CHAPTER VI

Into Neptune's Mysteries

"Metal, over all Neptune's surface!"

"A metal-covered world!"

Our stunned, astounded exclamation sounded together there as we gazed downward from our flier, whose drop I had instinctively halted. For it was metal indeed that lay beneath us, a gigantic surface of smooth dark metal or metallic substance that glinted dully in the pale light that fell on it, and that stretched away in all directions to the horizons, completely covering the giant planet Neptune as far as we could see! A metal-covered world! In amazement, in awe, we stared down upon it in that moment. For we had expected many things, many aspects which the surface of Neptune might have had, frozen ice-fields or flaming craters or even a liquid world, but never had we expected what we now saw beneath us. Never had we expected to find the huge planet thus sheathed in a dark metal covering that apparently extended over all its gigantic surface! And in all its vast smooth expanse, we saw, there was no higher structure of any sort, nothing but the level plain of smooth dark metal, sweeping far away to the flat horizons.

"Neptune a metal-covered world! And I think I see why, now," said Marlin quickly as we gazed down. "I think that I can understand why the beings of Neptune have covered their world with this shield----"

"But what lies beneath it?" Randall asked. "Do you mean that these beings of Neptune----"

"I mean that beneath this great shield they have built must lie the real world of the beings of Neptune--must lie the source of the giant force-ray that they're stabbing toward the sun!"

"But how to get down inside?" said Whitely. "There seems no opening in this gigantic metal shield----"

"We must go on, then," Marlin told us. "Must go on until we find some way of getting beneath, since beneath that shield there lies our goal!"

A moment we stared toward each other, and then I had snapped open one of the switches before me, turning the ray-direction dial, sending down slantwise toward the metal surface a force-ray, instead of the vertical ray that had upheld our flier. The pressure of this slanting ray at once sent our ball-like space-flier moving forward across Neptune's surface, across the smooth vast dark metal plain whose presence was so astounding to us. I glanced at the outside-temperature dial as we shot forward, saw that the atmosphere through which we moved though dense was cold indeed, hardly above zero in temperature. Then with Marlin and Whitely and Randall I turned my attention to the smooth great metal surface over which we were driving. On and on we shot, though, without finding any slightest change or opening or structure in that unending dark metal surface, that swept away in its vast, bare curve to the horizons, which were very far from us, so great was the radius of curvature of Neptune's mighty sphere. But after tense moments of this fruitless watch from our racing flier, Whitely uttered a low exclamation and pointed ahead, toward a round lighter circle in the dark metal plain far to the left, a circular opening in the giant metal shield!

None other of us spoke as we gazed toward that opening, but at once I had sent the space-flier rushing toward it. As we raced nearer to it we saw that that opening's circle was a full five hundred feet in diameter, and that we could see down through it a great, bright-lit space beneath! Tensely we watched, until in another moment I had sent the space-flier directly above the great opening, so that it hovered motionless above the circular opening's center. And as it hung there we four, forgetful for the moment of all else, were gazing down through the space-flier's window through that opening, down into the great more brightly-lit space that we could see beneath, beneath the huge metal shield that covered all this world!

The first thing that I noted, gazing downward, was that the space beneath the giant metal roof of Neptune was a great one, since it was a full mile from the opening in that roof to the surface of the world far below. Gazing down toward that surface, seeing at last the true surface of Neptune lying in the brighter light that existed in some strange way beneath the gigantic metal roof, we gasped. For upon that surface there loomed countless strange structures such as we had never seen before. Rectangular in shape were those structures, with straight black walls, of great size but seeming rather low in height, and they were without exception roofless! In them we could dimly make out from our great height the gleaming shapes of what seemed huge machines of one sort or another, but could not at that height see whether living beings of any sort moved among the structures. The great circle of the world beneath that we could see, hanging above the opening, was completely covered with these structures, the black walls of one roofless building being surrounded on all sides by the walls of others, there being no streets or open spaces whatever between them! It was as though, indeed, all the surface of the great world beneath had been divided into great compartments by a great checkerboard arrangement of intersecting black walls!

