The tunnel in which I found myself and along which Nah-ee-lah led me toward the city of Laythe was remarkable in several particulars. It was largely of natural origin, seemingly consisting of a series of caves which may have been formed by bubbles in the cooling lava of the original molten flow and which had later been connected by man to form a continuous subterranean corridor. The caves themselves were usually more or less spherical in shape and the debris from the connecting passageways had been utilized to fill the bottoms of them to the level of the main floor of the passageway. The general trend of the tunnel was upward from the point at which we had entered it, and there was a constant draught of air rushing along it in the same direction in which we were moving, assuring me that it was undoubtedly well ventilated for its full length. The walls and ceiling were coated with a substance of which radium was evidently one of the ingredients, since even after we had lost sight of the entrance the passageway was well illuminated. We had been moving along in silence for quite a little distance when I finally addressed Nah-ee-lah. “It must seem good,” I said, “to travel again this familiar tunnel of your native city. I know how happy I should be were I thus approaching my own birthplace.” “I am glad to be returning to Laythe,” she said, “for many reasons, but for one I am sorry, and as for this passageway it is scarcely more familiar to me than to you, since I have traversed it but once before in my life and that when I was a little girl and came here with my father and his court upon the occasion of his periodical inspection of the passageway, which is now practically never used.” “If you are not familiar with the tunnel,” I asked, “are you sure that there is no danger of our going astray at some fork or branch?” “There is but the one passageway,” she replied, “which leads from the crater to Laythe.” “And how long is the tunnel?” I asked. “Will we soon enter the city?” “No,” she replied, “it is a great distance from the crater to Laythe.” We had covered some little distance at this time, possibly five or six miles, and she had scarcely ceased speaking when a turn in the passageway led us into a cave of larger proportions than any through which we had previously passed and from the opposite side of which two passageways diverged. “I thought there were no branches,” I remarked. “I do not understand it,” she said. “There is no branch from the tunnel of Laythe.” “Could it be possible that we are in the wrong tunnel?” I asked, “and that this does not lead to Laythe?” “A moment before I should have been sure that we were in the right tunnel,” she replied, “but now, Julian, I do not know, for never had I heard of any branch of our own tunnel.” We had crossed the cave and were standing between the openings of the two divergent passageways. “Which one shall we take?” I asked, but again she shook her head. “I do not know,” she replied.