THE OCEAN CABLE.--The remaining department of Telegraphy is embodied in the startling departure from ancient ideas of the possible which we know as cable telegraphy, the messages by such means beingcablegrams. About these ocean systems there are many features not applying to lines on land, though they are intended to perform the same functions in the same way, with the same object of conveying intelligence in language, instantly and certainly, but under the sea.
The marine cables are not simple wires. There is in the center a strand of usually seven small copper wires, intended as the conductor of the current. These, twisted loosely into a small cable, are surrounded by repeated layers of gutta-percha, which is, in turn, covered with jute. Outside of all there is an armor of wires, and the entire cable appears much like any other of the wire cables now in common use with elevators, bridges, and for many purposes. In the shallow waters of bays and harbors, where anchors drag and the like occurrences take place, the armor of a submarine cable is sometimes so heavy as to weigh more than twenty tons to the mile.
There are peculiar difficulties encountered in sending messages by an ocean cable, and some of these grow out of the same induction whose laws are indispensable in other cases. The inner copper core sets up induction in the strands of the outer armor, and that again with the surrounding water. There is, again, a species of re-induction affecting the core, so that faint impulses may be received at the terminals that were never sent by the operators. All of these difficulties combined result in what electricians term "retardation." It is one of the departments of telegraphy that, like the unavoidable difficulties in all machines and devices, educates men to their special care, and keeps them thinking. It is one of the natural features of all the mechanical sciences that results in the continual making of improvements.
The first impression in regard to ocean cables would be that very strong currents are used in sending impulses so far. The opposite is true. The receiving instrument is not the noisy "sounder" of the land lines. There was, until recently, a delicate needle which swung to and fro with the impulses, and reflected beams of light which, according to their number and the space between them spelled out the message according to the Vail dot-and-dash alphabet. Now, however, a means still more delicate has been devised, resulting in a faint wavy ink-line on a long, unwinding slip of paper, made by a fountain pen. This strange manuscript may be regarded as the latest system of writing in the world, having no relationship to the art of Cadmus, and requiring an expert and a special education to decipher it. Those faint pulsations, from a hand three thousand miles away across the sea, are the realization of a magic incredible. The necromancy and black art of all antiquity are childish by comparison. They give but faint indications of what they often are--the messages of love and death; the dictations of statesmanship; the heralds of peace or war; the orders for the disposition of millions of dollars.
The story of the laying of the first ocean cable is worthy of the telling in any language, but should be especially interesting to the American boy and girl. It is a story of native enterprise and persistence; perhaps the most remarkable of them all.
The earliest ocean telegraph was that laid by two men named Brett, across the English Channel. For this cable, a pioneer though crossing only a narrow water, the conservative officials of the British government refused a charter. In August, 1850, they laid a single copper wire covered with gutta-percha from Dover in England to the coast of France. The first wire was soon broken, and a second was made consisting of several strands, and this last was soon imitated in various short reaches of water in Europe.
But the Atlantic had always been considered unfathomable. No line had ever sounded its depths, and its strong currents had invariably swept away the heaviest weights before they reached its bed. Its great feature, so far as known, was that strange ocean river first noted and described by Franklin, and known to us as the Gulf Stream. In 1853 a circumstance occurred which again turned the attention of a few men to the question of an Atlantic cable. Lieutenant Berryman, of the Navy, made a survey of the bottom of the Atlantic from Newfoundland to Ireland, and the wonderful discovery was made that the floor of the ocean was a vast plain, not more than two miles below the surface, extending from one continent to the other. This plain is about four hundred miles wide and sixteen hundred long, and there are no currents to disturb the mass of broken shells and unknown fishes that lie on its oozy surface. It was named the "Telegraphic Plateau," with a view to its future use. At either edge of this plateau huge mountains, from four to seven thousand feet high, rise out of the depths. There are precipices of sheer descent down which the cable now hangs. The Azores and Bermudas are peaks of ocean mountains. The warm river known as the Gulf Stream, coming northward meets the ice-bergs and melts them, and deposits the shells, rocks and sand they carry on this plain. When it was discovered the difficulty in the way of an Atlantic cable seemed no longer to exist, and those who had been anxious to engage in the enterprise began to bestir themselves.
Of these the most active was the American, Cyrus W. Field. He began life as a clerk in New York City. When thirty-five years old he became engaged in the building of a land line of telegraph across Newfoundland, the purpose of which was to transmit news brought by a fast line of steamers intended to be established, and the idea is said to have occurred to him of making a line not only so far, but across the sea. In November, 1856, he had succeeded in forming a company, and the entire capital, amounting to 350,000 pounds, was subscribed. The governments of England and the United States promised a subsidy to the stockholders. The cable was made in England. TheNiagarawas assigned by the United States, and theAgamemnonby England, each attended by smaller vessels, to lay the cable. In August, 1857, the Niagara left the coast of Ireland, dropping her cable into the sea. Even when it dropped suddenly down the steep escarpment to the great plateau the current still flowed. But through the carelessness of an assistant the cable parted. That was the beginning of mishaps. The task was not to be so easily done, and the enterprise was postponed until the following year.
That next year was still more memorable for triumph and disappointment. It was now designed that the two vessels should meet in mid-ocean, unite the ends of the cable, and sail slowly to opposite shores. There were fearful storms. The hugeAgamemnon, overloaded with her half of the cable, was almost lost. But finally the spot in the waste and middle of the Atlantic was reached, the sea was still, and the vessels steamed away from each other slowly uncoiling into the sea their two halves of the second cable. It parted again, and the two ships returned to Ireland.
In July they again met in mid-ocean. Europe and America were both charitably deriding the splendid enterprise. All faith was lost. It was known, to journalism especially, that the cable would never be laid and that the enterprise was absurd. But it was like the laying of the first land line. There was a way to do it, existing in the brains and faith of men, though at first that way was not known. From this third meeting the two ships again sailed away, theNiagarafor America, theAgamemnonfor Valencia Bay. This time the wire did not part, and on August 29th, 1858, the old world and the new were bound together for the first time, and each could read almost the thoughts of the other. The queen saluted America, and the president replied. There were salutes of cannon and the ringing of bells. But the messages by the cable grew indistinct day by day, and finally ceased. The Atlantic cable had been laid, and--had failed.
Eight years followed, and the cable lay forgotten at the bottom of the sea. The reign of peace on earth and good will to men had so far failed to come and they were years of tumult and bitterness. The Union of the United States was called upon to defend its integrity in a great war. A bitter enmity grew up between us and England. The telegraph, and all its persevering projectors, were almost absolutely forgotten. Electricians declared the project utterly impracticable, and it began, finally, to be denied that any messages had ever crossed the Atlantic at all, and Field and his associates were discredited. It was said that the current could not be made to pass through so long a circuit. New routes were spoken of--across Bering's Strait, and overland by way of Siberia--and measures began to be taken to carry this scheme into effect.
