Fig. 2 Types of Arrow-Heads.
"I should like to know what animal this belonged to?"
The Professor examined the bones critically, without venturing an opinion. "What is this?" were his first words. Directly behind the ear cavity was a split or broken cleavage in which they found a round piece of dark wood.
"Get the bolo, George; we may find something interesting here." With a few strokes the skull was opened, and embedded within the brain receptacle was an arrow.
"This animal was, as you see, killed by the inhabitants of the island. I infer that there are several tribes living here."
The boys looked at each other in astonishment.
"Why do you think so?"
"This arrow is different in shape and in structure from the sample we found this morning."
The boys now noticed the difference.
"Do different tribes make their implements differently?"
"There is just as much difference among savages in the way they make their weapons and different implements, as among civilized people. Our customs differ; our manufactured articles are not the same; and sometimes the manner of using the tools is unlike; and the divergence is frequently so wide that it has been difficult in many cases to trace the causes and explain the reasons. Such an instance may be found in the Chinese way of holding a saw, with the teeth projecting from the sawyer. For years all tools and machinery made in England could be instantly recognized by those versed in manufacturing, on account of the bulk, as their tools were uniformly made larger and heavy, as compared with the French and American manufacture."
This conclusion verified the Professor's observation, and you may be sure that the new discovery gave an air of gravity to the camp which it did not have before.
"I also wanted to say to-day," was the Professor's last remark that night, "I am satisfied that there is no intimate intercourse between the different tribes on the island." The boys looked at each other without questioning, as usual; but the next morning, as soon as George awoke, his first observation was: "I can't understand what makes you think that the natives of the different tribes do not associate with each other."
"Simply for the reason that the styles of the arrows differ so greatly. With them, as with civilized people, the intermingling of the races should tend to make their tools and implements alike."
The next night, after the evening meal, they sat in the wagon until late, discussing their future course. It was now fully nine months since they left home. The thought that their parents and friends would consider them lost was the hardest thing to bear. Did the boys ever get homesick? I need not suggest such an idea to make it more real than it was to them. With beautiful home surroundings, loving parents and brothers and sisters, absence, uncertainty; the fear that they would never again be able to return; danger all about them; the belief that perils still awaited them, which fears were now, in all probability, to be realized, all these things did not tend to produce a pleasant perspective to the mind.
But the Professor was a philosopher. He knew that the human mind craved activity. If it could not be exercised in a useful direction it would invariably spend its energies in dangerous channels. He knew this to be particularly true of young people.
Boys are naturally inquisitive. Their minds are active, like their bodies. They must have exercise; why not direct it into paths of usefulness, where their accomplishments could be seen and understood by the boys themselves.
That thought is the parent of the manual training system, where the education imparted comes through the joint exercise of brain and muscle. Boys resent all work which comes to them under the guise of play; and all play which is labeled "work." But when there is a need for a thing, and the inquisitive nature of the boy, or his mental side, starts an inquiry, the manual, or the muscular part of him, is stimulated to the production of the article needed to fill that want.
The Professor did not force any information upon the boys, as will be noticed. It was his constant aim to let inquiry and performance come from them.
Could anything have been more stimulating or encouraging than the building of the water wheel, the sawmill, or the wagon? See what enjoyment and profit they derived from it. Thus far they had not given their time and the great enthusiasm to their various enterprises because of the money returns. Do you think it would have made their labors lighter, or the knowledge of their success any sweeter if they had been paid for their work?
The "Baby" went to sleep early, as was his custom now, and the boys and the Professor sat up later that night than usual, talking over their condition, and the situation as it appeared to them. The day had been exceedingly warm, following the rains.
Harry, who was seated facing the river, suddenly sprang up and excitedly grasped the Professor's arm, as he pointed across the river: "Look at that light!"
There, plainly in the distance, was a light, not stationary, but flickering, and, apparently, moving slightly to and fro.
"It seems as though it is at the edge of the woods," remarked George. The distance was fully a half mile away.
"It can't be possible that people are over there," said Harry, not so much in a tone of inquiry as of surprise. "How far do you think it is from here?"
"Probably one-half mile, or more. We might be able to learn something if we should fire a gun," was the Professor's reply.
The boys were naturally astonished at the boldness of this remark. Other lights now appeared, some dim, others brighter. The firing of a gun seemed to them a most hazardous thing to do, but no doubt the Professor had a reason for making the suggestion.
