The terrain sloped upward, ending in a definite crest. I reached the top about 5:30 and saw ahead of me a very extensive plain with forests in the distance. This, without question, was the plateau mapped by Matsugawa from the air fifty years ago, and called on our maps 'Eryx' or the 'Erycinian Highland.' But what made my heart leap was a smaller detail, whose position could not have been far from the plain's exact centre. It was a single point of light, blazing through the mist and seeming to draw a piercing, concentrated luminescence from the yellowish, vapour-dulled sunbeams. This, without doubt, was the crystal I sought - a thing possibly no larger than a hen's egg, yet containing enough power to keep a city warm for a year. I could hardly wonder, as I glimpsed the distant glow, that those miserable man-lizards worship such crystals. And yet they have not the least notion of the powers they contain.
Breaking into a rapid run, I tried to reach the unexpected prize as soon as possible; and was annoyed when the firm moss gave place to a thin, singularly detestable mud studded with occasional patches of weeds and creepers. But I splashed on heedlessly - scarcely thinking to look around for any of the skulking man-lizards. In this open space I was not very likely to be waylaid. As I advanced, the light ahead seemed to grow in size and brilliancy, and I began to notice some peculiarity in its situation. Clearly, this was a crystal of the very finest quality, and my elation grew with every spattering step. It is now that I must begin to be careful in making my report, since what I shall henceforward have to say involves unprecedented - though fortunately verifiable - matters. I was racing ahead with mounting eagerness, and had come within a hundred yards or so of the crystal - whose position on a sort of raised place in the omnipresent slime seemed very odd - when a sudden, overpowering force struck my chest and the knuckles of my clenched fists and knocked me over backward into the mud. The splash of my fall was terrific, nor did the softness of the ground and the presence of some slimy weeds and creepers save my head from a bewildering jarring. For a moment I lay supine, too utterly startled to think. Then I half mechanically stumbled to my feet and began to scrape the worst of the mud and scum from my leather suit.
Of what I had encountered I could not form the faintest idea. I had seen nothing which could have caused the shock, and I saw nothing now. Had I, after all, merely slipped in the mud? My sore knuckles and aching chest forbade me to think so. Or was this whole incident an illusion brought on by some hidden mirage-plant? It hardly seemed probable, since I had none of the usual symptoms, and since there was no place near by where so vivid and typical a growth could lurk unseen. Had I been on the earth, I would have suspected a barrier of N-force laid down by some government to mark a forbidden zone, but in this humanless region such a notion would have been absurd.
Finally pulling myself together, I decided to investigate in a cautious way. Holding my knife as far as possible ahead of me, so that it might be first to feel the strange force, I started once more for the shining crystal - preparing to advance step by step with the greatest deliberation. At the third step I was brought up short by the impact of the knife - point on an apparently solid surface - a solid surface where my eyes saw nothing.
After a moment's recoil I gained boldness. Extending my gloved left hands I verified the presence of invisible solid matter - or a tactile illusion of solid matter - ahead of me. Upon moving my hand I found that the barrier was of substantial extent, and of an almost glassy smoothness, with no evidence of the joining of separate blocks. Nerving myself for further experiments, I removed a glove and tested the thing with my bare hand. It was indeed hard and glassy, and of a curious coldness as contrasted with the air around. I strained my eyesight to the utmost in an effort to glimpse some trace of the obstructing substance, but could discern nothing whatsoever. There was not even any evidence of refractive power as judged by the aspect of the landscape ahead. Absence of reflective power was proved by the lack of a glowing image of the sun at any point.
Burning curiosity began to displace all other feelings, and I enlarged my investigations as best I could. Exploring with my hands, I found that the barrier extended from the ground to some level higher than I could reach, and that it stretched off indefinitely on both sides. It was, then, a wall of some kind - though all guesses as to its materials and its purpose were beyond me. Again I thought of the mirage-plant and the dreams it induced, but a moment's reasoning put this out of my head.
Knocking sharply on the barrier with the hilt of my knife, and kicking at it with my heavy boots, I tried to interpret the sounds thus made. There was something suggestive of cement or concrete in these reverberations, though my hands had found the surface more glassy or metallic in feel. Certainly, I was confronting something strange beyond all previous experience.
The next logical move was to get some idea of the wall's dimensions. The height problem would be hard, if not insoluble, but the length and shape problem could perhaps be sooner dealt with. Stretching out my arms and pressing close to the barrier, I began to edge gradually to the left - keeping very careful track of the way I faced. After several steps I concluded that the wall was not straight, but that I was following part of some vast circle or ellipse. And then my attention was distracted by something wholly different - something connected with the still-distant crystal which had formed the object of my quest.
I have said that even from a great distance the shining object's position seemed indefinably queer - on a slight mound rising from the slime. Now - at about a hundred yards - I could see plainly despite the engulfing mist just what that mound was. It was the body of a man in one of the Crystal Company's leather suits, lying on his back, and with his oxygen mask half buried in the mud a few inches away. In his right hand, crushed convulsively against his chest, was the crystal which had led me here - a spheroid of incredible size, so large that the dead fingers could scarcely close over it. Even at the given distance I could see that the body was a recent one. There was little visible decay, and I reflected that in this climate such a thing meant death not more than a day before. Soon the hateful farnoth-flies would begin to cluster about the corpse. I wondered who the man was. Surely no one I had seen on this trip. It must have been one of the old-timers absent on a long roving commission, who had come to this especial region independently of Anderson's survey. There he lay, past all trouble, and with the rays of the great crystal streaming out from between his stiffened fingers.
