Mr. Swift approved Tom's policy of silence. Almost immediately the phone began ringing again with a succession of calls from other newspapers and wire services. Tom dashed off a brief, general statement and instructed Miss Trent to give it to all further callers. "Maybe this is a good time to make a private announcement to you fellows," Mr. Swift said to the two boys, his eyes twinkling. "Do you recall my telling you that Doc Simpson had isolated an unknown vitamin from the space plants? Well, we've now discovered that this vitamin can condition the human body to stay under water indefinitely. Doc is putting some up in capsule form." Both Tom and Bud gave whoops of glee at this news. "Dad, you've helped overcome one of the big problems in our search for the lost missile!" Tom exclaimed. CHAPTER XV MOUNTAIN HIKE "After adequate doses of your space vitamin, Dad, a skin diver could tackle almost any undersea job in my hydrolung!" Tom exclaimed. "He wouldn't be subjected to any antiosmosis troubles with his body tissues." His father nodded. "For the first time, man might become a _truly marine creature_!" "Wow! Think of it!" Bud gasped excitedly. "With Tom's hydrolung and a knife to hunt his own food, he could practically live in the sea!" "That's no farfetched dream, Bud." Tom's steel-blue eyes flashed at the thought of new fields of scientific conquest. "This discovery of Dad's and Doc Simpson's opens up some really amazing possibilities." Most important at the moment, the vitamin would be a great boon in carrying out search and digging operations for the Jupiter prober. With fresh enthusiasm, Tom returned to his laboratory to work on the new sonar gear. In his own mind, he had already named it a "quality analyzer sonar," since that exactly described the way it would function. "Hmm, let's see," Tom mused as he settled down at his workbench, pencil in hand. "Besides a regular sonarscope, I'll need at least three units for the gear." First, he would need an oscillator to produce the complex pulse. Next, of course, an oscilloscope to check the pulse as it was beamed out. Last--but highly important--a correlation calculator. This latter unit would compare the original pulse with the returning echoes. If an echo had a high enough "standard of acceptance"--that is, if its quality was very near the original pulse, it would show up on the screen in the normal way. If the echo came back blurred, or if "shadow echoes" showed up, these would be separated and appear on the screen colored red. "Whew!" Tom sighed as he realized the complicated job of circuit design that lay ahead. "This sure is going to burn some midnight oil!" The young inventor worked all afternoon at a furious pace, breaking off toward dinnertime to telephone his mother that he would be staying overnight at the lab. After a hasty meal, he resumed his layout job at the drawing board and by midnight had finished designing his quality analyzer sonar.