rrible mouth was pursed with
his concentration of thought.

"The electrodes partially break down the atoms of fuel passing from
the tank," explained Dex, desperately attempting scientific
phraseology for a matter as far over his head as the remote stars. He
raised his hand a trifle, bringing it nearer the Rogan's tube....

"Is that the outlet from the tank?" inquired the Rogan, pointing with
the tube, and so raising it out of Dex's reach.

"Yes," mumbled Dex, sick with disappointment: he'd been on the point
of leaping for the weapon. He sidled close again. Greca bit her lips
lest she cry out with suspense.

"The partially disintegrated atoms pass into the turbine chamber," he
went on, "and are there completely broken down by heat, which has been
generated by the explosive energy of the atoms passing in before
them."

"I warn you to speak true," said the leader, suddenly removing his
gaze from the specimen motor and staring icily down at Dex. Dex's hand
dropped abruptly from its place near the tube. Again his fingers had
come within a foot of it.

* * * * *

"We will get ahead faster," piped the Rogan, an edge of suspicion
sounding in his shrill voice, "if I conduct the explanation. I will
ask questions for you to answer. What is the fuel used?"

"Powdered zinc," Dex answered promptly. No harm in admitting that. The
Rogans must already know it; zinc was common to Jupiter, as Earth
spectroscopes had showed long since; and they had no doubt analyzed it
by now. The chances were that the leader was merely testing him, to
see if he were sincere in his ostensible surrender.

That his guess was right, he read in the fishy, dull eyes. The Rogan
leader nodded at his answer, and some of the lurking suspicion in his
gaze died down.

"How is it prepared?"

Now this marked the beginning of the end, Dex knew. The preparation of
the powdered metal was half the secret of atomic power--and Dex hadn't
the faintest idea what it was! This questions-and-answers affair was
going to pin him down in short order!

"How is it prepared?" repeated the Rogan leader inexorably. "Tell us,
or--"

But at that instant Dex attained his objective.

Once more his hand had crawled slowly toward the tube--till, once
more, it was within reach. Then, more bold as his position grew more
desperate, he straightened up--and, with a lightning move, had
wrenched it from the sucker-disk that held it!

He shouted his