scientific gentleman of note but particularly an aviator bent on startling the world through the agency of a monster seaplane which he had invented. He believed that a voyage across the ocean could easily be made in one of his safe aircraft, which combined many features not as yet in common use among the most advanced aviators. On Brig Island in Casco Bay, within sight of the Maine coast, they erected their factory, and manufactured various types of aëroplanes for the market. So far this wonderful seaplane had not been given to the world, for Doctor Perkins was shrewd enough to first get his patents in all foreign countries in order to protect his interests. In The Boy Aviators’ Flight for a Fortune have been related a series of remarkable adventures that befell the young air pilots when trying out the first of these enormous hydro-aëroplanes, that would skim along the water or sail through the air with equal swiftness and safety.
One of these enormous seaplanes had been boxed in sections and shipped over to France, with the design of giving the Government officials an actual exhibition before they would agree to making a large contract with the firm.
Then the terrible world war had broken out, and for some months it was not known just what had become of the precious machine.
Finally word was received that it was safe at Havre, under the protection of the French Government, which would adhere strictly to the letter of the written agreement which they had entered into with the American company.
An urgent request was sent across the sea for some competent aviators to come over and put the several parts together, so that an actual test could be made. The French Government, if the trial proved convincing, stood ready to make almost any kind of contract with the company. This would be either in the way of ordering a large number of seaplanes, providing they could be delivered without breaking the neutrality laws binding the United States, or else giving a royalty on each and every machine manufactured in France under the patents granted to the doctor.
This necessary but brief explanation puts the reader, who may not have previously known Frank and his chums, in possession of facts concerning their past. While Pudge Perkins, the doctor’s son, was not an experienced aviator, he had picked up more or less general knowledge in the factory, and had come abroad with Frank and Billy, as he was accustomed to say, just to “keep them from dying of the blues, in case the French Government kept putting them off from week to week, or if anything else disagreeable happened.”
Indeed, Pudge, with his abounding good nature, his love for fun, and great capacity for eating, might be looked upon as a pretty fine antidote for the dread disease known as the “blues.” No one could long remain depressed in mind when he was around. Besides, Pudge was really smarter than he looked; appearances in his case were apt to be deceptive; for the boy had a fund of native sagacity back of his jolly ways.
Their hangar had been built in a rather lonely spot close to the water. This was done for several purposes, chief among which might be mentioned their desire to avoid publicity.
The obliging French authorities had even placed a guard at the point where the road passed the open spot now enclosed with a high fence; and so effectual had this proved that up to now the Americans had really not been annoyed to any extent.
Frank, however, had known for some time that all their movements were being watched from different elevated stations in the way of hilltops, or the roofs of houses, by men who carried field glasses. He had many times caught the glint of the sun on the lens when a movement was made.
As long as it went no further than that Frank had not cared, because these suspected spies could see next to nothing. But of late serious fears had begun to annoy him. The seaplane was ready for its first trip, and in a condition where it might be stolen, if a band of daring men took it into their heads to make the attempt.
At one end of the hangar a long track with a gradual slope ran down to the water, so that the seaplane could be launched in that way if desired. A narrow stairway on the land side led up to the stout door which they always kept fastened with an odd padlock capable of resisting considerable pressure.
Each one of the three boys had a key for this lock, which they were very careful to keep fastened to a steel pocket chain. Pudge, having mounted the stair first, puffing from the exertion, was about to insert his key in the padlock when he was heard to utter an exclamation. The others saw him look closely, and then turn upon them with an expression of mingled alarm and consternation on his round face.
“As sure as you live, boys,” the stout boy gasped, “that’s a bit of wax sticking to our padlock! Someone’s been taking an impression so as to have a duplicate key made!”
CHAPTER II.
THE WORK OF GERMAN SPIES
When that astonishing declaration made by Pudge told the other two boys the nature of his discovery, they also glanced at the suspicious atom of wax sticking to the brass padlock.
“Sure enough, Frank; that it is,” gurgled Billy Barnes.
“There’s no question about it,” admitted Frank, as he took the fragment between his thumb and forefinger, and examined it.
“It wasn’t here when we came around this morning, I’d take my affidavy to that,” declared Billy.
“Dories and dingbats, not a bit of it!” exclaimed Pudge. “That padlock was as clean as a whistle, for I rubbed it with my sleeve to brighten it. There’s been some one snooping around here since then; and I guess they must mean to come back again to-night to steal the seaplane!”
“Open up, and let’s make sure things are all right still,” demanded Frank. “We can settle on some sort of plan to upset their scheme by putting on a new lock, or something like that.”
Pudge, with a trembling hand, managed to insert his key, and upon the door being opened the three boys hurried inside the curious elevated hangar. It had been built with a metal roof, though whether this would really prove bombproof in case of a German air raid, such as had occurred several times, was a question.
“Thank goodness! everything seems to be O. K., boys!” cried Billy, after he had taken a swift survey of the interior, including the monster seaplane built on so advanced a model that there was certainly nothing like it known to aviators.
Frank, too, breathed more freely, for he had not known what to expect.
“Yes,” he went on to say earnestly, “and we ought to be mighty thankful that we’ve managed to get along up to now without having our whole outfit wrecked by a bomb, set on fire by a German spy, or raided some night by a party of unknown persons who would have an interest in keeping the French Government from getting this sample seaplane.”
“My idea is this,” remarked Billy soberly. “They could have done the mischief at almost any time, but some one in authority thought it would be a brighter idea for them to wait until we had finished working on the plane, and then steal it, so that the Germans could copy our model for their army.”
“Gatling guns and grasshoppers, but I think you must be right, Billy,” exploded Pudge. “Haven’t we known that they kept a steady watch on us while we worked away here, even if they couldn’t see much? And many a time we disputed whether those chaps were German spies, or Frenchmen set on guard so as to make sure we didn’t take a notion to fly away some day to the enemy.”
Frank was looking unusually serious, and it could be plainly seen that he had a weight on his mind. The afternoon was near its close; and before long the shadows of a dark February night would be closing in around them.
“One thing sure, boys,” he finally said, “we must not leave our seaplane unguarded another night.”
“Do you think they mean to make away with it tonight, Frank?” demanded Billy.
“In some way they seem to know we’ve finished our work,” came the reply. “It puzzles me to guess how they learned it, when we only this noon notified the French authorities in secret that we were ready for any sort of long-distance test they might wish to order.”
“Must be a leak at Headquarters!” suggested Billy quickly.
“Tamales and terrapins, that would be a nice proposition,