,,faraday ,,as ,a ,,discoverer by ,john ,tyndall ,contents4 ,preface4 ,chapter #a4 ,parentage3 introduction to the royal institution3 earliest experiments3 first royal society paper3 marriage4 ,chapter #b4 ,early researches3 magnetic rotations3 liquefaction of gases3 heavy glass3 ,charles ,anderson3 contributions to physics4 ,chapter #c4 ,discovery of ,magneto-electricity3 ,explanation of ,argo's magnetism of rotation3 ,terrestrial magneto-electric induction3 ,the extra current4 ,chapter #d4 ,points of ,character4 ,chapter #e4 ,identity of electricities2 first researches on electro-chemistry4 ,chapter #f4 ,laws of electro-chemical decomposition4 ,chapter #g4 ,origin of power in the voltaic pile4 ,chapter #h4 ,researches on frictional electricity3 induction3 conduction3 specific inductive capacity3 theory of contiguous particles4 ,chapter #i4 ,rest needed--visit to ,switzerland4 ,chapter #aj4 ,magnetization of light4 ,chapter #aa4 ,discovery of diamagnetism--researches on magne-crystallic action4 ,chapter #ab4 ,magnetism of flame and gases--atmospheric magnetism4 ,chapter #ac4 ,speculations3 nature of matter3 lines of force4 ,chapter #ad4 ,unity and convertibility of natural forces3 theory of the electric current4 ,chapter #ae4 ,summary4 ,chapter #af4 ,illustrations of ,character4 ,preface to the fifth edition4 ,daily and weekly1 from all parts of the world1 ,i receive publications bearing upon the practical applications of electricity4 ,this great movement1 the ultimate outcome of which is not to be foreseen1 had its origin in the discoveries made by ,michael ,faraday1 sixty-two years ago4 ,from these discoveries have sprung applications of the telephone order1 together with various forms of the electric telegraph4 ,from them have sprung the extraordinary advances made in electrical illumination4 ,faraday could have had but an imperfect notion of the expansions of which his discoveries were capable4 ,still he had a vivid and strong imagination1 and ,i do not doubt that he saw possibilities which did not disclose themselves to the general scientific mind4 ,he knew that his discoveries had their practical side1 but he steadfastly resisted the seductions of this side1 applying himself to the development of principles2 being well aware that the practical question would receive due development hereafter4 ,during my sojourn in ,switzerland this year1 ,i read through the proofs of this new edition1 and by my reading was confirmed in the conviction that the book ought not to be suffered to go out of print4 ,the memoir was written under great pressure1 but ,i am not ashamed of it as it stands4 ,glimpses of ,faraday's character and gleams of his discoveries are there to be found which will be of interest to humanity to the end of time4 ,john ,tyndall4 ,hind ,head1 ,december1 #ahic4 ,note4--,it was1 ,i believe1 my husband's intention to substitute this ,preface1 written a few days before his death1 for all former ,prefaces4 ,as1 however1 he had not the opportunity of revising the old prefatory pages himself1 they have been allowed to remain just as they stood in the last edition4 ,louisa ,c4 ,tyndall4 ,preface to the fourth edition4 ,when consulted a short time ago as to the republication of ',faraday as a ,discoverer1' it seemed to me that the labours1 and points of character1 of so great a worker and so good a man should not be allowed to vanish from the public eye4 ,i therefore willingly fell in with the proposal of my ,publishers to issue a new edition of the little book4 ,royal ,institution1 ,february1 #ahhd4 ,preface to the second edition4 ,the experimental researches of ,faraday are so voluminous1 their descriptions are so detailed1 and their wealth of illustration is so great1 as to render it a heavy labour to master them4 ,the multiplication of proofs1 necessary and interesting when the new truths had to be established1 are however less needful now when these truths have become household words in science4 ,i have therefore tried in the following pages to compress the body1 without injury to the spirit1 of these imperishable investigations1 and to present them in a form which should be convenient and useful to the student of the present day4 ,while ,i write1 the volumes of the ,life of ,faraday by ,dr4 ,bence ,jones have reached my hands4 ,to them the reader must refer for an account of ,faraday's private relations4 ,a hasty glance at the work shows me that the reverent devotion of the biographer has turned to admirable account the materials at his command4 ,the work of ,dr4 ,bence ,jones enables me to correct a statement regarding ,wollaston's and ,faraday's respective relations to the discovery of ,magnetic ,rotation4 ,wollaston's idea was to make the wire carrying a current rotate round its own axis3 an idea afterwards realised by the celebrated ,ampere4 ,faraday's discovery was to make the wire carrying the current revolve round the pole of a magnet and the reverse4 ,john ,tyndall4 ,royal ,institution3 ,december1 #ahfi4 ,,faraday ,,as ,a ,,discoverer4 ,chapter #a4 ,parentage3 introduction to the royal institution3 earliest experiments3 first royal society paper3 marriage4 ,it has been thought desirable to give you and the world some image of ,,michael ,,faraday1 as a scientific investigator and discoverer4 ,the attempt to respond to this desire has been to me a labour of difficulty1 if also a labour of love4 ,for however well acquainted ,i may be with the researches and discoveries of that great master--however numerous the illustrations which occur to me of the loftiness of ,faraday's character and the beauty of his life--still to grasp him and his researches as a whole2 to seize upon the ideas which guided him1 and connected them2 to gain entrance into that strong and active brain1 and read from it the riddle of the world--this is a work not easy of performance1 and all but impossible amid the distraction of duties of another kind4 ,that ,i should at one period or another speak to you regarding ,faraday and his work is natural1 if not inevitable2 but ,i did not expect to be called upon to speak so soon4 ,still the bare suggestion that this is the fit and proper time for speech sent me immediately to my task3 from it ,i have returned with such results as ,i could gather1 and also with the wish that those results were more worthy than they are of the greatness of my theme4 ,it is not my intention to lay before you a life of ,faraday in the ordinary acceptation of the term4 ,the duty ,i have to perform is to give you some notion of what he has done in the world2 dwelling incidentally on the spirit in which his work was executed1 and introducing such personal traits as may be necessary to the completion of your picture of the philosopher1 though by no means adequate to give you a complete idea of the man4 ,the newspapers have already informed you that ,michael ,faraday was born at ,newington ,butts1 on ,september #bb1 #agia1 and that he died at ,hampton ,court1 on ,august #be1 #ahfg4 ,believing1 as ,i do1 in the general truth of the doctrine of hereditary transmission--sharing the opinion of ,mr4 ,carlyle1 that 'a really able man never proceeded from entirely stupid parents'--,i once used the privilege of my intimacy with ,mr4 ,faraday to ask him whether his parents showed any signs of unusual ability4 ,he could remember none4 ,his father1 ,i believe1 was a great sufferer during the latter years of his life1 and this might have masked whatever intellectual power he possessed4 ,when thirteen years old1 that is to say in #ahjd1 ,faraday was apprenticed to a bookseller and bookbinder in ,blandford ,street1 ,manchester ,square3 here he spent eight years of his life1 after which he worked as a journeyman elsewhere4 ,you have also heard the account of ,faraday's first contact with the ,royal ,institution2 that he was introduced by one of the members to ,sir ,humphry ,davy's last lectures1 that he took notes of those lectures2 wrote them fairly out1 and sent them to ,davy1 entreating him at the same time to enable him to quit trade1 which he detested1 and to pursue science1 which he loved4 ,davy was helpful to the young man1 and this should never be forgotten3 he at once wrote to ,faraday1 and afterwards1 when an opportunity occurred1 made him his assistant4#a ,mr4 ,gassiot has lately favoured me with the following reminiscence of this time3-- ',clapham ,common1 ,surrey1 ',november #bh1 #ahfg4 ',my ,dear ,tyndall1--,sir ,h4 ,davy was accustomed to call on the late ,mr4 ,pepys1 in the ,poultry1 on his way to the ,london ,institution1 of which ,pepys was one of the original managers2 the latter told me that on one occasion ,sir ,h4 ,davy1 showing him a letter1 said3 ,pepys1 what am ,i to do1 here is a letter from a young man named ,faraday2 he has been attending my lectures1 and wants me to give him employment at the ,royal ,institution--what can ,i do8 ,do8 replied ,pepys1 put him to wash bottles2 if he is good for anything he will do it directly1 if he refuses he is good for nothing4 ,no1 no1 replied ,davy2 we must try him with something better than that4 ,the result was1 that ,davy engaged him to assist in the ,laboratory at weekly wages4 ',davy held the joint office of ,professor of ,chemistry and ,director of the ,laboratory2 he ultimately gave up the former to the late ,professor ,brande1 but he insisted that ,faraday should be appointed ,director of the ,laboratory1 and1 as ,faraday told me1 this enabled him on subsequent occasions to hold a definite position in the ,institution1 in which he was always supported by ,davy4 ,i believe he held that office to the last4 ',believe me1 my dear ,tyndall1 yours truly1 ',j4 ,p4 ,gassiot4 ',dr4 ,tyndall4' ,from a letter written by ,faraday himself soon after his appointment as ,davy's assistant1 ,i extract the following account of his introduction to the ,royal ,institution3-- ',london1 ,sept4 #ac1 #ahac4 ',as for myself1 ,i am absent 7from home7 nearly day and night1 except occasional calls1 and it is likely shall shortly be absent entirely1 but this 7having nothing more to say1 and at the request of my mother7 ,i will explain to you4 ,i was formerly a bookseller and binder1 but am now turned philosopher1#b which happened thus3--,whilst an apprentice1 ,i1 for amusement1 learnt a little chemistry and other parts of philosophy1 and felt an eager desire to proceed in that way further4 ,after being a journeyman for six months1 under a disagreeable master1 ,i gave up my business1 and through the interest of a ,sir ,h4 ,davy1 filled the situation of chemical assistant to the ,royal ,institution of ,great ,britain1 in which office ,i now remain2 and where ,i am constantly employed in observing the works of nature1 and tracing the manner in which she directs the order and arrangement of the world4 ,i have lately had proposals made to me by ,sir ,humphry ,davy to accompany him in his travels through ,europe and ,asia1 as philosophical assistant4 ,if ,i go at all ,i expect it will be in ,october next--about the end2 and my absence from home will perhaps be as long as three years4 ,but as yet all is uncertain4' ,this account is supplemented by the following letter1 written by ,faraday to his friend ,de la ,rive1#c on the occasion of the death of ,mrs4 ,marcet4 ,the letter is dated ,september #b1 #aheh3-- ',my ,dear ,friend1--,your subject interested me deeply every way2 for ,mrs4 ,marcet was a good friend to me1 as she must have been to many of the human race4 ,i entered the shop of a bookseller and bookbinder at the age of thirteen1 in the year #ahjd1 remained there eight years1 and during the chief part of my time bound books4 ,now it was in those books1 in the hours after work1 that ,i found the beginning of my philosophy4 ,there were two that especially helped me1 the ,encyclopaedia ,britannica1 from which ,i gained my first notions of electricity1 and ,mrs4 ,marcet's ,conversation on ,chemistry1 which gave me my foundation in that science4 ',do not suppose that ,i was a very deep thinker1 or was marked as a precocious person4 ,i was a very lively imaginative person1 and could believe in the ,arabian ,nights as easily as in the ,encyclopaedia4 ,but facts were important to me1 and saved me4 ,i could trust a fact1 and always cross-examined an assertion4 ,so when ,i questioned ,mrs4 ,marcet's book by such little experiments as ,i could find means to perform1 and found it true to the facts as ,i could understand them1 ,i felt that ,i had got hold of an anchor in chemical knowledge1 and clung fast to it4 ,thence my deep veneration for ,mrs4 ,marcet--first as one who had conferred great personal good and pleasure on me2 and then as one able to convey the truth and principle of those boundless fields of knowledge which concern natural things to the young1 untaught1 and inquiring mind4 ',you may imagine my delight when ,i came to know ,mrs4 ,marcet personally2 how often ,i cast my thoughts backward1 delighting to connect the past and the present2 how often1 when sending a paper to her as a thank-offering1 ,i thought of my first instructress1 and such like thoughts will remain with me4 ',i have some such thoughts even as regards your own father2 who was1 ,i may say1 the first who personally at ,geneva1 and afterwards by correspondence1 encouraged1 and by that sustained me4' ,twelve or thirteen years ago ,mr4 ,faraday and myself quitted the ,institution one evening together1 to pay a visit to our friend ,grove in ,baker ,street4 ,he took my arm at the door1 and1 pressing it to his side in his warm genial way1 said1 ',come1 ,tyndall1 ,i will now show you something that will interest you4' ,we walked northwards1 passed the house of ,mr4 ,babbage1 which drew forth a reference to the famous evening parties once assembled there4 ,we reached ,blandford ,street1 and after a little looking about he paused before a stationer's shop1 and then went in4 ,on entering the shop1 his usual animation seemed doubled2 he looked rapidly at everything it contained4 ,to the left on entering was a door1 through which he looked down into a little room1 with a window in front facing ,blandford ,street4 ,drawing me towards him1 he said eagerly1 ',look there1 ,tyndall1 that was my working-place4 ,i bound books in that little nook4' ,a respectable-looking woman stood behind the counter3 his conversation with me was too low to be heard by her1 and he now turned to the counter to buy some cards as an excuse for our being there4 ,he asked the woman her name--her predecessor's name--his predecessor's name4 ',that won't do1' he said1 with good-humoured impatience2 'who was his predecessor8' ',mr4 ,riebau1' she replied1 and immediately added1 as if suddenly recollecting herself1 ',he1 sir1 was the master of ,sir ,charles ,faraday4' ',nonsense6' he responded1 'there is no such person4' ,great was her delight when ,i told her the name of her visitor2 but she assured me that as soon as she saw him running about the shop1 she felt-though she did not know why--that it must be ',sir ,charles ,faraday4' ,faraday did1 as you know1 accompany ,davy to ,rome3 he was re-engaged by the managers of the ,royal ,institution on ,may #ae1 #ahae4 ,here he made rapid progress in chemistry1 and after a time was entrusted with easy analyses by ,davy4 ,in those days the ,royal ,institution published ',the ,quarterly ,journal of ,science1' the precursor of our own ',proceedings4' ,faraday's first contribution to science appeared in that journal in #ahaf4 ,it was an analysis of some caustic lime from ,tuscany1 which had been sent to ,davy by the ,duchess of ,montrose4 ,between this period and #ahah various notes and short papers were published by ,faraday4 ,in #ahah he experimented upon ',sounding ,flames4' ,professor ,auguste ,de la ,rive had investigated those sounding flames1 and had applied to them an explanation which completely accounted for a class of sounds discovered by himself1 but did not account for those known to his predecessors4 ,by a few simple and conclusive experiments1 ,faraday proved the explanation insufficient4 ,it is an epoch in the life of a young man when he finds himself correcting a person of eminence1 and in ,faraday's case1 where its effect was to develop a modest self-trust1 such an event could not fail to act profitably4 ,from time to time between #ahah and #ahbj ,faraday published scientific notes and notices of minor weight4 ,at this time he was acquiring1 not producing2 working hard for his master and storing and strengthening his own mind4 ,he assisted ,mr4 ,brande in his lectures1 and so quietly1 skilfully1 and modestly was his work done1 that ,mr4 ,brande's vocation at the time was pronounced 'lecturing on velvet4' ,in #ahbj ,faraday published a chemical paper 'on two new compounds of chlorine and carbon1 and on a new compound of iodine1 carbon1 and hydrogen4' ,this paper was read before the ,royal ,society on ,december #ba1 #ahbj1 and it was the first of his that was honoured with a place in the ',philosophical ,transactions4' ,on ,june #ab1 #ahba1 he married1 and obtained leave to bring his young wife into his rooms at the ,royal ,institution4 ,there for forty-six years they lived together1 occupying the suite of apartments which had been previously in the successive occupancy of ,young1 ,davy1 and ,brande4 ,at the time of her marriage ,mrs4 ,faraday was twenty-one years of age1 he being nearly thirty4 ,regarding this marriage ,i will at present limit myself to quoting an entry written in ,faraday's own hand in his book of diplomas1 which caught my eye while in his company some years ago4 ,it ran thus3-- '#beth ,january1 #ahdg4 ',amongst these records and events1 ,i here insert the date of one which1 as a source of honour and happiness1 far exceeds all the rest4 ,we were married on ,june #ab1 #ahba4 ',m4 ,faraday4' ,then follows the copy of the minutes1 dated ,may #ba1 #ahba1 which gave him additional rooms1 and thus enabled him to bring his wife to the ,royal ,institution4 ,a feature of ,faraday's character which ,i have often noticed makes itself apparent in this entry4 ,in his relations to his wife he added chivalry to affection4 ,footnotes to ,chapter #a #a ,here is ,davy's recommendation of ,faraday1 presented to the managers of the ,royal ,institution1 at a meeting on the #ahth of ,march1 #ahac1 ,charles ,hatchett1 ,esq41 in the chair3-- ',sir ,humphry ,davy has the honour to inform the managers that he has found a person who is desirous to occupy the situation in the ,institution lately filled by ,william ,payne4 ,his name is ,michael ,faraday4 ,he is a youth of twenty-two years of age4 ,as far as ,sir ,h4 ,davy has been able to observe or ascertain1 he appears well fitted for the situation4 ,his habits seem good2 his disposition active and cheerful1 and his manner intelligent4 ,he is willing to engage himself on the same terms as given to ,mr4 ,payne at the time of quitting the ,institution4 ',resolved1--,that ,michael ,faraday be engaged to fill the situation lately occupied by ,mr4 ,payne1 on the same terms4' #b ,faraday loved this word and employed it to the last2 he had an intense dislike to the modern term physicist4 #c ,to whom ,i am indebted for a copy of the original letter4 ,chapter #b4 ,early researches3 magnetic rotations3 liquefaction of gases3 heavy glass3 ,charles ,anderson3 contributions to physics4 ,oersted1 in #ahbj1 discovered the action of a voltaic current on a magnetic needle2 and immediately afterwards the splendid intellect of ,ampere succeeded in showing that every magnetic phenomenon then known might be reduced to the mutual action of electric currents4 ,the subject occupied all men's thoughts3 and in this country ,dr4 ,wollaston sought to convert the deflection of the needle by the current into a permanent rotation of the needle round the current4 ,he also hoped to produce the reciprocal effect of causing a current to rotate round a magnet4 ,in the early part of #ahba1 ,wollaston attempted to realise this idea in the presence of ,sir ,humphry ,davy in the laboratory of the ,royal ,institution4#a ,this was well calculated to attract ,faraday's attention to the subject4 ,he read much about it2 and in the months of ,july1 ,august1 and ,september he wrote a 'history of the progress of electro-magnetism1' which he published in ,thomson's ',annals of ,philosophy4' ,soon afterwards he took up the subject of ',magnetic ,rotations1' and on the morning of ,christmas-day1 #ahba1 he called his wife to witness1 for the first time1 the revolution of a magnetic needle round an electric current4 ,incidental to the 'historic sketch1' he repeated almost all the experiments there referred to2 and these1 added to his own subsequent work1 