Maybe he could raise them with the radio. The robots' hearing and speaking apparatus extended beyond the range of audible sound into the realm of electro-magnetic waves. He went out to the sun deck, switched on the communicator. He was unable to contact them, though. There was no ionized strata of air on the asteroid to reflect the waves back to the surface, and he concluded they had wandered below the horizon. With a groan, he flung himself into a chair. He pulled the notebook out of his pocket, thumbed through the pages, reading bits here and there. "... machine thought processes diverging from human at progressively increasing rate ... amazing deductive and assimilative faculties. Able to assimilate page of text at a glance. But seem to lack creativeness...." He paused, frowned, wondering if the inability to perform creative, inductive thinking wasn't a fundamental limitation of the machine. Organic life differed in four precepts which until a short time ago science had been unable to duplicate. It was able to grow and reproduce itself; it felt emotion and thought. But the robots appeared to think. And some forms of organic life didn't feel emotion. Plants, for one. The oviparous man-like bowmen of Venus, who had emerged from the Great Swamp and which a few crackpot visionaries were hailing as homo superior, for another. Only the ability to grow and reproduce itself seemed inherently organic. The act of conception both in a biologic and mental sense was the birthright of the organism. With an increase of the uneasiness he had felt since the discovery of the robots' defection, he returned to his notes. "... robots showing aversion to water, oxygen, corrosive acids; believe to be caused by dread and/or attendant pain of oxidation ... have been forced to release air in mine and laboratory and discontinue atmosphere units to induce robots to return to work. Humidity of atmosphere being especially distasteful to them ... treated R-3 for mild acid corrosion of right pedal digit. Complained of itching sensation...." He frowned. How in the hell could a hunk of metal experience an itching sensation? From what source could it have plucked the mental pattern? He came to the end of his notes, wrote: "All work at stand still. Robots have disappeared." He returned the book to his pocket, elevated his feet on another chair, closed his eyes. He was still in that position when Sofi streamed out of her quarters with a towel draped about herself. "Resting the old brain?" she inquired brightly. Hen opened his eyes, said in a pained voice, "I'm thinking," and closed them again. "Which end do you use?" Hen allowed his feet to clomp to the floor, sat up. He said grimly, "The robots have run off." Sofi's blue eyes widened. "Wait a minute," she said breathlessly and flashed from the room. Hen kept his eyes studiously on the deck.