"I think I have found vanilla; or it is something that smells like it, but I did not know that the vanilla was a climber."
"You have found the wild vanilla, the flowers of which have, as you see, disappeared and the bean is the product."
"I have often wondered why it is that we are able to smell or to recognize different odors."
"Smell, like everything else in nature, is produced by vibrations. So is sound, and light, and taste. Each odor has its particular rate of vibration. They resemble very much the notes of a musical instrument, and, as in music, odors can be harmonized, or they may be so mixed together as to produce discord. Some perfumes, when used on the handkerchief, and are about to fade away, have a sickly and disagreeable odor. This is due to the admixture of the wrong or discordant tones. Thus, heliotrope, vanilla, orange blossom and almond blend together; citron, lemon, vervain and orange peel belong together, but they produce a stronger impression on the sense of smell, and are of a higher octave; and so with a still higher class, as patchouly, sandal-wood and vitavert."
"But what is it in the flowers or essences which make them smell as they do?"
"Carbon, hydrogen and oxygen. It is one of the most remarkable things in nature that many of the odors in plants are formed by the combination of only carbon and hydrogen, and the wonderful thing about it is, that while turpentine is composed of 88 parts of carbon and 12 parts of hydrogen, the odors of oils of lemon, orange and juniper and rosemary have the exact proportions of those elements."
It was one of the duties of the colony to preserve the seeds of different vegetables and grain, because the Professor intended to put out for their use, as soon as spring came, a garden, which would avoid the necessity of constantly putting them on the alert to hunt the different foods. Sometimes it was necessary to go considerable distances to get the various foods. As long as they were on the island it was the part of prudence to act like sensible business men, and prepare for the future.
"We haven't a very big variety of vegetables, and I wish we could find some real good sweet potatoes and peas; and tomatoes would come in handy."
"Of course, variety, or the wish for different kinds, is largely a matter of desire. It is not a necessity."
"But does not the desire for different kinds grow out of the need of man to get the different substances which vegetables have?"
"To a certain extent, yes; but it is a singular thing that the world over there seems to be a natural instinct to combine two or three vegetables, and those vegetables, although they may be different in different countries, make chemical combinations, when eaten, which are almost identically similar. Thus, the Irishman mixes cabbages with his potatoes; the Englishman bacon with his beans, and the Italian rich cheese with macaroni."
One morning the boys were surprised to find a startling increase in their herd of yaks. When the Professor arose and went out for his regular morning stroll he noticed the unusual number, and was not slow in informing the boys.
"I suppose," said the Professor, "that they are coming to board with us for the season."
"Well, I am going to inform them, in a not very polite way, that we don't need company."
He was off with a club, Harry following.
"Look at that immense fellow. Wouldn't he make good sole leather? What is that on his side; that funny patch?"
Harry called to the Professor. "Did you see the peculiar mark on the side of the big bull?"
The Professor was on hand at once. "That is certainly a mark of some kind. See if you can get near enough to ascertain just what it is."
George, who had been so anxious to get rid of them, was now just as eager to hold them. The bull was a magnificent specimen. Like all this species he was a dark red, and had immense horns. All yaks, male and female, have horns, and the Texas steer has no horns to compare with the yaks in size and gracefulness of curve.
As George advanced there was no action on the part of the herd to scatter. Their own stock took no notice as he walked among them, and this, in all probability, gave the wild herd confidence. The bull paid no attention, until George was within twenty-five feet, when, with a deep-voiced roar and an ominous lowering and shaking of his shaggy head, made a beeline for him. The Professor called out, and he and Harry both sprang forward to aid him, but the bull's rush was a fierce one, and as we have previously stated, they are very active creatures. George saw his peril, and now realized that he could not possibly reach a place of safety, so he sprang behind one of the cows, and from that point sought to find a way through the herd. The warning voice of the bull, and his mad rush, excited the entire herd, which started a stampede.
