sappear, the
most dreaded of all sights for a swimmer showed itself above the
water. It was the sinister triangle of a shark's-fin cutting the
surface of the sea as it advanced with terrifying speed to where Chris
gazed, almost paralyzed with horror.

Thrusting the knife into the pouch at his neck, Chris took the shape
of a dolphin and plunged deeply, even as the infuriated shark was
carried over and beyond him by its own impetus before it could turn.
But turn it did, with lightning speed, and Chris knew he had no
protection against that murderous underslung jaw racked above and
below with deadly teeth.

The shark, in one long powerful movement, had turned and gone under
the dolphin, which now raced upward from the dim, lightless depths of
the sea to the surface where it hoped to escape. The shark turned on
its back with a motion at once lazy and sickening in its assurance of
its prey. Its soft greenish-white belly glimmered slimily in the sea,
its frightful jaws open as it came almost languidly up through the
water, certain of snapping its adversary in half.

But in that one moment when it turned belly uppermost, its eyes were
unable to watch its goal, and in that moment the dolphin made a
desperate leap from the water and a sea bird soared into the air.

The sea bird had no more than wheeled to sight the shark below, when a
scream from the air above it made it instantly drop and shift to one
side as a hawk, talons spread and eyes red with hatred, plunged down
from a great height, its beak open to seize and to rend.

The sea bird, veering away on the wind, became a fly, but the hawk
instantly vanished to be replaced by a bat, which darted after the fly
with such velocity that it was the current of air from its wings that
drove the fly closer to the pirate ship.

[Illustration]

With a despairing effort, the fly flew directly into the smoke of the
battle, and at that moment a mouse hid in a corner near an overturned
cask shaking in all its limbs, its pointed teeth chattering with
fright. Finally regaining its breath, it ventured to look around the
corner. All seemed serene to the mouse, who saw no shadow of danger,
although sounds of battle still ebbed and flowed on the deck below it,
crisscrossed by shouts and orders, screams and groans, as the pirates
and the sailors of the _Mirabelle_ doggedly fought on. The mouse
wished to retake its own shape and continue its work with the magic
knife which had been interr