“Check. Let our minds—mine, anyway—get over the jitters and collywobbles.” “Mine, too, brother; and I’ve got a sort of feeling that what that mind of yours is going to develop into, little by little, is something slightly different from ordinary telepathy. But in the meantime, you’d better get back to work.” “I don’t know whether I can work up much enthusiasm for work right now or not.” “Sure you can, if you try. What were you doing to that chart when I came in? What have you got there, anyway?” “Come on over and I’ll show you.” They bent over the work-table, heads almost touching. “The pink area is the explored part of the First Galaxy. The marks represent all the loose vortices I know of. I’ve been applying all the criteria I can think of to give me some kind of a toe-hold, but up to the present moment I’m completely baffled.” “Have you tried chronology yet? Peeling ’em off in layers—by centuries, say?” “Not exactly, although I did run a correlation against time. Mostly been studying ’em either singly or en masse up to now. Might be worth a fling, though. Why? Got a hunch?” “No. And no particular reason; just groping for more detailed data. Before you can solve any problem, you know, you must know exactly what the problem is—must be able to state it clearly. You can’t do that yet, can you?” “You know I can’t. I’ve got some colored pins here somewhere . . . here they are. Read me the dates and I’ll stick colors accordingly.” They soon ran out of colors; then continued with numbered-head thumb-tacks. The job finished, they stood back and examined the results. “See anything, Joan?” “I see _something_, but before I mention it, give me a quick briefing on what you know already.” Cloud thought for a minute. “Well, the distribution in space is not random, but there is no significant correlation with location, age, size, power, load-factor, or actual number of power plants. Nor with nature, condition, or age of the civilization of any planet. Nor with anything else I’ve been able to dream up. “They aren’t random in time, either; but there again there’s no correlation with the age of the power-plant affected, the age-status of atomic power of any particular planet, or any other thing except one—there is an extremely high correlation—practically unity—with time itself.” “I thought so,” Joan nodded. “That was what I noticed. The older, the fewer.” “Exactly. But with your new classification, Joan, I think I see something else.” Cloud’s mathematical-prodigy’s mind pounced. “And _how_! Until very recently, Joan, the data will plot exactly on the ideal-growth-of-population curve.” “Oh, they breed, some way or other. Nice—that gives us a. . . .” “You said that, woman, I didn’t. I stated a fact; if you wish to extrapolate it, that’s your privilege—but it’s also your responsibility.” “Huh! Don’t go pedantic on me. Haven’t you got any guesses?”