Faraday, Michael (DNB00)
|←Fanshawe, Thomas (1596-1665)||Dictionary of National Biography, 1885-1900, Volume 18
|Farey, John (1766-1826)→|
FARADAY. MICHAEL (1791-1867), natural philosopher, was the son of James Faraday. In the parish register of Clapham, Yorkshire, between 1708 and 1730. 'Richard ffaraday,' stonemason, tiler, and 'separatist,' recorded the birth of ten children. Robert Faraday, son or nephew of this man, married Elizabeth Dean, the owner of a small but pleasant residence, called Clapham Wood Hall. He had by her ten children, one of whom, James, born 8 May 1761, was the father of Michael Faradoy. The published letters of Faraday's father and mother display intelligence and great religious earnestness. John Glas, followed by his son-in-law, John Sandeman, had seceded from the presbyterians, and most of Faraday's relatives, as subsequently himself, were members of the Sandemanian congregation. Faraday's father, James, married, in 1786, Margaret Hastwell, a farmer's daughter, and moved soon afterwards to Newington in Surrey.
Michael Faraday was horn at Newington Butts, 22 Sept. 1791. He died at Hampton Court — not in tha palace, but in a small house on the Green placed at his disposal by her majesty — 25 Aug. 1867. This act of royal kindness obviously delighted him, and indeed nothing could have been more delicate and considerate than the manner in which the house was offered him. It was understood to have been done at the instance and under the direction of the prince consort, though his name never appeared in the correepondence. Physically, Faraday was below the middle size, well set, active, and with extraordinary animation of countenance. His head from forehead to back was so long that he had usually to bespeak his hats. In youth his hair brown, curling naturally; later in life it approached to white, and was always parted in the centre. His voice was pleasant, and his laugh hearty. His christian name, 'Michael,' his wonderful vivacity, and his mastery of the Irish 'brogue,' gave countenance to a tradition that a portion of his blood was drawn from Ireland. In a journal entry written at Interlaakenon 2 Aug. he thus refers to his father: 'Cloutnail-making goes on here rather considerably, and is a very neat and pretty operation to observe. I love a smith's shop and anything relating to smithery. My father was a smith.'
The fact of Faraday's father being one of a family of ten children placed him at a disadvantage in beginning the battle of life. He had to be content with humble quarters and to accept the help of his children. From Newington James Faraday removed to Jacob's Well Mews, Charles Street, Manchester Square; and afterwards to No. 18 Weymouth Street, Portland Place, where he died in 1810. Not far from Jacob's Well Mews was a bookbinder and stationer's shop kept by a worthy man named Riebau, Michael Faraday began life as Riebau's errand-boy. After a year's trial, being then thirteen, he was bound apprentice to Riebau. The boy's conduct had been so exemplary that he was taken without fee. This was in 1804, Riebau's establishment was in Blandford Street, Manchester Square. When, many years ago, the present writer visited the place in Faraday's company, it was still a stationer's shop, the lady behind the counter mentioning incidentally that one of her predecessors had been master of Sir Charles Faraday,' At Riebau's, Faraday lived for eight years, working as a bookbinder. He subsequently worked with one De La Roche, a man so passionate and austere, that although he promised to leave to Faraday all that he possessed, his sensitive journeyman could not be prevailed upon to remain with him. A warm friendship had sprung up between Faraday and two intelligent young men, named Huxtable and Abbott, Brisk notes and letters passed between him and them, and his letters to Abbott have been happily preserved. He heard lectures from Mr. Tatum on natural philosophy at 53 Dorset Street, Fleet Street, the cost being a shilling a lecture. He read much, and was specially indebted to Mrs. Marcet's 'Conversations in Chemistry.' Mr. Dance, a member of the Royal Institution, was a customer of Riebau's, and Faraday had impressed him so favourably, that he gave the youth tickets for the last four lectures delivered by Davy in the Royal Institution. Their dates were 29 Feb., 14 March, 8 and 10 April 1812. He took notes of these lectures, wrote them fairly and fully out afterwards in a quarto volume, and sent them to Davy, asking to be enabled to quit trade, which he thought vicious and selfish, and to devote himself to science. In a most considerate note Davy replied to the young man on 24 Dec. 1812. One night, when undressing in Weymouth Street, be was startled by a loud knock, and found Davy's carriage before the door. Davy's servant handed him a note, as a result of which he called next morning at the Royal Institution, and was engaged by what interested the audience, and what failed to interest them. 'A lecturer,' he says, 'should appear easy and collected, undaunted and unconcerned. His thoughts about him, and his mind clear and free for the contemplation and description of his subject. His whole behaviour should evince respect for his audience, and he should in no case forgot that he is in their presence.' After laying down the canons of lecturing in this fashion, he obviously feels lifted by the dignity of the lecturers work. 'Then, and then only,' he exclaims, 'shall we do justice to the subject, please the audience, and satisfy our honour — the honour of a philosopher.' With this 'honour of a philosopher' Faraday was impregnated. By it his whole life was informed and ennobled.at a weekly wage of 35s. He soon began to help in the lectures; joined the City Philosophical Society, gathered together a little mutual improvement society of his own at the Royal Institution, and lectured on chemistry at the City Philosophical Society. He was daily in the laboratory assisting Davy in his experiments, some of which were dangerous. Both he and his master were wounded more than once by explosions of chloride of nitrogen, which had previously destroyed one of Dulong's eyes. Meanwhile he carried on a brisk and pleasant correspondence with his friend Abbott. The youth observed and reflected on all he saw. He writes sensibly and well about lecturing and lectures, notes
In the autumn of 1813 Davy and his wife went abroad, and Faraday went with them as an amanuensis. Davy had no valet, and it was understood that Faraday was to lend him some aid in this direction. He quitted London on Wednesday, 13 Oct. 1813, and accompanied Davy to France, Switzerland, Italy, and the Tyrol, keeping a journal, from which, in his 'Life and Letters of Faraday,' copious extracts have been made by Dr. Bence Jones. He described the experiments conducted by Davy with the eminent men whom he visited. One of the most interesting of these was the combustion of a diamond in oxygen in the Academy del Cimento, by means of the great lens of the Grand Duke of Tuscany. His letters to his mother are full of affection. At Rome they found Morrichini vainly seeking; to magnetise a needle by the solar rays. They visited Naples and Vesuvius, which was in active eruption. On Friday, 17 June 1814. Faraday saw M. Volta, who came to Sir H. Davy, a hale, elderly man, bearing the red ribbon, and very free in conversation.' In July he was at Geneva, from which city he writes very fully to his mother and his friends. Some very charming passages occur in his letters to Abbott. Speaking of the ills and trials of life he compares them to 'clouds, which intervened between me and the sun of prosperity, but which I found were refreshing, reserving to me that tone and vigour of mind which prosperity alone would enervate and ultimately destroy.' Such were the materials out of which the great natural philosopher was formed.
