Once more he set the material ablaze and put it into his mouth.  Bill Watson watched closely, and, at the end, the old clown shook his head.

“I saw you actually put the fire in your mouth,” he testified.  “No one can do more than that.  It takes nerve!”

Of course, no one can actually swallow fire and live.  The slightest breath of flame on the lungs or on the mucous membrane of the throat and passages is fatal.  So when the terms “fire-eating” or “fire-eater” are used it will be in the sense of its being a theatrical act.  There is a trick about it, and the trick is this: 

In the first place, the flame itself is produced by blazing alcohol.  This produces a blaze, and a hot one, too, but there is no smoke.  In other words, the combustion is almost perfect, there being no residue of carbon to remain hot after the actual flame is extinguished.

And now as to the actual putting into one’s mouth something that is blazing hot:  It all depends on a very simple principle.

If the hand be thoroughly wet in water it may be safely thrust for a fraction of a second into a flaming gas jet.  But mark this—­for the fraction of a second only.  The water forms a protecting film for the skin, and before it is evaporated the hand must be taken out of danger.  In other words, there is needed an appreciable time for the fire to beat the skin to the burning point.

This immunity from burns, to which the professional fire-eaters owe their success, comes from this film of moisture on their skin.  They do not always use water—­in fact, this is only serviceable for a momentary contact with flame, and, at that, on the hands or face.  In case a longer contact is desired, a fire-resisting chemical liquid is used.

It is about the contact of flame with the tender mucous membrane surfaces of the mouth and throat that Joe, as a fire-eater, was most concerned.

In the first place, there is a constant film of the secretion called saliva always flowing in the mouth.  It comes from glands in the throat and mouth, and is very necessary to good digestion.

Now, for a very brief period this saliva, which is just the same as a film of water on the hand, resists the fire.  But professional fire-eaters do not depend on saliva alone.  They use a chemical solution, and this is what Joe did when he drank something from a glass.

What that chemical solution was, Joe kept as a closely guarded professional secret.  He feared, too, that some boy might make it, rinse his mouth out with it, and then, getting an audience of his chums together, might try to eat some blazing coals.  He might, and very likely would, be severely burned, and his parents or those in charge of him would blame Joe for allowing such dangerous information to leak out.

So, though he guarded all his secrets of magic, he was particularly careful to 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.