pumps that emptied the tanks. The craft
rose slightly.

"Quick! Stop her!" shouted the old hunter, grasping the captain's arm.

Something black, like a grim shadow, loomed up in the dull glare of the
searchlight.

"What is it?" cried the professor.

"We're goin' to hit somethin' hard!" yelled Andy.

"It's the hull of a ship!" exclaimed the inventor as he jammed the
reversing lever hard over.

It was too late. The next instant the _Porpoise_, with a shock that made
her shiver from stem to stern, collided with the steel side of a small
warship.

CHAPTER IV

IN THE MIDST OF FIRE

"Pull the secondary emergency lever!" cried the professor through the
speaking tube to Washington. "We must reach the surface at once!"

"Are we damaged?" asked Andy, scrambling to his feet, for the shock had
knocked him down. The professor had not fallen because he clung to the
steering wheel.

The ship gave a sudden lurch.

"We're sinking!" cried Bill, rushing to the conning tower from the
engine-room.

"That's only the action of one of the emergency levers," said the
professor calmly. "It forces compressed air into the tanks the more
quickly to empty them of water. I think we are safe."

"What is it?" asked Mark, as, followed by Jack, he came forward.

"We tried to do the torpedo act to one of Uncle Sam's ships," explained
Andy.

The electric lights had been switched on, and, with the _Porpoise_
flooded with the bright beams, those on board waited anxiously for what
was to happen next.

Suddenly an upward motion was experienced. The next instant the craft
bounced out of the water and fell back in a smother of foam, shaking and
shivering, alongside a small armored warship that was anchored about two
miles and a half from shore.

"Open the manhole," commanded Mr. Henderson.

Mark sprang up the iron ladder that led to the opening in the deck of
the _Porpoise_ and threw back the cams that held the heavy iron in
place. Then he swung the cover back and stepped out on the small
platform, followed by the professor, Andy and Jack. They looked up to
find themselves observed by a curious throng that crowded to the rail of
the warship.

[Illustration: A CURIOUS THRONG CROWDED TO THE RAIL OF THE
WARSHIP.--_Page 28._]

"What are you trying to do? Ram me with a new-fangled torpedo?" asked an
angry voice, and a man in a gold laced uniform, who, from his importance
plainly showed himself to be the captain of the ship, shoo