"Look at Fig. 14. The edges are like the teeth of a saw. This is called the serrate leaf. The rose and the common nettle have such leaves.

"Fig. 15 shows a leaf with a saw tooth edge wherein the teeth themselves have a lot of little saw teeth, as in the nettle-leaved bell-flower, and this is called bi-serrate.

"Fig. 16 has very large, sharp teeth, not pointing in any particular direction, like the oak leaf. This is called the dentate, or tooth.

"Fig. 17 has rounded projections instead of angular teeth, and is called crenate. Ground ivy and horseradish have such leaves.

"When we make drawings of the shapes of the leaves that will take us along another step, and thus enable us to find out just what kind of tree or plant we are talking about."



The following day Harry proposed a trip over to the cave which George had discovered at the time he found the big air pocket that shot water and spray out into the ocean.

"I am interested," he said, "in seeing the air pocket George spoke about, and we might as well take our vacation to-day."

"As the distance is not great we need not bother about taking our luncheon along." And off they started, with the Professor bringing up the rear.

The course was first to Observation Hill, where they had erected a new and a larger pole than the one which had so mysteriously disappeared two months before. On every such visit it was the duty of the one who made the trip to scan the horizon in every direction.

It must not be inferred that because the boys were engaged in work which was all-absorbing that they had no thoughts of home, and had given up all hopes of a final rescue. If they could only let the people at home know they were alive and happy—that is, in learning the secrets of nature and in the exciting exploring trips, they would be satisfied.

They had no time to think of these things when they were at work, but in the night their thoughts often wandered back again to their homes and friends. Could they be blamed for that homesick feeling which came over them?

"Now lead the way, George; we want to see some more of your mysteries. Isn't it fortunate that the tide is out? It will give us a good chance to investigate."

The path which George had taken was farther to the right, but as he was in a hurry to get down as quickly as possible he followed a course, which was much steeper, with Harry and the Professor close on his heels.

When the bottom was reached there was no sign of a pocket, or a cave, or anything of that kind. George was very much annoyed. He could not be mistaken in the position, as it was directly to the right of Observation Hill, and not three hundred feet from the spot where Harry had landed on his first trip to the island.

"It seems to me, George, we are too low down. At high tide this place is all covered with water. It must he higher up in the cliff sides."

Harry scrambled up again part way, and shortly afterwards cried out: "I have found something here; come up at once."

He was distant not more than twenty feet above them, but so rugged were the cliffs that the opening was entirely hidden from below.



"This is an example of the corrosive effects of the sea, and of the elements in the water and in the rock. As these rocks are limestone formations, we may be able to see some beautiful decorations within, if the cave is of any extent."

"It is awful dark in there. I wish we hadn't forgotten the candles," he said, as he glanced at the Professor, who seemed to be quite absorbed in examining the rocks.

"Don't you think we had better go in?"

"I should like to do so, but we haven't any candles."

"I thought you came here for the purpose of examining the cave?"

"So we did."

"And came without making any preparations for it?" As he said this he drew out one of the small candles which they had been making and using for their evening work and recreation.

George and Harry were both very much ashamed of their carelessness. The Professor, on the other hand, did not make another remark on the subject. No doubt the silent rebuke was a lesson they would retain much better than if it should be more forcibly presented.

The boys, be it said to their credit, never resented any word or action on the part of the Professor. They had only love and veneration for him; and the Professor, by his constant attitude toward them, showed that even these careless actions or any other examples of thoughtlessness on the part of the boys, were part of the training that would teach lessons of value.

Below the mouth of the cave were little streams of water which looked like springs, and the Professor was of the opinion that the floor or interior of the cave must be lower than the entrance.

"Why do you think so?" was the inquiry.

"The springs below seem to indicate that when the high tide fills the cave, the bottom of the cave leaks enough to let out the water. The height of the mouth from the normal level of the water is much above the usual high tide level of the water, and it is only when there is an abnormally high tide, as on the day that George saw it, when the cave could be filled with water."

"Who will go in first?" said George. "I have no objection to taking the lead; so here goes."

George moved forward cautiously, holding the candle, and Harry followed with another. The opening was fully ten feet high, and at least that much in width, but irregularly formed. They went in straight for twenty feet or more, when George announced that he had reached a wall. The Professor, who was in the rear, called out: "Look to the right, there is a turn here."

Such was the case, but the broken up character of the sides and floor prevented them from readily grasping the formation. After making a jog the cave again turned into the cliff, practically on a line with the opening section or mouth of the cave. It was dark at first, but now, for some peculiar reason, it grew lighter as they advanced, and finally George stopped.

"What makes that peculiar light?"

"It is not a light; it is merely white walls and ceilings."

"What causes it?"

"Carbonate of lime, or chalk, which is caused by lime water coming from above and trickling down through to openings or crevices, and leaving the deposits there. It is not an uncommon thing in caves, and I foreshadowed it in the cave when I stated that the rocks were of limestone formation. You will remember we made lime from this kind of rock."

A loud splash and a groan-like noise put further conversation at an end. "What was that?" asked George, as he retreated. In doing so he tripped, and, in falling, the light he carried was extinguished as it flew from his hand.

Clearly there was water ahead. "Let us go forward, a little closer," said the Professor. "You might get your guns ready, in case of necessity."

Within thirty feet of them was the edge of water, and the light threw a beam beyond for a hundred feet or more.

"It seems as though we have reached the end of our explorations here." As they looked, the water was agitated, and it was plain that some aquatic animal was within the cave.

To return was the only thing to do, and as they went back the sides of the cavern were examined, and the Professor took a number of samples, as he said: "Don't lose the candle until we get where we can see daylight. Although we are not more than two hundred feet from the mouth of the cave, the remarkable bend or jog near the mouth of the cave makes it as dark as though we were in a thousand feet."

"What sort of animal do you suppose that was?"

"Possibly a sea lion, or a seal."

After the open air was reached the Professor said: "I do not see how this cave would account for the phenomena that George saw the other day."

"Why not?"

"The cave is too deep. It is not a true air pocket, and——"

"What is this? Here is another one, still larger, and lower down. Here, hold the candle." Harry was down in an instant.

"Probably this is what George saw."

True enough; it was an air pocket which extended in about fifty feet, and had no passageway beyond.



CHAPTER VII

INVESTIGATING THE PROSPECTOR'S HOLE

The knowledge that some marine animal inhabited the cave was now a constant topic, particularly with George, who was determined, sooner or later, to find out something more about it. With this end in view he made secret preparations, particularly in constructing a lamp which would not be liable to overturn or be put out by wind or in falling.

Thus far the only light available was obtained from candles made from the fat of the animals, and it was not the kind of illuminating material they had been used to. When people knew nothing better than tallow candles, that light was satisfactory, but when petroleum was once used tallow candles were entirely unsuitable and too primitive.

The statement by the Professor that the hole into which George fell, some months before, contained asphaltum, hinted at a possible source of petroleum, and through the persistent efforts of George, the Professor agreed to accompany him to the place to make an investigation.

The yaks were yoked, and a good luncheon put up, prepared for a day's jaunt, the trip being planned for the day of the week which had been set apart for exploration purposes. Within an hour the team was tethered at the spot where Harry and George put up the team when they started out on their former tour of investigation.

"Now, George, we shall have to depend on you to lead the way."

"When I left Harry we were on the little hill beyond that clump of bushes."

"We must have been much farther away," was Harry's opinion.

"Let us go over at any rate, and we can probably get our bearings from there."

The spot pointed out was just as much a mystery after reaching it as before. It was suggested that, as neither knew how to determine the direction of the "hole" from that point, time might be saved by each taking a different direction, with the understanding that if anything was discovered a shot should be fired as a signal.

After carefully noting the two large trees where the team was located, they separated, Harry going to the north, George to the northwest and the Professor directly west. The ridge on which they were ran north and south, and to the west was a decline. It was considerably south of the trail taken on their former trips, so it was really undiscovered territory.

The Professor passed down the long incline, carefully noting every set of bush, such as George declared he had passed through at the time he was deposited in the "hole." When the bottom of the ravine was reached he turned to the right, working his way diagonally up the hill.

George, on the other hand, made for some bush ahead of him, which looked familiar, but in this he was disappointed, and going to the left, considerably farther down the hill, was rewarded by the rediscovery of the "hole." Without waiting he fired a shot, and to his surprise found the Professor within a hundred feet.

"I have found it. See, that is the place I went through."

Harry was not far away, and he rushed up out of breath. The bushes were swept aside and George went in, followed by the Professor and Harry. He had not gone five feet when he stopped.



"This isn't the place. There is a big rock here; not a hole."

This was indeed the case.

George's countenance was a study. The Professor and Harry had a good laugh at the discomfiture of George.

"So you think you fell into a hole? It must have been a pretty solid hole." The rock was about ten feet across, and flat on top, and the bush grew all around it, thus entirely screening it from observation.

"Well, we must try again."

"I would like to know why vegetation accumulates around a stone, or around a hole, and gets so much larger than at other places?"

"It is accounted for by the little germs we talked about the other day. Did you ever notice the musty smell that comes up from an overturned stone?"

"Yes, and I have often wondered what it was."

"There is always more or less moisture under the stone, so that the germs are readily bred, and as they form carbonic and nitrogenous gases, which the plant must have, you can readily see why vegetation thrives around the stones."

"But where there is a hole it is drier, and the same thing occurs there?"

