tanding near the companionway leading down into the man-hole a ghostly
white shape.

"I'll find out what you are this time, or go overboard with you," said
Jack to himself, clenching his teeth. He crawled along the deck until he
thought he was within leaping distance of the weird white thing. Then he
made a leap.

He landed on something soft, which, the moment he struck it, let out a
yell that sounded loud on the quiet night. Then the thing began to
fight. But Jack fought back and held on bravely.

"Here! What are you tryin' to do?" exclaimed a voice in his ear.

"What are you trying to do?" asked Jack indignantly, finding that the
words came from the "ghost."

"Nice way to treat a man! Half kill him!" the white thing went on. "Just
when I'm trying to get a little sleep you come along and pull me out of
bed!"

"Why, it's Bill Jones," exclaimed Jack, as the light from the conning
tower lamp fell on the face of the "ghost."

"Of course it is; who did you think it was?" asked Bill.

"What are you doing on deck in your night shirt?" asked the boy, letting
the helper rise.

"Me? On deck? Ain't I in my bunk?"

"I should say not," replied Jack. "What are you doing on deck?"

"Well! well!" remarked Bill, rubbing his eyes. "I've gone and done it
again."

"Done what?"

"Walked in my sleep. I'm a great sleep walker. Greatest you ever knew.
Once I climbed to the top of our barn when I was asleep."

"So you're the ghost of the submarine," exclaimed Jack. "That explains
it."

"I guess you're right," admitted Bill, as the others came on deck to see
what all the row was about. "I never thought of it when I heard about
the ghost, but I can account for it now. I'd get out of my bunk, wander
out on deck, and then crawl back again. Of course, being barefoot, or in
fur slippers, I made no sounds. I don't wonder you thought I was a
spirit. Queer I didn't wake up after some of the things I went through."

"And you always managed to get back to your bunk in time so that we
never caught you at it," said Jack. "However, it's all over now."

And so it was, for after that Bill tied a chair in front of his bunk,
and if he did get out in his sleep he stumbled against it and awoke
before he had gone far.

Northward the _Porpoise_ continued on her journey. She entered a vast
field of ice, and only her ability to sink below the surface enabled her
to get through it unharmed. There were few adventures going home. Once a
big whale