Several large rocks were wedged under the front of the Terra-sphere.
"We won't be able to move forward," he called
A TERRIFYING FALL 165
up, "until these boulders are cleared away. And look, here are some wooden poles! Where'd they come from?"
Instinctively, Tom had looked up at the roof of the cave. He noticed that a deep cavity had been dug into it.
"That was no accidental cave-in!" he declared. "Several men placed those rocks in a hollow just above us. The rocks were held in position by those wooden poles. We must have tripped a release when we reached this point."
"Why, that's murder!" Craig exclaimed hotly. "And I'll bet on Hoplin and his gang. We're lucky to be alive!"
"I don't think our little tank would have fared so well," Tom said grimly, getting out to help lift the rocks to the side of the tunnel. "We must work fast if we hope to beat the tide."
They worked with a will, using the wooden poles to pry the boulders from beneath the Ter-rasphere. When the path was clear once more, the journey was resumed. But their enemies' attempt to annihilate the explorers kept them on edge. No one spoke, and they watched for further trouble every inch of the way, above, below, and to both sides of them.
Though the Terrasphere reached the rock barrier without further incident, Tom bemoaned the fact that so much time had been lost. "We have only two hours left," he said, "before we'll
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have to make a run from the gas, providing we break through the wall."
Tom seized his earth blaster, and with his friends' help, set it up. Then the digging commenced. Layers of rock were blown away. The wall proved to be only eight feet thick and soon a hole was bored through it.
Tom continued to drill until he had made an opening large enough for him to crawl through, then the blaster was withdrawn. Immediately a red glow could be seen in the opening.
Tom, his heart pounding excitedly, crawled through. He caught his breath at the sight.
Below was a deep pit whose red, green, and yellow phosphorescently glowing walls formed a sheer drop of over five hundred feet!
"A cave of nuclear fire!" Tom exclaimed.
Below he could hear a rushing river which he was sure no man had ever explored. He looked far down into the pit-he could hardly wait to descend into it at low tide with the sphere.
"No time left to do it now," Tom said to himself. "I'd better get out of here fast, before the gas starts forming."
As he started to crawl backward, the edge of the opening suddenly collapsed. Tom tried to grab the rocks alongside of him. They too gave way!
The young inventor lost his balance and plunged downward!
CHAPTER 21
MISSING EXPLORERS
"TOM!" screamed Bud, making a frantic grab for his friend, but too late. Tom disappeared into the yawning pit.
Bud's throat almost closed in terror, but he managed to tell Craig what had happened and added, "Hold my legs while I take a look! M-maybe Tom's safe!"
Bud crawled to the very edge of the small opening, and lying flat on his stomach, peered over the rim of the narrow ledge.
"Tom," he called. "Tom!"
All that Bud could hear was the tumbling, noisy water below. He reported this to Craig, who pulled him back from the rim.
"We mustn't give up hope," Bud murmured. "Tom may have struck his head on a ledge and blacked out. Get the strong searchlight. It will penetrate this foggy glow."
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Craig rushed into the Terrasphere and procured the light. Once more he held Bud's legs while the youth stretched over the edge and swung the beam around. "Tom! Tom!" he cried out frantically.
This time, Bud thought he heard a reply directly below him. He listened again. Yes! Tom was saying, "I'm . . . I'm ... all right!"
Joyfully Bud informed Craig, then shouted, "Where are you, Tom?"
"Just below your position," he answered.
As Bud concentrated the light, his eyes gradually penetrated the haze. He could see Tom on a slippery, four-foot ledge fifteen feet below. The young inventor was clinging desperately to a narrow protrusion of rock.
"Hold on!" Bud yelled. "I'll get a rope!"
"Hurry!" Tom advised. "We've less than twenty minutes before high tide!"
As Bud and Craig dashed to the Terrasphere, they wished there was time to widen the opening into the pit. In that case they could easily lower the sphere on the cables and rescue Tom. But this was not possible now.
From the equipment locker the boys procured a coil of stout metal rope which had been treated with Inertite. They secured one end of it to the crane and set a wooden box in the opening to the pit to keep the rope from rubbing against the hard rock.
MISSING EXPLORERS 169
Bud lowered the coil down into the pit. When the rope reached Tom, he tried to grab it but nearly lost his grip on the rock!
"I'll have to leap onto the rope," he called up.
"Don't do that!" Bud pleaded. "You might miss. I'll come and get you!"
Quickly he pulled the rope up, and making a noose, secured it under his shoulders, leaving the end free for Tom's use. With Craig watching tensely, Bud lowered himself over the edge and swung toward Tom. He obtained a slight footing on the narrow ledge and managed to tie a bowline around Tom. As the boys swung away from the wall, the rope strained under their weight.
"Pull us up!" Bud shouted to Craig.
Unable to lift them alone, Craig leaped into the Terrasphere and started the engine. He put the gear in reverse. The vehicle moved backward and slowly the two boys were hoisted upward.
Reaching the rim of the wall, they quickly crawled through the opening. There was only a moment for happy reunion as Tom and Bud untied the rope and climbed into the cabin. Then Craig began a hasty exit from the cave without even turning the vehicle around.
"We've less than ten minutes!" he exclaimed, checking the clock and putting on speed.
"There's the exit now!" Bud finally cried in relief. "With three minutes to spare."
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The vehicle rolled out of the cave and into the sunlight. Its passengers glanced around to locate the guards and pick them up. A moment later Chow came running from the mountainside. Craig opened the cabin door and helped the Texan inside.
"Where are Arv and Howard?" Tom asked quickly.
"They left in a big hurry a short while ago," the cook replied. "Arv spotted a white hombre an' a native sneakin' around the cave an' took off after the critters. Arv said he'd meet us at the Sky Queen."
As Craig turned his vehicle toward camp, Tom and the others wondered who the white man was and to which tribe the native belonged.
At that moment Hanson and Howard were racing after the suspects as quickly as their cumbersome suits and boots would permit. Their chase had carried them deep into a forest.