made him practical master of all that was then known regarding the voltaic current4 ,in #ahba1 he also touched upon a subject which subsequently received his closer attention--the vaporization of mercury at common temperatures2 and immediately afterwards conducted1 in company with ,mr4 ,stodart1 experiments on the alloys of steel4 ,he was accustomed in after years to present to his friends razors formed from one of the alloys then discovered4 ,during ,faraday's hours of liberty from other duties1 he took up subjects of inquiry for himself2 and in the spring of #ahbc1 thus self-prompted1 he began the examination of a substance which had long been regarded as the chemical element chlorine1 in a solid form1 but which ,sir ,humphry ,davy1 in #ahaj1 had proved to be a hydrate of chlorine1 that is1 a compound of chlorine and water4 ,faraday first analysed this hydrate1 and wrote out an account of its composition4 ,this account was looked over by ,davy1 who suggested the heating of the hydrate under pressure in a sealed glass tube4 ,this was done4 ,the hydrate fused at a blood-heat1 the tube became filled with a yellow atmosphere1 and was afterwards found to contain two liquid substances4 ,dr4 ,paris happened to enter the laboratory while ,faraday was at work4 ,seeing the oily liquid in his tube1 he rallied the young chemist for his carelessness in employing soiled vessels4 ,on filing off the end of the tube1 its contents exploded and the oily matter vanished4 ,early next morning1 ,dr4 ,paris received the following note3-- ',dear ,sir1--,the oil you noticed yesterday turns out to be liquid chlorine4 ',yours faithfully1 ',m4 ,faraday4'#b ,the gas had been liquefied by its own pressure4 ,faraday then tried compression with a syringe1 and succeeded thus in liquefying the gas4 ,to the published account of this experiment ,davy added the following note3--',in desiring ,mr4 ,faraday to expose the hydrate of chlorine in a closed glass tube1 it occurred to me that one of three things would happen3 that decomposition of water would occur2444 or that the chlorine would separate in a fluid state4' ,davy1 moreover1 immediately applied the method of self-compressing atmosphere to the liquefaction of muriatic gas4 ,faraday continued the experiments1 and succeeded in reducing a number of gases till then deemed permanent to the liquid condition4 ,in #ahdd he returned to the subject1 and considerably expanded its limits4 ,these important investigations established the fact that gases are but the vapours of liquids possessing a very low boiling-point1 and gave a sure basis to our views of molecular aggregation4 ,the account of the first investigation was read before the ,royal ,society on ,april #aj1 #ahbc1 and was published1 in ,faraday's name1 in the ',philosophical ,transactions4' ,the second memoir was sent to the ,royal ,society on ,december #ai1 #ahdd4 ,i may add that while he was conducting his first experiments on the liquefaction of gases1 thirteen pieces of glass were on one occasion driven by an explosion into ,faraday's eye4 ,some small notices and papers1 including the observation that glass readily changes colour in sunlight1 follow here4 ,in #ahbe and #ahbf ,faraday published papers in the ',philosophical ,transactions' on 'new compounds of carbon and hydrogen1' and on 'sulphonaphthalic acid4' ,in the former of these papers he announced the discovery of ,benzol1 which1 in the hands of modern chemists1 has become the foundation of our splendid aniline dyes4 ,but he swerved incessantly from chemistry into physics2 and in #ahbf we find him engaged in investigating the limits of vaporization1 and showing1 by exceedingly strong and apparently conclusive arguments1 that even in the case of mercury such a limit exists2 much more he conceived it to be certain that our atmosphere does not contain the vapour of the fixed constituents of the earth's crust4 ,this question1 ,i may say1 is likely to remain an open one4 ,dr4 ,rankine1 for example1 has lately drawn attention to the odour of certain metals2 whence comes this odour1 if it be not from the vapour of the metal8 ,in #ahbe ,faraday became a member of a committee1 to which ,sir ,john ,herschel and ,mr4 ,dollond also belonged1 appointed by the ,royal ,society to examine1 and if possible improve1 the manufacture of glass for optical purposes4 ,their experiments continued till #ahbi1 when the account of them constituted the subject of a ',bakerian ,lecture4' ,this lectureship1 founded in #aggd by ,henry ,baker1 ,esq41 of the ,strand1 ,london1 provides that every year a lecture shall be given before the ,royal ,society1 the sum of four pounds being paid to the lecturer4 ,the ,bakerian ,lecture1 however1 has long since passed from the region of pay to that of honour1 papers of mark only being chosen for it by the council of the ,society4 ,faraday's first ,bakerian ,lecture1 ',on the ,manufacture of ,glass for ,optical ,purposes1' was delivered at the close of #ahbi4 ,it is a most elaborate and conscientious description of processes1 precautions1 and results3 the details were so exact and so minute1 and the paper consequently so long1 that three successive sittings of the ,royal ,society were taken up by the delivery of the lecture4#c ,this glass did not turn out to be of important practical use1 but it happened afterwards to be the foundation of two of ,faraday's greatest discoveries4#d ,the experiments here referred to were commenced at the ,falcon ,glass ,works1 on the premises of ,messrs4 ,green and ,pellatt1 but ,faraday could not conveniently attend to them there4 ,in #ahbg1 therefore1 a furnace was erected in the yard of the ,royal ,institution2 and it was at this time1 and with a view of assisting him at the furnace1 that ,faraday engaged ,sergeant ,anderson1 of the ,royal ,artillery1 the respectable1 truthful1 and altogether trustworthy man whose appearance here is so fresh in our memories4 ,anderson continued to be the reverential helper of ,faraday and the faithful servant of this ,institution for nearly forty years4#e ,in #ahca ,faraday published a paper1 ',on a peculiar class of ,optical ,deceptions1' to which ,i believe the beautiful optical toy called the ,chromatrope owes its origin4 ,in the same year he published a paper on ,vibrating ,surfaces1 in which he solved an acoustical problem which1 though of extreme simplicity when solved1 appears to have baffled many eminent men4 ,the problem was to account for the fact that light bodies1 such as the seed of lycopodium1 collected at the vibrating parts of sounding plates1 while sand ran to the nodal lines4 ,faraday showed that the light bodies were entangled in the little whirlwinds formed in the air over the places of vibration1 and through which the heavier sand was readily projected4 ,faraday's resources as an experimentalist were so wonderful1 and his delight in experiment was so great1 that he sometimes almost ran into excess in this direction4 ,i have heard him say that this paper on vibrating surfaces was too heavily laden with experiments4 ,footnotes to ,chapter #b #a ,the reader's attention is directed to the concluding paragraph of the ',preface to the ,second ,edition written in ,december1 #ahfi4 ,also to the ,life of ,faraday by ,dr4 ,bence ,jones1 vol4 i4 p4 #cch et seq4 #b ,paris3 ,life of ,davy1 p4 #cia4 #c ,viz41 ,november #ai1 ,december #c and #aj4 #d ,i make the following extract from a letter from ,sir ,john ,herschel1 written to me from ,collingwood1 on the #crd of ,november1 #ahfg3--';,i will take this opportunity to mention that ,i believe myself to have originated the suggestion of the employment of borate of lead for optical purposes4 ,it was somewhere in the year #ahbb1 as well as ,i can recollect1 that ,i mentioned it to ,sir ,james 7then ,mr47 ,south2 and1 in consequence1 the trial was made in his laboratory in ,blackman ,street1 by precipitating and working a large quantity of borate of lead1 and fusing it under a muffle in a porcelain evaporating dish4 ,a very limpid 7though slightly yellow7 glass resulted1 the refractive index #a4hff6 7which you will find set down in my table of refractive indices in my article ,light1 ,encyclopaedia ,metropolitana74 ,it was1 however1 too soft for optical use as an object- glass4 ,this ,faraday overcame1 at least to a considerable degree1 by the introduction of silica4' #e ,regarding ,anderson1 ,faraday writes thus in #ahde3--';,i cannot resist the occasion that is thus offered to me of mentioning the name of ,mr4 ,anderson1 who came to me as an assistant in the glass experiments1 and has remained ever since in the laboratory of the ,royal ,institution4 ,he assisted me in all the researches into which ,i have entered since that time2 and to his care1 steadiness1 exactitude1 and faithfulness in the performance of all that has been committed to his charge1 ,i am much indebted4--,m4 ,f4' 7,exp4 ,researches1 vol4 iii4 p4 #c1 footnote47 ,chapter #c4 ,discovery of ,magneto-electricity3 ,explanation of ,argo's magnetism of rotation3 ,terrestrial magneto-electric induction3 ,the extra current4 ,the work thus referred to1 though sufficient of itself to secure no mean scientific reputation1 forms but the vestibule of ,faraday's achievements4 ,he had been engaged within these walls for eighteen years4 ,during part of the time he had drunk in knowledge from ,davy1 and during the remainder he continually exercised his capacity for independent inquiry4 ,in #ahca we have him at the climax of his intellectual strength1 forty years of age1 stored with knowledge and full of original power4 ,through reading1 lecturing1 and experimenting1 he had become thoroughly familiar with electrical science3 he saw where light was needed and expansion possible4 ,the phenomena of ordinary electric induction belonged1 as it were1 to the alphabet of his knowledge3 he knew that under ordinary circumstances the presence of an electrified body was sufficient to excite1 by induction1 an unelectrified body4 ,he knew that the wire which carried an electric current was an electrified body1 and still that all attempts had failed to make it excite in other wires a state similar to its own4 ,what was the reason of this failure8 ,faraday never could work from the experiments of others1 however clearly described4 ,he knew well that from every experiment issues a kind of radiation1 luminous in different degrees to different minds1 and he hardly trusted himself to reason upon an experiment that he had not seen4 ,in the autumn of #ahca he began to repeat the experiments with electric currents1 which1 up to that time1 had produced no positive result4 ,and here1 for the sake of younger inquirers1 if not for the sake of us all1 it is worth while to dwell for a moment on a power which ,faraday possessed in an extraordinary degree4 ,he united vast strength with perfect flexibility4 ,his momentum was that of a river1 which combines weight and directness with the ability to yield to the flexures of its bed4 ,the intentness of his vision in any direction did not apparently diminish his power of perception in other directions2 and when he attacked a subject1 expecting results he had the faculty of keeping his mind alert1 so that results different from those which he expected should not escape him through preoccupation4 ,he began his experiments 'on the induction of electric currents' by composing a helix of two insulated wires which were wound side by side round the same wooden cylinder4 ,one of these wires he connected with a voltaic battery of ten cells1 and the other with a sensitive galvanometer4 ,when connection with the battery was made1 and while the current flowed1 no effect whatever was observed at the galvanometer4 ,but he never accepted an experimental result1 until he had applied to it the utmost power at his command4 ,he raised his battery from #aj cells to #abj cells1 but without avail4 ,the current flowed calmly through the battery wire without producing1 during its flow1 any sensible result upon the galvanometer4 ',during its flow1' and this was the time when an effect was expected--but here ,faraday's power of lateral vision1 separating1 as it were1 from the line of expectation1 came into play--he noticed that a feeble movement of the needle always occurred at the moment when he made contact with the battery2 that the needle would afterwards return to its former position and remain quietly there unaffected by the flowing current4 ,at the moment1 however1 when the circuit was interrupted the needle again moved1 and in a direction opposed to that observed on the completion of the circuit4 ,this result1 and others of a similar kind1 led him to the conclusion 'that the battery current through the one wire did in reality induce a similar current through the other2 but that it continued for an instant only1 and partook more of the nature of the electric wave from a common ,leyden jar than of the current from a voltaic battery4' ,the momentary currents thus generated were called induced currents1 while the current which generated them was called the inducing current4 ,it was immediately proved that the current generated at making the circuit was always opposed in direction to its generator1 while that developed on the rupture of the circuit coincided in direction with the inducing current4 ,it appeared as if the current on its first rush through the primary wire sought a purchase in the secondary one1 and1 by a kind of kick1 impelled backward through the latter an electric wave1 which subsided as soon as the primary current was fully established4 ,faraday1 for a time1 believed that the secondary wire1 though quiescent when the primary current had been once established1 was not in its natural condition1 its return to that condition being declared by the current observed at breaking the circuit4 ,he called this hypothetical state of the wire the electro-tonic state3 he afterwards abandoned this hypothesis1 but seemed to return to it in later life4 ,the term electro-tonic is also preserved by ,professor ,du ,bois ,reymond to express a certain electric condition of the nerves1 and ,professor ,clerk ,maxwell has ably defined and illustrated the hypothesis in the ,tenth ,volume of the ',transactions of the ,cambridge ,philosophical ,society4' ,the mere approach of a wire forming a closed curve to a second wire through which a voltaic current flowed was then shown by ,faraday to be sufficient to arouse in the neutral wire an induced current1 opposed in direction to the inducing current2 the withdrawal of the wire also generated a current having the same direction as the inducing current2 those currents existed only during the time of approach or withdrawal1 and when neither the primary nor the secondary wire was in motion1 no matter how close their proximity might be1 no induced current was generated4 ,faraday has been called a purely inductive philosopher4 ,a great deal of nonsense is1 ,i fear1 uttered in this land of ,england about induction and deduction4 ,some profess to befriend the one1 some the other1 while the real vocation of an investigator1 like ,faraday1 consists in the incessant marriage of both4 ,he was at this time full of the theory of ,ampere1 and it cannot be doubted that numbers of his experiments were executed merely to test his deductions from that theory4 ,starting from the discovery of ,oersted1 the illustrious ,french philosopher had shown that all the phenomena of magnetism then known might be reduced to the mutual attractions and repulsions of electric currents4 ,magnetism had been produced from electricity1 and ,faraday1 who all his life long entertained a strong belief in such reciprocal actions1 now attempted to effect the evolution of electricity from magnetism4 ,round a welded iron ring he placed two distinct coils of covered wire1 causing the coils to occupy opposite halves of the ring4 ,connecting the ends of one of the coils with a galvanometer1 he found that the moment the ring was magnetised1 by sending a current through the other coil1 the galvanometer needle whirled round four or five times in succession4 ,the action1 as before1 was that of a pulse1 which vanished immediately4 ,on interrupting the circuit1 a whirl of the needle in the opposite direction occurred4 ,it was only during the time of magnetization or demagnetization that these effects were produced4 ,the induced currents declared a change of condition only1 and they vanished the moment the act of magnetization or demagnetization was complete4 ,the effects obtained with the welded ring were also obtained with straight bars of iron4 ,whether the bars were magnetised by the electric current1 or were excited by the contact of permanent steel magnets1 induced currents were always generated during the rise1 and during the subsidence of the magnetism4 ,the use of iron was then abandoned1 and the same effects were obtained by merely thrusting a permanent steel magnet into a coil of wire4 ,a rush of electricity through the coil accompanied the insertion of the magnet2 an equal rush in the opposite direction accompanied its withdrawal4 ,the precision with which ,faraday describes these results1 and the completeness with which he defines the boundaries of his facts1 are wonderful4 ,the magnet1 for example1 must not be passed quite through the coil1 but only half through2 for if passed wholly through1 the needle is stopped as by a blow1 and then he shows how this blow results from a reversal of the electric wave in the helix4 ,he next operated with the powerful permanent magnet of the ,royal ,society1 and obtained with it1 in an exalted degree1 all the foregoing phenomena4 ,and now he turned the light of these discoveries upon the darkest physical phenomenon of that day4 ,arago had discovered1 in #ahbd1 that a disk of non-magnetic metal had the power of bringing a vibrating magnetic needle suspended over it rapidly to rest2 and that on causing the disk to rotate the magnetic needle rotated along with it4 ,when both were quiescent1 there was not the slightest measurable attraction or repulsion exerted between the needle and the disk2 still when in motion the disk was competent to drag after it1 not only a light needle1 but a heavy magnet4 ,the question had been probed and investigated with admirable skill both by ,arago and ,ampere1 and ,poisson had published a theoretic memoir on the subject2 but no cause could be assigned for so extraordinary an action4 ,it had also been examined in this country by two celebrated men1 ,mr4 ,babbage and ,sir ,john ,herschel2 but it still remained a mystery4 ,faraday always recommended the suspension of judgment in cases of doubt4 ',i have always admired1' he says1 'the prudence and philosophical reserve shown by ,m4 ,arago in resisting the temptation to give a theory of the effect he had discovered1 so long as he could not devise one which was perfect in its application1 and in refusing to assent to the imperfect theories of others4' ,now1 however1 the time for theory had come4 ,faraday saw mentally the rotating disk1 under the operation of the magnet1 flooded with his induced currents1 and from the known laws of interaction between currents and magnets he hoped to deduce the motion observed by ,arago4 ,that hope he realised1 showing by actual experiment that when his disk rotated currents passed through it1 their position and direction being such as must1 in accordance with the established laws of electro-magnetic action1 produce the observed rotation4 ,introducing the edge of his disk between the poles of the large horseshoe magnet of the ,royal ,society1 and connecting the axis and the edge of the disk1 each by a wire with a galvanometer1 he obtained1 when the disk was turned round1 a constant flow of electricity4 ,the direction of the current was determined by the direction of the motion1 the current being reversed when the rotation was reversed4 ,he now states the law which rules the production of currents in both disks and wires1 and in so doing uses1 for the first time1 a phrase which has since become famous4 ,when iron filings are scattered over a magnet1 the particles of iron arrange themselves in certain determinate lines called magnetic curves4 ,in #ahca1 ,faraday for the first time called these curves 'lines of magnetic force'2 and he showed that to produce induced currents neither approach to nor withdrawal from a magnetic source1 or centre1 or pole1 was essential1 but that it was only necessary to cut appropriately the lines of magnetic force4 ,faraday's first paper on ,magneto-electric ,induction1 which ,i have here endeavoured to condense1 was read before the ,royal ,society on the #bdth of ,november1 #ahca4 ,on ,january #ab1 #ahcb1 he communicated to the ,royal ,society a second paper on ,terrestrial ,magneto-electric ,induction1 which was chosen as the ,bakerian ,lecture for the year4 ,he placed a bar of iron in a coil of wire1 and lifting the bar into the direction of the dipping needle1 he excited by this action a current in the coil4 ,on reversing the bar1 a current in the opposite direction rushed through the wire4 ,the same effect was produced when1 on holding the helix in the line of dip1 a bar of iron was thrust into it4 ,here1 however1 the earth acted on the coil through the intermediation of the bar of iron4 ,he abandoned the bar and simply set a copper plate spinning in a horizontal plane2 he knew that the earth's lines of magnetic force then crossed the plate at an angle of about #gj;degrees4 ,when the plate spun round1 the lines of force were intersected and induced currents generated1 which produced their proper effect when carried from the plate to the galvanometer4 ',when the plate was in the magnetic meridian1 or in any other plane coinciding with the magnetic dip1 then its rotation produced no effect upon the galvanometer4' ,at the suggestion of a mind fruitful in suggestions of a profound and philosophic character--,i mean that of ,sir ,john ,herschel--,mr4 ,barlow1 of ,woolwich1 had experimented with a rotating iron shell4 ,mr4 ,christie had also performed an elaborate series of experiments on a rotating iron disk4 ,both of them had found that when in rotation the body exercised a peculiar action upon the magnetic needle1 deflecting it in a manner which was not observed during quiescence2 but neither of them was aware at the time of the agent which produced this extraordinary deflection4 ,they ascribed it to some change in the magnetism of the iron shell and disk4 ,but ,faraday at once saw that his induced currents must come into play here1 and he immediately obtained them from an iron disk4 ,with a hollow brass ball1 moreover1 he produced the effects obtained by ,mr4 ,barlow4 ,iron was in no way necessary3 the only condition of success was that the rotating body should be of a character to admit of the formation of currents in its substance3 it must1 in other words1 be a conductor of electricity4 ,the higher the conducting power the more copious were the currents4 ,he now passes from his little brass globe to the globe of the earth4 ,he plays like a magician with the earth's magnetism4 ,he sees the invisible lines along which its magnetic action is exerted1 and sweeping his wand across these lines evokes this new power4 ,placing a simple loop of wire round a magnetic needle he bends its upper portion to the west3 the north pole of the needle immediately swerves to the east3 he bends his loop to the east1 and the north pole moves to the west4 ,suspending a common bar magnet in a vertical position1 he causes it to spin round its own axis4 ,its pole being connected with one end of a galvanometer wire1 and its equator with the other end1 electricity rushes round the galvanometer from the rotating magnet4 ,he remarks upon the 'singular independence' of the magnetism and the body of the magnet which carries it4 ,the steel behaves as if it were isolated from its own magnetism4 ,and then his thoughts suddenly widen1 and he asks himself whether the rotating earth does not generate induced currents as it turns round its axis from west to east4 ,in his experiment with the twirling magnet the galvanometer wire remained at rest2 one portion of the circuit was in motion relatively to another portion4 ,but in the case of the twirling planet the galvanometer wire would necessarily be carried along with the earth2 there would be no relative motion4 ,what must be the consequence8 ,take the case of a telegraph wire with its two terminal plates dipped into the earth1 and suppose the wire to lie in the magnetic meridian4 ,the ground underneath the wire is influenced like the wire itself by the earth's rotation2 if a current from south to north be generated in the wire1 a similar current from south to north would be generated in the earth under the wire2 these currents would run against the same terminal plate1 and thus neutralise each other4 ,this inference appears inevitable1 but his profound vision perceived its possible invalidity4 ,he saw that it was at least possible that the difference of conducting power between the earth and the wire might give one an advantage over the other1 and that thus a residual or differential current might be obtained4 ,he combined wires of different materials1 and caused them to act in opposition to each other1 but found the combination ineffectual4 ,the more copious flow in the better conductor was exactly counterbalanced by the resistance of the worse4 ,still1 though experiment was thus emphatic1 he would clear his mind of all discomfort by operating on the earth itself4 ,he went to the round lake near ,kensington ,palace1 and stretched #dhj feet of copper wire1 north and south1 over the lake1 causing plates soldered to the wire at its ends to dip into the water4 ,the copper wire was severed at the middle1 and the severed ends connected with a galvanometer4 ,no effect whatever was observed4 ,but though quiescent water gave no effect1 moving water might4 ,he therefore worked at ,london ,bridge for three days during the ebb and flow of the tide1 but without any satisfactory result4 ,still he urges1 ',theoretically it seems a necessary consequence1 that where water is flowing there electric currents should be formed4 ,if a line be imagined passing from ,dover to ,calais through the sea1 and returning through the land1 beneath the water1 to ,dover1 it traces out a circuit of conducting matter one part of which1 when the water moves up or down the channel1 is cutting the magnetic curves of the earth1 whilst the other is relatively at rest4444 ,there is every reason to believe that currents do run in the general direction of the circuit described1 either one way or the other1 according as the passage of the waters is up or down the channel4' ,this was written before the submarine cable was thought of1 and he once informed me that actual observation upon that cable had been found to be in accordance with his theoretic deduction4#a ,three years subsequent to the publication of these researches--that is to say1 on ,january #bi1 #ahce--;,faraday read before the ,royal ,society a paper ',on the influence by induction of an electric current upon itself4' ,a shock and spark of a peculiar character had been observed by a young man named ,william ,jenkin1 who must have been a youth of some scientific promise1 but who1 as ,faraday once informed me1 was dissuaded by his own father from having anything to do with science4 ,the investigation of the fact noticed by ,mr4 ,jenkin led ,faraday to the discovery of the extra current1 or the current induced in the primary wire itself at the moments of making and breaking contact1 the phenomena of which he described and illustrated in the beautiful and exhaustive paper referred to4 ,seven-and-thirty years have passed since the discovery of magneto-electricity2 but1 if we except the extra current1 until quite recently nothing of moment was added to the subject4 ,faraday entertained the opinion that the discoverer of a great law or principle had a right to the 'spoils'--this was his term--arising from its illustration2 and guided by the principle he had discovered1 his wonderful mind1 aided by his wonderful ten fingers1 overran in a single autumn this vast domain1 and hardly left behind him the shred of a fact to be gathered by his successors4 ,and here the question may arise in some minds1 ,what is the use of it all8 ,the answer is1 that if man's intellectual nature thirsts for knowledge1 then knowledge is useful because it satisfies this thirst4 ,if you demand practical ends1 you must1 ,i think1 expand your definition of the term practical1 and make it include all that elevates and enlightens the intellect1 as well as all that ministers to the bodily health and comfort of men4 ,still1 if needed1 an answer of another kind might be given to the question ',what is its use8' ,as far as electricity has been applied for medical purposes1 it has been almost exclusively ,faraday's electricity4 ,you have noticed those lines of wire which cross the streets of ,london4 ,it is ,faraday's currents that speed from place to place through these wires4 ,approaching the point of ,dungeness1 the mariner sees an unusually brilliant light1 and from the noble phares of ,la ,heve the same light flashes across the sea4 ,these are ,faraday's sparks exalted by suitable machinery to sunlike splendour4 ,at the present moment the ,board of ,trade and the ,brethren of the ,trinity ,house1 as well as the ,commissioners of ,northern ,lights1 are contemplating the introduction of the ,magneto-electric ,light at numerous points upon our coasts2 and future generations will be able to refer to those guiding stars in answer to the question4 ,what has been the practical use of the labours of ,faraday8 ,but ,i would again emphatically say1 that his work needs no such justification1 and that if he had allowed his vision to be disturbed by considerations regarding the practical use of his discoveries1 those discoveries would never have been made by him4 ',i have rather1' he writes in #ahca1 'been desirous of discovering new facts and new relations dependent on magneto-electric induction1 than of exalting the force of those already obtained2 being assured that the latter would find their full development hereafter4' ,in #ahag1 when lecturing before a private society in ,london on the element chlorine1 ,faraday thus expressed himself with reference to this question of utility4 ',before leaving this subject1 ,i will point out the history of this substance1 as an answer to those who are in the habit of saying to every new fact4 ,what is its use8 ,dr4 ,franklin says to such1 ,what is the use of an infant8 ,the answer of the experimentalist is1 ,endeavour to make it useful4 ,when ,scheele discovered this substance1 it appeared to have no use2 it was in its infancy and useless state1 but having grown up to maturity1 witness its powers1 and see what endeavours to make it useful have done4' ,footnote to ,chapter #c #a ,i am indebted to a friend for the following exquisite morsel3--',a short time after the publication of ,faraday's first researches in magneto-electricity1 he attended the meeting of the ,british ,association at ,oxford1 in #ahcb4 ,on this occasion he was requested by some of the authorities to repeat the celebrated experiment of eliciting a spark from a magnet1 employing for this purpose the large magnet in the ,ashmolean ,museum4 ,to this he consented1 and a large party assembled to witness the experiments1 which1 ,i need not say1 were perfectly successful4 ,whilst he was repeating them a dignitary of the ,university entered the room1 and addressing himself to ,professor ,daniell1 who was standing near ,faraday1 inquired what was going on4 ,the ,professor explained to him as popularly as possible this striking result of ,faraday's great discovery4 ,the ,dean listened with attention and looked earnestly at the brilliant spark1 but a moment after he assumed a serious countenance and shook his head2 ,i am sorry for it1 said he1 as he walked away2 in the middle of the room he stopped for a moment and repeated1 ,i am sorry for it3 then walking towards the door1 when the handle was in his hand he turned round and said1 ,indeed ,i am sorry for it2 it is putting new arms into the hands of the incendiary4 ,this occurred a short time after the papers had been filled with the doings of the hayrick burners4 ,an erroneous statement of what fell from the ,dean's mouth was printed at the time in one of the ,oxford papers4 ,he is there wrongly stated to have said1 ,it is putting new arms into the hands of the infidel4' ,chapter #d4 ,points of ,character4 ,a point highly illustrative of the character of ,faraday now comes into view4 ,he gave an account of his discovery of ,magneto-electricity in a letter to his friend ,m4 ,hachette1 of ,paris1 who communicated the letter to the ,academy of ,sciences4 ,the letter was translated and published2 and immediately afterwards two distinguished ,italian philosophers took up the subject1 made numerous experiments1 and published their results before the complete memoirs of ,faraday had met the public eye4 ,this evidently irritated him4 ,he reprinted the paper of the learned ,italians in the ',philosophical ,magazine1' accompanied by sharp critical notes from himself4 ,he also wrote a letter dated ,dec4 #a1 #ahcb1 to ,gay ,lussac1 who was then one of the editors of the ',annales de ,chimie1' in which he analysed the results of the ,italian philosophers1 pointing out their errors1 and defending himself from what he regarded as imputations on his character4 ,the style of this letter is unexceptionable1 for ,faraday could not write otherwise than as a gentleman2 but the letter shows that had he willed it he could have hit hard4 ,we have heard much of ,faraday's gentleness and sweetness and tenderness4 ,it is all true1 but it is very incomplete4 ,you cannot resolve a powerful nature into these elements1 and ,faraday's character would have been less admirable than it was had it not embraced forces and tendencies to which the silky adjectives 'gentle' and 'tender' would by no means apply4 ,underneath his sweetness and gentleness was the heat of a volcano4 ,he was a man of excitable and fiery nature2 but through high self-discipline he had converted the fire into a central glow and motive power of life1 instead of permitting it to waste itself in useless passion4 ',he that is slow to anger1' saith the sage1 'is greater than the mighty1 and he that ruleth his own spirit than he that taketh a city4' ,faraday was not slow to anger1 but he completely ruled his own spirit1 and thus1 though he took no cities1 he captivated all hearts4 ,as already intimated1 ,faraday had contributed many of his minor papers--including his first analysis of caustic lime--to the ',quarterly ,journal of ,science4' ,in #ahcb1 he collected those papers and others together in a small octavo volume1 labelled them1 and prefaced them thus3-- ',,papers1 ,,notes1 ,,notices1 c41 c41published in octavo1 up to #ahcb4 ,m4 ,faraday4' ',papers of mine1 published in octavo1 in the ,quarterly ,journal of ,science1 and elsewhere1 since the time that ,sir ,h4 ,davy encouraged me to write the analysis of caustic lime4 ',some1 ,i think 7at this date71 are good2 others moderate2 and some bad4 ,but ,i have put all into the volume1 because of the utility they have been of to me--and none more than the bad--in pointing out to me in future1 or rather1 after times1 the faults it became me to watch and to avoid4 ',as ,i never looked over one of my papers a year after it was written without believing both in philosophy and manner it could have been much better done1 ,i still hope the collection may be of great use to me4 ',m4 ,faraday4 ',aug4 #ah1 #ahcb4' ',none more than the bad6' ,this is a bit of ,faraday's innermost nature2 and as ,i read these words ,i am almost constrained to retract what ,i have said regarding the fire and excitability of his character4 ,but is he not all the more admirable1 through his ability to tone down and subdue that fire and that excitability1 so as to render himself able to write thus as a little child8 ,i once took the liberty of censuring the conclusion of a letter of his to the ,dean of ,st4 ,paul's4 ,he subscribed himself 'humbly yours1' and ,i objected to the adverb4 ',well1 but1 ,tyndall1' he said1 ',i am humble2 and still it would be a great mistake to think that ,i am not also proud4' ,this duality ran through his character4 ,a democrat in his defiance of all authority which unfairly limited his freedom of thought1 and still ready to stoop in reverence to all that was really worthy of reverence1 in the customs of the world or the characters of men4 ,and here1 as well as elsewhere1 may be introduced a letter which bears upon this question of self-control1 written long years subsequent to the period at which we have now arrived4 ,i had been at ,glasgow in #ahee1 at a meeting of the ,british ,association4 ,on a certain day1 ,i communicated a paper to the physical section1 which was followed by a brisk discussion4 ,men of great distinction took part in it1 the late ,dr4 ,whewell among the number1 and it waxed warm on both sides4 ,i was by no means content with this discussion2 and least of all1 with my own part in it4 ,this discontent affected me for some days1 during which ,i wrote to ,faraday1 giving him no details1 but expressing1 in a general way1 my dissatisfaction4 ,i give the following extract from his reply3-- ',sydenham1 ,oct4 #f1 #ahee4 ',my ,dear ,tyndall1--,these great meetings1 of which ,i think very well altogether1 advance science chiefly by bringing scientific men together and making them to know and be friends with each other2 and ,i am sorry when that is not the effect in every part of their course4 ,i know nothing except from what you tell me1 for ,i have not yet looked at the reports of the proceedings2 but let me1 as an old man1 who ought by this time to have profited by experience1 say that when ,i was younger ,i found ,i often misinterpreted the intentions of people1 and found they did not mean what at the time ,i supposed they meant2 and1 further1 that as a general rule1 it was better to be a little dull of apprehension where phrases seemed to imply pique1 and quick in perception when1 on the contrary1 they seemed to imply kindly feeling4 ,the real truth never fails ultimately to appear2 and opposing parties1 if wrong1 are sooner convinced when replied to forbearingly1 than when overwhelmed4 ,all ,i mean to say is1 that it is better to be blind to the results of partisanship1 and quick to see good will4 ,one has more happiness in oneself in endeavouring to follow the things that make for peace4 ,you can hardly imagine how often ,i have been heated in private when opposed1 as ,i have thought1 unjustly and superciliously1 and yet ,i have striven1 and succeeded1 ,i hope1 in keeping down replies of the like kind4 ,and ,i know ,i have never lost by it4 ,i would not say all this to you did ,i not esteem you as a true philosopher and friend4#a ',yours1 very truly1 ',m4 ,faraday4' ,footnote to ,chapter #d #a ,faraday would have been rejoiced to learn that1 during its last meeting at ,dundee1 the ,british ,association illustrated in a striking manner the function which he here describes as its principal one4 ,in my own case1 a brotherly welcome was everywhere manifested4 ,in fact1 the differences of really honourable and sane men are never beyond healing4 ,chapter #e4 ,identity of electricities2 first researches on electro-chemistry4 ,i have already once used the word 'discomfort' in reference to the occasional state of ,faraday's mind when experimenting4 ,it was to him a discomfort to reason upon data which admitted of doubt4 ,he hated what he called 'doubtful knowledge1' and ever tended either to transfer it into the region of undoubtful knowledge1 or of certain and definite ignorance4 ,pretence of all kinds1 whether in life or in philosophy1 was hateful to him4 ,he wished to know the reality of our nescience as well as of our science4 ',be one thing or the other1' he seemed to say to an unproved hypothesis2 'come out as a solid truth1 or disappear as a convicted lie4' ,after making the great discovery which ,i have attempted to describe1 a doubt seemed to beset him as regards the identity of electricities4 ',is it right1' he seemed to ask1 'to call this agency which ,i have discovered electricity at all8 ,are there perfectly conclusive grounds for believing that the electricity of the machine1 the pile1 the gymnotus and torpedo1 magneto-electricity and thermo-electricity1 are merely different manifestations of one and the same agent8' ,to answer this question to his own satisfaction he formally reviewed the knowledge of that day4 ,he added to it new experiments of his own1 and finally decided in favour of the ',identity of ,electricities4' ,his paper upon this subject was read before the ,royal ,society on ,january #aj and #ag1 #ahcc4 ,after he had proved to his own satisfaction the identity of electricities1 he tried to compare them quantitatively together4 ,the terms quantity and intensity1 which ,faraday constantly used1 need a word of explanation here4 ,he might charge a single ,leyden jar by twenty turns of his machine1 or he might charge a battery of ten jars by the same number of turns4 ,the quantity in both cases would be