Now Pelton felt a hand upon his shoulder. Turning he saw that Jerry was standing beside him. The man's face was pale with awe and when he spoke his voice was husky: "Congratulations, Capt. Pelton--here, shake! When it looks black as night, along you come and put those invaders in their proper place. I can't see through this at all. What wonder is it that you have created?" The fulfillment of his ambition beyond the wildest dreams of his school days had wrought the young scientist up to a pitch of excitement more intense than ever before, "It is the thing that killed Calhoun, the ace," he almost shrieked; "The crystal ray!" "You mean that your weapon inflicts death with just a beam of light? That sounds impossible." "But it isn't! I'll tell you about it." Pelton's eyes were glittering and his face was flushed: "Not more than a month and a half ago I was in Ecuador with Calhoun on leave of absence. We explored an extinct Andean volcano of particularly ghastly reputation. There I found a peculiar crystal, which, on analysis proved to be a complex compound of silicon, iron and the hitherto supposedly inert gas, krypton--I call it _andite_. "It was just by chance that I discovered what terrible things _andite_ could do. There was a big block of the material at the crater's western edge. The sun had been obscured by a cloud and, when it came out, its light struck the block, passed through it, and came out as a bluish beam. It hit my old friend and sent him on the long journey west. Thank God, it was not in vain! "After a lot of effort I learned more about the wonderful properties of the crystal. You know that light is the vibration of an all-pervading medium sometimes called the ether, just as are radio waves. When a beam of light passes through _andite_, its rate of vibration is enormously increased; so that it exceeds by many thousands of times the vibratory rate of even Hadley's Q-ray which is used as an anaesthetic. This super-vibration is the crystal ray. It will penetrate four feet of solid lead and a much greater thickness of any other metal. When it strikes a man it produces within his blood a poison that is instantly fatal. The process is comparable with that which goes on in the leaves of a plant when starch is produced by the action of sunlight. "The projectors of the crystal ray are merely specially constructed radio lamps, equipped with a receiver of wireless power, and fitted with a piece of _andite_ which modifies the light. "After I had learned what my discovery was capable of, I staged a demonstration before the best minds of America. They gave me the cooperation of the whole country and this is the result." "But what was the necessity of building this enormous power plant?" inquired Jerry: "Couldn't the old stations supply the needed energy?"