The Wonder Island Boys: The Mysteries of the Caverns

The boys looked at the Professor in amazement. They were too much excited and concerned at the new situation to be able to interpret what the sudden disappearance of their team meant.

The Professor turned to the boys: "Are you sure the yaks were tied before we left them?"

"I was particularly careful," answered Harry, "to tie both of them."

"I am pretty sure that both were securely fastened, and they were in that condition when I came back the last time," was George's reply.

To understand the peculiar situation above referred to, it will be necessary to go back and briefly relate some of the remarkable events which had taken place in the lives of the three people concerned in this history.

George Mayfield and Harry Crandall, together with a Professor, were mates on a ship training school, which sailed from New York one year before. A terrific explosion at sea cast them adrift in mid-Pacific Ocean, and after five days of suffering they were cast ashore on an apparently uncharted island, without any food, and entirely devoid of any tools, implements or weapons.

Exercising the knowledge of the Professor, and the ingenuity of the boys, they gradually dug from mother earth and from the rocks and trees the articles necessary to sustain life, and eventually they found different ores from which various implements and weapons were made. They constructed numerous machines, crude, at first, and gradually developed them. They succeeded in capturing yaks, a bovine species of animals, some of which were trained like oxen; wagons were built; a shop constructed; a water wheel installed; a primitive sawmill put up; a primary battery made; articles of clothing woven; felt made; and numerous things of this character originated from material which nature had furnished in its crude state.

While doing all this the desire to explore the island was a predominating one. Four trips into the interior had been made in order to ascertain whether or not it contained any human beings. During those trips numerous evidences were found to show that savages were there, and some indications that civilized people had visited the island.

The peculiar happenings which excited their interest were the mysterious things that occurred at various times, among which the following may be briefly enumerated: The disappearance of a boat, which they built, and which was left at the place where the team was lost; the subsequent finding of the boat among debris on the seashore, having oars and rope in it which were strange to them; the removal of the flagpole and flag which had been erected up on a high point near the ocean, called Observation Hill, and the fire in the forest.

To the foregoing may be added the discovery of a prospecting hole, which had been dug, evidently, by some one in the hope of finding mineral; a yak with a brand on it; wreckage of a boat, which, undoubtedly, belonged to their ill-fated ship; a gruesome skeleton on the seashore; and finally one of the lifeboats of the schoolship and a companion to their own, found on the shore of the stream where they now were.

All these things were sufficient not only to cause alarm, but the greatest consternation on the part of the boys. It must be said, however, that the trials of the boys, under the calm, calculating deportment of the Professor, had done much to make them self-reliant. George, the elder, was of an exceedingly inquisitive turn of mind; he was a theorist, and tried to find out the reason for everything. On the other hand, Harry was practical in all his efforts; he could take the knowledge obtained and profit by it, as the previous volumes show. It was fortunate, therefore, as the Professor put it, that theory and practice were personified in the two boys, who, although companionable, were the exact opposites as types.

The Professor never showed a preference, in any manner, for either. Like the true philosopher he saw the value of the two distinct qualities, the one useless without the other.

When they had fully recovered from their astonishment, George was the first to speak. "They may have broken the fastenings."

The Professor, who had been intently examining the tree to which they were hitched, said: "I can find no evidence of any undue wrench which might show that they had gotten away by their own exertions. Let us see whether we can follow the trail."

The ground was covered with leaves, so that no earth was visible, and the only sort of trail left in a forest, under those conditions, is the slightly depressed tracks which the wheels make. They examined this, noting also the overturned leaves, which are usually left in the wake of cattle.

The latter means seemed to be the only available way in which any trace could be made out, and this they followed. It led directly to the west, and toward the section they were desirous of exploring at the time the present trip was inaugurated.

"How fast do you suppose the team is traveling?"

"Certainly not faster than we are now going. They cannot be hurried very well, as you know, and we should be able to overtake them within an hour or two."

"But what shall we do if we find them in charge of somebody?"

