The Wonder Island Boys: The Mysteries of the Caverns

Fig 2-3. Working on the new boat

For the upper edges of the sides, called the gunwale (B, B), similar stringers were provided, but they extended farther fore and aft, and amidships were fully six and a half feet apart, whereas the lower stringers amidships were four and a half feet apart. This arrangement, therefore, provided for sloping sides, and the side pieces ran up and down on the inner course. It will be understood that the sides and bottom thus formed were to be overlaid with thin boards running fore and aft, as in Fig. 2, as they had no means for matching the boards and thus putting them together tightly.

The sides were two and a half feet high. Six and a half feet from the forward end was a cross beam (C), into which the mast was to be stepped. At the stern the bottom was sloping upwardly at an angle and brackets (D) were extended back and joined at their rear ends, to which the lower end of the rudder post was attached.

Amidships a keel (E) was formed, projecting down from the bottom, this keel being, at its widest part, two feet, and tapering down to merge with the bottom, fore and aft. The cross section (Fig. 4) shows how well he had formed the vessel, proportionally.

Fig. 4. Cross Section.

In addition to the cross seats, similar arrangements for comfort were made along the sides, and beneath the side seats were spaces in which their supplies were to be placed. The space forward of the mast was entirely closed over with a roof which sloped in both directions, and here provision was made for two berths. This would also afford them protection and serve as a means to keep out the water and insure at least one dry spot for their comfort.

As usual, George had some inquiries to make about the boat. "It has always been a matter of wonder why all boats are made with the big bulging part nearest the forward end?"

The Professor's eyes twinkled. "Probably there are a great many others who have had such thoughts. There is really no reason for it. It is not known how the custom originated, except that in sailing vessels the claim is that the ship can be maneuvered more easily by such construction."

"In what way does it make it easier to handle?"

"When a ship is driven forward by the wind, all the force exerted on the sails is transferred to the forward part of the ship, hence if made narrow at its forward end it would be driven down into the water, and the hull would, therefore, be submerged more at the forward than at the rear end. Furthermore, by having a tapering rear end, the rudder has a better opportunity of veering the ship around and you can see that the bulging part, being located forward of the middle portion of the ship, acts as a sort of pivot."

"But it seems to me that none of the reasons given will apply to a steamship, and still all the ships I have seen are made in the same way as the sailing vessels."

"That is exactly what I inferred in my answer to your first question. The truth is, that in experiments which have been made, it is shown that to have the widest part of a steamer near the stern, gives lines to a hull which has less resistance than if made in the conventional way."

"I thought probably the reason for making them so was just the same as in the case of an arrow, where the heaviest part is at the forward end."

"In that case an entirely different principle is involved. A body falls, or is projected through the air, with its heaviest end foremost, because of the greater momentum in that portion."

"It is the force of a body in motion. When a body is projected through the air it meets with the resistance of the atmosphere, and this also serves to turn the heavy side around to the forward end, because the force of momentum in the heavy end is much less affected by the resistance of the air than the lighter end." (See Fig. 5.)

Fig. 5.

Fig. 6. Red Angel.

Red Angel had now been with them more than six months, and he was probably a year old. When first captured he was a scrawny infant, dull and stupid, like all of his class. He had wonderful powers in the way of imitating habits and customs. The boys were very good vocalists, and while at work Harry would sing, but George whistled. It was an amusing sight to watch Red Angel when the boys engaged in the frequent concerts at night.

But of all the screamingly funny exhibitions, the attempt of Angel to imitate whistling was the most ludicrous. The orang's lips project too much to a point, and the jaws are so narrowed that the lips will not pucker. Whenever the boys commenced their concert Angel would be on hand, and enjoyed every moment of the time, and the boys had many a concert purely for his benefit.

At the end of each concert the whistling would begin. This invariably brought Angel to the front, and his exhibitions would be given with the utmost gravity and earnestness. The invariable result would be such uproarious fits of laughter on the part of all that he would take part in the jollification, little suspecting that the laughter was at his expense.

The only sound which he could emit during these performances sounded like a high-pitched stick rattling along a pale fence; but he was inordinately proud of it. It had always been on one key, heretofore, and without variation; but this evening Angel startled himself, as he did the others, by actually sounding two additional notes. He repeated this over and over.

"I wonder if we could make him talk?" asked George, after the laughter had subsided.

"There is no reason why some tones cannot be imitated. As the orang possesses wonderful powers of imitation and has, in captivity, developed many traits, I see no reason why simple words, or sounds, cannot be taught."

"I know there are words which he does understand. Time and again I have told him things, which he seems to understand. Now see if he understands this: 'Angel, do you want some honey?'"

His attempts at whistling ceased, and in a moment more was in the kitchen. Harry, who by this time had recovered from his mirth, thought it would be a good idea to attempt to teach him.

"If canary birds and dogs can understand language, I do not see why Angel shouldn't."

"Unquestionably, any animal, by patience, will learn the meaning of sounds. Constant repetition of certain notes causes birds to repeat them. I have known dogs to perform almost anything they were told to do, although they are not able to utter a single sound of the words emitted in giving the command."

"Well, what is it that causes sound?"

"The most wonderful thing in nature is, that she manifests herself in only one way, namely, by a movement, or a motion of some kind. Vibration is the term used to designate this. Sound, light, heat, taste, smell, and everything which becomes sensible to us is produced by vibration. The movements of the heavenly bodies, swinging back and forth around the sun, like huge pendulums, the movement of the sap in trees, up and down, the beating of the heart, the winking eyelids are all motions which show energy, development, life."

"But what is it that makes us understand one sound from the others?"

