Chapter 7
THE ELECTRIC LIGHT.
It has been stated that modern theory recognizes two classes of electricity, the _Static_ and the _Dynamic_. 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. [Footnote: As an illustration of the day of beginnings, a few years ago the _thalus_, 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 spark _continuous_. 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 momentarily _imperfect 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."
In the arc light the current passes across an _imperfect 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 a _curved_ path, 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. [Footnote: 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 familiar _burring_ sound 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 the _magneto-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 London _Standard_ of 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."
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 machines _gives 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. [Footnote: 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.]
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.
Then came Siemens, of Berlin, in 1857. He was probably the first to wind the iron core, what we now call the _armature_, 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.
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 a _ring 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.
And here arises a difference and a change of name. All generating machines to this date had been called "_Magneto-electric_" because they used _permanent_ steel 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 to _create_ something out of nothing. It is true that a _starting_ quantity 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.
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 by_ this 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. [Footnote: 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.] 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.
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 as _separately 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. [Footnote: The _National Intelligencer_, a prominent Washington newspaper, said with reference to Page's motor "He has shown that before long electro-magnetic action will have dethroned steam and will be the adopted motor," etc. This was an enthusiasm not based upon any fact then known about a machine not even in the line of the present facts of electro-dynamics.] 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.
Electric railroads.--There was an instance of almost simultaneous invention in the case of the first practical electric railroads. S. D. Field, Dr. Siemens, and Thomas A. Edison all applied for patents in 1880. Of these, Field was first in filing, and was awarded patents. The combined dynamo and motor were, of course, the parents of the practical idea. Field's patents covered a motor in or under the car, operated by a current from a stationary source of electricity--of course a dynamo. These first electric roads had the current carried on the rail. They were partially successful, but there was something wrong in the plan, and that something was induction by the earth. Later came, as a remedy for this, the "Trolley" system; the trolley being a small, grooved wheel running upon a current-carrying wire overhead. The question of how best to convey a current to the car-motor is a serious one, doubtless at this moment occupying the attention of highly-trained intelligence everywhere. The motor current is one of high power, and as such intractable; and it is in the character of this current, rather than in methods of insulation, that the remedy for the much-objected-to overhead wire is to be found. It will be remembered that all the phenomena of induction are _unhindered by insulation_.
Aside from the current-carrying problem, the electric road is explainable in all its features upon the theory and practice of the dynamo and motor. It is merely an application of the two machines. The last is, in usual practice, under the car, and geared to the truck-axle. A more modern mechanical improvement is to make the axle the shaft of the motor armature. When the motor has used the current it passes by most systems into the rail and the ground. By others there is a "metallic circuit"--two wires. Many men whose interest and occupation leads them to a study of such matters know that the use of electricity, instead of steam locomotion, is merely a question of time on all railroads. I have said elsewhere that the actual age of electricity had not yet fully come. It seems to us now that we have attained the end; that there is little more to know or to do. But so have all the generations thought in their day. In the field of electricity there are yet to come practical results of which one may have some foreshadowings in the experiments of men like Tesla, which will make our present times and knowledge seem tame and slow.
Electrolysis.--In all history, fire has been the universal practical solvent. It has been supplanted by the electrical current in some of the most beautiful and useful phenomena of our time. Electrolysis is the name of the process by which fluid chemicals are decomposed by the current.
A familiar early experiment in electrolysis is the decomposition of water--a chemical composed of oxygen and hydrogen, though always thought of and used as a simple, pure fluid. If the poles of a galvanic battery are immersed in water slightly mixed with sulphuric acid to favor electrical action, these poles will become covered with bubbles of gas which presently rise to the surface and pass off. These bubbles are composed of the two constituents of water, the oxygen rising from the positive and the hydrogen from the negative pole. Particles of the substance decomposed are transferred, some to one pole and some to the other; and, therefore, electrolysis is always practiced in a fluid in order that this transference may more readily occur.
The quantity of _electrolyte_--the substance decomposed--that is transferred in a given time is in proportion to the strength of the current. When this electrolyte is composed of many substances a current will act a little on all of them, and the quantity in which the elementary bodies appear at the poles of the current depends upon the quantities of the compounds in the liquid, and on the relative ease with which they yield to the electrical action.
The electrolytic processes are not the mere experiments a brief description of them would indicate, but are among the important processes for the mechanical products of modern times. The extensive nickel-plating that became a permanent fad in this country on the discovery of a special process some years ago, is all done by electrolysis. The silver plating of modern tableware and table cutlery, as beautiful and much less expensive than silver, and the fine finish of the beautiful bronze hardware now used in house-furnishing, are the results of the same process. Some use for it enters into almost every piece of fine machinery, and into the beautifying or preserving of innumerable small articles that are made and used in unlimited quantity.
