TOM SWIFT AND HIS AIR GLIDER

or

Seeking the Platinum Treasure

By

VICTOR APPLETON

CONTENTS

I	A Breakdown
II	A Daring Project
III	The Hand of the Czar
IV	The Search
V	A Clew from Russia
VI	Rescuing Mr. Petrofsky
VII	The Air Glider
VIII	In a Great Gale
IX	The Spies
X	Off in the Airship
XI	A Storm at Sea
XII	An Accident
XIII	Seeking a Quarrel
XIV	Hurried Flight
XV	Pursued
XVI	The Nihilists
XVII	On to Siberia
XVIII	In a Russian Prison
XIX	Lost in a Salt Mine
XX	The Escape
XXI	The Rescue
XXII	In the Hurricane
XXIII	The Lost Mine
XXIV	The Leaking Tanks
XXV	Homeward Bound—Conclusion

TOM SWIFT AND HIS AIR GLIDER

CHAPTER I

A BREAKDOWN

"Well, Ned, are you ready?"

"Oh, I suppose so, Tom. As ready as I ever shall be."

"Why, Ned Newton, you're not getting afraid; are you? And after you've been on so many trips with me?"

"No, it isn't exactly that, Tom. I'd go in a minute if you didn't have this new fangled thing on your airship. But how do you know how it's going to work—or whether it will work at all? We may come a cropper."

"Bless my insurance policy!" exclaimed a man who was standing near the two lads who were conversing. "You'd better keep near the ground, Tom."

"Oh, that's all right, Mr. Damon," answered Tom Swift. "There isn't any more danger than there ever was, but I guess Ned is nervous since our trip to the underground city of gold."

"I am not!" indignantly exclaimed the other lad, with a look at the young inventor. "But you know yourself, Tom, that putting this new propeller on your airship, changing the wing tips, and re-gearing the motor has made an altogether different sort of a craft of it. You, yourself, said it wasn't as reliable as before, even though it does go faster."

"Now look here, Ned!" burst out Tom. "That was last week that I said it wasn't reliable. It is now, for I've tried it out several times, and yet, when I ask you to take a trip with me, to act as ballast—"

"Is that all you want me for, Tom, to act as ballast? Then you'd better take a bag of sand—or Mr. Damon here!"

"Me? I guess not! Bless my diamond ring! My wife hasn't forgiven me for going off on that last trip with you, Tom, and I'm not going to take any more right away. But I don't blame Ned—"

"Say, look here!" cried Tom, a little out of patience, "you know me better than that, Ned. Of course you're more than ballast—I want you to help me manage the craft since I made the changes on her. Now if you don't want to come, why say so, and I'll get Eradicate. I don't believe he'll be afraid, even if he—"

"Hold on dar now, Massa Tom!" exclaimed an aged colored man, who was an all around helper at the Swift homestead, "was yo' referencin' t' me when yo' spoke?"

"Yes, Rad, I was saying that if Ned wouldn't go up in the airship with me you would."

"Well, now, Masa Tom, I shorely would laik t' 'blige yo', I shore would. But de fack ob de mattah am dat I has a mos' particular job ob white washin' t' do dish mornin', an' I 'spects I'd better be gittin' at it. It's a mos' particular job, an', only fo' dat, I'd be mos' pleased t' go up in de airship. But as it am, I mus' ax yo' t' 'scuse me, I really mus'," and the colored man shuffled off at a faster gait than he was in the habit of using.

"Well, of all things!" gasped Tom. "I believe you're all afraid of the old airship, just because I made some changes in her. I'll go up alone, that's what I will."

"No, I'll go with you," interposed Ned Newton who was Tom's most particular chum. "I only wanted to be sure it was all right, that was all."

"Well, if you've fully made up your mind," went on the young inventor, a little mollified, "lend me a hand to get her in shape for a run. I expect to make faster time than I ever did before, and I'm going to head out Waterford way. You'd better come along, Mr. Damon, and I'll drop you off at your house."

"Bless my feather bed!" gasped the man. "Drop me off! I like that, Tom Swift!"

"Oh, I didn't mean it exactly that way," laughed Tom. "But will you come."

"No, thanks, I'm going home by trolley," and then as the odd man went in the house to speak to Tom's father, the two lads busied themselves about the airship.

This was a large aeroplane, one of the largest Tom Swift had ever constructed, and he was a lad who had invented many kinds of machinery besides crafts for navigating the upper regions. It was not as large as his combined aeroplane and dirigible balloon of which I have told you in other books, but it was of sufficient size to carry three persons besides other weight.

Tom had built it some years before, and it had seemed good enough then. Later he constructed some of different models, besides the big combination affair, and he had gone on several trips in that.

He and his chum Ned, together with Eradicate Sampson, the colored man, and Mr. Damon, had been to a wonderful underground city of gold in Mexico, and it was soon after their return from this perilous trip that Tom had begun the work of changing his old aeroplane into a speedier craft.

This had occupied him most of the Winter, and now that Spring had come he had a chance to try what a re-built motor, changed propellers, and different wing tips would do for the machine.

The time had come for the test and, as we have seen, Tom had some difficulty in persuading anyone to go along with him! But Ned finally got over his feeling of nervousness.

"Understand, Tom," spoke Ned, "it isn't because I don't think you know how to work an aeroplane that I hesitated. I've been up in the air with you enough times to know that you're there with the goods, but I don't believe even you know what this machine is going to do."

"I can pretty nearly tell. I'm sure my theory is right."

"I don't doubt that. But will it work out in practice?"

"She may not make all the speed I hope she will, and I may not be able to push her high into the air quicker than I used to before I made the changes," admitted Tom, "but I'm sure of one thing. She'll fly, and she won't come down until I'm ready to let her. So you needn't worry about getting hurt."

"All right—if you say so. Now what do you want me to do, Tom?"

"Go over the wire guys and stays for the first thing. There's going to be lots of vibration, with the re-built motor, and I want everything tight."

"Aye, aye, sir!" answered Ned with a laugh.

Then he set at his task, tightening the small nuts, and screwing up the turn-buckles, while Tom busied himself over the motor. There was some small trouble with the carburetor that needed eliminating before it would feed properly.

"How about the tires?" asked Ned, when he had finished the wires.

"You might pump them up. There, the motor is all right. I'm going to try it now, while you attend to the tires."

Ned had pumped up one of the rubber circlets of the small bicycle wheels on which the aeroplane rested, and was beginning on the second, when a noise like a battery of machine guns going off next to his ear startled him so that he jumped, tripped over a stone and went down, the air pump thumping him in the back.

"What in the world happened, Tom?" he yelled, for he had to use all his lung power to be heard above that racket. "Did it explode?"

"Explode nothing!" shouted Tom. "That's the re-built motor in action."

"In action! I should say it was in action. Is it always going to roar like that?"

Indeed the motor was roaring away, spitting fire and burnt gases from the exhaust pipe, and enveloping the aeroplane in a whitish haze of choking smoke.

No, I have the muffler cut out, and that's why she barks so. But she runs easier that way, and I want to get her smoothed out a bit.

"Whew! That smoke!" gasped his chum. "Why don't you—whew—this is more than I can stand," and holding his hands to his smarting eyes, Ned, gasping and choking, staggered away to where the air was better.

"It is sort of thick," admitted Tom. "But that's only because she's getting too much oil. She'll clear in a few minutes. Stick around and we'll go up."

Despite the choking vapor, the young inventor stuck to his task of regulating the motor, and in a short while the smoke became less, while the big propeller blades whirled about more evenly. Then Tom adjusted the muffler, and most of the noise stopped.

"Come on back, and finish pumping up the tires," he shouted to Ned. "I'm going to stop her now, and then I'll give her the pressure test, and we'll take a trip."

Having cleared his eyes of smoke, Ned came back to his task, and this having been finished, Tom attached a heavy spring balance, or scales, to the rope that held the airship back from moving when her propellers were whirling about.

"How much pressure do you want?" asked Ned.

"I ought to get above twelve hundred with the way the motor is geared, but I'll go up with ten. Watch the needle for me."

It may be explained that when aeroplanes are tested on the earth the propellers are set in motion. This of course would send a craft whizzing over the ground, eventually to rise in the air, but for the fact that a rope, attached to the craft, and to some stationary object, holds it back.

Now if this rope is hooked to a spring balance, which in turn is made fast to the stationary object, the "thrust" of the propellers will be registered in pounds on the scale of the balance. Anywhere from five hundred to nine hundred pounds of thrust will take a monoplane or biplane up. But Tom wanted more than this.

Once more the motor coughed and spluttered, and the big blades whirled about so fast that they seemed like solid pieces of wood. Tom stood on the ground near the levers which controlled the speed, and Ned watched the scale.

"How much?" yelled the young inventor.

"Eight hundred."

Tom turned on a little more gasolene.

"How much?" he cried again.

"Ten hundred. That'll do!"

"No, I'm going to try for more."

Again he advanced the spark and gasolene levers, and the comparatively frail craft vibrated so that it seemed as if she would fly apart.

"Now?" yelled Tom.

"Eleven hundred and fifty!" cried Ned.

"Good! That'll do it. She'll give more after she's been running a while. We'll go up."

Ned scrambled to his seat, and Tom followed. He had an arrangement so that he could slip loose the retaining rope from his perch whenever he was ready.

Waiting until the motor had run another minute, the young inventor pulled the rope that released them. Over the smooth starting ground that formed a part of the Swift homestead darted the aeroplane. Faster and faster she moved, Ned gripping the sides of his seat.

"Here we go!" cried Tom, and the next instant they shot up into the air.

Ned Newton had ridden many times with his chum Tom, and the sensation of gliding through the upper regions was not new to him. But this time there was something different. The propellers seemed to take hold of the air with a firmer grip. There was more power, and certainly the speed was terrific.

"We're going fast!" yelled Ned into Tom's ear.

"That's right," agreed the young inventor. "She'll beat anything but my Sky Racer, and she'd do that if she was the same size." Tom referred to a very small aeroplane he had made some time before. It was like some big bird, and very swift.

Up and onward went the remodeled airship, faster and faster, until, when several miles had been covered, Ned realized that the young inventor had achieved another triumph.

"It's great, Tom! Great!" he yelled.

"Yes, I guess it will do, Ned. I'm satisfied. If there was an international meet now I'd capture some of the prizes. As it is—"

Tom stopped suddenly. His voice which had been raised to overcome the noise of even the muffled motor, sounded unnaturally loud, and no wonder, for the engine had ceased working!

"What's the matter?" gasped Ned.

"I don't know—a breakdown of some kind."

"Can you get it going again?"

"I'm going to try."

Tom was manipulating various levers, but with no effect. The aeroplane was shooting downward with frightful rapidity.

"No use!" exclaimed the young inventor. "Something has broken."

"But we're falling, Tom!"

"I know it. We've done it before. I'm going to volplane to earth."

This, it may be explained, is gliding downward from a height with the engine shut off. Aeroplanists often do it, and Tom was no novice at the art.

They shot downward with less speed now, for the young inventor had thrown up his headplanes to act as a sort of brake. Then, a little later they made a good landing in a field near a small house, in a rather lonely stretch of country, about ten miles from Shopton, where Tom lived.

"Now to see what the trouble is," remarked our hero, as he climbed out of his seat and began looking over the engine. He poked in among the numerous cogs, wheels and levers, and finally uttered an exclamation.

"Find it?" asked Ned.

"Yes, it's in the magneto. All the platinum bearings and contact surfaces have fused and crystallized. I never saw such poor platinum as I've been getting lately, and I pay the highest prices for it, too. The trouble is that the supply of platinum is giving out, and they'll have to find a substitute I guess."

"Can't we go home in her?" asked Ned.

"I'm afraid not. I've got to put in new platinum bearings and contacts before she'll spark. I only wish I could get hold of some of the better kind of metal."

The magneto of an aeroplane performs a service similar to one in an automobile. It provides the spark that explodes the charge of gas in the cylinders, and platinum is a metal, more valuable now than gold, much used in the delicate parts of the magneto.

"Well, I guess it's walk for ours," said Ned ruefully.

"I'm afraid so," went on Tom. "If I only had some platinum, I could—"

"Perhaps I could be of service to you," suddenly spoke a voice behind them, and turning, the youths saw a tall, bearded man, who had evidently come from the lonely house. "Did I hear you say you needed some platinum?" he asked. He spoke with a foreign accent, and Tom at once put him down for a Russian.

"Yes, I need some for my magneto," began the young inventor.

"If you will kindly step up to my house, perhaps I can give you what you want," went on the man. "My name is Ivan Petrofsky, and I have only lately come to live here."

"I'm Tom Swift, of Shopton, and this is my chum, Ned Newton," replied the young inventor, completing the introductions. He was wondering why the man, who seemed a cultured gentleman, should live in such a lonely place, and he was wondering too how he happened to have some platinum.

"Will that answer?" asked Mr. Petrofsky, when they had reached his house, and he had handed Tom several strips of the precious silverlike metal.

"Do? I should say it would! My, but that is the best platinum I've seen in a long while!" exclaimed Tom, who was an expert judge of this metal. "Where did you get it, if I may ask?"

"It came from a lost mine in Siberia," was the unexpected answer.

"A lost mine?" gasped Tom.

"In Siberia?" added Ned.

Mr. Petrofsky slowly nodded his head, and smiled, but rather sadly.

"A lost mine," he said slowly, "and if it could be found I would be the happiest man on earth for I would then be able to locate and save my brother, who is one of the Czar's exiles," and he seemed shaken by emotion.

Tom and Ned stood looking at the bearded man, and then the young inventor glanced at the platinum strips in his hand while a strange and daring thought came to him.

CHAPTER II

A DARING PROJECT

While Tom and his chum are in the house of the Russian, who so strangely produced the platinum just when it was most needed, I am going to take just a little time to tell you something about the hero of this story. Those who have read the previous books of this series need no introduction to him, but in justice to my new readers I must make a little explanation.

Tom Swift was an inventor, as was his father before him. But Mr. Swift was getting too old, now, to do much, though he had a pet invention—that of a gyroscope—on which he worked from time to time. Tom lived with his father in the village of Shopton, in New York state. His mother was dead, but a housekeeper, named Mrs. Baggert, looked after the wants of the inventors, young and old.

The first book of the series was called "Tom Swift and His Motor-Cycle," and in that I related how Tom bought the machine from a Mr. Wakefield Damon, of Waterford, after the odd gentleman had unintentionally started to climb a tree with it. That disgusted Mr. Damon with motor-cycling, and Tom had lots of fun on the machine, and not a few daring adventures.

He and Mr. Damon became firm friends, and the oddity of the gentleman—mainly that of blessing everything he could think of—was no objection in Tom's mind. The young inventor and Ned Newton went on many trips together, Mr. Damon being one of the party.

In Shopton lived Andy Foger, a bullying sort of a chap, who acted very meanly toward Tom at times. Another resident of the town was a Mr. Nestor, but Tom was more interested in his daughter Mary than in the head of the household. Add Eradicate Sampson, an eccentric colored man who said he got his name because he "eradicated" dirt, and his mule, Boomerang, and I think you have met the principal characters of these stories.

After Tom had much enjoyment out of his motor-cycle, he got a motor boat, and one of his rivals on Lake Carlopa was this same Andy Foger, but our hero vanquished him. Then Tom built an airship, which had been the height of his ambition for some years. He had a stirring cruise in the Red Cloud, and then, deserting the air for the water, Tom and his father built a submarine, in which they went after sunken treasure. In the book, "Tom Swift and His Electric Runabout," I told how, in the speediest car on the road, Tom saved his father's bank from ruin, and in the book dealing with Tom's wireless message I related how he saved the Castaways of Earthquake Island.

When Tom went among the diamond makers, at the request of Mr. Barco Jenks, and discovered the secret of phantom mountain the lad fancied that might be the end of his adventures, but there were more to follow. Going to the caves of ice, his airship was wrecked, but he and his friends managed to get back home, and then it was that the young inventor perfected his sky racer, in which he made the quickest flight on record.

Most startling were his adventures in elephant land whither he went with his electric rifle, and he was the means of saving a missionary, Mr. Illingway and his wife, from the red pygmies.

Tom had not been home from Africa long before he got a letter from this missionary, telling about an underground city in Mexico that was said to be filled with gold. Tom went there, and in the book, entitled, "Tom Swift in the City of Gold," I related his adventures.

How he and his friends were followed by the Fogers, how they eluded them, made their way to the ruined temple in a small dirigible balloon, descended to the secret tunnel, managed to turn aside the underground river, and reach the city of gold with its wonderful gold statues—all this is told in the volume.

Then, after pulling down, in the centre of the underground city, the big golden statue, the door of rock descended, and made our friends prisoners. They almost died, but Andy Foger and his father, in league with some rascally Mexicans and a tribe of head-hunters, finally made their way to the tunnel, and most unexpectedly, released Tom and his friends.

There was a fight, but our hero's party escaped with considerable gold and safely reached Shopton. Now, after a winter spent in work, fixing over an old aeroplane, we again meet Tom.

"Would you mind telling me something about where this platinum comes from, and if you can get any more of it?" asked Tom, after a pause, following the strange statement made by the Russian.

"I will gladly tell you the story," spoke Mr. Petrofsky, "for I am much interested in inventions, and I formerly did something in that line myself, and I have even made a small aeroplane, so you see I know the need of platinum in a high power magneto."

"But where did you get such pure metal?" asked Tom. "I have never seen it's equal."

"There is none like it in all the world," went on the Russian, "and perhaps there never can be any more. I have only a small supply. But in Siberia—in the lost mine—there is a large quantity of it, as pure as this, needing only a little refining.

"Can't we get some from there?" asked the young inventor eagerly. "I should think the Russian government would mine it, and export it."

"They would—if they could find it," said Ivan Petrofsky dryly, "but they can't—no one can find it—and I have tried very hard—so hard, in fact, that it is the reason for my coming to this country—that and the desire to find and aid my brother, who is a Siberian exile."

"This is getting interesting," remarked Ned to Tom in a low voice, and the young inventor nodded.

"My brother Peter, who is younger than I by a few years, and I, are the last of our family," began Mr. Petrofsky, motioning Tom and Ned to take chairs. "We lived in St. Petersburg, and early in life, though we were of the nobility, we took up the cause of the common people."

"Nihilists?" asked Ned eagerly, for he had read something of these desperate men.

"No, and not anarchists," said Mr. Petrofsky with a sad smile. "Our party was opposed to violence, and we depended on education to aid our cause. Then, too, we did all we could in a quiet way to help the poor. My brother and I invented several life-saving and labor-saving machines and in this way we incurred the enmity of the rich contractors and government officials, who made more money the more people they could have working for them, for they made the people buy their food and supplies from them.

"But my brother, and I persisted, with the result that we were both arrested, and, with a number of others were sent to Siberia.

"Of the horrors we endured there I will say nothing. However, you have probably read much. In the country near which we were quartered there were many mines, some of salt and some of sulphur. Oh, the horrors of those mines! Many a poor exile has been lost in the windings of a salt mine, there to die miserably. And in the sulphur mines many die also, not from being lost so much as being overcome by stifling gases. It is terrible! And sometimes they are purposely abandoned by their guides, for the government wants to get rid of certain exiles.

"But you are interested in platinum. One day my brother and I who had been sent to work in the salt mines, mistook a turning and wandered on and on for several miles, finally losing our way. We had food and water with us, or we would have perished, and, as it was, we nearly died before we finally found our way out of an abandoned opening.

"We came out in the midst of a terrible snowstorm, and wandered about almost frozen. At last we were found by a serf who, in his sled, took us to his poor cottage. There we were warmed and fed back to life.

"We knew we would be searched for, as naturally, our absence would lead to the suspicion that we had tried to escape. So as soon as we were able, we started back to the town where we were quartered. The serf wanted to take us in his sled, but we knew he might be suspected of having tried to aid us to get away, and he might be arrested. So we went alone.

"As might have been expected, we became lost again, and wandered about for several days. But we had enough food to keep us alive. And it was during this wandering that I came upon the platinum mine. It was down in a valley, in the midst of a country densely wooded and very desolate. There was an outcropping of the ore, and rather idly I put some of it in my pockets. Then we wandered on, and finally after awful suffering in terrific storms, were found by a searching party and brought back to the barracks."

"Did they think you had escaped?" asked Tom.

"They did," replied the Russian, "and they punished us severely for it, in spite of our denials. In time I managed secretly to smelt the platinum ore, and I found I had some of the purest metal I had ever seen. I was wishing I could find the mine, or tell some of my friends about it, when one of the officers discovered the metal in my bed.

"He demanded to know where I had gotten it, and knowing that refusal would only make it the worse for me I told him. There was considerable excitement, for the value of the discovery was recognized, and a search was at once made for the mine.

"But, even with the aid we were able to give, it could not be located. Many expeditions went out to hunt for it but came back baffled. They could not penetrate that wild country."

"They should have used an aeroplane," suggested Tom.

"They did," replied the Russian quickly, "but it was of no use."

"Why not?" the young inventor wanted to know.

"Because of the terrific winds that almost continually sweep over that part of Siberia. They never seem to cease, and there are treacherous air currents and 'pockets' that engulfed more than one luckless aviator. Oh, you may be sure the Russian government spared no means of finding the lost platinum mine, but they could not locate it, or even get near the place where they supposed it to be.

"Then, perhaps thinking that my brother and I were concealing something, they separated us. Where they sent him I do not know, but I was doomed to the sulphur mines. I was heartbroken, and I scarcely cared whether I lived or died. But an opportunity of escape came, and I took it. I wanted to save my brother, but I did not know where he was, and I thought if I could make my way to some civilized country, or to free America, I might later be able to save my brother.

"I went to England, taking some of my precious platinum with me, and stayed there for two years. I learned your language, but my efforts to organize an expedition to search for the lost mine, and for my brother, failed. Then I came here, and—well, I am still trying."

"My! That is certainly interesting!" exclaimed Ned, who had been all attention during the telling of the story.

"And you certainly had a hard time," declared Tom. "I am much obliged for this platinum. Have you set a price on it? It is worth much more than the ordinary kind."

"The price is nothing to you," replied the Russian, with a smile. "I am only too glad to help you fix your aeroplane. Will it take long? I should like to watch you."

"Come along," invited Tom. "I can soon have it going again, and I'll give you a ride, if you like."

"No, thank you, I'm hardly up to that yet, though I may be some day. The machine I made never flew well and I had several bad falls."

Tom and Ned worked rapidly on the magneto, and soon had replaced the defective bits of platinum.

"If the Russians had such a machine as this maybe they could have gotten to that mine," suggested Ned, who was very proud of Tom's craft.

"It would be useless in the terrific winds, I fear," answered Ivan Petrofsky. "But now I care little for the mine. It is my brother whom I want to save. He must be in some of the Siberian mines, and if I had such a craft as this I might be able to rescue him."

Tom Swift dropped the file he was using. A bright light sparkled in his eyes. He seemed strangely excited.

"Mr. Petrofsky!" he cried, "would you let me have a try at finding your brother, and would you come with me?"

"Would I?" asked the Russian eagerly. "I would be your debtor for life, and I would always pray for you, if you could help me to save my brother Peter."

"Then we'll have a try at it!" cried Tom. "I've got a different airship than this—one in which I can travel three thousand miles without coming down. I haven't had any excitement since I got back from the city of gold. I'm going to Russia to help you rescue your brother from exile, and I'm also going to have a try for that lost platinum treasure!"

