after you close the conning tower station yourself at the
emergency lever after we have donned the life preservers."

The cork jackets were adjusted and Mark clamped the manhole cover on.
The professor took one last look at the various levers and handles, and
then turned the wheel that admitted water to all four tanks. There was a
hissing sound as the sea water rushed in, and the _Porpoise_ gave a
sudden lurch.

Then they could all feel the submarine sinking. Down and down she went.
Would she ever stop? Would the professor be able to raise her again?
There were questions that troubled everyone.

Down and down the craft sunk, until by the gage it was indicated that
she was twenty feet below the surface. Then the professor shut off the
inrush of water and the _Porpoise_ floated away below the surface of the
waves.

There was a clicking sound and all the lights went out. The boys and
Washington gave a gasp of terror. What did the sudden blackness mean.

"Open the side windows," called the professor's voice, and the two
machinists obeyed. Heavy steel doors that covered plate glass windows in
either side of the craft were pulled back, and a cry of astonishment
broke from the boys.

They looked out and saw staring in at them, so close it seemed that they
could touch them, scores of fishes that looked in through the glass
bull's-eyes.

For the first time they realized that they were in the depths of the
ocean.

CHAPTER III

RUNNING DOWN A WARSHIP

"How do you like it?" asked the professor.

"Great!" exclaimed Jack.

"Fine!" cried Mark.

"It am simply coslostrousness!" exploded Washington. "'Nebber in all my
born days did I eber expansionate on such a sight!"

"Wish I had a fishing pole and line," remarked Andy Sudds. "There's some
pretty nice specimens out there."

"You'll see better ones than those before we finish our trip to the
pole," remarked the professor. "Now we will try moving forward. I am
going into the conning tower."

He turned on the lights once more, but the boys begged him to shut them
off, as they could see out into the ocean when the interior of the ship
was in darkness. So the professor obliged them.

In the tower he switched on the powerful searchlight that illuminated
the path in front of him. Then he started the engine, slowly at first,
and gradually increasing the speed. The _Porpoise_ forged ahead, riding
as evenly as an ordinary ship does on the surface.

The professor