Nothing but the dull, hollow roar of the cavern filled his ears, and that was like the very depth of silence itself. Not even the soft rustling of the night-wind among the trees far above his head could be detected. Applying his ear to the earth he instantly heard a regular _tip, tap, tip, tap_, as if made by the dropping of water, but which a moment’s listening satisfied him was produced by another cause. The uncertain character of the noise made it impossible to tell whether it was near or far, but he judged that it was a long way off. But, suddenly he started up, and reaching over shook his companion into wakefulness, for he had discovered the meaning of the singular sound, and it was high time that they were on their guard! “’Sh!” whispered Little Rifle; “there’s some one in the cavern besides us,” he replied, in the same cautious tone. “I can hear two persons walking, and they are coming this way!” The steps continued their approach, until, as near as the boys could judge, they were directly beneath the opening, and something like fifty feet from the spot where they were crouching upon the ground. Here they paused, and one of them said: “Give the signal, Tom!” A whistle followed, that screeched out like that of a locomotive engine, awakening strange echoes through the cavern, and only a few seconds had elapsed when a fainter reply came back from above their heads. The window was closed by the obtrusion of some dark body. “Helloa! Tom, is that you down there?” some one called through the opening. “Of course. Come, be lively now, and let down that rope.” “All right; there it comes; look out for it!” The listening lads soon heard sounds as if made by a person in drawing himself up “hand-over-hand” by means of the rope. Such in truth was the case, and a few minutes after they saw two bodies disappear, one by one, through the skylight. What they had heard of course told them that the three men whose voices they had heard were not Indians but white men. What their errand was in the cavern, it was hard to conjecture, as was also the question whether it would be prudent to advance and make their situation known to them. They could catch the muttering mumbling of words far above, but could not understand a syllable uttered. In a few moments the sound of voices ceased altogether, for the men evidently had gone away. While Little Rifle stood all attention, Harry was groping around with his hands. “By jingo! they have left the rope hanging down!” he exclaimed, in a delighted whisper, as he pushed it toward his friend. “I wonder if they didn’t do that on purpose for us?” The young trapper grasped it in his hands, and found that it was an ordinary hemp rope reaching to the floor of the cavern, and capable of bearing a heavy strain.