MAGNETS AND MAGNETISM.--Having described a magnet that is made and unmade at will, it may be appropriate to describe magnets generally. The ordinary, permanent magnet, natural or artificial, has little place in the arts. It cannot be controlled. In common phrase, it cannot be made to "let go" at will. The greatest value of magnetism, as connected with electricity, consists in the fact of the intimate relationship of the two. A magnet may be made at will with the electric current, as described above. A little later we shall see how the process may be reversed, and the magnet be made to produce the most powerful current known, and yet owe its magnetism to the same current.
The word _Magnet_ comes from the country of _Magnesia_, where "loadstone" (magnetic iron ore) seems first to have been found. The artificial magnet, as made and used in early experiments and still common as a toy or as a piece in some electrical appliances, is a piece of fine steel, of hard temper, which has been magnetized, usually by having had a current pa.s.sed through or around it, and sometimes by contact with another magnet. For the singular property of a magnet is that it may continually impart its quality, yet never lose any of its own. Steel alone, of all the metals, has the decided quality of retaining its property of being a magnet. A "bar" magnet is a straight piece of steel magnetized. A "horseshoe" magnet is a bar magnet bent into the form of the letter "U."
Every magnet has two "poles"--the positive, or North pole, and the negative, or South pole. If any magnet, of any size, and having as one piece two poles only, be cut into two, or a hundred pieces, each separate piece will be like the original magnet and have its two poles.
The law is arbitrary and invariable under all circ.u.mstances, and is a law of nature, as unexplainable and as invariable as any in that mysterious code. All bar magnets, when suspended by their centers, turn their ends to the North and South, a familiar example of this being the ordinary compa.s.s. But in magnetism, _like repels like_. The world is a huge magnet. The pole of the magnet which points to the North is not the North pole of the needle as we regard it, but the opposite, the South.
No one can explain precisely why iron, the purer and softer the better, becomes a powerful and effective magnet under the influence of the current, and instantly loses that character when the current ceases, and why steel, the purer and harder the better, at first rejects the influence, and comes slowly under it, but afterwards retains it permanently. Iron and steel are the magnetic metals, but there is a considerable list of metals not magnetic that are better than they as _conductors_ of the electric current. In a certain sense they are also the electric metals. A Dynamo, or Motor, made of bra.s.s or copper entirely would be impossible. All the phenomena of combined magnetism and electricity, all that goes to make up the field of industrial electric action, would be impossible without the indispensable of ordinary iron, and for the sole reason that it possesses the peculiar qualities, the affinities, described.
There is now an understanding of the electro-magnet, with some idea of the part it may be made to play in the movement of pieces, parts, and machines in which it is an essential. It has been explained how soft iron becomes a magnet, not necessarily by any actual contact with any other magnet, or by touching or rubbing, but by being placed in an electric field. It acquired its magnetism by induction; by _drawing in_ (since that is the meaning of the term) the electricity that was around it. But induction has a still wider field, and other characteristics than this alone. Some distinct idea of these may be obtained by supposing a simple case, in which I shall ask the reader to follow me.
[Ill.u.s.tration: DIAGRAM THEORY OF INDUCTION]
Let us imagine a wire to be stretched horizontally for a little s.p.a.ce, and its two ends to be attached to the two poles of an ordinary battery so that a current may pa.s.s through it. Another wire is stretched beside the first, not touching it, and not connected with any source of electricity. Now, if a current is pa.s.sed through the first wire a current will also show in the second wire, pa.s.sing in an _opposite direction_ from the first wire"s current. But this current in the second wire does not continue. It is a momentary impulse, existing only at the moment of the first pa.s.sing of the current through the wire attached to the poles of the battery. After this first instantaneous throb there is nothing more. But now cut off the current in the first wire, and the second wire will show another impulse, this time in the _same direction_ with the current in the first wire. Then it is all over again, and there is nothing more. The first of these wires and currents, the one attached to the battery poles, is called the _Primary_. The second unattached wire, with its impulses, is called the _Secondary_.
