Steam, Steel and Electricity Part 3

It was in June, 1752, that this great exemplar of the genius of common-sense descended to the trial of the experiment that was the simplest and the most ordinary and the most sublime; the commonest in conception and means yet the most famous in results; ever tried by man.

He had grown impatient of delay in the matter of the spire, and hastily, as by a sudden thought, made a kite. It was merely a silk handkerchief whose four corners were attached to the points of two crossed sticks. It was only the idea that was great; the means were infantile. A thunder shower came over, and in an interval between sprinklings he took with him his son, and went by back ways and alleys to a shed in an open field. The two raised the kite as boys did then and do now, and stood within the shelter. There was a hempen string, and on this, next his hand, he had tied a bit of ribbon and an ordinary iron key. A cloud pa.s.sed over without any indications of anything whatever. But it began to rain, and as the string became wet he noticed that the loose filaments were standing out from it, as he had often seen them do in his experiments with the electrical machine. He drew a spark from the key with his finger, and finally charged a Leyden jar from this key, and performed all the then known proof-experiments with the lightning drawn from heaven.

It is manifest that the slightest indication of the presence of the current in the string was sufficient to have demonstrated the fact which Franklin sought to fix. But it would have been insufficient to the general mind. The demonstration required was absolute. Even among scientists of the first cla.s.s less was then known about electricity and its phenomena, and the causes of them, than now is known by every child who has gone to school. No estimate of the boldness and value of Franklin's renowned experiment can be made without a full appreciation of his times and surroundings. He demonstrated that which was undreamed before, and is undoubted now. The wonders of one age have been the toys and tools of the next through the entire history of mankind. The meaning of the demonstration was deep; its results were lasting The experimenters thereafter worked with a knowledge that their investigations must, in a sense, include the universe. Perhaps the obscure man who had toyed with the lightnings himself but vaguely understood the real meaning of his temerity. For he had, as usual, an intensely practical purpose in view. He wished to find a way of "drawing from the heavens their lightnings, and conducting them harmless to the earth." He was the first inventor of a practical machine, for a useful purpose, with which electricity had to do. That machine was the lightning-rod. Whatever its purpose, mankind will not forget the simple greatness of the act. At this writing the statue of Franklin stands looking upward at the sky, a key in his extended hand, in the portico of a palace which contains the completest and most beautiful display of electrical appliances that was ever brought together, at the dawn of that Age of Electricity which will be noon with us within one decade.

The science and art of the civilized world are gathered about him, and on the frieze above his head s.h.i.+nes, in gold letters, that sentence which is a poem in a single line. "ERIPUIT CAELO FULMEN, SCEPTRUMQUE TYRANNIS." [Footnote: "He s.n.a.t.c.hed the lightning from heaven, and the sceptre from tyrants."]

THE MAN FRANKLIN.--Benjamin Franklin was born at Boston, Ma.s.s., Jan.

17th, 1706. His father was a chandler, a trade not now known by that term, meaning a maker of soaps and candles. Benjamin was the fifteenth of a family of seventeen children. He was so much of the same material with other boys that it was his notion to go to sea, and to keep him from doing so he was apprenticed to his brother, who was a printer. To be apprenticed then was to be absolutely indentured; to belong to the master for a term of years. Strangely enough, the boy who wanted to be a sailor was a reader and student, captivated by the style of the _Spectator_, a model he a.s.siduously cultivated in his own extensive writings afterwards. He was not a.s.sisted in his studies, and all he ever knew of mathematics he taught himself. Being addicted to literature by natural proclivity he inserted his own articles in his brother's newspaper, and these being very favorably commented upon by the local public, or at least noticed and talked about, his authors.h.i.+p of them was discovered, and this led to a quarrel between the two brothers.

Nevertheless, when James, the elder brother, was imprisoned for alleged seditious articles printed by him, the paper was for a time issued in young Benjamin's name. But the quarrel continued, the boy was imposed upon by his master, and brother, as naturally as might have been expected under the circ.u.mstances of the younger having the monopoly of all the intellectual ability that existed between the two, and in 1723, being then only seventeen, he broke his indentures, a heinous offense in those times, and ran away, first to New York and then to Philadelphia, where he found employment as a journeyman printer. He had attained a skill in the business not usual at the time.

