Russ, standing beside Greg at the control panel, looked out into space and marveled. They were flashing through space, their speed building up at a breath-taking rate, yet they had no real propulsion power. The discovery of the gravity concentrator had outdated such a method of driving a spaceship. Instead, they were falling, hurtling downward into the yawning maw of an artificial gravity field. And such a method made for speed, terrible speed. Jupiter seemed to leap at them. It became a great crimson and yellow ball that filled almost half the vision plate. * * * * * The _Invincible's_ speed was slacking off, slower and slower, until it barely crawled in comparison to its former speed. Slowly they circled Jupiter's great girth, staring out of the vision port for a sight of Craven's ship. They were nearing the position the little mechanical shadow had indicated. "There it is," said Russ suddenly, almost breathlessly. Far out in space, tiny, almost like a dust mote against the great bulk of the monster planet, rode a tiny light. Slowly the _Invincible_ crawled inward. The mote of light became a gleaming silver ship, a mighty ship--one that was fully as large as the _Invincible_! "That's it all right," said Greg. "They're lying behind a log out here raising hell with our television apparatus. Maybe we better tickle them a little bit and see what they have." Rising from the control board, he went to another control panel. Russ remained standing in front of the vision plate, staring down at the ship out in space. Behind him came a shrill howl from the power plant. The _Invincible_ staggered slightly. A beam of deep indigo lashed across space, a finger suddenly jabbing at the other ship. Space was suddenly colored, for thousands of miles, as the beam struck Craven's ship and seemed to explode in a blast of dazzling indigo light. The ship reeled under the impact of the blow, reeled and weaved in space as the beam struck it and delivered to it the mighty power of the screaming engines back in the engine room. "What happened?" Greg screamed above the roar. Russ shrugged his shoulders. "You jarred him a little. Pushed him through space for several hundred miles. Made him know something had hit him, but it didn't seem to do any damage." "That was pure cosmic I gave him! Five billion horsepower--and it just staggered him!" "He's got a space lens that absorbs the energy," said Russ. "The lens concentrates it and pours it into a receiving chamber, probably a huge photo-cell. Nobody yet has burned out one of those things on a closed circuit." Greg wrinkled his brow, perplexed. "What he must have is a special field of some sort that lowers the wave-length and the intensity. He's getting natural cosmics all the time and taking care of them." "That wouldn't be much of a trick," Russ pointed out. "But when he takes care of cosmics backed by five billion horsepower ... that's something else!"