s located, and, although the
terrible rays were again focused upon the intruder in all their
intensity, the carnage continued.

In a few minutes, however, the men heard, or rather felt, a low, intense
vibration, like a silent wave of sound--a vibration which smote upon the
eardrums as no possible sound could smite, a vibration which racked the
joints and tortured the nerves as though the whole body were
disintegrating. So sudden and terrible was the effect that Seaton
uttered an involuntary yelp of surprise and pain as he once more fled
into the safety of space.

"What the devil was that?" demanded DuQuesne. "Was it infra-sound? I
didn't suppose such waves could be produced."

"Infra-sound is right. They produce most anything here," replied Seaton,
and Crane added:

"Well, about three fur suits apiece, with cotton in our ears, ought to
kill any wave propagated through air."

The fur suits were donned forthwith, Seaton whispering in Crane's ear:

"I've found out something else, too. The repellers repel even the air.
I'm going to shoot enough juice through them to set up a perfect vacuum
outside. That'll kill those air-waves."

Scarcely were they back within range of the fleet when DuQuesne,
reaching for his gun to fire the first shot, leaped backward with a
yell.

"Beat it!"

Once more at a safe distance, DuQuesne explained.

"It's lucky I'm so used to handling hot stuff that from force of habit I
never make close contact with anything at the first touch. That gun
carried thousands of volts, with lots of amperage behind them, and if I
had had a good hold on it I couldn't have let go. We'll block that game
quick enough, though. Thick, dry gloves covered with rubber are all that
is necessary. It's a good thing for all of us that you have those fancy
condensite handles on your levers, Seaton."

"That was how they got Dunark, undoubtedly," said Crane, as he sent a
brief message to the girls, assuring them that all was well, as he had
been doing at every respite. "But why were we not overcome at the same
time?"

"They must have had the current tuned to iridium, and had to experiment
until they found the right wave for steel," Seaton explained.

"I should think our bar would have exploded, with all that current. They
must have hit the copper range, too?"

Seaton frowned in thought before he answered.

"Maybe because it's induced current, and not a steady battery impulse.
Anyway, it didn't. Let's go!"

"Ju