"Thank heaven, there is some hope for poor Peter at last," murmured Mr. Petrofsky earnestly.

"You never can get to the platinum mine," said Ned. "The winds will tear your airship to pieces."

"Not the kind I'm going to make," declared Tom. "It's going to be an air glider, that will fairly live on high winds. Ho! for Siberia and the platinum mines. Will you come?"

"I don't know what you mean by an air glider, Tom Swift, but I'll go to help rescue my brother," was the quick answer, and then, with the light of a daring resolve shining in his eyes, the young inventor proceeded to get his aeroplane in shape for the trip back to Shopton.

CHAPTER III

THE HAND OF THE CZAR

"Then you won't take a ride with me to-day?" asked the young inventor, of the Russian, as he completed the repairs to the magneto. "I'd like to have you meet my father, and a friend of his, Mr. Damon. Most likely he'll go to Siberia with us, if his wife will let him. I'd like to talk some plans over with you."

"I shall certainly call on you," answered Ivan Petrofsky, "but," he added with a smile, "I think I should prefer to take my first ride in your larger airship—the one that doesn't come down so often."

"Well, perhaps it is a little easier on an amateur," admitted Tom. "If you'll come over to our house at any time I'll take you out in it, or I'll call for you."

"I'll come over in a few days," answered the escaped exile. "Then I'll tell you all I know of the locality where the platinum mine is located, and we can make our plans. In the meanwhile don't say anything about what I have told you."

"Why?" asked Ned quickly.

Mr. Petrofsky approached closer to the lads, and in a low voice said:

"I am not sure about it, but of late I think I have been shadowed. I have seen strange men in the village near here and they have eyed me rather suspiciously. Then, too, I have surprised several men around my house. I live here all alone, you know, and do most of my own work, a woman coming in occasionally to clean. But I don't like these suspicious characters hanging about.

"Who do you think they are?" asked Tom.

"I'm almost afraid to think, but from my past experience I think—nay, I fear—they may be spies, or agents of the Russian government."

"Spies!" cried Ned.

"Hush. Not so loud," cautioned Mr. Petrofsky. "They may even now be in hiding, especially since your aeroplane landed so near my house. They may see something suspicious even in that."

"But why should the Russian government set spies on you?" asked Tom in a low voice.

"For two reasons. I am an escaped exile, and I am not a citizen of the United States. Therefore I may be sent back to the sulphur mines. And another reason is that they may think I know the secret of the platinum treasure—the lost mine."

"Say this is getting interesting!" exclaimed Tom. "If we are going to have a brush with some of the spies of the Russian government so much the better. I'm ready for 'em!"

"So am I!" added Ned.

"You don't know them," said Mr. Petrofsky, and he could not repress a shudder. "I hope they are not on my trail, but if they are—" he paused a moment, straightened himself up, and looked like what he was, a strong man—"if they are let them look out. I'd give my life to save my brother from the awful, living death to which he is consigned!"

"And we're with you!" cried Tom, offering the Russian his hand. "We'll turn the trick yet. Now don't forget to come and see us. Come along, Ned. If I'm going to build an air glider I've got to get busy." And waving farewells to their new friend, the lads took their places in the aeroplane and were soon on their way to Shopton.

"Well, what do you think of it?" asked Ned of his chum, as they sped along at a good elevation, the engine going at half speed to be less noisy and make talking easier.

"Lots. I think we're in for a good time, an exciting one, anyhow, if what he says is true. But what in the world is an air glider, Tom?"

"It's the last word in aeroplanes. You don't need a motor to make it go."

"Don't need a motor?"

"No, the wind does it all. It's a sort of aeroplane, but the motion comes from the wind, acting on different planes, and this is accomplished by shifting weights. In it you can stand still in a fierce gale, if you like."

"How, by tying her fast on the ground?"

"No, hovering in the air. It's all done by getting the proper balance. The harder the wind blows the better the air glider works, and that's why I think it will be just the thing for Siberia. I'm going to get right at work on it, and you'll help me; won't you?"

"I sure will. Say, is platinum worth much?"

"Worth much? I should say it was! It's got gold beat now, and the available supply is very small, and it's getting more scarce. Russia has several mines, and the metal is of good quality. I've used some Russian platinum, but the kind Mr. Petrofsky gave me to-day was better than the best I ever had. If we can only find that lost mine we'll be millionaires all right."

"That's what we thought when we found the city of gold, but the gold wasn't of as fine a grade as we hoped."

"Well, nothing like that can happen in this platinum deal. It sure is rich ore that Mr. Petrofsky and his brother found. Poor fellow! To think of being an exile in that awful country, not knowing where you may be sent next. No wonder Mr. Petrofsky wants to rescue him."

"That's right. Well, here we are. I wonder what your father will say when he hears you're thinking of another expedition, Tom?"

"Oh, he'll want me to go when he hears about the exile."

"And I'm sure my folks will let me go. How about Mr. Damon?"

"I don't believe we can hold him back. It will make a nice party, just you and I, and Mr. Damon and Mr. Petrofsky. That will leave room for the other Russian—if we can rescue him," and with that Tom shut off the engine and glided to earth.

It may well be imagined that Mr. Swift was surprised when his son told him the latest news, but he did not offer any serious objection to the young inventor going to Siberia.

"Only you must be careful," he said. "Those Russian officers are ugly when it comes to trying to take away any of their prisoners. And this air glider—I don't exactly know about that. It's a new machine, and you want to be sure it works before you trust yourself to it."

"I will," promised Tom. "Say, I've got plenty of work ahead of me,—to get my big airship in shape, and build the glider. You'll have to help me, dad."

"I will, son. Now tell me more about this Mr. Petrofsky." Which Tom did.

The days that followed were indeed busy ones for Tom. The young inventor made a model air glider that sailed fairly well, but he knew it would have to work better to be successful, and he bent all his energies in that direction. Meanwhile Mr. Damon had been told of the prospective trip.

"Bless my bank book! Of course I'll go," he said. "But don't say anything about it to my wife—that is, just yet. I'll bring her around to it gradually. She has always wanted a diamond ring set in platinum, and now I can get it for her. I know she'll let me go if I break it to her gently."

It may be mentioned here that many valuable diamonds are now set in platinum instead of gold.

"I want to keep busy," said Mr. Damon, so Tom set him, Ned and Eradicate at the task of getting the big airship in shape for the trip. This air craft has not figured in any of my previous stories, but as it is so nearly like the one that was crushed in the caves of ice, I will not give a description of it here. Those who care to may refer to the book telling of Tom's trip to the caves of ice for a detailed account of the craft.

Sufficient to say that this latest airship, named the Falcon, was the largest Tom had ever built. It contained much room, many comforts, and could sail for several thousand miles without descending, except in case of accident. It was a combined dirigible balloon and aeroplane, and could be used as either, the necessary gas being made on board. It was large enough to enable the air glider to be taken on it in sections.

It was about a week after their first meeting with him, that Ivan Petrofsky paid a visit to the Swift home. He was warmly welcomed by the aged inventor and Mr. Damon, and, closeted in the library of the house, he proceeded to go more into details of his own and his brother's exile to Siberia, and to tell about the supposed location of the lost platinum mine.

"I don't believe we can start for several weeks yet," said Tom, after some discussion. "It will take me that long to make the glider."

"And I, too, need a little time," said the Russian. "I will write to some friends in St. Petersburg and perhaps they can get some information for us, as to where my brother is.

"That will be good," declared Mr. Damon. "Bless my icicle! But the more I think of this trip the better I like it!"

It was arranged that the Russian should call again soon, when the plans would be nearer in shape, and in the meanwhile he must learn all he could from revolutionary friends in Siberia.

It was a week after this, during which Tom, Ned and the others had been very busy, that Tom decided to take a trip to see their Russian friend. They had not heard from him since his visit, and Tom wanted to learn something about the strength of the Siberian winds.

He and Ned went in one of the small airships and soon they were hovering over the grounds surrounding the lonely house where Ivan Petrofsky lived.

"He doesn't seem to be at home," remarked Ned, as they descended and approached the dwelling.

"No, and it looks quite deserted," agreed the young inventor. "Say, all the doors are open, too! He shouldn't go away and leave his house open like that—with the valuable platinum there."

"Maybe he's asleep," suggested Ned.

They knocked on the opened door, but there was no answer. Then they went inside. To their surprise the house was in confusion. Furniture was overturned, tables and chairs were broken, and papers were scattered about the room.

"There's been a fight here!" cried Tom.

"That's right," agreed Ned. "Maybe he's been hurt—maybe burglars came for the platinum!"

"Come on!" cried Tom, making a dash for the stairs. "We'll see if he's here."

The house was small, and it took but a moment to show that Mr. Petrofsky was not there. Upstairs, as below, was the same confusion—the overturned furniture and the papers scattered about.

Tom stooped and picked up a scrap that looked like a piece torn from a letter. On top was a seal—the black seal of Russia—the imperial arms of the Czar!

"Look!" cried Tom, holding out the paper.

"What is it?" asked Ned.

"The hand of the Czar!" answered his chum. "It has reached out from Russia, and taken Mr. Petrofsky away!"

CHAPTER IV

THE SEARCH

For a moment Ned could scarcely understand what Tom meant. It scarcely seemed possible that such a thing could happen. That some one in far-off Russia—be it the Czar or one of the secret police—could operate from such a distance, seeking out a man in an obscure house in a little American village, and snatching him away.

"It isn't possible!" declared Ned breathlessly.

"What difference does that make?" asked Tom. "The thing has happened, and you can't get out of it. Look at all the evidence—there's been a fight, that's sure, and Mr. Petrofsky is gone."

"But maybe he went away of his own accord," insisted Ned, who was sometimes hard to convince.

"Nonsense! If a man went away of his own accord would he smash up his furniture, leave his papers scattered all about and go off leaving the doors and windows open for any one to walk in? I guess not."

"Well, maybe you're right. But think of it! This isn't Russia!"

"No, but he's a Russian subject, and, by his own confession an escaped exile. If he was arrested in the usual way he could be taken back, and our government couldn't interfere. He's been taken back all right. Poor man! Think of being doomed to those sulphur mines again, and as he escaped they'll probably make it all the harder for him!"

"But I thought our government wouldn't help other nations to get back prisoners convicted of political crimes," suggested Ned. "That's all Mr. Petrofsky was guilty of—politics, trying to help the poor in his own country. It's a shame if our government stands for anything like that!"

"That's just the point!" exclaimed Tom. "Probably the spies, secret police, or whoever the Russian agents were, didn't ask any help from our government. If they did there might be a chance for him. But likely they worked in secret. They came here, sneaked in on him, and took him away before he could get help. Jove! If he could only have gotten word to me I'd have come in the airship, and then there'd be a different ending to this."

"I guess you're right, Tom. Well, that ends it I suppose."

"Ends what?"

"Our trip to the platinum mine."

"Not a bit of it. I'm going to have a hunt for it."

"But how can you when Mr. Petrofsky can't go along to show us the way? Besides, we wanted to help rescue his brother, and now we can't."

"Well, I'm going to make a big try," declared the young inventor firmly. "And the first thing I'm going to do is to get our friend out of the clutches of the Russian police."

"You are? How?"

"I'm going to make a search for him. Look here, Ned, he must have been taken away some time to-day—perhaps only a few hours ago—and they can't have gone far with him."

"How do you make that out?" Ned wanted to know.

"Well, I guess I'm detective enough for that," and Tom smiled. "Look here, the doors and windows are open. Now it rained last night, and there was quite a wind. If the windows had been open in the storm there'd be some traces of moisture in the rooms. But there isn't a drop. Consequently the windows have been opened since last night."

"Say, that's so!" cried Ned admiringly.

"But that's not all," went on Tom. "Here's a bottle of milk on the table, and it's fresh," which he proved by tasting it. "Now that was left by the milkman either late last night or early this morning. I don't believe it's over twelve hours old."

"Well, what does this mean?" asked Ned, who couldn't quite follow Tom's line of reasoning.

"To my mind it means that the spies were here no later than this morning. Look at the table upset, the dishes on the floor. Here's one with oatmeal in it, and you know how hard and firm cooked oatmeal gets after it stands a bit. This is quite fresh, and soft, and—"

"And that means—" interrupted Ned, who was in turn interrupted by Tom, who exclaimed:

"It means that Mr. Petrofsky was at breakfast when they burst in on him, and took him away. They had hard work overpowering him, I'll wager, for he could put up a pretty good fight. And the broken furniture is evidence of that. Then the spies, after tying him up, or putting him in a carriage, searched the house for incriminating papers. That's as plain as the nose on your face. Then the police agents, or whoever they were, skipped out in a hurry, not taking the trouble to close the windows and doors."

"I believe it did happen that way," agreed Ned, who clearly saw what Tom meant. "But what can we do? How can we find him?"

"By getting on the trail," answered his chum quickly. "There may be more clews in the house, and I'm sure there'll be some out of doors, for they must have left footprints or the marks of carriage wheels. We'll take a look, and then we'll get right on the search. I'm not going to let them take Mr. Petrofsky to Russia if I can help it. I want to get after that platinum, and he's the only one who can pilot us anywhere near the place; and besides, there's his brother we've got to rescue. We'll make a search for the exile."

"I'm with you!" cried Ned. "Jove! Wouldn't it be great if we could rescue him? They can't have gotten very far with him."

"I'm afraid they have quite a start on us," admitted Tom with a dubious shake of his head, "but as long as they're in the United States we have a chance. If ever they get him on Russian soil it's all up with him."

"Come on then!" cried Ned. "Let's get busy. What's the first thing to do?"

"Look for clews," replied Tom. "We'll begin at the top of the house and work down. It's lucky we came when we did, for every minute counts."

Then the two plucky lads began their search for the kidnapped Russian exile. Had those who took him away seen the mere youths who thus devoted themselves to the task, they might have laughed in contempt, but those who know Tom Swift and his sturdy chum, know that two more resourceful and brave lads would be hard to find.

CHAPTER V

A CLEW FROM RUSSIA

"Nothing much up here," remarked Tom, when he and Ned had gone all over the second floor twice. "That scrap of paper, which put me on to the fact that some one from the Russian government had been here, is about all. They must have taken all the documents Mr. Petrofsky had."

"Maybe he didn't have any," suggested Ned.

"If he was wise he'd get rid of them when he knew he was being shadowed, as he told us. Perhaps that was why they broke up the furniture, searching for hidden papers, or they may have done it out of spite because they didn't find anything. But we might as well go downstairs and look there."

But the first floor was equally unproductive of clews, save those already noted, which showed, at least so Tom believed, that Mr. Petrofsky had been surprised and overpowered while at breakfast.

"Now for outside!" cried the young inventor. "We'll see if we can figure out how they got him away."

There were plenty of marks in the soft ground and turf, which was still damp from the night's rain, though it was now afternoon. Unfortunately, however, in approaching the house after leaving the aeroplane, Ned and Tom had not thought to exercise caution, and, not suspecting anything wrong, they had stepped on a number of footprints left by the kidnappers.

But for all that, they saw enough to convince them that several men had been at the lonely house, for there were many marks of shoes. It was out of the question, however, to tell which were those of Mr. Petrofsky and which those of his captors.

"They might have carried him out to a carriage they had in waiting," suggested Ned. "Let's go out to the front gate and look in the road. They hardly would bring the carriage up to the door."

"Good idea," commented Tom, and they hurried to the main thoroughfare that passed the Russian's house.

"Here they are!" cried Ned, who was in the lead. "There's been a carriage here as sure as you're a foot high and it's a rubber-tired one too."

"GOOD!" cried Tom admiringly. "You're coming right along in your detective training. How do you make that out?"

"See here, where a piece of rubber has been broken or cut out of the tire. It makes a peculiar mark in the dirt every time the wheel goes around."

"That's right, and it will be a good thing to trace the carriage by. Come on, we'll keep right after it."

"Hold on a bit," suggested Ned, who, though not so quick as Tom Swift, frequently produced good results by his very slowness. "Are you going off and leave the airship here for some one to walk off with?"

"Guess they wouldn't take it far," replied the young inventor, "but I'd better make it safe. I'll disconnect it so they can't start it, though if Andy Foger happens to come along he might slash the planes just out of spite. But I guess he won't show up."

Tom took a connecting pin out of the electrical apparatus, making it impossible to start the aeroplane, and then, wheeling it out of sight behind a small barn, he and Ned went back to the carriage marks in the road.

"Hurry!" urged Tom, as he started off in the direction of the village of Hurdtown, near where the cottage stood. "We will ask people living along the highway if they've seen a carriage pass."

"But what makes you think they went off that way?" asked Ned. "I should think they'd head away from the village, so as not to be seen."

"No, I don't agree with you. But wait, we'll look at the marks. Maybe that will help us."

Peering carefully at the marks of horses' hoofs and the wheel impressions, Tom uttered a cry of discovery.

"I have it!" he declared. "The carriage came from the village, and kept right on the other way. You're right, Ned. They didn't go back to town.

"Are you sure?"

"Of course. You can see for yourself; if the carriage had turned around the track would show, but it doesn't and, even if they turned on the grass, there'd be two lines of marks—one coming out here and one returning. As it is there is only a single set—just as if the carriage drove up here, took on its load, and continued on. This way, Ned."

They hurried down the road, and soon came to a cluster of farm houses. Inquiries there, however, failed to bring anything to light, for either the occupants of the house had failed to notice passing vehicles, or there had been so many that any particular carriage was not recalled. And there were now so many impressions in the soft dirt of the highway—so many wheel tracks and hoof imprints—that it was impossible to pick out those of the carriage with the cut rubber tire. "Well, I guess it isn't of much use to go on any farther," spoke Ned, when they had traveled several miles and had learned nothing.

"We'll try one more house, and then go back," agreed Tom. "We'll tell dad about what's happened, and see what he says."

"Carriage?" repeated an old farmer to whom they next put the question. "Wa'al, now, come t' think of it, I did see one drivin' along here early this morning. It had rubber tires on too, for I recollect remarkin' t' myself that it didn't make much noise. Had t' talk t' myself," he added in explanation, "'cause nobody else in the family was up, 'ceptin' th' dog."

"Did the carriage have some Russians in it?" asked Tom eagerly, "and was one a big bearded man?"

"Wa'al, now you've got me," admitted the farmer frankly. "It was quite early you see, and I didn't take no particular notice. I got up early t' do my milkin' 'cause I have t' take it t' th' cheese factory. That's th' reason nobody was up but me. But I see this carriage comin' down th' road, and thinks I t' myself it was pretty middlin' early fer anybody t' be takin' a pleasure ride. I 'lowed it were a pleasure ride, 'cause it were one of them hacks that folks don't usually use 'ceptin' fer a weddin', or a funeral, an' it wa'n't no funeral."

"Then you can't tell us anything more except that it passed?" asked Ned.

"No, I couldn't see inside, 'cause it was rather dark at that hour, and then, too, I noticed that they had th' window shades down."

"That's suspicious!" exclaimed Tom. "I believe they are the fellows we're after," and, without giving any particulars he said that they were looking for a friend who might have been taken away against his will.

"Could you tell where they were going?" asked Tom, scarcely hoping to get an affirmative answer.

"Wa'al, th' man on th' seat pulled up when he see me," spoke the farmer with exasperating slowness, "an' asked me how far it was t' th' Waterville station, an' I told him."

"Why didn't you say so at first?" asked Tom quickly. "Why didn't you tell us they were heading for the railroad?"

"You didn't ask me," replied the farmer. "What difference does it make."

"Every minute counts!" exclaimed the young inventor. "We want to keep right after those fellows. Maybe the agent can tell us where they bought tickets to, and we can trace them that way.

"Shouldn't wonder," commented the farmer. "There ain't many trains out from Waterville at that time of day, an' mighty few passengers. Shouldn't wonder but Jake Applesauer could put ye on th' trail."

"Much obliged," called Tom. "Come on, Ned," and he started back in the direction of the house where the kidnapping had taken place.

"That ain't th' way t' 'vaterville!" the farmer shouted after them.

"I know it, we're going to get our airship," answered Tom, and then he heard the farmer mutter.

"Plumb crazy! That's what they be! Plumb crazy! Going after their airship! Shouldn't wonder but they was escaped lunatics, and the other fellers was keepers after 'em. Hu! Wa'al, I've got my work to do. 'Tain't none of my affair."

"Let him think what he likes," commented Ned as he and his chum hurried on. "We're on the trail all right."

If Jake Applesauer, the agent at the Waterville station, was surprised at seeing two youths drop down out of an aeroplane, and begin questioning him about some suspicious strangers that had taken the morning train, he did not show it. Jake prided himself on not being surprised at anything, except once when he took a counterfeit dollar in return for a ticket, and had to make it good to the company.

But, to the despair of Tom and Ned, he could not help them much. He had seen the party, of course. They had driven up in the hack, and one of the men seemed to be sick, or hurt, for his head was done up in bandages, and the others had to half carry him on the train.

"That was Mr. Petrofsky all right," declared Ned.

"Sure," assented Tom. "They must have hurt and drugged him. But you can't tell us for what station they bought tickets, Mr. Applesauer?"

"No, for they didn't buy any. They must have had 'em, or else they paid on the train. One man drove off in the coach, and that's all I know."

As Tom and Ned started back to Shopton in the aeroplane they discussed what could be done next. A hard task lay before them, and they realized that.

"They could have gotten off at any station between here and New York, or even changed to another railroad at the junction," spoke Tom. "It's going to be a hard job."

"Guess we'll have to get some regular detectives on it," suggested Ned.

"And that's what I'll do," declared the young inventor. "They may be able to locate Mr. Petrofsky before those spies take him out of this country. If they don't—it will be too late. I'm going to talk to dad about it, and if he agrees I'll hire the best private detectives."

Mr. Swift gave his consent when Tom had told the story, and, a day later, one of the best detectives of a well known agency called on Tom in Shopton and assumed charge of the case.

The early reports from the detective were quite reassuring. He got on the trail of the men who had taken Mr. Petrofsky away, and confirmed the suspicion that they were agents of the Russian police. He trailed them as far as New York, and there the clews came to an end.

"Whether they are in the big city, which might easily be, or in some of the nearby towns, will take some time to learn," the detective wrote, and Tom wired back telling him to keep on searching.

But, as several weeks went by, and no word came, even Tom began to give up hope, though he did not stop work on the air glider, which was nearing completion. And then, most unexpectedly a clew came—a clew from far-off Russia.

Tom got a letter one day—a letter in a strange hand, the stamp and postmark showing that it had come from the land of the Czar.

"What do you suppose it contains?" asked Ned, who was with his chum when the communication was received.

"Haven't the least idea; but I'll soon find out."

"Maybe it's from the Russian police, telling you to keep away from Siberia."

"Maybe," answered Tom absently, for he was reading the missive. "I say!" he suddenly cried. "This is great! A clew at last, and from St. Petersburg! Listen to this, Ned!

"This letter is from the head of one of the secret societies over there, a society that works against the government. It says that Mr. Petrofsky is being detained a prisoner in a lonely hut on the Atlantic sea coast, not far from New York—Sandy Hook the letter says—and here are the very directions how to get there!"

"No!" cried Ned, in disbelief. "How in the world could anybody in Russia know that."

"It tells here," said Tom. "It's all explained. As soon as the secret police got Mr. Petrofsky they communicated with the head officials in St. Petersburg. You know nearly everyone is a spy over there, and the letter says that Mr. Petrofsky's friends there soon heard the news, and even about the exact place where he is being held."

