Suddenly, from the engine room the mate rushed.

"Jump! Jump for your lives!" he exclaimed. "The ship is about to blow up!"

CHAPTER XI

MYSTERIOUS HAPPENINGS

THE voice of the mate echoed through the Mermaid. Those on deck heard it, as did Tony in the engine room, where he was vainly trying to understand the complicated machinery.

An instant later there sounded from beneath the ship a series of splashes. More sailors were leaping from the deck of the craft to the ocean. The distance was not great, particularly as they all landed in water.

"Quick!" cried the mate to a group of sailors that hesitated before taking the jump. "The ship may blow up any minute now."

The men needed no second urging. As soon as they struck the water they began to swim ashore, as it was not far away. One after another they jumped over the rail. Tony was the last to go. He urged the captives to follow him, but they all refused.

A minute later the only one of the pirate crew left on the ship was the mate. The others were all struggling in the sea. Eventually they all reached shore in safety.

The airship was now within about twenty feet of the water. It was still falling but not so rapidly.

"Better send her up, now," said the mate to Mark, and the boy turned the necessary levers to accomplish this.

Dipping into the water as a sea gull does when searching for food on the wing, for she had come quite low, the Mermaid mounted once more into the air, and was soon sailing along over the heads of Tony and his gang.

"What's it all about?" asked Mr. Henderson, who seemed in a sort of stupor. "I thought the ship was broken. How, then, can it rise?"

"It was only a trick of mine," Rodgers said. "The gas machine is not broken. I had Mark fix it so that only a little vapor would be generated. When the supply in the holder was not enough, and no more was being made, the ship had to sink. Mark and I pretended it was worse than it really was just to scare the scoundrels."

"And you evidently succeeded," observed Mr. Henderson. "They have all left us. I am glad you stayed."

"So am I," said Rodgers. "I was just waiting for a chance to escape from that crowd. This was the plan I thought of that night. I wanted to see the men put on some island where they could manage to live, and which was not too far away."

The Mermaid was now mounting upward rapidly, as Mark had adjusted the machinery properly. The craft was well rid of the pirate crew, and was able to proceed on its way, and enable Mr. Henderson to carry out his plans.

When the Mermaid had reached a certain height her prow was turned the other way, and she was sent back racing over the ground she had just covered. But now the ship was in the hands of friends. Fortunately no great damage had been done by the sailors, and the professor was soon able to get things in ship-shape. The engines had not been molested and were working better than ever.

"Now to make another attempt to reach the big hole in the earth," the professor cried. "We will be careful next time, who we rescue from ships at sea."

The island was soon left behind, becoming a mere speck on the ocean. Those aboard the Mermaid knew no harm could befall the sailors, as there were no savage tribes on the little spot of land. Eventually the sailors were picked up by a passing vessel and taken to their homes. The story of their first mutiny leaked out and they were properly punished.

It required several days travel before the airship regained the distance she had lost because of the plans of the pirates. Also, there were a number of minor repairs to make, and the professor and his friends were kept busy.

"How much longer before we come to the big hole?" asked Jack, one day.

"I think we ought to be near it in about two weeks," the professor replied. "I only hope we shall not be disappointed, and will be able to explore it."

"'Tain't goin' t' be no fun t' be decimated an' expurgitated inter a conglomerous aggregation of elements constituting th' exterior portion of human anatomy," said Washington in dubious tones.

"You mean you're afraid of being boiled in the steam from the big hole?" asked Mark.

"Jest so," replied the colored man.

"You don't need to worry about that," put in the professor. "I will not take the ship down if there is any danger, though of course there will be some risk."

The ship, having been fully repaired, was now able to be speeded up, and was sent scudding along toward her destination. Rodgers proved a valuable acquisition toward the crew, for he had sailed many years in the waters over which they were flying, and was able to give the professor many valuable hints. He had heard vague stories of the island with the big hole, but had never been near it. He did not make the trip however, as, at his request, he was put off at an inhabited island one night.

It was about a week after the sailors were frightened from the ship, that a curious experience befell Mark. Washington was on duty in the conning tower, attending to the apparatus as the ship flew through the air, and all the others had gone to bed. Mark had remained up, later than the others as he was interested in reading a book on science.

About ten o'clock he became hungry, and going to the pantry got some bread and cold meat. He set these on a table, and then, remembering he would need some water to drink, started after some in the cooler, which was in a little room near the tower.

Washington heard the boy as he turned the faucet to draw the liquid, and spoke to him, as the colored man was rather lonesome at his post. Mark did not linger more than a minute or two, but when he returned to where he had left the food he was much surprised.

There was not a trace of it to be seen. The dishes were on the table, but every vestige of bread and meat had disappeared.

"I wonder if a cat or dog has been here," was Mark's first thought. Then he remembered that no such animals were aboard the Mermaid.

Something on the floor caught his eye. He stooped and picked it up. It was a slice of bread, but in such shape that the boy stared at it, puzzled as to how it could have become so.

It was flattened out quite thin, but the strangest part of it was that it bore what seemed to be the marks of thumb and fingers from a very large hand. So big, in fact, was the print, that Mark's hand scarce covered half of it, and, where the bread had been squeezed into a putty like mass (for it was quite fresh) the peculiar markings on the skin of the tips of the fingers were visible.

"It looks as if a giant grabbed this slice of bread," Mark observed. "There are strange happenings aboard this ship. I wish I knew what they meant."

He looked all around for the food, thinking perhaps a rat had dragged it off, but there was no trace of it.

Suddenly the boy thought he heard a sound from the big storeroom. He was almost sure he heard something moving in there. He started toward the door when he was stopped by hearing the professor's voice call:

"Don't open that door, Mark. Have I not told you that place must not be entered?"

"I thought I heard some one in there," Mark replied.

"There is nothing in there but some apparatus of mine," Mr. Henderson said. "I want no one to see it. What is the matter?"

Mark explained matters to the scientist, who had, as he said later, arisen on hearing the boy, moving about.

"Oh, it was a rat that took your stuff," Mr. Henderson said. "I guess there are some pretty big ones on the ship. Get some more food and go to sleep."

Mark felt it best to obey, though he was by no means satisfied with the professor's explanation. He listened intently to see if any more noises came from the storeroom, but none did, and he went to bed.

Several times after that Mark tried the experiment of leaving food about. On each occasion it was taken.

"It looks as if the ship was haunted," he said. "Of course I know it isn't, but it's very queer. They must be strange rats that can get food from shelves when there is only the smooth side of the ship to climb up," for on some occasions Mark had tried the experiment of putting the food as nearly out of reach as possible.

It took several nights to learn all this, and, as he did not want to take any one into his confidence, he had to work in secret. But, with all his efforts he learned nothing, save that there was something odd about the ship that he could not fathom.

At first he believed the professor had some strange animal concealed in the storeroom, but he dismissed this idea almost as soon as he thought of it. For what could the scientist want with an animal when they were going to the interior of the earth? That some beast had slipped aboard was out of the question. Mark was much puzzled, but finally, deciding the matter did not concern him a great deal, gave up trying to solve the mystery, at least for a time.

The ship was now in the neighborhood of the equator and the climate had become much warmer. So hot indeed were some nights that they slept out on deck, with the Mermaid flying through the air at a moderate pace, for it was deemed best not to go at any great speed after dark.

One night the professor, after consulting various charts and maps, and making calculations which covered several sheets of paper announced:

"We should sight the mysterious island to-morrow."

"That's good news!" exclaimed Jack. "I'm anxious to see what's below inside of that big hole."

"Everybody git ready for their funerals!" exclaimed Washington in a deep voice. "I ain't got many——"

"Cheer up," interrupted Jack, poking Washington in the ribs. The colored man was very ticklish, and he began to laugh heartily, though, perhaps, he did not feel like it.

Suddenly, above the sound of his shouts, there came a crashing, grinding noise from the engine room.

CHAPTER XII

THE BIG HOLE

"SOMETHING has gone wrong!" exclaimed the professor as he jumped up. He reached the engine room ahead of any one else, and when the two boys got there they found him busy twisting wheels and shifting levers.

"Anything serious?" asked Jack.

"It's the gas machine again," Mr. Henderson replied. "It broke where we fixed it. However it doesn't matter. I was going to lower the ship anyhow, as I want to approach the island from the water. We will go down a little sooner than I counted on."

The disabling of the gas machine caused the vapor to escape slowly from the tank, and this made the ship sink gradually. By means of the emergency stop-cock the descent could be controlled almost as well as though the machinery was in working order. Half an hour later the Mermaid rested on the water.

It was a little rough, as there was quite a swell on, and not so pleasant as floating in the air on an even keel, but they made the best of it.

On account of the little accident, and not being certain of its extent, it was deemed best not to send the ship ahead. So they laid to until morning.

For the better part of two days all those on board the Mermaid had their hands full mending the break and making other repairs found necessary. In that time they lay to, floating idly with the currents, or blown by the wind, for the professor would not start any of the engines or apparatus until the ship was in good condition.

In this time Mark had several times recalled the curious happenings in regard to the disappearing food, and the mystery of the storeroom. But there were no further manifestations, and no other signs that there might be a strange visitor aboard.

"I couldn't have imagined it all," said Mark, "but I guess what did happen may have been caused by natural means, only I can't discover them."

It was about two days after this, the ship having sailed scores of miles on the surface of the water, that Mark, who was in the conning tower exclaimed:

"That looks like a waterspout ahead of us."

"That's what it is!" Jack agreed. "What shall we do?"

"Call the professor!" said Mark. "He'll know."

When Mr. Henderson came, he looked for a long time at a cloud of black vapor which hung low in the east.

"It may be a waterspout," he said. "We'll rise in the air and see if we can avoid it."

The ship was sent up into the air. As it rose higher and higher, the professor, making frequent observations from his conning tower, cried out:

"That is no waterspout!"

"What is it?" asked Mark.

"It is the steam and vapor rising from the big hole in the earth! Boys, we are almost there!"

"Are you sure that's it?" asked Mark.

"Almost positive," Mr. Henderson replied. "You can see how much warmer it has become of late, as we approached the equator. We are almost due at the island, and I have no doubt we have reached it."

As the ship flew forward the mass of dark vapor became more pronounced. Through the glasses it could be noticed to consist of rolling masses of clouds. What lay beneath them no one knew. The adventurers were going to try to find out.

Now that they had arrived at the beginning of the main part of their journey, the travelers felt their spirits sink a little. It was one thing to plan to go down into the depths of the earth, but it was quite another to make the actual attempt. Still, they were not going to give up the project. The professor had confidence in his ship and believed it could safely make the trip. Still it was with no little apprehension that Mr. Henderson watched the nearer approach of the craft to that strange island.

"Perfesser, are yo' really an' truly goin' t' depress this elongated spheroid an' its human consignment int' that conglomerous convoluted mass of gaseous vapor regardless of th' consequences?" asked Washington, as he gazed with wide opened eyes at the sight before him.

"If you mean am I going to let the Mermaid go down into that hole you are perfectly correct," the scientist answered, "though you could have said it in fewer words, Washington."

"I— I guess I'll get out an' walk," the colored man made reply.

"This isn't any trolley car," observed Mark. "Don't lose your nerve, Wash. Stay with us, and we'll discover a gold or diamond mine, maybe."

"Is there diamonds down there?" asked the colored man, his fright seeming to leave him.

"There are all sorts of things inside the earth," the professor answered.

"Then I'm goin' along!" Washington declared. "I always did want a diamond ring, an' I knows a little colored gal that wants one, too. I'm goin' all right! This suttenly am th' most kloslosterous conjunctivity of combativeness that I ever sagaciated!" and he began to do a sort of impromptu cake-walk.

CHAPTER XIII

DOWN INTO THE EARTH

IT was now noon, but the adventurers did not think of dinner in the excitement of approaching the mysterious island. The speed of the ship was increased that they might the more quickly come to it. As they approached they could see the masses of vapor more plainly, and it appeared that some great commotion must be going on inside the big hole, since clouds of steam arose.

"I only hope it doesn't prove too hot for us," observed the professor. "However, I provided a water jacket for the ship, and we may need it, as well as the vacuum chambers to keep the heat from us."

It was about three o'clock when the flying ship reached the edge of the island. From there it was about a mile to the rim of the big hole, over one side of which the waters of the ocean poured with a roar that could be heard over half a mile off.

"I think we had better halt and see that everything is in good shape before proceeding," said Mr. Henderson. "Jack, you and Mark make a thorough inspection of the engine room, and see that all the apparatus is in working order,"

The two boys prepared to do as they were told. Mark, who was walking a little ahead of Jack, entered the apartment from which the storeroom opened. As he did so he saw, or thought he saw, the door of the place where the extra supplies were kept, close. Without saying anything to Jack he hurried forward, and tried the knob. It would not turn.

"That's funny," said Mark to himself. "I could almost swear I saw some one go into that room. Yet I know the professor did not enter, for I just left him. And none of the others would dare to. I wonder if I will ever solve the mystery."

But he had too much to do to allow him to dwell on that matter. Several of the dynamos needed adjusting and for two hours he and Jack had all they could do.

In the meanwhile the professor had gone over the other parts of the ship, and gotten everything in readiness for the descent. The Mermaid was lowered to within a few hundred feet of the sea, and, through a hose that was let down, the compartments, provided for this emergency were filled with water. These compartments were between the outer and inner hulls of the lower part of the craft, and were designed to prevent the interior becoming heated in case the travelers found they had to pass close to fire. There were also vacuum chambers, and from these the air was exhausted, as of course every schoolboy knows a vacuum is a non-conductor of either heat or cold.

"Now I think we are ready," the professor announced at length.

"Everything's all right in the engine room," announced Jack.

"Yes, an' everything's all right in th' kitchen," put in Washington. "I've got a good meal ready as soon as any one wants to eat."

"It will have to wait a while," Mr. Henderson remarked. "We are going to start to make the descent before we dine."

The hose was reeled up, and the ship was sent a few hundred feet higher into the air, as Mr. Henderson wanted to take a last good observation before he went down into the hole.

But having risen some distance above the masses of rolling vapors he found he was at no advantage, since the strongest telescope he could bring to bear could not pierce the cloud masses.

"We'll just have to trust to luck," the scientist said. "I judge we're about over the centre of the opening. Lower away Mark!"

The boy, who, under the watchful eye of the professor, was manipulating the levers and wheels in the conning tower, shifted some handles. The gas was expelled from the holder, the negative gravity apparatus ceased to work, and the Flying Mermaid sank lower and lower, toward the mysterious hole that yawned beneath her.

The hearts of all beat strangely, if not with fear, at least with apprehension, for they did not know what they might encounter. Perhaps death in some terrible form awaited them. But the desire to discover something new and strange had gripped all of them, and not one would have voted to turn back.

Even old Andy, who seldom got excited, was in unusual spirits. He took down his gun and remarked:

"Maybe I can kill some new kind of animal, and write a book about its habits, for surely we will see strange beasts in the under-world."

Lower and lower sank the ship. Now it was amid the first thin masses of vapors, those that floated highest and were more like a light fog, than anything else. By means of a window in the bottom of the craft, which window was closed by a thick piece of plate glass, Professor Henderson could look down and see what was beneath them.

"The clouds seem to be getting thicker," he said, as he peered through the small casement. "If they would only clear away we could see something."

But instead of doing this the vapors accumulated more thickly about the ship. It was so dark inside the Mermaid now that the electric lights had to be switched on. In the room with the floor-window the lights were not used, as had they shone one could not have seen down below.

The professor maintained his position. The descent was a perilous one, and he wanted to be on the watch to check it at once if the Mermaid was liable to dash upon some pointed rock or fall into some fiery pit. His hand was on the signal levers.

Suddenly he looked up and glanced at a gage on the wall. The hand of it was slowly revolving.

"We are at the earth's surface," the scientist said. "Now we are below it. Now we are fairly within the big hole! Boys, we may be on the verge of a great discovery!"

An instant later it seemed as if a hot wave had struck the Mermaid, or as if the craft had been plunged into boiling water.

"It's going to be hot!" cried the professor. "Lucky I provided the water jackets!"

Then the lights in the interior of the ship went out, leaving the whole craft in darkness.

"What has happened?" cried Mark.

CHAPTER XIV

MANY MILES BELOW

"DON'T be alarmed," spoke the calm voice of the professor. "I have only turned off the electrics. I want to switch on the search lights, to see if we can learn anything about our position."

As he spoke he turned a switch, and, the gloom below the ship, as the boys could see by glimpses from the floor-window, was pierced by a dazzling glare. In the bottom of the Mermaid were set a number of powerful electric arc lights with reflectors, constructed to throw the beams downward. The professor had built them in for just this emergency, as he thought that at some time they might want to illuminate what was below the craft.

Not that it was of much avail on this occasion, for, though the lights were powerful, they could not pierce the miles of gloom that lay below them. The beams only served to accentuate the darkness.

"I guess we'll have to trust to luck," the professor said, after a vain attempt, by means of powerful glasses, to distinguish something. "There is too much fog and vapor."

"What makes it so warm?" asked Mark, removing his coat.

"Well, you must remember you are approaching the interior of the earth," the professor answered. "It has been calculated that the heat increases one degree for every fifty-five feet you descend. We have come down several hundred feet and of course it is getting warmer."

"Then if we go down very far it will get so hot we will not be able to stand it," Jack put in.

"I do not believe we will suffer any great inconvenience," Mr. Henderson went on. "I believe that after we pass a certain point it will become cooler. I think the inner fires of the earth are more or less heated gas in a sort of inner chamber between two shells. If we can pass the second shell, we will be all right."

"But aren't we liable to hit something, going down into the dark this way?" asked Mark.

"We will guard ourselves as far as possible," the scientist answered.

The Mermaid seemed to be going down on a side of the immense shaft a good way distant from the strange waterfall. When they had first dropped into the hole the travelers could hear the rush of waters, but now the noise was not audible.

"I think the hole must widen out the farther down we go," the professor said. "We are probably many miles from the fall now."

"I'm sure I hope so," put in Jack. "It would be no fun to have to take a shower bath in this place."

After a meal, the boys and the professor took some more observations, but with all their efforts nothing could be seen below the ship but a vast black void, into which they were steadily descending.

"I wonder when we're going to stop," asked Mark. "It's like playing the game 'Going to Jerusalem,' you keep wondering when the music will cease and you will have a chance to grab a chair. I only hope we have a chair or something else to sit on, in case we go to smash."

"We're not liable to have any accidents with the professor in charge," Jack answered. "Didn't he bring us safe out of some pretty tight holes when we went to the north pole in the airship, and again when we found the south pole in the submarine?"

"Yes, but this is different," objected Mark.

"Well, I'm not worrying," Jack went on. "It doesn't do any good, and only makes you lie awake nights. By the way, I wonder what time it is getting to be."

He looked at his watch and found it was close on to eight o'clock in the evening. So late had dinner been served, and so varied were the happenings of the last few hours, that time had passed quickly.

"Why it's almost bed-time," said Jack. "I wonder if we are to go on dropping into the depths of nowhere all night."

At that moment the professor entered the room where the boys were. He seemed quite pleased over something, and was smiling.

"Everything is going along famously," he said. "I have just tested the air and find it is rich in oxygen. We shall suffer nothing on that score. The heat too, seems to have decreased. On the whole, everything favors us."

"Are we going on down?" asked Mark.

"As far as we can," Mr. Henderson answered. "Let me see how far we are below now."

He went to the gage that indicated the vertical position of the ship. Because of the changed conditions, the craft now sinking below the surface of the earth instead of rising above it, as was its wont, some calculations were necessary. These the scientist made as quickly as he could.

"We are now ten miles underground!" he exclaimed. "That is doing very well. My theories are working out. I think we shall land somewhere before long."

"I hopes so!" exclaimed Washington coming in at this point. "I'm mighty skeered shootin' down int' this dark hole, and no time-table t' show when we's due t' arrive."

"We ought to land in a couple of days more," the professor answered. "Never mind about worrying Washington, I'll take care of you."

"I hopes so, Perfesser," the colored man said. "I got a little girl waitin' for me back in Georgia, an' I'd like t' see her 'fore I git burned up."

Accompanied by the professor, the boys made a tour of the ship to see that all the machinery and apparatus were in working order. Owing to the changed conditions the negative gravity engine had to be worked at faster speed than usual, since the downward pull of the earth was greater the farther they descended into the interior and they did not want to fall too swiftly. But this was easily provided for, since the professor had made the apparatus capable of standing a great strain.

The ten miles had become fourteen when the professor, finding that everything was in good shape, proposed that the boys go to bed. They, did not want to, though they were sleepy, and they feared to miss some strange sights.

But when the professor had promised to call them in case anything unusual developed, they consented to turn in, and Bill and Tom assumed their duties, which were light enough, now that the ship was merely falling into the immense shaft.

When Mark turned into his bunk he could not go to sleep at once. It may have been the excitement over their new position, or because he had eaten too hearty a supper, but the fact was he remained awake for some time.

While thus tossing restlessly on his bed, wondering what ailed him, he thought he heard a noise in the main apartment out of which the storeroom opened. He crawled softly from his bed, and looked from his stateroom door.

In the light of a shaded electric Mark saw the figure of some one glide across the floor and take refuge in the room, which Professor Henderson always was so particular about.

"I wonder what or who that was," reasoned Mark. "There is some mystery in this. Can the professor have concealed some one on this ship whose presence he does not want to admit? It certainly looks so."

Not wanting to awaken the ship's crew, and remembering what Mr. Henderson had said about any one entering the storeroom, Mark went back to bed, to fall into an uneasy slumber.

"Breakfast!" called Washington breaking in on a fine dream Jack was having about being captain of a company of automobile soldiers. "Last call for breakfast!"

"Hello! Is it morning?" asked Jack.

"Not so's you could notice it," Washington went on. "It's as dark as a stack of black cats and another one throwed in. But breakfast is ready jest the same."

The boys were soon at the table, and learned that nothing of importance had occurred during the night. The Mermaid had been kept going slowly down, and about seven o'clock registered more than fifty miles below the earth's surface.

Still there was no change in the outward surroundings. It remained as black as the interior of Egypt when that country was at its darkest. The powerful electrics could not pierce the gloom. The ship was working well, and the travelers were very comfortable.

Down, down, down, went the Mermaid. The temperature, which had risen to about ninety went back to sixty-nine, and there seemed to be no more danger from the inner fires.

They were now a hundred miles under the surface. But still the professor kept the Mermaid sinking. Every now and again he would take an observation, but only found the impenetrable darkness surrounded them.

"We must arrive somewhere, soon," he muttered.

It was about six o'clock that night that the alarm bell set up a sudden ringing. The professor who was making some calculations on a piece of paper jumped to his feet, and so did a number of the others.

"We are nearing the bottom!" he cried. "The bell has given us warning!"

CHAPTER XV

IN THE STRANGE DRAUGHT

THE boys ran to attend to the engines and apparatus to which they had been assigned in view of this emergency. The professor, Washington, Bill, Tom and Andy, who had kept to themselves since the descent, came running out of the small cabin where they usually sat, and wanted to know what it was all about.

"We may hit something, in spite of all precautions," Mr. Henderson remarked. "Slow down the ship."

The Mermaid was, accordingly checked in her downward flight, by a liberal use of the gas and the negative gravity machine.

The bell continued to ring, and the dials pointed to the mark that indicated the ship was more than one hundred and fifty miles down.

Mark, who had run to the engine room to check the descent, came back.

"Why didn't you slow her down?" asked the professor.

"I did," replied the boy. "The negative gravity and the gas machines are working at full speed."

"Then why are we still descending?" asked the scientist. "For a while our speed was checked, but now we are falling faster than before."

"I attended to the apparatus," Mark insisted.

Just then, from without the ship, came a terrible roaring sound, as though there was a great cyclone in progress. At the same time, those aboard the craft could feel themselves being pulled downward with terrific force.

"We are caught in a draught!" Mr. Henderson cried. "We are being sucked down into the depths of the earth!"

He ran to the engine room. With the help of the boys he set in motion an auxiliary gravity machine, designed to exert a most powerful influence against the downward pull of the earth. As they watched the great wheels spin around, and heard the hum and whirr of the dynamos, the boys watched the pointer which indicated how low they were getting.

And, as they watched, they saw that the needle of the dial kept moving, moving, moving.

"Our efforts are useless! We can't stop!" the professor cried.

Grave indeed was the plight of the adventurers. In their ship they were being sucked down into unknown regions and all their efforts did not avail to save them. It was an emergency they could not guard against, and which could not have been foreseen.

"What are to do?" asked Mark.

"We can only wait," Mr. Henderson replied. "The terrible suction may cease, or it may carry us to some place of safety. Let us hope for the best."

Seeing there was no further use in running the engines in an effort to check the downward rush the machines were stopped. Then they waited for whatever might happen.

Now that they seemed in imminent peril Washington was as cool as any one. He went about putting his kitchen in order and getting ready for the next meal as if they were sailing comfortably along on the surface of the ocean. As for old Andy he was nervous and frightened, and plainly showed it. With his gun in readiness he paced back and forth as if on the lookout for strange beasts or birds.

Bill and Tom were so alarmed that they were of little use in doing anything, and they were not disturbed in their staterooms where they went when it became known that the ship was unmanageable.

The boys and the professor, while greatly frightened at the unexpected turn of events, decided there was no use in giving way to foolish alarm. They realized they could do nothing but await developments.

At the same time they took every precaution. They piled all the bedding on the floor of the living room, so that the pillows and mattresses might form a sort of pad in case the ship was dashed down on the bottom of the big hole.

"Not that it would save us much," Jack observed with a grim smile, "but somehow it sort of makes your mind easier."

All this while the ship was being sucked down at a swift pace. The pointer of the gage, indicating the depth, kept moving around and soon they were several hundreds of miles below the surface of the earth.

The professor tried, by means of several instruments, to discover in which direction they were headed, and whether they were going straight down or at an angle. But some strange influence seemed to affect the gages and other pieces of apparatus, for the pointers and hands would swing in all directions, at one time indicating that they were going down, and, again, upward.

"There must be a strong current of electricity here," Mr. Henderson said, "or else there is, as many suspect, a powerful magnet at the center of the earth, which we are nearing."

"What will you do if the ship is pulled apart, or falls and is smashed?" asked Mark with much anxiety.

"You take a cheerful view of things," said Jack.

"Well, it's a good thing to prepare for emergencies," Mark added.

"If the ship was to be separated by the magnetic pull, or if it fell on sharp rocks and was split in twain, I am afraid none of us could do anything to save ourselves," the professor answered. "Still, if we were given a little warning of the disaster, I have means at hand whereby we might escape with our lives. But it would be a perilous way of——"

"I reckon yo' all better come out an' have supper," broke in Washington. "Leastways we'll call it supper, though I don't rightly know whether it's night or mornin'. Anyhow I've got a meal ready."

"I don't suppose any of us feel much like eating," observed Mr. Henderson, "but there is no telling when we will have the chance again, so, perhaps, we had better take advantage of it."

For a while they ate in silence, finding that they had better appetites than they at first thought. Old Andy in particular did full justice to the food Washington had prepared.

"I always found it a good plan to eat as much and as often as you can," the hunter remarked. "This is a mighty uncertain world."

"You started to tell us a little while ago, Professor," said Mark, "about a plan you had for saving out lives if worst came to worst, and there was a chance to put it into operation. What is it?"

"I will tell you," the aged inventor said. "It is something about which I have kept silent, as I did not want to frighten any of you. It was my latest invention, and I had only perfected it when we started off on this voyage. Consequently I had no chance to try it. The machine works in theory, but whether it does in practice is another question. That is why I say there is a risk. But we may have to take this risk. I have placed aboard this ship a——"

The professor was interrupted in what he was about to say by a curious tremor that made the whole ship shiver as though it had struck some obstruction. Yet there was no sudden jolt or jar such as would have been occasioned by that.

