FARADAY AND THE FIRST DYNAMO

Michael Faraday, a London newsboy, the son of a blacksmith, became the inventor of the dynamo, and prepared the way for the wonderful electrical inventions of the nineteenth century. He began his career as a book-binder's apprentice, employing his spare moments in reading the books he was binding. One of these books led him to make some simple experiments in chemistry. He also made an electrical machine, first with a glass bottle, and afterward with a glass cylinder.

While an apprentice he wrote to his young friend, Benjamin Abbott: "I have lately made a few simple galvanic experiments, merely to illustrate to myself the first principles of the science. I was going to Knight's to obtain some nickel, and bethought me that they had malleable zinc. I inquired, and bought some—have you seen any yet? The first portion I obtained was in the thinnest pieces possible. It was, they informed me, thin enough for the electric stick. I obtained it for the purpose of forming disks with which and copper to make a little battery. The first I completed contained the immense number of seven pairs of plates!!! and of the immense size of halfpence each!!!!!! I, sir, I my own self, cut out seven disks of the size of half pennies each! I, sir, covered them with seven halfpence, and I interposed between them seven, or rather six, pieces of paper soaked in a solution of muriate of soda (common salt). But laugh no longer, dear A., rather wonder at the effects this trivial power produced."

This tiny battery made of half pennies with zinc disks and salt solution would decompose a certain solution which Faraday tested. A larger battery made of copper and zinc disks with salt solution would decompose water from the cistern. When the wires from the larger battery were put in the cistern-water he saw a dense white cloud descending from the positive wire, and bubbles rising from the negative wire. This action continued until all the white substance was taken out of the water.

Because of his interest in science, young Faraday attracted the attention of a Mr. Dance, a member of the Royal Institution and a customer of his master, Mr. Riebau. Through the kindness of Mr. Dance he heard four lectures by Sir Humphry Davy. He took notes on the lectures, wrote them out carefully, and added drawings of the apparatus. These notes he sent to Davy with a letter expressing the wish that he might secure employment at the Royal Institution. In a short time, after a warning from Sir Humphry that he had better stick to his business of book-binding, that "Science is a harsh mistress," his wish was granted, and we find him cleaning and caring for apparatus in the Royal Institution and assisting Davy in preparing for his lectures.

Count Rumford

Our story now takes us back to the time of the American Revolution. In America, we find a young man of nineteen, Benjamin Thompson by name, serving as major in the Second Regiment of New Hampshire. The appointment of so young a man as major, and his evident hold on the governor's favor, aroused the jealousy of the older officers. He was accused of being unfriendly to the cause of liberty. He denied the charge, and was acquitted by the committee of the people of Concord. A mob gathered round his house, but he escaped. Driven from his refuge in his mother's home, he fled to England, leaving his wife and child. Appointed lieutenant-colonel in the British Army, he returned to America and fought against his former friends.

The war having ended, he returned to England, thence to the Continent, intending to take part in an expected war between Austria and Turkey. A chance meeting with a Bavarian prince, Maximilian, changed the course of his life. This prince, while commanding on parade, saw Thompson among the spectators mounted on a fine English horse, and addressed him. Thompson informed him that he came from serving in the American war. The prince, pointing to a number of his officers, said: "These gentlemen were in the same war, but against you. They belonged to the Royal Regiment of Deux Ponts, that acted in America under the orders of Count Rochambeau." Thompson dined with the prince and French officers. They conversed of war and the battles in which they met. The prince, attracted to the colonel, induced him to pass through Munich, and gave him a letter to his uncle, the Elector of Bavaria.

It was in Bavaria, the country to which such unexpected turns of fortune led him, that his greatest work was done. He entered the service of the Duke of Bavaria as aide-de-camp. It was his aim while in the service of the Bavarian Government to better the condition of the people. He introduced reforms in the army, used the soldiers to rid the country of beggars and robbers, and took steps to provide for the infirm and find employment for the strong, his motto being that people can best be made virtuous when first made happy.

A Military Workhouse was opened for the beggars, and a House of Industry for the poor. A Military Academy was formed with a view to the free education of young people of talent for the public service. He became absorbed in the one aim of helping the poor. So thorough was his devotion to the people, and so deeply did he win their affection, that when he was dangerously ill a multitude of hundreds went in procession to the church to make public prayers for his recovery.

