For an hour or so conditions were fairly comfortable. Then the same unpleasantness was experienced as was noticed before.

"If we could only open a window," sighed Mark, "and let in a lot of fresh air, how nice it would be."

The air rapidly became more foul. Soon Washington was gasping for breath. Tom and Bill showed signs of uneasiness.

"Lie down on the floor," counseled the professor. "You will find the air a little fresher down there."

They all did as he advised, the inventor himself stretching out at full length. A little relief was experienced.

They knew it could not last long. Even the professor seemed to have given up hope. The engine was not going to free the ship in time to save the lives of those on board.

Washington crawled to the engine room, as some of the bearings needed oiling. The professor seemed in despair. He opened one of the slides that covered the gla.s.s bulls eye windows. Then he turned off the electric lights. The opening was black, showing that the sea of gra.s.s still surrounded them. With a groan Mr. Henderson turned aside. The last hope was gone. He sank down on the floor of the darkened cabin.

Just then Mark happened to look at the bull's-eye. He saw a glimmer of light. Then he noticed several fishes swimming about. The water was clear. The gra.s.s had disappeared from the vicinity of the window.

"Look!" cried Mark to the professor.

The inventor peered forth. As he did so he uttered a cry. Then he staggered rather than ran to the engine room.

"What are you doing?" he called to Washington.

"I jest let some ob de sulphuric acid out ob de storage battery tank,"

replied the colored man.

"That's it! That's it!" exclaimed the professor. "Quick, let some more out, Washington. Let out all there is in that tank. It will save our lives."

Wonderingly Washington obeyed. The air in the ship was growing more foul every second. It was hard to breathe even on the floor, and all were gasping for breath. A few minutes more and they would all become unconscious and death would come in a little while if the air was not freshened.

The professor staggered back to the main cabin. He looked out of the bull's-eye windows. Then he exclaimed:

"See, it is getting lighter! Thank Heaven we are saved!"

The next instant the ship began to move backward. Then with increasing speed it pulled out of the grip of the long gra.s.s, and in another minute was floating on top of the water, at the edge of the Sarga.s.so Sea.

"Quick! Open the man hole cover!" said Amos Henderson.

Washington threw back the lever cams, and in rushed the fresh air. It was a blessed relief from the terrible oppressiveness of the foul atmosphere of the boat. They all breathed deeply, and, in a few minutes the effects of their long imprisonment had pa.s.sed off.

They went out on the small deck. It was getting dusk, and the reflection of the red sunset shone brightly on the heaving water.

"I 'spected I'd neber see dis again," said Washington. "Thought suah I was a gone chicken!"

"We had a most fortunate escape," said the professor. "You did the trick for us when you let the acid run from that tank into the sea. It mingled with the water and burned or ate through the stems of the gra.s.s so they no longer held the ship. I saw what had happened as soon as I looked out of the bull's-eye, and that's why I had you turn out all the acid you could. It was just as if liquid fire had touched the sea weed and burnt it off."

"Golly!" exclaimed Washington. "Fust I know I'll be a perfessor myself!"

Supper was eaten with the ship on the surface of the ocean, for it was impossible to go below until the leak in the air tanks had been repaired. Work was begun on this the next day, and though it proved a difficult job it was accomplished by Mr. Henderson and the boys.

There were several minor repairs to be made to the machinery, and it was a week before all was in readiness for another descent beneath the waves. In the meanwhile the craft had moved slowly southward on the surface, where no very great speed was possible.

Toward evening, on the seventh day after their adventure with the Sarga.s.so Sea, the travelers closed the man hole, and with air tanks well filled slowly sank beneath the waves. Supper was eaten at a depth of sixty feet, and after the meal, while Washington was washing the dishes, the others sat and looked out through the bull's-eyes at the big fishes which floated past.

"I wouldn't like to catch one of them air things on my hook an' line,"

observed Bill, as a particularly large fish went past. "I reckon I'd have trouble landin' him."

"More likely he'd pull you in," said Mark.

For several minutes they watched the strange procession of deep-sea life. Presently Jack, who was sitting near the engine room door, sprang up. At the same instant there was the sound of an explosion.

"What's the matter?" cried the professor.

"Come quick!" yelled Washington.

"It's a fire!" yelled Jack. "One of the electrical fuses has blown out, and the ship is on fire!"

CHAPTER XIII

THE GHOST OF THE SUBMARINE

They all rushed toward the engine room. It was dark, because the lights had gone out all over the ship, and they could see only by the glare of the flames, which were increasing.

"Light one of the oil lanterns!" called the professor, and Bill did so.

"Unreel the hose," the inventor continued, and Mark and Jack ran to do this.

In a few minutes the line was stretched into the engine room, and water was being thrown on the flames, for Washington had started the pump as soon as he saw the conflagration.

The fire was in one corner, near the electrical switch board, and had been caused by the blowing out of one of the fuses, which occasioned the little explosion. The wood work near the switches was blazing fiercely, and soon the ship was filled with smoke.

"Empty the ballast tanks!" called the professor. "We must rise to the surface!"

"We'll all be burned up!" cried Tom. "First we nearly smother and then we get on fire. Neber saw such luck!"

With a rush the _Porpoise_ began to rise, as her tanks were lightened.

With steady hands, though with fear in their hearts, Jack and Mark continued to play the water on the flames, while the professor and Washington got out a second line and aided them.

"The fire is dying out!" exclaimed Mr. Henderson. "We'll soon get the best of it."

In five minutes the worst was over, though it had been an anxious time, and one of danger. The ship came to the surface, and the open man-hole let out the thick smoke that had nearly suffocated the travelers.

As soon as it was cool enough in the engine room an examination was made of the damage done. It was not as bad as the professor had feared, and the running part of the ship was not harmed. A new fuse was put in and the electric lights turned on.

The night was spent with the ship floating on the surface of the ocean, only enough speed being kept up to give her steerage way. The professor did not want to go below the waves until he had repaired the switch board.

Watch was kept, for, though they were out of the regular line of ocean travel, there was no telling when a vessel might come along and run them down, for the _Porpoise_ did not show above the waves more than a few feet, and carried no lights.