"Simply the difference in the kind of vibration. There are three things which characterize sounds; namely, pitch, intensity and character. Pitch depends on the rapidity of the vibrations; intensity on the extent or the amplitude of the vibrations; and character on the substance or instrument producing them. To illustrate: When you sing a very high note the vibrations may be five thousand vibrations a second, or there may be only two thousand during that time. That represents the pitch. In singing that note you may sing it so loud that, like a pendulum, it will swing way over to one side, or it may move only a short distance. That represents intensity. If either you or George had sung that note I should have been able to detect it, whatever its pitch or intensity, because your voices are as unlike as different musical instruments, and that is character, or timbre, as the French call it."

THE HIDDEN MESSAGE

While the work of getting out the planking for the boat was going on, and the plowing had now been resumed, since the new yoke of oxen were fitted to do the work, the boys were not forgetful of the usual weekly outing. They had several quite important things right at home which needed looking into, if they wanted to solve some of the things on the island. First, the cave, which they had twice attempted to explore; the search for their lost boat, which had the strange rope and oars; and the mystery of the flag and pole.

These things weighed heavily on their minds, because these happenings were close at hand. But what made the greatest impression on the minds of all was the finding of the Investigator's lifeboat. It seemed almost like a call to them from the interior. The impatience of the boys was almost beyond restraint, at times.

"It does seem to me that we should not delay an hour in making some effort to explore the direction the boat came from," was George's view of the situation as they canvassed the subject.

"That is my idea, also, and I am not in favor of giving much more time to hunting or other forms of recreation until we know how that boat came to South River."

"Yes; I can appreciate how anxious you are," said the Professor, after the boys had given their views. "What we are doing, however, is essential from every point of view. We must prepare provisions, so that we shall be able to know where we can get them in case of need. On the other hand, weapons are necessary, which take time to construct. If, however, it is thought advisable, we might make a trip of explorations along the South River, beyond the falls, the time to be limited to a week; but I have my doubts of the wisdom of such a course."

This suggestion appealed strongly to the boys, who were always keen for anything which savored of adventure, and it was some time before the boys could reconcile themselves to the saner and more business-like course of completing the boat and making the trip by water.

The weather was beautiful, and vegetation was springing up in abundant profusion everywhere. Magnificent showers fell at intervals, and the rainbows, more beautiful than any they had ever heretofore seen, spanned the heavens after the showers.

This had been noticed during the previous year, but now, after nine months of their life, with the wonderful insight which their needs had instilled into them, made them very observant of every phenomenon.

"I have often wondered," observed George, as he gazed at the beautiful broad band which formed a crescent across the heavens, "why there are never any rainbows in the middle of the day. They are never seen except in the morning or in the evening, and usually only in the evening."

"In order to understand that it will be necessary to explain what a rainbow is. As I stated previously, light is merely vibration. Now colors are formed by the different lengths of the vibrations, just the same as the different musical notes are made by the different vibratory lengths. To understand this more fully, I make a sketch (Fig. 7), which shows just what I mean. You will see that red is the lowest musical pitch, which we will call C, and to the right is a long, wavy line. D, the next pitch higher, might resemble orange, with the wavy line a little shorter, and so on, until we reach the highest note in the scale, where the wave lengths are very short. You have probably noticed that a drop of water in the sunshine glistens, and, if closely observed, may have seen that it was colored, particularly blue or green. As the rays of the sun strike the globe of water, they produce different wave lengths, and in that way make it appear to you as being possessed of colors. Now, a rainbow is nothing more nor less than sunlight passing through the drops of water which are suspended in the air and causing a refraction of the light. At noon the sun shines down from overhead, and we are not in the proper position to see this refracted light; but in the morning or in the evening the sun shines against the earth at an angle. At those times we are able to see the effect of refraction by the colors produced.

Fig. 7. The Color Spectrum

Fig. 8. Reflection Angle

"When you throw a ball against a wall at an angle, it bounds away at the same angle. That is reflection, and is just exactly what light does when a ray strikes a mirror. If, on the other hand, the glass had no mercury on it to reflect the light, the ray would not go straight through, but would bend, just as you have seen a stick in a glass of water appearing as though it was bent below the water line. That is refraction."

Two weeks of very vigorous work had now been put in since the yaks had disappeared, and the wagon was still at the edge of the forest. George was anxious to recover it, with the new team, and with Harry started out early in the morning to make up as much as possible lost time, as every hour was considered valuable in their enterprises.

The yaks could be ridden as well as horses, but the greater part of the way were driven. One of the guns which had been completed was taken along, as well as the only pistol which the Professor had saved. In less than three hours the forest was reached and they were soon within sight of the wagon.

"What have we there?" cried Harry, as they neared the spot.

"Our yaks! And where do you suppose they have been?"

Close by the wagon were the yaks, as though patiently waiting for the boys. They made no resistance, nor show of fright, when the boys approached. One of them, Jack, still had the strap tied to the horns, and it was the halter which had been attached to the tree at South River.

A hasty examination was made, but if either of the boys came to any conclusion concerning it, nothing was said. Without wasting time, the team brought with them was yoked up and the broken wheel replaced by a new one. The repairs to the wagon tongue did not take long, and they were ready for the return.

"What shall we do with Jack and Jill?" Those were the names bestowed on the first team. "Let us see if they will follow us."

They had gone fully one hundred feet before the yaks made any sign, and then slowly followed, thus assuring them that no care or attention would be required in that direction. Both boys were intensely delighted at the recovery of their favorites and could not get home fast enough to give the Professor the good news.

Nearing home, the Professor, who was on the watch, came out to meet them, waving his hat at the sight of Jack and Jill. When the latter came up he went over and affectionately petted the creatures, who seemed to realize the welcome.

"I hope they are as glad as we are; I can understand why they got away; look at the end of this thong." It plainly showed the teeth of some animal which had gnawed the leather of which it was made.

"So you have been out prospecting, too?" was Harry's query, as he saw the queer-looking reeds on the table in the laboratory that evening. "What do you call that?"

"Our honey has been getting low, and I took the occasion to-day to bring in some samples of sugar."

"Is that sugar cane?"

"Yes; the true sugar cane."

"Is that different from sorghum?"

