"And so crowded were those vast hordes of the Neptunian races that for a time it seemed that they could not exist in such numbers upon Triton. This crowding was made less acute, however, by an expedient now adopted by us. As mentioned, the Neptunians who had settled upon Triton long before had found that the unchanging day on one side of it and the unchanging night on the other were inconvenient for them after the alternations of Neptune's day and night, and so had begun the custom of spending a day of ten hours upon the sunlit side of Triton and a night of equal length upon the dark side. And now we found that we could make the crowding of our races upon Triton less acute by having half of them working and active upon the sunward side for ten hours while the other half slept through their night on the dark side. Every ten hours these two halves of our people changed sides, changed from day to night, a signal having been devised to mark the hour for that change, a signal which consisted of a brilliant band of intense light, that passed swiftly around both Triton's dark and sunward sides. With this shifting of our peoples each ten hours it was possible to make use of all of Triton's surface, and thus the crowding of our peoples upon it was made less acute. "Yet that crowding was still very great. All the thronging Neptunians that had existed upon the surface of giant Neptune had been poured out on little Triton, far, far less in size than its great parent-world. And thus, though they could exist upon it, it was existence only that was possible to the Neptunians on Triton, since this awful crowding would grow worse, we knew, rather than better. And also, and more important, here on Triton the same deadly menace that had driven us from Neptune was again confronting us. For even as Neptune had cooled, Triton had cooled, was cooling also. And though we strained every effort to keep the warmth in Triton constant, though we sent cylinders constantly back to dead and deserted Neptune to bring from it more heat-mechanisms and other needed mechanisms, we found that even as on Neptune we were fighting a losing battle with nature. For Triton was cooling, was cooling still farther, and soon would be completely cold and dead, its interior heat gone out into space. And when that happened, no number of heat-mechanisms could keep warmth upon it, even beneath the great enclosing roof, and all life on it must perish.