TOM SWIFT AND HIS AIR SCOUT

or

Uncle Sam's Mastery of the Sky

by

Victor Appleton



CONTENTS

CHAPTER

I A SKY RIDE II A NEW IDEA III THE BIG OFFER IV MR. DAMON'S WHIZZER V TOM'S PROJECT VI MAKING PLANS VII A PROBLEM IN SOUND VIII THROUGH THE ROOF IX AFTER A SPY X A BIG SPLASH XI A NIGHT TRIP XII THE CRY FOR HELP XIII SOMETHING QUEER XIV THE TELEPHONE CALL XV A VAIN SEARCH XVI THE LONG NIGHT XVII SILENT SAM XVIII SUSPICIONS XIX ANOTHER FLIGHT XX QUEER MARKS XXI THE DESERTED CABIN XXII CLEWS AT LAST XXIII THE GOVERNMENT TEST XXIV IN THE MOONLIGHT XXV THE GOLD TOOTH



TOM SWIFT AND HIS AIR SCOUT



CHAPTER I

A SKY RIDE

"Oh Tom, is it really safe?"

A young lady—an exceedingly pretty young lady, she could be called—stood with one small, gloved hand on the outstretched wing of an aeroplane, and looked up at a young man, attired in a leather, fur-lined suit, who sat in the cockpit of the machine just above her.

"Safe, Mary?" repeated the pilot, as he reached in under the hood of the craft to make sure about one of the controls. "Why, you ought to know by this time that I wouldn't go up if it wasn't safe!"

"Oh, yes, I know, Tom. It may be all right for you, but I've never been up in this kind of airship before, and I want to know if it's safe for me."

The young man leaned over the edge of the padded cockpit, and clasped in his rather grimy hand the neatly gloved one of the young lady. And though the glove was new, and fitted the hand perfectly, there was no attempt to withdraw it. Instead, the young lady seemed to be very glad indeed that her hand was in such safe keeping.

"Mary!" exclaimed the young man, "if it wasn't safe—as safe as a church—I wouldn't dream of taking you up!" and at the mention of "church" Mary Nestor blushed just the least bit. Or perhaps it was that the prospective excitement of the moment caused the blood to surge into her cheeks. Have it as you will.

"Come, Mary! you're not going to back out the last minute, are you?" asked Tom Swift. "Everything is all right. I've made a trial flight, and you've seen me come down as safely as a bird. You promised to go up with me. I won't go very high if you don't like it, but my experience has been that, once you're off the ground, it doesn't make any difference how high you go. You'll find it very fascinating. So skip along to the house, and Mrs. Baggert will help you get into your togs."

"Shall I have to wear all those things—such as you have on?" asked Mary, blushing again.

"Well, you'll be more comfortable in a fur-lined leather suit," asserted Tom. "And if it does make you look like an Eskimo, why I'm sure it will be very becoming. Not that you don't look nice now," he hastened to assure Miss Nestor, "but an aviation suit will be very—well, fetching, I should say."

"If I could be sure it would 'fetch' me back safe, Tom—"

"That'll do! That'll do!" laughed the young aviator. "One joke like that is enough in a morning. It was pretty good, though. Now go on in and tog up."

"You're sure it's safe, Tom?"

"Positive! Trot along now. I want to fix a wire and—"

"Oh, is anything broken?" and the girl, who had started away from the aeroplane, turned back again.

"No, not broken. It's only a little auxiliary dingus I put on to make it easier to read the barograph, but I think I'll go back to the old system. Nothing to do with flying at all, except to tell how high up one is."

"That's just what I don't care to know, Tom," said Mary Nestor, with a smile. "If I could imagine I was sailing along only about ten feet in the air I wouldn't mind so much."

"Flying at that height would be the worst sort of danger. You leave it to me, Mary. I won't take you up above the clouds on this sky ride; though, later, I'm sure you'll want to try that. This is only a little flight. You've been promising long enough to take a trip with me, and now I believe you're trying to back out."

"No, really I'm not, Tom! Only, at the last minute, the machine looks so small and frail, and the sky is so—big—"

She glanced up and seemed to shiver just a trifle.

"Don't be thinking of those things, Mary!" laughed Tom Swift. "Trot along and get ready. The motor never worked better, and we may break a few speed records this morning. No traffic cops to stop us, either, as there might be if we were in an auto."

"There you go, Mary!" exclaimed Tom, as if struck with a new thought. "You've ridden in an auto with me many a time, and you never were a bit afraid, though we were in more danger than we'll be this morning."

"Danger, Tom, in an auto? How?"

"Why, danger of a wheel collapsing as we were going full speed; or the steering knuckle breaking and sending us into a tree; danger of running into a stone wall or a ditch; danger of some one running into us, or of us running into some one else. There isn't one of these dangers on a sky ride."

"No," said Mary slowly. "But there's the danger of falling."

"One against twenty. That's the safety margin. And, if we do fall, it will be like landing in a feather bed! There, don't wait any longer. Go and get ready."

Mary sighed, and then, seeming to summon her nerve to her aid, she smiled brightly, waved her hand to Tom, and hastened toward his home, where Mrs. Baggert the matronly housekeeper, was waiting to help the girl attire herself in a flying-suit of leather.

Mary Nestor, who had a very warm place in the heart of Tom Swift, had, as he stated, some time since promised to take a trip in the air with the young inventor. But she had kept putting it off, for one reason or another, until Tom began to despair of ever getting her to accompany him. To-day, however, when she had called to inquire about his father, who had been slightly ill, Tom had, after the social visit, insisted on the promise being kept.

He had his mechanic get out one of the safest, though a speedy, double machine, and, with Mary to watch, Tom had taken a trial flight, just to show her how easy it was. It was not the first time she had seen him take to the air, but now she watched with different emotions, for she was vitally interested.

Tom had sailed down from aloft, making a landing in the aviation field he had constructed near his home, and then he had insisted that Mary should keep her promise to take a sky ride with him.

"Don't be too long now!" called Tom to the girl, as she hurried toward the house. "Never mind about your hair, or whether your hat's on straight. You're going to wear a cap, anyhow, and tuck your hair up under that. It's hot down here, but it will be cold up above; so tell Mrs. Baggert to see that you're warmly dressed."

"All right," and gaily she waved her hand to him. Now that she had made her decision, and was really going up, she was not half so frightened as she had been in the contemplation of it.

As Tom climbed out of the machine, to give it a careful inspection, though he was certain there was nothing wrong, an aged colored man shuffled toward him.

"Yo'—yo'll be mighty careful ob Miss Nestor now, won't yo', Massa Tom?" asked the man.

"Of course I will, Eradicate," was the young inventor's answer.

"Case we ain't got many laik her no mo', an' dat's de truf, Massa Tom," went on the old man. "So be mighty careful laik!"

"That's what I will, Rad! And, while I'm up in the air, don't you and Koku have any trouble."

"Ho! Trouble wif dat onery no-'count giant! I guess not!" and the colored man limped off, highly indignant.

Satisfied, from an inspection of his machine, that it was as nearly mechanically perfect as it was possible to be, Tom Swift finished his trip around it and stood near the big propeller, waiting for Mary Nestor to reappear. Presently she did so, and Tom gaily waved his hand to her.

"You're a picture!" he cried, as he saw how particularly "fetching" she looked in the aviator's costume which was like his own. Because of the danger of entanglement, Miss Nestor had doffed her skirts, and wore the costume of all aviators—men and women.

"I wish I had my camera!" cried Tom. "You look—stunning!"

"I hope that isn't any comment on how I'm going to feel if we have to make a—forced landing, I believe you call it," she retorted.

"Oh, I'll take care of that!" exclaimed Tom. "Now up you go, and we'll start," and he helped her to climb into the padded seat of the cockpit, behind where he was to sit.

"Oh, Tom! Don't be in such a hurry!" expostulated Mary. "Let me get my breath!"

"No!" laughed the young inventor. "If I did you might back out. Get in, fasten the strap around you and sit still. That's all you have to do. Don't be afraid, I'll be very careful. And don't try to yell at me to go slower or lower once we're up in the air.

"Why not?" Mary wanted to know, as she settled herself in her seat.

"Because I can't very well bear you, or talk to you. The motor makes so much noise, you know. We can do a little talking through this speaking tube," and he indicated one, "but it isn't very satisfactory. So if you have anything to say—"

"In the language of the poets," interrupted Mary, "if I have words to spill, prepare to spill them now. Well, I haven't! Now I'm here, go ahead! I shall probably be too frightened to talk, anyhow."

"Oh, no you won't—after the first little sensation," Tom assured her. "You'll be crazy about it. Come on, Jackson!" he called to the mechanician. "Start the ball rolling!"

Tom was in his place, his goggles and cap well down over his face, and he was adjusting the switch as the mechanic prepared to spin the propellers.

Suddenly a man came running from the Swift house, waving his arms not unlike the blades of an aircraft propeller, he also shouted, but Tom, whose ears were covered with his fur cap, could not hear. However, Jackson did, and stopped whirling the blades, turning about to see what was wanted.

"Why, it's Mr. Damon!" exclaimed Tom, as he caught sight of the excited man. "Hello, what's the matter?" the youth asked, pulling aside one flap of his head-covering so he might hear the answer.

"Tom! Wait a minute! Bless my mouse trap!" exclaimed Mr. Damon, "I want to speak to you!" He was panting from his run across the field. "I just got to your house—saw your father—he said you were going up with Miss Nestor, but—bless my dog biscuit—"

"Can't stop now, Mr. Damon!" answered Tom, with a laugh. "I have only just succeeded, by hard work, in getting Mary to a point where she has consented to take a sky ride. If I stop now she'll back out and I'll never get her in again. See you when I come back," and Tom pulled the covering over his ear once more.

"But, Tom, bless my shoe laces! This is important!"

"So's this!" answered Tom, with a grin. He saw, by the motion of Mr. Damon's lips, what the latter had said.

Around swung the propeller blades. The gasoline vapor in the cylinders was being compressed.

