“If you play, leader,” called the officer, in a low voice that carried, nevertheless, “don’t imagine that your music is to welcome the ‘Benson.’  Submarine boats don’t travel under steam power.  They can’t.”

So, too, on shore, the understanding was quickly reached that the smoke did not indicate the whereabouts of the expected submarine.  Half and hour later it was found that the smoke came from the tug of a fruit transporting company.

Where, then, was the “Benson?”

It was not in the least like young Captain Jack Benson to be behind time when he had an appointment to get anywhere.  Nor did that very youthful companion expect to arrive late on this day of days.

Some miles away from Spruce Beach the submarine boat, as shown by her submersion gauge, was running along at six miles an hour some fifty-two feet under the surface of the ocean.

Young Eph Somers, auburn-haired and ofttimes impulsive, now looked as sober as a judge as he sat perched up in the conning tower, beyond which, at that depth, he could not see a thing.  However, a shaded incandescent light dropped its rays over the surface of the compass by the aid of which Eph was steering with mathematical exactness.

Out in the engine room stood Hal Hastings, closely watching every movement of even as trusted and capable a man as Williamson, one of the machinists from the Farnum shipyards.

At the cabin table sat Captain Jack Benson himself, his head bent low as he scanned a chart.  His right hand held a pair of nickeled dividers.  Near his left lay a scale rule.  A paper pad, half covered with figures, also lay within reach.

On the opposite side of the table sat Jacob Farnum, owner of the Farnum shipyard and president of the Pollard Submarine Boat Company.  Beside Mr. Farnum sat David Pollard, the inventor.

Readers of the preceding volumes in this series are familiar with all these people, now decidedly famous in the submarine boat world.  In the first volume, “The Submarine Boys on Duty,” was related how all these people came together; how the boys, by sheer force of character “broke into” the submarine boating world.  In that volume the building of the first of the company’s boats, the “Pollard” was described, and all the exciting adventures that were connected with the event were fully narrated.

Our former readers will also remember all the wonderful adventures and the rollicking fun set forth in the second volume, under the title of “The Submarine Boys’ Trial Trip.”  In this book, bristling with adventures, and made lighter, in spots, by accounts of humorous doings, was told how the boys gained fame as submarine experts.  It was their fine, loyal work that interested the United States government in buying that first boat, the “Pollard.”

The third volume in the series, entitled “The Submarine Boys and the Middies” told how our young friends secured the prize detail at Annapolis; where, for a brief time, the three submarine boys served as instructors in submarine work to the young midshipmen at the Naval Academy.  Nor was this accomplished without serious, and even sensational, opposition from the representative of a rival submarine company.  Hence the boys went through some rousing adventures.  Incidentally, they fell against practical instruction in hazing at the Naval Academy.