During his stay at Geneva, Davy was the guest of his friend De La Rive, father of the celebrated electrician, and grandfather of the present worthy proprietor of the beautiful country residence at Présinge. Host and guest were sportemen, and they frequently went out shooting. On these occasions Faraday loaded Davy's gun, and for a tima he had his meals 'with the servants. From nature Faraday had received the warp and woof of a gentleman, and this, added to hisbright intelligence, soon led De La Rive tothe discovery that he was Davy's laboratory assistant, not his servant. Somewhat shocked at the discovery. De La Rive proposed that Faraday should dine with the family, instead of with the domestics, "to this Lady Davy demurred, and De La Rive met the case by sending Faraday's meals to his own room. Davy appears to have treated Faraday with every consideration, He sometimes brushed his own clothes to relieve his assistant of the duty, but Lady Davy was of a different temper. She treated Faraday as a menial, and his fiery spirit so chafed under this treatment, that be was frequently on the point of returning home, after Faraday's death rumours of his relations to Davy were spread abroad, and among them was the circumstantial anecdote that De La Rive, finding Faraday's company at table objected to, gave the young man a banquet all to himself. The anecdote on the face of it was absurd, for Faraday at the time had done nothing to furnish a reason for such an entertainment. In 1869 the brief and true history of the transaction was drawn up for the present writer by Professor De La Rive. There was no banquet of the kind referred to, but Faraday always entertained a grateful remembrance of the kindness and consideration shown him by the elder De La Rive when he was a mere garçon de laboratoire.
In 1815 he returned with Davy to the Royal Institution, and according to stipulation, was re-engaged by the managers on 15 May of that year. His first contribution to science was an analysis of caustic lime from Tuscany. It was published in the 'Quarterly Journal of Science' for 1816. Various notes and short papers followed during the next two years. In 1818 he experimented on 'Sounding Flames,' correcting and completing, with great acuteness, a previous investigation by the elder De La Rive. Then followed various notes and notices, the 'Quarterly Journal' being the storehouse of all these small communications. In 1820 he sent to the Royal Society a paper 'On Two New Compounds of Chlorine and Carbon, and on a New Compound of Iodine, Carbon, and Hydrogen,' This was the first paper of his that was published in the 'Philosophical Transactions.'
At this time he had made the acquaintance and won the esteem, of Miss Sarah Barnard. Their friendship ripened into love, which, on his part, was accompanied by more than the usual oscillations of hope and fear. His passion so ardent, that she for a time doubted her ability to return it with adequate strength. His utterances at this crisis of his life were marked by the delicacy and considerateness which defused themselves throughout his entire character. She at length yielded, and they were married on 12 June 1821. An entry in a book containing his diplomas ran thus: 'Amongst these records of events I here insert the date of one which, is a source of honour and happiness, for exceeds all the rest. We were married on 12 June 1821.' At the time of their marriage Miss Barnard was twenty-one, while Faraday was thirty. It is pleasant lo record the manner in which Davy received the intelligence of the marriage; 'I hope you will continue quite well, and do much during the summer, and I wish you in your new state all that happiness which I am sure you deserve." 'A month after his marriage he made his confession of sin and profession of faith before the Sandemanian Church. When his wife asked him why he had not told her what he was about, to do, he only replied, "That is between me and my God"' (Bence Jones, Life and Letters).
Œrsted discovered in 1820 that a freely suspended magnetic needle was deflected by a voltaic current, and soon afterwards the penetrative mind of Wollaston conceived the idea of causing the needle to rotate round the current, and the wire carrying the current to rotate round a magnet. Faraday's attention is soon directed to this question, but before touching it he went through the discipline of writing a 'History of the Progress of Electro-Magnetism.' Immediately afterwards he attacked the subject of 'Magnetic Rotations,' and on the morning of Christmas day he led his young wife into the laboratory, and showed her the revolution of a magnetic needle round an electric current. He had also in the same year made experiments on the vaporisation of mercury at common temperatures, Immediately afterwards, and jointly with Mr. Stoddart, he worked with success on the alloys of steel. A razor made of one of these alloys, and presented to the present writer by Faraday himself, is still in his possession.
We now approach a subject of high importance. In the spring of 1823 Faraday analysed a substance proved bv Davy to be the hydrate of chlorine, and which, prior to Davy's experiments, had been regarded as chlorine itself. The paper describing the analysis looked over by Davy, who suggested on the spot the heating of the hydrate under pressure, in a sealed glass tube. The hydrate fused at a moderate heat, the tube became filled with a yellow gas, and was found to contain an oily liquid. When the end of the tube was broken off an explosion occurred, and the oily matter vanished. Next morning Faraday, writing to Dr. Paris, was able to make the following important communication; 'The oil you noticed yesterday turns out to be liquid chlorine.' Davy, on being informed of what had occurred, immediately applied the method of self-compressing atmospheres to the liquefaction of muriatic gas. Faraday afterwards liquefied chlorine by a compressing syringe, and succeeded in reducing a number of other gases, up to that time deemed permanent, to the liquid condition. He followed up the subject in 1844, and considerably expanded its limits. A sure and certain addition was made to our knowledge of matter by these important experiments. They rendered the conclusion next to certain that all gases are but the vapours of liquids possessing very low boiling points — a conclusion triumphantly vindicated by the liquefaction of atmospheric air, and other refractory gases, in our own day.
