“And I guess we might as well sink, also,” said Lord Hastings.

“Wait a moment,” protested the German prisoner. “What are you going to do with me? You remember you promised me my liberty before we entered the Baltic.”

“That is true,” replied Lord Hastings, “but so far no opportunity has presented itself. There has been no chance to fulfill my promise.”

“Well,” said the prisoner, “I am willing to take a chance. Give me a boat and enough provisions for a day, and set me adrift.”

“But you may not make shore that way,” protested Lord Hastings.

“That will be my funeral, not yours. I am willing to take the chance. I know these waters pretty well, and if you can furnish me with a pair of oars, I will guarantee that I will find a place of safety within twenty-four hours.”

Lord Hastings turned the matter over in his mind for some moments.

“So be it,” he said at length. “When would you start?”

“At once.”

“Mr. Templeton,” said Lord Hastings, “you will have one of the small boats stocked with provisions and water sufficient for twenty-four hours. We shall not submerge until our prisoner has left us.”

Jack saluted.

“Very well, sir,” he said, and disappeared below.

It was but the work of minutes to water and provision the small boat, and when at last all was in readiness, the boat was lowered into the sea. The prisoner climbed in and took up the oars that had been furnished him.

“Goodbye,” he called to the three officers. “Thanks for your hospitality. I hope to be able to return it some of these days.”

“I hope you will never have to,” Lord Hastings called back. “Goodbye.”

The German waved his hand in reply, and the three aboard the bridge of the D-16 waved back at him. Then he bent to his oars, and set out in a direction that, barring accident, would take him to Heligoland.

“Good luck to him,” said Jack, as the German rowed away.

“The same,” said Frank.

“Now,” said Lord Hastings, “for that long deferred dive.”

All three went below and soon the D-16 sank from sight.

There was no further incident as the D-16 wended her way along. She reached Dover Harbor without difficulty, where Lord Hastings put in to replenish his supply of coal and food. Here he also filed his report to the Admiralty. Upon the morning of the following day, the submarine pointed her nose up the English Channel toward the Atlantic Ocean.

Once upon the broad expanse of the Atlantic the D-16 turned her prow southward and ran down the coast of France at full speed, finally emerging into the sunny waters of the Mediterranean.

“I believe,” said Lord Hastings, “that, on our way to the Dardanelles, we might run into the Adriatic and see what success the French fleet is having with the Austrians.”

“Good,” said Frank. “Ever since we left there I have been anxious to get back for a day or two.”

“Suits me, too,” declared Jack.

Accordingly the submarine, instead of going straight to the allied fleet off the Dardanelles, swerved at the entrance of the Adriatic, and soon was among the French fleet gathered there.

The blockade of the Austrian fleet in the Adriatic, up to this time, had been maintained with all vigilance, and in spite of several attempts of the enemy to run the blockade, they were still bottled up. What attempts they had made had been defeated with heavy losses, and it seemed that there would not be another.

There was no denying the fact that the French fleet was superior to that of the Austrians, but it was still something of a mystery to naval authorities why the Austrians did not venture forth to give battle.

True, they had done this once in the earlier stages of the war, assisted by four Zeppelin dirigibles, but they had been driven back after several of their most powerful ships had been sunk and the dirigibles hurled into the sea. After that the Austrians made no more attacks in force, but confined their operations to raids by single ships, one or two of which had been successful enough to dispose of one or two French battleships, or cruisers.

But, for weeks, now, there had been a dearth of active operations in the Adriatic. This, then, was the situation there when the D-16 moved in to spend a quiet day among the French men-of-war.

It soon proved that the day was not to be a quiet one. In fact, the D-16 had hardly time to let go her anchor, close under the lee of the French flagship, before she was engaged.

Lord Hastings, once the D-16 had anchored, went aboard the French flagship to pay his respects to the French admiral. The latter greeted him warmly, for the two, before the war, had been close friends.

“Pretty quiet, eh, admiral?” was Lord Hastings’ greeting.

“Well, it has been, Hastings,” was the reply, “but my nose tells me there is something in the wind. It is too all-fired quiet to suit me. This stillness spells trouble, or I miss my guess.”

“Where do you get that idea?” asked Lord Hastings. “It seems to me that you have these fellows bottled up so tight that they won’t make another break.”

