all back upon the water,
as if dragged down by a powerful but invisible hand,--the hand of some
sea-god or demon,--perhaps of Neptune himself!

Not only the plank, but the whole raft moved under this inexplicable
impulsion,--which had communicated to it a rocking motion, not from side
to side, but upwards and downwards! So quick and violent was this
mysterious oscillation, that it was with difficulty the three
individuals who still occupied the decks of the craft could keep either
their balance or their feet.

Along with the motion of the raft there was a corresponding commotion in
the water,--accompanied by a loud splashing noise that seemed to proceed
from under the timbers, on which, like so many acrobats, they were
endeavouring to balance themselves; and in a few seconds after they had
felt the great shock, the sea all around exhibited a surface of high
waves crested with foam!

Snowball, who had risen to the surface after the somersault that had
plunged him deep down into the sea, perceiving that the raft still
continued to heave upward and downward, made no attempt to get on board;
but swimming alongside, sputtered forth his terrified ejaculations.
Even the brave man-o'-war's-man, who had faced death in a thousand
shapes, was, at that moment, the victim of fear.

How could it be otherwise? He could think of nothing in nature capable
of causing that mysterious commotion and who, without trembling, could
withstand the assaults of the supernatural?

"Shiver my timbers!" cried Ben, himself shivering as he spoke the words,
"what in old Nick's name has got under us? Be it a whale that's bumpin'
its back against the rail? Or--"

Before he could pronounce the second interrogatory, a loud crash sounded
in the ears of all,--as if the plank heaving so mysteriously had been
suddenly torn in twain!

This sound, whatever had caused it, seemed to proclaim the climax of the
commotion: for immediately after the _Catamaran_ began to compose
herself, the waves caused by her continued rocking gradually grew less,
until at length, once more "righted," she lay in her customary position
upon the tranquil surface of the sea.

CHAPTER FIFTY ONE.

A THRUST THROUGH AND THROUGH.

As soon as the _Catamaran_ had fairly recovered her equilibrium,
Snowball condescended to climb aboard. The ludicrous appearance of the
negro, as he stood dripping upon the deck, might have excited laughter;
but neither Ben Brace, nor his acoly