“Yet Mr. Hastings is your only engineer officer.”

“True, but two of our enlisted men are trained as engine-tenders.  Our engines are rather simple, in the main, and an enlisted engine-tender can run our engine room for hours at a stretch under ordinary conditions.  Of course, if anything out of the usual should happen while Mr. Hastings were taking his trick in his berth, he would have to be wakened.  But we can often make as long a trip as from New York to Havana without needing to call Mr. Hastings once from his berth during his hours of rest.”

“Then you have two enlisted men aboard who thoroughly understand your engines?” pressed Dave Darrin.

“Ordinarily,” replied Hal Hastings, here breaking in.  “But one of our engine-tenders reached the end of his enlisted period to-day, and, as he wouldn’t re-enlist, we had to let him go.  So the new enlisted man whom we took aboard is just starting in to learn his duties.”

“Small loss in Morton,” laughed Lieutenant Jack Benson.  “He was enough of a natural genius around machinery, but he was a man of sulky and often violent temper.  Really, I am glad that Morton took his discharge to-day.  I never felt wholly safe while we had him aboard.”

“He was a bad one,” Ensign Hal Hastings nodded.  “Morton might have done something to sink us, only that he couldn’t do so without throwing away his own life.”

“I don’t know, sir, what I’d do, if I were a commanding officer and found that I had such a man in the crew,” replied Midshipman Darrin.

“Why, in a man’s first enlistment,” replied Lieutenant Jack, “the commanding officer is empowered to give him a summary dismissal from the service.  Morton was in his second enlistment, or I surely would have dropped him ahead of his time.  I’m glad he’s gone.”

Ensign Eph had now finished his meal and was sitting back in his chair.  Lieutenant Jack therefore gave the rising sign.

“I want to show the midshipmen everything possible on this trip,” said the very young commanding officer.  “So we won’t lie here in the mud any more.  Mr. Somers, you will return to the tower steering wheel, and you, Mr. Hastings, will take direct charge of the engines.  I will gather the midshipmen around me here in the cabin, and show the young gentlemen how easily we control the rising of a submarine from the bottom.”

Hal and Eph hurried to their stations.  The midshipmen followed Jack Benson over to what looked very much like a switchboard.  The young lieutenant held a wrench in his right hand.

“I will now turn on the compressed air device,” announced Lieutenant Jack.  “First of all I will empty the bow chambers of water by means of the compressed air; then the middle chambers, and, lastly, the stern chambers.  On a smaller craft than this we would operate directly with the wrench.  On a boat of the ‘Dodger’s’ type we must employ the wrench first, but the work must be backed up with the performance of a small electric motor.”