"That is a good observation. Two things are required to cultivate the germs, aside from the food. One is moisture and the other is heat. The earth is full of bacteria from which plants get their food; some places the bacteria go down only one or two feet; at other places, where it is warm, as in the tropics, they have been found five or six feet below the surface. When a hole is made, and the sun strikes it, the bottom of the hole gets warm, and thus facilitates the growth of the germs around the hole, so that the plants in the immediate vicinity get an extra supply of nitrogen."

"But where do they get the moisture?"

"That is another one of nature's great surprises, and shows how every contingency seems to be provided for. I suppose you have both cultivated corn—that is, have gone between the rows with a cultivator, and stirred up the earth. You did this, as you were told, to keep down the weeds. That was one reason, but it is not the principal one. A dry crust forms over the surface of the ground, owing to the heat of the sun. When the cultivator breaks up the crust the heat from the sun draws up the moisture from below, and you are therefore watering your corn, and what is more, you are breeding bacteria so as to supply food for the plants."

"After learning this I am glad we discovered the stone."

A more persistent search was now made, and George's "hole" was really found to exist. It was just as he described it. Everywhere along the hillside were rocks projecting out from the surface, but here was a depression, or hole, fully fifteen feet square, with rocky sides, the wall on the upper side of the hill being fully fifteen feet high, whereas the lower margin of the hole had a wall not over four feet high, so that it will be seen George had no difficulty in getting out after he had recovered from his fall.

The Professor was in the hole in an instant. The growth about the depression was so dense that it made the hole dark, but there was an unmistakable odor of asphaltum. Some of the overhanging branches were trimmed off, and every portion of the walls examined.

"What do you think made this? Was it washed out?"

"Some one dug this hole," was the Professor's response.

"What makes you think it was dug out?"

"There is plenty of evidence to show that. Look at the marks of tools on the walls all about you."

"Do you suppose it was made to get oil?"

"No; but to get metals."

"What kinds, do you think?"

"Gold or silver; most likely silver."

"Do you think we have silver here?"

"Unquestionably; we have some samples of it at the Cataract now."

"When did you get it?"

"At the time we found the lead ore. Silver is usually a partner of lead, and from my examination of the samples we have it is rich in silver. It is likely that the indications of lead and silver all along this ridge attracted the attention of a mining engineer, and this was a test hole in prospecting for the ore."

"But if this hole was dug out, as you say, where did they put the dirt and rock which came out of it?"

"Examine below and you will see."

Below the hole the side was rather steep, but when the surface of the hill was examined there was no longer any doubt of the human agency which made it.

It was with a certain sense of joy that the boys heard this news. The island had been explored by white people; it might again be visited by some wanderers on the sea. This was a comforting assurance. It had the effect of giving new courage, as no other event had, since they reached the rocky shore during that tempestuous night, nearly eight months before.

"Don't you think we can get kerosene here?" was George's inquiry.

"I do not think it is likely. What we see here is a mere trace of surface oozing, found in many places, and it generally indicates petroleum at some depth, but whether in sufficient quantities to pay cannot be determined without boring."

George's hope of a better light faded.

Under the direction of the Professor the balance of the day was spent in gathering samples of minerals, and George, in one of his searches, brought a sample of very peculiar greenish ore, interlaid with patches of brown substance. The Professor was much delighted with this.

"You have found a fine sample of zinc, and if you direct us to the place we must take a quantity of it. I have been specially looking out for samples of this."

The ore was readily found, and a sufficient amount uncovered to complete their load, and late that evening they reached home very tired, but happy.

"Let us do some preliminary work with the furnaces to-day," was the Professor's first observation. "The ore we found yesterday is too good a thing to lie idle. You will remember I told you some time ago that we want some of these metals to be working for us?"

"Just like the germs do?"

"Not just in that way, but nevertheless they must serve us."

"If people get to know so much and have the different things do all the work there will not be much left for us to do?"

"Do you think so?"

"If one thing after the other is discovered, and it is found that one or two elements can be made to do our work, the time may come when everybody will know so much that man will do nothing but——"

"But direct?"

"Yes."

"Isn't that something? Working with the hands or thinking are not the only things which man can do, in order to go forward and to advance."

"What I mean is this: We are told that idleness is wrong, and that people are happier when they are busy at some useful occupation."

"If that is a good definition of happiness, then we should make everything we use as crude and primitive as the people used to make them a thousand years ago. There would be no object in learning, because learning makes people discontented."

"I heard a story once about some wise man who offered his fortune to the man who could prove he was contented. The first applicant wanted the fortune, because he said he was contented. The wise man answered by saying, that if he was contented he would not want the fortune."

"Quite true; the contented man does not exist, because it is not human nature to be so. That is one of the qualities which distinguishes man from the rest of the animal creation."

"But is it true that the invention of labor-saving tools has caused a lot of misery to working people?"

"Do you know of any tools that are not labor-saving? The mason's trowel is a labor-saving tool, invented to prevent him from using his hands to put on the mortar; the bolo or the knife is just as much a labor-saving tool as the planing machine; the sickle saves labor and so does the reaper. The difficulty is that some people do not stop to think that the saving of labor applies just as forcibly to a simple tool as to a complicated one."

"What shall we try in our furnace to start with?"

"The ore you found yesterday. The first thing to do is to crush it up as fine as possible. When that is done we can put it in the round furnace."

"You mean in the firebrick furnace?"

"Yes; although we do not need such a high heat. Almost any furnace would do, as the roasting of the ore does not require a high heat."

"What is the best way to roast it?"

"It will be necessary to put it on one of the iron plates, and great care must be taken to keep it a uniform heat, but not too intense."

The process of roasting is a very particular one and requires quite a time to get the best results. When this was done the next step was to take the roasted ore, and mix it with half its weight of powdered coke. They had a good quantity of the coke on hand, which was also crushed.

"You remember, George, we had a crucible made with a hole at the bottom. Get that and also some fire clay dust, and moisten the dust so we can make a stiff mortar from it. We must make a tubular connection with the hole in the bottom of the crucible."

When this was done the crucible was put into the furnace, after it had been charged with the coke dust and crushed zinc ore.

"Why is it necessary first to crush the ore and roast it, and then afterwards put it in the crucible with the crushed coke?"

"Zinc is not found in a native state. This ore is in the form of an oxide, as it is called. In roasting, certain of the impurities are driven off in gases, and mixing it with charcoal or coke and then applying heat to the confined mass, causes the zinc to melt and finally go off into a gas, as we shall presently see."

After the heat had been applied for some time a white smoke began to appear at the mouth of the clay tube, and a little later a blue vapor appeared.

"Now bring that pan here, so we can catch it."

Soon the dripping commenced, and as it ran out and came into contact with the air, it turned into a solid, greyish color.

"This is what is called spelter, or the pig of zinc, and this is what is sold to refiners, who take out all the dross or impurities so it can be rolled or used for galvanizing iron, or for other purposes."

"I do not see how we can use this metal, now that we have it."

"You said the other night that you wished we had a better light."

"That was the reason I was so anxious to see whether we couldn't get some kerosene at the 'hole.'"

"As we didn't succeed in finding petroleum we shall have to depend on our zinc, I suppose."

"What, light out of zinc?"

"No; but by the zinc route."

That was another new development to the boys.

"Harry made a sage remark some months ago. It was to the effect that in order to start to make anything we had to make something that made something to make something with. In order to make electricity by means of a battery, we had to go through all this process of turning out the zinc, which we have just completed; then, if you have not forgotten it, we had quite a time in converting our copper ore into a copper which we could use. We were compelled to make charcoal, and then coke, with the aid of the charcoal; and now that we have coke, we must again grind it up and make a mortar, so we can form it into little plates or slabs. From the copper we got a liquid, which I asked you to save, and that is vitriol, or sulphate of copper. You see, all these things are necessary before we could possibly attempt to set up a primary battery, and start the first lighting plant."

Not an hour was lost at the Cataract home and factory. All took the keenest delight in forwarding any new enterprise and in looking out for new things to do which would contribute to their pleasure and comfort. The boys now learned what they had never dreamed of before; that life is a most complex problem; that to secure pleasures toil is necessary, and that the greatest happiness comes from knowing you have succeeded. Pursuit, not possession, is man's greatest joy. To the brute the reverse is true.

"Where is the Professor? I have been bitten by a cat."

"A cat, Harry? Where did you find the cat?"

"Across the river, where I was cutting the oak log."

The Professor was soon at hand. "What is this? A cat, you say?"

"It looked just like a big cat, about two feet long?"

"Did it have a pointed nose?"

"Then it must have been a Zibet, a specie not unlike the American civet. It is a cat, but not what is known as the 'wildcat,' and can be tamed."

"Do you think there is any danger from the bite?"

"Some animals have a species of rabies, like those possessed by mad dogs, and cats have been known to be infected. I do not think we need to have any fear from that source. The wound should, however, be cleansed."



CHAPTER VIII

THE BULL FIGHT

As the boys grew more and more familiar with the island the greater was its store of abundance shown to them. Each journey to the interior brought some surprise in the way of fruit, flower or vegetable. Some were of species well known to them; others unknown, and most of such came to them under names of chemicals only.

"There is one plant, at any rate," said Harry, "that makes this seem like home, and that is the thistle."

"Yes, and it is the one common enemy of man in every part of the world. It is the most successful business plant, in this particular, that it is equipped to resist attacks from other plants and from animals as well."

"But donkeys and some cattle will eat them."

"For the reason that nature has given such animals the proper coating and linings of mouth and stomach that the thorns do not affect them. There is hardly a plant which is as nutritious as the thistle. In England, the thistle leaves, in early days, were used as salads."

