eye every time you looked at him. And it spurred me on to keeping closer tab over his ways."

"Are they still up there, d'ye think?" queried Frank; while Larry, Elephant, and Stuttering Nat hung around, saying nothing, but listening for all they were worth.

"No," replied Andy; "I've got an idea they began to suspect some of you were looking that way. Anyhow, I saw Marsh duck his head, and think they came down. No use going in to take a shy at 'em now."

"I'd give a fit to know what they are up to?" mused Frank, a thoughtful look on his face.

"Well, perhaps we can hit somewhere near the facts if we start guessing," remarked Andy, with a knowing nod.

"Look here, you've been turning it over your mind, then?" asked his cousin.

"Sure I have," grinned Andy, promptly. "Never could bear to let anything puzzle me long. Used to lie awake half the night trying to clinch a name that had just slipped a cog in my memory."

"All right. Suppose you give us the benefit of what you decided might be the answer to this problem. Who are these two men, Andy?"

"You know they admit being well up in aviation?" the other remarked as a preliminary.

"So Larry and Elephant said," Frank replied.

"And that not only had they attended many meets but admitted being well acquainted with a lot of people whose names we see in the papers every day—men who have done things along the line of aviation. Get that, Frank?"

"I have. Now go on with your answer," nodded the other, encouragingly.

"These gentlemen have been sent up here for a purpose! Perhaps they are in the pay of some unscrupulous manufacturer of aeroplanes, who would not be above stealing the ideas of two boys, and applying them to his up-to-date machines, placed on the market, and for sale to the public!"

"Gosh!" exclaimed Elephant.

"That sounds all to the good to me!" remarked Larry; while Nat tried to express himself intelligently along similar lines; but being suddenly seized with one of his spasms, was obliged to take it out in numerous mouthings, and a working of his facial muscles, all the while making unintelligible sounds.

Frank seemed to consider this startling proposition of his cousin, for there were lines about his forehead, and his eyes took on a reflective look.

"Now, I can see already that you don't agree with me wholly," Andy said, quickly for he was accustomed to studying that countenance of his cousin, and could read between the lines.

"Well, I'd hate to think that any maker of aeroplanes could descend that low as to want to steal ideas from any one," Frank answered. "They are few in number, and so far as we know, honorable men. If they wanted to get something that you and I, or any other fellow, had happened to hit on, and which would be of value to aviators, the chances are they'd send somebody to open up negotiations, and offer to buy the improvement outright, or take it on a royalty basis."

"Perhaps you're right, Frank," admitted the other; "but all the same there was something I didn't like about that Mr. Marsh. I warrant you he's a sharp one in a dicker. He looked it. But see here, what've you got to offer in place of my poor little kicked-out suggestion? There's some sort of answer to the puzzle; and five to one you've guessed it."

Frank laughed as he replied:

"Hold on, now, I may be just as far off as you are. As usual we look at things on opposite sides, you know, Andy. But we never disagree, and that's one good thing about our partnership. Either you convince me, or I show you."

"Sure we do, Frank; and nine times out of ten it's your game. When I make a hit it's a great day for Andy Bird. But please hurry up, and tell us what you think!"

"Yes," said Larry, who had been moving restlessly about, being consumed with the fever of curiosity, "who do you say Mr. Marsh and his friend are, Frank?"

"To begin with, just as you did, the fact that they admit knowing many people connected with the game, strengthens my suspicion. I too believe they may be connected with some maker of aeroplanes like the Wrights; but instead of being sent up here to steal our ideas, they have come as detectives, to find out if the Bird boys have been lifting any patented inventions belonging to their employers!"

"Whew! that takes my breath away!" gasped Andy.

"It's sure a screamer, that's what!" cried Larry.

"Frank, go up head!" said Elephant, solemnly.

Stammering Nat wanted to say something the worst kind; but being still under the domination of his nervous excitement, he could only work his jaws and violently nod his head; but then that stood for acclamation on his part, and so they all understood it.

"Frank, I begin to cave already," declared Andy. "Because that would account for the way they stared so hard at our hydroplane, and the aluminum pontoons under the body. But we bought those from the patentee, and have the bill of sale to show for it."

"And there isn't a single stolen idea about the machine," Frank went on. "I've been mighty careful about that. I believe in an inventor having full credit for his work. If ever I do happen on a valuable device, I would want to feel that it couldn't be stolen away from me."

"Listen, boys," Larry spoke up. "That would account for something that Mr. Marsh said when we were talking to them, before little Tommy took our attention. As near as I can remember I'd been telling them about your shop, and how you fellows just haunted it all winter, working on lots of ideas. He turned to his friend, and he says, says he: 'Longley, they might be willing to let us have a little peep into that wonderful shop of theirs, eh?'"

"Yes, that sounds interesting," remarked Frank. "Go on, Larry. What did you say to that?"

"Oh! Elephant here took the words right out of my mouth, Frank. He up and says: 'I wouldn't bank too much on that, mister. Both of us are chums of the Bird boys; and if they wouldn't let us come inside their shop all winter, I guess they ain't inviting strangers there!'"

"How did they take that?" continued Frank.

"Mr. Marsh just laughed, and asked the other man what he thought of that. Said it was mighty interesting to run across a couple of bright young inventors so unexpectedly; and that Wright and Curtiss ought to know the Bird boys. Also remarked, as he winked at Longley, that you might be induced to join the big aeroplane makers' trust that was being talked of; but I believed he was just joshing when he said that, Frank."

"It's all in the wash, though, and mighty interesting," Frank continued, still thoughtful.

"And you can take it from me, them gentlemen never just happened on
Bloomsbury, like they said," Elephant declared, emphatically.

"I agree with you there, Elephant," Frank echoed. "They came here to do something. It may be as Andy said, to steal our thunder, if so be we had anything worth lifting; and then again my idea may be the right one, and that they represent owners of patents who are determined to protect their rights in things they've spent time and money in perfecting. Perhaps we may never know the truth. And then again before many days, or even hours, we might run across the answer."

"Well," remarked Andy, complacently, "one thing sure, we've got to take extra measures to protect our shop, and keep prying fingers from meddling. I'll speak to my father and Colonel Josiah about it. They may hire old Shea again to watch of