Signalling to my companion that I wished to have the fellows go on with their work, I approached the nearest slab of rock. It was the same fine grained whitish rock of which the city was built, and, lying upon it where they had been dropped by the stone cutters, were several small hammers, chisels and an adze-like tool. That they were not bronze or any alloy of copper I knew at the first glance. Their color was that of tempered steel and they seemed ridiculously small for the purpose of working this hard stone. If these people used steel then I had indeed made a discovery, and intent on this matter I picked up one of the tools to examine it. No sooner had I lifted it that I uttered an involuntary exclamation of surprise. The hammer, although hardly larger than an ordinary tack hammer, weighed fully ten pounds! It was heavier than if made of solid gold. There was only one known metal that could be so heavy and that was platinum. But platinum it could not be, for that metal is softer than gold and would be of no more use for cutting rock than so much lead. The tools, however, were undoubtedly hard—the polished surface of the hammer-head and the chisels, and the unscarred keen edges of the latter, showed this, and, anxious to test their hardness, I held a chisel against the rock and struck it sharply with a hammer. Once more I cried out in wonder, for the chisel had bitten fully half an inch into the stone! It had cut it as easily as if the rock were cheese! What marvel was this? What magic lay in these tools? And then the secret dawned upon me and a moment’s examination of the stone confirmed my suspicions. It was not that the tools were so very hard or keen but that the rock was soft—so soft that I could readily cut it with my pocket knife, a wax-like earthy rock which no doubt became hard upon exposure to the air exactly like the coral rock of Bermuda, which may be quarried with saws and even planed, but becomes as hard as limestone after exposure to the elements. Still, the tools were far harder than any metal except tempered steel, and for some time I puzzled over the matter as I watched the workmen, now over their fright and adoration, skilfully cutting and squaring the blocks of stone. It was one more conundrum I could not solve, and it was not until long afterwards, when a careful analysis of the metal was made, that I knew the truth. The metal was an alloy of platinum and iridium—the later one of the hardest of all known metals.