It was quite a time before either of the boys responded to this proposal. In their minds it was a daring enterprise.
"If we should fire a gun the noise would likely startle them, and the first impulse of the savages would be to extinguish the lights."
George, who had the spirit of adventure more strikingly developed than Harry, was the first to concur.
"I am going to try it at any rate; we might just as well know what we have to face now, as later on."
"So you are really going to shoot?" said the Professor.
"If you so urge it, yes."
"Then let me suggest what to do. All savages have a keen sense of direction. It is one of their chief accomplishments. You and Harry go back, up the river, a quarter of a mile, or so, and take with you one of our coverings. Then shoot behind the blanket, so the flash will not be seen, and I will remain here and watch the effect."
There was no delay in their preparations. Within fifteen minutes the shot rang out, and almost immediately thereafter every light had disappeared. The boys were also keen enough to note the extinguished lights, and returned to the Professor in a hurry.
"The disappearance of the lights is not conclusive evidence that human beings were there. It might have been a mere coincidence."
"Coincidence! What do you mean by that?"
"Did it not occur to you that the lights might be natural phenomena?"
"Of what?"
"Of phosphorescence."
"Do you mean 'will-o'-the-wisp'?"
"It is sometimes called by that name. It is caused by decaying vegetable matter, and exhibits itself in the form of gases of phosphorus, which appears to burn, but does not, like the vapor which is produced by rubbing certain matches in the dark."
"But how do you account for the disappearance after we shot?"
"I thought they might have disappeared naturally, after you fired, and, therefore, said it might have been a mere coincidence."
This explanation was not a satisfying one for the boys, and the Professor did not place much faith in it, for the following reasons:
"I believe it is our duty now to keep watches during the night, which we can do by turns, so that the sentinel will quietly awaken the next one in his turn, or both in the event of any unusual happening; and furthermore, we should make an early start in the morning."
George was the first watch, and, by agreement, Harry was to be the next, in two hours, for the second period. Before that time passed Baby was very restless, and George tried to soothe him; but before long he began crying. A lusty orang, however small, in a still night, makes an awfully loud noise. The boys never heard anything as loud and as frightful as that cry appeared to them.
All were awake, of course, but the Baby refused to be quieted for fully a quarter of an hour.
"Don't you think Baby's cries will direct the savages to us?"
"It is not at all likely. The savages have no doubt heard the cries many times. It is your imagination which is playing you tricks. Do you suppose the savages know we are here and have a captive orang?"
During the rest of the night they took sleep in snatches, and morning was long in coming. Harry had busied himself in getting a hasty breakfast while the others slept, and Baby was up leaping around nervously, and springing from branch to branch on the adjacent trees.
Having finished breakfast, the yaks were yoked, and before the sun was visible they were on their way to the north, as fast as the yaks could travel.
The whole camp partook of watchfulness now. Every hour and every mile they scanned the landscape, and, for further precaution, kept away from close proximity to the river bed. That was not a safe route, as enemies on the other side of the river would have an unobstructed view, whereas by traveling inland, but within sight of the river, they could still view the banks of the stream.
"The scout who leads the way must go a certain distance, then make observations in all quarters. He must take particular note of objects which afford places of concealment, and the eye must be alert enough to observe every undue movement in limb or leaf. Sound is one of the things he must cultivate. A noise of any kind should be analyzed. A scout once told me that on one occasion during the war, his life was saved because he saw one limb of a tree move more than an adjoining one. At another time, in trailing through a forest, he saw a leaf on the ground, differing in color from those around it. In walking along he had noticed that some of the leaves he overturned had the same color, and inferred that as no wind had been blowing, and all the trees were bare, something must have turned the leaf, and subsequent events confirmed his reasonings."
The boys quickly learned their lessons. Each knew that every step forward meant an entrance to an unknown world.
CHAPTER III
THE BEAR FIGHT
During the day, following the night when the mysterious lights appeared in the lowland directly to the west and beyond the river, they passed through several dense forests. George, who was in the lead at this time, emerged from the thickest wood into a rather open plain. He saw the river make a long circular sweep, and directly ahead noticed a coast line of steep hills which marked the shore of the river on the opposite side.