The native, being a swift runner and familiar with the jungle, soon managed to evade his pursuers. But the white man was not so clever. In a short time Hanson had him trapped in a small bog.
Arv was startled when he recognized the man he had been chasing. "You're Burgess!" he exclaimed.
"That's right!" The other scowled, staring at the explorers' outfits.
Bud lowered himself and swung toward Tom
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"You're no hunter!" accused Howard. "You're a spy!"
"Shut up or I'll wing you!" the big man shouted angrily.
Hanson nudged the crewman to calm down and said to Burgess, "What were you doing near the sacred mountain?"
"I was looking for one of my rifles," the man snapped. "Anyway, what I do is my business!"
"You certainly ran for cover quickly after I spotted you," Hanson retorted.
"A man has to be careful in this jungle country," Burgess responded testily. "How'd I know who you were in that crazy get up? I just wanted to avoid trouble."
Hanson, without explaining the reason for the suits and helmets, and recalling that Tom had forgotten to inquire where the hunter was staying, asked, "You have a camp?"
"Of course!" Burgess answered.
"We'd like to see it," said Hanson. "Would you mind if we go along with you?"
"I can't permit you to come," Burgess stated flatly.
"Why not?"
"One of our hunters has contracted a dangerous disease," Burgess replied. "You'd be putting yourself in a hazardous position. In fact, I may be getting the disease myself. You shouldn't even be talking to me."
MISSING EXPLORERS 173
Howard, accepting Burgess* story, looked uneasy. The crewman insisted that he and Hanson return to the Sky Queen and Arv agreed. They said good-by to Burgess, turned around, and the two parties went in opposite directions.
But once the hunter was out of sight, Hanson said, "Howard, I don't believe one word of that fellow's story. Let's follow him to his camp."
The two men easily picked up the hunter's trail. After beating through the bush and woodland for an hour they still had not come to a camp.
"You don't suppose Burgess is onto us," said Howard, "and is leading us in circles."
"Possibly he is," Hanson conceded. "But we'll wear him down."
Eventually Burgess led them to a clearing with a mountain in the background. As he stalked across the open space, the others held back, so they would not be observed.
"Why, this is the taboo mountain!" Hanson exclaimed. "We're not far from where we started trailing Burgess!"
"Say, where'd he go?" Howard asked suddenly.
The hunter had vanished!
"He must be hiding," Hanson declared. "But where?"
He and the crewman hurried across the clearing and made a thorough search of the area. Not a single trace of Burgess was found.
174 THE CAVES OF NUCLEAR FIRE
"Maybe he's in the cave!" Howard suggested.
"If that's where he went," Hanson replied, "his life is in jeopardy. He wasn't wearing protective clothing."
The two searchers made their way to the cave. Reaching it, they noted that Chow was gone and assumed that he had returned to the Flying Lab with Tom and the others.
Hanson stepped to the cave entrance, lifted the mouthpiece of his helmet, and shouted, "Burgess! Come outl Your life's in danger from radiation!"
There was no response and the man did not appear, though the warning was repeated several times.
"Let's go!" Howard urged. "It's a long trek back to camp. We don't want to get caught in the jungle after dark."
Hanson suggested that they take a different route back to the Sky Queen from the beaten path the Terrasphere had made. Their enemies might try to ambush them on this path!
"Let's skirt the mountain for about a mile, then head for camp," Hanson proposed.
"I'll be glad when we're far enough away from this mountain, so we can shed these clothes," said Howard, as they set off. "I'm practically parboiled!"
Meanwhile, Tom and his companions had arrived at the Sky Queen and Doc Simpson was
MISSING EXPLORERS 175
giving Tom a thorough examination. A little manipulation at the shoulder blade put a wrenched arm back in place. This, together with a cut over the young inventor's right eye, where his helmet had pressed deeply, were the only bad results o£ Tom's fall.
Chow prepared a hearty meal which everyone enjoyed, but when it was over, Tom expressed his concern over Hanson and Howard's absence. "Maybe we should go back toward the mountain and search for them," he said. "Come on, Bud!"
Once more the Terrasphere repeated the journey, but the missing men were not located. The boys returned to camp. Hours passed. The sun set.
"I'm alarmed," said Tom to the others finally. "Arv and Howard may have been captured!"
CHAPTER 22
A SIGNAL FOR HELP
"COME on!" shouted Tom to Bud.
"Where?"
"We're going to search for Hanson and Howard again!"
"I'm all for it," said Bud. "But at night we don't stand a chance of finding them."
"We must try," Tom declared. "Let's take the Skeeter and look around."
The boys rushed to the hangar of the Sky Queen and let down the ramp. Then they rolled out the small helicopter.
Tom climbed behind the controls while Bud took the seat beside him. After a brief warm-up of the motor, the pilot set the rotor blades in motion.
"Are you planning to hunt near the mountain?" Bud asked.
"I'll fly over the jungle within a radius of five
176
A SIGNAL FOR HELP 177
miles," Tom answered. "If Arv and Howard can possibly do it, they'll give us a signal with the flashlights that they're carrying."
Tom edged the throttle forward. The blades spun faster and the craft lifted into the air. A moment later he and Bud were soaring above the treetops.
Under a moonless sky the terrain was spread below them like a murky blanket. The horizon was obscure and Tom found it difficult to maintain straight and level flight by visual means alone. He had to keep referring to his flight instruments.
As Bud gazed down at the black surface, he suddenly noticed low-burning campfires. The next moment he realized that it was the village of the friendly Mabawiki tribe. They flew on in ever-widening circles, but saw no sign of a signal from the ground. Half an hour later, however, Bud spotted more fires.
"Another village," he remarked.
Tom checked the location. "It's probably the Onari camp. I wonder if Hanson and Howard could be there." The pilot set his jaw firmly. "There's only one way to find out!"
"I know what you're going to say," Bud retorted. "That you intend to land there."