Amid these discouragements, Field and his associates revived their company, made a new cable, and provided everything that science could then suggest to aid final success. This new cable was more perfect than any of the former ones, and there was a mammoth side-wheel steamer known as theGreat Eastern, unavailable as it proved for the ordinary uses of commerce, and this vessel was large enough to carry the entire cable in her hold. In July, 1865, the huge steamer left Ireland, dropping the endless coil into the sea. The same men were engaged in this last attempt that had failed in all the previous ones. It is one of the most memorable instances of perseverance on record. But on August 6th a flaw occurred, and the cable was being drawn up for repairs. The sound of the wheel suddenly stopped; the cable broke and sunk into the depths. TheGreat Easternreturned unsuccessful to her port.
Field was present on board on this occasion, and had been present on several similar ones. There was, so far as known, no record made by him of his thoughts. There were now five cables in the bed of the Atlantic, and each one had carried down with it a large sum of money, and a still larger sum of hopes. Yet the Great Eastern sailed again in July, 1866, her tanks filled with new cable and Field once more on her decks. It was the last, and the successful attempt. The cable sank steadily and noiselessly into the sea, and on July 26th the steamer sailed into Trinity Bay. The connection was made at Heart's Content, a little New Foundland fishing village, and one for this occasion admirably named. Then the lost cable of 1865 was found, raised and spliced.
In these later times, if a flaw should occur, science would locate it, and go and repair it. Even if this were not true, the fact remains that this last cable, and that of 1865, have been carrying their messages under the sea for nearly thirty years. The lesson is that repeated failures do not meanfinalfailure. There is often said to be a malice, a spirit of rebellion, in inanimate things. They refuse to become slaves until they are once and for all utterly subdued, and then they are docile forever. Yet the malice truly lies in the inaptitude and inexperience of men. Had Field and his associates known how to make and lay an Atlantic cable in the beginning as well as they did in the end, the first one laid would have been successful. The years were passed in the invention of machinery for laying, and in improving the construction of each successive cable. Many have been laid since then, certainly and without failure. Men have learned how. [24]
24.At present the total mileage of submarine cables is about 152,000 miles, costing altogether $200,000,000. The length of land wires throughout the world is over 2,000,000 miles, costing $225,000,000. The capital invested in all lines, land and sea, is about $530,000,000.
Thirteen years were passed in this succession of toils, expenditures, trials and failures. Field crossed the Atlantic more than fifty times in these years, in pursuit of his great idea. At last, like Morse, he was crowned with wealth, success, medals and honors. He was acquainted with all the difficulties. It is now known that he knew through them all that an ocean cable could finally be laid.
THE TELEPHONE.--The telegraph had become old. All nations had become accustomed to its use. More than thirty years had elapsed--a long time in the last half of the nineteenth century--before mankind awoke to a new and startling surprise; the telegraph had been made to transmit not only language, but the human voice in articulate speech. [25] The fact first became known in 1873, and was the invention of Alexander G. Bell, of Chicago.
25.It has been noted that Morse's idea was arecordingtelegraph, that being in his mind its most valuable point, and that this idea has long been obsolete. In like manner, when the Telephone was invented there was a general business opinion that it was perhaps an instrument useful in colleges for demonstrating the wonders of electricity, but not useful for commercial purposesbecause it made no record. "Business will always be done in black and white" was the oracular verdict of prominent and experienced business men. It may be true, but a little conversation across space has been found indispensable. The telephone is a remarkable business success.
DIAGRAM OF TELEPHONE.--THE BLAKE TRANSMITTER
There were several, no one knows how many, attempts to accomplish this remarkable feat previous to the success of Professor Bell. One of these was by Reis, of Frankfort, in 1860. It did not embrace any of the most valuable principles involved in what we know as the telephone, since it could not transmitspeech. Professor Bell's first operative apparatus was accompanied by simultaneous inventions by Gray, Edison, and others. This remarkable instance of several of the great electricians of the country evolving at nearly the same time the same principal details of a revolutionary invention, has never been fully explained. The first rather crude and ineffective arrangements were rapidly improved by these men, and by others, prominent among whom is Blake, whose remarkable transmitter will be described presently. The best devices of these inventors were finally embodied, and in the resulting instrument we have one of the chiefest of those modern wonders whose first appearance taxed the credulity of mankind. [26]
26.There were, until a recent period, a line of statements, alleged facts and reasonings, that were incredible in proportion to intelligence. The occurrences of recent times have reversed this rule with regard to all things in the domain of applied science. It is the ignorant and narrow only who are incredulous, and the ears of intelligence are open to every sound. All that is not absurd is possible, and all that is possible is sure to be accomplished. The telephone, as a statement,wasabsurd, but not to the men who worked for its accomplishment and finally succeeded. The lines grow narrow. It requires now a high intelligence to decide even upon the fact of absurdity within the domain of natural law.
In reality the telephone is simple in construction. Workmen who are not accomplished electricians constantly erect, correct and repair the lines and instruments. The machine is not liable to derangement. Any person may use it the first time of trying, and this use is almost universal. Yet it is, from the view of any hour in all the past, an incomprehensible mystery. A moment of reflection drifts the mind backward and renders it almost incredible in the present. The human voice, recognizable, in articulate words, is apparently borne for miles, now even for some hundreds of miles, upon an attenuated wire which hangs silent in the air carrying absolutely nothing more than thousands of little varying impulses of electricity. Not a word that is spoken at one end of it is ever heard at the other, and the conclusion inevitable to the reason of even twenty years ago would be that if one person does not actually hear the other talk there is a miracle. Probably this idea that the voice is actually carried is not very uncommon. The facts seem incomprehensible otherwise, and it is not considered that if that idea were correct itwouldbe a miracle.
The entire explanation of the magic of the telephone lies in electrical induction. To the brief explanation of that phenomenon previously given the reader is again referred for a better understanding of what now follows.
But, first, a moment's consideration may be given to the results produced by the use of this appliance, which, as an illustration of the way of the world was an innovation that, had it remained uninvented or impossible, would never have been even desired. One third more business is said now to be transacted in the average day than was possible previously. Since many things can now go on together which previously waited for direction, authority and personal arrangement, a man's business life is lengthened one-third, while his business may mostly be done, to his great convenience, from one place. It has given employment to a large number of persons, a large proportion of whom are young women. The status of woman in the business world has been, fortunately or unfortunately, by so much changed. It has introduced a new necessity, never again to be dispensed with. It has changed the ancient habits, and with them, unconsciously,the habit of thought. Contact not personal between man and man has increased. Thethoughtof others is quickly arrived at. It has caused us to become more appreciative of the absolute meanings and values of words, without assistance from face, manner or gesture. Laughter may be heard, but tears are unseen. It has induced caution in speech and enforces brevity. While none of its conveniences are now noted, and all that it gives is expected, the telephone, with all its effects, has entered--into the sum of life.
On the wall or table there is a box, and beside this box projects a metal arm. In a fork of this arm hangs a round, black, trumpet-shaped, hard rubber tube. This last is the receiving instrument. It is taken from its arm and held close to the ear. The answers are heard in it as though the person speaking were there concealed in an impish embodiment of himself. Meantime the talking is done into a hole in the side of the box, while the receiver is held to the ear. This is all that appears superficially. An operation incredible has its entire machinery concealed in these simplicities. It is difficult to explain the mystery of the telephone in words--though it has been said to be simple--and it is almost impossible unless the reader comprehends, or will now undertake to comprehend, what has been previously said on the subject of the production of magnetism by a current of electricity, as in the case of the electro-magnet, and on the subject of induction and its laws.
