“I certainly didn’t,” declared Joe.  “Who in the world could have put it there?”

“Have you any enemies?” asked Ham.  “I mean some one who would like to see your circus acts spoiled, or even see you laid up for a while?”

“Well, I guess perhaps there are some I’ve made enemies of by having to discharge them, or something like that,” admitted Joe, his thoughts going naturally to Bill Carfax.  “There’s one man, but he hasn’t been seen around for a good while.”

“That doesn’t count.  He may have gotten some one to do his trick for him,” asserted Ham.  “You’d better look out, Mr. Strong.”

“I will!” declared Joe.  “And thank you for your watchfulness.  As you say, I didn’t know that bottle was there, and I might have broken it by accident or have opened it and spilled some out.  How did you come to discover it?”

“Just by accident.  The smell is something you never forget.  It comes up even around the glass stopper.  As soon as I began overhauling your things, as you told me to, I smelled the stuff and I went on a still hunt for it.

“I was careful, too.  I knew what it meant to get any of that acid on you, or on any of the things about you.  I used to work in the chemical plant where they made the stuff—­that was after I left the circus.  Well, it can’t do any harm now,” he said as he got a shovel and covered with clean earth the bits of broken glass and the still fuming drops of add.

“Thank you,” said Joe fervently.

He went into his private tent.  Presently he came out with a bit of wire cable, such as is used in making circus trapezes.  One end was blackened and partly fused, as though it had been in the fire.  Joe held out this bit of wire rope.  It was part of the trapeze he used in his big swing.

“What would you say had eaten through these strands?” he asked.

Ham Logan looked carefully at the cable.  He sniffed it cautiously.  He held it up to the light and again smelled it.

“It was this same acid that ate those strands,” he declared.  “I know how it used to eat metal out at the chemical works, and it does so in a queer way.  This wire rope is eaten through just like that.  There isn’t any odor left, though sometimes it lasts a long time.  But I’m sure the same kind of acid was used.  You don’t mean to tell me you have been experimenting with it!” and he looked in surprise at Joe.

“No indeed!” and the young fire-eater shook his head.  “I never handle the acid.  And the fact that the cable was eaten through nearly caused an accident.”  He then explained how he had discovered the partly severed wire rope just in time.

“They must have put on a weak solution of the acid,” declared Ham.  “Otherwise it would have eaten the rope through in jig time.  So that’s the game, is it?  Well, they may have been trying it on a larger scale.  Did you find out who doped the rope?”

“There was a man who might have done it,” said Joe, thinking of Harry Loper.  “But I don’t believe he did.”