Harry and the Professor, who were behind with the team, had not yet reached the clearing. As George passed into the open space he saw an animal cross his path, and without waiting to inform the others, he shot. This alarmed Harry, who was out of the wagon without waiting for any word from the Professor. Immediately after George's shot was heard, they plainly heard another from the direction of the river ahead of them. The Professor, too, jumped from the wagon and followed Harry. George fired a second time, and another shot came from the river. Harry turned and looked back at the Professor in amazement.
"What can that mean? Did you hear four shots?"
"Yes; run ahead, and find George."
In a brief time both boys returned. "George says he did not hear the shots from the river."
"They were as plain as your own."
George did not know how to explain it. The Professor moved forward. "Let us get out into the opening."
As they reached the clearing beyond the wood, and the Professor saw the steep bluffs beyond, he laughed, and looking at the hills, said:
"That is where the shots came from."
His amusing smile was reassuring, although his words were not.
"That bluff over there is about 2,000 feet from here. We had better find out what he is doing there."
"Two thousand feet; and somebody there!"
"I did not say somebody was there, but that the noise of the shot came from that place."
"Do you think it was simply an echo?"
"Undoubtedly; didn't you hear Baby's cries repeated?"
"But how do you know that the hills are 2,000 feet away?"
"Sound travels at the rate of 1,040 feet per second, and I made a mental calculation that it took four seconds for Baby's cries to come back from the hills. In that case the sound had to go to the hills and back again, and it would, therefore, take two seconds to travel one way. Do you understand?"
"Oh, yes; that is perfectly clear."
The land now became more rolling, and was occasionally broken by ravines; and sometimes they had difficulty in getting their yaks and wagon across and over the rough ground.
Fallen trees were numerous; there were little mounds here and there, made by the remains of uprooted trees, which had long ago decayed, all of which made their traveling laborious and slow.
Here wild animals became more abundant, and wild game was found on every side. Several good shots by the boys replenished their larder with bird meat.
"See that bear!" cried Harry in great excitement.
The boys, as well as the Professor, were out with their guns at once. "Follow him up quickly now," and the Professor could hardly keep pace with them. The bear did not seem to be greatly frightened, and when Harry, who was ahead, stopped and aimed his gun for a shot, he was less than a hundred feet away. The shots from the two boys came close together, and bruin stopped in surprise, then, with a snarl, turned around and in a lumbering, shuffling movement started for the boys.
If either shot had taken effect it was not noticeable. The boys turned to run, one going to the right and the other to the left. This did not seem to disconcert him in the least, as he went right on. He had seen the Professor, who stopped and sprang to one side and bringing up his gun awaited the charge of the bear.
The boys, encouraged by the tactics of the bear in avoiding them, turned again, because they now appreciated that the Professor was in the bear's path.
"Don't shoot, boys; let him come nearer."
When he came within fifteen feet the Professor fired, and the boys also shot. The bear reared up, gave a terrific growl and again shambled forward, this time making a beeline for the wagon. This was too much for the yaks; they turned, almost upsetting the wagon, and Baby commenced to shriek in the most approved fashion.
Fig 3 The Bear
Neither George nor Harry could wait any longer. They followed and rushed past the Professor, who now had the only loaded gun.
"Take this, Harry; your guns are not loaded."
Harry turned and grasped it and without stopping went in pursuit. Before he had reached the former location of the wagon the animal ran into a tree, which threw him back on his haunches, and after several efforts to raise himself, fell over on his side.
The Professor's shot had entered his left eye, but the vitality of the animal was such that he ran nearly a hundred feet before it took effect.
The yaks were soon rounded up. It is a wonder that more damage was not done. Aside from the displacement of their bedding, and the ditching of some of the cooking utensils, everything was found intact.
"That was a rather ill-advised adventure on our part. We should have guarded our supplies; but I was as much to blame as you were. We must be more careful in the future."
On every side the rough character of the land was more apparent, and it was becoming more and more difficult to find tracks which were suitable for the team.
"This matter of going further with our wagon is now getting to be a serious problem. I think we should turn to the right and move in the direction of home, or direct our course southeast toward the mountains on the other side of South River."
"I think we have discovered enough on this trip," was Harry's conclusion.
George assented, so that on the twelfth day of their journey the yaks were directed towards home. For two days the travel was southeasterly, through the most broken and tortuous paths, crossing innumerable small streams and rivulets on their course. During this troublesome part of their journey the weather was stormy, with numerous rains, some of them so prolonged as to prevent traveling for hours, so that they made less than twenty miles during that time.
