Michael Faraday : Electricity and Magnetism

By Edwin J. Houston, PH.D.
1791-1867.

“No man is born into the world whose work
Is not born with him. There is always work,
And tools to work withal, for those who will.”
LOWELL

A man was born into the world, on the 22d of September, 1791, whose work was born with him, and who did this work so well that he became one of its greatest benefactors. Indeed, much of the marvellous advance made in the electric arts and sciences, during the last half-century, can be directly traced to this work.

It was in Newington Butts, in London, England, that the man-child first opened his eyes on the wonders of the physical world around him. To those eyes, in after years, were given a far deeper insight into the mysteries of nature than often falls to the lot of man. This man-child was Michael Faraday, who has been justly styled, by those best capable of judging him, “The Prince of Experimental Philosophers.”

The precocity so common in the childhood of men of genius was apparently absent in the case of young Faraday. The growing boy played marbles, and worried through a scant education in reading, writing, and arithmetic, unnoticed, and most probably, for the greater part, severely left alone, as commonly falls to the lot of nearly all boys, whether ordinary or extraordinary. At the early age of thirteen, he was taken from school and placed on trial as errand-boy in the book-shop of George Ribeau, in London. After a year at this work, he was taken as an apprentice to the bookbinding trade, by the same employer, who, on account of his faithful services, remitted the customary premium. At this work he spent some eight years of his life.

But far be it from us even to hint at the absence of genius in the young child. Genius is not an acquired gift. It is born in the individual. Apart from the marvellous achievements of the man, a mere glance at the magnificent head, with its high intellectual forehead, the firm lips, the intelligent inquiring eyes, and the bright face, as seen in existing pictures, assures us that they portray an unusual individuality, incompatible with even a suspicion of belonging to an ordinary man. Doubtless the growing child did give early promise of his future greatness. Doubtless he was a formidable member of that terrible class of inquiring youngsters who demand the why and the wherefore of all around them, and refuse to accept the unsatisfactory belief of their fathers that things “are because they are.” In its self-complacency, the busy world is too apt to fail to notice unusual abilities in children,–abilities that perhaps too often remain undeveloped from lack of opportunities. But whether young Faraday did or did not, at an early age, display any unusual promise of his life-work, all his biographers appear to agree that he could not be regarded as a precocious child.

Faraday disclaimed the idea that his childhood was distinguished by any precocity. “Do not suppose that I was a very deep thinker, or was marked as a precocious person,” says Faraday, when alluding to his early life. “I was a very lively, imaginative person, and could believe in the ‘Arabian Nights’ as easily as the ‘Encyclopaedia,’ but facts were important to me, and saved me. I could trust a fact and always cross-examined an assertion. So when I questioned Mrs. Marcet’s book [he is alluding to her ‘Conversations on Chemistry’], by such little experiments as I could find means to perform, and found it true to the facts as I could understand them, I felt that I had got hold of an anchor in chemical knowledge, and clung fast to it.”

But while there may be a question as to the existence of precocity in the young lad, there does not appear to be any reason for believing that his unusual abilities were the result of direct heredity. His father, an ordinary journeyman blacksmith, never exhibited any special intellectual ability, though possibly poverty and poor health may have been responsible for this failure. His mother, too, it appears, was of but ordinary mentality.

The environment of those early years–that is, from 1804 to 1813, while in the book-binding business–was far from calculated to develop any marked abilities inherent in our young philosopher. What would seem less calculated to inspire a wish to obtain a deeper insight into the mysteries of the physical world than the trade of book-binding, especially in the case of a boy whose scholastic education ceased at fourteen years and was limited to the mere rudiments of learning? But, fortunately for the world, the inquiring spirit of the lad led him to examine the inside of the books he bound, and thus, by familiarizing himself with their contents, he received the inspiration that good writing is always ready to bestow on those who properly read it. Two books, he afterwards informs us, proved of especial benefit; namely, “Marcet’s Conversations on Chemistry,” already referred to, and the “Encyclopaedia Britannica.” To the former he attributes his grounding in chemistry, and to the latter his first ideas in electricity, in both of which studies he excelled in after years. As we have seen, even at this early age he followed the true plan for the physical investigator, cross-questioned all statements, only admitting those to the dignity of facts whose truth he had established by careful experimentation.

But our future experimental philosopher has not as yet fairly started on the beginnings of his life-work. The possibilities of the book-binding trade were too limited to permit much real progress. A circumstance occurred in the spring of 1812 that shaped his entire after-life. This was the opportunity then afforded him to attend four of the last lectures delivered at the Royal Institution, by the great Sir Humphry Davy. Faraday took copious notes of these lectures, carefully wrote them out, and bound them in a small quarto volume. It was this volume, which he afterwards sent to Davy, that resulted in his receiving, on March 1, 1813, the appointment of laboratory assistant in the Royal Institution. His pay for this work was twenty-five shillings a week, with a lodging on the top floor of the Institute, a very fair compensation for the times.

Very congenial were the duties of the young assistant. They were to keep clean the beloved apparatus of the lecturers, and to assist them in their demonstrations. The new world thus opened was full of bright promise. He keenly felt the deficiencies of his early education, and did his best to extend his learning, so that he might be able to make the most of his opportunities. But what he perhaps appreciated the most was the inspiration he received from the great teacher Davy, who was then Professor of Chemistry and Director of the Laboratory of the Royal Institution; for Faraday assisted at Davy’s lectures, and in an humble way even aided his investigations, sharing the dangers arising from the explosion of the unstable substance, chloride of nitrogen, that Davy was then investigating. Faraday has repeatedly acknowledged the debt owed to the inspiration of this teacher. Davy also, in later life generously recognized, in his former assistant, a philosopher greater than himself. As the renowned astronomer, Tycho Brahe, discovered in one of his pupils, John Kepler, an astronomer greater than the master, and as Bergman, the Swedish chemist, in a similar manner, discovered the greater chemist Scheele, so when Davy, in after years, was asked what he regarded as his greatest discovery, he briefly replied, “Michael Faraday.”

The task of the scientific historian, who endeavors honestly to record the progress of research, and to trace the influence of the work of some individual on the times in which he lived, is by no means an easy one; for, in scientific work one discovery frequently passes so insensibly into another that it is often difficult to know just where one stops and the other begins, and much difficulty constantly arises as to whom the credit should be given, when, as is too often the case, these discoveries are made by different individuals. It is only when some great discovery stands alone, like a giant mountain peak against the clear sky, that it is comparatively easy to determine the extent and character of its influence on other discoveries, and justly to give the credit to whom the credit is due. Such discoveries form ready points of reference in the intellectual horizon, and mark distinct eras in the world’s progress. This is true of all work in the domain of physical science, but it is especially true in that of electricity and magnetism, in which Faraday was preeminent. The scope of each of these sciences is so extended, the number of workers so great, and the applications to the practical arts so nearly innumerable, that it is often by no means an easy task correctly to trace their proper growth and development.