Let us now imagine the primary to be attached to the battery-poles permanently. We will not make or break the circuit, and we can still produce currents, "impulses," in the secondary. Let us imagine the primary to be brought nearer to the secondary, and again moved away from it, the current pa.s.sing all the time through it. Every time it is moved nearer, an impulse will be generated in the secondary which will be opposite in direction to the current in the primary. Every time it is moved away again, an impulse in the secondary will be in the same direction as the primary current. So long, as before, as the primary wire is quiet, there will be no secondary current at all.
There is still a third effect. If the current in the primary be _increased or diminished_ we shall have impulses in the secondary.
This is a supposed case, to render the facts, the laws of induction, clear to the understanding. The experiment might actually be performed if an instrument sufficiently delicate were attached to the terminals of the secondary to make the impulses visible. The following facts are deduced from it in regard to all induced currents. They are the primary laws of induction:--
A current which begins, which approaches, or which increases in strength in the primary, induces, with these movements or conditions, a momentary current in the _opposite direction_ in the secondary.
A current which stops, which retires, or which decreases in strength in the primary, induces a momentary current _in the same direction_ with the current in the primary.
To make the results of induction effective in practice, we must have great length of wire, and to this end, as in the case of the electro-magnet, we will adopt the spool form. We will suppose two wires, insulated so as to keep them from actually touching, held together side by side, and wound upon a core in several layers. There will then be two wires in the coil, and the opposite ends of one of these wires we will attach to the poles of a battery, and send a current through the coil.
This would then be the primary, and the other would be the secondary, as described above. But, since the power and efficiency of an induced current depends upon the length of the secondary wire that is exposed to the influence of the current carried by the primary, we fix two separate coils, one small enough to slip inside of the other. This smaller, inner coil is made with coa.r.s.er wire than the outer, and the latter has an immense length of finer wire. The current is pa.s.sed through the smaller, inside coil, and each time that it is stopped, or started, there will be an impulse, and a very strong one, through the outer--the secondary coil. Leave the current uninterrupted, and move the outer coil, or the inner one, back and forth, and the same series of strong impulses will be observed in the coil that has no connection with any source of electricity.
What I have just described as an ill.u.s.tration of the laws governing the production of induced currents, is, in fact, what is known as the _Induction Coil_. In the old times of a quarter of a century ago it was extensively used as an ill.u.s.trator of the power of the electric current. Sometimes the outer coil contained fifty miles of wire, and the spark, a close imitation of a flash of lightning, would pa.s.s between the terminals of the secondary coil held apart for a distance of several feet, and would pierce sheets of plate gla.s.s three inches thick. Before the days of practical electric lighting the induction-coil was used for the simultaneous lighting of the gas-jets in public buildings, and is still so used to a limited extent. Its description is introduced here as an ill.u.s.tration of the laws of induction which the reader will find applied hereafter in newer and more effective ways. The commonest instance now of the use of the induction-coil is in the very frequent small machine known as a medical battery. There must be a means of making and breaking the current (the circuit) as described above. This, in the medical battery, is automatic, and it is that which produces the familiar buzzing sound. The mechanism is easily understood upon examination.
At some risk of tediousness with those who have already made an examination of elementary electricity, I have now endeavored to convey to the reader a clear idea of (1), what electricity is, so far as known.
(2) Of how the current is conducted, and its influence in the field surrounding the conductor. (3) The nature of the induced current, and the manner in which it is produced. The sum of the information so far may be stated in other words to be how to make an electromagnet, and how to produce an induced current. Such information has an end in view. A knowledge of these two items, an understanding of the details, will be found, collectively or separately, to underlie an understanding of all the machines and appliances of modern electricity, and in all probability, of all those that are yet to come.
