Faraday_90_Minutes

8/7/2019 Faraday_90_Minutes

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FARADAY IN 90 MINUTES


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In the same series by the same authors:Curie in 90 minutesDarwin in 90 minutesEinstein in 90 minutesHalley in 90 minutesGalileo in 50 minutesMendel in 90 minutesNewton in 90 minutes


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John and Mary Gribbin

FARADAY(1791-1867)in 90 minutes

Universities Press


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Universities Press (India) LimitedRegistered Office3-5-819 Hyderguda, Hyderabad 500 029 (A.P.), INDIADistributed byOrient Longman LimitedRegistered Office3-6-272 Himayatnagar, Hyderabad 500 029 (A.P.), INDIAOther OfficesBangalore, Bhopal, Bhubaneshwar, Calcutta, Chennai, Emakularn,Guwahati, Hyderabad, Jaipur, Lucknow, Mumbai, New Delhi, Patna John and Mary Gribbin, 1997Originally published in Great Britain by Constable and Co. Ltdunder the title Faraday in 90 minutes.First published in India byUniver.ities Press (India) Limited 1997Reprinted 1998ISBN 81 7371 077 5For sale in India, Nepal, Bhutan, Bangladesh, Sri Lanka,the Maldives, Singapore, Malaysia and the Middle East only.Not for export to other countries.Printed in India atBaba Barkha Nath PrintersNew Delhi 110 015Published byUniversities Press (India) Limited3-5-819 Hyderguda, Hyderabad 500 029


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ContentsFaraday in context 7Life and work 13Afterword 64A brief historyof science 67


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ACKNOWLEDGEMENTThanks to Bill Murray for help in trackingdown reference material.


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Faraday in contextMichael Faraday was one of the first modernscientists. He discovered the principles of, andinvented, both the electric motor and the gen-erator, without which modern society couldnot function. In order to explain his dis-coveries and inventions he came up with theidea of a field of force, a concept which nowunderpins our understanding of everythingfrom the gravitational force holding the Uni-verse together to the forces operating betweenquarks inside the protons and neutrons thatmake up the nuclei of atoms of ordinary mat-ter. Yet when Faraday first became interestedin chemistry, early in the nineteenth century,even the concept of atoms was a controversialidea, and chemistry had scarcely emergedfrom its origins in alchemy.Only in the final quarter of the eighpeenthcentury, thanks to the work of AntoineLavoisier in France and Joseph Priestley inEngland, had it become clear that the processof burning involves something from the air(oxygen) combining with the thing that isburning - not a loss of 'phlogiston' from the

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thing being burnt. In later experimentsLavoisier began to show how compounds likecarbon dioxide and water are produced bycombustion, and also during the respirationof living things - an early indication that lifedoes not involve any unique 'life force'. Hiscareer was cut short (literally) by the guillo-tine during the French Revolution.

In 1805 Lavoisier's widow married anAmerican-born scientist, Benjamin Thomson,who had been made Count Rumford in 1791for his services to the Elector of Bavaria.Rumford's wide-ranging career (he had hadto leave America after fighting on the losingside in the War of Independence) had madehim rich and influential, and during a periodspent in England at the end of the eighteenthcentury and the beginning of the nineteenth,he had been instrumental in establishingLondon's Royal Institution (usually known asthe RI), in 1800. This would be where Fara-day carried out all his work; it was Rumfordwho would be responsible for appointingHumphry Davy as the RI's' first director and,as we shall see, it was Davy who would giveFaraday his first big break.

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FARADAY IN CONTEXT

The discovery that an electric current couldbe produced without using animal tissue(another indication that there is no uniquelife force) was announced by the ItalianAlessandro Volta at the end of the eighteenthcentury. Before then, people had knownabout what is now called 'static' electricity,which can be produced by friction. This ismost familiar today as the electric charge thatbuilds up in your body if you walk aroundon a carpet made of synthetic fibres on a dryday; it can be enough to give you a sharpshock when you touch a metal object and theelectricity is discharged. This is the kind of.electricity that was studied by BenjaminFranklin, who lived from 1706 to 1790, andwas lucky not to have been killed halfwaythrough that long span in one of his famouskite-flying experiments during thunder-storms.Interest in the kind of electricity thatinvolves a current - a flow of charge - was

fired in the eighteenth century by studies ofelectric fish and eels. Luigi Galvani, a com-patriot and friend of Volta, found that thelegs of a dissected frog would twitch when

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given a jolt of static electricity, and that thesame sort of twitching would occur when theleg was laid across two different metals (suchas copper and iron). He concluded (wrongly,it turned out) that electricity was being madein the muscles of the legs by a process likethat by which an eel makes electricity. ItwasVolta who showed that the production of anelectric current in this way does not requireliving (or formerly living) tissue at all, but willhappen when two metals are in a solution ofsalt - the frog's legs were only acting as adamp, salty connection between the iron andthe copper.Volta was working at the University ofPavia in Lombardy at the end of the eight-

eenth century when he made this discovery.He found that a steady electric current couldbe produced by making a pile of alternatingcopper and iron (or zinc) discs, separated bylayers of cloth soaked in salt solution. Whenthe top and bottom of the pile were joinedwith a wire, a current would flow.Because of the Napoleonic Wars, the state

of Lombardy passed repeatedly betweenFrench and Austrian hands at this time, and

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FARADAY IN CONTEXT

in 1799. the Austrians gained control andclosed the University of Pavia. So Volta sentnews of his discovery to London, where itwas published, in 1800, by the Royal Society.The same year, the French retook Lombardyand the University was reopened; Napoleoninvited Volta to Paris to demonstrate his pile,and made him a count in recognition of thework. Volta's discovery was sensational, and(among other things) inspired a burst of workby Davy, once he was securely installed at theRI.Davy pioneered the development of electro-chemistry, using the current provided by a'voltaic pile' (what we would now call a

battery) to break compounds into their con-stituent elements. Using this technique, he dis-covered several 'new' elements, includingpotassium and sodium. In 1808, Davyreceived a prize of 3000 francs offered byNapoleon for the best research on currentelectricity (the fact that England and Francewere at war having little effect on the flowof scientific ideas and honours). The kind ofbattery that Faraday would use in much ofhis early work was developed by William

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Cruikshank, and consisted of copper and zincplates soldered together in pairs, sealed intogrooves in a wooden trough using wax, andimmersed in acid - not that different from ainodern car battery.So the first decade of the nineteenth century

was an exciting time for anyone interestedin science, with news of new elements beingdiscovered, the invention of the electric bat-tery, and speculation about what this mysteri-ous thing called electricity was. In London,interest in science in fashionable society wasfired by Davy's lectures at the RI. This wassomewhat ironic, because Rumford's aim inestablishing the RI was to provide a placewhere ordinary people could learn about sci-ence. The snag was, ordinary folk had nomoney, and the RI was kept afloat by thecontributions of fashionable young women,in particular, attracted to the lectures not somuch by love of science as by Davy's goodlooks and animal magnetism. Nevertheless,Rumford's hopes for the RI were soon to berealized in the most dramatic fashion.

