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 manœuvers 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.