"This is the species which grows in the southern part of the United States. The kind you know and which is cultivated in the Northern States, is the Chinese Sorgo, or, as we call it, sorghum. It is equal in quality and in quantity to the southern species and is readily treated to produce molasses or sugar."

"What is that peculiar flower, if it is a flower? I never saw a flower like that; it seems to be hard."

"I was surprised to find this. It is called the Tamarisk. This long, oval-shaped part is made by an insect which inhabits the plant, and is eaten by the inhabitants in the plains east of the Mediterranean Sea. It is there called Mount Sinai Manna, and is supposed to be the Manna which the Jews found when they were in the Wilderness after the Exodus."

"I think we have properly named this place Wonder Island."

In the volume preceding this, when they first considered the building of a new boat, it was decided to graft an extension to the after part of their wrecked lifeboat; but when the second one was found, and calculations were made as to its usefulness, it was discovered that such a course would not be wise; hence the larger vessel was found to be the only solution.

The newly discovered boat was, however, a valuable addition, as it afforded a means by which short trips could be made, and Harry quietly set to work making a sail and rigging up a mast, so that the long-cherished desire to make these trips could be undertaken before they were ready to launch the real vessel. It was hauled up on shore and caulked and new parts added to make it adaptable for the purpose.

While engaged at this work he removed the cross seat which still remained, and in doing so was surprised to find a piece of cardboard which had been hidden, apparently, at the end of the board. Eagerly picking it up, he saw writing on it, with the following words: "We cannot hold out much longer. Wright and Walters were captured yesterday. Will."

Fig. 9. The Hidden Message

Harry could hardly contain himself, as he rushed up to the laboratory, crying out: "George, come here, quickly! I have found something!" Without waiting to see whether George heard, he rushed into the Professor's den with the paper in his outstretched hand. "Look at this; don't you remember Will Sayers? I am sure it is Will."

George heard his excited voice, and appeared without any delay.

"What is it now?"

The Professor was reading the scrap, and silently handed it to George. "Did you know either of the boys mentioned in this?"

Neither had any recollection of Wright or Walters, but they inferred that the writer must be Will Sayers, one of the companions. The Professor had no recollection of the boy, nor could he remember the other names.

"Let us examine every part of the boat," was the Professor's first suggestion. "We may find something more to give some clue."

The boys rushed down to the beach where the boat was moored, the Professor following.

"Show us the exact location of this strip."

"I had just taken off this cross seat, and as I did so this piece fell from the end."

"Let us put it back again and see how it fits into that place."

When it was replaced they noticed that a crack was left at each end of the seat, not exceeding an eighth of an inch.

"It is very plain that the piece you found was at this end, and if it was folded as this crease indicates, it could have been concealed there and thus escaped our observation." After some minutes' examination, he continued: "This piece must have been there for some time."

"Why do you think so?"

"You will notice that the end of the board has the marks of the folded paper, showing it must have been in its place of concealment for some time. Furthermore, the paper itself indicates that it has been there for some time, by the discoloration on its outer side."

"How long do you think it may have been there?"

"It is impossible to say; but certainly for several months."

"Doesn't it seem reasonable," Harry inquired, "to think it was some one from the Investigator? Otherwise, how is it that they had possession of the boat?"

"That is the problem we shall now have to find out."

Thus, in another direction, was found an evidence that savages were on the island and that others had been wrecked and found a refuge there. How much of a refuge it was to them they had no means of knowing. They were thankful their own lives had been preserved and had been permitted to accomplish so much during their enforced stay.

"We are now vigorous and strong and have been blessed with energy as well as health. It is our first duty to take up the task of finding our comrades, whatever the cost may be. If that is your view, we should proceed with that determination, but let us prepare for it in the best manner possible. How long will it take to finish the six guns you are now at?" said the Professor, looking at Harry.

"I will try to have them ready within another week," was his reply.

"In the meantime, George and I will prepare a new lot of powder; and for your further information, I will state that I have been busy during the past week in making preparations to extract some lead for bullets."

This announcement was hailed with joy. Heretofore they had to depend on the iron slugs which had been turned out, and they were not at all satisfactory, because they lacked the proper weight.

"Which is the lead?" asked George, who was examining the samples.

"It is this bluish-gray sample of galena, which, as you see, looks like lead itself, and is often mistaken for it; but it is far from being lead of the kind we can work."

"Why not?"

"Because it is in what is called a sulphide form. Do you remember what a sulphide is?"

"Yes; it is where it is in combination with something."

"That is a fairly good definition. More or less sulphur is found in all metals, but when found in large quantities the ore is called a sulphide."

"How can we get rid of the sulphur?"

"We can cook it and drive it off like steam. Lead melts at a low temperature, comparatively, about 600 degrees Fahrenheit, so that with our furnaces it will be a very easy matter to get a pure lead."

During the rest of the day all were in the laboratory, superintending the preparation for the work, and at the Professor's suggestion the boys took the team in the morning and brought in over a hundred pounds of galena to be treated.

Before noon they had forty pounds of a very fine quality lead, and the work of making molds for the bullets was begun. The Professor, however, suggested that the boys should devote their time to the construction of the boat and guns, and it was difficult to decide what was the proper thing to do first.

The Professor saw the dilemma and had a very earnest conference on the subject.

"You must not, by any means, be carried away with undue eagerness and a desire for haste. The first essential of good business is to do everything in order. It is better to plan carefully every step in advance, so that you will know just when your energies will be required for the next step. An eminent engineer, on one occasion, in answer to a question as to why he was always prepared for an emergency, laid down this rule: Whenever you have a problem to solve, work it out in more ways than one. If one fails, you can apply the other immediately. This can be done without a moment's delay. Therein lies the answer—preparedness."

The boys readily saw the force of the lesson. From that time on it was not necessary to direct the order of events. Each saw to it that the part allotted to him was carried out in a determined spirit.