He saw that the poor may be helped by teaching them to save, and in nothing is there greater need of saving than in fuel and heat. In the kitchens of the Military Academy and the House of Industry he carried out a series of experiments on the economy of fuel, and succeeded in greatly reducing the amount of fuel needed for cooking the food. He did this by using a "closed fireplace," the forerunner of the stove. The closed fireplace was in reality a brick stove, and was a great improvement over the open chimney fireplaces then in common use. He made the covers of the cooking utensils double, to save the heat, for he had found that heat cannot escape through confined air.

Benjamin Thompson was knighted by George III., and in 1791 he was made a Count of the Holy Roman Empire, and is known to the world of science as Count Rumford.

Count Rumford's Experiment with the Cannon

While in the service of the Duke of Bavaria, it became his duty to organize the field artillery. To provide cannon for this purpose, he erected a foundry and machine-shops. Being alert for any unusual fact relating to heat, he observed the very high temperature produced by the boring of the cannon. He was eager to learn how so much heat could be produced. For this purpose he took a cannon in the rough, as it came from the foundry, fixed it in the machine used for boring, and caused the cannon to be turned by horses while a blunt borer was forced against the end of the cannon. He first tested the temperature of the metal itself as it turned. Then he surrounded the end of the cannon with water in an oblong box fitted water-tight (Fig. 20).

The cannon had been turning but a short time when he found by putting his hand in the water that heat had been produced. In two hours and thirty minutes the water actually boiled. Astonishment was expressed in the faces of the bystanders on seeing so large a quantity of water heated and actually made to boil without any fire.

"Heat," Count Rumford said; "may thus be produced merely by the strength of a horse, and, in case of necessity, this heat might be used in cooking victuals. But no circumstance can be imagined in which there is any advantage in this method of procuring heat, for more heat might be obtained by burning the fodder which the horse would eat." The meaning of this last remark was not understood until the time of Robert Mayer, about fifty years later. Rumford had found that the work of a horse can produce heat, and heat, in a steam-engine, can do the work of a horse. Thus surely, though slowly, men were learning of the forces that move the world and do man's bidding.

Count Rumford, true to his adopted land, returned to London and became the founder of the Royal Institution in which Faraday and his successors have achieved such marvellous results. He believed that the poor can be helped in no better way than by giving them knowledge, so that they can better their own condition. For this purpose he founded the Royal Institution. Here he intended that men skilled in discovery should gain new knowledge that would add to the comfort and happiness of the people.

Davy

In the English coal-fields many accidents due to the burning of fire-damp had occurred. Fire-damp is caused by gas issuing from the coal. On the approach of a flame this gas catches fire, and as it burns it produces a violent wind, driving the flame before it through the mine. Miners were scorched to death, suffocated, or buried under ruins from the roof. Hundreds of miners had been killed. No means of lighting the mines in safety had been devised. Sir Humphry Davy, Professor of Chemistry in the Royal Institution, was appealed to. After many experiments he devised a "safe lamp," which was a common miner's lamp enclosed in a wire gauze. This proved a perfect protection from fire-damp, and the Davy safety lamp has been used by miners the world over for more than a century.

But Davy's best work was with the electric battery. Some of the facts most familiar to us were discovered by him. Volta had contended that the contact of the metals in a battery produces a current, that the liquid merely carries the electricity from one metal plate to the other. But Davy proved that there can be no current without chemical action. Whenever we put two metals in an acid or other solution that will dissolve one metal faster than the other, and connect the metals with a wire, an electric current is produced. If we use water with silver and gold, there is no current, because water will not dissolve either the silver or the gold.

Davy discovered the metal, potassium, by means of his electric battery. Potassium is found in common potash and saltpetre, and, when separated, is a very soft metal. The newly discovered metal aroused great interest in other countries. When Napoleon heard of it, he inquired impetuously how it happened the discovery had not been made in France. On being told that in France there had not been made an electric battery of sufficient power, he exclaimed: "Then let one be instantly made without regard to cost or labor." His command was obeyed, and he was called to witness the action of the new battery. Before any one could interfere he placed the ends of the wires under his tongue and received a shock that nearly deprived him of sensation. On recovering he left the laboratory without a word, and was never afterward heard to refer to the subject.

Davy made many great discoveries, but the greatest was his discovery of Faraday.