Faraday’s investigations covered vast fields in the domain of chemistry, electricity, and magnetism. It is to the last two only that reference will here be made. Faraday’s life-work in electricity and magnetism began practically in 1831, when he made his immortal discovery of the direct production of electricity from magnetism. His best work in electricity and magnetism was accomplished between 1831 and 1856, extending, therefore, over a period of some twenty-five years, although it is not denied that good work was done since 1856. Consequently, it was at so comparatively recent a date that most of Faraday’s work was done that some of the world’s distinguished electricians yet live who began their studies during the latter years of Faraday’s life. The difficulties of tracing, at least to some extent, the influence that Faraday’s masterly investigations have had on the present condition of the electrical arts and sciences will, therefore, be considerably lessened.

The extent of Faraday’s researches and discoveries in magnetism and electricity was so great that it will be impossible, in the necessarily limited space of a brief biographical sketch, to notice any but the more prominent. Nor will any attempt be made, except where the nature of the research or discovery appears to render it advisable, to follow any strict chronological order; for, our inquiry here is not so much directed to a mere matter of history as to the influence which the investigation or discovery exerted on the life and civilization of the age in which we live.

There is a single discovery of Faraday that stands out sharply amidst all his other discoveries, great as they were, and is so important in its far-reaching results that it alone would have stamped him as a philosophical investigator of the highest merits, had he never done anything else. This was his discovery of the means for developing electricity directly from magnetism. It was made on the 29th of August, 1831, and should be regarded as inspired by the great discovery made by Oersted in 1820, of the relations existing between the voltaic pile and electro-magnetism. It was in the same year that Ampere had conducted that memorable investigation as to the mutual attractions and repulsions between circuits through which electric currents are flowing, which resulted in a theory of electro-magnetism, and finally led to the production of the electro-magnet itself. Ampere had shown that a coil of wire, or helix, through which an electric current is passing, acted practically as a magnet, and Arago had magnetized an iron bar by placing it within such a helix.

In common with the other scientific men of his time, Faraday believed that since the flow of an electric current invariably produced magnetism, so magnetism should, in its turn, be capable of producing electricity. Many investigators before Faraday’s time had endeavored to solve this problem, but it was reserved to Faraday alone to be successful. Since success in this investigation resulted from some experiments he made while endeavoring to obtain inductive action on a quiescent circuit from a neighboring circuit through which an electric current was flowing, we will first briefly examine this experiment. All his experiments in this direction were at first unsuccessful. He passed an electric current through a circuit, which was located close to another circuit containing a galvanometer,–a device for showing the presence of an electric current and measuring its strength,–but failed to obtain any result. He looked for such results only when the current had been fully established in the active circuit. Undismayed by failure, he reasoned that probably effects were present, but that they were too small to be observed owing to the feeble inducing current employed. He therefore increased the strength of the current in the active wire; but still with no results.

Again and again he interrogates nature, but unsuccessfully. At last he notices that there is a slight movement of the galvanometer needle at the moment of making and breaking the circuit. Carefully repeating his experiments in the light of this observation, he discovers the important fact that it is only at the moment a current is increasing or decreasing in strength–at the moment of making or breaking a circuit–that the active circuit is capable of producing a current in a neighboring inactive circuit by induction. This was an important discovery, and in the light of his after-knowledge was correctly regarded as a solution of the production of electricity from magnetism.

Observing that the galvanometer needle momentarily swings in one direction on making the circuit, and in the opposite direction on breaking it, he establishes the fact that the current induced on making flows in the opposite direction to the inducing current, and that induced on breaking flows in the same direction as the inducing current.

Having thus established the fact of current induction, he makes the step of substituting magnets for active circuits; a simple step in the light of our present knowledge, but a giant stride at that time. Remembering that current induction, or, as he called it, voltaic current induction, takes place only while some effect produced by the current is either increasing or decreasing, he moves coils of insulated wire towards or from magnet poles, or magnet poles towards or from coils of wire, and shows that electric currents are generated in the coils while either the coils or the magnets are in motion, but cease to be produced as soon as the motion ceases. Moreover, these magnetically induced currents differ in no respects from other currents,–for example, those produced by the voltaic pile,–since, like the latter, they produce sparks, magnetize bars of steel, or deflect the needle of a galvanometer. In this manner Faraday solved the great problem. He had produced electricity directly from magnetism!

With, perhaps, the single exception of the discovery by Oersted, in 1820, of the invariable relation existing between an electric current and magnetism, this discovery of Faraday may be justly regarded as the greatest in this domain of physical science. These two master minds in scientific research wonderfully complemented each other. Oersted showed that an electric current is invariably attended by magnetic effects; Faraday showed that magnetic changes are invariably attended by electric currents. Before these discoveries, electricity and magnetism were necessarily regarded as separate branches of physical science, and were studied apart as separate phenomena. Now, however, they must be regarded as co-existing phenomena. The ignorance of the scientific world had unwittingly divorced what nature had joined together.

In view of the great importance of Faraday’s discovery, we shall be justified in inquiring, though somewhat briefly, into some of the apparatus employed in this historic research. Note its extreme simplicity. In one of his first successful experiments he wraps a coil of insulated wire around the soft iron bar that forms the armature or keeper of a permanent magnet of the horse-shoe type, and connects the ends of this coil to a galvanometer. He discovers that whenever the armature is placed against the magnet poles, and is therefore being rendered magnetic by contact therewith, the deflection of the needle of the galvanometer shows that the coiled wire on the armature is traversed by a current of electricity; that whenever the armature is removed from the magnet poles, and is therefore losing its magnetism, the needle of the galvanometer is again deflected, but now in the opposite direction, showing that an electric current is again flowing through the coiled wire on the armature, but reversed in direction. He notices, too, that these effects take place only while changes are going on in the strength of the magnetism in the armature, or when magnetic flux is passing through the coils; for, the galvanometer needle comes to rest, and remains at rest as long as the contact between the armature and the poles remains unbroken.

In another experiment he employs a simple hollow coil, or helix, of insulated wire whose ends are connected with a galvanometer. On suddenly thrusting one end of a straight cylindrical magnet into the axis of the helix, the deflection of the galvanometer needle showed the presence of an electric current in the helix. The magnet being left in the helix, the galvanometer needle came to rest, thus showing the absence of current. When the bar magnet was suddenly withdrawn from the helix, the galvanometer needle was again deflected, but now in the opposite direction, showing that the direction of the current in the helix had been reversed.