“Well, it would look that way. I suppose I base my prediction on the fact that in the Austrian admiral’s place, I should take some sort of action. I know I couldn’t remain bottled up like that without chafing a bit.”

“Nor I,” Lord Hastings admitted, “but you must remember that the Austrians are of a different breed.”

“Still they have been known to fight,” mused the admiral.

“Oh, yes, they have been known to fight; but, to my knowledge, they have never been known to beat anyone and I don’t think they ever will.”

“I have learned,” said the admiral, “they have completed several submarine vessels, and I fear that they may attempt a raid beneath the water. Of course, I have my own submarines, but the enemy may get by.”

“In which case,” said Lord Hastings, “it is a good thing, perhaps, that I arrived just when I did.”

“I fail to see,” said the admiral, “how your vessel can hope to discover the enemy any easier than my own.”

“Well, I’ll tell you,” and Lord Hastings went into a detailed account of the capabilities of the D-16, laying particular emphasis upon her huge searchlight compartment, separated from the water only by thick glass, and upon her ability to remain indefinitely under the water.

The French admiral was greatly astonished, but when Lord Hastings told him of his course and assured him that the D-16 was capable of all he claimed for her, the admiral was delighted.

“Then you may really be of assistance to me,” he said.

“I shall be glad to aid in any way possible,” declared Lord Hastings. “You have but to command me. Consider me under your orders for the next twenty-four hours.”

“In that event,” said the French admiral, “I wish that you would try and creep into the harbor and learn what is going on. ‘Forewarned is forearmed,’ you know.”

“I shall be glad to do so.”

Lord Hastings bade the admiral goodbye and returned aboard the D-16 immediately.

When Frank and Jack learned that there was work ahead of them, both at once became very enthusiastic and could hardly wait to be on their way.

“We may as well submerge right here and then advance,” said Lord Hastings.

The order was given and the D-16 disappeared from the sight of the other ships. Then she moved forward slowly.

Frank, at his place in the lookout compartment, kept his eyes wide open for the sign of an enemy, or of the enemy’s mines.

Suddenly a dark object appeared directly ahead of him and, swerving quickly, dashed by before he could give the alarm.

Immediately he informed Lord Hastings and the D-16 was brought about quickly and headed after the object.

“I don’t know whether it is an enemy or not,” said Lord Hastings, “but we can afford to take no chances. We’ll have to go after it.”

The D-16 dashed on, but after half an hour saw no sign of what all believed to have been an Austrian submarine.

“Might as well go up and take a look about,” said Lord Hastings. “We should be among the French fleet again.”

And among the French fleet they were, as they learned as soon as they bobbed up on the surface.

But now the air of quiet that had been prevalent before the D-16 submerged was changed. The peaceful appearance of the French fleet, which had been lying quietly in the water, was gone.

As the three officers stepped upon the bridge, hoarse cries of command came to their ears. Battleships began to move from their moorings, and all were cleared for action.

“Great Scott!” ejaculated Frank. “What do you suppose is the matter?”

“I don’t know,” said Lord Hastings, but Jack cried:

“Look!”

Lord Hastings and Frank gazed in the direction indicated, and both cried out in alarm and amazement.

Not half a mile away a French cruiser of the first class was sinking by the head. Members of her crew were throwing themselves into the sea, and boats from other ships were standing by to pick them up.

“What do you suppose is the matter? Explosion?” asked Frank.

“Looks like it,” answered his commander. “I——”

But Jack supplied the answer.

“The Austrian submarine that passed us!” he exclaimed. “She is responsible for this.”

“By Jove!” exclaimed Lord Hastings. “You must be right.”

At this moment the French Admiral signalled Lord Hastings.

“Torpedoed by Austrian submarine,” read the signal flags.

Frank hastened to get out the D-16’s flags, and in response to Lord Hastings’ command, signalled the flagship:

“She escaped us, but we’ll get her.”

The flagship signalled “good luck” and Lord Hastings gave the command to submerge.

“Unless I am much mistaken,” he said, “the Austrian will make for the open sea. Probably she will make for the Mediterranean and attempt to sink some of our merchant vessels. They may have established a base some place.”

“I wouldn’t be surprised if you are right, sir,” said Jack. “But we’ll get her.”

“We will,” said Lord Hastings. “We’ll get her if I have to chase her around the world.”

The D-16, with her periscope protruding slightly above the water, dashed on at full speed.