sensibly the same1 but the intensity of the single jar would be the greatest1 for here the electricity would be less diffused4 ,faraday first satisfied himself that the needle of his galvanometer was caused to swing through the same arc by the same quantity of machine electricity1 whether it was condensed in a small battery or diffused over a large one4 ,thus the electricity developed by thirty turns of his machine produced1 under very variable conditions of battery surface1 the same deflection4 ,hence he inferred the possibility of comparing1 as regards quantity1 electricities which differ greatly from each other in intensity4 ,his object now is to compare frictional with voltaic electricity4 ,moistening bibulous paper with the iodide of potassium--a favourite test of his--and subjecting it to the action of machine electricity1 he decomposed the iodide1 and formed a brown spot where the iodine was liberated4 ,then he immersed two wires1 one of zinc1 the other of platinum1 each #a_/acth of an inch in diameter1 to a depth of #e_/hths of an inch in acidulated water during eight beats of his watch1 or #c_/bjths of a second2 and found that the needle of his galvanometer swung through the same arc1 and coloured his moistened paper to the same extent1 as thirty turns of his large electrical machine4 ,twenty-eight turns of the machine produced an effect distinctly less than that produced by his two wires4 ,now1 the quantity of water decomposed by the wires in this experiment totally eluded observation2 it was immeasurably small2 and still that amount of decomposition involved the development of a quantity of electric force which1 if applied in a proper form1 would kill a rat1 and no man would like to bear it4 ,in his subsequent researches ',on the absolute ,quantity of ,electricity associated with the ,particles or ,atoms of matter1' he endeavours to give an idea of the amount of electrical force involved in the decomposition of a single grain of water4 ,he is almost afraid to mention it1 for he estimates it at #hjj1jjj discharges of his large ,leyden battery4 ,this1 if concentrated in a single discharge1 would be equal to a very great flash of lightning2 while the chemical action of a single grain of water on four grains of zinc would yield electricity equal in quantity to a powerful thunderstorm4 ,thus his mind rises from the minute to the vast1 expanding involuntarily from the smallest laboratory fact till it embraces the largest and grandest natural phenomena4#a ,in reality1 however1 he is at this time only clearing his way1 and he continues laboriously to clear it for some time afterwards4 ,he is digging the shaft1 guided by that instinct towards the mineral lode which was to him a rod of divination4 ',er riecht die ,wahrheit1' said the lamented ,kohlrausch1 an eminent ,german1 once in my hearing3--',he smells the truth4' ,his eyes are now steadily fixed on this wonderful voltaic current1 and he must learn more of its mode of transmission4 ,on ,may #bc1 #ahcc1 he read a paper before the ,royal ,society ',on a new ,law of ,electric ,conduction4' ,he found that1 though the current passed through water1 it did not pass through ice3--why not1 since they are one and the same substance8 ,some years subsequently he answered this question by saying that the liquid condition enables the molecule of water to turn round so as to place itself in the proper line of polarization1 while the rigidity of the solid condition prevents this arrangement4 ,this polar arrangement must precede decomposition1 and decomposition is an accompaniment of conduction4 ,he then passed on to other substances2 to oxides and chlorides1 and iodides1 and salts1 and sulphurets1 and found them all insulators when solid1 and conductors when fused4 ,in all cases1 moreover1 except one--and this exception he thought might be apparent only--he found the passage of the current across the fused compound to be accompanied by its decomposition4 ,is then the act of decomposition essential to the act of conduction in these bodies8 ,even recently this question was warmly contested4 ,faraday was very cautious latterly in expressing himself upon this subject2 but as a matter of fact he held that an infinitesimal quantity of electricity might pass through a compound liquid without producing its decomposition4 ,de la ,rive1 who has been a great worker on the chemical phenomena of the pile1 is very emphatic on the other side4 ,experiment1 according to him and others1 establishes in the most conclusive manner that no trace of electricity can pass through a liquid compound without producing its equivalent decomposition4#b ,faraday has now got fairly entangled amid the chemical phenomena of the pile1 and here his previous training under ,davy must have been of the most important service to him4 ,why1 he asks1 should decomposition thus take place8--what force is it that wrenches the locked constituents of these compounds asunder8 ,on the #bjth of ,june1 #ahcc1 he read a paper before the ,royal ,society ',on ,electro-chemical ,decomposition1' in which he seeks to answer these questions4 ,the notion had been entertained that the poles1 as they are called1 of the decomposing cell1 or in other words the surfaces by which the current enters and quits the liquid1 exercised electric attractions upon the constituents of the liquid and tore them asunder4 ,faraday combats this notion with extreme vigour4 ,litmus reveals1 as you know1 the action of an acid by turning red1 turmeric reveals the action of an alkali by turning brown4 ,sulphate of soda1 you know1 is a salt compounded of the alkali soda and sulphuric acid4 ,the voltaic current passing through a solution of this salt so decomposes it1 that sulphuric acid appears at one pole of the decomposing cell and alkali at the other4 ,faraday steeped a piece of litmus paper and a piece of turmeric paper in a solution of sulphate of soda3 placing each of them upon a separate plate of glass1 he connected them together by means of a string moistened with the same solution4 ,he then attached one of them to the positive conductor of an electric machine1 and the other to the gas-pipes of this building4 ,these he called his 'discharging train4' ,on turning the machine the electricity passed from paper to paper through the string1 which might be varied in length from a few inches to seventy feet without changing the result4 ,the first paper was reddened1 declaring the presence of sulphuric acid2 the second was browned1 declaring the presence of the alkali soda4 ,the dissolved salt1 therefore1 arranged in this fashion1 was decomposed by the machine1 exactly as it would have been by the voltaic current4 ,when instead of using the positive conductor he used the negative1 the positions of the acid and alkali were reversed4 ,thus he satisfied himself that chemical decomposition by the machine is obedient to the laws which rule decomposition by the pile4 ,and now he gradually abolishes those so-called poles1 to the attraction of which electric decomposition had been ascribed4 ,he connected a piece of turmeric paper moistened with the sulphate of soda with the positive conductor of his machine2 then he placed a metallic point in connection with his discharging train opposite the moist paper1 so that the electricity should discharge through the air towards the point4 ,the turning of the machine caused the corners of the piece of turmeric paper opposite to the point to turn brown1 thus declaring the presence of alkali4 ,he changed the turmeric for litmus paper1 and placed it1 not in connection with his conductor1 but with his discharging train1 a metallic point connected with the conductor being fixed at a couple of inches from the paper2 on turning the machine1 acid was liberated at the edges and corners of the litmus4 ,he then placed a series of pointed pieces of paper1 each separate piece being composed of two halves1 one of litmus and the other of turmeric paper1 and all moistened with sulphate of soda1 in the line of the current from the machine4 ,the pieces of paper were separated from each other by spaces of air4 ,the machine was turned2 and it was always found that at the point where the electricity entered the paper1 litmus was reddened1 and at the point where it quitted the paper1 turmeric was browned4 ',here1' he urges1 'the poles are entirely abandoned1 but we have still electrochemical decomposition4' ,it is evident to him that instead of being attracted by the poles1 the bodies separated are ejected by the current4 ,the effects thus obtained with poles of air he also succeeded in obtaining with poles of water4 ,the advance in ,faraday's own ideas made at this time is indicated by the word 'ejected4' ,he afterwards reiterates this view3 the evolved substances are expelled from the decomposing body1 and 'not drawn out by an attraction4 ,having abolished this idea of polar attraction1 he proceeds to enunciate and develop a theory of his own4 ,he refers to ,davy's celebrated ,bakerian ,lecture1 given in #ahjf1 which he says 'is almost entirely occupied in the consideration of electrochemical decompositions4' ,the facts recorded in that lecture ,faraday regards as of the utmost value4 ,but 'the mode of action by which the effects take place is stated very generally2 so generally1 indeed1 that probably a dozen precise schemes of electrochemical action might be drawn up1 differing essentially from each other1 yet all agreeing with the statement there given4' ,it appears to me that these words might with justice be applied to ,faraday's own researches at this time4 ,they furnish us with results of permanent value2 but little help can be found in the theory advanced to account for them4 ,it would1 perhaps1 be more correct to say that the theory itself is hardly presentable in any tangible form to the intellect4 ,faraday looks1 and rightly looks1 into the heart of the decomposing body itself2 he sees1 and rightly sees1 active within it the forces which produce the decomposition1 and he rejects1 and rightly rejects1 the notion of external attraction2 but beyond the hypothesis of decompositions and recompositions1 enunciated and developed by ,grothuss and ,davy1 he does not1 ,i think1 help us to any definite conception as to how the force reaches the decomposing mass and acts within it4 ,nor1 indeed1 can this be done1 until we know the true physical process which underlies what we call an electric current4 ,faraday conceives of that current as 'an axis of power having contrary forces exactly equal in amount in opposite directions'2 but this definition1 though much quoted and circulated1 teaches us nothing regarding the current4 ,an 'axis' here can only mean a direction2 and what we want to be able to conceive of is1 not the axis along which the power acts1 but the nature and mode of action of the power itself4 ,he objects to the vagueness of ,de la ,rive2 but the fact is1 that both he and ,de la ,rive labour under the same difficulty4 ,neither wishes to commit himself to the notion of a current compounded of two electricities flowing in two opposite directions3 but the time had not come1 nor is it yet come1 for the displacement of this provisional fiction by the true mechanical conception4 ,still1 however indistinct the theoretic notions of ,faraday at this time may be1 the facts which are rising before him and around him are leading him gradually1 but surely1 to results of incalculable importance in relation to the philosophy of the voltaic pile4 ,he had always some great object of research in view1 but in the pursuit of it he frequently alighted on facts of collateral interest1 to examine which he sometimes turned aside from his direct course4 ,thus we find the series of his researches on electrochemical decomposition interrupted by an inquiry into 'the power of metals and other solids1 to induce the combination of gaseous bodies4' ,this inquiry1 which was received by the ,royal ,society on ,nov4 #cj1 #ahcc1 though not so important as those which precede and follow it1 illustrates throughout his strength as an experimenter4 ,the power of spongy platinum to cause the combination of oxygen and hydrogen had been discovered by ,dobereiner in #ahbc1 and had been applied by him in the construction of his well-known philosophic lamp4 ,it was shown subsequently by ,dulong and ,thenard that even a platinum wire1 when perfectly cleansed1 may be raised to incandescence by its action on a jet of cold hydrogen4 ,in his experiments on the decomposition of water1 ,faraday found that the positive platinum plate of the decomposing cell possessed in an extraordinary degree the power of causing oxygen and hydrogen to combine4 ,he traced the cause of this to the perfect cleanness of the positive plate4 ,against it was liberated oxygen1 which1 with the powerful affinity of the 'nascent state1' swept away all impurity from the surface against which it was liberated4 ,the bubbles of gas liberated on one of the platinum plates or wires of a decomposing cell are always much smaller1 and they rise in much more rapid succession than those from the other4 ,knowing that oxygen is sixteen times heavier than hydrogen1 ,i have more than once concluded1 and1 ,i fear1 led others into the error of concluding1 that the smaller and more quickly rising bubbles must belong to the lighter gas4 ,the thing appeared so obvious that ,i did not give myself the trouble of looking at the battery1 which would at once have told me the nature of the gas4 ,but ,faraday would never have been satisfied with a deduction if he could have reduced it to a fact4 ,and he has taught me that the fact here is the direct reverse of what ,i supposed it to be4 ,the small bubbles are oxygen1 and their smallness is due to the perfect cleanness of the surface on which they are liberated4 ,the hydrogen adhering to the other electrode swells into large bubbles1 which rise in much slower succession2 but when the current is reversed1 the hydrogen is liberated upon the cleansed wire1 and then its bubbles also become small4 ,footnotes to ,chapter #e #a ,buff finds the quantity of electricity associated with one milligramme of hydrogen in water to be equal to #de1dhj charges of a ,leyden jar1 with a height of #dhj millimetres1 and a diameter of #afj millimetres4 ,weber and ,kohlrausch have calculated that1 if the quantity of electricity associated with one milligramme of hydrogen in water were diffused over a cloud at a height of #ajjj metres above the earth1 it would exert upon an equal quantity of the opposite electricity at the earth's surface an attractive force of #b1bfh1jjj kilogrammes4 7,electrolytische ,maasbestimmungen1 #ahef1 p4 #bfb47 #b ,faraday1 sa ,vie et ses ,travaux1 p4 #bj4 ,chapter #f4 ,laws of electro-chemical decomposition4 ,in our conceptions and reasonings regarding the forces of nature1 we perpetually make use of symbols which1 when they possess a high representative value1 we dignify with the name of theories4 ,thus1 prompted by certain analogies1 we ascribe electrical phenomena to the action of a peculiar fluid1 sometimes flowing1 sometimes at rest4 ,such conceptions have their advantages and their disadvantages2 they afford peaceful lodging to the intellect for a time1 but they also circumscribe it1 and by-and-by1 when the mind has grown too large for its lodging1 it often finds difficulty in breaking down the walls of what has become its prison instead of its home4#a ,no man ever felt this tyranny of symbols more deeply than ,faraday1 and no man was ever more assiduous than he to liberate himself from them1 and the terms which suggested them4 ,calling ,dr4 ,whewell to his aid in #ahcc1 he endeavoured to displace by others all terms tainted by a foregone conclusion4 ,his paper on ,electro-chemical ,decomposition1 received by the ,royal ,society on ,january #i1 #ahcd1 opens with the proposal of a new terminology4 ,he would avoid the word 'current' if he could4#b ,he does abandon the word 'poles' as applied to the ends of a decomposing cell1 because it suggests the idea of attraction1 substituting for it the perfectly natural term ,electrodes4 ,he applied the term ,electrolyte to every substance which can be decomposed by the current1 and the act of decomposition he called ,electrolysis4 ,all these terms have become current in science4 ,he called the positive electrode the ,anode1 and the negative one the ,cathode1 but these terms1 though frequently used1 have not enjoyed the same currency as the others4 ,the terms ,anion and ,cation1 which he applied to the constituents of the decomposed electrolyte1 and the term ,ion1 which included both anions and cations1 are still less frequently employed4 ,faraday now passes from terminology to research2 he sees the necessity of quantitative determinations1 and seeks to supply himself with a measure of voltaic electricity4 ,this he finds in the quantity of water decomposed by the current4 ,he tests this measure in all possible ways1 to assure himself that no error can arise from its employment4 ,he places in the course of one and the same current a series of cells with electrodes of different sizes1 some of them plates of platinum1 others merely platinum wires1 and collects the gas liberated on each distinct pair of electrodes4 ,he finds the quantity of gas to be the same for all4 ,thus he concludes that when the same quantity of electricity is caused to pass through a series of cells containing acidulated water1 the electro-chemical action is independent of the size of the electrodes4#c ,he next proves that variations in intensity do not interfere with this equality of action4 ,whether his battery is charged with strong acid or with weak2 whether it consists of five pairs or of fifty pairs2 in short1 whatever be its source1 when the same current is sent through his series of cells the same amount of decomposition takes place in all4 ,he next assures himself that the strength or weakness of his dilute acid does not interfere with this law4 ,sending the same current through a series of cells containing mixtures of sulphuric acid and water of different strengths1 he finds1 however the proportion of acid to water might vary1 the same amount of gas to be collected in all the cells4 ,a crowd of facts of this character forced upon ,faraday's mind the conclusion that the amount of electro-chemical decomposition depends1 not upon the size of the electrodes1 not upon the intensity of the current1 not upon the strength of the solution1 but solely upon the quantity of electricity which passes through the cell4 ,the quantity of electricity he concludes is proportional to the amount of chemical action4 ,on this law ,faraday based the construction of his celebrated ,voltameter1 or ,measure of ,voltaic electricity4 ,but before he can apply this measure he must clear his ground of numerous possible sources of error4 ,the decomposition of his acidulated water is certainly a direct result of the current2 but as the varied and important researches of ,,mm4 ,becquerel1 ,de la ,rive1 and others had shown1 there are also secondary actions which may materially interfere with and complicate the pure action of the current4 ,these actions may occur in two ways3 either the liberated ion may seize upon the electrode against which it is set free1 forming a chemical compound with that electrode2 or it may seize upon the substance of the electrolyte itself1 and thus introduce into the circuit chemical actions over and above those due to the current4 ,faraday subjected these secondary actions to an exhaustive examination4 ,instructed by his experiments1 and rendered competent by them to distinguish between primary and secondary results1 he proceeds to establish the doctrine of ',definite ,electro-chemical ,decomposition4' ,into the same circuit he introduced his voltameter1 which consisted of a graduated tube filled with acidulated water and provided with platinum plates for the decomposition of the water1 and also a cell containing chloride of tin4 ,experiments already referred to had taught him that this substance1 though an insulator when solid1 is a conductor when fused1 the passage of the current being always accompanied by the decomposition of the chloride4 ,he wished to ascertain what relation this decomposition bore to that of the water in his voltameter4 ,completing his circuit1 he permitted the current to continue until 'a reasonable quantity of gas' was collected in the voltameter4 ,the circuit was then broken1 and the quantity of tin liberated compared with the quantity of gas4 ,the weight of the former was #c4b grains1 that of the latter #j4digdb of a grain4 ,oxygen1 as you know1 unites with hydrogen in the proportion of #h