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Life and workFaraday was born on 22 September 1791. Hehad an elder brother, Robert, born in 1788,and an elder sister, Elizabeth, born in 1787.The family came from what was then West-morland, in the north of England. James Fara-day brought his wife, Margaret, and their firsttwo children south in search of work in 1791.He was a blacksmith, and by all accounts agood one, but suffered from bad health andbarely earned enough to keep the familytogether. They lived briefly in Newington(then a village in Surrey, now part of theurban sprawl of south London), whereMichael was born, then moved north of theRiver Thames to cramped rooms over a coachhouse in Jacob's Well Mews, near ManchesterSquare. There, another child, Margaret, .wasborn in 1802.Although desperately poor, the family wasa loving and happy one, at least partly thanks

to their religious faith. The Faradays weremembers of a sect known as the Sandeman-ians, which originated in the 1730s in a break-away from the Scottish Presbyterians. (The

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Sandeman who gave his name to the sect,incidentally, was a relation of the Sandemanswho gave us the port.) Sandemanians re-garded themselves as members of the onlytrue Church, and therefore assured of sal-vation, a belief which made it easier for themto tolerate the hardships of the present world.They tended not to socialize much outsidetheir own sect (although they were by nomeans as exclusive as, say, the PlymouthBrethren), were not interested in worldlygoods and wealth, and made unostentatiousdonations to charity.All this provided Faraday with a strictmoral code, and a certain serenity with whichto cope with life's vicissitudes. It also encour-aged him in his scientific work, through thebelief that an understanding of God's 'bookof nature' was as important as an understand-ing of the Bible. The Sandemanians werenot evangelical, believing that those whobelonged in their community would naturallyfind a way to them; hardly surprisingly, thesect never had more than a few hundredadherents and has now essentially died out.We shall not say much more about Faraday's

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Sandemanian faith in this book, but it isworth remembering as an important part ofthe background to the story.Faraday received only the most basic edu-

cation, in the traditional 'three Rs' of reading,(w)riting and (a)rithmetic. 'My hours out ofschool,' he later wrote, 'were passed at homeand in the streets.' In 1804, when he was 13,it was time for Faraday to start contributingto the family income. He ran errands forGeorge Riebau, a bookseller and bookbinderwho had a shop in Blandford Street, close towhere the Faradays lived, and just off BakerStreet, mythical home of Sherlock Holmes.One of Faraday's main duties was to deliver

newspapers and fetch them back to the shop- at that time, some people could not affordto buy newspapers, but paid a smaller sumfor the loan of one, which had to be returnedafter being read. Riebau was a kindly man,and through this work Faraday was "intro-duced to the world of books. A year later,when he was 14 and had to learn a trade, itwas natural for him to be apprenticed toRiebau to learn bookbinding.Little is known about Faraday's life during

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his first four years with Riebau, but from themany volumes still in. existence which hebound for himself later in life, it is clear thathe -learned his trade well. The fact that hebecame a superb experimental scientist who,built his ewn apparatus and carried out deli-cate experiments with skill must owe some-thing to the manual dexterity that hedeveloped for bookbinding.But it wasn't all work. Some idea of the

atmosphere that prevailed at George Riebau'spremises may be gleaned from the fact thatFaraday had two fellow-apprentices there,one of whom went on to become a pro-fessional singer, while the other achieved suc-cess on the boards as a comedian. Theyworked hard, but they also played hard, andthere were opportunities for each of theyoung men to develop their own interests inwhat was, in effect, a happy family unit.Faraday soon moved in to live - on thepremises.In Faraday's case, 'play' largely amounted

to study, He read voraciously from the stockin Riebau's shop and the books that came infor binding, and he would carefully copy out

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interesting passages from the volumes thatpassed through his hands. When he becameinterested in chemistry, he bought a standardfour-volume introduction to the subject,which he dismantled and rebound with blankpages between the pages of text, so that hecould make his own notes as he slowly cameto grips with the topic.His fascination with electricity was fired byreading the article on the subject in a copy ofthe third edition of the Encyclopaedia Britan-nica that was brought in for binding. As wellas reading, Faraday carried out experiments,building apparatus (including a voltaic pile)out of any bits and pieces he could lay hishands on. But these electrical experiments didnot take place until 1812, by which time Fara-day was well and truly hooked on science.The turning-point came at the beginning of1810, when Faraday, now 18, saw an adver-

tisement for a series of evening lectures onnatural philosophy - the term then used forwhat we now call science. The lectures wereopen to members of the grandly styled CityPhilosophical Society, actually a fledglingorganization founded two years before by

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a group of young men eager for self-improvement. Membership cost a shilling;Faraday's subscription was paid by hisbrother Robert (by now working as a black-smith). Over the next two years he attendedlectures on a variety of scientific topics, takingcareful notes which he wrote up in elaboratedetail back in Blandford Street.At the Society he made new friends (not-

ably Benjamin Abbott, with whom he carriedon an extensive correspondence, much ofwhich survives), and gained in confidence suf-ficiently first to join in discussions at the meet-ings and then to give a lecture (on electricity)himself. But he was also painfully aware ofhis own lack of education and of his roughways. The correspondence with Abbott wasdeliberately started as an exercise in improv-ing Faraday's skill at written communication,ami he persuaded another new friend,Edward Magrath, to spend two hours a weekhelping him improve his grammar, spellingand punctuation. This tuition was to continuefor seven years.Faraday's father did not live to see much

of this development in his youngest son; he

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died in October 1810, when he was 49 andMichael was just 19 (Faraday's mother, Mar-garet, survived until 1838, dying at the ageof 74). Faraday himself cannot even havedreamed where his interest in science wouldtake him. But the next great step came in1812, when he was a few months short of his21st birthday, and increasingly aware that his,time as an apprentice would soon be at anend; and it was as a direct result of hisinvolvement with the City PhilosophicalSociety.This is where stories of Faraday the book-binder's apprentice usually begin. By now,

Faraday had put together four bound volumesof his notes from meetings of the Society.Riebau, proud of the presence of such anenthusiastic natural philosopher in his house-hold, used to show these volumes to hisfriends and customers. One of those cus-tomers, Riebau later. recalled, was a youngMr Dance, who thought the work so remark-able that he asked if he could borrow thebooks so he could show them to his father.The upshot was that the elder Mr Dance senttickets for Faraday to attend lectures given by

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Humphry Davy at the Royal Institution. Aswas his habit, the enthralled Faraday tookcareful notes, which he wrote up, with accom-panying drawings of the experiments carriedout by Davy, and bound. Riebau tells us that'this he took also to the Above Gent. [MrDance senior] who was well pleased.'In the spring of 1812, Faraday attendedfour lectures at the RI. Itwas almost too muchof a good thing. The experience reinforcedhis interest in science, and he now desperatelywanted to make a career out of it, but thereseemed to be no prospect at all of this happen-ing. Faraday's apprenticeship ended on 7October 1812, a couple of weeks after his21st birthday, and he began working as abookbinder for a Mr De La Roche. De LaRoche seems to have been a difficult master,but it is hard to imagine anyone living up toGeorge Riebau - and, to be fair, Faraday'sheart was certainly not in his work. He wroteto a friend that he was 'now working at myold trade, the which I wish to leave at the firstconvenient opportunity'. He even wrote toSir Joseph Banks, the President of the RoyalSociety, asking if there was any way to get

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even the most menial job in science; Banksdidn't bother to reply.Before the end of October, though, Faradayhad a stroke of luck. Davy was temporarilyblinded by an explosion, and needed some-body who could act as his secretary for a fewdays - preferably someone who knew a bitabout chemistry. Almost certainly en therecommendation of the elder Mr Dance, Fara-day got the job. How he got time off fromhis bookbinding duties we do not know; itcan hardly have improved the relationshipwith his new employer. But Davy soon recov-ered his sight, Faraday went back to work,and the future closed in on him again. ByDecember, he was trying to build on the con-tact with Davy, writing to him and sendinghim the bound volume of notes from Davy'sown lectures earlier that year, again beggingto be considered for even the most menial ofscientific posts.Davy was impressed, both by the bound

lecture notes and by Faraday's enthusiasm,but there were simply no openings at the RI,which was being run on a shoestring budget.In February 1813, though, came the final

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piece of good fortune that turned a book-binder's apprentice into one of the greatestscientists of all time. For ten years, a certainWilliam Payne had served as laboratory assis-tant at the RI, without achieving any distinc-tion in that role. Never a particularlytemperate character, Payne now got involvedin a public brawl, and was dismissed. Davysent for Faraday and offered him the job, ata guinea a week, with accommodation pro-vided in two rooms at the top of the RI build-ing in Albemarle Street, candles and fuelincluded. With enough presence of mind toinsist that the RI should provide him withaprons and agree that he could use the appar-atus there for his own experiments in his sparetime, Faraday accepted. He was officiallyappointed on 1 March 'to fill the situationlately occupied by Mr Payne on the sameterms'.From the outset, Faraday's duties as Davy'sassistant at the RI involved rather more thanmere bottle-washing. He was given routinetasks to carry out, including the extraction of

sugar from beet (in the nineteenth century,the development of a home-grown source of

