"Can't you see? Somebody is trying to show us they know how to add. Someone out in space. Keep watching. I wonder if they use duodecimal system, or what? Where is it coming from?" Nautunal dropped his skeptical pose, and watched the emerging tape in silence. The growing table of symbols built all the simple additions up to 10 plus 10, by the laborious accumulation of dots. Then it began again, systematically, "One and one are two, two and two--" Pehn turned his wondering eyes on his friend. "Is this trick? Joke you rigged up for my benefit?" [Illustration: A. D. 2120: "_Is this a trick?_"] Nautunal shook his head, and his voice was hardly a whisper. "No. That stuff is really coming through space--through phase space." Twice more, the table of additions appeared. Then, after a brief pause, came simple multiplications. Hour after hour the signals continued, endlessly repeated, and shortly after midnight the two could recognize the periodic table of chemical elements, with atomic weights and numbers of isotopes. "If those numbers which follow atomic weights are abundances," said Pehn, "composition of their planet is not quite same as ours. Look how rare 235 is. Where do you suppose this is coming from?" "You guess," said Nautunal. He waved his arm towards the transparent dome through which the stars shone, and grinned. "From little data I have so far, signals might be coming from somewhere in Weaver, perhaps from neighborhood of Topaz, but it's too early to be sure of anything." Suddenly a marked change occurred in the pattern of the signals. The clear symmetry of mathematics ended and was replaced by a formless jumble, but a jumble whose repetition suggested that it, too, contained a pattern if it could once be glimpsed. Meters and meters of tape piled up, and the young men stared at it in frustration. Nautunal stood up in sudden decision. "Bidagha is right. There must be intelligent life in another part of galaxy. We need help, Pehn. We can't decipher this stuff, and yet it may be key to basic vocabulary. We need mathematicians, linguists, semanticists. I'll put out call to director." He lifted a finger to activate the visiphone in his wrist band, but before touching it he glanced at his friend in some concern. "But you don't look well. Perhaps you ought to go home and get some sleep?" Pehn shook his head. "No, pain will probably be gone by morning, and at time like this sleep would be only gift from Evil Ones. I'm going to get Bidagha. He'll be more use to us than dozen semanticists." "Call him on visiphone." "You know he can't wear one. He's at Cave tonight, holding Ceremony. I'll go after him." "All right, Pehn. But remember, government will probably disapprove of this business. Whatever you do--don't tell your father!"