"Not the least. Of course I know I have enemies, Ned. Every successful inventor has persons who imagine he has stolen their ideas, whether he has ever seen them or not. It may have been one of those persons, or some half-mad crank, who was jealous. It would be impossible to say, Ned."

"It wouldn't be Andy Foger, would it?"

"No; I don't believe Andy has been in this neighborhood for some time.

The last lesson we gave him sickened him, I guess."

"How about those diamond-makers, whose secret you discovered? They wouldn't be trying to get back at you, would they?"

"Well, it's possible, Ned. But I don't imagine so. They seem to have been pretty well broken up. No, I don't believe it was the diamond-makers who put this fire bomb in the red shed. Their line of activities didn't include this branch. It takes a chemist to know just how to blend the things contained in the bomb, and even a good chemist is likely to fail--as this one did, as far as time went."

"What are you going to do about it?" Ned asked.

"I don't know," and Tom spoke slowly, "I hoped I was done with all that sort of thing," he went on; "fighting enemies whom I have never knowingly injured. But it seems they are still after me. Well, Ned, this gives us something to do, at all events."

"You mean trying to find out who these fellows are?"

"Yes; that is, if you are willing to help."

"Well, I guess I am!" cried the bank clerk with sparkling eyes. "I wouldn't ask anything better. We've been in things like this before, Tom, and we'll go in again--and win! I'll help you all I can. Now, let's see if we can pick up any other clues. This is like old times!"

and Ned laughed, for he, like Tom, enjoyed a good "fight," and one in which the odds were against them.

"We sure will have our hands full," declared the young inventor.

"Trying to solve the problem of carrying guns on an aerial warship, and finding out who set this fire."

"Then you're not going to give up your aerial warship idea?"

"No, indeed!" Tom cried. "What made you think that?"

"Well, the way your father spoke--"

"Oh, dear old dad!" exclaimed Tom affectionately. "I don't want to argue with him, but he's dead wrong!"

"Then you are going to make a go of it?"

"I sure am, Ned! All I have to solve is the recoil proposition, and, as soon as we get straightened out from this fire, we'll tackle that problem again--you and I. But I sure would like to know who put this in my red shed," and Tom looked in a puzzled manner at the empty fire bomb he still held.

Tom paused, on his way to the house, to put the bomb in one of his offices.

"No use letting dad know about this," he went on. "It would only be something else for him to worry about."

"That's right," agreed Ned.

By this time nearly all evidences of the fire, except for the blackened ruins of the shed, had been cleared away. High in the air hung a cloud of black smoke, caused by some chemicals that had burned harmlessly save for that pall. Tom Swift had indeed had a lucky escape.

The young inventor, finding his father quieted down and conversing easily with Mr. Damon, who was blessing everything he could think of, motioned to Ned to follow him out of the house again.

"We'll leave dad here," said Tom, "and do a little investigating on our own account. We'll look for clues while they're fresh."

But, it must be confessed, after Tom and Ned had spent the rest of that day in and about the burned shed, they were little wiser than when they started. They found the place where the fire bomb had evidently been placed, right inside the main entrance to the shed. Tom knew it had been there because there were peculiar marks on the charred wood, and a certain queer smell of chemicals that confirmed his belief.

"They put the bomb there to prevent anyone going in at the first alarm and saving anything," Tom said. "They didn't count on the roof burning through first, giving me a chance to use the sand. I made the roof of the red shed flimsy just on that account, so the force of the explosion if one ever came, would be mostly upward. You know the expanding gases, caused by an explosion or by rapid combustion, always do just as electricity does, seek the shortest and easiest route. In this case I made the roof the easiest route."

"A lucky provision," observed Ned.

That night Tom had to confess himself beaten, as far as finding clues was concerned. The empty fire bomb was the only one, and that seemed valueless.

Close questioning of the workmen failed to disclose anything. Tom was particularly anxious to discover if any mysterious strangers had been seen about the works. There was a strict rule about admitting them to the plant, however, and it could not be learned that this had been violated.

"Well, we'll just have to lay that aside for a while," Tom said the next day, when Ned again came to pay a visit. "Now, what do you say to tackling, with me, that recoil problem on the aerial warship?"

"I'm ready, if you are," Ned agreed, "though I know about as much of those things as a snake does about dancing. But I'm game."

The two friends walked out toward the shed where Tom's new craft was housed. As yet Ned had not seen it. On the way they saw Eradicate walking along, talking to himself, as he often did.

"I wonder what he has on his mind," remarked Ned musingly.

"Something does seem to be worrying him," agreed Tom.

As they neared the colored man, they could hear him saying:

"He suah did hab nerve, dat's what he did! De idea ob askin' me all dem questions, an' den wantin' t' know if I'd sell him!"

"What's that, Eradicate?" asked Tom.

"Oh, it's a man I met when I were comin' back from de ash dump,"

Eradicate explained. One of the colored man's duties was to cart ashes away from Tom's various shops, and dump them in a certain swampy lot.

With an old ramshackle cart, and his mule, Boomerang, Eradicate did this task to perfection.

"A man--what sort of a man?" asked Tom, always ready to be suspicious of anything unusual.

"He were a queer man," went on the aged colored helper. "First he stopped me an' asted me fo' a ride. He was a dressed-up gen'man, too, an' I were suah s'prised at him wantin' t' set in mah ole ash cart,"

said Eradicate. "But I done was polite t' him, an' fixed a blanket so's he wouldn't git too dirty. Den he asted me ef I didn't wuk fo' yo', Ma.s.sa Tom, an' of course I says as how I did. Den he asted me about de fire, an' how much damage it done, an' how we put it out. An' he end up by sayin' he'd laik t' buy mah mule, Boomerang, an' he wants t' come heah dis arternoon an' talk t' me about it."

"He does, eh?" cried Tom. "What sort of a man was he, Rad?"

"Well, a gen'man sort ob man, Ma.s.sa Tom. Stranger t' me. I nebber seed him afo'. He suah was monstrous polite t' ole black Eradicate, an' he gib me a half-dollar, too, jest fo' a little ride. But I aint' gwine t'

sell Boomerang, no indeedy, I ain't!" and Eradicate shook his gray, kinky head decidedly.

"Ned, there may be something in this!" said Tom, in an excited whisper to his chum. "I don't like the idea of a mysterious stranger questioning Eradicate!"

CHAPTER VI

THE AERIAL WARSHIP

Ned Newton looked at Tom questioningly. Then he glanced at the unsuspicious colored man, who was industriously polishing the half-dollar the mysterious stranger had given him.