"Did you make this machine yourself?" asked the stranger of Tom, as the young inventor worked at the damaged part of his craft.

Mr. Damon had also alighted, taken off his goggles, and was looking aloft, where the army aircraft were going through various evolutions, and down below, where the young soldiers were drilling under such conditions, as far as possible, as they might meet with when some of their number went "over the top." Mr. Damon was murmuring to himself such remarks as:

"Bless my fountain pen! look at that chap turning upside down! Bless my inkwell!"

"I beg your pardon," remarked Tom Swift, following the remark of the man, whose face he was trying to recall. It was not that Tom had not heard the question, but he was trying to gain time before answering.

"I asked if you made this machine yourself," went on the man, as he peered about at the Hawk. "It isn't like any I've ever seen before, and I know something about airships. It has some new wrinkles on it, and I thought you might have evolved them yourself. Not that it's an amateur affair, by any means!" he added hastily, as if fearing the young inventor might resent the implication that his machine was a home-made product

"Yes, I originated this," answered Tom, as he put a new turn-buckle in place; "but I didn't actually construct it-- that is, except for some small parts. It was made in the shop--"

"Over at the army construction plant, I presume," interrupted the man quickly, as he motioned toward the big factory, not far from Shopton, where aircraft for Uncle Sam's Army were being turned out by the hundreds.

"Might as well let him think that," mused Tom; "at least until I can figure out who he is and what he wants."

"This is different from most of those up there," and the stranger pointed toward the circling craft on high. "A bit more speedy, I guess, isn't it?"

"Well, yes, in a way," agreed Tom, who was lending over his craft. He stole a side look at the man. The face was becoming more and more familiar, yet something about it puzzled Tom Swift.

"I've seen him before, and yet he didn't look like that," thought the young inventor. "It's different, somehow. Now why should my memory play me a trick like this? Who in the world can he be?"

Tom straightened up, and tossed a monkey wrench into the tool box.

"Get everything fixed?" asked the stranger.

"I think so," and the young inventor tried to make his answer pleasant. "It was only a small break, easily fixed."

"Then you'll be on your way again?"

"Yes. Are you ready?" called Tom to Mr. Damon.

"Bless my timetable, yes! I didn't think you'd start back again so soon. There's one young fellow up there who has looped the loop three times, and I expect him to fall any minute."

"Oh, I guess he knows his business," Tom said easily. "We'll be getting back now."

"One moment!" called the man. "I beg your pardon for troubling you, but you seem to be a mechanic, and that's just the sort of man I'm looking for. Are you open to an offer to do some inventive and constructive work?"

Tom was on his guard instantly.

"Well, I can't say that I am," he answered. "I am pretty busy--"

"This would pay well," went on the man eagerly. "I am a stranger around here, but I can furnish satisfactory references. I am in need of a good mechanic, an inventor as well, who can do what you seem to have done so well. I had hopes of getting some one at the army plant"

"I guess they're not letting any of their men go," said Tom, as Mr. Damon climbed to his seat in the Hawk.

"No, I soon found that out. But I thought perhaps you--"

Tom shook his head.

"I'm sorry," he answered, "but I'm otherwise engaged, and very busy."

"One moment!" called the man, as he saw Tom about to start "Is the Swift Company plant far from here?"

Tom felt something like a thrill go through him. There was an unexpected note in the man's voice. The face of the young inventor lightened, and the doubts melted away.

"No, it isn't far," Tom answered, shouting to be heard above the crackling bangs of the motor. And then, as the craft soared into the air, he cried exultingly:

"I have it! I know who he is! The scoundrel! His beard fooled me, and he probably didn't know me with these goggles on. But now I know him!"

"Bless my calendar!" cried Mr. Damon. "What are you talking about?"

But Tom did not answer, for the reason that just then the Hawk fell into an "air pocket," and needed all his attention to straighten her out and get her on a level course again.

And while Tom Swift is thus engaged in speeding his aircraft along the upper regions toward his home, it will take but a few moments to acquaint my new readers with something of the history of the young inventor. Those who have read the previous books in this series need be told nothing about our hero.

Tom Swift was an inventor of note, as was his father. Mr. Swift was now quite aged and not in robust health, but he was active at times and often aided Tom when some knotty point came up.

Tom and his father lived on the outskirts of the town of Shopton, and near their home were various buildings in which the different machines and appliances were made. Tom's mother was dead, but Mrs. Baggert, the housekeeper, was as careful in looking after Tom and his father as any woman could be.

In addition to these three, the household consisted of Eradicate Sampson, an aged colored servant, and, it might almost be added, his mule Boomerang; but Boomerang had manners that, at times, did not make him a welcome addition to any household. Then there was the giant Koku, one of two big men Tom had brought back with him from the land where the young inventor had been held captive for a time.

