Our wild attempt at escape had failed, it was evident, for now, as the Neptunian leader of the crimson circle rose, he was addressing to the others a sharp, snapping order, and at the same time motioning Marlin and me peremptorily to the seats we had formerly occupied. We took them with no further resistance, for we knew that our desperate outbreak had put the Neptunians upon their guard and that the slightest suspicious motion on our part might well mean instant death. And as we seated ourselves once more with the guards on either side, one from beneath replacing the one I had killed, the despair that formerly had filled us seemed immeasurably intensified. For now the cylinder was sinking down after the others, through the great opening in Triton's roof, and even as Marlin and I looked outward we saw the great opening in that roof closing again above us with a clang that to our ears was like the clang of doom.
Above our sinking cylinders now there stretched the great roof, and, even as Neptune's enclosing roof, this one was almost entirely transparent from below, though opaque from above. And here as on Neptune we could see no supporting pillars whatever for this vast spherical roof that enclosed all Triton. This world seemed, indeed, but a smaller replica of mighty Neptune. For, as our cylinders sank down through the shadows of its darker side and then leveled out and began to race back around its curving surface toward the sunward side once more, we saw that all of Triton's surface was covered, even like Neptune, with a great compartment-city whose intersecting black walls stretched in their vast checkerboard arrangement over all the great moon's surface. But as our cylinders shot over these, over the darkened portion of the surface of Triton and toward the sunward side, we saw that the compartment-city beneath was different, in some features, from that of Neptune.
For one thing, there were moving to and fro above it a number of great cylinders like that in which we were, and in the compartments of the darkened side moved, too, a few Neptunians here and there. And the great globes of metal that dotted this compartment-city of Triton, even as that of Neptune, were here glowing with radiant light; glowing, I knew, with radiant heat. For this was the secret of the Neptunians' existence on Triton, this heat that glowed from the numberless giant globes set in compartments here and there. Those great glowing globes kept the air beneath Triton's great roof warm and comfortable, the great roof itself preventing that warmer air from escaping into the moon's colder outer atmosphere. As we shot on over the darkened side of Triton, the side turned away from the sun, I could not but think that the remnants of the Neptunian race must be few indeed, so few of them moved in the shadowy compartments beneath.
At last, as Marlin and I gazed ahead, we could make out a brighter crescent of light at the edge of the strange moon-world, and as we shot on we saw that we were approaching the edge of the sunward or sunlit side. A moment more and we could see it clearly and as we did so Marlin and I gasped in utter amazement. For that part of the great compartment-city that lay on Triton's sunward side, in the pale sunlight, was swarming with incalculable millions upon tens of millions of Neptunians! Crowding, seething, pressing together, they were pouring to and fro through the compartments in the pale light of day, busy with the mechanisms that scarce had room in those compartments, so great were their crowds! And over this sunward side hundreds upon hundreds of cylinders swarmed, rushing to and fro!
"Neptunians! Neptunians in countless millions here on the sunward side of Triton! But why then are there so few upon the dark side?"
Marlin shook his head at my exclamation. "I can't guess," he said. "And I never dreamed that——"
Before he could finish the sentence there came an amazing interruption from beneath. As we gazed downward from our speeding cylinder we saw a giant band of intensely brilliant white light spring suddenly into being at the very line that marked where dark side and sunlit side of Triton met. A mile in width, that great brilliant band of light seemed to extend clear from Triton's north pole to its south, as far north and south of us as our eyes could reach. And then, even as we stared, astounded at it, that brilliant and immense band of light was moving around Triton's surface over the dark side! Swiftly it moved, like a great wave of brilliant light sweeping around Triton's surface, and in a moment had disappeared from view far around the horizon from us on the dark side!
And as that dazzling light-band moved around the big moon-world's dark side, around the almost empty compartment-city that covered that dark side, we saw emerging into that compartment-city of the dark side, as though from its walls themselves, millions on millions of disk-bodied Neptunians that matched in number the vast swarms on the sunlit side! And as we gazed down in utter amazement we saw from whence they came. There were in the dark compartment-city's extent many compartments like those we had seen upon Neptune, with nothing in them save shelving, which formed in their walls myriads of shelfed openings a few feet in height and some four feet in width, one above the other. And in these narrow, flat shelf-openings countless Neptunians had been sleeping! Their disk-bodies, with the flexible legs drawn up, fitted snugly into those flat, strange openings in the walls, and vast hordes of them, countless millions of them, had been sleeping in the shelf-compartments on Triton's dark side!
As that band of brilliant light swept swiftly across the dark side, though, they had awakened, were pouring forth in all their hordes into and through the compartments, all streaming toward the sunward side, while the more remote of them were heading toward the same side in flashing cylinders above. Then, as we gazed toward that sunward side, we saw the brilliant band of light reappearing there, moving swiftly still around Triton's surface, through the pale dim light of its sunward side, having in those moments moved completely around Triton! It moved on until in a moment more it had stopped where first it had formed, at the junction of the dark and sunward sides. There it hung for a moment, dazzling, and then had suddenly snapped out of being. And now we saw that all the crowding millions of Neptunians that had been busy upon the sunlit side were streaming through the compartments toward the dark side!
"The Neptunians' day and night!" Marlin exclaimed, as we gazed downward. "Triton must keep one face always toward the sun and one dark, so these Neptunians spend their day on the sunlit side and sleep their night on the dark side!"