"Contact!" called Tom sharply, as he pressed the switch to give the igniting spark at the proper moment. The mechanic had stepped back out of the way, in case there should be a premature starting of the powerful engine, in which event the blades would have cut him to pieces.

"Wait, Tom! Wait! This is very important! Bless my collar button, Tom Swift, but this is—"

Bang! Bang! Bang!

With a series of explosions, like those of a machine gun, the motor started, and further talk was out of the question. Tom turned on more gas. The propellers became almost invisible blades of light and shadow, and the aeroplane began moving over the grassy field. The mechanic had sprung out of the way, pulling Mr. Damon with him.

"Come back! Come back! Wait a minute, Tom Swift! Bless my pansy blossoms, I want to tell you something!" cried the little man.

But Tom Swift was away and out of hearing. He had started on his sky ride with Mary Nestor.



CHAPTER II

A NEW IDEA

Any one who has taken a flight in an aeroplane or gone up in a balloon, will know exactly how Mary Nestor felt on this, her first sky ride of any distance. For a moment, as she looked over the side of the machine, she had a distinct impression, not that she was going up, but that some one had pulled the earth down from beneath her and, at the same time, given her a shove off into space. Such is the first sensation of going aloft. Then the rush of air all about her, the slightly swaying motion of the craft, and the vibration caused by the motor took her attention. But the sensation of the earth dropping away from beneath her remained with Mary for some time.

This sensation is much greater in a balloon than in an aeroplane, for a balloon, unless there is a strong wind blowing, goes straight up, while an aeroplane ascends on a long slant, and always into the teeth of the wind, to take advantage of its lifting power on the underside of the planes. The reason for this sensation—that of the earth's dropping down, instead of one's feeling, what really happens, that one is ascending—is because there are no objects by which comparison can be made. If one starts off on the earth's surface at slow, or at great speed, one passes stationary objects—houses, posts, trees, and the like—and judges the speed by the rapidity with which these are left behind.

Going up is unlike this. There is nothing to pass. One simply cleaves the air, and only as it rushes past can one be sure of movement. And as the air is void of color and form, there is no sensation of passing anything.

So Mary Nestor, as she shot into the air with Tom Swift, had a sensation as though the earth were dropping from beneath her. For a moment she felt as though she were in some vast void—floating in space—and she had a great fear. Then she calmed herself. She looked at Tom sitting in front of her. Of course, all she could see was his back, but it looked to be a very sturdy back, indeed, and he sat there in the aircraft as calmly as though in a chair on the ground. Then Mary took courage, and ceased to grasp the sides of the cockpit with a grip that stiffened all her muscles. She was beginning to "find herself."

On and on, and up and up, went Mary and Tom, in this the girl's first big sky ride. The earth below seemed farther and farther away. The wide, green fields became little emerald squares, and the houses like those in a toy Noah's ark.

Down below, Mr. Wakefield Damon, who had hurried over from his home in Waterfield to see Tom Swift, gazed aloft at the fast disappearing aeroplane and its passengers.

"Bless my coal bin!" cried the eccentric man, "but Tom is in a hurry this morning. Too bad he couldn't have stopped and spoken to me. It might have been greatly to his advantage. But I suppose I shall have to wait."

"You want to see Master?" asked a voice behind Mr. Damon, and, turning, he beheld a veritable giant.

"Yes, Koku, I did," Mr. Damon answered, and he did not appear at all surprised at the sight of the towering form beside him. "I wanted to see Tom most particularly. But I shall have to wait. I'll go in and talk to Mr. Swift."

"Yaas, an' I go talk to Radicate," said the giant. "Him diggin' up ground where Master told me to make garden. Radicate not strong enough for dat!"

"Huh! there's trouble as soon as those two get to disputing," mused Mr. Damon, as he went toward the house.

Meanwhile, Mary was beginning to enjoy herself. The sensation of moving rapidly through the air in a machine as skillfully guided as was the one piloted by Tom Swift was delightful. Up and up they went, and then suddenly Mary felt a lurch, and the plane, which was now about a thousand feet high, seemed to slip to one side.

Mary screamed, and began reaching for the buckle of the safety belt that fastened her to her seat. She saw that something unusual had occurred, for Tom was working frantically at the mechanism in front of him.

But, in spite of this, he seemed aware that Mary was in danger, not so much, perhaps, from what might happen to the machine, as what she might do in her terror.

"Oh! Oh!" cried the girl, and Tom heard her above the terrific noise of the motor, for she was speaking with her lips close to the tube that served as a sort of inter-communicating telephone for the craft. "Oh, we are falling! I'm going to jump!"

"Sit still! Sit still for your life!" cried Tom Swift. "I'll save you all right! Only sit still! Don't jump!"

Mary, her red cheeks white, sank back, and the young inventor redoubled his efforts at the controls and other mechanisms.

And that Tom was perfectly qualified to make a safe landing, even with engine trouble, Mary Nestor well knew. Those of you who have read the previous books of this series know it also, but, for the benefit of my new readers, I shall state that this was by no means Tom's first ride in an aeroplane.

He had operated and built gasoline engines ever since he was about sixteen years old. As related in the initial volume of this series, entitled, "Tom Swift and His Motorcycle," he became possessed of this machine after it had started to climb a tree with Mr. Damon on board. After that experience the eccentric man—blessing everything he could think of—had no liking for the speedy motorcycle and sold it to Tom at a low price.

That was the beginning of a friendship between the two, and also started Tom on his career as an inventor and a possessor of many gasoline craft. For he was not content with merely riding the repaired motorcycle. He made improvements on it.

Tom lived with his father in the town of Shopton, their home being looked after, since the death of Mrs. Swift, by Mrs. Baggert. Mr. Wakefield Damon lived in the neighboring town of Waterfield, and spent much time at Tom's home, often going on trips with him in various vehicles of the land, sea or air.

As related in the various volumes of this series, Tom was not content to remain on earth. He built a speedy motor boat, and then secured an airship, following that with a submarine. He also made an electric runabout that was the speediest car on the road. Sending wireless messages, having thrilling experiences among the diamond makers, journeying to the caves of ice, and making perilous trips in his sky racer took up part of the young inventor's time.

With his electric rifle he did some wonderful shooting, and in the "City of Gold" made some strange discoveries, part of the fortune he secured enabling him to build his sky racer. It was in a land of giants that Tom was made captive, but he succeeded in escaping, and brought two giants, of whom Koku was one, away with him.

Following this achievement Tom invented a wizard camera and a great searchlight, which, with his giant cannon, was purchased by the United States Government. Work on his photo-telephone and his aerial warship, the problem of digging a big tunnel, and then traveling to the land of wonders, kept Tom Swift very busy, and he had just completed a wonderful piece of work when the present story opens.

This last achievement was the perfecting of a machine to aid in the great World War and you will find the details set down in the volume which immediately precedes this. "Tom Swift and His War Tank," it is called, and in that is related how he not only invented a marvelous machine, but succeeded in keeping its secret from the plotters who tried to take it from him. In this Tom was helped by the inspiration of Mary Nestor, whom he hoped some day to marry, and by Ned Newton, a chum, who, though no inventor himself, could admire one.

Ned and Tom had been chums a long while, but Ned inclined more to financial and office matters than to machinery. At times he had managed affairs for Tom, and helped him finance projects. Ned was now an important bank official, and since the United States had entered the war had had charge of some Red Cross work, as well as Liberty Bond campaigns.

Somehow, as she sat there in the craft which seemed disabled, Mary Nestor could not help thinking of Tom's many activities, in some of which she had shared.

"Oh, if he falls now, and is killed!" she thought. "Oh, what will happen to us?"

"It's all right, Mary! Don't worry! It's all right!" cried Tom, through the speaking tube.

"What's that? I can't hear you very well!" she called back.

"No wonder, with the racket this motor is making," he answered. "Why can't something be done so you can talk in an aeroplane as well as in a balloon? That's an idea! If I could tell you what was the matter now you wouldn't be a bit frightened, for it isn't anything. But, as it is—"

"What are you saying, Tom? I can't hear you!" cried Mary, still much frightened.

"I say it's all right—don't get scared. And don't jump!" Tom shouted until his ears buzzed. "It's all nonsense—having a motor making so much noise one can't talk!" he went on, irritatedly.

A strange idea had come to the young inventor, but there was no time to think of it now. Mentally he registered a vow to take up this idea and work on it as soon as possible. But, just now, the aeroplane needed all his attention.

As he had told Mary, there was really nothing approaching any great danger. But it was rather an anxious moment. If Tom had been alone he would have thought little of it, but with Mary along he felt a double responsibility.

What had happened was that the craft had suddenly gone into an "air pocket" or partial vacuum, and there had been a sudden fall and a slide slip. In trying to stop this too quickly Tom had broken one of his controls, and he was busily engaged in putting an auxiliary one in place and trying to reassure Mary at the same time.

"But it's mighty hard trying to do that through a speaking tube with a motor making a noise like a boiler factory," mused the young inventor. Tom worked quickly and to good purpose. In a few moments, though to Mary they seemed like hours, the machine was again gliding along on a level keel, and Tom breathed more easily.

"And now for my great idea!" he told himself.

But it was some time before he could give his attention to that.



CHAPTER III

THE BIG OFFER

Working with all the skill he possessed, Tom had got the aeroplane in proper working order again. As has been said, the accident was a trivial one, and had he been alone, or with an experienced aviator, he would have thought little of it. Then, very likely, he would have volplaned to earth and made the repairs there. But he did not want to frighten Mary Nestor, so he fixed the control while gliding along, and made light of it. Thus his passenger was reassured.

"Are we all right?" asked Mary through the tube, as they sailed along.

"Right as a fiddle," answered Tom, shouting through the same means of communication.

"What's that about a riddle?" asked Mary, in surprise at his seeming flippancy at such a time.

"I didn't say anything about a riddle—I said we are as fit as a fiddle!" cried Tom. "Never mind. No use trying to talk with the racket this motor makes, and it isn't the noisiest of its kind, either. I'll tell you when we get down. Do you like it?"

