ake that thing if this
whole fort blows up and kills me. That math has blown up in my face for
four solid months, and half killed me, so I'm going to kill it. Come on,
we'll make that damned junk."

Angrily, furiously, Kendall drove his helpers to the task. He had worked
out the apparatus in plan a dozen times, and now he had the plans turned
into patterns, the patterns into metal.

Saucily, the "S Doradus" made the trip to and from Earth with patterns,
and with metal, with supplies and with apparatus. But she had to dodge
and fight every inch of the way as the Miran ships swooped down angrily
at her. A fighting craft could get through when the Miran fleet was
withdrawn to some distance, but the Mirans were careful that no
heavy-loaded freighter bearing power supply should get through.

And Gresth Gkae waited off Luna in his great ship, and watched the
steady streams of magnetic bombs exploding on the magnetic shield of the
Lunar Fort. Presently more ships came up, and added their power to the
attack, for here, the photo-cell banks could gather tremendous energy,
and Gresth Gkae knew he would need to overcome this, and drain the
accumulated power.

Gresth Gkae felt certain if he could once crack this nut, break down
Earth, he would have the system. This was the home planet. If this fell,
then the two others would follow easily, despite the fact that the few
forts on the innermost planet, Mercury, could gather energy from the sun
at a rate greater than their ships could generate.

It took Kendall two weeks and three days to set up his preliminary
apparatus. They had power for perhaps four days more, thanks to the fact
that the long Lunar day had begun shortly after Gresth Gkae's impatient
attack had started. Also, the "S Doradus" had brought in several hundred
tons of charged mercury on each trip, though this was no great quantity
individually, it had mounted up in the ten trips she had made. The
"Cepheid," her sister ship, had gone along on seven of the trips, and
added to the total.

But at length the apparatus was set up. It was peculiar looking, and it
employed a great deal of power, nearly as much as a UV beam in fact.
McLaurin looked at it sceptically toward the last, and asked Buck: "What
do you expect it to do?"

"I am," said Kendall sourly, "uncertain. The result will be uncertainty
itself."

Which, considering things, was a surprisingly accurate statement.
Kendall gave the exact answer. He meant to gi