At the same time Washington, who was out in the kitchen, came running into the dining room, crying:

"We're droppin' into a ragin' fire, Perfesser!"

"What do you mean?" asked Mr. Henderson.

"I jest took a look down through th' hole in th' bottom of the ship!" cried Washington. "It's all flames an' smoke below us!"

"I wonder if it is the end," the professor muttered in a low voice.

Followed by the boys, the inventor hastened to the floor-window. The lights were turned off to enable a better view to be had of what was below them.

Leaning over the glass protected aperture the boys and the professor saw, far, far down, a bright light shining. It was as if they were miles above a whole town of blast furnaces, the stacks of which were belching forth flames and smoke. The rolling clouds of vapor were illuminated by a peculiar greenish light, which, at times, turned to red, blue, purple and yellowish hues.

The effect was weird and beautiful though it was full of terror for the travelers. It seemed as if they were falling into some terrible pit of fire, for the reflection of what they feared were flames, could plainly be seen.

"I wish I'd never come on this terrible voyage!" wailed Washington. "I'd rather freeze to death than be burned up."

"Washington, be quiet!" commanded the professor sternly. "This is no time for foolishness. We must work hard to save our lives, for we are in dire peril.

"Mark, you and Washington, with Jack, start the engines. Turn on every bit of power you can. Fill the gas holder as full as it will hold, and use extra heavy pressure. I will see if I can not work the negative gravity apparatus to better advantage than we did before. We must escape if possible!"

The boys, as was also Washington, were only too glad to have something to do to take their mind off their troubles. All three were much frightened, but Mark and Jack tried not to show it. As for Washington he was almost crying.

Soon the whirr and hum of the machinery in the Mermaid was heard. The craft, which was rushing in some direction, either downward, ahead or backwards within the unknown depths, shivered from the speed of the dynamos and other apparatus. Soon the boys could hear the professor starting the negative gravity engine, and then began a struggle between the forces of nature and those of mankind.

Once more the adventurers anxiously watched the gages and indicators. For a while the ship seemed to be holding out against the terrible influence that was sucking her down. She appeared to hesitate. Then, as the downward force triumphed over the mechanical energy in the craft, she began to settle again, and soon was descending, if that was the direction, as fast as before.

"It is of no use," said the professor with a groan. "I must try our last resort!"

He started from the engine room where Mark and Jack had gone. As he did so, he glanced at a thermometer hanging on the wall near the door.

"Has any one turned on the heat?" he asked.

"It's shut off," replied Mark, looking at the electric stove.

"Then what makes it so hot?" asked the scientist.

He pointed to the little silvery column in the tiny tube of the instrument. It registered close to one hundred degrees, though a few minutes before it had been but sixty. And the starting of the machinery could not account for the rise in temperature, since most of the apparatus was run by electricity and developed little heat save in the immediate proximity. The thermometer was fully ten feet away from any machine.

"It's the fiery furnace that's doing it!" cried Washington. "We're falling into th' terrible pit an' we're goin' t' be roasted alive!"

"It certainly is getting warmer," observed Mark, as he took off his coat. Soon he had to shed his vest, and Jack and the professor followed his example. The others too, also found all superfluous garments a burden, and, in a little while they were going about in scanty attire.

Still the heat increased, until it was almost torture to remain in the engine room. Nor was it much cooler elsewhere. In vain did the professor set a score of big electric fans to whirring. He even placed cakes of ice, from the small ice machine that was carried, in front of the revolving blades, to cool off the air. But the ice was melted almost as soon as it was taken from the apparatus.

"Them flames is gittin' worser!" Washington cried a little later. "We's comin' nearer!"

From the bottom window the professor and the boys looked down. True enough the curious, changing, vari-colored lights seemed brighter. They could almost see the tongues of flame shooting upward in anticipation of what they were soon to devour.

The heat was increasing every minute. The sides of the ship were hot. The heads of the travelers were getting dizzy. They could hardly talk or move about.

"I must save our lives! I must trust to the——" The professor, who was muttering to himself started toward the storeroom. As in a dream Mark watched him. He remembered afterward that he had speculated on what might be the outcome of the mystery the professor threw about the place. "I will have to use it," he heard the scientist say softly.

Just as Mr. Henderson was about to open the door there came a fiercer blast of heat than any that had preceded. At the same instant the conditions in the Mermaid became so fearful that each of the travelers felt himself fainting away.

"Go to— storeroom— get cylinder— get in——" the professor murmured, and then he fell forward in a faint.

CHAPTER XVI

THE NEW LAND

"WHAT is it? Tell us!" exclaimed Jack, almost in his last breath, for, a few seconds later he too toppled over senseless. Then Washington went down, while Andy, Bill and Tom succumbed to the terrible heat.

Mark felt his head swimming. His eyes were almost bulging from their sockets. He dimly remembered trying to force himself to go to the storeroom and see what was there. He started toward it with that intention, but fell half way to it.

As he did so he saw something which impressed itself on his mind, half unconscious as he was.

The door of the storeroom suddenly opened, and from it came a giant shape, that seemed to expand until it filled the whole of the apartment where the stricken ones lay. It was like the form of some monster, half human, half beast. Mark shuddered, and then, closing his eyes, he felt himself sinking down into some terrible deep and black pit. A second later the whole ship was jarred as though it had hit something.

How long he and the others remained unconscious Mark did not know. He was the first to revive, and his first sensation was one as though he had slept hard and long, and did not want to get up. He felt very comfortable, although he was lying flat on the floor, with his head jammed against the side of a locker. It was so dark that he could not distinguish his hand held close to his face.

"I wonder if I'm dead, and if all the others are dead too," he thought to himself. "What has happened? Let's see, the last I remember was some horrible shape rushing from the storeroom. I wonder what it could have been? Surely that was not the secret the professor referred to."

Mark shuddered as he recalled the monster that seemed to have grown more terrible as each second passed. Then the boy raised himself up from his prostrate position.

"Well, at any rate, some one has turned off the heat," he murmured. "It's very comfortable in here now. I wish I could strike a light."

He listened intently, to learn if any of the others were moving about. He could hear them breathing, but so faintly as to indicate they were insensible. Mark stretched out his hand and felt that some one was lying close to him, but who of the adventurers it was he could not determine.

"If only the dynamo was working we could have light," he said. "But it seems to have stopped," and, indeed there was a lacking of the familiar purr and hum of the electrical machine. In fact none of the apparatus in the ship was working.

"The storage battery!" exclaimed Mark. "That would give light for a while, if I can only find the switch in the dark."

He began crawling about on his hands and knees. It was so intensely black that he ran into many things and received severe bruises. At last he came to a doorway, and as he did so his hand came in contact with an easy chair. It was the only one aboard, and by that he knew he had passed into the sitting room. He had his general direction now, and knew if he kept straight on he would come to the engine room. There he was familiar enough with the apparatus and levers to be able to turn the electric switch.

Crawling slowly and cautiously, he reached the room where all the engines were. Then he had to feel around the sides to locate the switch. At length he found it. There was a click, a little flash of greenish fire, and the copper conductors came together, and the ship was flooded with the glow from the incandescents.

Mark hurried back to where the others were lying. They were still unconscious, but an uneasy, movement on the part of Jack told that he was coming out of the stupor. Mark got some ammonia and held it beneath his comrade's nose. The strong fumes completed the work that nature had started and Jack opened his eyes.

"Where am I? What has happened? Are any of them dead?" he asked quickly.

"I hope no one is dead," Mark replied. "As to the other question, I can't answer. I don't know whether we are a thousand miles underground, or floating on the ocean, though I'm more inclined to the former theory. But never mind that now. Help me to bring the others back to their senses. I'll work on the professor and you can begin on Bill or Tom. Washington seems to be all right," for at that moment the colored man opened his eyes, stared about him and then got up.

"I thought I was dead for suah!" he exclaimed.

"Some of the others may be if we don't hurry," said Mark. "Get to work, Wash!"

With the colored man to help them the two boys, by the use of the ammonia, succeeded in reviving Bill, Tom and old Andy. But the professor, probably on account of his advanced age, did not respond so readily to the treatment. The boys were getting quite alarmed, as even some of the diluted ammonia, forced between his lips, did not cause him to open his eyes, or increase his heart action.

"If he should die, and leave us all alone with the ship in this terrible place, what would we do?" asked Jack.

"He's not going to die!" exclaimed Mark. "Here I have another plan. Washington bring that medical electrical battery from the engine room." This was a small machine the professor had brought along for experimental purposes.

Quickly adjusting it, Mark placed the handles in the nerveless fingers of Mr. Henderson. Then he started the current. In about a minute the eyelids of the aged inventor began to quiver, and, in less than five minutes he had been revived sufficiently to enable him to sit up. He passed his hand across his forehead.

"What has happened?" he asked in a faint voice.

"I don't know; none of us knows," Mark answered. "We all lost our senses when it got so hot, and there seemed to be some peculiar vapor in the air. The last I remember was seeing some horrible shape rush from the storeroom, soon after the ship struck. Then I fainted away. When I woke up I managed to turn the lights on, and then I came back here."

"I wonder where we are," the old man murmured. "I must find out. We must take every precaution. Washington, go and look at the gage indicating our depth."

The colored man was gone but a few seconds. When he returned his eyes were bulging in terror.

