can't
have him here, Mr. Swift, I can arrange to have him sent to a hospital."

"I wouldn't dream of it!" Tom exclaimed. "Let him stay here by all
means. We have plenty of room, and Mrs. Baggert has been wishing for
some one to nurse. Now she has him."

So it was arranged that the chemist should remain at the Swift home,
and he gave a languid assent when they spoke to him of the matter. He
really was much more ill than seemed at first.

But as everything possible had been done, Tom decided to go ahead with
the new idea that had come to him--that of inventing an aerial chemical
fire-fighting machine.

"And if we get a chance, Ned, we'll try to get back those secret
formulae Mr. Baxter claims to have lost," Tom declared. "I have heard
some stories about that fireworks firm, which make me believe there may
be something in Baxter's story."

"All right, Tom, I'm with you any time you need me," Ned promised.

The young inventor lost little time in beginning his operations. As he
had said, the chief need was a fire extinguishing chemical solution or
powder. Tom resolved to try the solution first, as it was easier to
make. With this end in view he proceeded to delve into old and new
chemistry books. He also sought the advice of his father.

And one day, when Ned called, Tom electrified his chum with the
exclamation:

"Well, I'm going to give it a try!"

"What?"

"My aerial chemical fire-fighting apparatus. Of course I only have the
chemical yet. I haven't worked on the carrying apparatus nor decided
how I will attach it to an airship. But I'm going up now with some of
my new solution and drop it on a blaze from above."

"Where are you going to get the fire?" asked Ned. "You can't have a
sky-scraper blaze made to order, you know."

"No, but as this is only an experiment," Tom said, "a big bonfire will
answer the purpose. I'm having Koku and Rad make one now down in our
big meadow. As soon as it gets hot enough and fierce enough, I'll sail
over it in my small machine, drop the extinguisher on it, and see what
happens. Want to come?"

"Sure thing!" cried Ned. "And I hope the experiment is a success!"

"Thanks," murmured Tom. "I'm about ready to start. All I have to do is
to take this tank up with me," and he pointed to one containing his new
mixture. "Of course the arrangement for dumping it out of the aircraft
is very crude," Tom said. "But I can work on that later."

Ned and he were busy putting the can of Tom