Marlin's eyes were gleaming with excitement as he gazed down. "The city of the creatures of Neptune!" he breathed, as in awe we four stared down. "The city of Neptune that lies beneath the colossal roof, and that must hold somewhere that which we have come to seek!"

"You're going to venture down into this city--down under the great roof?" I asked, and he nodded.

"We must, Hunt, to find the giant force-ray's source. But stand ready to flash the space-flier back upward--for if we're discovered by whatever beings inhabit this strange world, I think we'll get short shrift!"

A moment we paused there, and then as my hands moved upon the switch-controls, decreasing the power of the force-ray that held us upward the space-flier was sinking smoothly and slowly downward, down through the great opening! Tensely and with fascinated interest we gazed about now as we sank into the great space that lay beneath the huge metal roof. That space was brighter-lit than above the roof, we saw, and as we turned a moment to glance upward we saw that looking upwards, the roof was perfectly transparent! Dark, opaque metal when seen from above, it was almost invisible in its transparency when seen from below! And, seeing that, we understood the great roof's purpose. It had been constructed and placed above all Neptune, encircling the great planet and enclosing it, to retain that planet's heat as much as possible. For it was apparent that heat and light radiations or vibrations could not pass up through the metal of the roof from beneath, making it appear black and perfectly opaque from above, but could pass freely down through it from above, making it appear almost perfectly transparent from below!

* * * * *

Even as we grasped the wonder of that, though, we had forgotten it, in the greater wonder of the things that lay now before our eyes. For as we sank down in our space-flier into the great space beneath that roof we could see the surface of great Neptune itself, stretching far away beneath that mighty enclosing shield above it, and covered to the horizons by the strange rectangular and roofless structures such as we had already seen. These were formed, indeed, by smooth black walls of some two hundred feet in height that ran in straight lines in checkerboard arrangement across all the surface of this huge planet, apparently, forming upon all its surface, without streets or parks or openings of any kind, a vast city of rectangular compartments, large and small! A titanic streetless city that covered apparently all the surface of giant Neptune!

But most wonderful of all the things that lay before us in that moment was the fact that nowhere about us could we see any sign of supporting pillars or piers for the giant roof that stretched far above us! For though we could gaze far away to the distant horizons of this great world, we could find no single support for that huge metal roof that apparently covered all the great planet, and whose weight must have been incalculable! And another feature of the giant roof puzzled us. It puzzled us to see the great openings in it like that down which we had come, great circular openings which we could see in it here and there at great distances from each other. Those openings were provided on their under-side with great sliding shutters for closing them tightly, yet all were open! Why should they be open, we silently asked ourselves, if the purpose of the roof was to retain Neptune's heat within that roof? For the existence of those great and unclosed openings in the roof must surely be defeating that purpose, for our outside-temperature dial recorded the same zero temperature as prevailed above the roof!

Yet even these strange things could not wholly draw our interest and attention from the strange compartment-city beneath, as our space-flier sank toward it. We were within a few hundred feet of it, now, and as we dropped nearer, Marlin and Whitely and Randall staring eagerly down beside me, my hands were tense upon the switch-controls, ready to send our flier leaping instantly upward. For if the beings of the city beneath, whatever their nature, caught sight of us, we could expect nothing but instant attack. So that a tenseness held all of us as our great flier's faceted polyhedron dropped on through the pale light beneath the great roof toward the black-walled, checkerboard-like city that stretched across the surface of the great world beneath us. And now, as we sank lower, our eyes were making out ever more clearly the details of that amazing city.

