"The maestro is thinking, I perceive," remarked Dorothy, sweetly, entering the projector from an airboat. "You must all be blind, I guess--you no hear the bell blow, what? I've come after you--it's time to eat!" "'At-a-girl, Dot--never miss the eats! Thanks," and Seaton put his problem away, with perceptible effort. "This is going to be a job, Mart," he went back to it as soon as they were seated in the airboat, flying toward "home." "I can nail them, with an increasing shift in azimuth, up to about thirty thousand light-years, but after that it gets awfully hard to get the right shift, and up around a hundred thousand it seems to be darn near impossible--gets to be pure guesswork. It can't be the controls, because they can hold a point rigidly at five hundred thousand. Of course, we've got a pretty short back-line to sight on, but the shift is more than a hundred times as great as the possible error in backsight could account for, and there's apparently nothing either regular or systematic about it that I can figure out. But.... I don't know.... Space is curved in the fourth dimension, of course.... I wonder if ... hm--m--m." He fell silent and Crane made a rapid signal to Dorothy, who was opening her mouth to say something. She shut it, feeling ridiculous, and nothing was said until they had disembarked at their destination. "Did you solve the puzzle, Dickie?" "Don't think so--got myself in deeper than ever, I'm afraid," he answered, then went on, thinking aloud rather than addressing any one in particular: "Space is curved in the fourth dimension, and fifth-order rays, with their velocity, may not follow the same path in that dimension that light does--in fact, they do not. If that path is to be plotted it requires the solution of five simultaneous equations, each complete and general, and each of the fifth degree, and also an exponential series with the unknown in the final exponent, before the fourth-dimensional concept can be derived ... hm--m--m. No use--we've struck something that not even Norlaminian theory can handle." "You surprise me." Crane said. "I supposed that they had everything worked out." "Not on fifth-order stuff--it's new, you know. It begins to look as though we'd have to stick around until every one of those torpedoes gets somewhere near its mother-ship. Hate to do it, too--it'll take six months, at least, to reach the vessels clear across the Galaxy. I'll put it up to the gang at dinner--guess they'll let me talk business a couple of minutes overtime, especially after they find out what I've got to say." He explained the phenomenon to an interested group of white-bearded scientists as they ate. Rovol, to Seaton's surprise, was elated and enthusiastic. "Wonderful, my boy!" he breathed. "Marvelous! A perfect subject for years after year of deepest study and the most profound thought. Perfect!"