It has been shown that electricity produces magnetism; that the current, properly managed as described, creates instantly a powerful magnet out of a piece of soft iron, and leaves it again a mere piece of iron at the will of the operator. This process also will work backwards. An electric current produces a magnet, anda magnet also may be made to produce an electric current. It is one more of the innumerable, almost universal, cases where scientific and mechanical processes may be reversed. When the dynamo is examined this process is still further exemplified, and when we examine the dynamo and the motor together we have a striking example of the two processes going on together.
The application of this making of a current, or changing its intensity, in the telephone, is apparently totally unlike the continuous manufacture of the induced current for daily use by means of the steam engine and dynamo. But it is in exact accord with the same laws. It will, perhaps, be more readily understood by recalling the results of the experiment of the two wires, where it was found that anapproach to, or areceding from, a wire carrying a current, produces an impulse over the wire that has by itself no current at all. Now, it must be added to that explanation that if the battery were detached from that conducting wire, and if, instead of its being a wire for the carrying of a battery currentit were itself a permanent magnet, the same results would happen in the other wire if it were rapidly moved toward and away from this permanent magnet. If the reader should stretch a wire tightly between two pegs on a table, and should then hold the arms of a common horseshoe magnet very near it, and should twang the stretched wire with his finger, as he would a guitar string, the electrometer would show an induced alternate current in the wire. Since this is an illustration of the principle of the dynamo, stated in its simplest form, it may be well to remember that in this manner--with the means multiplied and in all respects made the most of--a very strong current of electricity may be evolved without any battery or other source of electricity except a magnet. In connection with this substitution of a magnet for a current-carrying wire, it must be remembered that moving the magnet toward or from the wire has the same result as moving the wire instead. It does not matter which piece is moved.
In addition to the above, it should be stated that not only will an induced current be set up in the wire, but alsothe magnetism in the magnet will be increased or diminished as the tremblings of the wire cause it to approach or recede from it. Therefore if a wire be led away from each pole of a permanent magnet, and the ends united to form a circuit, an induced current will appear in this wire if a piece of soft iron is passed quickly near the magnet.
There is an essential part of the telephone that it is necessary to go outside of the field of electricity to describe. It is undoubtedly understood by the reader that all sound is produced by vibrations, or rapid undulations, of the surrounding air. If a membrane of any kind is stretched across a hoop, and one talks against it, so to speak, the diaphragm or membrane will be shaken, will vibrate, with the movement of the air produced by the voice. If a cannon be fired all the windows rattle, and are often broken. A peal of thunder will cause the same jar and rattle of window panes, manifestly by what we call "sound"--vibrations of the air. The window frame is a "diaphragm." The ear is constructed on the same principle, its diaphragm being actually moved by the vibrations of air, being what we call hearing. With these facts about sound understood in connection with those given in connection with the substitution of a magnet for a battery current, it is entirely possible for any non-expert to understand the theory of the construction of the telephone.
In the Bell telephone, now used with the Blake transmitter [which differs somewhat from the arrangement I shall now describe] a bar magnet has a portion of its length wound with very fine insulated wire. Across the opposite end of this polarized [27] magnet, crosswise to it, and very close, there is placed a diaphragm of thin sheet iron. This is held only around its edge, and its center is free to vibrate toward and from the end of this polarized magnet. This thin disc of iron, therefore, follows the movements, the "soundwaves," of the air against it, which are caused by the human voice. We have an instance of apiece of soft iron moving toward, and away from, a magnet. It moves with a rapidity and violence precisely proportioned to the tones and inflections of the voice. Those movements are almost microscopic, not perceptible to the eye, but sufficient.
27."Polarized" means magnetized; having the two poles of a permanent magnet. The term is frequently used in descriptions of electrical appliances. Instead of using the termspositiveandnegative, it is also customary to speak of the "North" or the "South" of a magnet, battery or circuit.
The approaching and receding have made a difference, in the quality of the magnet. Its magnetism has been increased and diminished, and the little coil of insulated wire around it has felt these changes, and carried them as impulses over the circuit of which it is a part. In that circuit, at the other end, there is a precisely similar little insulated coil, upon a precisely similar polarized magnet. These impulses pass through this second coil, and increase or diminish the magnetism in the magnet round which it is coiled. That, in turn, affects by magnetic attraction the diaphragm that is arranged in relation to its magnet precisely as described for the first. The first being controlled as to the extent and rapidity of its movements by the loudness and other modifications of the voice, the impulses sent over the circuit vary accordingly. As a consequence, so does the strength of the magnet whose coil is also in the circuit. So, therefore, does its power of attraction over its diaphragm vary. The result is that the movements that are caused in the first diaphragm by the voice, are caused in the second by anattractionthat varies in strength in proportion to the vibrations of the voice speaking against the first diaphragm.
This is the theory of the telephone. The sounds are not carried, butmechanically producedagain by the rattle of a thin piece of iron close to the listener's ear. The voice is full, audible, distinct, as we hear it naturally, and as it impinges upon the transmitting diaphragm. In reproduction at the receiving instrument it is small in volume; almost microscopic, if the phrase may be applied to sound. We hear it only by placing the ear close to the diaphragm. It will be seen that this is necessarily so. No attempts to remedy the difficulty have so far been successful. There is no means of reproducing the volume of the voice with the minute vibrations of a little iron disc.
In actual service an electro-magnet is used instead of, or in addition to, the bar magnets described above. A steady flow from a battery is passed through an instrument which throws this current into proper vibrations by stopping the flow of the current at each interval between impulses. There is a piece of carbon between the diaphragm and its support. The wires are connected with the diaphragm and its support, and the current passes through the carbon. When the diaphragm vibrates, the carbon is slightly compressed by it. Pressure reduces its resistance, and a greater current passes through it and over the wires of the circuit for the instant during which the touch remains. This is the Blake transmitter. It should be explained that carbon stands low on the list of conductors of electricity. The more dense it is, the better conductor. The varying pressures of the diaphragm serve to produce this varying density and the consequent varying impulses of the current which effect the receiving diaphragm.
The transmitter, as above described, is in the square box, and its round black diaphragm may be seen behind the round hole into which one talks. [28] The receiver is the trumpet-shaped tube which hangs on its side, and is taken from its hook to be used. The call-bell has nothing to do with the telephone. It is operated by a small magneto-generator,--a very near relative of the dynamo-the current from which is sent over the telephone circuit (the same wires) when the small crank is turned. Sometimes the question occurs: "Why ring one's own bell when one desires to ring only that at the central office?" The answer is that both bells are in the same circuit. If the circuit is uninterrupted your bell will ring when you ring the other, and a bell at each end of your circuit is necessary in any case, else you could not yourself be called.
28.Shouting into a telephone doubtless comes of the idea, unconscious, that one is speaking to a person at a distance. To speak distinctly is better, and in an ordinary tone.
When the receiving instrument is on its hook its weight depresses the lever slightly. This slight movementconnectsthe bell circuit anddisconnectsthe telephone circuit. Take it off the hook and the reverse is effected.
The long-distance telephone differs from the ordinary only in larger conductors, improved instruments, and a metallic circuit--two wires instead of the ordinary single wire and ground connections.
