“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 pass by boys trained as well as you three have been.”