In the meantime they had not noticed the presence of their own bull, which was a fine animal, and was now thoroughly domesticated. The Professor was the first to notice the appearance of their bull, who, it seems, had been relegated to the background when their neighbors came to town for their holiday.
Apollo was Harry's name for the bull, and when George got mixed up in the herd, the strange bull made his charge and emitted the challenging bellow, the scene was a truly terrific one. George was carried along with the rush, and his only danger now was to escape being trampled under foot.
Harry stopped suddenly: "Look at Apollo!" He was making a charge down into the herd, and headed straight for the big bull.
"I thought it strange that we didn't hear our herd give them a welcome during the night."
"Welcome! what do you mean?"
"It is singular that Apollo didn't dispute the governorship of the herd when the new arrivals came, as that is one of the customs. One of them must be master."
"Just look at him! Good old Apollo!"
At that moment Apollo was within ten feet of the wild bull. He did not cease his onslaught. The wild animal saw his enemy attacking him from the right quarter, but his rush had been so impetuous that when Apollo struck him he rolled over, one of his large horns striking the earth and serving as a fulcrumed lever to turn him around in his path. He was up in an instant, and now began the battle for mastery.
"Get the guns, Harry; get the guns," and this was a sufficient reminder that neither of them had a weapon.
Harry bounded over to the house, and within a minute was back with them. In the meantime, where was George? He did not need to be told that he must run for his life, and was wise enough to seek the security among the cows, but he could not foresee a stampede. It was fortunate that the big bull was behind the herd when the stampede began, and it was lucky that there was plenty of room for the animals, or he surely would have been trampled to death. Naturally, the noise of the rushing animals drowned the roar of the fighting bulls, but the stampeded yaks gradually checked themselves, and George was the most surprised individual imaginable when he found the bull was not behind them.
And now another curious thing happened. They had run fully a quarter of a mile, and when the running stopped, the yaks leisurely turned around and slowly walked back. The movement seemed to be a concerted one. George accompanied them. He didn't know what else to do.
When Apollo and the bull locked horns, after the latter had again gained his feet, his tremendous bulk pushed Apollo back, at the first onset; but they noticed a peculiar tactic on the part of Apollo. The latter at each forward plunge twisted his head, first to the right, and then to the left, as though he was boring his way in. This was an astonishing thing to the stranger. This was done by Apollo over and over again, and now, every time they met, and the twisting motion was repeated, his enemy would be thrown back on his haunches.
For a period of twenty minutes the combat continued. Back and forth they ranged. Harry, although intensely excited, wanted to give the bull a shot, but the Professor restrained him. He felt that the youth of Apollo was enough to overbalance the strength of his enemy.
"No, Harry, when they get through with this battle the big fellow will not cause us any more trouble, and we need him."
The herd of cows came up and remained standing at a respectable distance. They seemed instinctively to know that the question of kingship was being decided. It was entirely immaterial to them who won. George did not wait with the herd. He saw the combat, and beyond the Professor and Harry.
"Well, you did kick up a fuss, didn't you?" said Harry.
"Apollo's got him; he'll lick him sure. See that lunge? My, what a shaking he gave him that time!" George was a dancing Dervish by this time. Then noticing the guns for the first time, seized one of them. "I'll finish him."
"No, no, George," was Harry's reply, as he grasped the gun. "The Professor is right; Apollo will finish him."
There was now no question of the fighting ability of Apollo, and of his youth and vigor, and he knew it. His antagonist did not rush any more. Apollo did that; the bull's main business now was to keep out of Apollo's way.
He had been whipped, and he knew it. He turned and fled. Did he go toward the cows? Not at all; but in the opposite direction. Instinct told him that if he had gone toward the cows it would have meant another fight. To leave them was the bovine manner of saying, "Well, then, take them."
The big bull did not go far. His head hung low, and the heaving flanks showed he was tired. But Apollo's head was high in the air. Dejection on one side and absolute mastery on the other were as plainly exhibited in the manners of the animals as though it had been written out and proclaimed.
"What will he do if I go up to him now?"