The 'Philosophical Transactions' for 1835 contains a paper by Faraday 'On New Compounds of Carbon and Hydrogen.' In it was announced the discovery of benzol, which has been turned to such profitable commercial account as the basis of our splendid aniline dyes. In 1826 be published in the 'Transactions' another paper 'On Sulphonaphthalic Acid,' and afterwards occupied himself with experiments on the limits of vaporisation. In 1823 Sir John Herschel had suggested the use of borate of lead in the manufacture of a highly refractive optical glass. Ha and Mr. (afterwards Sir James) South had actually succeeded in producing a glass with a refractive index of 1.866. The glass, however, proved too soft for optical purposes. In 1825 a committee, embracing Faraday, Sir John Herschel, and Dollond was formed with a view of pursuing this subject. The experiments were begun at the Falcon Glass Works, but completed in the yard of the Royal Institution. It was at this time that Faraday engaged as assistant Sergeant Anderson of the Royal Artillery, to whose 'care, steadiness, exactitude, and faithfulness in the performance of all that has been committed to his charge,' he avowed his indebtednees. Anderson's sense of duty and obedience was so precise that it was said of him that if the Institution were on fire he would not quench the flame except by Faraday's command. An elaborate paper 'On the Manufacture of Glass for Optical Purposes' formed the material of Faraday's first Bakerian lecture, which was delivered before the Royal Society at the close of 1829. Three successive sittings of the society were taken up by this lecture. The glass, however, did not turn out to be of important practical use, but it afterwards proved to be the foundation of two of Faraday's greatest discoveries. In 1831 he published a paper 'On a Pecidiar Class of Optical Deceptions,' to which, the chromatrope owes its origin. In the same year he made a communication on vibrating surfaces, wherein be explained the gathering up of light powders at the places of most intense vibration, while heavy powders like sand, as beautifully shown by Chladni, arrange themselves along the nodal lines.
Faraday had now reached the threshold of a career of discovery unparalleled in the history of pure experimental science. Towards the end of 1831 he discovered and subdued the domain of magneto-electricity. The inductive action of an electrified body on an adjacent unelectrified body was familiar to him; and he thought that something similar — he knew not what — ought to occur when a wire curbing an electric current was brought near another wire carrying no current. He went thus to work. Two wires overspun with silk were wound side by side over the same wooden cylinder. The two ends of one of the wires were connected with a voltaic battery, and the two ends of the other with a galvanometer. Faraday was never satisfied until he had applied the greatest force at his command, and in the present instance a battery power varying from 10 to 130 cells was called into play. But no matter how powerful he made his currents in the one wire, the other wire remained absolutely quiescent, while the electricity was flowing through its neighbour, The attention of the keen-eyed experimenter was, however, soon excited by a small motion of his galvanometer needle which occurred at the moment the current from the battery first started through its wire. After this first slight impulse the needle came to rest; but on interrupting the battery circuit another feeble motion was observed, opposite in direction to the former one. This result, and many others of a similar kind, led him to the conclusion that the battery current through the one wire did in reality induce a similarcurrent through the other, but that it continued for an instant only, and partook more of the nature of the electric wave from a common Leyden jar, than of the current from a voltaic battery.' The momentary currents thus generated as if by a kind of kick, or reaction, he called 'induced currents.'
Faraday next showed that the mere approach of a wire forming a closed curve to another wire through which a current was flowing, aroused in the former an induced current. The withdrawal of the wire also excited a current in the opposite direction. These currents existed only during the time of approach and withdrawal, and vanished when the motion ceased. Prior to these experiments magnetism had been evoked by electricity. He now aimed at exciting electricity by magnetism. Round a welded iron ring he wound two coils of insulated copper wire, the coils occupying opposite halves of the ring. The ring, with its two coils, is represented in Foley's admirable statue as held in Faraday's hand. Through one of the two coils be sent a voltaic current, which powerfully magnetised the iron. During the moment of magnetisation a pulse was sent through the other coil strong enough to whirl round the needle of the galvanometer four or five times in succession. On interrupting the circuit a whirl of the needle in the opposite direction was observed. It was only during the moments of magnetisation and demagnetisation that these effects were produced. From his welded ring he passed on to straight bars of iron, and obtained with them the effects produced by his ring.
At that time the 'magnetism of rotation' excited universal attention. A non-magnetic metallic disk placed beneath a magnetic needle and set in rotation drew the needle after it. On reversing the motion of the disk the needle first stopped and then turned backwards, following the new rotation. Arago was the discoverer of this action, but he ventured on no explanation of it. Its solution was reserved for Faraday. The disk being a conductor of electricity, he clearly saw that his newly discovered induced currents must be excited in it by the adjacent needle. He forthwith established the existence of these currents, proving their direction to be such as must, in accordance with the laws of Œrsted, produce the observed rotation.