The process and its principle is general, but there are many details observed in the actual work of electroplating which interest only those engaged. One of the most usual of these is that of making an electrotype. This may mean the making of an exact impression of a medal, coin, or other figure, or a depositing of a coating of the same on any metallic surface. Formerly the faces of the types used in printing were very commonly faced with copper to give them finish and a wearing quality. Even fresh, natural fruits that have been evenly coated with plumbago may be covered with a thin shell of metal. A silver head may be placed on the wood of a walking stick, precisely conforming on the outside to the form of the wood within.
The deposit of metal in the electrotyping process always takes place at the negative pole--the pole by which the current passes out of the fluid into its conductor. This is the "_cathode_." The other is the "_anode_." The "bath," as the fluid in which the process is accomplished is called, for silver, gold or platinum contains one hundred parts of water, ten of potassium cyanide, and one of the cyanide of whichever of those metals is to be deposited. The articles to be plated are suspended in this bath and the battery-power, varying in intensity according to circumstances, is applied. After removal they are buffed and finished. A varying detail is practiced for different metals, and the current now commonly used is from a dynamo. [Footnote: Among modern modifications of the dynamic current, is its use, modified by proper appliances, for the telegraph and the telephone circuits of cities and the larger towns. Every electric current may now be safely attributed to that source, and from the same circuit and generator all modifications may be produced at once.]
The origin of electrolysis is said to be with Daniell, who noticed the deposit of copper while experimenting with the battery that bears his name. Jacobi, at St. Petersburg, first published a description of the process in 1839. The Elkingtons were the first to actually put the process into commercial practice.
It would be interesting now, were it apropos, to describe the seemingly very ancient processes by which our ancestors gilded, plated, were deceived and deceived others, previous to about 1845. For those things were done, and the genuineness of life has by no means been destroyed by the modern ease with which a precious metal may be deposited upon one utterly base. A contemplation of the moral side of the subject might lead at once to the conclusion that we could now spare one of the least in actual importance of the processes of the all-pervading and wonderful essence that alike makes the lightning-stroke and gilds the plebeian pin that fastens a baby's napkin. But from any other view we could not now dispense with anything electricity does.
General facts.--The names of many of the original investigators of electrical phenomena are perpetuated in the familiar names of electrical measurements. For, notwithstanding its seeming subtlety, there is no force in use, or that has ever been used by men, capable of being so definitely calculated, measured, determined beforehand, as electricity is. As time passes new measurements are adopted and named, some of them being proposed as lately as 1893. An instance of the value of some of these old determinations of a time when all we now know of electrical science was unknown, may be given in what is known as Ohm's Law. Ohm was a native of Erlangen, in Bavaria, and was Professor of Physics at Munich, where he died in 1874. He formulated this Law in 1827, and it was translated into English in 1847. He was recognized at the time, and was given the Copley medal of the Royal Society of London. The Law--for by that distinctive name is it still called, though the name "Ohm," also expresses a unit of measurement--is that _the quantity of current that will pass through a conductor is proportional to the pressure and inversely proportional to the distance_. That is:
Current = Pressure / Resistance.
Transposing the terms of the equation we may get an expression for either of those elements, current, pressure, or resistance, in the terms of the other two. This relation holds true and is accurate in every possible case and condition of practical work. This remarkable precision and definiteness of action has made possible the creation of an extensive school of electrical testing, by which we are not only enabled to make accurate measurement of electrical apparatus and appliances, but also to make determinations in _other_ fields by the agency of electricity. When an ocean cable is injured or broken the precise location of the trouble is made _by measuring the electrical resistance of the parts on each side of the injury_.
The magnitudes of measurements of electricity are expressed in the following convenient electrical units:
The VOLT (named from Volta) equals a unit of _pressure_ that is equal to one cell of a gravity battery.
The OHM, as a unit of measurement, equals a unit of _resistance_ that is equivalent to the resistance of a hundred feet of copper wire the size of a pin.
The AMPÈRE (named from Ampère, 1775-1836, author of a "Collection of Observations on Electro-Dynamics" and other works, and a profound practical investigator) equals a unit of _current_ equivalent to the current which one Volt of pressure will produce through one Ohm of wire (or resistance).
The Coulomb (1736--inventor of the means of measuring electricity called the "Torsion balance," and general early investigator) equals a unit of _quantity_ of one Ampere flowing for one second.