"The fight is all out of him."
This was true. He exhibited no alarm when they approached, and when they walked around to get a view of his other side, the mark plainly showed the following brand: "M—V."
"That is undoubtedly the brand of some person who captured the animal when young."
"How old do you suppose he is?"
"It is difficult to fix his age with any certainty, but I do not think he is over ten."
"What do you suppose the brand means!"
"It is some arbitrary term, the initials of a person, or it may be intended to designate something. Branding is a very common way of marking cattle, so as to indicate ownership; nearly all savage tribes have a habit of branding, or tattooing; and sailors also. Various civilized countries in the past have branded criminals as a means of identifying them."
They now had an opportunity of taking an inventory of their stock. The original herd comprised Apollo, six cows and four calves, or half-grown cattle. The new acquisition brought the count up to twenty-six cows and twenty young animals. The vanquished bull was very meek from that time forward, and the surprising thing was that Apollo was thereafter the same quiet, unobtrusive animal he had been before.
But there was work to do in the factory. Harry was now engaged in building an iron lathe for their further work. A drilling machine was his next tool, and as the weeks passed the boys devoted much of their time to making such articles of machinery as could be used advantageously to turn out the simple products which future needs might demand.
The leather vats were examined and the skins found in excellent condition. These were then taken out, and grease and oil worked into them until they were pliable. The thick parts of the hides had been previously cut out, so that they could be used for the soles of contemplated boots and shoes, which they soon hoped to turn out.
Every morning the yaks would leave the enclosure and start out on trips to the feeding grounds, and sometimes Harry or George would follow them and hunt for game. On one occasion, while Harry was on the opposite hill, George saw the flash of Harry's gun, and almost immediately thereafter heard the report. This was the first time the difference between the flash and the noise attracted his attention.
"Will you tell me why I saw Harry's fire before the sound reached me?"
"Did you say 'sound' or 'noise'?"
George looked at the Professor quizzically. "Is there any difference between sound and noise?"
"Technically, there is a difference, although in common practice one word is used for the other without discriminating. Sound means a succession of vibrations produced in their regular order, like music, whereas noise is a disorganized vibration. For instance, falling water, like our cataract here, is sound, but the report of George's gun was a noise."
"I can see the difference. Would a wagon going rapidly over a pavement be a noise or a sound?"
"It would be a noise if the pavement should be irregular, but if the pavement is regular and the vibrations or beats are uniform, it is then called a sound. But you wanted to know why you saw the shot before you heard it. Simply because sound does not travel as fast as light. Sound moves 1,040 feet in a second, and light over 186,000 miles a second, which is about 850,000 times faster than sound."
"Do soft and light sounds travel at the same speed?"
"Theoretically, yes; but numerous experiments have been made, and many of them go to show that a loud noise really travels faster than a soft noise."
"What is the cause of that?"
"It is attributed to the belief that a loud noise causes greater wave motions, although the sound waves may be the same lengths in both cases. Or, it might be said that loud noises have greater strength."
"When we were going to New York in the cars, a train was coming toward us, and the engineer on that train blew his whistle when he was off quite a distance, and kept it up until long after he had passed us. I noticed that when the whistle started the sound had a very low pitch, which kept increasing to a higher and higher pitch until the train passed; what was the cause of that?"
"As the sound waves are uniform movements, and are at regular intervals, the vibratory action of the whistle, in case the trains were at rest, would all be the same distance apart; but as the two trains were coming together two things happened. At each moment your ear came nearer the whistle, and the distance through which the sound had to travel decreased. This made increasingly shorter waves, and not long, regular waves, as when at rest. Short waves make a high pitch, and long waves low pitch. After you passed the train the waves began to get longer, but they increased in length more rapidly than when you were approaching each other, so that if the whistle kept on blowing the waves would finally get to be so long and so far below their original pitch that the sound would cease.
"A little sketch will show this. (Figure 23.) The line A is the pitch of the whistle; B its pitch when you first heard it; C shows the point where you passed the whistle, and D shows how low the pitch was when it died away."
