“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 explain a few of the points.

Then the questions began, directed at Hal.  This time none of the cadets, under the watchful eyes of Mr. Mayhew, forgot to say “sir” when speaking to Hastings.

Sam Truax edged up behind the big cadet whose eyes he had seen flash a few moments before.

“Go after Benson, good and hard,” whispered Truax.

The cadet looked keenly at Truax.

“You can have a lot of fun with Benson,” whispered Truax, “if you fire a lot of questions at him, hard and fast.  Benson is a conceited fellow, who knows a few things about the boat, but you can get him rattled and red-faced in no time.”

CHAPTER X:  A SQUINT AT THE CAMELROORELEPHANT

The big cadet wheeled upon Jack.

“Mr. Benson, how long have you been engaged on submarine boats, sir?”

“Since July,” Jack replied.

“July of this year?”

“Yes.”

“And it is now October.  Do you consider that enough time, sir, in which to learn much about submarine boats?”

“That depends,” Skipper Jack replied, “upon a man’s ability in such a subject.”

“Is it long enough time, sir, for a boy?”

That was rather a hard dig.  Instantly the other cadets became all attention.

“It depends upon the boy, as it would upon the man,” Jack answered.

“Do you consider, Mr. Benson, that you know all about submarine boats, sir?”

“Oh, no.”

“Who does, sir?”

“No one that I ever heard of,” Jack answered.  “Few men interested in submarine boats know much beyond the peculiarities of their own boats.”