For fully five minutes I stood there staring in bewilderment and apprehension. A curious dread assailed me, and I had an unreasonable impulse to run away. It could not have been done by those slinking man-lizards, for he still held the crystal he had found. Was there any connexion with the invisible wall? Where had he found the crystal? Anderson's instrument had indicated one in this quarter well before this man could have perished. I now began to regard the unseen barrier as something sinister, and recoiled from it with a shudder. Yet I knew I must probe the mystery all the more quickly and thoroughly because of this recent tragedy.
Suddenly - wrenching my mind back to the problem I faced - I thought of a possible means of testing the wall's height, or at least of finding whether or not it extended indefinitely upward. Seizing a handful of mud, I let it drain until it gained some coherence and then flung it high in the air toward the utterly transparent barrier. At a height of perhaps fourteen feet it struck the invisible surface with a resounding splash, disintegrating at once and oozing downward in disappearing streams with surprising rapidity. Plainly, the wall was a lofty one. A second handful, hurled at an even sharper angle, hit the surface about eighteen feet from the ground and disappeared as quickly as the first.
I now summoned up all my strength and prepared to throw a third handful as high as I possibly could. Letting the mud drain, and squeezing it to maximum dryness, I flung it up so steeply that I feared it might not reach the obstructing surface at all. It did, however, and this time it crossed the barrier and fell in the mud beyond with a violent spattering. At last I had a rough idea of the height of the
wall, for the crossing had evidently occurred some twenty or twenty-one feet aloft.
With a nineteen - or twenty-foot vertical wall of glassy flatness, ascent was clearly impossible. I must, then, continue to circle the barrier in the hope of finding a gate, an ending, or some sort of interruption. Did the obstacle form a complete round or other closed figure, or was it merely an arc or semi-circle? Acting on my decision, I resumed my slow leftward circling, moving my hands up and down over the unseen surface on the chance of finding some window or other small aperture. Before starting, I tried to mark my position by kicking a hole in the mud, but found the slime too thin to hold any impression. I did, though, gauge the place approximately by noting a tall cycad in the distant forest which seemed just on a line with the gleaming crystal a hundred yards away. If no gate or break existed I could now tell when I had completely circumnavigated the wall.
I had not progressed far before I decided that the curvature indicated a circular enclosure of about a hundred yards' diameter - provided the outline was regular. This would mean that the dead man lay near the wall at a point almost opposite the region where I had started. Was he just inside or just outside the enclosure? This I would soon ascertain.
As I slowly rounded the barrier without finding any gate, window, or other break, I decided that the body was lying within. On closer view the features of the dead man seemed vaguely disturbing. I found something alarming in his expression, and in the way the glassy eyes stared. By the time I was very near I believed I recognized him as Dwight, a veteran whom I had never known, but who was pointed out to me at the post last year. The crystal he clutched was certainly a prize - the largest single specimen I had ever seen. I was so near the body that I could - but for the barrier - have touched it, when my exploring left hand encountered a corner in the unseen surface. In a second I had learned that there was an opening about three feet wide, extending from the ground to a height greater than I could reach. There was no door, nor any evidence of hingemarks bespeaking a former door. Without a moment's hesitation I stepped through and advanced two paces to the prostrate body - which lay at right angles to the hallway I had entered, in what seemed to be an intersecting doorless corridor. It gave me a fresh curiosity to find that the interior of this vast enclosure was divided by partitions.
Bending to examine the corpse, I discovered that it bore no wounds. This scarcely surprised me, since the continued presence of the crystal argued against the pseudo-reptilian natives. Looking about for some possible cause of death, my eyes lit upon the oxygen mask lying close to the body's feet. Here, indeed, was something significant. Without this device no human being could breathe the air of Venus for more than thirty seconds, and Dwight - if it were he - had obviously lost his. Probably it had been carelessly buckled, so that the weight of the tubes worked the straps loose - a thing which could not happen with a Dubois sponge-reservoir mask. The half-minute of grace had been too short to allow the man to stoop and recover his protection - or else the cyanogen content of the atmosphere was abnormally high at the time. Probably he had been busy admiring the crystal - wherever he may have found it. He had, apparently, just taken it from the pouch in his suit, for the flap was unbuttoned.
I now proceeded to extricate the huge crystal from the dead prospector's fingers - a task which the body's stiffness made very difficult. The spheroid was larger than a man's fist, and glowed as if alive in the reddish rays of the weltering sun. As I touched the gleaming surface I shuddered involuntarily - as if by taking this precious object I had transferred to myself the doom which had overtaken its earlier bearer. However, my qualms soon passed, and I carefully buttoned the crystal into the pouch of my leather suit. Superstition has never been one of my failings.
