Listening intently for a moment I heard no sound, either within or without the building, so that it was with considerable confidence that I started to ascend the ramp. Upward I continued from floor to floor, each of which consisted of a single large chamber, a fact which finally convinced me that the building had been a warehouse for the storing of goods passing through this ancient port. From the upper floor a wooden ladder extended upward through the center of the tower above. It was of solid skeel, which is practically indestructible, so that though I knew it might be anywhere from five hundred thousand to a million years old, I did not hesitate to trust myself to it. The circular interior core of the tower, upward through which the ladder extended, was rather dark. At each landing there was an opening into the tower chamber at that point, but as many of these openings were closed only a subdued light penetrated to the central core. I had ascended to the second level of the tower when I thought that I heard a strange noise beneath me. Just the suggestion of a noise it was, but such utter silence had reigned over the deserted city that the faintest sound must have been appreciable to me. Pausing in my ascent, I looked down, listening; but the sound which I had been unable to translate was not repeated, and I continued my way on upward. Having it in my mind to climb as high up in the tower as possible, I did not stop to examine any of the levels that I passed. Continuing upward for a considerable distance my progress was finally blocked by heavy planking that appeared to form the ceiling of the shaft. Some eight or ten feet below me was a small door that probably led to one of the upper levels of the tower and I could not but wonder why the ladder had been continued on upward above this doorway, since it could serve no practical purpose if it merely ended at the ceiling. Feeling above me with my fingers I traced the outlines of what appeared to be a trap door. Obtaining a firm footing upon the ladder as high up as I could climb, I placed a shoulder against the barrier. In this position I was able to exert considerable pressure upward with the result that presently I felt the planking rise above me and a moment later, to the accompaniment of subdued groans, the trap door swung upward upon ancient wooden hinges long unused. Clambering into the apartment above I found myself upon the top level of the tower, which rose to a height of some two hundred feet above the avenue below. Before me were the corroded remains of an ancient and long obsolete beacon-light, such as were used by the ancients long before the discovery of radium and its practical and scientific application to the lighting requirements of modern civilization upon Barsoom. These ancient lamps were operated by expensive machines which generated electricity, and this one was doubtless used as a beacon for the safe