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 21 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 semicircle? 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 an 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 an 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 recognised 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 hinge-marks 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 westering 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.