But in the prominent field of electric lighting (to which presently we shall come), there is still another principle involved, and this requires some explanation (as well given here as elsewhere) of the current theory as to what electricity is. [Footnote: There are several "schools" among scientists, those who pursue pure science, irrespective of practical applications, and who are rather disposed to narrow the term to include that field alone, that are divided among themselves upon the question of what electricity is. The "Substantialists" believe that it is a kind of matter. Others deny that, and insist that it is a "form of Energy," on which point there can be no serious question. Still others reject both these views. Tesla has said that "nothing stands in the way of our calling electricity "ether a.s.sociated with matter, or bound ether."" Professor Lodge says it is "a form, or rather a mode of manifestation, of the ether" The question is still in dispute whether we have only one electricity or two opposite electricities. The great field of chemistry enters into the discussion as perhaps having the solution of the question within its possibilities. The practical electrician acts upon facts which he knows are true without knowing their cause; empirically; and so far adheres to the molecular hypothesis. The demonstrations and experiments of Tesla so far produce only new theories, or demonstrate the fallacies of the old, but give us nothing absolute. Nevertheless, under his investigations, the possibilities of the near future are widely extended. By means of currents alternating with very high frequency, he has succeeded in pa.s.sing by induction, through the gla.s.s of 1 lamp, energy sufficient to keep a filament in a state of incandescence _without the use of any connecting wires_.
He has even lighted a room by producing in it such a condition that an illuminating appliance may be placed anywhere and lighted without being electrically connected with anything. He has produced the required condition by creating in the room a powerful electrostatic field alternating very rapidly. He suspends two sheets of metal, each connected with one of the terminals of the coil. If an exhausted tube is carried anywhere between these sheets, or placed anywhere, it remains always luminous.
Something of the unquestionable possibilities are shown in the following quotation from _Nature_, as expressed in a lecture by Prof. Crookes upon the implied results of Tesla"s experiments.
The extent to which this method of illumination may be practically available, experiments alone can decide. In any case, our insight into the possibilities of static electricity has been extended, and the ordinary electric machine will cease to be regarded as a mere toy.
Alternating currents have, at the best, a rather doubtful reputation.
But it follows from Tesla"s researches that, is the rapidity of the alternation increases, they become not more dangerous but less so. It further appears that a true flame can now be produced without chemical aid--a flame which yields light and heat without the consumption of material and without any chemical process. To this end we require improved methods for producing excessively frequent alternations and enormous potentials. Shall we be able to obtain these by tapping the ether? If so, we may view the prospective exhaustion of our coal-fields with indifference; we shall at once solve the smoke question, and thus dissolve all possible coal rings.
Electricity seems destined to annex the whole field, not merely of optics, but probably also of thermotics.
Rays of light will not pa.s.s through a wall, nor, as we know only too well, through a dense fog. But electrical rays of a foot or two wave-length, of which we have spoken, will easily pierce such mediums, which for them will be transparent.
Another tempting field for research, scarcely yet attacked by pioneers, awaits exploration. I allude to the mutual action of electricity and life. No sound man of science indorses the a.s.sertion that "electricity is life." nor can we even venture to speak of life as one of the varieties or manifestations of energy. Nevertheless, electricity has an important influence upon vital phenomena, and is in turn set in action by the living being--animal or vegetable. We have electric fishes--one of them the prototype of the torpedo of modern warfare. There is the electric slug which used to be met with in gardens and roads about Hoinsey Rise; there is also an electric centipede. In the study of such facts and such relations the scientific electrician has before him an almost infinite field of inquiry.
The slower vibrations to which I have referred reveal the bewildering possibility of telegraphy without wires, posts, cables, or any of our present costly appliances. It is vain to attempt to picture the marvels of the future. Progress, as Dean Swift observed, may be "too fast for endurance."] As to this, all we may be said to know, as has been remarked, is that it is one of the _forms of energy_, and its manifestations are in the form of _motion_ of the minute and invisible atoms of which it is composed. This movement is instantaneously communicated along the length of a conductor. There must, of course, be an end to this process in theory, because all the molecules once moved must return to rest, or to a former condition, before being moved again. Therefore it is necessary to add that when the motion of the last molecule has been absorbed by some apparatus for applying it to utility, the last particles, atoms, molecules, are restored to rest, and may again receive motion from infringing particles, and this transmission of energy along a conductor is continuous--continually absorbed and repeated. This is _dynamic_ electricity; not differing in kind, in essence, from any other, but only in application.
If the conductor is entirely insulated, so that no molecular movements can be communicated by it to contiguous bodies, all its particles become energized, and remain so as long as the conductor is attached to a source of electricity. In such a case an additional charge is required only when some of the original charge is taken away, escapes. This is _Static_ electricity; the same as the other, but in theory differing in application.