The rectangular black-walled compartments held, as we had half-realized from above, various strange-shaped mechanisms and objects which we could even now only vaguely discern. We could see clearly, though, that here and there across all the vast city's compartmented surface there stood giant metal globes, each a hundred feet in diameter and each occupying a square compartment of its own. There seemed hundreds of these great gleaming globes, scattered here and there in compartments across the city's surface as far as we could see, though their purpose was then quite incomprehensible to us. But as we sank lower still, ever more cautiously, it was not the globes or the compartments' contents that held our attention so much as the astounding, stupefying fact that now was thrust upon us--namely that in all the gigantic compartmented city, in all its strange great black-walled rectangular and roofless enclosures, _there moved no living being_!

"Dead!" Randall's cry expressed in that instant the stupefaction of all of us. "A dead world!"

"Neptune--a dead world!"

A dead world! For truly it seemed a dead world that lay there in the dim pale light beneath us! A world whose strange contiguous compartments stretched away from horizon to horizon to form the colossal city above which we hovered, but a world, a city, in which was no single discernible thing of life! The endless black-walled compartments, the strange-shaped structures and mechanisms, the great enigmatic globes--all these things lay beneath us in a silence and a death that were stunning to our senses! Lay beneath us as though death had reached out of the unknown to annihilate suddenly all living things upon this alien world, leaving in it only the cold and the silence and the death that enwrapped it now! Neptune--we had flown across the awful void toward it for week upon week, prepared to find within it any strange beings, any alien and terrible form of life, but never had we been prepared to find it without any life whatever--an utterly lifeless world!

As we stared down toward it in utter silence it seemed to me that my brain was spinning from the stupefying shock of amazement that was ours. For if the world beneath us was truly a dead one, if Neptune lay now without life, its colossal compartment-city entirely lifeless, whence came that giant force-ray that was stabbing across the solar system from Neptune to turn the sun ever faster toward its division? Whence came that doom which was being loosed upon our Earth and upon all the solar system, almost, by that gigantic ray? Was that great ray, after all, only some incomprehensible freak of natural forces, impossible to withstand, and had Neptune, once the home of some alien, mighty civilization, lain for eons in silence and death? Had our desperate mission which alone held a chance for Earth, our terrific race out through the unthinkable reaches of the solar system's spaces toward its outermost planet, been in vain?

Marlin must have felt something of the same despair in that moment, but his strong face betrayed no trace of it as he turned to us. "It's evident that this vast compartment-city, this whole world, perhaps, is deserted," he said. "But where does the great ray come from?"

Whitely shook his head, glancing at his instruments. "Impossible to say," he said. "The recording-instruments here show only that we are close to the great ray's source, that that source is in the region around Neptune. But the emanations or reflections from it striking the instruments are so powerful as to make it impossible to determine the ray's source exactly."

"But the city beneath!" I cried. "Even if it is dead, deserted, we might be able to find in it some clue to what has happened here, some idea of what manner of creatures the Neptunians were, and perhaps some clue to the great ray's source!"

Marlin pondered, then nodded. "Hunt's right," he said. "If we explore this deserted compartment-city beneath we may find some suggestion that will lead us to the great ray's source. And we _must_ find out soon, for only eighty-five days are left before the sun divides into a double star and dooms Earth!"

"But we shouldn't risk all of us on this venture," I said. "The safest way would be to keep the space-flier, with two of us inside, hovering here above the city while the other two go down to it and explore it in their space-walkers."

This we finally agreed to do, and Marlin and I insisted upon being the two to make the venture, Whitely and Randall reluctantly agreeing at last to remain within the space-flier, watching and waiting for us. So, bringing the space-flier down to a height of a thousand feet above the compartmented city, I set the force-ray to hold it motionless there, Randall taking my place at its controls. Then Marlin and I were quickly getting into our two cylindrical space-walkers. Once inside them, we each gripped in a great pincer-hand the pointed bars of steel that we were to take with us, and then unscrewed the inner door and passed into the vestibule-chamber. Another moment and with the inner door closed, the outer one was swinging open, and the denser and colder air from without was rushing into the vestibule-chamber. We did not feel its cold, however, snug in the insulated and heated cylinders of the space-walkers, but drew ourselves to the outer door, turning on the force-rays from the bottoms of our cylinders. Then as we drew ourselves out through the door and into empty air, we were both sinking gently downward, our fall slowed to a mere floating drop by the down-pressing power of our force-rays.

* * * * *

Down through the dim pale light of Neptune's day we sank, down until just beneath us lay one of the intersecting black walls. As I saw this I shot my supporting force-ray outward at a slant, and as this sent me down obliquely, I floated down past that wall, Marlin doing the same beside me, and in another moment we had come gently to rest just above the black smooth floor of one of the great compartments, the force-rays from the bottoms of our space-walkers holding us a foot or so above the floor. Resting there, Marlin and I looked up first. Beside us towered the black two-hundred foot wall of the compartment, and far above we could make out the hovering space-flier, its great gleaming polyhedron hanging motionless and watchful above. We waved the great metal arms of our space-walkers toward it, toward Whitely and Randall inside it, and then turned to examine the place in which we stood.

It was an oblong compartment some four hundred feet in length, and half that in width, its great black walls towering on all sides of us. Ranged around the compartment against those walls were rows of strange squat mechanisms of a roughly pear-like form, that loomed each a score of feet in height. Marlin and I shot our space-walkers toward the nearest of these mechanisms, to examine it. We saw that in the top of it was an odd cone-like opening, and that there ran out of the gleaming metal cover of the thing a thick pipe or tube that connected with a larger pipe that encircled the compartment, connected to each of the mechanisms. Then as we reached forward, swung aside the metal cover of the mechanism, exposing an intricate system of sections inside it through which ran slender tubes acted upon by what seemed projectors of electro-magnetic force about them, Marlin pointed toward them, leaned toward me until his space-walker touched mine and spoke to me through the touching metal.

"A water-making mechanism this seems to be, Hunt," he said. "In some way it must draw down ceaseless supplies of hydrogen and oxygen atoms from the great vapor-masses above the roof, and then recombine them here into water."

I nodded, gazing at the thing. "But it hasn't been used for years--for centuries, perhaps," I said. "Look--that dust upon it----"

For upon the pear-shaped mechanism before us, and on all those others and all other things about us, there rested a coating of fine dust that was inches thick, a dust-coating that we knew only a great period of time could have deposited there. A moment we stared at that, two grotesque figures there in the great cylinders of our space-walkers, and then were moving on, along the wall. That black smooth wall, we saw now, was composed of a material that looked much like a black seamless stone, but one that seemed diamond-hard. For our pointed steel bars could make not the slightest impression upon it, and it was evident, from the monolithic construction of the great walls about us and of the smooth black paving upon which we walked, that this diamond-like smooth stone had been artificially made. Later we were to learn that it was constructed by a building up of molecules into a deliberate crystalline formation that far exceeded the strength and stability of any other material's crystalline structure, and thus gave to the black artificial stone a diamond-like hardness and a tensile strength exceeding that of steel.

Around the great compartment we walked, our eyes ranging over the great pear-shaped mechanisms and the great pipes connecting them, and then Marlin and I stopped short. For there in the black wall before us was a door, an opening that connected with the adjoining compartment on that side. It was by means of doors like that, it was plain, that the necessity of streets in this compartment-city had been obviated, making it possible to pass across the city through the compartments themselves if needed. Yet it was in stupefying surprise that Marlin and I now gazed toward that door. For it was all of six feet in width, but hardly more than four feet in height! Its opening stretched there in the black wall as though an ordinary door-opening of one of Earth's buildings had been set in that wall sidewise! And as we looked stunnedly about we saw that all the doors set in the compartment's four walls were of the same size and shape!

"Those doors!" I cried to Marlin, leaning beside me. "Those were never made for human beings or for near-human beings!"