During the nine months' life on the island all had the best of health. The Professor grew strong, and he declared that his constitution was more robust than it had been for years. They lived in the open much of the time; their fare was plain and mostly devoid of sweets; the store of honey which had been several times replenished, was the stock article in the absence of sugar.
It was, therefore, a matter of surprise that Harry should complain of having a tired and uncomfortable feeling, and would frequently lie down during the day while in the workshop. The Professor was always at his side during these periods, and while he had no instruments to enable him to determine whether there was a high fever present, the flushed face of his patient showed unmistakable symptoms.
"Do you think he has a very severe fever?" was George's inquiry, as the Professor left Harry.
"It seems so, and in order to determine whether there is any change we must at once set to work making a thermometer."
"We have neither mercury nor glass, and even if we had, how can we make a tube for it?"
"That being the case, we must make a substitute for both."
"But we must have something which will expand."
"We can use iron for that. Get a piece of small steel bar, say two inches long, and bend it in the form of a C. In the meantime I will make a base to hold the thermometer."
"For your guidance I make a drawing (Figure 24), in which A is the base, about five inches long, three inches at its widest end, and an inch wide at the narrow end. This should be made of a thin piece of hard wood. Bore a small hole in each end of the C-shaped piece. The next thing is to make a pointer (B) nearly as long as the base, pointed at one end, and provided with two holes at the other. The pointer is attached to the base by a pin (D). One end of the C-shaped piece of metal is then hinged to the other hole (E), and the other end of the C-shaped piece is hinged, as at F, to the base. You will now see that if the ends of the C-shaped piece spread apart the least bit the long end of the pointer will swing over to the other side of the base."
"Do you intend to make the thermometer show the exact degrees of heat we really have?"
"Yes; as nearly as possible."
"Why can't we make it exact!"
"For the reason that to make what is called the Fahrenheit scale we should have freezing weather. The scale adopted by Fahrenheit was an arbitrary one. He determined it in this way: The temperature of his body was taken as one point in the scale. For zero he took the lowest temperature observed by him in the year 1709. As the temperature of his body was 86 he made a scale with 86 degrees on it, and then when he observed ice melting in water he put his thermometer in and found it registered at 32 degrees. It was not a very scientific way of doing it, but it answered the purpose, as, of course, temperature is merely a relative thing."
"But isn't there another scale to measure heat by?"
"The Centigrade method is on a more scientific basis. It is determined by taking the freezing and the boiling points of water, and dividing the scale into 100 degrees between those points."
It required the work of several hours to make the device as here shown, so that the tension of the C-shaped piece would hold the point to one side. The temperature of the atmosphere was about 65, as nearly as the Professor could judge, but when the C-shaped piece was held in the palm of the hand, the pointer moved to the lower edge of the base piece, and a mark of 80 was put there as the starting point. As they had no immediate use for a scale beyond 110 degrees, the end of the base was marked off, as you see in regular divisions.
The C-shaped piece was put under the tongue or in the armpit, so that the temperature of Harry could be determined, and it registered 102 degrees. It might be that Harry's temperature was really much higher, as the thermometer, for the reasons stated, was not accurate.
"I wish you would test the thermometer, George, so we can pretty well determine, within a range of two or three degrees, how nearly right we are."
George's temperature was found to register 98, whereas the Professor's was only 90. He explained that the temperature of youth is normally greater than old age, but it was remarkably close to the average normal temperature of two healthy persons.
"The advantage of the instrument now is to enable us to ascertain whether Harry's temperature will increase or decrease."
"Is there no other way in which we can find out about a fever?"
"When the fever comes on the pulse is usually quickened, as well as the breathing; the bowels are apt to be constipated; and thirst, loss of appetite, headache, and vague pains are felt. When the temperature goes beyond 105 it is very dangerous, and it is for this reason that physicians want to know the temperature."
"I am anxious to know why that C-shaped piece should try to straighten itself out when heat is applied to it?"