"What are they holding him for?" asked Ned.

"That's explained, too. It seems they can't legally take him back until certain papers are received from his former prison in Siberia, and those are now on the way. His friends write to me to hasten and rescue him."

"But how did they ever get your address?"

"That's easy, though you wouldn't think so. It seems, so the letter explains, that as soon as Mr. Petrofsky got acquainted with us he wrote to friends in St. Petersburg, giving my address, and telling them, in case anything ever happened to him, to notify us. You see he suspected that something might, after he found he was being shadowed that way.

"And it all worked out. As soon as his friends heard that he was caught, and learned where he was being held, they wrote to me. Hurrah, Ned! A clew at last! Now to wire the detective—no, hold on, we'll go there and rescue him ourselves! We'll go in the airship, and pick up Detective Trivett in New York."

"That's the stuff! I'm with you!"

"Bless my suspender buttons! So am I, whatever it is!" cried Mr. Damon, entering the room at that moment.

CHAPTER VI

RESCUING MR. PETROFSKY

"We ought to be somewhere near the place now, Tom."

"I think we are, Ned. But you know I'm not going too close in this airship."

"Bless my silk hat!" exclaimed Mr. Damon. "I hope we don't have to walk very far in such a deserted country as this, Tom Swift."

"We'll have to walk a little way, Mr. Damon," replied the young inventor. "If I go too close to the hut they'll see the airship, and as those spies probably know that Mr. Petrofsky has been dealing with me, They'd smell a rat at once, and run away, taking him with them, and we'd have all our work to do over again."

"That's right," agreed Detective Trivett, who was one of the four in the airship that was now hovering over the Atlantic coast, about ten miles below the summer resorts of which Asbury Park was one.

It was only a few hours after Tom had received the letter from Russia informing him of the whereabouts of the kidnapped Russian, and he had acted at once.

His father sanctioned the plan of going to the rescue in one of Tom's several airships and, Mr. Damon, having been on hand, at once agreed to go. Of course Ned went along, and they had picked up the private detective in New York, where he was vainly seeking a clew to the whereabouts of Mr. Petrofsky.

Now the young inventor and his friends were hovering over the sandy stretch of coast that extends from Sandy Hook down the Atlantic seaboard. They were looking for a small fishing hamlet on the outskirts of which, so the Russian letter stated, was situated the lonely hut in which Mr. Petrofsky was held a prisoner.

"Do you think you can pick it out from a distance, Tom?" asked Mr. Damon, as the airship floated slowly along. It was not the big one they intended taking on their trip to Siberia, but it was sufficiently large to accommodate the four and leave room for Mr. Petrofsky, should they succeed in rescuing him.

"I think so," answered the young inventor.

In the letter from Russia a comparatively accurate description of the prisoner's hut had been given, and also some details about his guards. For there is little goes on in political circles in the realm of the Czar that is not known either to the spies of the government or those of the opposition, and the latter had furnished Tom with reliable information.

"That looks like the place," said Tom at length, when, after peering steadily through a powerful telescope, during which time Ned steered the ship, the young inventor "picked up" a fishing settlement. "There is the big fish house, spoken of in the letter," he went on, "and the Russians know a lot about fish. That house makes a good landmark. We'll go down now, before they have a chance to see us."

The others thought this a good idea, and a little later the airship sank to the ground amid a lonely stretch of sand dunes, about two miles from the hamlet on the outskirts of which the prison hut was said to be located.

"Now," said Tom, "we've got to decide on a plan of campaign. It won't do for all of us to go to the hut and make the rescue. Some one has got to stay with the airship, to be ready to start it off as soon as we come back with Mr. Petrofsky—if we do come.

"Then there's no use in me staying here," spoke Detective Trivett. "I don't know enough even to turn on the gasolene."

"No, it's got to be Ned or me," said the young inventor.

"I'll stay," volunteered Ned quickly, for though he would very much have liked to be in at the rescue, he realized that his place was in the airship, as Mr. Damon was not sufficiently familiar with the machinery to operate it.

Accordingly, after looking to everything to see that it was in working order, Tom led the advance. It was just getting dusk, and they figured on getting to the hut after dark.

"Have everything ready for a quick start," Tom said to Ned, "for we may come back running."

"I will," was the prompt answer, and then, getting their bearings, the little party set off.

They had to travel over a stretch of sandy waste that ran along the beach. Back in shore were a few scattered cottages, and not yet opened for the summer, and on the ocean side was the pounding surf. The hut, as Tom recalled the directions, lay just beyond a group of stunted hemlock trees that set a little way back from the ocean, on a bluff overlooking the sea. It was not near any other building.

Slowly, and avoiding going any nearer the other houses than they could help, the little party made its way. They had to depend on their own judgement now, for the minor details of the location of the hut could not be given in the letter from Russia. In fact the spies themselves, in writing to their head officers about the matter, had not described the location in detail.

"That looks like it over there," said Tom at last, when they had gone about a mile and a half, and saw a lonely hut with a light burning in it.

Cautiously they approached and, as they drew nearer, they saw that the light came through the window of a small hut.

"Looks like the place," commented the detective.

"We'll have a look," remarked Tom.

He crept up so he could glance in the window, and no sooner had he peered in, than he motioned for the others to approach.

Looking under a partly-drawn curtain, Mr. Damon and Mr. Trivett saw the Russian whom they sought. He was seated at a table, his head bowed on his hands, and in the room were three men. A rifle stood in one corner, near one of the guards.

"They're taking no chances," whispered Mr. Damon. "What shall we do, Tom?"

"It's three to three," replied the young inventor. "But if we can get him away without a fight, so much the better. I think I have it. I'll go up to the door, knock and make quite a racket, and demand admittance in the name of the Czar. That will startle them, and they may all three rush to answer. Mr. Damon, you and the detective will stay by the window. As soon as you see the men rush for the door, smash in the window with a piece of driftwood and call to Mr. Petrofsky to jump out that way. Then you can run with him toward the airship, and I'll follow. It may work."

"I don't see why it wouldn't," declared the detective. "Go ahead, Tom. We're ready."

Looking in once more, to make sure that the guards were not aware of the presence of the rescuing party, Tom went to the front door of the hut. It was a small building, evidently one used by fishermen.

Tom knocked loudly on the portal, at the same time crying out in a voice that he strove to make as deep and menacing as possible:

"Open! Open in the name of the Czar!"

Looking through the window, ready to act on the instant, Mr. Damon and the detective saw the three guards spring to their feet. One remained near Mr. Petrofsky, who also leaped up.

"Now!" called the detective to his companion. "Smash the window!"

The next instant a big piece of driftwood crashed through the casement, just as the two men were hurrying to the front door to answer Tom's summons.

"Mr. Petrofsky! This way!" yelled Mr. Damon, sticking his head in through the broken sash. "Come out! We've come to save you! Bless my putty blower, but this is great! Come on!"

For a moment the exile stared at the head thrust through the broken window, and he listened to Tom's emphatic knocks and demands. Then with a cry of delight the Russian sprang for the open casement, while the guard that had remained near him made a leap to catch him, crying out:

"Betrayed! Betrayed! It's the Nihilists! Look out, comrades!"

CHAPTER VII

THE AIR GLIDER

Mr. Damon continued to hammer away at the window sash with the piece of driftwood. There were splinters of the frame and jagged pieces of glass sticking out, making it dangerous for the exile to slip through.

"Come on! Come on!" the eccentric man continued to call. "Bless my safety valve! We'll save you! Come on!"

Mr. Petrofsky was leaping across the room, just ahead of the one guard. The other two were at the open door now, through which Tom could be seen. Then the spies, realizing in an instant that they had been deceived, made a dash after their comrade, who had his hand on the tails of the exile's coat.

"Break away! Break loose!" cried Mr. Damon, who, by this time had cleared the window so a person could get through. "Don't let them hold you!"

"I don't intend to!" retorted Mr. Petrofsky, and he swerved suddenly, tearing his coat, from the grasp of the guard.

In another instant the exile was at the casement, and was being helped through by Mr. Damon, and there was need of it, for the three guards were there now, doing their best to keep their prisoner.

"Pull away! Pull away!" cried Mr. Damon.

"We'll help you!" shouted Tom, who, now that his trick had worked, had sped around to the other side of the hut.

"Don't be afraid, we're with you!" exclaimed the detective, who was with the young inventor.

"Grab him! Keep him! Hold him!" fairly screamed the rearmost of the three guards. "It is a plot of the Nihilists to rescue him. Shoot him, comrades. He must not get away!"

"Don't you try any of your shooting games, or I'll take a hand in it!" shouted the detective, and, at the same moment he drew his revolver and fired harmlessly in the air.

"A bomb! A bomb!", yelled the guards in terror.

"Not yet, but there may be!" murmured Tom. The firing of the shot produced a good effect, for the three men who were trying to detain Ivan Petrofsky at once fell back from the window and gave him just the chance needed. He scrambled through, with the aid of Mr. Damon, and before the guards could again spring at him, which they did when the echoes of the shot had died away. They had realized, too late, that it was not a bomb, and that there was no immediate danger for them.

"Come on!" cried Tom. "Make for the airship! We've got to get the start of them!"

Leading the way, he sprinted toward the road that led to the place where the airship awaited them. He was followed by Mr. Damon and the detective, who had Mr. Petrofsky between them.

"Are you all right?" Tom called back to the exile. "Are you hurt? Can you run?"

"I'm all right," was the reassuring answer. "Go ahead; But they'll be right after us."

"Maybe they'll stop when they see this," remarked the detective significantly, and he held his revolver so that the rays of the newly-risen moon glinted on it.

"Here they come!" cried Tom a moment later, as three figures, one after the other, came around the corner of the house. They had not taken the shorter route through the window, as had Mr. Petrofsky, and this gained a little time for our friends.

"Stop! Hold on!" cried one of the guards in fairly good English. "That is our prisoner."

"Not any more!" the young inventor yelled back. "He's ours now."

"Look out! They're going to shoot!" cried Mr. Damon. "Bless my gunpowder! can't you stop them some way or other, Mr. Detective?"

"The only way is by firing first," answered Mr. Trivett, "and I don't want to hurt them. Guess I'll fire in the air again."

He did, and the guards halted. They seemed to be holding a consultation, as Tom learned by glancing hastily back, and he caught the glisten of some weapon. But if the three men had any notion of firing they gave it up, and once more came on running. Doubtless they had orders to get their prisoner back to Russia alive, and did not want to take any chances of hitting him.

"Leg it!" cried Tom. "Leg it!"

He was well ahead, and wanted the others to catch up to him, but none of the men was a good runner, and Mr. Petrofsky, by reason of being rather heavily built, was worse than the other two, so they had to accommodate their pace to his.

"I wonder if we can make it," mused Tom, as he realized that the airship was a good distance off yet the guards, though quite a way in the rear now were coming on fast. "It's going to be a close race," thought the young inventor. "I wish we'd brought the airship a little nearer."

It was indeed a race now, for the guards, seeming to know that they would not be shot at, were coming on more confidently, and were rapidly lessening the distance that separated them from their recent prisoner.

"We've got to go faster!" cried Tom.

"Bless my shoe leather!" yelled Mr. Damon. "I can't go any faster."

Still he did make the attempt, and so did the exile and the detective. Little was said now, for each of the parties was running a dogged race, and in silence. They had gone possibly half a mile, and the first advantage of Tom and his friends was rapidly being lost, when suddenly there sounded in the air above a curious throbbing noise.

"Bless my gasolene! What's that?" cried Mr. Damon.

"The airship! It's the airship!" yelled Tom, as he saw a great dark shape slowly approaching. "Ned is bringing her to meet us."

"Good!" cried the detective. "We need it I'm about winded!"

"This way, Ned! This way!" cried Tom, and, an instant later, they were in the midst of a brilliant glow, for Ned had turned the current into the great searchlight on the bow of the air craft, and the beams were focused on our friends. Ned could now see the refugees, and in a moment he sent the graceful craft down, bringing it to a halt on the ground near Tom.

"In with you!" cried the lad. "She's all ready to start up again!"

"Come on!" yelled Tom to the others. "We're all right now, if you hustle!"

"Bless my pin cushion!" gasped Mr. Damon, making a final spurt.

The three guards had halted in confusion on seeing the big, black bulk of the airship, and when they noted the gleaming of the searchlight they must have realized that their chances were gone. They made a rush, however, but it was too late. Over the side of the craft scrambled Tom, Mr. Damon, the detective and Ivan Petrofsky, and an instant later Ned had sent it aloft. The race was over, and the young inventor and his friends had won.

"You're the stuff!" cried Tom to Ned, as he went with his chum to the pilot house to direct the progress of the airship. "It's lucky you came for us. We never could have made the distance. We left the ship too far off."

"That's what I thought after you'd gone," replied his chum. "So I decided to come and meet you. I had to go slowly so as not to pass you in the darkness."

They were speeding off now, and Ned, turning the beams of the great searchlight below them, picked up the three guards who were gazing helplessly aloft after their fast disappearing prisoner.

"You're having your first ride in an airship, Mr. Petrofsky," remarked Tom, when they had gone on for some little distance. "How do you like it?"

"I'm so excited I hardly know, but it's quite a sensation. But how in the world did you ever find me to rescue me?"

Then they told the story of their search, and the unexpected clew from Russia. In turn the exile told how he had been attacked at the breakfast table one morning by the three spies—the very men who had been shadowing him—and taken away secretly, being drugged to prevent his calling for help. He had been kept a close prisoner in the lonely hut, and each day he had expected to be taken back to serve out his sentence in Siberia.

"Another day would have been too late," he told Tom, when he had thanked the young inventor over and over again, "for the papers would have arrived, and the last obstacle to taking me back to Russia would have been removed. They dared not take me out of the United States without official documents, and they would have been forged ones, for they intended trumping up a criminal charge against me, the political one not being strong enough to allow them to extradite me."

"Well I'm glad we got you," said Tom heartily. "We will soon be ready to start for Siberia."

"In this kind of a craft?"

"Yes, only much larger. You'll like it. I only hope my air glider works."

By putting on speed, Tom was able to reach Shopton before midnight, and there was quite an informal celebration in the Swift homestead over the rescue of the exile. The detective, for whom there was no further need, was paid off, and Mr. Petrofsky was made a member of the household.

"You'd better stay here until we are ready to start," Tom said, "and then we can keep an eye on you. We need you to show us as nearly as possible where the platinum field is."

"All right," agreed the Russian with a laugh. "I'm sure I'll do all I can for you, and you are certainly treating me very nicely after what I suffered from my captors."

Tom resumed work on his air glider the next day, and he had an additional helper, for Mr. Petrofsky proved to be a good mechanic.

In brief, the air glider was like an aeroplane save that it had no motor. It was raised by a strong wind blowing against transverse planes, and once aloft was held there by the force of the air currents, just like a box kite is kept up. To make it progress either with or against the wind, there were horizontal and vertical rudders, and sliding weights, by which the equilibrium could be shifted so as to raise or lower it. While it could not exactly move directly against the wind it could progress in a direction contrary to which the gale was blowing, somewhat as a sailing ship "tacks."

And, as has been explained, the harder the wind blew the better the air glider worked. In fact unless there was a strong gale it would not go up.

"But it will be just what is needed out there in that part of Siberia," declared the exile, "for there the wind is never quiet. Often it blows a regular hurricane."

"That's what we want!" cried Tom. He had made several models of the air glider, changing them as he found out his errors, and at last he had hit on the right shape and size.

Midway of the big glider, on which work was now well started, there was to be an enclosed car for the carrying of passengers, their food and supplies. Tom figured on carrying five or six.

For several weeks the work on the air glider progressed rapidly, and it was nearing completion. Meanwhile nothing more had been heard or seen of the Russian spies.

"Well," announced Tom one night, after a day's hard work, "we'll be ready for a trial now, just as soon as there comes a good wind."

"Is it all finished?" asked Ned.

"No, but enough for a trial spin. What I want is a big wind now."

CHAPTER VIII

IN A GREAT GALE

There was a humming in the air. The telegraph wires that ran along on high poles past the house of Tom Swift sung a song like that of an Aeolian harp. The very house seemed to tremble.

"Jove! This is a wind!" cried Tom as he awakened on a morning a few days after his air glider was nearly completed. "I never saw it so strong. This ought to be just what I want I must telephone to Mr. Damon and to Ned."

He hustled into his clothes, pausing now and then to look out of his window and note the effects of the gale. It was a tremendous wind, as was evidenced by the limbs of several trees being broken off, while in some cases frail trees themselves had been snapped in twain.

"Coffee ready, Mrs. Baggert?" asked our hero as he went downstairs. "I haven't got time to eat much though."

In spite of his haste Tom ate a good breakfast and then, having telephoned to his two friends, and receiving their promises to come right over, our hero went out to make a few adjustments to his air glider, to get it in shape for the trial.

He was a little worried lest the wind die out, but when he got outside he noted with satisfaction that the gale was stronger than at first. In fact it did considerable damage in Shopton, as Tom learned later.

It certainly was a strong wind. An ordinary aeroplane never could have sailed in it, and Tom was doubtful of the ability of even his big airship to navigate in it. But he was not going to try that.

"And maybe my air glider won't work," he remarked to himself as he was on his way to the shed where it had been constructed. "The models went up all right, but maybe the big one isn't proportioned right. However, I'll soon see."

He was busy adjusting the balancing weights when Ned Newton came in.

"Great Scott!" exclaimed the lad, as he labored to close the shed door, "this is a blow all right, Tom! Do you think it's safe to go up?"

"I can't go up without a gale, Ned."

"Well, I'd think twice about it myself."

"Why, I counted on you going up with me."

"Burr-r-r-r!" and Ned pretended to shiver. "I haven't an accident insurance policy you know."

"You won't need it, Ned. If we get up at all we'll be all right. Catch hold there, and shift that rear weight a little forward on the rod. I expect Mr. Damon soon."

The eccentric man came in a little later, just as Tom and Ned had finished adjusting the mechanism.

"Bless my socks!" cried Mr. Damon. "Do you really mean to go up to-day, Tom?"

"I sure do! Why, aren't you going with me?" and Tom winked at Ned.

"Bless my—" began Mr. Damon, and then, evidently realizing that he was being tested he exclaimed: "Well, I will go, Tom! If the air glider is any good it ought to hold me. I will go up."

"Now, Ned, how about you?" asked the young inventor.

"Well, I guess it's up to me to come along, but I sure do wish it was over with," and Ned glanced out of the window to see if the gale was dying out. But the wind was as high as ever.

It was hard work getting the air glider out of the shed, and in position on top of a hill, about a quarter of a mile away, for Tom intended "taking off" from the mound, as he could not get a running start without a motor. The wind, however, he hoped, would raise him and the strange craft.

In order to get it over the ground without having it capsize, or elevate before they were ready for it, drag ropes, attached to bags of sand were used, and once these were attached the four found that they could not wheel the air glider along on its bicycle wheels.

"We'll have to get Eradicate and his mule, I guess," said Tom, after a vain endeavor to make progress against the wind. "When it's up in the air it will be all right, but until then I'll need help to move it. Ned, call Rad, will you?"

The colored man, with Boomerang, his faithful mule, was soon on hand. The animal was hitched to the glider, and pulled it toward the hill.

"Now to see what happens," remarked Tom as he wheeled his latest invention around where the wind would take it as soon as the restraining ropes were cast off, for it was now held in place by several heavy cables fastened to stakes driven in the ground.

Tom gave a last careful look to the weights, planes and rudders. He glanced at a small anemometer or wind gage, on the craft, and noted that it registered sixty miles an hour.

"That ought to do," he remarked. "Now who's going up with me? Will you take a chance, Mr. Petrofsky?"

"I'd rather not—at first."

"Come on then, Ned and Mr. Damon. Mr. Petrofsky and Rad can cast off the ropes."

The wind, if anything, was stronger than ever. It was a terrific gale, and just what was needed. But how would the air glider act? That was what Tom wanted very much to know.

"Cast off!" he cried to the Russian and Eradicate, and they slipped the ropes.

The next moment, with a rush and whizzing roar, the air glider shot aloft on the wings of the wind.

CHAPTER IX

THE SPIES

"We're certainly going up!" yelled Ned, as he sat beside Tom in the cabin of the air glider.

"That's right!" agreed the young inventor rather proudly, as he grasped two levers, one of which steered the craft, the other being used to shift the weights. "We're going up. I was pretty sure of that. The next thing is to see if it will remain stationary in the air, and answer the rudder."

"Bless my top knot!" cried Mr. Damon. "You don't mean to tell me you can stand still in a gale of wind, Tom Swift."

"That's exactly what I do mean. You can't do it in an aeroplane, for that depends on motion to keep itself up in the air. But the glider is different. That's one of its specialties, remaining still, and that's why it will be valuable if we ever get to Siberia. We can hover over a certain spot in a gale of wind, and search about below with telescopes for a sign of the lost platinum mine.

"How high are you going up?" demanded Ned, for the air glider was still mounting upward on a slant. If you ever scaled a flat piece of tin, or a stone, you'll remember how it seems to slide up a hill of air, when it was thrown at the right angle. It was just this way with the air glider—it was mounting upward on a slant.

"I'm going up a couple of hundred feet at least," answered Tom, "and higher if the gale-strata is there. I want to give it a good test while I'm at it."

Ned looked down through a heavy plate of glass in the floor of the cabin, and could see Mr. Petrofsky and Eradicate looking up at them.

"Bless my handkerchief!" cried Mr. Damon, when his attention had been called to this. "It's just like an airship."

"Except that we haven't a bit of machinery on board," said Tom. "These weights do everything," and he shifted them forward on the sliding rods, with the effect that the air glider dipped down with a startling lurch.

"We're falling!" cried Ned.

"Not a bit of it," answered Tom. "I only showed you how it worked. By sliding the weights back we go up."

He demonstrated this at once, sending his craft sliding up another hill of air, until it reached an elevation of four hundred feet, as evidenced by the barograph.

"I guess this is high enough," remarked Tom after a bit. "Now to see if she'll stand still."

Slowly he moved the weights along, by means of the compound levers, until the air glider was on an "even keel" so to speak. It was still moving forward, with the wind now, for Tom had warped his wing tips.

"The thing to do," said the young inventor, "is to get it exactly parallel with the wind-strata, so that the gale will blow through the two sets of planes, just as the wind blows through a box kite. Only we have no string to hold us from moving. We have to depend on the equalization of friction on the surfaces of the wings. I wonder if I can do it."

It was a delicate operation, and Tom had not had much experience in that sort of thing, for his other airships and aeroplanes worked on an entirely different principle. But he moved the weights along, inch by inch, and flexed the tips, planes and rudders until finally Ned, who was looking down through the floor window, cried out:

"We're stationary!"

"Good!" exclaimed Tom. "Then it's a success."

"And we can go to Siberia?" added Mr. Damon.

"Sure," assented the young inventor. "And if we have luck we'll rescue Mr. Petrofsky's brother, and get a lot of platinum that will be more valuable than gold."

It would not be true to say that the air glider was absolutely stationary. There was a slight forward motion, due to the fact that it was not yet perfected, and also because Tom was not expert enough in handling it.

The friction on the plane surfaces was not equalized, and the gale forced the craft along slightly. But, compared to the terrific power of the wind, the air glider was practically at a standstill, and this was remarkable when one considers the force of the hurricane that was blowing above, below and through it.

For actually that was what the hurricane was doing. It was as if an immense box kite was suspended in the air, without a string to hold it from moving, and as though a cabin was placed amidships to hold human beings.

"This sure is great!" cried Ned. "Have you got her in control, Tom?"

"I think so. I'll try and see how she works."

By shifting the weights, changing the balance, and warping the wings, the young inventor sent the craft higher up, made it dip down almost to the earth, and then swoop upward like some great bird. Then he turned it completely about and though he developed no great speed in this test made it progress quarteringly against the wind.

"It's almost perfect," declared Tom. "A few touches and she'll be all right."

"Is it all right?" asked Ivan Petrofsky anxiously, as the three left the cabin, and Eradicate hitched his mule to the glider to take it back to the shed.

"I see where it can be improved," he said, as they made ready to descend. "I'll soon have it in shape."

"Then we can go to Siberia?"

"In less than a month. The big airship needs some repairs, and then we'll be off."

The Russian said nothing, but he looked his thanks to Tom, and the manner in which he grasped the hand of our hero showed his deep feelings.

The glider was given several more trials, and each time it worked better. Tom decided to change some of the weights, and he devoted all his time to this alteration, while Ned, Mr. Damon, and the others labored to get the big airship in shape for the long trip to the land of the exiles.

So anxious was Tom to get started, that he put in several nights working on the glider. Ned occasionally came over to help him, while Mr. Damon was on hand as often as his wife would allow. Mr. Petrofsky spent his nights writing to friends in Russia, hoping to get some clew as to the whereabouts of his brother.

It was on one of these nights, when Tom and Ned were laboring hard, with Eradicate to help them that an incident occurred which worried them all not a little. Tom was adjusting some of the new weights on the sliding rods, and called to Ned:

"I say, old man, hand me that big monkey wrench, will you. I can't loosen this nut with the small one. You'll find it on the bench by that back window."

As Ned went to get the tool he looked from the casement. He started, stood staring through the glass for a moment into the outer darkness, and then cried out:

"Tom, we're being watched! There are some spies outside!"

"What?" exclaimed the young inventor "Where are they? Who are they?"

"I don't know. Those Russian police, maybe out front, and maybe we can catch them!"

Grabbing up the big monkey wrench, Ned made a dash for the large sliding doors, followed by Tom who had an iron bar, and Eradicate with a small pair of pliers.

"By golly!" cried the colored man, "ef I gits 'em I'll pinch dere noses off!"

CHAPTER X

OFF IN THE AIRSHIP

Going from the brightly lighted shop into the darkness of the night, illuminated as it was only by the stars, neither Tom, Ned, nor Eradicate, could see anything at first. They had to stand still for a moment to accustom their eyes to the gloom.

"Can you see them?" cried Tom to his chum.

"No, but I can hear them! Over this way!" yelled Ned, and then, being able to dimly make out objects, so he would not run into them, he started off, followed by the young inventor.

Tom could hear several persons running away now, but he could see no one, and from the sound he judged that the spies, if such they were, were hurrying across the fields that surrounded the shop.

It was almost a hopeless task to pursue them, but the two lads were not the kind that give up. They rushed forward, hoping to be able to grapple with those who had looked in the shop window, but it was not to be.

The sound of the retreating footsteps became more and more faint, until finally they gave no clew to follow.

"Better stop," advised Tom. "No telling where we'll end up if we keep on running. Besides it might be dangerous."

"Dangerous; how?" panted Ned.

"They might dodge around, and wait for us behind some tree or bush."

"An' ef dat Foger feller am around he jest as soon as not fetch one ob us a whack in de head," commented Eradicate grimly.

"Guess you're about right," admitted Ned. "There isn't much use keeping on. We'll go back."

"What sort of fellows were they?" asked Tom, when, after a little further search, the hunt was given up. "Could you see them well, Ned?"

"Not very good. Just as I went to get you that wrench I noticed two faces looking in the window. I must have taken them by surprise, for they dodged down in an instant. Then I yelled, and they ran off."

"Did you see Andy Foger?"

"No, I didn't notice him."

"Was either of them one of the spies who had Mr. Petrofsky in the hut?"

"I didn't see those fellows very well, you remember, so I couldn't say."

"That's so, but I'll bet that's who they were."

"What do you think they're after, Tom?"

"One of two things. They either want to get our Russian friend into their clutches again, or they're after me—to try to stop me from going to Siberia."

"Do you think they'd go to such length as that?"

"I'm almost sure they would. Those Russian police are wrong, of course, but they think Mr. Petrofsky is an Anarchist or something like that, and they think they're justified in doing anything to get him back to the Siberian mines. And once the Russian government sets out to do a thing it generally does it—I'll give 'em credit for that."

"But how do you suppose they know you're going to Russia?"

"Say, those fellows have ways of getting information you and I would never dream of. Why, didn't you read the other day how some fellow who was supposed to be one of the worst Anarchists ever, high up in making bombs, plotting, and all that sort of thing—turned out to be a police spy? They get their information that way. I shouldn't be surprised but what some of the very people whom Mr. Petrofsky thinks are his friends are spies, and they send word to headquarters of every move he makes."

"Why don't you warn him?"

"He knows it as well as I do. The trouble is you can't tell who the spies are until it's too late. I'm glad I'm not mixed up in that sort of thing. If I can get to Siberia, help Mr. Petrofsky rescue his brother, and get hold of some of that platinum I'll be satisfied. Then I won't go back to the land of the Czar, once I get away from there."

"That's right. Well, let's go back and work on the glider."

"And we'll have Eradicate patrolling about the shop to make sure we're not spied on again."

"By golly! Ef I sees any oh 'em, I suah will pinch 'em!" cried the colored man, as he clicked the pliers.

But there was no further disturbance that night, and, when Tom and Ned ceased work, they had made good progress toward finishing the air glider.

The big airship was almost ready to be given a trial flight, with her motors tuned up to give more power, and as soon as the Russian exile had a little more definite information as to the possible whereabouts of his brother, they could start.

In the days that followed Tom and his friends worked hard. The air glider was made as nearly perfect as any machine is, and in a fairly stiff gale, that blew up about a week later, Tom did some things in it that made his friends open their eyes. The young inventor had it under nearly as good control as he had his dirigible balloons or aeroplanes.

The big airship, too, was made ready for the long voyage, extra large storage tanks for gasolene being built in, as it was doubtful if they could get a supply in Siberia without arranging for it in advance, and this they did not want to do. Besides there was the long ocean flight to provide for.

"But if worst comes to worst I can burn kerosene in my motor," Tom explained, for he had perfected an attachment to this end. "You can get kerosene almost anywhere in Russia."

At last word was received from Russia, from some Revolutionist friends of the exile, stating that his brother was supposed to be working in a certain sulphur mine north of the Iablonnoi mountains, and half way between that range and the city of Iakutsk.

"But it might be a salt mine, just as well," said Mr. Petrofsky, when he told the boys the news. "Information about the poor exiles is hard to get."

"Well, we'll take a chance!" cried Tom determinedly.

The preparations went on, and by strict watchfulness none of the spies secured admission to the shop where the air glider was being finished. The big airship was gotten in shape for the voyage, and then, after a final trial of the glider, it was taken apart and put aboard the Falcon, ready for use on the gale-swept plains of Siberia.

The last of the stores, provisions and supplies were put in the big car of the airship, a route had been carefully mapped out, and Tom, after saying good-bye to Mary Nestor, his father, the housekeeper, and Eradicate, took his place in the pilot house of the airship one pleasant morning at the beginning of Summer.

"Don't you wish you were going, Rad?" the young inventor asked, for the colored man had decided to stay at home.

"No indeedy, Massa Tom," was the answer. "Dat's a mighty cold country in Shebeara, an' I laik warm wedder."

"Well, take care of yourself and Boomerang," answered Tom with a laugh. Then he pulled the lever that sent a supply of gas into the big bag, and the ship began to rise.

"I guess we've given those spies the slip," remarked Ned, as they rose from the ground calling good-byes to the friends they left behind.

"I hope so," agreed Tom, but could he have seen two men, of sinister looks, peering at the slowly-moving airship from the shelter of a glove of trees, not far off, he might have changed his opinion, and so would Ned.

Then, as the airship gathered momentum, it fairly sprang into the air, and a moment later, the big propellers began revolving. They were off on their long voyage to find the lost platinum mine, and rescue the exile of Siberia.

CHAPTER XI

A STORM AT SEA

Tom had the choice of two routes in making his voyage to far-off Siberia. He could have crossed the United States, sailed over the Pacific ocean, and approached the land of the Czar from the western coast above Manchuria. But he preferred to take the Atlantic route, crossing Europe, and so sailing over Russia proper to get to his destination. There were several reasons for this.

The water voyage was somewhat shorter, and this was an important consideration when there was no telling when he might have an accident that would compel him to descend. On the Atlantic he knew there would be more ships to render assistance if it was needed, although he hoped he would not have to ask for it.

"Then, too," he said to Ned, when they were discussing the matter, "we will have a chance to see some civilized countries if we cross Europe, and we may land near Paris."

"Paris!" cried Ned. "What for?"

"To renew our supply of gasolene, for one thing," replied the young inventor. "Not that we will be out when we arrive, but if we take on more there we may not have to get any in Russia. Besides, they have a very good quality in France, so all told, I think the route over Europe to be the best."

Ned agreed with him, and so did Mr. Petrofsky. As for Mr. Damon, he was so busy getting his sleeping room in order, and blessing everything he could think of, that he did not have time to talk much. So the eastern route was decided on, and as the big airship, carrying our friends, their supplies, and the wonderful air glider rose higher and higher, Tom gradually brought her around so that the pointed nose of the gas bag aimed straight across the Atlantic.

They were over the ocean on the second day out, for Tom did not push the craft to her limit of speed, now they had time to consider matters at their leisure, for they had been rather hurried on leaving.

The machinery was working as nearly to perfection as it could be brought, and Tom, after finding out that his craft would answer equally well as a dirigible balloon or an aeroplane, let it sail along as the latter.

"For," he said, "we have a long trip ahead of us and we need to save all the elevating gas we can save. If worst comes to worst, and we can't navigate as an aeroplane any more, we can even drift along as a dirigible. But while we have the gasolene we might as well make speed and be an aeroplane."

The others agreed with him, and so it was arranged. Tom, when he had seen to it that his craft was working well, let Ned take charge and devoted himself to seeing that all the stores and supplies were in order for quick use.

Of course, until they were nearer the land of the Czar, and that part of Siberia where Mr. Petrofsky's brother was held as an exile, they could do little save make themselves as comfortable as possible in the airship. And this was not hard to do.

Naturally, in a craft that had to carry a heavy load, and lift itself into the air, as well as propel itself along, not many things could be taken. Every ounce counted. Still our friends were not without their comforts. There was a well stocked kitchen, and Mr. Damon insisted on installing himself as cook. This had been Eradicate's work but the eccentric man knew how to do almost everything from making soup to roasting a chicken, and he liked it. So he was allowed free run of the galley.

Tom and Ned spent much time in the steering tower or engine room, for, though all of the machinery was automatic, there was need of almost constant attention, though there was an arrangement whereby in case of emergency, the airship would steer herself in any set direction for a certain number of hours.

There were ample sleeping quarters for six persons, a living room and a dining saloon. In short the Falcon was much like Tom's Red Cloud, only bigger and better. There was even a phonograph on board so that music, songs, and recitations could be enjoyed.

"Bless my napkin! but this is great!" exclaimed Mr. Damon, about noon of the second day, when they had just finished dinner and looked down through the glass windows in the bottom of the cabin at the rolling ocean below them. "I don't believe many persons have such opportunities as we have."

"I'm sure they do not," added Mr. Petrofsky. "I can hardly think it true, that I am on my way back to Siberia to rescue my dear brother."

"And such good weather as we're having," spoke Ned. "I'm glad we didn't start off in a storm, for I don't exactly like them when we're over the water."

"We may get one yet," said Tom. "I don't just like the way the barometer is acting. It's falling pretty fast."

"Bless my mercury tube!" cried Mr. Damon. "I hope we have no bad luck on this trip."

"Oh, we can't help a storm or two," answered Tom. "I guess it won't do any harm to prepare for it."

So everything was made snug, and movable articles on the small exposed deck of the airship were lashed fast. Then, as night settled down, our friends gathered about in the cheerful cabin, in the light of the electric lamps, and talked of what lay before them.

As Mr. Damon could steer as well as Tom or Ned, he shared in the night watch. But Mr. Petrofsky was not expert enough to accept this responsibility.

It was when Mr. Damon finished his watch at midnight, and called Tom, that he remarked.

"Bless my umbrella, Tom. But I don't like the looks of the weather."

"Why, what's it doing?"

"It isn't doing anything, but it's clouding up and the barometer is going down."

"I was afraid we were in for it," answered the young inventor. "Well, we'll have to take what comes."

The airship plunged on her way, while her young pilot looked at the various gages, noting that to hold her way against the wind that had risen he would have to increase the speed of the motor.

"I don't like it," murmured Tom, "I don't like it," and he shook his head dubiously.

With a suddenness that was almost terrifying, the storm broke over the ocean about three o'clock that morning. There was a terrific clap of thunder, a flash of lighting, and a deluge of rain that fairly made the staunch Falcon stagger, high in the air as she was.

"Come on, Ned!" cried Tom, as he pressed the electric alarm bell connected with his chum's berth. "I need you, and Mr. Damon, too."

"What's the matter?" cried Ned, awakened suddenly from a sound sleep.

"We're in a bad storm," answered Tom, "and I'll have to have help. We need more gas, to try and rise above it."

"Bless my hanging lamp!" cried Mr. Damon, "I hope nothing happens!"

And he jumped from his berth as the Falcon plunged and staggered through the storm that was lashing the ocean below her into white billow of foam.

CHAPTER XII

AN ACCIDENT

For a few moments it seemed as if the Falcon would surely turn turtle and plunge into the seething ocean. The storm had burst with such suddenness that Tom, who was piloting his air craft, was taken unawares. He had not been using much power or the airship would have been better able to weather the blast that burst with such fury over her. But as it was, merely drifting along, she was almost like a great sheet of paper. Down she was forced, until the high-flying spray from the waves actually wet the lower part of the car, and Ned, looking through one of the glass windows, saw, in the darkness, the phosphorescent gleam of the water so near to them.

"Tom!" he cried in alarm. "We're sinking!"

"Bless my bath sponge! Don't say that!" gasped Mr. Damon.

"That's why I called you," yelled the young inventor. "We've got to rise above the storm if possible. Go to the gas machine, Ned, and turn it on full strength. I'll speed up the motor, and we may be able to cut up that way. But get the gas on as soon as you can. The bag is only about half full. Force in all you can!

"Mr. Damon, can you take the wheel? It doesn't make any difference which way we go as long as you keep her before the wind, and yank back the elevating rudder as far as she'll go! We must head up."

"All right, Tom," answered the eccentric man, as he fairly jumped to take the place of the young inventor at the helm.

"Can I do anything?" asked the Russian, as Tom raced for the engine room, to speed the motor up to the last notch.

"I guess not. Everything is covered, unless you want to help Mr. Damon. In this blow it will be hard to work the rudder levers."

"All right," replied Ivan Petrofsky, and then there came another sickening roll of the airship, that threatened to turn her completely over.

"Lively!" yelled Tom, clinging to various supports as he made his way to the engine room. "Lively, all hands, or we'll be awash in another minute!"

And indeed it seemed that this might be so, for with the wind forcing her down, and the hungry waves leaping up, as if to clutch her to themselves, the Falcon was having anything but an easy time of it.

It was the work of but an instant however, when Tom reached the engine room, to jerk the accelerator lever toward him, and the motor responded at once. With a low, humming whine the wheels and gears redoubled their speed, and the great propellers beat the air with fiercer strokes.

At the same time Tom heard the hiss of the gas as it rushed into the envelope from the generating machine, as Ned opened the release valve.

"Now we ought to go up," the young inventor murmured, as he anxiously watched the barograph, and noted the position of the swinging pendulum which told of the roll and dip of the air craft.

For a moment she hung in the balance, neither the increased speed of the propellers, nor the force of the gas having any seeming effect. Mr. Damon and the Russian, clinging to the rudder levers, to avoid being dashed against the sides of the pilot house, held them as far back as they could, to gain the full power of the elevation planes. But even this seemed to do no good.

The power of the gale was such, that, even with the motor and gas machine working to their limit, the Falcon only held her own. She swept along, barely missing the crests of the giant waves.

"She's got to go up! She's got to go up!" cried Tom desperately, as if by very will power he could send her aloft. And then, when there came a lull in the fierce blowing of the wind, the elevation rudder took hold, and like a bird that sees the danger below, and flies toward the clouds, the airship shot up suddenly.

"That's it!" cried Tom in relief, as he noted the needle of the barograph swinging over, indicating an ever-increasing height. "Now we're safe."

They were not quite yet, but at last the power of machinery had prevailed over that of the elements. Through the pelting rain, and amid the glare of the lightning, and the thunder of heaven's artillery, the airship forced her way, up and up and up.

Setting the motor controller to give the maximum power until he released it, Tom hastened to the gas-generating apparatus. He found Ned attending to it, so that it was now working satisfactorily.

"How about it, Tom?" cried his chum anxiously.

"All right now, Ned, but it was a close shave! I thought we were done for, platinum mine, rescue of exiles, and all."

"So did I. Shall I keep on with the gas?"

"Yes, until the indicator shows that the bag is full. I'm going to the pilot house."

Running there, Tom found that Mr. Damon and the Russian had about all they could manage. The young inventor helped them and then, when the Falcon was well started on her upward course, Tom set the automatic steering machine, and they had a breathing spell.

To get above the sweep of the blast was no easy task, for the wind strata seemed to be several miles high, and Tom did not want to risk an accident by going to such an elevation. So, when having gone up about a mile, he found a comparatively calm area he held to that, and the Falcon sped along with the occupants feeling fairly comfortable, for there was no longer that rolling and tumbling motion.

The storm kept up all night, but the danger was practically over, unless something should happen to the machinery, and Tom and Ned kept careful watch to prevent this. In the morning they could look down on the storm-swept ocean below them, and there was a feeling of thankfulness in their hearts that they were not engulfed in it.

"This is a pretty hard initiation for an amateur," remarked Mr. Petrofsky. "I never imagined I should be as brave as this in an airship in a storm."

"Oh, you can get used to almost anything," commented Mr. Damon.

It was three days before the storm blew itself out and then came pleasant weather, during which the Falcon flew rapidly along. Our friends busied themselves about many things, talked of what lay before them, and made such plans as they could.

It was the evening of the fifth day, and they expected to sight the coast of France in the morning. Tom was in the pilot house, setting the course for the night run, and Ned had gone to the engine room to look after the oiling of the motor.

Hardly had he reached the compartment than there was a loud report, a brilliant flash of fire, and the machinery stopped dead.

"What is it?" cried Tom, as he came in on the run, for the indicators in the pilot house had told him something was wrong.

"An accident!" cried Ned. "A breakdown, Tom! What shall we do?"

CHAPTER XIII

SEEKING A QUARREL

There was an ominous silence in the engine room, following the flash and the report. The young inventor took in every bit of machinery in a quick glance, and he saw at once that the main dynamo and magneto had short-circuited, and gone out of commission. Almost instantly the airship began to sink, for the propellers had ceased revolving.

"Bless my barograph!" cried Mr. Damon, appearing on the scene. "We're sinking, Tom!"

"It's all right," answered our hero calmly. "It's a bad accident, and may delay us, but there's no danger. Ned, start up the gas machine," for they were progressing as an aeroplane then. "Start that up, and we'll drift along as a dirigible."

"Of course! Why didn't I think of that!" exclaimed Ned, somewhat provoked at his own want of thought. The airship was going down rapidly, but it was the work of but a moment to start the generator, and then the earthward motion was checked.

"We'll have to take our chance of being blown to France," remarked Tom, as he went over to look at the broken electrical machinery. "But we ought to fetch the coast by morning with this wind. Lucky it's blowing our way."

"Then you can't use the propellers?" asked Mr. Petrofsky.

"No," replied Tom, "but if we get to France I can easily repair this break. It's the platinum bearings again. I do hope we'll locate that lost mine, for I need a supply of good reliable metal.

"Then we'll have to land in France?" asked the Russian, and he seemed a trifle uneasy.

"Yes," answered Tom. "Don't you want to?"

"Well, I was thinking of our safety."

"Bless my silk hat!" cried Mr. Damon. "Where is the danger of landing there? I rather hoped we could spend some time in Paris."

"There is no particular danger, unless it becomes known that I am an escaped exile, and that we are on our way to Siberia to rescue another one, and try to find the platinum mine. Then we would be in danger."

"But how are they to know it?" asked Ned, who had come back from the gas machine.

"France, especially in Paris and the larger cities, is a hot-bed of political spies," answered Mr. Petrofsky. "Russia has many there on the secret police, and while the objectors to the Czar's government are also there, they could do little to help us."

"I guess they won't find out about us unless we give it away," was Tom's opinion.

"I'm afraid they will," was the reply of the Russian. "Undoubtedly word has been cabled by the spies who annoyed us in Shopton, that we are on our way over here. Of course they can't tell where we might land, but as soon as we do land the news will be flashed all over, and the word will come back that we are enemies of Russia. You can guess the rest."

"Then let's go somewhere else," suggested Mr. Damon.

"It would be the same anywhere in Europe," replied Ivan Petrofsky. "There are spies in all the large centres."

"Well, I've got to go to Paris, or some large city to get the parts I need," said Tom. "Unfortunately I didn't bring any along for the dynamo and magneto, as I should have done, and I can't get the necessary pieces in a small town. I'll have to depend on some big machine shop. But we might land in some little-frequented place, and I could go in to town alone."

"That might answer," spoke the Russian, and it was decided to try that.

Meanwhile it was somewhat doubtful whether they would reach France, for they were dependent on the wind. But it seemed to be blowing steadily in the desired direction, and Tom noted with satisfaction that their progress was comparatively fast. He tried to repair the broken machinery but found that he could not, though he spent much of the night over it.

"Hurrah!" cried Ned when morning came, and he had taken an observation. "There's some kind of land over there."

The wind freshened while they were at breakfast and using more gas so as to raise them higher Tom directed the course of his airship as best he could. He wanted to get high enough so that if they passed over a city they would not be observed.

At noon it could be seen through the glass that they were over the outskirts of some large place, and after the Russian had taken an observation he exclaimed:

"The environs of Paris! We must not land there!"

"We won't, if the wind holds out," remarked Tom and this good fortune came to them. They succeeded in landing in a field not far from a small village, and though several farmers wondered much as the sight of the big airship, it was thought by the platinum-seekers that they would be comparatively safe.

"Now to get the first train for Paris and get the things I need," exclaimed Tom. He set to work taking off the broken pieces that they might be duplicated, and then, having inquired at an inn for the nearest railroad station, and having hired a rig, the young inventor set off.

"Can you speak French?" asked Mr. Petrofsky. "If not I might be of service, but if I go to Paris I might be----"

"Never mind," interrupted Tom. "I guess I can parley enough to get along with."