"Not exactly," said Tom. "We can hover low over the camp. That may scare the natives away, then we can drop down and take a look."
178 THE CAVES OF NUCLEAR FIRE
"The Onari warriors are pretty dangerous fellows," Bud warned. "Suppose they start using spears again? Those weapons may be primitive, but they're mighty effective!"
"We'll try to keep far enough above the men's throwing distance," Tom told him with a wry smile.
Still a mile away from the village, he watched his turn-and-bank indicator, then swung the Skeeter into a wide turn. When the helicopter was straight and level again, they flew directly over the Onari camp.
Tom circled the area, well above the reach of any native weapons. The boys could make out the figures of running men in the light from the campfires.
"Those natives certainly are excited!" Bud stated.
"Undoubtedly they've heard our engine," said Tom.
Both boys studied the camp for several moments, their eyes alert for any signals from Hanson and Howard. They saw none, but Tom, taking a deep breath, said, "I'm going lower."
Just then Bud, glancing off in the distance, sighted a light stabbing the blackness northeast of them. "Hold it, Tom! Look over there!"
The pilot gazed to where his friend was pointing. A small light was blinking in the darkness below.
A SIGNAL FOR HELP 179
"Bit, dit, ditl.. .Dah, dah, dah!.. .Bit, dit, dit!" chimed Bud, as he watched.
"It's an SOS!" Tom exclaimed.
He sent the helicopter speeding forward and hovered directly above the signal which continued to flash, evidently from a treetop. But now the dots and dashes were more than the distress signal. They were spelling words. Bud translated the message excitedly.
Arv. . .Howard. . .O.K.. . .rescue us!
"I'll say we will," shouted Tom in relief.
Unable to land among the trees, and wishing to light up the area, he released an electric flare. It cast an intense brightness on the scene. Hanson stood near the base of a baobab tree, while Howard was shinning down the trunk.
Bud uncoiled a rope ladder which he lowered from the side door. As the ladder brushed the surface, the two men grasped it and pulled themselves up. Moments later, Hanson and Howard, carrying their radiationproof suits, were safe inside the Skeeter. They expressed their thanks for the rescue, and Hanson added:
"Are we glad to see you! I sure didn't like the idea of spending the night in the jungle with those Onaris so close."
"What happened?" asked Tom.
"We got lost," Arv confessed sheepishly, then told about their encounter with Burgess and the native.
Tom was particularly interested in the hunter's disappearance not far from the cave entrance. Did the man know of another underground trail to the pit?
"It wasn't too bad being lost," Hanson continued, "until that same native who was with Burgess saw us not far from his village. We figured that he was from the Onaris and would send their warriors after us. Sure enough, he did."
"That's when we climbed the tree and hid," Howard added. "Boy, I certainly feel a lot happier now than I did twenty minutes ago!"
Tom was greatly perturbed over the situation. Burgess was in league with the ruthless tribe! What was the significance of it?
When the Skeeter returned to camp, the occupants of the Sky Queen rushed out to greet the helicopter. They were relieved to learn that Hanson and Howard had been rescued. Chow prepared a light supper for everyone. During the meal Tom asked Craig if he had any idea as to

182 THE CAVES OF NUCLEAR FIRE
how Burgess had managed to become friendly with the Onaris.
"I can think of one way," said the flier. "Perhaps he convinced the natives that he's a god!"
Bud snorted. "We're the best gods in the business," he said, grinning. "Why don't we win the Onaris to our side the same way?"
"By this time," Craig replied, "Burgess probably has the tribe turned against us. And if Burgess is in league with Hoplin and Cameron, they're no doubt friends with the Onaris too."
"What really baffles me," Tom said, frowning, "is what those three scoundrels are after."
"Do you think their headquarters might be near the cave?" asked Doc Simpson.
"I'm beginning to think so," Tom replied. Turning to Bud, he said, "In the morning take up the Skeeter. Search every inch of ground around the sacred mountain. Look for signs of a camp. And also keep your eyes open for a camouflaged plane on the ground."
Craig suggested further that the Mabawikis might be able to help them. Through the tribe's excellent scouting system, Makua's men probably knew every move the Onaris made.
"I can't go myself because I've been near the mountain. In fact, most of us have and we promised the chief that if we went into the taboo area, we'd stay away from the village."
Chow suddenly grinned broadly. "Ain't no law
A SIGNAL FOR HELP 183
against meetin' a villager in the woods outside their camp," the cook said. "An' I got another date to go herb huntin' in the mornin'."
"Great!" said Tom. "Then I'll delegate you for the job. Find out all you can."
Chow stuck out his chest importantly. "Brand my detective boots, I'm goin' to be jest like one o' them FBI inves-tee-gators!"
In the morning the Texan set off through the woods while Bud and Sterling took to the air in the Skeeter. Tom sought out Craig. He was eager to resume work in the cave of nuclear fire before high tide and needed the flier's help.
"Our first job," he said, "is to enlarge the opening in the wall, so the Terrasphere can anchor in it."
"I'm ready," said Craig. "But who will stand guard over the entrance? We shouldn't take everyone from here and leave the Sky Queen unprotected."
"Right," said Tom. "I'd forgotten." He thought a moment. "I'll rig up an electric eye at the entrance, and as we drive through, I'll lay a tiny cable with an alarm at our end of it. That should be warning enough."
Accompanied by Howard, the two started for the mountain in the Terrasphere. Within the hour they were drilling with the earth blaster. The opening in the rock barrier grew larger and larger.
184 THE CAVES OF NUCLEAR FIRE
Finally, Tom called a halt to make an inspection. To his dismay the edges of the hole crumbled under his touch. "I can't understand it," he said. "The rock appears to be very hard. In the lab it was not easy to crush."
He took additional time to study the problem. Suddenly he snapped his fingers. "I believe I know the answer!"
"What is it?" Craig asked.
"Vibration from the Terrasphere causes a resonance in the rock. As a result, it breaks up."