"When you bent the metal piece of which it is made you crowded the metal on the inside of the piece together, and also stretched the metal on the outside of the bend. As the application of heat expands the metal, the contracted particles of the metal on the inside of the piece pushed against each other with greater force than those on the outside, and the bar tried to straighten itself out again."
"I have noticed that if a hose is coiled up and water is forced through under pressure it will straighten out the hose. Is that also the case with the hose?"
"To a certain extent only. Another principle comes into play in that case. Water under pressure acts as a solid, and has a tendency to move along the shortest route or in the most direct way. If, therefore, there is a crook in the pipe the water tries to straighten it out. Steam gauges are made of flattened spirally coiled tubes. One end of the tube is open and the other has an inlet for the steam. The dial finger has a connection with the moving end, and by that means pressure is indicated."
The next morning Harry's temperature was fully one degree higher than the previous day, and the Professor advised that it would be necessary to administer some fever medicine.
"Last week you found several samples of the gentian flower. It is a first-class fever medicine and tonic. Do you think you could distinguish it by its large blue-colored, fringed flowers?"
"I know what you mean; it has one central stalk, with big leaves at the bottom which gradually grow smaller, and in which the stem seems to go up through the flowers."
"That describes it exactly. Get some of the roots, and peel them, then scrape a quantity, so we can give some to Harry."
This is a simple remedy, in the absence of regular fever medicines which were not available to them.
To their great relief the fever abated before morning, and by persistently taking the gentian tonic Harry was soon well again.
This little experience was sufficient notice that in health at least some preparation should be made for illness, which is sure to come to all at most unexpected times. It had also a stimulating effect in more pointedly directing the attention of the boys to the wonders of the vegetable world.
It was now the latter part of June, and the weather was not at all cold. Plenty of rain had fallen, and the Cataract stream had risen so high that their water wheel had been out of commission for several weeks, and Harry's illness or indisposition had somewhat retarded the work in the factory.
"Wouldn't it be a good idea to look up that animal over in the cave?" was George's first suggestion, one morning, shortly after Harry's recovery. "We might put in a little time there, and then go down around the bay on a little tour."
This was agreeable to all, and then George remembered the want of the candles. Zinc had been turned out, as previously told, but no steps had been taken toward making a battery which would be the starting point for an electric lighting system, as Harry and George both hoped for.
"It seems to me," said Harry, "that we ought to explore the coast line to the southeast of us, as we have never been in that direction, and then work our way around to the cliff cave."
Without further words the yaks were yoked up, and taking a hearty luncheon they were off for the east coast, where the bay indented the land. The coast was reached within two hours, a great deal of the time en route being spent in gathering samples of plants, flowers, and fruit, of which some species of trees were filled.
To the right of the place where they struck the sea was a cape which ran out into the sea for fully a quarter of a mile, and to the south of this was the mouth of the South River. As they had definitely planned to go north along the coast line to the cliff rocks, the explorations to the south must be reserved for some future day.
The sea front showed delightful stretches of beach, but at intervals small trees and bushes grew close to the ocean on the elevated spurs which broke up the otherwise smooth beach line.
The clam, as a source of food supply, had practically been neglected, because it was quite a distance from the Cataract home to the beach, and principally for the reason that other foods were so plentiful. Harry wanted some clams, and with one of their bags the beach was scoured for fully a mile, until he gathered a staggering load.
As he reached one of the little knolls which broke off abruptly close to the sea, Harry dropped the bag and ran to the brush. The Professor looked on in wonder. When Harry disappeared in the bush George and the Professor both hurried forward. Harry reappeared in an instant.
"What do you think I have found?"
"Another cave?" queried George, without stopping.
"No; our boat."
There, perched less than five feet above the level of the ocean, was the boat which they had left at the foot of the falls in the South River, fully three months before. One of the puzzling mysteries was solved.
It was some labor to dislodge the boat from its position between the cleft branches of shrubbery which also held other debris, and furthermore the boat was full of all sorts of rubbish. This was laboriously removed.