That suggestion brought up at once a very serious question. They had made six pistols, very crude, it is true, but which served admirably as weapons of defense; but the hazardous part of the present situation was that only the Professor had one of the pistols, the others having been left with the team. The only thing which added some comfort was the knowledge that as the pistols required a special hook to enable them to cock the firing plug, and as the Professor had this hook, those who took the team might not be able to use the weapons against them.

At this place it might be well to refer to Red Angel. Nearly nine months before, on one of their trips, a baby orang-outan had been captured, and the boys educated him, as best they could, and he really developed many reasonable instincts. It was Red Angel who left the wagon and followed them down the river, and who by his peculiar actions attracted attention to their missing team.

"We owe something to Angel for his cuteness in coming for us," said Harry.

The orang progressed rapidly, swinging, as he did, from tree to tree on the route, and when no trees were in sight, would shamble along in a peculiar way, as it is difficult for them to walk erect. Their feet are not adapted to promote a graceful gait.

"The track seems to be lost," said the Professor. "I cannot make it out, either from the leaves or the depression. However, it appears best to follow this course."

Without stopping they proceeded in the same general direction. Red Angel, who up to this time had followed the route taken by the party, now turned to the right, and when George called, refused to return. As George walked toward him, he kept advancing to the right, and could not be induced to come back.

"Probably we should follow him," was the Professor's conclusion.

It was evident from Angel's antics that the change in the course delighted him.

George, who was ahead, soon stopped, and shouted back, gleefully. "Here are the tracks! Good fellow, come here!"

Angel understood this. He had actually sensed the direction taken by the missing team, for here were the tracks. The only thing that grieved George was the absence of the honey pot. Angel's weakness was honey, and that was now with the team.

Suddenly Angel, who was now in one of the large trees which grew all along the course, began an excitable chatter, and vigorously jumped from one limb to the next, and George, who knew his antics pretty well by this time, stopped and prepared himself for some new and unexpected development in this remarkable journey. Angel, on the other hand, started off through the trees with wonderful agility, and it was all the boys could do to follow.

There, ahead of them, was the wagon perched against a tree, one of the front wheels and an axle broken, and the tongue wrenched off; but the yaks had disappeared. It is singular that the team had gone thus far without meeting an obstruction. As it was, one wheel had locked with a tree, and the yaks, by their tremendous power, had broken the parts mentioned and gone on.

Before the wagon was reached, however, numbers of articles were found scattered along the trail, which were gathered up.

The finding of the wagon was an intense relief. Their minds had been perturbed with this occurrence, as never before, and they had met numerous thrilling episodes before.

"Something must have frightened the yaks, and they were going at a much greater speed than at a walk when they collided with the tree," observed the Professor.

"Why do you think so?" asked Harry.

"In the first place, the fact that our articles were scattered along the path before they reached the tree; and, secondly, the wagon pole and the wheel were strong enough to hold the yaks against the tree if they had been moving along at their usual gait."

"Well, I am thankful that we have the wagon, even though the yaks are gone," said George, as he crawled into it. He peered out and continued in a surprised tone: "Where do you suppose the pistols are? Did you leave yours in the box, Harry?"

"Yes; on the right side. Yours were there at the time. I saw all of them."

"They are not here now, and it is likely they have been lost with some of the other things." Harry was up in an instant.

"Where is the ammunition?"

"It was all in the bottom of the box."

It did not seem at all likely that the pistols or the ammunition could fall out of the box. It is true other things had fallen along the way, but this seemed to be such an unlikely occurrence that they could scarcely credit it.

The provisions were safe, and you may be sure that Angel was not only petted, but he received a good share of the delicious sweet.

It was now nearing night, and they were fully ten miles from home. Ten miles is not a long tramp, but to travelers like ours, already weary with their trudging and with the excitements of the day, it was concluded to camp in the wagon for the night, and then proceed home early in the morning. To take the wagon would be an impossibility.