"Yes, I like it better than I did at first," answered Mary, for she had managed to understand the last of Tom's questions. Then he sailed a little higher, circled about, and, a little later, not to get Mary too tired and anxious, he headed for his landing field.

"I'll take you home in the auto," he cried to his passenger. "We could go up to your house this way—in style—if there was a field near by large enough to land in. But there isn't. So it will have to be a plain, every-day auto."

"That's good enough for me," said Mary. "Though this trip is wonderful—glorious! I'll go again any time you ask me."

"Well, I'll ask you," said Tom. "And when I do maybe it won't be so hard to hold a conversation. It will be more like this," and he shut off the motor and began to glide gently down. The quiet succeeding the terrific noise of the motor exhaust was almost startling, and Tom and Mary could converse easily without using the tube.

Then followed the landing on the soft, springy turf, a little glide over the ground, and the machine came to a halt, while mechanics ran out of the hangar to take charge of it.

"I'll just go in and change these togs," said Mary, as she alighted and looked at her leather costume.

"No, don't," advised Tom. "You look swell in em. Keep 'em on. They're yours, and you'll need 'em when we go up again. Here comes the auto. I'll take you right home in it. Keep the aviation suit on.

"I wonder what Mr. Damon could have wanted," remarked Tom, as he drove Mary along the country road.

"He seemed very much excited," she replied.

"Oh, he almost always is that way—blessing everything he can think of. You know that. But this time it was different, I'll admit. I hope nothing is the matter. I might have stopped and spoken to him, but I was afraid if I did you'd back out and wouldn't come for a sky ride."

"Well, I might have. But now that I've had one, even with an accident thrown in, I'll go any time you ask me, Tom," and Mary smiled at the young inventor.

"Shucks, that wasn't a real accident!" he laughed. "But I do wonder what Mr. Damon wanted."

"Better go back and find out, Tom," advised Mary, as they stopped in front of her house.

"Oh, I want to come in and talk to you. Haven't had a chance for a good talk today, that motor made such a racket."

"No, go along now, but come back and see me this afternoon if you like."

"I do like, all right! And I suppose Mr. Damon will be fussing until he sees me. Well, glad you liked your first ride in the air, Mary—that is, the first one of any account," for Mary had been in an aeroplane before, though only up a little way—a sort of "grass-cutting stunt," Tom called it.

Waving farewell to the pretty girl, the young aviator turned the auto about and speeded for his home and the shops adjoining it. His father had not been well, of late, and Tom was a bit anxious about him.

"Mr. Damon may bother him, though he wouldn't mean to," thought Tom. "He seemed to have his mind filled with some new idea. I wonder if it is anything like mine? No, it couldn't be. Well, I'll soon find out," and, putting his foot on the accelerator, Tom sent the machine along at a pace that soon brought him within sight of his home.

"Is father all right?" he asked Mrs. Baggert, who was out on the front porch, as though waiting for him.

"Oh, yes, Tom, he's all right," the housekeeper answered.

"Is Mr. Damon with him?"

"No."

"He hasn't gone home, has he?"

"No, he's around somewhere. But some one else is with your father. Some visitors."

"Any relations?"

"No; strangers. They came to see you, and they're rather impatient. I came out to see if you were in sight. Your father sent me."

"Are they bothering him—talking business that I ought to attend to when he's ill? That mustn't be."

"Well, I suppose it is business that the strangers are talking over with your father, Tom," said Mrs. Baggert, "for I heard sums of money spoken of. But your father seems to be all right, only a trifle anxious that you should come."

"Well, I'm here now and I'll attend to things. Where are the strangers, and who are they?"

"I don't know," answered the housekeeper. "I never saw them before, but they're in the library with your father. Do you think they'll stay to dinner? If you do, I'll have Eradicate or Koku catch and kill a chicken."

"If you let one do it don't tell the other about it," said Tom with a laugh, "or you'll have a chicken race around the yard that will make the visitors sit up and take notice."

There was great rivalry between Eradicate Sampson, the aged colored man, and Koku, the giant, and they were continually disputing. Each one loved and served Tom in his own way, and there was jealousy between them. Koku, the giant Tom had brought with him from the land where the young inventor had been made captive, was a big, powerful man, and could do things the aged colored servant could not attempt. But "Rad," as he was often called, and his mule "Boomerang" had long been fixtures on the Swift homestead. But old age crept on apace with Eradicate, though he hated to admit it, and Koku did many things the colored man had formerly attended to, and Rad was always on the lookout not to be supplanted. Hence Tom's warning to Mrs. Baggert about letting the two be entrusted with the same mission of catching a chicken for the pot.

"Better get the fowl yourself and say nothing to either of them about it," Tom advised the housekeeper. "Mr. Damon will stay to dinner, as he always does when he comes, and as it's near twelve now, and as I may be delayed talking business to these strangers, you'd better get up a bigger meal than usual."

"I will, Tom," promised Mrs. Baggert. And then the young inventor, having seen that one of the men took the automobile to the garage, went into the house.

"Oh, here you are!" was his father's greeting, as he came out into the hall from the library. "I've been waiting anxiously for you, my boy. I couldn't think what was keeping you."

"Oh, I had a little trouble with the air machine—nothing serious."

A moment later Tom was standing before two well-dressed, prosperous-looking business men, who smiled pleasantly at him.

"Mr. Thomas Swift?" interrogated one, the elder, as he held out his hand.

"That's my name," answered Tom, pleasantly.

"I'm Peton Gale, and this gentleman is Boland Ware," went on the man who had taken Tom's hand. "I'm president and he's treasurer of the Universal Flying Machine Company, of New York."

"Oh, yes," said Tom, as he shook hands with Mr. Ware. "I have heard of your concern. You are doing a lot of government work, are you not?"

"Yes; war orders. And we're up to our neck in them. This war is going to be almost as much fought in the air as on the ground, Mr. Swift."

"I can well believe that," agreed Tom. "Won't you have a chair?"

"Well, we didn't come to stay long," said Mr. Gale with a laugh, which, somehow or other, grated on Tom and seemed to him insincere. "Our business is such a rushing one that we don't spend much time anywhere. To get down to brass tacks, we have come to see you to put a certain proposition before you, Mr. Swift. You are open to a business proposition, aren't you?"

"Oh, yes," answered Tom. "That's what I'm here for."

"I thought so. Well, now I'll tell you, in brief, what we want, and then Mr. Ware, our treasurer, can elaborate on it, and give you facts and figures about which I never bother myself. I attend to the executive end and leave the details to others," and again came that laugh which Tom did not like.

"You came here to make me an offer?" asked the young inventor, wondering to which of his many machines the visitors had reference.

"Yes," went on Mr. Gale, "we came here to make you a big offer. In short, Mr. Swift, we want you to work for our company, and we are willing to pay you ten thousand dollars a year for the benefit of your advice and your inventive abilities. Ten thousand dollars a year! Do you accept?"



CHAPTER IV

MR. DAMON'S WHIZZER

Characteristic it was of Tom Swift that he did not seem at all surprised at what most young men would call a liberal offer. Certainly not many youths of Tom's age would be sought out by a big manufacturing concern, and offered ten thousand dollars a year "right off the reel," as Ned Newton expressed it later. But Tom only smiled and shook his head in negation.

"What!" cried Mr. Gale, "you mean you won't accept our offer?"

"I can't," answered Tom.

"You can't!" exclaimed the treasurer, Mr. Ware. "Oh, I see. Mr. Gale, a word with you. Excuse us a moment," he added to Tom and his father.

The two men consulted in a corner of the library for a moment, and then, with smiles on their faces, once more turned toward the young inventor.

"Well, perhaps you are right, Tom Swift," said Mr. Gale. "Of course, we recognize your talents and ability, but you cannot blame us for trying to get talent, as well as material for our airships, in the cheapest market. But we are not hide-bound, nor sticklers for any set sum. We'll make that offer fifteen thousand dollars a year, if you will sign a five-year contract and agree that we shall have first claim on anything and everything you may patent or invent in that time. Now, how does that strike you? Fifteen thousand dollars a year—paid weekly if you wish, and our Mr. Ware, here, has a form of contract which can be fixed up and signed within ten minutes, if you agree."

"Well, I don't like to be disagreeable," said Tom with a smile; "but, really, as I said before, I can't accept your very kind offer. I may say liberal offer. I appreciate that."

"You can't accept!" cried Mr. Gale.

"Are you sure you don't mean 'won't'?" asked Mr. Ware, in a half growl.

"You may call it that if you like," replied Tom, a bit coolly, for he did not like the other's tone, "Only, as I say, I cannot accept. I have other plans."

"Oh, you—" began the brusk treasurer, but Mr. Gale, the president of the Universal Flying Machine Company, stopped his associate with a warning look.

"Just a moment, Mr. Swift," begged the president. "Don't be hasty. We are prepared to make you a last and final offer, and I do not believe you can refuse it."

"Well, I certainly will not refuse it without hearing it," said Tom, with a smile he meant to make good-natured. Yet, truth to tell, he did not at all like the two visitors. There was something about them that aroused his antagonism, and he said later that even if they had offered him a sum which he felt he ought not, in justice to himself and his father, refuse, he would have felt a distaste in working for a company represented by the twain.

"This is our offer," said Mr. Gale, and he spoke in a pompous manner which seemed to say: "If you don't take it, why, it will be the worse for you." He looked at his treasurer for a confirmatory nod and, receiving it, went on. "We are prepared to offer and pay you, and will enter into such a contract, with the stipulation about the inventions that I mentioned before—we are prepared to pay you—twenty thousand dollars a year! Now what do you say to that, Tom Swift?

"Twenty-thousand-dollars-a-year!" repeated Mr. Gale unctuously, rolling the words off his tongue. "Twen-ty-thou-sand-dol-lars-a-year! Think of it!"

"I am thinking of it," said Tom Swift gently, "and I thank you for your offer. It is, indeed, very generous. But I must give you the same answer. I cannot accept."

"Tom!" exclaimed his aged father.

"Mr. Swift!" exclaimed the two visitors.

