CHAPTER IV
AERIAL ATTACK
"Yes, son," Mr. Swift went on. "What's needed is a new type of breathingdevice--one that will eliminate bulky air tanks and permit a skin diverto stay down for long periods."
"Quite an order, Dad."
Grabbing a pencil, the young inventor began sketching. In both his FatMan suits and his osmotic air conditioner, Tom had already perfectedways of drawing oxygen from sea water.
"But a small gadget for skin divers," he said, "will take a fantasticjob of electronic miniaturization." After a pause he added, "It couldreally speed up recovery of the Jupiter prober, though."
Lunch over, Tom hopped a jet scooter and sped off to his privatelaboratory. The modernistic glass-walled structure--designed by Tomhimself--had every tool of modern scientific research, from electronicmicroscope to helium cryostat.
As always, whenever he was absorbed in a new idea, Tom was eager to getto work. "Let's see what I'm shooting for. A small container, slungaround the diver's neck?... No, too dangerous. Better hook it to hisweight belt, with a tube to his face mask."
Using a plastic foam "breadboard," Tom began experimenting with variouscircuit designs. He worked through the afternoon and returned to theproblem early the next morning.
He was interrupted by a message from Art Wiltessa, reporting no luck sofar in finding the missile. Later, shortly before lunch, Tom receivedanother call, this time from Admiral Walter. "Just wanted to keep youposted, Tom. Our task force reports no success on their part in findingthe buried missile. No sign of the enemy, either."
"They'd probably hesitate to attack any official U.S. Navy units," Tomsaid. "Or it might mean they've already found the missile themselves."
"That's what I fear," Admiral Walter confessed gloomily. "However, we'llcontinue searching."
Tom promised to fly down to the site at the first opportunity, saying hewas developing a new device that might assist in the search. Aftersnatching a hasty lunch, Tom returned to work.
Arv Hanson machined several parts and molded the plastic face mask toTom's specifications. By evening the new device was completed.
"Now for a test," the young inventor said to himself.
Sandy Swift and Phyl Newton were eager to watch the test, so the nextmorning they drove to the plant in Phyl's white convertible. Tom, cladin swim trunks, was waiting for them with Chow near the edge of amammoth concrete tank. Set in bedrock, at one end of the Enterprisesgrounds, the tank was used for submarine testing.
When Sandy saw the power unit strapped to Tom's weight belt, sheexclaimed, "_That_ little gadget will supply all the air you need? Why,it's no bigger than a pocket transistor radio!"
Tom grinned. "I hope it will. That's what I intend to find out."
"How does it work?" Phyl asked, fascinated.
Tom explained, "Actually its function is to replace the carbon dioxidethat I exhale with fresh oxygen drawn from the water. Otherwise,although the carbon dioxide I'd breathe out would be a very small amountat a time, it soon would make the air unfit. The nitrogen, which makesup much of the air we breathe, is chemically inert and can be used againand again."
He pointed to a round screen on one side of the unit. "This is the waterintake," Tom went on, "and this other screen is where the water comesout after we've removed its oxygen."
Near the forward end of the unit, a semirigid plastic tube wasconnected, leading up to the face mask. At the rear was a power port forinserting a small solar battery.
"What about this little tuning knob?" Sandy asked.
"That's the rate control for adjusting the output frequency to thewearer's breathing rate." Tom added, "I've decided to call the wholeapparatus an 'electronic hydrolung.'"
Chow pushed back his ten-gallon hat and scratched his head dubiously."Wal, I'm keepin' a net handy to drag you out, boss, just in case."
Tom chuckled and fitted the mask over his face, then made a clean diveinto the tank. For the next ten minutes the girls and Chow watchedwide-eyed as he swam, walked around, and went through vigorous exercisesat the bottom of the tank without once coming up for air.
"Whee!" Sandy exclaimed when Tom finally climbed out. "Make me one, so Ican take up skin diving!"
"It's wonderful!" Phyl added admiringly.
Tom took off his mask. "I'm pretty pleased with it myself," he admitted,grinning.
The girls stayed at Enterprises for lunch. Then the group, accompaniedby Doc Simpson, flew to Fearing Island so Tom could test his inventionin deep water. Boarding a small motor launch, with Doc at the helm, theycruised out to a suitable depth and dropped anchor.
"Don't become too confident, Tom," Doc warned. "I'll drop a signal lineover the side in case of emergency."
Tom buckled on his equipment belt and adjusted the face mask. Then heheld up crossed fingers and back-flipped over the gunwale into thewater. Chow, Doc, and the girls watched his plummeting figure fade fromview.
Tom, an expert skin diver, had never before felt such a sense of easeand freedom under water. He was moving, light and self-contained, in agreen, magical world. With no air tanks chafing his back, he felt akinto the fishes themselves.
"Wish I'd brought a hook and line along." He chuckled, as a school ofmackerel darted past.