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A journey on the Continent with Davy was an event in the life of Faraday, who up to that time had never to his own recollection travelled twelve miles from London. On this journey he met Volta, whom he describes as "an hale elderly man, very free in conversation." He visited the Academy del Cimento, in Florence, and wrote: "Here was much to excite interest; in one place was Galileo's first telescope, that with which he discovered Jupiter's satellites. It was a simple tube of wood and paper, about three and a half feet long, with a lens at each end. There was also the first lens which Galileo made. It was set in a very pretty frame of brass, with an inscription in Latin on it."

Faraday crossed the Alps and the Apennines, climbed Vesuvius, visited Rome, and saw a glow-worm. The last he thought as wonderful as the first.

Shortly after his return to London he fell in love. Now, Faraday had determined that he would not be conquered by the master passion. In fact, he had written various aspersions on love, of which the following is a sample:

But he reckoned not with his own heart. It is not long until we find him writing to Miss Sarah Barnard, a bright girl of twenty-one: "You have converted me from one erroneous way, let me hope you will attempt to correct what others are wrong.... Again and again I attempt to say what I feel, but I cannot. Let me, however, claim not to be the selfish being that wishes to bend your affections for his own sake only. In whatever way I can minister to your happiness, either by close attention or by absence, it shall be done. Do not injure me by withdrawing your friendship or punish me for aiming to be more than a friend by making me less."

They were married and lived in rooms at the Royal Institution. No poet ever loved more tenderly than Faraday. Truly, science does not dry up the heart's blood. At the age of seventy-one he wrote to his wife while absent from home for a few days: "Remember me; I think as much of you as is good for either you or me. We cannot well do without each other. But we love with a strong hope of love continuing ever."

Faraday's Electrical Discoveries

Now we shall turn to Faraday's electrical discoveries and inventions. Men had long known that, in houses that have been struck by lightning, steel objects such as knives and needles are sometimes found to be magnetized. Ships struck by lightning had found their compass-needles pointing south instead of north, or wandering in direction and worthless. Men had wondered how an electrical discharge could magnetize steel. They had tried the spark of the electrical machine with no definite result. Franklin, in his experiment of magnetizing a steel needle by passing an electric spark through it, could not tell before the spark was passed through the needle which end would be the north pole. There was no seeming connection between the direction of the electric discharge and the polarity of the needle. After the discovery of the electric battery, men tried to discover a relation between the electric current and magnetism.

Oersted and Electromagnetism

The first success in this direction was achieved by Hans Christian Oersted, a native of Denmark. Poverty impelled his father to take him from school at the age of twelve and place him in an apothecary's shop. The boy, Hans, found delight in the chemical work of the apothecary. His eagerness to learn and the pressure of poverty led him to neglect the usual sports of boyhood and devote his leisure time to reading and study. Again he entered school, and, though paying his way by his own work, he graduated with honor from the University of Copenhagen. He was appointed Professor of Physics in this university, and here he made his first great discovery in electromagnetism.

After working for seven years to discover a relation between current electricity and magnetism, he made a discovery which proved to be the first step in the invention of the dynamo. He was using a magnetic compass, which is a small magnetic needle balanced on a steel point. The needle points nearly north and south unless disturbed by a magnet brought near it. He had tried to find if a wire through which a current is flowing would disturb the compass as a magnet does. He had tried placing the wire east and west, thinking the compass-needle would follow the wire as it does a magnet. One day, while lecturing to his students, it occurred to him for the first time to place the wire north and south over the compass-needle. He was surprised and perplexed as he did so to see the needle swing round and point nearly east and west (Fig. 21). On reversing the current the needle swung in the opposite direction. He had discovered the magnetic action of an electric current. It was learned soon afterward that a coil of wire with an electric current flowing through it acts like a magnet, and that a current flowing around a bar of soft iron makes the iron a magnet (Figs. 22 and 23).

AmpÈre

The news of Oersted's discovery aroused great interest throughout Europe. Soon after its announcement in France, AndrÉ Marie AmpÈre made a discovery of equal importance. Oersted had discovered electromagnetism. AmpÈre discovered electrical power or motion produced by an electrical current.

The youth of AmpÈre was passed amid the stormy scenes of the French Revolution. His father had moved from his country home to Lyons and become a justice of the peace. In the destruction of the city of Lyons during the Reign of Terror he lost his head under the guillotine.

The blow was too great for AmpÈre, then a youth of eighteen. He had been a precocious child, advanced beyond his years in all the studies of the schools. But now his strong mind failed. For a year he wandered about mechanically piling up heaps of sand or gazing upon the sky. Then his mental power returned, and he took up with eagerness the study of botany and poetry.

