air supply?" asked Jack.

"We can't go," replied the inventor.

"Then we will die."

"Not necessarily. We will steam along until we come to a place where
there is no ice above us."

"But I thought you said there was nothing but ice above us now."

"So there is, but I intend to head due south and there, I believe, we
will find an open polar sea. If we do my theory will be proved and we
will have made a great discovery."

"Forward then!" exclaimed Jack. "Let us strike for the open sea."

The _Porpoise_ began to move ahead. She steamed slowly, for Mr.
Henderson realized that he was in dangerous waters. He took his position
in the conning tower, and had Jack with him to assist in looking for
any obstructions that they might unexpectedly meet.

The big searchlight gave a fine illumination, for the ice above and
below reflected back the beams, and what would otherwise have been a sea
of darkness was made one of daylight.

The water swarmed with fish, but they were like none that the
adventurers had ever seen or dreamed of before. There were monsters with
hideous heads, and eyes so large that they occupied nearly half of the
ugly bodies.

Then there were serpent-like forms, fish with long slender bodies and
whip-fashioned tails, with jaws that extended before them for ten feet
or more. Others there were, great lumbering monsters that crawled along
on the ice, somewhat as seals do.

After several hours' travel the submarine ran into a school of fish that
had shapes like those of polar bears, while their heads were like those
of sharks. The creatures swarmed up to the side of the vessel, and some
scratched with their claw-like fins on the glass windows of the conning
tower and the side bull's-eyes.

A meal was prepared by Washington, and all the adventurers brought good
appetites to the table. On and on rushed the ship, every hour coming
nearer and nearer to the pole.

Professor Henderson had turned the steering of the craft over to Mark,
who, with Jack as an assistant was sending her along at a good speed,
when suddenly the submarine seemed to slacken in her progress.

"What's the matter now I wonder?" asked Mark.

"Maybe the engine bearings got hot, and Washington had to slow up to
cool them," suggested Jack.

He looked through one of the side windows in the conning tower, a moment
later, and uttered a cry of fear.

"What is it?" asked Mark.

Jack pointed with a hand that trembled from fright. Staring a