Tom smiled and shook his head.

"Oh, I know very well what I am saying, and what I am turning down," he said. "But I simply cannot accept. I have other plans. I am sorry you have had your trip for nothing," he added to the visitors, "but, really, I must refuse."

"Is that your final answer?" asked Mr. Gale.

"Yes."

"Don't you want to take a day or two to think it over?" asked the treasurer. "Don't be hasty. Remember that very few young men can command that salary, and I may say you will find us liberal in other ways. You would have some time to yourself."

"That is what I most need," returned Tom. "Time to myself. No, thank you, gentlemen, I cannot accept."

"Be careful!" warned Mr. Gale, and it sounded as though there might be a threat in his voice. "This is our last offer, and your last chance. We will not renew this. If you do not accept our twenty thousand dollars now, you will never get it again."

"I realize that," said Tom, "and I am prepared to take the consequences.

"Very well, then," said Mr. Gale. "There seems nothing for us to do, Mr. Ware, but to go back to New York. I bid you good-day," and he bowed stiffly to Tom. "I hope you will not regret your refusal of our offer."

"I hope so myself," said Tom, lightly.

When the visitors had gone Mr. Swift turned toward his son, and, shaking his head, remarked:

"Of course, you know your own business best, Tom. Yet I cannot but feel you have made a mistake."

"How?" asked Tom. "By not taking that money? I can easily make that in a year, with an idea I have in mind for an improvement on an airship. And your new electric motor will soon be ready for the market. Besides, we don't really need the money."

"No, not now, Tom, but there is no telling when we may," said Mr. Swift, slowly. "This big war has made many changes, and things that brought us in a good income before, hardly sell at all, now."

"Oh, don't worry, Dad! We still have a few shots left in the locker—in other words, the bank. I'm expecting Ned Newton over any moment now, to give us the annual statement of our account, and then we'll know where we stand. I'm not afraid from the money end. Our business has done well, and it is going to do better. I have a new idea."

"That's all very well, Tom," said Mr. Swift, who seemed oppressed by something. "As you say, money isn't everything, and I know we shall always have enough to live on. But there is something about those two men I do not like. They were very angry at your refusal of their offer. I could see that. Tom, I don't want to be a croaker, but I think you'll have to watch out for those men. They're going to be your enemies—your rivals in the airship field," and Mr. Swift shook his head dolefully.

"Well, rivalry, when it's clean and above board, is the spice of trade and invention," returned Tom, lightly. "I'm not afraid of that."

"No, but it may be unfair and underhand," said Mr. Swift. "I think it would have been better, Tom, to have accepted their offer. Twenty thousand a year, clear money, is a good sum."

"Yes, but I may make twice that with something that occurred to me only a little while ago. Forget about those men, Dad, and I'll tell you my new idea. But wait, I want Mr. Damon to hear it, too. Where is he?"

"He was here a little while ago. He went out when those two men came and—"

At that moment, from the garden at the side of the library, the sound of voices in dispute could be heard.

"Now yo' all g'wan 'way from yeah!" exclaimed some one who could be none other than Eradicate Sampson. "Whut fo' yo' all want to clutter up dish yeah place fo'? Massa Tom said I was to do de garden wuk, an' I'se gwine to do it! G'wan 'way, Giant!"

"Ho! You want me to get out, s'pose you put me, black face!" cried a big voice, that of Koku, the giant.

"There they go! At it again!" cried Tom with a smile. "Might have known if I told Rad to do anything that Koku would be jealous. Well, I'll have to go out now and give that giant something to do that will tax his strength."

But as Tom was about to leave the room another voice was heard in the garden.

"Now, boys, be nice," said some one soothingly. "The garden is large enough for you both to work in. Rad, you begin at the lower end and spade toward the middle. Koku, you begin at the upper end and work down. Whoever gets to the middle first will win."

"Ha! Den I'll show dat giant some spade wuk as is spade wuk!" cried the colored man. "Garden wuk is mah middle name."

"Be careful, Rad!" laughed Mr. Damon, for he it was who was trying to act as peacemaker. "Remember that Koku is very strong."

"Yas, sah! He may be strong, but he's clumsy!" chuckled Eradicate. "You watch me beat him!"

"Ho! Black man get stuck in mud!" challenged Koku. "I show him!"

Then there was silence, and Tom and his father, looking out, saw the two disputants beginning to spade the soil while Mr. Damon, satisfied that he had, for the time being, stopped a quarrel, turned toward the house.

"I was just coming to look for you," said Tom. "Sorry I had to go off in such a hurry and leave you, but I had promised to take Mary for a ride, and as it was her first one, for a distance, I didn't want her to back out."

"That's all right, Tom, that's all right!" said Mr. Damon genially. "Ladies first every time. But I do want to see you, and it's about something important."

"No trouble, I hope?" queried Tom, for the manner of the eccentric man was rather grave.

"Trouble? Oh, no! Bless my frying pan, no trouble, Tom! In fact, it may be the other way about. Tom, I have an idea, and there may be millions in it! That's it—millions!"

"Good!" cried the young inventor. "Might as well bite off a big lump while you're at it. So you have a new idea! Well, I have myself, but I'll listen to yours first. What is it, Mr. Damon?"

"It's a new kind of airship, Tom. I haven't got it all worked out yet, but I can give you a rough outline. On my way over I got to thinking about balloons, aeroplanes and the like, and it occurred to me that the present principles are all wrong."

"So I evolved a new type of machine. I'm going to call it the Damon Whizzer. Maybe Demon Whizzer would be more appropriate, but we won't decide on that now. Anyhow, it's going to be a whizzer, and I want to talk to you about it. There is an entirely new principle of elevation and propulsion involved in my Whizzer, and I—"

At that moment there came a crash and clatter of steel and wood from the garden, out of sight of which Tom and Mr. Damon had walked while talking. Then followed a jangle of words.

"They're at it again!" cried Tom, as he ran toward the side of the house. "I guess it's a fight this time!"



CHAPTER V

TOM'S PROJECT

Curious was the sight that met the gaze of Tom Swift and Mr. Wakefield Damon as they rounded the corner of the house and looked into the newly spaded garden. There stood the giant, Koku, holding aloft in the air, by one hand, the form of the struggling colored man, Eradicate Sampson. And Eradicate was vainly trying to get at his enemy and rival, but was prevented by the long-distance hold the giant had on him.

"Yo' let me go, now! Yo' let me go, big man" cried Eradicate. "Ef yo' don't I'll bust yo' wide open, dat's whut I'll do! An' 'sides, I'll tell Massa Tom on yo', dat's whut I'll do!"

"Ho! You tell—I let you fall!" threatened Koku.

His threat was dire enough, for such was his size and strength that he held the colored man nearly nine feet from the ground, and a fall from that distance would seriously jar Eradicate, if it did nothing else. The colored man's eyes opened wide as he heard what Koku said, and then he cried:

"Let me down! Let me down, an' I won't say nuffin!"

"An' you let me scatter dirt?" asked Koku, for such was the giant's idea of working in the garden.

"Yes, yo' kin scatter de dirt seben ways from Sunday fo' all I keers!" conceded Eradicate. Then, as he was lowered to the ground, he and the giant turned and saw Mr. Damon and Tom approaching.

"What's wrong?" asked the young inventor.

"'Scuse me, Massa Tom," began Eradicate, "but didn't yo' tell me to spade de garden?"

"I guess I did," admitted Tom Swift.

"An' you tell me help—yes?" questioned Koku.

"Well, I thought it would be a little too much for you, Rad," said Tom, gently. "I thought perhaps you'd like help."

"Hu! Not him, anyhow!" declared the colored man in great disgust. "When I git so old dat I cain't spade a garden, den me an' Boomerang, we-all gwine to die, dat's all I got to say. I was a-spadin' my part ob de garden, Massa Tom, same laik Mr. Damon done tole me to, an' dish yeah big mess ob bones steps on my side ob de middle an—"

"Him too slow. Koku scatter dirt twice times so fast!" declared the giant, whose English was not much better than Eradicate's.

"Yes, I see," said Tom. "You are so strong, Koku, that you finished your part before Eradicate did. Well, it was good of you to want to help him."

At this the giant grinned at his rival.

"At the same time," went on Tom, winking an eye at Mr. Damon, "Eradicate knows a little more about garden work, on account of having done it so many years."

"Ha! Whut I tell yo', Giant!" boasted the colored man. It was his turn to smile.

"And so," went on Tom, judicially, "I guess I'll let Rad finish spading the garden, and you, Koku, can come and help me lift some heavy engine parts. Mr. Damon wants to explain something to me."

"Ha! Nothing what so heavy Koku not lift!" boasted the giant.

"Go on! Lift yo'se'f 'way from heah!" muttered Eradicate as he picked up his dropped spade. And then, with a smile of satisfaction, he fell to work in the mellow soil while Tom led Koku to one of the shops where he set him to lifting heavy motor parts about in order to get at a certain machine that was stored away in the back of one of the rooms.

"That will keep him busy," said the young inventor. "And now, Mr. Damon, I can listen to you. Do you really think you have a new idea in airships?"

"I really think so, Tom. My Whizzer is bound to revolutionize travel in the air. Let me tell you what I mean. Now cast your mind back. How many ways are now used to propel an airship or a dirigible balloon through the air? How many ways?"

"Two, as far as I know," said Tom. "At least there are only two that have proved to be practical."

"Exactly," said Mr. Damon. "One with the propeller, or propellers, in front, and that is the tractor type. The other has the propeller in the rear, and that is the pusher type. Both good as far as they go, but I have something better."

"What?" asked Tom with a smile.

"It's a Whizzer," said the eccentric man. "Bless my gold tooth! but that is the best name I can think of for it. And, really, the propeller I'm thinking of inventing does whiz around."

"But are you going to use a tractor or pusher type?" Tom wanted to know.

"It's a combination of both," answered Mr. Damon. "As it is now, Tom, you have to get an aeroplane in pretty speedy motion before it will rise from the ground, don't you?"

