The light appeared again only a few hundred yards away. The water swirled and the sphere swayed drunkenly as some gigantic body moved past it with express train speed and entered the mouth of the cavern. The light turned toward them and they could see the dim outlines of a small submarine on which it was mounted. Another rush of water came as the object which had entered the cave started to leave it, and the light swung around. It bore on a huge black body, and was reflected with a red glow from huge eyes, and the creature backed again into the cave. Back and forth across the mouth of the cavern the light played, and the watchers caught a glimpse of a huge parrot beak which could have engulfed a freight car. From the cavern projected twisting tentacles of gargantuan dimensions, and red eyes, thirty feet in diameter, glared balefully at them. For several minutes the light of the submarine played across the mouth of the cave, and then the floodlights on the cliff sprang into full glow and bathed the ball and the mouth of the tunnel in a flood of light. Before their horrified gaze was an octopus of a size to make them disbelieve their eyes. The submarine had moved up to within a few feet of them, and the light from it played full on the ball. The submarine maneuvered in the vicinity, keeping the ball full in the beam of its light, and then drew back. As it did so, the floodlights on the cliff died out and the beam of the submarine's light was directed away from them. Dr. Bird jumped to the telephone. "Head straight out to sea and full speed ahead!" he shouted. "Don't try to pull us in; tow us!" * * * * * The ball swayed as the _Minneconsin's_ mighty engines responded to his orders and the cliff wall disappeared. "As long as they know we're here, we might as well announce our presence in good style," said the doctor grimly as he closed a switch and threw all of the sphere's huge lights into action. He had turned on the lights just in time, for even as he did so a mighty tentacle shot out of the darkness and wrapped itself around the ball. For a moment it clung there and then was withdrawn. "The thing can't stand light," remarked the doctor as he threw off the switch. "That sub was herding it like a cow by the use of a light beam. As long as we are lighted up we are safe from attack." "Then for God's sake turn on the lights!" cried Carnes. "I want it to attack us," replied the doctor calmly. "We have no offensive weapons and only by meeting an attack can we harm the thing."