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sugar was of great economic importance toBritain). He worked with Davy on the viol-ently reactive nitrogen chloride, and wrote toAbbott in tones of glee about the explosionsthat resulted. Because of his skill at makingapparatus, and making it work, he was soonin demand as the demonstrator at the lecturesthat were the RI's raison d'etre. He continued,whenever possible, to attend the meetings ofthe City Philosophical Society. But just asFaraday was settling in to a happy routine atthe RI, his life was changed again.Davy, to the despair of many of the fashion-able ladies of London, had married a wealthy.widow in 1812 (the same year that he wasknighted by the Prince Regent). He had afancy to take his bride on a tour of Europe,undaunted by the fact that Britain and Francewere at war - after all, he had been awardedthe Napoleon Prize for his work. Scientificexchanges between the two countries were, ifnot exactly routine, at least possible in thosedays, and when Davy applied for a specialpassport to enable him to travel on the conti-nent for scientific reasons (one of the aims ofthe expedition was to study the chemistry of

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volcanic lavas), the French agreed to hisrequest. Davy invited Faraday to go alongwith them. It would mean resigning his postat the RI, but with a guarantee that he wouldget it back when they returned to England.Faraday, who had never travelled more than12 miles from the centre of London, leapedat the opportunity.The party set offon 13 October 1813. Itconsisted of Sir Humphry and Lady Jane

Davy, Lady Jane's maid and Faraday. Davy'svalet was supposed to accompany them, but,perhaps deterred by the prospect of Napo-leonic France, refused at the last minute. Davyasked Faraday if he would mind taking onsome of the valet's duties, just until they gotto Paris, where a replacement would be hired;again, he agreed. This was to lead to consider-able friction, because somehow a suitablereplacement valet was never found, and Fara-day was in the uncomfortable position ofbeing both colleague and servant to Davythroughout the eighteen-month trip. Itwasn'tso bad with Sir Humphry, but Lady Jane wasa class-conscious woman who believed inkeeping servants firmly in their place. But for

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Faraday the delights of the trip amply out-weighed these inconveniences.Faraday kept a journal in which those

delights were recorded, starting with his awe-struck impressions of the 'rnopntainousnature' of the Devonshire countrysidethrough which they travelled down to Ply-mouth to join their ship. As eager as ever forself-improvement, Faraday made the most ofthe European trip. He met leading scientistsin France, Switzerland and Italy; he saw Parisand Rome, real mountains, and a waterspoutin the Mediterranean. In Paris, he workedwith Davy and French chemists on the identi-fication of a newly discovered element, iodine.In Florence, he-saw the telescope that Galileohad used to discover the moons of Jupiter.During these travels, the wars continued.

Napoleon was defeated at Leipzig and forcedto abdicate in 1814, but escaped from Elbaand returned to France in February 1815. Per-haps even Davy's insouciance was shaken bythis, since his party returned home in somehaste in April that year, travelling back fromItaly via Switzerland and Germany, avoidingFrance. Napoleon's ultimate defeat took place

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a few weeks later, on 18 June 1815, atWaterloo.'Butall of this seems to have passed Faraday

by. He never took any interest in politics, andthe matters of the world meant little to him,happy as he was with his science, his religiousfaith and (soon) his wife. Even so, the youngman who returned to England in 1815 wasfar more sophisticated than the laboratoryassistant who had left in the autumn of 1813.He had learned to read French and Italian,and to speak French adequately; he hadcarried out real scientific research, as the part-ner (albeit the junior partner) to Davy, notmerely as his assistant. He was now a realnatural philosopher, and his status was recog-nized by the RI, where instead of getting backhis old job as promised, he was made Super-intendent of the Apparatus and Assistant inthe Laboratory and Mineralogical Collection,with remuneration of 30 shillings per week(an increase of almost 50 per cent on his pre-vious income), and better rooms at the RI aswell.Davy, seduced by the delights of society,

spent less time at the RI than before, and

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was often out of London. Faraday spent moretime than ever helping the lecturers, and heworked particularly closely with the Professorof Chemistry at the RI, William Brande - bothin his lecturing and in the analytical work thathe carried out for commercial clients. Faradaybegan to carry out research on his own, andpublished a series of modest papers. Over athree-year period from January 1816, he gavea total of sixteen lectures to the City Philo-sophical Society covering the entire subject ofinorganic chemistry.All the while, he continued to read andlearn as part of his programme of self-improvement. There was as yet no hint,though, of the way Faraday would revol-utionize scientific thinking. He had developedinto a steady, reliable chemist, not consideredto be in the same league as Davy, but soundenough. He had settled down, and in 1821, on12 June, he married Sarah Barnard, anothermember of the Sandemanian community (fiveyears later, Michael's sister Margaret marriedSarah's brother John). The first hint of whatwas to be Faraday's masterwork came in theyear that he married - but it proved a mixed

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blessing, and something of a false dawn.In 1820, the Danish scientist Hans Chris-tian Oersted had discovered the first linkbetween electricity and magnetism. He hadfound that when a magnetic compass needlewas held over a wire carrying an electric cur-rent, the needle was deflected to point acrossthe wire, at right angles. If the needle washeld under the wire, it pointed in the oppositedirection, but still at right angles to the cur-rent flowing in the wire. This was a sen-sational discovery, because it seemed to implythat the magnetic force associated with thecurrent acted in a circle around the wire. Itdid not push or pull the tiny magnet of thecompass towards or away from the wire, andseemed to be completely different from thepush-pull effects of static electricity and mag-netism, and the pulling of gravity.Scientists across Europe attempted to

explain the phenomenon, and began to carryout experiments in electromagnetism. InBritain, William Wollaston developed atheory that the electric current in a wire musttra vel in a helix down the wire, like a childsliding down a helter-skelter, and that this

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circulating current was responsible for the cir-cular magnetic force. He reasoned that if thatwere so, a wire carrying a current ought toturn on its axis, like a spinning top, if it werebrought near a magnet. In April,1821, hewent along to the RI and carried out someexperiments with Davy to search for thiseffect, but without success. Faraday was notpresent at the experiments, but joined in thediscussion of their significance afterwards.Faraday's own interest in electromagnetismwas, triggered when, a little later in the year,

he was asked to write a historical account ofthe phenomenon for the journal Annals ofPhilosophy. In order to do a thorough job,he repeated all the experiments described bythe scientists whose work he was summariz-ing. He realized that there really was a circu-lar force associated with an electric current,and came up with an ingenious demon-stration of the effect. In one experiment, awire carrying a current was made to circleround and round a fixed magnet, while in avariation on the theme the wire carrying thecurrent was .fixed and the magnet movedround the wire. 'The effort of the wire,' he

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wrote, 'is always to pass off at a right anglefrom the pole [of the magnet], indeed to goin a circle round it.'This was completely different from theeffect predicted by Wollaston, and which

Wollaston and Davy had failed to find. Butwhen Faraday's paper announcing the dis-covery (his first really important paper) waspu blished in Octo ber 1821 ( j ust after his 30thbirthday), many people who had not followedthe story closely but vaguely rememberedWollaston talking about rotations leaped tothe conclusion that at best Faraday hadsimply developed Wollaston's idea, and atworst he might be guilty of stealing Wollas-ton's work. Even Davy, who ought to haveknown better, felt that Faraday had behavedbadly, and this was the beginning of a riftbetween the two men that was never healed.Itmay be that Davy resented the prospect ofbeing overshadowed by his former lab assis-tant and part-time valet; whatever hismotives, when Faraday was proposed as aFellow of the Royal Society in 1823, Davyled the opposition to his election. Davy wasthen President of the Royal Society, but in