"You will remember I stated at the time of the disappearance the most likely explanation would be that high water coming on suddenly would wrench the boat from its fastenings, and——"
The Professor got no further; he suddenly stopped and glanced to the forward end of the boat. "Who tied on that rope? It really does look as though some one has used the boat. That is not one of the oars we made."
"But where are the lockers we had on the boat, in which we put our provisions?"
"They have been removed by some one. This is a rope entirely unlike any we have had, and it is a native, or rather, hand-made article."
"Well, we have struck a greater mystery now than when we lost the boat."
This discovery brought up several other questions which, as it now appeared, might be linked together. The removal of the flag and flagstaff; the "hole" in the hill; the fire in the forest; the branded bull, all indicated that people had, at various times, visited the island. But the finding of their boat, with the positive evidence furnished by the oar and the rope, was conclusive, and what made it the more interesting was the fact that the island must have had such a visit within two, or at the most, not over three months ago.
Each was too busy to give much time for discussing the probabilities. They had entirely forgotten the cave. It was, by common consent, agreed that the boat must be taken home, and it was finally decided that the boys should pilot it around the point, past the cliffs, and in that way reach the mouth of the Cataract River, where it would always be convenient for cruising purposes.
It was fortunate that the sea was calm when the boys pushed the boat from the shore. It showed signs of leaking here and there, but the Professor assured them that the water would close up the joints before long. The Professor, himself, drove the team to the Cataract, and after unyoking them, followed the course of the river down to its mouth, to await the coming of the boys. He waited there until sundown, but the boys did not appear.
Let us now follow the boys. Lashed in the boat were two oars, as carefully secured as though tied only the day before. At the bow was the rope which the Professor discovered, after he had noticed the one tied around the oars. It will be remembered that the boat had been fitted with a mast and a sail. Those had been removed, as well as the crosspiece and the brace which held them in place. It was, therefore, necessary to row the boat around the point. The distance, as calculated by the Professor, was two miles or more to the cliffs, and fully a mile from the extreme point of the cliff to the mouth of the river.
Shortly after they started on the journey a light wind sprang up, which, however, did not seriously interfere with their progress, but it was sufficient to induce them to take a course outside of the point, instead of attempting to thread their way inshore between the rocks.
When abreast of the extreme point George's attention was directed toward an object on the cliff.
"What is that up on the rocks?"
Harry stopped rowing, and looked in the direction of George's extended arm. "It looks like a boat. Let us go in."
The boat was pointed to the shore, and drawn up, and in their eagerness, each tried to gain the elevation first. A miscalculation was made, in the attempt to reach the object, which was not visible from their location, and they were compelled to thread their way down again and go around the broken side of the cliff walls.
As they were about to ascend Harry called out: "Look at the boat, George! Run quick, it is adrift!" The wind had quickened, and they realized their carelessness in securing it at the landing place, and before George, who was lower down, could reach the water's edge, it was washed around the point of the rock, out of his reach.
Here was a dilemma. The boat lost, and no means to reach the mainland without swimming. The place where they landed was less than five hundred feet from the spot where they were cast ashore months before. Innumerable large rocks, detached from each other, formed the immense tier of sentinels for this part of the coast, and Harry's trip across, when he had the benefit of the life-preserver, was an entirely different thing from their present condition.
To add to the perplexity of the situation, George was not a good swimmer, and he doubted his ability to make the trip across the channels between the rocks which separated them from the mainland.
"Why not try to find the object we saw while we were out at sea?"
"Good idea. But I would like to know how we are going to get up?"
"Wasn't that a silly trick, to be so careless about our boat. What will the Professor say?"
At last, after repeated trials, they found a way which led them up the craggy sides, to the object they had seen.
"It is our life-boat," was Harry's excited cry. "That is, what is left of it."
We have previously detailed how, when they struck the rock, on that eventful day, months before, the boat had apparently been broken in two, and they saw only the stern of the boat held within a saddle of the rock; and how, at the next great wave, even that portion had disappeared. Here was the battered and broken-up part that remained.
