“Station Biffens by the firing lever, then,” called down Captain Benson.  “Tell him to fire on the instant that he gets the order.  Now, Mr. Somers, stand by the submerging apparatus.  Drop just forty-two feet below the surface, then report instantly to me.”

“Aye, aye, sir.”

Lieutenant Danvers stood by the submarine boy, intently watching, listening, and digesting Benson’s plan.  Yet the naval officer ventured no interference.

In another moment the hull of the “Hastings” began to disappear under the waves.

“Forty-two feet—­sir—­and—­stopped!” shouted up Eph Somers.

“Ready to fire!” Jack hailed.

“Aye, aye, sir!”

“Fire!”

“Fire it is, sir.”

“Have you fired, Mr. Somers?” rolled down Jack’s next question.

“Yes, sir.”

“Then turn on the compressed air, and bring us to the surface.”

“Aye, aye, sir!”

The instant that the conning tower stood up, dripping, through the waves, Jack turned on searchlight again.  Slow speed ahead he next signaled.

As the piercing rays of light gleamed out over the waters before them the surface of the sea ahead was seen to be covered with floating litter.

“Jove, look at the wreckage!” uttered Lieutenant Danvers, jubilantly.  “Everything about that old derelict that could float has come up to the surface.”

“Do you think the derelict is utterly smashed, sir?” inquired Jack Benson, respectfully, for this trained naval officer knew more about such things than he did.

“That derelict is blown to kindling wood,” exclaimed Danvers, himself manipulating the searchlight as they sailed through a sea littered with small wreckage.  “That derelict will never menace any skipper afloat, from now on.  Benson, lad, you did a wonderfully keen job.”

“You don’t think there’d be any risk, then, in sailing back and forth amid this wreckage?” asked Jack.

“Risk?  Not a bit,” retorted Danvers.  “Why, look over there!” as he swung the searchlight in a new direction.  “There’s that submerged mast-stump, free of the wreck and floating horizontally, now.”

Nor was it long before it was clear to trained eyes that the sunken derelict had been efficiently blown up.  That water-logged ghost of a ship would never again be a source of peril to navigators.

“Now, you can turn your nose for Dunhaven, and with a clear conscience,” chuckled Lieutenant Danvers.  “And, while you’re doing that, I’m going below for another look at the little leak.”

Jack ran the “Hastings” the first few miles of her homeward course.  Then he called Eph Somers to the wheel and went below to relax.

It was well on toward eight o’clock when the “Hastings” ran into the little harbor at Dunhaven and made moorings.  The night watchman of the yard rowed out to meet them, bringing the news that Mr. Farnum, in the “Benson,” had picked up the crew of the “Mary Bond” from two small boats at sea.