down the ladder onto the
landing-stage, gasping and choking in the rarefied air that lay like a
blanket at the bottom of the crater. And the reason for this was only
too apparent to Nat as soon as he was on the level stage.

Overhead, at an altitude of about a mile, the black ship hung, and
from its bow a stupendous searchlight played to and fro over the
bottom of the crater, making it as light as day. And where had been
the mining machinery, the great buildings that had housed convicts and
Moon people, and the huge edifice that contained the pumping station,
there was--nothing.

The devilish ray of Axelson had not merely destroyed them, it had
obliterated all traces of them, and the crew of the liner were
breathing the remnants of the atmosphere that still lay at the bottom
of the Crater of Pytho.

But beside the twin landing-stages, constructed by the World
Federation, another building arose, with an open front. And that front
was a huge mirror, now scintillating under the searchlight from the
black ship.

"That's it, Sir!" shouted Brent.

"That's what?" snapped Nat.

"The deflecting mirror I was speaking of. That's what deflected the
ray that wiped out China. The ray didn't come from the Moon. And
that's the mirror that deflects the teleradio waves, the
super-Hertzian rays that carry the sound."

Nat did not answer. Sick at heart at the failure of his mission, he
was watching the swarm of Moon men who were at work upon the
landing-stage, turning the steel clamps and regulating the mechanism
that controlled the apparatus. Dwarfed, apish creature, with tiny
limbs, and chests that stood out like barrels, they bustled about,
chattering in shrill voices that seemed like the piping of birds.

It was evident that Axelson, though he had wiped out the Moon convicts
and the Moon people in the crater, had reserved a number of the latter
for personal use.

* * * * *

The black ship was dropping into its position at the second
landing-stage, connected with the first by a short bridge. The
starboard hold swung open, and a file of shrouded and hooded forms
appeared, masked men, breathing in condensed air from receptacles upon
their chests, and staring with goggle eyes at their captives. Each one
held in his hand a lethal tube containing the ray, and, as if by
command, they took up their stations about their prisoners.

Then, at a signal from their leader, they suddenly doffed their mas