The molecular theory is, unquestionably, tenable under present conditions. It is that to which science has attained in its inquiries to the present date. The electric light is scarcely explainable upon any other hypothesis. The remaining conclusions may be left in abeyance, and without argument.
Science began with static electricity, so called, because its sources were more readily and easily discovered in the course of scientific accidents, as in the original discovery of the property of rubbed amber, etc., and the long course of investigations that were suggested by that antique, accidental discovery. What we know as the dynamic branch of the subject was created by the investigations of Faraday; induction was its mother. It is the practically important branch, but its investigation required the invention of machinery to perform its necessary operations.
Between the two branches the sole difference--a difference that may be said not actually to exist--is in _quant.i.ty and pressure_.
To the department of static electricity all those industrial appliances first known belong, as the telegraph, electro-plating, etc. I shall first consider this cla.s.s of appliances and machines. The most important of the cla.s.s is
[Ill.u.s.tration]
THE ELECTRIC TELEGRAPH.--The word is Greek, meaning, literally, "to write from a distance." But long since, and before Morse"s invention, it had come to mean the giving of any information, by any means, from afar.
The existence of telegraphs, not electric, is as old as the need of them. The idea of quickness, speedy delivery, is involved. If time is not an object, men may go or send. The means used in telegraphing, in ancient and modern times, have been sound and sight. Anything that can be expressed so as to be read at a distance, and that conveys a meaning, is a telegram. [Footnote: This word is of American coinage, and first appeared in the _Albany Evening Journal_, in 1852. It avoids the use of two words, as "Telegraphic Message," or "Telegraphic Dispatch,"
and the ungrammatical use of "Telegraph," for a message by telegraph.
The new word was at once adopted.] Our plains Indians used columns of smoke, or fires, and are the actual inventors of the _heliograph_, now so called, though formerly meaning the making of a picture by the aid of the sun--photography. The vessels of a squadron at sea have long used telegraphic signals. Some of the celebrated sentences of our history have been written by visual signals, such as "Hold the fort, for I am coming," "Don"t give up the ship," etc. Order of showing, positions, and colors are arbitrarily made to mean certain words. The sinking of the "_Victoria_" in 1893, was brought about by the orders conveyed by marine signals. Bells and guns signal by sound. So does the modern electric telegraph, contrary to original design. It is all telegraphy, but it all required an agreed and very limited code, and comparative nearness. None of the means in ancient use were available for the multifarious uses of modern commerce.
As soon as it was known that electricity could be sent long distances over wires, human genius began to contrive a way of using it as a means of conveying definite intelligence. The first idea of the kind was attempted to be put into effect in 1774. This was, however, before the discovery of the electro-magnet (about 1800), or even the Galvanic battery, and it was seriously proposed to have as many wires as there were letters; each wire to have a frictional battery for generating electricity at one end of the circuit, and a pith-ball electroscope at the other. The modern reader may smile at the idea of the hurried sender of a message taking a piece of cat-skin, or his silk handkerchief, and rubbing up the successive letter-b.a.l.l.s of gla.s.s or sulphur until he had spelled out his telegram. Later a man named Dyer, of New York, invented a system of sending messages by a single wire, and of causing a record to be made at the receiving office by means of a point pa.s.sing over litmus paper, which the current was to mark by chemical action, the paper pa.s.sing over a roller or drum during the operation. The battery for this arrangement was also frictional. They knew of no other. Then came the deflected-needle telegraph, first suggested by Ampere, and a few such lines were constructed, and to some extent operated. In one of the original telegraph lines the wires were bound in hemp and laid in pipes on the surface of the ground. The expedient of poles and atmospheric insulation was not thought of until it was adopted as a last resort during the construction of Morse"s first line between Washington and Baltimore.
In the year 1832, an American named Samuel F. B. Morse was making a voyage home from Havre to New York in the sailing packet _Sully_.
He was an educated man, a graduate of Yale, and an artist, being the holder of a gold medal awarded him for his first work in sculpture, and no want of success drove him to other fields. But during this tedious voyage of the old times in a sailing vessel he seems to have conceived the idea which thenceforth occupied his life. It was the beginning of the present Electric Telegraph. During this same voyage he embodied his notions in some drawings, and they were the beginnings of vicissitudes among the most long-continued and trying for which life affords any opportunity. He abandoned his studies. He paid attention to no other interest. He pa.s.sed years in silent and lonesome endeavors that seemed to all others useless. He subjected himself to the reproaches of all his friends, lost the confidence of business men, gained the reputation of being a monomaniac, and was finally given over to the following of devices deemed the most useless and unpromising that up to that time had occupied the mind of any man.