They really learned to love the patient yaks. For fully five months they had been daily companions, and were now so well trained that some discouragement was felt at being compelled again to break in others. They had an ample supply of good material in the herd to pick from, but it took time and patience to develop such a team as had been lost.

During the entire night one of the trio kept watch, not so much from a feeling of fear as in the hope the yaks would return during the night; but they were doomed to disappointment. Morning came, but the yaks did not, and after gathering together the most useful belongings, and putting them into convenient bundles for carrying purposes, set out for home.

The first question taken up by the boys after their return was the selection of a pair of young steers for the new team; and the work of making a new pair of yokes was carried forward with energy. They were in the midst of the planting season which had been interrupted when the last journey was undertaken.

Hitherto it had been the custom to devote at least one day each week to hunting, on which occasions they also made trips to such points in the island as had not been previously visited; and it was also a part of their duty to examine the woods and the fields to find new specimens of plants, fruits and flowers; and among the hills and ravines were many kinds of ore, some of which they had been fortunate enough to find on their entry to the island.

The metals thus found were utilized, because they had set up a workshop alongside the sawmill, and in it had a crude lathe adapted to work in wood or iron. It will thus be seen that each tour was for prospecting purposes, to supply their needs, as well as to learn what the island contained.

Each evening it was the habit to have a general discussion concerning the events of the day, or with reference to matters of moment about the work to be done on the morrow.

George was much interested in the planting program. "What kinds of vegetable would it be most advisable to plant in the space we have prepared?"

"One of the important points to consider in the planting of all crops is whether the soil is adapted for it. When the United States were first settled it was a surprising thing that many of the original settlers would go miles inland, exposed to every sort of danger, to find land, when there was plenty nearer the seashore or close to civilization. There was a reason for that which we are only now beginning fully to understand. Plants have a habit of growing in soil adapted for their needs, and it would be an interesting study in going over our island to consider the habits of plants in this respect."

"Is that the reason why different countries have such different kinds of plants?"

"Yes; plants select their soil, and owing to these habits, every variety of soil, in every climate, supports its own vegetable tribes. Of the five thousand flowering plants of central Europe, only three hundred grow on peaty soils, and those are mainly rushes and sedges. In the native forests of northern Europe and America, the unlettered explorer hails with joy the broad-leaved trees glittering in the sun among the pines, as a symptom of good land, which he knows how to cultivate. The rudest peasant in Europe knows that wheat and beans seek clay soils; the northern German knows that rye alone and the potato are best adapted for the blowing sands of that country; the Chinese peasant, that the warm sloping banks of light land are fitted for the tea plant, and stiff, wet, impervious flooded clays for his rice. Even the slaves in the Southern States were aware that open alluvial lands were best suited to cotton; and the degraded slaves of Pernambuco know that the cocoa grows only on the sandy soils of the coast, just the same as in west Africa the oil palms flourish on the moist sea sand that skirts the shore, and the mangroves where muddy shallows are daily deserted by the retiring tide."

"Some time ago you stated in one of our talks that soil was the necessary thing to select in order to propagate, or make good fruit and grain out of the poor or wild kind. Were all our vegetables and grains originally wild?"

"Originally nothing in the way of fruit, flower, grain or garden vegetables was anything but wild and unproductive, or bitter, tasteless or unprofitable. Chemical changes are made in the plant by the soil in which it grows, because it is from the soil that it gets its food. The large and juicy carrot found at home is nothing but the woody spindle of the wild carrot, and I have found several species of it here. Cabbages, cauliflowers, Brussels sprouts and a host of other like vegetables were, in their natural state, poor, woody, bitter stems, and had useless roots. As I have already stated, the wild potato, which we are now cultivating, has, in its original state, a bitter root, as you have discovered."

* * *

Early the following morning Harry sprang out of bed and hurriedly shouted: "What did we do with the lifeboat in South River? Do you remember whether we secured it when Angel came up and let us know about the team?"

The Professor and George were up in an instant. George was the first to answer. "I left it the moment Angel came up."

