Certainly all flowers once were wild - and all animals, too. There are certain kinds of flowers and animals which men have developed by choosing the kind of thing they wanted and leaving the rest, and so gradually getting such things as the garden rose, the pouter pigeon, and so on.

These are what we call cultivated varieties, but all of them, even the most curious and newest orchid, or pigeon or breed of dog, have been made from wild or natural forms. Even now, if we are careless, our garden plants will return sometimes more or less completely to their natural state, and so will domestic animals.

Plant breeders can do wonderful things in the way of developing new varieties, and it is now possible for them to secure patents on their new specimens. One of the most interesting patented flowers is the super-double nasturtium, holding flower patent 141. The ordinary single nasturtium has five petals; the ordinary double blossom has ten or twelve. The super-double nasturtium has about fifty petals. Mr. Joseph Simson, president of the W. Atlee Burpee Company which owns the patent, tells you the story.

“Nasturtiums were first found growing wild in South America over three hundred and fifty years ago and seed was taken to Europe. They became favorite garden flowers, and as time passed, many new colors were found, but until ‘93’, all of the garden nasturtiums had only five petals, just like the wild ones first found in South America. Then some plants were found in Mexico whose flowers had from ten to twelve petals. Seed of this new double nasturtium called Golden Gleam was brought to the United States.

“It became so popular that seedsmen immediately wanted to get doubles in other colors. To get these, David Burpee had over 40,000 crosses made. Golden Gleam was crossed with all the different colored singles known. Mr. Burpee knew that it would take at least two generations to get the colored doubles he wanted, so the work was speeded up by shipping the valuable crossed seed by airplane to parts of the world where the winters were warm. All of the plants in this first generation were single, like their parents.. The seed was carefully saved, and planted and the second generation watched carefully. When the plants came into bloom, about one out of every four had double flowers.

“One evening Mr. Burpee was walking through the greenhouses looking at his new double nasturtiums when all at once he noticed one that was different from all the rest. Instead of having ten or twelve petals, like the other doubles it had about fifty petals and looked like a begonia. This new super-double nasturtium was watched with the greatest of care, but it would not set any seed because the flowers did not have any pistils.

“New plants could be grown, however, by cutting off pieces of the branches and sticking them in wet sand, where they would take root. Although the super-double nasturtiums did not give any seed, the flowers had some pollen, and this was used to make crosses on ordinary doubles.

“Finally, by making many crosses and taking cuttings, success was achieved.”

There are two kinds of balls that bounce, those that are solid, like a solid rubber ball or a golf ball, and those that are hollow, like a tennis ball.

No matter whether the ball is solid or hollow, its bounce is due to the fact that it is elastic. A thing is said to be elastic when it tends to return to its former size or shape after being pressed down or stretched. Rubber is a very elastic substance, as you know. Press a rubber ball on the ground. It loses its perfect roundness, but the instant you take away the pressure of your hand, it springs back into shape. Throw it sharply on the ground; it loses shape against the ground but springs back so sharply that it bounces.

Now a great law of science is that nothing is ever lost and that everything has to be paid for.

When the ball starts bouncing it has a certain amount of motion in it, which is force, or power, or energy. When it stops, that has gone. Either we must show that the energy has gone somewhere and has not been destroyed, or, according to the great law of the persistence of power, the ball should bounce forever. If it did not bounce forever, the law would be false. It is, however, quite easy to show that the ball does lose the power with which it started. What, then? Why does it stop bouncing? And what happens to the energy when it stops?

To begin with, the ball is moving, both up and down, through the air, and forcing millions of particles of air aside. All the motion it gives to the air it loses.

If a ball were bounced in a space as far as possible emptied of air, it would bounce far longer than it does in the atmosphere, just as a top will spin longer in the same circumstances. Suppose that, instead of bouncing the ball on something hard, we bounce it on a pillow or on loose sand. It will not bounce long in such a case. Its power has gone to move the pillow or the sand as well as the air. The ball itself is not completely elastic, nor is the ground. If the ball and the ground were completely elastic, and there were no air to move, and the ball never turned and rubbed the ground in falling, it would bounce forever.

In the case of a hollow rubber ball, it is not by any means the rubber only that explains why the ball is so elastic. The ball is filled with a mixture of several gases, which we call air. The air is elastic. It is pressed in upon itself when the ball hits the ground, but quickly tends to go back to its old space in the ball. We can see how much the air bounces if we compare an ordinary soft rubber ball with another one which has a small hole in it.

The air is expelled from the hole when the ball is bounced, and we find that the ball bounces very little, because its elasticity is so poor. But the other ball bounces exceedingly well, because, when it is bounced, the air in it is not squeezed out, but only compressed for an instant.

Someday there no longer will be any coal or oil for man to use. How soon can not be predicted exactly; there are differences of opinion among scientists. Yet that time will surely come—one thousand, ten thousand, or perhaps one hundred thousand years from now—if we continue using fuel at the present rate. How, then, will man do the world’s work? Trains and steamships would stop, since they require coal or oil. A great many of the machines operated by electricity would cease to turn because most electric generators are driven by engines requiring steam or oil. The few that are driven by water turbines would be hardly sufficient for modern purposes. Electric cells and batteries can not do the work. The automobile would be motionless. No airplane could leave the ground.

Many homes would be cold, and most factories would be silent. Of course, we should still have the wind and flowing water, such wood as could be had from forests and the fuel that can be manufactured from plants. Yet modern civilization could not get along on these sources of power alone.

Few of us realize how much we depend upon coal and oil. What are these substances and how did they accumulate on and in the earth? For the present it is sufficient to say that coal and oil are the remains of certain plants and tiny animals which lived millions of years ago. These ancient living things used sunshine, just as plants and animals do today. Each time we burn a lump of coal, and each time we “step on the gas,” we are using up the energy of ancient sunshine.

The sun is still shining and its energy is being used by living things that could some day form great deposits of coal and oil. But we can not afford to wait for that slow process. A way must somehow be found for putting to use more of the present-day sunshine; or else we must find sources of energy that do not depend upon the sun. Scientists are beginning to make progress in both directions. Let us consider first what might be done to harness the sun for doing some of the work of the world.