The boy had, up to this time, read everything that came into his hands.

A book of any kind had a charm for him. His father observing this had intended him for the ministry, that being the natural drift of a pious father's mind in the time of Franklin's youth, when he discovered any inclination to books on the part of a son. But, later, he would neglect the devotions of the Sabbath if he had found a book, notwithstanding the piety of his family. Sometimes he distressed them further by neglecting his meals, or sitting up at night, for the same reason. There is no question that young Franklin was a member of that extensive fraternity now known as "cranks." [Footnote: Most people, then and now, can point to people of their acquaintance whom they hold in regard as originals or eccentrics. It is a somewhat dubious t.i.tle for respect, even with us who are reckoned so eccentric a nation. And yet all the great inventions which have done so much for civilization have been discovered by eccentrics--that is, by men who stepped out of the common groove; who differed more or less from other men in their habits and ideals.] He read a book advocating exclusive subsistence upon a vegetable diet and immediately adopted the idea, remaining a disciple of vegetarianism for several years. But there is another reason hinted. He saved money by the vegetable scheme, and when his printer's lunch had consisted of "biscuits (crackers) and water" for some days, he had saved money enough to buy a new book.

This young printer, who, at school, in the little time he attended one, had "failed entirely in mathematics," could a.s.similate "Locke on the Understanding," and appreciate a translation of the Memorabilia of Xenophon. Even after his study of this latter book he had a fondness for the calm reasoning of Socrates, and wished to imitate him in his manner of reasoning and moralizing. There is no question but that the great heathen had his influence across the abyss of time upon the mind of a young American destined also to fill, in many respects, the foremost place in his country's history. There was one, at least, who had no premonition of this. His brother chastised him before he had been imprisoned, and after he had begun to attract attention as a writer in one of the only two newspapers then printed in America, and beat him again after he was released, having meantime been vigorously defended by his apprentice editorially while he languished. To have beaten Benjamin Franklin with a stick, when he was seventeen years old, seems an absurd anti-climax in American history. But it is true, and when the young man ran away there was still another odd episode in a great career.

Upon his first arrival in Philadelphia as a runaway apprentice, with one piece of money in his pocket, occurs the one gleam of romance in Franklin's seemingly Socratic life. He says he walked in Market Street with a baker's loaf under each arm, with all his s.h.i.+rts and stockings bulging in his pockets, and eating a third piece of bread as he walked, and this on a Sunday morning. Under these circ.u.mstances he met his future wife, and he seems to have remembered her when next he met her, and to have been unusually prepossessed with her, because on the first occasion she had laughed at him going by. He was one of those whose sense of humor bears them through many difficulties, and who are even attracted by that sense in others. He was, at this period, absurd without question. Having eaten all the bread he could, and bestowed the remainder upon another voyager, he drank out of the Delaware and went to church; that is, he sat down upon a bench in a Quaker meeting-house and went to sleep, and was admonished thence by one of the brethren at the end of the service.

Franklin had, in the time of his youth, the usual experiences in business. He made a journey to London upon promises of great advancement in business, and was entirely disappointed, and worked at his trade in London. Afterwards, during the return voyage to America, he kept a journal, and wrote those celebrated maxims for his own guidance that are so often quoted. The first of these is the gem of the collection: "I resolve to be extremely frugal for some time, until I pay what I owe." A second resolve is scarcely less deserving of imitation, for it declares it to be his intention "to speak all the good I know of everybody." It must be observed that Franklin was afterwards the great maximist of his age, and that his life was devoted to the acquisition of worldly wisdom.

In his body of philosophy there is included no word of confidence in the condemnation of offenses by the act or virtue of another, no promise of, or reference to, the rewards of futurity.

