I laid my ear to the ground and listened. The noise grew louder, and the voices seemed to be shouting against a more powerful sound--the waterfall, possibly. I thought perhaps the floor of the hut would give me more opportunity to locate the source of the disturbance. I threw caution to the winds and slipped through the wide windows into the room. I moved as carefully as I could, however, once my feet found the floor, for if there should be anyone below they would probably hear me up above. I turned back the carpet in order to hear more distinctly, and as I did so I noticed a rectangular shaft of light which trickled through the floor. There was a trap-door. I knelt down and lifted it cautiously by a leather tab which was attached to one side of it and peered through. I can never understand how it was I did not drop that hatch again with a self-confessing crash when I realised the extraordinary nature of the sight that greeted my eyes. There was I in the smoking-hut of a peaceful American citizen, where only a few hours before I had spent a pleasant hour in friendly conversation, and now I was lying on the edge of the entrance to a great cavern. Below me there was a confused mass of machinery and men. Some were working on scaffolding, others were many feet below. The nearest of them was so close to me that I could have leaned down and laid my hand on his head. I tried to make out what they were doing, but except that they were dismantling the machinery, whatever it might be, I could make nothing of it. I watched them breathlessly, trembling lest at any moment one of them should look up and detect my presence. The place was lighted by electricity, though there were not enough lamps to illuminate the cavern very brightly, and as my eyes got accustomed to the lights and shadows I was able to make out the cause of this. Evidently there was a turbine engine below, driven by the water from the falls, which supplied the necessary power. After a moment or two it dawned on me how the cavern came to be there; it was, or had been, the course of a hidden river, such as are common enough among the mountains, but the stream had been diverted, probably by some sort of landslide, and had left this tumbler-shaped cave, resembling a pit shaft. Now, I thought, I have only to find out what all this machinery is for and the whole mystery is solved. I opened the trap a little further, and allowed my body to hang slightly over the edge.