"Do you think this part would float?"
"I suppose it would, but how can we get it down?"
They sat down, not discouraged, but annoyed at their own stupidity and carelessness. Night was approaching, and sitting down would not remedy matters. It was low tide, and the waters had receded, so that the wrecked boat was now fully twenty-five feet from the water. It was held within a wedge in the rocks, tilted up, and it was too heavy for them to lift. If they could possibly dislodge it, so as to push it over the edge, it would probably be crushed to pieces in tumbling down.
Even such a calamity would be better than remaining there, and it was decided to be the only course now available. Every vestige of the locker, or seats, or other appendages of the boat were swept away. The bare shell of the stern portion remained.
It was now growing dark, and when the wreck was finally dislodged and fell down with a crash the boys made their way down the sides very cautiously. It was now but the work of moments to get afloat. The boat originally had water-tight compartments, but these were now utterly useless as a means of sustaining the vessel; nevertheless, it was a means by which they might reach land, as they felt sure it would not sink. Here was another difficulty. They had neither oar nor other means of propelling it to shore. After considerable effort a portion of the side of the boat was broken off, and tired and worn with the effort and excitement they steered the craft shoreward. To do so was not an easy task, as the wind had increased, and the waves beat stronger, but this had no terror for them after all their previous experiences.
When the shore was reached Harry had one positive observation to make: "I am going to see that this boat is so fixed that it won't get away."
George looked around, and in spite of their trials, could not help laughing at Harry. "I should like to know how you are going to do it. I don't see any ropes around here, and trying to pull it up this steep beach wall will not be an easy job."
"Then we have got to take it where we can pull it up. I am tired of losing things in this way. We'll have a nice story to tell the Professor."
The Professor was by this time thoroughly alarmed, as well he might be, for it was past eight o'clock that evening when, going down from Observation Hill, he heard voices in the distance, and recognized the boys. He called to them, and you may be sure that their answering voices were joyful sounds.
When the boys appeared both began excitedly to detail their experiences, getting details of the story involved without any sequence just as we might expect an exciting, mixed-up recital of this kind to be under the circumstances.
"You lost your boat and found the other one. You are having enough experiences to fill a book."
You may be sure that the interesting topic of conversation that night had relation to the events of the day. All previous experiences were insignificant now in comparison. Every phase of the question was discussed, and a solution sought.
The Professor did not attempt to conceal his doubts. "I have a theory that we are or may be near some other island, possibly inhabited by white or civilized people. It is likely that people from those islands may visit this place at intervals, and that the boat which we left at the falls was really washed down to the sea and found by some of them."
"If that is the case, why should it be washed up on shore, as it was? They, no doubt, used the boat, as the oars and rope showed. But I can't possibly make out the meaning of its being in the driftwood."
"That boat we made is a hoodoo," was Harry's conclusion. "Twice lost is enough for me."
"Well, I would take a sail in it the next day if we could only find it."
"I am interested in it," observed the Professor, "not so much for the purposes of its use, as to enable us to find out something more about it, and how it came to be there. If it had occurred to me that we should lose it so soon you may be sure I should have made a more careful examination of it when we had it. But it is too late now."
Harry's solution was the one most acceptable. "Let us make another boat, and with that we can carry on our investigations more satisfactorily."
"Harry is right. A good vessel will be a measure of safety, in the event we should be attacked by savages, and it will at least enable us to visit the shore line of our continent."
The sanitary arrangements of their kitchen had been for some time very unsatisfactory, and somewhat cramped, and the Professor thought it would be wise, for their comfort and health, to cleanse it thoroughly.
"I am inclined to think that Harry's sickness was caused by the condition of the kitchen. We are apt to overlook these things in the multiplicity of our work."
"What is the best way to clean it, by washing?"
"That is necessary, of course, but it is impossible, even by a liberal use of hot water and soap, to remove many of the poisonous germs. Some good disinfectant should be used."