When about twenty-one years of age, we find this old young man tired of a drifting life and many projects, and desiring to adopt some occupation permanently. He had courted the girl who had laughed at him, and then gone to England and forgotten her. She had meantime married another man, and was now a widow. In 1730 he married her. Meantime, entering into the printing business on his own account, he often trundled his paper along the streets in a wheelbarrow, and was intensely occupied with his affairs. His acquisitive mind was never idle, and in 1732 he began the publication of the celebrated "Poor Richard's Almanac." This was among the most successful of all American publications, was continued for twenty-five years, and in the last issue, in 1757, he collected the princ.i.p.al matter of all preceding numbers, and the issue was extensively republished in Great Britain, was translated into several foreign languages, and had a world-wide circulation. He was also the publisher of a newspaper, _The Pennsylvania Gazette_, which was successful and brought him into high consideration as a leader of public opinion in times which were beginning to be troubled by the questions that finally brought about a separation from the mother country.

Time and s.p.a.ce would fail in anything like a detailed account of the life of this remarkable man. His only son, the boy who was with him at the flying of the kite, was an illegitimate child, and it is a remarkable instance of unlikeness that this only son became a royalist governor of New Jersey, was never an American in feeling, and removed to England and died there. The sum of Franklin's life is that he was a statesman, a financier of remarkable ability, a skillful diplomat, a law-maker, a powerful and felicitous writer though without imagination or the literary instinct, and a controversialist who seldom, if ever, met his equal. He was always a printer, and at no period of his great career did he lose his affection for the useful arts and common interests of mankind. He is the founder of the American Philosophical Society, and of a college which grew into the present University of Pennsylvania. To him is due the origin of a great hospital which is still doing beneficent work. He raised, and caused to be disciplined, ten thousand men for the defense of the country. He was a successful publisher of the literature of the common people, yet a literature that was renowned. He could turn his attention to the improvement of chimneys, and invented a stove still in use, and still bearing his name as the author of its principle. [Footnote: The stove was not used in Franklin's time to any extent. The "Franklin Stove" was a fireplace so far as the advantages were concerned, such as ventilation and the pleasure of an open fire. But it also radiated heat from the back and sides as well as the front, and was intended to sit further out into a room; to be both fireplace and stove.] He organized the postal system of the United States before the Union existed. He was a signer of the Declaration of Independence. He sailed as commissioner to France at the age of seventy-one, and gave all his money to his country on the eve of his departure, yet died wealthy for his time. Serene, even-tempered, philosophical, he was yet far-seeing, care-taking, sagacious, and intensely industrious. He acquired a knowledge of the Italian and Spanish languages, and was a proficient French speaker and writer. He possessed, in an extraordinary degree, the power of gaining the regard, even the affection, of his fellow-men. He was even a competent musician, mastering every subject to which his attention was turned; and province-born and reared in the business of melting tallow and setting types, without collegiate education, he shone in a.s.sociation with the men and women who had place in the most brilliant epoch of French intellectual history. At fourscore years he performed the work that would have exhausted a man of forty, and at the same time wrote, for mere amus.e.m.e.nt, sketches such as the "Dialogue between Franklin and the Gout," and added, with the cool philosophy of all his life still lingering about his closing hours: "When I consider how many terrible diseases the human body is liable to, I think myself well off that I have only three incurable ones, the gout, the stone, and old age."

[Ill.u.s.tration: THE FRANKLIN STOVE.]

After Franklin, electrical experiments went on with varying results, confined within what now seems to have been a very narrow field, until 1790. The great facts outside of the startling disclosure made by Franklin's experiments remained unknown. It was another forty years of amused and interested playing with a scientific toy. But in that year the key to the _utility_ of electricity was found by one Galvani.

He was not an electrician at all, but a professor of anatomy in the university of Bologna. It may be mentioned in pa.s.sing that he never knew the weight or purport of his own discovery, and died supposing and insisting that the electric fluid he fancied he had discovered had its origin in the animal tissues. Misapprehending all, he was yet unconsciously the first experimenter in what we, for convenience, designate _dynamic_ electricity. He knew only of _animal_ electricity, and called it by that name; a misnomer and a mistake of fact, and the cause of an early scientific quarrel the promoting of which was the actual reason of the advance that was made in the science following his accidental and enormously important discovery.