The preceding are but some of the results that Faraday obtained by means of his experimental researches in the direct production of electricity from magnetism. Let us now briefly examine just what he was doing, and the means whereby he obtained electric currents from magnetism. We will consider this question from the views of the present time, rather than from those of Faraday, although the difference between the two are in most respects immaterial.

Faraday knew that the space or region around a magnet is permeated or traversed by what he called magnetic curves, or lines of magnetic force. These lines are still called “lines of magnetic force,” or by some “magnetic streamings” “magnetic flux,” or simply “magnetism.” They are invisible, though their presence is readily manifested by means of iron filings. They are present in every magnet, and although we do not know in what direction they move, yet in order to speak definitely about them, it is agreed to assume that they pass out of every magnet at its north-seeking pole (or the pole which would point to the magnetic north, were the magnet free to move as a needle), and, after having traversed the space surrounding the magnet, reenter at its south-seeking pole, thus completing what is called the magnetic circuit. Any space traversed by lines of magnetic force is called a magnetic field.

But it is not only a magnet that is thus surrounded by lines of magnetic force, or by ether streamings. The same is true of any conductor through which an electric current is flowing, and their presence may be shown by means of iron filings. If an active conductor–a conductor conveying an electric current, as, for example, a copper wire–be passed vertically through a piece of card-board, or a glass plate, iron filings dusted on the card or plate will arrange themselves in concentric circles around the axis of the wire. It requires an expenditure of energy both to set up and to maintain these lines of force. It is the interaction of their lines of force that causes the attractions and repulsions in active movable conductors. These lines of magnetic force act on magnetic needles like other lines of magnetic force and tend to set movable magnetic needles at right angles to the conducting wire.

The setting up of an electric current in a conducting wire is, therefore, equivalent to the setting up of concentric magnetic whirls around the axis of the wire, and anything that can do this will produce an electric current. For example, if an inactive conducting wire is moved through a magnetic field; it will have concentric circular whirls set up around it; or, in other words, it will have a current generated in it as a result of such motion. But to set up these whirls it is not enough that the conducting wire be moved along the lines of force in the field. In such a case no whirls are produced around the conductor. The conductor must be moved so as to cut or pass through the lines of magnetic force. Just what the mechanism is by means of which the cutting of the lines of force by the conductor produces the circular magnetic whirls around it, no man knows any more than he knows just what electricity is; but this much we do know,–that to produce the circular whirls or currents in a previously inactive conductor, the lines of force of some already existing magnetic field must be caused to pass through the conductor, and that the strength of the current so produced is proportional to the number of lines of magnetic force cut in a given time, say, per second; or, in other words, is directly proportional to the strength of the magnetic field, and to the velocity and length of the moving conductor.

Or, briefly recapitulating: Oersted showed that an electric current, passed through a conducting circuit, sets up concentric circular whirls around its axis; that is, an electric current invariably produces magnetism; Faraday showed, that if the lines of magnetic force, or magnetism, be caused to cut or pass through an inactive conductor, concentric circular whirls will be set up around the conductor; that is, lines of magnetic force passed across a conductor invariably set up an electric current in that conductor.

The wonderful completeness of Faraday’s researches into the production of electricity from magnetism may be inferred from the fact that all the forms of magneto-electric induction known to-day–namely, self-induction, or the induction of an active circuit on itself; mutual induction, or the induction of an active circuit on a neighboring circuit; and electro-magnetic induction, and magneto-electric induction, or the induction produced in conductors through which the magnetic flux from electro and permanent magnets respectively is caused to pass–were discovered and investigated by him. Nor were these investigations carried on in the haphazard, blundering, groping manner that unfortunately too often characterizes the explorer in a strange country; on the contrary, they were singularly clear and direct, showing how complete the mastery the great investigator had over the subject he was studying. It is true that repeated failures frequently met him, but despite discouragements and disappointments he continued until he had entirely traversed the length and breadth of the unknown region he was the first to explore.

Let us now briefly examine Faraday’s many remaining discoveries and inventions. Though none of these were equal to his great discovery, yet many were exceedingly valuable. Some were almost immediately utilized; some waited many years for utilization; and some have never yet been utilized. We must avoid, however, falling into the common mistake of holding in little esteem those parts of Faraday’s work that did not immediately result either in the production of practical apparatus, or in valuable applications in the arts and sciences, or those which have not even yet proved fruitful. Some discoveries and devices are so far ahead of the times in which they are produced that several lifetimes often pass before the world is ready to utilize them. Like immature or unripe fruit, they are apt to die an untimely death, and it sometimes curiously happens that, several generations after their birth, a subsequent inventor or discoverer, in honest ignorance of their prior existence, offers them to the world as absolutely new. The times being ripe, they pass into immediate and extended public use, so that the later inventor is given all the credit of an original discovery, and the true first and original inventor remains unrecognized.

We will first examine Faraday’s discovery of the relations existing between light and magnetism. Though the discovery has not as yet borne fruit in any direct practical application, yet it has proved of immense value from a theoretical standpoint. In this investigation Faraday proved that light-vibrations are rotated by the action of a magnetic field. He employed the light of an ordinary Argand lamp, and polarized it by reflection from a glass surface. He caused this polarized light to pass through a plate of heavy glass made from a boro-silicate of lead. Under ordinary circumstances this substance exerted no unusual action on light, but when it was placed between the poles of a powerful electro-magnet, and the light was passed through it in the same direction as the magnetic flux, the plane of polarization of the light was rotated in a certain direction.

Faraday discovered that other solid substances besides glass exert a similar action on a beam of polarized light. Even opaque solids like iron possess this property. Kerr has proved that a beam of light passed through an extremely thin plate of highly magnetic iron has its plane of polarization slightly rotated. Faraday showed that the power of rotating a beam of polarized light is also possessed by some liquids. But what is most interesting, in both solids and liquids, is that the direction of the rotation of the light depends on the direction in which the magnetism is passing, and can, therefore, be changed by changing the polarity of the electro-magnet.