THE TERRIBLE MONSOONS

Of the two most urgent articles, namely, weapons or the boat, it was decided that the guns should be completed first. The feeling that the time would come when a visit from the savages might be expected at their home, contributed to this decision.

Six barrels, each eighteen inches long, and with a bore three-eighths of an inch in diameter, had been turned out, and several of the stocks had been made at odd times during the evenings. As Harry had sufficient steel left for four barrels more, two days were devoted to boring them out, in the hope that they would ultimately be able to finish them up. They would then have a battery of ten guns, and the necessity of having a number arose from the fact that they were muzzle-loaders, and could not be reloaded rapidly.

A sketch of the gun with the firing mechanism is furnished, in which it will be seen that the firing plug travels in a bore formed through the stock; in a line with the barrel. This plug had an upwardly extending finger, so it could be drawn back against the resistance of the spring. Below the plug was a trigger, with a hook-shaped forward end, in such a position that when the plug was drawn back the hook would catch and hold the plug until the lower right-angled projection of the trigger was pulled back. This would release the plug, and the spring would then be driven forward and explode the cap.

Fig. 10. The First Gun

"It would be well," said the Professor, "to polish the inside of the bored barrels, and thus make a much better weapon."

"How can we do this?" asked Harry.

"There are several ways, but the better plan would be to take a good polishing material, in the form of a fine sand or grit, and mix it with oil. This can then be put on a wiper which will snugly fit the bore, and the barrel may then be put in the lathe and rotated at a high rate of speed with the wiper in the bore, and during the rotation the wiper is drawn in and out. This operation should be continued for an hour at least, frequently withdrawing it to add more of the polishing grit."

"What is the best grit to use?"

"If we can find a sample of the adamantine spar, in sufficient quantities, it would be the best substance."

"What kind of material is that?"

"It is a substance known as corundum."

"Is that the same as emery?"

"What is known as emery is the more or less impure product from the same source. I think I have stated heretofore that both of these products come from the precious gems; the blue variety is known under the name of sapphire; the red as ruby; the yellow as oriental topaz, and the violet as oriental amethyst."

During that and the following day the Professor spent some time in prospecting for the gems, but if he succeeded in finding any samples he did not make the discovery known.

A few days after this Harry announced that he was ready to lay the keel of the new boat. All the material had been prepared, and was at the beach. Prior to this the island had been visited by a heavy storm. They had been frequent within the past month, but this was not considered unusual.

The Professor insisted that a temporary shed should be erected to cover the material, as moisture would make it very undesirable for the vessel, and a day was occupied in putting up the structure.

An entire week thus passed, every hour of which was devoted with the utmost diligence to the various enterprises. The keel was laid and the work of putting on the bottom boards was progressing rapidly. One night, a few days after the laying of the keel, a brisk wind sprang up, which continued during the night, increasing in fury, and in the morning evidences were seen on all sides of the effect of the tempest.

"It seems very singular," was George's observation, "that we should have such terrible winds here."

The Professor had evidently expected the storms. "Do you remember the experience we had less than a year ago? We had five days of this on the ocean."

"I had forgotten that. Do they occur every year?"

"You may have heard of the monsoons, a periodical wind in the Indian Ocean, which is a northeast wind, and they blow with greater or less force from November to March."

"What causes them to blow with such regularity during those periods?"

"Ah! that is one of the things which it has been difficult to determine. They appear to be modifications of the trade winds. While, as stated, the northeast winds blow during the periods mentioned, they have the southwest monsoons, which blow from April to October. As these violent winds are the most tempestuous during the period when the sun crosses the equator, it has been argued that it is due to the action of the sun being in such a position that its rays strike the earth in the center of its rotation, thus heating up the air and causing it to rise rapidly along the middle belt."

"Is that what we understand by the equinoctial storms?"

"The equinoctial storms come in March and September, when the days and nights are of equal length."

"I was told by a teacher that the summers are longer north of the equator than south of it; is that true?"

"Yes; the summer north of the equator is about seven and a half days longer."

"What is the cause of that?"

"The earth is at its greatest distance from the sun during the summer months, and the angular motion of the earth in its orbit is slower. The result is, that the interval from the March to the September equinoxes is greater than from September to March."

Harry made his way through the violent wind and rain to the boat shed. He came back with a sorry-looking countenance. "I am afraid everything is soaked beyond recovery." He was almost on the verge of tears.

Before noon the rain abated somewhat, but the winds still blew strongly, and when they ventured out to take stock of their surroundings, George was the first to notice the disappearance of the flag on Observation Hill. Rushing in to the Professor, he cried: "Our flag is gone."

Harry was at the boathouse, and when George went down to inform him of the new calamity, he was almost heart-broken. The Professor, however, was not in the least perturbed. He laughingly chided them and soon restored the boys to their usual gay and happy demeanor.

"Such little incidents as we have met with this morning only give us variety. We need something of this kind to add zest to life. Just imagine what life would be if everything turned out just as you wanted it or willed it? You would commit suicide within a week."

The boys smiled, but at the same time their eyelids did double duty in the blinking line for a little while.

George straightened himself out and looked up the hill. "Well, I am going for that flag whether it blows or not," and he started for the hill. Angel, who was in the loft, swung down and made his way out of the door, and before George had gone fifty feet, was at his heels. "And you are going, too? Good boy!" and George actually hugged Angel. He understood.

Arriving at the hill he made an examination, and found that the halliards had been broken and the wind carried away the flag, halliards and all. As the wind came from the sea, the flag must be inland somewhere. Search was made in every direction, but to no purpose. Every rock and lodging place was examined, but it had disappeared. Angel was an interested searcher. He really seemed to divine George's mission. At every bush, or rock, or other possible landing place, he would be the first, and peer around, and look up and down, just as he had seen George do.

The quest kept up for over an hour, and, sadly disappointed, he returned with the news of his failure. The Professor took the loss lightly. "I presume it is intended that we should work out our own rescue. After all, I think that is the proper thing to do. If we depend on others we are sure to meet with disappointment and failure. Cheer up, boys; flag or no flag, let us do our duty."