Fig. 4. Diagram of Their Trip
On the third day, however, the ground became more level and less broken, the sun appeared, and they felt happy at the thought of getting back again.
Thus far in their wanderings they had kept their reckonings, as well as they could without instruments, and that evening the chart was again consulted, as usual. The drawing (Figure 4) shows how it looked with the course of their journey.
When they started from the Cataract home at nine o'clock in the morning, they made an observation of the sun, using a vertical pole so as to get the exact direction of the falling shadow. A distant object was then selected, a prominent tree, as far off as possible. The Professor had prepared an adjustable bevel square, which was simply two legs hinged together at one end, by means of a set screw, like a compass.
Fig. 5. Bevel Square
"Now, boys, I want to show you how we can make a fairly good chart simply by the use of this adjustable square, and this will also be of service to us in measuring heights of objects, as well as directing our course. It is now nine o'clock, and you will see that our pole (A) throws a shadow to the southwest. Supposing now, we direct the first leg of our journey to that large tree (C), to the west of us. If, now, we put one leg (D) of our rule along the shadow line, and the other leg (E) along the sight of the line (F), which goes to the tree, we shall find that the distance across between the ends of the bevel square is just two feet. It happens in this case that the tree (C) is due west from our observation point; so we have at nine o'clock each morning a means whereby we can always determine the true east and west."
"But supposing we lose our reckoning during the day, on account of cloudy weather, or by going through the forest, where we cannot make observations?"
Fig. 6. Sighting the Direction
"We could, probably, travel an entire day in one general direction, without being more than a few miles out of our course, north or south, and our direction immediately made out the next day."
"Wouldn't it be a good idea to prepare angles at different times of the day, in the forenoon and in the afternoon?"
"That is the proper thing to do, so as to enable you to make observations from the angles at all times. A chart could then be made from that which would show at a glance what the value of each angle is."
"We shall certainly have to do that; but what interests me as much is, to know how far we have traveled. Can we also tell that by the sun?"
"Yes; but to do so will depend on the accuracy of the observation. For the present, with only a single instrument, the bevel square, we must be content to make our calculations exactly at midday, when the shadow points due south. Or, in the northern hemisphere, when the shadow points due north. I want you, in the meantime, to think over that problem, as it is a very interesting one, and we will take it up when we are not so tired."
CHAPTER IV
THE DISAPPEARANCE OF THE YAKS
It was a relief to get on fairly even ground again, where it would not be necessary to make turns and twists around all sorts of obstructions, to say nothing of ravines and water courses. On the evening of the fifteenth day, calculations showed that they were halfway back from the point farthest west, but they still had no knowledge of their distance from the sea, which undoubtedly was to the east, or, possibly, northeast. West River flowed to the north, and all the streams crossed flowed north or northeasterly, how far, it was impossible to say.
Two days afterward the scene changed somewhat. There had been little wind during the journey thus far; but now breezes sprang up for two successive days, at about four in the afternoon, which came from the north.
"I think the sea is not far away."
"Why do you think so, Professor?"
"Did you notice the warm breezes this evening, and also last night at about the same time?"
"Why should the breezes from the ocean blow warm winds to us at this time of the year when it ought to be cold?"
"It is not at all likely that the breezes are any warmer than at other times of the year. Heat is merely a relative matter. We feel the difference of the wind temperatures principally for the reason that when the vast body of water in moving ocean streams is giving off its heat, it imparts it to the atmosphere and modifies it, so that as it sweeps over the land it is warmer than the natural temperature."
The following day, late in the afternoon, they caught the first glimpse of the sea, and it was welcomed. A camp was made for the night in the open, and with an early start next morning the explorers reached the last hill to the west of the cataract.
When they arrived home, which was not without considerable misgiving, owing to their long absence, they were overjoyed at finding everything at the house in perfect order, but their yaks were missing.
This was, at first, a sore grief to them, especially to George, who considered it to be a personal loss. Milk was a luxury, as well as a necessity, to him. The team was now all that remained of their herd.
"It is strange we did not see any of them on our journey."
It was a surprising thing to see their water wheel in motion, although they had taken considerable pains to push the wheel back so the blades would not be in contact with the water. It was found that the Cataract River was much swollen with the rains, so that the water had come into contact with the wheel.