Faraday did not seem to thoroughly understand this phenomenon. He spoke as if he thought the lines of magnetic force had been rendered luminous by the light rays; for, he announced his discovery in a paper entitled, “Magnetization of Light and the Illumination of the Lines of Magnetic Force.” Indeed, this discovery was so far ahead of the times that it was not until a later date that the results were more fully developed, first by Kelvin, and subsequently by Clerk Maxwell. In 1865, two years before Faraday’s death, Maxwell proposed the electro-magnetic theory of light, showing that light is an electro-magnetic disturbance. He pointed out that optical as well as electro-magnetic phenomena required a medium for their propagation, and that the properties of this medium appeared to be the same for both. Moreover, the rate at which light travels is known by actual measurement; the rate at which electro-magnetic waves are propagated can be calculated from electrical measurements, and these two velocities exactly agree. Faraday’s original experiment as to the relation between light and magnetism is thus again experimentally demonstrated; and, Maxwell’s electro-magnetic theory of light now resting on experimental fact, optics becomes a branch of electricity. A curious consequence was pointed out by Maxwell as a result of his theory; namely, that a necessary relation exists between opacity and conductivity, since, as he showed, electro-magnetic disturbances could not be propagated in substances which are conductors of electricity. In other words, if light is an electro-magnetic disturbance, all conducting substances must be opaque, and all good insulators transparent. This we know to be the fact: metallic substances, the best of conductors, are opaque, while glass and crystals are transparent. Even such apparent exceptions as vulcanite, an excellent insulator, fall into the law, since, as Graham Bell has recently shown, this substance is remarkably transparent to certain kinds of radiant energy.

In 1778, Brugmans of Leyden noticed that if a piece of bismuth was held near either pole of a strong magnet, repulsion occurred. Other observers noticed the same effect in the case of antimony. These facts appear to have been unknown to Faraday, who, in 1845, by employing powerful electro-magnets rediscovered them, and in addition showed that practically all substances possess the power of being attracted or repelled, when placed between the poles of sufficiently powerful magnets. By placing slender needles of the substances experimented on between the poles of powerful horseshoe magnets, he found that they were all either attracted like iron, coming to rest with their greatest length extending between the poles; or, like bismuth, were apparently repelled by the poles, coming to rest at right angles to the position assumed by iron. He regarded the first class of substances as attracted, and the second class as repelled, and called them respectively paramagnetic and diamagnetic substances. In other words, paramagnetic substances, like iron, came to rest axially (extending from pole to pole), and diamagnetic substances, like bismuth, equatorially (extending transversely between the poles). He reserved the term magnetic substances to cover the phenomena of both para and dia-magnetism. He communicated the results of this investigation to the Royal Society in a paper on the “Magnetic Condition of All Matter,” on Dec. 18, 1845.

The properties of paramagnetism and diamagnetism are not possessed by solids only, but exist also in liquids and gases. When experimenting with liquids, they were placed in suitable glass vessels, such as watch crystals, supported on pole pieces properly shaped to receive them. Under these circumstances paramagnetic liquids, such as salts of iron or cobalt dissolved in water, underwent curious contortions in shape, the tendency being to arrange the greater part of their mass in the direction in which the flux passed; namely, directly between the poles. Diamagnetic liquids, such as solutions of salts of bismuth and antimony, in a similar manner, arranged the greater part of their mass in positions at right angles to this direction, or equatorially.

Michael Faraday Photograph

At first Faraday attributed the repulsion of diamagnetic substances to a polarity, separate and distinct from ordinary magnetic polarity, for which he proposed the name, diamagnetic polarity. He believed that when a diamagnetic substance is brought near to the north pole of a magnet, a north pole was developed in its approached end, and that therefore repulsion occurred. He afterwards rejected this view, though it has been subsequently adopted by Weber and Tyndall, the latter of whom conducted an extended series of experiments on the subject. The majority of physicists, however, at the present time, do not believe in the existence of a diamagnetic polarity. They point out that the apparent repulsion of diamagnetic substances is due to the fact that they are less paramagnetic than the oxygen of the air in which they are suspended.

During this investigation Faraday observed some phenomena that led him to a belief in the existence of another form of force, distinct from either paramagnetic or diamagnetic force, which he called the magne-crystallic force. He had been experimenting with some slender needles of bismuth, suspending them horizontally between the poles of an electro-magnet. Taking a few of these cylinders at random from a greater number, he was much perplexed to find that they did not all come to rest equatorially, as well-behaved bars of diamagnetic bismuth should do, though, if subjected to the action of a single magnetic pole, they did show this diamagnetic character by their marked repulsion. After much experimentation, he ascribed this phenomenon to the crystalline condition of the cylinder. By experimenting with carefully selected groups of crystals of bismuth, he believed he could trace the cause of the phenomenon to the action of a force which he called the magne-crystallic force.

Extended experiments carried on by Plücker on the influence of magnetism on crystalline substances led him to believe that a close relation exists between the ultimate forms of the particles of matter and their magnetic behavior. This subject is as yet far from being fully understood.

There was another series of investigations made by Faraday between the years 1831 and 1840, that has been wonderfully utilized, and may properly be ranked among his great discoveries. We allude to his researches on the laws which govern the chemical decomposition of compound substances by electricity. The fact that the electric current possesses the power of decomposing compound substances was known as early as 1800, when Carlisle and Nicholson separated water into its constituent elements, by the passage of a voltaic current. Davy, too, in 1806, had delivered his celebrated discourse “On Some Chemical Agencies of Electricity,” and in 1807, had announced his great discovery of the decomposition of the fixed alkalies.

Faraday showed that the amount of chemical action produced by electricity is fixed and definite. In order to be able to measure the amount of this action, he invented an instrument which he called a voltameter, or a volta-electrometer. It consisted of a simple device for measuring the amount of hydrogen and oxygen gases liberated by the passage of an electric current through water acidulated with sulphuric acid. He showed, by numerous experiments, that the decomposition effected is invariably proportional to the amount of electricity passing; that variations in the size of the electrodes, in the pressure, or in the degree of dilution of the electrolyte, had nothing to do with the result, and that therefore a voltameter could be employed to determine the amount of electricity passing in a given circuit. He also demonstrated that when a current is passed through different electrolytes (compound substances decomposed by the passage of electricity), the amount of the decompositions are chemically equivalent to each other.

The extent of Faraday’s work in the electro-chemical field may be judged by considering some of the terms he proposed for its phenomena, most of which, with some trifling exceptions, are still in use. It was he who gave the name electrolysis to decomposition by the electric current; he also proposed to call the wires, or conductors connected with the battery, or other electric source, the electrodes, naming that one which was connected with the positive terminal, the anode, and that one connected with the negative terminal, the cathode. He called the separate atoms or groups of atoms into which bodies undergoing electrolysis are separated, the radicals, or ions, and named the electro-positive ions, which appear at the cathode, the kathions, and the electro-negative radicals which appear at the anode, the anions.