"Yes, of course. That's the principle on which an aeroplane rises and keeps aloft, by its speed in the air. As soon as that speed stops it begins to fall, or volplane, as we call it."

"Exactly. Now, instead of having to depend on the speed of the aeroplane for this, why not depend on the speed of the propeller—in other words, the whizzer?"

"Well, we do," said Tom, a bit puzzled as to what his friend was trying to get at. "If the propeller didn't move the airship wouldn't rise—that is, unless it's of the balloon type."

"What I mean," said Mr. Damon, "is to have an aeroplane that will move in the air the same as a boat moves in the water. You don't have to get the propeller of a boat racing around at the rate of a million revolutions a minute, more or less, before your boat will travel, do you? If the engine turns the screw, or propeller, just over say fifty times a minute you would get some motion of the boat, wouldn't you?"

"Why, yes, some," admitted Tom.

"And what causes it?" asked Mr. Damon, anticipating a triumph.

"The resistance of the water to the blades of the screw, or propeller," answered Tom.

"Exactly! And it's the resistance of the air to the blades of an airship propeller that sends the craft along, isn't it?"

"Yes. And because of the difference in density between air and water it becomes necessary to revolve an aeroplane propeller many times faster than a boat propeller. It's the density that makes the difference, Mr. Damon. If air were as dense as water we could have comparatively slow-moving motors and propellers and—"

"Ha! There you have it, Tom! And there is where my Whizzer—Wakefield Damon's Whizzer—is going to revolutionize air travel!" cried the eccentric man. "The difference in density! If air were as dense as water the problem would be solved. And I have solved it! I'm going to turn the trick, Tom! One more question. How can air be made as dense as water, Tom Swift?"

"Why, by condensation or compression, I suppose," was the rather slow answer. "You know they have condensed, or compressed, air until it is liquid. I've done it myself, as an experiment."

"That's it, Tom! That's it!" cried Mr. Damon in delight. "Compressed air will do the trick! Not compressed to a liquid, exactly, but almost so. I'm going to revolve the propellers of my new airship in compressed air, so dense that they will not have to have a speed of more than seven hundred revolutions a minute. What's that compared to the three to ten thousand revolutions of the propellers now used? The propellers of Damon's Whizzer will be of the pusher type, and will revolve in dense, compressed air, almost like water, and that will do away with high speed motors, with all their complications, and make traveling in the clouds as simple as taking out a little one-cylinder motor boat. How's that, Tom Swift? How's that for an idea?"

To Mr. Damon's disappointment, Tom was not enthusiastic. The young inventor gazed at his eccentric friend, and then said slowly:

"Well, that's all right in theory, but how is it going to work out in practice?"

"That's what I came to see you about, Tom," was the reply. "Bless my tall hat! but that's just why I hurried over here. I wanted to tell you when I saw you going off on a trip with Miss Nestor. That's my big idea—Damon's Whizzer—propellers revolving in compressed air like water. Isn't that great?"

"I'm sorry to shatter your air castle," said Tom; "but for the life of me I can't see how it will work. Of course, in theory, if you could revolve a big-bladed propeller in very dense, or in liquid, air, there would be more resistance than in the rarefied atmosphere of the upper regions. And, if this could be done, I grant you that you could use slower motors and smaller propeller blades—more like those of a motor boat. But how are you going to get the condensed air?"

"Make it!" said Mr. Damon promptly. "Air pumps are cheap. Just carry one or two on board the aeroplane, and condense the air as you go along. That's a small detail that can easily be worked out. I leave that to you."

"I'd rather you wouldn't," said Tom. "That's the whole difficulty—compressing your air. Wait! I'll explain it to you."

Then the young inventor went into details. He told of the ponderous machinery needed to condense air to a form approximating water, and spoke of the terrible pressure exerted by the liquid atmosphere.

"Anything that you would gain by having a slow-speed motor and smaller propeller blades, would be lost by the ponderous air-condensing machinery you would need," Tom told Mr. Damon. "Besides, if you could surround your propellers with a strata of condensed air, it would create such terrible cold as to freeze the propeller blades and make them as brittle as glass.

"Why, I have taken a heavy piece of metal, dipped it into liquid air, and I could shatter the steel with a hammer as easily as a sheet of ice. The cold of liquid air is beyond belief.

"Attempts have been made to make motors run with liquid air, but they have not succeeded. To condense air and to carry it about so that propellers might revolve in it, would be out of the question."

"You think so, Tom?" asked Mr. Damon.

"I'm sure of it!"

"Oh, dear! That's too bad. Bless my overshoes, but I thought I had a new idea. Well, you ought to know. So Damon's Whizzer goes on the scrap heap before ever it's built. Well, we'll say no more about it. You ought to know best, Tom. I wasn't thinking of it so much for myself as for you. I thought you'd like some new idea to work on."

"Much obliged, Mr. Damon, but I have a new idea," said Tom.

"You have? What is it? Tell me—that is, if it isn't a secret," went on the eccentric man, as much delighted over Tom's new plan as he had been over his own Whizzer, doomed to failure so soon.

"It isn't a secret from you," said Tom. "I got the idea while I was riding with Mary. I wanted to talk to her—to tell her not to jump out when we had a little accident—but I had trouble making myself understood because of the noise of the motor."

"They do make a great racket," conceded Mr. Damon. "But I don't suppose anything can be done about it."

"I don't see why there can't!" exclaimed Tom. "And that's my new idea—to make a silent aircraft motor—perhaps silent propeller blades, though it's the motor that makes the most noise. And that's what I'm going to do—invent a silent aeroplane. Not because I want so much to talk when I take passengers up in the air, but I believe such a motor would be valuable, especially for scouting planes in war work. To go over the enemy's lines and not be heard would be valuable many times.

"And that's what I'm going to do—work on a silent motor for Uncle Sam. I've got the germ of an idea and now—"

"Excuse me," said a voice behind Mr. Damon and Tom, and, turning, the young inventor beheld the form of Mr. Peton Gale, president of the Universal Flying Machine Company.



CHAPTER VI

MAKING PLANS

Tom Swift had drawn pencil and paper from his pocket, and, as he and Mr. Damon were sitting on the steps of one of the shops, the young inventor was about to demonstrate by a drawing part of his new project, when the interruption came in the shape of one of the men who had, an hour before, made a business offer to Tom.

"Excuse me," went on Mr. Peton Gale, "but Mr. Ware and I got to talking it over on our way to the station—the matter of having you in our company, Mr. Swift—and we concluded that it was worth twenty-five thousand dollars a year for us to have you. So I came back—"

"It isn't of the slightest use, Mr. Gale, I assure you," said Tom, a bit heatedly, for he did not like the persistency of this man, nor did he like his coming on the factory grounds unannounced and in this secret manner. "I told you I could not accept your offer. It is not altogether a matter of money. My word was final."

"Oh very well, if you put it that way," said Mr. Gale stiffly, "of course there is nothing more to say. But I thought perhaps you did not consider we had offered you enough and—"

"Your offer is fair enough from a financial standpoint," said Tom; "but I simply cannot accept it. I have other plans. Jackson!" he called to one of his mechanics who was passing, "kindly see Mr. Gale to the gate, and then let me know how it was any one came in here without a permit."

"Yes, sir," said the mechanic, as he stood significantly waiting.

"There was no one at the gate when I came in," said Mr. Gale, and his manner was antagonizing. "I wanted to speak to you—to ask you to reconsider your offer—so I came back."

"It is against the rules to admit strangers to the shop grounds," said Tom. "Good-day!"

The president of the Universal Flying Machine Company did not respond, but there was a look on his face as he turned away that, had Tom seen it, might have caused him some uneasiness. But he did not see. Instead, he resumed his talk with Mr. Damon.

"Tom, your idea is most interesting," declared the eccentric man. "I hope you will be able to work it out!"

"I'm going to try," said the young inventor. "I hope that man—Mr. Gale—didn't hear anything of what I was saying. He sneaked up on us before I was aware any one was near but ourselves."

"I don't imagine he heard very much, Tom," said Mr. Damon. "He may have heard you mention a silent motor—"

"That's just what I wish he hadn't heard," broke in Tom. "That's the germ of the idea, and once it becomes known that I am working on that— Well, there's no use crying over spilled milk," and he smiled at the homely proverb. "I'll have to work in secret, once I've started."

"Do you think the government would use it, Tom?" asked his friend.

"I should think it would be glad to. Consider what a wonderful part airships are playing in the present war. It really is a struggle to see which will be the master of the sky—the Allies or the Germans—and, up to recently, the Huns had the advantage. Then the Allies, recognizing how vital it was, began to forge ahead, and now Uncle Sam with his troops under General Pershing is leading everything, or will lead shortly. We have been a bit slow with our aircraft production, but now we are booming along. Uncle Sam will soon have the mastery of the sky."

"I hope so," sighed Mr. Damon. "We must beat the Germans!"

Briefly, Tom spoke of what Pershing's men were doing with their aeroplanes in France, and mention was made of what the French and British had done prior to the entrance of the United States into the World War.

"While we were yet neutral, Americans had made gallant names for themselves flying for France, and with my silent motor they ought to do better," declared Tom.

"Is silence its chief recommendation?" asked Mr. Damon.

"Yes," replied Tom. "Or rather, it will be when I have it perfected. Aeroplane motors now are about as compact and speedy as they can be made. It is only the terrific noise that is a handicap. It is a handicap to the pilots and observers in the craft, as they cannot communicate except through a special speaking tube, and this is not always satisfactory or sure. Then, too, the noise of an airship proclaims its approach to the enemy, sometimes long before it can be seen.

"With a silent motor all this would be done away with. With my new craft, in case I can perfect it, the enemy's lines can be approached as silently as the Indians used to approach the log cabins of the white settlers. That will be its great advantage—not that conversation can be more easily carried on, for that is, after all, an unimportant detail. But to approach the enemy's lines in the silence of the night would be a distinct gain."

"I believe it would, Tom!" exclaimed Mr. Damon. "And I should think, too, that Uncle Sam would be glad to get such a motor," he added.

