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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

"What other fellows?" asked Mr. Damon.

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

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

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

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

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

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

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

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

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

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