The first book of this series is called "Tom Swift and His Motor Cycle," and it was in acquiring possession of that machine that Tom met his friend Mr. Wakefield Damon, who lived in a neighboring town. Mr. Damon owned the motor cycle originally, but when it attempted to climb a tree with him he sold it to Tom.

Tom had many adventures on the machine, and it started him on his inventive career. From then on he had had a series of surprising adventures. He had traveled in his motor boat, in an airship, and then had taken to a submarine. In his electric runabout he showed what the speediest car on the road Could do, and when he sent his wireless message, the details of which can be found set down in the volume of that name, Tom saved the castaways of Earthquake Island.

Tom Swift had many other thrilling escapes, one from among the diamond makers, and another from the caves of ice; and he made the quickest flight on record in his sky racer.

Tom's wizard camera, his great searchlight, his giant cannon, his photo telephone, his aerial warship and the big tunnel he helped to dig, brought him credit, fame, and not a little money. He had not long been back from an expedition to Honduras, dubbed "the land of wonders," when he was again busy en some of his many ideas. And it was to get some relief from his thoughts that he had taken the flight with Mr. Damon on the day the present story opens.

"What are you so excited about, Tom?" asked his friend, as the Hawk alighted near the shed hack of the young inventor's home. "Bless my scarf pin! but any one would think you'd just discovered the true method of squaring the circle."

"Well, it's almost as good as that, and more practical," Tom said, with a smile, as he motioned to Koku to put away the aircraft "I know who that man is, now."

"What man, Tom?"

"The one who was questioning me when I was fixing the airship. I kept puzzling and puzzling as to his identity, and, all at once, it came to me. Do you know who he is, Mr. Damon?"

"No, I can't say that I do, Tom. But, as you say, there was something vaguely familiar about him. It seemed as if I must have seen him before, and yet--"

"That's just the way it struck me. What would you say if I told you that man was Blakeson, of Blakeson and Grinder, the rival tunnel contractors who made such trouble for us?"

"You mean down in Peru, Tom?"

"Yes."

Mr. Damon started in surprise, and then exclaimed:

"Bless my ear mufflers, Tom, but you're right! That was Blakeson! I didn't know him with his beard, but that was Blakeson, all right! Bless my foot-warmer! What do you suppose he is doing around here?"

"I don't know, Mr. Damon, but I'd give a good deal to know. It isn't any good, I'll wager on that. He didn't seem to know me or you, either--unless he did and didn't let on. I suppose it was because of my goggles--and you were gazing up in the air most of the time. I don't think he knew either of us."

"It didn't seem so, Tom. But what is he doing here? Do you think he is working at the army camp, or helping make Liberty Motors for the aircraft that are going to beat the Germans?"

"Hardly. He didn't seem to be connected with the camp. He wanted a mechanic, and hinted that I might do. Jove! if he really didn't know who I was, and finds out, say! won't he be surprised?"

"Rather," agreed Mr Damon. "Well, Tom, I bad a nice little ride. And now I must be getting back. But if you contemplate a trip anywhere, don't forget to let me know."

"I don't count on going anywhere soon," Tom answered. "I have something on hand that will occupy all my time, though I don't just like it. However, I'm going to do my best," and he waved good-bye to Mr. Damon, who went off blessing various parts of his anatomy or clothing, an odd habit he had.

As Tom turned to go into the house, the unsettled look still on his face, some one hailed him.

"I say, Tom. Hello! Wait a minute! I've got something to show you!"

"Oh, hello, Ned Newton!" Called back the young inventor. "Well, if it's Liberty Bonds, you don't need to show me any, for dad and I will buy all we can without seeing them."

"I know that, Tom, and it was a dandy subscription you gave me. I didn't come about that, though I may be around the next time Uncle Sam wants the people to dig down in their socks. This is something different," and Ned Newton, a young banker of Shopton and a lifelong friend of Tom's, drew a paper from his pocket as he advanced across the lawn.

"There, Tom Swift!" he cried, flipping out an illustrated page, evidently from some illustrated newspaper. "There's the very latest from the other side. A London banker friend of mine sent it to me, and it got past the censor all right. It's the first authentic photograph of the newest and biggest British tank. Isn't that a wonder?"

Ned held up the paper which had in it a fullpage photograph of a monster tank--those weird machines traveling on endless steel belts of caterpillar construction, armored, riveted and plated, with machine guns bristling here and there.

"Isn't that great, Tom? Can you beat it? It's the most wonderful machine of the age, even counting some of yours. Can you beat it?"

Tom took the paper indifferently, and his manner surprised his chum.

"Well, what's the matter, Tom?" asked Ned. "Don't you think that great? Why don't you say something? You don't mean to say you've seen that picture before?"

"No, Ned."

"Then what's the matter with you? Isn't that wonderful?"