Day after day, the sun pours out vast amounts of energy. It is estimated that the earth’s surface receives from the sun each year the equivalent of many thousand horsepower for every square mile. If we could make good use of the energy absorbed by even a dozen square miles the threat of a coal-and-oil famine would be banished forever. In the last one hundred years, the minds of many men have been busy trying to solve this problem.

In the year 1866, Emperor Napoleon III of France visited the shop of a French inventor named August Mouchot. In the yard of the shop stood a large, cone-shaped object resembling a huge lampshade. The opening of the cone was directed toward the sun; its inside was lined with a thin film of silver. At the small end of the cone lay a small copper box, blackened on the inside. The Emperor was told that this curious device was a solar engine, that is, a sun engine. The rays of the sun were gathered by the cone and reflected by the silver lining down upon the small copper box which contained water. The heat caused the water to boil. So impressed was the Emperor that he urged his government to support and finance the building of many of these solar engines. Yet, the scheme was not very successful.

After Mouchot came several other inventors of sun engines. All of them used one or more of three important arrangements for collecting the sun’s rays—the conical mirror; the cylindrical reflector, and the hot-box - an airtight box, black inside, and covered with two layers of glass. Heat waves pass through glass; and black absorbs heat.

A solar engine was set up in the Arizona desert in 1904. It used a cone-shaped reflector and weighed about 8,300 pounds. Seven hundred square feet of sunshine was collected, which boiled water into steam, which, in turn, operated an engine. In 1913 a solar engine erected in Egypt gathered sunshine falling on an area of 13,000 square feet. This engine developed about 55 horsepower every hour. However, the machine proved to be too costly and could not be kept running easily.

One of the most workable solar engines ever built stands atop Mount Wilson in California. It consists of a large cylindrical aluminum mirror that is free to rotate about an axis parallel to that of the earth’s. A clock mechanism causes the mirror to follow the apparent motion of the sun. The rays of the sun are focused on three continuously connected oil-filled glass tubes about six feet long. Each of these tubes is covered with two other tubes which enclose a vacuum, so that very little heat is lost by the oil. As the oil gets warm it rises and soon a circulation is set up from the oil tubes to a storage tank and from the tank to the tubes. As this continues in the sunshine, the oil gets warmer and warmer, sometimes reaching a temperature of about 390 degrees Fahrenheit—which is hot enough to bake bread, cook food or boil water into steam for power purposes.

Seven hours of sunshine a day are enough to keep the machine going day and night at a temperature near that of boiling water. This machine is sometimes called a sun cooker.

There have been other efforts to make use of direct sunshine. One of the most interesting is to use the sun’s heat to produce cold. You are familiar with the type of kitchen refrigerator which is operated by a gas flame. The heat of this flame evaporates a specIal liquid called a refrigerant. The evaporated refrigerant (now a gas) is then compressed. When the gas is allowed to expand again rapidly, it produces a cooling effect which freezes the ice cubes and keeps the food cold. Similarly, the sun’s heat pouring down upon the roof of a tropical bungalow can be made to evaporate a refrigerant which can then keep the air inside the bungalow cool.

Another scheme for making direct use of the sun’s energy is to allow it to heat the junction of two pieces of different metals. When this is done an electric current begins to flow in the metals. The current, though small in amount, can ring a bell, light a lamp, or run a motor. The metal junctions are called thermocouples. Some years ago a German scientist, by using several thermocouples, succeeded in keeping an electric lamp lit by sunshine for several months. A French scientist has proposed a plant for connecting together half a million thermocouples.

The junctions would all be exposed to the sun and the ends would be embedded in concrete, so as to keep them at a lower temperature. In this way, huge amounts of electricity would be obtained. Unfortunately, the cost of building the arrangement would be too great as long as there is still enough cheap coal and oil available for generating electricity.

The most likely use of direct sunshine in the near future is the opening up of desert areas. These regions have plenty of steady sunshine. If this almost boundless energy can be caught by some form of solar engine, it can be changed either into the heat energy of steam or into electrical energy. With energy available, many such deserts can be irrigated and transformed into fertile farms and gardens. Excess electrical energy can be sent out to other regions which do not enjoy such intense and steady sunshine.

We spoke of finding sources of energy that do not depend on the sun. Men have dreamed for years of using the power of the tides; and successful experiments have been made. The greatest field for power research today is within the atom. Ceaseless activity goes on inside the atom, and an enormous amount of energy is occasionally developed accidentally when atomic particles collide. Some atoms, as you know, are breaking up and giving off (radiating) energy. Radium is one of these elements whose atoms are breaking up. Other atoms can be made to break up. We call the process atom-smashing. For some years atom-smashing has been going on in laboratories all over the world. Not until 1945 was a way found to employ the energy thus created. This use, as you know, was in the terrible atomic bomb. When we can learn how to harness the enormous energy that is now locked within the atom, we can have all the heat and mechanical power, all the electric power and light that we need. But even then we shall be dependent upon the sun for other things.

The Enormous Heat of the Sun, Our Source of Energy 

The sun is a star some 93,000,000 miles away. It consists of many different layers of gases at a very high temperature. The temperature of the surface of the sun is estimated at about i r,ooo degrees Fahrenheit. This is twice as hot as anything man has been able to devise. The sun’s interior may be ten times hotter. At these temperatures, the molecules in matter break down into the smaller particles called atoms. The atoms themselves undergo change, sending out rays of light and heat. Though these rays travel for 93,000,000 miles before they reach the earth, they can cause a pretty severe sunburn in less than fifteen minutes.

The sun is the basis of our existence and the source of all our usable energy. There are several forms of energy: light, heat, mechanical, electrical and chemical. Each form can be changed into another. The starting point for most of these changes, however, is the light energy which pours down from the sun. You have probably tried to concentrate the light rays of the sun with a magnifying glass or a mirror. The light changes into heat, which can boil water into steam. The steam can turn a small dynamo.

Thus the heat energy is changed into mechanical energy. The dynamo generates electricity, showing how mechanical energy can be changed into electrical energy. Electricity can decompose water into hydrogen and oxygen. This is a change from electrical to chemical energy. Aside from certain kinds of chemical energy and the energy within the atoms of matter, all means for carrying on life activities come to us from the sun.