There are many stories of the details of the ordinarily entirely unimportant circ.u.mstances that led to _Galvanism_ and the _Galvanic Battery_. Volta actually made this battery, then known as the Voltaic Pile, but he made it because of Galvani's discovery. The reader is requested to bear these names in mind; Galvani and Volta. They have a unique claim upon us. With others that will follow, they have descended to all posterity in the immortal nomenclature of the science of electricity. It is through the accidental discovery of the plodding demonstrator of anatomy in a medical college, a man who died at last in poverty and in ignorance of the meaning of his own work, that we have now the vast web of telegraph and telephone wires that hangs above the paths of men in every civilized country, and the cables that lie in the ooze of the oceans from continent to continent. His discovery was the result of one of the commonest incidents of domestic life. Variously described by various writers, the actual circ.u.mstance seems reducible to this.

In Galvani's kitchen there was an iron railing, and immediately above the railing some copper hooks, used for the purpose of hanging thereon uncooked meats. His wife was an invalid, and wis.h.i.+ng to tempt her appet.i.te he had prepared a frog by skinning it, and had hung it upon one of the copper hooks. The only use intended to be asked of this renowned batrachian was the making of a little broth. Another part of the skinned anatomy touched the iron rail below, and the anatomist observed that this casual contact produced a convulsive twitching of the dead reptile's legs. He groped about this fact for many years. He fancied he had discovered the principle of life. He made the phenomenon to hang upon the facts cl.u.s.tering about his own profession, familiar to him, and about which it was natural for him to think. He promulgated theories about it that are all now absurd, however tenable then. His was an instance of how the fatuities of men in all the fields of science, faith or morals, have often led to results as extraordinary as they have been unexpected. That he died in poverty in 1798 is a mere human fact. That in this life he never knew is merely another. It is but a part of that sadness that, through life, and, indeed, through all history, hangs over the earthly limitations of the immortal mind.

Volta, his contemporary and countryman, finally solved the problem as to the reason why. and made that "Voltaic Pile" which came to be our modern "battery." Acting upon the hint given by Galvani's accident, this pile was made of thin sheets of metal, say of copper and zinc, laid in series one above the other, with a piece of cloth wet with dilute acid interposed between each sheet and the next. The sheets were connected at the edges in pairs, a sheet of zinc to a sheet of copper, and the pile began with a sheet of one metal and ended with one of the other. It is to be noted that a single pair would have produced the same result as a hundred pairs, only more feebly. A single large pair is, indeed, the modern electric battery of one cell. The beginning and the ending sheets of the Voltaic pile were connected by a wire, through which the current pa.s.sed. We, in our commonest industrial battery, use the two pieces of metal with the fluid between. The metals are usually copper and zinc, and the fluid is water in which is dissolved sulphate of copper. The wire connection we make hundreds of miles long, and over this wire pa.s.ses the current. If we part this wire the current ceases. If we join it again we instantly renew it. There are many forms of this battery.

The two metals, the _electrodes_, are not necessarily zinc and copper and no others. The acidulated fluid is not invariably water with sulphate of copper dissolved in it. Yet in all modifications the same thing is done in essentially the same way, and the Voltaic pile, and a little back of that Galvani's frog, is the secret of the telegraph, the telephone, the telautograph, the cable message. In the case of Galvani's frog, the fluids of the recently killed body furnished the liquid containing the acid, the copper hook and the iron railing furnished the dissimilar metals, and the nerves and muscles of the frog's body, connecting the two metals, furnished the wire. They were as good as Franklin's wet string was. The effect of the pa.s.sage of a current of electricity through a muscle is to cause it to spasmodically contract, as everyone knows who has held the metallic handles of an ordinary small battery. Many years pa.s.sed before the mystery that has long been plain was solved by acute minds. Galvani thought he saw the electric quality _in the tissues of the_ frog. Volta came to see them as produced _by chemical action upon two dissimilar metals_. The first could not maintain his theories against facts that became apparent in the course of the investigations of several years, yet he a.s.serted them with all the pertinacious conservatism of his profession, which it has required ages to wear away, and died poor and unhonored. The other became a n.o.bleman and a senator, and wore medals and honors. It is a world in which success alone is seen, and in which it may be truthfully said that the contortions of an eviscerated and unconscious frog upon a casual hook were the not very remote cause of the greatest advancements and discoveries of modern civilization.

