He who made the first actual machine to evolve a current in compliance with Faraday's formulated laws was an Italian named Pixu, 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 Pixu, 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.

[Ill.u.s.tration: 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 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.

[Ill.u.s.tration: 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 s.p.a.ce 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 cla.s.s 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.

[Ill.u.s.tration: 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 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, pa.s.sing 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_ quant.i.ty 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 pa.s.s 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.

[Ill.u.s.tration: 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 ill.u.s.trated 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 pa.s.sage 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 s.p.a.ce, 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 employe 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, Ma.s.s., 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 Inst.i.tute, in which the motive power consisted in a round rod, acting as a plunger, being pulled into the s.p.a.ce 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 pa.s.ses 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 pa.s.s off. These bubbles are composed of the two const.i.tuents 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 quant.i.ty 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 quant.i.ty in which the elementary bodies appear at the poles of the current depends upon the quant.i.ties 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 quant.i.ty.

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 sh.e.l.l 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 pa.s.ses 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 pota.s.sium 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 circ.u.mstances, 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 pa.s.ses 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 quant.i.ty of current that will pa.s.s 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 AMPeRE (named from Ampere, 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 _quant.i.ty_ 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 pa.s.sage 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 un.o.btrusive 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 pa.s.sed, 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.