As the team was now the sole reliance, so far as the herd was concerned, the Professor suggested that they should thereafter keep the team within the enclosure, so as to prevent their straying, as they might, in the absence of their fellows, try to escape.
The present house, which had been built since coming to the Cataract, had originally only one room, and two of the sides were formed, as stated, by the walls of the right-angled rocks, the room being about ten feet square.
After the water wheel was built and put in and the sawmill erected, they were enabled to get lumber, and an extension twelve by fifteen feet was put up, to be used as a sleeping and living room.
A small addition was also added, which was converted into a kitchen, so that the original enclosure could be used as a storeroom.
A sort of roadway passed the new addition, and beyond was the Cataract, not fifty feet away. Directly below the Cataract another building was put up, in one end of which was the sawmill, and at the other end was a sort of shed in which they had put up a furnace, blacksmith shop, and a kind of primitive foundry.
Within the workshop work was done during the rainy weather, and it was made as comfortable as possible.
They were now back, ready to take up active life again. Not that the past nineteen days were inactive ones. By no means; but they loved the work which every day had brought to them in the past, and were happy in the thought that they were accomplishing things of the greatest value to themselves. They were really tired, and for a few days did little active work.
"Do you think we have accomplished very much on our trip?" was George's inquiry the evening of their arrival.
"We saw a light, didn't we?"
The boys laughed, when they saw that the Professor said it with a broad smile. They had no doubt, but he wished to convey the impression that they had seen a light, just as many others had, without being able to understand it. George saw the point at once. "I hope we may be able to profit by it. But, really, how much more do we know than we knew a month ago?"
"The West River, the bear, the wildcat, the Baby; why, you had entirely forgotten him and his cute ways. We learned that there are, without doubt, savage tribes on the island. I am inclined to think the trip has taught us something."
The Baby was an interesting little chap. He would sit up at the table with innocent blinking eyes, and gravely imitate the motions of eating, especially if there was something sweet in sight.
That night a startling noise was heard, made by the unmistakable tramp of animals passing their home. Harry was the first to open the small port, which served as a window.
"Hurrah for our yaks!" There they were, back again, with two additional calves. The next morning they were contentedly lying down outside of the enclosure which held their team.
Didn't "Baby" enjoy the milk! So did the boys. The cattle had not strayed away far, but merely found a better feeding ground. The barley field had been exhausted.
"If there is anything I missed on the journey, it was the clock. I don't like guessing at time," was George's comment, after they had fully gone over their experiences on the trip.
"I suppose," said Harry, "we can make watches, but they will be rather cumbersome, because our tools are not very delicate. What do you think, Professor?"
"That is for you to decide. I am of the opinion that as we have a pretty good clock, and as it is susceptible of being nicely regulated, we could put in our time more profitably in doing some other much needed work."
"What is that? I am willing to do anything?"
"We have some hides that need tanning, and the fresh bear pelt must be cured. As our herd of cattle has increased we might slaughter several of them, so that we can dehair the pelts and tan them all at the same time; then we need some contrivances to enable us to determine the location of our island; and also to afford a means to measure distances in traveling, because, I presume, you are just as anxious as ever to know what we have on the island."
There was a hearty assent to this view of the situation.
"I want to do everything we can to learn about our surroundings," was George's response; "and I would like to have the fire, and the mystery of the boat, and the flagpole cleared up."
The thing which most interested Harry after their return, was the disposition of the barley which they had harvested before the last journey was undertaken. This was welcomed by the Professor as a necessity. Accordingly a level floor was provided, on which was spread a thick layer of barley stalks, and this was beaten with flails. A flail is simply a piece of wood about the thickness and length of a broom handle. To this was attached, by means of leather strips, a club, not unlike a baseball bat, so the bat portion swung on the end of the handle, and in this manner the barley was threshed out.
Fig. 7. Threshing Flail.
Before the invention of the threshing machine this was the universal method of threshing, although it was also customary to tramp it out with horses, which were driven over a thick layer of the straw hour after hour.
In one day they threshed out five bushels; beautiful golden grain. The boys who had often seen wheat and oats threshed out, never appreciated grain as they did their own, acquired in the manner this was.
The grinding-stones, which they had previously made, were then set to work, making the meal, or flour, as they preferred to call it. Heretofore flour had been a luxury, and there was a longing for it, so it was decided to make up the first batch of bread.