Craig frowned. "The tremendous power used for the crane of the Terrasphere will cause a great disturbance," he said. "The whole wall here might crumble away. Using it for any exploration of the pit would be risky business."
"What can you do?" Howard asked.
"There's one possible answer," Tom replied. "I can construct anchors on the rear of the ve-1 hide that will go so deep into the floor of the cave they can't possibly pull out. The ones I planned on won't do it. Another half hour of drilling here should be enough. Then we'll go back to the Flying Lab. I want to get started on those new anchors as soon as possible."
While they worked Tom kept wondering how Chow and Bud were progressing with their tasks.
Meanwhile, Bud was guiding the Skeeter at a very low altitude over the surrounding area.
A SIGNAL FOR HELP 185
Sterling sat beside him, gazing downward through binoculars. At a higher level he had detected nothing suspicious.
"Hoplin and his gang must be gophers," Bud said finally. "We know they're hiding around here. But where?"
"They've probably rigged an effective camouflage job," Sterling answered as the helicopter passed over the edge of the forest that came within a mile of the mountain. "A jungle isn't a difficult place in which to hide a camp or plane from the air. For instance-" He stopped abruptly as he stared through the glasses. "Bud," he cried out, "a plane down there has just been uncovered! It had a leafy blanket over part of it and the rest is painted green and brown. It's taking off!"
"Where is it?" Bud asked excitedly.
"Down there! About two o'clock low!"
"We must find out who the pilot is," said Bud. "It's the same kind of two-engine plane Hoplin had."
He lowered the helicopter, but by this time the plane was racing across open ground. Soon it took off.
"We've lost him!" Bud said, frowning in disappointment. "We never could catch him in this bus."
The plane's pilot rolled his craft into a steep, climbing turn. To the astonishment of Bud and Sterling, the mysterious craft sped by them in a
186 THE CAVES OF NUCLEAR FIRE
close pass but its pilot held one hand over his face to avoid detection.
"He wanted to find out who we are," Bud remarked, "without giving us a chance to recognize him."
Sterling's face had gone white. "Did you see what was in the nose of that plane?" he exclaimed. "Rocket mounts! The same type that are used in air combat! Does this mean an attack?"
The pilot of the plane maneuvered into a tight turn and came head-on toward the helicopter.
"It's going to shoot!" Sterling shouted.
CHAPTER 23
THE NATIVES ATTACK
BUD shoved the Skeeter down with elevator swiftness. The maneuver was effective and the attacking plane shot overhead on its second pass. The helicopter hovered at treetop level to prevent an assault from below.
"Let's land this thing quick," Sterling pleaded, "and make a run for cover."
"It wouldn't work," Bud retorted. "Then we'd really be sitting ducks! Our only chance is to try to outmaneuver that pilot!"
The plane swung into another turn. Bud tensed for the next defensive move, his hands gripping the controls hard. Since the Skeeter lacked the maneuverability of a plane, Bud's enemy had a tremendous advantage.
The attacker roared closer for a head-on shot. Bud waited. Then, at the last instant, he skidded the Skeeter to one side.
187
188 THE CAVES OF NUCLEAR FIRE
In the meantime a sudden point of light shot out from the nose of the plane. A split second later a small explosive rocket streaked by the Skeeter, missing it by inches. The turbulence created in its wake almost forced the helicopter out of control.
The rocket dropped, exploding in the jungle. Bits of trees and rocks shot skyward.
"I hope no one was injured," said Sterling. "That pilot is as ruthless as they come!"
Their enemy now adopted a new tactic and came at the Skeeter from the rear. Bud flew the helicopter into an even tighter turn. The attacking pilot attempted to circle with the Skeeter, but the maneuver proved to be too tight for him and his craft nearly went into an accelerated stall.
Twice again he tried this maneuver but each time he had to fight from spinning wildly into the jungle.
"That guy hasn't had real combat service," said Bud, "or he'd dive on us and shoot."
"Lucky for us he hasn't," Sterling replied. "He's dangerous enough."
The assault continued, but Bud was confident that he could outwit his foe. At last, after the enemy pilot had gone into a partial spin and pulled out just in time to save himself, he zoomed his plane into a steep climb and flew off.
"Whewl" said Sterling, mopping the perspira-
THE NATIVES ATTACK 189
tion from his face. "I was sure we were goners that time! Bud, your skill at that stick and those pedals is superb!"
"Thanks, pal," replied the young pilot who was trembling, now that the tension was over. "We'd better head back to the Sky Queen!" he suggested. "If that pilot has any rockets left, he may try for revenge and release them on our camp!"
Bud and Sterling were relieved, however, to find the camp still intact. The mysterious plane had not even flown over it.
When Tom returned with Craig and Howard, Bud informed him of the attack. The young inventor gave Bud and Sterling a warmhearted look. "Thank goodness you're alive!" Then he added angrily, "I'm sure that pilot was Hoplin. He and his gang are going too far when they start shooting rockets! We must put a stop to this!"
Tom went to the radio compartment of the Sky Queen and turned on the powerful shortwave set. Within a few minutes he was talking to his father.
"It's great to hear from you, Tom," Mr-Swift's voice crackled over the receiver. "How are things going?"
Tom gave him the news, ending with Bud and Sterling's experience that afternoon. Mr. Swift said he would personally contact the Belgian Congo authorities. "And I'll take the matter up
190 THE CAVES OF NUCLEAR FIRE
with the Belgian government if necessary!" he declared.
After warning Tom to be more alert than ever, the elder inventor said good-by. Tom switched off his set. When he met the others in the lounge for cool drinks of lemonade, Craig remarked, "Chow hasn't come back yet."
"His detective work probably is taking him more time than he expected," Tom replied.
"If I know Chow," Bud spoke up, "he's introducing his Mabawiki friend to a few Texas-style meals."
The next morning Hanson and Sterling aided Tom in building larger anchors for the Terra-sphere with stronger expansion bolts. Tests proved them to be very efficient.
