Three skilled mechanics, who had helped to construct the apparatus on Eleanor's instructions, shook their heads doubtfully over the completed instrument. "The lady must be crazy," they muttered in private, "if she thinks such a rigamagig can save the world!" The skeptics were, it is true, just a little impressed by the first demonstration. The machine was wheeled into a courtyard adjoining the Research Institute; and its mouth was pointed upward into the mists that precluded visibility above a hundred feet. At a signal, the power was turned on; there came a low whirring, accompanied by blue flashes; and almost instantly, as if some unseen fist had thrust its way through them, the vapors disappeared from a circle of sky about ten degrees across, and the azure of heaven appeared for the first time in many days. Equally impressive was the next experiment. A number of open jars of gelatin were placed against the walls of the building, and the machine was pointed toward them. For half a dozen seconds they were bombarded by the rays; then, upon examination, the gelatin was found to have vanished--to have dissolved despite the intervening glass of the jars, which themselves had seemingly been unaffected! A faint glow of hope came to the girl's mind as she witnessed these results. Could it be that, after all, not everything was lost? A machine that could work such miracles might also perform wonders against the Planetoids! But even as this thought flashed over her, there came another realization--a numb, dull realization that struck her like a hand of lead. On one of the Planetoids, hundreds if not thousands of humans were held--at least, so she judged from the reports of the many that disappeared mysteriously after setting out to see Gates dangled from the web of the invaders. Worst of all! The man she loved was a prisoner! If she destroyed the Planetoids, she would destroy Ronald! And after that, though the world lived on, what meaning would life have for her? But only for a moment did she hesitate. They had reached a point where the fate of individuals did not matter. The sacrifice of all the captives, lamentable as it would be--the sacrifice of her lover--the sacrifice of herself--what did all this count beside the future of the human race? Gritting her teeth and clenching her fists, she turned back to the Electronic Space Ray. Her eyes were desolate but her manner was determined as she picked up the range finder and revolved the telescope through a newly cleared circle of blue sky. CHAPTER XII Prelude to Battle