TELEAUTOGRAPH TRANSMITTING INSTRUMENT
THE TELAUTOGRAPH.--This, the latest of modern miracles in the field of electricity, comes naturally after the telegraph and telephone, since it supplements them as a means of communication between individuals. It also is the invention of Prof. Elisha Gray, who seems to be as well the author of the name of his extraordinary achievement. It is not the first instrument of the kind attempted. The desire to find a means of writing at a distance is old. Bain, of Edinburgh, made a machine partially successful fifty years ago. Like the telegraph as intended by Morse, there was the interposition of typesetting before a message could be sent. It did not write, or follow the hand of the operator in writing, though it did reproduce at the other end of the circuit in facsimile the faces of the types that had been set by the sender. It was a process by electrolysis, well understood by all electricians. Several of this variety of writing telegraphs have been made, some of them almost successful, but all lacking the vital essential. [29] In 1856 Casselli, of Florence, made a writing telegraph which had a pendulum arrangement weighing fourteen pounds. Only one was ever made, but it resulted in many new ideas all pertaining to the facsimile systems--the following of the faces of types--and all were finally abandoned.
29.The lack ofone vital essentialhas been fatal to hundreds of inventions. Inventors unconsciously follow paths made by predecessors. The entire class of transmitting instruments must dispense with tedious preliminaries, and must usewords. Vail accomplished this in telegraphy. Bell and others in the telephone, and Gray has borne the same fact in mind in the present development of the telautograph.
The invention of Gray is a departure. The sender of a message sits down at a small desk and takes up a pencil, writing with it on ordinary paper and in his usual manner. A pen at the other end of the circuit follows every movement of his hand. The result is an autograph letter a hundred miles or more away. A man in Chicago may write and sign a check payable in Indianapolis. Personal directions may be given authoritatively and privately. As in the case of the telephone, no intervening operator is necessary. No expertness is required. Even the use of the alphabet is not necessary. A drawing of any description, anything that can be traced with a pen or pencil, is copied precisely by the pen at the receiving desk. The possibilities of this instrument, the uses it may develop, are almost inconceivable. It might be imagined that the lines drawn would be continuous. On the contrary, when the pen is lifted by the writer at the sending desk it also lifts itself from the paper at that of the receiver.
The action of the telautograph depends upon the variations in magnetic strength between two small electro-magnets. It has been seen that an electro-magnet exerts its attractive force in proportion to the current which passes through its coil. To use a phrase entirely non-technical, it will "pull" hard or easy in proportion to the strength of the passing current. This fact has been observed as the cause of action in the telephone, where one diaphragm, moved by the air-vibrations caused by the voice, causes a varying current to pass over the wire, attracting the other diaphragm less or more as the first is moved toward or away from its magnet. In the telautograph the varying currents are caused not by the diaphragm influenced by the voice, butby a pencil moved by the hand.
To show how these movements may be caused let us imagine a case that may occur in nature. It is an interesting mechanical study. There is an upright rush or reed growing in the middle of a running stream. The stem of this rush has elasticity naturally; it has a tendency to stand upright; but it bends when there is a current against it. It is easy enough to imagine it bending down stream more or less as the current is more or less strong.
Imagine now another stream entering the first at right angles to it, and that the rush stands in the center of both currents. It will then bend to the force of the second stream also, and the direction in which it will lean will be a compromise between the forces of the two. Lessen the flow of the current in one of the streams, and the rush will bend a little less before that current and swing around to the side from which it receives less pressure. Cut off either of the currents entirely, and it will bend in the direction of the other current only. In a word,if the quantity or strength of the current of both streams can be controlled at will, the rush can be made to swing in any direction between the two, and its tip will describe any figure desired, aided, of course, by its own disposition to stand upright when there is no pressure.
Let us imagine the rush to be a pen or pencil, and the two streams of water to be two currents of electricity having power to sway and move this pencil in proportion to their relative strength, as the streams did the rush. Imagine further that these two currents are varied and changed with reference to each other by the movements of a pen in a man's hand at another place. It is an essential part of the mechanism of the telautograph, and the movement is known among mechanicians as "compounding a point."
Gray, while using the principles involved in compounding a point, seems to have discarded the ways of transmitting magnetic impulses of varying strength commonly in use. His method he calls the "step-by-step" principle, and it is a striking example of what patience and ingenuity may accomplish in the management of what is reputedly the most elusive and difficult of the powers of nature. The machine was some six years in being brought into practical form, and was perfected only after a long series of experiments. In its operation it deals with infinitesimal measurements and quantities. The first attempts were on the "variable current" system, which was later discarded for the "step-by-step" plan mentioned.
In writing an ordinary lead pencil may be used. From the point of this two silk cords are extended diagonally, their directions being at right angles to each other, and the ends of these cords enter openings made for them in the cast iron case of the instrument on each side of the small desk on which the writing is done.
Inside the case each cord is wound on a small drum which is mounted on a vertical shaft. Now if the pencil-point is moved straight upward or downward it is manifest that both shafts will move alike. If the movement is oblique in any direction, one of the shafts will turn more than the other, and the degree of all these turnings of each shaft in reference to the other will be precisely governed by the direction in which the pencil-point is moved.
DIAGRAM OF MECHANICAL TELAUTOGRAPH. BOW-DRILL ARRANGEMENT
Now, suppose each shaft to carry a small, toothed wheel, and that upon these teeth a small arm rests. As the wheel turns this arm will move as a pawl does on a ratchet. Imagine that at each slight depression between the ratchet-teeth it breaks a contact and cuts off a current, and at each slight rise renews the contact and permits a current to pass. This current affects an electro-magnet--one for each shaft--at the receiving end, and each of these magnets, when the current is on, attracts an armature bearing a pawl, which, being lifted, allows the notched wheel, upon which it bears, to turnto the extent of one notch. The arrangement may be called an electric clutch, that may be arranged in many ways, and the detail of its action is unimportant in description, so that it be borne in mind thateach time a notch is passed in turning the shaft by drawing upon or relaxing the cords attached to the pencil-point, an impulse of electricity is sent to an electro-magnet and armature which allowsa corresponding wheel and its shaft to turn one notch, or as many notches, as are passed at the transmitting shaft. In moving the pencil one inch to one side, we will suppose it permits the shaft on which the cord is wound to turn forty notches. Then forty impulses of electricity have been sent over the wire, the clutch has been released forty times, and the shaft to which it is attached has turned precisely as much as the shaft has which was turned, or was allowed to turn, by the cord wound upon it and attached to the pencil.
It will be remembered that the arrangement is double. There are two shafts operated by the writer's pencil--one on each side of it. Two corresponding shafts occupy relative positions in respect to the automatic pen of the receiving instrument. There are two circuits, and two wires are at present necessary for the operation of the instrument. It remains to describe the manner of operating the automatic pen by connection with its two shafts which are turned by the step-by-step arrangement described, precisely as much and at the same time as those of the transmitting instrument are.