"Then these Neptunians that once were here--" Marlin began, and then stopped; we gazed in silence at each other through the vision-windows of our space-walkers.

And silence seemed oppressive all about us then, a silence that lay as thickly over the deserted compartment-city as the thick dust of unguessable years that covered it. A chill seemed to have struck home to us in some strange fashion with the discovery of those grotesque door-openings and their significance. I glanced upward, saw that the faceted ball of the space-flier was still hanging motionless high above, and then as I turned back saw that Marlin had moved toward the low door toward which we had been gazing. A moment he contemplated it, then motioned to me with the big metal arm of his space-walker, and as I came to his side, grasped that door's edge with his great arms and lowered his space-walker's big cylinder until it lay on its side on the smooth black paving. Then he was drawing it through the door, aiding himself with a force-ray shot from the opening in its bottom toward the compartment's opposite wall behind us. When he was through, he drew himself erect, and in a moment I had followed him and was standing with him in the next compartment.

That second compartment, we found, was a replica of the first, being of the same size and holding within it several dozen more of the pear-shaped water-manufacturing mechanisms. We passed through it, therefore, over the dust-strewn paving and through the low similar door on its opposite side, to find ourselves in still another compartment of water-manufacturers. Pressing on, rapidly becoming able to pass through the low strange doors easily in our cumbrous space-walkers, we passed through a half-score more of similar compartments all holding only the dust-covered, pear-shaped water-mechanisms, and then at last we passed into a different compartment, one that held a strange shelving that covered all its walls, at which we stared in perplexity for some time.

This shelving consisted of horizontal and perpendicular shelves of smooth black stone like that of the walls themselves, running along and up and down those walls and forming thus a continuous series of box-like openings, each some four feet in length and two in height. There were hundreds of these shelves in the compartment, we could see, yet all of them were quite empty, and in the compartment there seemed to be no other object. They suggested the equipment of a store-room, yet there was no faintest clue as to what had been stored in those shelf-tiers of openings, ranged one above the other all around the walls. Had Marlin and I been able to guess the astounding truth as to those tiers of compartments as to their significance and purpose, much would have been clear to us right then. As it was, after vainly endeavoring to fathom the purpose of the things, we gave it up and moved on out of the compartment, and through similar shelf-tiered compartments beyond it.

* * * * *

By this time we had passed some distance from beneath our hovering space-flier, but still could see its gleaming polyhedron hanging high in the air behind us. Reassured by the sight of it, we passed on, and in the next half-hour progressed through many more compartments. Some of these contained water-manufacturing mechanisms or tiers of strange shelf-openings such as we had already seen. But many others held mechanisms or objects strange to our eyes, before which Marlin and I stood entranced. We almost forgot, in the overpowering interest of the things that we found in those compartments, the object of our exploring search through the strange compartment-city, our search for clues as to the beings of Neptune and as to the great force-ray that was turning the sun ever faster.

Compartments we found in which were structures that puzzled us as completely as had the tiers of shelf-openings. These structures were great flat metal containers, each scores of feet in length and width but hardly more than a foot or two in depth. They were ranged one above the other in great supporting frameworks, and each container was filled with black fine soil. The compartments that held these had set in their walls great white disks which were connected to intricate apparatus that seemed generators of some kind of force, but more than that we could not ascertain from our inspection of them. The whole arrangement, the great shallow containers of soil, the disks in the walls, the generators connected to them--all was utterly enigmatic and perplexing to us, and we were forced to give up the riddles and pass on into other compartments, in which were other things almost as mysterious.

Some held giant globes of burnished metal, now dust-covered, which occupied almost a whole compartment each. These great gleaming globes were among the most puzzling things we had found, since there was, in the compartment of each one, no other object or indication of their purpose, save for a few switches mounted upon a panel, the combination of which we could not discover, opening and closing them in vain. We had seen these great globes from above, dotting the vast compartment-city here and there in great numbers, but we could learn no more of their purpose standing there beside them than we had been able to guess from above. And near these there were strange looming machines, many-cogged and with a great hopper above whose purpose we guessed, at least, guessing that these were the mechanisms that produced from some raw materials the artificial diamond-hard black stone-material that made up all the intersecting walls of this strange huge city-world.