He had a small knowledge of the tongue, and with that, and knowing that English was spoken in many places, he felt that he could make out. And indeed he had no trouble. He easily found his way about the happy capital, and located a machine shop where a specialty was made of parts for automobile and airship motors. The proprietor, knowing the broken pieces belonged to an aeroplane, questioned Tom about his craft but the young inventor knew better than to give any clew that might make trouble, so he returned evasive answers.

It was nearly night when he got back to the place where he had left the Falcon, and he found a curious crowd of rustics grouped about it.

"Has anything happened?" he asked of his friends.

"No, everything is quiet, I'm glad to say," replied Mr. Petrofsky. "I don't think our presence will create stir enough so that the news of it will reach the spies in Paris. Still I will feel easier when we're in the air again."

"It will take a day to make the repairs," said Tom, "and put in the new pieces of platinum. But I'll work as fast as I can."

He and Ned labored far into the night, and were at it again the next morning. Mr. Damon and the Russian were of no service for they did not understand the machinery well enough. It was while Tom was outside the craft, filing a piece of platinum in an improvised vise, that a poorly-clothed man sauntered up and watched him curiously. Tom glanced at him, and was at once struck by a difference between the man's attire and his person.

For, though he was tattered and torn, the man's face showed a certain refinement, and his hands were not those of a farmer or laborer in which character he obviously posed.

"Monsieur has a fine airship there," he remarked to Tom.

"Oh, yes, it'll do." Tom did not want to encourage conversation.

"Doubtless from America it comes?"

The man spoke English but with an accent, and certain peculiarities.

"Maybe so," replied the young inventor.

"Is it permit to inspect the interior?"

"No, it isn't," came from Tom shortly. He had hurt his finger with the file, and he was not in the best of humor.

"Ah, there are secrets then?" persisted the stranger.

"Yes!" said Tom shortly. "I wish you wouldn't bother me. I'm busy, can't you see."

"Ah, does monsieur mean that I have poor eyesight?"

The question was snapped out so suddenly, and with such a menacing tone that Tom glanced up quickly. He was surprised at the look in the man's eyes.

"Just as you choose to take it," was the cool answer. "I don't know anything about your eyes, but I know I've got work to do."

"Monsieur is insulting!" rasped out the seeming farmer. "He is not polite. He is not a Frenchman."

"Now that'll do!" cried Tom, thoroughly aroused. "I don't want to be too short with you, but I've really got to get this done. One side, if you please," and having finished what he was doing, he started toward the airship.

Whether in his haste Tom did not notice where he was going, or whether the man deliberately got in his way I cannot say, but at any rate they collided and the seeming farmer went spinning to one side, falling down.

"Monsieur has struck me! I am insulted! You shall pay for this!" he cried, jumping to his feet, and making a rush for our hero.

"All right. It was your own fault for bothering me but if you want anything I'll give it to you!" cried Tom, striking a position of defense.

The man was about to rush at him, and there would have been a fight in another minute, had not Mr. Petrofsky, stepping to the open window of the pilot house, called out:

"Tom! Tom! Come here, quick. Never mind him!"

Swinging away from the man, the young inventor rushed toward the airship. As he entered the pilot house he noticed that his late questioner was racing off in the direction of the village.

"What is it? What's the matter?" he asked of the Russian. "Is something more wrong with the airship?"

"No, I just wanted to get you away from that man.

"Oh, I could take care of myself."

"I know that, but don't you see what his game was? I listened to him. He was seeking a quarrel with you."

"A quarrel?"

"Yes. He is a police spy. He wanted to get you into a fight and then he and you would be arrested by the local authorities. They'd clap you into jail, and hold us all here. It's a game! They suspect us, Tom! The Russian spies have had some word of our presence! We must get away as quickly as we can!"

CHAPTER XIV

HURRIED FLIGHT

The announcement of Ivan Petrofsky came to Tom with startling suddenness. He could say nothing for a moment, and then, as he realized what it meant, and as he recalled the strange appearance and actions of the man, he understood the danger.

"Was he a spy?" he asked.

"I'm almost sure he was," came the answer. "He isn't one of the villagers, that's sure, and he isn't a tourist. No one else would be in this little out-of-the-way place but a police official. He is in disguise, that is certain."

"I believe so," agreed Tom. "But what was his game?"

"We are suspected," replied the Russian. "I was afraid a big airship couldn't land anywhere, in France without it becoming known. Word must have been sent to Paris in the night, and this spy came out directly."

"But what will happen now?"

"Didn't you see where he headed for? The village. He has gone to send word that his trick failed. There will be more spies soon, and we may be detained or thrown into jail on some pretext or other. They may claim that we have no license, or some such flimsy thing as that. Anything to detain us. They are after me, of course, and I'm sorry that I made you run such danger. Perhaps I'd better leave you, and—"

"No, you don't!" cried Tom heartily. "We'll all hang together or we'll hang separately', as Benjamin Franklin or some of those old chaps once remarked. I'm not the kind to desert a friend in the face of danger."

"Bless my revolver! I should say not!" cried Mr. Damon. "What's it all about? Where's the danger?"

They told him as briefly as possible, and Ned, who had been working in the motor room, was also informed.

"Well, what's to be done?" asked Tom. "Had we better get out our ammunition, or shall I take out a French license."

"Neither would do any good," answered the Russian. "I appreciate your sticking by me, and if you are resolved on that the only thing to do is to complete the repairs as soon as possible and get away from here."

"That's it!" cried Ned. "A quick flight. We can get more gasolene here, for lots of autos pass along the road through the village. I found that out. Then we needn't stop until we hit the trail for the mine in Siberia!"

"Hush!" cautioned the Russian. "You can't tell who may be sneaking around to listen. But we ought to leave as soon as we can."

"And we will," said Tom. "I've got the magneto almost fixed!"

"Let's get a hustle on then!" urged Ned. "That fellow meant business from his looks. The nerve of him to try to pick a quarrel that way."

"I might have told by his manner that something was wrong," commented Tom, "but I thought he was a fresh tramp and I didn't take any pains in answering him. But come on, Ned, get busy."

They did, with such good effect that by noon the machinery was in running shape again, and so far there had been no evidence of the return of the spy. Doubtless he was waiting for instructions, and something might happen any minute.

"Now, Ned, if you'll see to having some gasolene brought out here, and the tanks filled, I'll tinker with the dynamo and get that in running shape," said Tom. "It only needs a little adjustment of the brushes. Then we'll be off."

Ned started for the village where there was a gasolene depot. He fancied the villagers regarded him rather curiously, but he did not stop to ask what it meant. Another odd fact was that the usual crowd of curious rustics about the airship was missing. It was as though they suspected trouble might come, and they did not want to be mixed up in it.

Never, Ned thought, had he seen a man so slow at getting ready the supply of gasolene. He was to take it out in a wagon, but first he mislaid the funnel, then the straining cloth, and finally he discovered a break in the harness that needed mending.

"I believe he's doing it on purpose to delay us," thought the youth, "but it won't do to say anything. Something is in the wind." He helped the man all he could, and urged him in every way he knew, but the fellow seemed to have grown suddenly stupid, and answered only in French, though previously he had spoken some English.

But at last Ned, by dint of hard work, got him started, and rode on the gasolene wagon with him. Once at the anchored airship, Tom and the others filled the reserve tanks themselves, though the man tried to help. However he did more harm than good, spilling several gallons of the fluid.

"Oh, get away, and let us do it!" cried Tom at last. "I know what you—"

"Easy!" cautioned Mr. Petrofsky, with a warning look, and Tom subsided.

Finally the tanks were full, the man was paid, and he started to drive away.

"Now to make a quick flight!" cried Tom, as he took his place in the pilot house, while Ned went to the engine room. "Full speed, Ned!"

"Yes, and we'll need it, too," said the Russian.

"Why?" asked Tom.

"Look!" was the answer, and Ivan Petrofsky pointed across the field over which, headed toward the airship, came the man who had sought a quarrel with Tom. And with the spy were several policemen in uniform, their short swords dangling at their sides.

"They're after us!" cried Mr. Damon. "Bless my chronometer they're after us!"

"Start the motor, Ned! Start the motor!" cried Tom, and a moment later the hum of machinery was heard, while the police and the spy broke into a run, shouting and waving their hands.

CHAPTER XV

PURSUED

Slowly the airship arose, almost too slowly to suit those on board who anxiously watched the oncoming officers. The latter had drawn their short swords, and at the sight of them Mr. Damon cried out:

"Bless my football! If they jab them into the gas bag, Tom, we're done for!"

"They won't get the chance," answered the young inventor, and he spoke truly, for a moment later, as the big propellers took hold of the air, the Falcon went up with a rush, and was far beyond the reach of the men. In a rage the spy shook his fist at the fast receding craft, and one of the policemen drew his revolver.

"They're going to fire!" cried Ned.

"They can't do much damage," answered Tom coolly. "A bullet hole in the bag is easily repaired, and anywhere else it won't amount to anything."

The officer was aiming his revolver at the airship, now high above his head, but with a quick motion the spy pulled down his companion's arm, and they seemed to be disputing among themselves.

"I wonder what that means?" mused Mr. Damon.

"Probably they didn't want to risk getting into trouble," replied the Russian. "There are strict laws in France about using firearms, and as yet we are accused of no crime. We are only suspected, and I suppose the spy didn't want to get into trouble. He is on foreign ground, and there might be international complications."

"Then you really think he was a spy?" asked Tom.

"No doubt of it, and I'm afraid this is only the beginning of our trouble."

"In what way?"

"Well, of course word will be sent on ahead about us, and every where we go they'll be on the watch for us. They have our movements pretty well covered."

"We won't make a descent until we get to Siberia," said Tom, "and I guess there it will be so lonesome that we won't be troubled much."

"Perhaps," admitted the Russian, "but we will have to be on our guard. Of course keeping up in the air will be an advantage but they may—"

He stopped suddenly and shrugged his shoulders.

"What were you going to say?" inquired Ned.

"Oh, it's just something that might happen, but it's too remote a possibility to work about. We're leaving those fellows nicely behind," he added quickly, as though anxious to change the subject.

"Yes, at this rate we'll soon be out of France," observed Tom, as he speeded the ship along still more. The young inventor wondered what Mr. Petrofsky had been going to say, but soon after this, some of the repaired machinery in the motor room needed adjusting, and the young inventor was kept so busy that the matter passed from his mind.

The dynamo and magneto were doing much more efficient work since Tom had put the new platinum in, and the Falcon was making better time than ever before. They were flying at a moderate height, and could see wondering men, women and children rush out from their houses, to gaze aloft at the strange sight. Paris was now far behind, and that night they were approaching the borders of Prussia, as Mr. Petrofsky informed them, for he knew every part of Europe.

The route, as laid down by Tom and the Russian, would send the airship skirting the southern coast of the Baltic sea, then north-west, to pass to one side of St. Petersburg, and then, after getting far enough to the north, so as to avoid the big cities, they would head due east for Siberia.

"In that way I think we'll avoid any danger from the Russian police," remarked the exile.

For the next few days they flew steadily on at no remarkable speed, as the extra effort used more gasolene than Tom cared to expend in the motor. He realized that he would need all he had, and he did not want to have to buy any more until he was homeward bound, for the purchase of it would lead to questions, and might cause their detention.

Mr. Damon gave his friends good meals and they enjoyed their trip very much, though naturally there was some anxiety about whether it would have a successful conclusion.

"Well, if we don't find the platinum mine we'll rescue your brother, if there's a possible chance!" exclaimed Tom one day, as he sat in the pilot house with the exile. "Jove! it will be great to drop down, pick him up, and fly away with him before those Cossacks, or whoever has him, know what's up."

"I'm afraid we can't make such a sensational rescue as that," replied Mr. Petrofsky. "We'll have to go at it diplomatically. That's the only way to get an exile out of Siberia. We must get word to him somehow, after we locate him, that we are waiting to help him, and then we can plan for his escape. Poor Peter! I do hope we can find him, for if he is in the salt or sulphur mines it is a living death!" and he shuddered at the memory of his own exile.

"How do you expect to get definite information as to where he might be?" asked Tom.

"I think the only thing to do is to get in touch with some of the revolutionists," answered the Russian. "They have ways and means of finding out even state secrets. I think our best plan will be to land near some small town, when we get to the edge of Siberia. If we can conceal the airship, so much the better. Then I can disguise myself and go to the village."

"Will it be safe?" inquired the young inventor.

"I'll have to take that chance. It's the only way, as I am the only one in our party who can speak Russian."

"That's right," admitted Tom with a laugh. "I'm afraid I could never master that tongue. It's as hard as Chinese."

"Not quite," replied his friend, "but it is not an easy language for an American."

They talked at some length, and then Tom noticing, by one of the automatic gages on the wall of the pilot house, that some of the machinery needed attention, went to attend to it.

He was rather surprised, on emerging from the motor compartment, to see Mr. Damon standing on the open after deck of the Falcon gazing earnestly toward the rear.

"Star-gazing in the day time?" asked Tom with a laugh.

"Bless my individuality!" exclaimed the odd man. "How you startled me, Tom! No, I'm not looking at stars, but I've been noticing a black speck in the sky for some time, and I was wondering whether it was my eyesight, or whether it really is something."

"Where is it?"

"Straight to the rear," answered Mr. Damon, "and it seems to be about a mile up. It's been hanging in the same place this ten minutes."

"Oh, I see," spoke Tom, when the speck had been pointed out to him. "It's there all right, but I guess it's a bird, an eagle perhaps. Wait, I'll get a glass and we'll take a look."

As he was taking the telescope down from its rack in the pilot house, Mr. Petrofsky saw him.

"What's up?" asked the Russian, and the youth told him.

"Must be a pretty big bird to be seen at such a distance as it is," remarked Tom.

"Maybe it isn't a bird," suggested Ivan Petrofsky. "I'll take a look myself," and, showing something of alarm in his manner, he followed Tom to where Mr. Damon awaited them. Ned also came out on deck.

Quickly adjusting the glass, Tom focused it on the black speck. It seemed to have grown larger. He peered at it steadily for several seconds.

"Is it a bird?" asked Mr. Damon.

"Jove! It's another airship—a big biplane!" cried Tom, "and there seems to be three men in her."

"An aeroplane!" gasped Ned.

"Bless my deflecting rudder!" cried Mr. Damon. "An airship in this out-of-the-way place?" for they were flying over a desolate country.

"And they're coming right after us," added Tom, as he continued to gaze.

"I thought so," was the quiet comment of Mr. Petrofsky. "That is what I started to say a few days ago," he went on, "when I stopped, as I hardly believed it possible. I thought they might possibly send an aeroplane after us, as both the French and Russian armies have a number of fast ones. So they are pursuing us. I'm afraid my presence will bring you no end of trouble."

"Let it come!" cried Tom. "If they can catch up to us they've got a good machine. Come on, Ned, let's speed her up, and make them take more of our star dust."

"Wait a minute," advised the Russian, as he took the telescope from Tom, and viewed the ever-increasing speck behind them. "Are you sure of the speed of this craft?" he asked a moment later.

"I never saw the one yet I couldn't pull away from, even after giving them a start," answered the young inventor proudly. "That is all but my little sky racer. I could let them get within speaking distance, and then pull out like the Congressional Limited passing a slow freight."

"Then wait a few minutes," suggested Mr. Petrofsky. "That is an aeroplane all right, but I can't make out from what country. I'd like a better view, and if it's safe we can come closer."

"Oh, it's safe enough," declared Tom. "I'll get things in shape for a quick move," and he hurried back to the machine room, while the others took turns looking at the oncoming aeroplane. And it was coming on rapidly, showing that it had tremendous power, for it was a very large one, carrying three men.

"How do you suppose they got on our track?" asked Ned.

"Oh, we must have been reported from time to time, as we flew over cities or towns," replied Mr. Petrofsky. "You know we're rather large, and can be seen from a good distance. Then too, the whole Russian secret police force is at the service of our enemies."

"But we're not over Russia yet," said Mr. Damon.

Ivan Petrofsky took the telescope and peered down toward the earth. They were not a great way above it, and at that moment they were passing a small village.

"Can you tell where we are?" asked the odd man.

"We are just over the border of the land of the Czar," was the quiet answer. "The imperial flag is flying from a staff in front of one of the buildings down there. We are over Russia."

"And here comes that airship," called Ned suddenly.

They gazed back with alarm, and saw that it was indeed so. The big aeroplane had come on wonderfully fast in the last few minutes.

"Tom! Tom!" cried his chum. "Better get ready to make a sprint."

"I'm all ready," calmly answered our hero. "Shall I go now?"

"If you can give us a few seconds longer I may be able to tell who is after us," remarked Mr. Petrofsky, turning his telescope on the craft behind them.

"I can let them get almost up to us, and get away," replied Tom.

The Russian did not answer. He was gazing earnestly at the approaching aeroplane. A moment later he took the glass down from his eye.

"It's our spy again," he said. "There are two others with him. That is one of the aeroplanes owned by the secret police. They are stationed all over Europe, ready for instant service, and they're on our trail."

The pursuing craft was so near that the occupants could easily be made out with the naked eye, but it needed the glass to distinguish their features, and Mr. Petrofsky had done this.

"Shall I speed up?" cried Tom.

"Yes, get away as fast as you can!" shouted the Russian. "No telling what they may do," and then, with a hum and a roar the motor of the Falcon increased its speed, and the big airship shot ahead.

CHAPTER XVI

THE NIHILISTS

From the pursuing aircraft came a series of sharp explosions that fairly rattled through the clear air.

"Look out for bombs!" yelled Ned.

"Bless my safety match!" cried Mr. Damon. "Are they anarchists?"

"It's only their motor back-firing," cried Tom. "It's all right, They're done for now, we'll leave them behind."

He was a true prophet, for with a continued rush and a roar the airship of our friends opened up a big gap between her rear rudders and the forward planes of the craft that was chasing her. The three men were working frantically to get their motor in shape, but it was a useless task.

A little later, finding that they were losing speed, the three police agents, or spies, whatever they might be, had to volplane to earth and there was no need for the Falcon to maintain the terrific pace, to which Tom had pushed her. The pursuit was over.

"Well, we got out of that luckily," remarked Ned, as he looked down to where the spies were making a landing. "I guess they won't try that trick again."

"I'm afraid they will," predicted Mr. Petrofsky. "You don't know these government agents as I do. They never give up. They'll fix their engine, and get on our trail again."

"Then we'll make them work for what they get," put in Tom, who, having set the automatic speed accelerator, had rejoined his companions. "We'll try a high flight and if they can pick up a trail in the air, and come up to us, they're good ones!"

He ran to the pilot house, and set the elevation rudder at its limit. Meanwhile the spies were working frantically over their motor, trying to get it in shape for the pursuit. But soon they realized that this was out of the question, for the Falcon was far away, every moment going higher and higher, until she was lost to sight beyond the clouds.

"I guess they'll have their own troubles now," remarked Ned. "We've seen the last of them."

"Don't be too sure," spoke the Russian. "We may have them after us again. We're over the land of the Czar now, and they'll have everything their own way. They'll want to stop me at any cost."

"Do you think they suspect that we're after the platinum?" asked Tom.

"They may, for they know my brother and I were the only ones who ever located it, though unless I get in the exact neighborhood I'd have trouble myself picking it out. I remember some of the landmarks, but my brother is better at that sort of work than I am. But I think what they are mostly afraid of is that I have some designs on the life of, say one of the Grand Dukes, or some high official. But I am totally opposed to violent measures," went on Mr. Petrofsky. "I believe in a campaign of education, to gain for the down-trodden people what are their rights."

"Do you think they know you are coming to rescue your brother?" asked Tom.

"I don't believe so. And I hope not, for once they suspected that, they would remove him to some place where I never could locate him."

Calmer feelings succeeded the excitement caused by the pursuit, and our friends, speculating on the matter, came to the conclusion that the aeroplane must have started from some Prussian town, as Mr. Petrofsky said there were a number of Russian secret police in that country. The Falcon was now speeding along at a considerable height, and after running for a number of miles, sufficient to preclude the possibility that they could be picked up by the pursuing aeroplane, Tom sent his craft down, as the rarefied atmosphere made breathing difficult.

It was about three days after the chase when, having carefully studied the map and made several observations through the telescope of the Country over which they were traveling, that Ivan Petrofsky said:

"If it can be managed, Tom, I think we ought to go down about here. There is a Russian town not far away, and I know a few friends there, There is a large stretch of woodland, and the airship can be easily concealed there.

"All right," agreed the young inventor, "down we go, and I hope you get the information you want."

Flying high so as to keep out of the observation of the inhabitants of the Russian town, the young inventor sent his craft in a circle about it, and, having seen a clearing in the forest, he made a landing there, the Falcon having come to rest a second time since leaving Shopton, now several thousand miles away.

"We'll hide here for a few days," observed Tom, "and you can spend as much time in town as you like, Mr. Petrofsky."

The Russian, disguising himself by trimming his beard, and putting on a pair of dark spectacles, went to the village that afternoon.

While he was gone Tom, Ned and Mr. Damon busied themselves about the airship, making a few repairs that could not very well be done while it was in motion. As night came on, and the exile did not return, Tom began to get a little worried, and he had some notion of going to seek him, but he knew it would not be safe.

"He'll come all right," declared Ned, as they sat down to supper. All about them was an almost impenetrable forest, cut here and there by paths along which, as Mr. Petrofsky had told them, the wood cutters drove their wagons.

It was quite a surprise therefor, when, as they were leaving the table, a knock was heard on the cabin door.

"Bless my electric bell!" cried Mr. Damon. "Who can that be?"

"Mr. Petrofsky of course," answered Ned.

"He wouldn't knock—he'd walk right in," spoke Tom, as he went to the door. As he opened it he saw several dark-bearded men standing there, and in their midst Mr. Petrofsky.

For one moment our hero feared that his friend had been arrested and that the police had come to take the rest of them into custody. But a word from the exile reassured him.

"These are some of my friends," said Mr. Petrofsky simply. "They are Nihilists which I am not, but—"

"Nihilists yes! Always!" exclaimed one who spoke English. "Death to the Czar and the Grand Dukes! Annihilation to the government!"

"Gently my friend, gently," spoke Mr. Petrofsky. "I am opposed to violence you know." And then, while his new friends gazed wonderingly at the strange craft, he led them inside. Tom and the others were hardly able to comprehend what was about to take place.

CHAPTER XVII

ON TO SIBERIA

"Has anything happened?" asked Tom. "Are we suspected? Have they come to warn us?"

"No, everything is all right, so far," answered Ivan Petrofsky. "I didn't have the success I hoped for, and we may have to wait here for a few days to get news of my brother. But these men have been very kind to me," he went on, "and they have ways of getting information that I have not. So they are going to aid me."

"That's right!" exclaimed the one who had first spoken. "We will yet win you to our cause, Brother Petrofsky. Death to the Czar and the Grand Dukes!"

"Never!" exclaimed the exile firmly. "Peaceful measures will succeed. But I am grateful for what you can do for me. They heard me describe your wonderful airship," he explained to Tom, "and wanted to see for themselves."

The Nihilists were made welcome after Mr. Petrofsky had introduced them. They had strange and almost unpronounceable names for the ears of our friends, and I will not trouble you with them, save to say that the one who spoke English fairly well, and who was the leader, was called Nicolas Androwsky. There was much jabbering in the Russian tongue, when Mr. Petrofsky and Mr. Androwsky took the others about the craft, explaining how it worked.

"I can't show you the air glider," said Tom, who naturally acted as guide, "as it would take too long to put together, and besides there is not enough wind here to make it operate."