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spite of his opposition Faraday was elected aFellow in January 1824; there was a singleblack ball among the votes.As a result of all this unpleasantness, Fara-

day cut himself off even more from, society,and became almost a recluse. He and his wifealready lived literally above his place of work,and life revolved around the domestic worldupstairs, the laboratories and lecture roombelow, and the Sandemanian church. Not thatFaraday didn't enjoy. life, either upstairs ordownstairs. Family visitors, especially hisnieces (Michael and Sarah had no children oftheir own) later recalled the fun they had onvisits, and how Uncle Michael would enter-tain them with chemical tricks in the labora-tory - which was also a convenient place tobrew the ginger wine for Christmas ..Faraday's demonstration of how a wirecarrying a current could be made to rotate in

a magnetic field used simple apparatus thatwas soon copied, and the effect was studiedall over Europe. It made his name, as hisprompt election to the Royal Society shows,and it led directly to the development of theelectric motor. Sixty years after the demon-

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stration of Faraday's table-top experiment,electric trains were running in Germany,Britain and the United States. If he did noth-ing else, Faraday would now have beenassured.of a place in scientific history.In fact, as far as electromagnetism was con-

cerned, he did very little else for the next tenyears. He returned to chemistry, and becamethe first person to liquefy chlorine in 1823,using a technique devised by Davy. This wasquite an achievement at the time, and Faradaywent on to liquefy other gases that had pre-viously stubbornly resisted all attempts tomake them do so. But this was hardly in thesame league as his work on electromagnetism.In 1825 he discovered the compound nowcalled benzene, which is now known to have aring-shaped structure of linked carbon atomsthat is very important in molecules of life,such as DNA; but this was no more than acuriosity in his lifetime. Throughout much ofthe 1820s, Faraday was involved in a mam-moth project to find ways to manufacturebetter kinds of glass for use in navigationalinstruments.By 1825, Faraday's prestige was so high,

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and his value to the RI so clear, that it seemedappropriate to give him a new status at theInstitute. Davy had originally held the jointposts of Professor of Chemistry and Directorof the Laboratory at the RI. He had alreadygiven up the former in favour of Brande, andnow he retired as Director of the Laboratory.(Although he was not yet 50, Davy seems tohave lost interest in science; he became ill in1827, and died of a heart attack in 1829.) AtDavy's suggestion (and in spite of the damagedone to their friendship by the Wollaston inci-dent), on 7 February 1825 Faraday becameDirector of the Laboratory, although therewere initially no funds to give him anincreased remuneration. He had already madehis debut as a lecturer at the RI the previousyear, standing in for Brande on a course ofchemistry for medical students, and now hedeveloped his interest in lecturing activities intwo directions.First, he introduced a series of Friday

evening meetings, which grew into an insti-tution in their own right, the Friday EveningDiscourses, at which different speakers, but'often Faraday himself in the early years,

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reported the latest developments in science toa general audience of paying customers. Thetradition continues to this day. He thenstarted a series of lectures for children, to begiven each Christmas. Again, the traditioncontinues to this day, and now the ChristmasLectures, given by a different guest lecturereach year, are broadcast onTV. Together, theFriday Evening Discourses and the ChristmasLectures have introduced generations ofpeople to the wonders of science. Along theway, Faraday became a superb and famouslecturer who could always draw a crowd.Between 1825 and 1862, when he retired,Faraday gave more than a hundred of theFriday lectures himself.All this activity, including the lengthy pro-

ject on glass, brought money in to the RI andsaved it from extinction in the late 1820s.Without Faraday, the Institution would prob-ably have gone bust, and this largely explainswhy he expended so much effort on the com-mercial side of the RI's activities instead ofconcentrating on electromagnetism. Fara-day's feelings for the RI were clearlyexpressed in his response to an offer from the

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University of London of the Chair of Chemis-try, in 1827. Although flattered, he repliedthat:

I think it a matter of duty and gratitude onmy part to do what I can for the good ofthe Royal Institution in the present attemptto establish it firmly. The Institution hasbeen a source of knowledge and pleasure tome for the last fourteen years, and though itdoes not pay me in salary for what I nowstrive to do for it, yet I possess the kindfeelings and good-will of its authorities andmembers, and all the privileges it can grantor I require; and, moreover, I remember theprotection it has afforded me during thepast years of my scientific life ... I havealready (and to a great extent for the sakeof the Institution) pledged myself to a verylaborious and expensive series of experi-ments on glass ...

And besides, Faraday loved the opportunitythe RI gave for public lecturing. His loyaltywas rewarded in 1833, when a new endow-

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ment to the RI made him Fullerian Professorof Chemistry at the Royal Institution.Although Faraday had little time for elec-

tromagnetism in the 1820s, he did dabble init occasionally. Like other researchers of hisday, he reasoned that if an electric currentcould produce magnetism, then magnetismought to produce an electric current. Butnobody could find any evidence for such aneffect. In 1825, returning briefly to the puzzle,Faraday took two pieces of wire a metre orso long, tied them together side by side withonly a single sheet of paper separating them,and connected one of the wires to a battery,so that a current flowed along it. An instru-ment set up to measure any current flowingin the other wire (a galvanometer, named in'honour of Galvani) did not even flicker, andFaraday went back to his other work.Some of that other work had an influenceon how Faraday developed his ideas aboutthe way electric and magnetic forces are trans-mitted from one object to another. Between1828 and 1830, Faraday used several of theFriday Evening Discourses to describe, anddemonstrate, the work of Charles Wheatstone

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on sound and musical instruments.Wheatstone was notoriously shy and a reluc-tant lecturer, and Faraday enjoyed the oppor-tunity to speak on his behalf.One of the tricks they demonstrated washow the vibration of an object such as a thinmetal plate could set a similar one some dis-tance away vibrating in sympathy. It was akind of acoustic induction, caused by thepassage of sound waves as a vibration,through the air or the laboratory bench, fromone plate to the other. A force was clearlybeing transmitted, not leaping instan-taneously across space as a so-called 'actionat a distance'. When Faraday returned to thestudy of electromagnetism in 1831, in his40th year, with his work on glass completed,his innovatory lecture series at the RI estab-lished as a great success, and the RI's financeson a more secure footing than ever before,the idea of induction provided the key to hisnext great discovery.There had been one important discoveryabout electromagnetic induction in the pastten years, but nobody had interpreted it cor-rectly. In 1824) the Frenchman Francois

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Arago had found that when a compass needlewas suspended over a copper disc, and thedisc was rotated, the needle was deflected.Peter Barlow and Samuel Christie indepen-dently noticed the same effect in England,using a rotating iron disc. But Arago's workmade a greater impression on scientists at thetime, because copper, unlike iron, is not mag-netic. So how could a rotating-copper discgenerate a magnetic force?Nobody realized why the compass needlewas affected by the rotating disc. It was

thought that it was the act of rotation thathad somehow made the disc magnetic, inde-pendently of the presence of the magneticcompass. Even when it was found that rotat-ing a magnet near the disc would make thedisc turn in response, not even the greatestscientific minds of the time guessed that whatwas happening was that an electric currentwas being set up in the disc, and that thiscurrent had a magnetic field of its own whichinteracted with the magnet or compass needlenearby.. The electric current is produced bythe relative motion of the disc and the magnet(even when the magnet is only a tiny compass

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needle). So if the disc turns and the magneticcompass needle is still, there is an effect; andif a magnet moves relative to the disc whilethe disc is still, there is also an effect. It wasthe flurry of interest in electromagnetic induc-tion caused by Arago's discovery that led toFaraday's unsuccessful experiments whichpaired wires in 1825. (Arago's wheel also pro-vided the subject for a Friday Evening Dis-course, given by Faraday on 26 June 1827.)When he returned to the puzzle in 1831,Faraday devised a new piece of equipment -

the induction ring. By then, it was clear thatif an electric current was passed through awire wound in a coil (actually a helix), thecoil of wire would act like a bar magnet, witha north pole at one end and a south pole atthe other. If the coil of wire was woundaround an unmagnetized iron rod, the rodwould become a magnet when the currentwas switched on. Faraday wound two coilsof wire on to the opposite sides of a ringof iron about 15 centimetres across; the ironmaking up the ring was itself about 2 centi-metres thick. He reasoned that if an electriccurrent was passed through one of the coils,