to #a1 to form water4 ,calling the equivalent1 or as it is sometimes called1 the atomic weight of hydrogen #a1 that of oxygen is #h2 that of water is consequently #h #a or #i4 ,now if the quantity of water decomposed in ,faraday's experiment be represented by the number #i1 or in other words by the equivalent of water1 then the quantity of tin liberated from the fused chloride is found by an easy calculation to be #eg4i1 which is almost exactly the chemical equivalent of tin4 ,thus both the water and the chloride were broken up in proportions expressed by their respective equivalents4 ,the amount of electric force which wrenched asunder the constituents of the molecule of water was competent1 and neither more nor less than competent1 to wrench asunder the constituents of the molecules of the chloride of tin4 ,the fact is typical4 ,with the indications of his voltameter he compared the decompositions of other substances1 both singly and in series4 ,he submitted his conclusions to numberless tests4 ,he purposely introduced secondary actions4 ,he endeavoured to hamper the fulfilment of those laws which it was the intense desire of his mind to see established4 ,but from all these difficulties emerged the golden truth1 that under every variety of circumstances the decompositions of the voltaic current are as definite in their character as those chemical combinations which gave birth to the atomic theory4 ,this law of ,electro-chemical ,decomposition ranks1 in point of importance1 with that of ,definite ,combining ,proportions in chemistry4 ,footnotes to ,chapter #f #a ,i copy these words from the printed abstract of a ,friday evening lecture1 given by myself1 because they remind me of ,faraday's voice1 responding to the utterance by an emphatic 'hear6 hear6'--,proceedings of the ,royal ,institution1 vol4 ii4 p4 #acb4 #b ,in #ahch he expresses himself thus3--',the word current is so expressive in common language that when applied in the consideration of electrical phenomena1 we can hardly divest it sufficiently of its meaning1 or prevent our minds from being prejudiced by it4'--,exp4 ,resear41 vol4 i4 p4 #eae4 7 #afag47 #c ,this conclusion needs qualification4 ,faraday overlooked the part played by ozone4 ,chapter #g4 ,origin of power in the voltaic pile4 ,in one of the public areas of the town of ,como stands a statue with no inscription on its pedestal1 save that of a single name1 ',volta4' ,the bearer of that name occupies a place for ever memorable in the history of science4 ,to him we owe the discovery of the voltaic pile1 to which for a brief interval we must now turn our attention4 ,the objects of scientific thought being the passionless laws and phenomena of external nature1 one might suppose that their investigation and discussion would be completely withdrawn from the region of the feelings1 and pursued by the cold dry light of the intellect alone4 ,this1 however1 is not always the case4 ,man carries his heart with him into all his works4 ,you cannot separate the moral and emotional from the intellectual2 and thus it is that the discussion of a point of science may rise to the heat of a battle-field4 ,the fight between the rival optical theories of ,emission and ,undulation was of this fierce character2 and scarcely less fierce for many years was the contest as to the origin and maintenance of the power of the voltaic pile4 ,volta himself supposed it to reside in the ,contact of different metals4 ,here was exerted his ',electro-motive force1' which tore the combined electricities asunder and drove them as currents in opposite directions4 ,to render the circulation of the current possible1 it was necessary to connect the metals by a moist conductor2 for when any two metals were connected by a third1 their relation to each other was such that a complete neutralisation of the electric motion was the result4 ,volta's theory of metallic contact was so clear1 so beautiful1 and apparently so complete1 that the best intellects of ,europe accepted it as the expression of natural law4 ,volta himself knew nothing of the chemical phenomena of the pile2 but as soon as these became known1 suggestions and intimations appeared that chemical action1 and not metallic contact1 might be the real source of voltaic electricity4 ,this idea was expressed by ,fabroni in ,italy1 and by ,wollaston in ,england4 ,it was developed and maintained by those 'admirable electricians1' ,becquerel1 of ,paris1 and ,de la ,rive1 of ,geneva4 ,the ,contact ,theory1 on the other hand1 received its chief development and illustration in ,germany4 ,it was long the scientific creed of the great chemists and natural philosophers of that country1 and to the present hour there may be some of them unable to liberate themselves from the fascination of their first-love4 ,after the researches which ,i have endeavoured to place before you1 it was impossible for ,faraday to avoid taking a side in this controversy4 ,he did so in a paper ',on the ,electricity of the ,voltaic ,pile1' received by the ,royal ,society on the #gth of ,april1 #ahcd4 ,his position in the controversy might have been predicted4 ,he saw chemical effects going hand in hand with electrical effects1 the one being proportional to the other2 and1 in the paper now before us1 he proved that when the former was excluded1 the latter were sought for in vain4 ,he produced a current without metallic contact2 he discovered liquids which1 though competent to transmit the feeblest currents--competent therefore to allow the electricity of contact to flow through them if it were able to form a current--were absolutely powerless when chemically inactive4 ,one of the very few experimental mistakes of ,faraday occurred in this investigation4 ,he thought that with a single voltaic cell he had obtained the spark before the metals touched1 but he subsequently discovered his error4 ,to enable the voltaic spark to pass through air before the terminals of the battery were united1 it was necessary to exalt the electro-motive force of the battery by multiplying its elements2 but all the elements ,faraday possessed were unequal to the task of urging the spark across the shortest measurable space of air4 ,nor1 indeed1 could the action of the battery1 the different metals of which were in contact with each other1 decide the point in question4 ,still1 as regards the identity of electricities from various sources1 it was at that day of great importance to determine whether or not the voltaic current could jump1 as a spark1 across an interval before contact4 ,faraday's friend1 ,mr4 ,gassiot1 solved this problem4 ,he erected a battery of #djjj cells1 and with it urged a stream of sparks from terminal to terminal1 when separated from each other by a measurable space of air4 ,the memoir on the ',electricity of the ,voltaic ,pile1' published in #ahcd1 appears to have produced but little impression upon the supporters of the contact theory4 ,these indeed were men of too great intellectual weight and insight lightly to take up1 or lightly to abandon a theory4 ,faraday therefore resumed the attack in a paper1 communicated to the ,royal ,society on the #fth of ,february1 #ahdj4 ,in this paper he hampered his antagonists by a crowd of adverse experiments4 ,he hung difficulty after difficulty about the neck of the contact theory1 until in its efforts to escape from his assaults it so changed its character as to become a thing totally different from the theory proposed by ,volta4 ,the more persistently it was defended1 however1 the more clearly did it show itself to be a congeries of devices1 bearing the stamp of dialectic skill rather than of natural truth4 ,in conclusion1 ,faraday brought to bear upon it an argument which1 had its full weight and purport been understood at the time1 would have instantly decided the controversy4 ',the contact theory1' he urged1 'assumed that a force which is able to overcome powerful resistance1 as for instance that of the conductors1 good or bad1 through which the current passes1 and that again of the electrolytic action where bodies are decomposed by it1 can arise out of nothing2 that1 without any change in the acting matter1 or the consumption of any generating force1 a current shall be produced which shall go on for ever against a constant resistance1 or only be stopped1 as in the voltaic trough1 by the ruins which its exertion has heaped up in its own course4 ,this would indeed be a creation of power1 and is like no other force in nature4 ,we have many processes by which the form of the power may be so changed1 that an apparent conversion of one into the other takes place4 ,so we can change chemical force into the electric current1 or the current into chemical force4 ,the beautiful experiments of ,seebeck and ,peltier show the convertibility of heat and electricity2 and others by ,oersted and myself show the convertibility of electricity and magnetism4 ,but in no case1 not even in those of the ,gymnotus and ,torpedo1 is there a pure creation or a production of power without a corresponding exhaustion of something to supply it4' ,these words were published more than two years before either ,mayer printed his brief but celebrated essay on the ,forces of ,inorganic ,nature1 or ,mr4 ,joule published his first famous experiments on the ,mechanical ,value of ,heat4 ,they illustrate the fact that before any great scientific principle receives distinct enunciation by individuals1 it dwells more or less clearly in the general scientific mind4 ,the intellectual plateau is already high1 and our discoverers are those who1 like peaks above the plateau1 rise a little above the general level of thought at the time4 ,but many years prior even to the foregoing utterance of ,faraday1 a similar argument had been employed4 ,i quote here with equal pleasure and admiration the following passage written by ,dr4 ,roget so far back as #ahbi4 ,speaking of the contact theory1 he says3--',if there could exist a power having the property ascribed to it by the hypothesis1 namely1 that of giving continual impulse to a fluid in one constant direction1 without being exhausted by its own action1 it would differ essentially from all the known powers in nature4 ,all the powers and sources of motion with the operation of which we are acquainted1 when producing these peculiar effects1 are expended in the same proportion as those effects are produced2 and hence arises the impossibility of obtaining by their agency a perpetual effect2 or in other words a perpetual motion4 ,but the electro-motive force1 ascribed by ,volta to the metals1 when in contact1 is a force which1 as long as a free course is allowed to the electricity it sets in motion1 is never expended1 and continues to be excited with undiminished power in the production of a never-ceasing effect4 ,against the truth of such a supposition the probabilities are all but infinite4' ,when this argument1 which he employed independently1 had clearly fixed itself in his mind1 ,faraday never cared to experiment further on the source of electricity in the voltaic pile4 ,the argument appeared to him 'to remove the foundation itself of the contact theory1' and he afterwards let it crumble down in peace4#a ,footnote to ,chapter #g #a ,to account for the electric current1 which was really the core of the whole discussion1 ,faraday demonstrated the impotence of the ,contact ,theory as then enunciated and defended4 ,still1 it is certain that two different metals1 when brought into contact1 charge themselves1 the one with positive and the other with negative electricity4 ,i had the pleasure of going over this ground with ,kohlrausch in #ahdi1 and his experiments left no doubt upon my mind that the contact electricity of ,volta was a reality1 though it could produce no current4 ,with one of the beautiful instruments devised by himself1 ,sir ,william ,thomson has rendered this point capable of sure and easy demonstration2 and he and others now hold what may be called a contact theory1 which1 while it takes into account the action of the metals1 also embraces the chemical phenomena of the circuit4 ,helmholtz1 ,i believe1 was the first to give the contact theory this new form1 in his celebrated essay1 ,ueber die ,erhaltung der ,kraft1 p4 #de4 ,chapter #h4 ,researches on frictional electricity3 induction3 conduction3 specific inductive capacity3 theory of contiguous particles4 ,the burst of power which had filled the four preceding years with an amount of experimental work unparalleled in the history of science partially subsided in #ahce1 and the only scientific paper contributed by ,faraday in that year was a comparatively unimportant one1 ',on an improved ,form of the ,voltaic ,battery4' ,he brooded for a time3 his experiments on electrolysis had long filled his mind2 he looked1 as already stated1 into the very heart of the electrolyte1 endeavouring to render the play of its atoms visible to his mental eye4 ,he had no doubt that in this case what is called 'the electric current' was propagated from particle to particle of the electrolyte2 he accepted the doctrine of decomposition and recomposition which1 according to ,grothuss and ,davy1 ran from electrode to electrode4 ,and the thought impressed him more and more that ordinary electric induction was also transmitted and sustained by the action of 'contiguous particles4' ,his first great paper on frictional electricity was sent to the ,royal ,society on ,november #cj1 #ahcg4 ,we here find him face to face with an idea which beset his mind throughout his whole subsequent life1--the idea of action at a distance4 ,it perplexed and bewildered him4 ,in his attempts to get rid of this perplexity1 he was often unconsciously rebelling against the limitations of the intellect itself4 ,he loved to quote ,newton upon this point2 over and over again he introduces his memorable words1 ',that gravity should be innate1 inherent1 and essential to matter1 so that one body may act upon another at a distance through a vacuum and without the mediation of anything else1 by and through which this action and force may be conveyed from one to another1 is to me so great an absurdity1 that ,i believe no man who has in philosophical matters a competent faculty of thinking1 can ever fall into it4 ,gravity must be caused by an agent acting constantly according to certain laws2 but whether this agent be material or immaterial1 ,i have left to the consideration of my readers4'#a ,faraday does not see the same difficulty in his contiguous particles4 ,and yet1 by transferring the conception from masses to particles1 we simply lessen size and distance1 but we do not alter the quality of the conception4 ,whatever difficulty the mind experiences in conceiving of action at sensible distances1 besets it also when it attempts to conceive of action at insensible distances4 ,still the investigation of the point whether electric and magnetic effects were wrought out through the intervention of contiguous particles or not1 had a physical interest altogether apart from the metaphysical difficulty4 ,faraday grapples with the subject experimentally4 ,by simple intuition he sees that action at a distance must be exerted in straight lines4 ,gravity1 he knows1 will not turn a corner1 but exerts its pull along a right line2 hence his aim and effort to ascertain whether electric action ever takes place in curved lines4 ,this once proved1 it would follow that the action is carried on by means of a medium surrounding the electrified bodies4 ,his experiments in #ahcg reduced1 in his opinion1 this point of demonstration4 ,he then found that he could electrify1 by induction1 an insulated sphere placed completely in the shadow of a body which screened it from direct action4 ,he pictured the lines of electric force bending round the edges of the screen1 and reuniting on the other side of it2 and he proved that in many cases the augmentation of the distance between his insulated sphere and the inducing body1 instead of lessening1 increased the charge of the sphere4 ,this he ascribed to the coalescence of the lines of electric force at some distance behind the screen4 ,faraday's theoretic views on this subject have not received general acceptance1 but they drove him to experiment1 and experiment with him was always prolific of results4 ,by suitable arrangements he placed a metallic sphere in the middle of a large hollow sphere1 leaving a space of something more than half an inch between them4 ,the interior sphere was insulated1 the external one uninsulated4 ,to the former he communicated a definite charge of electricity4 ,it acted by induction upon the concave surface of the latter1 and he examined how this act of induction was effected by placing insulators of various kinds between the two spheres4 ,he tried gases1 liquids1 and solids1 but the solids alone gave him positive results4 ,he constructed two instruments of the foregoing description1 equal in size and similar in form4 ,the interior sphere of each communicated with the external air by a brass stem ending in a knob4 ,the apparatus was virtually a ,leyden jar1 the two coatings of which were the two spheres1 with a thick and variable insulator between them4 ,the amount of charge in each jar was determined by bringing a proof-plane into contact with its knob and measuring by a torsion balance the charge taken away4 ,he first charged one of his instruments1 and then dividing the charge with the other1 found that when air intervened in both cases the charge was equally divided4 ,but when shellac1 sulphur1 or spermaceti was interposed between the two spheres of one jar1 while air occupied this interval in the other1 then he found that the instrument occupied by the 'solid dielectric' takes more than half the original charge4 ,a portion of the charge was absorbed by the dielectric itself4 ,the electricity took time to penetrate the dielectric4 ,immediately after the discharge of the apparatus1 no trace of electricity was found upon its knob4 ,but after a time electricity was found there1 the charge having gradually returned from the dielectric in which it had been lodged4 ,different insulators possess this power of permitting the charge to enter them in different degrees4 ,faraday figured their particles as polarized1 and he concluded that the force of induction is propagated from particle to particle of the dielectric from the inner sphere to the outer one4 ,this power of propagation possessed by insulators he called their ',specific ,inductive ,capacity4' ,faraday visualizes with the utmost clearness the state of his contiguous particles2 one after another they become charged1 each succeeding particle depending for its charge upon its predecessor4 ,and now he seeks to break down the wall of partition between conductors and insulators4 ',can we not1' he says1 'by a gradual chain of association carry up discharge from its occurrence in air through spermaceti and water1 to solutions1 and then on to chlorides1 oxides1 and metals1 without any essential change in its character8' ,even copper1 he urges1 offers a resistance to the transmission of electricity4 ,the action of its particles differs from those of an insulator only in degree4 ,they are charged like the particles of the insulator1 but they discharge with greater ease and rapidity2 and this rapidity of molecular discharge is what we call conduction4 ,conduction then is always preceded by atomic induction2 and when1 through some quality of the body which ,faraday does not define1 the atomic discharge is rendered slow and difficult1 conduction passes into insulation4 ,though they are often obscure1 a fine vein of philosophic thought runs through those investigations4 ,the mind of the philosopher dwells amid those agencies which underlie the visible phenomena of ,induction and ,conduction2 and he tries by the strong light of his imagination to see the very molecules of his dielectrics4 ,it would1 however1 be easy to criticise these researches1 easy to show the looseness1 and sometimes the inaccuracy1 of the phraseology employed2 but this critical spirit will get little good out of ,faraday4 ,rather let those who ponder his works seek to realise the object he set before him1 not permitting his occasional vagueness to interfere with their appreciation of his speculations4 ,we may see the ripples1 and eddies1 and vortices of a flowing stream1 without being able to resolve all these motions into their constituent elements2 and so it sometimes strikes me that ,faraday clearly saw the play of fluids and ethers and atoms1 though his previous training did not enable him to resolve what he saw into its constituents1 or describe it in a manner satisfactory