You may be sure that the Professor did not object to activities in this direction; and they had long ago learned his peculiarities, particularly not to venture any information voluntarily, so the boys concluded to make bread on their own knowledge. They had often seen bread made.
"All you have to do is to mix up the flour with a little water, put some rising in it and let it stand until it raises and then bake it."
"That's all well enough, Harry, I suppose we can do all that, but where shall we get the yeast?"
"That's so; yeast is necessary; I suppose we shall have to see the Professor, after all; but hold on; I have seen sour milk used, George."
"So have I; but I think mother used something else with it."
"Well, there we are; who would think we could have trouble with such a simple thing as making bread?"
The Professor came smiling. "You want to make bread, and the only thing that troubles you is to raise it so it will be light?"
"Wouldn't it be bread if you didn't raise it? You know the Jews used unleavened, or unraised, bread."
"But we want regular bread, of course, and we want to know what to use to raise it with."
"I don't see that you particularly need anything."
"Why not?"
"If you let the dough stand in a temperature of between 90 and 120 degrees for a certain time, fermentation will take place, and it can then be baked."
"But why should it ferment?"
"Bread raising is merely fermentation. All flour is largely composed of starch. The high temperature, of 100 degrees or over, causes the starch to turn first into sugar, then into alcohol and carbonic acid, and the gases thus formed force their way up through the dough, causing it to swell, as you have often noticed."
Fig. 8. Imperfectly leavened. Perfectly Leavened. Samples of Bread
Without further instructions the boys began the making of bread. Shortly afterwards the Professor appeared laughing immoderately.
"Come and see the Baby."
The boys were out in an instant. The Baby was in the storeroom adjoining, and discovered the honey pot. It was a "sight." He sat there, both hands and arms covered with honey, blinking innocently, and licking his fingers and arms with the greatest joy imaginable.
"You little rascal, you are getting too fat now," was George's greeting; but Baby didn't mind. He knew George by this time.
The bread raised, but it, too, was a "sight." It was full of holes and at some places the bread had no appearance of having "come up," which is kitchen parlance for unraised bread.
"What is the matter with it, Harry?"
"Did you work it before you put it into the oven?"
"I forgot that."
When the Professor saw the sample he divined the trouble at once.
"Of course, you have to work it, for the reason that 'working' distributes the gases through the mass. I think you made the mistake in working it and then putting it into the oven immediately."
"How long should it stand after working?"
"That depends on the amount of carbonic gas which is developed. When it first raises the gas forces its way through the dough irregularly, and by then working it the gas is broken up and distributed evenly, so that if the mass is allowed to stand after the second working every part of it will be leavened. When it is then put into the oven, the heat at first causes a more rapid expansion, or raising, of the dough, and as the heat increases, fermentation is stopped, and the baking process sets the dough. The result is tiny little holes throughout the bread, where the gases were."
"But why do they use yeast if it can be done without?"
"Because it makes the raising process easier, and more positive."
"Is it the carbonic acid which makes some bread sour?"
"Yes; sour bread results if the fermentation is continued too long."
Fig. 9. Air Pocket.
It was George's custom each day to watch the movements of the yaks, because it was through them that they learned of the barley field which was such a source of usefulness to them. One day while out on an expedition of this kind, he wandered down to the rock cliffs, probably five hundred feet west of Observation Hill, this hill, it will be remembered, being close to the landing place when they were cast on the island. The sea was heavy and the tide coming in. He could not help reflecting, and his home, his parents, and his beautiful life there came up to his inward vision. The dreary pounding sea made him homesick, and for the first time he burst into tears. But George was a brave boy. He knew that crying was useless, and felt a little ashamed of himself.
His reflections were not long, however. To his left he saw a peculiar sight. At every inrushing wave there was a report like a cannon shot, followed by a tremendous stream and spray of water, which was shot out to sea high up above the waves.
This was an extraordinary sight to him, and unexplainable. The story was related to the Professor that evening.
"That was an air pocket in the rocks."
"What is an air pocket?"
"From your description it is probably a large cave, so situated in the wall of the cliff, that at a certain period the waves will entirely close the mouth. When the wave dashes up against the cliff and closes the mouth of the cave, the water tries to enter the cave. In doing so air is compressed in the pocket, and when the wave again starts to go out to sea, and the pressure is partly taken away, the compressed air explodes, so to say, and shoots out the water into a spray, and also causes the noise you heard."
