Yet despite this we had grimly driven the flier to the utmost acceleration possible, its speed steadily mounting toward the maximum in those succeeding days that we flashed inward from Neptune. For behind us Neptune's calm, green little disk of light, though diminishing steadily in size as we receded from it, seemed like a baleful signal of doom shining there behind us. For out from Neptune, or rather out from its moon, Triton, the giant force-ray of the Neptunians was still radiating toward the sun, thus shadowing all the solar system with the cataclysmic doom to come. For, as we flashed inward, Marlin had used his astronomical instruments to determine the fact that the sun's rotatory period had now decreased to a little over eight days, and was decreasing still by the same amount of four hours each day, its spin accelerated each day by the same amount as the colossal force-ray from Triton kept upon its side its unrelenting pressure. And within half a hundred days more, as we knew, that rotatory period of the sun would have decreased until its huge mass would be spinning once in every hour, would be spinning then so fast that it must inevitably be riven asunder into a new double star by its own centrifugal force, engulfing all its planets save Neptune alone! So it was that we spared not ourselves but drove the space-flier in through the solar system toward Earth with a speed unthinkable, almost, using an acceleration that was all but death for us. For the one hope of preventing that colossal sun-cataclysm, as Marlin had said and as we all knew, was to reach Earth soon and then at once fly back out from Earth toward Neptune again with the great space-flier fleet, which, if the World President and the World Congress had not failed us, would be waiting on Earth for us. With that fleet we must sally back across the solar system once more to its outer edge, to great Neptune, and must fall upon Triton and the giant force-ray that was shooting from Triton to the sun, with all our power. If we could vanquish the Neptunians long enough to destroy the giant sun-ray's mechanism, to halt that ray, we would have halted the acceleration of the sun's spin, would have saved the sun and its planets from the cataclysmic doom that now threatened them. But if we could not, if the Neptunians with their countless cylinders and great weapons were too strong for us, then we could but perish there in struggling with them, since in that case nothing could halt the doom that they were loosing from Triton upon the sun and the solar system.