be very well versed, indeed, in all the arts of their peculiar profession."

A cheer went up from the principal throng over at the beach. Smoke had been sighted off on the eastern horizon, and this must come from the long expected craft.

From boat to boat the news passed, and so it traveled to the deck of the "Waverly," where the sailors received it with broad smiles. The leader of the impromptu band raised his baton, rapping for attention. But Lieutenant Featherstone, below, caught the leader's eye in time and held up his hand for a pause.

"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.

Adventures enough had befallen the submarine boys to last any man for a lifetime. Yet, as fate decreed it, Captain Jack Benson and his staunch young comrades were now destined to adventures greater and further reaching than any of which they could have dreamed. In advance, this winter trip to Spruce Beach promised to be little more than a pleasant relaxation for the youngsters. What it really turned out to be will soon be made clear in the pages of this volume.

"It seems a very risky plan that you're trying, Jack," remarked Jacob
Farnum, at last.

"Don't you want me to do it, sir?" asked the young skipper, looking up instantly from his chart.

"Why, er—"

But here David Pollard, the inventor of these boats broke in, eagerly:

"Of course we ought to do it, Farnum. Jack is wholly right. If we enter the harbor at Spruce Beach in this fashion, and carry through our entire plan successfully, what on earth can there be left for opponents of our class of boats to say?"

"Not if we succeed, of course," smiled Farnum. "It's only the pesky little 'if' that's bothering me at all. I don't want any of you to think me a coward—"

"We know, very well, you're not, sir," Captain Jack interposed, very quietly.

"But if we make any slip in our calculations," continued Jacob Farnum, "the first bad thing about it is that we'll smash a fine boat which, otherwise, the United States Government is likely to want at a price around two hundred thousand dollars. That, however, is not the greatest risk that I have in mind. On board this craft are five people without whom it would be rather hopeless for anyone to go on building the Pollard type of boat. Therefore, besides risking a valuable craft and our own rather inconsequential lives, we go further and put the United States Navy in danger of having only a couple of our boats. Now, the fact is, we want the Navy to have three or four dozen of our submarine craft, for we ourselves believe implicitly in the great worth of the Pollard boats."

"That's just the point, sir," cried Captain Jack Benson.

"Eh? What is?" inquired Mr. Farnum, looking at his young skipper in some bewilderment.

"Why, sir," laughed Jack, "the point is that we believe our boats to be infinitely ahead of anything owned in any other navy on earth. We believe it possible to do things, with boats like this one, that can be accomplished with no other submarine craft in the world. Now, it's a fact that, in all the navies, lest an accident happen to a submarine, that craft is obliged to travel about, always, in the company of a steam craft of war, which is known as the parent ship. Yet we've come, straight from the shipyard at Dunhaven, many hundreds of miles, without any such escort. We've been running along under our own power, night and day, without accident, stop or bother. Thus we've shown that the Pollard boat can do things that no other submarine craft are ever trusted to try alone. And now, all that remains to show is that, at the end of a long voyage, we can approach a coast, unseen, even though thousands of people are probably looking for us, and that we can get into a harbor without being detected; that, in fact, we could do anything we might have a mind to do to an enemy's ships that might be in that harbor. But now, sir, you propose that, lest we have accidents, it will be best to rise to the surface and enter the harbor at Spruce Beach as plainly and stupidly as though the 'Benson' were some mere lumber schooner."

"I see the thing just the way Jack Benson does," murmured David Pollard, thrusting his hands down deep in his trousers pockets.

"Oh, well, if I'm voted down, I'll give in," laughed Jacob Farnum. "I wonder, though, how Hal and Eph feel