ntaneous explosion, was not that. Other ships have
been destroyed, and they seemed to catch fire, and burn, but with
terrific speed, more like gun powder than coal. It seems to start a
spreading decomposition, the ship lasts perhaps ten minutes. If it went
instantly, the shock of such a tremendous energy release would disrupt
the planet.

"At any rate, the great fleet separated, twelve went to the North Pole
of Earth, twelve to the south, and similarly twelve to each pole of
Venus. Then one of them turned, and went back to wherever it had come
from, to report. Just turned and vanished. Similarly one from Venus
turned and vanished. That leaves twelve at each of the four poles, for,
as I said, there were an even fifty.

"They all followed the same tactics on landing, so I'll simply tell what
happened in Attica. In the North they had to pick one of the islands a
bit to the south of the pole. They melted about a hundred square miles
of ice to find one.

"The ships arranged themselves in a circle around the place, and
literally hundreds of men poured out of each and fell to work. In a
short time, they had set up a number of machines, the parts coming from
the ships. These machines at once set to work, and they built up a relux
wall. That wall was at least six feet thick; the floor was lined with
thick relux as well as the roof, which is simply a continuation of the
wall in a perfect dome. They had so many machines working on it, that
within twenty-four hours they had it finished.

"We attacked twice, once in practically our entire force, with some
ray-shield machines. The result was disastrous. The second attack was
made with ray shielded machines only, and little damage was done to
either side, though the enemy were somewhat impeded by masses of ice
hurled into their position. Their relux disintegration ray was
conspicuous by its absence.

"Yesterday--and it seems a lot longer than that, son--they started it
again. They'd been unloading it from the ship evidently. We had had
ray-shielded machines out, but they simply melted. They went down, and
Earth retreated. They're in their fortress now. We don't know how to
fight them. Now, for God's sake, tell us you have learned of some
weapon, son!"

The older man's face was lined. His iron gray head showed his fatigue
due to hours of concentration on his work.

"Some," replied Arcot briefly. He glanced around. Other men had arrived,
men whom he met in his work. But there w