Satisfied, Tom installed several in the aft section of his Terrasphere. Then, after consulting his tide table, the young inventor got ready for another excursion to the sacred mountain to test the anchors in place.
Bud, Craig, and Howard accompanied him. When the explorers arrived at the cave, Craig volunteered to stand guard at the entrance as a double precaution, even though the alarm system was to be used.
"It will be an extra precaution," he argued.
"Okay," Tom conceded.
Tom drove the vehicle to where the rock barrier had been. Then, slowly, he eased the Terra-
THE NATIVES ATTACK 191
sphere through the opening that he had drilled the day before.
"Take it easy!" Bud advised. "That pit is a long way down!"
Tom stopped as near the edge as he dared, then fired the anchors into the cave floor.
"Let's hope this works," he said, and applied a small amount of forward power.
The anchors held firmly!
Bud thumped his friend on the back. "Good work, Tom! But the past few minutes have aged me ten years!"
Tom chuckled. "After you've been down in the pit with me," he said, "you'll take on a hundred years."
Tom detached the anchors and left them buried deep in the rocky floor. "When we come back to explore the pit," he said, "I can simply reattach them to the Terrasphere."
"When do we descend?" Bud inquired.
"Tomorrow, I hope."
The explorers started out of the cave. As they emerged, they saw Craig standing guard. He looked worried and motioned for the others to come out of the cabin quickly.
"What is it?" Tom asked as they descended.
"I heard screams in the forest."
There was no question but that a great commotion was taking place. Suddenly, from out of the brush, burst a spectacular sight.
192 THE CAVES OF NUCLEAR FIRE
Chow was clinging to the back of a zebra which was racing at full gallop!
"Run fer your lives!" screamed the Texan when he saw his friends.
Thinking that he wanted to avoid running them down, they watched carefully. All of them broke into laughter. Apparently a zebra was no harder for Chow to manage than a wild horse!
The zebra suddenly halted and the cook was thrown to the ground. As the animal bounded off, Chow's friends ran to assist him.
"That animal has a mind of its own," Tom remarked as he drew nearer to the Texan. "But where did you-"
He stopped abruptly. Tom found himself facing an unexpected and terrifying situation. Now he realized the real import of Chow's shouted warning. The surrounding jungle seemed to be filled with Onari warriors! Their faces were painted in white, grotesque designs. Each native was armed with a shield and a spear.
"Yi! Ikumu! Yi!" they screamed.
For a few seconds Tom's senses were numbed, then he collected his wits and ordered Chow and the others to run for the shelter of the Terra-sphere. The young inventor took one more look at the natives, then turned to follow his companions.
But though he ran with all possible speed, his delay proved costly. Two Onari warriors sprung
THE NATIVES ATTACK 193
from a flanking position in the brush and blocked his escape.
One of the natives threw his spear, but Tom side-stepped, and it plunged into the soft dirt beside him. Tom experienced a surge of panic. "Where can I go?"
Deciding on the forest, he made a wild dash for the thickest section of brush he could find. The two warriors took after him but he outran them.
The young inventor quickly lay down and remained perfectly still. The two pursuing Onaris crashed through the thickets, prodding the brush with their spears.
Tom was unable to see the men but he could hear them mumbling excitedly to each other. Finally they separated to continue the search.
In the distance, Tom could detect the noise and confusion of a hand-to-hand encounter. His friends apparently were putting up a real fight. "I must get back to help them!" Tom determined.
His own dilemma was becoming more crucial, however. One of the warriors was drawing close to his position! Should he wait it out or run? His pursuer sounded as if he was only a few feet away, but Tom was still unable to catch a glimpse of the Onari.
"No!" Tom decided. "Running is not the answer! Too many natives between me and the Terrasphere!"
The Onari stepped very close. Tom could see
194 THE CAVES OF NUCLEAR FIRE
the man's legs. Luckily, the dense upper portion of the brush prevented the native from spotting the young inventor.
"I must act fast!" Tom said to himself. "That fellow will poke his spear around here any second!"
Realizing that his only chance was to catch the Onari off guard, Tom tensed himself for quick action. Rolling over on his back, he hooked one foot behind the ankle of the warrior. With his other foot he pushed hard against the native's knee.
The Onari, taken completely by surprise, crashed backward to the ground. Tom leaped up for a getaway, but the warrior grabbed his ankle and brought him down.
Both Tom and his adversary scrambled to their feet, facing each other. The native towered a head over Tom, who realized instantly that wrestling was out of the question. But primitive peoples, he recalled, know nothing of boxing. Tom had often boxed with Bud. This was his only advantage over the lunging native.
Thud! A left hook hit the man's midsection. As the Onari doubled up with pain, Tom landed a right uppercut to his chin. The warrior spun to the ground in a clean knockout.
Tom stumbled groggily out of the brush. He looked around the clearing. All the Onaris were gone and his friends as well.
THE NATIVES ATTACK 195
"I must find Bud and the others," the inventor told himself.
As his mind and vision cleared, Tom saw something that sent a chill down his spine. The Terrasphere had been covered with dry branches and bark to which the warriors had set fire.
Tom watched in horror as the vehicle was lost in a mountain of flame!
CHAPTER 24
AT NATURE'S MERCY
THE Terrasphere would be ruined!
As Tom stared at the burning mass, a wave of hot air swept past him. The heat of the fire was growing more intense!
Then, as if coming out of an anesthetic, Tom's brain began to function at full speed. "The Terrasphere can't burn! It's resistant to high temperatures!"
As his concern for the vehicle diminished, Tom's thoughts turned again to his companions. "Bud! Craig! Howard!" he shouted.
"Over here," responded a voice weakly. Bud was staggering away from the roaring fire.
Tom rushed over to help him. "Are you all right?" he asked.
"I guess so," Bud muttered. He rubbed his head gingerly. "Somebody clouted me. I just came to."
196
AT NATURE'S MERCY 197
The boys looked around for the other members of their party. Finally they spotted Craig and Howard lying unconscious a short distance away. First aid from Tom and Bud soon revived them.
