asked for my telegram?"

"No, I've never seen him before as far as I know."

"Same here. Come on."

"What are you going to do?"

"Go back to the airship, and tell Mr. Nestor. As one of the directors
in the concern I'm working for. I want his advice."

"Good idea," replied Ned, and they turned to leave the office. The
spying stranger, and William Eckert, were not in sight when the two
lads came out.

"They got away mighty quick," remarked Tom, as he looked up and down
the street.

"Yes, they probably saw us turn to come out, and made a quick get-away.
They might be in any one of these places along here," for the street,
on either side of the telegraph office, contained a number of hotels,
with doors opening on the sidewalk.

"They must be on your trail yet," decided Mr. Nestor when Tom, reaching
the anchored airship, told what had happened. "Well, my advice is to go
to Africa as soon as we can. In that way we'll leave them behind, and
they won't have any chance to get your camera."

"But what I can't understand," said Tom, "is how they knew I was coming
here. It was just as if that one man had been waiting in the telegraph
office for me to appear. I'm sorry, now, that I mentioned to Ned where
we were ordered to. But I didn't think."

"They probably knew, anyway," was Mr. Nestor's opinion. "I think this
may explain it. The rival concern in New York has been keeping track of
Mr. Period's movements. Probably they have a paid spy who may be in his
employ. They knew when he sent you a telegram, what it contained, and
where it was directed to. Then, of course, they knew you would call
here for it. What they did not know was when you would come, and so
they had to wait. That one spy was on guard, and, as soon as you came,
he went and summoned Eckert, who was waiting somewhere in the
neighborhood."

"Bless my detective story!" cried Mr. Damon. "What a state of affairs!
They ought to be arrested, Tom."

"It would be useless," said Mr. Nestor. "They are probably far enough
away by this time. Or else they have put others on Tom's track."

"I'll fight my own battles!" exclaimed the young inventor. "I don't go
much on the police in a case like this, especially foreign police.
Well, my camera is all right, so far," he went on, as he took a look at
it, in the compartment where he kept it. "Some one must always remain
near it, after this. But we'll soon start for Africa, to get some
pictures of a native battle. I hope