r, "are Mr.
Benson, Mr. Hastings and Mr. Somers. All three are thoroughly
familiar with the Pollard type of boat. As the Navy has purchased
one Pollard boat, and may acquire others, it is well that you cadets
should understand all the working details of the Pollard Submarine
Company's crafts. A few of you at a time will now step into the conning
tower, and Mr. Benson will explain to you the steering and control
gear used there."

Half a dozen of the cadets managed to squeeze into the conning tower.
Jack experienced an odd feeling, half of embarrassment, as he explained
before so many attentive pairs of eyes. Then another squad of cadets
took the place of the first on-lookers. After a while all had been
instructed in the use of the conning tower appliances.

"Mr. Benson," continued the lieutenant commander, "will now lead the
way for all hands to the cabin. There he will explain the uses of the
diving controls, the compressed air apparatus, and other details
usually worked from the cabin."

Down below came the cadets, in orderly fashion, without either haste
or lagging. Having warmed up to his subject, Jack Benson lectured
earnestly, even if not with fine skill. At last he paused.

"Any of the cadets may now ask questions," announced Lieutenant Commander
Mayhew.

There was a pause, then one of the older cadets turned to Jack to ask:

"What volume of compressed air do you carry at your full capacity?"

"Mr. Benson's present status," rapped Mr. Mayhew, quickly, "is that of
a civilian instructor. Any cadet who addresses Mr. Benson will
therefore say 'sir,' in all cases, just as in addressing an officer
of the Navy."

The cadet so corrected, who was at least twenty-one years old, flushed
as he glanced swiftly at sixteen-year-old Jack. To say "sir" to such
a youngster seemed almost like a humiliation. Yet the cadet repeated
his question, adding the "sir." Jack quickly answered the question.
Then two or three other questions were asked by other cadets. It was
plain, however, that to all of the cadets the use of "sir" to so young
a boy appealed, at least, to their sense of humor.

Through the engine room door Sam Truax and Williamson stood taking it
all in. Sam saw a flash in the eye of one big cadet when the question
of "sir" came up.

Presently the squad filed into the engine room. Here Hal Hastings had
the floor for instruction. He did his work coolly, admirably, though
he asked Jack Benson to ex