to a mind versed in mechanics4 ,and then again occur1 ,i confess1 dark sayings1 difficult to be understood1 which disturb my confidence in this conclusion4 ,it must1 however1 always be remembered that he works at the very boundaries of our knowledge1 and that his mind habitually dwells in the 'boundless contiguity of shade' by which that knowledge is surrounded4 ,in the researches now under review the ratio of speculation and reasoning to experiment is far higher than in any of ,faraday's previous works4 ,amid much that is entangled and dark we have flashes of wondrous insight and utterances which seem less the product of reasoning than of revelation4 ,i will confine myself here to one example of this divining power4 ,by his most ingenious device of a rapidly rotating mirror1 ,wheatstone had proved that electricity required time to pass through a wire1 the current reaching the middle of the wire later than its two ends4 ',if1' says ,faraday1 'the two ends of the wire in ,professor ,wheatstone's experiments were immediately connected with two large insulated metallic surfaces exposed to the air1 so that the primary act of induction1 after making the contact for discharge1 might be in part removed from the internal portion of the wire at the first instance1 and disposed for the moment on its surface jointly with the air and surrounding conductors1 then ,i venture to anticipate that the middle spark would be more retarded than before4 ,and if those two plates were the inner and outer coatings of a large jar or ,leyden battery1 then the retardation of the spark would be much greater4' ,this was only a prediction1 for the experiment was not made4#b ,sixteen years subsequently1 however1 the proper conditions came into play1 and ,faraday was able to show that the observations of ,werner ,siemens1 and ,latimer ,clark1 on subterraneous and submarine wires were illustrations1 on a grand scale1 of the principle which he had enunciated in #ahch4 ,the wires and the surrounding water act as a ,leyden jar1 and the retardation of the current predicted by ,faraday manifests itself in every message sent by such cables4 ,the meaning of ,faraday in these memoirs on ,induction and ,conduction is1 as ,i have said1 by no means always clear2 and the difficulty will be most felt by those who are best trained in ordinary theoretic conceptions4 ,he does not know the reader's needs1 and he therefore does not meet them4 ,for instance he speaks over and over again of the impossibility of charging a body with one electricity1 though the impossibility is by no means evident4 ,the key to the difficulty is this4 ,he looks upon every insulated conductor as the inner coating of a ,leyden jar4 ,an insulated sphere in the middle of a room is to his mind such a coating2 the walls are the outer coating1 while the air between both is the insulator1 across which the charge acts by induction4 ,without this reaction of the walls upon the sphere you could no more1 according to ,faraday1 charge it with electricity than you could charge a ,leyden jar1 if its outer coating were removed4 ,distance with him is immaterial4 ,his strength as a generalizer enables him to dissolve the idea of magnitude2 and if you abolish the walls of the room--even the earth itself--he would make the sun and planets the outer coating of his jar4 ,i dare not contend that ,faraday in these memoirs made all his theoretic positions good4 ,but a pure vein of philosophy runs through these writings2 while his experiments and reasonings on the forms and phenomena of electrical discharge are of imperishable importance4 ,footnotes to ,chapter #h #a ,newton's third letter to ,bentley4 #b ,had ,sir ,charles ,wheatstone been induced to resume his measurements1 varying the substances through which1 and the conditions under which1 the current is propagated1 he might have rendered great service to science1 both theoretic and experimental4 ,chapter #i4 ,rest needed--visit to ,switzerland4 ,the last of these memoirs was dated from the ,royal ,institution in ,june1 #ahch4 ,it concludes the first volume of his ',experimental ,researches on ,electricity4' ,in #ahdj1 as already stated1 he made his final assault on the ,contact ,theory1 from which it never recovered4#a ,he was now feeling the effects of the mental strain to which he had been subjected for so many years4 ,during these years he repeatedly broke down4 ,his wife alone witnessed the extent of his prostration1 and to her loving care we1 and the world1 are indebted for the enjoyment of his presence here so long4 ,he found occasional relief in a theatre4 ,he frequently quitted ,london and went to ,brighton and elsewhere1 always choosing a situation which commanded a view of the sea1 or of some other pleasant horizon1 where he could sit and gaze and feel the gradual revival of the faith that ',nature never did betray ,the heart that loved her4' ,but very often for some days after his removal to the country1 he would be unable to do more than sit at a window and look out upon the sea and sky4 ,in #ahda1 his state became more serious than it had ever been before4 ,a published letter to ,mr4 ,richard ,taylor1 dated ,march #aa1 #ahdc1 contains an allusion to his previous condition4 ',you are aware1' he says1 'that considerations regarding health have prevented me from working or reading on science for the last two years4' ,this1 at one period or another of their lives1 seems to be the fate of most great investigators4 ,they do not know the limits of their constitutional strength until they have transgressed them4 ,it is1 perhaps1 right that they should transgress them1 in order to ascertain where they lie4 ,faraday1 however1 though he went far towards it1 did not push his transgression beyond his power of restitution4 ,in #ahda ,mrs4 ,faraday and he went to ,switzerland1 under the affectionate charge of her brother1 ,mr4 ,george ,barnard1 the artist4 ,this time of suffering throws fresh light upon his character4 ,i have said that sweetness and gentleness were not its only constituents2 that he was also fiery and strong4 ,at the time now referred to1 his fire was low and his strength distilled away2 but the residue of his life was neither irritability nor discontent4 ,he was unfit to mingle in society1 for conversation was a pain to him2 but let us observe the great ,man-child when alone4 ,he is at the village of ,interlaken1 enjoying ,jungfrau sunsets1 and at times watching the ,swiss nailers making their nails4 ,he keeps a little journal1 in which he describes the process of nailmaking1 and incidentally throws a luminous beam upon himself4 ',august #b1 #ahda4--;,clout nailmaking goes on here rather considerably1 and is a very neat and pretty operation to observe4 ,i love a smith's shop and anything relating to smithery4 ,my father was a smith4' ,from ,interlaken he went to the ,falls of the ,giessbach1 on the pleasant lake of ,brientz4 ,and here we have him watching the shoot of the cataract down its series of precipices4 ,it is shattered into foam at the base of each1 and tossed by its own recoil as water-dust through the air4 ,the sun is at his back1 shining on the drifting spray1 and he thus describes and muses on what he sees3-- ',august #ab1 #ahda4--,to-day every fall was foaming from the abundance of water1 and the current of wind brought down by it was in some places too strong to stand against4 ,the sun shone brightly1 and the rainbows seen from various points were very beautiful4 ,one at the bottom of a fine but furious fall was very pleasant1--there it remained motionless1 whilst the gusts and clouds of spray swept furiously across its place and were dashed against the rock4 ,it looked like a spirit strong in faith and steadfast in the midst of the storm of passions sweeping across it1 and though it might fade and revive1 still it held on to the rock as in hope and giving hope4 ,and the very drops1 which in the whirlwind of their fury seemed as if they would carry all away1 were made to revive it and give it greater beauty4' ,footnote to ,chapter #i #a ,see note1 p4 #gg4 ,chapter #aj4 ,magnetization of light4 ,but we must quit the man and go on to the discoverer3 we shall return for a brief space to his company by-and-by4 ,carry your thoughts back to his last experiments1 and see him endeavouring to prove that induction is due to the action of contiguous particles4 ,he knew that polarized light was a most subtle and delicate investigator of molecular condition4 ,he used it in #ahcd in exploring his electrolytes1 and he tried it in #ahch upon his dielectrics4 ,at that time he coated two opposite faces of a glass cube with tinfoil1 connected one coating with his powerful electric machine and the other with the earth1 and examined by polarized light the condition of the glass when thus subjected to strong electric influence4 ,he failed to obtain any effect2 still he was persuaded an action existed1 and required only suitable means to call it forth4 ,after his return from ,switzerland he was beset by these thoughts2 they were more inspired than logical3 but he resorted to magnets and proved his inspiration true4 ,his dislike of 'doubtful knowledge' and his efforts to liberate his mind from the thraldom of hypotheses have been already referred to4 ,still this rebel against theory was incessantly theorising himself4 ,his principal researches are all connected by an undercurrent of speculation4 ,theoretic ideas were the very sap of his intellect--the source from which all his strength as an experimenter was derived4 ,while once sauntering with him through the ,crystal ,palace1 at ,sydenham1 ,i asked him what directed his attention to the magnetization of light4 ,it was his theoretic notions4 ,he had certain views regarding the unity and convertibility of natural forces2 certain ideas regarding the vibrations of light and their relations to the lines of magnetic force2 these views and ideas drove him to investigation4 ,and so it must always be3 the great experimentalist must ever be the habitual theorist1 whether or not he gives to his theories formal enunciation4 ,faraday1 you have been informed1 endeavoured to improve the manufacture of glass for optical purposes4 ,but though he produced a heavy glass of great refractive power1 its value to optics did not repay him for the pains and labour bestowed on it4 ,now1 however1 we reach a result established by means of this same heavy glass1 which made ample amends for all4 ,in ,november1 #ahde1 he announced his discovery of the ',magnetization of ,light and the ,illumination of the ,lines of ,magnetic ,force4' ,this title provoked comment at the time1 and caused misapprehension4 ,he therefore added an explanatory note2 but the note left his meaning as entangled as before4 ,in fact ,faraday had notions regarding the magnetization of light which were peculiar to himself1 and untranslatable into the scientific language of the time4 ,probably no other philosopher of his day would have employed the phrases just quoted as appropriate to the discovery announced in #ahde4 ,but ,faraday was more than a philosopher2 he was a prophet1 and often wrought by an inspiration to be understood by sympathy alone4 ,the prophetic element in his character occasionally coloured1 and even injured1 the utterance of the man of science2 but subtracting that element1 though you might have conferred on him intellectual symmetry1 you would have destroyed his motive force4 ,but let us pass from the label of this casket to the jewel it contains4 ',i have long1' he says1 'held an opinion1 almost amounting to conviction1 in common1 ,i believe1 with many other lovers of natural knowledge1 that the various forms under which the forces of matter are made manifest have one common origin2 in other words1 are so directly related and mutually dependent1 that they are convertible1 as it were1 into one another1 and possess equivalents of power in their action4444 ,this strong persuasion1' he adds1 'extended to the powers of light4' ,and then he examines the action of magnets upon light4 ,from conversation with him and ,anderson1 ,i should infer that the labour preceding this discovery was very great4 ,the world knows little of the toil of the discoverer4 ,it sees the climber jubilant on the mountain top1 but does not know the labour expended in reaching it4 ,probably hundreds of experiments had been made on transparent crystals before he thought of testing his heavy glass4 ,here is his own clear and simple description of the result of his first experiment with this substance3--',a piece of this glass1 about two inches square1 and #j4e of an inch thick1 having flat and polished edges1 was placed as a diamagnetic#a between the poles 7not as yet magnetized by the electric current71 so that the polarized ray should pass through its length2 the glass acted as air1 water1 or any other transparent substance would do2 and if the eye-piece were previously turned into such a position that the polarized ray was extinguished1 or rather the image produced by it rendered invisible1 then the introduction of the glass made no alteration in this respect4 ,in this state of circumstances1 the force of the electro-magnet was developed by sending an electric current through its coils1 and immediately the image of the lamp-flame became visible and continued so as long as the arrangement continued magnetic4 ,on stopping the electric current1 and so causing the magnetic force to cease1 the light instantly disappeared4 ,these phenomena could be renewed at pleasure1 at any instant of time1 and upon any occasion1 showing a perfect dependence of cause and effect4' ,in a beam of ordinary light the particles of the luminiferous ether vibrate in all directions perpendicular to the line of progression2 by the act of polarization1 performed here by ,faraday1 all oscillations but those parallel to a certain plane are eliminated4 ,when the plane of vibration of the polarizer coincides with that of the analyzer1 a portion of the beam passes through both2 but when these two planes are at right angles to each other1 the beam is extinguished4 ,if by any means1 while the polarizer and analyzer remain thus crossed1 the plane of vibration of the polarized beam between them could be changed1 then the light would be1 in part at least1 transmitted4 ,in ,faraday's experiment this was accomplished4 ,his magnet turned the plane of polarization of the beam through a certain angle1 and thus enabled it to get through the analyzer2 so that 'the magnetization of light and the illumination of the magnetic lines of force' becomes1 when expressed in the language of modern theory1 the rotation of the plane of polarization4 ,to him1 as to all true philosophers1 the main value of a fact was its position and suggestiveness in the general sequence of scientific truth4 ,hence1 having established the existence of a phenomenon1 his habit was to look at it from all possible points of view1 and to develop its relationship to other phenomena4 ,he proved that the direction of the rotation depends upon the polarity of his magnet2 being reversed when the magnetic poles are reversed4 ,he showed that when a polarized ray passed through his heavy glass in a direction parallel to the magnetic lines of force1 the rotation is a maximum1 and that when the direction of the ray is at right angles to the lines of force1 there is no rotation at all4 ,he also proved that the amount of the rotation is proportional to the length of the diamagnetic through which the ray passes4 ,he operated with liquids and solutions4 ,of aqueous solutions he tried #aej and more1 and found the power in all of them4 ,he then examined gases2 but here all his efforts to produce any sensible action upon the polarized beam were ineffectual4 ,he then passed from magnets to currents1 enclosing bars of heavy glass1 and tubes containing liquids and aqueous solutions within an electro-magnetic helix4 ,a current sent through the helix caused the plane of polarization to rotate1 and always in the direction of the current4 ,the rotation was reversed when the current was reversed4 ,in the case of magnets1 he observed a gradual1 though quick1 ascent of the transmitted beam from a state of darkness to its maximum brilliancy1 when the magnet was excited4 ,in the case of currents1 the beam attained at once its maximum4 ,this he showed to be due to the time required by the iron of the electro-magnet to assume its full magnetic power1 which time vanishes when a current1 without iron1 is employed4 ',in this experiment1' he says1 'we may1 ,i think1 justly say that a ray of light is electrified1 and the electric forces illuminated4' ,in the helix1 as with the magnets1 he submitted air to magnetic influence 'carefully and anxiously1' but could not discover any trace of action on the polarized ray4 ,many substances possess the power of turning the plane of polarization without the intervention of magnetism4 ,oil of turpentine and quartz are examples2 but ,faraday showed that1 while in one direction1 that is1 across the lines of magnetic force1 his rotation is zero1 augmenting gradually from this until it attains its maximum1 when the direction of the ray is parallel to the lines of force2 in the oil of turpentine the rotation is independent of the direction of the ray4 ,but he showed that a still more profound distinction exists between the magnetic rotation and the natural one4 ,i will try to explain how4 ,suppose a tube with glass ends containing oil of turpentine to be placed north and south4 ,fixing the eye at the south end of the tube1 let a polarized beam be sent through it from the north4 ,to the observer in this position the rotation of the plane of polarization1 by the turpentine1 is right-handed4 ,let the eye be placed at the north end of the tube1 and a beam be sent through it from the south2 the rotation is still right-handed4 ,not so1 however1 when a bar of heavy glass is subjected to the action of an electric current4 ,in this case if1 in the first position of the eye1 the rotation be right-handed1 in the second position it is left-handed4 ,these considerations make it manifest that if a polarized beam1 after having passed through the oil of turpentine in its natural state1 could by any means be reflected back through the liquid1 the rotation impressed upon the direct beam would be exactly neutralized by that impressed upon the reflected one4 ,not so with the induced magnetic effect4 ,here it is manifest that the rotation would be doubled by the act of reflection4 ,hence ,faraday concludes that the particles of the oil of turpentine which rotate by virtue of their natural force1 and those which rotate in virtue of the induced force1 cannot be in the same condition4 ,the same remark applies to all bodies which possess a natural power of rotating the plane of polarization4 ,and then he proceeded with exquisite skill and insight to take advantage of this conclusion4 ,he silvered the ends of his piece of heavy glass1 leaving1 however1 a narrow portion parallel to two edges diagonally opposed to each other unsilvered4 ,he then sent his beam through this uncovered portion1 and by suitably inclining his glass caused the beam within it to reach his eye first direct1 and then after two1 four1 and six reflections4 ,these corresponded to the passage of the ray once1 three times1 five times1 and seven times through the glass4 ,he thus established with numerical accuracy the exact proportionality of the rotation to the distance traversed by the polarized beam4 ,thus in one series of experiments where the rotation required by the direct beam was #ab;degrees1 that acquired by three passages through the glass was #cf;degrees1 while that acquired by five passages was #fj;degrees4 ,but even when this method of magnifying was applied1 he failed with various solid substances to obtain any effect2 and in the case of air1 though he employed to the utmost the power which these repeated reflections placed in his hands1 he failed to produce the slightest sensible rotation4 ,these failures of ,faraday to obtain the effect with gases seem to indicate the true seat of the phenomenon4 ,the luminiferous ether surrounds and is influenced by the ultimate particles of matter4 ,the symmetry of the one involves that of the other4 ,thus1 if the molecules of a crystal be perfectly symmetrical round any line through the crystal1 we may safely conclude that a ray will pass along this line as through ordinary glass4 ,it will not be doubly refracted4 ,from the symmetry of the liquid figures1 known to be produced in the planes of freezing1 when radiant heat is sent through ice1 we may safely infer symmetry of aggregation1 and hence