Yet the mystery is not yet entirely explained. In the study of electricity we are accustomed to accept demonstrated facts as we find them. When it is asked _how_ a battery acts, what produces the mysterious current, the only answer that can now be given is that it is _by the conversion of the energy of chemical affinity into the energy of electrical vibrations_. Many mixtures produce heat. The explanation can be no clearer than that for electricity. Electricity and heat are both _forms of energy_, and, indeed, are so similar that one is almost synonymous with the other. The enquiry into the original sources of energy, latent but present always, will, when finally answered, give us an insight into mysteries that we can only now infer are reserved for that hereafter, here or elsewhere, which it is part of our nature to believe in and hope for. The theory of electrical vibrations is explained elsewhere as the only tenable one by which to account for electrical action. One may also ask how fire burns, or, rather, why a burning produces what we call "heat," and the actual question cannot be answered. The action of fire in consuming fuel, and the action of chemicals in consuming metals, are similar actions. They each result in the production of a new form of energy, and of energy in the form of vibrations. In the action of fire the vibrations are irregular and spasmodic; in electricity they are controlled by a certain rhythm or regularity. Between heat and electricity there is apparently only this difference, and they are so similar, and one is so readily converted into the other, that it is a current scientific theory that one is only a modified form of the other. Many acute minds have reflected upon the problem of how to convert the latent energy of coal into the energy of electricity without the interposition of the steam engine and machinery. There apparently exist reasons why the problem will never be solved. There is no intelligence equal to answering the question as to precisely where the heat came from, or how it came, that instantly results upon the striking of a common match. It was _evolved_ through friction. The means were necessary. Friction, or its precise equivalent in energy, must occur. The result is as strange, and in the same manner strange, as any of the phenomena of electricity.

Precisely here, in the beginning of the study of these phenomena, the student should be warned that an att.i.tude of wonder or of awe is not one of enquiry. The demonstrations of electricity are startling chiefly for three reasons: newness, silence, and inconceivable rapidity of action.

Let one hold a wire in one's hand six or eight inches from the end, and then insert that end into the flame of a gas-jet. It is as old as human experience that that part of the wire which is not in the flame finally grows hot, and burns one's fingers. A change has taken place in the molecules of the wire that is not visible, is noiseless, and that has _traveled along the wire_. It excites neither wonder nor remark. No one asks the reason why. Yet it cannot be explained except by some theory more or less tenable, and the phenomenon, in kind though not in degree, is as unaccountable as anything in the magic of electricity. In a true sense there is, nothing supernatural, or even wonderful, in all the vast universe of law. If we would learn the facts in regard to anything, it must be after we have pa.s.sed the stage of wonder or of reverence in respect to it. That which was the "Voice of G.o.d"--as truly, in a sense, it was and is--until Franklin's day, has since been a concussion of the air, an echo among the clouds, the pa.s.sage of an electric discharge. It is the first lesson for all those who would understand.

The time had now come when that which had seemed a lawless wonder should have its laws investigated, formulated and explained. A man named Coulomb, a Frenchman, is the author of a system of measurements of the electric current, and he it was who discovered that the action of electricity varies, not with the distance, but, like gravity, _in the inverse ratio of the square of the distance_. Coulomb was the maker of the first instrument for measuring a current, which was known as the _torsion balance_. The results of his practical investigations made easier the practical application of electrical power as we now use it, though he foresaw nothing of that application; and the engineer of to-day applies his laws, and those of his fellow scientists, as those which do not fail. Volta was one of these, and he also furnished, as will hereafter be seen, a name for one of the units of electrical measurement.

Both Galvani and Volta pa.s.sed into shadow, when, in 1820, Professor H.

C. Oersted, of Copenhagen, discovered the law upon which were afterwards slowly built the electrical appliances of modern life. It was the great principle of INDUCTION. The student of electricity may begin here if he desires to study only results, and is not interested in effects, causes, and the pains and toils which led to those results. The term may seem obscure, and is, doubtless, as a name, the result of a sudden idea; but upon induction and its laws the simplest as well as the most complicated of our modern electrical appliances depend for a reason for action. Its discovery set Ampere to work. They had all imagined previously that there was some connection between electricity and magnetism, and it was this idea that instigated the investigations of Ampere. It was imagined that the phenomena of electricity were to be explained by magnetism.