"I don't mind the loss of the flag so much because it prevents us from having a signal, but I hate to think that we lost so much good time in making and putting it up."

The flag alluded to was sixteen feet long, laboriously made out of ramie fiber, which was woven, and then dyed, and it was a hard task to haul the pole, which was over fifty feet long, from the forest ten miles away, to say nothing of the labor required to raise it.

As soon as the thoroughly drenched material at the boathouse could be brought out and dried in the sun, which now came out bright and warm, the work proceeded with renewed vigor. Late that evening the Professor appeared at the rear of the laboratory, and called loudly to the boys.

When they appeared at the laboratory he was laughing immoderately, and Angel stood on one of the tables with a simian grin.

"What is the matter? Has Angel been experimenting again?"

Before the Professor could answer, George caught sight of the flag.

"What! The flag! Where did you get it?"

"Ask Angel."

The boys laughed, and George actually hugged the animal, in his delight. Did Angel know what he had done? Ask those delvers into the mysterious realms of thought, what prompted him to search for and restore the flag? Is that any more remarkable than the recorded tricks of dogs and many other animals?

You know just how boys can laugh when they are really happy. Angel imitated that laugh, and he had not been taught to do it, either. It came without teaching.

When the Professor had wiped away some of the tears which had come from the excess of laughter at the imitating efforts of the animal, he said:

"Did it ever occur to you why Angel has always had a solemn look? The facial expression seldom, if ever, changes, and they rarely ever exhibit mirth. You may imagine the condition of those animals, living in the forests, with enemies all about them, and the struggle for existence an everlasting one. They have never known amusing incidents as we understand them. Naturally, the muscles of mobility in the face, which express pleasure, never have been exercised, and those indicating fear and anger unduly developed. Here is Angel, in a new atmosphere, where he sees delight depicted on the countenance, and, gifted as he is, with wonderful powers of imitation, has learned to actually laugh, and to enjoy the scene."

"Well, Professor, as we have one of the guns polished up and completed, wouldn't it be well to make the bullets?"

"For that purpose I suggest that we make the molds out of a metal or alloy which has a higher fusing point than lead."

"What is best for the purpose?"

"We might make an alloy of copper and zinc."

"Oh! You mean brass?"

"Yes; that is readily cast and easily worked."

"But what shape shall we make the bullets?"

"They should be made long, with a pointed forward end."

"Why is a long bullet better than a round or globe-shaped ball?"

"There are several very important reasons. First, momentum is a prime element in a missile. A long one contains double the metal of a spherical one. Second, it can be made so that it will expand when the explosion of the powder takes place."

"In what way does it expand?"

"You have noticed that the rear end of the bullet has a cavity. When the explosion takes place the thin shell at the rear end of the bullet expands, so that it tightly hugs the bore of the gun."

"What is the object of having it do that?"

"To give the ball the benefit of the charge of powder exploded. If it does not fit tightly in the bore, more or less of the powder will pass the ball, and thus the ball loses part of its force."

"What is the object of rifling the gun?"

"The object is to impart to the bullet a spiral motion, as it moves through the air. Metals have not the same density on all sides and this is particularly true of molded balls. As a result, when projected from the gun, the heaviest side has a tendency to divert the ball and make it more or less erratic in its motion, and, therefore, inaccurate. The spiral motion has the effect of minimizing this difficulty. The cavity formed at the rear of the projectile was devised particularly to cause the thin lip of the bullet to be driven into the grooves formed in the gun barrel, and by that means the boring motion was transmitted to the bullet."

"But as we have no means of rifling our guns, there will be no necessity of putting the cavity in the rear end of our bullets."

"We must have the cavity there, by all means."

"What for?"

"Simply because we do not want the bullet to turn around and travel end over end after it leaves the gun."

"How does the cavity prevent this?"

"You have probably forgotten that a body travels through the air with its heaviest end foremost. When a cavity is made it is lighter at that end. Without the cavity, if the forward end is pointed, it will, on leaving the gun, turn around and go through the air with the blunt end foremost."

The molds were made, as directed, of a hard brass composition, and when they were ready to cast them the Professor cautioned against making any castings with the molds in any position except upright, so that any inequality in the density of the metal would not form itself on the side of the cast article.

Fig. 11. The Bullet

Quite a time had now elapsed since the last exploration of the cave beyond Observation Hill. The Professor had spoken about it on several occasions. For some reason he was intensely interested in doing that. In fact, he appeared to be more concerned about that than any other of the unknown things about the island.

The boys could not understand this peculiarity. He had never been questioned on the subject directly, but it was evident he had a reason for this predominating wish to continue the exploration.

George was just as much interested, but, as the sequel will show, for an entirely different reason. Ever restless, and always willing to undertake anything which promised to delve into hidden things, he approached the Professor one day with the suggestion about the cave.

"I think we ought to take one day off and go to the cave."

The Professor was interested at once. "It will not do to attempt it now."

"And why not?"

"I am afraid we could not get in very far, unless we had a boat."

"Then why not use our lifeboat?"

This suggestion met with instant favor.

"True, I had forgotten about that."

It did not take George long to reach Harry with the news that the cave was to be explored by means of the boat. After considering the matter for some time it was decided to put off the trip for several days at least, principally because the late heavy rains had, in all probability, so filled the cave that they might be stopped in their progress before going very far.

It should be stated that when they entered the cave the first time, water was found about two hundred feet from its mouth and that barred their further progress. On the second trip the water had receded, so they could go in six hundred feet before coming to the water's edge. The late rains may have filled the cavities, thus making progress still more difficult.