"I can't understand the attack," said Craig. "I've never known any natives to venture this close to the mountain."
"I guess the answer is Hoplin and his gang," Tom remarked. "But those crooks must have offered the Onaris a mighty big reward to get them to break a taboo."
Suddenly the group realized that Chow was missing. Worried, they began a search in the cave and the woods, shouting the Texan's name. Chow did not reply.
"Last time I saw him," said Craig, "he was swinging one of his high-heeled boots at those natives like a club. Onaris were flying in every direction."
"The natives must have taken Chow with them," ventured Howard.
"But why would they take Chow prisoner and leave the rest of us behind?" Craig asked.
"Chow may have escaped on that zebra he was riding," Bud suggested. Then he looked at his watch. "It'll be time for the gas to emit pretty soon. We'd better get out of here."
Tom nodded. "We'll go back to the Sky Queen. And if Chow doesn't appear very soon,
198 THE CAVES OF NUCLEAR FIRE
we'll pay the Onari village an unexpected visit!"
The branches and bark which had been piled over the Terrasphere had burned out. Except for a few minor scorched streaks, the vehicle had suffered no damage.
The group climbed into the cabin and made their way back to camp. To their astonishment, they discovered that the Flying Lab also had been attacked by the warring natives. Fortunately, no harm had come to Doc Simpson or the crewmen and no appreciable damage had been done to the plane.
"Nevertheless," said Tom, "Hoplin made an all-out effort to drive us away."
Bud growled, "I'll say he did. But if you ask me, I'd prefer dealing with the natives to men with rocket-shooting planes!"
More than an hour passed. Still Chow failed to return.
"I'm going to organize a rescue party!" declared Tom. "If the Onaris have Chow, they're going to give him up!"
At that moment he heard shouting outside the Sky Queen and rushed to one of the windows to find out who it was. Galloping into camp was a zebra and mounted on its back was the plump figure of Chow!
Tom ran out to greet him. "I'm sure glad to see you," he said. "Where were you?"
AT NATURE'S MERCY T99
"Brand my passport," roared Chow, "this here striped cow pony run me all over Africa before I got her broke!"
"Tell us what happened," Tom urged.
The Texan explained that the zebra belonged to his Mabawiki friend, who had captured it in hope of training the animal for riding.
"But he couldn't get nowheres," Chow declared. "So I been tryin' Texas-style bronc-bustin' on the critter. Lucky I was astride when those wild natives showed up." He patted the zebra, adding, "We sure made a fast getaway."
"What occurred after the Onaris attacked us here?" Tom urged.
"Well," replied the Texan, "I grabbed onto this critter again. Guess she's gettin' to like me. But when I tried to steer her back here fer help, she took off in the opposite direction. It took me more'n an hour to simmer her down."
The others laughed and Tom said, "We thought the natives had captured you!"
The cook looked hurt. "It'd take more'n a tribe o' spear throwers to corral me!" he boasted.
Tom asked if the cook had had any luck obtaining the information he had requested.
Chow's eyes sparkled with enthusiasm. "I sure did!" he said. "Wait'll you hear what I found out!"
The Texan explained that he had been in-
200 THE CAVES OF NUCLEAR FIRE
troduced to a Mabawiki who acted as spy against the Onari tribe. "He says the Onaris' leaders are in cahoots with a group of white men."
"Our suspicions were right!" Craig interrupted.
"Did the native know any of the white men's names?" Tom asked.
"No," replied Chow, "but he described the fellers pretty well. Burgess was one o' them. The other two I'd bet a mustang are Hoplin an' Cameron."
"Did he know what Hoplin and the others are doing here in Africa?" Tom queried the cook.
Chow said they were carrying on some kind of mining operations on the other side of the sacred mountain. The cook's expression suddenly became very serious. "Tom," he said grimly, "them white fellers have sworn that you're never goin' to leave Africa alive!"
"Their intentions have been mighty obvious already," Bud remarked.
"That ain't all," Chow went on. "Them Onaris ain't goin' to wait. They're plannin' to get rid o' the whole bunch o' us right away!"
"Wow!" cried Bud.
Doc Simpson, who had made no comment up to this time, asked if the Onaris helped in the mining operations.
"I reckon they do," Chow answered.
The physician was thoughtful. "A terrible
AT NATURE'S MERCY 201
idea just came to me," he said. "I doubt that any of the gang wear radiationproof suits. And if not, Nature will mete out a horrible fate to all of them!"
This thought sobered the members of the Swift expedition. Nevertheless, they felt that their enemies would attack them as long as it was possible for them to do so. For this reason, Tom worked out a plan for a rotation of guards. When he himself was not on duty, Tom prepared his equipment for the big experiment. He gave the Terrasphere, the explorers' suits, and every gadget to be carried a fresh coat of Inertite paint. Then, to the bottom of the spherical cabin, he attached a special digging device.
"That looks mighty complicated," remarked Craig.
"I hope it works as well in the cave," said Tom hopefully, "as it did in the laboratory."
"What is it?" the flier asked.
"I call it a hypersonic drill," replied the young inventor. "The device generates ultrahigh-fre-quency waves. These waves cause the molecules in a substance to vibrate vigorously. As a result, the material breaks down into a fine dust. I can bore through most anything at which I aim the waves."
"I'll take your word for it!" Craig said with a grin. "But tell me one thing. What advantage does this have over your earth blaster?"
202 THE CAVES OF NUCLEAR FIRE
"I can direct the beam of the hypersonic drill very accurately," Tom replied. "Besides, there'll be no chance of friction and a resultant explosion in the pit where I plan to use it, as there might be with the blaster."
"You're planning to get samples of the rock at the bottom of the pit?" Craig questioned in astonishment.
"That's right," Tom answered. "In fact, it's my main reason for going into the cave of nuclear fire."