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FARADAY lN 90 MINUTES

it would create some sort of magnetic tensionin the iron ring, with the iron acting to focusthe effect on the opposite side of the ring,where the other coil was wound. He hopedthat the effect would be to induce an electriccurrent in' the second coil, which was connec-ted to a galvanometer.Everything was ready on 29 August 1831.The second coil was connected to the galva-nometer, and then the first coil was hookedup to the current. To Faraday's surprise, theneedle of the galvanometer flickered just atthe moment the connection was made, butfell back to its zero position when a steadycurrent was flowing in the first coil. When theconnection to the battery was disconnected,the galvanometer flickered again, in the oppo-site direction. Faraday had discovered that themagnetic force associated with the first coilcould indeed induce an electric current in thesecond coil - but only when the magneticforce was changing, either building up ordying away. The effect even worked, althoughless strongly, using two coils alone, with noIron core.So far, Faraday had only made electricity

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using electricity, even if the intermediary wasthe magnetism generated by the electricity inthe first coil. In September 1831, though, hefound that moving a magnet in and out of acircuit caused a brief pulse of electricity toflow, and in October he made the key dis-covery that when a coil was wound rounda hollow paper cylinder and connected to agalvanometer, electricity could be made toflow by pulling a bar magnet in or out of thehollow centre of the coil. Itwas this discoverythat quickly led to the development of electricgenerators, or dynamos, in which a magnetis made to rotate past a coil (or the coil ismade to rotate past a fixed magnet) to gener-ate electricity.Faraday himself did not develop commer-

cially useful generators, but he did invent alittle dynamo in which a disc of copper, likethe disc used in Arago's experiments, spanbetween the magnetic poles of a large horse-shoe magnet. Using springy metal strips tomake sliding connections to the rotating disc,one near the centre of the disc and the otheron the rim near the magnet, he obtained asteady electric current from the rotating disc.

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The practical importance of all this is soobvious that we do not need to dwell on itat length. The story has often been told ofhow the Prime Minister, Robert Peel, visitedthe RI so(:mafter Faraday's discovery of thedynamo effect, and asked what use it was.According to legend, Faraday replied 'I knownot, but 1 wager that one day your govern-ment will tax it.' The discoveries, announcedin a paper read to the Royal Society on 24November 1831, raised Faraday to the veryhighest rung on the scientific ladder, in boththe public eye and among his peers.Faraday's own investigations thendeveloped in two different directions - onepublic and the other, for a long time, private.On the one hand, he sought ways to use elec-tricity, now readily available from generators,in chemistry. (He also took the trouble tocarry out a series of experiments proving thatelectricity from all the different sourcesknown at the time, including electric fish,static electricity, voltaic piles and dynamos,was indeed a single phenomenon.)He used electricity to break down variouscompounds into their component parts ielec-

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trolysis), and in a paper published in 1834he introduced many terms that have becomestandard in industry and are familiar fromour schooldays: electrolyte, for a liquidthrough which an electric current is passed;electrodes, for the two connections whereelectricity enters and leaves the liquid; anode,for the positively charged electrode; cathode,for the negatively charged electrode; ions, forthe electrically charged particles in the elec-trolyte. Electroplating became establishedcommercially in the 1840s, and electrolysisbecame an important method for the indus-trial production of some chemicals. Chlorine,for example, is produced by passing an elec-tric current through salty water (brine, astrong solution of sodium chloride). But allof this was stuff that anybody could do, onceFaraday had pointed the way.From 1831 onwards, Faraday's own deepinterest was in the nature of the forces ofelectricity and magnetism, and how theseforces were communicated across space.When a magnet is placed underneath a sheetof paper, and iron filings are sprinkled on tothe paper as it is gently tapped, the filings

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form curved lines linking the poles of the mag-net. These curved lines show the path that atiny magnetic pole would follow if it werefree to drift between the two poles of the mag-net, and this led Faraday to develop the ideaof lines o f force linking the magnetic poles,and forming a field of force extending out-ward from the magnet.The idea of a line of force is particularly

useful in picturing what happens during theinduction of an electric current by a magnet.If a conductor is stationary relative to themagnet, it is stationary relative to the lines offorce, and no current flows. But if the conduc-tor moves relative to the magnet, it is cuttingthrough the lines of force, and it is this relativemotion of the lines of force across the conduc-tor that induces a current in the conductor.So why is there a brief flicker of current inthe secondary coil of the induction ring when

the current in the first coil is switched on oroff? Because switching on the current causesa magnetic field to build up, pushing out linesof force from the.coil; while the lines are push-ing out through and past the secondary coil,they cause a current to flow. But once the

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field is steady, there is no induced current.Exactly the same thing happens in reversewhen the current in the primary coil isswitched off, and the field collapses.Faraday first used the term 'line of force'in a scientific paper as early as isrt, and bythen he was also convinced that as well asnot acting in straight lines, the magnetic forcemight not be transmitted instantaneously, butwould take time to propagate through space- it would have to, after all, to fit this pictureof current being induced by lines of forcespreading out from, or collapsing back into,the primary coil in the induction ring.The idea was so revolutionary that he hesi-

tated to publish it. But he wanted to establishhis scientific priority, so on 12 March 1832he wrote a note which was placed in a sealedand dated envelope in a safe at the RoyalSociety. It was opened only after his death.Among other things, the note expressed Fara-day's belief that:when a magnet acts upon a distant magnetor piece of iron, the influencing cause(which I may for the moment call magnet-

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ism) proceeds gradually from the magneticbodies, and requires time for its trans-mission ... I am inclined to compare thediffusion of magnetic forces from a mag-netic pole, to the vibrations upon the sur-face of disturbed water, or those of air inthe phenomena of sound: i.e. I am inclinedto think the vibratory theory will apply tothese phenomena, as it does to sound, andmost probably to light.

It would be more than twelve years beforeFaraday went public with these ideas, a delaycaused partly by his work on electrochemis-try, partly by his reluctance to publish suchoutrageous claims, and partly by a seriousbout of ill-health, brought on by overwork,at the end of the 1830s.Faraday's achievements in the years 1831to 1838 were at an astonishing level for any

scientist, and highly unusual for a man in hisforties - the greatest original ideas in scienceusually come from people in their twenties orearly thirties. The strain had been particularlyhard on Faraday, though. For a long time,perhaps since as early as 1816, he had suf-

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fered from such a bad memory that he hadto make detailed notes for himself to remindhim of progress with his work. It all becametoo much in 1839, and he suffered a classicnervous breakdown, brought o~. by over-work. In one of his notes, complaining aboutdoctors who refused to listen properly towhat he had to tell them, he wrote:When I say I am not able to bear muchtalking, it means really, and without anymistake, or equivocation, or oblique mean-ing, or implication, or subterfuge, or omis-sion, that I am not able; being at presentrather weak in the head, and able to workno more.There had, with hindsight, been signs of

what might happen. The first biography ofFaraday, written by his successor at the RI,John Tyndall, and published in 1868, tells usthat:Underneath his sweetness and gentlenesswas the heat of a volcano. He was a manof excitable and fiery nature; but through

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high self-discipline he had converted the fireinto a central glow and motive power oflife, instead of permitting it to waste itselfin useless passion ... he completely ruledhis own spirit.

In other words, he was a self-control freak.Faraday was also obsessive about timekeep-ing. It is a tradition, inherited from his habits,that the Friday Evening discourses at the RI,which are otherwise relatively informaloccasions, begin precisely at the stroke of 9o'clock, when the door flies open and thespeaker rushes to his place.Things were not all sweetness and light dur-ing the hectic period of work in the 1830s.

One of Faraday's nieces, Margery Ann Reid(who was the daughter of Sarah's sister Eliza-beth, and later married James, the son ofMichael's brother Robert) lived with theFaradays in the 1830s. She later noted that'when [Faraday was] dull and dispirited, ashe sometimes was to an extreme degree, myaunt used to carry him off to Brighton, orsomewhere, for a few days, and they generallycame back refreshed and invigorated.'