WORK OF THE TELAUTOGRAPH. COLUMBIAN EXPOSITION, 1893
To each shaft of the receiving instrument is attached an aluminum pen-arm by means of cords, each arm being fixed, in regard to its shaft, as a bow drill is in regard to its drill. These arms meet in the center of the writing tablet, V-shaped, as the cords are with relation to the writer's pencil in the sending instrument. A small tube conveys ink from a reservoir along one of the pen-arms, and into a glass tube upright at the junction of the arms. This tube is the pen. Now, let us imagine the pencil of the writer pushed straight upward from the apex of the V-shaped figure the cords and pencil-point make on the writing desk. Then both the shafts at the points of the arms of the V will rotate equally. [30] The number of impulses sent from each of these shafts, by the means explained, will be equal. Each of the shafts of the receiving instrument will rotate alike, and each draw up its arm of the automatic pen precisely as though one took hold of the points of the two legs of the V, and drew them apart to right and left in a straight line. This moves the apex of the V, with its pen, in a straight line upward at the same time the writer at the sending instrument pushed his pencil upward. If this one movement, considered alone, is understood, all the rest follow by the same means. This is, as nearly as it may be described without the use of technical mechanical terms, the principle of the telautograph. It must be seen that all that is necessary to describe any movement of the sender's pencil upon the paper under the receiving pen is that the rotating upright shafts of the latter should move precisely as much, and at the same time, with those two which get their movement from the wound cords and attached pencil-points in the hand of the writer.
30.See diagram of mechanical Telautograph, and of bow drill. In the latter, in ordinary use, the stick and string; rotate the spool. Rotating the spool will, in turn, move the stick and string, and this is its action in the pen-arms of the Telautograph.
Only one essential item of the movement remains. The shafts of both instruments must be rotated by some separate mechanical agency, capable of being automatically reversed. By an arrangement unnecessary to explain in detail, the pencil of the writer lifted from the paper resting on the metallic table which forms the desk; results in the automatic lifting of the pen from the paper at the receiving desk.
Prof. Elisha Gray was born in 1835, in Ohio. He was a blacksmith, and later, a carpenter. But he was given to chemical and mechanical experiments rather than to the industries. When twenty-one, he entered Oberlin College, remaining there five years, and earning all the money he spent. He devoted his time chiefly to studies of the physical sciences. As a young man he was an invalid. Later he was not remarkably successful in business, failing several times in his beginnings. His first invention was a telegraph self-adjusting relay. It was not practically successful. Afterwards he was employed with an electrical manufacturing company at Cleveland and Chicago. Most of his earlier inventions in the line of electrical utility are not distinctively known. He has never been idle, and they all possessed practical merit. For many years before he was known as the wizard of the telautograph, he was foremost in the ranks of physicists and electricians. He is not a discoverer of great principles, but is professionally skillful and accomplished, and eminently practical. His every effort is exerted to avoid intricacy and clumsiness in machinery. In 1878 he was awarded the grand prize at the Paris Exposition, and was given the degree of Chevalier and the decorations of the Legion of Honor by the French Government, and again in 1881, at the Electrical Exposition at Paris, he was honored with the gold medal for his inventions. He secured the degree of A.M. at Oberlin College, and was the recipient of the degree of Ph.D. from the Ripon (Wis.) College. For years he was connected with those institutions as non-resident Lecturer in Physics. Another University gave him the degree of LL.D. He is a member of the American Philosophical Society, the Society of Electrical Engineers of England, and the Society of Telegraph Engineers of London. He received an award and a certificate from the Centennial Exposition for his inventions in electricity.
The same lesson is to be gathered from his career, so far, that is given by the life of every noted American. It means that money, family, prestige, have no place as leverages of success in any field. The rule is toward the opposite. The qualities and capacities that win do so without these early advantages, and all the more surely because there is an inducement to use them. There is no "luck."
THE ELECTRIC LIGHT.
It has been stated that modern theory recognizes two classes of electricity, theStaticand theDynamic. The difference is, however, solely noticeable in operation. Of the dynamic class there can be no more common and striking example than the now almost universal electric light. Yet, with a sufficient expenditure of chemicals and electrodes, and a sufficient number of cells, electric lighting, either arc or incandescent, can be as effectively accomplished as with the current evolved by a powerful dynamo. [31]
31.As an illustration of the day of beginnings, a few years ago thethalus, or lantern, the pride of the rural Congressman, on the dome of the Capitol at Washington was lighted by electricity, and an immense circular chamber beneath the dome was occupied by hundreds of cells of the ordinary form of battery. The lamps were of the incandescent variety, and what we now know as the filament was platinum wire. Vacuum bulb, filament, carbon, dynamo, were all unknown. But the current, and the heat of resistance, and every fact now in use in electric lighting, were there in operation.
The reader will understand that modern dynamic electricity owes its development to the principle of economy in production. Practical science most effectively awakens from its lethargy at the call of commerce. Nevertheless, from the earliest moment in which it became known that electricity was akin to heat--that an interruption of the easy passage of a current produced heat--the minds of men were busy with the question of how to turn the tremendous fact to everyday use. Progress was slow, and part of it was accidental. The great servant of modern mankind was first an untrained one. It was a marked advance when the gaslights in a theater could be all lighted at once by means of batteries and the spark of an induction coil. The bottom of Hell Gate, in New York harbor, was blown out by Gen. Newton by the same means, and would have been impossible otherwise. But these were only incidents and suggestions. The question was how to make this instantaneous sparkcontinuous. There was pondering upon the fact that the only difference between heat and electricity is one of molecular arrangement. Heat is a molecular motion like that of electricity, without the symmetry and harmony of action electricity has. The vibrations of electricity are accomplished rapidly, and without loss. Those of heat are slow, and greatly radiated.When a current of electricity reaches a place in the conductor where it cannot pass easily, and the orderly vibrations of its molecules are disturbed, they are thrown into the disorderly motion known as heat.So, when the conductor is not so good; when a large wire is reduced suddenly to a small one; when a good conductor, such as copper, has a section of resisting conduction, such as carbon; heat and light are at once evolved at that point, and there is produced what we know as the electric light. However concealed by machinery and devices, and all the arrangements by which it is made more lasting, steady, economical and automatic, it is no more nor less than this.The difference between heat and electricity is only a difference in the rates of vibration of their molecules.Whatever the theory as to molecules, or essence, or actual nature and origin, the practical fact that heat and light are the results of the circumstances described above remains. This has long been known, and the question remained how to produce an adequate current economically. The result was the machine we know as the Dynamo.
The first electric light was very brief and brilliant and was made by accident. Sir Humphrey Davy, in 1809, in pulling apart the two ends of wires attached to a battery of two thousand small cells, the most powerful generator that had been made to that time, produced a brief and brilliant spark, the result of momentarilyimperfect contact.Every such spark, produced since then innumerable times by accident, is an example of electric lighting. There are now in use in the United States some two million arc lights and nearly double that number of incandescent.
There are two principal systems of electric lighting; one is by actually burning away the ends of carbon-points in the open air. This is the "arc." The other is by heating to a white heat a filament of carbon, or some substance of high resistance, in a glass bulb from which the air has been exhausted. This is the "incandescent."