"Well, he'll have one to take if he wants it, if I can make my plans a success," declared Tom. "That is, unless those other fellows get ahead of me."

"What other fellows?" asked Mr. Damon.

"Gale, Ware and their crowd," was the answer. "I fancy they are provoked because I wouldn't agree to work for them, and now, that Gale overheard—as he must have—what I propose working on, they may try that game themselves."

"You mean try to turn out a silent motor?"

"Yes. It would be a big feather in their cap for their company, so far, hasn't been very successful on government orders. That's why they came to me, I guess."

"I shouldn't be surprised, Tom," conceded Mr. Damon. "Since the government accepted your giant cannon and your great searchlight, you have come into greater prominence than ever before. And those two things are a wonderful success."

"Yes," admitted Tom, modestly enough, "the big electric light seems to have been of some benefit on the European battle front, and though they haven't been able to make and transport as many of my giant cannons as I'd like to see over there, it is progressing, I understand."

And this is true. For the details of these two inventions of Tom Swift's I refer my readers to the books bearing those titles. Sufficient to state here that the government was using these two inventions, and there had been no necessity for commandeering them either, since Tom had freely offered them at the declaration of war with Germany.

"Well, since I can't help you with my 'Whizzer,'" said Mr. Damon, with a smile, "let me do what I can toward your silent motor, Tom. What are you going to call it?"

"Oh, I don't know—hadn't thought of a name. I guess 'Air Scout' would be as good as any. That's what it will be—a machine for silently scouting in the air. And now to get down to brass tacks, as the poet says, I believe I will—"

"Gentleman to see you, Mr. Swift," interrupted Jackson.

"Bless my penwiper!" cried Mr. Damon. "More visitors! I hope it isn't Gale or Ware come back to see what they can spy on!"



CHAPTER VII

A PROBLEM IN SOUND

Tom Swift looked up with a distinct appearance of being annoyed that was unusual with him, for he was, nearly always, good-natured. But the frown that had replaced the pleasant look on his face while he was talking to Mr. Damon about the projected new air scout was at once wiped away as he looked at the card Jackson held out to him.

"Bring him in right away!" he ordered. "He needn't have stood on that ceremony."

"Well, he said it was a business call," returned the mechanician with a cheerful grin, "and he said he wanted it done according to form. So he gave me his card to bring you."

"Who is it?" asked Mr. Damon, with the privilege of an old friend.

"It's Ned Newton," Tom answered; "though why he's putting on all this formality I can't fathom."

Jackson went back to the main gate and told the man on guard there to admit Ned, who had so formally sent in his card.

"Ah, Mr. Swift, I believe?" began the bank employee with that suave, formal air which usually precedes a business meeting.

"That is my name," said Tom, with a suppressed grin, and he spoke as stiffly as though to a perfect stranger.

"Mr. Tom Swift, the great inventor?" went on Ned.

"Yes."

"Ah, then I am at the right place. Just sign here, please, on the dotted line," and he held out a blank form, and a fountain pen to Tom, who took them half mechanically.

"Huh? What's the big idea, Ned?" asked the young inventor, unable longer to carry on the joke. "Is this a warrant for my arrest, or merely a testimonial to you. If it's the latter, and concerns your nerve, I'll gladly sign it."

"Well, it's something like that!" laughed Ned. "That's your application for another block of Liberty Bonds, Tom, and I want you, as a personal favor to me, as a business favor to the bank, and as your plain duty to Uncle Sam, to double your last subscription."

Tom looked at the sum Ned had filled in on the blank form, and uttered a slight whistle of surprise.

"That's all right now," said Ned, with the air of a professional salesman. "You can stand that and more, too. I'm letting you off easy. Why, I got Mary's father—Mr. Nestor—for twice what he took last time, and Mary herself—hard as she's working for the Red Cross—gave me a nice application. So it's up to you to—"

"Nuff said!" exclaimed Tom, sententiously, as he signed his name. "I may have to reconsider my recent refusal of the offer of the Universal Flying Machine Company, though, if I haven't money enough to meet this subscription, Ned."

"Oh, you'll meet it all right! Much obliged," and Ned folded the Liberty Bond subscription paper and put it in his pocket. "But did you turn down the offer from those people?"

"I did," answered Tom. "But how did you know about it, Ned?"

"First let me say that I'm glad you decided to have nothing to do with them. They're a rich firm, and have lots of money, but I wouldn't trust 'em, even if they have some government contracts. The way I happened to know they were likely to make you an offer is this," continued Ned Newton.

"They do business with one of the New York banks with which my bank—notice the accent on the my, Tom—is connected. The other day I happened to see some correspondence about you. These flying machine people asked our bank to find out certain things about you, and, as a matter of business, we had to give the information. Sort of a commercial agency report, you know, nothing unusual, and it isn't the first time it's been done since your business got so large. But that's how I happened to know these fellows contemplated dickering with you."

"Do you know Gale or Ware?" Tom asked.

"Not personally. But in a business way, Tom, I'd warn you to look out for them, as they're sharp dealers. They put one over on the government all right, and there may be some unpleasant publicity to it later. But they're putting up a big bluff, and pretending they can turn out a lot of flying machines for use in Europe. Why don't you get busy on that end of the game, Tom?"

"I know you've more than done your bit, with Liberty Bonds, subscriptions to the Y. M. C. A. and other war work, besides your war tank and other inventions. But you're such a shark on flying machines I should think you'd offer your factory to the government for the production of aeroplanes."

"I would in a minute, Ned, and you know it; but the fact of the matter is my shops aren't equipped for the production of anything in large numbers. We do mostly an experimenting business here, making only one or two of a certain machine. I have told the government officials they can have anything I've got, and you know they wouldn't let me enlist when I was working on the war tank."

"Yes, I remember that," said Ned. "You're no slacker! I wanted to shoulder a rifle, too, but they keep me at this Liberty Loan work. Well, Uncle Sam ought to know."

"That's what I say," agreed Tom, "and that's why I haven't gone to the front myself. And now, as it happens, I've got something else in mind that may help Uncle Sam."

"What is it?"

"A silent flying machine for scout work on the battle front," Tom told his friend, and then he gave a few details, such as those he had been telling Mr. Damon.

"Then I don't wonder you turned down the offer of the Universal people," remarked Ned, at the conclusion of the recital. "This will be a heap more help to the government, Tom, than working for those people, even at twenty-five thousand dollars a year. And if you get short, and can't meet your newest Liberty Bond payments, why, I guess the bank will stretch your credit a little."

"Thanks!" laughed Tom, "but I'll try not to ask them."

The friends talked together a little longer, and then Ned had to take his departure to solicit more subscriptions, while Mr. Damon went with him, the eccentric man saying he would go home to Waterfield.

"But, bless my overshoes, Tom!" he exclaimed, as he departed, "don't forget to let me know when you have your silent motor working. I want to see it."

"I'll let you know," was the promise given by the young inventor.

"And watch out for those Universal people," warned Ned. "I'm not telling you this as a bank official, for I'm not supposed to, but it's personal."

"I'll be on the watch," said Tom. And, as he went into his private workshop, he wondered why it was his father and Ned had both warned him not to trust Gale and Ware.

The next few days were busy ones for Tom Swift. Once he had made up his mind to go to work seriously on a silent motor, all else was put aside. He sent a note to Mary Nestor, telling her what he was going to do, and, asking her to say nothing about it, which, of course, Mary agreed to.

"Come and see me when you can," she sent back word, "but I know you won't have much chance when you're experimenting with your invention. And I shall be working so hard for the Red Cross that I sha'n't get much chance to entertain you. But the war can't last forever."

"No," agreed Tom with a sigh, as he put away her letter, "and thank goodness that it can't!"

The young inventor threw himself into the perplexing work of inventing a silent motor with all the fervor he had given to the production of his war tank, his giant cannon, his wonderful searchlight and other machines.

"And," mused Tom, as he sat at his work table with pencil and paper before him, "since this is a problem in acoustics, I had best begin. I suppose by going back to first principles, and after determining what makes an aeroplane engine noisy, try to figure out how to make it quiet. Now as to the first, the principle causes of noise are—"

And at that instant there broke on Tom's ears a succession of discordant sounds which seemed to be a combination of an Indian's war whoop and a college student's yells at a football game.

"Now I wonder what that is!" mused the young inventor as he hastily arose. "Better solve that problem before I tackle the aeroplane motor."



CHAPTER VIII

THROUGH THE ROOF



Tom rushed from his private office, and when he reached the outer door he heard with more distinctness the sounds that had alarmed him. They seemed to come from a small building given over to electrical apparatus, and which, at the time, was not supposed to be in use. It had been Tom's workroom, so to speak, when he was developing his electric runabout and rifle, but of late he had not spent much time in it.

"Somebody's in there!" reflected the young inventor, as he heard yells coming from the open door of the place. "And if it isn't Koku and Eradicate I miss my guess! Wonder what they can be doing there."

He crossed the yard between his private office and the electrical shop in a few rapid strides, and, as he entered the latter place, he was greeted with a series of wild yells.

"Good volume of sound here, at all events," mused Tom. "Almost as much as my motor made when I was trying to talk to Mary. Hello there! What's going on? Is any one hurt? What's the matter?" he cried, for, at first, he could see no one in the dim light of the place. The interior was a maze of electrical apparatus.

"Who's here?" demanded Tom, as he advanced.

"Oh, Master! Come quick! Koku 'most dead an' no can let go!" was the cry.

"Yo' jest bet yo' cain't let go!" chimed in the voice of Eradicate. "I done knowed yo would git into trouble ef yo' come heah, an' I'se glad ob it! So I is!"

"What is it, Rad? What has happened to Koku?" cried Tom, running forward, for though no very powerful current could be turned on in the electrical shop at this period of unuse, there was enough to be very painful. "What is it, Rad?"

"Oh, dat big foolish giant, Koku, done got his se'f into trouble!" chuckled the colored man. "He done got holt ob one ob dem air contraptions, Massa Tom, an' he cain't let go! Ha! Ha! Golly! Look at him squirm!" and Rad laughed shrilly, which accounted for some of the sounds Tom had heard.