"Then you need much wind?" asked Nicolas Androwsky.

"The harder the gale the better she flies," answered Tom proudly.

"Bless my sand bag, but that's right!" exclaimed Mr. Damon, who, up to now had not taken much part in the conversation. He followed the party about the airship, keeping in the rear, and he eyed the Nihilists as if he thought that each one had one or more dynamite bombs concealed on his person.

"Ha!" exclaimed Mr. Androwsky, turning suddenly to the odd man. "Are you not one of us? Do you not believe that this terrible kingdom should be destroyed—made as nothing, and a new one built from its ashes? Are you not one of us?" and with a quick gesture he reached into his pocket.

"No! No!" exclaimed Mr. Damon, starting back. "Bless my election ticket! No! Never could I throw a bomb. Please don't give me one." Mr. Damon started to run away.

"A bomb!" exclaimed the Nihilist, and then he drew from his pocket some pamphlets printed in Russian. "I have no bombs. Here are some of the tracts we distribute to convert unbelievers to our cause," he went on. "Read them and you will understand what we are striving for. They will convert you, I am sure."

He went on, following the rest of the party, while Mr. Damon dropped back with Ned.

"Bless my gas meter!" gasped the odd man, as he stared at the queerly-printed documents in his hand. "I thought he was going to give me a bomb to throw!"

"I don't blame you," said Ned in a low voice. "They look like desperate men, but probably they have suffered many hardships, and they think their way of righting a wrong is the only way. I suppose you'll read those tracts," he added with a smile.

"Hum! I'm afraid not," answered Mr. Damon. "I might just as well try to translate a Chinese laundry check. But I'll save 'em for souvenirs," and he carefully put them in his pocket, as if he feared they might unexpectedly turn into a bomb and blow up the airship.

The tour of the craft was completed and the Nihilists returned to the comfortable cabin where, much to their surprise, they were served with a little lunch, Mr. Damon bustling proudly about from the table to the galley, and serving tea as nearly like the Russians drink it as possible.

"Well, you certainly have a wonderful craft here—wonderful," spoke Mr. Androwsky. "If we had some of these in our group now, we could start from here, hover over the palace of the Czar, or one of the Grand Dukes, drop a bomb, utterly destroy it, and come back before any of the hated police would be any the wiser."

"I'm afraid I can't lend it to you," said Tom, and he could scarcely repress a shudder at the terrible ideas of the Nihilists.

"It would never do," agreed Ivan Petrofsky. "The campaign of education is the only way."

There were gutteral objections on the part of the other Russians, and they turned to more cheerful subjects of talk.

"What are your plans?" asked Tom of the exile. "You say you can get no trace here of your brother?"

"No, he seems to have totally disappeared from sight. Usually we enemies of the government can get some news of a prisoner, but poor Peter is either dead, or in some obscure mine, which is hidden away in the forests or mountains."

"Maybe he is in the lost platinum mine," suggested Ned.

"No, that has not been discovered," declared the exile, "or my friends here would have heard of it. That is still to be found."

"And we'll do it, in the air glider," declared Tom. "By the way, Mr. Petrofsky, would it not be a good plan to ask your friends the location of the place where the winds constantly blow with such force. It occurs to me that in some such way we might locate the mine."

"It would be of use if there was only one place of the gales," replied the exile. "But Siberia has many such spots in the mountain fastnesses—places which, by the peculiar formation of the land, have constant eddys of air over them. No, the only way is for us to go as nearly as possible to the place where my brother and I were imprisoned, and search there."

"But what is that you said about us having to stay here, to get some news of your brother?" asked Tom.

"I had hoped to get some information here," resumed Mr. Petrofsky, "but my friends here are without news. However, they are going to make inquiries, and we will have to stay here until they have an answer. It will be safe, they think, as there are not many police in town, and the local authorities are not very efficient. So the airship will remain here, and, from time to time I will go to the village, disguised, and see if any word has come."

"And we will bring you news as soon as we get it," promised Mr. Androwsky. "You are not exactly one of us, but you are against the government, and, therefor, a brother. But you will be one of us in time."

"Never," replied the exile with a smile. "My only hope now is to get my brother safely away, and then we will go and live in free America. But, Tom, I hope I won't put you out by delaying here."

"Not a bit of it. More than half the object of our trip is to rescue your brother. We must do that first. Now as to details," and they fell to discussing plans. It was late that night when the Nihilists left the airship, first having made a careful inspection to see that they were not spied upon. They promised at once to set to work their secret methods of getting information.

For several days the airship remained in the vicinity of the Russian town. Our friends were undisturbed by visitors, as they were in a forest where the villagers seldom came and the nearest wood-road was nearly half a mile off.

Every day either Mr. Petrofsky went in to town to see the Nihilists or some of them came out to the Falcon, usually at night.

"Well, have you any word yet?" asked Tom, after about a week had passed.

"Nothing yet," answered the exile, and his tone was a bit hopeless. "But we have not given up. All the most likely places have been tried, but he is not there. We have had traces of him, but they are not fresh ones. He seems to have been moved from one mine to another. Probably they feared I would make an attempt to rescue him. But I have not given up. He is somewhere in Siberia."

"And we'll find him!" cried Tom with enthusiasm.

For three days more they lingered, and then, one night, when they were just getting ready to retire, there was a knock on the cabin door. Mr. Petrofsky had been to the village that day, and had received no news. He had only returned about an hour before.

"Some one's knocking," announced Ned, as if there could be any doubt of it.

"Bless my burglar alarm!" gasped Mr. Damon.

"I'll see who it is," volunteered Mr. Petrofsky, and Tom looked toward the rack of loaded rifles, for that day a man, seemingly a wood cutter had passed close to the airship, and had hurried off as if he had seen a ghost.

The knock was repeated. It might be their friends, and it might be—

But Mr. Petrofsky solved the riddle by throwing back the portal, and there stood the Nihilist, Nicolas Androwsky.

"Is there anything the matter?" asked the exile quickly.

"We have news," was the cautious answer, as the Nihilist slipped in, and closed the door behind him.

"News of my brother?"

"Of your brother! He is in a sulphur mine in the Altai Mountains, near the city of Abakansk."

"Where's that?" asked Tom for he had forgotten most of his Russian geography.

"The Altai Mountains are a range about the middle of Siberia," explained Mr. Petrofsky. "They begin at the Kirghiz Steppes, and run west. It is a wild and desolate place. I hope we can find poor Peter alive."

"And this city of Abakansk?" went on the young inventor.

"It is many miles from here, but I can give you a good map," said the Nihilist. "Some of our friends are there," he added with a half-growl. "I wish we could rescue all of them."

"We'd like to," spoke Tom. "But I fear it is impossible. But now that we have a clew, come on! Let's start at once! It may be dangerous to stay here. On to Siberia!"

CHAPTER XVIII

IN A RUSSIAN PRISON

The news they had waited for had come at last. It might be a false clew, but it was something to work on, and Tom was tired of inaction. Then, too, even after they had started, the prisoner might be moved and they would have to trace him again.

"But that is the latest information we could get," said Mr. Androwsky. "It came through some of our Anarchist friends, and I believe is reliable. Can you soon make a thousand miles in your airship?"

"Yes," answered Tom, "if I push her to the limit."

"Then do so," advised the Nihilist, "for there is need of haste. In making inquiries our friends might incur suspicions and Peter Petrofsky may be exiled to some other place."

"Oh, we'll get there," cried Tom. "Ned, see to the gas machine. Mr. Damon, you can help me in the pilot house."

"Here is a map of the best route," said the Nihilist, as he handed one to Mr. Petrofsky. "It will take you there the shortest way. But how can you steer when high in the air?"

"By compass," explained Tom. "We'll get there, never fear, and we're grateful for your clew."

"I never can thank you enough!" exclaimed the exile, as he shook hands with Mr. Androwsky.

The Nihilist left, after announcing that, in the event of the success of Tom and his friends, and the rescue of the exile from the sulphur mine, it would probably become known to them, as such news came through the Revolutionary channels, slowly but surely.

"Here we go!" cried the young inventor gaily, as he turned the starting lever in the pilot house, and silently, in the darkness of the night, the Falcon shot upward. There was not a light on board, for, though small signal lamps had been kept burning when the craft was in the forest, to guide the Nihilists to her, now that she was up in the air, and in motion, it was feared that her presence would become known to the authorities of the town, so even these had been extinguished.

"After we get well away we can turn on the electrics," remarked Tom, "and if they see us at a distance they may take us for a meteor. But, so close as this, they'd get wise in a minute."

Mr. Damon, who had done all that Tom needed in the starting of the craft, went to the forward port rail, and idly looked down on the black forest they were leaving. He could just make out the clearing where they had rested for over a week, and he was startled to see lights bobbing in it.

"I say, Mr. Petrofsky!" he called. "Did we leave any of our lanterns behind us?"

"I don't believe so," answered the exile. "I'll ask Tom."

"Lanterns? No," answered the young inventor. "Before we started I took down the only one we had out. I'll take a look."

Setting the automatic steering apparatus, he joined Mr. Damon and the Russian. The lights were now dimly visible, moving about in the forest clearing.

"It's just as if they were looking for something," said Tom. "Can it be that any of your Nihilist friends, Mr. Petrofsky are—"

"Friends—no friends—enemies!" cried the Russian. "I understand now! We got away just in time. Those are police agents who are looking for us! They must have received word about our being there. Androwsky and the others never carry lights when they go about. They know the country too well, and then, too, it leads to detection. No, those are police spies. A few minutes later, and we would have been discovered."

"As it is we're right over their heads, and they don't know it," chuckled Tom. The airship was moving silently along before a good breeze, the propellers not having been started, and Tom let her drift for several miles, as he did not want to give the police spies a clew by the noise of the motor.

The twinkling lights in the forest clearing disappeared from sight, and the seekers went on in the darkness.

"Well, we've got the hardest part of our work yet ahead of us," remarked Tom several hours later when, the lights having been set aglow, they were gathered in the main cabin. There was no danger of being seen now, for they were quite high.

"We've done pretty well, so far," commented Ned. "I think we will have easier work rescuing Mr. Petrofsky's brother than in locating the mine.

"I don't know about that," answered the Russian. "It is almost impossible to rescue a person from Siberia. Of course it is not going to be easy to locate the lost mine, but as for that we can keep on searching, that is if the air glider works, but there are so many forces to fight against in rescuing a prisoner."

They had a long journey ahead of them, and not an easy route to follow, but as the days passed, and they came nearer and nearer to their goal, they became more and more eager.

They were passing over a desolate country, for they avoided the vicinity of large towns and cities.

"I wonder when we'll strike Siberia?" mused Tom one afternoon, as they sat on the outer deck, enjoying the air.

"At this rate of progress, very soon," answered the exile, after glancing at the map. "We should be at the foot of the Ural mountains in a few hours, and across them in the night. Then we will be in Siberia."

And he was right, for just as supper was being served, Ned, who had been making observations with a telescope, exclaimed:

"These must be the Urals!"

Mr. Petrofsky seized the glass.

"They are," he announced. "We will cross between Orsk and Iroitsk. A safe place. In the morning we will be in Siberia—the land of the exiles."

And they were, morning seeing them flying over a most desolate stretch of landscape. Onward they flew, covering verst after verst of loneliness.

"I'm going to put on a little more speed," announced Tom, after a visit to the storeroom, where were kept the reserve tanks of gasolene. "I've got more fluid than I thought I had, and as we're on the ground now I want to hurry things. I'm going to make better time," and he yanked over the lever of the accelerator, sending the Falcon ahead at a rapid rate.

All day this was kept up, and they were just making an observation to determine their position, along toward supper time, when there came the sound of another explosion from the motor room.

"Bless my safety valve!" cried Mr. Damon. "Something has gone wrong again."

Tom ran to the motor, and, at the same time the Falcon which was being used as an aeroplane and not as a dirigible, began to sink.

"We're going down!" cried Ned.

"Well, you know what to do!" shouted his chum. "The gas bag! Turn on the generator!"

Ned ran to it, but, in spite of his quick action, the craft continued to slide downward.

"She won't work!" he cried.

"Then the intake pipe must be stopped!" answered the young inventor. "Never mind, I'll volplane to earth and we can make repairs. That magneto has gone out of business again."

"Don't land here!" cried Ivan Petrofsky.

"Why not?"

"Because we are approaching a large town—Owbinsk I think it is—the police there will be there to get us. Keep on to the forest again!"

"I can't!" cried Tom. "We've got to go down, police or no police."

Running to the pilot house, he guided the craft so that it would safely volplane to earth. They could all see that now they were approaching a fairly large town, and would probably land on its outskirts. Through the glass Ned could make out people staring up at the strange sight.

"They'll be ready to receive us," he announced grimly.

"I hope they have no dynamite bombs for us," murmured Mr. Damon. "Bless my watch chain! I must get rid of that Nihilist literature I have about me, or they'll take me for one," and he tore up the tracts, and scattered them in the air.

Meanwhile the Falcon continued to descend.

"Maybe I can make quick repairs, and get away before they realize who we are," said Tom, as he got ready for the landing.

They came down in a big field, and, almost before the bicycle wheels had ceased revolving, under the application of the brakes, several men came running toward them.

"Here they come!" cried Mr. Damon.

"They are only farmers," said the exile. He had donned his dark glasses again, and looked like anything but a Russian.

"Lively, Ned!" cried Tom. "Let's see if we can't make repairs and get off again."

The two lads frantically began work, and they soon had the magneto in running order. They could have gone up as an aeroplane, leaving the repairs to the gas bag to be made later but, just as they were ready to start, there came galloping out a troop of Cossack soldiers. Their commander called something to them.

"What is he saying?" cried Tom to Mr. Petrofsky.

"He is telling them to surround us so that we can not get a running start, such as we need to go up. Evidently he understands aeroplanes."

"Well, I'm going to have a try," declared the young inventor.

He jumped to the pilot house, yelling to Ned to start the motor, but it was too late. They were hemmed in by a cordon of cavalry, and it would have been madness to have rushed the Falcon into them, for she would have been wrecked, even if Tom could have succeeded in sending her through the lines.

"I guess it's all up with us," groaned Ned.

And it seemed to; for, a moment later, an officer and several aides galloped forward, calling out something in Russian.

"What is it?" asked Tom.

"He says we are under arrest," translated the exile.

"What for?" demanded the young inventor.

Ivan Petrofsky shrugged his shoulders.

"It is of little use to ask—now," he answered. "It may be we have violated some local law, and can pay a fine and go, or we may be taken for just what we are, or foreign spies, which we are not. It is best to keep quiet, and go with them."

"Go where?" cried Tom.

"To prison, I suppose," answered the exile. "Keep quiet, and leave it to me. I will do all I can. I don't believe they will recognize me.

"Bless my search warrant!" cried Mr. Damon. "In a Russian prison! That is terrible!"

A few minutes later, expostulations having been useless, our friends were led away between guards who carried ugly looking rifles, and who looked more ugly and menacing themselves. Then the doors of the Russian prison of Owbinsk closed on Tom and his friends, while their airship was left at the mercy of their enemies.

CHAPTER XIX

LOST IN A SALT MINE

The blow had descended so suddenly that it was paralyzing. Tom and his friends did not know what to do, but they saw the wisdom of the course of leaving everything to Ivan Petrofsky. He was a Russian, and he knew the Russian police ways—to his sorrow.

"I'm not afraid," said Tom, when they had been locked in a large prison room, evidently set apart for the use of political, rather than criminal, offenders. "We're United States citizens, and once our counsel hears of this—as he will—there'll be some merry doings in Oskwaski, or whatever they call this place. But I am worried about what they may do to the Falcon."

"Have no fears on that score," said the Russian exile. "They know the value of a good airship, and they won't destroy her."

"What will they do then?" asked Tom.

"Keep her for their own use, perhaps."

"Never!" cried Tom. "I'll destroy her first!"

"If you get the chance!" interposed the exile.

"But we're American citizens!" cried Tom, "and—"

"You forget that I am not," interrupted Mr. Petrofsky. "I can't claim the protection of your flag, and that is why I wish to remain unknown. We must act quietly. The more trouble we make, the more important they will know us to be. If we hope to accomplish anything we must act cautiously."

"But my airship!" cried Tom.

"They won't do anything to that right away," declared the Russian in a whisper for he knew sometimes the police listened to the talk of prisoners. "I think, from what I overheard when they arrested us, that we either trespassed on the grounds of some one in authority, who had us taken in out of spite, or they fear we may be English or French spies, seeking to find out Russian secrets."

They were served with food in their prison, but to all inquiries made by Ivan Petrofsky, evasive answers were returned. He spoke in poor, broken Russian, so that he would not be taken for a native of that country. Had he been, he would have at once been in great danger of being accused as an escaped exile.

Finally a man who, the exile whispered to his Companions, was the local governor, came to their prison. He eagerly asked questions as to their mission, and Mr. Petrofsky answered them diplomatically.

"I don't think he'll make much out of what I told him," said the exile when the governor had gone. "I let him think we were scientists, or pleasure seekers, airshipping for our amusement. He tried to tangle me up politically, but I knew enough to keep out of such traps."

"What's going to become of us?" asked Ned.

"We will be detained a few days—until they find out more about us. Their spies are busy, I have no doubt, and they are telegraphing all over Europe about us."

"What about my airship?" asked Tom.

"I spoke of that," answered the exile. "I said you were a well-known inventor of the United States, and that if any harm came to the craft the Russian Government would not only be held responsible, but that the governor himself would be liable, and I said that it cost much money. That touched him, for, in spite of their power, these Russians are miserably paid. He didn't want to have to make good, and if it developed that he had made a mistake in arresting us, his superiors would disclaim all responsibility, and let him shoulder the blame. Oh, all is not lost yet, though I don't like the looks of things."

Indeed it began to seem rather black for our friends, for, that night they were taken from the fairly comfortable, large, prison room, and confined in small stone cells down in a basement. They were separated, but as the cells adjoined on a corridor they could talk to each other. With some coarse food, and a little water, Tom and his friends were left alone.

"Say I don't like this!" cried our hero, after a pause.

"Me either," chimed in Ned.

"Bless my burglar alarm!" exclaimed Mr. Damon. "It's an awful disgrace! If my wife ever heard of me being in jail—"

"She may never hear of it!" interposed Tom.

"Bless my heart!" cried the odd man. "Don't say such things."

They discussed their plight at length, but nothing could be done, and they settled themselves to uneasy slumber. For two days they were thus imprisoned, and all of Mr. Petrofsky's demands that they be given a fair trial, and allowed to know the nature of the charge against them, went for naught. No one came to see them but a villainous looking guard, who brought them their poor meals. The governor ignored them, and Mr. Petrofsky did not know what to think.

"Well, I'm getting sick of this!" exclaimed Tom—"I wish I knew where my airship was."

"I fancy it's in the same place," replied the exile. "From the way the governor acted I think he'd be afraid to have it moved. It might be damaged. If I could only get word to some of my Revolutionary friends it might do some good, but I guess I can't. We'll just have to wait."

Another day passed, and nothing happened. But that night, when the guard came to bring their suppers, something did occur.

"Hello! we've got a new one!" exclaimed Tom, as he noted the man. "Not so bad looking, either."

The man peered into his cell, and said something in Russian.

"Nothing doing," remarked the young inventor with a short laugh. "Nixy on that jabbering."

But, no sooner had the man's words penetrated to the cell of Ivan Petrofsky, that the exile called out something. The guard started, hastened to that cell door, and for a few seconds there was an excited dialogue in Russian.

"Boys! Mr. Damon! We're saved!" suddenly cried out Mr. Petrofsky.

"Bless my door knob! You don't say so!" gasped the odd man. "How? Has the Czar sent orders to release us."

"No, but somehow my Revolutionary friends have heard about my arrest, and they have arranged for our release—secretly of course. This guard is affiliated with the Nihilist group that got on the trail of my brother. He bribed the other guard to let him take his place for to-night, and now—"

"Yes! What is it?" cried Tom.

"He's going to open the cell doors and let us out!"

"But how can we get past the other guards, upstairs?" asked Ned.

"We're not going that way," explained Mr. Petrofsky. "There is a secret exit from this corridor, through a tunnel that connects with a large salt mine. Once we are in there we can make our way out. We'll soon be free."

"Ask him if he's heard anything of my airship?" asked Tom. Mr. Petrofsky put the question rapidly in Russian and then translated the answer.

"It's in the same place."

"Hurray!" cried Tom.

Working rapidly, the Nihilist guard soon had the cell doors open, for he had the keys, and our friends stepped out into the corridor.

"This way," called Ivan Petrofsky, as he followed their liberator, who spoke in whispers. "He says he will lead us to the salt mine, tell us how to get out and then he must make his own escape."

"Then he isn't coming with us?" asked Ned.

"No, it would not be safe. But he will tell us how to get out. It seems that years ago some prisoners escaped this way, and the authorities closed up the tunnel. But a cave-in of the salt mine opened a way into it again."

They followed their queer guide, who led them down the corridor. He paused at the end, and then, diving in behind a pile of rubbish, he pulled away some boards. A black opening, barely large enough for a man to walk in upright, was disclosed.

"In there?" cried Tom.

"In there," answered Mr. Petrofsky. He and the guard murmured their good-byes, and then, with a lighted candle the faithful Nihilist had provided, and with several others in reserve, our friends stepped into the blackness. They could hear the board being pulled back into place behind them.

"Forward!" cried the exile, and forward they went.

It was not a pleasant journey, being through an uneven tunnel in the darkness. Half a mile later they emerged into a large salt mine, that seemed to be directly beneath the town. Work in this part had been abandoned long ago, all the salt there was left being in the shape of large pillars, that supported the roof. It sparkled dully in the candle light.

"Now let me see if I remember the turnings," murmured Mr. Petrofsky. "He said to keep on for half an hour, and we would come out in a little woods not far from where our airship was anchored."

Twisting and turning, here and there in the semi-darkness, stumbling, and sometimes falling over the uneven floor, the little party went on.

"Did you say half an hour?" asked Tom, after a while.

"Yes," replied the Russian.

"We've been longer than that," announced the young inventor, after a look at his watch. "It's over an hour."

"Bless my timetable!" cried Mr. Damon.

"Are you sure?" asked Mr. Petrofsky.

"Yes," answered Tom in a low voice.

The Russian looked about him, flashing the candle on several turnings and tunnels. Suddenly Ned uttered a cry.

"Why, we passed this place a little while before!" he said. "I remember this pillar that looks like two men wrestling!"

It was true. They all remembered it when they saw it again.

"Back in the same place!" mused the Russian. "Then we have doubled on our tracks. I'm afraid we're lost!"

"Lost in a Russian salt mine!" gasped Tom, and his words sounded ominous in that gloomy place.

CHAPTER XX

THE ESCAPE

For a space of several seconds no one moved or spoke. In the flickering light of the candle they looked at one another, and then at the fantastic pillars of salt all about them. Then Mr. Damon started forward.

"Bless my trolley car!" he exclaimed. "It isn't possible! There must be some mistake. If we'll keep on we'll come out all right. You know your way about, don't you, Mr. Petrofsky?"

"I thought I did, from what the guard told us, but it seems I must have taken a wrong turning."

"Then it's easily remedied," suggested Tom "All we'll have to do will be to go to the place where we started, and begin over again."

"Of course," agreed Ned, and they all seemed more cheerful.