The following morning Tom, together with Bud, Craig, Hanson, and Sterling, boarded the Terrasphere. Anxiously, the remaining group waved a farewell and wished the explorers luck. Reaching the cave, Tom set the alarm system, then drove in. Although conditions were the same as on previous trips, the men were tense. This adventure, they knew, held an even greater element of danger than the former ones.
When the Terrasphere arrived at the pit, Tom skillfully maneuvered it through the opening and halted close to the edge. At once the anchors that had been left in the rocky floor were secured to the aft end of the vehicle.
The group held a brief consultation. Then Hanson and Sterling assumed their appointed posts in the stationary compartment where they always rode. From this point the two men could operate the hoist in the event that the controls
AT NATURE'S MERCY 203
in the spherical cabin failed to work properly.
"Well," Tom said with a smile, "this is it, fellows!" He studied the faces of Bud and Craig. "If either of you wants to change his mind about going-now is the time!"
"Who will keep you out of trouble if we don't go?" Bud jested, trying to hide the fact that he felt far from calm.
"I wouldn't miss this trip for a gold mine," Craig rejoined.
The three climbed into the sphere and Tom seated himself behind an array of levers and switches. First he unhooked the cabin from the chassis of the Terrasphere. Then he set the crane in motion. The cabin rocked for a moment before it lifted clear of the vehicle. It swung gently out over the mysterious pit.
Tom payed out the cables for descent. As the cabin slowly traveled downward, the adventurers gazed in awe at the unscalable walls of the phosphorescent pit. What beauty of color! The lower they went, the brighter the hues became.
"It's magnificent!" Craig exclaimed.
Tom checked his depth indicator. "We're about three hundred feet down."
"How deep are we going?" Bud asked.
"I want to stop approximately one hundred feet above the bottom and try an experiment," Tom replied.
At four hundred feet he checked their descent
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and peered at the flowing river below. It glowed with the brilliance of a fierce fire.
"I'd never guess anything like this existed in the world," said Craig. "Utterly fantastic."
"Yes," Bud agreed, "but nothing would stand a chance in that racing water. See where it disappears under the mountain-not even headroom!"
Tom glanced around the cabin, then put his hand on a special control Bud had not noticed before.
"What are you going to do with that?" he asked curiously.
"Drop a metal block that's attached to the bottom of the sphere," Tom answered. "I want to splash some water along the banks."
From the windows they watched the plunge of the metal block. As it hit, water splashed on the rocky banks of the river. At once a series of green luminous clouds were formed.
"It's the gas!" yelled Bud excitedly. "The glowing gas!"
Elated, Tom descended lower into the pit, hovering less than forty feet above the river. "I'm going to obtain some samples of that rock!" he told the others excitedly, and switched on the hypersonic drill.
With meticulous care he aimed a narrow beam of high-energy waves as the stratum of rock beneath them. When a quantity of the rock had been pulverized, Tom shut off the ray.
 
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He now lowered a special bucket, the bottom of which was formed by two metal vanes. These opened electrically and scooped up the rock, steam-shovel fashion.
The young scientist had just hoisted the bucket aboard when the spherical cabin tilted abruptly. The occupants almost lost their footing.
"Bud," commanded Tom, "look through the overhead hatch and check the cables!"
Bud scrambled up the small ladder and peered outside. "Good night!" he yelled. "One of the cables is broken where it joins the sphere! Another is giving way!"
Frantically Tom clicked on the microphone which connected the cabin with the vehicle above. "Arv! Hank!" he shouted.
There was no response!
"We've lost contact with them!" Craig cried out.
Tom shuddered. "It must have been the communication cable that parted!"
The cabin tilted a bit more. The explorers looked at one another, fear clutching them. Could they hoist themselves out of the pit before all the cables might go?
Tom switched on his hoist control. To his horror the power was gone. The explorers were completely helpless!
CHAPTER 25
A SURPRISE VICTORY
IN desperation Tom tried the communication device again. Still no answer from Hanson and Sterling.
"Were they attacked by Hoplin?" Tom wondered grimly. "Is that fiend in charge of this operation now?"
The cabin listed at a sickening angle. No one spoke as Tom tried every control mechanism again. The thought came to him that his experiment in producing the deadly gas had caused a reaction on the strands of the cables. Probably the Inertite paint had not been thick enough at the point where they connected with the cabin.
As the hopes of the young inventor and his friends reached low ebb, they suddenly felt a jolt.
"There goes another cable!" Craig cried out.
"Wait a minute!" Tom exclaimed. "Look out the window! We're rising!"
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It was true. Slowly, with creaks and groans, the sphere was lifting.
"Good old Hanson and Sterling!" murmured Tom.
Bud was very quiet. "We aren't out of trouble yet," he thought. "We still have four hundred feet to go and half the cables are gone!"
The occupants of the sphere waited nervously. Seconds seemed like hours. Finally, the cabin made the remaining climb and hung opposite the rim of the pit. Slowly, the hoist was swung around and in a few moments the cabin was resting securely on the chassis of the Terrasphere.
The three boys hugged one another in relief and thankfulness. Then, as they climbed out, they saw Hanson and Sterling running toward them.
"You're safe! All of you are here!" Arv cried in relief.
He explained that he and Hank had been fearful one or more of the explorers might have been out of the cabin when they started hoisting it.
"When we tried contacting you to tell some news of our own, we didn't get any response. Then, when we discovered that some of the cables had parted, we brought you up in a hurry."
The rescued trio expressed their deep-felt thanks, then Tom added, "You said you have some news of your own?"
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Hanson and Sterling smiled and the model-maker replied, "Come look in the driver's cabin."
They all hurried forward and peered in. On the floor, securely trussed, was Burgess! He eyed his captors fiercely but did not speak.
"What? How?" Craig exclaimed.
"Burgess tried his last trick," Sterling explained. "He came in here with a time bomb but he didn't notice our alarm system at the entrance. We were ready for himl"
Tom slapped Burgess' captors on their backs. "Great work!" he said. "Now if we can just round up Hoplin and Cameron-"
As the young inventor drove the Terrasphere back to camp, the prisoner refused to say one word. Reaching the Sky Queen, Tom immediately went to the short-wave set to contact his father and ask him to notify the authorities about Burgess.