Then came yells of rage and pain from the giant, and they were so loud and vigorous, mingling with Eradicate's as they did, that it was no wonder Tom was startled. The sounds were heard in the other shops, and men came running out. But before then Tom had put an end to the trouble.

One look showed him what had happened. Just how or why Koku and Eradicate had entered the electrical shop Tom did not then stop to inquire. But he saw that the giant had grasped the handles of one of the electric machines, designed for charging Leyden jars used in Tom's experiments, and the powerful, though not dangerous, current had so paralyzed, temporarily, the muscles of the giant's hands and arms that he could not let go, and there he was, squirming, and not knowing how to turn off the current, and unable to ease himself, while Eradicate stood and laughed at him, fairly howling with delight.

"Ha! Guess yo' won't do no mo' spadin' in' Massa Tom's garden right away, big man!" taunted Eradicate.

"Be quiet, Rad!" ordered Tom, as he reached up and pulled out the switch, thus shutting off the current. "This isn't anything to laugh at."

"But he done look so funny, Massa Tom!" pleaded the colored man. "He done squirm laik—"

But Eradicate did not finish what he intended to say. Once free from the powerful current, the giant looked at his numb hands, and then, seeming to think that Eradicate was the cause of it all, he sprang at the colored man with a yell. But Eradicate did not stay to see what would happen. With a howl of terror, he raced out of the door, and, old and rheumatic as he was, he managed to gain the stable of his mule, Boomerang, over which he had his humble but comfortable quarters.

"Well, I guess he's safe for a while!" laughed Tom, as he saw the giant turn away, shaking his fist at the closed door, for Koku, big as he was, stood in mortal terror of the mule's heels.

Tom locked the door of the electrical shop and Went back to his interrupted problem. From Jackson he learned that Koku and Eradicate had merely happened to stroll into the forbidden place, which had been left open by accident. There, it appeared, Koku had handled some of the machinery, ending by switching on the current of the machine the handles of which he later unsuspectingly picked up. Then he received a shock he long remembered, and for many days he believed Eradicate had been responsible for it, and there was more than the usual hostile feeling between the two. But Eradicate was innocent of that trick, at all events.

"Though," said Tom, telling his father about it later, "Rad would have turned on the current if he had known he could make trouble for Koku by it. I never saw their like for having disagreements!"

"Yes, but they are both devoted to you, Tom," said the aged inventor. "But what is this you hinted at—a silent motor you called it, I believe? Are you really serious in trying to invent one?"

"Yes, Dad, I am. I think there's a big field for an aeroplane that could travel along over the enemy's lines—particularly at night—and not be heard from below. Think of the scout work that could be done.

"Well, yes, it could be done if you could get a silent motor, or propellers that made no noise, Tom. But I don't believe it can be done."

"Well, maybe not, Dad. But I'm going to try!" and Tom, after a further talk with his father, began work in earnest on the big problem. That it was a big one Tom was not disposed to deny, and that it would be a valuable invention even his somewhat skeptical father admitted.

"How are you going to start, Tom?" asked Mr. Swift, several days after the big idea had come to the young man.

"I'm going to experiment a bit, at first. I've got a lot of old motors, that weren't speedy enough for any of my flying machines, and I'm going to make them over. If I spoil them the loss won't amount to anything, and if I succeed—well, maybe I can help out Uncle Sam a bit more."

As Tom had said he would do, he began at the very foundation, and studied the fundamental principles of sound.

"Sound," the young inventor told Ned Newton, in speaking about the problem, "is a sensation which is peculiar to the ear, though the vibrations caused by sound waves may be felt in many parts of the body. But the ear is the great receiver of sound."

"You aren't going to invent a sort of muffler for the ears, are you, Tom?" asked Ned. "That would be an easy way of solving the problem, but I doubt if you could get the Germans to wear your ear-tabs so they wouldn't hear the sound of the Allied aeroplanes."

"No, I'm not figuring on doing the trick that way," said Tom with a laugh. "I've really got to cut down the sound of the motor and the propeller blades, so a person, listening with all his ears, won't hear any noise, unless he's within a few feet of the plane."

"Well, I can tell you, right off the reel, how to do it," said the bank employee.

"How?" asked Tom eagerly.

"Run your engine and propellers in a vacuum," was the prompt reply.

"Hum!" said Tom, musingly. "Yes, that would be a simple way out, and I'll do it, if you'll tell me how to breathe in a vacuum."

"Oh, I didn't agree to do that," laughed Ned.

But he had spoken the truth, as those who have studied physics well know. There must be an atmosphere for the transmission of sound, which is the reason all is cold and silent and still at the moon. There is no atmosphere there. Sound implies vibration. Something, such as liquid, gas, or solid, must be set in motion to produce sound, and for the purpose of science the air we breathe may be considered a gas, being composed of two.

Not only must the object, either solid, liquid, or gaseous, be in motion to produce sound, but the air surrounding the vibrating body must also be moving in unison with it. And lastly there must be some medium of receiving the sound waves—the ear or some part of the body. Totally deaf persons may be made aware of sound through the vibrations received through their hands or feet. They receive, of course, only the more intense, or largest, sound waves, and can not hear notes of music nor spoken words, though they may feel the vibration when a piano is played. And, as Ned has said, no sound is produced in a vacuum.

"But," said Tom, "since I can't run my aeroplane in a vacuum, or even have the propellers revolve in one, it's up to me to solve the problem some other way. The propellers don't really make noise enough to worry about when they're high in the air. It's the exhaust from the motor, and to get rid of that will be my first attempt."

"Can it be done?" asked Ned.

"I don't know," was Tom's frank answer.

"They do it on an automobile to a great extent," went on Ned. "Some of 'em you cant hardly hear."

"Yes, but an aeroplane engine runs many, many times faster than the motor of an auto," said Tom, "and there are more explosions to muffle. I doubt if the muffler of an auto would cut down the sound of an aero engine to any appreciable extent. But, of course, I'll try along those lines."

"They have mufflers or silencers for guns and rifles," went on Ned. "Couldn't you make a big one of those contraptions and put it on an aeroplane?"

"I doubt it," said Tom, shaking his head. "Of course it's the same principle as that in an auto muffler, or on a motor boat—a series of baffle plates arranged within a hollow cylinder. But all such devices cut down power, and I don't want to do that. However, I'm going to solve the problem or—bust!"

And Tom came near "busting," Ned remarked later, when he and his friend talked over the progress of the invention.

Two weeks had passed since the start of his evolution of his new idea, and following the visiting of the representatives of the Universal Flying Machine Company. Since then neither Gale nor Ware had communicated with Tom.

"But I must be on the watch against them," thought the young inventor. "I'm pretty sure Gale heard me mention what I was going to try to invent, and he may get ahead of me, and put a silent motor on the market first. Not that I'm afraid of being done out of any profits, but I simply don't want to be beaten."

The details of Tom's invention cannot be gone into, but, roughly, it was based on the principle of not only a muffler but also of producing less noise when the charges of gasoline exploded in the cylinders. It is, of course, the explosion of gasoline mixed with air that causes an internal combustion engine to operate. And it is the expulsion of the burned gases that causes the exhaust and makes the noise that is heard.

Tom was working along the well-known line of the rate of travel of sound, which progresses at the rate of about 1090 feet a second when air is at the freezing point. And, roughly, with every degree increase in the atmosphere's temperature the velocity of sound increases by one foot. Thus at a temperature of 100 degrees Fahrenheit, or 68 degrees above freezing, there would be added to the 1090 feet the 68 feet, making sound travel at 100 degrees Fahrenheit about 1158 feet a second.

Tom had set up in his shop a powerful, but not very speedy, old aeroplane engine, and had attached to it the device he hoped would help him toward solving his problem of cutting down the noise. He had had some success with it, and, after days and nights of labor, he invited his father and Ned, as well as Mr. Damon, over to see what he hoped would be a final experiment.

His visitors had assembled in the shop, and Eradicate was setting out some refreshments which Tom had provided, the colored man being in his element now.

"What's all this figuring, Tom?" asked Mr. Damon, as he saw a series of calculations on some sheets of paper lying on Tom's desk.

"That's where I worked out how much faster sound traveled in hydrogen gas than in the ordinary atmosphere," was the answer. "It goes about four times as fast, or nearly four thousand two hundred feet a second. You remember the rule, I suppose. 'The speed of sonorous vibrations through gases varies inversely as the squares of the weights of equal volumes of the gases,' or, in other words—"

"Give it to us chiefly in 'other words,' if you please, Tom!" pleaded Ned, with a laugh. "Let that go and do some tricks. Start the engine and let's see if we can hear it."

"Oh, you can hear it all right," said Tom, as he approached the motor, which was mounted on a testing block. "The thing isn't perfected yet, but I hope to have it soon. Rad! Where is that black rascal? Oh, there you are! Come here, Rad!"

"Yaas sah, Massa Tom! Is I gwine to help yo' all in dish yeah job?"

"Yes. Just take hold of this lever, and when I say so pull it as hard as you can."

"Dat's whut I will, Massa Tom. Golly! ef dat no 'count giant was heah now he'd see he ain't de only one whut's got muscle. I'll pull good an' hard, Massa Tom."

"Yes, that's what I want you to. Now I guess we're all ready. Can you see, Dad—and Ned and Mr. Damon?"

"Yes," they answered. They stood near the side wall of the shop, while Tom and Eradicate were at the testing block, on which the motor, with the noise-eliminating devices attached, had been temporarily mounted.

"All ready," called the young inventor, as he turned on the gas and threw over the electrical switch. "All ready! Pull the starting lever, Rad, and when it's been running a little I'll throw on the silencer and you can see the difference."

The motor began to hum, and there was a deafening roar, just as there always is when the engine of an aeroplane starts. It was as though half a dozen automobile engines were being run with the mufflers cut out.

"Now I'll show you the difference!" yelled Tom, though such was the noise that not a word could be heard. "This shows you what my silencer will do."