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At the end of the 1830s, though, somethingmore than a few days in Brighton was needed.Faraday spent much of his convalescence inSwitzerland, attended by Sarah and herbrother George, and did not really return toresearch until 1845 - in his 54th year. Bythen, he was well established as the grand oldman of British science. Perhaps acknowledg-ing that he could not go on for ever, hehad taken the opportunity of a FridayEvening Discourse in 1844, when he wasalmost fully recovered from his breakdown,to give his ideas about lines of force a publicamng.The subject of the lecture, on 19 January1844, was really an attack on the atomic

theory of matter. Faraday argued that therecould be no real distinction between spaceand the hypothetical atoms, and proposedinstead that these atoms were simply thecentres of concentration of forces. Instead ofthinking of an atom as something that wasthe source of a web of forces, actually creatingthose forces, Faraday asked his audience toaccept that what was fundamentally real wasthe web of forces itself, and that the atoms

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were simply concentrations of the lines offorce making up the web - knots in the field.This idea is remarkably similar to the picturein modern quantum field theory, in whichonly fields have independent existence, andall particles are products of the field. But itmade very little impact at the time, in spiteof Faraday's use of graphic imagery to makehis case.In a classic example of a 'thought experi-ment', Faraday made it clear that he was talk-ing about all the forces of nature, not justelectricity and magnetism. He asked people toimagine the Sun sitting alone in space. Whatwould happen if the Earth was suddenly, bymagic, placed in its position at the appropri-ate distance from the Sun? How would it'know' that the Sun was there? Faradayargued that even before the Earth was put inits place, the Sun's influence would extendthrough space, and through that place, in theform of lines of force. When the Earth wasdropped into the web of lines of force, itwould respond instantly to the presence ofthe lines of force - to the gravitational field- at the location of the Earth itself. As far as

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the Earth is concerned, what matters is thenature of the field at the Earth's location, notthe nature of the source of the field - if,indeed, the Sun could really be regarded asthe source of the field. To Faraday.jhe fieldwas the reality, and matter (even matter onthe scale of the Sun) merely associated withplaces where the field was concentrated.In 1846, Faraday returned to the theme inanother Friday Evening Discourse. This time,he was standing in for a speaker who hadfailed to appear. Legend has it that CharlesWheatstone was supposed to speak aboutsome of his work, on 10 April 1846, but hadan attack of stage fright and ran off at thelast minute, leaving Faraday to hold the fort.One of us is among the many writers thathave been guilty of repeating this delightfultale without checking it out iSchrodinger'sKittens, Phoenix). Alas for the legend, accord-ing to the RI's records the speaker booked forthat evening was James Napier, and he hadsent his apologies a full week before the meet-ing. Although Faraday was a stand-in lectureron that occasion, and did indeed spend muchof the talk describing Wheatstone's work, he

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did know in reasonable time what he wasletting himself in for.Whatever the background, though, the

audience could hardly have expected thatFaraday. would use the spare time at the endof the lecture to air his 'Thoughts on Ray-vibrations'. Now, he suggested that lightcould be explained in terms of the vibrationsof the electric lines of force. In the publishedversion of the lecture, he said:.The view which I am so bold as to put forthconsiders, therefore, radiation as a highspecies of vibration in the lines of forcewhich are known to connect particles, andalso masses of matter, together. It endeav-ours to dismiss the aether, but not thevibrations.

The 'aether' was a hypothetical substance,thought to fill all of 'empty space' and to pro-vide a medium through which light wavescould move, like ripples moving across apond. Faraday then spelled out the nature ofthe kind of wave he was talking about:

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[It] is not the same as '" the waves ofsound in gases or liquids, for the vibrationsin these cases are direct, or to and from thecentre of action, whereas the former arelateral.

Faraday pointed out that the propagation oflight takes time, and that this fits the ideaof a ripple moving along a line of force. Hespeculated that gravity must propagate in asimilar way, and also take time to travel fromone object to another.It was this package of great ideas that Fara-day passed on to the next generation of scien-

tists. James Clerk Maxwell was to developa complete wave theory of lightin terms ofelectromagnetic vibrations, building on Fara-day's speculations, in the 1860s. Maxwell'swork put those speculations on a securemathematical footing, and also led him topredict the existence of similar electromag-netic waves with longer wavelengths thanlight. These waves (now known as radiowaves) were duly discovered by HeinrichHertz, in 1888.Even in his late fifties, Faraday continued

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to carry out scientific research, in short burstsbetween renewed bouts of ill-health. Hestudied the magnetic properties of glass andflames, liquids, solids and gases, and he inves-tigated the effect of magnetic fields on light.All this was good stuff, and much of it helpedhim to develop his ideas about fields and linesof force. But, like his earlier work in chemis-try, any competent scientist could have doneit, and somebody else surely would have doneit if Faraday had not. The great crowningachievement of Faraday's career, althoughthis was scarcely appreciated in his time (evenin Tyndall's biography of Faraday the ideasabout lines of force are relegated to a sectionheaded 'Speculations'), was laying the foun-dations of field theory. In any moderndescription, his later scientific work inevitablyappears anticlimactic.

In a way, the end of Faraday's life wasanticlimactic. He never fully recovered fromhis illness at the end of the 1830s, andalthough he summed up his great work onfield theory in the mid-1840s, pointing theway for Maxwell, his memory became so badthat he could not read of the developments

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in science, and could not keep pace with otherscientists breaking new ground. He couldeasily remember events that had happenedlong before, but had trouble remembering theeveryday details of his life, including thenames of his friends.The illness seems to have been progressive.At first, after his recovery from the attack at

the end of the 1830s, he was almost fullyrestored, but successive minor attacks left himwith increasing difficulties. After the mid-1850s he became increasingly confused, andit seems that by the 1860s he was more oftenin the confused state than in his previouslyclear state of mind.This deterioration is usually attributed to

advancing years - in 1861, after all, Faradaywas 70. Some people have suggested that theproblems may have been made worse bychemical poisoning, as a result of all the toxicsubstances that he had handled in his earlyyears at the RI. But .nobody has ever beenable to match his exact symptoms with anyknown form of long-term poisoning of thiskind ..Whatever the causes, Faraday himselfwas painfully aware of his declining powers.

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In 1862, he wrote to an old friend and long-time correspondent:Again and again I tear up my letters, for Iwrite. nonsense. I cannot spell or write aline continuously. Whether I shall recover- this confusion - do not know. I will notwrite any more. My love to you.

ever affectionately yours,M. FaradayBut we do not want to end our story on toogloomy a note. If Faraday's mental powersdid decline, they did so from a great height;and even late in life he was able to makeimportant contributions in his role as a publicscientist.Or perhaps we should say public servant,because that is how Faraday always saw him-self. His religious beliefs would not"allow himto hold public office, or any position of greatauthority, and also discouraged him fromaccepting public honours. He turned downthe offer of a knighthood, and the Presidencyof the Royal Society - twice, in 1848 and1857. On the second occasion he commented

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to Tyndall that 'if I accepted the honourwhich the Royal Society desires to confer onme, I would not answer for the integrity ofmy intellect for a single year'. Significantly,Faraday was also among the early supportersof the British Association for the Advance-ment of Science, founded at the end of the1850s. This was intended as an organizationof professional scientists as equals, withoutthe trappings of a gentlemen's club and the airof social prestige that were such an importantpart of the Royal Society. In 1864, Faradaywas invited to become President of the RoyalInstitution, a largely honorary position recog-nizing his great contribution to putting the RIon a secure footing, but even this could not beconsidered. Itwas, he said, 'quite inconsistentwith all my life and views'.But that life and those views were consist-ent with public service, and Sandemanians

were specifically expected to be loyal to theCrown. This has led to one delightful, butprobably apocryphal, story. Faraday wasinvited to take lunch with Queen Victoria oneSunday early in 1844. The trouble was, theSandemanians required their members to

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attend church every Sunday, without excep-tion. On the other hand, they required theirmembers to be loyal servants of the Queen.The story goes that Faraday chose loyalty tothe Crown over his loyalty to the church, and,worse, when reprimanded for his action hewas far from penitent, and defended hisaction. This lack of penitence, it is said, iswhat led to him losing the status of Elder,which he had held since 15 October 1840,and which was not restored to him until 21October 1860. He was even excluded fromthe church from 31 March to 5 May 1844.The point of the story is that, to Faraday'scontemporaries, it clearly rang true that hewould take such an action, and be so stub-born in defending his corner. Unfortunately,there is not a shred of evidence that the lunchwith Queen Victoria took place. But there isevidence of a mysterious schism in theLondon Sandemanian church at this time,with no fewer than nineteen members (includ-ing Faraday) briefly excluded for someobscure reason. They cannot, surely, all havebeen excluded for defending Faraday's rightto have lunch with the Queen!