"And if we start out once more, and get lost again, then what?" asked Mr. Damon.

"Well, if worst comes to worst, we can go, back in the tunnel, go to our cells and ask the guard to come with us and show us the way went on Tom.

"Never!" cried the exile. "It would be the most dangerous thing in the world to go back to the prison. Our escape has probably been discovered by this time, and to return would only be to put our heads in the noose. We must keep on at any cost!"

"But if we can't get out," suggested Tom, "and if we haven't anything to eat or drink, we—"

He did not finish, but they all knew what he meant.

"Oh, we'll get out!" declared Ned, who was something of an optimist. "You've been in salt mines before, haven't you, Mr. Petrofsky?"

"Yes, I was condemned to one once, but it was not in this part of the country, and it was not an abandoned one. I imagine this was only an isolated mine, and that there are no others near it, so when they abandoned it, after all the salt was taken out, most people forgot about it. I remember once a party of prisoners were lost in a large salt mine, and were missed for several days."

"What happened to them?" asked Tom.

"I don't like to talk about it," replied the Russian with a shudder.

"Bless my soul! Was it as bad as that?" asked Mr. Damon.

"It was," replied the exile. "But now let's see if we can find our way back, and start afresh. I'll be more careful next time, and watch the turns more closely."

But he did not get the chance. They could not find the tunnel whence they had started. Turn after turn they took, down passage after passage sometimes in such small ones that they almost had to crawl.

But it was of no use. They could not find their way back to the starting place, and they could not find the opening of the mine. They had used two of the slow burning candles and they had only half a dozen or so left. When these were gone—

But they did not like to think of that, and stumbled on and on. They did not talk much, for they were too worried. Finally Ned gasped:

"I'd give a good deal for a drink of water."

"So would I," added his chum. "But what's the use of wishing? If there was a spring down here it would be salt water. But I know what I would do—if I could."

"What?" asked Mr. Damon.

"Go back to the prison. At least we wouldn't starve there, and we'd have something to drink. If they kept us we know we could get free—sometime."

"Perhaps never!" exclaimed Ivan Petrofsky. "It is better to keep on here, and, as for me, I would rather die here than go back to a Russian prison. We must—we shall get out!"

But it was idle talk. Gradually they lost track of time as they staggered on, and they hardly knew whether a day had passed or whether it was but a few hours since they had been lost.

Of their sufferings in that salt mine I shall not go into details. There are enough unpleasant things in this world without telling about that. They must have wandered around for at least a day and a half, and in all that while they had not a drop of water, and not a thing to eat. Wait, though, at last in their desperation they did gnaw the tallow candles, and that served to keep them alive, and, in a measure, alleviate their awful sufferings from thirst.

Back and forth they wandered, up and down in the galleries of the old salt mine. They were merely hoping against hope.

"It's worse than the underground city of gold," said Ned in hollow tones, as he staggered on. "Worse—much worse." His head was feeling light. No one answered him.

It was, as they learned later, just about two days after the time when they entered the mine that they managed to get out. Forty-eight hours, most of them of intense suffering. They were burning their last candle, and when that was out they knew they would have the horrors of darkness to fight against, as well as those of hunger and thirst.

But fate was kind to them. How they managed to hit on the right gallery they did not know, but, as they made a turn around an immense pillar of salt Tom, who was walking weakly in advance, suddenly stopped.

"Look! Look!" he whispered. "Another candle! Someone—someone is searching for us! We are saved!"

"It may be the police!" said Ned.

"That is not a candle," spoke the Russian in hollow tones as he looked to where Tom pointed, to a little glimmer of light. "It is a star. Friends, we are saved, and by Providence! That is a star, shining through the opening of the mine. We are saved!"

Eagerly they pressed forward, and they had not gone far before they knew that the exile was right. They felt the cool night wind on their hot cheeks.

"Thank heaven!" gasped Tom, as he pushed on.

A moment later, climbing over the rusted rails on which the mine cars had run with their loads of salt, they staggered into the open. They were free—under the silent stars!

"And now, if we can only find the airship," said Tom faintly, "we can—"

"Look there!" whispered Ned, pointing to a patch of deeper blackness that the surrounding night. "What's that."

"The Falcon!" gasped Tom. He started toward her, for she was but a short distance from a little clump of trees into which they had emerged from the opening of the salt mine. There, on the same little plane where they had landed in her was the airship. She had not been moved.

"Wait!" cautioned Ivan Petrofsky. "She may be guarded."

Hardly had he spoken than there walked into the faint starlight on the side of the ship nearest them, a Cossack soldier with his rifle over his shoulder.

"We can't get her!" gasped Ned.

"We've got to get her!" declared Tom. "We'll die if we don't!"

"But the guards! They'll arrest us!" said the exile.

An instant later a second soldier joined the first, and they could be seen conversing. They then resumed their pacing around the anchored craft. Evidently they were waiting for the escaped prisoners to come up when they would give the alarm and apprehend them.

"What can we do?" asked Mr. Damon.

"I have a plan," said Tom weakly. "It's the only chance, for we're not strong enough to tackle them. Every time they go around on the far side of the airship we must creep forward. When they come on this side we'll lie down. I doubt if they can see us. Once we are on hoard we can cut the ropes, and start off. Everything is all ready for a start if they haven't monkeyed with her, and I don't think they have. We've got room enough to run along as an aeroplane and mount upward. It's our only hope."

The others agreed, and they put the plan into operation. When the Cossack guards were out of sight the escaped prisoners crawled forward, and when the soldiers came into view our friends waited in silence.

It took several minutes of alternate creeping and waiting to do this, but it was accomplished at last and unseen they managed to slip aboard. Then it was the work of but a moment to cut the restraining ropes.

Silently Tom crept to the motor room. He had to work in absolute darkness, for the gleam of a light would have drawn the fire of the guards. But the youth knew every inch of his invention. The only worriment was whether or not the motor would start up after the breakdown, not having been run since it was so hastily repaired. Still he could only try.

He looked out, and saw the guards pacing back and forth. They did not know that the much-sought prisoners were within a few feet of them.

Ned was in the pilot house. He could see a clear field in front of him.

Suddenly Tom pulled the starting lever. There was a little clicking, followed by silence. Was the motor going to revolve? It answered the next moment with a whizz and a roar.

"Here we go!" cried the young inventor, as the big machine shot forward on her flight. "Now let them stop us!"

Forward she went until Ned, knowing by the speed that she had momentum enough, tilted the elevation rudder, and up she shot, while behind, on the ground, wildly running to and fro, and firing their rifles, were the two amazed guards.

CHAPTER XXI

THE RESCUE

"Have we—have we time to get a drink?" gasped Ned, when the aeroplane, now on a level keel, had been shooting forward about three minutes. Already it was beyond the reach of the rifles.

"Yes, but take only a little," cautioned Tom. "Oh! it doesn't seem possible that we are free!"

He switched on a few interior lights, and by their glow the faint and starving platinum-seekers found water and food. Their craft had, apparently, not been touched in their absence, and the machinery ran well.

Cautiously they ate and drank, feeling their strength come back to them, and then they removed the traces of their terrible imprisonment, and set about in ease and comfort, talking of what they had suffered.

Onward sped the aeroplane, onward through the night, and then Tom, having set the automatic steering gear, all fell into heavy slumbers that lasted until far into the next day.

When the young inventor awoke he looked below and could see nothing—nothing but a sea of mist.

"What's this?" he cried. "Are we above the clouds, or in a fog over some inland sea?"

He was quite worried, until Ivan Petrofsky informed him that they were in the midst of a dense fog, which was common over that part of Siberia.

"But where are we?" asked Ned.

"About over the province of Irtutsk," was the answer. "We are heading north," he went on, as he looked at the compass, "and I think about right to land somewhere near where my brother is confined in the sulphur mine."

"That's so; we've got to drop," said Tom. "I must get the gas pipe repaired. I wish we could see over what soft of a place we were so as to know whether it would be safe to land. I wish the mist would clear away."

It did, about noon, and they noted that they were over a desolate stretch of country, in which it would be safe to make a landing.

Bringing the aeroplane down on as smooth a spot as he could pick out, Tom and Ned were soon at work clearing out the clogged pipe of the gas generator. They had to take it out in the open air, as the fumes were unpleasant, and it was while working over it that they saw a shadow thrown on the ground in front of them. Startled they looked up, to see a burly Russian staring at them.

The sudden appearance of a man in that lonely spot, his calm regard of the lads, his stealthy approach, which had made it possible for him to be almost upon them before they were aware of his presence, all this made them suspicious of danger. Tom gave a quick glance about, however, and saw no others—no Cossack soldiers, and as he looked a second time at the man he noted that he was poorly dressed, that his shoes were ragged, his whole appearance denoting that he had traveled far, and was weary and ill.

"What do you make of this, Ned?" asked Tom, in a low voice.

"I don't know what to make of it. He can't be an officer, in that rig, and he has no one with him. I guess we haven't anything to be afraid of. I'm going to ask him what he wants."

Which Tom did in his plainest English. At once the man broke into a stream of confused Russian, and he kept it up until Tom held up his hand for silence.

"I'm sorry, but I can't understand you," said the young inventor. "I'll call some one who can, though," and, raising his voice, he summoned Ivan Petrofsky who, with Mr. Damon, was inside the airship doing some small repairs.

"There's a Russian out here, Mr. Petrofsky," said Tom, "and what he wants I can't make out."

The exile was quickly on the scene and, after a first glance at the man, hurried up to him, grasped him by the hand and at once the two were talking such a torrent of hard-sounding words that Tom and Ned looked at each other helplessly, while Mr. Damon, who had come out, exclaimed:

"Bless my dictionary! they must know each other."

For several minutes the two Russians kept up their rapid-fire talk and then Mr. Petrofsky, evidently realizing that his friends must wonder at it, turned to them and said:

"This is a very strange thing. This man is an escaped convict, as I once was. I recognized him by certain signs as soon as I saw him, though I had never met him before. There are certain marks by which a Siberian exile can never be forgotten," he added significantly. "He made his escape from the mines some time ago, and has suffered great hardships since. The revolutionists help him when they can, but he has to keep in concealment and travels from town to town as best he may. He has heard of our airship, I suppose from inquiries the revolutionists have been making in our behalf, and when he unexpectedly came upon us just now he was not frightened, as an ordinary peasant would have been. But he did not know I was aboard."

"And does he know you?" asked Tom. "Does he know you are trying to rescue your brother?"

"No, but I will tell him."

There was another exchange of the Russian language, and it seemed to have a surprising result. For, no sooner had Ivan Petrofsky mentioned his brother, than the other, whose name was Alexis Borious seemed greatly excited. Mr. Petrofsky was equally so at the reply his new acquaintance made, and fairly shouted to Tom, Ned and Mr. Damon.

"Friends, I have unexpected good news! It is well that we met this man or we would have gone many miles out of our way. My brother has been moved to another mine since the revolutionists located him for me. He is in a lonely district many miles from here. This man was in the same mine with him, until my brother was transferred, and then Mr. Borious escaped. We will have to change our plans."

"And where are we to head for now?" asked Tom.

"Near to the town of Haskaski, where my poor brother is working in a sulphur mine!"

"Then let's get a move on!" cried Tom with enthusiasm. "Do you think this man will come with us, Mr. Petrofsky, to help in the rescue, and show us the place?"

"He says he will," translated the exile, "though he is much afraid of our strange craft. Still he knows that to trust himself to it is better than being captured, and sent back to the mines to starve to death!"

"Good!" cried Tom. "And if he wants to, and all goes well, we'll take him out of Russia with us. Now get busy, Ned, and we'll have this machine in shape again soon."

While Ivan Petrofsky took his new friend inside, and explained to him about the workings of the Falcon, Tom and Ned labored over the gas machine with such good effect that by night it was capable of being used. Then they went aloft, and making a change in their route, as suggested by Mr. Borious, they headed for the desolate sulphur region.

For several days they sailed on, and gradually a plan of rescue was worked out. According to the information of the newcomer, the best way to save Mr. Petrofsky's brother was to make the attempt when the prisoners were marched back from the mines to the barracks where they were confined.

"It will be dark then," said Mr. Borious, "and if you can hover in your airship near at hand, and if Mr. Petrofsky can call out to his brother to run to him, we can take him up with us and get away before the guards know what we are doing."

"But aren't the prisoners chained?" asked Tom.

"No, they depend on guards to prevent escapes."

"Then we'll try that way," decided the young inventor.

On and on they sailed, the Falcon working admirably. Verst after verst was covered, and finally, one morning, Mr. Borious, who knew the country well, from having once been a prisoner there, said:

"We are now near the place. If we go any closer we may be observed. We had better remain hidden in some grove of trees so that at nightfall we can go forth to the rescue."

"But how can we find it after dark?" asked Ned.

"You can easily tell by the lights in the barracks," was the answer. "I can stand in the pilot house to direct you, for nearly all these exile prisons are alike. The prisoners will march in a long line from the mine. Then for the rescue."

It was tedious waiting that day, but it had to be done, and to Tom, who was anxious to effect the rescue, and proceed to the place of the winds to try his air glider, it seemed as if dusk would never come as they remained in concealment.

But night finally approached and then the great airship went silently aloft, ready to hover over the prison ground. Fortunately there was little wind; and she could be used as a balloon, thus avoiding the noise of the motor.

"The next thing I do, when I get home," remarked Tom, as they drifted along. "Will be to make a silent airship. I think they would be very useful."

With Mr. Borious in the pilot house, to point out the way, Tom steered through the fast-gathering darkness. The Russian had soon become used to the airship, and was not at all afraid.

"Can you go just where you want to, as a balloon?" asked the new guide.

"No, but almost," replied Tom. "At the last moment I've got to take a chance and start the motor to send us just where we want to go. That's why I think a silent airship would be a great thing. You could get up on the enemy before he knew it."

"There are the prison barracks," said the guide a little later, his talk being translated by Mr. Petrofsky. Below and a little ahead of them could been seen a cluster of lights.

"Yes, that looks like a line of prisoners," remarked Ned, who was peering through a pair of night glasses.

"Where?" asked Tom eagerly, and they were pointed out to him. He took an observation, and exclaimed:

"There they are, sure enough. Now if your brother is only among them, Mr. Petrofsky, we'll soon have him on board."

"Heaven grant that he may be there!" said the exile in a low voice.

A moment later, the Falcon, meanwhile having been allowed to drift as close as possible to the dimly-seen line of prisoners, Tom set in motion the great motor, the propeller blades heating the air fiercely.

At the sound there was a shout on the ground below, but before the excitement had time to spread, or before any of the guards could form a notion of what was about to take place, Tom had sent his craft to earth on a sharp slant, closer to the line of prisoners than he had dared to hope.

Mr. Petrofsky sprang out on deck, and in a loud voice called in Russian:

"Peter! Peter! If you are there, come here! Come quickly! It is I, your brother Ivan who speaks. I have come to save you—save you in the wonderful airship of Tom Swift! Come quickly and we will take you away! Peter Petrofsky!"

For a moment there was silence, and then the sound of some one running rapidly was borne to the ears of the waiting ones. It was followed, a moment later, by angry shouts from the guards.

"Quick! Quick, Peter!" cried the brother, "over this way!"

For an instant only the exile showed a single electric flash light, that his brother might see in which direction to run. The echo of the approaching footsteps came nearer, the shouts of the guards redoubled, and then came the sound of many men running in pursuit.

"Hurry, Peter, hurry!" cried Mr. Petrofsky, and, as he spoke in Russian the guards, of course, understood.

Suddenly a rifle shot rang out, but the weapon seemed to have been fired in the air. A moment later a dark figure clambered aboard the airship.

"Peter, is it you?" cried Ivan Petrofsky, hoarsely.

"Yes, brother! But get away quickly or the whole guard will be swarming about here!"

"Praise the dear Lord you are saved!"

"Is it all right?" cried Tom, who wanted to make sure they were saving the right man.

"Yes! Yes, Tom! Go quickly!" called Ivan Petrofsky, as he folded his brother in his arms. A moment later, with a roar, the Falcon shot away from the earth, while below sounded angry cries, confused shouts and many orders, for the guards and their officers had never known of such a daring rescue as this.

CHAPTER XXII

IN THE HURRICANE

There was a volley of shots from the prison guards, and the flashes of the rifles cut bright slivers of flame in the darkness, but, so rapidly did the airship go up, veering off on a wide slant, under the skillful guidance of Tom that the shots did no harm.

"Bless my bullet pouch!" cried Mr. Damon. "They must be quite excited."

"Shouldn't wonder," calmly observed Ned, as he went to help his chum in managing the airship. "But it won't do them any good. We've got our man."

"And right from under their noses, too," added Ivan Petrofsky exultingly. "This rescue of an exile will go down in the history of Russia."

The two exile brothers were gazing fondly at each other, for now that the Falcon was so high, Tom ventured to turn on the lights.

A moment later the three Russians were excitedly conversing, while Tom and Ned managed the craft, and Mr. Damon, after listening a moment to the rapid flow of the strange language, which quite fascinated him, hurried to the galley to prepare a meal for the rescued one, who had been taken away before he had had a chance to get his supper.

His wonder at his startling and unexpected rescue may well be imagined, but the joy at being reunited to his brother overshadowed everything for the time being. But when he had a chance to look about, and see what a strange craft he was in, his amazement knew no bounds, and he was like a child. He asked countless questions, and Ivan Petrofsky and Mr. Borious took turns in answering them. And from now on, I shall give the conversation of the two new Russians just as if they spoke English, though of course it had to be translated by Ivan Petrofsky, Peter's brother.

If Peter was amazed at being rescued in an airship, his wonder grew when he was served with a well-cooked meal, while high in the air, and while flying along at the rate of fifty miles an hour. He could not talk enough about it.

By degrees the story of how Tom and his friends had started for Russia was told, and there was added the detail of how Mr. Borious came to be picked up.

"But brother Ivan, you did not come all that distance to rescue me; did you?" asked Peter.

"Yes, partly, and partly to find the platinum mine."

"What? The lost mine that you and I stumbled upon in that terrible storm?"

"That is the one, Peter."

"Then, Tom Swift may as well return. I doubt if we can even locate the district where it was, and if we did find it, the winds blow so that even this magnificent ship could not weather the gales."

"I guess he doesn't understand about my air glider," said Tom with a smile, when this was translated to him. "I wish I had a chance to put it together, and show him how it works."

"Oh, it will work all right," replied Ned, who was very proud of his friend's inventive ability.

"Now, what is the next thing to be done?" asked Tom, a little later that evening, when, supper having been served, they were sitting in the main cabin, talking over the events of the past few days. "I'd like to get on the track of that platinum treasure."

"And we will do all in our power to aid you," said Ivan Petrofsky. "My brother and I owe much to you—in fact Peter owes you his life; do you not?" and he turned to him.

"I do," was the firm answer.

"Oh, nonsense!" exclaimed Tom, who did not like to be praised. "I didn't do much."

"Much! You do not call taking me away from that place—that sulphur mine—that horrible prison barrack with the cruel guards—you do not call that much? My friend," spoke the Russian solemnly, "no one on earth has done so much for me as you have, and if it is the power of man to show you where that lost mine is, my brother and I will do so!"

"Agreed," spoke Ivan quietly.

"Then what plans shall we make?" asked Tom, after a little more talk. "Are we to go about indiscriminately, or is there any possible way of getting on the trail?"

"My brother and I will try and decide on a definite route," spoke Ivan Petrofsky. "It is some time since I have seen him, and longer since we accidently found the mine together, but we will consult each other, and, if possible make some sort of a map."

This was done the next day, the present maps aboard the Falcon being consulted, and the brothers comparing notes. They began to lay out a stretch of country in which it was most likely the lost mine lay. It took several days to do this, for sometimes one brother would forget some point, and again the other would. But at last they agreed on certain facts.

"This is the nearest we can come to it," said Ivan Petrofsky to Tom. "The lost platinum mine lies somewhere between the city of Iakutsk and the first range of the Iablonnoi mountains. Those are the northern and southern boundaries. As for the western one, it is most likely the Lena river, and the eastern one the Amaga river. So you see you have quite a large stretch of country to search, Tom Swift."

"Yes, I should say I had," agreed the young inventor. "But I have had harder tasks. Now that I know where to head for I'll get there as soon as possible."

"And what will you do when you arrive?" asked Ned.

"Fly about in the Falcon, in ever-widening circles, starting as near the centre of that area as possible," replied Tom. "And as soon as I run into a steady hurricane I'll know that I'm at the place of the big winds, and I'll get out my glider, for I'll be pretty sure to be near the place."

"Bless my gas meter!" cried Mr. Damon. "That's the talk!"

Tom put his plan into operation at once, by heading the nose of his craft for the desolate region mapped out by the Russian brothers.

The days that followed were filled with weary searching. It was like the time when they had sought for the plain of the great ruined Temple in Mexico, that they might locate the underground city of gold. Only in this case they had no such landmark as a great Aztec ruin to guide them.

What they were seeking for was something unseen, but which could be felt—a mysterious wind—a wind that might be encountered any time, and which might send the Falcon to the earth a wreck.

The Russian brothers, staggering about in the storm, had seen the mine under different conditions from what it would be viewed now. Then it was winter in Siberia. Now it was summer, though it was not very warm.

On and on sailed the Falcon. The weather could not have been better, but for once Tom wanted bad weather. He wanted a blow—the harder the better—and all eyes anxiously watched the anemometer, or wind gage. But ever it revolved lazily about in the gentle breeze.

"Oh, for a hurricane!" cried Tom.

He got his wish sooner than he anticipated. It was about two days after this, when they were going about in a great circle, about two hundred miles from the imaginary centre of the district in which the mine lay, that, as Mr. Damon was getting dinner a dish he was carrying to the table was suddenly whisked out of his hand.

"I say, what's the matter?" he cried. "Bless my—"

But he had no time to say more. The airship fairly stood on end, and then, turning completely about, was rapidly driven in the opposite direction, though her propellers were working rapidly.

"What's up?" yelled Ned.

"We are capsizing!" shouted Ivan Petrofsky, and indeed it seemed so, for the airship was being forced over.

"I guess we've struck what we want!" cried Tom. "We're in a hurricane all right! This is the place of the big wind! Now for my air glider, if I can get the airship to earth without being wrecked! Ned, lend a hand! We've got our work cut out for us now!"

CHAPTER XXIII

THE LOST MINE

For several moments it seemed as if disaster would overtake the little band of platinum-hunters. In spite of all that Tom and Ned could do, the Falcon was whipped about like a feather in the wind. Sometimes she was pointing her nose to the clouds, and again earthward. Again she would be whirling about in the grip of the hurricane, like some fantastic dancer, and again she would roll dangerously. Had she turned turtle it probably would have been the last of her and of all on board.

"Yank that deflecting lever as far down as it will go!" yelled Tom to his chum.

"I am. She won't go any farther."

"All right, hold her so. Mr. Damon, let all the gas out of the bag. I want to be as heavy as possible, and get to earth as soon as we can."

"Bless my comb and brush!" cried the odd man. "I don't know what's going to become of us."

"You will know, pretty soon, if the gas isn't let out!" retorted Tom grimly, and then Mr. Damon hastened to the generator compartment, and opened the emergency outlet.

Finally, by crowding on all the possible power, so that the propellers and deflecting rudders forced the craft down, Tom was able to get out of the grip of the hurricane, and landed just beyond the zone of it on the ground.