The well-known arrangement of iron filings round a magnet profoundly impressed Faraday from the first. By 'action at a distance,' coupled with the law of inverse squares, the position of these filings had been previously explained. Faraday never made himself at home with this idea, but visualised a something round the magnet which gave the filings their position. This conception, which he used for a long time as a mere 'representative idea,' fearing to commit himself to physical theory, lay at the root of his experiments. He called the lines along which the iron filings ranged themselves 'lines of force,' and his showed how by cutting these lines, whether they belonged to an artificial magnet or to the earth, induced currents were generated. Causing, for example, a copper disk to spin across the earth's lines of force, he produced such currents, and described with precision the positions of the disk wherein no current could be produced by its motion. He played with the earth as with a magnetic toy. Placing an iron bar within a helix, he lifted the bar into the direction of the dipping needle. As induced current was instantly roused in the helix. On reversing the bar, a current in the opposite direction declared itself. Holding the helix in the line of dip, the introduction and withdrawal of an unmagnetised bar of iron produced currents in opposite directions. Barlow and Christie had experimented on iron shells and iron disks, but Faraday, with a brass globe and a copper disk, obtained all their effects. They had their eye upon the metal as capable of magnetism; he had his eye upon it as a conductor of electricity. His speculations and experiments on the possible action of the earth when water, whether tidal or fluvial, flowed over its surface, are deeply interesting. The following avowal and prediction, made in 1831, breathe the very spirit of the true investigator: 'I have rather 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 full development hereafter.' The electric lighting of the present day is surely a splendid fulfilment of this prediction.
Every well-known experimenter is sure to be flooded with proposals and suggestions from outsiders. Crowds of such proposals came to Faraday, but one of them only, he declared, bore the slightest fruit. A young man named William Jenkin had observed a shock and spark of a peculiar character on the interruption of a voltaic current passing through a circuit containing a helix. He was anxious to follow the subject up, but his father, knowing that science was but a poor paymaster, dissuaded him from its pursuit. The examination of the facts noticed by Jenkin led Faraday to the discovery of the 'extra current,' his beautiful investigation on this subject being communicated to the Royal Society on 29 Jan. 1835. It bore the title 'On the Influence by Induction of the Electric Current upon itself.'
In 1831 Faraday had tapped new and inexhaustible sources of electricity. Pondering on the whole subject, he asked himself whether these various kinds of electricity were all alike. Are the electricities of the machine, the pile, the gymnotus and torpedo, magneto-electricity, and thermo-electricity, merely different manifestations of one and the same agent. He reviewed the knowledge of the time, turned upon the subject his power as an experimenter, and decided in favour of the 'identity of electricities." His investigation was read before the Royal Society on 10 and 17 Jan. 1833.
He now aimed at obtaining some knowledge of their relations as to quantity. Moistening bibulous paper with the iodide of potassium he decomposed the iodide by the electricity of the machine, producing a brown spot where the iodine was liberated. He then immersed two thin wires, the one of zinc, the other of platinum, to a depth of five-eighths of an inch in acidulated water. During eight beats of his watch he found that the electricity generated by this minutevoltaic arrangement produced the same effect on his galvanometer and on his moistened paper as thirty turns of his large electrical machine. The quantity of water here decomposed was immeasurably small, and still, if applied in the concentrated form which it assumes in the Leyden jar, it would, Faraday averred, be competent to kill a rat, and no man would like to bear it. He next determines the amount of electrical force involved in the decomposition of single grain of water. He is almost afraid to mention it, finding it equal to 800,000 discharges, not of the conductor, not of a single Leyden jar, but of the large Leyden battery of the Royal Institution. If concentrated in a single discharge, this amount of electricity would produce a great flush of lightning, while the chemical action of asinele grain of water on four grains of zinc would yield a quantity of electricity equal to that of a powerful thunderstorm.
His next subject was the influence of the state of aggregation upon electric conduction. He found that the selfsame substance conducts, or refuses to conduct, according as it is liquid or solid. The current, for example, which passes through water cannot pass through ice. Oxides, chlorides, iodides, and sulphides were proved to be insulators when solid, and conductors when fused; the passage of the current through the fused mass being always accompanied by decomposition. Whether any trace of electricity could pass through a compound liquid without decomposing it was a disputed point. Faraday leaned to the idea that a small quantity might do so. Other investigators, foremost among whom was the celebrated De La Rive, contended that no trace of electricity can pass through a liquid compound without producing its equivalent decomposition. Faraday's paper on this 'New Law of Electric 'Conduction' was read before Royal Society on 23 May 1833. On 20 June he communicated a paper on electro-chemical decomposition, in which be combated the notion of an attractive force exerted by the poles immersed in the decomposing cell. He wishes obviously to get rid of the idea of a current, substituting for it that of 'an axis of power, having contrary forces exactly equal in amount in opposite directions.' This definition could have yielded him but little help; it however left him free from the trammels of a definite symbol. He now glances at a subject of collateral interest. The power of spongy platinum to provoke the combination of oxygen and hydrogen was discovered by Dobereiner in 1823, and applied in the construction of his philosophic lamp. Dulong and Thénard proved afterwards that a well-cleansed platinum wire could be raised to incandescence by its action on a jet of cold hydrogen. Faraday found this power of provoking combination to be possessed in a striking degree by the positive platinum plate of his decomposing cell. The purification of the platinum by the oxygen discharged against it was the cause of its activity.