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The kind of stubbornness and adherence toprinciple that made people believe the anec-dote had surfaced more publicly in 1835,when Faraday was offered a Civil List pension- an income from the government" indepen-dent of his income from the RI. In a recentchange of government, the Whig Lord Mel-bourne had replaced the Tory Robert Peel asPrime Minister. Peel had intended to awardFaraday a pension in recognition of his scien-tific work. Melbourne felt under some obliga-tion at least to discuss the matter withFaraday, but opened their conversation bysaying that he regarded 'the whole system ofgiving pensions to literary and scientificpeople as a piece of gross humbug'. Faradaysaid that in that case he certainly did not wantto have a pension, and took his leave.The story caused a flurry of excitement inthe Tory press, with both Melbourne and

Faraday initially sitting on their high horsesand refusing to compromise. Eventually, Mel-bourne offered an apology. Itwas made clearthat the pension was something Faraday hadearned on merit, and he accepted it.As his ability to carry out lengthy pieces of

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scientific research declined, Faraday devotedmore time, after the mid-1840s, to public ser-vice. In 1844, ninety-five miners were killed inan explosion at Haswell Colliery, in CountyDurham., The government (once again underPeel) sent Faraday and the geologist CharlesLyell to find out what had happened. Faradayproved an able forensic scientist, taking akeen interest in both the forensic and thescientific aspects of the work, and noting that:testimony is like an arrow shot from a long-bow; the force of it depends on the strengthof the hand that draws it. Argument is likean arrow shot from a crossbow, which hasequal force though shot by a child.The investigation found that the explosion

had probably been caused by human careless-ness. The miners were equipped with Davylamps (devised by Faraday's old mentor atthe RI), which could not cause explosions,even in a build-up of flammable gas. Faradayand Lyell learned that the miners had foundthey could light a pipe from such a lamp, andthat smoking had been going on in places

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where dangerous gases were likely to buildup.Faraday was also called in to help advise onhow to protect the paintings in the NationalGallery from the filthy air of London in the1850s, and to advise on the proposed restor-ation of the Elgin Marbles, housed in theBritish Museum. He was a scientific adviserto Trinity House, the organization respon-sible for lighthouses around the coast ofBritain, from 1836 to 1865. For most of thattime there is no record of his activities in thiscapacity, because the papers covering the firsttwenty . years or so of the period weredestroyed in an air raid on London in theSecond World War. But we do know that heinvestigated the use of limelight and electricarc lights to replace the old oil-burning lamps.And he carried out a great deal of work inthe field. In February 1860, in his 69th year,he reached a lighthouse in Kent only byscrambling across snow-filled fields, overhedges and walls. But as he happily reportedto Trinity House, 'I succeeded in . getting thereand making the necessary inquiries and obser-vations.'

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In one of his last public duties, in 1862,Faraday gave evidence to a Royal Com-mission set up to investigate the educationprovided in the public schools, at that timestill based almost entirely on Latin and GreekClassics. Faraday advised the Commissionthat not only was it desirable to teach scienceat this level, but it was possible to do so ina structured way, with the effectiveness of apupil's mastery of the subject being tested byexaminations;This must have been a poignant occasion,

because Faraday's greatest public achieve-ments had been as an educator and teacher,in the broadest sense of the term. But by thetime he gave that evidence, even those abilitieshad generally failed him. In 1861, he had con-ceded that he could no longer fulfil his obliga-tions at the ,RI, and that, in particular, hecould no longer deliver the lectures for youngpeople that had been one of his great inno-vations. In October that year, just after his70th birthday, he offered his resignation. TheRI accepted that he could no longer give lec-tures, but asked him to stay on as Superinten-dent of the house and the laboratories. He

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gave his last Friday Evening Discourse on 20June 1862, and severed his last connectionswith the RI in 1865.By then, Michael and Sarah Faraday had

already moved out of the building. In 1858,at the suggestion of Prince Albert, Queen Vic-toria had offered the couple a house atHampton Court. The house was in a bad stateof repair, and Faraday worried about the costof making it properly habitable, but when theQueen learned of his concern, she paid forthe renovations as well. But it was only from1862 onwards that this became the Faradays'real home; before then, they still spent mostof their time at the RI. Faraday increasinglylost his mental powers after 1865, sinkinginto senility. He died quietly, as he sat in hisfavourite armchair, on 25 August 1867. Inaccordance with his own wishes he wasburied quietly in Highgate Cemetery. Hisheadstone bears this simple inscription:

MICHAEL FARADAYBorn 22 September 1791Died 25 August 1867

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AfterwordWe don't need to stress how important Fara-day's work on electricity has been in shapingthe modern world. But even some scientistsare not m < f S well aware as they should be ofthe way his field theory underpins the mostfundamental aspects of theoretical physicstoday.The basic concept of a field is easy enough

to grasp. It grew from the idea of lines offorce. You can think of lines of force as beinglike the ribs in a spider's web, reaching outfrom a centre - say, the location of a chargedparticle. Particles that interact with the linesof force are pulled into the centre along thelines.But there are spaces in a spider's web. The

field idea comes from the image of filling inthose gaps to make a smooth surface. Onewidely used example of this idea is in AlbertEinstein's general theory of relativity, whichdescribes gravity in terms of fields. The grav-ity of the Sun, for example, is seen as makinga dent in spacetime (as if the spider's webwere a rubber sheet, poked in its centre).

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Objects under the influence of the Sun's grav-ity are then pictured as marbles rolling incurved paths around the dent the Sun makes.The big difference between modern field

theory and Faraday's version, though, is thatthe modern theory is quantized. Faraday andMaxwell thought of the electromagnetic fieldas continuous, with light being conveyed byripples in the field. But in the early part ofthe twentieth century it became clear thatlight could also be described in terms of littleparticles, field quanta, that came to be knownas photons. Indeed, light must be describedin this way if we are to explain many aspectsof its behaviour. In this picture the classicalidea of a field is replaced by the concept ofparticles, such as photons, carrying forces asthey are exchanged between other particles,such as electrons.But at the same time, things that we areused to thinking of as particles (such as elec-trons) can be thought of as waves. Thesewaves can be described in terms of ripples inanother kind of field (one field for each typeof particle), and the particles themselves canbe described as field quanta, just as photons

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can be described as the quanta of the electro-magnetic field. In quantum field theory (thecurrent bee's knees in physics, responsible forideas such as quarks and quantum electro-dynamics), there are only fields to worryabout. All-'particles, whether matter particleslike electrons or force carriers like the photon,are regarded as excited states of the appropri-ate fields.Apart from the sometimes hairy mathe-matics involved in the modern calculations,this is exactly the situation described byMichael Faraday in his famous FridayEvening Discourse in 1844. There is no doubtthat Faraday was not just a competent chem-ist, or merely a technician who was good withhis hands and clever enough to invent theelectric motor and the dynamo. He was atheorist of the first rank, in many waysthe first modern physicist - not bad for apoor blacksmith's son and bookbinder'sapprentice.

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A brief history of scienceAll science is either physics or stamp collecting.

Ernest Rutherford

c. 2000 Be First phase of construction atStonehenge, an earlyobservatory.

430 Be Democritus teaches thateverything is made of atoms.

c. 330 Be Aristotle teaches that theUniverse is made ofconcentric spheres, centred onthe Earth.Euclid gathers together andwrites down the mathematicalknowledge of his time.Archimedes discovers hisprinciple of buoyancy whilehaving a bath.Eratosthenes of Cyrenecalculates the size of theEarth with commendable

300 Be

265 Be

c. 235 Be

accuracy.

