“You’re pretty independent for a boy.”

“Let Captain Jack alone,” drawled Farnum, expelling some cigar smoke between his lips.  “He generally knows what he’s doing.”

Though there was nothing in the builder’s tone at which offense could be taken, this reply quieted both Melvilles for the time being.

“Come on.  We’ll all go down to the shore and see what it is,” added the yard’s owner.

Captain Jack hurried ahead, entered the shore boat and was rowed out alongside the “Pollard.”

“It’s all right, fellows,” he called, as soon as he boarded.  “Everything ready?”

Receiving assurance that all was ready, Captain Jack turned to wave his hand to the little group watching from the shore.  Two or three minutes later the “Pollard” slipped slowly away from her moorings, going out where the little harbor was deeper.  Then, the manhole being closed, the submarine began to sink.  Her conning tower was soon out of sight beneath the surface.

“There’s about seventy feet of water, where the boat is going down,” observed Farnum, to his guests.

“What’s the aim of all this mysterious work?” demanded Mr. Melville, with some irritation.

“You know as much as I do,” drawled Farnum, smilingly.

“It seems to me that you allow this young boat tender a good deal of latitude, and tolerate a good deal of mystery in him,” cried the capitalist, impatiently.

“I have a good deal of confidence in my young captain,” returned Farnum, good-humoredly, though with considerable emphasis on the title.  “So far I have never had any need to regret giving Captain Benson rather a free hand.”

“Yet you—­”

Mr. Melville stopped right there, for Jacob Farnum, his eyes turned in a steady look out over the water, suddenly emitted an incredulous whoop.  Then, without explanation, the boatbuilder broke into a dead run that carried him along the shore to the northern edge of the little harbor.

Nor was Mr. Farnum’s astonishment to be wondered at, for he had just caught sight of Jack Benson’s head, above the water at the point where the submarine had gone down.  And now, Captain Jack, after blowing out a mouthful of water, had started to swim ashore with long, easy strokes.

Not quite catching the great significance of it all, the Melvilles and the lawyer hurried after the builder.

Captain Jack Benson, clad only in a bathing suit, stepped out of the water and stood laughing before his employer.

“Jack, how on earth did you—­” began Farnum, then stopped, overpowered by another wave of amazement.

“What’s the meaning of all this?” demanded the elder Melville, pantingly, as he reached the scene.

“Mr. Melville, and gentlemen,” cried the boatbuilder, wheeling upon his guests, “do you even begin to grasp the importance of the marvel you have just witnessed?  One of the great indictments found against the submarine torpedo boat is that, when one sinks and cannot be brought to the surface again, the crew must miserably perish.  Very humane people shudder at the very idea of ordering men into a craft that may go to the bottom and become the hopeless grave of the crew.  Yet the ‘Pollard’ lies at the bottom of this harbor, and Captain Benson has just come to the surface, laughing and uninjured.”