The rank and file of humanity had no definite idea of the plan, or of the results that would follow if it were successful. In reality no one cared. It was Morse"s enterprise exclusively--a crank"s fad alone. There has been no period in the history of society when the public, as a body, was interested in any great change in the systems to which it was accustomed. There is always enmity against an improver. In reality, the question of how much money Morse should make by inventing the electric telegraph was the question of least importance. Yet it was regarded as the only one. He is dead. His profits have gone into the ma.s.s, his honors have become international. The patents have long expired. The public, the entire world, are long since the beneficiaries, and the benefits continue to be inconceivably vast. Nothing in all history exceeds in moral importance the invention of the telegraph except the invention of printing with movable types.
[Ill.u.s.tration: AN ELECTRO-MAGNET OF MORSE"S TIME.]
After eight years of waiting, and the repeated instruction of the entire Congress of the United States in the art of telegraphy, that body was finally induced to make an appropriation of thirty thousand dollars to be expended in the construction of an experimental line between Washington and Baltimore. And now begins the actual strangeness of the story of the Telegraph. After many years of toil, Morse still had learned nothing of the efficient construction of an electro-magnet. The magnet which he attempted to use unchanged was after the pattern of the first one ever made--a bent U-shaped bar, around which were a few turns of wire not insulated. The bar was varnished for insulation, and the turns of wire were so few that they did not touch each other. The apparatus would not work at a distance of more than a few feet, and not invariably then. Professor Leonard D. Gale suggested the cause of the difficulty as being in the spa.r.s.eness of the coils of wire on the magnet and the use of a single-cell battery. He furnished an electro-magnet and battery out of his own belongings, with which the efficiency of the contrivance was greatly increased. The only insulated wire then known was bonnet-wire, used by milliners for shaping the immense flaring bonnets worn by our grandmothers, and when it finally came to constructing the instruments of the first telegraphic system the entire stock of New York was exhausted. The immense stocks of electrical supplies now available for all purposes was then, and for many years afterwards, unknown. Previous to the investigations of Professor Henry, in 1830, only the theory of causing a core of soft iron to become a magnet was known, and the actual magnet, as we make it, had not been made. Morse, in his beginnings, had not money enough to employ a competent mechanic, and was himself possessed of but scant mechanical skill or knowledge of mechanical results. Persistency was the quality by which he succeeded.
[Ill.u.s.tration: DIAGRAM OF MORSE"S INSTRUMENT, 1830, WITH ITS WRITING.]
The battery used first by Morse, as stated, was a single cell. The one made later by his partner, Alfred Vail, the real author of all the workable features of the Morse telegraph, and of every feature which identifies it with the telegraph of the present, was a rectangular wooden box divided into eight compartments, and coated inside with beeswax so that it might resist the action of acids. The telegraphic instrument as made by Morse was a rectangular frame of wood, now in the cabinet of the Western Union Telegraph Company, at New York, which was intended to be clamped to the edge of a table when in use. He knew nothing of the splendid invention since known as the "Morse Alphabet,"
and the spelling of words in a telegram was not intended by him. His complicated system, as described in his caveat filed by him in 1837, consisted in a system of signs, by which numbers, and consequently words and sentences, were to be indicated. There was then a set of type arranged to regulate and communicate the signs, and rules in which to set this type. There was a means for regulating the movement forward of the rule containing the types. This was a crank to be turned by the hand. The marking or writing apparatus at the receiving instrument was a pendulum arranged to be swung _across_ the slip of paper, as it was unwound from the drum, making a zig-zag mark the points of which were to be counted, a certain number of points meaning a certain numeral, which numeral meant a word. A separate type was used to represent each numeral, having a corresponding number of projections or teeth. A telegraphic dictionary was necessary, and one was at great pains prepared by Morse. His process was, therefore, to translate the message to be sent into the numerals corresponding to the words used, to set the types corresponding to those numerals in the rule, and then to pa.s.s the rule through the appliance arranged for the purpose in connection with the electric current. The receiver must then translate the message by reference to the telegraphic dictionary, and write out the words for the person to whom the message was sent. This was all changed by Vail, who invented the "dot-and-dash" alphabet, and modified the mechanical action of the instrument necessary for its use. The arrangement of a steel embossing-point working upon a grooved roller--a radical difference--was a portion of this change. The invention of the axial magnet, also Vail"s, was another. Morse had regarded a mechanical arrangement for transmitting signals as necessary. Vail, in the practice of the first line, grew accustomed to sending messages by dipping the end of the wire in the mercury cup,--the beginning of the present transmitting instrument, which is also his invention--and Morse"s "port-rule," types, and other complicated arrangements, went into the sc.r.a.p-heap.