Harry was an ardent admirer of flowers, and was constantly bringing in some specimen for examination. "Here is a very pretty flower which is differently colored from any that I have seen before. It looks like the wood sorrel."

"It is the sorrel, but if you should be in Ireland, the people there would call it the shamrock. St. Patrick taught the people that it typifies the trinity with its three leaves. The plant has some very peculiar qualities. It actually goes to sleep at night. It folds up its leaves. It is so sensitive to light that it has at least four different methods by which it can adjust itself with the greatest nicety to the amount of light which it receives."



"I think I have found vanilla; or it is something that smells like it, but I did not know that the vanilla was a climber."

"You have found the wild vanilla, the flowers of which have, as you see, disappeared and the bean is the product."

"I have often wondered why it is that we are able to smell or to recognize different odors."

"Smell, like everything else in nature, is produced by vibrations. So is sound, and light, and taste. Each odor has its particular rate of vibration. They resemble very much the notes of a musical instrument, and, as in music, odors can be harmonized, or they may be so mixed together as to produce discord. Some perfumes, when used on the handkerchief, and are about to fade away, have a sickly and disagreeable odor. This is due to the admixture of the wrong or discordant tones. Thus, heliotrope, vanilla, orange blossom and almond blend together; citron, lemon, vervain and orange peel belong together, but they produce a stronger impression on the sense of smell, and are of a higher octave; and so with a still higher class, as patchouly, sandal-wood and vitavert."

"But what is it in the flowers or essences which make them smell as they do?"

"Carbon, hydrogen and oxygen. It is one of the most remarkable things in nature that many of the odors in plants are formed by the combination of only carbon and hydrogen, and the wonderful thing about it is, that while turpentine is composed of 88 parts of carbon and 12 parts of hydrogen, the odors of oils of lemon, orange and juniper and rosemary have the exact proportions of those elements."

It was one of the duties of the colony to preserve the seeds of different vegetables and grain, because the Professor intended to put out for their use, as soon as spring came, a garden, which would avoid the necessity of constantly putting them on the alert to hunt the different foods. Sometimes it was necessary to go considerable distances to get the various foods. As long as they were on the island it was the part of prudence to act like sensible business men, and prepare for the future.

"We haven't a very big variety of vegetables, and I wish we could find some real good sweet potatoes and peas; and tomatoes would come in handy."

"Of course, variety, or the wish for different kinds, is largely a matter of desire. It is not a necessity."

"But does not the desire for different kinds grow out of the need of man to get the different substances which vegetables have?"

"To a certain extent, yes; but it is a singular thing that the world over there seems to be a natural instinct to combine two or three vegetables, and those vegetables, although they may be different in different countries, make chemical combinations, when eaten, which are almost identically similar. Thus, the Irishman mixes cabbages with his potatoes; the Englishman bacon with his beans, and the Italian rich cheese with macaroni."

One morning the boys were surprised to find a startling increase in their herd of yaks. When the Professor arose and went out for his regular morning stroll he noticed the unusual number, and was not slow in informing the boys.

"I suppose," said the Professor, "that they are coming to board with us for the season."

"Well, I am going to inform them, in a not very polite way, that we don't need company."

He was off with a club, Harry following.

"Look at that immense fellow. Wouldn't he make good sole leather? What is that on his side; that funny patch?"

Harry called to the Professor. "Did you see the peculiar mark on the side of the big bull?"

The Professor was on hand at once. "That is certainly a mark of some kind. See if you can get near enough to ascertain just what it is."

George, who had been so anxious to get rid of them, was now just as eager to hold them. The bull was a magnificent specimen. Like all this species he was a dark red, and had immense horns. All yaks, male and female, have horns, and the Texas steer has no horns to compare with the yaks in size and gracefulness of curve.

As George advanced there was no action on the part of the herd to scatter. Their own stock took no notice as he walked among them, and this, in all probability, gave the wild herd confidence. The bull paid no attention, until George was within twenty-five feet, when, with a deep-voiced roar and an ominous lowering and shaking of his shaggy head, made a beeline for him. The Professor called out, and he and Harry both sprang forward to aid him, but the bull's rush was a fierce one, and as we have previously stated, they are very active creatures. George saw his peril, and now realized that he could not possibly reach a place of safety, so he sprang behind one of the cows, and from that point sought to find a way through the herd. The warning voice of the bull, and his mad rush, excited the entire herd, which started a stampede.



In the meantime they had not noticed the presence of their own bull, which was a fine animal, and was now thoroughly domesticated. The Professor was the first to notice the appearance of their bull, who, it seems, had been relegated to the background when their neighbors came to town for their holiday.

Apollo was Harry's name for the bull, and when George got mixed up in the herd, the strange bull made his charge and emitted the challenging bellow, the scene was a truly terrific one. George was carried along with the rush, and his only danger now was to escape being trampled under foot.

Harry stopped suddenly: "Look at Apollo!" He was making a charge down into the herd, and headed straight for the big bull.

"I thought it strange that we didn't hear our herd give them a welcome during the night."

"Welcome! what do you mean?"

"It is singular that Apollo didn't dispute the governorship of the herd when the new arrivals came, as that is one of the customs. One of them must be master."

"Just look at him! Good old Apollo!"

At that moment Apollo was within ten feet of the wild bull. He did not cease his onslaught. The wild animal saw his enemy attacking him from the right quarter, but his rush had been so impetuous that when Apollo struck him he rolled over, one of his large horns striking the earth and serving as a fulcrumed lever to turn him around in his path. He was up in an instant, and now began the battle for mastery.

"Get the guns, Harry; get the guns," and this was a sufficient reminder that neither of them had a weapon.

Harry bounded over to the house, and within a minute was back with them. In the meantime, where was George? He did not need to be told that he must run for his life, and was wise enough to seek the security among the cows, but he could not foresee a stampede. It was fortunate that the big bull was behind the herd when the stampede began, and it was lucky that there was plenty of room for the animals, or he surely would have been trampled to death. Naturally, the noise of the rushing animals drowned the roar of the fighting bulls, but the stampeded yaks gradually checked themselves, and George was the most surprised individual imaginable when he found the bull was not behind them.

And now another curious thing happened. They had run fully a quarter of a mile, and when the running stopped, the yaks leisurely turned around and slowly walked back. The movement seemed to be a concerted one. George accompanied them. He didn't know what else to do.

When Apollo and the bull locked horns, after the latter had again gained his feet, his tremendous bulk pushed Apollo back, at the first onset; but they noticed a peculiar tactic on the part of Apollo. The latter at each forward plunge twisted his head, first to the right, and then to the left, as though he was boring his way in. This was an astonishing thing to the stranger. This was done by Apollo over and over again, and now, every time they met, and the twisting motion was repeated, his enemy would be thrown back on his haunches.

For a period of twenty minutes the combat continued. Back and forth they ranged. Harry, although intensely excited, wanted to give the bull a shot, but the Professor restrained him. He felt that the youth of Apollo was enough to overbalance the strength of his enemy.

"No, Harry, when they get through with this battle the big fellow will not cause us any more trouble, and we need him."

The herd of cows came up and remained standing at a respectable distance. They seemed instinctively to know that the question of kingship was being decided. It was entirely immaterial to them who won. George did not wait with the herd. He saw the combat, and beyond the Professor and Harry.

"Well, you did kick up a fuss, didn't you?" said Harry.

"Apollo's got him; he'll lick him sure. See that lunge? My, what a shaking he gave him that time!" George was a dancing Dervish by this time. Then noticing the guns for the first time, seized one of them. "I'll finish him."

"No, no, George," was Harry's reply, as he grasped the gun. "The Professor is right; Apollo will finish him."

There was now no question of the fighting ability of Apollo, and of his youth and vigor, and he knew it. His antagonist did not rush any more. Apollo did that; the bull's main business now was to keep out of Apollo's way.

He had been whipped, and he knew it. He turned and fled. Did he go toward the cows? Not at all; but in the opposite direction. Instinct told him that if he had gone toward the cows it would have meant another fight. To leave them was the bovine manner of saying, "Well, then, take them."

The big bull did not go far. His head hung low, and the heaving flanks showed he was tired. But Apollo's head was high in the air. Dejection on one side and absolute mastery on the other were as plainly exhibited in the manners of the animals as though it had been written out and proclaimed.

"What will he do if I go up to him now?"

"The fight is all out of him."

This was true. He exhibited no alarm when they approached, and when they walked around to get a view of his other side, the mark plainly showed the following brand: "M—V."

"That is undoubtedly the brand of some person who captured the animal when young."

"How old do you suppose he is?"

"It is difficult to fix his age with any certainty, but I do not think he is over ten."

"What do you suppose the brand means!"

"It is some arbitrary term, the initials of a person, or it may be intended to designate something. Branding is a very common way of marking cattle, so as to indicate ownership; nearly all savage tribes have a habit of branding, or tattooing; and sailors also. Various civilized countries in the past have branded criminals as a means of identifying them."



They now had an opportunity of taking an inventory of their stock. The original herd comprised Apollo, six cows and four calves, or half-grown cattle. The new acquisition brought the count up to twenty-six cows and twenty young animals. The vanquished bull was very meek from that time forward, and the surprising thing was that Apollo was thereafter the same quiet, unobtrusive animal he had been before.

But there was work to do in the factory. Harry was now engaged in building an iron lathe for their further work. A drilling machine was his next tool, and as the weeks passed the boys devoted much of their time to making such articles of machinery as could be used advantageously to turn out the simple products which future needs might demand.