"What is it?" asked Mr. Henderson, who, thanks to the battery, had almost completely recovered.

"It ain't possible!" gasped Washington. "I'll never believe it!"

"What is it?" asked Mr. Henderson, while the others waited in anxiety for the answer.

"We're five hundred miles down!" declared Washington.

"Five hundred miles!" muttered the inventor. "It does not seem possible, but it must be so. We fell very rapidly and the terrible draught sucked us down with incredible rapidity. But come, we must see what our situation is, and where we are. We are stationary, and are evidently on some solid substance."

They all felt much recovered now, and, as the terrible fright of being consumed in a fiery furnace had passed, they all were in better spirits.

At the suggestion of the professor, the boys and Washington made a tour of the ship. They found, for some unaccountable reason, that nearly all the engines and apparatuses were out of gear. In some the parts had broken, and others were merely stopped, from the failure of some other machine, on which they were dependent.

"I'm afraid this is the end of the Mermaid," said Mark, in a sorrowful tone.

"Nonsense!" replied Jack, who was of a more cheerful nature. "Things are not so bad as they look. The professor can fix everything."

"I'm sure I hope so," Mark went on, not much encouraged, however, by Jack's philosophy. "It would be no joke to have to stay five hundred miles underground the rest of our lives."

"You don't know," retorted Jack. "Don't judge of a country you've never seen. This may be as fine a place as it is on the surface of the earth. I want a chance to see it," and Jack began to whistle a cheerful tune.

They completed the tour of the ship, and found, that, aside from the damage to the machinery, the Mermaid had not sustained any harm. The hull was in good order, though of course they could not tell about the gas holder. It was not possible to see this except by going into the conning tower or out on the small deck, and this they did not venture to do. The connections between the holder and the main ship seemed to be all right, and there was still a small quantity of gas in the big tank, as Mark found on opening a stop-cock.

They went back to the professor and told him what they had observed. He seemed somewhat alarmed, the more so as the experience he had just passed through had weakened him considerably.

"I hope I shall be able to make the repairs," he said. "It is our only hope."

As he spoke he looked up at the electric lights that shone overhead from wall brackets.

"Who is shutting down the power?" he asked.

"There is no power on, Professor," replied Mark. "I am running the lights from the storage battery. But something is the matter, for they are growing dim."

The filaments were now mere dull red wires, and the ship was being shrouded in gloom again.

"The battery is failing!" exclaimed Mr. Henderson. "We shall be left in darkness, and there is no other way to produce light. I ought to have brought some lamps or candles along in case of emergency,"

The next instant the Mermaid became as black as Egypt is popularly supposed to be, and something like an exclamation of terror came from the professor.

For several minutes they all sat there in the blackness and gloom, waiting for they knew not what. Then, suddenly, there sounded throughout the ship, a creaking as of metal sliding along metal. Some big lever creaked, and, a second later the whole place was flooded with light.

"What has happened?" cried the professor, starting to his feet in alarm.

"We are going to be burned up!" exclaimed old Andy.

"It's all right! It's all right!" yelled Washington from the engine room where the boys had left him. "Don't git skeered! I done it! I opened the port holes, by yanking on the lever. Golly, but we's arrived at the new land! Look out, everybody!"

CHAPTER XVII

A STRANGE COUNTRY

THEY all ran to the port holes, which were openings in the side of the ship. They were fitted with thick, double glass, and covered on the outside with steel shutters. These shutters were worked by a single lever from the engine room, so that one person could open or close them in a second or two. Washington, by accident, it appeared later, had slid back the protecting pieces of steel, and the rest followed.

As the adventurers looked from the glass ports they saw that the light which had flooded the ship came from without. They were in the midst of a beautiful glow, which seemed to be diffused about them like rays from a sun.

Only, in place of being a yellow or white light, such as the sun gives off at varying times, the glow was of violet hue. And, as they watched, they saw the light change color, becoming a beautiful red, then blue, and again green.

"Well, this is certainly remarkable!" the professor said. "I wonder what causes that."

"We've arrived! We're here, anyhow!" Washington cried, coming into the room. "See the country!"

Then, for the first time, the travelers, taking their attention from the curious light that was all around them, saw that they had indeed arrived. They were on a vast plain, one, seemingly, boundless in extent, though off to the left there was a range of lofty mountains, while to the right there was the glimmer of what might be a big lake or inland sea.

"See, we are resting on the ground!" exclaimed Jack. He pointed out of the window, and the others, looking close at hand, noted that the Mermaid had settled down in the midst of what seemed to be a field of flowers. Big red and yellow blossoms were all in front, and some grew so tall as to almost be up to the edge of the port.

"I wonder if we can be seeing aright," the professor muttered. "Is this really the interior of the earth; such a beautiful place as this?"

There could be little doubt of it. The ship had descended through the big shaft, had been sucked down by the terrible air current, and had really landed in a strange country.

Of its size, shape and general conditions the adventurers, as yet, could but guess. They could see it was a pleasant place, and one where there might be the means to sustain life. For, as the professor said afterward, he felt that where there were flowers there would be fruits, and where both of these provisions of nature were to be found there would likely be animal life, and even, perhaps, human beings.

But, for the time, they were content to look from the port on the beautiful scene that lay stretched out before them. The ship rested on an even keel and had landed so softly that none of the plates were strained.

"We have plenty of air, at all events," said the professor as he took a deep breath. "I was afraid of that, but it seems there was no need. The air appears to be as good and fresh as that on the surface of the earth, only there is a curious property to it. It makes one feel larger. I imagine it must be thinner than the air of the earth, which is a rather strange thing, since the higher one goes the more rarefied the air becomes, and the lower, the more dense. Still we can not apply natural philosophy to conditions under the earth. All the usual theories may be upset. However, we should be content to take things as we find them, and be glad we were not dashed to pieces when the ship was caught in the terrible current."

"What do you suppose caused the awful heat, and then made it go away again?" asked Jack.

"I can only make a guess at it," Mr. Henderson answered. "There are many strange things we will come across if we stay here long, I believe. As for the fire I think we must have passed a sort of interior volcano."

"But what sort of a place do you think we have come to, Professor?" asked Mark.

"It is hard to say," the scientist replied. "We are certainly somewhere within the earth. Our gage tells us it is five hundred miles. That may or may not be correct, but I believe we are several hundred miles under the crust, at all events. As to what sort of a place it is, you can see for yourselves."

"But how is it we can breathe here, and things can grow?" asked Bill, who was beginning to lose his fright at the thought of being practically buried alive.

"I do not know what makes such things possible," Mr. Henderson replied, "but that there is air here is a certainty. I can hardly believe it is drawn from the surface of the earth, down the big hole, and I am inclined to think this place of the under-world has an atmosphere of its own, and one which produces different effects than does our own."

"They certainly have larger flowers than we have," said Mark. "See how big they grow, and what strong colors they have."

He pointed to the port, against which some of the blooms were nodding in the wind that had sprung up, for, in spite of the many differences, the under-world was in some respects like the upper one.

"Probably the difference in the atmosphere accounts for that," the professor said. "It enables things to grow larger. And, by the way, Mark, that reminds me of something you said about seeing some horrible monster fleeing from the ship. Did you dream that?"

"I did see something horrible, Professor," he answered. "I'm not positive what it was, but I'll tell you as nearly as I can what it was like."

Thereupon Mark detailed what he had seen.

"But how could anything, least of all some big monster, be concealed in the storeroom, and we not know anything about it?" asked Mr. Henderson.

"I thought you did know something of it," replied Mark.

"Who, me? My dear boy, you must be dreaming again. Why should I want to conceal any being in the storeroom? Come, there is something back of this. Tell me all you know of it. I can't imagine why you think I was hiding something in the apartment."

"I thought so because you were always so anxious not to have me go near it," answered the boy. "Don't you remember when you saw me going toward it, several times, you warned me away?"

"So I did!" exclaimed Mr. Henderson, a light breaking over his face. "But, Mark, it was not because I had hidden some human being or animal there. I can't tell you what it is yet, save that I can say it is merely a machine of mine that I have invented. For reasons of my own I don't want any one to see it yet. Perhaps it may never be seen. I thought, not long ago, that we might have to undertake a terrible risk in escaping from this place. I directed you to go to the storeroom— but there, I can't say any more, my friends. Sufficient that I had nothing in the animal line concealed there."

"But I am certain there was some beast or human being in there," insisted Mark. "I heard curious noises in there. Besides, how do you account for the food disappearing and the door being open at times?"

"It might have been rats," said Jack.

"I don't believe there are rats in the ship," put in the professor. "More likely it was one of us who got up hungry and took the victuals."

"I'm sorry I can't agree with you," Mark added respectfully. "I am sure some strange being was on board this ship, and I believe it has now escaped. Who or what it was I can't say, but you'll find I'm right, some day."

"All right," spoke Mr. Henderson with a laugh. "I like to see any one brave enough to stick up for his opinion, but, at the same time, I can't very well imagine any person or thing being concealed in that storeroom ever since we started. How could it get in?"

Mark did not; answer, but there came to him the recollection of that night, previous to the sailing of the Flying Mermaid, when he had observed some strange shadow that seemed to glide aboard the craft.

"Now let's forget all about such things," the professor went on. "We are in a strange country, and there are many things to see and do. Let's explore a little. Then we must see what we can do with the ship. We are dependent on it, and it will not do to allow it to remain in a damaged state. We expect to travel many miles in the interior of the earth if it is possible, and we have only our craft to go in."