There were many other researches made by Faraday, such as his experiments on disruptive electric discharges, his investigations on the electric eel, his many researches on the phenomena both of frictional electricity and of the voltaic pile, his investigations on the contact and chemical theories of the voltaic pile, and those on chemical decomposition by frictional electricity; these are but some of the mere important of them. Those we have already discussed will, however, amply suffice to show the value of his work. Rather than take up any others, let us inquire what influence, if any, the various groups of discoveries we have already discussed have exerted on the electric arts and sciences in our present time. What practical results have attended these discoveries? What actual, useful, commercial machines have been based on them? What useful processes or industries have grown out of them?

And, first, as to actual commercial machines. These researches not only led to the production of dynamo-electric machines, but, in point of fact, Faraday actually produced the first dynamo. A dynamo-electric machine, as is well known, is a machine by means of which mechanical energy is converted into electrical energy, by causing conductors to cut through, or be cut through by, lines of magnetic force; or, briefly, it is a machine by means of which electricity is readily obtained from magnetism.

Faraday’s invention of the first dynamo is interesting because at the same time he made the invention he solved a problem which up to his time had been the despair of the ablest physicists and mathematicians. This was the phenomenon of Arago’s rotating disc. It was briefly as follows: If a copper disc be rotated above a magnet, the needle tends to follow the plate in its rotation; or, if a copper plate be placed at rest above or below an oscillating magnet, it tends to check its oscillations and bring the needle quickly to rest. Faraday investigated these phenomena and soon discovered that a copper disc rotated below two magnet poles had electric currents generated in it, which flowed radially through the disc between its circumference and centre. By placing one end of a conducting circuit on the axis of the disc, and the other end on its circumference, he succeeded in drawing off a continuous electric current generated from magnetism, and thus produced the first dynamo. This was in 1831. Faraday produced many other dynamos besides this simple disc machine.

Although the disc dynamo in its original form was impracticable as a commercial machine, yet it was not only the forerunner of the dynamo, but was, in point of fact, the first machine ever produced that is entitled to be called a dynamo. He generously left to those who might come after him the opportunity to avail themselves of his wonderful discovery. “I have rather, however,” he says, “been desirous of discovering new facts and new relations dependent on magneto-electric induction than of exalting the force of those already obtained, being assured that the latter would find their development hereafter.” How profoundly prophetic! Could the illustrious investigator see the hundreds of thousands of dynamos that are to-day in all parts of the world engaged in converting millions of horse-power of mechanical energy into electric energy, he would appreciate how marvellously his successors have “exalted the force” of some of the effects he had so ably shown the world how to obtain.

Faraday lived to see his infant dynamo, the first of its kind, developed into a machine not only sufficiently powerful to maintain electric arc lights, but also into a form sufficiently practicable to be continuously engaged in producing such light, in one of the lighthouses on the English coast. Holmes produced such a machine in 1862, or some years before Faraday’s death. It was installed under the care of the Trinity House, at the Dungeness Lighthouse, in June, 1862, and continued in use for about ten years. When this machine was shown to Faraday by its inventor, the veteran philosopher remarked, “I gave you a baby, and you bring me a giant.”

The alternating-current transformer is another gift of Faraday to the commercial world. As is well known, this instrument is a device for raising or lowering electric pressure. The name is derived from the fact that the instrument is capable of taking in at one pressure the electric energy supplied to it, and giving it out at another pressure, thus transforming it. Faraday produced the first transformer during his investigations on voltaic-current induction. The modern alternating-current transformer, though differing markedly in minor details from Faraday’s primitive instrument, yet in general details is essentially identical with it. The enormous use of both step-up and step-down transformers–transformers which respectively induce currents of higher and of lower electromotive forces in their secondary coils than are passed through their primaries–shows the great practical value of this invention. The wonderful growth of the commercial applications of alternating currents during the past few decades would have been impossible without the use of the alternating-current transformer.

It is an interesting fact that it was not in the form of the step-down alternating-current transformer that Faraday’s discovery of voltaic-current induction was first utilized, but in the form of a step-up transformer, or what was then ordinarily called an induction coil. As early as 1842, Masson and Bréguet constructed an induction coil by means of which minute sparks could be obtained from the secondary, in vacuo. In 1851, Ruhmkorff constructed an induction coil so greatly improved, by the careful insulation of its secondary circuit, that he could obtain from it torrents of long sparks in ordinary air. The Ruhmkorff induction coil has in late years been greatly improved both by Tesla and Elihu Thomson, who, separately and independently of each other, have produced excellent forms of high-frequency induction coils.

Induction coils have long been in use for purposes of research, and in later years have been employed in the production both of the Röntgen rays used in the photography of the invisible, and the electro-magnetic waves used in wireless telegraphy.

Röntgen’s discovery was published in 1895. It was rendered possible by the prior work of Geissler and Crookes on the luminous phenomena produced by the passage of electric discharges through high vacua in glass tubes. Röntgen discovered that the invisible rays, or radiation, emitted from certain parts of a high-vacuum tube, when high-tension discharges from induction coils were passing, possessed the curious property of traversing certain opaque substances as readily as light does glass or water. He also discovered that these rays were capable of exciting fluorescence in some substances,–that is, of causing them to emit light and become luminous,–and that these rays, like the rays of light, were capable of affecting a photographic plate. From these properties two curious possibilities arose; namely, to see through opaque bodies, and to photograph the invisible. Röntgen called these rays X, or unknown rays. They are now almost invariably called by the name of their distinguished discoverer.

Let us briefly investigate how it is possible both to see and to photograph the invisible. Shortly after Röntgen’s discovery, Edison, with that wonderful power of finding practical applications for nearly all discoveries, had invented the fluoroscope,–a screen covered with a peculiar chemical substance that becomes luminous when exposed to the Röntgen rays. Suppose, now, between the rays and such a screen be interposed a substance opaque to ordinary light, as, for example, the human hand. The tissues of the hand, such as the flesh and the blood, permit the rays to readily pass through them, but the bones are opaque to the rays, and, therefore, oppose their passage; consequently, the screen; instead of being uniformly illumined, will show shadows of the bones, so that, to an eye examining the screen, it will seem as though it were looking through the flesh and blood directly at the bones. In a similar manner, if a photographic plate be employed instead of the screen, a distinct photographic picture will be obtained.

Both the fluoroscope and the photographic camera have proved an invaluable aid to the surgeon, who can now look directly through the human body and examine its internal organs, and so be able to locate such foreign bodies as bullets and needles in its various parts, or make correct diagnoses of fractures or dislocations of the bones, or even examine the action of such organs as the liver and heart.