The leather vats were examined and the skins found in excellent condition. These were then taken out, and grease and oil worked into them until they were pliable. The thick parts of the hides had been previously cut out, so that they could be used for the soles of contemplated boots and shoes, which they soon hoped to turn out.

Every morning the yaks would leave the enclosure and start out on trips to the feeding grounds, and sometimes Harry or George would follow them and hunt for game. On one occasion, while Harry was on the opposite hill, George saw the flash of Harry's gun, and almost immediately thereafter heard the report. This was the first time the difference between the flash and the noise attracted his attention.

"Will you tell me why I saw Harry's fire before the sound reached me?"

"Did you say 'sound' or 'noise'?"

George looked at the Professor quizzically. "Is there any difference between sound and noise?"

"Technically, there is a difference, although in common practice one word is used for the other without discriminating. Sound means a succession of vibrations produced in their regular order, like music, whereas noise is a disorganized vibration. For instance, falling water, like our cataract here, is sound, but the report of George's gun was a noise."

"I can see the difference. Would a wagon going rapidly over a pavement be a noise or a sound?"

"It would be a noise if the pavement should be irregular, but if the pavement is regular and the vibrations or beats are uniform, it is then called a sound. But you wanted to know why you saw the shot before you heard it. Simply because sound does not travel as fast as light. Sound moves 1,040 feet in a second, and light over 186,000 miles a second, which is about 850,000 times faster than sound."

"Do soft and light sounds travel at the same speed?"

"Theoretically, yes; but numerous experiments have been made, and many of them go to show that a loud noise really travels faster than a soft noise."



"What is the cause of that?"

"It is attributed to the belief that a loud noise causes greater wave motions, although the sound waves may be the same lengths in both cases. Or, it might be said that loud noises have greater strength."

"When we were going to New York in the cars, a train was coming toward us, and the engineer on that train blew his whistle when he was off quite a distance, and kept it up until long after he had passed us. I noticed that when the whistle started the sound had a very low pitch, which kept increasing to a higher and higher pitch until the train passed; what was the cause of that?"

"As the sound waves are uniform movements, and are at regular intervals, the vibratory action of the whistle, in case the trains were at rest, would all be the same distance apart; but as the two trains were coming together two things happened. At each moment your ear came nearer the whistle, and the distance through which the sound had to travel decreased. This made increasingly shorter waves, and not long, regular waves, as when at rest. Short waves make a high pitch, and long waves low pitch. After you passed the train the waves began to get longer, but they increased in length more rapidly than when you were approaching each other, so that if the whistle kept on blowing the waves would finally get to be so long and so far below their original pitch that the sound would cease.

"A little sketch will show this. (Figure 23.) The line A is the pitch of the whistle; B its pitch when you first heard it; C shows the point where you passed the whistle, and D shows how low the pitch was when it died away."



CHAPTER IX

EXCITING EXPERIENCES WITH THE BOATS

During the nine months' life on the island all had the best of health. The Professor grew strong, and he declared that his constitution was more robust than it had been for years. They lived in the open much of the time; their fare was plain and mostly devoid of sweets; the store of honey which had been several times replenished, was the stock article in the absence of sugar.

It was, therefore, a matter of surprise that Harry should complain of having a tired and uncomfortable feeling, and would frequently lie down during the day while in the workshop. The Professor was always at his side during these periods, and while he had no instruments to enable him to determine whether there was a high fever present, the flushed face of his patient showed unmistakable symptoms.

"Do you think he has a very severe fever?" was George's inquiry, as the Professor left Harry.

"It seems so, and in order to determine whether there is any change we must at once set to work making a thermometer."

"We have neither mercury nor glass, and even if we had, how can we make a tube for it?"

"That being the case, we must make a substitute for both."

"But we must have something which will expand."

"We can use iron for that. Get a piece of small steel bar, say two inches long, and bend it in the form of a C. In the meantime I will make a base to hold the thermometer."

"For your guidance I make a drawing (Figure 24), in which A is the base, about five inches long, three inches at its widest end, and an inch wide at the narrow end. This should be made of a thin piece of hard wood. Bore a small hole in each end of the C-shaped piece. The next thing is to make a pointer (B) nearly as long as the base, pointed at one end, and provided with two holes at the other. The pointer is attached to the base by a pin (D). One end of the C-shaped piece of metal is then hinged to the other hole (E), and the other end of the C-shaped piece is hinged, as at F, to the base. You will now see that if the ends of the C-shaped piece spread apart the least bit the long end of the pointer will swing over to the other side of the base."



"Do you intend to make the thermometer show the exact degrees of heat we really have?"

"Yes; as nearly as possible."

"Why can't we make it exact!"

"For the reason that to make what is called the Fahrenheit scale we should have freezing weather. The scale adopted by Fahrenheit was an arbitrary one. He determined it in this way: The temperature of his body was taken as one point in the scale. For zero he took the lowest temperature observed by him in the year 1709. As the temperature of his body was 86 he made a scale with 86 degrees on it, and then when he observed ice melting in water he put his thermometer in and found it registered at 32 degrees. It was not a very scientific way of doing it, but it answered the purpose, as, of course, temperature is merely a relative thing."

"But isn't there another scale to measure heat by?"

"The Centigrade method is on a more scientific basis. It is determined by taking the freezing and the boiling points of water, and dividing the scale into 100 degrees between those points."

It required the work of several hours to make the device as here shown, so that the tension of the C-shaped piece would hold the point to one side. The temperature of the atmosphere was about 65, as nearly as the Professor could judge, but when the C-shaped piece was held in the palm of the hand, the pointer moved to the lower edge of the base piece, and a mark of 80 was put there as the starting point. As they had no immediate use for a scale beyond 110 degrees, the end of the base was marked off, as you see in regular divisions.

The C-shaped piece was put under the tongue or in the armpit, so that the temperature of Harry could be determined, and it registered 102 degrees. It might be that Harry's temperature was really much higher, as the thermometer, for the reasons stated, was not accurate.

"I wish you would test the thermometer, George, so we can pretty well determine, within a range of two or three degrees, how nearly right we are."

George's temperature was found to register 98, whereas the Professor's was only 90. He explained that the temperature of youth is normally greater than old age, but it was remarkably close to the average normal temperature of two healthy persons.

"The advantage of the instrument now is to enable us to ascertain whether Harry's temperature will increase or decrease."

"Is there no other way in which we can find out about a fever?"

"When the fever comes on the pulse is usually quickened, as well as the breathing; the bowels are apt to be constipated; and thirst, loss of appetite, headache, and vague pains are felt. When the temperature goes beyond 105 it is very dangerous, and it is for this reason that physicians want to know the temperature."

"I am anxious to know why that C-shaped piece should try to straighten itself out when heat is applied to it?"

"When you bent the metal piece of which it is made you crowded the metal on the inside of the piece together, and also stretched the metal on the outside of the bend. As the application of heat expands the metal, the contracted particles of the metal on the inside of the piece pushed against each other with greater force than those on the outside, and the bar tried to straighten itself out again."

"I have noticed that if a hose is coiled up and water is forced through under pressure it will straighten out the hose. Is that also the case with the hose?"

"To a certain extent only. Another principle comes into play in that case. Water under pressure acts as a solid, and has a tendency to move along the shortest route or in the most direct way. If, therefore, there is a crook in the pipe the water tries to straighten it out. Steam gauges are made of flattened spirally coiled tubes. One end of the tube is open and the other has an inlet for the steam. The dial finger has a connection with the moving end, and by that means pressure is indicated."

The next morning Harry's temperature was fully one degree higher than the previous day, and the Professor advised that it would be necessary to administer some fever medicine.

"Last week you found several samples of the gentian flower. It is a first-class fever medicine and tonic. Do you think you could distinguish it by its large blue-colored, fringed flowers?"

"I know what you mean; it has one central stalk, with big leaves at the bottom which gradually grow smaller, and in which the stem seems to go up through the flowers."

"That describes it exactly. Get some of the roots, and peel them, then scrape a quantity, so we can give some to Harry."

This is a simple remedy, in the absence of regular fever medicines which were not available to them.

To their great relief the fever abated before morning, and by persistently taking the gentian tonic Harry was soon well again.

This little experience was sufficient notice that in health at least some preparation should be made for illness, which is sure to come to all at most unexpected times. It had also a stimulating effect in more pointedly directing the attention of the boys to the wonders of the vegetable world.

It was now the latter part of June, and the weather was not at all cold. Plenty of rain had fallen, and the Cataract stream had risen so high that their water wheel had been out of commission for several weeks, and Harry's illness or indisposition had somewhat retarded the work in the factory.

"Wouldn't it be a good idea to look up that animal over in the cave?" was George's first suggestion, one morning, shortly after Harry's recovery. "We might put in a little time there, and then go down around the bay on a little tour."

This was agreeable to all, and then George remembered the want of the candles. Zinc had been turned out, as previously told, but no steps had been taken toward making a battery which would be the starting point for an electric lighting system, as Harry and George both hoped for.

"It seems to me," said Harry, "that we ought to explore the coast line to the southeast of us, as we have never been in that direction, and then work our way around to the cliff cave."

Without further words the yaks were yoked up, and taking a hearty luncheon they were off for the east coast, where the bay indented the land. The coast was reached within two hours, a great deal of the time en route being spent in gathering samples of plants, flowers, and fruit, of which some species of trees were filled.