"I reckon we'd all better assimilate into our interior progression some molecules and atoms of partly disentegrated matter in order to supply combustion for the carbonaceous elements and assist in the manufacture of red corpuscles," said Washington, appearing in the door, with a broad grin on his good-natured face.

"Which, being interpreted," the professor said, "means, I suppose, that we had better eat something to keep our digestive apparatus in good working order?"

"Yo' done guessed it!" exclaimed the colored man, relapsing into his ordinary speech. "I'se got a meal all ready."

They agreed that they might not have another opportunity soon to partake of food, so they all gathered about the table, on which Washington had spread a good meal.

"Come on, let's go outside and view this new and strange land at closer quarters," the professor said, when they had satisfied their appetites. "We can't see much from inside the ship."

Accordingly the heavy door in the side of the Mermaid was slid back, and, for the first time the travelers stepped out on the surface of the land in the interior of the earth.

At first it seemed no different than the ordinary land to which they were accustomed. But they soon found it had many strange attributes. The queer shifting and changing light, with the myriad of hues was one of them, but to this the adventurers had, by this time, become accustomed, though it was, none the less, a marvel to them. It was odd enough to see the landscape blood red one instant, and a pale green the next, as it does when you look through differently colored glasses.

Then, too, they noticed that the grass and flowers grew much more abundantly than in the outer part of the world. They saw clover six feet high, and blades of grass even taller. In some places the growth of grass was so big that they were in danger of getting lost in it.

"If the grass is like this, what will the trees be?" asked Mark.

"There are some away over there," Jack replied. "We'll have to take a sail over. They must be several hundred feet high."

"Well, at any rate, here's a little brook, and the water looks good to drink," went on Mark. "I'm thirsty, so here goes."

He hurried to where a stream was flowing sluggishly between grassy banks. The water was as clear as crystal, and Mark got down on his face and prepared to sip some of the liquid up.

But, no sooner had his lips touched it, than he sprang up with a cry and stood gazing at the water.

"What's the matter?" asked Jack. "Hot?"

"No, it isn't hot," Mark replied, "but it isn't water. It's white molasses!"

"White molasses?" repeated the professor, coming up at that moment. "What are you talking about?"

He stooped down and dipped his finger into the stream. He drew it up quickly, and there ran from it big drops that flowed as slowly as the extract of the sugarcane does in cold weather.

"You're about right, Mark," he said. "It's water but it's almost as thick as molasses." He touched his finger to his tongue. "It's good to drink, all right," he went on, "only it will be a little slow going down."

Then he dipped up a palm full, and let it trickle down his throat.

"It is the strangest water I ever saw," he added. "It must be that the lack of some peculiar property of air, which we have on the surface, has caused this. I must make some notes on it," and he drew out pencil and paper. He was about to jot down some facts when he was interrupted by a cry from Washington.

"Come and see what's the matter with this stone!" he cried.

CHAPTER XVIII

CAUGHT BY A STRANGE PLANT

"WASHINGTON is in trouble!" exclaimed Mr. Henderson. Followed by the two boys he ran to where the colored man stood in a stooping position over a small pile of stones.

"What is it? Has something bit you?" asked the scientist, as he came up on the run.

"No, but I can't git this stone up!" Washington said. "Look at what a little stone it is, but I can't lift it. Something must have happened to me. Maybe some one put th' evil eye on me! Maybe I'm bewitched!"

"Nonsense!" exclaimed the professor, "what did you want the stone for?"

"Nothin' in particular," replied Washington, still tugging away at the stone, which was the size of his head. "I was just goin' t' throw it at a big bird, but when I went to lift it this little stone 'peared t' be glued fast."

Washington moved aside to give Mr. Henderson a chance to try to pick up the piece of rock. As the scientist grasped it a look of surprise came over his features:

"This is most remarkable!" he exclaimed. "I can't budge it. I wonder if a giant magnet is holding it down."

He tugged and tugged until he was red in the face. Then he beckoned to the two boys, and they came to his aid. There was barely room for them all to each get one hand on the rock, and then, only after a powerful tug did it come up. Almost instantly it dropped back to the earth.

"This is remarkable!" the professor said. "I wonder if the other stones are the same."

He tried several others, and one and all resisted his efforts. It was only the small stones he was able to lift alone, and these, he said, were so weighty that it would have been a task to throw them any distance.

"The water and the stones are strangely heavy in this land," he said. "I wonder what other queer things we shall see."

"I saw a bird a little while ago, when I went to pick up that stone," observed Washington.

"What kind was it?" asked the inventor.

"I don't know, only it was about as big as an eagle."

The travelers wandered about a quarter of a mile from the ship. They avoided the tall grass and the lofty nodding flowers that seemed to grow in regular groves, and kept to places where they could walk with comparative freedom.

"Have you formed any idea, Professor, as to the nature of this country?" asked Mark, who liked to get at the bottom of things.

"I have, but it is only a theory," Mr. Henderson answered. "I believe we are on a sort of small earth that is inside the larger one we live on. This sphere floats in space, just as our earth does, and we have passed through the void that lies between our globe and this interior one. I think this new earth is about a quarter the size of ours and in some respects the same. In others it is vastly different.

"But we will not think of those things now. We must see what our situation is, whether we are in any danger, and must look to repairing our ship. There will be time enough for other matters later."

The travelers were walking slowly along, noting the strange things on every side. As they advanced the vegetation seemed to become more luxuriant, as if nature had tried to out-do herself in providing beautiful flowers and plants. The changing lights added to the beauty and weirdness of the scene.

The plain was a rolling one, and here and there were small hills and hollows. As the travelers topped a rise Jack, who was in advance, called out:

"Oh what queer plants! They are giant Jacks-in-the-pulpit!"

The others hastened forward to see what the boy had discovered. Jack was too eager to wait, and pressed on. The hill which sloped away from the top of the little plateau on which he stood, was steeper than he had counted on. As he leaned forward he lost his balance and toppled, head foremost, down the declivity, rolling over.

"Look out!" cried Mark, who had almost reached his comrade's side.

The scene that confronted the travelers was a strange one. Before them in a sort of hollow, were scores of big plants, shaped somewhat like a Jack-in-the-pulpit, or a big lily, with a curved top or flap to it.

The plants were about eight feet tall, three feet across the top, and the flap or covering was raised about two feet. They were nodding and swaying in the wind on their short stems.

"He's headed right for one of them!" Mr. Henderson exclaimed. "I hope he'll not fall into one of the openings."

"Is there any danger?" asked Mark.

"I'm afraid there is," the inventor added. "Those plants are a variety of the well-known pitcher plant, or fly-trap, as they are sometimes called. In tropical countries they grow to a large size, but nothing like these. They are filled, in the cup, with a sort of sticky, sweet mixture, and this attracts insects. When one enters the cup the top flap folds over, and the hapless insect is caught there. The plant actually devours it, nature providing a sort of vegetable digestive apparatus. These giant plants are the same, and they seem large enough to take in a man, to say nothing of Jack!"

With anxious faces the adventurers turned to watch the fate of their comrade. Jack was slipping, sliding and rolling down the hill. He could not seem to stop, though he was making desperate efforts to do so. He was headed straight for one of the largest of the terrible plants.

In vain, as he saw what was in front of him, did he try to change the course of his involuntary voyage. Over and over he rolled, until, at length, he struck a little grassy hummock, bounced into the air, and right into the opening of a monster pitcher plant.

"It has him!" cried Mark. "We must save him! Come on everyone!"

He raced down the hill, while the others came closely after him. They reached the plant into which Jack had bounced. The flap, or top piece, had closed down, tightly over the unfortunate boy.

"Quick! We must save him or he will be smothered to death or drowned in the liquid the cup contains!" Mr. Henderson exclaimed. "Attack the plant with anything you can find!"

"Let's cut through the side of the flower-cup!" suggested Mark. "That seems softer than the stem."

His idea was quickly put into operation. Andy's long hunting knife came in very handy. While the sides of the long natural cup were tough, the knife made an impression on them, and, soon, a small door or opening had been cut in the side of the pitcher plant, large enough to enable a human body to pass through.

When the last fibre had been severed by Andy, who was chosen to wield the knife because of his long practice as a hunter, there was a sudden commotion within the plant. Then a dark object, dripping water, made a spring and landed almost at the feet of the professor.

It was Jack, and a sorry sight he presented. He was covered from head to foot with some sticky substance, which dripped from all over him.

With hasty movements he cleared the stuff from his eyes and mouth, and spluttered:

"It's a good thing you cut me out when you did. I couldn't have held on much longer!"

CHAPTER XIX

THE BIG PEACH

JACK soon recovered from his remarkable experience. The terrible plant that had nearly eaten him alive was a mass of cut-up vegetable matter which attracted a swarm of insects. Most of them were ants, but such large ones the boys had never seen before, and the professor said they exceeded in size anything he had read about. Some of them were as large as big rats. They bit off large pieces of the fallen plant and carried them to holes in the ground which were big enough for Washington to slip his foot into, and he wore a No. 11 shoe.

But the adventurers felt there were more important things for them to look at than ants, so they started away again, the professor telling them all to be careful and avoid accidents.

It was while they were strolling through a little glade, which they came upon unexpectedly, that Washington, who was in the lead called out:

"Gracious goodness! It must be Thanksgivin'!"

"Why so?" asked Jack.