"I cannot remember," said the Professor, slowly, "but it seems to me, now that I think of it, we left it on the banks, and it wouldn't do to leave it there. You must go for it at once, and bring it down to the bay, even though you cannot bring it around the cliffs."

A hurried breakfast was prepared and the boys started off at an eager pace for the river. They went directly southwest, aiming to strike the river near the falls, and after passing over familiar ground, came within several miles of it, when, in going down one of the sloping descents, saw, in the distance, what appeared to be portion of the yoke which the yaks carried.

They hurried forward, and great was the delight at finding it was really one of those they had made and used for months. It was a gratification to know that the animals were east of the falls, and, probably, sooner or later, would turn up at their home. Only one of the yokes was found, but there was evidence that both of the yaks were freed, since the part of the other yoke was still attached to the part found.

The boys were glad of this, as they had such a friendly feeling for the animals that they could not but feel that to be yoked together in the forest would be a cruelty to them.

"The Professor will be glad to know this," said George. "Look at this part of the yoke, where it has been broken. I have no doubt that this is where they struck the tree where the wagon caught."

* * *

Fig. 1. The Broken Yoke

* * *

"Let us take it with us, by all means," said Harry. An examination of the yoke plainly showed where it had come in contact with bark with considerable force. "What do you suppose caused them to be so frightened as to run away?"

They quickened their steps, and soon reached the river. There, on the shore, was the lifeboat, as they had left it, and it was the work of minutes only to set it adrift, and after depositing the yoke in the bottom, the first task was to supply themselves with a pair of oars.

The first article turned out in the way of tools was a bolo, a heavy cleaver-like blade, used by many primitive tribes. This article was duplicated by them, and always carried on all their expeditions. With this several small trees were cut down, and a pair of oars fashioned for each, and within an hour they were on their way down the stream, and in two hours more had rounded the point of projecting land east of the river mouth.

"Don't let us take any more chances of losing this boat. I am in favor of taking it around, and am willing to risk the tide, whatever it may be."

Harry's suggestion met with favor on the part of George, and when the point was rounded and they were out in the ocean, the tide, although coming in, had no terrors for them, but they boldly plied the oars, and before four o'clock had rounded the cliff point, and steered the craft into the mouth of Cataract River.

The Cataract was a much smaller stream than South River, and it was on the northern side of the island; whereas South River was on the southerly side of the island. Less than a quarter of a mile from the open sea was a cataract, at which their home was located, and the cataract was utilized as the means for producing water power.

Their appearance below the Cataract was hailed with delight by the Professor, and you may be sure that when the boat was finally landed and hauled up on the beach, all of them joined in the congratulations, which was their due.

"Just to think of it. If we had the boat we made, our lifeboat and all the parts of the wreck of the other boat, we would have a pretty respectable navy," was Harry's observation, when they landed. As it was, they now had the wrecked after part of their own lifeboat, and here was the other lying alongside. They knew the history of one of them. Would they soon know why the other should have been found in the interior of the island under such peculiar circumstances?

"And where did you get the yoke?" asked the Professor, as his eye caught sight of it.

"Two miles this side of the falls."

They little knew at this time what an important bearing the finding of this boat would have on their future course, nor could they know how this little incident would be of the greatest value to some of their companions on the ill-fated ship.

They now had possession of a boat which, while it was practically unsinkable, was not of such size as to meet their demands for the intended explorations. They felt that to attempt to circumnavigate the island and take all the chances which a meeting with natives might involve, would necessitate a much larger vessel. To add to the difficulty, all the pistols but one had been lost in the last trip, and to attempt to make explorations without proper weapons would be foolhardy. If they knew one thing, with any degree of certainty, it was that the island contained savages of some description, and provision must be made for every contingency.

Harry took upon himself the task of turning out more of the weapons, and with the experience of the past four months in this line of work, concluded he would attempt a better job than simply making pistols. It was his ambition to make a firearm that would enable them to bag the largest game, and also, at the same time, carry the bullets a greater distance than the short eight-inch barrels could.

