Monday morning he was ready to try the outfit. The sonarscope with its tiny viewing screen was strapped to his left forearm. Another small unit was fastened to the inside of his wrist, with four plungers in finger-tip reach. "What in tarnation's that?" Chow asked. "Simplified controls," Tom explained. "One's for breathing adjustment, one's for the density unit, one is my ion-drive 'throttle,' and this last is for the sonar pulse--which will duplicate the porpoise sound." The suit worked perfectly in a tank test. Chow was amazed as he listened to Tom gliding about, via an underwater microphone. "If that don't beat all!" he declared. "Can't tell the difference 'twixt you an' Smiley!" As Tom emerged from the tank, the portly cook rolled up his own pantlegs and waddled up the metal ladder to the tank brim. He summoned the porpoise with a whistle and straddled its back. "What in the name of aquanautics do you think _you're_ doing?" Tom gasped. "I'll show you a real broncobustin' act in the water," Chow bragged. Smiley glided off gently at first, Chow fanning the air with his hat and yipping like a rodeo star. He did, in fact, cling to his slippery perch with considerable skill. But suddenly Smiley began bobbing and humping like an eel. Chow's face froze in alarm. A moment later the porpoise dived and the cook let out a yell of terror, "He-e-elp!" Roaring with laughter, Tom dived in and rescued him. "Guess he ain't quite broke yet, pardner!" "Reckon not." Now that Tom had all his technical problems solved, he plunged eagerly into the job of fitting out his expedition to the South Atlantic to search for the lost Jupiter missile. [Illustration] Besides the _Sea Hound_ and the other diving seacopter which had already been rigged with antisonar and antidetection equipment, Tom ordered a large cargo jetmarine to be similarly equipped. [Illustration] Then he drew up a list of supplies and underwater search gear needed for the missile hunt. Tom phoned orders to a dozen different departments. Food, space-plant pills, extra clothing, tools, including a midget atomic earth blaster, grappling hooks--nothing was overlooked. "I'd better take along a Damonscope too," Tom reflected. "Judging by those Navy reports, ordinary Geiger counters haven't revealed anything." Tom's Damonscope, one of his early inventions, was a photographic device which worked on fluorescent principles. It was amazingly sensitive to any form of radioactivity--and the missile, of course, would be "hot" from exposure to cosmic rays. Meanwhile, Tom had ordered his new hydrolung suit, with its four-plunger control unit and porpoise sonar, to be flown back to Enterprises. Arv Hanson had promised to make up several duplicates with a team of technicians working on all-night shifts. Late the next afternoon Tom returned to the mainland to confer with his father. Mr. Swift reviewed the expedition plans with approval.