turning over in my mind the riddle of that omnipresent symbol, and then forgetting it, as I observed the things about me.
'That long street was like the avenue of sphinxes at Kamak, down which Pharaoh swung in his litter, borne to his temple on the necks of men. But the statues that made up its sides were not sphinx shaped. They were carved in strange forms, shapes of animals unknown to us, as far removed from anything we can imagine as the beasts of another world. I can not describe them, any more than you could describe a dragon to a man who had been blind all his life. Yet they were of evil, reptilian shapes; they tore at my nerves as I looked at them.
'Down between the two rows of them I went, until I came to the end of the avenue. Standing there between the last two figures, I could see nothing before me but the yellow sands of the desert, as far as the eye could reach. I was puzzled. What had been the object of all the pains that had been taken, the wall, the two great statues, and this long avenue, if it but led into the desert?
'Gradually I began to see that there was something queer about the part of the desert that lay directly before me. It was flat. For an area, seemingly round in shape, that must have covered several acres the surface of the desert seemed absolutely level. It was as though the sands within that great circle had been packed down with tremendous force, leaving not even the littlest ridge of dune on its surface. Beyond this flat area, and all around it, the desert was broken up by small hills and valleys, and traversed by whirling sand-cloud but nothing stirred on the flat surface of the circle.
'Interested at once, I strode forward to the edge of the circle, only a few yards away. I had just reached that edge when an invisible hand seemed to strike me a great blow on the face and chest, knocking me backward in the sand.
'It was minutes before I advanced again, but I did advance, for all my curiosity was now aroused. I crawled toward the circle's edge, holding my pistol before me, pushing slowly forward.
'When the automatic in my outstretched hand reached the line of the circle, it struck against something hard, and I could push it no farther. It was exactly as if it had struck against the side of a wall, hut no wall or anything else was to be seen. Reaching out my hand, I touched the same hard barrier, and in a moment I was on my feet.
'For I knew now that it was solid matter I had run into, not force. When I thrust out my hands, the edge of the circle was as far as they would go, for there they met a smooth wall, totally invisible, yet at the same time quite material. And the phenomenon was one which even I could partly understand. Somehow, in the dead past, the scientists of the city behind me, the 'wise men' mentioned in the inscription, had discovered the secret of making solid matter invisible, and had applied it to the work that I was now examining. Such a thing was far from impossible. Even our own scientists can make matter partly invisible, with the X-ray. Evidently these people had known the whole process, a secret that had been lost in the succeeding ages, like the secret of hard gold, and malleable glass, and others that we find mentioned in ancient writings. Yet I wondered how they had done this, so that, ages after those who had built the thing were wind-driven dust, it remained as invisible as ever.
'I stood back and threw pebbles into the air, toward the circle. No matter how high I threw them, when they reached the line of the circle's edge they rebounded with a clicking sound; so I knew that the wall must tower to a great height above me. I was on fire to get inside the wall, and examine the place from the inside, but how to do it? There must be an entrance, but where? And I suddenly remembered the two guardian statues at the head of the great avenue, with their carven tablets, and wondered what connection they had with this place.
'Suddenly the strangeness of the whole thing struck me like a blow. The great, unseen wall before me, the circle of sand, flat and unchanging, and myself, standing there and wondering, wondering. A voice from out the dead city behind me seemed to sound in my heart, bidding me to turn and flee, to get away. I remembered the warning of the inscription, 'Go not to Mamurth.' And as I thought of the inscription, I had no doubt that this was the great temple described by San-Drabat. Surely he was right: the like of it was not on earth elsewhere.
'But I would not go, I could not go, until I had examined the wall from the inside. Calmly reasoning the matter, I decided that the logical place for the gateway through the wall would be at the end of the avenue, so that those who came down the street could pass directly through the wall. And my reasoning was good, for it was at that spot that I found the entrance: an opening in the barrier, several yards wide, and running higher than I could reach, how high I had no means of telling.
