Terrestrials stared in amazement another of the
immense hexagonal buildings burst into fragments; its upper structure
flying wildly into scrap metal, its lower half subsiding drunkenly below
the surface of the boiling sea.

The three Earth-people seized whatever supports were at hand as the
Nevian space-ship struck the water with undiminished speed, but the
precaution was needless--Nerado knew thoroughly his vessel, its strength
and its capabilities. There was a mighty splash, but that was all. The
artificial gravity was unchanged by the impact; to the passengers the
vessel was still motionless and on even keel as, now a submarine, she
snapped around like a very fish and attacked the rear of the nearest
fortress.

For fortresses they were; vast structures of green metal, plowing
forward implacably upon immense caterpillar treads. And as they crawled
they destroyed, and Costigan, exploring the strange submarine with his
visiray beam, watched and marveled. For the fortresses were full of
water; water artificially cooled and aerated, entirely separate from the
boiling flood through which they moved. They were manned by fish some
five feet in length. Fish with huge, goggling eyes; fish plentifully
equipped with long, armlike tentacles; fish poised before control panels
or darting about intent upon their various duties. Fish with brains,
waging war!

Nor was their warfare ineffectual. Their heat-rays boiled the water for
hundreds of yards before them and their torpedoes were exploding against
the Nevian defenses in one appallingly continuous concussion. But most
potent of all was a weapon unknown to Triplanetary warfare. From a
fortress there would shoot out, with the speed of a meteor, a long,
jointed, telescopic rod; tipped with a tiny, brilliantly-shining ball.
Whenever that glowing tip encountered any obstacle, that obstacle
disappeared in an explosion world-wracking in its intensity. Then what
was left of the rod, dark now, would be retracted into the fortress-only
to emerge again in a moment with a tip once more shining and potent.

Nerado, apparently as unfamiliar with the peculiar weapon as were the
Terrestrials, attacked cautiously; sending out far to the fore his
murkily impenetrable screens of red. But the submarine was entirely
non-ferrous, and its officers were apparently quite familiar with Nevian
beams which licked at and clung to the green walls in impotent fury.
Through the red veil came stabbing ball a