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AD 79 Pliny the Elder dies whilestudying an eruption ofMount Vesuvius.The term 'chemistry' is usedfor the first time, by scholarsin Alexandria.Alhazen, the greatest scientistof the so-called Dark Ages,explains the workings oflenses and parabolicmirrors.

1054 Chinese astronomers observe

400

c. 1020

a supernova; the remnant isvisible today as the CrabNebula.

1490 Leonardo da Vinci studies thecapillary action of liquids.

1543 In his book Derevolutionibus, NicholasCopernicus places the Sun,not the Earth, at the centre ofthe Solar System. AndreasVesalius studies humananatomy in a scientific way.

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c. 1550

1572

1580

1596

1608

1609-19

1610

1628

1643

The reflecting telescope, andlater the refracting telescope,pioneered by Leonard Digges.Tycho Brahe observes asupernova.Prospero Alpini realizes thatplants come in two sexes.Botanical knowledge issummarized in JohnGerrard's Herbal.Hans Lippershey's inventionof a refracting telescope is thefirst for which there is firmevidence.Johannes Kepler publishes hislaws of planetary motion.Galileo Galilei observes themoons of Jupiter through atelescope.William Harvey publishes hisdiscovery of the circulation ofthe blood.Mercury barometer inventedby Evangelista Torricelli.

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1656 Christiaan Huygens correctlyidentifies the rings of Saturn,and invents the pendulumclock.

1662 The law relating the pressureand volume of a gasdiscovered by Robert Boyle,and named after him.

1665 Robert Hooke describesliving cells.

1668 A functional reflectingtelescope is made by IsaacNewton, unaware of Digges'searlier work.

1673 Antony van Leeuwenhoeckreports his discoveries withthe microscope to the RoyalSociety.

1675 Ole Roemer measures thespeed of light by timingeclipses of the moons ofJupiter.

1683 Van Leeuwenhoeck observesbacteria.

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1687 Publication of Newton'sPrincipia, which includes hislaw of gravitation.1705 Edmond Halley publishes his

prediction of the reHlrn of thecomet that now bears hisname.1737 Carl Linnaeus publishes hisclassification of plants.

1749 Georges Louis Leclerc, Comtede Buffon, defines a species inthe modern sense.1758 Halley's Comet returns, aspredicted.

1760 John Michell explainsearthquakes.

1772 Carl Scheele discoversoxygen; Joseph Priestleyindependently discovers ittwo years later.

1773 Pierre de Laplace begins hiswork on refining planetaryorbits. When asked byNapoleon why there was no

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mention of God in hisscheme, Laplace replied, 'Ihave no need of thathypothesis. '1783 John Michell is the firstperson to suggest the

existence of 'dark stars' -now known as black holes.1789 Antoine Lavoisier publishes atable of thirty-one chemicalelements.1796 Edward Jenner carries out thefirst inoculation, againstsmallpox.1798 Henry Cavendish determinesthe mass of the Earth.1802 Thomas Young publishes hisfirst paper on the wavetheory of light.Jean-Baptiste Lamarck inventsthe term 'biology'.1803 John Dalton proposes the

atomic theory of matter.1807 Humphry Davy discovers

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sodium and potassium, andgoes on to find several otherelements.

1811 Amedee Avogadro proposesthe law that gases containequal numbers of moleculesunder the same conditions.

1816 Augustin Fresnel develops hisversion of the wave theory oflight.

1826 First photograph from natureobt(1ined by NicephoreNi~pce.

1828 Friedrich Wohler synthesizes.an organic compound (urea)frorn inorganic ingredients.

1830 Publication of the firstvolume of Charles Lyell's.P rinciples of G eology.1831 Michael Faraday and Joseph

Henry discoverelectromagnetic induction.Charles Darwin sets sail onthe Beagle.

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1837 Louis Agassiz coins the term'ice age' (d ie E isze it).1842 Christian Doppler describes

the effect that now bears hisname.

1849 Hippolyte Fizeau measuresthe speed of light to within 5per cent of the modern value.

1851 Jean Foucault uses hiseponymous pendulum todemonstrate the rotation ofthe Earth.

1857 Publication of Darwin'sO rigin of Species.Coincidentally, GregorMendel begins hisexperiments with peabreeding.

1864 James Clerk Maxwellformulates equationsdescribing all electric andmagnetic phenomena, andshows that light is anelectromagnetic wave.

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1868 Jules Janssen and NormanLockyer identify helium fromits lines in the Sun'sspectrum.

1871 Dmitri Mendeleyev predicrsthat 'new' elements will befound to fit the gaps in hisperiodic table.

1887 Experiment carried out byAlbert Michelson and EdwardMorley finds no evidence forthe existence of an 'aether'.1895 X-rays discovered by WilhelmRontgen. Sigmund Freudbegins to developpsychoanalysis.

1896 Antoine Becquerel discoversradioactivity .

1897 Electron identified by J. J .Thomson.1898 Marie and Pierre Curiediscover radium.1900 Max Planck explains howelectromagnetic radiation is

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absorbed and emitted asquanta. Various biologistsrediscover Medel's principlesof genetics and heredity.

1903 First powered and controlledflight in an aircraft heavierthan air, by Orville Wright.1905 Einstein's special theory ofrelativity published.

1908 Hermann Minkowski showsthat the special theory ofrelativity can be elegantlyexplained in geometricalterms if time is the fourthdimension.

1909 First use of the word 'gene',by Wilhelm Johannsen.1912 Discovery of cosmic rays by

Victor Hess. Alfred Wegenerproposes the idea ofcontinental drift, which led inthe 1960s to the theory ofplate tectonics.1913 Discovery of the ozone layer

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by Charles Fabry.1914 Ernest Rutherford discoversthe proton, a name he coinsin 1919.

1915 Einstein presents his'generaltheory of relativity to thePruss ian Academy ofSciences.

1916 Karl Schwarzschild showsthat the general theory ofrelativity predicts theexistence of what are nowcalled black holes.

1919 Arthur Eddington and othersobserve the bending ofstarlight during a total eclipseof the Sun, and so confirmthe accuracy of the generaltheory of relativity.Rutherford splits the atom.

1923 Louis de Broglie suggests thatelectrons can behave aswaves.

1926 Enrico Fermi and Paul Dirac

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1927

1928

1929

1930s

1932

1937

1942

1940s

discover the statistical ruleswhich govern the behaviourof quantum particles such aselectrons.Werner Heisenberg developsthe uncertainty principle.Alexander Fleming discoverspenicillin.Edwin Hubble discovers thatthe Universe is expanding.Linus Pauling explainschemistry in terms ofquantum physics.Neutron discovered by JamesChadwick.Grote Reber builds the firstradio telescope.First controlled nuclearreaction achieved by EnricoFermi and others.George Gamow, RalphAlpher and Robert Hermandevelop the Big Bang theoryof the origin of the Universe.

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1948 Richard Feynman extendsquantum theory bydeveloping quantumelectrodynamics.

1951 Francis Crick and JamesWatson work out the helixstructure of DNA, usingX-ray results obtained byRosalind Franklin.

1957 Fred Hoyle, together withWilliam Fowler and Geoffreyand Margaret Burbidge,explains how elements aresynthesized inside stars. Thelaser is devised by GordonGould. Launch of firstartificial satellite,Sputnik 1.

1960 Jacques Monod and FrancisJacob identify messengerRNA.

1961 First part of the genetic codecracked by MarshallNirenberg.

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1963 Discovery of quasars byMaarten Schmidt.1964 W.D. Hamilton explainsaltruism in terms of what is

now called sociobiology.1965 Arno Penzias and Robert

Wilson discover the cosmicbackground radiation leftover from the Big Bang.

1967 Discovery of the first pulsarby Jocelyn Bell.

1979 Alan Guth starts to developthe inflationary model of thevery early Universe.1988 Scientists at Caltech discover

that there is nothing in thelaws of physics that forbidstime travel.

1995 Top quark identified.1996 Tentative identification of

evidence of primitive life in ameteorite believed to haveoriginated on Mars.

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