“Are you going to use the other loaded torpedo to-day, sir?” asked Jack.

“Against what?” demanded Danvers.  “You’ve sunk the scow as deep as the bottom of the Atlantic Ocean.”

“Then I suppose we may as well put back to Dunhaven, sir?”

“Yes, Benson.”

Jack accordingly signaled for slow speed ahead, turning the nose of the “Hastings” toward the west.  Hal and Eph, as the submarine started back, took a drill in loading and unloading torpedoes into the tube, performing this work with one of the dummies, Ewald and Billens assisting.

Knowing that Hal was not in the engine room, Captain Jack was content to run along at slow speed.  Nor had the boat gone more than two miles when something struck the bow.

At the first impact alert Jack Benson felt his heart leap into his mouth.  It was as though the “Hastings” had struck, lightly, on a reef.  Almost by instinct Jack threw the wheel over to port.  Something was rasping, forcefully, under the hull of the submarine.  As the helm went to port that something underneath, whatever it was, sheered off.

“What was that, Benson?” called up Lieutenant Danvers, sharply.

“Struck something, sir, I’m sure,” Jack called back.

At the first sound of trouble, Hal Hastings leaped into the engine room.  Lieutenant Danvers sprang up the stairs into the conning tower.  He was in time to find Captain Jack swinging the nose of the “Hastings” around.  Then the youthful commander signaled for the stop and the reverse.

“Mr. Somers!” shouted Jack, coolly but promptly.

“Aye, sir,” called up Eph.

“Take a lantern and get down into the compartments along the keel forward.  See whether we’re taking in any water.”

“Aye, aye, sir.”

“We struck part of a derelict, or something else submerged,” guessed Lieutenant Danvers.  “We’re lucky, indeed, if our plates are not sprung.”

Then he called down to Biffens to follow and aid Eph Somers.

It was almost dark now.  Jack, reaching over, switched on the electric sidelights outside, and also the white light at the signal masthead.  Then he turned on the searchlight, sending its bright ray through the gathering darkness.

“Look over there, sir,” muttered Jack, holding the searchlight ray steadily on an object he believed he saw.  “Don’t you make out, sir, bobbing up and down when the waves part, what looks like the stump of the broken-off mast of a vessel submerged?  Is it a death-dealing derelict in the very path of coastwise navigation!”

“By Jove, yes!” gasped Lieutenant Danvers, hoarsely.  “Your eyes are sharp, Benson, and your judgment sound.  That, then, was what we struck on—­the mast-stump of a water-logged, sunken derelict!  If our underhull plates are sprung, down we go to the bottom!”

They waited, in dreadful anxiety, for the report of Eph from the region of the keel plates.