“You have shown us more than we can quite digest,” admitted Lieutenant Commander Briscoe.  “But how is this all done?”

“That,” responded Mr. Farnum, gravely, “the Government will know when the boat is purchased for the American Navy.”

The anchor being again lowered, both Jack and Hal dived below.  In five minutes the “Pollard” was on the surface.  Mr. Farnum asked: 

“Have we shown you enough at one time?”

“Yes,” admitted the officers.  “This evening, after dark, we may ask you to take us out and show us your boat’s diving powers.”

“Jack, my boy,” whispered Jacob Farnum, when the young captain joined the party on shore, “your trick of leaving and returning to the boat when it lies on the bottom has gotten our friends of the Navy into a state of hard guessing.  Do you think we’d better show them some more of it at another time?”

“If you want my opinion, sir, I think we’d better not.  We’ve puzzled them this time, but if we keep on doing the trick for them, I’m afraid they’ll soon guess how it’s done.  I don’t believe, sir, you can fool the American Navy more than once.”

CHAPTER XV

SERVING IN THE CAUSE OF PEACE, NOT WAR

“It seems almost a shame to have to go below,” sighed Lieutenant McCrea.

It was evening, the time about nine o’clock.  For nearly an hour the “Pollard” had been running out to sea at something below her full speed.  She was now something like a dozen miles off the coast.

Commander Ennerling had just decided that it would be a good time to test the diving capabilities of the submarine.

Ventilators were shipped, and all other preparations had been made for going below the surface.

Eph was left in the conning tower, Lieutenant McCrea with him.

“How far do you want the dive to be made, sir?” asked Jack Benson.

“A depth of forty feet ought to serve the purpose,” stated the president of the board.

“Then, sir, we will make a sloping dive to that depth, then complete the curve until we strike the surface again,” proposed the submarine boy.  “How will that suit you, sir?”

“Excellently,” agreed the Navy commander.

“Do you want to take the record with your stop watch?”

“Yes?”

“All ready, sir.”

As Captain Jack gave the word he threw open the forward water tanks, so that water rushed in, tilting the bow of the craft downward.  The “Pollard” moved on a decided slant until Captain Jack read the depth of forty feet on the gauge.  Then, with a barely perceptible rest.  On an even keel, the young submarine expert threw compressed air into the forward tanks, expelling the water, at the same time admitting water to the tanks aft.

Gracefully, and with, the precision of a trained living being, the submarine craft curved upward until Lieutenant McCrea shouted down: