eep to that course under water,
Mr. Surles?"

"Yes, sir."

Going down to the cabin floor, Jack ordered two more midshipmen to the
tower as observers.

"The rest crowd about me and ask questions while I handle the submerging
machinery."

Under the impetus from the electric motors, the propeller shafts began to
throb. The next instant the submarine shot below, going down at so steep
an angle that many of the middies were forced to reach for new footing.

"The gauge registers sixty feet below," announced Jack.

In another moment, by the quick flooding of some of the compartments
astern, the young skipper brought the boat to an even keel.

Having finished the prescribed distance under water, Captain Jack turned
on the compressed air to expel the water from the compartments. The
conning tower soon rose above the water, and a moment later the "Pollard"
also emerged.

Other cadets were transferred from the gunboat to the submarines, and the
instruction proceeded. The manoeuvers for the day were ended with a
half-hour run under water.

"By the way, sir, did you question Truax to see what you could learn about
his reasons for acting as he did on the 'Farnum'?" asked Jack Benson the
next day. Jack and Doctor McCrea were talking with Mr. Mayhew.

"I had him before me last night, and again this morning," replied Mr.
Mayhew. "He said he hadn't an idea what I meant, and that is all I could
get out of him."

Jack looked thoughtfully at Doctor McCrea for a moment before he
exclaimed:

"Doctor, if I had anything like your chance, I'd have Sam Truax talking!"

"How?" Doctor McCrea looked interested.

"Why, I'd--" Jack hesitated, glancing toward the gunboat's commanding
officer.

"I'd better go and see how the midshipmen are doing," laughed Mr. Mayhew,
rising.

For some minutes Jack talked with Doctor McCrea. As the medical officer
listened, he grinned, then laughed unrestrainedly.

"Mr. Benson, you're certainly ingenious!"

"Will you do what I've suggested?"

"Why, I--er--er--" Doctor McCrea hesitated. "I--well, I'll think it over."
Again Doctor McCrea roared with laughter.

CHAPTER XX: CONCLUSION

Sam Truax sat in the brig, between decks on the "Hudson," his scowling
face turned toward the barred door, when the marine guard, taking a turn,
peered in.

"Good heavens, man! What ails you?" demanded the marine.

"I'm all right," growled the prisoner.

"I'll be hanged if yo