conclude that the line perpendicular to the planes of freezing is a line of no double refraction2 that it is1 in fact1 the optic axis of the crystal4 ,the same remark applies to the line joining the opposite blunt angles of a crystal of ,iceland spar4 ,the arrangement of the molecules round this line being symmetrical1 the condition of the ether depending upon these molecules shares their symmetry2 and there is1 therefore1 no reason why the wavelength should alter with the alteration of the azimuth round this line4 ,annealed glass has its molecules symmetrically arranged round every line that can be drawn through it2 hence it is not doubly refractive4 ,but let the substance be either squeezed or strained in one direction1 the molecular symmetry1 and with it the symmetry of the ether1 is immediately destroyed and the glass becomes doubly refractive4 ,unequal heating produces the same effect4 ,thus mechanical strains reveal themselves by optical effects2 and there is little doubt that in ,faraday's experiment it is the magnetic strain that produces the rotation of the plane of polarization4#b ,footnotes to ,chapter #aj #a ',by a diamagnetic1' says ,faraday1 ',i mean a body through which lines of magnetic force are passing1 and which does not by their action assume the usual magnetic state of iron or loadstone4' ,faraday subsequently used this term in a different sense from that here given1 as will immediately appear4 #b ,the power of double refraction conferred on the centre of a glass rod1 when it is caused to sound the fundamental note due to its longitudinal vibration1 and the absence of the same power in the case of vibrating air 7enclosed in a glass organ-pipe71 seems to be analogous to the presence and absence of ,faraday's effect in the same two substances4 ,faraday never1 to my knowledge1 attempted to give1 even in conversation1 a picture of the molecular condition of his heavy glass when subjected to magnetic influence4 ,in a mathematical investigation of the subject1 published in the ,proceedings of the ,royal ,society for #ahef1 ,sir ,william ,thomson arrives at the conclusion that the 'diamagnetic' is in a state of molecular rotation4 ,chapter #aa4 ,discovery of diamagnetism--researches on magne-crystallic action4 ,faraday's next great step in discovery was announced in a memoir on the ',magnetic ,condition of all matter1' communicated to the ,royal ,society on ,december #ah1 #ahde4 ,one great source of his success was the employment of extraordinary power4 ,as already stated1 he never accepted a negative answer to an experiment until he had brought to bear upon it all the force at his command4 ,he had over and over again tried steel magnets and ordinary electro-magnets on various substances1 but without detecting anything different from the ordinary attraction exhibited by a few of them4 ,stronger coercion1 however1 developed a new action4 ,before the pole of an electro-magnet1 he suspended a fragment of his famous heavy glass2 and observed that when the magnet was powerfully excited the glass fairly retreated from the pole4 ,it was a clear case of magnetic repulsion4 ,he then suspended a bar of the glass between two poles2 the bar retreated when the poles were excited1 and set its length equatorially or at right angles to the line joining them4 ,when an ordinary magnetic body was similarly suspended1 it always set axially1 that is1 from pole to pole4 ,faraday called those bodies which were repelled by the poles of a magnet1 diamagnetic bodies2 using this term in a sense different from that in which he employed it in his memoir on the magnetization of light4 ,the term magnetic he reserved for bodies which exhibited the ordinary attraction4 ,he afterwards employed the term magnetic to cover the whole phenomena of attraction and repulsion1 and used the word paramagnetic to designate such magnetic action as is exhibited by iron4 ,isolated observations by ,brugmanns1 ,becquerel1 ,le ,baillif1 ,saigy1 and ,seebeck had indicated the existence of a repulsive force exercised by the magnet on two or three substances2 but these observations1 which were unknown to ,faraday1 had been permitted to remain without extension or examination4 ,having laid hold of the fact of repulsion1 ,faraday immediately expanded and multiplied it4 ,he subjected bodies of the most varied qualities to the action of his magnet3--mineral salts1 acids1 alkalis1 ethers1 alcohols1 aqueous solutions1 glass1 phosphorus1 resins1 oils1 essences1 vegetable and animal tissues1 and found them all amenable to magnetic influence4 ,no known solid or liquid proved insensible to the magnetic power when developed in sufficient strength4 ,all the tissues of the human body1 the blood--though it contains iron--included1 were proved to be diamagnetic4 ,so that if you could suspend a man between the poles of a magnet1 his extremities would retreat from the poles until his length became equatorial4 ,soon after he had commenced his researches on diamagnetism1 ,faraday noticed a remarkable phenomenon which first crossed my own path in the following way3 ,in the year #ahdi1 while working in the cabinet of my friend1 ,professor ,knoblauch1 of ,marburg1 ,i suspended a small copper coin between the poles of an electro-magnet4 ,on exciting the magnet1 the coin moved towards the poles and then suddenly stopped1 as if it had struck against a cushion4 ,on breaking the circuit1 the coin was repelled1 the revulsion being so violent as to cause it to spin several times round its axis of suspension4 ,a ,silber-groschen similarly suspended exhibited the same deportment4 ,for a moment ,i thought this a new discovery2 but on looking over the literature of the subject1 it appeared that ,faraday had observed1 multiplied1 and explained the same effect during his researches on diamagnetism4 ,his explanation was based upon his own great discovery of magneto-electric currents4 ,the effect is a most singular one4 ,a weight of several pounds of copper may be set spinning between the electro-magnetic poles2 the excitement of the magnet instantly stops the rotation4 ,though nothing is apparent to the eye1 the copper1 if moved in the excited magnetic field1 appears to move through a viscous fluid2 while1 when a flat piece of the metal is caused to pass to and fro like a saw between the poles1 the sawing of the magnetic field resembles the cutting through of cheese or butter4#a ,this virtual friction of the magnetic field is so strong1 that copper1 by its rapid rotation between the poles1 might probably be fused4 ,we may easily dismiss this experiment by saying that the heat is due to the electric currents excited in the copper4 ,but so long as we are unable to reply to the question1 ',what is an electric current8' the explanation is only provisional4 ,for my own part1 ,i look with profound interest and hope on the strange action here referred to4 ,faraday's thoughts ran intuitively into experimental combinations1 so that subjects whose capacity for experimental treatment would1 to ordinary minds1 seem to be exhausted in a moment1 were shown by him to be all but inexhaustible4 ,he has now an object in view1 the first step towards which is the proof that the principle of ,archimedes is true of magnetism4 ,he forms magnetic solutions of various degrees of strength1 places them between the poles of his magnet1 and suspends in the solutions various magnetic bodies4 ,he proves that when the solution is stronger than the body plunged in it1 the body1 though magnetic1 is repelled2 and when an elongated piece of it is surrounded by the solution1 it sets1 like a diamagnetic body1 equatorially between the excited poles4 ,the same body when suspended in a solution of weaker magnetic power than itself1 is attracted as a whole1 while an elongated portion of it sets axially4 ,and now theoretic questions rush in upon him4 ,is this new force a true repulsion1 or is it merely a differential attraction8 ,might not the apparent repulsion of diamagnetic bodies be really due to the greater attraction of the medium by which they are surrounded8 ,he tries the rarefaction of air1 but finds the effect insensible4 ,he is averse to ascribing a capacity of attraction to space1 or to any hypothetical medium supposed to fill space4 ,he therefore inclines1 but still with caution1 to the opinion that the action of a magnet upon bismuth is a true and absolute repulsion1 and not merely the result of differential attraction4 ,and then he clearly states a theoretic view sufficient to account for the phenomena4 ',theoretically1' he says1 'an explanation of the movements of the diamagnetic bodies1 and all the dynamic phenomena consequent upon the action of magnets upon them1 might be offered in the supposition that magnetic induction caused in them a contrary state to that which it produced in ordinary matter4' ,that is to say1 while in ordinary magnetic influence the exciting pole excites adjacent to itself the contrary magnetism1 in diamagnetic bodies the adjacent magnetism is the same as that of the exciting pole4 ,this theory of reversed polarity1 however1 does not appear to have ever laid deep hold of ,faraday's mind2 and his own experiments failed to give any evidence of its truth4 ,he therefore subsequently abandoned it1 and maintained the non-polarity of the diamagnetic force4 ,he then entered a new1 though related field of inquiry4 ,having dealt with the metals and their compounds1 and having classified all of them that came within the range of his observation under the two heads magnetic and diamagnetic1 he began the investigation of the phenomena presented by crystals when subjected to magnetic power4 ,this action of crystals had been in part theoretically predicted by ,poisson1#b and actually discovered by ,plucker1 whose beautiful results1 at the period which we have now reached1 profoundly interested all scientific men4 ,faraday had been frequently puzzled by the deportment of bismuth1 a highly crystalline metal4 ,sometimes elongated masses of the substance refused to set equatorially1 sometimes they set persistently oblique1 and sometimes even1 like a magnetic body1 from pole to pole4 ',the effect1' he says1 'occurs at a single pole2 and it is then striking to observe a long piece of a substance so diamagnetic as bismuth repelled1 and yet at the same moment set round with force1 axially1 or end on1 as a piece of magnetic substance would do4' ,the effect perplexed him2 and in his efforts to release himself from this perplexity1 no feature of this new manifestation of force escaped his attention4 ,his experiments are described in a memoir communicated to the ,royal ,society on ,december #g1 #ahdh4 ,i have worked long myself at magne-crystallic action1 amid all the light of ,faraday's and ,plucker's researches4 ,the papers now before me were objects of daily and nightly study with me eighteen or nineteen years ago2 but even now1 though their perusal is but the last of a series of repetitions1 they astonish me4 ,every circumstance connected with the subject2 every shade of deportment2 every variation in the energy of the action2 almost every application which could possibly be made of magnetism to bring out in detail the character of this new force1 is minutely described4 ,the field is swept clean1 and hardly anything experimental is left for the gleaner4 ,the phenomena1 he concludes1 are altogether different from those of magnetism or diamagnetism3 they would appear1 in fact1 to present to us 'a new force1 or a new form of force1 in the molecules of matter1' which1 for convenience sake1 he designates by a new word1 as 'the magne-crystallic force4' ,he looks at the crystal acted upon by the magnet4 ,from its mass he passes1 in idea1 to its atoms1 and he asks himself whether the power which can thus seize upon the crystalline molecules1 after they have been fixed in their proper positions by crystallizing force1 may not1 when they are free1 be able to determine their arrangement8 ,he1 therefore1 liberates the atoms by fusing the bismuth4 ,he places the fused substance between the poles of an electro-magnet1 powerfully excited2 but he fails to detect any action4 ,i think it cannot be doubted that an action is exerted here1 that a true cause comes into play2 but its magnitude is not such as sensibly to interfere with the force of crystallization1 which1 in comparison with the diamagnetic force1 is enormous4 ',perhaps1' adds ,faraday1 'if a longer time were allowed1 and a permanent magnet used1 a better result might be obtained4 ,i had built many hopes upon the process4' ,this expression1 and his writings abound in such1 illustrates what has been already said regarding his experiments being suggested and guided by his theoretic conceptions4 ,his mind was full of hopes and hypotheses1 but he always brought them to an experimental test4 ,the record of his planned and executed experiments would1 ,i doubt not1 show a high ratio of hopes disappointed to hopes fulfilled2 but every case of fulfilment abolished all memory of defeat2 disappointment was swallowed up in victory4 ,after the description of the general character of this new force1 ,faraday states with the emphasis here reproduced its mode of action3 ',the law of action appears to be that the line or axis of ,,magne-,,crystallic force 7being the resultant of the action of all the molecules7 tends to place itself parallel1 or as a tangent1 to the magnetic curve1 or line of magnetic force1 passing through the place where the crystal is situated4' ,the magne-crystallic force1 moreover1 appears to him 'to be clearly distinguished from the magnetic or diamagnetic forces1 in that it causes neither approach nor recession1 consisting not in attraction or repulsion1 but in giving a certain determinate position to the mass under its influence4' ,and then he goes on 'very carefully to examine and prove the conclusion that there was no connection of the force with attractive or repulsive influences4' ,with the most refined ingenuity he shows that1 under certain circumstances1 the magne-crystallic force can cause the centre of gravity of a highly magnetic body to retreat from the poles1 and the centre of gravity of a highly diamagnetic body to approach them4 ,his experiments root his mind more and more firmly in the conclusion that 'neither attraction nor repulsion causes the set1 or governs the final position' of the crystal in the magnetic field4 ,that the force which does so is therefore 'distinct in its character and effects from the magnetic and diamagnetic forms of force4 ,on the other hand1' he continues1 'it has a most manifest relation to the crystalline structure of bismuth and other bodies1 and therefore to the power by which their molecules are able to build up the crystalline masses4' ,and here follows one of those expressions which characterize the conceptions of ,faraday in regard to force generally3--',it appears to me impossible to conceive of the results in any other way than by a mutual reaction of the magnetic force1 and the force of the particles of the crystals upon each other4' ,he proves that the action of the force1 though thus molecular1 is an action at a distance2 he shows that a bismuth crystal can cause a freely suspended magnetic needle to set parallel to its magne-crystallic axis4 ,few living men are aware of the difficulty of obtaining results like this1 or of the delicacy necessary to their attainment4 ',but though it thus takes up the character of a force acting at a distance1 still it is due to that power of the particles which makes them cohere in regular order and gives the mass its crystalline aggregation1 which we call at other times the attraction of aggregation1 and so often speak of as acting at insensible distances4' ,thus he broods over this new force1 and looks at it from all possible points of inspection4 ,experiment follows experiment1 as thought follows thought4 ,he will not relinquish the subject as long as a hope exists of throwing more light upon it4 ,he knows full well the anomalous nature of the conclusion to which his experiments lead him4 ,but experiment to him is final1 and he will not shrink from the conclusion4 ',this force1' he says1 'appears to me to be very strange and striking in its character4 ,it is not polar1 for there is no attraction or repulsion4' ,and then1 as if startled by his own utterance1 he asks--',what is the nature of the mechanical force which turns the crystal round1 and makes it affect a magnet8'444 ',i do not remember1' he continues 'heretofore such a case of force as the present one1 where a body is brought into position only1 without attraction or repulsion4' ,plucker1 the celebrated geometer already mentioned1 who pursued experimental physics for many years of his life with singular devotion and success1 visited ,faraday in those days1 and repeated before him his beautiful experiments on magneto-optic action4 ,faraday repeated and verified ,plucker's observations1 and concluded1 what he at first seemed to doubt1 that ,plucker's results and magne-crystallic action had the same origin4 ,at the end of his papers1 when he takes a last look along the line of research1 and then turns his eyes to the future1 utterances quite as much emotional as scientific escape from ,faraday4 ',i cannot1' he says1 at the end of his first paper on magne-crystallic action1 'conclude this series of researches without remarking how rapidly the knowledge of molecular forces grows upon us1 and how strikingly every investigation tends to develop more and more their importance1 and their extreme attraction as an object of study4 ,a few years ago magnetism was to us an occult power1 affecting only a few bodies1 now it is found to influence all bodies1 and to possess the most intimate relations with electricity1 heat1 chemical action1 light1 crystallization1 and through it1 with the forces concerned in cohesion2 and we may1 in the present state of things1 well feel urged to continue in our labours1 encouraged by the hope of bringing it into a bond of union with gravity itself4' ,supplementary remarks ,a brief space will1 perhaps1 be granted me here to state the further progress of an investigation which interested ,faraday so much4 ,drawn by the fame of ,bunsen as a teacher1 in the year #ahdh ,i became a student in the ,university of ,marburg1 in ,hesse ,cassel4 ,bunsen's behaviour to me was that of a brother as well as that of a teacher1 and it was also my happiness to make the acquaintance and gain the friendship of ,professor ,knoblauch1 so highly distinguished by his researches on ,radiant ,heat4 ,plucker's and ,faraday's investigations filled all minds at the time1 and towards the end of #ahdi1 ,professor ,knoblauch and myself commenced a joint investigation of the entire question4 ,long discipline was necessary to give us due mastery over it4 ,employing a method proposed by ,dove1 we examined the optical properties of our crystals ourselves2 and these optical observations went hand in hand with our magnetic experiments4 ,the number of these experiments was very great1 but for a considerable time no fact of importance was added to those already published4 ,at length1 however1 it was our fortune to meet with various crystals whose deportment could not be brought under the laws of magne-crystallic action enunciated by ,plucker4 ,we also discovered instances which led us to suppose that the magne-crystallic force was by no means independent1 as alleged1 of the magnetism or diamagnetism of the mass of the crystal4 ,indeed1 the more we worked at the subject1 the more clearly did it appear to us that the deportment of crystals in the magnetic field was due1 not to a force previously unknown1 but to the modification of the known forces of magnetism and diamagnetism by crystalline aggregation4 ,an eminent example of magne-crystallic action adduced by ,plucker1 and experimented on by ,faraday1 was ,iceland spar4 ,it is what in optics is called a negative crystal1 and according to the law of ,plucker1 the axis of such a crystal was always repelled by a magnet4 ,but we showed that it was only necessary to substitute1 in whole or in part1 carbonate of iron for carbonate of lime1 thus changing the magnetic but not the optical character of the crystal1 to cause the axis to be attracted4 ,that the deportment of magnetic crystals is exactly antithetical to that of diamagnetic crystals isomorphous with the magnetic ones1 was proved to be a general law of action4 ,in all cases1 the line which in a diamagnetic crystal set equatorially1 always set itself in an isomorphous magnetic crystal axially4 ,by mechanical compression other bodies were also made to imitate the ,iceland spar4 ,these