Harry was carrying forward the boat construction, and by the occasional aid of George was bringing the hull to a completed state. While this was being done, George was at work with the loom, slowly weaving out the fabric for the sails. As the mast had been stepped back over six feet from the prow, it was concluded to make a mainsail and a jib, a small triangular sail which is attached to the forwardly projecting jib-boom. The two sails would afford greater speed than a single sail, and that was one consideration. The other was, that with two sails the mast would not need to be so long, and the dimension of the mainsail could be reduced, and still get the same efficiency.

Fig. 12. The Sea-going Boat

The weaving of a large sail in one piece was impossible, as the loom could turn out goods only thirty inches wide, and as it could be operated by hand power solely, it will be seen that the sails required not only time, but an immense amount of patience. It is no wonder that George was anxious to take a day off at the cave, or anywhere else that afforded a change.

While at work Angel was his constant companion. It is remarkable what a degree of friendship and companionship grew up between the two. In the course of time the weaving process became so familiar to Angel that whenever George would throw the bobbin, containing the weft, through the opening of the woof threads, the animal stood ready to pull the heddles forward, so as to force the last weft thread up against the one previously threaded across.

THE VOYAGE FOR THE BENEFIT OF ANGEL, AND THE DISCOVERY

Within the next week the boat hull was practically completed, and now needed caulking. For this purpose the hemp, which had been found, as previously stated, was broken up, and as much of the woody portions removed as could be taken out, so as to make it available for filling in the crevices between the planking.

The mast was stepped in, and a sufficient quantity of manilla rope twisted for the sails, and also a supply put aboard for other needs. The sails were not yet completed, but they would doubtless be ready by the time the other parts were.

In one of their evening conferences George expressed his concern about the future of Angel.

"For my part I do not want to leave him behind."

"Then why not take him with us?" asked the Professor.

Harry had some doubts on this point, but George was too insistent to brook any thought of leaving him behind.

"I make this suggestion, George: Before the time of sailing it would be advisable for you to make several trips with Angel in the small boat, and see how he behaves. In some respects he would be an acquisition to us."

The boys had not forgotten how the animal, during their various trips, had been of material assistance, nor the times when nutting how Angel understood what they were after, and would climb trees and shower them down, and then gravely help to load them into the wagon; and they remembered the recovery of the flag. Such service was appreciated.

As it was, Angel was invited to take a sail. The lifeboat recovered in South River had been named No. 2, as they insisted on calling their own wrecked vessel No. 1.

No. 2 was launched. A small sail, had been rigged up, and two good oars provided for it. Angel was completely at the command of George, and when he was called and taken down to the landing in front of the boathouse, he went without any hesitancy. But to induce him to enter the boat was another matter.

Suspecting there would be some difficulty, George pulled a small jar of honey from his pocket, and silently began to eat it. Angel's eyes blinked. It was such an unheard of thing for George to do this without extending an invitation to join. He shambled over, but George walked to the boat and sat down in it, not appearing to notice the eager look on the animal's face.

Without further urging he stepped aboard, and George put his arm around him, as Harry, with oar in hand, pushed the boat from the shore. Angel was startled, and tried to get away, but soothing words soon quieted him, and before they reached the mouth of the Cataract he was leaning over the gunwale and playing with the water in the most approved boy-like fashion.

When, however, they had passed the comparatively calm waters in the estuary, and were rounding the cliffs, poor Angel forgot his sport, and sat as one paralyzed, gazing at the sight of the waves beating against the shore line. George went up to him, and spoke encouragingly, and it was fully a half hour before he was restored to his usual calm. Then, apparently, he noticed for the first time the peculiar rocking motion of the vessel. Every time it swayed to the right or to the left he would give that peculiar chuckle which always indicated delight.

They went around the point to the east, and passed down the coast in a southerly direction, going as far as the cape north and east of the mouth of South River.

"Steer for the shore, George; steer for the shore; what is that to the right?" said Harry, pointing to the beach.

"It looks like a boat, sure enough."

As the wind was coming directly from the shore they had to depend on the oars to bring the vessel around, and as they came in could distinctly make out the side of a boat lying among debris, in an inclined position, against a rather steep beach.

"It is our boat, Harry." The moment their vessel came alongside, Angel jumped off and leaped over to the boat on the shore. Evidently he also had recognized it.

"Well, isn't this a find?"

"How long do you suppose this has been here? I am glad we gave Angel an outing."

"Shall we take it with us?"

"Yes; if we have to carry it overland," was Harry's reply.

"Let us float it."

It was not much of a task to do this, and with a short rope it was hitched to the stern of No. 2. Angel remained in the recovered boat, and when No. 2 was pushed from the shore, and the sail set, its movement did not seem to perturb him in the least, but when the oscillations again began to be perceptible, he commenced to gurgle, and George knew they had a good sailor to take with them.

The sail took a little over three hours, and as they passed up the Cataract River, and approached their home, the boys set up a welcoming shriek, in imitation of incoming steamers, which so delighted Angel that he scampered in a delirium of joy from one end of the craft to the other. It is doubtful whether he had ever in his short life had such a glorious time, and that he remembered it his subsequent history furnishes the best evidence.

The Professor was just as much delighted as the boys at the sight of their first marine production, which had gotten away from them and stranded them on the cliffs three months before. "I am sorry now that you named the other boats, because this is really No. 1."

"Never mind; this is good enough to be No. 3. Just look at our navy!"

"Where did you find it?"

"Near the point, south of the bay."

"Then it must have been washed there during the late storms, because I do not think it is possible that it could have gone there at the time it escaped you, as the wind was blowing directly to the west at that time."

The boys now remembered the circumstance, and as they recalled the condition of the driftwood around it when they found it on the beach, it was plain that the storm had been their friend in this case.

"Have you been using oars on the boat?" was the Professor's inquiry, as he bent over the side and examined the notches which were made for the oars.

"No; why do you ask?"

"This boat has been used by some one, and not very long ago, at that. Notice how the forward sides of these notches are worn. It also seems that civilized people have been using the boat."

The information was so startling that neither of the boys could answer for a moment. Did they have another mystery to contend with?