"Whew! That was a narrow squeak!" cried Ned, as he got out. "How'd you do it, Tom?"

"I hardly know myself. But it's evident that we're on the right spot now."

"But the wind has stopped blowing," said Mr. Damon. "It was only a gust."

"It was the worst kind of a gust I ever want to see," declared the young inventor. "My air glider ought to work to perfection in that. If you think the wind has died out, Mr. Damon, just walk in that direction," and Tom pointed off to the left.

"Bless my umbrella, I will," was the reply and the odd man started off. He had not gone far, before he was seen to put his hand to his cap. Still he kept on.

"He's getting into the blow-zone," said Tom in a low voice.

The next moment Mr. Damon was seen to stagger and fall, while his cap was whisked from his head, and sent high into the air, almost instantly disappearing from sight.

"Some wind that," murmured Ned, in rather awe-struck tones.

"That's so," agreed his chum. "But we'd better help Mr. Damon," for that gentleman was slowly crawling back, not caring to trust himself on his feet, for the wind had actually carried him down by its force.

"Bless my anemometer!" he gasped, when Tom and Ned had given him a hand up. "What happened?"

"It was the great wind," explained Tom. "It blows only in a certain zone, like a draft down a chimney. It is like a cyclone, only that goes in a circle. This is a straight wind, but the path of it seems to be as sharply marked as a trail through the forest. I guess we're here all right. Does this location look familiar to you?" he asked of the Russian brothers.

"I can't say that it does," answered Ivan. "But then it was winter when we were here."

"And, another thing," put in Peter. "That wind zone is quite wide. The mine may be in the middle, or near the other edge."

"That's so," agreed Tom. "We'll soon see what we can do. Come on, Ned, let's get the air glider out and put her together. She'll have a test as is a test, now."

I shall not describe the tedious work of re-assembling Tom Swift's latest invention in the air craft line—his glider. Sufficient to say that it was taken out from where it had been stored in separate pieces on board the Falcon, and put together on the plain that marked the beginning of the wind zone.

It was a curious fact that twenty feet away from the path of the wind scarcely a breeze could be felt, while to advance a little way into it meant that one would at once be almost carried off his feet.

Tom tested the speed of it one day with a special anemometer, and found that only a few hundred feet inside the zone the wind blew nearly one hundred miles an hour.

"What is it like inside, I wonder?" asked Ned.

"It must be terrific," was his chum's opinion.

"Dare you risk it, Tom?"

"Of course. The harder it blows the better the glider works. In fact I can't make much speed in a hundred-mile wind for with us all on board the craft will be heavy, and you must remember that I depend on the wind alone to give me motion."

"What do you think causes the wind to blow so peculiarly here Tom?" went on Ned.

"Oh, it must be caused by high mountain ranges on either side, or the effects of heat and cold, the air being evaporated over a certain area because of great heat, say a volcano, or something like that; though I don't know that they have volcanoes here. That creates a vacuum, and other air rushes in to fill the vacant space. That's all wind is, anyhow, air rushing in to fill a vacuum, or low pressure zone, for you remember that nature abhors a vacuum."

It took nearly a week to assemble the Vulture, as Tom had named his latest craft, from the fact that it could hover in the air motionless, like that great bird. At last it was completed and then, weights being taken aboard to steady it, all was ready for the test. Tom would have liked to have taken all his passengers in the glider, for it would work better then, but the three Russians were timid, though they promised to get aboard after the trial.

The test came off early one morning, Tom, Ned and Mr. Damon being the only ones aboard. Bags of sand represented the others. The glider was wheeled to the edge of the wind zone and they took their places in the car. It was hard work for the gale, that had never ceased blowing for an instant since they found its zone, was very strong. But the glider remained motionless in it, for the wing planes, the rudders, and equalizing weights had been adjusted to make the strain of the wind neutral.

"All ready?" asked Tom, when his chum and his friend were in the enclosed car of the glider.

"As ready as I ever shall be," answered Ned.

"Bless my suspenders! Let her go, Tom, and have it over with!" cried the odd man.

The young inventor pulled a lever, and almost instantly the glider darted forward. A moment later it soared aloft, and the three Russians cheered. But their voices were lost in the roar of the hurricane, as Tom sent his craft higher and higher.

It worked perfectly, and he could direct it almost anywhere. The wind acted as the motive power, the bending and warping wings, and the rudders and weights controlling its force.

"I'm going higher, and see if I can remain stationary!" yelled Tom in Ned's ear. His chum only nodded. Mr. Damon was seated on a bench, clinging to the sides of it as if he feared he would fall off.

Higher and higher went the Vulture, ever higher, until, all at once, Tom pulled on another lever and she was still. There she hung in the air, the wind rushing through her planes, but the glider herself as still and quiet as though she rested on the ground in a calm. She hardly moved a foot in either direction, and yet the wind, as evidenced by the anemometer was howling along at a hundred and twenty miles an hour!

"Success!" cried Tom. "Success! Now we can lie stationary in any spot, and spy out the land through our telescope. Now we will find the lost platinum mine!"

"Well, I'm not deaf," responded Ned with a smile, for Tom had fairly yelled as he had at the start, and there was no need of this now, for though the wind blew harder than ever it was not opposed to any of the weights or planes, and there was only a gentle humming sound as it rushed through the open spaces of the queer craft.

Tom gave his glider other and more severe tests, and she answered every one. Then he came to earth.

"Now we'll begin the search," he said, and preparations were made to that end. The Russians, now that they had seen how well the craft worked, were not afraid to trust themselves in her.

As I have explained, there was an enclosed car, capable of holding six. In this were stores, supplies and food sufficient for several days. Tom's plan was to leave the airship anchored on the edge of the wind zone, as a sort of base of supplies or headquarters. From there he intended to go off from time to time in the wind-swept area to look for the lost mine.

There were weary days that followed. Hour after hour was spent in the air in the glider, the whole party being aboard. Observation after observation was taken, sometimes a certain strata of wind enabling them to get close enough to the earth to use their eyes, while again they had to use the telescopes. They covered a wide section but as day after day passed, and they were no nearer their goal, even Tom optimistic as he usually was, began to have a tired and discouraged look.

"Don't you see anything like the place where you found the mine?" he asked of the exile brothers.

They could only shake their heads. Indeed their task was not easy, for to recognize the place again was difficult.

More than a week passed. They had been back and forth to their base of supplies at the airship, often staying away over night, once remaining aloft all through the dark hours in the glider, in a fierce gale which prevented a landing. They ate and slept on board, and seldom descended unless at or near the place where they had left the Falcon. Once they completely crossed the zone of wind, and came to a calm place on the other side. It was as wild and desolate as the other edge.

Nearly two weeks had passed, and Tom was almost ready to give up and go back home. He had at least accomplished part of his desire, to rescue the exile, and he had even done better than originally intended, for there was Mr. Borious who had also been saved, and it was the intention of the young inventor to take him to the United States.

"But the platinum treasure has me beat, I guess," said Tom grimly. "We can't seem to get a trace of it."

Night was coming on, and he had half determined to head back for the airship. Ivan Petrofsky was peering anxiously down at the desolate land, over which they were gliding. He and his brother took turns at this.

They were not far above the earth, but landmarks, such as had to be depended on to locate the mine, could not readily be observed without the glass. Mr. Damon, with a pair of ordinary field glasses, was doing all he could to pick out likely spots, though it was doubtful if he would know the place if he saw it.

However, as chance willed it, he was instrumental in bringing the quest to a close, and most unexpectedly. Peter Petrofsky was relieving his brother at the telescope, when the odd man, who had not taken his eyes from the field glasses, suddenly uttered an exclamation.

"Bless my tooth-brush!" he cried. "That's a most desolate place down there. A lot of trees blown down around a lake that looks as black as ink."

"What's that!" cried Ivan Petrofsky. "A lake as black as ink? Where?"

"We just passed it!" replied Mr. Damon.

"Then put back there, as soon as you can, Tom!" called the Russian. "I want to look at that place."

With a long, graceful sweep the young inventor sent the glider back over the course. Ivan Petrofsky glued his eyes to the telescope. He picked out the spot Mr. Damon had referred to, and a moment later cried:

"That's it! That's near the lost platinum mine! We've found it again, Tom—everybody! Don't you remember, Peter," he said turning to his brother, "when we were lost in the snow we crawled in among a tangle of trees to get out of the blast. There was a sheet of white snow near them, and you broke through into water. I pulled you out. That must have been a lake, though it was lightly frozen over then. I believe this is the lost mine. Go down, Tom! Go down!"

"I certainly will!" cried the youth, and pulling on the descending lever he shunted the glider to earth.

CHAPTER XXIV

THE LEAKING TANKS

Like a bird descending from some dizzy height, the Vulture landed close to the pool of black water. It was a small lake and the darkness must have been caused by its depth, for later when they took some out in a glass it was as clear as a crystal. Then, too, there might have been black rocks on the bottom.

"Can it be possible that we are here at last?" cried Tom, above the noise of the gale, for the wind was blowing at a terrific rate. But our friends knew better now how to adjust themselves to it, and the lake was down in a valley, the sides of which cut off the power of the gale. As for the glider it was only necessary to equalize the balance and it would remain stationary in any wind.

"This is the place! This is the place!" cried Ivan Petrofsky. "Don't you remember, Peter?"

"Indeed I do! I have good cause to! This is where we found the platinum!"

"Bless my soul!" cried Mr. Damon. "Where is it, in the lake?"

"The mine itself is just beyond that barrier of broken and twisted trees," replied the elder Russian brother. "It is an irregular opening in the ground, as though once, centuries ago, an ancient people tried to get out the precious metal. We will go to it at once."

"But it is getting late," objected Ned.

"No matter," said Tom. "If we find any platinum we'll stay here all night, and longer if necessary to get a good supply. This is better than the city of gold, for we're in the open."

"I should say we were," observed Mr. Damon, as he bent to the blast, which was strong, sheltered even as they were.

"Will it be safe to remain all night?" asked Mr. Borious, with a glance about the desolate country.

"We have plenty of food," replied Tom, "and a good place to stay, in the car of the glider. I don't believe we'll be attacked."

"No, not here," said the elder Petrofsky. "But we still have to go back across Siberia to escape."

"We'll do it!" cried Tom. "Now for the platinum treasure!"

They went forward, and it was no easy work. For the wind still blew with tremendous force though nothing like what it did higher up. And the ground was uneven. They had to cling to each other and it was very evident that no airship, not even the powerful Falcon, could have reached the place. Only an air glider would answer.

It took them half an hour to get to the opening of the ancient mine, and by that time it was nearly dark. But Tom had thought to bring electric torches, such as he had used in the underground city of gold, and they dispelled the gloom of the small cavern.

"Will you go in?" asked Ivan Petrofsky, when they had come to the place. He looked at Tom.

"Go in? Of course I'll go in!" cried our hero, stepping forward. The others followed. For some time they went on, and saw no traces of the precious metal. Then Ned uttered a cry, as he saw some dull, grayish particles imbedded in the earth walls of the shaft.

"Look!" he cried.

Tom was at his chum's side in a moment.

"That's platinum!" cried the young inventor. "And of the very highest grade! But the lumps are very small."

"There are larger ones beyond," said the younger Russian brother.

Forward they pressed, and a moment later coming around a turn in the cavern where some earth had fallen away, evidently recently, Tom could not repress a cry of joy. For there, in plain sight, were many large lumps of the valuable metal, in as pure a state as it is ever found. For it is always mixed with other metals or chemicals.

"Look at that!" cried Tom. "Look at that! Lumps as large as an egg!" and he dug some out with a small pick he had brought along, and stuffed them into his pocket.

"Bless my check book!" cried Mr. Damon, "and that stuff is as valuable as gold!"

"More so!" cried Tom enthusiastically.

"Oh, here's a whopping big one!" cried Ned. "I'll bet it weighs ten pounds."

"More than that!" cried Tom, as he ran over and began digging it out, and they found later that it did. Platinum is usually found in small granules, but there are records of chunks being found weighing twenty pounds while others, the size of pigeons' eggs, are not uncommon.

"Say, this is great!" yelled Ned, discovering another large piece, and digging it out.

"I am glad we could lead you to it," said the elder Russian brother. "It is a small return for what you did for us!"

"Nonsense!" cried Tom. "These must be a king's ransom here. Everybody dig it out! Get all you can."

They were all busy, but the light of the two torches Tom had brought was not sufficient for good and efficient work, so after getting several thousand dollars worth of the precious metal, they decided to postpone operations until morning, and come with more lights.

They were at the work soon after breakfast, the night in the air glider having passed without incident. The treasure of platinum proved even richer than the Russians had thought, and it was no wonder the Imperial government had tried so hard to locate it, or get on the trail of those who sought it.

"And it's all good stuff!" cried Tom eagerly. "Not like that low-grade gold of the underground city. I can make my own terms when I sell this."

For three days our friends dug and dug in that platinum mine, so many years lost to man, and when they got ready to leave they had indeed a king's ransom with them. But it was to be equally divided. Tom insisted on this, as his Russian friends had been instrumental in finding it. Toward the end of the excavation large pieces were scarce, and it was evident that the mine was what is called a "lode."

"Well, shall we go back now?" asked Tom one day, after the finish of their mining operations. The work was comparatively simple, as the platinum lumps had merely to be dug out of the sides of the cave. But the loneliness and dreariness of the place was telling on them all.

"Can't we carry any more?" asked Ned.

"We could, but it might not be safe. I don't want to take on too much weight, as my glider isn't as stable as the airship. But we have plenty of the metal.

"Indeed we have," agreed Ivan Petrofsky. "Much of mine and my brother's will go toward helping relieve the sufferings of the Siberian exiles," he added.

"And mine, too," said Alexis Borious.

They started back early the next morning in a more terrific gale than in any the glider had yet flown. But she proved herself a stanch craft, and soon they were at the place where they had left the airship. It was undisturbed.

Four days were spent in taking apart the glider and packing it on board the Falcon. Then, with the platinum safely stored away Tom, with a last look at the desolate land that had been so kind to them, sent his craft on her homeward way.

It was when they were near the city of Pirtchina, on the Obi river, that what might have proved a disastrous accident occurred. They were flying along high, and at great speed, for Tom wanted to make all the distance he could, to get out of Siberia the more quickly. They had had a fair passage so far, and were congratulating themselves that they would soon be in civilization again.

Suddenly, Mr. Damon, who had been on the after deck, taking observations through a telescope, came running forward, crying out:

"Tom! Tom! What is that water dripping from the back part of the airship?"

"Water?" exclaimed Tom. "No water is dripping from there."

"Come and look," advised Mr. Damon.

The young inventor raced back with him. He saw a thin, white stream trickling down from the lower part of the craft. Tom sniffed the air suspiciously.

"Gasolene! It's gasolene!" he cried. "We must have a leak in the supply tanks!"

He dashed toward the reserve storeroom, and at that moment, with a suddenness that was startling, the motor stopped and the Falcon lurched toward the earth.

CHAPTER XXV

HOMEWARD BOUND—CONCLUSION

"All right!" yelled Ned, as soon as he heard Tom's cry. "I've got her under control. We'll volplane down."

"Is it dangerous? Are we in danger?" asked Peter Petrofsky of his brother, in Russian.

"I guess there's no danger, where Tom Swift's concerned," was the answer. "I have not volplaned much, but it will be all right I think."

And it was, for with Ned Newton to guide the craft, while Tom did his best to stop the leak, the craft came gently to earth on the outskirts of a fairly large Siberian city. Almost instantly the Falcon was surrounded by a curious throng.

"You had better keep inside," said Ivan Petrofsky to his brother and Mr. Borious. "Descriptions of you are probably out broadcast by now, but I am still sufficiently disguised, I think."

"But what is to be done?" demanded the younger Russian brother. "If the gasolene is gone, how can we leave here?"

"Trust Tom Swift for that," was the reply. "Keep out of sight now, there is a large crowd outside."

Tom came from the tank room. There was a despondent look on his face.

"It's all gone—every drop," he said. "That's what made the motor stop."

"What's gone?" asked Mr. Damon.

"The gasolene. We sprung a leak in the main tank, somehow, and it all flowed out while we were flying along."

"Haven't you any more?"

"Not a bit. I was drawing on the reserve tank, hoping to get to civilization before I needed more. But its too late now. We will have to—"

"Bless my snow shoes!" cried Mr. Damon. "Don't say we'll have to stay here—in Siberia! Don't say that. My wife—"

"No, we won't have to stay here if we can get a supply of kerosene," interrupted Tom. "The motor will burn that. The only trouble is that we may be detained. The authorities probably know us by this time, and are on the watch."

"Then get it before they know we are here," advised Ned.

"I'll try," said Tom, and he at once conferred with the elder Petrofsky. The latter said he was sure kerosene could be had in town, and, rather than risk going in themselves, they hired a wagoner who agreed, for liberal pay, to go and return with a quantity. Until then there was nothing to do but wait.

Meanwhile the crowd of curiosity seekers grew. They thronged around the airship, some of them meddling with various devices, until Tom had to order them away with gestures.

One particularly inquisitive man insisted on pulling or twisting everything, until he happened to touch a couple of live wires, giving himself quite a shock, and then he ran away howling. But still the crowd increased, and at last Mr. Petrofsky said:

"I don't like this, Tom?"

"Why not?" They were all inside the craft, looking out and waiting for the return of the man with the kerosene. The leak in the tank had proved to be a small one, and had quickly been soldered. It had been open a long time, which accounted for the large amount of gasolene escaping. "What don't you like, Mr. Petrofsky?"

"So many men surrounding us. I believe some of them are officers dressed in civilians' clothes, and a Russian officer never does that unless he has some object."

"And you think the object is—?"

"To capture us."

"If it was that, wouldn't they have done it long ago—when we first came down?"

"No, they are evidently waiting for something perhaps for some high official, without whose orders they dare do nothing. Russia is overrun with officialdom."

And a little later Ivan Petrofsky's suspicion proved true. There arrived a man in uniform, who spoke fairly good English, and who politely asked Tom if he would not delay the start of the airship, again, until the governor could arrive from his country place to see it.

"We know you are going to leave us," said the Russian with a smile, "for you have sent for kerosene. But please wait."

"If your governor comes soon we'll wait," replied Tom. "But we are in a hurry. I wish that kerosene fellow would get a move on," he murmured.

"Oh, he will doubtless be here soon," said the officer. "Might I be permitted to come aboard and wait for my chief?"

"Sorry, but it's not allowed," replied our hero, straining his eyes down the road for a sight of the wagoner. At last he came, and Tom breathed easier.

But the crowd was bigger, and some of the men, though poorly dressed, seemed to be persons in authority. Tom had no doubt but what there was a plot afoot to detain him, and arrest the exiles, and that there were disguised soldiers in the throng. But they could not act without the governor's orders, and he was probably on his way with all haste.

"Lively now, get that kerosene in the tanks!" cried Tom to the man, motioning in lieu of using Russian. The youth was not going to meet the governor if he could help it.

Now it was a curious thing, but the more that wagoner and his helpers seemed to try to hurry, and pour the oil from the cans into the tank-opening of the airship, the slower they worked. They got in each others' way, dropped some cans, spilled others, and in general made such poor work at it that Tom saw there was something in the wind.

"Ned!" he exclaimed, "they're doing all they can to detain us. We've got to put that oil in ourselves. Just as we did the gasolene in France. It's the same sort of a delay game."

"Right, Tom! I'm with you."

"And I'll warn the crowd back, by telling them we are likely to blow up any minute!" added Ivan Petrofsky, which warning he shouted in Russian a moment later.

Backward leaped the throng, as though a bomb bad been thrown into their midst, even the supposed officers joining in the retreat. The oil wagon was now easy of access, and Tom and Ned, with Mr. Damon to aid them, hastened toward it. Then the work of filling the tanks went on in something like good old, United States fashion.

The last gallon of kerosene had been put aboard, and Tom and Ned with Mr. Damon, had climbed on deck, when the gaily uniformed officer, who had requested the delay, came riding up furiously.

"Hold! Hold! If you please!" he cried. "The governor has come. He wants to see you."

"Too late!" answered Tom. "Give him our best regards and ask him to come to the United States if he wants to see us. Sorry we haven't cards handy. Ned, take the pilot house, and shoot her up sharp when you get the signal. I'm going to run the motor. I don't know just how she'll behave on the kerosene."

"You must remain!" angrily cried the officer.

"The United States doesn't take 'must' from anybody, from the Czar down!" cried Tom as he disappeared into the motor room. The window was open, and the youth turned on the power the official cried again to him:

"Halt! Here comes the governor! I declared you arrested by his orders, and in the name of the Czar!"

"Nothing doing!" yelled Tom, and then, looking from the window, he saw approaching a troop of Cossacks, in the midst of whom rode a man in a brilliant uniform—evidently the governor.

"Stop! Stop!" cried the official.

"Here we go, Ned!" yelled Tom, and turning on more power the Falcon arose swiftly, before the very eyes of the angry governor, and his staff of Cossack soldiers.

Up and up she went, faster and faster, the motors working well on the kerosene. Higher and higher. The governor and his soldiers were directly below her now.

"Stop! Stop! You must stop. The Imperial governor orders it!" yelled the officer, evidently his Excellency's aide-de-camp.

"We can't hear you!" shouted Tom, waving his hand from the motor room window, and then, turning on still more power he flew over the city, taking his friends and the valuable supply of platinum with him. So surprised were the soldiers that they did not fire a shot, but had they done so it is doubtful if much damage could have been done.

"And now for home!" cried Tom, and homeward hound the Falcon was after a perilous trip through two storms. But she weathered them well.

In due season they reached Paris again, and now, having no reason for concealment, they flew boldly down, to change what remained of the kerosene for gasolene, as the motor worked better on that. The secret police learned that the exiles were aboard, but they could do nothing, as the offenses were political ones, and so Tom kept his friends safe.

Then they started on the long voyage across the Atlantic, and though they had one bad experience in a storm over that mighty ocean, they got safely home to Shopton in due season.

There is little more to tell. The platinum proved to be even more valuable than Tom had expected. He could have sold it all for a large sum, but he preferred to keep most of what he had for his inventive work, and he used considerable of it in his machinery. Ned disposed of his, selling Tom some at a lower price than market quotations, and the Russians got a good price for theirs, turning the money into the fund to help their fellow exiles. Mr. Damon also made a good donation to the cause, as did Tom and Ned.

Mr. Petrofsky and his brother, with the other exile, joined friends in New York, and promised to come and see Tom when they could.

"Well, I suppose you'll take a long vacation now," said Mary Nestor, to Tom, when he called on her one evening to present her a unique ring, with the stones set in some of the platinum he had dug in the Siberian mine.

"Vacation? I have no time for vacations!" said the young inventor. "I'm soon going to work on my silent airship, and on some other things I have in mind. I want more adventures."

"Oh, you greedy boy!" exclaimed Mary with a laugh.

And what adventures Tom had next will be found in the next book of this series, which will be entitled, "Tom Swift in Captivity; Or, a Daring Escape by Airship."

Tom had several offers to give exhibitions in his air glider, from aviation committees at various meets, but he declined.

"I haven't time," he declared. "I'm too busy."

"You ought to rest," his chum Ned advised him.

"'Bless my alarm clock!' as Mr. Damon would say," exclaimed Tom. "The best rest is new work," and then he began sketching his ideas for a silent motor craft, during which we will take leave of him for a while.