"How much can air be compressed?"
"It is not known definitely how far. It has been compressed to less than one-eight-hundredth of its bulk. It is the most elastic substance known."
"Isn't water compressible?"
"No; if it had been compressible you would not have had that exhibition at the air pocket."
CHAPTER V
AN EXCITING HUNT
"What is that rocking?" cried Harry, jumping out of his couch, one night.
The Professor was awake and had noticed it.
"Probably an earthquake."
The rocking continued for several minutes, and then gradually subsided. They boys were so excited that sleep was out of the question, for the time, besides the shaking might again recur at any moment.
"Do you think there is any danger, Professor?"
"It is impossible to say what will happen when these symptoms in the earth's crust take place."
"Are there not some instruments which indicate the extent and possible dangers of the quakes?"
"There is an instrument called the seismograph, which records the vibratory movements of the earth, and also locates the distances at which the shocks are from the observer, but there is nothing to indicate what the extent and probable dangers are."
"Is it true that the interior of the earth is in a liquid state?"
"Such has been the theory for many years; but it is now believed to be a solid—a body with a density five and a half times greater than water."
"If that is the case, why is it that the molten metal flows out of the volcanoes?"
"There may be fissures in the earth, or portions less dense than others which, by the general disarrangements of the adjacent parts, and by the enormous pressure exerted by the force of gravity, are contracted, and the movement causes such friction and intense heat as to liquefy the rock. In doing so a large amount of gas is evolved, the movement of which causes the disturbance of the earth's crust, which manifests itself to us in the form of earthquakes. At the same time the confined gases seek an outlet, which they find at the weakest part, and the volcanoes spout forth the lava, flame, and gases. There is an undoubted connection between earthquakes and volcanic eruptions. Earthquakes usually precede volcanic action. This internal combustion is going on at all times, and is only more violent at some period than at others. The lava in the Crater of Stromboli has been in a liquid state for more than two thousand years."
"Before we left home I saw in a paper that some scientist described the kind of rock and other matter which was seven miles down in the earth."
"Was anyone ever down as far as that?"
"No; a little over a mile is as far as man has actually penetrated the earth."
"Then, I should like to know how geologists can tell with any certainty what the rock is like several miles down?"
"That is known just as positively as though a hole had been dug down that distance."
"I don't see how that is possible."
"I am going to make you a sketch which you can examine at leisure, that will show how he knows. Assuming that the earth has a crust—that is, the outside or cooled part, let the first sketch (Figure 10) represent this crust, before the mountains and valleys were formed. The slightly curved horizontal lines merely represent the different layers of the crust, such as rock, clay, coal, slate, and the like. When the cooling process took place the earth grew smaller within, so that the crust was forced together.
Fig. 10. Normal Crust of the Earth
"The second sketch (Figure 11) shows this crust forced together, so that when the upheaval took place, two mountain ranges, A and B, were formed, with a valley (C) between them, and the broken lines (D), where the crust separated, were exposed, and by that means examinations can be readily made way down into the crust, without ever leaving the surface of the earth."
As it was understood that the boys should take at least a day each week for hunting, particularly since such sport would develop expertness in the use of their weapons, an early start was made on the day selected, which was within a week of the time they returned home.
Ever since the disappearance of the boat left at the falls in South River, there was some anxiety on that score. It was a frequent topic of conversation, and after they left home it was by a mutual impulse that they wended their way south, taking a trail which was now familiar to them.
"See here, Harry, I should like to go to the place where I discovered South River, and where I had the experience with the snake and the strange animal, which frightened me so."
Fig. 11. Mountain Upheaval
"Then we must go to the left, because, you remember, you came up between these hills, and crossed the stream where I found you."
It was about three miles across from the Cataract house, but less from their original home. When they reached the river the surroundings were very much unlike anything George had seen before, and he could not identify the place where the ramie plant had been found.
The ocean could be seen plainly from their position, and George thought they were too far east, which proved to be the case.
"Here it is, Harry; here is a low place, and you can see the ramie plant all about here. I am sure of it."
"Is this the place you lost the hatchet?"
"So I did: I'll show you the place." But he failed to find the hatchet. Subsequently Harry stumbled across it, but it was found some distance from the place where George declared he lost it.
"Let us try to cross the river. We can do it if we find a couple of logs."
At a bend of the river they found a lot of driftwood caught in the roots of a tree, and after some work a number of pieces were cut and laid crosswise on each other.