He became a professor in the Polytechnic School in Paris, and it was while teaching in this school that he made his great discoveries. He found that two coils of wire can be made to attract or repel each other by an electric current. If the current flows through the two coils in the same direction, they attract each other (Fig. 24). If the current flows in opposite directions through the coils, they repel each other (Fig. 25). This is not very strange to us, for we know that a coil with a current flowing through it acts just like a magnet. Each coil then has a north pole and a south pole. If the coils are placed so that the two north poles or the two south poles are together, they will repel each other. If the north pole of one coil is near the south pole of the other, they will attract each other.

AmpÈre believed that electric currents are flowing around within the earth, and that the earth has a north and a south magnetic pole for the same reason that a coil of wire has magnetic poles; that these poles are caused by the currents flowing around in the earth just as the poles of the coil are caused by the current flowing around in the coil.

We do honor to the name of AmpÈre whenever we measure an electric current, for electric currents are measured in "amperes."

Arago

Another important discovery was made by a young Frenchman, FranÇois Arago, within a year of the time when Oersted and AmpÈre made their discoveries. The three great discoveries of these men were made in the years 1819 and 1820. The youth of Arago was full of adventure. He had assisted in making a survey in the Pyrenees, the haunt of daring robber-bands. Twice in his cabin he was visited by a chief of a robber-band who claimed to be a custom-house guard. On the second visit he said to the robber: "Your position is perfectly known to me. I know that you are not a custom-house guard. I have learned that you are the chief of the robbers of the country. Tell me whether I have anything to fear from your confederates." The robber replied: "The idea of robbing you did occur to us; but, on the day that we molested an envoy from the French, they would direct against us several regiments of soldiers, and we are not so strong as they. Allow me to add that the gratitude which I owe you for the night's shelter is your surest guarantee."

At a later time, when war between Spain and France was threatened, he was accused of being a spy, and a mob was formed to put him out of the way. He escaped in disguise through the midst of the mob and boarded a Spanish ship. He was carried to Morocco, ran the gantlet of bloodthirsty Mussulmans in Algiers, escaped death by a hair's-breadth, and through it all clung to the papers which recorded the results of the survey in the mountains, and delivered them in safety to the office of the Bureau of Longitude in Paris.

Arago made a discovery which, with those of Oersted and AmpÈre, prepared the way for Faraday's great electrical discoveries and the invention of the dynamo. He found that a plate of copper whirling above or below a magnetic needle will draw the needle after it (Fig. 26). He could make the speed of the whirling copper plate so great that the needle would whirl rapidly, following the copper plate. Faraday was the first to explain Arago's experiment.

Faraday's First Electric Motor

Faraday's first electrical discovery was made soon after that of Arago. Oersted had proven that an electric current acts on a magnet. The magnet turns at right angles to the wire. Faraday saw that this is because the north pole of the magnet tries to go round the wire in one direction, and the south pole tries to go round in the opposite direction. He placed a magnet on end in a dish of mercury, with one pole of the magnet above the mercury, and found that the magnet would spin round a wire carrying a current. When the current acts on one pole of the magnet only, the magnet spins round the wire (Fig. 27). So Faraday's first electrical discovery prepared the way for the electric motor.

An Electric Current Produced by a Magnet

He had written in his note-book: "Convert magnetism into electricity." An electric current would magnetize iron. Would not a magnet produce an electric current? This was his problem.

He connected a coil of wire to an instrument that would tell when a current was flowing, and placed a magnet in the coil. Others had claimed, and Faraday at first believed, that a current would flow while the magnet lay quiet within the coil. But Faraday was alert for the unexpected, and the unexpected happened. For an instant, as he thrust the magnet into the coil, his instrument showed that a current was flowing. Again, as he drew the magnet quickly from the coil, a current flowed, but in the opposite direction (Fig. 28). From this simple experiment has grown the alternating-current machinery by which the power of Niagara is made to light cities and drive electric cars at a distance of many miles.

A friend of Faraday, on learning of this discovery, wrote the following impromptu lines:

A magnet will produce an electric current in a wire, but only when the magnet or the wire is in motion.

