And then came another distant rumble, showing that the earthquake, or landslide, was not yet at an end. The boy held his breath, wondering if it would come closer and annihilate him. But the rumble remained at a distance, and in less than a minute passed away completely. "Thank fortune, that didn't come here!" he murmured, and passed his hand over his forehead, upon which the thick beads of cold perspiration had gathered. He strained his ears for several seconds longer, but all around him was now as silent as a tomb. "Oh, I must get out!" he muttered, despairingly. "I must! There must be some kind of an opening somewhere!" Again he stumbled onward, into one passageway after another. Once the place was so narrow that he became fairly wedged fast and had all he could do to draw back. Then a sudden chill swept through his body, making his teeth chatter. Must he give up? Was that cave to become his tomb? The thought forced itself upon Dave in spite of his effort to take a more cheerful view of the situation. He was hemmed in--not an avenue of escape seemed open. "I won't give up! I won't! I won't!" he muttered, half savagely, and got up from the rock on which he had sunk down to rest. Climbing around in that place where the footing was so uncertain had taken both his wind and his strength, and he was panting, and his knees shook beneath him. Only a short time had elapsed since that dreadful first shock had come, yet to the youth it seemed an age. He looked at the torch. It had burned well down and would not last much longer. And when it was gone he would be left in total darkness! This was a new cause for fear, and it made Dave move around faster than ever. Suddenly he stopped short. A new sound had reached his ears--a strange, weird sound that made his flesh creep and his hair stand on end. It was the cry of a wildcat--shrill and uncanny in that pent-up space. Slowly it came nearer, although from what direction our hero could not at first make out. He waited behind a spur of rocks and the cry--it was more a whine of fright than anything else--came closer. Then, on a shelf of rocks but a short distance away, Dave caught sight of the beast. It was limping along on three feet, dragging a bleeding hind leg and a bleeding tail behind it. Evidently it had been caught between the falling stones as in a trap and had pulled itself loose in a mad effort to save its life. For the moment Dave forgot his other perils as he faced the beast. Evidently the wildcat had scented the youth, for it gave a savage cry as of defiance. Perhaps it thought that Dave was responsible in some way for the pain it was suffering. The youth's hand was on the rocks and almost unconsciously it closed on a sharp stone about as big as his fist. Raising the stone, he took quick aim and threw it at the wildcat.