er. "Remember what happened to the instruments?"

[Illustration]

"Uranium!" exclaimed Astro.

The word echoed in the kitchen like the blast of a bomb. The boys looked
at each other, too startled to explain to Logan and Jane, who, though
they were listening intently, were unable to fathom the boys' reasoning.

"Where were you last night?" asked Jeff quickly.

Roger described as nearly as he could remember the exact route that they
had traveled in making their way to the Logan farm.

"Hey, I think I've got the answer, fellows!" Tom suddenly exclaimed.
"If Vidac came out here last night and took over Mr. Logan's farm, and
we're falsely accused of getting rid of the professor, and the professor
is missing, there must be something to tie it all together. Vidac
wouldn't do the things he's done, unless he's got a rocket-blasting good
reason!"

Roger quickly added, "And he wouldn't try to buck Captain Strong unless
he was playing for high stakes!"

"Right," said Tom. "The only thing that could have caused our watches to
go haywire, like the ships instruments, would be uranium. Lots of
uranium. And uranium is the only thing valuable enough to make Vidac
take such long chances."

"But how can you tell it's uranium?" asked Logan.

"Our watches are not ordinary timepieces, sir," explained Tom. "They are
specially constructed for use in space travel. Each watch is
electrically controlled and highly sensitive."

"Electric?" repeated Logan in amazement. "Electric wrist watches? That
small thing?"

Tom smiled. "Each is charged by a miniature power pack, sir."

"The uranium deposits out in the hills affected these watches,"
continued Astro, "the same way they affected the electronic instruments
on the spaceships coming in to Roald."

"I'll tell you what," said Jeff. "I'll make a check."

"Wait a minute," said Logan. "I just remembered something--"

"What, sir?" asked Tom.

"Professor Sykes! He was out here poking around in my fields and up in
the hills from dawn till dark. Said he was making some soil tests. I
yelled at him for stepping all over some baby fruit trees."

"That's it, then," said Roger grimly. "This area is jumping with
uranium and Vidac now has title to the land!"

"Don't be so sure," said Tom. "We still need proof."

"Isn't using force to take the land away proof enough?" snapped Logan.

"Wait a minute!" said Jeff. "If you want proof, I know where to get it."

"Where?" asked Tom.

"The profe