Tom had put the silencer on a larger machine than the one he and Jackson had used. It held three easily, and, on a pinch, four could be carried. Tom"s plan was to take Mr. Damon and Mr. Terrill, fly with them for some time in the air, and demonstrate how quiet his new craft was. Then, by contrast, a machine without the m.u.f.fler and the new motor with its improved propellers would be flown, making as much noise as the usual craft did.
"I only wish," said Tom, as the time arrived for the official government test, "that Mary could be here to see it. She was the one who really started me on this idea, so to speak, as it was because I couldn"t talk to her that I decided to get up a silent motor."
But Mary Nestor was too grief-stricken over her missing father to come to the test, which was to take place late one afternoon, starting from the aerodrome of the Swift plant.
"First," said Tom, to Mr. Terrill, "I"ll show you how the machine works on the ground. I"ll run the motor while the plane is held down by means of ropes and blocks. Then we"ll go up in it."
"That suits me," said the agent. "If it does all you say it will do, and as much as I believe it will do, Uncle Sam will be your debtor, Mr.
Swift."
"Well, we"ll see," said Tom with a smile.
Preparations were made with the greatest care, and Tom went over every detail of the machine twice to make certain that, in spite of the precautions, no spy had done any hidden damage, that might be manifested at an inopportune moment. But everything seemed all right, and, finally, the motor was started, while Mr. Terrill, and some of his colleagues from the Army Aviation department looked on.
"Contact!" cried Tom, as Jackson indicated that the compression had been made.
The mechanic nodded, gave the big propeller blades a quarter turn and jumped back. In an instant the motor was operating, and the craft would have leaped forward and cleaved the air but for the holding ropes and blocks. Tom speeded the machinery up to almost the last notch, but those in the aerodrome hardly heard a sound. It was as though some great, silent dynamo were working.
"Fine!"
"Wonderful!"
"Wouldn"t have believed it possible!"
These were some of the comments of the government inspectors.
"And now for the final test--that in the air," said Mr. Terrill.
Previous to this he and his colleagues had made a minute examination of the machinery, and had been shown the interior construction of the silencer by means of one built so that a sectional view could be had.
Tom"s principles were p.r.o.nounced fundamental and simple.
"So simple, in fact, that it is a wonder no one thought of it before,"
said a navy aviation expert. "It is the last word in aircraft construction--a silent motor that will not apprise the enemy of its approach! You have done wonders, Mr. Swift!"
"I"d rather hear you say that after the air test," replied Tom, with a laugh. "Are you ready, Mr. Terrill?"
"Whenever you are."
"How about you, Mr. Damon?"
"Oh, I"m always ready to go with you, Tom Swift. Bless my trench helmet, but you can"t sail any too soon for me!"
There was a genial laugh at his impetuosity, and the three took their seats in the big craft. Once more the engine was started. It operated as silently as before, and the first good impressions were confirmed.
Even as the machine moved along the ground, just previous to taking flight into the air, there was no noise, save the slight crunch made by the wheels. This, of course, would be obviated when Silent Sam was aloft.
Up and up soared the great craft, with Tom at the engine and guide controls, while Mr. Terrill and Mr. Damon sat behind him, both eagerly watching. Mr. Terrill was there to find fault if he could, but he was glad he did not have to.
"The machine works perfectly, Mr. Swift," he said. "My report cannot be otherwise than favorable."
"We mustn"t be in too much of a hurry," said Tom, who had learned caution some time ago. "I want to sail around for several hours.
Sometimes a machine will work well at first, but defects will develop when it is overheated. I"m going to do my best to make a noise with this new motor."
But it seemed impossible. The machinery worked perfectly, and though Silent Sam took his pa.s.sengers high and low, in big circles and small ones, there was no appreciable noise from the motor. The pa.s.sengers could converse as easily, and with as little effort, as in a balloon.
"Of course that isn"t the prime requisite," said Mr. Terrill, "but it is a good one. What we want is a machine that can sail over the enemy"s lines at night without being heard, and I think this one will do it--in fact, I"m sure it will. Of course the ability of the pa.s.sengers to converse and not have to use the uncertain tube is a great advantage."
As Tom Swift sailed on and on, it became evident that the test was going to be a success. The afternoon pa.s.sed, and it began to grow dark, but a glorious full moon came up.
"Shall I take you down?" the young inventor asked Mr. Terrill.
"Not quite yet. I thoroughly enjoy this, and it isn"t often I get a chance for a moonlight airship ride. Go a little lower, if you please, and we"ll see if we attract any attention from the inhabitants of the earth. We"ll see if they can possibly hear the machine, though I don"t see how they can."
And they did not. Tom piloted the machine over Shopton, sailing directly over the center of the town, where there was a big crowd walking about. Though the airship sailed only a few hundred feet above their heads, not a person was aware of it, since the craft"s lights were put out for this test.
"That settles it," said Mr. Terrill. "You have succeeded, Tom Swift!"
But Tom was not yet satisfied. He wanted a longer test. Hardly knowing why he did it he sent the craft in the direction of Mary Nestor"s home.
As he sailed across her lawn he saw, in the moonlight, that she and her mother were walking in the garden. They did not look up as the aircraft pa.s.sed over their heads, and were totally unaware of its presence, unless they caught a glimpse of it as it flitted silently along, like some great bird of the night.
"It is perfectly wonderful!" declared Mr. Terrill, and he spoke in ordinary tones, that carried perfectly to the ears of Tom and Mr. Damon.
"Wonderful!" cried the eccentric man. "Bless my chimney, but it"s the greatest invention in the world! Yes, it is! Don"t tell me it "isn"t!"
And no one did.
Pa.s.sing the Nestor home, the saddened occupants of which were unaware of the pa.s.sage, Tom sent the Air Scout about in a circle, intending to proceed to the hangar. And then, some whim, perhaps, caused him to guide Silent Sam out toward the lonely hut. Mr. Damon and Mr. Tenrill seemed perfectly content to sail on and on indefinitely in the moonlight. Tom thought he would take them over a lonely neighborhood, and then bring them back.
In a little while the craft was directly over the stretch of country where the aeroplane accident had occurred, and where Tom and Jackson had found the deserted hut.
Rather idly Tom looked down, wondering if the Secret Service men were on the watch and if they had discovered anything.
Suddenly Tom was aware of an automobile moving along the field path toward the cabin. There were two men in the car, both on the front seat, and as Tom looked down the brilliant moonlight showed him the figure of another man, behind, and huddled in the tonneau of the car.
The aeroplane was low enough for all these details to be seen by the moon"s gleam, but the men in the car, not hearing any noise, did not look up, so they were unconscious of this aerial espionage.
"Look! Look!" exclaimed Tom in a low voice to his companions. "Doesn"t that seem suspicious?"
CHAPTER XXV
THE GOLD TOOTH
Eagerly Mr. Damon and the government agent leaned over and looked down.
In the moonlight they saw the same sight that had attracted Tom Swift.
The touring car, the two men in front, and the huddled, bound figure in the back.
"Can you go down, Tom, without letting them hear you?" asked Mr. Damon, using a low voice, as if fearful the men in the automobile would hear him.