About 1886, Hertz discovered that if a small Leyden jar is discharged through a short and simple circuit, provided with a spark-gap of suitable length, a series of electro-magnetic waves are set up, which, moving through space in all directions, are capable of exciting in a similar circuit effects that can be readily recognized, although the two circuits are at fairly considerable distances apart. Here we have a simple basic experiment in wireless telegraphy, which, briefly considered, consists of means whereby oscillations or waves, set up in free space by means of disruptive discharges, are caused to traverse space and produce various effects in suitably constructed receptive devices that are operated by the waves as they impinge on them.

At first a doubt was expressed by eminent scientific men as to the practicability of successfully transmitting wireless messages through long distances, since these waves, travelling in all directions, would soon become too attenuated to produce intelligible signals; but when it was shown, from theoretical considerations, that these waves when traversing great distances are practically confined to the space between the earth’s surface and the upper rarified strata of the atmosphere, the possibility of long-distance wireless telegraphic transmission was recognized. To increase the distance, it was only necessary either to increase the energy of the waves at the transmitting station, or to increase the delicacy of the receiving instruments, or both.

It has been but a short time since both the scientific and the financial worlds were astounded by the actual transmission of intelligible wireless signals across the Atlantic, and the name of Marconi will go down to posterity as the one who first accomplished this great feat.

The principal limit to the distance of transmission lies in the delicacy of the receiving instruments. The most sensitive are those in which a telephone receiver forms a part of the receiving apparatus. The almost incredibly small amount of electric energy required to produce intelligible speech in an ordinary Bell telephone receiver nearly passes belief. The work done in lifting such an instrument from its hook to the ear of the listener, would, if converted into electric energy, be sufficient to maintain an audible sound in a telephone for 240,000 years! Even extremely attenuated waves may therefore produce audible signals in such a receiver.

The electric motor was another gift of Faraday to commercial science, although in this case there are others who can, perhaps, justly claim to share the honor with him. Faraday’s early electric motor consisted essentially in a device whereby a movable conductor, suspended so as to be capable of rotation around a magnet pole, was caused to rotate by the mutual interaction of the magnetic fields of the active conductor and the magnet. The magnet, which consisted of a bar of hardened steel, was fixed in a cork stopper, which completely closed the end of an upright glass tube. A small quantity of mercury was placed in the lower end of the tube, so as to form a liquid contact for the lower end of a movable wire, suspended so as to be capable of rotating at its lower extremity about the axis of the tube. On the passage of an electric current through the wire, a continuous rotary motion was produced in it, the direction of which depends both on the direction of the current, and on the polarity of the end of the magnet around which the rotation occurs.

The great value of the electric motor to the world is too evident to need any proof. The number of purposes for which electric motors are now employed is so great that the actual number of motors in daily use is almost incredible, and every year sees this number rapidly increasing.

The above are the more important machines or devices that have been directly derived from Faraday’s great investigation as to the production of electricity from magnetism. Let us now inquire briefly as to what useful processes or industries have been rendered possible by the existence of these machines.

Apparently one of the most marked requirements of our twentieth-century civilization is that man shall be readily able to extend the day far into the night. He can no longer go to sleep when the sun sets, and keep abreast with his competitors. Of all artificial illuminants yet employed, the arc and the incandescent electric lights are unquestionably the best, whether from a sanitary, aesthetic, or truest economical standpoint. Now, while it is a well-known matter of record that both arc and incandescent lights were invented long before Faraday’s time, yet it was not until a source of electricity was invented, superior both in economy and convenience to the voltaic battery, that either of these lights became commercial possibilities. Such an electric source was given to the world by Faraday through his invention of the dynamo-electric machine, and it was not until this machine was sufficiently developed and improved that commercial electric lighting became possible. The energy of burning coal, through the steam-engine, working the dynamo, is far cheaper and more efficient for producing electricity than the consumption of metals through the voltaic pile.

It is characteristic of the modesty of Faraday that when, in after-life, he heard inventors speaking of their electric lights, he refrained from claiming the electric light as his own, although, without the machine he taught the world how to construct, commercial lighting would have been an impossibility.

The marvellous activity in the electric arts and sciences, which followed as a natural result of Faraday giving to the world in the dynamo-electric machine a cheap electric source, naturally leads to the inquiry as to whether at a somewhat later day a yet greater revolution may not follow the production of a still cheaper electric source. In point of fact such a discovery is by no means an impossibility. When a dynamo-electric machine is caused to produce an electric current by the intervention of a steam-engine, the transformation of energy which takes place from the energy of the coal to electric energy is an extremely wasteful one. Could some practical method be discovered by means of which the burning of coal liberates electric energy, instead of heat energy, an electric source would be discovered that would far exceed in economy the best dynamo in existence. With such a discovery what the results would be no one can say; this much is certain, that it would, among other things, relegate the steam-engine to the scrap-heap, and solve the problem of aerial navigation.

What is justly regarded as one of the greatest achievements of modern times is the electrical transmission of power over comparatively great distances. At some cheap source of energy, say, at a waterfall, a waterwheel is employed to drive a dynamo or generator, thus converting mechanical energy into electrical energy. This electricity is passed over a conducting line to a distant station, where it is either directly utilized for the purpose of lighting, heating, chemical decomposition, etc., or indirectly utilized for the purpose of obtaining mechanical power for driving machinery, by passing it through an electric motor. The electric transmission of power has been successfully made in California over a distance of some 220 miles, at a pressure on transmission lines of 50,000 volts.

The high pressures required for the economical use of transmission lines necessitates the employment of transformers at each end of the line; namely, step-up transformers at the transmitting end, to raise the voltage delivered by the generators, and step-down transformers, at the receiving end, to lower it for use in the various translating devices. These transformers are employed in connection with alternating-current dynamos. Faraday not only gave to the world the first electric generator, but also the first transformer, and one of the first electric motors, and without these gifts the electric transmission of power over long distances, which has justly been regarded as one of the most marvellous achievements of our age, would have been an impossibility.

In high-tension circuits over which such pressures as 50,000 volts is transmitted, no little difficulty is experienced from leakage and consequent loss of energy. This leakage occurs both between the line conductors and at the insulators placed on the pole lines forming the line circuit. The insulators are made either of glass or porcelain, and are of a peculiar form known as triple petticoat pattern. The loss on such lines, due to leakage between wires, is greater than that which takes place at the pole insulators, and is diminished by keeping the circuit wires as far apart as possible.

In the early history of the art, electric transmission of power was effected by means of direct-current generators and motors,–generators and motors through which the current always passed in the same direction. Such generators and motors, however, possessed inconveniences that prevented extensive commercial transmission of power, since, as we have seen, high pressure was necessary for efficiency in such transmission, and the collecting-brushes and commutators employed in all direct-current generators and motors to carry the current from the machine or to the motor, were a constant source of trouble and danger.