This was not untrue, but it was only a part of the truth. Ampere proved that _magnetism could also readily be produced by a current of electricity_. From this idea, practically carried out, grew the ELECTRO MAGNET, and to Ampere we are indebted for the actual discovery of the elementary principles of what we now call electrodynamics, or dynamic electricity, [Footnote: In all science there is a continual going back to the past for a means of expression for things whose application is most modern. _Dynamic_; DYNAMO, is the Greek word for power; to be able. Once established, these names are seldom abandoned. There is no more reason for calling our electrical power-producing machine a "Dynamo" than there would be in so designating a steam engine or a water-wheel. But, a term of general significance if used at all, it has come to be the special designation of that one machine. It is brief, easily said, and to the point, but is in no way necessarily connected with _electrical_ power distinctively.] in which are included the Dynamo, and its twin and indispensable, the Motor. Ampere is also the author of the _molecular theory_, by which alone, with our present knowledge, can the action of electricity be explained in connection with the iron core which is made a magnet by the current, and left again a mere piece of iron when the current is interrupted. Ten years later Faraday explained and applied the laws of Induction, basing them upon the demonstrations of Ampere. The use of a core of soft iron, magnetized by the pa.s.sage of a current through a helix of wire wrapping it as the thread does a spool, is the indispensable feature, in some form meaning the same thing, with the same results, in all machines that are given movement to by an electric current. This is the electro-magnet. It is made a magnet not by actual contact, or by being made the conductor of a current, but by being placed in the "electrical field" and temporarily magnetized by induction.

Faraday began his brilliant series of experiments in 1831. To express briefly the laws of action under which he worked, he wrote the celebrated statement of the Law of Magnetic Force. He proved that the current developed by induction is the same in all its qualities with other currents, and, indeed, demonstrated Franklin's theory that all electricity is the same; that, as to _kind_, there is but one. All electrical action is now viewed from the Faradic position.

The story of electricity, as men studied it in the primary school of the science, ends where Faraday began. Under the immutable laws he discovered and formulated we now enter the field of result, of action, of commercial interest and value. We might better say the field of usefulness, since commercial value is but another expression for usefulness. A revolution has been wrought in all the ways and thoughts of men since a date which a man less than sixty years old can recall.

The laws under which the miracle has been wrought existed from all eternity. They were discovered but yesterday. Progress, the destiny of man, has kept pace in other fields. We live our time in our predestined day, learning and knowing, like grown-up children, what we may. In a future whose distance we may not even guess, the children of men shall reap the full fruition of the prophesy that has grown old in waiting, and "shall be as G.o.ds, knowing good from evil."

MODERN ELECTRICITY

CHAPTER I.

Electricity, in all its visible exhibitions, has certain unvarying qualities. Some of these have been mentioned in the preceding chapter.

Others will appear in what is now to follow. These qualities or habits, invariable and unchangeable, are, briefly:

(1) It has the unique power of drawing, "attracting" other objects at a distance.

(2) For all human uses it is instantaneous in action, through a conductor, at any distance. A current might be sent around the world while the clock ticked twice.

(3) It has the power of decomposing chemicals (Electrolysis), and it should be remembered that even water is a chemical, and that substances composed of one pure organic material are very rare.

(4) It is readily convertible into heat in a wire or other conductor.

These four qualities render its modern uses possible, and should be remembered in connection with what is presently to be explained.

These uses are, in application, the most startling in the entire history of civilization. They have come about, and their applications have been made effective, within twenty years, and largely within ten. This subtlest and most elusive essence in nature, not even now entirely understood, is a part of common life. Some years ago we began to spell our thoughts to our fellow-men across land and sea with dots and dashes.