To his surprise the boy's mother came on. "Your father has gone to Leopoldville," she said. "He'll see you soon. A great deal has happened here. Harlan Ames traced the missing manuscript to a safe-deposit box in the name of Taylor. Hoplin was going to sell the information on antipro-tons to a foreign power but never had a chance to deliver it. He and Cameron had to take off for Africa in a hurry to keep you from finding out about some kind of work they're doing there."
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Tom told her about the prisoner and she advised her son to keep him at the Sky Queen for at least a day. "Dad will be there by that time, I'm sure."
While waiting for Mr. Swift to arrive, Tom spent the time working in the laboratory to determine the contents of the powdered-rock samples he had obtained from the bottom of the pit. Within a few hours, he reached a sound conclusion concerning the mystery of the glowing gas. Just as his experiments were completed, Chow entered the room. Tom told him he had learned the secret of the cave of nuclear fire.
"Can you tell me?" the cook asked.
"Certainly," Tom said, smiling. "At high tide, the water passes over a bed of uranium ore and a nuclear catalyst. The protons produced from the water trigger a nuclear fusion of the uranium with other atoms in the mineral bed to produce Exploron."
Chow, wearing a confused expression, already regretted that he had requested an explanation. "Brand my ole schoolbooks," he said, "I'd ruther tangle with a wild stampede than try to savvy that lingo!"
At that moment they heard the whirring of giant rotor blades and saw a huge helicopter descending next to the Sky Queen. Tom, Chow, and the other members of the expedition rushed outside.
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"Dad!" Tom shouted excitedly, as Mr. Swift climbed from the cabin.
"Hello, son!" After an affectionate hug, he said, "I've brought some men you'll be glad to see."
From the helicopter came Frederick Shopfer, the Leopoldville police officer, and behind him three handcuffed prisoners-two white and one African native.
"Hoplin and Cameron!" Tom shouted.
"Yes," said Mr. Swift, "and the chief of the Onaris. They have confessed everything. They've been carrying on bootleg mining activities in the mountain."
Shopfer took a small silk bag from his pocket and opened the drawstring. Into Tom's hand he poured green gems of various sizes. These, he explained, had been found on Hoplin when the three men were arrested in Leopoldville.
"Diamonds," said Mr. Swift. "I suspect the strong radiation from the mountain has affected their molecular structure and turned them a beautiful green. The mine has a rich deposit."
"So that's it!" Tom cried out. He turned to Hoplin. "When you learned that I was planning an expedition to the scene of your diamond operations, you did everything to stop me!"
"And you even tried murder by shooting a rocket from your plane," Bud accused the prisoner.
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"I was only trying to scare you into leaving here," Hoplin answered.
He broke down completely, admitting he had planned on organizing an immense diamond market. The fabulous green jewels were to be sold through fences of the underworld, so Hoplin could avoid taxes and duty.
He and Cameron had sailed for the United States to make the necessary arrangements at the same time Craig had left. They feared that he might know about their operations.
"By the time legitimate diamond brokers learned of our operation," Hoplin confessed, "we would have made a fortune."
"Your worst crime," Mr. Swift spoke up, "was stealing the antiproton papers and planning to deliver them to a hostile foreign power. The information contained in them could lead to the destruction of the whole world!"
The white prisoners winced but still looked defiant.
"Any blame for that goes to the agent who asked us to steal it!" retorted Hoplin.
Doc Simpson moved forward to ask them a question. "Did you men wear any protection against radiation while you were near the mountain?"
"No," responded Cameron. "We didn't know there was any."
"You've been heavily exposed to it-I'm afraid
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too often and for too long," the physician told them. "We can soon find out in our lab where there's a testing machine."
The prisoners, utterly defeated and trembling from the shock of the medical man's news, submitted to an examination. When Hoplin and Cameron were told their conditions were beyond help, they began to scream in terror. After they were led away, the Onari chief was put into the examination chair. To everyone's amazement, the report on radiation sickness for him was negative.
"This is astounding!" Mr. Swift exclaimed. "How do you account for it, Doc?"
Chow stepped forward. "Bet you I got the answer," he said. "Herbs! This here jungle's full o' all kinds o' queer plants. One of them ate reg'lar by the natives. They give me a yarn 'bout it keepin' that there fire god from gettin' mad at them, but mebbe it's true!"
Doc Simpson beamed. "Chow, I believe you may have stumbled on a marvelous discovery. I'll work with Tom to prove your idea. But I'm inclined to think you're right that the herb keeps the natives from being affected by the mountain's radiation. You know, Nature is very kind, if we'll only pay attention to what she has to offer. Everywhere she maintains a balance."
"Does this mean," Bud spoke up, "that some day we can discard those heavy suits and avoid the effects of radiation by just sitting down to a special jungle meal prepared by our famous medicine man Chow?" He winked at the others. "I don't know which would be worse!"
After the three prisoners had left in the helicopter, Mr. Swift told the others that he and Tom had been asked to build an experimental station near the mountain for further research.
Tom smiled. "Great! But if we've opened up a new field which may revolutionize the study of atomic energy, the credit goes to you, Craig. Without you, we'd never have heard about this magic mountain."
Later, Tom and his father went to the laboratory to do some experimenting. That evening the younger inventor announced to his friends that he and Mr. Swift had worked out a new formula.
"Only one-thousandth of an inch of Inertite painted on any object will be needed to protect it from strong cosmic rays," he said excitedly.
Bud grinned. "Marvelous, pall And of course that means another trip into space. I can see the adventure looming up already: Tom Swift on the Phantom Satellite."
"I hope you're right," said Tom. "And this time let's find those space friends of ours we've never seen!"

THE END
IN THE CAVES OF NUCLEAR FIRE
By VICTOR APPLETON II
No. 8 in the Tom Swift Jr. series.