To the right of the place where they struck the sea was a cape which ran out into the sea for fully a quarter of a mile, and to the south of this was the mouth of the South River. As they had definitely planned to go north along the coast line to the cliff rocks, the explorations to the south must be reserved for some future day.

The sea front showed delightful stretches of beach, but at intervals small trees and bushes grew close to the ocean on the elevated spurs which broke up the otherwise smooth beach line.

The clam, as a source of food supply, had practically been neglected, because it was quite a distance from the Cataract home to the beach, and principally for the reason that other foods were so plentiful. Harry wanted some clams, and with one of their bags the beach was scoured for fully a mile, until he gathered a staggering load.

As he reached one of the little knolls which broke off abruptly close to the sea, Harry dropped the bag and ran to the brush. The Professor looked on in wonder. When Harry disappeared in the bush George and the Professor both hurried forward. Harry reappeared in an instant.

"What do you think I have found?"

"Another cave?" queried George, without stopping.

"No; our boat."

There, perched less than five feet above the level of the ocean, was the boat which they had left at the foot of the falls in the South River, fully three months before. One of the puzzling mysteries was solved.

It was some labor to dislodge the boat from its position between the cleft branches of shrubbery which also held other debris, and furthermore the boat was full of all sorts of rubbish. This was laboriously removed.

"You will remember I stated at the time of the disappearance the most likely explanation would be that high water coming on suddenly would wrench the boat from its fastenings, and——"

The Professor got no further; he suddenly stopped and glanced to the forward end of the boat. "Who tied on that rope? It really does look as though some one has used the boat. That is not one of the oars we made."

"But where are the lockers we had on the boat, in which we put our provisions?"

"They have been removed by some one. This is a rope entirely unlike any we have had, and it is a native, or rather, hand-made article."

"Well, we have struck a greater mystery now than when we lost the boat."

This discovery brought up several other questions which, as it now appeared, might be linked together. The removal of the flag and flagstaff; the "hole" in the hill; the fire in the forest; the branded bull, all indicated that people had, at various times, visited the island. But the finding of their boat, with the positive evidence furnished by the oar and the rope, was conclusive, and what made it the more interesting was the fact that the island must have had such a visit within two, or at the most, not over three months ago.

Each was too busy to give much time for discussing the probabilities. They had entirely forgotten the cave. It was, by common consent, agreed that the boat must be taken home, and it was finally decided that the boys should pilot it around the point, past the cliffs, and in that way reach the mouth of the Cataract River, where it would always be convenient for cruising purposes.

It was fortunate that the sea was calm when the boys pushed the boat from the shore. It showed signs of leaking here and there, but the Professor assured them that the water would close up the joints before long. The Professor, himself, drove the team to the Cataract, and after unyoking them, followed the course of the river down to its mouth, to await the coming of the boys. He waited there until sundown, but the boys did not appear.

Let us now follow the boys. Lashed in the boat were two oars, as carefully secured as though tied only the day before. At the bow was the rope which the Professor discovered, after he had noticed the one tied around the oars. It will be remembered that the boat had been fitted with a mast and a sail. Those had been removed, as well as the crosspiece and the brace which held them in place. It was, therefore, necessary to row the boat around the point. The distance, as calculated by the Professor, was two miles or more to the cliffs, and fully a mile from the extreme point of the cliff to the mouth of the river.

Shortly after they started on the journey a light wind sprang up, which, however, did not seriously interfere with their progress, but it was sufficient to induce them to take a course outside of the point, instead of attempting to thread their way inshore between the rocks.

When abreast of the extreme point George's attention was directed toward an object on the cliff.

"What is that up on the rocks?"

Harry stopped rowing, and looked in the direction of George's extended arm. "It looks like a boat. Let us go in."

The boat was pointed to the shore, and drawn up, and in their eagerness, each tried to gain the elevation first. A miscalculation was made, in the attempt to reach the object, which was not visible from their location, and they were compelled to thread their way down again and go around the broken side of the cliff walls.

As they were about to ascend Harry called out: "Look at the boat, George! Run quick, it is adrift!" The wind had quickened, and they realized their carelessness in securing it at the landing place, and before George, who was lower down, could reach the water's edge, it was washed around the point of the rock, out of his reach.

Here was a dilemma. The boat lost, and no means to reach the mainland without swimming. The place where they landed was less than five hundred feet from the spot where they were cast ashore months before. Innumerable large rocks, detached from each other, formed the immense tier of sentinels for this part of the coast, and Harry's trip across, when he had the benefit of the life-preserver, was an entirely different thing from their present condition.

To add to the perplexity of the situation, George was not a good swimmer, and he doubted his ability to make the trip across the channels between the rocks which separated them from the mainland.

"Why not try to find the object we saw while we were out at sea?"

"Good idea. But I would like to know how we are going to get up?"

"Wasn't that a silly trick, to be so careless about our boat. What will the Professor say?"

At last, after repeated trials, they found a way which led them up the craggy sides, to the object they had seen.

"It is our life-boat," was Harry's excited cry. "That is, what is left of it."

We have previously detailed how, when they struck the rock, on that eventful day, months before, the boat had apparently been broken in two, and they saw only the stern of the boat held within a saddle of the rock; and how, at the next great wave, even that portion had disappeared. Here was the battered and broken-up part that remained.

"Do you think this part would float?"

"I suppose it would, but how can we get it down?"

They sat down, not discouraged, but annoyed at their own stupidity and carelessness. Night was approaching, and sitting down would not remedy matters. It was low tide, and the waters had receded, so that the wrecked boat was now fully twenty-five feet from the water. It was held within a wedge in the rocks, tilted up, and it was too heavy for them to lift. If they could possibly dislodge it, so as to push it over the edge, it would probably be crushed to pieces in tumbling down.

Even such a calamity would be better than remaining there, and it was decided to be the only course now available. Every vestige of the locker, or seats, or other appendages of the boat were swept away. The bare shell of the stern portion remained.

It was now growing dark, and when the wreck was finally dislodged and fell down with a crash the boys made their way down the sides very cautiously. It was now but the work of moments to get afloat. The boat originally had water-tight compartments, but these were now utterly useless as a means of sustaining the vessel; nevertheless, it was a means by which they might reach land, as they felt sure it would not sink. Here was another difficulty. They had neither oar nor other means of propelling it to shore. After considerable effort a portion of the side of the boat was broken off, and tired and worn with the effort and excitement they steered the craft shoreward. To do so was not an easy task, as the wind had increased, and the waves beat stronger, but this had no terror for them after all their previous experiences.

When the shore was reached Harry had one positive observation to make: "I am going to see that this boat is so fixed that it won't get away."

George looked around, and in spite of their trials, could not help laughing at Harry. "I should like to know how you are going to do it. I don't see any ropes around here, and trying to pull it up this steep beach wall will not be an easy job."

"Then we have got to take it where we can pull it up. I am tired of losing things in this way. We'll have a nice story to tell the Professor."

The Professor was by this time thoroughly alarmed, as well he might be, for it was past eight o'clock that evening when, going down from Observation Hill, he heard voices in the distance, and recognized the boys. He called to them, and you may be sure that their answering voices were joyful sounds.

When the boys appeared both began excitedly to detail their experiences, getting details of the story involved without any sequence just as we might expect an exciting, mixed-up recital of this kind to be under the circumstances.

"You lost your boat and found the other one. You are having enough experiences to fill a book."



CHAPTER X

THE BIRTHDAY PARTY; AND THE SURPRISE

You may be sure that the interesting topic of conversation that night had relation to the events of the day. All previous experiences were insignificant now in comparison. Every phase of the question was discussed, and a solution sought.

The Professor did not attempt to conceal his doubts. "I have a theory that we are or may be near some other island, possibly inhabited by white or civilized people. It is likely that people from those islands may visit this place at intervals, and that the boat which we left at the falls was really washed down to the sea and found by some of them."

"If that is the case, why should it be washed up on shore, as it was? They, no doubt, used the boat, as the oars and rope showed. But I can't possibly make out the meaning of its being in the driftwood."

"That boat we made is a hoodoo," was Harry's conclusion. "Twice lost is enough for me."

"Well, I would take a sail in it the next day if we could only find it."

"I am interested in it," observed the Professor, "not so much for the purposes of its use, as to enable us to find out something more about it, and how it came to be there. If it had occurred to me that we should lose it so soon you may be sure I should have made a more careful examination of it when we had it. But it is too late now."

Harry's solution was the one most acceptable. "Let us make another boat, and with that we can carry on our investigations more satisfactorily."

"Harry is right. A good vessel will be a measure of safety, in the event we should be attacked by savages, and it will at least enable us to visit the shore line of our continent."

The sanitary arrangements of their kitchen had been for some time very unsatisfactory, and somewhat cramped, and the Professor thought it would be wise, for their comfort and health, to cleanse it thoroughly.

"I am inclined to think that Harry's sickness was caused by the condition of the kitchen. We are apt to overlook these things in the multiplicity of our work."

"What is the best way to clean it, by washing?"

"That is necessary, of course, but it is impossible, even by a liberal use of hot water and soap, to remove many of the poisonous germs. Some good disinfectant should be used."

"Have we anything which could be used for the purpose?"

"There is nothing better than charcoal. Common wood charcoal has the capacity of purifying and rendering odorless almost all impurities."

"In what way does charcoal do this?"

"When charcoal is crushed up finely its remarkable porosity enables it to absorb an enormous quantity of gases, and when so absorbed it condenses them, in which condition they are harmless, or they are retained in the charcoal."

