"Cheerful thing to fight against, isn't it?" he asked, with a smile. "Tactics, mustn't run above the black flyer and mustn't run below it. He can probably shoot it straight down, too." "And almost certainly from the sides," said Teddy. "The man must have been working on this thing for years, and even if he's insane he'd be a fool not to make his weapon as efficient as possible." Davis' expression became rueful. "And so I'm supposed to keep my distance," he remarked, "and take pot shots at him while dancing merrily around in mid-air. Can't we do anything about that stuff to nullify it?" "Burn it," suggested Evelyn. "Liquid hydrogen burns just as readily as the same gas at normal temperatures." The three of them were silent for a moment. "Would rockets set it afire?" asked Davis presently. "I could keep a stream of fire balls shooting out before my machine." "They ought to." Teddy was losing his discouragement in this new prospect of coming to grips with Varrhus. "I say, will your machine burn readily?" "Only the gas tank. The wings and struts are fireproof. New process." Davis stood up suddenly. "Would it bother you to come over and look at my machine? We could probably figure out the thing better then." Teddy rose almost enthusiastically. "We'll go over now if you say so." The taxicab bearing Teddy and the young aviator down to the fort was forced to travel slowly amid the throngs of apprehensive people that overflowed the sidewalks and made the streets almost impassable. The launch took them swiftly to the fort, and in a few moments they had arrived at the small aviation field behind the fortifications on Staten Island. Davis led Teddy directly to the shed that contained the swift machine of which he was so proud. It was a splendid product of the aircraft maker's art. Twin Liberty Motors developed nearly eight hundred horse power between them, and two great shining propellers pulled the machine through the air with irresistible force. "You see," said Davis, with some enthusiasm, "the motors aren't in the fusilage, so the gunner sits up here in the bow and can fire freely in any direction. The one-man planes with synchronized machine guns firing through the propeller aren't in it with these for real fighting. They're splendid little machines--I drove one in France--but I honestly believe this is better than they are. This one responds to the controls every bit as readily, and with a good gunner----" "Machine gunner in France myself," said Teddy, touching his breast. "Would you take a chance on letting me sit up front to-night?" "To-night?" asked Davis. "I believe Varrhus will appear to drop another cold bomb to-night. It will probably be dropped inside the harbor so the ice cake will touch the Battery. That will set the people frantic, and make them beg the government to enter into a parley with Varrhus. It's paid no official attention to him so far, you know." Davis' expression became keen and rather stern.