When the alternating-current motor first same into general use, it was employed, in connection with the alternating-current generator, in electric transmission systems; but such motors also possess the inconvenience of not readily starting from a state of rest, with their full turning power, or torque, and of therefore being unsuitable where the motor requires to be frequently stopped or started. Had these difficulties remained unsolved, long-distance electric transmission of power, so successful in operation to-day, and which bids fair to be still more successful in the near future, would have been impossible. Fortunately, these difficulties were overcome by the genius of Nikola Tesla, in the invention of the multiphase alternating-current motor, or the induction motor, as it is now generally called. Although Baily, Deprez, and Ferraris had accomplished much before Tesla’s time, yet it was practically to the investigations and discoveries made by Tesla, between 1887 and 1891, that the induction motor of to-day is due.

Another requirement of our twentieth-century civilization is rapid transit, either urban or inter-urban, and this is afforded by various systems of electric street railways or electric traction generally, including electric locomotives and electric automobiles. The wonderful growth in this direction which has been witnessed in the last few decades would have been impossible without the electric generator and motor, both gifts of Faraday to the world. Their application in this direction must, therefore, go to swell the debt our civilization owes to the labors of this great investigator.

In the system of electric street-car propulsion very generally employed to-day, a single trolley wheel is employed for taking the driving current from an overhead conductor, suspended above the street. The trolley wheel is supported by a trolley pole, and is maintained in good electric contact with the trolley wire, or overhead conductor. By this means the current passes from the wire down the conductor connected with the trolley pole, thence through the motors placed below the body of the car, and from them, through the track or ground-return, back to the power station. A small portion of the current is employed for lighting the electric lamps in the car. In some systems an underground trolley is employed.

An important device, called the series-parallel controller, is employed in all systems of electric street-car propulsion. It consists of means by which the starting and stopping of the car, and changes, both in its speed and direction, are placed under the control of the motorman. A separate controller is placed on both platforms of the car. The series-parallel controller consists essentially of a switch by means of which the several motors, that are employed in all street cars, can be variously connected with each other, or with different electric resistances, or can be successively cut out or introduced into the circuit, so that the speed of the car can be regulated at will, as the handle of the controller is moved by the motorman to the various notches on the top of the controller box. As generally arranged, the speed increases from the first notch or starting position to the last notch, movements in the opposite direction changing connections in the opposite order of succession, and, therefore, slowing the car. There is, however, no definite speed corresponding to each notch, for this will vary with the load on each car, and with the gradient upon which it may be running.

But there is another valuable gift received by the world as a result of this great discovery of Faraday; namely, that most marvellous instrument of modern times, the speaking telephone. This instrument was invented in 1861, by Philip Ries, and subsequently independently reinvented in 1876, by Elisha Gray and Alexander Graham Bell.

As is well known, it is electric currents and not sound-waves that are transmitted over a telephone circuit. The magneto-electric telephone in its simplest form consists of a pair of instruments called respectively the transmitter and the receiver. We talk into the transmitter and listen at the receiver. Both transmitter and receiver consist of a permanent magnet of hardened steel around one end of which is placed a coil of insulated wire. In front of this coil a diaphragm, or thin plate, of soft iron, is so supported as to be capable of freely vibrating towards and from the magnet pole.

The operation of the transmitting instrument is readily understood in the light of Faraday’s discovery. It is simply a dynamo-electric machine driven by the voice of the speaker. As the sound-waves from the speaker’s voice strike against the diaphragm, which has become magnetic from its nearness to the magnet pole, electric currents are generated in the coil of wire surrounding such pole, since the to-and-fro motions cause the lines of electro-magnetic force to pass through the wire on the moving coil. The operation of the receiving instrument is also readily understood. It acts as an electric motor driven by the to-and-fro currents generated by the transmitter. As these currents are transmitted over the wire, they pass through the coil of wire on the receiving instrument, and reproduce therein the exact movements of the transmitting diaphragm, since, as they strengthen or weaken the magnetism of the pole, they cause similar motions in the diaphragm placed before it. Consequently, one listening at the receiving diaphragm will hear all that is uttered into the transmitting diaphragm. It was thus, by the combination of the dynamo and motor, both of which were given by Faraday to the world, that we have received this priceless instrument, which has been so potent in its effects on the civilization of the Twentieth century.

The electric telegraph had its beginnings long before Faraday’s time. As early as 1847, Watson had erected a line some two miles in length, extending over the housetops in London, and operated it by means of discharges from an ordinary frictional electric machine. In 1774, Lesage had erected in Geneva an electric telegraph consisting of a number of metallic wires, one for each letter of the alphabet. These wires were carefully insulated from each other. When a message was to be sent over this early telegraphic line an electric discharge was passed through the particular wire representing the letter of the alphabet to be sent; this discharge, reaching the other end, caused a pithball to be repelled and thus laboriously, letter by letter, the message was transmitted. How ludicrously cumbersome was such an instrument when contrasted with the Morse electro-magnetic telegraph of to-day, which requires but a single wire; or with the harmonic telegraph of Gray, which permits the simultaneous transmission of eight or more separate messages over a single wire; or with the wonderful quadruplex telegraphic system of Edison which permits the simultaneous transmission of four separate and distinct messages over a single wire, two in one direction, and two in the opposite direction at the same time; or with the still more wonderful multiplex telegraph of Delaney, which is able to simultaneously transmit as many as seventy-two separate messages over a single wire, thirty-six in one direction and thirty-six in the opposite direction. These achievements have been possible only through the researches and discoveries of Oersted, Faraday, and hosts of other eminent workers; for, it was the electro-magnet, rendered possible by Oersted, together with the magnificent discoveries of Faraday, and others since his time, that these marvellous advances in electro-telegraphic transmission of intelligence have become possibilities.

Before completing this brief sketch of some of the effects that Faraday’s work has had on the practical arts and sciences, let us briefly examine the generating plants that are either in operation or construction at Niagara Falls.

Some idea of the size of the Niagara Falls generating plant on the American side may be gained from the fact that there have already been installed eleven of the separate 5,000 horse-power generators. The remaining capacity of the tunnel will permit of the installation of 50,000 additional horse-power, or 105,000 horse-power in all.

On the Canadian side of the Falls another great plant is about to be erected with an ultimate capacity of several hundred thousand horse-power. Here, however, the size of the generating unit will be double that on the American side, or 10,000 horse-power. These generators will be wound to produce an electric pressure of 12,000 volts, raised by means of step-up transformers to 22,000, 40,000, and 60,000 volts, according to the distance of transmission. Each of the revolving parts of these machines will weigh 141,000 pounds. To what gigantic proportions has the little infant dynamo of Faraday grown in this short time since its birth!