In our conceptions and reasonings regarding the forces of nature we perpetually make use of symbols which, when they possess a high representative value, we dignify with the name of theories. Thus, prompted by certain analogies, we ascribe electrical phenomena to the action of a peculiar fluid, sometimes flowing, sometimes at rest. Such conceptions have their advantages and their disadvantages; they afford peaceful lodging to the intellect for a time, hut they also circumscribe it, and by-and-by, when the mind has grown too large for its lodging, it often finds difficulty in breaking down the walls of what has become its prison instead of its home,' These words are quoted because they so chime in with Faraday's views, that when he heard them he could not repress a warm expression of assent. In regard to what may be called the philosophy of the voltaic pile, he was anxious to abolish all terms which tended to pledge him to theory. Aided by Dr. Whewell, he sought to invent a neutral terminology. For the word 'poles,' previously applied to the plates plunged in a decomposition cell, he substituted the word 'electrodes.' The decomposing liquid he called an 'electrolyte.' and the act of decomposition 'electrolysis.' These terms are now of everyday use in science. The term 'anode 'for the positive electrode and 'cathode 'for the negative one, are less frequently used, while the terms 'anion' and 'cation,' names given to the respective constituents of the decomposed electrolyte, and the term 'ion,' including both anions and cations, are hardly used at all. Having thus cleared his way, he fixed, as a measure of voltaic electricity, on the quantity of water decomposed by the voltaic current. The correctness of this measure was first established. He sent the same current through a series of cells with electrodes of different sizes—some of them plates of platinum, others strips, others mere wires — and found the quantity of gas collected to be the same for all the cells. The electro-chemical action was therefore independent of the site of the electrodes. It was also independent of the intensity of the current. Whether the battery was charged with strong acid or weak, whether it consisted of five pairs or of fifty, in short, whatever its force might be, the same current, cent through the series of cells, decomposed the same amount of water in all. Hence the conclusion that electro-chemical decomposition depends solely upon the quantity of electricity which passes through the decomposing cell. On this law Faraday based the construction of his celebrated 'voltameter.' And now he swoops down upon one of his moat considerable discoveries. In the same circuit he introduced his voltameter and a cell containing chloride of tin, and measured the decomposition in both cases. The water and the chloride were found to be broken up in proportions expressed by their respective chemical equivalents. The electric force which severed the constituents of the water molecule proved competent, and neither more nor leas than competent, to sever the constituents of the molecule of the chloride of tin. The fact was typical. With the electrolysis of water, as measured by his voltameter, he compared the electrolysis of other substances, both singly and in series, and proved beyond doubt that the decompositions of the voltaic battery are as definite in their character as those chemical combinations which gave birth to the atomic theory.
In 1800 Volta discovered the pile and sent an account of his discovery to Sir Joseph Banks, who lodged it, as a pearl of great price, in the 'Philosophical Transactions.' the source of power in the pile, the force which generated the current and urged it forward, was long a subject of fierce contention. Volta himself supported it to be excited by the contact of different metals. He established beyond all doubt that electricity is developed by such contact, and he assumed that at the place of contact an electro-motive force came into play which severed the two electricities, pouring the positive over one metal, and the negative over the other. Volta knew nothing of the chemical actions of the pile. The decomposition of water was first noticed by Nicholson and Carlisle. The study of its phenomena soon introduced the idea that chemical action, and not the mere contact of different metals, was the true source of voltaic power. Faraday plunged with ardour into this controversy. He saw chemical effects going hand in hand with electrical effects, the one being strictly proportional to the other. He produced currents without metallic contact; he discovered liquids which, though competent to transmit the feeblest current, were absolutely powerless when chemically inactive. This investigation was communicated to the Royal Society, 17 April 1834. But, despite the cogency of the facts and the conclusiveness of the logic, the supporters of the contact theory remained long immovable. With our present views of the interaction and convertibility of natural forces such a position is hardly conceivable. The astounding consequences of Volta's assumptions and of the views of his followers were laid bare by Dr. Roget as early as 1820. His words deserve to be kept in perpetual remembrance. 'If,' he says, 'there could exist a power having the property ascribed to it by the hypothesis, namely that of giving continual impulse to a fluid in one constant direction, without being exhausted by its own action, it would differ essentially from all the known powers in nature. All the powers and sources of motion with the operation of which we are acquainted, when producing these peculiar effects, are expended in the same proportion as those effects are produced; and hence arises the impossibility of obtaining by their agency a perpetual effect, or, in other words, a perpetual motion.'
Faraday's experiments and reasonings on electrolysis compelled him to look into the very heart of his decomposing liquids and to bring their ultimate molecules within his range of vision. He had no doubt that the current propagated from particle to particle of the electrolyte, and he became more end more impressed with the conviction that ordinary electric induction was also transmitted and sustained by the action of contiguous particles. The idea of action at a distance obviously perplexed and bewildered him, and it may be added that in our own day this retreating more and more; both electric and magnetic actions, like those of light, being held to be transmitted through an all embracing medium. In relation to this subject, Faraday repeatedly quotes the memorable words of Newton: 'That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance through a vacuum, and without the mediation of anything else, by and through which this action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking will ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws, but whether this agent be material or immaterial, I have left to the consideration of my readers.' Two great tests were accepted by Faraday as sufficient to prove the existence of a medium: the transmission of power in curved lines, and the consumption of time in transmission. As regards the electric force he thought he had proved that it could act round a corner. His experiments on this subject were not accepted as conclusive, nor were his views clearly expressed. They formed, however, a groundwork for his successors, who are now successfully working in the direction which he pointed out. But if electric induction be transmitted as he supposed, by contiguous particles, is it not probable that the particles of different bodies will exhibit different powers of transmission? He set to work to test this idea, and ended by the discovery of that quality of 'di-electrics' which in submarine cables now plays so important a part, and which retains the name that Faraday gave it. By suitable devices he placed a small metal sphere in the middle of a larger hollow one, leaving a space of somewhat more than half on inch between them. The inside sphere was insulated, the outside one uninsulated. To the former he communicated a measured charge of electricity, which acted by induction upon the concave surface of the larger sphere. Two instruments of this kind, and of the same size and form, were constructed, the inside sphere of each communicating with the external air by an insulated brass stem ending in a knob. The apparatus was obviously a Leyden jar, having the two spheres as coatings, between which any insulator could be introduced. One of the jars being charged, and its knob caused to touch the knob of the other jar, it was found, when air was the insulator, that the charge was equally divided. Permitting shellac, sulphur, or spermaceti in one of the jars to take the place of the air, it was found that the jar occupied by the 'solid di-electric' took more than half the original charge. The electricity was obviously absorbed by the di-electric. It, moreover, took time to penetrate the latter, from which it gradually returned. This is an effect familiar to experimenters with the Leyden jar. Faraday figured the particles of the di-electric as polarised, and concluded that electric induction was carried on from particle to particle from the inner sphere to the outer one. To this power of propagation he gave the name 'specific inductive capacity.' He then glanced at conduction in its relation to induction, and generalised thus: 'Can we not, by a gradual chain of association, carry up the discharge from its occurrence in air through spermaceti and water to solutions, and then on to chlorides, oxides and metals, without any essential change in its character?' The action of the particles of the best conductor differs, according to Faraday, only in degree from that of the particles of the insulator. Particles of copper, for example, are first chained in succession by induction; but they rapidly discharge themselves, and this quick molecular discharge is what we call conduction. It may be stated here that Faraday, in 1838, foresaw that retardation must occur in wires circumstanced like those of submarine cables.