'I felt my way through the gate, and stepped at once upon a floor of hard material, not as smooth as the wall's surface, but equally invisible. Inside the entrance lay a corridor of equal width, leading into the center of the circle, and I felt my way forward.
'I must have made a strange picture, had there been any there to observe it. For while I knew that all around me were the towering, invisible walls, and I knew not what else, yet all my eyes could see was the great flat circle of sand beneath me, carpeted with the afternoon sunshine. Only, I seemed to be walking a foot above the ground, in thin air. That was the thickness of the floor beneath me, and it was the weight of this great floor, I knew, that held the circle of sand under it for ever flat and unchanging.
'Iwalked slowly down the passageway, with hands outstretched before me, and had gone but a short distance when I brought up against another smooth wall that lay directly across the corridor, seemingly making it a blind alley. But I was not discouraged now, for I knew that there must be a door somewhere, and began to feel around me in search of it.
'I found the door. In groping about the sides of the corridor my hands encountered a smoothly rounded knob set in the wall, and as I laid my hand on this, the door opened. There was a sighing, as of a little wind, and when I again felt my way forward, the wall that had I lain across the passageway was gone, and I was free to go forward. But I dared not go through at once. I went back to the knob on the wall, and found that no amount of pressing or twisting of it would close the door that had opened. Some subtle mechanism within the knob had operated, that needed only a touch of the hand to work it, and the whole end of the corridor had moved out of the way, sliding up in grooves, I think, like a portcullis, though of this I am not sure.
'But the door was safely opened, and I passed through it. Moving about, like a blind man in a strange place, I found that I was in a vast inner court, the walls of which sloped away in a great curve. When I discovered this, I came back to the spot where the corridor opened into the court, and then walked straight out into the court itself.
'It was steps that I encountered: the first broad steps of what was evidently a staircase of titanic proportions. And I went up, slowly, carefully, feeling before me every foot of the way. It was only the feel of the staircase under me that gave reality to it, for as far as I could see, I was simply climbing up into empty space. It was weird beyond telling.
'Up and up I went, until I was all of a hundred feet above the ground, and then the staircase narrowed, the sides drew together. A few more steps, and I came out on a flat floor again, which, after some groping about, I found to be a broad landing, with high, railed edges. I crawled across this landing on hands and knees, and then struck against another wall, and in it, another door. I went through this too, still crawling, and though everything about me was still in. visible, I sensed that I was no longer in the open air, but in a great room.
'I stopped short, and then, as I crouched on the floor, I felt a sudden prescience of evil, of some malignant, menacing entity that was native here. Nothing I could see, or hear, but strong upon my brain beat the thought of something infinitely ancient, infinitely evil, that was a part of this place. Was it a consciousness, I wonder, of the horror that had filled the place in ages long dead? Whatever caused it, I could go no farther in the face of the terror that possessed me; so I drew back and walked to the edge of the landing, leaning over its high, invisible railing and surveying the scene below.
'The setting sun hung like a great ball of red-hot iron in the western sky, and in its lurid rays the two great statues cast long shadows on the yellow sands. Not far away, my two camels, hobbled, moved restlessly about. To all appearances I was standing on thin air, a hundred feet or more above the ground, but in my mind's eye I had a picture of the great courts and corridors below me, through which I had felt my way.
'As I mused there in the red light, it was clear to me that this was the great temple of the city. What a sight it must have been, in the time of the city's life! I could imagine the long procession of priests and people, in somber and gorgeous robes, coming out from the city, between the great statues and down the long avenue, dragging with them, perhaps, an unhappy prisoner to sacrifice to their god in this, his temple.
'The sun was now dipping beneath the horizon, and I turned to go, but before ever I moved, I became rigid and my heart seemed to stand still. For on the farther edge of the clear stretch of sand that lay beneath the temple and the city, a hole suddenly appeared in the sand, springing into being on the desert's face exactly like the one I
