Before we could fully comprehend the meaning of that fact, though, there came a low clanking of metal and before our eyes a section in each of the curving sides of the cylinders, near the base of each, was abruptly sliding aside, leaving in the metal wall of each cylinder a low oblong door-opening like those of the compartments about us. Now we heard from inside that opening a stir of movement, and saw vaguely a shape or shapes that moved in the cylinder's dark interior. Then, as we gazed with tense nerves toward that opening, there moved out of the cylinder's dark interior through that opening, into the pale dim light of the Neptunian day, a creature at which Marlin and I stared in that moment with horror-stunned minds! A being so grotesque and so awful in appearance that for the moment it seemed to me that it needs must be a creation only of our over-strained nerves and brains!

It was a creature that bore no conceivable resemblance to the human form or to any other in our knowledge. The body was a great flat disk of pale-green flesh, five feet in diameter and hardly a foot in thickness. It was supported in a flat or horizontal position above the ground by seven short thick limbs of muscle or flesh, which were each three feet in length and which projected down from the big disk-body at equal intervals around its circle. The only visible features of the creature were the eyes and mouth. The eyes were two in number, and were set close together in the edge of the disk-body. They were like the eyes of some insect, being each inches across and bulging outward, being composed each of a myriad smaller glistening lens-divisions, like the eye of a fly! And as I saw with shuddering horror those two bulging strange eyes gazing about, it came to me that it was only by means of such great, powerful eyes and their many lenses that any creature here in the dim light of Neptune could see clearly all things about it!

The mouth was a white-lipped circular opening, and was set at the very center of the horizontal disk-body's upper surface! No stranger combination can be imagined than that which presented itself thus in the appearance of that creature before us, with the two bulging glassy eyes staring forth from the edge of the great disk-body, and the round mouth gaping there in that disk-body's flat upper surface. Slung around the disk-body the creature wore a flexible armor or dress of connected straps of flexible metal. In a loop of this rested a metal tube formed by the joining together of two tubes of dissimilar thickness. And attached to the flexible straps in another position, at the disk-body's edge, was one of the strangest features of its appearance, a small metal ball that seemed glowing with unceasing radiant light!

The creature gazed about him, unaware of our awe-stricken gaze, and then half-turned and seemed to call to others in the cylinder from which he had emerged, a strange sound issuing from his mouth-opening. That sound was like a swift succession of staccato snaps of sound, as clear and sharp as the snap of metal on metal. From the variation in their utterance, though they were in a single pitch only, it was evident that they formed the speech of the strange creature, and as he gave utterance to them, others like him, other similar disk-bodied green beings, were emerging from the cylinder behind him and from the other cylinders. In a moment a score or more were gathered there, moving toward the great cogged mechanisms beside them, and as they did so the staccato snapping of their strange speech came loud to our ears. And as they did so, too, we saw that the seven strange limbs of each of them served him as arms as well as supporting legs, since some used some of those limbs to carry tools, holding them tightly in fingerless, muscled grasp!

"Neptunians!" whispered Marlin beside me. "Neptunians, Hunt—those squat, flat disk-bodies—those great eyes——!"

Neptunians! Yet I had seen myself that they must be so, that only on a great planet like Neptune, with far greater gravitational power than Earth, could those squat, flat bodies have evolved. For the greater the power of a planet's gravitation, the lower and the more squat will be the forms of life that evolve upon it. And just as these Neptunians had evolved in their strange disk-form here on the great planet, due to its greater gravitational power, so had their great light-gathering eyes been evolved by the dimness that reigned here always. And it was these beings, it was clear, who had built the vast compartment-city that covered all of the great planet's surface about us, since it was only beings like these who would have built such strange, low doors in it for their own flat disk-bodies, only such beings as these who, with their seven great limbs, could manipulate the controls of the mechanisms we had seen!

"Neptunians!" I whispered it, myself. "But if it's beings like these who inhabit Neptune, who have sent the great force-ray stabbing toward the sun to divide it, where are they all? Why have they left all this city, all this world, dead and deserted?"

Marlin, inside his space-walker, shook his head. "God knows, Hunt! If all these Neptunians have deserted their world, where have they gone? I know no more than you. But it's clear that they've come back for more of those great mechanisms."

It was, indeed, evident that that was the object of the Neptunians' visit to the compartment-city, for now the score or more in the adjoining compartment were busily working with their tools upon three or four of the great cogged mechanisms that loomed there. Swiftly they were taking down those mechanisms, were dissembling them into a myriad intricate parts which were stowed away in the four great cylinders. More than once some of them passed close to the low door through which Marlin and I were gazing, but none ventured through it into the compartment in which we hid, seeming all to be intent upon the business at hand. And as they worked on we began to understand some of the features about them that had puzzled us in our first horror-stricken sight of them.

We had been puzzled, indeed, that they were able thus to move about unheedingly without protection of any sort in the zero-cold that reigned about us. But now as one or two of them passed close to the door by which we crouched, I gazed closely at the glowing little ball that each had attached to his metal armor, and guessed then what I was later to learn was the truth, that that ball was glowing with radiant heat and had the power of heating to comfortable temperature the atmosphere for a few feet directly around its wearer. Thus the wearer of it moved always in a little volume of warm air, though the air outside that area might be at zero temperature. And thus it was that the Neptunians were able to withstand the bitter cold about us, from which we were protected by our space-walkers.