But George was alert on the questioning end of any proposition. "Do you really think white people have had the boat? I do not see anything that would make you think so."

"If they were savages they wouldn't use the oarlocks or notches, as they row free-hand, almost without exception; but get a white man in a boat, and the first thing he looks for is a place to put his oars in. This incident in itself shows one of the distinguishing features between the civilized and the uncivilized people."

"In what way is one civilized and the other not?"

"I did not say one was civilized and the other uncivilized. The most wonderful thing in the advancement of the human race from a state of savagery to civilization, was the discovery and utilization of a fulcrum. Whenever man, in an advanced state, undertakes to do anything, he uses a fulcrum of some kind."

"In what way is it so useful?"

"Primarily, in the form of a wedge, a pulley, a wheel and axle, an inclined plane, a screw or a lever. All these forms do the same thing as the simple lever; and what sort of mechanism could be made without some of these elements? The row-lock is simply the fulcrum for the oar, is it not? When Archimedes discovered the principles of the lever, he was so excited that he declared he could move the earth if he could find a fulcrum."

A careful examination of the notched gunwale showed conclusively that it had been used to a considerable extent. George sat and pondered over this. "I am sure we never used the boat enough with the oars to wear it in this way. Had you examined this when you said that the boat had not been long at the point where we found it?"

"No," answered the Professor; "I simply remembered that on the day you lost it the wind was blowing to the west, and as you found it to the east of the cliffs, I inferred it must have been carried around since that time."

"It is evident then that the people who used this boat live to the west of us?"

"That is my only conclusion."

"Then you think the fire in the forest, and the light which we saw that night beyond the West River, were made by those people?"

"I am sure the fire we saw was made by savages, but I am not so certain about the lights having been made by them."

Harry looked at the Professor, and then at George, and slowly shook his head. "Wasn't it lucky we didn't meet them when we made our trip to the river?"

That evening the inevitable subject of their forthcoming voyage was again discussed, and to the surprise of the boys, the Professor urged delay. His reasons were expressed as follows:

"While we have had some very severe storms of the kind which may be expected, we are not sure that the weather is yet fully settled. That is the only reason I urge delay. If, on the other hand, we should decide to take an overland journey, we could set out at once."

Harry was opposed to taking another trip by land. "We have really found out more by the water route than going by land. For that reason it would be well for us to make at least one adventure by sea."

These arguments prevailed in the minds of all, and while it would take some time before all preparations could be made, all were happy at the thought that when they did undertake the journey something definite would be learned to clear up a few of the mysteries of Wonder Island.

The Professor did find some samples of tourmaline, in a finely divided state, and this gem was used to polish the gun barrels, so that all the weapons were finally put into condition where they could be used. During an hour each day all took a part in practicing in a range specially prepared near the workshop. Distances were laid off accurately, and the regulation targets set up. In this manner they became accustomed to loading and firing with facility and a considerable degree of accuracy.

If anyone, not knowing the situation, had dropped in on this scene, he would have considered himself in the midst of a great naval and military camp. At the workshop were the guns, arranged in order; boxes provided for the bullets; small turned out wooden cups for powder, each cup carrying twenty little tubes of bamboo, each with a measured charge of powder, and longer bamboo tubes with percussion caps in them.

It was Harry's brilliant idea to separate each charge of powder and put it into a special tube. This tube had one end closed, and the other provided with a stopper, so that in loading the stopper could be drawn out and held by the teeth while the powder was poured into the gun. The caps were put into a bamboo tube which was just large enough to take the caps, which were dropped in, one after the other, and it can be seen that it would be an easy matter to turn the tube upside down, and thus bring out one cap at a time. This also facilitated the reloading of the gun.

During the practice with the gun one serious defect was found; and that was to remove the cap after each shot. Sometimes the body of the cap would not split, and as a result, a knife or some pointed instrument would have to be employed to dislodge it so as to make room for the new cap.

Harry found a way to remedy this. An opening was made through the stock at one side, and a sliding piece, like a collar, put over the nipple which holds the cap. A finger attached to this collar enabled the marksman to draw back the collar, and this would bring with it the cap, which would then fall out of the side opening.

All these little details may seem to be useless care, but rapidity in loading and firing, with muzzle-loaders, in an engagement might be their salvation.

A test was made of the improved firearm, to determine how fast the gun could be loaded and fired. The test made by Harry showed that it took two seconds, after a shot, to bring down the piece, and draw back the collar to release the cap; three seconds to grasp one of the powder tubes, remove the stopper and bring it to the muzzle of the gun; two seconds to pour in the powder; two seconds to drop the tube in its receptacle and grasp the bullet; two seconds to ram it home, and three seconds to put on the cap and cock the gun for firing. That was nearly a quarter of a minute.

He was very much dissatisfied with this exhibition of speed—or rather of slowness, so after considering the matter for some time, hit upon the plan of reducing the rear end of the bullet, so he could wrap a paper tube on that and tie it. Then he purposed filling the tube with powder, and closing the rear end by folding over the end of the tube. In this way he would entirely overcome the need of the little bamboo tubes for holding the powder.

But no paper was available, nor could he think of anything which could be used as a substitute. In despair he repaired to the Professor.

"What is the difficulty now?" said the Professor, with a smile.

"No difficulty, particularly, but I wish we could have paper, or something like it. I want to make cartridges."

"I thought you had all that arranged for?"

"So I did, but it takes me a quarter of a minute to load, and I must do better than that."

He mused a while. "We could make paper, and I think we have the facilities at hand for doing it; but it will take quite a time to arrange for it. Aside from that I do not, at this moment, know of anything which will be a fair substitute."

He was chagrined at this failure. But, after all, four shots a minute were not so bad. The perfection of the guns must await their return.