THE INCANDESCENT LIGHT
In the arc light the current passes across animperfect contact, and this imperfection consists in a gap of about one-sixteenth of an inch between the extremities of two rods of carbon carrying a current. This small gap is a place of bad conduction and of the piling up of atoms, producing heat, burning, light. In the body of the lamp there are appliances for the automatic holding apart of the two points of the carbon, and the causing of them to continually creep together, yet never touch. Many devices have been contrived to this end. With all theories and reasons well known, and all effects accurately calculated, upon this small arrangement depends the practical utility of the arc light. The best arrangement is the invention of Edison, and is controlled most ingeniously by the current itself, acting through the increased difficulty of its passage when the two carbon-points are too far apart, and the increased ease with which it flows when they are too near together. The current, in leaping the small gap between the carbon-points, takes acurvedpath, hence the name "arc" light. In passing from the positive to the negative carbon it carries small particles of incandescent carbon with it, and consequently the end of the positive carbon is hollowed out, while the end of the negative is built up to a point.
The incandescent light is in principle the same as the arc, produced by the same means and based upon the same principle of impediment to the free passage of the current. It was first produced by heating with the current to incandescence a fine platinum wire. As stated above, electricity that quietly traverses a large wire will suddenly develop great heat upon reaching a point where it is called upon to traverse, a smaller one. Platinum was attempted for this place of greater resistance because of its qualities. It does not rust, has a low specific heat, and is therefore raised to a higher temperature with less heat imparted. But it was a scarce and expensive material, and so long as it was heated to incandescence in the open air, that is, so long as its heat was fed as other heat is, by oxygen, it was slowly consumed. Platinum is no longer in the field of electric lighting, and the substitute which takes its place in the present incandescent lamp, and which is known as a "filament," is not heated in contact with the air. The experiments and endeavors that brought this result constitute the story of the incandescent lamp.
The result is due to the patient intelligence of the American scientist and inventor, Thomas A. Edison. After all the absolute essentials of a practical incandescent lamp had been thought out; after the qualities and characteristics of the current were all known under the circumstances necessary to its use in lighting, the practical accomplishment still remained. Edison is said to have once worked for several weeks in the making of a single loop-shaped carbon filament that would bear the most delicate handling. This was then carefully carried to a glass-worker to be inclosed in a bulb, and at the first movement he broke it, and the work must be done over and done better. It finally was. The little pear-shaped bulb with its delicate loop of filament, which cost months of toil and experiment at first, is now a common article, manufactured at an absurdly small cost, packed in barrelfuls and shipped everywhere, and consumed by the million. A means has been found for producing the vacuum of its interior rapidly, cheaply and thoroughly, and the beautiful incandescent glow hangs in lines and clusters over the civilized world. The phenomenon of incandescence without oxygen seems peculiar to these lights alone. [32]
32.The "electric field," previously explained, seemed to exist by giving a magnetic quality to the surrounding air. It would be as true if one should speak of a magnetized vacuum, since the same field would exist in that as in surrounding air.
So simple are great facts when finally accomplished that there remains little to add on the subject of the mechanism of the electric light. The two varieties, arc and incandescent, are used together as most convenient, the large and very brilliant arc being especially adapted to out-of-doors situations, and the gentler, steadier and more permanent glow of the incandescent to interiors. The latter is also capable of a modification not applicable to the arc. It can, in theaters and other buildings, be "turned down" to a gentle, blood-red glow. The means by which this is accomplished is ingenious and surprising, since it means that the supply of electricity over a wire--seemingly the most subtle and elusive essence on earth--may be controlled like a stream from a cock, or the gas out of a burner. But this reduction of the current that makes the red glow in the clusters in a theater is by no means the only instance. The trolley-car, and even the common motor, may be made to start very slowly, and the unseen current whose touch kills is fed to its consumer at will.
THE DYNAMO.--To the man who has been all his life thinking of the steam engine as the highest and almost only embodiment of controlled mechanical power, another machine, both supplementary to the steam engine and far excelling it, whose familiarburringsound is now heard in almost every village in the United States and has become the characteristic sound of modern civilization, must constitute a source of continual question and surprise. To be accustomed to the dynamo, to look upon it as a matter of course and a conceded fact, one must have come to years of maturity and found it here.
Its practical existence dates back at furthest to 1870. Yet it is based upon principles long since known, and can scarcely be said to be the invention of any one mind or man. Its lineal ancestor was themagneto-electric machine, in the early construction of which figure the names of Siemens, Wilde, Ladd, and earlier and later electricians. Kidder's medical battery used forty years ago or more, and still used and purchasable in its first form, was a dynamo. A footnote in a current encyclopedia states that: "An account of the Magneto-electric machine of M. Gramme, in the LondonStandardof April 9th, 1873, confirmed by other information, leads to the belief that a decided improvement has been made in these machines." The word "dynamo" was then unknown. Later, Edison, Weston, Thompson, Hopkinson, Ferranti and others appear as improvers in the mechanism necessary for best developing a well-known principle, and many of these improvements may be classed among original inventions. As soon as the magneto-electric machine attained a size in the hands of experimenters that took it out of the field of scientific toys it began to be what we now know as a dynamo. A paragraph in the encyclopedia referred to says, in speaking of Ladd, of London, "These developments of electric action are not obtained without corresponding expenditure of force. The armatures are powerfully attracted by the magnets, and must be forcibly pulled away. Indeed, one of Wilde's machines, when producing a very intense electric light, required about five horse power to drive it."
MAGNETO-ELECTRIC MACHINE. THE PREDECESSOR OF THE DYNAMO
Thus was the secret in regard to electric power unconsciously divulged some twenty years ago.
In all nature there is no recipe for getting something for nothing. The modern dynamo, apparently creating something out of nothing, like all other machinesgives back only what is given to it, minus a fair percentage for waste, loss, friction, and common wear. Its advantages amount to a miracle of convenience only. So far as power is concerned, it merely transfers it for long distances over a single wire. So far as light is considered, it practically creates it where wanted, in new and convenient forms, with a new intensity and beauty, but with the same expenditure of transmitted energy in the form of burned coal as would be used in manufacturing the gas that was new, wonderful, and a luxury at the beginning of the century.
The dynamo is the most prominent instance of actual mechanical utility in the field of electrical induction. It seems almost incredible that the apparently small facts discovered by Faraday, the bookbinder, the employé of Sir Humphrey Davy at weekly wages the struggling experimenter in the subtleties of an infant giant, should have produced such results within sixty years. [33]
33.Faraday was not entirely alone in his life of physical research. He was associated with Davy, and quarreled with him about the liquefaction of chlorine and other gases, and was the companion of Wallaston, Herschel, Brand, and others. In connection with Stodart, he experimented with steel, with results still considered valuable. The scientific world still speaks of his quarrel with Davy with regret, since the personalities of great men should be free from ordinary weaknesses. But Lady Davy was not a scientist, and while the brilliant young mechanic was in her husband's employment for scientific purposes she insisted upon treating him as a servant, whereat the independence of thinking which made him capable of wandering in fields unknown to conventionality and routine blazed into natural resentment. The quarrel of 1823 must have been greatly augmented, in the lady's eyes, in 1824, for in that year Faraday was made a member of the Royal Society.
In his lectures and public experiments he was greatly assisted by a man now almost forgotten, an "intelligent artilleryman" named Andersen. This unknown soldier with a taste for natural science doubtless had his reward in the exquisite pleasure always derived from the personal verification of facts hitherto unknown. There is often a pecuniary reward for the servant of science. Just as often there is not, and the work done has been the same.