How We Use Heat Energy to Get Electrical Energy 

The rays of the sun cause the water of lakes, rivers and oceans to evaporate into the air. Later the air moisture condenses and falls as rain, snow or hail. This fills the rivers, which can be dammed so as to store water at a height. When allowed to fall and press against the blades of a turbine or water-wheel, the mechanical energy is changed to electrical energy.

The sun warms the land and the water; but water heats up more slowly than land, and then holds the heat for a longer time. When the land is warmer (during the day) the air over it rises, letting in the cooler sea breezes. When the sea is warmer (during the night) the air over it rises, letting the cooler land air blow toward the sea.

You know that the earth is tilted with respect to its path around the sun. You know that because of this tilt certain regions of the earth receive the direct and concentrated rays of the sun, while other regions receive rays that are slanting and spread thinly over the area. The summer season comes to those parts of the earth which are bathed by direct sunshine, and the winter season arrives where a section of the earth receives the rays slantwise. Regions near the earth’s Equator receive rays that are close to perpendicular during the entire trip. Hence such regions enjoy hot summer weather all the time.

Areas near the Poles never receive direct rays, and have periods when they receive no sunshine. So polar regions are always cold.

The fact that certain areas are always warm and others always cold, sets up huge movements of the air. As the earth spins, these air movements are caused to swerve and give rise to the well-known wind belts. It is in these moving air masses that weather conditions start. In a sense, then, the sun is responsible for our weather. It is the sun’s energy which heats the land, heats the air, causes the air to rise and evaporates the water into the air. Even the electric storms are due to the sun, because evaporation produces electrical charges on the moisture particles and some of the sun’s rays help to increase these charges. We owe to the sun our seasons, our climate and our weather.

Light can stimulate the retina of the eye. The eye lens forms an image on the retina and the brain interprets the stimulus as the picture which we see. Certain chemicals are also affected by light. A piece of photographic film contains small grains of a chemical called silver bromide. This silver bromide is colorless and opaque. (Light can not pass through it.) When light strikes the film, the molecules of silver bromide are changed so as to leave a black silver deposit. This is what happens when a camera lens forms an image n the film. Even when you take a snapshot, the momentary flash of light produces an effect on the silver bromide. The effect is later continued when the film is developed and the picture printed.

Contained in sunlight is a kind of ray called ultraviolet. This ultraviolet light is colorless and invisible to our eyes, yet it makes its presence known and felt. It is very penetrating, and is responsible for sunburn. This can be observed in the effects produced by the mercury-vapor lamp, which is a rich source of ultraviolet light. While direct sunlight can produce a burn in about fifteen minutes, a mercury lamp can cause a similar, or even more serious, burn in two or three minutes. The nature of skin burning or tanning is quite interesting. The action of sunlight on the skin, or of the ultraviolet light contained in sunlight, is to produce a substance called vitamin D on the surface of the skin. The same vitamin D can be produced in foods, such as milk or oils and fats, by exposing them to ultraviolet light. The process is called irradiation. As you know, vitamin D is necessary if our bones are to grow strong, and it is most important to general good health.

It has been shown that ordinary window glass allows most of the sun’s light to pass but blocks the rays of ultraviolet. That is why we are warmed but not burned by the sun in a glassed-in porch, or sun-room. There are special types of glass which permit the passage of the ultraviolet rays. There is room for much further study and improvement in this field.

Every leaf, every blade of grass enjoys a secret which the wisest scientist does not know. For years scientists have been trying to find out how plants make use of sunshine. We know that water and minerals come up from the soil through the roots and stems of plants to the leaves. We know, too, that there are millions of openings on the under surfaces of leaves which let in air containing carbon dioxide. Then, in the presence of a green material called chlorophyl, and while the sun sends down its rays, a chemical action takes place in the cells of the leaves. As a result of this action, carbohydrates are formed and oxygen is released to the air. Carbohydrates—starches and sugars are examples of carbohydrates—are the food which the plant makes for its own use. Then we eat the plants. Thus corn, wheat, fruits and vegetables are the products which plants manufacture with the help of sunshine. They are the food for all animal life, including man. Yet we do not know all we should like to know about the chemical process in the leaf which means so much to our lives.

The Secret of Photosynthesis

It is estimated that one hour of sunshine, falling upon a square yard of leaf surface results in the manufacture of about one gram of carbohydrates. No wonder each plant always turns its leaves so that they catch as much direct sunshine as possible! In an acre of plants there are about two acres of leaf surface. During a summer’s growth, a wheat field may take from the air about eleven tons of carbon dioxide, and with the help of sun energy it will manufacture about seven tons of wheat.

Several scientists have already been able to duplicate the process of photosynthesis on a small scale, in the laboratory. It is as yet too costly for large-scale manufacture. Many are studying the substance, chlorophyl, whose presence is essential to the process. In the Boyce Thompson Laboratory for Plant Research, at Yonkers, New York, some very interesting experiments are now in progress. While the plant’s secret is not yet discovered, some strange results have been obtained.

Marine plant life is also affected by the light and heat of the sun. In the oceans there exists a kind of one-celled plant called the diatom. Diatoms are bacteria of a sort which, with the help of sunshine, can produce the starch needed for their growth. Small marine animals feed on the diatoms. Larger fish feed on the smaller ones, and so on. Thus the sun maintains ocean life.

The heat of the sun also affects all animal life. In the winter time, in the Northern Hemisphere, the sun is closest to the earth. However, since the sun’s rays at this time reach us slantwise and not perpendicularly, little heat can be gathered. This absence of heat and the decrease in amount of sunlight (since the days are short) causes many animals to hibernate, that is, to go into a sleepy state for the winter. Snakes, lizards, frogs, most wild bears, ants and squirrels retire for the winter. If it were not necessary to come out occasionally for food, it is likely that many animals would scarcely be seen during the winter months. As the earth revolves about the sun, and spring arrives, the animals come out of their partial sleep. They become active. Everywhere on the earth animals tend to follow the sun. This is not just accidental. It is necessary for the preservation of their lives.

It is sometimes asked how long could life exist without the sun. Would life suddenly cease, or would there be a gradual decay? As you know, in the far north there is an almost total lack of sunlight for about six months. Does life cease during that time, to be revived with the coming of the sun? No, enough energy is stored away during the dark period to maintain the necessities of life. Animals hibernate and become dormant. Man needs more than just food and shelter. He can not afford to hibernate. Life must go on.