Tom pulled another lever. There was at once a cessation of the deafening racket, though it was not altogether ended. Then, after a moment or two, there suddenly came a roar as though a blast had been let off in the shop.

Tom and Eradicate were tossed backward, head over heels, as though by the giant hands of Koku himself, and Mr. Damon, Ned, and Tom's father saw the motor fly from the testing block and shoot through the roof of the building with a rending, crashing, and splintering sound that could be heard for a mile.



CHAPTER IX

AFTER A SPY

Curious as it may seem, Eradicate, the oldest and certainly not the most energetic of the party assembled in the experiment room, was the first to recover himself and arise. Tottering to his feet he gave one look at the testing block, whence the motor had torn itself. Then he looked at the prostrate figures around him, none of them hurt, but all stunned and very much startled. Then the gaze of Eradicate traveled to the hole in the roof. It was a gaping, ragged hole, for the motor was heavy and the roof of flimsy material. And then the colored man exclaimed:

"Good land ob massy! Did I do dat?"

His tone was one of such startled contrition, and so tragic, that Tom Swift, rueful as he felt over the failure of his experiment and the danger they had all been in, could not help laughing.

"I take it, hearing that from you, Tom, that we're all right," said Ned Newton, as he recovered himself and brushed some dirt off his coat. Ned was a natty dresser.

"Yes, we seem to be all right," replied Tom slowly. "I can't say what damage the flying motor has done outside, but—"

"Bless my insurance policy! but what happened?" asked Mr. Damon. "I saw Eradicate pull on that lever as you told him to, Tom, and then things all went topsy-turvy! Did he pull the wrong handle?"

"No, it wasn't Rad's fault at all," said Tom. "The trouble was, as I guess I'll find when I investigate, that I put too much power into the motor, and the muffler didn't give any chance for the accumulated exhaust gases to expand and escape. I didn't allow for that, and they simply backed up, compressed and exploded. I guess that's the whole explanation."

"I'm inclined to agree with you, Son," said Mr. Swift dryly. "Don't try to get rid of all the noise at once. Eliminate it by degrees and it will be safer."

"I guess so," agreed Tom.

By this time a score of workmen from the other shops had congregated around the one though the roof of which the motor had been blown. Tom opened the door to assure Jackson and the others that no one was hurt, and then the young inventor saw the exploded motor had buried in the dirt a short distance away from the experiment building.

"Lucky none of us were standing over it when it went up," said Tom, as he made an inspection of the broken machine. "We'd have gone through the roof with it."

"She certainly went sailing!" commented Ned. "Must have been a lot of power there, Tom."

And this was evidenced by the bent and twisted rods that had held the motor to the testing block, and by the cylinders, some of which were torn apart as though made of paper instead of heavy steel. But for the fact that all the force of the explosion was directly upward, instead of at the sides, none might have been left alive in the shop. All had escaped most fortunately, and they realized this.

"Well," queried Ned, as Tom gave orders to have the damaged machine removed and the roof repaired, "does this end the wonderful silent motor, Tom?"

"End it! What do you mean—"

"I mean are you going to experiment any further?"

"Why, of course! Just because I've had one failure doesn't mean that I'm going to give up. Especially when I know what the matter was—not leaving any vent for the escaping gases. Why this isn't anything. When I was perfecting my giant cannon I was nearly blown up more than once, and you remember how we got stuck in the submarine."

"I should say I did!" exclaimed Ned with a shudder. "I don't want any more of that. But as between being blown through a roof and held at the bottom of the sea, I don't know that there's much choice."

"Well, perhaps not," agreed Tom. "But as for ending my experiments, I wouldn't dream of such a thing! Why, I've only just begun! I'll have a silent motor yet!"

"And a non-explosive one, I hope," added Mr. Damon dryly. "Bless my shoe buttons, Tom, but if my wife knew what danger I'd been in she'd never let me come over to see you any more."

"Well, the next time I invite you to a test I'll be more careful," promised the young inventor.

"There isn't going to be any next time as far as I'm concerned!" laughed Ned. "I think it's safer to sell Liberty Bonds."

And, though they joked about it, they all realized the narrow escape they had had. As for Eradicate, once he knew he had not been the one who caused the damage, he felt rather proud of the part he had taken in the mishap, and for many days he boasted about it to Koku.

True to his determination, Tom Swift did not give up his experimental work on the silent motor. The machine that had been blown through the roof was useless now, and it was sent to the scrap heap, after as much of it as possible had been salvaged. Then Tom got another piece of apparatus out of his store room and began all over again.

He worked along the same lines as at first—providing a chamber for the escaping gases of the exhaust to expend their noise and energy in, at the same time laboring to cut down the concussion of the explosions in the cylinder without reducing their force any. And that it was no easy problem to do either of these, Tom had to admit as he progressed. All previous types of mufflers or silencers had to be discarded and a new one evolved.

"Jackson, I need some one to help me," said Tom to his chief mechanician one day. "Haven't you a good man who is used to experimental work that you can let me take from the works?"

"Why, yes," was the answer. "Let me see. Roberts is busy on the new bomb you got up, but I could take him off that—"

"No, don't!" interposed Tom. "I want that work to go on. Isn't there some one else you can let me have?"

"Well, there's a new man who came to me well recommended. I took him on last week, and he's a wonderful mechanic. Knows a lot about gas engines. I could let you have him—Bower his name is. The only thing about it, though, is that I don't like to give you a man of whom I am not dead certain, when you're working on a new device."

"Oh, that will be all right," said Tom. "There won't be any secrets he can get, if you mean you think he might be up to spy work."

"That's what I did mean, Tom. You never can tell, you know, and you have some bitter enemies."

"Yes, but I'll take care this man doesn't see the plans, or any of my drawings. I only want some one to do the heavy assembling work on the experimental muffler I'm getting up. We can let him think it's for a new kind of automobile."

"Oh, then I guess it will be all right. I'll send Bower to you."

Tom rather liked the new workman, who seemed quiet and efficient. He did not ask questions, either, about the machine on which he was engaged, but did as he was told. As Tom had said, he kept his plans and drawing under lock and key—in a safe to be exact—and he did not think they were in any danger from his new helper.

But Tom Swift held into altogether too slight regard the powers of those who were opposed to him. He did not appreciate the depths to which they would stoop to gain their ends.

He had been working hard on his new device, and had reached a point further along than when the other motor had exploded. He began to see success ahead of him, and he was jubilant. Whether this made him careless does not matter, but the fact was that he left Bower more to himself, and alone in the experimental shop several times.

And it was on one of these occasions, when Tom had been for some time in one of the other shops, where he and Jackson were in consultation over a new machine, that as he came back to the test room unexpectedly, he saw Bower move hastily away from in front of the safe. Moreover, Tom was almost certain he had heard the steel door clang shut as he approached the building.

And then, before he could ask his helper a question, Tom looked from a window and saw a stranger running hastily along the side of the building where his trial motor was being set up.

"Who's that? Who is that man? Did he come in here? Was he tampering with my safe?" cried Tom. He saw Bower hesitate and change color, and Tom knew it was time to act.

The window was open, and with one bound the young inventor was out and running after the stranger he had seen departing in such a hurry. The man was but a short distance ahead of him, and Tom saw he was stuffing some papers into his pocket.

"Here! Come back! Stop!" ordered Tom, but the man ran on the faster.

"That's a spy as sure as guns!" reflected Tom Swift. "And Bower is in with him!" he added. "I've got to catch that fellow!" and he speeded his pace as he ran after the fellow.



CHAPTER X

A BIG SPLASH

There was no question in the mind of Tom Swift but that the man he was running after was guilty of some wrong-doing. In the first place he was a stranger, and had no right inside the big fence that surrounded the Swift machine plant. Then, too, the very fact that he ran away was suspicious.

And this, coupled with the confusion on the part of Bower, and his proximity to the safe, made Tom fear that some of his plans had been stolen. These he was very anxious to recover if this strange man had them, and so he raced after him with all speed.

"Stop! Stop!" called Tom, but the on-racing stranger did not heed.

The cries of the young inventor soon attracted the attention of his men, and Jackson and some of the others came running from their various shops to give whatever aid was needed. But they were all too far away to give effective chase.

"Bower might have come with me if he had wanted to help," thought Tom. But a backward glance over his shoulder did not show that the new helper was engaging in the pursuit, and he could have started almost on the same terms as Tom himself.

The runaway, looking back to see how near the young inventor was to him, suddenly changed his course, and, noting this, Tom Swift thought:

"I've got him now! He'll be bogged if he runs that way," for the way led to a piece of swampy land that, after the recent rains, was a veritable bog which was dangerous for cattle at least; and more than one man had been caught there.

"He can't run across the swamp, that's sure," reflected Tom with some satisfaction. "I'll get him all right!"

But he wanted to capture the man, if possible, before he reached the bog, and, to this end, Tom increased his speed to such good end that presently, on the firm ground that bordered the swamp, Tom was almost within reaching distance of the stranger.

But the latter kept up running, and dodged and turned so that Tom could not lay hands on him. Suddenly, turning around a clump of trees the fleeing man headed straight for a veritable mud hole that lay directly in his path. It was part of the swamp—the most liquid part of the bog and a home of frogs and lizards.

Too late, the man, who was evidently unaware of the proximity of the swamp, saw his danger. His further flight was cut off by the mud hole, but it was too late to turn back. Tom Swift was at his heels now, and seeing that it was impossible to grab the man, Tom did the next best thing. He stuck out his foot and tripped him, and tripped him right on the edge of the mud hole, so that the man fell in with a big splash, the muddy water flying all around, some even over the young inventor.

For a moment the man disappeared completely beneath the surface, for the mud hole was rather deep just where Tom had thrown him. Then there was another violent agitation of the surface, and a very woebegone and muddy face was raised from the slough, followed by the rest of the figure of the man. Slowly he got to his feet, mud and water dripping from him. He cleared his face by rubbing his hands over it, not that it made his countenance clean, but it removed masses of mud from his eyes, nose, and mouth, so that he could see and speak, though his first operation was to gasp for breath.