Detecting and Measuring an Electric Current

The instrument which Faraday used to detect a current was derived from Oersted's experiment. When a current flows in a north-and-south direction over a compass-needle, the needle swings round. When the current stops flowing the needle swings back to the north-and-south position. The effect on the needle is stronger if the current flows through a coil of wire and the coil is placed in a north-and-south position around the needle (Fig. 29). The stronger the current flowing through the coil the farther the needle will turn from the north-and-south position.

FIG. 29–A COIL OF WIRE AROUND A COMPASS-NEEDLE FIG. 29–A COIL OF WIRE AROUND A COMPASS-NEEDLE

The needle tells when a current is flowing, and how strong the current is.

The coil and the needle together are called a galvanometer, and may be used to tell when a current is flowing, and also to indicate the strength of the current.

An Electric Current Produced by the Magnetic Field of Another Current

Faraday had found that a current flowing around a piece of iron will make the iron a magnet, and that a magnet in motion will cause a current to flow in a wire. It seemed to him that a second wire placed near the first should have a current produced in it without the presence of iron. He wound two coils of copper wire upon the same wooden spool. The wire of the two coils he separated with twine and calico. One coil was connected with a galvanometer, the other with a battery of ten cells, yet not the slightest turning of the needle could be observed. But he was not deterred by one failure. He raised his battery from ten cells to one hundred cells, but without avail. The current flowed calmly through the battery wire without producing, during its flow, any effect upon the galvanometer. During its flow was the time when an effect was expected.

Again the unexpected happened. At the instant of making contact with the battery there was a slight movement of the needle. When the contact was broken, another slight movement, but in the opposite direction to the first (Fig. 30). The current in one wire caused a current to flow in the other, but the current in the second wire continued for an instant only at the making and breaking of the contact with the battery. This was the beginning of the induction-coil used to-day in wireless telegraphy.

FIG. 30–FARADAY'S INDUCTION-COIL FIG. 30–FARADAY'S INDUCTION-COIL

Starting and stopping the battery current in the primary coil causes a changing magnetic field, and this causes a current to flow in the secondary coil.

Drawing reproduced by permission of Joseph G. Branch.

What was the secret of it? Simply this: that a current in one wire will cause a current to flow in another wire near it, but only while the current in the first wire is changing. That is, at the instant when the first wire is connected to the battery, or its connection broken, a current is induced in the second wire. There is no battery or other source of current connected to the second wire; but a current flows in this wire because it is near a wire in which a current is rapidly starting and stopping. When these two wires are wound in coils, together they form an induction-coil. The wire which we have called the first wire forms the "primary" coil, and the one we have called the second wire forms the "secondary" coil. By repeatedly making and breaking the circuit in the primary coil we get an alternating current in the secondary coil. Fig. 31 is from a photograph of some of the coils actually used by Faraday.

FIG. 31–HISTORICAL APPARATUS OF FARADAY IN THE ROYAL INSTITUTION FIG. 31–HISTORICAL APPARATUS OF FARADAY IN THE ROYAL INSTITUTION

Some of Faraday's transformer coils are shown here. The instrument on the left in a glass case is his galvanometer.

Faraday's Dynamo

To invent a new electrical machine was Faraday's next aim. Arago's disk of copper whirling near a magnet had a current induced in it, so Faraday thought. It was the action of this induced current which caused the magnet to follow the whirling disk. Could the current in Arago's disk be collected and caused to flow through a wire? He placed a copper disk between the poles of a magnet. One galvanometer wire passed around the axis of the disk, the other he held in contact with the edge. He whirled the disk. The galvanometer needle moved. A current was flowing in the disk as it whirled. The current from the whirling disk flowed through the galvanometer. Faraday had discovered the dynamo (Fig. 32).

FIG. 32–FARADAY'S FIRST DYNAMO FIG. 32–FARADAY'S FIRST DYNAMO

A current flows in the copper disk as it whirls between the poles of the magnet.

By permission of Joseph G. Branch.]

All this work occupied but ten days in the autumn of 1831, though years of preparation had gone before. In these ten days the foundation was laid for the induction-coil, modern dynamo-electric machinery, and electric lighting. Fig. 33 shows the laboratory in which Faraday did this work.

FIG. 33–FARADAY'S LABORATORY, WHERE THE FIRST DYNAMO WAS MADE FIG. 33–FARADAY'S LABORATORY, WHERE THE FIRST DYNAMO WAS MADE

From the water-color drawing by Miss Harriet Moore.

