When, presently, he had finished his simple preparations and everything was ready for the grand finale, he gave the signal that Billy was expectantly awaiting.
“Open up, Billy!”
Immediately both wide doors flew back, for the boys had arranged things so that it required but a simple movement to accomplish this. Then Billy hustled toward the seaplane, which no longer stood there like a black shadow; for Frank had, with the pressure of his finger, caused the powerful searchlight placed in the bow of the remarkable craft to flood the space in front of the hangar down to and out on the water of the harbor.
Billy swung himself aboard almost in the twinkling of an eye. Then a lever was manipulated and with a rush the monster seaplane started. Even as it left the shelter of the building, Billy, hanging on with nervous hands, could see several figures in the dazzling flood of white light spring wildly aside so as to avoid being crushed by the oncoming giant seaplane as it tore down the inclined track leading to the water.
CHAPTER IV.
THE ESCAPE.
Ahead of them lay that track of dazzling light. Every fragment of timber used in the construction of the inclined trestle upon which the seaplane was expected to reach the water was as plainly visible as at midday, with the sun shining above.
Billy fairly held his breath in fear lest the swift rush of the hydro-aëroplane should catch the two men on the slope unprepared, and hurl them into space. Just in the nick of time they threw themselves to one side, and the plunging monster glided by, so close that had he so willed, Billy could have thrust out a hand and touched one of the shrinking figures.
Then came a tremendous splash as they struck the water. Frank had made his calculations so carefully that there was not the slightest danger of a mishap. The boat was descending at such an angle that it instantly shot off the wheels that were underneath, and skimmed along the surface of the water like a great duck.
Billy drew his breath again, for it seemed as though they had actually run the gauntlet in safety. He heard the familiar throb of the reliable motors beginning to take up their sweet song, which told that Frank had started the machinery at the proper second, so that they did not lose any of the impetus gained in that rush down the slope.