At a sign from the young skipper Eph hurried below, to relieve Hal Hastings, who wished to see some of the fun. Hal came up into the conning tower to take the wheel while Jack Benson slipped below to direct the loading of the torpedo into the tube. Then Biffens, the sailor, took his post by the firing lever, while Ewald stood back to pa.s.s the word from the conning tower.

This loaded torpedo, like the dummies, had been set to run four hundred yards. Captain Jack, therefore, determined to release the torpedo at a range of three hundred yards.

The "Hastings" had drifted somewhat away from the scow, but Jack, one hand on steering wheel and the other at the signals, ran the submarine over so that he could head the craft around to deliver a broadside fire at the scow, at right angles. When he had the "Hastings" in this position he shouted down:

"Be ready, Ewald!"

"Aye, aye, sir!"

A breathless instant followed, during which the young submarine commander took his last sight from the conning tower.

"Fire!"

"Fire it is, sir."

Jack and Hal could just barely see, from the tower, the slight commotion that the torpedo made in the water at the bow when released.

Hal, watch in hand was counting: "One, two, three, four--" and so on.

Suddenly there came a low rumble, followed by--

Boo-oom!

The explosion was a dull and sullen one, but loud enough to make the blood of the submarine boys tingle. A column of spray shot up, followed by detached whiffs of smoke, for the torpedo had exploded beneath the surface.

In the same instant a sound of rending timbers reached their ears. Then the scow--where was it? Only the waters rolled where the scow had been. Captain Jack and Hal rubbed their eyes.

"The same thing would have happened to a battleship," smiled Lieutenant Danvers, who had come up behind them. "Now, you young men begin to have something like an idea of what an engine of war you are handling, because this craft would be much more deadly, and vastly more nerve-racking to an enemy, because she would approach under water, and those on the battleship would have little or no means of gauging their peril. Incidentally, Mr. Benson, I must congratulate you upon the neatness of the shot."

"To accept congratulations for that would be like robbing a poor-box in a church," laughed Jack. "It called for nothing but aiming the nose of the boat straight."

"And, even under water," replied Danvers, "it calls for but few more calculations. With really trained men all through the crew of a submarine, you can now understand what show the battleship of coming days will have against a single hostile torpedo boat. Why, the captain of a torpedo boat, if he has but one torpedo on board, could sail in under a fleet, pick out his battleship, sink it and then scuttle away, under water, from the rest of the enemy's fleet."

"It seems almost like cowardice, doesn't it?" asked Hal Hastings, soberly.

"Not exactly," replied Lieutenant Danvers, grimly. "In the first place, the game of war is to destroy the enemy with as little loss as possible to yourself. Moreover, the commander and crew of a submarine torpedo boat, during a naval campaign, would have to take risks enough to make most men's hair turn gray."

"I'm not wishing for war," muttered Jack Benson. "Still, if one has to come, I hope I'll be in command of a torpedo craft that sees service."

"And I think you'd have your wish, my lad," nodded Lieutenant Danvers.

"Of course, none but regularly commissioned naval officers may command the craft of the Navy. Still, in our Civil War, and in the War with Spain, we had to commission a good many volunteers. So, in the event of another war coming, I don't believe the Navy Department would feel that it could possibly pa.s.s by boys trained as well as you three have been."

"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 a.s.sisting.

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, hoa.r.s.ely. "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.

They were far out to sea, and a submarine cannot carry a lifeboat!

CHAPTER IV

A SUBMARINE'S REVENGE

All now waited on Eph's word during the next few moments.

If the "Hastings," striking on that stub of a submerged mast, had had her plates so badly sprang that pumping would not drive out the water as fast as it came in, then this newest of the submarines was doomed to go to the bottom.