"But how about the impure liquids?"

"Its affinity for sour and stinking liquids is so great that two tablespoonfuls of charcoal will purify a pint of the foulest sewage; it will also, in that quantity, absorb 100 cubic inches of gaseous ammonia."

"Have we anything else that can be used?"

"The sulphur that is in the samples of copper ore, if burned, will make a sulphurous acid gas, and while it must be carefully used, on account of its noxious and offensive odor, is a most powerful germicide. Or if we take some of the green acid of the copper, and make a liquid of it, and then pour this over common salt we are making what is known as muriatic acid. The vapor of this acid will destroy all germs. The objection to this, however, is, that it has an odor which is worse than the impure or unhealthful gases. In the last samples of ore we brought home, you may have noticed a very black lot of stuff. That was manganese. If we take the muriatic acid, which I have just referred to, and pour it over the manganese, we can make the most powerful agent of all, namely, chlorine."

"Chlorine is used for bleaching, isn't it?"

"That is its great use in the arts; but as a purifier it has no equal. It will decompose every gaseous compound and evil-smelling gas which escapes from decayed animal or vegetable matter."

Harry did not let the Professor forget the matter of the primary electric battery which he had been making preparations for, and after they had gone over the sanitary features of their kitchen, he was anxious to make a start. George was equally insistent, because the question of a better light was ever uppermost in his mind.

"Then here goes for the primary battery. We haven't any glass, nor have we found any rubber lying around, so we can make cells out of them, so what shall we use?" was the Professor's first inquiry.

"Why not use some of these iron pots we made?"

"I am afraid iron would not last very long, with sulphuric acid in them. We should use some non-conductor of electricity."

"What do you mean by non-conductor?"

"That quality in a material which will not allow electricity to pass."

"Then why can't we use clay? Will that conduct electricity?"

"That is just the thing. Isn't it wonderful what a friend common clay has been to us since we have been on this island!"

"I think we ought to erect a monument to Monsieur Clay?"

"It would be a fitting thing to do, because at the end we are all bound to go back to him."

"I believe you said, Professor, that we should have to grind up the coke and then mix it up and make plates out of it?"

"Yes; we can use either carbon or copper for the negative plates."

"What are the other plates?"

"The positive. That is what I wanted the zinc for, which we made several weeks ago."

"Why should we have positive and negative plates in a battery?"

"Everything must have an opposite. If there is an up there must be a down; there would be no darkness without light; no heat without cold; no strength without weakness, and no joy without sorrow. Like all these things, the electric current flows from one to the other."

"But in electricity the current flows only one way, does it not?"

"In the primary battery that is the case; but when electricity is generated and sent over the wires, the natural current flows in both directions—that is, it goes in one direction as much as in the other."

"I do not understand what you mean by that."

"The current alternates. What is meant by that is this: For an instant the current flows from the positive to the negative, and the next instant it flows from the negative to the positive, and so on, making the alternate current."

"Then the primary battery we are going to make will be another kind of current?"

"We shall make what is called the direct current which goes in one direction only—that is, within the battery it moves from the positive plate, the zinc, to the copper plate, or negative, and outside of the battery it moves from the negative to the positive plate."

"Why does it do so?"

"In order that you may understand, I shall make a drawing so Harry will not have so much trouble in arranging the parts. So if you will examine the sketch (Figure 25), you will see that the clay cell, which we are to make, has in it the two electrodes, A and B. That is what they are called when they are spoken of together; but the positive one (A), the zinc, is called the anode, and the negative (B), or copper, is called the cathode. You should keep these terms in mind.



"The liquid in the cell, marked C, is used as the electrolyte, and for that we shall take some of the sulphate of copper which the copper ore furnishes. A good strong salt solution would also answer the purpose. The two electrodes are separated, and a wire connects the two outside of the cell. Now you will notice that within the cell the current flows, as shown by the dart E, from the positive to the negative plate, but outside of the battery the current flows through the wires F from the negative to the positive plate."

"I can understand it now. The current from the battery will always go from the negative to the positive pole."

"You are mistaken. I am glad you referred to that. It shows the importance of using correct terms. You must not confound the terms 'negative plate' with 'negative pole.' All currents leave the battery or dynamo from the negative plate, but that negative plate is called the positive pole of the dynamo."

"It seems to me that is a curious way to do it."

"Such is the case, however; but there is no real positive or negative in the alternating current, so that either side may be termed positive or negative."

Work on the battery continued for some days, as lack of fine tools made much of the work difficult, and in doing this work, as in everything else, a certain amount of preparation was necessary. They had no screws, and no facilities for making them, so a substitute had to be devised, but the difficult part now to encounter was the preparation of the wire.

"A battery is of no use unless we can have wire, and it will be a big job to beat out wire long enough for our purposes," Harry observed as the battery neared completion.

"Then we must draw some wire?"

"From what?"

"From the copper?"

"Is that better than iron?"

"Copper should be used for several reasons; first, because electricity travels through a copper wire more easily than through iron, and second, for the reason that copper is more ductile than iron, and can be drawn into a wire with greater facility."

"Doesn't electricity flow through different substances at the same rate of speed?"

"Yes; but it retards the amount or the force."

"You say, 'Amount' or 'Force.' I can understand that if applied to water, that there might be a large or small quantity of water, or a greater or less pressure, but I do not see how this applies to electricity."

"In measuring the pressure of water, calculation is made by taking the height of the water in the tank. For every 28 inches in height a column one inch square weighs one pound. This represents the force of the water when it issues from the orifice below. Now the orifice may be large or it may be small. The amount or quantity which flows out is dependent on the size of the opening. Electricity is measured in a somewhat similar manner. What is called 'Volts' is the same as the force in the tank—that is, voltage means the pressure. Amperage, on the other hand, refers to the amount of current which is passing, and a greater quantity will pass over a large wire just the same as a greater amount of water will flow through a large than a small pipe. Is this perfectly clear to you?"

"Yes; I understand the difference, now."

The drawing of wire is not a difficult task where facilities are at hand, but it must be remembered that all their tools were of the crudest kind. Harry had prepared a number of bars of copper, each having been beaten out to form pieces about ten inches long and a half inch thick. A steel plate about three-eighths of an inch thick, two inches wide, and six inches long, had a number of holes bored through it, the largest hole being a half inch in diameter, and gradually increasing in size, the smallest being about a sixteenth of an inch in diameter.



When all was ready Harry was instructed to hammer out one end, so it would go through the largest hole. The projecting end was then grasped by a pair of heavy pliers, and pulled through, so that the bar was formed the size and shape of the first hole, and of course the bar was lengthened. The end was then hammered out so that it would go through the next smaller hole, and the same process was repeated, and when the wire got larger they had a tool which pushed the wire in at the same time it was being pulled out at the other side.

It was laborious work, and a long time was consumed in fully drawing out each bar. In this way a quantity of serviceable wire was prepared.

"Why does this plate get so hot when we pull the wire through?"

"Why do you make a fire by rubbing together two substances?" replied the Professor.

"On account of the friction."

"For that same reason you are making the heat in drawing the copper through the die."

"But I notice that if I hammer a piece of cold iron it will get hot. There is not any rubbing motion there to make friction."

"Do you think not? You have by that means made the most intense friction. The iron is composed of tiny particles, called atoms, and molecules. When you strike a piece of iron you force these particles in among themselves, and the friction caused by this movement produces the heat."

"Is that true of all substances?"

"Yes."

"Well, if air is forced together will it heat in the same way?"

"Yes, and for the same reason. The tiny particles, of which air is composed, move among each other with such rapidity, under compression, that the heat their frictional contact develops is dependent on the pressure exerted."

"You used the terms 'atom' and 'molecules' a moment ago. What is the difference between them?"

"A molecule is always composed of two or more atoms. An atom is smaller than a molecule, for this reason. Furthermore, an atom comprises only one substance. A molecule has two or more substances in its make-up. For instance, water is composed of two parts of hydrogen and one part of oxygen. One molecule of water, therefore, has three atoms, two of the atoms being hydrogen, and one atom oxygen."

"Baby," the infant orang-outan, had now grown to be a pretty good-sized boy. He would sit at the table and gravely eat with a knife and fork, which he had learned to handle most intelligently. In the various trips which had been made from time to time, the Baby was kept at home, but on more than one occasion he would follow up the wagon, and would as often be welcomed when he did come.

Harry found a good use for him later on, and from that time forward Baby knew that a jaunt into the forest meant a trip for him as well. When it came to tree climbing Baby was in his glory. He would swing from branch to branch, and shake the nuts, and the amusing thing was to see him help gather and throw the nuts into the wagon, in the most business-like fashion. He was never known to laugh, but they had many occurrences which, no doubt, made him smile in his own way.

George was an adept cook. He was fond of making surprising delicacies, and boy-like, they were always the kind that had honey of some sort in their composition. Without any knowledge of cooking, but knowing, in a general way, that eggs and milk were the principal things used in puddings, it was not long before he was regarded as the chef. Baby was sure to be present whenever George occupied the kitchen. And help! Why certainly! He knew what flour meant, and particularly honey. The truth is, that he knew what that meant if George merely looked in the direction of the honey pot.

And talking about eggs! Harry found out about this accomplishment in Baby. In the tall grass beyond the barley fields were flocks of prairie chickens, and during one of the hunting expeditions he found several nests of eggs. They are just as much more delicious than the common egg as the prairie chicken is more delicate than the hen. Baby never thereafter forgot the eggs. Singularly, he never ate any of them. Apparently the orang does not crave them in his native state, but the little rascal had an eye to the good things, and when he saw the eggs go into the pudding and cake, there were no scruples on his part.