After the experiences of several expeditions of this kind, to say nothing of the exploring trips, the need of the bolo and ropes impressed itself on their minds. They were never without them.
The river at this point was fully one hundred feet wide, but by the aid of long poles the raft was not long in making the trip. After properly securing it they took up their weapons and at once made a dive for the interior.
The trees were fairly thick, and before going very far Harry checked George with the statement that there was game ahead, as he had heard rustling sounds in the leaves.
Both were now looking forward intently, expecting and hoping that some game worthy of attention would appear. Whenever they stopped, the animal, or what it was, would stop, to resume its motion whenever they moved. This was getting to be decidedly interesting, and at the same time trying to the hunters. The distance was fully a mile from the river. The noise which came from the slight rustling of the leaves and the occasional breaking of a twig was growing acute.
"Are we hunting or being hunted?" said George, under breath.
Not forgetting the Professor's story of the hunter's careful scrutiny of leaves, they adopted that plan, but it gave them no clue. Whatever it was, it was in front of them, but they were unable to get a glimpse of it.
Once, by agreement, they stopped and were silent for several minutes. The silence was just as profound and continued as their own. It was getting tense, when George hit upon a plan.
"Let us be quiet for a minute or so, and then suddenly bound forward and give a whoop. I think that will frighten him, and enable us to sight him."
"Before doing that get the guns ready for a shot, and don't fire too soon. Don't get excited. Remember the Professor's warning; a shot close at hand, deliberately aimed, is more positive than a dozen shots excitedly fired at a distance."
When all was ready Harry whispered, "Now!"
With a whoop both started forwardly on a run as fast as the dense underbrush would permit. Before they had gone twenty feet a large leopard-like animal sprang transversely across their path, then, seeing the boys, crouched for a spring. The guns were cocked and ready, and it is a wonder that in the excitement there was not a premature shot.
"Now, steady," said Harry. "Aim, fire!" and the moment both shots rang out. Harry cried excitedly, "Now for the other guns!"
The other guns were not necessary then. The animal gave a savage growl and bounded to the left, and after they had time to recover, both moved toward the spot.
"We have hit him, sure," was George's exultant shout. "See the blood on the leaves. My! he was as big as a lion!"
"Let's follow him," was Harry's determination. And off they started, the blood tracks plainly showing the way. Not a further view was obtainable of the animal, and in less than a quarter of a mile all blood traces disappeared, to the chagrin of both.
They directed their steps toward the river, but within two hundred feet of the spot where they had last stopped, George stepped back and cried: "There he is now, right ahead of us."
"Let us be careful now; he may be angry." There was no alternative but to fire. The shots were almost at the same instant, and to their great relief the animal, after a single leap, fell down without a groan.
The approach was cautious, because experience had not taught them whether it was safe immediately to make an examination of the body. After some hesitation they went up closer, and when all doubts as to his death had been dispelled a careful examination was made.
They found only a single shot wound between the shoulders.
Here was a dilemma, surely enough. The river fully a half mile away, if not more, and the brute too large to carry, made them hesitate about attempting to skin it in the absence of the Professor.
"I wish we knew what kind of an animal it is. We had better go home and bring the Professor back with us in the morning."
So taking note of the surroundings, to familiarize themselves with the location, they hurried back to the river, and rafted themselves over. The Cataract home was reached about four o'clock, after one of the most adventurous days spent on the island, although, in some respects, not as exciting as their earlier experiences. They had begun to be veterans. They were not merely boys.
Naturally, the Professor heard a stirring tale, and when it was all told over and over again, he told them he thought that undoubtedly the region beyond the river would turn out to be their hunting preserves, a statement which the boys did not forget to profit by, as we shall see later on.
"I wonder why we haven't seen more animals north of the South River? There have been very few in this section," was George's observation.
"Undoubtedly the mountain region affords them safer retreats, and it is one of the things which indicate to me that we shall find that section very wild, and when we are in shape to do so may be able to have some interesting and exciting times in that part of our domain," was the Professor's response.
"But in South Africa wild animals are found in abundance on the plains."
"True; but they have very thick brush, or cover, owing to the luxurious growth of vegetation. That affords them means for covering their retreat when attacked."
Following out the usual custom while on expeditions of this kind, they constantly, while on the way, stopped to examine specimens of plants and trees.