Tom or Mel quickly, then swim away, evidently expecting to be
chased in turn!

"I give up!" Mel snorted in disgust.

Tom grinned and bobbed to the surface. He waved his hand several times
in a prearranged signal. Zimby at last spotted him and brought the _Sea
Hound_ to the scene.

Raising his mask, Tom called, "Let's have the net!"

Zimby lowered a nylon net and some pieces of fish to the two swimmers as
they came alongside. With the food as bait they tried to lure the
porpoise to the seacopter. But just as they thought they had it, the
monster would scoot off.

"It's just laughing at us!" Mel fumed.

At last, after winning its confidence with several bits of fish, the
boys succeeded in snaring the porpoise. Tom clambered onto the _Sea
Hound_'s deck and helped Zimby haul their catch aboard. "Quacking"
reproachfully, it was lowered through the hatch and placed in the tank,
which was then pumped full of salt water.

As soon as the _Sea Hound_ arrived at Fearing, Tom phoned Chow Winkler
at Enterprises and asked him to fly out to the base.

"Pardner, how'd you like to ride herd on this critter and gentle it down
for me?" Tom asked, when he showed Chow the porpoise.

It had been transferred to a huge, glass-paneled tank which had been set
up just outside Tom's Fearing Island laboratory during his flight to the
Florida Keys.

"Reckon I kin try makin' friends with it," Chow declared.

The porpoise stared morosely at Chow. The kindly old Texan's heart was
touched by the odd creature. To his delight, it soon responded to his
friendly overtures and quickly recovered its good nature. By the next
morning the porpoise was playing catch with Chow, or else swimming over
to have its back scratched. The cook named it Smiley.

"She's kind of a sea cow," he told Tom, "and you got to talk to my
Smiley like any cow!" Tom grinned and refrained from explaining to Chow
that a real "sea cow" was a walrus.

Meanwhile, the young inventor was busy with his own experiments. By
means of a microphone placed in the tank, he made exact recordings of
Smiley's "talk." Using Mel Flagler as a subject, Tom also tape-recorded
the sound of a skin diver propelled through the water by ion drive.

The next step was to compare the sound pattern of the tapes. Tom
filtered out the difference in the two sounds with the correlation
calculator unit of one of his quality analyzer sonars.

"Uh-huh. So you got the difference betwixt Smiley's talk an' th