"Yet after a time we were forced to recognize that this check also was but temporary. For we were fighting the most grim and hopeless battle in the universe; we were fighting against the relentless and inevitable changes caused by the immutable physical laws of the universe. So that, aid its failing heat as we might with artificial heat-producers, the interior heat of Neptune was waning still, and more and more globe heat-radiators were required to keep the temperature of Neptune at its usual height. The Neptunians of Triton were faced with the same problem, but their situation was not so desperate as of those upon Neptune, since though Triton had cooled as quickly, its enclosed space was so much smaller than Neptune's, its great roof so close to it also, that it was possible with an effort to keep enough heat-mechanisms going there to maintain the warmth.
"On Neptune, however, the struggle became more and more desperate, our great struggle against the blind laws of nature. For as Neptune's interior heat declined farther and farther, it became more and more impossible for us to keep enough heat-mechanisms going to keep it warm enough for life. And at last, after years upon years of that awful struggle against fate, we of Neptune realized at last that it was no longer possible to keep Neptune warm enough for us to exist there, and that we must leave it at once for some other world if we were to escape extinction; since as the great planet's interior heat declined, it became more and more agonizing for us to keep enough heat for life by means of the heat-mechanisms, and it was clear to all that the end was at hand unless we left Neptune!
"But where could we go? Even if one of the other planets were suitable to receive us, we could not have transported all our masses from Neptune to another planet in time to escape the doom of cold and death that was closing down upon Neptune. To transport all those masses would have required countless trips with our limited number of cylinders. And to take refuge upon another planet, even had time been ours, was almost out of the question. For long our scientists had studied the other planets with their instruments, and though some of them were so cloud-wreathed and others so distant as to make observation difficult, it had long been known to us that none of the other planets, due to their natural conditions or to the presence of intelligent alien beings already upon them, would be possible as a world for us Neptunians. It was for those reasons, indeed, that no expeditions of cylinders had ever been sent to the other planets.
"There remained, then, but one place where we might go, but one place to which our millions might go before Neptune's cold grew too great for life. That place was Triton, our peopled moon. For peopled as that moon was with its own masses of Neptunians, struggling against the same menacing cold that had vanquished us on Neptune, it was the one refuge for our peoples. By crowding into its every corner, the countless millions of Neptune's peoples would be able to exist upon Triton. And though the cooling of Triton had menaced it with cold also, it has been found, as we have mentioned, that it was not so hard to keep Triton warm by means of the artificial globular heat-mechanisms, the space enclosed by its great spherical roof being much smaller. It was a desperate expedient, truly, to mass all the thronging millions from the compartment-city that covered all giant Neptune, to mass all those millions upon little Triton, yet that was the one expedient open, and so it was followed at once.
"Out from Neptune to Triton went all the cylinders of both worlds, loaded with as many Neptunians as they could carry, depositing those Neptunians upon Triton and racing back for more. Countless trips made those thousands of cylinders, trip after swift trip, each occupying but little time because Triton was so near. And so at last there came a day when the whole of Neptune's millions had been transported out to Triton, when there remained on Neptune itself no single one of our races, our giant world lying cold and deserted and dead, no longer a habitable world, its vast compartment-city empty of the millions that had for ages swarmed through it, while all those millions were crowded now upon little Triton.
"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.
"The Neptunian races had come to their last stand! Crowded upon our refuge of Triton, striving with all our power to keep upon it the warmth, without which we could not live, we saw at last that some new and radically different plan must be found, or we could no longer exist. So all the greatest of our Neptunian scientists were called together by us, the Council of Thirty. Into a great conclave here on Triton they were called, and to them, without equivocation of any sort, and to the races of the Neptunians, the situation that confronted us was stated. We had been driven from Neptune by the relentless growing cold, and now that same cold was upon us here at Triton, was threatening us here also with annihilation. How were we to meet this great menace that threatened to wipe us out?
"Countless were the plans that were advanced in answer to that menace by our scientists. The first, and most obvious plan, was migration to another planet. But here we were checked by the same considerations that had made us unwilling to try that before, for we knew by observation of the other planets that upon none of them could we live as we lived upon Neptune. Some of them were greater in size than Neptune, with greater gravitational power, and that was a difficulty that could not be overcome by us since upon those planets our weight would be so increased as to make us helpless, even had those planets been fit for our life. Some planets were peopled by intelligent and powerful races which we might be able to conquer after terrible struggles. Others were too near the sun for us to ever inhabit them, who had evolved on the dim, cool world of Neptune, the outermost world. Other planets, as far as we could tell, were quite uninhabitable. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus—not one of them was suitable as a world for us Neptunians. And we had, also, no desire to move to another planet, in truth, since so many ages had it taken for us to build our great compartment-cities upon Neptune and Triton, to shield them with their great roofs, that it was impossible for us to leave them, even had we been able, to start anew upon another world.