Then the great red crabs began to climb out of the water, heat-ray tubes grasped in their claws. Ray fired as fast as he could load and aim. Still he shot with deliberate care, and almost every shot was effective. Intense, ruby-red rays flashed up from the lake shore. Twice, one of them beat scorchingly upon us for a moment. Once a rock beside us was fused and cracked with the heat. But Ray fired rapidly, and the rays winked out as fast as they were born. He was powder-stained, black and grimy. The heat-ray had singed his clothing. He was dripping perspiration. The gun was so hot that he could hardly handle it. But still the angry bark of the rifle rang out, almost with a deliberate rhythm. Ray was a fine shot in his youth on his father's Arizona ranch, but his best shooting, I think, was done from above that cascade of liquid fire, at the hordes of monster scarlet crabs. Mildred scrambled over the edge, unharmed. Her breast was heaving, but her face was bright with joy. "You are wonderful!" she gasped to Ray. We seized the packs and beat a hurried retreat. A crimson forest of the heat-rays flashed up behind us, and flamed upon the black walls and roof of the cavern until glistening lava became incandescent, cracked and fused. We were below the line of the rays. Quickly we made the bend in the cavern and followed at a halting run up the path beside the shimmering river of opalescent light. Before us the torrent of fire fell in a magnificent flaming arc from the roof. We rounded the pool of lambent milk of flame, passed the roaring torrent of coruscating liquid radiance and reached the ladder in the square, metal shaft. "If we can get to the top before they can get up here, we're safe," Ray said. "If we don't, this shaft will be a chimney of fire." In the haste of desperation, we attacked the thousand-foot climb. I went first, Mildred below me, and Ray, with the rifle, in the rear. Our heavy packs were a terrible impediment, but we dared not attempt to go on without them. The metal rungs were four feet apart; it was no easy task to scramble from one to the next, again and again, for hundreds of times. * * * * * It must have taken us an hour to make it. We should have been caught long before we reached the top, but the giant crabs were slow in their lumbering movements. Despite their evident intelligence, they seemed to lack anything like our railways and automobiles. The cold gray light of the polar sky came about us; a dull, purple-blue square grew larger above. I clambered over the last rung, flung myself across the top of the metal shaft. Looking down at the tiny fleck of white light so far below, I saw a bit of red move in it. "A crab!" I shouted. "Hurry!" Mildred was just below me. I took her pack and helped her over the edge. Red flame flared up the shaft. We reached over, seized Ray's arms and fairly jerked him out of the ruby ray.