Harry took the proffered hand again, with an apology for his rashness, and they progressed slowly and deliberately, but with a much more confident air than heretofore. “Don’t you hear how much louder it grows every minute?” asked the impulsive lad, almost dragging his friend after him. “We have been over this ground before, and what is the need of such tardiness? We were glad enough to get away from the falls, but we will be gladder still to get back to them again.” But Little Rifle was not to be moved from his deliberate tread, and he compelled Harry to keep pace with him, though it was hard work to restrain him. “You will lose nothing by care!” he admonished, “and can gain nothing by haste. Take my advice, and feel every step of ground before you put your foot down.” “Strange we can not see any thing of the water,” remarked Harry; “there ought to be some dim sort of light to show where we entered, for the sound shows that we are close to them.” He was still walking forward, in his confident way, when Little Rifle seized his arm with such violence as almost to throw him backward to the ground. “Before you go a step further, strike one of your matches.” “All right,” replied the lad; “but what’s the use of jerking a fellow’s arm off, when you want to tell him to do a thing?” After some delay the match was produced and struck, and it showed them a sight that made their blood run cold with terror! Less than two paces in front of Harry Northend yawned a black abyss, fully twenty feet in width, through whose fathomless depths roared a torrent of water, with a hollow, reverberating sound, as if it were hundreds of feet below. Another moment, and both would have walked over into eternity. As the match flickered and fell from the hand of Harry, he gasped and clutched the arm of his comrade, exclaiming, in a horrified whisper: “What an escape! You saved me again.” “I doubted from the first,” he replied, in a calm voice, “because the sound was not natural to me. We are lost, as you can see for yourself; but we will not give up nor keep idle. It is better to push ahead, if we do get wrong.” “Hello! see there!” exclaimed Harry, the next moment. “There is something of a different order.” Both saw at the same instant a small, dim point of light, that looked like the shining of a pale star through mist or vapor. “What can that be?” he asked, as they paused and gazed toward it. “I can not guess even,” replied Little Rifle; “let us go toward it and see whether we can not find out!” CHAPTER XIII. THE HOLE IN THE AIR. Little Rifle and Harry Northend stood in the cavern, gazing in wonder at the pale, glimmering point of light, neither able to guess what it could mean.