George had been planning a surprise for the Professor. In many devious ways he learned his age, and August was the month, so in concert with Harry, planned to treat the Professor with a birthday party, the first real attempt at jollification which had been proposed since they landed.

"I remember, he said he would be sixty-five years old on the tenth of August."

"But the trouble is, we don't know when we get to the 10th of the month."

"The chances are he doesn't know, either. But what difference does a day or two make, anyway?"

Among the delicacies which George had prepared were 65 little sweet cakes, because they couldn't put that many candles on the big cake, and the boys knew, from experience, that they would have to use candles, or something else to typify the age.

The "tenth of August" came, and the Professor, in all innocence, proposed a day for hunting. Both boys opposed this, to his surprise. The Professor did not press the matter. As usual, when at home, he was shut up in what they called the laboratory. Even though he should be present in the kitchen he would not be likely to take notice of any extra preparations.

In the meantime Harry had made a bell out of a flat sheet of steel. It was really a gong. When the noon hour arrived and the table had been set ready for the symbolic cake pyramid of little cakes, George ordered the gong to sound, and Harry made such a frightful din with the unexpected noise, that Baby was terribly frightened, and scampered to the loft, his usual place of retreat when reproved or unduly excited.

The Professor was out of the laboratory like a shot, and hurried over to the house. At the same time George returned. "Who has taken my cakes?" he cried. "There are less than a dozen left." Baby chattered in the loft. The Professor could not understand the commotion. All he knew was that Baby was swinging along the rafters and that George was flying around the kitchen hunting cakes.

"Hello, and what is all this? Expecting company?"

"Yes; this is a birthday party."



"That is a good idea. I suppose you have invited all your friends?"

"Yes; we have invited all we know; just one."

The Professor did not need to be told any more than this. His eyes filled with tears, the first real thing that the boys ever saw on his part that strongly affected them, and when the Professor, his heart so full that he could not speak, silently looked at them, they forgot the feast, and the cakes, and Baby. They thought of home and of what they were doing there, and whether the time would ever come when they might be rescued.

Brave Harry was the first to recover. Like a veteran he grasped the Professor by the hand, and wished him many a happy return of the day, and George, though not so demonstrative, joined Harry in this wish and prayer. Just then one of George's cakes fell at his feet. He picked it up and Harry glanced at the Baby. The mysterious disappearance had been solved.

No! Baby was not spanked. He came down without any coaxing, with several of the cookies in his hand, and gravely took his place at the table. What a very narrow margin there is between tears and laughter. They roared as though such a thing as tears were unknown.

When they recovered from their fits of laughter, and attempted to proceed with the feast in some semblance of order, a glance at Baby was sufficient to start them up anew. And here a surprising thing occurred. As before stated, he never had been known to laugh. But now Baby laughed, for the first time. And then the boys and the Professor knew that this was also the first time they had indulged in a hearty laugh.

"You may say what you please," said the Professor, "but laughter is infectious. How much farther a smile will go than a frown. And this reminds me of a very curious thing in nature. What are called perfumes have been known to carry through the air for ten miles. The odor from the balsam-yielding Humeriads has been perceived at a distance of four miles from the shores of South America; a species of Tetracera sends its perfume as far as that from Cuba, and the aroma of the Spice Islands is wafted many miles to sea. Now the singular thing is, that vile and injurious odors are not carried such distances."

"Why not?"

"For the reason that the oxygen of the air destroys the bad odors."

"I thought of this when we were laughing here so merrily a while ago. Laughter is like a perfume, it goes a long way and does not need a purifying agent; but the harsh and angry word is like the evil smelling substance, which needs to be purified."



CHAPTER XI

THE GRUESOME SKELETON

The merry party lingered long over the meal. Roast prairie chicken was the chief dish. The Professor had found lentils, and this, with potatoes, or cassava, formed the principal dish, to say nothing of the sago pudding and the residue of the little cakes which just suited Baby's palate.

For drink there was plenty of cold water, fresh and sparkling, obtained from a natural spring not far away. The Cataract River furnished a good water, in the sense that it was clear, but it had an unpleasant taste at times, so for all cooking purposes the water used had to be carried from the spring, which was sometimes burdensome.

"I wish we could purify the Cataract water, as it would be a great convenience," was George's remark, when they were considering their work and duties.

"We can easily do that by using the chips of the common oak tree or the charcoal can be used, as I have before stated."

"It is a curious thing that oak chips will purify it. Does it act in purifying the same way as charcoal?"

"We used oak bark for the purpose of tanning leather because of the tannic acid it contained. The chips of the wood contain tannic acid as well, and it does the same thing to the impurities in water that boiling does—namely, it coagulates it. In Egypt, the muddy waters of the Nile are clarified and purified by using bitter almonds. In India, they use a nut called the Strychnos for this, purpose."

"It seems people everywhere had some idea of purifying drinking water."

"Yes, and through all ages; even the Bible speaks of it."

"Where?"

"The Book of Exodus. I think the fifteenth chapter, says:

"'So Moses brought Israel from the Red Sea; and they went out into the wilderness of Shur; and they went three days in the wilderness and found no water. And when they came to Marah, they could not drink of the waters of Marah, for they were bitter; therefore the name of it was called Marah. And the people murmured against Moses saying, What shall we drink? And he cried unto the Lord, and the Lord showed him a tree, which, when he had cast into the waters, the waters were made sweet.'

"Our Cataract water, flowing, as it does, largely through forests and past vegetable banks, takes up a large quantity of albuminous matter, which is so great in quantity that the atmosphere, or the oxygen in the air, cannot purify it by the time it reaches us, so that if any astringent matter like oak, or birch, or beech, or even alum, is put in the water it will cause the albumen to precipitate. In the district of La Gironde, France, the waters of the Landes are naturally very impure from these causes, but since the cutting and floating down of the immense oak forests, the water has been made sweet and wholesome."

"Isn't all this curious and wonderful to think about?"

The work of preparing and putting into practical form the primary electric battery was going forward steadily, and at the Professor's suggestion a number of cells were made, which it might be well to describe briefly.

As the clay was the only available material, each cell had to be made rather heavy and clumsy in appearance, and was baked when completed. Each was ten inches deep and three by six and a half inches within. The electrodes, made of zinc, were each one-half inch thick, six inches wide, and nine inches long. The copper electrodes were the same dimensions, except that they were a quarter inch thick. These were stood in the cell, a short distance apart, and held in position by means of notched wooden blocks.

When all this was completed the cells were filled with sulphuric acid that had been made from the copper ore. It was, of course, much diluted with water, so as not to make it too strong.

"What is the object in making so many cells?"

"So as to get the voltage."

"Does the voltage depend on the number of the cells?"

"Each cell gives practically two volts, so that if we have 20 cells there will be 40 volts; 30 cells, 60 volts, and so on."

"But where do the amperes come in?"

"That depends on the size of the plates forming the battery. Surface is required for amperage, and quantity of plates for voltage."

"Suppose I had plates the size of this table, wouldn't I get more electricity than if I had the plates cut up into smaller pieces?"

"Electricity means both volts and amperes. There is no such thing as electricity with one of those qualities alone. A current may have 2 amperes and 40 volts, or 40 amperes and 2 volts. Multiplying the volts by the amperes gives what is called watts, and there would be 80 watts in each case."



The determination of the boys to build a new and better boat than the old one was now manifesting itself in plans, which were considered. George was in favor of building a large vessel, by means of which they could sail anywhere they wanted to; but Harry and the Professor opposed that plan, for several reasons. Harry, particularly, objected.

"I am just as anxious as George to build a large boat, but the difficulty is that to do so would take a long time, longer that we ought to take at this time. Furthermore, a large vessel would be hard to manage with our small crew, as we would have to make it a sailing vessel."

"Then why not make it a steam vessel?"

"That would make the job still harder and longer."

"I think Harry is quite right. A boat but little, if any, larger than the one we built, would be the most serviceable. If the one we made had been smaller, or lighter, we should have been able to carry it around the falls. Instead of that we had to leave it there."

Harry insisted in his views. "What we can do with our present supplies is to build a boat, even larger than our former one, and make it still lighter."

"Yes," said the Professor; "we now have lumber which is dried, and with the improvement in the tools we can turn out a boat which will be a credit to any community."

That question settled, the plan of the boat was drawn up. It was decided to build the boat on the general plan of the former one, as to size, namely, from sixteen to eighteen feet in length, and at least five feet wide, with a flat bottom, the prow to be contracted, and the bottom of the forward end to be bent upwardly, as much as their material would permit of bending.

For this purpose Harry stated that the body of the boat would be made of double thickness of material, as their sawing machinery had been so much improved that they could cut it into five-eighth inch lumber, and in that way the joints could be lapped, and the sides and bottom more easily bent into the required curves to make a graceful-looking boat.

The sawmill was at once put into good working condition, and within a week the principal parts of the boat were ready to be assembled.

"In your next weekly jaunt, I suggest that you might get our old life-boat. We should not neglect our friend."

The Professor's suggestion met with a hearty response, and on the following day the boys were off early to bring the boat to the Cataract.

First going to Observation Hill, which was the custom of one to do each day, they crawled up the rocky sides, and surveyed the horizon. From that position they could see across the neck of land, east of the Cataract, to the point southeast; to the southwest was the mountain range; to the west the forests, and to the northwest the irregular cliff line, which ended with another projecting point several miles beyond. Along the sea line this was the limit of their knowledge.

