As he did this, he heard a peculiar rumbling sound, coming from a distance. He stopped to listen, and the rumble grew louder and louder. "What in the world can that be?" he asked himself. "Sounds like a train of cars rushing through a tunnel. I wonder----Oh!" Dave stopped short, and it is no wonder that a sudden chill passed over him. The very rocks on which he was standing had begun to quake. Then from overhead several stones fell, one so close that it brushed his shoulder. "It's an earthquake, or another landslide!" he gasped. "I must get out of this, or I'll be buried alive!" And then, torch in hand, he started for the opening to the mine. He had hardly covered half the distance to the outer air when there came another quaking, and more rocks fell, one hitting him on the arm. The torch was knocked from his hand and he tripped and fell. Then came a crash and a roar, and to Dave it seemed as if the end of the world had come. He was more than half-stunned, and he fell against a wall of rocks, wondering what would happen next. CHAPTER XXIX ANOTHER LANDSLIDE It was another landslide, crashing and roaring down the side of the mountain, carrying rocks, dirt, and brushwood before it. The earth roared and shook, and it was said afterwards that the slide could be heard many miles away. Down in the mine that he had but just discovered, Dave remained crouching against a wall of rock, murmuring a prayer for his safe deliverance from the peril that encompassed him. Every moment he expected would be his last--that those rocky walls would crash in on him and become his tomb. Roar followed roar, as the landslide continued and more rocks fell. Then the air around him seemed to be compressed, until he could scarcely breathe. "Oh, if I were only out of this!" he thought, and at that moment he would have gladly given all he was worth to have been in the outer air once more. Gradually the roaring and the quaking ceased, and Dave breathed a little more freely. He groped around in the darkness and managed to locate the fallen torch, which still glowed faintly. He swung it into a blaze with nervous energy. Was the landslide at an end? Fervidly he prayed that it was. Torch in hand, he tried to make his way to the spot where he had entered the mine. He soon found this impossible, for the reason that the passageway had shifted, and huge rocks blocked his way. Several times he tried to climb over the rocks, only to fall back helplessly. He cut his hands and broke his finger-nails, but this availed him nothing. "But I've got to get out! I've got to!" he told himself, over and over again. "I can't stay here!" And then he tried to climb the rocks in front of him once more. It was hard work, especially with the torch in hand. Once Dave tried to carry the torch between his teeth, but it was too short, and his face was scorched, while the smoke almost strangled him.