Should the sun fail to make an appearance for a single year the result would be ruinous. Plant life as we know it would vanish and animal life would soon follow.

Is there a substitute for the sun? Can an artificial sun be created? The nearest thing to an artificial sun is artificial ultraviolet light. However, it requires electricity to operate the mercury-vapor lamps, and electricity is dependent upon the sun.

Our debt to the sun is one that can not be repaid. All our lives we are indebted to the sun for food, clothing and shelter. There is only one thing we can do to repay in part this great debt. We can practice conservation. This means saving and not wasting. It is true that the sun’s energy is apparently endless, yet we must learn to take all we need and yet leave some for succeeding generations. In this sense, conservation means careful and purposeful use. Only in this way can we repay partially our debt to the sun.

Thomas Alva Edison, Inventor

Suppose you are a boy or girl living on a farm remote from town. Only fifty years ago you would have been dependent upon the feeble and uncertain light of candles or kerosene lamps at the coming of nightfall. But now the wonderful electric light is at your beck and call. You have only to reach out your hand and turn a switch, and the room in which you are will be flooded with light. You will be able to read or write and play games by artificial light that rivals even the light of the lordly sun.

Perhaps you may wish to hear a great orchestra or violinist or singer. Your radio may not provide you with what you want, but it does not matter. You have but to select the proper phonograph record, place it on your phonograph or combination phonograph and radio, and soon you will be listening to the magnificent chords of the orchestra or the singing tones of the violin or the superb voice of a great soprano. You may even study a foreign language through phonograph records.

Perhaps it is Friday evening. Home lessons are laid aside, for you are going to a movie in the nearest town. For two hours or more you will be taken to places of interest in your own country or in one far distant; you laugh heartily over a comedy, or your heart aches over some sad, pathetic story. A great parade is held in a distant city, and within a few days the men and women will march down toward you on the picture screen. You see the launching of a proud ship, the forging of a giant anchor, a carnival held in New Orleans or in Rome, or perhaps a native wedding procession in faroff Bombay, or a football game at Yale. Here we are going to read something about the man to whom we owe the fact that our lives are so much richer than the lives of our grandfathers and grandmothers, or even our fathers and mothers when they were young.

Thomas Alva Edison worked out his inventions by known laws of science. He had studied these laws, so that he was able to apply them to make real the visions of his imagination. Yet he had few advantages and little help, and his story is one of those that inspire us to great effort to cultivate the talents that have been given to each one of us.

He was born in February, 1847, in the little village of Milan, in Ohio. His parents were poor because his father did not keep to a settled occupation. Mr. Edison senior had the same kind of mind as his wonder - working son - the kind of mind that is called versatile, that can turn easily from one thing to another. He had not learned, however, that it is wise for a man with a versatile mind to find out how to do one thing thoroughly before he turns to another, and so he was not successful.

Thomas Alva Edison was a quiet, thoughtful little boy, but very inquisitive and always wanting to know how things were done. He was not very strong, however, and was not sent to school until he was quite a big child. When he did go, his teacher, who does not seem to have been very wise, thought him stupid because he asked so many questions. So his mother, who had herself been a teacher, took him away from school at the end of two months and taught him at home. With so kind and loving a teacher he made rapid progress; and above all, he learned to think. His mother had some good books, which he learned to enjoy; and when he was ten years old he read Gibbon’s Decline and Fall of the Roman Empire and Hume’s History of England. About that time he began to study an encyclopedia. It was probably from the encyclopedia that he first learned to take an interest in chemistry and to make experiments.

Edison’s First Sample Laboratory 

By this time his parents, who had moved with him to Port Huron, Michigan, were able to indulge him in his love for making experiments. He bought some books, made a little laboratory in the cellar of his home, and there, by himself, with no teacher, laid the foundation of his knowledge of chemistry.

When he was twelve years old he decided to start out in life for himself, and he became a newsboy on the train which ran from Port Huron to Detroit. Such a newsboy had never been seen before. He was given a corner in the baggage car in which to keep his stocks of newspapers, magazines and candy. To this corner he moved his little laboratory and library of chemical books, and when he was not engaged in his business, went on with his experiments. Still time hung heavy on his hands, and to fill it up he bought a printing-press and type and published on the train a weekly newspaper filled with local news, stories of things that happened on the railway and notes of the markets. The trainmen and passengers were glad to buy the paper from this enterprising young publisher.

An Accident With Sad Consequences

All went well for two or three years. But when he was in his sixteenth year, one day a phosphorus bottle was jarred off one of his shelves and broke on the floor. It set fire to the baggage car, and in his anger at the danger to his train the conductor not only put the boy off the train, but soundly boxed his ears. That was the most unfortunate part of the accident, for as a result of the boxing Edison gradually lost his hearing and became almost totally deaf. His stock was lost, but an act of great bravery and presence of mind on his part brought to his aid a new resource and opened up a new field for him to work in.

He was standing one day on the platform of the depot at Mt. Clemens, Michigan, watching a train come in, when he saw the station agent’s little boy on the track right in front of the oncoming engine. Another moment and the child would have been crushed, but Edison sprang to the track, seized the little one in his arms, and rolled with him to one side, just in time to escape the wheels. To show his gratitude the baby’s father offered to teach Edison telegraphy. The offer was gratefully accepted, and now that his career as a train newsboy was closed, he turned to his new accomplishment as a means of making a living.

First Jobs in Telegraphy

He worked at telegraphy for some years, first in Port Huron, Michigan, thea at Stratford, Canada, and a little later in the western states, and finally in Boston. At the same time he spent all his spare moments studying chemistry and electricity and experimenting on improved telegraph apparatus. It was during these years that he first turned his attention to duplex telegraphy, but through no fault of his own he was unable to sell his invention, and the matter dropped for a time.

In 1869, when he was in his twenty second year, he went to New York. He arrived penniless in the City; but he was a good telegraph-operator, and was fearless of the future. And now a strange thing happened. He applied to the Gold and Stock Telegraph Company for work, and while he was waiting for a reply part of the apparatus broke down. No one knew what was the matter, and everything was in confusion until Edison said he could set the machine at work again. Permission was given him to try, and at the end of two hours, work in the office was going on as if nothing had happened. Edison was asked if he would accept a position at a salary of three hundred dollars a month and, needless to say, he accepted.

