hed."

"And now, Joe, tell me all about it!" demanded Helen, when the circus
was over for the afternoon, and the box and vanishing tricks had been
successfully performed. "What happened to your trapeze?"

"Some one spilled acid on one of the wire ropes, and it ate into the
metal, corroding it and separating a number of the strands so that a
little extra weight broke them," said Joe.

"Acid on the cable?" cried Helen. "How did you find out?"

"I just examined the wire. I knew it couldn't have rusted naturally in
such a short time. There was a peculiar smell about the wire, and I know
enough of chemistry to make a simple acid test! What kind of acid was
used I don't know, but it was strong enough to eat the steel."

"Who could have put it on?"

"That I've got to find out!"

"Was it Harry Loper?"

"I taxed him with it, but he swears he knew nothing of it," said Joe.
"I'm inclined to believe him, too. I charged him with drinking, and he
could not deny that. But he said he met some old friends and they
induced him to have a little convivial time with them. No, I don't
believe he'd do it. He's weak and foolish, but he had no reason to try
to injure me."

"Who would, Joe? Of course there's Bill Carfax, but he hasn't been seen
near the circus of late."

"No, I don't believe it could have been Bill. I'll have to be on my
guard."

"Do, Joe!" urged Helen. "Oh, I can't bear to think of it!"

"Don't then!" laughed Joe, trying to make light of it. "Let's go down
town and I'll buy you some ice cream."

"But you're not going to give up trying to find out who put acid on the
trapeze, are you?"

"No, indeed!" declared the young performer. "I have two problems on my
hands now--that and trying to learn how too many persons came to the
circus this afternoon," and he told Helen about the extra tickets.

"That's queer!" she exclaimed. "Some jinx bug must be after us!"

"Don't get superstitious!" warned Joe. "Now we'll forget our troubles.
They may not amount to anything after all."

But, though he spoke lightly, Joe was worried, and he was not going to
let Helen know that. They went into an ice-cream parlor and "relaxed,"
as Helen called it.

The two were on their way back to the circus lot, intending to go to
supper and prepare for the evening entertainment, when there was a
sudden alarm down the street, and, in an instant, the fire engines and
other apparatus dashed past.

"A fire!" cried Joe. "Come on, Helen! It's