"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 that derelict's sunken hull in order to locate it and make your soundings. Now, you run a big chance of running plumb on to some other stump of a mast. The 'Hastings' may easily get an injury, fr