Within the memory of the present high school boy we began to talk with each other across the miles. Now there is no reason why we shall not begin to write to each other letters of which the originals shall never leave our hands, yet which shall stand written in a distant place in our own characters, indisputably signed by us with our own names. We apparently produce out of nothing but the whirling of a huge bobbin of wire any power we may wish, and send it over a thin wire to where we wish to use it, though every adult can remember when the difficulty of distance, in the propelling of machinery, was thought to have been solved to the satisfaction of every reasonable man by the making of wire cables that would transmit power between grooved wheels a distance of some hundreds of feet. We turn night into day with the glow of lamps that burn without flame, and almost without heat, whose mysterious glow is fed from some distant place, that hang in cl.u.s.ters, banners, letters, in city streets, and that glow like new stars along the treeless prairie horizon where thirty years ago even the beginnings of civilization were unknown. Yet the mysterious agent has not changed. It is as it was when creation began to shape itself out of chaos and the abyss. Men have changed in their ability to reason, to deduce, to discover, and to construct. To know has become a part of the sum of life; to understand or to abandon is the rule. When the ages of tradition, of a.s.sertion without the necessity for proof, of content with all that was and was right or true because it was a standard fixed, went by, the age not necessarily of steam, or of steel, or of electricity, but the age of thought, came in. Some of the results of this thought, in one of the most prominent of its departments, I shall attempt to describe.

A wire is the usual concomitant in all electrical phenomena. It is almost the universally used conductor of the current. In most cases it is of copper, as pure as it can be made in the ordinary course of manufacture. There are other metals that conduct an electrical current even better than copper does, but they happen to be expensive ones, such as silver. The usual telegraph-line is efficient with only iron wire.

We habitually use the words "conductor" and "conduct" in reference to the electric current. A definition of that common term may be useful. It is a relative one. _A conductor is any substance whose atoms, or molecules, have the power of conveying to each other quickly their electricities_. Before the common use of electricity we were accustomed to commonly speak of conductors of heat; good, or poor. The same meaning is intended in speaking of conductors of electricity.

_Non-conductors are those whose molecules only acquire this power under great pressure_. Electricity always takes the _easiest_ road, not necessarily the shortest. This is the path that electricians call that of "least resistance." There are no absolutely perfect conductors, and there are no substances that may be called absolutely non-conductors. A non-conductor is simply a reluctant, an excessively slow, conductor. In all electrical operations we look first for these two essentials: a good conductor and a good non-conductor. We want the latter as supports and attachments for the first. If we undertake to convey water in a pipe we do not wish the pipe to leak. In conveying electricity upon a wire we have a little leak wherever we allow any other conductor to come too near, or to touch, the wire carrying the current. These little electrical leaks constantly exist. All nature is in a conspiracy to take it wherever it can find it, and from everything which at the moment has more than some other has, or more than its share with reference to the air and the world, of the mysterious essence that is in varying quant.i.ties everywhere. Gla.s.s is the usual non-conductor in daily use. A glance at the telegraph poles will explain all that has just been said. Water in large quant.i.ty or widely diffused is a fair conductor. Therefore, the gla.s.s insulators on the telegraph-poles are cup-shaped usually on the under side where the pin that holds them is inserted, so that the rain may not actually wet this pin, and thus make a water-connection between the wire, gla.s.s, pin, pole and ground.

We are accustomed to things that are subject to the law of gravity.

Water will run through a pipe that slants downward. It will pa.s.s through a pipe that slants upward only by being pushed. But electricity, in its far journeys over wires, is not subject to gravity. It goes indifferently in any direction, asking only a conductor to carry it.

There is also a trait called _inertia_; that property of all matter by which it tends when at rest to remain so, and when in motion to continue in motion, which we meet at every step we take in the material world. Electricity is again an exception. It knows neither gravity, nor inertia, nor material volume, nor s.p.a.ce. It cannot be contained or weighed. Nothing holds it in any ordinary sense. It is difficult to express in words the peculiar qualities that caused the early experimenters to believe it had a soul. It is never idle, and in its ceaseless journeyings it makes choice of its path by a conclusion that is unerring and instantaneous.

We find that it is the constant endeavor of electricity to _equalize its quant.i.ties and its two qualities, in all substances that are near it that are capable of containing it_. To this end, seemingly by definite intention, it is found on the outsides of things containing it.

It gathers on the surfaces of all conductors. If there are k.n.o.bs or points it will be found in them, ready to leap off. When any electrified body is approached by a conductor, the fluid will gather on the side where the approach is made. If in any conductor the current is weak, very little of it, if any, will go off into the conductor before actual contact is made. If it is strong, it will often leap across the s.p.a.ce with a spark. One body may be charged with positive, and another with negative, electricity. There is then a disposition to equalize that cannot be easily repressed. The positive and the negative will a.s.sume their dual functions, their existence together, in spite of obstacles.