"Have we anything which could be used for the purpose?"
"There is nothing better than charcoal. Common wood charcoal has the capacity of purifying and rendering odorless almost all impurities."
"In what way does charcoal do this?"
"When charcoal is crushed up finely its remarkable porosity enables it to absorb an enormous quantity of gases, and when so absorbed it condenses them, in which condition they are harmless, or they are retained in the charcoal."
"But how about the impure liquids?"
"Its affinity for sour and stinking liquids is so great that two tablespoonfuls of charcoal will purify a pint of the foulest sewage; it will also, in that quantity, absorb 100 cubic inches of gaseous ammonia."
"Have we anything else that can be used?"
"The sulphur that is in the samples of copper ore, if burned, will make a sulphurous acid gas, and while it must be carefully used, on account of its noxious and offensive odor, is a most powerful germicide. Or if we take some of the green acid of the copper, and make a liquid of it, and then pour this over common salt we are making what is known as muriatic acid. The vapor of this acid will destroy all germs. The objection to this, however, is, that it has an odor which is worse than the impure or unhealthful gases. In the last samples of ore we brought home, you may have noticed a very black lot of stuff. That was manganese. If we take the muriatic acid, which I have just referred to, and pour it over the manganese, we can make the most powerful agent of all, namely, chlorine."
"Chlorine is used for bleaching, isn't it?"
"That is its great use in the arts; but as a purifier it has no equal. It will decompose every gaseous compound and evil-smelling gas which escapes from decayed animal or vegetable matter."
Harry did not let the Professor forget the matter of the primary electric battery which he had been making preparations for, and after they had gone over the sanitary features of their kitchen, he was anxious to make a start. George was equally insistent, because the question of a better light was ever uppermost in his mind.
"Then here goes for the primary battery. We haven't any glass, nor have we found any rubber lying around, so we can make cells out of them, so what shall we use?" was the Professor's first inquiry.
"Why not use some of these iron pots we made?"
"I am afraid iron would not last very long, with sulphuric acid in them. We should use some non-conductor of electricity."
"What do you mean by non-conductor?"
"That quality in a material which will not allow electricity to pass."
"Then why can't we use clay? Will that conduct electricity?"
"That is just the thing. Isn't it wonderful what a friend common clay has been to us since we have been on this island!"
"I think we ought to erect a monument to Monsieur Clay?"
"It would be a fitting thing to do, because at the end we are all bound to go back to him."
"I believe you said, Professor, that we should have to grind up the coke and then mix it up and make plates out of it?"
"Yes; we can use either carbon or copper for the negative plates."
"What are the other plates?"
"The positive. That is what I wanted the zinc for, which we made several weeks ago."
"Why should we have positive and negative plates in a battery?"
"Everything must have an opposite. If there is an up there must be a down; there would be no darkness without light; no heat without cold; no strength without weakness, and no joy without sorrow. Like all these things, the electric current flows from one to the other."
"But in electricity the current flows only one way, does it not?"
"In the primary battery that is the case; but when electricity is generated and sent over the wires, the natural current flows in both directions—that is, it goes in one direction as much as in the other."
"I do not understand what you mean by that."
"The current alternates. What is meant by that is this: For an instant the current flows from the positive to the negative, and the next instant it flows from the negative to the positive, and so on, making the alternate current."
"Then the primary battery we are going to make will be another kind of current?"
"We shall make what is called the direct current which goes in one direction only—that is, within the battery it moves from the positive plate, the zinc, to the copper plate, or negative, and outside of the battery it moves from the negative to the positive plate."
"Why does it do so?"
"In order that you may understand, I shall make a drawing so Harry will not have so much trouble in arranging the parts. So if you will examine the sketch (Figure 25), you will see that the clay cell, which we are to make, has in it the two electrodes, A and B. That is what they are called when they are spoken of together; but the positive one (A), the zinc, is called the anode, and the negative (B), or copper, is called the cathode. You should keep these terms in mind.