e _Porpoise_ began to rise slowly, and to the suffering men and boys
it seemed that she never went up so reluctantly. The heat was becoming
unbearable. They could hear the water bubbling even through the steel
sides of the submarine.

CHAPTER XXX

CONCLUSION

Could they live to reach the surface? was the thought in the mind of
every one. The heat was terrific. They were breathing in gasps.
Professor Henderson went to the water tank, thinking to throw some of
the fluid over himself and his companions, but he found it so warm that
it almost burned his hand.

"Keep up your courage!" exclaimed the inventor. "We will soon be at the
top!"

Almost as he spoke the _Porpoise_ bounded from the waves, and fell back
in a splash of foam on the surface of the billows. They were at the
surface.

The professor rushed for the manhole and soon opened it. He crawled out
on the deck, followed by the others. They breathed in deep breaths of
the fresh air.

The submarine continued to sail on. Every minute the sea seemed to boil
more violently, until at last the waves were covered with a cloud of
steam, through which it was difficult to observe where they were going.

"Hadn't we better turn back," suggested Mark.

"Our only hope is to press on," replied Mr. Henderson. "We may cross
this zone of boiling water soon."

He went into the conning tower to make an observation. He came on the
deck the next minute, very much excited.

"What's the matter? Are we sinking?" asked Andy.

"We are directly over the south pole!" exclaimed the professor. "We have
reached the goal! We have come to the spot hundreds of men have tried to
reach! It has been left for us to succeed. Look at the deflecting
needle!"

They crowded into the conning tower to note it. The slender hand of
steel stood straight up and down, indicating that the ship was over the
south pole, one of the two chief centres of magnetism of the earth.

"If we only dared stop to make some scientific notes and observations,"
said the professor, "we could render much valuable aid to the seekers
after truth. But it would be sure death to stay in the boiling water!"

"I guess we'd better be getting out of this if we want to reach home
alive," spoke Andy.

Indeed they were all suffering very much, for the heat from the water
was awful.

"Speed her up, Washington!" called the professor. "We must get out of
here!"

"Which way shall I steer?" asked the colored man.

"Stra