It was on Christmas morning, 1821, that Faraday first succeeded in making a magnetic needle rotate around a wire carrying an electric current. He was the discoverer of benzole, the basis of our modern brilliant aniline dyes. In 1831 he made the discovery he had been leading to for many years--that of magneto-electric induction. All we have of electricity that is now a part of our daily life is the result of this discovery.
Faraday was born in 1791, and died August, 1867, in a house presented to him by Victoria, who had not the same opinion of his relations to the aristocracy that Lady Davy seems to have had. His insight into science was something explainable only on the supposition that he was gifted with a kind of instinct. He was a scientific prophet. A man who could, in 1838, foresee the ocean cable, and describe those minute difficulties in its working that all in time came true, must be classed as one of the great, clear, intuitive intellects of his race. He was in youth apprenticed to a bookbinder, "and many of the books he bound he read." A line in his indentures says: "In consideration of his faithful service, no premium is to be given." When these words were written there was no dream that the "faithful service" should be for all posterity.
Faraday's Spark. Striking the leg of a horseshoe magnet with an iron bar wound with insulated wire causes a contact between loose end of wire and small disc, and a spark.
Faraday's First Magneto-Electric Experiment. A horseshoe magnet passed near a bent soft iron wound with insulated wire caused an induced current in the wire.
TWO OF FARADAY'S EARLY EXPERIMENTS IN INDUCTION.
He who made the first actual machine to evolve a current in compliance with Faraday's formulated laws was an Italian named Pixü, in 1832. His machine consisted of a horseshoe magnet set on a shaft, and made to revolve in front of two cores of, soft iron wound with wire, and having their ends opposite the legs of the magnet. Shortly after Pixü, the inventors of the times ceased to turn the magnet on a shaft, and turned the iron cores instead, because they were lighter. In like manner, the huge field magnets of a modern dynamo are not whirled round a stationary armature, but the armature is whirled within the legs of the magnet with very great rapidity. The next step was to increase the number of magnets and the number of wire-wound iron cores--bobbins. The magnets were made compound, laminated; a large number of thin horseshoe magnets were laid together, with opposite poles touching. These were all comparatively small machines--what we now, with some reason, regard as having been toys whose present results were rather long in coming.
THE SIEMENS ARMATURE AND WINDING. THE FIRST STEP TOWARD THE MODERN DYNAMO
Then came Siemens, of Berlin, in 1857. He was probably the first to wind the iron core, what we now call thearmature, with wire from end to end,lengthwise, instead of round and round as a spool. This resulted, of course, in the shaft of the armature being also placed crosswise to the legs of the magnet, as it is in the modern dynamo. One of the ends of the wire used in this winding was fastened to the axle of the armature, and the other to a ring insulated from the shaft, but turning with it. Two springs, one bearing on the shaft and the other on the ring, carried away the current through wires attached to them. Siemens also originated the mechanical idea of hollowing out the legs of the magnet on the inside for the armature to turn in close to the magnet, almost fitting. It was the first time any of these things had been done, and their author probably had no idea that they would be prominent features of the dynamo of a little later time, in all essentials closely imitated.
DIAGRAM OF SHAFT, SPLIT RING AND 'BRUSHES.'
It will be guessed from what has been previously said on the subject of induction that the currents from such an electro-magnetic machine would be alternating currents, the impulses succeeding each other in alternate directions. To remedy this and cause the currents to flow always in the same direction, the "commutator" was devised. The ring mentioned above was split, and the two springs both bore upon it, one on each side. The ends of the wires were both fastened to this ring. The springs came to be known as "brushes." The effect was that one of them was in the insulated space between the split halves of the ring while the other was bearing on the metal to which the wire was attached. This action was alternate, and so arranged that the current carried away was always direct. When an armature has a winding of more than one wire, as the practical dynamo always has, the insulated ring is divided into as many pieces as there are wires, and the two brushes act as above for the entire series.
Pacinotti, of Florence, constructed a magneto-electric machine in which the current flows always in one direction without a commutator. It has what is known as aring armature, and is the mother of all dynamos built upon that principle. It is exceedingly ingenious in construction, and for certain purposes in the arts is extensively used. A description of it is too technical to interest others than those personally interested in the class of dynamo it represents.
Wilde, of Manchester, England, improved the Siemens machine in 1866 by doing that which is the feature that makes possible the huge "field magnet" of the modern dynamo, which is not a magnet at all, strictly speaking. He caused the current, after it had been rectified by the commutator, to return again into coils of wire round the legs of his field magnets, as shown in the diagram. This induced in them a new supply of magnetism, and this of course intensified the current from the armature. It is true he had a separate smaller magneto-electric machine, with which he evolved a current for the coil around the legs of the field magnet of a greatly larger machine upon which he depended for his actual current, and that he did not know, although he was practically doing the same thing, that if he should divert this current made by the larger machine itself back through the coils of its field magnet, he would not need the extra small machine at all, and would have a much more powerful current.
SIMPLEST FORM OF DYNAMO
And here arises a difference and a change of name. All generating machines to this date had been called "Magneto-electric" because they usedpermanentsteel magnets with which to generate a current by the whirling of the bobbin which we now call an armature. The time came, led to by the improvement of Wilde, in which those steel permanent magnets were no longer used. Then the machine became the "dynamo-electric" machine, and leaving off one word, according to our custom, "dynamo."
Siemens and Wheatstone almost simultaneously invented so much of the dynamo as was yet incomplete. It has "cores"--the parts that answer to the legs of a horseshoe magnet--of soft iron, sometimes now even of cast iron. These, at starting, possess very little magnetism--practically none at all--yet sufficient to generate a very weak current in the coils, windings, of the armature when it begins to turn. This weak current, passing through the windings of the field magnet, makes these still stronger magnets, and the effect is to evolve a still stronger current in the armature. Soon the full effect is reached. The big iron field magnet, often weighing some thousands of pounds, is then the same as a permanent steel horseshoe magnet, which would hardly be possible at all. One who has watched the installation of a dynamo, knowing that there is nowhere near any ordinary source of electricity, and has seen its armature begin to whirl and hum, and then in a few moments the violet sparklings of the brushes and the evident presence of a powerful current of electricity, is almost justified in the common opinion that the genius of man has devised a machine tocreatesomething out of nothing. It is true that astartingquantity of electricity is required. It exists in almost every piece of iron. Sometimes, to hasten first action, some cells of a galvanic battery are used to pass a current through the coils of the field magnet. After the first use there is always enough magnetism remaining in them during rest or stoppage to make a dynamo efficient after a few moments operation.
PACINOTTI'S RING-ARMATURE DYNAMO
This is the dynamo in principle of action. The varieties in construction now in use number scores, perhaps hundreds. Some of them are monsters in size, and evolve a current that is terrific. They are all essentially the same, depending for action upon the laws illustrated in the simplest experiment in induced electricity. One of the best known of the modern machines is Edison's, represented in the picture at the head of this article. In it the field magnet--answering to the horseshoe magnet of the magneto-electric machine--is plainly distinguishable to the unskilled observer. It is not even solid, but is made of several pieces bolted together. Its legs are hollowed at the ends to admit closely the armature which turns there. There are valuable peculiarities in its construction, which, while complying in all respects with the dynamo principle, utilize those principles to the best mechanical advantage. So do others, in other respects that did not occur even to Edison, or were not adopted by him. Probably the modern dynamo is the most efficient, the most accurately measurable, the least wasteful of its power, and the most manageable, of any power-machine so far constructed by man for daily use.
