then experimented with
various dials.

"There ought to be some way of cutting that beam," he pondered audibly,
"but I don't know enough about their system to do it, and I'm afraid to
monkey around with things too much, because I might accidentally release
the screens we've already got out, and they're stopping altogether too
much stuff for us to do without them right now."

He frowned as he studied the flaring defensive screens, now radiating an
incandescent violet under the concentration of forces being hurled
against them by the warlike fishes, then stiffened suddenly.

"I thought so--they _can_ shoot 'em!" he exclaimed, throwing the
lifeboat into a furious corkscrew turn, and the very air blazed into
flaming splendor as a dazzlingly scintillating ball of energy sped past
them and high into the air beyond.

Then for minutes a spectacular battle raged. The twisting, turning,
leaping airship, small as she was and agile, kept on eluding the
explosive projectiles of the fishes, and her screens neutralized and
re-radiated the full power of the attacking beams. More--since Costigan
did not need to think of sparing his iron, the ocean around the great
submarine began furiously to boil under the full-driven offensive beams
of the tiny Nevian ship. But escape Costigan could not. He could not cut
that tractor beam and the utmost power of his drivers could not wrest
the lifeboat from its tenacious clutch. And slowly but inexorably the
ship of space was being drawn downward toward the ship of ocean's
depths. Downward, in spite of the utmost possible effort of every
projector and generator; and Clio and Bradley, sick at heart, looked
once at each other. Then they looked at Costigan, who, jaw hard set and
eyes unflinchingly upon his plate, was concentrating his attack upon one
turret of the green monster as they settled lower and lower.

"If this is ... if our number is going up, Conway," Clio began,
unsteadily.

"Not yet, it isn't!" he snapped. "Keep a stiff upper lip, girl. We're
still breathing air, and the battle's not over yet!"

Nor was it; but it was not Costigan's efforts, mighty though they were,
that ended the attack of the fishes of the greater deeps. The tractor
beams snapped without warning, and so prodigious were the forces being
exerted by the lifeboat that as it hurled itself away the three
passengers were thrown violently to the floor, in spite of the powerful
gravity controls. Scrambling up on hands and k