e noise
Mel made," muttered Chow as he watched the jagged lines of light
flashing on the pulse-check oscilloscope. "Now what're you fixin' to do
with it?"

"This will be fed into the diver's sonar along with his own noise
output," Tom said, "to make him sound like a porpoise."

Chow howled. "That I've got to hear!"

The young inventor worked feverishly throughout the day and into the
next, perfecting his new "porpoise sonar." Using microelectronic
components, he was able to reduce all the units to amazingly small size.

Next, Tom began tailoring himself a completely new skin-diving suit.
Mask, ion-drive jet, and the various hydrolung units were molded into
the plastic, with no loose wires or tubes showing.

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 div