Since then these survivors and their descendants had been voyaging through space on their marvelous disc. For hundreds of years they had given no thought to the future, content to drift on and on in the interstellar void, breathing an atmosphere produced artificially. But at length the inevitable had happened. This superb piece of mechanism devised by their super-genius, Ravv, was beginning to show signs of wear. Some of its mighty engines were nearing the exhaustion point. Either they must soon find a planet comparable with the one they had once known, where they could pause and rehabilitate their machinery, or they must disintegrate and pass into oblivion. Faced with that crisis, Cor had long been seeking such a planet. He had found it, at last, in the earth--and had resolved that this was where they were going to alight and transplant the civilization of ancient Vada, pending such time as they could take to space again. * * * * * For some months now they had been hovering over various portions of the earth, studying its geography and its peoples, with the result that they had concluded the United States offered the most logical point for launching the attack. Once this country was subdued, they were in possession of the richest and most advanced section of the planet. The conquest of the rest of it could await their leisure. With such an invasion in view, their scientists had mastered the language of the country. This had been accomplished very easily, since in addition to their power of mingling with the populace in an invisible form, they had the principles of radio developed to a high degree and were able to tune in on any station they wanted. Kendrick sat there, stunned, as Cor followed his astounding revelation of their origin with this calm plan for the conquest of America, of the world. Why, of all people on earth, had he alone been singled out for this disclosure? He asked the question now. "My dear Professor, can't you really guess?" replied Cor, with that leathery smile. "Hasn't it dawned that you were a little too near our own field with that machine of yours? A trifle more research, a slightly different application--and you would have become a dangerous enemy." "You--you mean--?" "I mean there isn't a great deal of difference between the experiments you have been making and those our great Ravv once made. For instance, had you broadcast your heatricity, as you call it, instead of trying to transmit it on wires--well, picture a receiving apparatus in each home of the land, like your commercial radio sets. You would have become a billionaire, don't you see?" * * * * * Kendrick saw indeed. It was simple, so simple! Fool--why hadn't he thought of it?