Edison Sells His Telegraph Inventions 

In a little over a year Edison sold his telegraph inventions for a large sum of money; this enabled him to set up in business for himself. First he built a factory at Newark, New Jersey, for the manufacture of telegraph apparatus.

He gave up this factory in 1876, and set up a laboratory at Menlo Park, New Jersey. Later this laboratory was moved to West Orange, New Jersey. His chief business now was making inventions. He gave employment to hundreds of workmen and his inventions made him famous the world over.

His first great invention was the quadruplex system of telegraphy.

The First Phonograph is Invented 

It was about the same time that he invented the phonograph. The idea of an instrument which would “write sound” and reproduce it had been thought of before by scientists, though it is doubtful if Edison knew of their efforts to make such an instrument. At any rate, he was the first to make an instrument which would work, and even he did not know that it would work until he heard it repeat the words that he shouted into it.

Edison patented his invention, which from the first excited the wonder of the world. Of course, like all first things, it was crude, and the sounds that it gave back were harsh. For the time he had to lay it aside, for he was busied with many other important projects. But others took it up, and from his parent idea the phonograph and other instruments were invented. Later on, when he had more leisure, Edison himself worked out a phonograph that gave back each beautiful vibration from voice or instrument.

Wonderful Improvements in Electric Lights

When electricity was first used for illumination only large arc-lights were used. The lamps sputtered and scattered sparks, and the light was so harsh that it could be used only for street-lighting and large buildings, such as factories, drill halls and the like. Such a thing as incandescent lights, which make possible the use of softly shaded lamps or indirect lighting in our homes, or brilliant illumination of concert halls and theatres, was not even thought of. For this work Edison put aside the work of his phonograph. He believed that a number of lights could be supplied from one distributing wire, and he believed that the light could be improved so that its use would be a common thing, so he invented the incandescent lamp, from which our modern light.ing has grown. He spent a couple of years over tH work, and to perfect his system improved dynamo machines, and invented a whole scheme of distributing electricity so that it might be used on a large scale for supplying light, heat and power.

Now we come to the moving pictures, where again Edison took up an idea which others had had before him. While it can not be said that Edison invented the moving pictures, he did work out the underlying principle on which they are based, insofar as motion is shown on a screen. The development of “sound” pictures came later and was worked out by others.

Some Other Industrial Inventions

Other inventions of his were hardly less wonderful. He invented the apparatus called the Giant Rolls, by means of which huge rocks could be reduced to fragments in a few seconds. He perfected a new type of storage battery, which did away with the lead and sulphuric acid of the old type. He increased the speed of cement manufacture with his “Long Kiln,” used in burning the mixture of cement material. His new method of cement pouring made it possible to pour the cement for a complete house in a few hours.

When World War I broke out, he found himself in danger of being cut off from his source of supply of carbolic acid for his factories at West Orange. He therefore devised a means of making it for himself. He also erected a number of plants for manufacturing products which formerly had been obtained from Europe.

Artificial Rubber from Goldenrod

During the last years of his life he was busied with the problem of producing synthetic, or artificial rubber. Finally, in 1930, he patented a process for extracting rubber from goldenrod. He died October x8, i9r, at the age of eighty-four.

We have mentioned here but a few of the numberless inventions of this wonderful man. An attempt was made, indeed, to estimate the value of these inventions. When the United States Congress awarded Edison its Gold Medal, it set the value of his contributions to mankind at $15,599,000,000. Any estimate of this sort is futile. It is enouch to say that few men have done so much to make life more complete for countless millions.

Shortly before the death of this great man another important inventor, Henry Ford, established near Dearborn, Michigan, a museum known as Edison Institute. Among the memorials to Edison that it contains is his original laboratory, moved from Menlo Park.

We have learned that there are three methods for transferring heat energy, namely: conduction, which takes place mainly in solids; convection, which takes place mainly in fluids, either gases or liquids; and radiation, which applies to the transfer of energy through space.

Conduction

The knowledge of these principles and the application of them are very important to our everyday life. In heating and cooling our homes, offices and factories, and in cooking food, we are interested in methods of transferring heat from one place to another. In other cases, such as in the use of refrigerators, we are mainly interested in preventing a transfer of heat. In other words, we control the transfer of heat so that we can get it to a place where it is needed or keep it out of places where it is not needed.

You already know that if you hold one end of a poker while the other end is placed in a bed of live coals, within a few minutes the entire poker becomes hot. The molecules of the hot coals are in very rapid vibration. The molecules of the iron poker which are near the coals receive some of this energy of vibration and in turn transmit this vibration to their less active neighbors. These transmit energy to the next molecules and so on, until the whole poker is heated. In no case does one molecule from the live bed of coals move along the poker to your hand; the molecules of a solid are held in the same positions with respect to one another. Only the vibrations are communicated along the poker.

Silver is the best conductor of heat known, copper is next, and gold and aluminum are not very far behind. Metals are much better conductors than other substances.

Feathers, fur, straw, wool and cork are poor conductors of heat. Liquids and gases in general are very poor conductors. A very poor conductor is called an insulator. The poor conductivity of such things as wool, fur and so on, is chiefly due to the fact that they contain such large air spaces. Substances which contain a large number of small air spaces are in general poor conductors.

We see therefore that substances differ widely in their ability to conduct heat. The following simple experiment will prove this point. Twist the ends of two thick wires of iron and copper together. Place some wax on the end of each wire and heat the twisted part in a flame. In a few minutes you will notice that the wax at the end of the copper wire will melt first. This proves the superior conducting power of copper.

If you have ever stood barefooted, on a tile floor, you know that your feet feel much colder than when you stand on a rug in the same room. Heat from your feet is quickly conducted to the tile. This proves that the tile is a better conductor of heat than the rug. You probably know that most modern cooking utensils are made of copper or aluminum; and now you know the reason why. They conduct well the heat from the stove to the food that is to be cooked.