The motor.--This is the twin of the dynamo. In all essentials the two are of the same construction. A difference in the arrangement of the terminals of the wire coils or the wrappings of armature and field magnet, makes of the one a dynamo and of the other a motor. Nevertheless, they are separate studies in electrical science. Practice has brought about modified constructions, as in the case of the dynamo. The differences between the two machines, and their similarities as well, may be explained by a general brief statement.
It is the work of the dynamo to convert mechanical energy into the form of electrical energy. The motor, in turn, changes this electrical energy back again into mechanical energy.
Where the electric light is produced by the dynamo current no motor intervenes. The current is converted into heat and light by merely having an impediment, a restriction, a narrowness, interposed to its free passage on a conducting wire, as heretofore explained, very much as water in a pipe foams and struggles at a narrow place or an obstruction. Where mechanical movements are to be produced by the dynamo current the motor is always the intermediate machine. In the dynamo the armature is rotated by steam power, producing an electrical energy in the form of a powerful current transmitted by a wire. In the motor the armature, in turn,is rotated bythis current. It is but another instance of that ability to work backwards--to reverse a process--that seems to pervade all machines, and almost all processes. I have mentioned steam power, and, consequently, the necessary burning of coal and expenditure of money in producing the dynamo current. The dynamo and motor are not necessarily economical inventions, but the opposite when the force produced is to be transmitted again, with some loss, into the same mechanical energy that has already been produced by the burning of coal and the making of steam. Across miles of space, and into places where steam would not be possible, the power is invisibly carried. Suggestions of this convenience--stated cases--it is not necessary to cite. The fact is a prominent one, to be noted everywhere.
And it may be made a mechanical economy. The most prominent instance of this is the new utilization of Niagara as a turbine water-power with which to whirl the armatures of gigantic dynamos, using the power thus obtained upon motors, and in the production of light and the transmission of power to neighboring cities.
The discovery of the possibility of transmitting power by a wire, and converting it again into mechanical energy, is a strange story of the human blindness that almost always attends an acuteness, a thinking power, a prescience, that is the characteristic of humanity alone, but which so often stops short of results. This discovery has been attributed to accident alone; the accident of an employé mistaking the uses of wires and fastening their ends in the wrong places. But a French electrician thus describes the occurrence as within his own experience. His name is Hypolyte Fontaine.
But let us first advert to the forgetfulness of the man who really invented the machine that was capable of the opposite action of both dynamo and motor. This was the Italian, Pacinotti. [34] He mentioned that his machine could be used either to generate a current of electricity on the application of motive power to its armature, or to produce motive power on connecting it with a source of electricity. Yet it did not occur to him to definitely experiment with two of his machines for the purpose of accomplishing that which in less than twenty years has revolutionized our ideas and practice in transmitted force. He did not suggest that two of his machines could be run together, one as a generator and the other as a motor. He did not think of its advantages with the facilities for it, of his own creation, in his hands.
34.Moses G. Farmer, an American, and celebrated in his day for intelligent electrical researches, is claimed to have made the first reversible motor ever contrived. A small motor made by Farmer in 1847, and embodying the electro-dynamic principle was exhibited at the great exposition at Chicago in 1893. If the genealogy of this machine remains undisputed it fixes the fact that the discovery belongs to this country, and to an American.
M. Fontaine states that at the Vienna Exposition of 1873 there was a Gramme machine intended to be operated by a primary battery, to show that the Gramme was capable of being worked by a current, and, as there was also a second machine of the same kind there, of also generating one. These two machines were to demonstrate this range of capacity asseparately worked, one by power, the other with a battery. There was, then, no intention of coupling them together as late as 1873, with the means at hand and the suggestion almost unavoidable. The dynamo and motor had not occurred to any one. But M. Fontaine states that he failed to get the primary (battery) current in time for the opening, and was troubled by the dilemma. Then the idea occurred to him, as he could do no better, to work one of the machines with a current "deprived," partly stolen, from the other, as a temporary measure. A friend lent him the necessary piece of wire, and he connected the two machines. The machine used as a motor was connected with a pumping apparatus, and when the machine intended as a generator started, and this make-shift, temporarily-stolen current was carried to the acting motor, the action of the last was so much more vigorous than was intended that the water was thrown over the sides of the tank. Fontaine was forced to remedy this excessive action by procuring an additional wire of such length that its resistance permitted the motor to work more mildly and throw less water. This accidentally established the fact of distance, convenience, a revolution in the power of the industrial world. Fontaine states that Gramme had previously told him that he had done the same thing with his machines. The idea was never patented. Neither Pacinotti, who invented the machine originally, nor Gramme, one of the great names of modern electricity, nor this skilled practical electrician, Fontaine, who had charge of the exhibit of the Gramme system at Vienna, considered the fact of the transmission of concentrated power over a thin wire to a great distance as one of value to its inventor or to the industries of mankind. With the motor and the dynamo already made, it was an accident that brought them together after all.
It may be amusing, if not useful, to spend a moment in reviewing of the efforts of men to utilize the power of the electrical current in mechanics before the day of the dynamo and a motor, and while yet the electric light was an infant in the nursery of the laboratory. They knew then, about 1835 to 1870, of the laws of induction as applied to the electro-magnet, or in small machines the generating power, so called, of the magneto-electric arrangement embodied, as a familiar example, in Kidder's medical battery. There is a long list of those inventors, American and European. The first patent issued for an American electro-motor was in 1837, to a man named Thomas Davenport, of Brandon, Vt. He was a man far ahead of his times. He built the first electric railroad ever seen, at Springfield, Mass., in 1835, and considering the means, whose inadequacy is now better understood by any reader of these lines than it then was by the deepest student of electricity, this first railroad was a success. Davenport came as near to solving the problem of an electric motor as was possible without the invention of Pacinotti. Following this there were many patents issued for electro-magnetic motors to persons residing in all parts of the country, north and south. One was made by C. G. Page, of the Smithsonian Institute, in which the motive power consisted in a round rod, acting as a plunger, being pulled into the space where the core would be in an ordinary electro-magnet, and thereby working a crank. [35] A large motor of this kind is alleged, in 1850, to have developed ten horse power. It was actually applied to outdoor experiment as a car-motor on an actual railroad track, and was efficient for several miles. But it carried with it its battery-cells, and they were disarranged and stirred by the jolting, and being made of crockeryware were broken. The chemicals cost much more than fuel for steam, and there could be no economical motive for further experiment. It was a huge toy, as the entire sum of electrical science was until it was made useful first in the one instance of the telegraph, and long after that date the use of the electro-magnet, with a cam to cut off and turn on again the current at proper intervals, which was the one principle of all attempts, was a repeated and invariable failure. That which was wanted and lacking was not known, and was finally discovered and successively developed as has been described.