In 1841 his health broke down, and for three years he did nothing, not even 'reading on science.' Memoranda written by Faraday at this time prove that his mind was seriously shaken. He went to Switzerland accompanied by bis wife and brother-in-law. His nerves bad been shattered, but his muscles were strong. At the table d'hôte he was quite unable to enter into conversation; but outside he was capable of great physical exertion. A journal entry of his made at Interlaaken has been already quoted. Another, which strikingly reveals the religious tone of his mind, may be given here. On 12 Aug. 1841 he stood before the falls of the Giessbach. 'The sun shone brightly, and the rainbows seen from various points were very beautiful. One, at the bottom of a fine but furious fall, was very pleasant — there it remained motionless while the gusts of cloud and spray swept furiously across its place, and were dashed against the rock. It looked like a spirit strong in faith and steadfast in the midst of the storm of passions sweeping across it; and, though it might fade and revive, still it held on to the rock, as in hope, and giving hope.
As soon as his health permitted, be resumed his work, and in November 1846 announced a discovery which he called 'the magnetisation of light, and the illumination of the lines of electric force.' The title provoked comment at the time, and caused misapprehension. It was soon, however, translated into 'the rotation of the plane of polarisation by magnets and by electric currents,' However it may have been described, this a one of Faraday's most pregnant and beautiful discoveries. He always thought that more lay concealed in it than was admitted by the scientific men of his time, and 'this thought is even now in process of verification. The discovery was made by means of that heavy glass which had failed to produce the optical effects expected from it. 'A piece of this glass, about 2 inches square, and 0.5 of an inch thick, having flat and polished edgeswas placed between the poles (not as yet magnetised by the electric current), so that the polarised ray should pass through its length. The glass acted as air, water, or any other transparent substance would do; and if the eye-piece were previously turned into such a position that the polarised ray was extinguished, then the introduction of the glass made no alteration in this respect. In this state of circumstances the force of the electro-magnet was developed by sending an electric current through its coils, and immediately the image of the lamp flame became visible, and continued so as long as the arrangement continued magnetic. On stopping the electric current, and so causing the magnetic force to cease, the light instantly disappeared. These phenomena could be renewed at pleasure at any instant of time, and upon any occasion, showing a perfect dependence of cause and effect. Many substances, oil of turpentine and quartz for example, caused the plane of polarisation to rotate without the intervention of magnetism. The difference, however, between Faraday's rotation and the rotation known before his time is profound. If, for example, a polarised beam, after having been caused to rotate by oil of turpentine, could by any means be reflected back through the liquid, the rotation impressed on the direct beam would he exactly neutralised by that impressed on the reflected one. Not so with Faraday's rotation, which was doubled by the act of reflection. With exquisite skill be augmented his effect by multiplying his reflections. When, for example, the rotation impressed on the direct beam was 12° that acquired by three passages through the glass was 36°, while that derived from five passages was 60°.
Faraday's next great step was the discovery of diamagnetism. Brugmanns, Becquerel, Le Baillif, Saigy, and Seebeck had previously indicated the existence of a repulsive force exerted by a magnet on two or three substances. It is surprising that the observation was not pushed further. Every indication of this kind, however small, roused Faraday's ardour, causing him to expand and multiply it. It was a fragment of his famous heavy glass that revealed to him the fact of diamagnetic repulsion. Suspended before either pole of an electro-magnet it was repelled when the force was developed. Suspended as a bar between the two poles, it retreated when the magnet was excited, setting its length at right angles to the line joining the poles. A magnetic bar, similarly suspended, always set its length from pole to pole. The first of these positions Faraday called the 'equatorial' position, the second the 'axial' position. In accordance with his usual habit he pushed his experiments on diamagnetism in all possible directions. He subjected bodies of all kinds to the action of his magnet, and found that no known solid or liquid was insensible to magnetic power when it was developed in sufficient strength. Faraday himself was the first to throw out the hypothesis that the deportment of diamagnetic bodies could be explained by assuming in their case a polarity the reverse of that exhibited by magnetic bodies. This hypothesis, however, was but loosely held, and his own experiments failed to furnish any evidence of its truth. The instruments employed by Faraday in his investigations on diamagnetic polarity lacked the necessary delicacy, and failed to show him a quality and character of this new repellent force, in every respect as certain as ordinary magnetic polarity. But though this fundamental quality of the force he had discovered eluded his experimental devices during the course of the discussion were of surpassing beauty. His experiments and speculations in the deportment of crystals in the magnetic field, a deportment predicted by Poisson, and discovered experimentally by the illustrious geometrician Plucker, are profoundly interesting and instructive. They throw more light than any others on the character of Faraday's mind and culture. He invented new terms to describe and new forces to explain magne-crystallic phenomena. It is marvellous how true his instincts were, even where his speculations were invalid. Through reasonings often confused, he passed to experimental results which he at the very core of the question in hand. The explanation of this complex phenomena of magne-crystallic action was rendered impossible to him through his rejection of the doctrine of diamagnetic polarity. Applying this principle to magnetic and diamagnetic crystals the force proper to each is always found acting in 'couples' in the magnetic field, and from the action of such couples the observed phenomena flow as simple mechanical consequences.