To do this it was necessary to provide longer bits, and as the design of the new guns contemplated a barrel at least eighteen inches long, the bits had to be longer, in proportion, and the making of these consumed nearly as much time as the actual drilling out of the barrels.

George and the Professor put in a great deal of time with the new team. Their knowledge of training, in view of the former experience with these animals, was such that within a week they could drive the yaks without much difficulty, although the new team was not by any manner of means as efficient as the lost one.

When the question of the kind of material for the guns came up, Harry was much concerned, as in making the barrels that length would necessarily greatly increase the weight.

"I think it would be better to make an alloy for your purposes," said the Professor, as they were discussing the matter.

"What is an alloy?"

"It is the combination of two or more metals."

"In what way does the alloy make it better than the hardest steel?"

"It is not hardness you want, but toughness. Metals have several properties, which are utilized for various purposes in the arts. Surprising as it may seem, wood has greater resisting power than diamond, and yet the precious stone is the hardest of all substances."

"But if we unite two metals are we not then making a new metal?"

"Not necessarily so. In the case of brass it is true. This is made by uniting two parts of copper and one of zinc. Both copper and zinc in themselves are very soft, and copper cannot well be polished in its pure state. Brass, however, is not only much harder, but is susceptible of a very fine polish."

"Are the alloys of all metals harder than the metals of which they are made?"

"This seems to be a universal law in the compounding of metals. Very few metals are used alone in the various arts and manufactures. For every purpose some combination has been found which makes the product better. Even coins are so alloyed. Silver and gold in the form of money would be entirely too soft, unless alloyed with some hardening metal. Some substances, like arsenic, antimony and bismuth, are too brittle to be used alone. The only metals which can be used alone are aluminum, zinc, iron, tin, copper, lead, mercury, silver, gold and platinum."

"What is bronze, of which all the ancient guns were made?"

"That is a combination of copper and tin. This product was known fully seven hundred years before the Christian era, and was used in the making of guns until superseded by the various steel alloys of our day."

"In what proportions are copper and tin united to make bronze?"

"The proportions vary greatly. Ancient Celtic bronze had 12 parts tin and 88 of copper; Egyptian, 22 tin, 78 copper; Chinese, 20 tin, 80 copper; Roman, 15 tin, 85 copper; and in many specimens lead and zinc were also used. Tin has a capacity to harden almost any metal."

"What is the best metal to harden steel?"

"Manganese, of which you will remember we have some samples; it is the most serviceable, as we have neither nickel nor chromium."

"What amount of that metal should we use to get the best results?"

"About 14 per cent. of manganese has been found the best for such purposes as would be required in gun barrels. There is a curious thing which has been discovered in uniting manganese with steel. It becomes fairly tough if 1 per cent. is used with the steel; if the quantity added is between 1-1/4 and 3-1/2 the strength and ductility decrease; but above that, up to 5 per cent., the steel becomes brittle; above 6-1/2 per cent. it again returns to ductility and toughness and its maximum strength is found at 14 per cent."

During the evenings all took a hand at cutting out the stocks for the guns, and the plans upon which they were constructed will be fully explained and illustrated in the order of the work done.

Meanwhile it must not be supposed that work on the new boat had ceased. Harry's plan, when fully worked out, provided for one twenty feet long and six and a half feet wide amidships.

The drawing (Fig. 2) shows the construction of the hull. As they had no means for doing any fancy bending of the boards, the bottom was made flat, and the sides sloping. The bottom and the sides were made in the following manner: Two stringers (A, A) were first constructed, which were made up of thin pieces nailed together, so they could be bent in the proper shape for the bottom boards, which were laid crosswise and nailed to these stringers.

* * *

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."

* * *

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.

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Fig. 7. The Color Spectrum

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Fig. 8. Reflection Angle

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"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."

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Fig. 9. The Hidden Message

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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.

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