tor carries five inches. What shall we
do?"

"Tell him to lower his screen, and let loose at once on all operating
forts. His relux will stand for the time needed to shut them down for
their own screens, unless some genius decides to fight it out. As soon
as the other ships can lower their screens, tell them to do so, and tell
them to join in. I'll be able to help then. My relux has been burned,
and I'm afraid to lower the screen. It's mighty thin already."

The squadron commander was smiling joyously as he relayed the advice as
a command.

Almost at once a single ship, blunt, an almost perfect cylinder, lowered
its screen. In an instant the opalescence of the transformation showed
on it, but its dozen ray projectors were at work. Fort after fort glowed
opalescent, then flashed into protective ionization of screening.
Quickly other ships lowered their screens, and joined in. In a moment
more, the forts had been forced to raise their screens for protection.

A disc of artificial matter ten feet across suddenly appeared beside the
_Ancient Mariner_. It advanced with terrific speed, struck the great
dome of the fort, and the dome caved, bent in, bent still more--but
would not puncture. The disc retreated, became a sharp cone, and drove
in again. This time the point smashed through the relux, and made a
small hole. The cone seemed to change gradually, melting into a cylinder
of twenty foot diameter, and the hole simply expanded. It continued to
expand as the cylinder became a huge disc, a hundred feet across, set in
the wall.

Suddenly it simply dissolved. There was a terrific roar, and a mighty
column of white rushed out of the gaping hole. Figures of Thessians
caught by the terrific current came rocketing out. The inside was at
last visible. The terrific pressure was hurling the outside line of
ships about like thistledown. The _Ancient Mariner_ reeled back under
the tremendous blast of expanding gas. The snow that fell to the boiling
water below was not water, _in toto_; some was carbon dioxide--and some
oxygen chilled in the expansion of the gas. It was snowing within the
dome. The falling forms of Thessians were robbed of the life-giving air
pressure to which they were accustomed. But all this was visible for but
an instant.

Then a small, thin sheet of artificial matter formed beside the fort,
and advanced on the dome. Like a knife cutting open an orange, it simply
went around the dome's edge, the great dome li