Bancalari had established the magnetism of flame. It is an interesting experiment to place a lighted candle betweon two pointed poles to split the flame in two by the of the magnet. According to the position of the flame it can be depressed, elevated, or blown aside, by the magnetic force. Faraday repeated Bancalari's experiments, and, passing from flames to gases generally, established their magnetic and diamagnetic powers. He made numerous experiments with oxygen and nitrogen, which, as constituents of the earth's atmosphere, had an importance of their own. Oxygen he found to be strongly magnetic, nitrogen at first feebly diamagnetic but afterwards neutral. As a boy he loved to play with soap-bubbles, and he now applied them to a more serious purpose. The deportment of oxygen in air 'was very impressive, the bubble being pulled inward, or towards the axial line, sharply and suddenly, as if the oxygen were highly magnetic.' A strong vein of metaphysics runs through the speculations of Faraday, but his experiments are always handled with regal power. He thought it important to fix the magnetic xero, to discover if possible a substance neutral to the magnet when excited to its uttermost. A bubble of nitrogen suspended in air was repelled, and a hasty observer might infer that nitrogen was diamagnetic, but Faraday saw that the apparent repulsion might be really due to the attraction of the surrounding atmospheric oxygen. After a series of experiments of the rarest beauty and precision, he came to the conclusion that nitrogen was 'like space itself' — neither magnetic nor diamagnetic.
He next compared the magnetic intensity of oxygen with that of a solution of sulphate of iron, and found that, bulk for bulk, oxygen is equally magnetic with such a solution 'containing seventeen times the weight of the oxygen in crystalised protosulphate of iron, or 3.4 times its weight of metallic iron in that state of combination.' The attraction of a bubble of oxygen at the distance of an inch from the magnetic axis he found to be about equal to the gravitating force of the same bubble. His thoughts now widen so as to embrace the earth's atmosphere and the possible action of its oxygen on the magnetic needle. Two elaborate memoirs on atmospheric magnetism were sent to the Royal Society on 9 Oct. and 19 Nov. 1850. The effect of heat and cold upon the magnetism of the air and the resultant action on the magnetic needle ore discussed. Faraday here makes a masterly of the convergence and divergence of the lines of terrestrial magnetic force. Those lines are his guiding light through this most difficult domain. He applied his results to the explanation of the annual and diurnal considered irregular , including magnetic storms. Whether in these inquiries Faraday succeeded in establishing the points at which he aimed is more than can be asserted, but that a body so magnetic as oxygen, swathing the earth, and subject to local variations of temperature, diurnal and annual must influence the manifestations of terrestrial magnetism can hardly be doubted. The air that stands on a square foot of the earth's surface is equivalent in magnetic force to 8,160 pounds of crystallised protosulphate of iron. Such an envelope can hardly be absolutely neutral as regards the deportment of the magnetic needle.
Faraday's speculations on matter and force are in the highest degree curious and interesting. He sought, among other things, to liberate himself from the bondage of the atomic theory, and his views have probably had a serious influence on his chemical successors. Some of these consider, as he did, 'that the words definite proportions, equivalents, primes, &c. ... express all the facts of what is usually called the atomic theory in chemistry.' Outside chemistry proper, however, domains of philosophy exist where the words quoted by Faraday would have no meaning, and which the conception of the atom is essential. We cannot, for example, put a definite proportion or an equivalent number us the origin of a train of waves in the luminiferous ether. Here the vibrating atom must be regarded as the real source of the motion. Still Faraday's reasonings are in the highest degree curious and ingenious. Grappling with the notion that matter is made up of molecules separated from each other by intermolecular spaces, he observes that 'space must be taken as the only continuous part of a body so constituted.' He turns to electricity in search of a test for this notion. Consider, he argues, the case of a nonconductor like shellac. Space must here be an insulator, for if it were a conductor it would resemble a 'fine metallic web' penetrating the lac in every direction. But the fact is that it resembles the wax of black sealing wax, which surrounds and insulates the particles of conducting carbon, to which the blackness is due. In the case of shellac, therefore, space is an insulator. But in the case of a conductor we have, as before, space surrounding every atom. If space be an insulator, as proved a moment ago, there can be no transmission of electricity from atom to atom. But there is transmission, hence space is a conductor. Thus he hampers the atomic theory. 'The reasoning ends in a subversion of that theory altogether; for, if space be an insulator, it cannot exist in conducting bodies, and if it be a conductor, it cannot exist in in insulating bodies. Any ground of reasoning,' he adds, abandoning his usual temperate caution, 'which tends to such conclusions as these, must in itself be false.' Like Boscovich, Faraday abolished the atom, and put a 'centre of force' in its place.
Another strange speculation is embodied in a letter to Mr. Phillips published in the 'Philosophical Magazine' for May 1846. It is entitled 'Thoughts on Ray Vibrations,' and seems to show that Faraday looked upon what he called the lines of gravitating force as so many fine strings capable of vibration. Along these lines he supposes the undulations of light to be propagated. He concludes that 'this notion, as far as it is admitted, will dispense with the ether,' adding that his view' endeavours to dismiss the ether, but not the vibration.' There was a vast vagueness, and an immeasurable hopefulness in Faraday's views of matter and force. A strong imagination is required to understand him and to sympathise with him. His views had to him almost the stimulus of a religion, and they urged him to work with expectation and success in regions where a less original, though better trained, man of science would have laid down his tools in despair.
His 'lines of magnetic force' took possession more and more of Faraday's mind. The last three papers of his experimental researches are occupied with this subject. In these papers experiments of exquisite beauty, on wires moving round magnets, are described. At first regarding them as a mere 'representative idea,' he leaned in after years more and more to the notion that the 'lines of force 'were connected with a physical substratum. In this connection the title of his lost paper is significant: 'On the Physical Character of the Lines of Magnetic Force.' He has been known to hold up a magnet in one of his lectures and. knocking it with his knuckle, to exclaim: 'Not only is the force here, but it is also here, and here, and here,' passing at the same time his bond through the air round the magnet. For the sake of reference Faraday numbered all the paragraphs in his memoirs, the last number being 3299.