Insulators

Many materials are useful, not because they are good conductors, but because they are poor conductors. Our woolen winter clothing, for instance. Air is a much poorer conductor of heat than wool and since there are many air spaces in wool, this material is one of the best heat insulators known. Wool clothing does not actually give us any warmth in winter; it prevents the heat of the body from escaping. Clothing made from the poorest conductors is “warmest.” Several light sweaters are warmer than one heavy sweater because there is a layer of non-conducting air between each two. The warmth of a fur coat is much appreciated by women, but its beauty is apparently appreciated more. If it were not so, fur coats would be worn with the fur on the inside instead of on the outside. Linen and cotton conduct heat twice as fast as wool and are therefore more suitable for summer clothing. On cold winter nights fowls on the roost spread their feathers to increase the size of the air spaces. A pad of flannel is good for lifting hot pans, and a wooden handle is put on a soldering iron because flannel and wood are poor conductors. Glass is also a poor conductor of heat. When hot tea is poured into a glass it is liable to crack because the inside of the glass gets heated first and expands, while the outside has not yet been heated—unless a good conductor, such as a metal spoon, is put into the glass to conduct the heat away.

The walls and doors of your refrigerator contain materials which are poor conductors of heat, such as sawdust and cork. They keep the heat of the room from being conducted into the refrigerator. While we are on the subject of refrigerators, it may be interesting to point out that they were an important part of the equipment of polar explorers. Can you tell why?

Furnaces and hot-water pipes are covered with asbestos or magnesia prepared in a form so as to contain a great number of air spaces. These substances will withstand high temperatures and are poor conductors of heat; so the heat is not wasted by leaking out through the walls of the furnace, or the pipes. Houses are built with double walls and sometimes with double roofs and double windows. The air spaces between the walls keep the heat from escaping in winter and the outside heat from coming in during the hot weather. Thus the house is warmer in winter and cooler in summer. We say such a house is well insulated. A well-insulated house needs less fuel than one that is not insulated.

Advertisements in newspapers and magazines now call your attention to many kinds of insulating materials that are used in the construction of houses.

Convection

We often warm our hands by holding them over a radiator or stove. Heat is carried from the stove or radiator to the hands by a stream of air. Thus we see that warm air is streaming upward from the source of heat to some colder place. The reason for this is that substances expand when heated, and their density is correspondingly decreased. This means that air over a heated surface is less dense than the surrounding air. The colder, heavier air will displace this lighter air and push it upward. Such convection currents may be produced in either liquids or gases. Ordinary ventilation depends upon convection. Air which is exhaled (breathed out) from your lungs is warmer and lighter than the cold air in a room. If the window is open at the top, this warm, used air will escape out the window, pushed up by the colder air which comes in from nearer the floor.

The hot gases in a ‘chimney are lighter than the air outside and the effect we call the draft is due to the greater pressure exerted by colder air. The speed with which the air is forced up the chimney depends in part on the difference in weight between the column of hot gases in the chimney and a column of outside air of the same height and cross section. The hotter the gases and the taller the chimney, the greater the draft.

This accounts for the tall chimneys constructed for factories. A stack built for smelting copper ores in Montana is 580 feet high.

A cheap and convenient heating system for a house is found in the hot-air furnace. This system consists of a stove with a jacket about it from the top of which pipes lead to the rooms to be heated. Through the pipes air is pushed up by convection currents.

Cold air is led into the base of the jacket where it is heated, in turn, and pushed up into the pipes by the colder air behind it. The cold air in each room is forced out through openings near the floors. In many of the more modern homes convection alone is not relied upon for the circulation of warm air. An electrically operated fan or blower circulates the air by pushing it through. In such cases the air is made to pass through a pad of loosely woven felt or other fibrous material to take out dust and smoke. Such systems are commonly referred to as air conditioning.

Land and sea breezes are also caused by convection. The land has a lower specific heat than the water. In other words, the land heats up more quickly than the water but it also loses its heat more quickly. Therefore during the daytime the land has a higher temperature than the water. The air over the land is pushed upward by the cooler air from the sea. About noon a cool sea breeze begins to blow toward the land. At night, the reverse is true; that is, the land cools more quickly, going below the temperature of the water. The warmer air over the water is forced upward and the winds consequently blow offshore, from the land toward the water. This is commonly known as a land breeze. For these reasons fishermen along the coast go to sea at night with the land breeze and return in the forenoon with the sea breeze.

In steam-heating systems, water is heated to boiling and the steam, which occupies about i,óoo times as much volume as the water had occupied, expands through the pipes and into the radiators. It is distributed by its own pressure throughout the system. When the steam reaches a radiator in a room, the cooler air outside the radiator causes the steam to condense, because heat must flow from a higher heat-level to a lower heat-level—from a hotter thing to a cooler thing. As enough heat leaves the steam, the steam becomes water; it condenses. As the steam condenses in the radiator, each gram sets free 540 calories of heat; this much heat was added to the gram of boiling water in order to convert it to steam. The heat from the radiators is distributed to the room by convection and by radiation. After condensation the water at a temperature below xoo degrees Centigrade returns to the boiler, usually through the same pipe. This process is repeated as long as the boiler produces steam.

Radiation

We have already spoken briefly about the process of transmission of energy without the aid of intervening molecules—radiation. If you stand before an open fire you are heated. Since the air is a non-conductor, you do not receive this heat by conduction. Since convection carries the heated air upward, you do not get the heat by convection. The energy must be transmitted to you by some other method. Heat comes to us from the sun across millions of miles of space where there is no material in which conduction or convection can take place. In such cases the heat is called radiant heat. Radiant heat may pass through objects without heating them. Energy, or radiant heat, from the sun passes through the upper layers of the earth’s atmosphere without heating them.

Glass permits short waves of radiant energy from the sun to penetrate, but not longer waves like those of a flame. If a pane of glass be held before a gas flame, it will transmit only a little of the heat and will become very hot because it has absorbed much of this heat. The reason is that the flame emits long waves. The sun’s heat, however, passes readily through a glass-enclosed greenhouse; yet the heat from inside the greenhouse can not escape through the glass. Heat comes from the sun through the atmosphere without heating it. The short waves from the sun can penetrate the atmosphere, but when they strike the earth they are absorbed and warm it up.

The earth radiates longer waves which are mostly absorbed by the surrounding atmosphere. If the atmosphere were not present, we would burn to death during the day and freeze to death at night. This is one of the reasons why life can not be maintained on the moon, which does not have a thick blanket of atmosphere. Orange-growers in Florida and California protect their crop from sudden frost by burning smudge pots. These smoky fires are built for the purpose of providing a layer of smoke which absorbs radiation from the earth, and thus provides a sort of extra blanket.

