of-fact reply.

"When I went below you made some remark about not letting the derelict
off too easily, Benson. What did you mean?"

"Why, I believe we ought to get square with that old sunken hulk,"
retorted Captain Jack, wheeling around and eyeing the naval officer.

"Great Scott! You mean that we ought to blow up the derelict?"

"Isn't it usually the Navy, sir, that gets such jobs to do?"

"Yes, yes, Benson. But the Navy Department always sends out a vessel
fitted for such work."

"This is a submarine boat. We have one loaded torpedo left on board.
Don't you think we answer the description of a vessel fitted for
destroying a derelict?" smiled Captain Jack, coolly. "To say nothing
of the itch, for revenge that we feel."

"It'll be a ticklish business," muttered Danvers, thoughtfully.

"So is a lot of the Navy's work, isn't it?" persisted Captain Jack.

"See here, lad, do you really mean that you want to make a sure-enough
job of blowing up the derelict?"

"That's what I'm staying here for, sir," rejoined Jack, again swinging
the searchlight. "And over there, three hundred yards yonder, I can
still make out, once in a while, that bit of mast. What do you say,
Lieutenant?"

"Why, if you boys have the grit to go ahead and tackle a job like that
in the night, the Navy isn't going to feel chilled and run away,"
laughed Danvers, shortly. "Yet, my boy, do you think you fully
understand the dangers of the undertaking?"

"I think I do," nodded Captain Jack.

"It's to be a duel between this submarine and the old derelict. You
can't just hang off like this over here, and shoot at that mast. That
wouldn't do any good."

"Yes, I know all that," said Jack, eagerly.

"Then what's your plan, Benson?"

"Why, sir, we've got, first of all, to sail as close as we dare to that
mast-stump. Then we've got to use a sounding line to find out in which
direction the hull of the sunken derelict lies. We must also get an
idea of the length of the hull. Then, having gotten our figures, we'll
have to glide back a little way, so as to give a right-angle broadside
on at the hull of the derelict. Before firing the torpedo we'll first
have to go far enough below water so that we'll know we're in fair line
with that sunken hull yonder, for we've got to make our one loaded
torpedo do the trick."

"You've got the figures down all right," nodded Lieutenant Danvers,
thoughtfully. "The risky part is in trying to run over th