Each of these machines had before it a very low, round metal seat, with in front of that seat the controls of the machine, a half-dozen burnished metal levers. As we saw them Marlin and I exchanged startled glances. Had the being who operated that machine, who sat before it, held and operated _all_ those control-levers of the mechanism? Back to our minds flashed the strange low openings of the doors through which we had come, and for a moment the same strange sense of dread chilled me. But I shook off the feeling, followed Marlin on into another compartment, glancing back through to where our space-flier poised in the air now far across the city behind us.

It was into another long rectangular compartment that we passed, one that held, like that out of which we had just come, rows of strange many-cogged mechanisms. But one feature of that compartment caught our attention instantly, held us motionless and staring. And that was that those rows of great mechanisms were not complete! Here and there in those rows were gaps, as though machines had been removed from the compartment, and where those gaps were, where the missing machines had stood, were squares on the floor where their bases had rested, _squares that were entirely free of the inch-thick dust that lay over all else_! And even as we stared, as we comprehended the astounding significance of that, we saw that upon the dust-coated floor before us were many tracks, small round and strange tracks in the thick dust that were of great number and that had been made, it was apparent from their dust-free condition, but days or hours before!

"Marlin!" I whispered, grasping my companion's space-walker with the great metal arm of my own and touching head casing to head casing. "Marlin--those tracks--someone, something has been here--and but recently!"

"It can't be!" he exclaimed, his voice hushed strangely like my own. "Neptune--all this great compartment-city--it's all dead, deserted----"

"But those tracks!" I insisted. "Those squares in the dust--something's been here and has taken a half-dozen of these great machines away with them! And we know that something on Neptune is sending the great force-ray out to the sun!"

"It can't be," Marlin repeated. "We found no source of the great ray on Neptune's sunward side, and, too, how can that ray shoot always toward the sun from some spot on Neptune when Neptune itself is constantly turning? No, Hunt, I think that this means--_but look up there_!"

As he cried out he was gazing suddenly upward, his space-walker's great arms pointing up, and at that horror-stricken cry, I glanced up to see a sight that froze me motionless there in astonishment. For there, high above us and above the great compartment-city, a dozen strange great shapes were dropping down through the air toward us, were dropping down through one of the openings in the great roof! Long great cylinders of gleaming metal those shapes seemed, dropping silently and smoothly down from the opening, toward the compartment-city, but even as we looked in amazement and terror up toward them, they had halted in mid-air, as though seeing the faceted ball of our hovering space-flier hanging above the city far behind us. Then the next instant all the dozen great cylinders were flashing with unbelievable speed toward our space-flier, a half-score narrow, pencil-like rays of pale, almost invisible light or force stabbing ahead of them toward the space-flier!

Marlin and I cried out in the same instant as those great cylinders whirled through the air toward the space-flier, and in that moment it seemed to us that our wild cries had been heard, for we saw the space-flier whirl itself to one side suddenly, as though Randall and Whitely in it had caught sight suddenly of that onrushing menace. The pale, almost unseen stabbing little rays of force or light shot past them as they swerved thus, and then the next moment cylinders and space-flier seemed to be whirling in a wild melange of geometrical metal forms there in the pale dim light above the great compartment-city. We saw the slender, pencil-like shafts of force stabbing this way and that, saw one cylinder, struck by the shafts of its fellows, riven asunder by those shafts as though by swords of steel and then suddenly the gleaming polyhedron of the space-flier had plunged up out of the wild mêlée and was rocketing up toward one of the great openings in the vast roof above!