Now, let us go down to the marine works, on the shore below the Cataract. Here were the three vessels lined up side by side, and also the after part of the lifeboat. The shed, which was the boathouse, had nearly all their tools, and besides the bench, was a forge and the primitive blower which the Professor and George had made and set up. Wood, parts of planks, thin boards, of all sorts and description, were scattered about. It looked business-like, and Harry was intensely proud of it.

The sail was completed, and taken down to be bent on the cable. The jib had already been installed in place, and when the sails were hoisted and they walked out from the shore and glanced back to get a full view, the entire Naval Bureau congratulated itself on the magnificent appearance of the fleet, and particularly of the new creation in maritime architecture.

It is not out of place to say that the Professor and George both showered the highest compliments on Harry, for he deserved it. But the officials of the establishment were not the only ones to admire the fine sight. Angel came, and he took it in. It was the finest climbing he had enjoyed in many a day. The Professor took off his hat. "I propose three cheers for our ship."

They were given, and with each cheer the hats circled their heads. This was a new code of procedure to Angel. He couldn't understand it. Without waiting for explanations, he shot down the mast, and landed on shore. It was the most comical proceeding they had ever witnessed on his part, and when he looked at the group, and then at the ship, he said as plainly as though he had uttered it: "What does all this mean?"

When the laughter was over, George proposed three cheers for Angel. The hats came off and the cheers were given. Then the same smile which he had so well learned illuminated his projecting face, and he swung his long arm around as he had seen it done, and another step had been taken in his education.

THE GRUESOME FINDS IN THE CAVE

Another week had thus passed by—seven days of unceasing toil. The Professor again brought up the subject of the cave. The subject did not need any argument. It fell on willing ears.

"How shall we take the boat around?" was the matter which interested George.

"Sail it around, of course," was Harry's view.

Both looked at the Professor. "If we sail it there, which will be an easy matter, how can we haul it up the sides of the cliffs? From my present recollection the mouth of the cave is fully thirty feet or more from the water line. The air pocket is not over eight or ten feet. At any rate, it is much lower."

"Then why not haul it around on the wagon, and lower it down the walls?"

"That seems the most feasible plan."

They now knew what preparations were needed for the exploration. Two lamps had been taken before, and one was lost in the cave. Since that several more had been made, so that three were provided, together with a supply of matches.

When the wagon was ready the Professor brought out several boards, and deposited them in the wagon. The boys looked at the boards inquiringly, as the Professor turned back from the wagon. "Oh, yes, the boards; we want something to write on so that we can chart the cave. We must not be caught as we were the last time."

"But how can we possibly chart the cave when we have only one boat?" And George laughed at the idea of making a plan of the interior by standing at one point.

"You measured the height of the falls without going to the top, if you will remember."

He had forgotten that. But the boat was at last secured in the wagon, and proceeded to the cliffs. It was fortunate that the team could be taken to a point directly over the mouth of the cave, and in a little while the ropes were attached to it and slowly lowered, Harry taking the precaution to follow it down and to dislodge it from the steps which appeared in its path.

The team was then securely hitched, and taking all their implements, such as lamps and boards, together with two of the guns and an ample supply of ammunition, descended to the entrance. The boat was at the mouth, and it was suggested that a preliminary survey of the interior should first be made, in order to ascertain how far the boat would have to be carried before reaching the water.

The lamps were lighted, and the boys led the way. After passing the point, about two hundred feet from the mouth, and at almost the identical spot where the water was found at the first exploration, the water glistened before them. Returning toward the opening a loud beating sound was heard, which at first startled them. It was evidently at the mouth of the cave. It sounded like the beating of a stick against some hard substance.

The nearer they came to daylight, the more distinct were the sounds. As heretofore explained, near the entrance the cave made a turn to the right at an angle, so that when at a distance of fifty feet from the opening it was impossible to see daylight, except what little was diffracted from the angle at the turn.

This angle was reached, and the beating, rather irregular, was plain enough to cause some alarm. The boat was beyond the open mouth and at one side, so that it could not be seen by anyone within the recessed walls.

All stood still, while the beatings continued. Occasionally there would be a cessation, to be repeated again. Whatever it was it was not far away. The Professor whispered: "Get the guns ready; we must take some chances."

Cautiously the company moved forward; the end of the boat first appeared in sight, and as George peered beyond the projecting point of the ledge, he threw up his hands and burst out in laughter. Angel was in the boat, imitating Harry in the building operation. The sudden appearance did not startle him in the least, nor did he stop beating his lullaby, after he noticed the broad smiles that greeted him.

With an eye to every advantage, Harry had attached to the sides of the boat, amidships, two short standards, about three feet high, on top of which two of the lamps were mounted, so they would be out of the way, and thus give them freedom to handle the oars and the weapons, as well as afford them a better light, than if carried by hand. The Professor was much pleased with this arrangement.

The boat was not particularly heavy, but it was a task to drag it over the uneven floor and along the tortuous path which had to be taken by their burden, but when the water was reached they were repaid for the labor by the ease with which they could explore the interior.

Before starting the journey the Professor, as usual, uttered a few words of advice: "One of us must sit in the bow, one at the stern, and the other amidships. The one at the stern must propel the boat, as we cannot row through many of the places, and as the water is not deep, that will not be a difficult task. The ones at the bow and amidships should have the guns, and if there is no objection, I will take my place on the middle seat, where I can best take the observations on the way. The other places you should decide between yourselves."

"I am willing to take the bow, if Harry agrees." Harry sanctioned the arrangement, and when the lamps were securely fastened, Harry pushed the boat forward through the cavern. It did not take long to reach the slight turn which led to the large chamber, which was over one hundred feet long.

On the way to the chamber Harry had an opportunity to measure the depths of the water, and at intervals the Professor would call out for the depths, as he was making notes of the descent formed by the floor to the chamber. The oars gave a pretty fair idea, showing that the floor was only about five feet lower at the chamber than where the boat was launched.

Reaching the chamber Harry was directed to steer it to the right and skirt the wall going to the left, so that every part of it could be examined.