Remarkable testimony as to Faraday's power as a lecturer is given by the late Sir Frederick Pollock in his 'Remembrances.' To prepare himself for lecturing he took lessons in elocution; his indebtedness to them was, however, small. His influence as a lecturer consisted less in the logical and lucid arrangement of his materials than in the grace, earnestness, and refinement of his whole demeanour. In his juvenile lectures, rather than in those addressed to adults, his lucidity was at its best. Except by those well acquaintedwith his subjects, his Friday evening discourses were sometimes difficult to follow. But he exercised a magic on his hearers which often sent them away persuaded that they knew all about a subject of which they knew but little.
In early days he added to his modest salary from the Royal Institution a supplementary income derived from what he called 'commercial work,' This supplement might have been vast, but just as it allowed signs of expansion, Faraday abandoned it. Between 1823 and 1829 his average annual earnings from such sources were 241l. Between 1830 and 1839 he made by commercial work an average income of 306l. In l83l his highest figure, 1,090l. 4s., was attained. In 1838, on other hand, it was zero. The fall in Faraday's commercial income synchronised with his discovery of magneto-electricity, "when worldly gains became contemptible in comparison with the rich scientific province which he had subdued. In 1836 be became scientific adviser to the Trinity House. From time to time he gave evidence in the law courts but such work was congenial to him. He was too sensitive to bear the browbeating of cross-examining counsel. The late Lord Cardwell was witness to a gentle but crushing reproof once administered by Faraday to a barrister who attempted to bully him. He, however, soon cut himself adrift from such employment, which as just stated was entirely foreign to his taste. In 1835 Sir Robert Peel wished to offer Faraday a pension; but it fell to Lord Melbourne to perform this gracious act. At the outset, however, his lordship did not acquit himself graciously, being unaware of the sensitive independence of the man with whom he had to deal. By the prime minister's desire, Faraday called to see him. The brusqueness of Lord Melbourne did not please Faraday. He seemed to ridicule the idea of pensions, and in reference to them the term 'humbug' was incautiously used. After quitting the minister, Faraday wrote a short and decisive note declining the pension. But after a good deal of effort on the part of common friends, the matter ended in a manner creditable to all parties. Lord Melbourne sent a written apology to Faraday, who enjoyed the pension of 300l. to the end of his life.
For the relaxation of his mind, he frequently visited the theatres. His food was simple but generous. At his two o'clock dinner he ate his meat and drunk his wine. He began the meal by lifting both hands over the dish before him, and in the tones of a son addressing a father of whose love he was sure, asked a blessing on the food. To those whom he knew to be animated by something higher than mere curiosity, he talked freely of religion; but be never introduced the subject himself. Nearer than anybody known to the writer, he came to the fulfilment of the precept, 'Take no thought for the morrow.' He had absolute confidence that, in case of need, the Lord would provide. A man with such feeling and such faith was naturally heedless of laying by for the future. His faith never wavered; but remained to the end as fresh as when in 1821 he made his 'confession of sin and profession of faith.' In reply to a question from Lady Lovelace, he described himself as belonging to 'a very small and despised sect of Christians, known — if known at all — as Sandemanians; and our hope is founded on the faith as it is in Christ.' He made a strict severance of his religion from his science. Man could not, by reasoning, find out God. He believed in a direct communion between God and the human soul, and these whisperings and monitions of the Divinity were in his view qualitatively different from the data of science.
Faraday was a man of strong emotions. He was generous, charitable, sympathising with human suffering. His five-pound note was ever ready for the meritorious man who had been overtaken by calamity. The tenderness of his nature rendered it difficult for him to refuse the appeal of distress. Still, he knew the evil of indiscriminate almsgiving, and had many times detected imposture; so that be usually distributed his gifts through some charity organisation which assured him that they would be well bestowed.
It has been intimated that in 1841 his health completely broke down. His distress of mind, which was very great, was mainly dur to the conviction that his physician did not understand his condition. Scraps of paper covered with remarks in pencil, shown to the present writer, illustrate his nervous prostration at the time here referred to. The following outburst of discontent is a sample: 'Whereas, according to the declaration of that true man of the world Talleyrand, the true use of language is to conceal the thoughts; this is to declare in the present instance, when I say I am not able to bear much talking, it means really, and without any mistake, or equivocation, or oblique meaning, or implication, or subterfuge, or omission, that I am not able; being at present rather weak in the head, and able to work no more.' Some of his best work was, however, done afterwards. On the resignation of Lord Wrottesley, a deputation waited upon Faraday, asking him to accept the presidentship of the Royal Society. He declined the honour. Later on he was strongly pressed to accept the presidency of the Royal Institution; but to the great disappointment of one of his most steadfast friends, who was then honorary Secretary, the late Dr. Bence Jones, he firmly refused the office. In fact, he, before others, had noticed the failing strength of his brain, and be declined to impose upon it a weight greater than it could bear.
Faraday's intellectual power cannot be traced to definite antecedents; and it is still more difficult to account by inheritance for the extraordinary delicacy of his character. On a memorable occasion, a friend who knew him well described him thus: 'Nature, not education, made Faraday strong and refined. A favourite experiment of his own was representative of himself. He loved to show that water, in crystallising, excluded all foreign ingredients however intimately they might be mixed with it. Out of acids, alkalis, or saline solutions, the crystal sweet and pure. By some such natural process in the formation of this man, beauty and nobleness coalesced, to the exclusion of everything vulgar and low.' Faraday died on 25 Aug, 1867, and was buried in Highgate cemetery.[Experimental Researches in Electricity, by Michael Faraday, D.C.L., F.R.S., 3 vols., 1839-1855; Researches in Chemistry and Physics, by Michael Faraday, D.C.L. F.R.S., 1 vol., London, 1859; Life and Letters of Faraday, by Dr. Bence Jones, 2 vols., London, 1870; Quarterly Journal of Science; Proceedings of the Royal Institution; Philosophical Magazine; Faraday as a Discoverer, by John Tyndall, 1 vol., with portait, 1868, 1870.]