"'Cause here's th' remarkablest extraordinary and expansionist of a pumpkin that ever I laid eyes on!" the colored man cried.

They all hurried to where Washington had come to a halt. There, on the ground in front of him, was a big round object, about the size of a hogshead. It was yellow in color, and was not unlike the golden vegetable from which mothers make such delicious pies.

"I allers was fond of pumpkins," said Washington, placing his hand on the thing, which was almost as tall as he was, "but I never thought I'd come across such a one as this."

The professor and the two boys went closer to the monstrosity. Mr. Henderson passed his hand over it and then, bending closer, smelled of it.

"That's not a pumpkin!" he exclaimed.

"What is it then?" asked Washington.

"It's a giant peach," the inventor remarked. "Can't you see the fuzz, and smell it? Of course it's a peach."

"Well I'll be horn-swoggled!" cried Washington, leaning against the big fruit, which easily, supported him.

"Hurrah!" cried Jack, drawing his knife from his pocket and opening the largest blade. "I always did like peaches. Now I can have all I want," and he drove the steel into the object, cutting off a big slice which he began to eat.

"It may be poisonous!" exclaimed Mark.

"Too late now," responded Jack, the juice running down from his mouth. "Taste's good, anyhow."

They all watched Jack while he devoured his slice of fruit. Washington acted as if he expected his friend to topple over unconscious, but Jack showed no bad symptoms.

"You'd better all have some," the boy said. "It's the best I ever tasted."

Encouraged by Jack's example, Mark thought he, too, would have some of the fruit. He opened his knife and was about to take off some of the peach when suddenly the thing began to roll forward, almost upon him.

"Hi! Stop your shoving!" he exclaimed. "Do you want to have the thing roll over me, Jack?"

"I'm not shoving!" replied Jack.

"Some one is!" Mark went on. He dodged around the far side of the immense fruit and what he saw made him cry out in astonishment.

Two grasshoppers, each one standing about three feet high, were standing on their hind legs, and with their fore feet were pushing the peach along the ground. They had been attracted to the fruit by some juice which escaped from a bruise on that side, which was the ripest, and, being fond of sweets had, evidently decided to take their find to some safe place where they could eat it at their leisure. Or perhaps they wanted to provide for their families if grasshoppers have them.

"Did you ever see such monsters?" asked Jack. "They're as big as dogs!"

At the sound of his voice the two grasshoppers, becoming alarmed, ceased their endeavors to roll the peach along, and, assuming a crouching attitude seemed to be waiting.

"They certainly are remarkable specimens," Mr. Henderson said. "If the other animals are in proportion, and if there are persons in this new world, we are likely to have a hard time of it."

This time the immense insects concluded the strangers were not to their liking. With a snapping of their big muscular legs and a whirr of their wings that was like the starting of an automobile, the grasshoppers rose into the air and sailed away over the heads of the adventurers. Their flight was more than an eighth of a mile in extent, and they came down in a patch of the very tall grass.

"Let's go after them!" exclaimed old Andy. "I was so excited I forgot to take a shot at them. Come on!"

"I think we'd better not," counseled the professor. "In the first place we don't need them. They would be no good for food. Then we don't know but what they might attack us, and it would be no joke to be bitten by a grasshopper of that size. Let them alone. We may find other game which will need your attention, Andy. Better save your ammunition."

Somewhat against his will, Andy had to submit to the professor's ruling. The old hunter consoled himself with the reflection that if insects grew to that size he would have some excellent sport hunting even the birds of the inner world.

"I wonder what sort of a tree that peach grew on," Jack remarked, as he cut off another slice, when the excitement caused by the discovery of the grasshoppers had subsided. "It must be taller than a church steeple. I wonder how the fruit got here, for there are no trees around."

"I fancy those insects rolled it along for a good distance," Mr. Henderson put in. "You can see the marks on the ground, where they pushed it. They are wonderful creatures."

"Are we going any farther?" asked Mark. "Perhaps we can find the peach tree, and, likely there are other fruit trees near it."

At the professor's suggestion they strolled along for some distance. They were now about three miles from the airship, and found that what they had supposed was a rather level plain, was becoming a succession of hills and hollows. It was while descending into a rather deep valley that Jack pointed ahead and exclaimed:

"I guess there's our peach orchard, but I never saw one like it before."

Nor had any of the others. Instead of trees the peaches were attached to vines growing along the ground. They covered a large part of the valley, and the peaches, some bigger than the one they first discovered, some small and green, rose up amid the vines, just as pumpkins do in a corn field.

"Stranger and stranger," the professor murmured. "Peaches grow on vines. I suppose potatoes will grow on trees. Everything seems to be reversed here."

They made their way down toward the peach "orchard" as Jack called it, though "patch" would have been a better name. Besides peaches they found plums, apples, and pears growing in the same way, and all of a size proportionate to the first-named fruit.

"Well, one thing is evident," Mr. Henderson remarked, "we shall not starve here. There is plenty to eat, even if we have to turn vegetarians."

"I wonder what time it is getting to be," Jack remarked. "My watch says twelve o'clock but whether it's noon or midnight I can't tell, with this colored light coming and going. I wonder if it ever sets as the sun does."

"That is something we'll have to get used to," the professor said. "But I think we had better go back to the ship now. We have many things to do to get it in order again. Besides, I am a little afraid to leave it unguarded so long. No telling but what some strange beast— or persons, for that matter— might injure it."

"I'm going to take back some slices of peaches with me, anyhow," Mark said, and he and Jack cut off enough to make several meals, while Bill, Tom and Washington took along all they could carry.

As they walked back toward the ship the strange lights seemed to be dying out. At first they hardly noticed this, but as they continued on it became quite gloomy, and an odd sort of gloom it was too, first green, then yellow, then red and then blue.

"I believe whatever serves as a sun down here is setting," the professor observed. "We must hurry. I don't want to be caught out here after dark."

They hurried on, the lights dying out more and more, until, as they came in sight of their ship, it was so black they could hardly see.

Mark who was in the rear turned around, glancing behind him. As he did so he caught sight of a gigantic shadow moving along on top of the nearest hill. The shadow was not unlike that of a man in shape, but of such gigantic stature that Mark knew it could be like no human being he had ever seen. At the same time it bore a curious resemblance to the weird shadow he had seen slip into the Mermaid that night before they sailed.

"I wonder if it can be the same— the same thing— grown larger, just as the peach grows larger than those in our world," Mark thought, while a shiver of fear seemed to go over him. "I wonder if that— that thing could have been on the ship——"

Then the last rays of light died away and there was total darkness.

CHAPTER XX

OVERHAULING THE SHIP

"KEEP together!" shouted the professor. "It will not do to become lost now. We are close to the ship, and will soon be there. Come after me."

It was more by following the sound of the scientist's voice, than by any sight which the others could get of him, that they managed to trail along behind. They reached the ship in safety, however, and entered. There was no sound as of beasts or insects within, and, though Mark felt a little apprehensive on account of what he had seen, he and the others as well, were glad to be again in something that seemed like home.

"I wish we had some candles, or some sort of a light to see by," the professor remarked. "We can do nothing in the dark, and there is no telling how long this night is going to last once it has set in. If I could have a little illumination, I might be able to fix the dynamo, and then we could turn on the incandescents. That portable light we had is broken.

"By cracky!" exclaimed Andy. "I believe I have the very thing!"

"You don't mean to say you have a torch or a candle with you, do you?" asked Mr. Henderson.

"No, but I have my patent pipe lighting apparatus," the hunter said. "I always carry it. It gives a little light, but not much, though it may be enough to work by."

Not until after several hours work, handicapped as they were by lack of light, were the repairs to the ship completed.

"Now we'll start the engine and see how we will come out," the inventor exclaimed, as he wiped his hands on some waste.

It did not take long to generate enough power to turn the dynamo. Soon the familiar hum and whirr was heard, and, a few seconds later the filaments in the lamps began to glow a dull red, which gradually brightened until they were shining in all their usual brilliancy.

"Hurrah!" cried the boys. "Now we can see!"

They all felt in better spirits with the restoration of the lights, and, washing off the grease and dirt of their labors in the engine room, they prepared to sit down to the meal which Washington prepared.

As soon as the dynamo was working well, care had to be taken not to speed it too much on account of a mended belt. The professor turned off part of the lights and switched some of the current into the storage batteries, to provide for emergencies. For there was no telling how long the night might last.

Jack was the first one to finish the meal— they did not know whether to call it dinner, supper or breakfast. He went into the conning tower, and, as soon as he reached it he called out:

"Come on up here, professor! There's something strange going on!"

Mr. Henderson, followed by Mark, hurried to the tower. As he reached it and looked out of the forward window, a beautiful white glow illuminated the whole scene, and then, from below the horizon, there arose seven luminous disks. One was in the centre, while about it circled the other six, like some immense pin-wheel.

"It's the moon!" cried Mark.

"It's seven moons!" Jack exclaimed. "Why it's almost as light as day!"

And so it was, for the seven moons, if that is what they were, gave an illumination not unlike the sun in brilliancy though it was like the beams from the pale moon of the earth.

"I guess we need not have worried about the darkness," the professor remarked. "Still it is a good thing I fixed the dynamo."

For some time he and the other adventurers watched the odd sight of the moons, as they rose higher and higher overhead. The scene was a beautiful, if weird one, for the whole plain was bathed in the soft light.