The Farad (from Faraday, the discoverer of the laws of Induction, see _ante_), equals that unit of _capacity_ which is the capacity for holding one Coulomb. Death current.--What is now spoken of as the "Death Current" is one that will instantly overcome the "resistance" of the human, or animal, body. It is a current of from one to two thousand Volts--about the same as that used in maintaining the large arc lights. This question of the killing capacity of the current became officially prominent some years ago, upon the passage by the legislature of the State of New York of a statute requiring the death penalty to be inflicted by means of electricity. The object was to deter evildoers by surrounding the penalty with scientific horror, [Footnote: Hence also the new lingual atrocity, the word "electrocute," derived from "execute" by decapitation and the addition of "electro"] and the idea had its origin in the accidents which formerly occurred much more frequently than now. The "death current" is now almost everywhere, though the care of the men who continually work about "live" wires has grown to be much like that of men who continually handle firearms or explosives, and accidents seldom happen. At first it was apparently difficult for the general public to appreciate the fact that the silent and harmless-looking wires must be avoided. There was suddenly a new and terrific power in common use, and it was as slender, silent and unobtrusive as it was fatal.
Insulation of the hands by the use of rubber gloves, and extreme care, are the means by which those who are called "linemen"--a new industry--protect themselves in their occupation. But there is a new commandment added to the list of those to be memorized by the body-politic. "Do not tread upon, drive over, or touch _any_ wire." It may be, and probably is, harmless. But you cannot positively know. [Footnote: It is a common trait of general human nature to refuse to learn save by the hardest of experiences, and so far as the crediting of statements is concerned, to at first believe everything that is not true, and reject most that is. The supernatural, the phenomena of alleged witchcraft and diabolism, and of "luck," "hoodoo," "fate," etc., find ready disciples among those who reject disdainfully the results of the working of natural law. When the railroads were first built across the plains the Indians repeatedly attempted to stop moving trains by holding the ends of a rope stretched across the track in front of the engine, and with results which greatly surprised them When the lines were first constructed in northern Mexico the Mexican peasant could not be induced to refrain from trying personal experiments with the new power, and scores of him were killed before he learned that standing on the track was dangerous. In the United States the era of accidents through indifference to common-looking wires has almost passed, but for some years the fatality was large because people are always governed by appearances connected with _previous_ notions, until _new_ experiences teach them better.]
INSTRUMENTS OF MEASUREMENT.--Some of the most costly and beautiful of modern scientific instruments are those used in the measurements and determinations of electrical science. There are many forms and varieties for every specific purpose. Electrical measurement has become a department of physical science by itself, and a technical, extensive and varied one. Already the electrical specialist, no more an original experimenter or investigator than the average physician is, has become professional. He makes plans, submits facts, estimates cost, and states results with almost certainty.
ELECTRICITY AS AN INDUSTRY.--Immense factories are now devoted to the manufacture of electrical goods exclusively. Large establishments in cities are filled with them. The installation of the electric plant in a dwelling house is done in the same way, and as regularly, as the plumbing is. Soon there must be still another enlargement, since the heating of houses through a wire, and the kitchen being equipped with cooking utensils whose heat is for each vessel evolved in its own bottom, is inevitable.
The following are some of the facts, in figures, of the business side of electricity in the United States at the present writing. In 1866, about twenty years after the establishment of the telegraph, but with a population of only a little more than half the present, there were 75,686 miles of telegraph wire in use, and 2,520 offices. In 1893 there were 740,000 miles of wire, and more than 20,000 offices. The receipts for the year first named are unknown, but for 1893 they were about $24,000,000. The expenses of the system for the same year were $16,500,000.
The telephone, an industry now about sixteen years old, had in 1893, for the Bell alone, over 200,000 miles of wire on poles, and over 90,000 miles of wire under ground. The instruments were in 15,000 buildings. There were 10,000 employés, and 233,000 subscribers. All companies combined had 441,000 miles of wire. Ninety-two millions of dollars were invested in telephone _fixtures_.
In 1893, the average cost of a telegram was thirty-one and one six-tenths cents, and the average alleged cost of sending the same to the companies was twenty-two and three-tenths cents, leaving a profit of nine and three-tenths cents on every message. It must be remembered that with mail facilities and cheapness that are unrivalled, the telegraph message is always an extraordinary mode of communication; an emergency. These few figures may serve to give the reader a dim idea of the importance to which the most ordinary and general of the branches of electrical industry have grown in the United States.
MEDICAL ELECTRICITY.--For more than fifty years the medical fraternity in regular practice persisted in disregarding all the claims made for the electric current as a therapeutic agent. In earlier times it was supposed to have a value that supplanted all other medical agencies. Franklin seems to have been one of the earliest experimenters in this line, and to have been successful in many instances where his brief spark from the only sources of the current then known were applicable to the case. The medical department of the science then fell into the hands of charlatans, and there is a natural disposition to deal in the wonderful, the miraculous or semi-miraculous, in the cure of disease. Divested of the wonder-idea through a wider study and greater knowledge of actual facts, electricity has again come forward as a curative agent in the last ten years. Instruction in its management in disease is included in the curriculum of almost every medical school, and most physicians now own an outfit, more or less extensive, for use in ordinary practice. To decry and utterly condemn is no longer the custom of the steady-going physician, the ethics of whose cloth had been for centuries to condemn all that interfered with the use of drugs, and everything whose action could not be understood by the examples of common experience, and without special study outside the lines of medical knowledge as prescribed.