[Ill.u.s.tration: MODERN TRANSMITTER.]
Yet there were some strange things still left. The receiving relay weighed 185 pounds. An equally efficient modern one need not weigh more than half a pound. Morse had intended to make a _recording_ telegraph distinctively; it was to his mind its chiefest value. Almost in the beginning it ceased to be such, and the recording portion of the instrument has for many years been unknown in a telegraph office, being replaced by the "sounder." This was also the invention of Vail. The more expert of the operators of the first line discovered that it was possible to read the signals _by the sound_ made by the armature lever. In vain did the managers prohibit it as unauthorized. The practice was still carried on wherever it could be without detection.
Morse was uncompromising in his opposition to the innovation. The wonderful alphabet of the telegraph, the most valuable of the separate inventions that make up the system, was not his conception. The invention of this alphabetical code, based on the elements of time and s.p.a.ce, has never met with the appreciation it has deserved. It has been found applicable everywhere. Flashes of light, the raising and lowering of a flag, the tapping of a finger, the long and short blasts of a steam whistle, spell out the words of the English language as readily as does the sounder in a telegraph-office. It may be interpreted by sight, touch, taste, hearing. With a wire, a battery and Vail"s alphabet, telegraphy is entirely possible without any other appliances.
[Ill.u.s.tration: MODERN "SOUNDER."]
A brief sketch of the difficulties attending the making of the first practical telegraph line will be interesting as showing how much and how little men knew of practical electricity in 1843. [Footnote: There was no possibility of their knowing more, notwithstanding that, viewed from the present, their inexperienced struggles seem almost pathetic. So, also, do the ideas of Galvani and the experiments and conclusions of all except Franklin, until we come to Faraday. It is one of the features of the time in which we live that, regardless of age, we are all scholars of a new school in which mere diligence and behavior are not rewarded, and in which it is somewhat imperative that we should keep up with our cla.s.s in an understanding of _what are now the facts of daily life_, wonders though they were in the days of our youth.] To begin with, it was a "metallic circuit;" that is, two wires were to be used instead of one wire and a "ground connection." They knew nothing of this last. Vail discovered and used it before the line was finished. The two wires, insulated, were inclosed in a pipe, lead presumably, and the pipe was placed in the ground. Ezra Cornell, afterwards the founder of Cornell University, had been engaged in the manufacture and sale of a patent plow, and undertook to make a pipe-laying machine for this new telegraph line. After the work had been begun Vail tested and united the conductors as each section was laid. When ten miles were laid the insulation, which had been growing weaker, failed altogether. There was no current. Probably every schoolboy now knows what the trouble was. The earth had stolen the current and absorbed it. The modern boy would simply remark "Induction," and turn his attention to some efficient remedy. Then, there was consternation. Cornell dexterously managed to break the pipe-laying machine, so as to furnish a plausible excuse to the newspapers and such public as there may be said to have been before there was any telegraph line. Days were spent in consultation at the Relay House, and in finding the cause of the difficulty and the remedy.
Of the congressional appropriation nearly all had been spent. The interested parties even quarreled, as mere men will under such circ.u.mstances, and the want of a little knowledge which is now elementary about electricity came near wrecking forever an enterprise whose vast importance could not be, and was not then, even approximately measured.
[Ill.u.s.tration: ALFRED VAIL.]