Absorption and Reflection of Heat

Have you ever wondered why light-colored clothes are worn in summer, or why the Arabian horses are white?

Surfaces differ in their ability to absorb radiant heat. Polished materials are good reflectors of heat; hence they are poor absorbers. Clean snow is a good reflector; hence it will not absorb much heat. This accounts for the fact that the snow in the country does not melt so rapidly as the snow in the city. In the city the snow gets dirty more rapidly and it melts faster. All black substances are found to be good absorbers of heat. Lay a black cloth and a white cloth in the sun on a cold day. In a short time you will find that more snow has melted under the black cloth than under the white cloth. The black cloth has absorbed more heat, and ha in turn, radiated more heat, and so melted the snow more quickly. Can you now see why light-colored clothes are worn in the summer? The Arabians use white horses because in that hot country dark-colored horses would more easily be exhausted from heat. A good absorber of heat is also a good radiator of heat; and a poor absorber of heat is a poor radiator of heat.

Refrigeration

In many homes a gas flame is used directly to produce ice in a refrigerator while in others an electrical motor is used. In either type of refrigerator we have one of the most interesting examples of repeated transmissions of energy. In the second type, the electric refrigerator, the energy of burning fuel is transformed into electrical energy at the power house; this energy is changed by means of a motor to mechanical energy y operating a pump which in turn compresses a gas until it liquefies. The heat produced when this gas is compressed is carried away by running water or by the circulation of air. We choose a gas which liquefies easily such as sulphur dioxide or the new commercial preparation “freon.” The cooled liquid then evaporates through a valve with a small opening into coils of pipe in the compartment of the refrigerator where the ice cubes are kept. The pressure in these pipes is kept very low by the pump which acts both as an exhaust pump and as a compressor. In order to evaporate in the coils the liquid must have heat energy supplied to it. The only place heat energy can come from is the food and if the food gives up this heat energy, it will be cooled. Thus we see that to evaporate, the liquid must take heat from the food.

Most of us are familiar with the cooling effect of evaporation. You have often heard swimmers say that it is warmer in the water than out of it. This should not be surprising to us if we understand the principles of evaporation. When you come out of the water, your body is wet and water evaporates from it. The heat necessary to vaporize the water is taken from the body, leaving the body cool. Some liquids evaporate even faster than water. If a little alcohol or ether is poured on the hand and allowed to evaporate, your hand will become cooled. Every molecule that evaporates from your hand must take enough heat away from it to give it sufficient energy to leave your hand. Only the fast-moving alcohol molecules will escape, leaving the slower ones behind. As you already know, slow-moving molecules in a liquid mean low temperature. In the summer-
time people use electric fans for the sole purpose of evaporating the moisture from their bodies at a faster rate. This evaporation takes heat from their bodies.

Converting Heat to Work

Heat energy can be converted into mechan a1 energy by means of a machine called a heat engine. For example, if we boil water in a covered pot, we may notice the cover moving up and down. When sufficient heat energy is added to the water molecules they are converted into a gas—steam—and the pressure of the steam against the cover is sufficient to raise it. This is a crude but simple example of how we convert heat energy into mechanical energy. With this principle in mind let us devise a simple ideal steam engine just for the sake of understanding the principle of operation. Watt, the inventor of the steam engine, probably went through the same reasoning process. If we allow steam from the boiler to enter inlet i, it will enter the cylinder and push the piston to the right as shown in diagram i. Now if we close inlet i and open inlet number 2, the expanding steam will drive the piston to the left provided that outlet r is open for the spent steam to escape. If now inlet 2 is closed and inlet i is open, the steam will expand against the piston and drive it to the right provided that outlet 2 is open. Outlet x must, of course, be closed, otherwise a pressure will not be built up against the piston. In this ideal model of steam engine everything would work fine if all the inlets and outlets were opened and closed at the right time. In a real steam engine the opening and closing of the inlets and outlets, called valves, is entirely automatic.

The principle of the modern steam engine is based on the ideal engine we have just described. The steam chest, contains an ingenious device called a slide valve, that slides from one end of the box to the other. Its purpose is to uncover the inlets, or ports, which allow steam to pass either to the right-hand or left-hand side of the piston, P. (The piston slides in the cylinder) Since the slide valve, must move left and right, it is connected to an eccentric on the shaft of the flywheel through a rod. Steam flows from the boiler through the pipe, into the cylinder, and exerts a force, pushing the piston, to the left. As the piston moves, it turns the shaft by means of the driving rod and a crank. This in turn moves the eccentric rod which causes the slide valve to move to the right. When the piston has moved about one-third of its stroke, the slide valve closes the port. The steam is now trapped in the cylinder and continues to expand, driving the piston forward. When the piston reaches the left end, the slide valve has moved far enough to the right to admit fresh steam through the port and to open the right end of the cylinder through to the exhaust port.

The piston is then pushed back toward the right, which in turn forces the cool steam in the right end out of the exhaust port. As the piston moves back and forth, the slide valve also moves back and forth. First it admits steam into one side of the cylinder and then into tile other, at the same time opening one exhaust port, and then the other. This back-and-forth motion of the piston, known as reciprocating motion, is changed to a rotary motion of the shaft by a connecting rod and crank. Actually the inlet ports opening to the steam chest are shut off before the piston reaches the end of the stroke, and the piston is driven the remainder of the way by the expansion of the steam trapped in the cylinder. The inertia of the heavy flywheel steadies the motion of the crankshaft and insures constant speed of rotation.

A mirage is an optical illusion, or deception. It occurs especially in certain conditions of the air when the air is very hot. Sometimes in deserts there are spots called oases, where there is water, and, as there is water, there are also green trees and shade. We are told that sometimes travelers think they are coming to an oasis only a few miles away, where they can get water and shade; and then, as they travel on, it disappears. A great explorer once “discovered” and named a mountain which did not exist, but which he had seen as a mirage.

