whence the rockets had been fired there now suddenly flared up a
great reach of flames.

Watching these, the interested aviators saw them change to a reddish
hue. Three times, at brief intervals, they did this.

"Don't you see?" persisted Hiram.

"See what?" asked Dave.

"A signal."

"You think so?"

"I surely do. Now, then, look sharp. There are figures about the
fire. The fire is pitch or oil, or something that could be made to
flame up quickly. One of the men threw something into it from a
box. It was red fire."

"Why, yes," observed Dave slowly. "I'll admit that was some kind of
a signal."

"For the airship," interrupted Hiram quickly. "Look, look again,
Dave! One of the men is shading his eyes from the glare of the
fire, and is looking straight up into the sky. Why, it's plain as
day. They saw our airship when that searchlight caught us. They
were waiting for an airship to come along."

"Another airship than ours, you mean?"