robed in white garments.

Jack was now within ten feet of the strange object. It was a man, he was
sure of it, but whether a present or former inhabitant of the earth he
could not decide. Jack's hair was beginning to raise. A cold shiver ran
down his spine as the white thing lifted an arm and seemed to point
directly at him. At the same time it groaned in a deep tone.

Jack let out a yell that could be heard all over the ship. He made a
spring for the object, determined to discover what it was or die.

At that instant the whole ship seemed to rise in the air. It left the
water and began moving skyward. Right out of the waves the _Porpoise_
was lifted until the big screw was clear of the water and it was
churning around in the tunnel without any resistance, racing at top
speed now that it had no water to thrust against.

Then the ghost seemed to vanish into thin air, and Jack felt himself
falling down the hatchway.

CHAPTER XX

ON A VOLCANIC ISLAND

In an instant the ship was in confusion. The professor, followed by old
Andy, Washington, Mark, Bill and Tom, came rushing from their berths,
all in their night clothing, to see what the trouble was. They met in a
tangled mass, stumbling over Jack at the foot of the steps.

"Is the ship on fire?" called Mrs. Johnson from her cabin.

"I hope not!" called the professor. "But something has happened. Don't
be frightened!"

By this time Jack, who had been somewhat stunned, recovered his senses
and worked his way out of the mass of bodies.

"The ghost! The ghost!" he cried. "I saw him again!"

"Land a' massy!" yelled Washington.

"What has happened to the ship?" cried the professor. "Is it a tidal
wave?"

"I was on deck," panted Jack. "I saw the white thing! I crept up on it!
All at once the ship rose in the air!"

"And it's still rising!" shouted the inventor. "I must see what this
means!"

He made his way to the deck, and his loud shout soon brought the others
up to him.

"Shut off the engine!" Mr. Henderson called down to Washington, who
hurried to obey.

"What has happened?" asked Andy, rushing towards him.

"We have run upon an island," answered the professor. "This is the worst
thing that has yet happened to us."

"What sort of an island is it that shoots you up in the air?" asked the
old hunter.

"It's hard to say," replied Mr. Henderson. "We will have to wait until
morning to find out."

The boys and men went up on deck and there behe