Perhaps the developments based upon the discoveries of Faraday have had much to do with the adoption of electricity as a curative agent. The current usually used is the Faradic; the induced alternate current from an induction coil. This is, indeed, the current most useful in the majority of the nervous derangements in the treatment of which the current is of acknowledged utility.
In surgery the advance is still greater. "Galvano-cautery" is the incandescent light precisely; the white-hot wire being used to cut off, or burn off, and cauterize at the same time, excrescences and growths that could not be easily reached by other means than a tube and a small loop of platinum wire. A little incandescent lamp with a bulb no bigger than a pea is used to light up and explore cavities, and this advance alone, purely mechanical and outside of medical science, is of immense importance in the saving of life and the avoidance of human suffering.
It may be added that there is nothing magical, or by the touch, or mysterious, in the treatment of disease by the electrical current. The results depend upon intelligent applications, based upon reason and experience, a varied treatment for varying cases. Nor is it a remedy to be applied by the patient himself more than any other is. On the contrary, he may do himself great injury. The pills, potions, powders and patent medicines made to be taken indiscriminately, and which he more or less understands, may be still harmful yet much safer. Even the application of one or the other of the two poles with reference to the course of a nerve, may result in injury instead of good.
INCOMPLETE POSSIBILITIES.--There are at least two things greatly desired by mankind in the field of electrical science and not yet attained. One of these, that may now be dismissed with a word, is the resolving of the latent energy of, say a ton of coal, into electrical energy without the use of the steam engine; without the intervention of any machine. For electricity is not manufactured; not created by men in any case. It exists, and is merely gathered, in a measure and to a certain extent confined and controlled, and sent out as a _concentrated form of energy_ on its various errands. Should a means for the concentration of this universally diffused energy be found whereby it could be made to gather, by the new arrangement of some natural law such as places it in enormous quantities in the thundercloud, a revolution that would permeate and visibly change all the affairs of men would take place, since the industrial world is not a thing apart, but affects all men, and all institutions, and all thought.
The other desideratum, more reasonable apparently, yet far from present accomplishment, is a means of storing and carrying a supply of electricity when it has been gathered by the means now used, or by any means.
THE STORAGE BATTERY is an attempt in this last direction. The name is misleading, since even in this attempt electricity is in no sense "stored," but a chemical action producing a current takes place in the machine. The arrangement is in its infancy. Instances occur in which, under given circumstances, it is more or less efficient, and has been improved into greater efficiency. But many difficulties intervene, one of which is the great weight of the appliances used, and another, considerable cost. The term "storage battery" is now infrequently used, and the name "secondary" battery is usually substituted. The principle of its action is the decomposing of combined chemicals by the action of a current applied from a stationary generator or dynamo, and that these chemicals again unite as soon as they are allowed to do so by the completing of a circuit, _and in re-combining give off nearly as much electricity as was first used in separating them._ The action of the secondary, "storage," battery, once charged, is like that of a primary battery. The current is produced by chemical action. Two metals outside of the solution contained in a primary battery cell, but under differing physical conditions from each other, will yield a current. A piece of polished iron and a piece of rusty iron, connected by a wire, will yield a small current. Rusty lead, so to speak, so connected with bright lead, has a high electromotive force. Oxygen makes lead rusty, and hydrogen makes it bright. Oxygen and hydrogen are the two gases cast off when water is subjected to a current. (See _ante_ under _Electrolysis_) So Augustin Planté, the inventor of as much as we yet have of what is called a storage or secondary battery, suspended two plates of lead in water, and when a current of electricity was passed through it hydrogen was thrown off at one plate, making it bright, and oxygen at the other plate, peroxydizing its surface. When the current was removed the altered plates, connected by a wire, would send off a current which was in the opposite direction from the first, and this would continue until the plates were again in their original condition. This is the principle and mode of action of the storage battery. So far it has assumed many forms. Scores of modifications have been invented and patented. The leaden plates have taken a variety of forms, yet have remained leaden plates, one cleaned and the other fouled by the electrolytic action of a current, and giving off an almost equivalent current again by the return process. The arrangement endures for several repetitions of the process, but is finally expensive and always inconvenient. The secondary battery, in its infancy, as stated, presents now much the same obstacles to commercial use the galvanic, or primary, battery did before the induced current had become the servant of man.