It was plain now that that was the astounding truth. These countless millions of Neptunians, coming here to Triton for some reason, had been accustomed upon their own great turning planet to a day and night of ten hours each, much like those of Earth. Triton, though, as we had already guessed, kept the same face always toward the sun, it was evident, turning at just such a rate of rotation as compensated for its revolutions around Neptune and its slower movements with Neptune around the sun. Thus, with one face always toward the sun and the other always in darkness, the Neptunians had been forced to establish arbitrary day and night periods, dividing their millions into two great bodies, apparently. While half of them worked on the sunlit side for ten hours, in their day, the other half were sleeping upon the dark side. Then, when the ten hours ended, the great band of light went around Triton as a signal, and the two bodies of them changed places, the millions who had worked upon the sunward side taking their places for an equal period of sleep on the dark side, while those who had slept on the dark side streamed to the sunlit side for ten hours! Even as we watched from our speeding cylinder we saw that great change taking place, millions upon millions of the Neptunians streaming from one side to the other in great throngs through the compartment-city, while, from farther around Triton's two sides, rushed countless cylinders, in which hosts of others were changing sides. Within a few minutes, it seemed, that change had taken place, and beneath us on Triton's sunward side there thronged in the pale light of its day the vast hordes that so lately had been sleeping, while on the dark side the other masses of the Neptunians had disappeared into the countless shelf-like openings of the sleep-compartments, to lie in sleep for another ten hours. In marveling wonder Marlin and I stared, and then woke suddenly to a realization of our own position.