But a true mirage is not an appearance in the sky due to nothing at all, and it is not pure imagination on the part of those who see it. When the traveler sees an oasis in the desert, and it fades and deceives him, what he has seen is the image of a real oasis, much farther on, below the horizon. The light from the real oasis has been reflected from a layer of air, and the traveler sees it as if there were a huge mirror in the sky placed at such an angle as to give a view of the oasis to the traveler’s eyes. The oasis itself may be many weary miles distant.

The reason for this is that there are layers of air of different temperatures, and therefore of different density, and whenever light passes from one thing into another of different density, part of it does not go on, but is deflected back. Appearances due to a similar cause are often seen at sea. A ship near the horizon may seem to have another ship, exactly like itself, perched upside down upon it.

Resin is the name given to a gummy liquid that is found in many plants, but it is used especially to mean the crude turpentine that is exuded by various pine, fir and larch trees. The crude turpentine is distilled to separate the oil of turpentine from the solid matter. It is this solid matter which we call rosin. Rosin comes in hard, brittle lumps, ranging in color from a pale amber to a very dark brown.

Rosin is used for many purposes. Varnishes, sealing-wax, soap and cement are among the useful articles which contain it. Violinists rub rosin on their bows to make them grip the violin strings properly, and ballet dancers use it to prevent their shoes from slipping on the floor. Sometimes rosin is sold in solid form and sometimes as a powder.

A great deal of the world’s supply of resin and turpentine comes from the belt of long- leaf pine forest that extends from North Carolina to Florida and across the Gulf states as far as Texas. The resin, turpentine, pitch and tar obtained from these forests are called Naval Stores, because they were used in the building of ships in the days of wooden sailing vessels. Nowadays these products are not needed for shipbuilding, but they are widely used in a great many other ways, especially in the paint industry.

“The dark” is the absence of light. Now, what is the name for the absence of sound? What do we call the state of things when we hear no sound? The answer is silence. By darkness we mean absence of light, just as silence is absence of sound.

But there is more to say. There may be a wave motion in the ether, but it is hardly proper to call that light until someone sees it. Similarly, there may be a wave movement in the air, but it is hardly proper to call that sound unless someone actually hears it. Seeing and hearing, then, depend, ‘first of all, on there being something outside of us - a particular kind of wave; and secondly, on our being able to feel that something.

A blind man cannot see, even in the light. Our great poet Milton, in his poem on Samson, makes Samson say, when he had lost his sight: “Oh, dark, dark, dark amid the blaze of noon”. That famous line will help us to understand what darkness may depend on - either the absence of light or the absence of the power to see light.

It is often supposed that cats and tigers can “see in the dark,” but we must know that nobody at all can see if it is perfectly dark - that is to say, if there is no light at all. When we speak of being in the dark we usually mean that there is so little light at we see hardly anything.

That is because our eyes are so made that they cannot alter themselves to suit the conditions of very dim light; but some animals can make the pupil of the eye so wide as to get the benefit of whatever rays of light are about. This is the case with cats, and if we watch the cat’s eye when it is in the dark, we see that the pupil appears much enlarged. This allows all the light possible to enter the eye, and the cat, and lions and tigers and other night-prowling animals that have eyes like the cat, are able to see very much better in dim light than we can. But even among human beings there are some people, especially seamen, who can see farther in the dark than others.

It has been discovered that there is light which we cannot see. Our eyes are keyed to a certain scale or band of wave lengths. Beyond this band are shorter waves, which we call ultra-violet rays, still shorter ones, which we call X-rays, and unbelievably tiny ones, gamma rays. There may even be shorter ones than the gamma rays, called cosmic rays. Beyond the other end of the scale of light rays that are visible to us are invisible rays with longer waves. They are called infra-red rays. Instruments can detect these very short and very long rays, though our eyes cannot. Some insects are thought to see them. Some cameras can take pictures by infra-red light, which are the very long light rays; and you probably have seen X-ray photographs, which are pictures taken by extremely short waves.

There is a very easy way to measure the height of a wall or tree - a method that anyone can use if he or she can do a problem in simple proportion. It is necessary that the sun should be shining at the time and that a shadow should be cast. That is all that is required to do this easy problem.

Suppose that you wish to measure a tree and that the sun is shining; then the shadow of the tree is cast on the ground. You must measure the distance from the tip of the shadow to the place right under the top of the tree. If the top point of the tree is right above the middle of the trunk, you must calculate half the diameter of the trunk in making your measurements.

Suppose that the distance from the point of the shadow to the trunk of the tree is 40 feet, and that the tree is 2 feet thick. Then the total distance is 41 feet (40 feet + half the diameter of the tree). Now take a stick of which you know the exact length. Suppose that it is 3 feet long.

Hold this upright with one end on the ground, and notice how far its shadow extends. You will find, perhaps, that it is 6 feet long. Multiply the length of the tree’s shadow (41 feet) by the length of the stick (3 feet); divide by the length of the stick’s shadow (6 feet). This gives 20.5; that is, the tree is 20.5 feet high.

You can also get the answer, though not quite so correctly, by seeing how many steps it takes to go from the edge of the shadow to the tree, being careful to make your steps as nearly equal as possible. Then, after measuring the length of one step, multiply its length by the number of steps. This is the distance from the shadow’s edge to the tree.

Be sure that you take the distance to a point right under the highest point. If it is a church spire, for example, make allowance for the distance between the wall up to which you measure and the center of the church tower topped by the spire.

When a hot current of air passes between an object and our eyes, the object appears to quiver. It is only an appearance, however, and the phenomenon is one out of many illustrations of the fact that the eyes are very easily deceived. This is what happens. The air is a mixture of gases, and gas, like other things, expands when heated. It becomes lighter in density; the same bulk is now lighter.

When light is passing through a gas, it travels in a straight line as long as the gas remains of exactly the same density.

Whenever the density changes, light alters its course. Therefore, when hot currents come between an object and our eyes, the light coming from the object, and passing through the hot air which is continually changing in density, is bent this way and that. So it comes about that the eye, instead of seeing the object stationary, as it really is, sees it wobbling because the light is made to wobble by the changing temperature of the air.

Scientists term this bending of light, when it passes from one density to another, refraction. This refraction plays a large part in matters of sight. It is by taking advantage of this peculiarity of light that we are able to make all sorts of valuable optical instruments, including magnifying glasses, microscopes, telescopes, cameras, sextants and so on. All these are based on refraction, or light-bending.