To my surprise, I discovered she was right. I _had_ mentioned the ideas and theories I had formed in Mictolan, but these, I had later found, were not entirely correct. Fortunately I had preserved the bamboo tube, and my friend Dr. Farrabee had written a special treatise on it. Its contents were, he found, an entirely new element related to radium but possessing several unique properties. Thus, while lead is (to all intents and purposes) a radium insulator, it offers no resistance to the rays of this new element that Dr. Farrabee has named Nohulite at my request. But remarkably enough, any cellulose tissue or fibre completely isolates Nohulite. As is well known, radium destroys organic tissue and affects bone. But Nohulite appears to have no effect upon bone itself, though it destroys animal fat almost instantly. Its most remarkable property, however, is that in the presence of metals it discharges rays or electrons in inconceivable quantities without appreciable loss of energy or bulk to itself. Although this discharge, this fusillade, if I may use the term, is quite invisible to the human eye, yet the instant it comes into contact with a metallic element it produces an intense heat and a colored glow, the amount of heat and the color of the glow depending upon the metal and its purity. This phenomenon, according to Dr. Farrabee’s exhaustive monograph, is due to resistance. In other words, just as current of electricity passing through a resistant material, such as iron, will cause that material to become incandescent, so the discharge of electronic energy from Nohulite, striking a resistant material, produces heat and an incandescent glow. But contrary to what one would expect, the purer the metal the greater the resistance. Hence, when, in the passages of the temple, I turned the ray upon the rocks, a red glow--due to the presence of iron--resulted with comparatively little heat. But when it was turned upon gold--or pure copper--a tremendous amount of heat was generated instantly. Even the mysterious and seemingly inexplicable manner in which the rays had revealed the otherwise green arrows in the Cave of the Bats has been explained by Dr. Farrabee’s experiments. Chromium oxides glow brilliant green under the rays, and no doubt the arrows were either cut into the rock, and filled with chrome--which would be indistinguishable by the naked eye from the rest of the stone--or they had been painted with some chromium oxide upon the rocks. Even if they were completely covered with a thin layer of limestone--as they probably were--they would still be revealed by the ray of Nohulite.