"I guess we can turn off the incandescents, and use all the power for the storage batteries," Mr. Henderson went on, as he descended into the ship, and opened the port shutters which had been closed when they started off on their exploring tour. The interior of the Mermaid was almost as light as when the odd colored beams had been playing over the new earth to which they had come.

"I think we had better continue with our work of making repairs," Mr. Henderson said. "We can't count on these moons remaining here any length of time, and I want to take advantage of them. So though some of us perhaps need sleep, we will forego it and fix up the Mermaid. I want to take a trip and see what other wonders await us."

They all agreed that they would rather work than sleep, and soon the entire force was busy in the engine room. There was much to be done, and the most important things were attended to first. The motive power was overhauled and found to be in need of several new parts. These were put in and then the gas generator, and the negative gravity machine, were put in shape.

It would have taken something very substantial to have awakened any one on board the Mermaid that night. They all slept soundly and awoke to find the strange colored lights shining in through the glass covered port holes.

"Well, the sun, or what corresponds to it, is up," observed Jack, "and I guess we had better do as the little boy in the school reader did, and get up, too, Mark."

Soon all the travelers were aroused, and the sound of Washington bustling about in the kitchen, whence came the smell of coffee, bacon and eggs, told the hungry ones that breakfast was under way.

After the meal work was again started on repairing the ship, and by noon the professor remarked:

"I think we shall try a little flight after dinner. That is, if one thing doesn't prevent us."

"What is that?" asked Jack.

"We may be held down, as were those stones," was the grave answer.

CHAPTER XXI

THE FISH THAT WALKED

IT was with no little apprehension that the professor prepared to take his first flight aboard the ship in the realms of the new world. He knew little or nothing of the conditions he might meet with, the density of the atmosphere, or how the Mermaid would behave under another environment than that to which she was accustomed.

Yet he felt it was necessary to make a start. They would have to attempt a flight sooner or later, and Mr. Henderson was not the one to delay matters. So, the last adjustment having been made to the repaired machinery, they all took their places in the ship.

The boys and the professor went to the conning tower to direct matters, while Washington and the others were in the engine room to see that the machinery worked properly. Mark gave a last look outside as he closed the big steel cover over the hole through which admission was had to the craft. He thought he might catch a glimpse of the queer shadow, but nothing was in sight. It was like a beautiful summer's day, save for the strange lights, shifting and changing. But the travelers had become somewhat used to them by this time.

The professor turned the valve that allowed the gas to enter the holder. There was a hissing sound and a sort of trembling throughout the entire ship. The dynamos were whizzing away and the negative gravity machine was all ready to start.

For several minutes the travelers waited until the big lifting tank was filled with the strong vapor. They watched the gages which indicated the pressure to be several hundred pounds.

"I think we can chance it now," remarked Mr. Henderson, as he threw over several levers. "We'll try, at any rate."

With a tremor the Mermaid left the surface of the inner earth and went sailing upward toward the— well it wasn't exactly the sky, but it was what corresponded to it in the new world, though there were no clouds and no blue depths such as the boys were used to. At all events the Mermaid was flying again, and, as the adventurers felt themselves being lifted up they gave a spontaneous cheer at the success which had crowned their efforts.

The ship went up several hundred feet, and then, the professor, having brought her to a stop, sent her ahead at a slow pace. He wanted to be sure all the apparatus was in good working order before he tried any speed.

The Mermaid responded readily. Straight as an arrow through the air she flew.

"Well, this is almost as good as being on the regular earth!" exclaimed Jack.

"It's better," put in Mark. "We haven't seen half the wonders yet. Let's open the floor shutter, and see how it looks down below."

He and Jack went to the room where there was an opening in the floor of the ship, covered by heavy glass. They slid back the steel shutter and there, down below them, was the strange new, world they had come to, stretched out like some big map.

They could see mountains, forests, plains, and rivers, the water sparkling in the colored light. Over green fields they flew, then across some stretches where only sand and rocks were to be seen. Faster and faster the ship went, as the professor found the machinery was once more in perfect order. Jack was idly watching the play of tinted lights over the surface of the ground.

"I wonder what makes it," he said.

"I have tried to account for it in several ways," said the professor, who had called Washington to the conning tower and come to join the boys. "I have had first one theory and then another, but the one I am almost sure is correct is that hidden volcanic fires cause the illumination.

"I think they flare up and die away, and have become so regular that they produce the same effect as night and day with us. Probably the fires go out for lack of fuel, and when it is supplied they start up again. Perhaps it is a sort of gas that they burn."

"Well, it's queer enough, whatever it is," Jack remarked. "What strikes me as funny, though, is that we haven't seen a single person since we came here. Surely this place must be inhabited."

Mark thought of the strange shadow he had seen, but said nothing.

"I believe it is," the professor answered. "We will probably come upon the inhabitants soon. I only hope they are a people who will do us no harm."

"If they tried any of their tricks we could mount up in our ship and escape them," said Andy.

"Provided they gave us the chance," Mr. Henderson put in. "Well, we'll not worry about that now."

For several hours the ship traveled on, until it had come to a different sort of country. It was wilder and not so level, and there were a number of streams and small lakes to be seen.

"Are you going to sail all night?" asked Jack.

"No," replied the professor. "I think we'll descend very soon now, and camp out for a while. That lake just ahead seems to offer a good place," and he pointed to a large sheet of water that sparkled in the distance, for by this time they had all gone back to the conning tower.

The lake was in the midst of a wood that extended for some distance on all sides, and was down in a sort of valley. The ship headed toward it, and in a short time a landing was made close to shore.

"Maybe we can have some fresh fish for supper," exclaimed Jack as he ran from the ship as soon as the sliding door in the side was opened. "Looks as if that lake had some in it. It is not thick water like in that stream we stopped at," he added.

"I believe you're right," old Andy put in, as he turned back to look for some lines and hooks among his traps. He soon found what he wanted, and gave them to the boys, taking his trusty gun along for himself.

While the professor, Washington, Tom and Bill remained behind to make some adjustments to the machinery, and to get things in shape for the night, which, they calculated would soon be upon them, Jack, Mark and Andy went down to the shore of the lake. The boys cut some poles from the trees, and baiting the hooks with some fat worms found under the bark, threw in.

"Let's see who'll get the first bite," spoke Jack. "I'm pretty generally lucky at fishing."

"Well, while you're waiting to decide that there contest, I think I'll take a stroll along shore and see if I can see anything to shoot," Andy remarked.

For several minutes the boys sat in silence on the bank of the lake, watching the play of the vari-colored lights on the water. Suddenly Jack felt a quiver on his line, and his pole began to shake.

"I've got something!" he cried. Then his pole bent almost double and he began to pull for all he was worth. "It's a whopper!" he cried. "Come and help me, Mark!"

Mark ran to his friend's aid. Whatever was on the other end of the line was strong enough to tax the muscles of both boys. They could hear the pole beginning to break. But for the excellent quality of Andy's line that would have parted some time before.

All at once there came a sudden slacking of the pull from whatever was in the water. And so quickly did it cease that both boys went over backward in a heap.

"He's got away!" cried Jack, getting up and brushing some of the dirt from his clothes.

"There's something that didn't get away!" cried Mark, who had risen to his knees, and was pointing at the lake. Jack looked and what he saw made him almost believe he was dreaming.

For, emerging from the water, dragging the pole and line the boys had dropped along with it, was a most curious creature. It was a big fish, but a fish with four short legs on which it was walking, or rather waddling along as much as a duck, with a double supply of feet, might do.

"Say, do I see that or is there something the matter with my eyes?" sung out Jack, making ready to run away.

"It's there all right!" exclaimed Mark. "Hi! Andy! Here's something to shoot!" he yelled, for indeed the creature was big enough to warrant attack with a gun. It was about five feet long and two feet through.

On and on it came, straight at the boys, as if to have revenge for the pain the fish hook must have caused it, for the barb could be seen dangling from its lip. On and on it came, waddling forward, the water dripping from it at every step. It had the body and general shape of a fish, save that the tail was rather large in proportion. As it came nearer the boys noted that the feet were webbed, like those of a water fowl.

"Come on!" cried Jack. "It may attack us!"

At that moment the creature opened its mouth, showing a triple row of formidable teeth, and gave utterance to a sort of groan and grunt combined.

This was enough to send Jack and Mark off on a run up the bank, and did they stop until they heard Andy's voice hailing them.

"What's the matter, boys?"

"Come here! Quick!" answered Jack.

The fish-animal had halted and seemed to be taking an observation. To do this, as it could not turn its neck, it had to shift its whole body. Old Andy came up on the run, his gun held in readiness.

"Where is it?" he asked, and the boys pointed silently.

The hunter could not repress a start of astonishment as he saw the strange creature. But he did not hesitate a second. There was a crack of the rifle, and the thing, whatever it was, toppled over, dead.

Andy hurried up to it, to get a closer view.

"Well, this is the limit!" he exclaimed. "First we have grasshoppers that can roll peaches as big as hogsheads, and now we come across fish that walk. I wonder what we will see next."

"I don't want to go fishing in this lake any more," spoke Jack, as he looked at the repulsive creature. "I never want to eat fish any more."

"Same here," agreed Mark, and old Andy was of the opinion that the thing killed would not make a wholesome dish for the table.

"There don't seem to be any game in this section," he remarked. "Not a sign could I see, nor have I since we have been here, unless you count those grasshoppers. But the fruit is good, I'll say that."