Astounding Stories of Super-Science, August 1930

Henderson Blake was among them, as was Marjorie. She stepped forward, as he prepared to make the demonstration. "I know, somehow, you're going to be successful!" she murmured, pressing his hand, meeting his eyes with a smile of confidence. "I hope you're right--Marjorie!" he replied, letting slip the last word almost unconsciously. Her face colored warmly as the stepped back and rejoined her father. Kendrick's heart was beating fast as he turned to his instruments. How could he fail, with faith like that behind him?--love, even, perhaps! He mustn't fail--nor would he, if his theories were sound. Addressing the assemblage, he explained briefly the complicated apparatus. "These towers," he said, pointing to four steel structures about ten feet high, arranged at the corners of a square roughly twenty feet across, "are miniature radio masts. The area enclosed by them, we will assume, is the city of New York. That metal disc suspended above the area represents the invader. It contains a miniature heat-generator such as I was experimenting with recently in the Arizona desert." He paused, threw a switch. Somewhere in the laboratory a dynamo began to whir. "I am now sending electro-magnetic waves from the four towers," he resumed. "But instead of broadcasting them in every direction. I am bending them in concave cathode of force over the city. You may picture this cathode as an invisible shield, if you choose, but it is more than that. It it a reflector. If my theories are right, the radio-energetic ray I am about to project upon it from my miniature disc will be flung back to its source as though it had been a ray of light falling on a mirror. The success of the experiment depends upon what the result will be."