do not believe the creature will follow us there. Empty
the tanks, Washington."

The colored man started the pumps, and the professor watched the gages
that told the depth of the craft. The pointer should have begun to swing
around in a few seconds after the tanks began to empty. Instead it
remained stationary.

"Strange," said Mr. Henderson. "I wonder if anything is wrong with the
machinery."

"More like the whale, or whatever it is, is on top of the boat, holding
her down," suggested Andy.

There was no doubt of this a moment later, for there were several
violent blows on the upper part of the _Porpoise_.

The crew of the submarine were held prisoners below the surface by the
unknown monster!

For a few minutes the thought of the awful fate that would be theirs if
the ship should be wrecked under the water made each one speechless. As
they stood looking at each other, not knowing what to do, the attack was
renewed on the port side.

The big fish, whale or whatever it was, kept pounding away.

"I have an idea!" cried Andy suddenly.

"What is it?" asked the professor quickly.

"Let me put a diving dress on," began the old hunter.

"I tell you we can't sink to the bottom in this depth of water,"
interrupted the professor.

"We don't need to," put in Andy. "All I want is a diving suit and a
chance to stand out in the diving chamber. I guess I can fix Mr. Whale,
if I have one of those electric guns."

"Quick! Get a diving suit, Washington!" cried Mr. Henderson. He saw what
the old hunter planned to do.

In a few minutes Andy was dressed in the suit. The attacks of the
monster had redoubled in frequency, and the ship rocked as in a storm.

Andy stepped into the diving chamber, clasping the electric gun. The
inner door was tightly closed and then the sea cocks that admitted water
from the outside were opened. When the pressure inside the chamber was
equal to that of the ocean outside some one pulled the lever that
opened the outer door.

Andy knew better than to step outside. He remained in the chamber, like
a sentinel hid in the embrasure of a wall, for the chamber was a sort of
big dent in the side of the _Porpoise_.

Once more the ship rocked from a terrific blow, and the old hunter was
nearly thrown out and into the fathomless depths below.

He clung to the door lever and peered out. Through the big glass eyes of
his copper helmet he saw headed straight at him a whale that seemed
larger than the