He stooped down in the shelter of the pilot house.

The submarine drew close to the Ventura, and a voice hailed Captain Griswold:

"Thought you'd get away did you, you Yankee pig."

It was the voice of the German commander.

"Oh, we may get away yet," said Captain Griswold.

"Don't depend on the destroyer this time," shouted the commander of the submarine. "I see her approaching, but she won't be soon enough. I'll sink you and submerge before she can fire a shot."

"Well, you big cut throat," shouted Captain Griswold, losing his temper, "why don't you do it?"

"You dare to talk to a German officer like that?" thundered the submarine commander. "You shall be sunk immediately. But first I wanted a word with you. I just wanted to tell you what fate I hold in store for you."

"It's my opinion," said Captain Griswold, "that you're a big bluff, like all the rest of your stripe."

Meantime, realizing that the German commander did not intend to board the Ventura a second time, Jack crept from the shelter of the pilot house unobserved and stole across the deck until he was beside the rail just above the U-Boat, whose sides almost scraped the Ventura, so close were the two vessels together.

Jack removed his coat and his cap, which he dropped on deck. Then he stood up in full view of the German submarine commander. The latter gazed at him carelessly, for without his cap and coat Jack showed no sign of being a British naval officer.

Jack took in the scene about him with a careful eye. The German commander stood close to the conning tower. There were perhaps half a dozen men beside him, presumably his officers. The commander was directly below the spot where Jack stood.

One of the Germans, Jack noticed, kept a close eye on the approaching Essex and from time to time spoke to the commander in a low tone.

"Oh, these English can't shoot," Jack heard the commander say at last.

"However, I guess we have delayed long enough. Inside with you, gentlemen."

Two of the Germans descended through the conning tower. This left four on the deck of the submarine besides the commander. These, too, moved toward the conning tower.

"Guess it's time to get busy," Jack muttered.

With a single movement he leaped to the rail of the Ventura, and with a second hurled himself to the deck of the submarine, landing in the midst of the startled Germans.

At the same moment, Captain Griswold, on the Ventura, signalled his engine room for full speed ahead in accordance with Jack's instructions.

The reason for this was obvious. First, it would take the steamer out of the way of the torpedoes already trained on her, which would not be launched without a command from one of the enemy officers, and, second, it would draw the Ventura away so as to present the submarine as a clear target for the guns of the approaching Essex.

Jack, on the deck of the submarine, recovered himself before the German officers could get over their surprise. He sprang to his feet and waded into them, striking out right and left.

Two men went staggering across the narrow deck and toppled into the sea.

The others reached for their revolvers. Before they could fire, however, Jack sprang forward quickly and floored one of the enemy with a smashing blow. This left the commander and one other officer on deck.

The commander fired at Jack, but in his haste the bullet went wild. Jack hurled himself forward, and the men gave ground. One, retreating, lost his balance and went staggering across the deck and fell overboard.

Only the commander of the submarine now faced Jack, and he covered the lad with a revolver.

"Hands up!" he said.

For answer Jack smiled slightly, and took a quick step forward.

"Crack!" the German's revolver spoke sharply, and Jack felt a hot pain in his left arm. But the German had no time to fire again, for Jack was upon him, pinning his revolver arm to his side.

"Now," said the lad, "I've got you!"

The two wrestled across the deck.

CHAPTER XVI

THE FIGHT ON THE U-87

In the meantime, members of the crew hearing the commotion on deck, rushed up to see what was going on. Seeing their commander struggling with an enemy, they hurried across the deck.

Jack saw them coming out of the tail of his eye. It was not time to hesitate and the lad knew it.

With his arms still wrapped about the German commander, Jack struggled to the rail and leaped into the sea. Down and down he went, never for a moment relaxing his hold on the German. Then they came to the surface.

With a sudden jerk the German freed himself and aimed a heavy blow at Jack. This Jack dodged and sought to regain his hold on his foe. But the German wriggled away and struck out for the submarine.

In the meantime, Captain Griswold of the Ventura had been watching the struggle as his vessel sped away from the scene. There was a strange light in his eyes and he muttered to himself. At last he muttered an imprecation.

"He's a brave boy," he said. "I can't run away and leave him like that."

He brought the head of the vessel around in spite of the protests of some of the passengers, and headed back for the submarine.

"Man the forward gun there!" he cried.

For the Ventura, like other allied ships plying in the seas in those days, carried small guns for defensive purposes. The gun crew sprang to obey this order and the gun was trained on the submarine.

"Fire!" shouted Captain Griswold.

"Crash!"

The gun spoke and a geyser of water was kicked up just beyond the submarine.

At this point the officer left in command of the submarine seemed to realize his own danger. He sprang to the conning tower, unmindful of the fact that his commander was struggling in the water.

"Down, men!" he cried.

But it appeared that the German sailors were made of sterner stuff than was the officer. They refused to go below until their commander had been brought safely aboard. In vain the officer pointed out their danger.

Jack struck out after the German commander as the latter swam for the submarine. The lad was a powerful swimmer and he felt confident he could overtake the man before help could reach him.

The destroyer Essex had now drawn close. Frank had been afraid to order a shot at the submarine for fear the shell might hit Jack in the water.