“And that’s what it is, Ned.”

“Not one of those you’re going to use on your aerial warship, is it, Tom?”

“Not exactly.  I never saw this before, but it’s what started the fire in the red shed all right; I’m sure of that.”

“Do you really mean it?” cried Ned.

“I sure do.”

“Well, if that’s the case, I wouldn’t leave such dangerous things around where there are explosives, Tom.”

“I didn’t, Ned.  I wouldn’t have had this within a hundred miles of my shed, if I could have had my way.  It’s a fire bomb, and it was set to go off at a certain time.  Only I think something went wrong, and the bomb started a fire ahead of time.

“If it had worked at night, when we were all asleep, we might not have put the fire out so easily.  This sure is suspicious!  I’m glad you found this, Koku.”

Tom was carefully examining the bomb, as Ned had correctly named it.  The bank clerk, now that he was assured by his chum that the, object had done all the harm it could, approached closer.

What he saw was merely a hollow shell of iron, with a small opening in it, as though intended for a place through which to put a charge of explosives and a fuse.

“But there was no explosion, Tom,” explained Ned.

“I know it,” said Tom quietly.  “It wasn’t an explosive bomb.  Smell that!”

He held the object under Ned’s nose so suddenly that the young bank clerk jumped back.

“Oh, don’t get nervous,” laughed Tom.  “It can’t hurt you now.  But what does that smell like?”

Ned sniffed, sniffed again, thought for a moment, and then sniffed a third time.

“Why,” he said slowly, “I don’t just know the name of it, but it’s that funny stuff you mix up sometimes to put in the oxygen tanks when we go up in the rarefied atmosphere in the balloon or airship.”

“Manganese and potash,” spoke Tom.  “That and two or three other things that form a chemical combination which goes off by itself of spontaneous combustion after a certain time.  Only the person who put this bomb together didn’t get the chemical mixture just right, and it went off ahead of time; for which we have to be duly thankful.”

“Do you really think that, Tom?” cried Ned.

“I’m positive of it,” was the quiet answer.

“Why—­why—­that would mean some one tried to set fire to the red shed, Tom!”

“They not only tried it, but did it,” responded Tom, more coolly than seemed natural under the circumstances.  “Only for the fact that the mixture went off before it was intended to, and found us all alert and ready—­well, I don’t like to think what might have happened,” and Tom cast a look about at his group of buildings with their valuable contents.

“You mean some one purposely put that bomb in the red shed, Tom?”

“That’s exactly what I mean.  Some enemy, who wanted to do me an injury, planned this thing deliberately.  He filled this steel shell with chemicals which, of themselves, after a certain time, would send out a hot tongue of flame through this hole,” and Tom pointed to the opening in the round steel shell.