A few whiffs from a bottle of ammonia the professor carried soon brought Jack's color back.

"Do you feel better now?" asked Mark.

"I guess so. Yes, I'm all right," replied Jack, struggling to his feet. "What happened? Feels as if I had been tied up with a lot of rope."

"That's about what you were," Andy replied, "only it was the worst kind of rope I ever saw. Those snake-trees are terrible things. I've read of 'em, but I never saw one before. The book that told of them says they squeeze their victims to death just as a snake does. The only way to do is to make some smoke and fire at the bottom. This sort of kills the branches or makes them stupid and they let go. The trees are half animal, and awful things. I hope we don't meet with any more."

"Same here," added Jack fervently, as he grasped Andy's hand, and thanked him for saving his life.

"Do you think you can go on, or shall we return to the ship'?" the professor asked.

"Oh I can trail along, if you move a little slowly," Jack replied.

"I'm a bit stiff, that's all."

So they resumed their journey. They had gone, perhaps, three miles when Washington, who was in the lead, suddenly stopped and called:

"Sounds like thunder."

The others listened. Sure enough there was a dull rumble and roar audible. It seemed off to the left, but they could see no clouds in the sky, nor any signs of a storm.

"Let's take a walk over that way and see what it is," Mr. Henderson suggested.

As they walked on the noise became louder, until in about half an hour it was like the sound from a blast furnace.

"What do you suppose it can be?" asked Mark.

"Perhaps some new freak of nature," the professor replied. "We seem to have a good many of them here."

They were all on their guard now, for there was no telling into what danger they might run. As they went up a little hill the noise became much louder. The professor and Andy, who had taken the lead, kept a sharp lookout ahead, that they might not unexpectedly fall into some hidden stream or lake. As they topped the hill they saw before them a deep valley, and in the midst of it was that which was causing the roaring sound.

From the centre of an immense mound of rock and earth there spouted up a great column of water, three hundred feet or more, as straight as a flag staff. It was about ten feet in diameter, and at the top it broke into a rosette of sparkling liquid, which as the vari-colored lights played on it, resembled some wonderful flower.

"It's a great geyser!" the professor exclaimed. "We have come to a place like Yellowstone Park. We must be very careful. The crust may be very thin here, and let us down into some boiling spring."

The others gathered around the professor, and, from a safe distance watched the ever rising and falling shaft of water.

It was not regular in motion. Sometimes it would shoot up to a great distance, nearly a thousand feet, the professor estimated. Again it would sink down, as the power sending it out lessened, until it was only a few hundred feet above the rounded top of the mound from which it spurted. But it never fell below this. All the while there was the constant roaring sound, as though the forces of nature below the surface were calling to be let out.

"I hope there are not many of those about," Mr. Henderson remarked after a pause. "If the ship should hit one during the night it would be all up with us. We must keep a careful look-out."

The spouting column had a fascination which held them to the spot for some time. From the hill they had a good view of the surrounding country, but did not see any more geysers.

"Do you think it is hot water?" asked Mark.

"There is no vapor," the professor answered, "but most of the geysers are produced by the action of steam in the interior of the earth.

However we'll not take any chances by investigating. I fear it would not be safe to go into that valley."

"Look there!" cried Andy. "I guess we're better off here!" He pointed a little to the right of where the water spouted. The others looked, and saw, coming from a hole in the ground, some s.h.a.ggy black object.

"What is it?" asked Jack.

"It looks like a bear," replied the hunter, "but I never saw one like it before."

Nor had any of the others, for the creature was a terrible one. It had the body of a bear, but the feet and legs were those of an alligator, while the tail trailed out behind like a snake, and the head had a long snout, not unlike the trunk of an elephant. The creature was about ten feet long and five feet in height.

"Let me try a shot at it!" exclaimed Andy. "That is something worth shooting," and he c.o.c.ked his rifle.

"Don't!" exclaimed the professor shortly. "You might only wound it, and it would pursue us. We are not ready to fight such creatures as that, and you are the only one armed."

"I never missed anything I aimed at yet," said Andy, a little hurt that any one should doubt his ability to kill at the first shot.

"Perhaps not, but how do you know but what this creature has a bullet proof armor under its hide. This is a strange world, Andy. It is better to take no chances."

"I hate to see him get away," the hunter said.

But, as it happened, the beast was not to get away. As they watched they saw the horrible animal approach the mound from which the water spurted. Up the sides it climbed.

"I guess he's going to get a drink," said Mark.

That was evidently the beast's intention. It went close to the spouting column of water, and thrust its head out so that its tongue could lap from the side. It seemed to have been in the habit of doing this.

For once, and for the last time, however, it made a mistake. The water seemed to veer to one side. In its eagerness to get a drink the animal took another step forward. At that moment the direction of the column changed again, and it tilted over toward the beast.

Suddenly, as the travelers watched, the full force of the big column caught the beast just under the fore shoulders. Up into the air the creature shot, propelled by thousands of pounds pressure. Right up to the top of the column it went, and this time the water rose a thousand feet into the air.

Up and up went the animal, struggling to get away from the remorseless grip. Then, when the water had reached its height, it shot the beast off to one side. Then the brute began to fall, twisting, turning, wiggling and struggling. Down it came with a thud that could be heard above the noise of the geyser.

"I reckon that finishes him," observed Andy. And it had, for there was not a sign of life from the creature.

"I guess we have seen enough for one morning," the professor said, "Let's go back to the airship. It must be nearly dinner time."

They started away. Mark gave a last look at the queer column of water and the dead body of the strange animal. As he pa.s.sed down the hill he thought he saw the creature move, and stayed to see if this was so.

But a second glance convinced him he was mistaken.

The others had gone on and were some distance ahead. Mark hurried on to join them. As he got a last glance at the top of the column, over the brow of the hill, he happened to look off to the left. There was another hill, about the size of the one they had been on.

And, as Mark looked he saw something move. At first he thought it was another beast. But, to his terror he saw that the creature had only two legs, and that it stood upright like a man, but such a man as Mark had never seen before, for he was nearly twelve feet tall.

He was about to cry out and warn the others, when the thing, whatever it was, sunk down, apparently behind some tall bushes, and disappeared as if the earth had opened and swallowed it.

"I wonder if I had better tell them," thought Mark. "I can't show them anything. I wonder if I really saw it, or if it was only a shadow. I guess I'll say nothing. But it is very strange."

Then he hurried on to join the others.

"What makes you so pale?" asked Jack of his chum.

"Nothing," said Mark, somewhat confused. "I guess I'm a little tired, that's all."

They reached the ship in safety, and, having dinner started the machinery and took the Mermaid up into the air.