“Except for this recent jump, which we can probably ascribe to Fairchild and explosives, nary a guess. I can’t see any possible point of application.” “Neither can I. But if that’s the only positive correlation you can find, and it’s just about unity, it must mean _something_.” “Check. It’s _got_ to mean something. All we have to do is find out what . . . I think maybe I see something else.” Bending over, he sighted across the chart from various angles. “Too many pins. Let’s clear a belt through here.” They did so. “Will you read ’em to me in order, beginning with the oldest?” “At your service, sir. Sol.” Cloud stuck a pin in Sol. “Galien—Salvador—DuPont—Eastman—Mercator—Centralia— Tressilia—Chickladoria—Crevenia—DeSilva—Wynor—Aldebaran. . . .” “Hold it! Don’t want Aldebaran—can’t use it. Take a look at this!” For this first time Cloud’s voice showed excitement. She looked, and saw a gently curving line of pins running three-quarters of the way across the chart. “Why—that’s a smooth curve—looks as though it could be the arc of a circle—clear across all explored space!” she exclaimed. Cloud’s mind pounced again. “It is a circle—pretty close, that is, according to these rough figures. Will you read me the exact coordinates—spatial—from the book?” She did so, and through Cloud’s mind there raced the appropriate equations of solid analytic geometry. “Even closer. Now let’s apply a final refinement. From their proper motions we can put each star back to where it was at the vortex date. It’ll take a little time, but it may be worth it.” It was. Cloud’s mien was solemn as he announced his final figures. “Those twelve suns all lay on the surface of a sphere. Radius, 53,327 parsecs, with a probable error of one point three zero parsecs—which, since the average density of the stars along that line is about point zero four five per cubic parsec, makes it as perfect a spherical surface as it is physically possible for it to be. The center of that sphere is almost exactly on the ecliptic; its coordinates are: Theta, 225°—12′—31.2647″; distance, 107.2259.” “Good heavens! It’s _that_ exact? And _that_ far outside the Rim? That spoils my original idea of radiation from a center. But all of the twelve oldest vortices are on that surface, and _none_ of them are anywhere else!” “So they are. Which gets us where, lady?” “Nowhere that I can see, with a stupendous velocity.” “You and me both. Another thing, why that particular time-space relationship in the first twelve? I can accept Tellus being first, because we had atomics first, but that logic doesn’t follow through. Instead, the time order goes from Sol through Galien and so on to Eastman—to the very edge of unexplored territory along that arc—then, jumping back to the other side of Sol, goes straight on to the edge of Civilization in the opposite direction. Can you play _that_ on any one of your brains, from Alice to Margie?” “I don’t see how.”