"What is it?" Jack managed to ask.

"We are caught in a whirlpool!" Mr. Henderson yelled as he leaped down the companionway and pulled the heavy steel cover after him.

Stricken with a nameless dread, Jack closed the water-tight door of the conning tower and made his way to the cabin. He could hardly get down the stairs, so swiftly was the ship whirling about.

He found the captain busy in the engine room and, in response to calls, Washington and Mark came hurrying in. They had been awakened by the commotion and the strange movements of the _Porpoise_.

"Turn on all the lights," ordered the inventor. "We must prepare for the worst."

The incandescents were soon glowing and in the glare the frightened adventurers gathered about Mr. Henderson, wondering what new terror had befallen them.

"See!" exclaimed the inventor. "We are going comparatively slow now, but we are on the outer edge. Wait until we reach the centre."

He pointed to a compa.s.s and, as the needle pointed steadily to the north the card seemed to be going around like the hands of a clock that has lost the balance and escapement wheels. The ship made three complete circles a minute.

Pale and frightened, Mrs. Johnson came from her cabin, whence the terrified cries of Nellie could be heard.

"Are we sinking?" she asked.

"Sinking will never harm the _Porpoise_," replied Mr. Henderson. "This is something decidedly worse."

"I know! It is a whirlpool!" exclaimed the lady.

"I'm dizzy; I'm so dizzy!" wailed Nellie. "Please stop the ship from going round, Mr. Henderson."

She came from her bed crying, and all her mother could do did not quiet her.

Meanwhile the submarine continued to whirl about faster and faster in the swirling waters. Five times each minute now it made the circuit, and, like the coils of a boa constrictor that is enfolding its victim, the circles continually grew smaller.

"We are being sucked down," said Jack in a low tone as he glanced at the depth gage, and noted that it showed them to be thirty feet under water.

"That is so," remarked Mr. Henderson quietly.

"What will be the result?" asked Mrs. Johnson.

"I do not know," was the answer, and the captain turned aside. He seemed to have lost all courage in the face of the new disaster.

"Can't we empty the tanks and rise to the surface?" asked Andy.

"The tanks are not filled," replied Mr. Henderson. "What is taking us down is the force of the whirlpool and not the weight of water."

"Then you fear for the worst?" asked Andy.

"I do," said the captain simply.

"Don't give up the ship!" exclaimed the old hunter suddenly. "Never say die! It's a long lane that has no turns! Hip! Hip! Hurrah!"

They all turned to stare at the old man.

"Never mind," said Mr. Henderson in a soothing tone, that one would use toward a baby, or a person not right in their head. "Never mind. We may be saved."

"Oh I'm not crazy!" exclaimed Andy. He tried to caper about but the motion of the ship made him dizzy and he had to sit down. "I'm all right! I just happened to think of something!"

"What is it?" asked the captain eagerly.

"Send the ship ahead!" exclaimed Andy. "Speed her as fast as she will go. Try her strength against the force of the whirlpool! We may win!"

"Good!" exclaimed Mr. Henderson. "I was too much depressed to think of that! The ship has powerful engines. Queer you should remember that instead of me. Come, Washington, start the screw going! We will try to beat the whirlpool!"

The submarine was now whirling around so rapidly that it was difficult for any one to stand without leaning against the sides or holding on to something. It was going lower and lower down, as the gage showed.

Soon a throb that was felt through the length of the craft told that the engine had started. The vibration increased until it seemed that the ship would be torn apart. Never had the big screw revolved at greater speed.

For a while the struggle between the force of man represented by the engine, and the power of nature, embodied in the whirlpool, seemed equal. Neither could gain the mastery. The ship continued to slide around in ever narrowing circles while the big cable of water, forced through the tunnel by the screw, was like a cataract.

"Which will win?" asked the professor softly to himself.

He crawled to the gages and watched them. Only by their needles could it be told when the battle had turned in favor of the adventurers.

The circular motion, that was now terrible in its speed and power, seemed to culminate in a rush that almost overturned the ship. In the engine room Washington was laboring to keep the machine at top speed. He put on the last ounce of power.

"Hurrah!" yelled the professor suddenly. "I think we shall win!"

He pointed to the depth gage. The needle, which had showed a constantly increasing record, until it was now at two hundred feet, had stopped. It showed they were going no lower.

Then Mr. Henderson looked at the indicator which showed the progress straight ahead. The needle was beginning to tremble. As he watched he saw it move, slowly at first, until, as the powerful screw won a victory over the terrible whirlpool. The gage marked one, two and then three miles an hour.

"We are leaving the swirling waters!" cried Mr. Henderson.

Then, all at once, as though it was an arrow shot from a gigantic bow, the _Porpoise_ cleft the under-billows and shot ahead, free at last from the grip of the whirlpool.

Man had triumphed over nature!

On rushed the ship like a race horse, for the engine was working as it never had before, and it did not have the pool to contend against.

"Slow down," said Mr. Henderson, "and we will go to the surface."

Two minutes later, under the buoyancy of her empty tanks, the _Porpoise_ lay floating on the top of the waves, under the shining stars.

CHAPTER XXII

UNDER FIRE

"I shouldn't want to go through that experience again," remarked Mr.