A chorus of cheers went up from the deck of the steamer as its passengers caught sight of the airship. Only for a moment, however, was the brilliant sky picture in view. Dave turned the head of the machine on a volplane sweep, and the searchlight operator could not locate it again. "Well, we've been seen," observed Hiram, "I'm sorry for it," replied Dave simply. "Look there!" cried Hiram abruptly. Dave had selected a course leading over the land, away from the water. As Hiram spoke, his own eye caught sight of some brilliant sparkles of light. It was a rocket, exploding in mid air directly in their course, and it was to this that Hiram Dobbs had directed the attention of the young aviator. CHAPTER XX ACROSS THE BORDER "Did you see it?" asked Hiram, in a great state of excitement. "Yes," responded Dave. "A rocket." "See! See!" continued Hiram-"there's it second one!" "Sure enough." "Dave, this means something." "For us, you think?" "Yes, I do. Keep near the place where these rockets were fired, Dave. Now then, what do you think?" Dave slowed down. There was certainly something to his companion's surmises or suspicions, whatever they were. Directly at the spot 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?" "That's it, and I'll bet the Drifter! They took ours for the Drifter. They want us to land. Why, see there, one of the fellows is looking through a field glass--as if he could make us out in the dark away up here!" It did not take Dave long to drift to Hiram's way of thinking. The spot where the fire showed seemed to be a large yard of some kind, attached to a factory. "Of course this is all guess work, Hiram," said Dave, after a moment's thought. "Just the same, it fits in to your theory." "Say," spoke Hiram suddenly, "I've an idea." "What is it, Hiram?" "Make a stop just as soon as you can." "What's that for?" "Let me out, and give me a chance to find out who that signal was intended for." "I declare, it's not a bad plan," said Dave at once. "Can't you find some safe place where we can land?"