Now came the real test. Deeper and deeper, Tom cleaved his way downward.Reaching bottom, he prowled about the ocean bed for a while, thenstarted up again. Suddenly a stab of pain shot through his chest--awarning of nitrogen bubbles forming in his blood!
Tom swam toward the signal cord, dangling dimly in the distance. By thetime he reached it, his muscles were knotting with cramps.
"It's the bends again, all right!" Tom realized. Gritting his teeth, heyanked hard on the line, then summoned his strength to hang on.
Doc and Chow hauled up frantically. Tom's face was contorted with painwhen they finally got him aboard and stripped off his mask.
"Oh! How awful!" Phyl gasped.
Sandy cradled Tom's head in her lap, and Phyl held his handsympathetically, while Doc Simpson injected a hypodermic to ease thepain. Chow steered the launch back to shore, and Tom was rushed to thebase infirmary in an ambulance.
Here he was placed in a decompression chamber for several hours andlater transferred to a hospital bed. Bud Barclay came to visit him.
"We're a fine couple of fish," he said.
Tom chuckled wryly. "_Live_ fish, anyhow."
"In my case, thanks to you," Bud said.
"Forget it, pal. The score's about even, I should think," Tom said,recalling the many life-or-death adventures they had shared.
Bud was thrilled to hear of Tom's electronic hydrolung. The younginventor spent the evening sketching out an improved design to eliminatefuture accidents.
"I'll install a special device to remove the nitrogen as the wearerexhales," Tom explained. "Then a valve will feed in helium to replaceit. Since helium doesn't dissolve in the blood like nitrogen does, itwill not bubble out when the pressure is reduced. Should have thought ofthat before!"
"But you'll need a tank for the helium, won't you?" Bud objected.
Tom shook his head. "Enough can be compressed into a small capsule tosupply the wearer's needs. Remember, it can be used over and overagain."
"Pretty neat," Bud commented.
By morning Tom felt thoroughly recovered. He insisted upon flying backto Enterprises to make the necessary changes in his hydrolung. Budaccompanied him, eager to get back on the job.
In a few hours Tom had added a small fitting to his power unit toprovide for helium substitution. Then the two boys hopped back toFearing for a second deep-water test. This time, Tom was delighted tofind that he could operate comfortably at great depths, as well as riseor descend suddenly without ill effect.
Bud was aglow with enthusiasm. "Boy, we can really explore now!"
After the boys had returned to Enterprises, Tom phoned Arv Hanson andasked that a duplicate of the hydrolung be turned out in the shop assoon as possible. It was ready the follow
ing Monday morning, so Tomsuggested to his father that the two visit the proposed underwater siteand make some sample plantings.
"Great idea, son," Mr. Swift agreed. "I want to try out your new divingapparatus myself. If it's successful, we'll be able to tackle twoproblems at once--recover the Jupiter prober and start the 'sea farm.'"
They flew to Fearing, then went by boat to the farm site, about half amile offshore. Each carried several of the valuable Far Eastern plants.
The silt beds which Mr. Swift had selected were just deep enough tokeep the plants from being discovered, yet enable them to receivesufficient sunlight.
Tom and his father started their planting. But no sooner had the firstplants been embedded than fish darted in to nibble them. Even the rootsdisappeared into their greedy maws.
"Looks as though we'll have to build some sort of net enclosure aroundand over our farm," Mr. Swift said, after they had climbed back intothe boat. "But at least your hydrolung device is a great success, son!"
Tom was thoughtful. "Dad, I wonder if the fish would eat those plantsfrom space which you've been growing under salt water?"
Tom was referring to certain strange plants rocketed to earth by unknownspace friends with whom the Swifts had been in communication.
"I have a hunch," Tom went on, "that the fish might be repelled by theunusual scent of those space plants. If so, we could scatter them amongthe earth plants to keep the fish away."
Mr. Swift was impressed by Tom's idea. As soon as they had returned toEnterprises, he proposed that the experiment get under way.
Tom volunteered to undertake the job at once with Bud. While the younginventor phoned his copilot, Mr. Swift went to his own laboratory toprepare the plants for shipment.
Twenty minutes later the boys took off in a jet. The plants had beenparceled in transparent plastic film. Glistening with a red metallicsheen, they looked somewhat like tulips with honeycombed centers.
"Scarecrow plants to drive off fishes," Bud joked. "What will scientiststhink of next!"
Tom laughed, then abruptly frowned. "Hey! What's that character up to?"he said. "Trying to buzz us?"
A sleek gray jet without markings was arrowing in on them from threeo'clock. Bud flicked on the radio and barked a warning. The plane madeno response. As it kept coming, Tom increased speed--then rolled, dived,and changed course, but failed to shake off their pursuer.
Bud, meanwhile, was frantically calling Enterprises and a nearbyairport, but getting no response. Yet their radio was working, for avoice suddenly crackled:
"_Follow the mystery plane for a landing and you won't be harmed!_"