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 hand, 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 greater distance the shining object’s position seemed indefinably queer — on a slight mound rising from the slime. Now — at about an 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.