cadets,
calling their attention to the lines and outer construction of the
"Farnum." Then he turned to the three submarine boys, signing to them to
crowd forward.

"These young gentlemen," announced the lieutenant commander, "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 cad