Placing the man's helmet over his dead, staring face, I straightened up and stepped back through the unseen doorway to the entrance hall of the great enclosure. All my curiosity about the strange edifice now returned, and I racked my brains with speculations regarding its material, origin, and purpose. That the hands of men had reared it I could not for a moment believe. Our ships first reached Venus only seventy-two years ago, and the only human beings on the planet have been those at Terra Nova. Nor does human knowledge include any perfectly transparent, non-refractive solid such as the substance of this building. Prehistoric human invasions of Venus can be pretty well ruled out, so that one must turn to the idea of native construction. Did a forgotten race of highly-evolved beings precede the man-lizards as masters of Venus? Despite their elaborately-built cities, it seemed hard to credit the pseudo-reptiles with anything of this kind. There must have been another race aeons ago, of which this is perhaps the last relique. Or will other ruins of kindred origin be found by future expeditions? The purpose of such a structure passes all conjecture - but its strange and seemingly non-practical material suggests a religious use.
Realizing my inability to solve these problems, I decided that all I could do was to explore the invisible structure itself. That various rooms and corridors extended over the seemingly unbroken plain of mud I felt convinced; and I believed that a knowledge of their plan might lead to something significant. So, feeling my way back through the doorway and edging past the body, I began to advance along the corridor toward those interior regions whence the dead man had presumably come. Later on I would investigate the hallway I had left.
Groping like a blind man despite the misty sunlight, I moved slowly onward. Soon the corridor turned sharply and began to spiral in toward the centre in ever-diminishing curves. Now and then my touch would reveal a doorless intersecting passage, and I several times encountered junctions with two, three, and four diverging avenues. In these latter cases I always followed the inmost route, which seemed to form a continuation of the one I had been traversing. There would be plenty of time to examine the branches after I had reached and returned from the main regions. I can scarcely describe the strangeness of the experience - threading the unseen ways of an invisible structure reared by forgotten hands on an alien planet! At last, still stumbling and groping, I felt the corridor end in a sizeable open space. Fumbling about, I found I was in a circular chamber about ten feet across; and from the position of the dead man against certain distant forest landmarks I judged that this chamber lay at or near the centre of the edifice. Out of it opened five corridors besides the one through which I had entered, but I kept the latter in mind by sighting very carefully past the body to a particular tree on the horizon as I stood just within the entrance.
There was nothing in this room to distinguish it - merely the floor of thin mud which was everywhere present. Wondering whether this part of the building had any roof, I repeated my experiment with an upward-flung handful of mud, and found at once that no covering existed. If there had ever been one, it must have fallen long ago, for not a trace of debris or scattered blocks ever halted my feet. As I reflected, it struck me as distinctly odd that this apparently primordial structure should be so devoid of tumbling masonry, gaps in the walls, and other common attributes of dilapidation.
What was it? What had it ever been? Of what was it made? Why was there no evidence of separate blocks in the glassy, bafflingly homogenous walls? Why were there no traces of doors, either interior or exterior? I knew only that I was in a round, roofless, doorless edifice of some hard, smooth, perfectly transparent, non-refractive and non-reflective material, a hundred yards in diameter, with many corridors, and with a small circular room at the centre. More than this I could never learn from a direct investigation. I now observed that the sun was sinking very low in the west - a golden-ruddy disc floating in a pool of scarlet and orange above the mist-clouded trees of the horizon. Plainly, I would have to hurry if I expected to choose a sleeping-spot on dry ground before dark. I had long before decided to camp for the night on the firm, mossy rim of the plateau near the crest whence I had first spied the shining crystal, trusting to my usual luck to save me from an attack by the man-lizards. It has always been my contention that we ought to travel in p
arties of two or more, so that someone can be on guard during sleeping hours, but the really small number of night attacks makes the Company careless about such things. Those scaly wretches seem to have difficulty in seeing at night, even with curious glow torches. Having picked out again the hallway through which I had come, I started to return to the structure's entrance. Additional exploration could wait for another day. Groping a course as best I could through the spiral corridors - with only general sense, memory, and a vague recognition of some of the ill-defined weed patches on the plain as guides - I soon found myself once more in close proximity to the corpse. There were now one or two farnoth flies swooping over the helmet-covered face, and I knew that decay was setting in. With a futile instinctive loathing I raised my hand to brush away his vanguard of the scavengers - when a strange and astonishing thing became manifest. An invisible wall, checking the sweep of my arm, told me that - notwithstanding my careful retracing of the way - I had not indeed returned to the corridor in which the body lay. Instead, I was in a parallel hallway, having no doubt taken some wrong turn or fork among the intricate passages behind. Hoping to find a doorway to the exit hall ahead, I continued my advance, but presently came to a blank wall. I would, then, have to return to the central chamber and steer my course anew. Exactly where I had made my mistake I could not tell. I glanced at the ground to see if by any miracle guiding footprints had remained, but at once realized that the thin mud held impressions only for a very few moments. There was little difficulty in finding my way to the centre again, and once there I carefully reflected on the proper outward course. I had kept too far to the right before. This time I must take a more leftward fork somewhere - just where, I could decide as I went.