keep this one to himself.

But Joe protected his mouth and throat with a fire-resisting liquid, the
formula for which was given him by the chemist to whom he submitted the
circus tickets.

The success of Joe and others of his kind depends also in this on a
well known natural law. It is that there can be no combustion in the
ordinary sense where there is no oxygen. As a candle will surely go out
if enclosed in an air-tight receptacle--that is, it will go out as soon
as it has burned up all the oxygen--just so surely will flame of any
kind go out when a person closes his mouth on it. And as there is
scarcely any air in the closed mouth--all of it going down the bronchial
tubes into the lungs--it follows that the flame dies out almost
instantly. That fact being considered, and the mouth and throat having
been previously treated with the secret chemical, there is really not so
much danger as appears.

As a matter of fact, a person inadvertently swallowing hot tea or coffee
will burn or scald his mouth or tongue much more painfully than will a
professional fire-eater. Most people know how painful a burned tongue
is.

Joe told something of the history of fire-eating "champions" to his
audience of friends, for it appeared that he had been reading up on the
subject and was well informed. Then he announced that the private
rehearsal was over.

"But I'm going to work this fire-eating up into something that will
cause a sensation," he said. And he made good his promise.

It was about a week after this, and the circus had been traveling
about, playing to good business, when Joe received a letter. In the
upper left-hand corner was the imprint of Herbert Waldon, Chemist.

"I hope he has some news about the circus tickets!" exclaimed Joe. For
the show had been losing money steadily by means of the bogus coupons;
not as much as at first, but enough to make it necessary to discover the
fraud. And, so far, Mr. Moyne had not been successful.

"Perhaps this explains the mystery," mused Joe as he opened the letter.

CHAPTER X

THE PET CAT

The typewritten sheet of the letter from Mr. Waldon enclosed two of the
engraved circus coupons. They fluttered to the floor of Joe's private
tent as he tore open the envelope.

"Well, either he has discovered something, or he has sent them back and
given up," mused the young magician. "Let's see what he says."

Joe quickly took in the contents of the letter. In effect it stated t