Tom made a gesture of disappointment, and swung his craft around in a
sharp, banking turn. He had no more chemicals to drop, as he had
thought this supply would be sufficient. However, he had guessed badly.
The fire burned on, doing no damage, of course, for that had been
thought of when it was started in the meadow.

"Something wrong!" declared the young inventor, when they were back at
the hangar, climbing out of the machine.

"What was it?" asked Ned.

"Didn't use the right kind of chemicals," Tom answered. "From the way
the flames shot up, you'd think I had poured oil on the blaze instead
of carbon dioxide."

"Bless my insurance policy, Tom!" cried Mr. Damon, "but I'd hate to
trust to your apparatus if my house caught."

"Don't blame you," Tom assented. "But I'll do the trick yet! This is
only a starter!"

During the next two weeks the young inventor worked hard in his
laboratory, Mr. Swift sometimes helping him, but more often Koku and
Eradicate. Mr. Baxter had recovered sufficiently to leave the Swift
home. But though the chemist seemed well physically, his mind appeared
to be brooding over his loss.

"If I could only get my secret formulae back!" he sighed, as he thanked
Tom for his kindness. "I'm sure Field and Melling have them. And I
believe they got them the night of the fireworks blaze; the scoundrels!"

"Well, if I can help you, please let me," begged Tom. And then he
dismissed the matter from his mind in his anxiety to hit upon the right
chemical mixture for putting out fires from the air.

One afternoon, at the end of a week in which he had been busily and
steadily engaged on this work, Tom finally moved away from his
laboratory table with a sigh of relief, and, turning to Eradicate, who
had been helping him, exclaimed:

"Well, I think I have it now!"

"Good lan' ob massy, I hopes so!" exclaimed the colored man. "It sho'
do smell bad enough, Massa Tom, to make any fire go an' run an' drown
hisse'f! Whew-up! It's turrible stuff!"

"Yes, it isn't very pleasant," Tom agreed, with a smile. "Though I am
getting rather used to it. But when it's in a metal tube it won't
smell, and I think it will put out any fire that ever started. We'll
give it a test now, Rad. Just take that flask of red stuff and pour it
into this one of yellow. I'll go out and light the bonfire, and we'll
make a small test."

Leaving Rad to mix some of the chemicals, a task the colored man had
often done before, Tom we