The low rates at which electric power can be sold in the immediate neighborhood of the Niagara generating plant have naturally resulted in an enormous growth of the electro-chemical industries, for these industries could never otherwise develop into extended commercial applications. Of the total output of, say, 55,000 horsepower at the Niagara Falls generating plant, no less than 23,200 horse-power is used in various electrolytic and electro-thermal processes in the immediate neighborhood. Some of the more important consumers of the electric power, named in the order of consumption, are for the manufacture of the following products: calcium carbide, aluminium, caustic soda and bleaching salt, carborundum, and graphite.

Calcium carbide, employed in the production of acetylene gas, either for the purposes of artificial illumination, or for the manufacture of ethyl alcohol, is produced by subjecting a mixture of carbon and lime to the prolonged action of heat in an electric furnace.

Aluminium, the now well-known valuable metal, present in clay, bauxite, and a variety of other mineral substances, is electrolytically deposited from a bath of alumina obtained by dissolving bauxite either in potassium fluoride or in cryolite. Aluminium is now coming into extended use in the construction of long-distance electric power transmission lines.

Caustic soda and bleaching salt are produced by the electrolytic decomposition of brine (chloride of sodium). The chlorine liberated at the anode is employed in the manufacture of bleaching-salt, and the sodium is liberated at a mercury cathode, with which it at once enters into combination as an alloy. On throwing this alloy into water the sodium is liberated as caustic soda.

Carborundum, a silicide of carbon, is a valuable substance produced by the action of the heat of an electric furnace on an intimate mixture of carbon and sand. It has an extensive use as an abrasive for grinding and polishing.

Artificial graphite is another product produced by the long-continued action of the heat of the electric furnace on carbon under certain conditions.

According to reports from the United States Geological Survey, the graphite works at Niagara Falls produced in 1901, 2,500,000 lbs. of artificial graphite, valued at $119,000. This was an increase from 860,270 lbs., valued at $69,860 for 1900, and from 162,382 lbs., valued at $10,140, in 1897, the first year of its commercial production. In 1901, more than half of the output was in the form of graphitized electrodes employed in the production of caustic soda and bleaching salt, and in other electrolytic processes.

The Niagara Falls power transmission system stands to-day as a magnificent testimonial to the genius of Faraday, and as a living monument of the varied and valuable gifts his researches have bestowed upon mankind. For here we have not only the dynamo, motors, and transformers that he gave freely to the world, not only the alternating-current transformer, and the system of transmission of power, but we even find that the principal consumers of the enormous electric power produced are employing it in carrying on some of the many processes in electro-chemistry, a science that he had done so much to advance.

Among some of the surprises electro-chemistry may have in store for the world in the comparatively near future, may be a nearer approach to a mastery of the laws which govern the combination of elementary substances when under the influence of plant-life. If these laws ever become so well known that man is able to form hi his laboratory the various food products that are now formed naturally in plant organisms, such a revolution would be wrought that the work of the agriculturist would be largely transferred to the electro-chemist. Some little has already been done in the direct formation of some vegetable substances, such as camphor, the peculiar flavoring substance present in the vanilla bean, and in many other substances. Should such discoveries ever reach to the direct formation of some food staple, the wide-reaching importance and significance of the discovery would be almost beyond comprehension.

But, while the direct electro-synthetic formation of food products is yet to be accomplished on a practical scale, the problem appears to be nearing actual solution in an indirect manner. It has been known since the time of Cavendish, in 1785, that small quantities of nitric acid could be formed directly from the nitrogen and oxygen of the atmosphere by the passage of electric sparks; but heretofore, the quantity so found has been too small to be of any commercial value. Quite recently, however, one of the electro-chemical companies at Niagara Falls has succeeded in commercially solving the important problem of the fixation of the nitrogen of the atmosphere; it being claimed that the cost of thus producing one ton of commercial nitric acid, of a market value of over eighty dollars, does not greatly exceed twenty dollars. Since sodium nitrate can readily be produced by the process, and its value as a fertilizer of wheat-fields is too well known to need comment, there would thus, to a limited extent, be indirectly solved the electro-chemical production of food staples.

Faraday’s high rank as an investigator in the domain of natural science was fully recognized by the learned societies of his time, by admission into their fellowships. As early as 1824, he was honored by the Royal Society of London by election as one of its Fellows, and in 1825 he had become a member of the Royal Institution. It is recorded of the great philosopher that the membership in the Royal Institution was the only one which he personally sought; all others came unsought, but they came so rapidly from all portions of the globe that in 1844 he was a member of no less than seventy of the leading learned societies of the world. Ries, the German electrician, so well known in connection with his invention of the speaking telephone, addressed Faraday as “Professor Michael Faraday, Member of all the Academies.” Besides his membership in the learned societies, Faraday received numerous degrees from the colleges and universities of his time. Among some of these are the following: The University of Prague, the degree of Ph.D.; Oxford, the degree of D.C.L.; and Cambridge, the degree of LL.D. He also received numerous medals of honor, and was offered the Presidency of the Royal Society, which, however, he declined, as he did also a knighthood proffered by the government of England. Faraday died on the 25th of August, 1867, after a long, well-spent, useful life.

We have thus briefly traced some of the more important discoveries of Michael Faraday. Many have necessarily been passed by, but what we have given are more than sufficient to stamp him as a great philosopher and investigator. Speaking of Faraday in this connection, Professor Tyndall says: “Take him for all in all, I think it will be conceded that Michael Faraday is the greatest experimental philosopher the world has ever seen; and I will add the opinion that the progress of future research will tend not to diminish or decrease, but to enhance and glorify, the labors of this mighty investigator.”

Authorities.

Experimental Researches in Electricity. By Michael Faraday. From the Philosophical Transactions.

Abstracts of the Philosophical Transactions from 1800 to 1837.

Faraday’s Experimental Researches in Electricity and Magnetism. 3 vols.

Life and Letters of Faraday. By Dr. Bence Jones.

Michael Faraday. By J.H. Gladstone.

Students’ Text-Book of Electricity. By Henry M. Noad. Revised by W.H. Preece.

Michael Faraday. By John Tyndall.

Pioneers of Electricity. By J. Munro.

Dynamo-Electric Machinery. By Silvanus P. Thompson.

A Dictionary of Electrical Words, Terms, and Phrases. By Edwin J. Houston.

Electricity and Magnetism. By Edwin J. Houston.