Faraday continued to explore the field opened up before him. In one experiment two small pencils of charcoal lightly touching were connected to the ends of a secondary coil. A spark passed between the charcoal points when the primary circuit was closed. This was the first transformer producing a tiny electric light (Fig. 34).

FIG. 34–THE FIRST TRANSFORMER FIG. 34–THE FIRST TRANSFORMER

Faraday discovered the induction-coil, the dynamo, and the transformer, and he showed that, in each of these, it is magnetism which produces the electric current. He had discovered the secret when he obtained a current by thrusting a magnet into a coil of wire. The space about a magnet in which the magnet will attract iron he called the "magnetic field" (Figs. 35 and 36). In every case of magnetism causing an electric current to flow in a coil of wire, the coil is in a magnetic field, and the magnetic field is changing—that is, the magnetic field is made alternately stronger and weaker, or the coil moves across the magnetic field. The point is that magnetism at rest will not produce an electric current. There must be a changing magnetic field or motion. In Faraday's dynamo a copper disk whirled between the poles of a magnet and the whirling of the disk in the magnetic field caused an electric current. In the modern dynamo it is the whirling of a coil of wire in a magnetic field that causes a current to flow. In the induction-coil it is the change in the magnetic field that causes a current to flow in the secondary coil. A coil of wire with an electric current flowing through it will attract iron like a magnet. The primary coil with a current from a battery flowing through it acts in all respects like a magnet; but as soon as the current ceases to flow the magnetic field disappears—the coil is no longer a magnet. When we make and break the connection between the primary coil and the battery, then, we repeatedly make and destroy the magnetic field, and this changing magnetic field causes a current to flow in the secondary coil. The induction-coil is one form of transformer. We shall see later how the dynamo and the transformer developed in the nineteenth century.

FIG. 35–THE "MAGNETIC FIELD" IS THE SPACE AROUND A MAGNET IN WHICH IT WILL ATTRACT IRON FIG. 35–THE "MAGNETIC FIELD" IS THE SPACE AROUND A MAGNET IN WHICH IT WILL ATTRACT IRON

The iron filings over the magnet arrange themselves along the "lines of force."

FIG. 36–MAGNETIC FIELD OF A HORSESHOE MAGNET FIG. 36–MAGNETIC FIELD OF A HORSESHOE MAGNET

When a boy, Faraday had passed the current from his little battery through a jar of cistern-water, and saw in the water a "dense white cloud" descending from the positive wire, and bubbles arising from the negative wire. Something was being taken out of the water by the electric current. When he tried the experiment later in his laboratory, he found that, whenever an electric current is passed through water, bubbles of two gases, oxygen and hydrogen, rise through the water. He found that if the current is made stronger the bubbles are formed faster. The water in time disappears, for it has been changed or "decomposed" into the two gases.

It was the current from a battery that would decompose water. The electricity from the electrical machine would do other things that he had never seen a battery current do. "Do the battery and the electrical machine produce different kinds of electricity, or is electricity one and the same in whatever way it is produced?" This was the query that troubled him. The answer to this question had been so uncertain that the effect of the voltaic battery had been termed "galvanism," while that of the friction machine retained the name "electricity."

Faraday tried many experiments in searching for an answer to this question. He found that the electricity of the machine will produce the same effect as that of a battery if the machine is compelled to discharge slowly. An electrical machine or a battery of Leyden jars can be made to give out an electric current, and this current will affect a magnetic needle in the same way that a battery current will. It will magnetize steel. If passed through water, it will decompose the water into the two gases oxygen and hydrogen. In short, a current from an electrical machine or a Leyden jar will do everything that a current from an electric battery will do. Faraday caused the Leyden jar to give a current instead of a spark by connecting the two metal coatings with a wet string. On the other hand, the discharge from a powerful electric battery will produce a spark and affect the human nerves in the same way as the discharge from the electrical machine. The same effects may be obtained from one as from the other.

In the discharge from the machine, a small quantity of electricity is discharged under high pressure, as water may be forced through a small opening by very high pressure. The voltaic cell, on the other hand, furnishes a large quantity of electricity at low pressure, as a street may be flooded by a broken water-main though the pressure is low. In fact, the quantity of electricity required to decompose a grain of water is equal to that discharged in a stroke of lightning, while the action of a dilute acid on the one-hundredth part of an ounce of zinc in a battery yields electricity sufficient for a powerful thunder-storm.