As Whitely and Randall thus whirled the space-flier up in an effort to escape their outnumbering, unknown attackers, we saw three of the great cylinders rushing up after them. In another moment the space-flier, closely followed by its three pursuers, had rushed up through the opening and disappeared above, and as they did so we saw that the remaining eight cylinders were dropping now again toward the compartment-city! Watching stupefied still in our amazement, Marlin and I saw that four of the cylinders were heading down toward a point in the great city somewhat to the right of us, while the other four were slanting down now almost straight toward the compartment in which we stood! And as I saw that, as I saw and understood the significance of the tracks and missing mechanisms in this compartment, I grasped Marlin's great metal arm with one of my own, again touching head-armors.

"They're coming down to this compartment!" I cried. "It was they who took the missing mechanisms from here--they've come for more!"

"Out of the compartment, then!" Marlin shouted. "They're after Whitely and Randall in the flier, and if they find us here----!"

With the words we were throwing ourselves, prisoned in our great cumbrous space-walkers as we were, toward the low door through which we had come. In a moment we were through that door, were in the adjoining compartment, but hardly had we gained it than there swept through the pale light from high above four great cylindrical shapes, slanting smoothly down toward the compartment we had just left! From above they could see us easily, whatever beings were inside those descending cylinders, so that as they shot down over our roofless great compartment, Marlin and I poised motionless, praying that our great gleaming space-walkers might be mistaken for mechanisms. Far across the compartment-city we could glimpse the four other cylinders dropping down toward a different point, also, and then in the next moment the four above us had shot down over us and with a throbbing sound coming clearly to us from those cylinders' interiors, were coming to rest in the compartment we had just left!

* * * * *

Glancing for a moment at each other through the vision-windows of our space-walkers, Marlin and I then softly moved in them toward the low door through which we had just come. For though our fear was great, our curiosity, our realization of the mission that had brought us out here to Neptune, was greater. In a moment we were at the door, were lowering ourselves awkwardly and silently to a position from which we could gaze through it into the adjoining compartment. In that compartment, we saw now, the four great cylinders had landed, and were resting upon the floor at its center. Each cylinder was of forty feet diameter and twice that in height, and their gleaming metal sides were broken here and there by small windows. They were broken too, we saw with a start, by ray-openings like those of our own space-flier, and it was evident from those that the cylinders were propelled through space by the same force-rays that moved our flier!

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.

As we gazed toward the Neptunians, they were completing the process of dissembling and stowing away the great mechanisms, and now I moved closer to Marlin, my thoughts being on retreat from the dangerous position in which we were. Not only might we be discovered at any moment by the Neptunians before us, but somewhere in the compartment-city behind us were others, we knew, who had landed in their four cylinders at another point. Whatever had happened to Whitely and Randall in the space-flier, Marlin and myself were in the most perilous of positions. Even were we to escape the Neptunians we could not exist for long in our space-walkers in this dead and deserted city, in the cold of this strange and terrible world of death. Yet to escape from them was our first consideration, and I whispered as much to Marlin through our touching space-walkers.

"We've got to get clear of these Neptunians," I whispered to him. "Back farther in the city we can hide until they go."

He was gazing toward the strange creatures and their tools and mechanisms with intense scientific interest, but turned toward me at my whisper. "We'll get back, then," he whispered. "It may be that Whitely and Randall----"

It was a sentence that he never finished. For we had hardly turned to cross the compartment in which we crouched than we had to stop short in our space-walkers. There behind us a dozen or more great disk-creatures had been standing--a dozen or more great Neptunians! Even as we faced them there in that stunned moment, their bulging glassy eyes upon us, I saw the tracks in the thick dust at our feet, realized that these creatures were of the others who had landed in the compartment-city, and that finding our space-walkers' tracks here and there in the thick dust, they had followed them, had trailed us and stolen behind us while we watched their fellows! Then in the next moment had come a staccato cry from the foremost of the Neptunians, and in the instant following they had flung themselves straight forward upon us!

For in this atmosphere sound penetrated our cylinders.