So as to quant.i.ty. That which has most cannot be restrained from imparting to that which has less. The demonstration of these facts belongs to the field of experimental, or laboratory, electricity. The most common of the visible experiments is on a vast scale. It is the thunder-storm. Mother Earth is the great depository of the fluid. The heavy clouds, as they gather, are likewise full. Across the s.p.a.ce that lies between the exchange takes place--the lightning-flash.

In the preceding chapter I have hastily alluded to the phenomenon known as the key to electricity as a utilitarian science; a means of material usefulness. These uses are all made possible under the laws of what we term INDUCTION. To comprehend this remarkable feature of electric action, it must first be understood that all electrical phenomena occur in what has been termed an "_Electrical Field_" This field may be ill.u.s.trated simply. A wire through which a current is pa.s.sing _is always surrounded by a region of attractive force_. It is scientifically imagined to exist in the form of rings around the wire.

In this field lie what are termed "lines of force." The law as stated is that the lines in which the magnetism produced by electricity acts _are always at right angles with the direction in which the current is pa.s.sing_. Let us put this in ordinary phrase, and say that in a wire through which a current is pa.s.sing there is a magnetic attraction, and that the "pull" is always _straight toward the wire_. This magnetism in a wire, when it is doubled up and multiplied sufficiently, has strong powers of attraction. This multiplying is accomplished by winding the wire into a compact coil and pa.s.sing a current through it.

If one should wind insulated wire around a core, or cylinder, and should then pull out the cylinder and attach the two ends of the wire to the opposite poles of a battery, when the current pa.s.sed through the coil the hollow interior of it would be a strong magnetic field. The air inside might be said to be a magnet, though if there were no air there, and the coil were under the exhausted receiver of an air-pump, the effect would be the same, and the _vacuum_ would be magnetized. A piece of iron inserted where the core was, would instantly become a magnet, and when the insulated wire is wound around a soft iron core, and the core is left in place, we have at once what is known as an _Electro-Magnet_.

The wire windings of an electro-magnet are always insulated; wound with a non-conductor, like silk or cotton; so that the coils may not touch each other in the winding and thus permit the current to run off through contact by the easiest way, and cut across and leave most of the coil without a current. For it may as well be stated now that no matter how good a conductor a wire may be, two qualities of it cause what is called "_resistance_"--the current does not pa.s.s so easily. These two qualities are _thinness_ and _length_. The current will not traverse all the length of a long coil if it can pa.s.s straight through the same ma.s.s, and it is made to go the long way _by keeping the wires from touching each other_--preventing "contact," and lessening the opportunity to jump off which electricity is always looking for.

When this coil is wound in layers, like the thread upon a spool, it increases the intensity of the magnetism in the core by as many times as there are coils, up to a certain point. If the core is merely soft iron, and not steel, it becomes magnetized instantly, as stated, and will draw another piece of iron to it with a snap, and hold it there as long as there is a current pa.s.sing through the coil. But as instantly, when the current is stopped, this soft iron core ceases to be a magnet, and becomes as it was before--an inert and ordinary piece of iron. What has just been described is always, in some form, one of the indispensable parts of the electromagnetic machines used in industrial electricity, and in all of them except the appliances of electric lighting, and even in that case it is indispensable in producing the current which consumes the points of the carbon, or heats the filament to a white glow. The current may traverse the wire for a hundred miles to reach this little coil. But, instantly, at a touch a hundred miles away that forms a contact, there is a continuous "circuit;" the core becomes a magnet, and the piece of iron near it is drawn suddenly to it. Remove the distant finger from the b.u.t.ton, the contact is broken, and the piece of iron immediately falls away again. It is the wonder of _the production of instant movement at any distance, without any movement of any connecting part_. It is a mysterious and incredible transmission of force not included among human possibilities forty years ago. It is now common, old, familiar. Conceive of its possibilities, of its annihilation of time and s.p.a.ce, of its distant control, and of that which it is made to mean and represent in the spelled-out words of language, and it still remains one of the wonders of the world: the Electric Telegraph.