Many tests were made, and the result was a convincing proof that electricity is the same whatever its source, the different effects being due to difference in pressure and quantity. "But in no case," said Faraday, "not even in those of the electric eel and torpedo, is there a production of electric power without something being used up to supply it."

Faraday's professional work would have made him wealthy. In one year he made £1000 ($5000), and the amount would have increased had he sold his services at their market value. But then there would have been no Faraday the discoverer. The world would have had to wait, no one knows how long, for the laying of the foundations of electrical industries. He chose to give up wealth for the sake of discovery. He gave up professional work with the exception of scientific adviser to Trinity House, the body which has charge of Great Britain's lighthouse service. Nor did he carry his discoveries to the point of practical application. As soon as he discovered one principle, he set out in pursuit of others, leaving the practical application to the future.

Faraday loved the beauty of nature. The sunset he called the scenery of heaven. He saw the beauty of electricity, which he said lies not in its mystery, but in the fact that it is under law and within the control of the human intellect.

A Wonderful Law of Nature

Not long after Faraday made his first dynamo, Robert Mayer, a physician from Germany, was making a voyage to the East Indies which proved to be a voyage of discovery. He had sailed as the ship's physician, and after some months an epidemic broke out among the ship's company. In his treatment he drew blood from the veins of the arms. He was startled to see bright-red blood issue from the veins. He might almost have believed that he had opened an artery by mistake. It was soon explained to him by a physician who had lived long in the tropics that the blood in the veins of the natives, and of foreigners as well, in the tropics is of nearly the same color as arterial blood. In colder climates the venous blood is much darker than the arterial.

He reasoned upon this curious fact for some time, and came to the conclusion that the human body does not make heat out of nothing, but consumes fuel. The fuel is consumed in the blood, and there the heat is produced. In the tropics less heat is needed, less fuel is consumed, and therefore there is less change in the color of the blood.

When a man works he uses up fuel. If a blacksmith heats a piece of iron by hammering, the heat given to the iron and the heat produced in his body are together equal to the heat of the fuel consumed in his blood. The work a man does, as well as the heat of his body, comes from the burning of the fuel in his blood.

What is true of a man is true of an engine. The work the engine does, as well as the heat it produces, comes from the heat of the fuel in the furnace. Mayer found that one hundred pounds of coal in a good working engine produces the same amount of heat as ninety-five pounds in an engine that is not working. In the working engine the heat of the five pounds of coal is used up in the work of running the engine, and therefore does not heat the engine. Heat that is used in running the engine is no longer heat, but work. So Mayer said the heat is not destroyed, but only changed into work. He said, further, that the work of running the engine may be changed again into heat.

Mayer's theory was opposed by many scientific men of Europe. One great scientist said to him that if his theory were correct water could be warmed by shaking. He remembered what the helmsman had remarked to him on the voyage to Java, that water beaten about by a storm is warmer than quiet sea-water; but he said nothing. He went to his laboratory, tried the experiment, and some weeks later returned, exclaiming: "It is so! It is so!" He had warmed water simply by shaking it.

These results mean that work or energy cannot be destroyed. Though it changes form in many ways, it is never destroyed. Neither can man create energy; he can only direct its changes as the engineer, by the motion of his finger in opening a valve, sets the locomotive in motion. He does not move the locomotive. He directs the energy already in the steam.

Since the time of Galileo, men had caught now and then a glimpse of this great law. Galileo had stated his law of machines; that, when a machine does work, a man or a horse or some other power does an equal amount of work upon the machine. Count Rumford had performed his experiment with the cannon, showing that heat is produced by the work of a horse. Davy had proved that, in the voltaic battery, something must be used up to produce the current—the mere contact of the metals is not sufficient. Faraday had said that in no case is there a production of electrical power without something being used up to supply it. Mayer stated clearly this law of energy when he said that energy cannot be created or destroyed, but only changed from one form to another.

And yet inventors have not learned the meaning of this law. They continue trying to invent perpetual-motion machines—machines that will produce work from nothing. This is what a perpetual-motion machine would be if such a machine were possible. For a machine without friction is impossible, and friction means wasted work—work changed into heat. A machine to keep itself running and supply the work wasted in friction must produce work from nothing. The great law of nature is that you cannot get something for nothing. Whether you get work, heat, electricity, or light, something must be used up to produce it. For whatever you get out of a machine you must give an equivalent. This law cannot be evaded, and from it there is no appeal.

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