"While we are here let us examine the sides of Observation point and try to find the old flagstaff. I still think it was blown away."

Harry's suggestion was acted upon, and they made the trip together over the rocky side toward the sea. Observation point was on the mainland, and formed the extreme northern limit. It was fully half a mile from the grim rock where they had been wrecked. Between the two points were detached rocks which sprang up out of the water, and in which the water was constantly swaying to and fro. When the sea was heavy these rock islands made navigation among them a dangerous occupation.

The tide was then coming in, and eddies and cross currents were rushing hither and thither, so that it was easy to see that to float the wrecked life-boat it must be taken out to sea around the rocks. They hesitated to do this under the circumstances.

All sides of the hill were now examined with care. As they were about to leave the hill and go to the point where the life-boat lay, some wreckage was discovered below them, caught within the clefts of the rock. Here, packed in with seaweed and brush, was an object which interested them.

"What is this, George? It looks like the fragment of a boat; and here is another piece. Let us dig it out."

Both were excited beyond measure at this discovery. Not only one, but a number of pieces were finally removed. It was, beyond question, portions of a boat.

"Harry, this is part of our boat. See this piece of rope; and here is part of an oar. Wait till I get to the bottom of this mass."

"Run for the Professor, and I will remove the pieces while you are away," was George's answer.

Harry was off at the instant, and in less than half an hour, reappeared with the Professor, who examined the recovered portions of the wreck.

"It is certainly parts of a boat; but I am sure, from the present examination, that it cannot be our boat."

The boys were surprised at the information.

"My reasons for saying so," continued the Professor, "is, that the pieces here are not part of a life-boat, such as our craft was, although it was a part of a ship's boat. Where is the stern portion of our boat that you found? Let us get that, and we will be in a better condition to judge."

"We landed it beyond the point where Harry first reached the shore the day we were wrecked."

"Let us get it at once."

In less than a half hour the broken portion of the boat was landed at the foot of the cliff in front of Observation Hill.

Harry now had no doubt that the Professor's observation was correct. "See, this has no double hull, which the life-boat has, and no part of these pieces can be made to fit. Look at this stern. All of the stern post is still on the boat below."

It was, undoubtedly, another boat; but there was no name or number on any of the pieces by means of which it could be identified.

"I believe it was a part of the Investigator's equipment," was the Professor's final conclusion. "Have you recovered all the parts from the debris?"

"I don't think we can find anything else. While Harry was away I hunted all along the point in the hope that some more pieces might have been found."

The most minute examination was made for some mark of identification, but nothing was found which would give the least clue.

"Let us gather all these pieces and keep them for further observation, particularly for the reason that other parts may be found eventually, and identification will then be easier."

"Shouldn't we take the remnant of our life-boat to the Cataract?" asked George.

"By all means. It has just occurred to me that we might use that as part of the new boat we are building."

That was an idea which had not occurred to either of the boys. Considering that the portion recovered was the stern, and by far the largest part of the vessel, and that it had the double hull construction, made the suggestion a most acceptable one.

After all parts of the wreckage had been assembled, the Professor, accompanied by the boys, made another tour, much to the left, and on returning to the boat, the Professor's eye caught a white object lying partially hidden behind a rock.

"What is that by the rock to the right?" Without waiting for a further suggestion from the Professor, Harry made his way up, and when the object was reached, threw up his hands, without uttering a word. George had followed, and before the Professor had time to reach the spot, he cried: "A skull!"

"There is more than that," said the Professor. "Remove the debris."

The boys saw portions of the skeleton plainly now. It was such a shock to them that they could scarcely speak.

"Probably that solves the mystery of the wreckage we found."

"Undoubtedly," was the Professor's only comment.

The boys were now absolutely unnerved, but the Professor, without noticing their agitated state, carefully removed the seaweed and other accumulation, and found the skeleton largely disjointed, excepting the torso, or upper portion of the frame.



When the entire skeleton had been taken out and arranged, the Professor said: "It seems we are to have one mystery after the other."

"How long do you suppose this body has been here?"

"Probably ten months or more."

The boys looked at each other. "Ten months? That is as long as we have been here."

"That is one of the reasons why I said ten months."

The boys knew what that meant. This was, very likely, one of the Investigator's boats, and the skeleton the remains of one of their shipmates.

"Probably it was one of the boys," was George's inquiry.

"I do not think so," said the Professor. "The skeleton shows that of an individual past middle age."

"Why do you think so?"

"Principally, from my examination, so far, on account of the condition of the skull. You see, these saw teeth lines, which cross the top portion. These are called the sutures, and in infancy they are not joined. Before the third period of life these joints grow together, so as to form an undivided skull. But wait; here is another indication. The teeth seem to be greatly worn, showing that the person must have been close to the sixth period of life."

This discovery was the cause of very conflicting emotions in the boys. They reverently gathered the bones, and at Harry's suggestion the boys went to the Cataract for the team. The Professor volunteered to remain.

We may well imagine the feelings of the boys as they went on their mission. Here was mute evidence that others of the ill-fated ship had met disaster. They had often speculated on the fate of their companions. How many had been left to tell the tale!

The yaks were yoked, and taking with them a rude box, which had been put together, as the Professor suggested, they shortly returned.

"Have you found anything new?" was George's first question.

"The poor fellow was undoubtedly killed when he landed, and I think he was a sailor."

"Have you found anything which makes you think so?"

"Nothing but what you see before you. That break in the skull was, in my opinion, made by contact with a rock; furthermore, several of the bones were broken, as you see, at the time he met with his calamity; and one of the legs shows where it was broken before his death, and had mended."

It was a remarkable funeral cortege which wended its way slowly back over the hills to their home. They felt it was paying a tribute to a friend and companion. All doubts on their part had been dispelled. He had been one of their companions on that terrible night when the explosion had sent their ship to the bottom, and had cast them adrift on a sea which welcomed them in raging fury.

"What shall we do with the skeleton?"

The Professor was silent a long time before he answered. "I do not know what to advise. Perhaps, in the future fate may be kind enough to restore us to our homes and friends, and if it should be that we are the only ones so rescued, the skeleton would be a positive means of enabling us to ascertain whether or not he was one of our companions, and also to advise his friends."

A stone sarcophagus was built, in which the remains were deposited after a funeral service at which the Professor presided.

This event had a most depressing influence on the boys, as well it might, during the entire day, and it was the principal topic of their conversation while together. During the two days following only brief references were made to the Professor, but the second evening George's inquisitive nature could not hold in any longer.

"When we were on the rocks examining the skeleton, you referred to the fourth and the sixth ages of man."

"Yes; in point of growth man has seven ages. The first is infancy, which ends at the second year; second, the age which ends at the seventh year; third, at the end of fourteen years; fourth, at the end of twenty-two years; fifth, at the end of forty-seven years; sixth, at the end of sixty-five years; and seventh, which ends at death. These divisions vary somewhat between males and females, and I have given you merely the average between the two sexes."

"I can't help feeling sad, when I think of the things that have happened, and at the thought that all our friends may have been lost."

"Sadness is a natural feeling under the circumstances, but after all, why should it be so? Why should the sight of the skeleton bring sorrow to you? Probably the Egyptians had the right idea when they always had a skeleton at the feast."

"Skeleton at the feast? What was that for?"

"As a reminder of death?"

"There is one thing I could never make myself understand. Why is death necessary? Why couldn't man have been made so he could live always?" was Harry's query.

"You have asked a very broad question. It is one which has a great many answers. At this time I shall give only one of the reasons. The earth would not be big enough to hold the people. I do not know the population of the globe to-day. It is about 1,000,000,000; and if we take the age of the earth at only 5,000 years, we should have in that time 125 generations, counting each generation as 40 years. Do you know what that would mean in population at this time? You could not comprehend the figures. Let us take the United States alone, as an example. Assuming that the population is 90,000,000 at the present time, and that the natural rate of increase is only double in each forty years. This is how it figures out: In forty years we would have 270,000,000; in eighty years, 810,000,000; in one hundred and twenty years, 2,430,000,000; and in one hundred and sixty years, 7,290,000,000. At that rate New York City would have 480,000,000 of people and its boundaries would take in the whole of the State of New Jersey and nearly half of the entire State of New York, as thickly settled as that city now is."



CHAPTER XII

THE DISTANT SHIP AND ITS DISAPPEARANCE

"What is that weed you have, Professor? The root looks like a parsnip."

"It may be something we can drink."

"It looks just like a weed that grows all over our farm at home."

"I have no doubt of it. This is the endive, as it is known in the States, but it is really chicory."

"I have heard of chicory; isn't it used as a substitute for coffee?"

"Principally on account of the bitterness in it. The French make the greatest use of it, because they claim it gives strength to coffee."

"What part of it is used?"

"The root; the bulb you see here, and they have a curious way of preparing it. The root is dug up before the plant shoots into flower, and is washed, sliced and dried! it is then roasted until it is of a chocolate color. Two pounds of lard are roasted with each hundredweight; and afterwards, when ground and exposed to the air, it becomes moist and clammy, increases in weight, and smells like licorice. When put into cold water it gives a sweetish bitter taste, not unlike coffee."

"Let me try some of it, and don't say anything about it to Harry. And now, while I think about it, why couldn't we make some crocks out of our clay, so we can use them for our milk. We can't put them in the copper vessels and the iron is just as bad."