“Humph!  I don’t believe the Benson boy carries the size or the weight to put me ashore.”

“He doesn’t need any size or weight,” retorted Williamson, crisply.  “If Captain Benson wants you off this boat, it’s only the matter of a moment for him to get a squad of marines on board—­and you’ll march off to the ‘Rogues’ march’.”

“So that’s the way he’d work it, eh?” demanded Sam Truax, turning green and ugly around the lips.

“You bet it is,” retorted the machinist.  “We’re practically a part of the United States Navy for these few days, and naval rules will govern any game we may get into.”

On that hint things went along better in the engine room.  When Hal Hastings came in to inspect he found nothing to criticise.

At the minute of eleven o’clock a squad of some twenty cadets came marching down to the landing in front of the boat house.  There Lieutenant Commander Mayhew and one of his engineer officers met them.  Two cutters manned by sailors brought the party out alongside, where Jack and Hal stood ready to receive them.

A very natty looking squad of future admirals came aboard, grouping themselves about on the platform deck.  It was rather a tight squeeze for so many human beings in that space.

After greeting the submarine boys, Mr. Mayhew turned to the 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: