h anti-magnetic apparatus darted out. One hundred and four
passed the struggling fields. One found lodgement on a Miran ship, and
crushed in a metal wall, to be stopped by a bulkhead.

The Chief engineer watched his power declining. All ten UV beams were
united in one now, driving a terrible sword of energy that made the
attacked ship skip for safety instantly, yet the beams were all but
useless. For the Miran reserves filled the gap, and the magnetic tornado
continued.

For seventeen long minutes the station resisted the attack. Then the
last of the strained mercury flowed into the receivers, and the vast
power of the atostors was exhausted. Slowly the magnetic fields
declined. The great walls of the station felt the clutching lines of
force--they began to heat and to strain. A low, harsh grinding became
audible over the roar of the atomic bombs. The whole structure trembled,
and jumped slightly. The roar of bombs ceased suddenly, as the station
jerked again, more violently. Then it turned a bit, rolled clumsily.
Abruptly it began to spin violently, more and more rapidly. It started
rolling clumsily across the plateau--

A rain of atomic bombs struck the unprotected metal, and the eighth
breached the walls. The twentieth was the last. There was no longer an
IP station on Europa.

"The difference," said Buck Kendall slowly, when the reports came in
from scout-ships in space that had witnessed the last struggle, "between
an atomic generator and an atomic power-store, or accumulator, is
clearly shown. We haven't an adequate _source_ of power."

McLaurin sighed slowly, and rose to his feet. "What can we do?"

"Thank our lucky stars that Faragaut here, and I, bought up all the
mercury in the system, and had it brought to Earth. We at least have a
supply of materials for the atostors."

"They don't seem to do much good."

"They're the best we've got. All the photocells on Earth and Venus and
Mercury are at present busy storing the sun's power in atostors. I have
two thousand tons of charged mercury in our tanks here in the 'Lunar
Bank.'"

"Much good that will do--they can just pull and pull and pull till it's
all gone. A starfish isn't strong, but he can open the strongest oyster
just because he can pull from now on. You may have a lot of power--but."

"But--we also have those new fifteen-foot UV beams. And one fifteen-foot
UV beam is worth, theoretically, nine five-foot beams, and practically,
a dozen. We have a