Houston shouted, and they hastened to the rescue, and the entrance was very quickly cleared sufficiently for Houston to crawl through. Before passing through, himself, however, he lifted Bull-dog, and carefully handed the unconscious form to Jack. "Who is this?" the latter asked in surprise. "Bull-dog, the little hero who has saved our lives by sacrificing his own," Houston replied. "Is he still living?" "Yes, but unconscious." Silently and tenderly Jack handed the little fellow to the tender-hearted Mike, who at once started toward the tunnel with his burden, while Jack turned to assist Houston. At that instant, there came the third explosion, which was farther underground than either of those preceding. It was but a short distance from them, and an immense scale of overhanging rock quivered for an instant, then fell, throwing its fragments in every direction. Mike, at the distance which he had already gained, escaped unhurt. Jack and Houston sprang in opposite directions, but the pieces of flying rock overtook them, though they escaped being buried beneath the mass as it fell. They were both thrown to the ground; Houston staggered to his feet, badly bruised and cut and his left arm broken, but Jack remained motionless. Hearing Houston's call, Mike quickly returned, and he and Houston found that Jack was still alive, though badly injured about the head. The full extent of his injuries they realized they would be unable to ascertain until they could reach the surface. Together they consulted as to the best course to pursue. Mike wished to go back and get help immediately, but Houston insisted that they must first remove Jack and little Bull-dog as speedily as possible, as there was danger of other explosions following now in rapid succession, and also danger from the smoke and gases of the gradually approaching flames, which were consuming the timbering of the various shafts, and would at length communicate with the tunnels also. Instructing Mike to lay Jack's head across his shoulder, Houston then clasped his right arm closely about Jack's neck and shoulders. Mike, carrying Bull-dog on one arm, with the other was to lift Jack underneath the knees; and in this way they started for the tunnel. Houston suffered excruciating pain from the arm hanging helpless at his side, but he traveled forward without a murmur, scarcely conscious of his own suffering in his anxiety for Jack. The cut was comparatively short, but their progress was slow. Nearly overcome by the suffocating gases and the smoke, and faint from pain and loss of blood, Houston had just staggered into the tunnel, when he heard the welcome sound of the voices of Lyle and of Morton Rutherford, and knew that they were saved. CHAPTER XLVI.