"Looks like land, off there to the left," remarked the old hunter.

"Get the gla.s.ses, Washington," said Mr. Henderson. "It may be a ship."

He took a long and careful look through the binoculars.

"It's some sort of land," he announced. "We'll go over in the morning and see what it is. Probably it's an island, for there's no main land in these parts. We are in the middle of the southern Atlantic now."

The next morning, after breakfast, the _Porpoise_ was headed toward the dark spot on the surface of the water that the professor had gazed at the evening before. As they came nearer it was seen that the place was a large island.

"But it's a mighty queer one," spoke Mr. Henderson. "It looks more like a big volcano than anything else."

As the ship came nearer it was seen that this was true. The island rose abruptly from the surface of the sea in a big ridge, slightly rounded.

There appeared to be no signs of life on the land, but in the air overhead hovered several big birds. These circled about and then fluttered down, seemingly about the middle of the island.

"We'll sail around and see if there's a place to land," spoke the inventor. "There doesn't seem to be a good harbor on this side."

Slowly the _Porpoise_ made the circuit. The island appeared to be almost round. When they had gone about half way around Andy, who was staring ahead, cried out:

"Look out Professor! Don't go any nearer or we'll be sucked into the whirlpool!"

The inventor looked where the hunter pointed. Then he beheld the strangest sight he had ever seen. The island was low toward where Andy pointed and they beheld the waters of the ocean pouring over the edge of it, and falling down into an immense hole with a roar like that of Niagara Falls.

"Reverse the ship!" cried Professor Henderson. "Send her back quickly, Washington, or we'll be sucked down!"

The colored man lost no time, and the big screw was sent whirling in the opposite direction. And it was high time, for already the onward rush of the falling waters was slowly drawing the ship toward the big cavern.

"That was a lucky escape," commented Amos Henderson. "Well, as we can't land there we'll try the other way around."

The ship was headed in the opposite direction, and, after an hour's sailing, a good harbor was discovered. The _Porpoise_ was anch.o.r.ed in shallow water close to the sh.o.r.e and in a small boat the professor, Andy and the two boys went to the strange island.

They found it merely an immense circle of land with the middle part taken up by the big hole. And such a hole as it was! It was so wide across that they could not see the farther side, and the depth they could only guess at. Looking down they could only see great rolling ma.s.ses of clouds or vapor.

"Perhaps it's steam," suggested Jack.

"Maybe it is," agreed the professor. "If this is a volcano, with lava in it, the water of the ocean, pouring in on the other side, may be changed to steam."

"Do you suppose this hole leads to the centre of the earth?" asked Mark.

"I've read somewhere, that the earth is hollow."

"Some scientists believe it," commented the professor. "This looks like a big enough hole to lead clear through to China. Hark, you can hear the roar of the water now."

They listened, and the wind brought to them the sound of the sea pouring down into the unfathomable depths.

"Let's throw a big rock down," suggested Jack. "Maybe we can hear it strike bottom."

With the aid of Mark he cast a big boulder down into the depths. They listened intently, but not the slightest sound echoed back.

"I guess the bottom is too far away for you to hear the stone land,"

said the professor.

CHAPTER XVI

THE GHOST AGAIN

They spent some time looking down into the hole. The ma.s.ses of vapor, or clouds, rolled and swirled hundreds of feet below them, but never broke sufficiently to allow of a clear sight.

"Well, we had better go back to the ship," remarked the professor. "We must continue our voyage."

They were soon on the _Porpoise_ and steaming away from the strange island, the inventor deciding to get far off out of the influence of the terrible waterfall.

The night was, as usual, spent with the ship slowly steaming ahead on the surface of the water. It was getting on toward twelve o'clock and Washington had the watch. He was to be relieved by Jack.

The latter had been awakened by the alarm clock at the head of his bed, which time-piece he had set to arouse him so that he might take Washington's place. Jack was just getting the sleep from his eyes by a vigorous rubbing when he heard a loud yell.

"Land a' Ma.s.sy!" cried Washington from the deck above. "I's goin' t' die suah! De ghostess am after me ag'in!"

Without waiting to dress, Jack sprang up the ladder and was soon out on the deck. He saw Washington kneeling down in front of the conning tower door while, at the after end of the deck, was a mysterious white object; the same strange shape that had been observed before.

"I'm going to solve this puzzle!" exclaimed Jack to himself as he made a dive toward the object in white. "This ghost business will have to stop!"

But, unfortunately for his plans, his foot slipped on the smooth steel deck, and he went down in a heap. When he got up the ghost was nowhere to be seen.

Washington, however, was still kneeling down and praying to be spared from the attack of the midnight visitor. Jack limped over to the colored man.

"Keep still," said the boy. "It's gone now. What was it, anyhow?"

"Some ghost from de grabeyard," replied Washington.

"When did you see it first?" went on Jack.

"'Bout ten minutes ago," replied Washington.

"Well it's gone now," said Jack, though he had to admit to himself that the affair was somewhat puzzling. Professor Henderson had been awakened by the yells of the colored man and came on deck to see what the trouble was. He appeared somewhat annoyed when Washington told him what had happened.

"There are no ghosts!" declared the inventor in positive tones.

"You wouldn't say so, Perfessor, if you'd seen him," spoke Washington.

"He were all in white, tall an' slim, an' big red eyes, an' a green nose, an' fire comin' from his mouth an'--"

"Nonsense," interrupted Jack. "It was nothing but a white object, Professor Henderson. I saw it."

"And what do you think it was?" asked the inventor.

"I--I can hardly say," replied Jack. "Of course I don't believe in ghosts, but this--"