and numerous other results bearing upon the question were published at the time in the ',philosophical ,magazine' and in ',poggendorff's ,annalen'2 and the investigation of diamagnetism and magne-crystallic action was subsequently continued by me in the laboratory of ,professor ,magnus of ,berlin4 ,in ,december1 #ahea1 after ,i had quitted ,germany1 ,dr4 ,bence ,jones went to the ,prussian capital to see the celebrated experiments of ,du ,bois ,reymond4 ,influenced1 ,i suppose1 by what he there heard1 he afterwards invited me to give a ,friday evening discourse at the ,royal ,institution4 ,i consented1 not without fear and trembling4 ,for the ,royal ,institution was to me a kind of dragon's den1 where tact and strength would be necessary to save me from destruction4 ,on ,february #aa1 #ahec1 the discourse was given1 and it ended happily4 ,i allude to these things1 that ,i may mention that1 though my aim and object in that lecture was to subvert the notions both of ,faraday and ,plucker1 and to establish in opposition to their views what ,i regarded as the truth1 it was very far from producing in ,faraday either enmity or anger4 ,at the conclusion of the lecture1 he quitted his accustomed seat1 crossed the theatre to the corner into which ,i had shrunk1 shook me by the hand1 and brought me back to the table4 ,once more1 subsequently1 and in connection with a related question1 ,i ventured to differ from him still more emphatically4 ,it was done out of trust in the greatness of his character2 nor was the trust misplaced4 ,he felt my public dissent from him2 and it pained me afterwards to the quick to think that ,i had given him even momentary annoyance4 ,it was1 however1 only momentary4 ,his soul was above all littleness and proof to all egotism4 ,he was the same to me afterwards that he had been before2 the very chance expression which led me to conclude that he felt my dissent being one of kindness and affection4 ,it required long subsequent effort to subdue the complications of magne-crystallic action1 and to bring under the dominion of elementary principles the vast mass of facts which the experiments of ,faraday and ,plucker had brought to light4 ,it was proved by ,reich1 ,edmond ,becquerel1 and myself1 that the condition of diamagnetic bodies1 in virtue of which they were repelled by the poles of a magnet1 was excited in them by those poles2 that the strength of this condition rose and fell with1 and was proportional to1 the strength of the acting magnet4 ,it was not then any property possessed permanently by the bismuth1 and which merely required the development of magnetism to act upon it1 that caused the repulsion2 for then the repulsion would have been simply proportional to the strength of the influencing magnet1 whereas experiment proved it to augment as the square of the strength4 ,the capacity to be repelled was therefore not inherent in the bismuth1 but induced4 ,so far an identity of action was established between magnetic and diamagnetic bodies4 ,after this the deportment of magnetic bodies1 'normal' and 'abnormal'2 crystalline1 amorphous1 and compressed1 was compared with that of crystalline1 amorphous1 and compressed diamagnetic bodies2 and by a series of experiments1 executed in the laboratory of this ,institution1 the most complete antithesis was established between magnetism and diamagnetism4 ,this antithesis embraced the quality of polarity1--the theory of reversed polarity1 first propounded by ,faraday1 being proved to be true4 ,the discussion of the question was very brisk4 ,on the ,continent ,professor ,wilhelm ,weber was the ablest and most successful supporter of the doctrine of diamagnetic polarity2 and it was with an apparatus1 devised by him and constructed under his own superintendence1 by ,leyser of ,leipzig1 that the last demands of the opponents of diamagnetic polarity were satisfied4 ,the establishment of this point was absolutely necessary to the explanation of magne-crystallic action4 ,with that admirable instinct which always guided him1 ,faraday had seen that it was possible1 if not probable1 that the diamagnetic force acts with different degrees of intensity in different directions1 through the mass of a crystal4 ,in his studies on electricity1 he had sought an experimental reply to the question whether crystalline bodies had not different specific inductive capacities in different directions1 but he failed to establish any difference of the kind4 ,his first attempt to establish differences of diamagnetic action in different directions through bismuth1 was also a failure2 but he must have felt this to be a point of cardinal importance1 for he returned to the subject in #ahej1 and proved that bismuth was repelled with different degrees of force in different directions4 ,it seemed as if the crystal were compounded of two diamagnetic bodies of different strengths1 the substance being more strongly repelled across the magne-crystallic axis than along it4 ,the same result was obtained independently1 and extended to various other bodies1 magnetic as well as diamagnetic1 and also to compressed substances1 a little subsequently by myself4 ,the law of action in relation to this point is1 that in diamagnetic crystals1 the line along which the repulsion is a maximum1 sets equatorially in the magnetic field2 while in magnetic crystals the line along which the attraction is a maximum sets from pole to pole4 ,faraday had said that the magne-crystallic force was neither attraction nor repulsion4 ,thus far he was right4 ,it was neither taken singly1 but it was both4 ,by the combination of the doctrine of diamagnetic polarity with these differential attractions and repulsions1 and by paying due regard to the character of the magnetic field1 every fact brought to light in the domain of magne-crystallic action received complete explanation4 ,the most perplexing of those facts were shown to result from the action of mechanical couples1 which the proved polarity both of magnetism and diamagnetism brought into play4 ,indeed the thoroughness with which the experiments of ,faraday were thus explained1 is the most striking possible demonstration of the marvellous precision with which they were executed4 ,footnotes to ,chapter #aa #a ,see ,heat as a ,mode of ,motion1 ninth edition1 p4 #ge4 #b ,see ,sir ,wm4 ,thomson on ,magne-crystallic ,action4 ,phil4 ,mag41 #ahea4 ,chapter #ab4 ,magnetism of flame and gases--atmospheric magnetism ,when an experimental result was obtained by ,faraday it was instantly enlarged by his imagination4 ,i am acquainted with no mind whose power and suddenness of expansion at the touch of new physical truth could be ranked with his4 ,sometimes ,i have compared the action of his experiments on his mind to that of highly combustible matter thrown into a furnace2 every fresh entry of fact was accompanied by the immediate development of light and heat4 ,the light1 which was intellectual1 enabled him to see far beyond the boundaries of the fact itself1 and the heat1 which was emotional1 urged him to the conquest of this newly-revealed domain4 ,but though the force of his imagination was enormous1 he bridled it like a mighty rider1 and never permitted his intellect to be overthrown4 ,in virtue of the expansive power which his vivid imagination conferred upon him1 he rose from the smallest beginnings to the grandest ends4 ,having heard from ,zantedeschi that ,bancalari had established the magnetism of flame1 he repeated the experiments and augmented the results4 ,he passed from flames to gases1 examining and revealing their magnetic and diamagnetic powers2 and then he suddenly rose from his bubbles of oxygen and nitrogen to the atmospheric envelope of the earth itself1 and its relations to the great question of terrestrial magnetism4 ,the rapidity with which these ever-augmenting thoughts assumed the form of experiments is unparalleled4 ,his power in this respect is often best illustrated by his minor investigations1 and1 perhaps1 by none more strikingly than by his paper ',on the ,diamagnetic ,condition of ,flame and ,gases1' published as a letter to ,mr4 ,richard ,taylor1 in the ',philosophical ,magazine' for ,december1 #ahdg4 ,after verifying1 varying1 and expanding the results of ,bancalari1 he submitted to examination heated air-currents1 produced by platinum spirals placed in the magnetic field1 and raised to incandescence by electricity4 ,he then examined the magnetic deportment of gases generally4 ,almost all of these gases are invisible2 but he must1 nevertheless1 track them in their unseen courses4 ,he could not effect this by mingling smoke with his gases1 for the action of his magnet upon the smoke would have troubled his conclusions4 ,he1 therefore1 'caught' his gases in tubes1 carried them out of the magnetic field1 and made them reveal themselves at a distance from the magnet4 ,immersing one gas in another1 he determined their differential action2 results of the utmost beauty being thus arrived at4 ,perhaps the most important are those obtained with atmospheric air and its two constituents4 ,oxygen1 in various media1 was strongly attracted by the magnet2 in coal-gas1 for example1 it was powerfully magnetic1 whereas nitrogen was diamagnetic4 ,some of the effects obtained with oxygen in coal-gas were strikingly beautiful4 ,when the fumes of chloride of ammonium 7a diamagnetic substance7 were mingled with the oxygen1 the cloud of chloride behaved in a most singular manner1--',the attraction of iron filings1' says ,faraday1 'to a magnetic pole is not more striking than the appearance presented by the oxygen under these circumstances4' ,on observing this deportment the question immediately occurs to him1--,can we not separate the oxygen of the atmosphere from its nitrogen by magnetic analysis8 ,it is the perpetual occurrence of such questions that marks the great experimenter4 ,the attempt to analyze atmospheric air by magnetic force proved a failure1 like the previous attempt to influence crystallization by the magnet4 ,the enormous comparative power of the force of crystallization ,i have already assigned as a reason for the incompetence of the magnet to determine molecular arrangement2 in the present instance the magnetic analysis is opposed by the force of diffusion1 which is also very strong comparatively4 ,the same remark applies to1 and is illustrated by1 another experiment subsequently executed by ,faraday4 ,water is diamagnetic1 sulphate of iron is strongly magnetic4 ,he enclosed 'a dilute solution of sulphate of iron in a tube1 and placed the lower end of the tube between the poles of a powerful horseshoe magnet for days together1' but he could produce 'no concentration of the solution in the part near the magnet4' ,here also the diffusibility of the salt was too powerful for the force brought against it4 ,the experiment last referred to is recorded in a paper presented to the ,royal ,society on the #bnd ,august1 #ahej1 in which he pursues the investigation of the magnetism of gases4 ,newton's observations on soap-bubbles were often referred to by ,faraday4 ,his delight in a soap-bubble was like that of a boy1 and he often introduced them into his lectures1 causing them1 when filled with air1 to float on invisible seas of carbonic acid1 and otherwise employing them as a means of illustration4 ,he now finds them exceedingly useful in his experiments on the magnetic condition of gases4 ,a bubble of air in a magnetic field occupied by air was unaffected1 save through the feeble repulsion of its envelope4 ,a bubble of nitrogen1 on the contrary1 was repelled from the magnetic axis with a force far surpassing that of a bubble of air4 ,the deportment of oxygen in air 'was very impressive1 the bubble being pulled inward or towards the axial line1 sharply and suddenly1 as if the oxygen were highly magnetic4' ,he next labours to establish the true magnetic zero1 a problem not so easy as might at first sight be imagined4 ,for the action of the magnet upon any gas1 while surrounded by air or any other gas1 can only be differential2 and if the experiment were made in vacuo1 the action of the envelope1 in this case necessarily of a certain thickness1 would trouble the result4 ,while dealing with this subject1 ,faraday makes some noteworthy observations regarding space4 ,in reference to the ,torricellian vacuum1 he says1 ',perhaps it is hardly necessary for me to state that ,i find both iron and bismuth in such vacua perfectly obedient to the magnet4 ,from such experiments1 and also from general observations and knowledge1 it seems manifest that the lines of magnetic force can traverse pure space1 just as gravitating force does1 and as statical electrical forces do1 and therefore space has a magnetic relation of its own1 and one that we shall probably find hereafter to be of the utmost importance in natural phenomena4 ,but this character of space is not of the same kind as that which1 in relation to matter1 we endeavour to express by the terms magnetic and diamagnetic4 ,to confuse these together would be to confound space with matter1 and to trouble all the conceptions by which we endeavour to understand and work out a progressively clearer view of the mode of action1 and the laws of natural forces4 ,it would be as if in gravitation or electric forces1 one were to confound the particles acting on each other with the space across which they are acting1 and would1 ,i think1 shut the door to advancement4 ,mere space cannot act as matter acts1 even though the utmost latitude be allowed to the hypothesis of an ether2 and admitting that hypothesis1 it would be a large additional assumption to suppose that the lines of magnetic force are vibrations carried on by it1 whilst as yet we have no proof that time is required for their propagation1 or in what respect they may1 in general character1 assimilate to or differ from their respective lines of gravitating1 luminiferous1 or electric forces4' ,pure space he assumes to be the true magnetic zero1 but he pushes his inquiries to ascertain whether among material substances there may not be some which resemble space4 ,if you follow his experiments1 you will soon emerge into the light of his results4 ,a torsion-beam was suspended by a skein of cocoon silk2 at one end of the beam was fixed a cross-piece #a #a_/b inch long4 ,tubes of exceedingly thin glass1 filled with various gases1 and hermetically sealed1 were suspended in pairs from the two ends of the cross-piece4 ,the position of the rotating torsion-head was such that the two tubes were at opposite sides of1 and equidistant from1 the magnetic axis1 that is to say from the line joining the two closely approximated polar points of an electro-magnet4 ,his object was to compare the magnetic action of the gases in the two tubes4 ,when one tube was filled with oxygen1 and the other with nitrogen1 on the supervention of the magnetic force1 the oxygen was pulled towards the axis1 the nitrogen being pushed out4 ,by turning the torsion-head they could be restored to their primitive position of equidistance1 where it is evident the action of the glass envelopes was annulled4 ,the amount of torsion necessary to re-establish equidistance expressed the magnetic difference of the substances compared4 ,and then he compared oxygen with oxygen at different pressures4 ,one of his tubes contained the gas at the pressure of #cj inches of mercury1 another at a pressure of #ae inches of mercury1 a third at a pressure of #aj inches1 while a fourth was exhausted as far as a good air-pump renders exhaustion possible4 ',when the first of these was compared with the other three1 the effect was most striking4' ,it was drawn towards the axis when the magnet was excited1 the tube containing the rarer gas being apparently driven away1 and the greater the difference between the densities of the two gases1 the greater was the energy of this action4 ,and now observe his mode of reaching a material magnetic zero4 ,when a bubble of nitrogen was exposed in air in the magnetic field1 on the supervention of the power1 the bubble retreated from the magnet4 ,a less acute observer would have set nitrogen down as diamagnetic2 but ,faraday knew that retreat1 in a medium composed in part of oxygen1 might be due to the attraction of the latter gas1 instead of to the repulsion of the gas immersed in it4 ,but if nitrogen be really diamagnetic1 then a bubble or bulb filled with the dense gas will overcome one filled with the rarer gas4 ,from the cross-piece of his torsion-balance he suspended his bulbs of nitrogen1 at equal distances from the magnetic axis1 and found that the rarefaction1 or the condensation of the gas in either of the bulbs had not the slightest influence4 ,when the magnetic force was developed1 the bulbs remained in their first position1 even when one was filled with nitrogen1 and the other as far as possible exhausted4 ,nitrogen1 in fact1 acted 'like space itself'2 it was neither magnetic nor diamagnetic4 ,he cannot conveniently compare the paramagnetic force of oxygen with iron1 in consequence of the exceeding magnetic intensity of the latter substance2 but he does compare it with the sulphate of iron1 and finds that1 bulk for bulk1 oxygen is equally magnetic with a solution of this substance in water 'containing seventeen times the weight of the oxygen in crystallized proto-sulphate of iron1 or #c4d times its weight of metallic iron in that state of combination4' ,by its capability to deflect a fine glass fibre1 he finds that the attraction of this bulb of oxygen1 containing only #j4aag of a grain of the gas1 at an average distance of more than an inch from the magnetic axis1 is about equal to the gravitating force of the same amount of oxygen as expressed by its weight4 ,these facts could not rest for an instant in the mind of ,faraday without receiving that expansion to which ,i have already referred4 ',it is hardly necessary1' he writes1 'for me to say here that this oxygen cannot exist in the atmosphere exerting such a remarkable and high amount of magnetic force1 without having a most important influence on the disposition of the magnetism of the earth1 as a planet2 especially if it be remembered that its magnetic condition is greatly altered by variations of its density and by variations of its temperature4 ,i think ,i see here the real cause of many of the variations of that force1 which have been1 and are now so carefully watched on different parts of the surface of the globe4 ,the daily variation1 and the annual variation1 both seem likely to come under it2 also very many of the irregular continual variations1 which the photographic process of record renders so beautifully manifest4 ,if such expectations be confirmed1 and the influence of the atmosphere be found able to produce results like these1 then we shall probably find a new relation between the aurora borealis and the magnetism of the earth1 namely1 a relation established1 more or less1 through the air itself in connection with the space above it2 and even magnetic relations and variations1 which are not as yet suspected1 may be suggested and rendered manifest and measurable1 in the further development of what ,i will venture to call ,atmospheric ,magnetism4 ,i may be over-sanguine in these expectations1 but as yet ,i am sustained in them by the apparent reality1 simplicity1 and sufficiency of the cause assumed1 as it at present appears to my mind4 ,as soon as ,i have submitted these views to a close consideration1 and the test of accordance with observation1 and1 where applicable1 with experiments also1 ,i will do myself the honour to bring them before the ,royal ,society4' ,two elaborate memoirs are then devoted to the subject of ,atmospheric ,magnetism2 the first sent to the ,royal ,society on the #ith of ,october1 and the second on the #aith of ,november1 #ahej4 ,in these memoirs he discusses the effects of heat and cold upon the magnetism of the air1 and the action on the magnetic needle1 which must result from thermal changes4 ,by the convergence and divergence of the lines of terrestrial magnetic force1 he shows how the distribution of magnetism1 in the earth's atmosphere1 is effected4 ,he applies his results to the explanation of the ,annual and of the ,diurnal ,variation3 he also considers irregular variations1 including the action of magnetic storms4 ,he discusses1 at length1 the observations at ,st4 ,petersburg1 ,greenwich1 ,hobarton1 ,st4 ,helena1 ,toronto1 and the ,cape of ,good ,hope2 believing that the facts1 revealed by his experiments1 furnish the key to the variations observed at all these places4 ,in the year #ahea1 ,i had the honour of an interview with ,humboldt1 in ,berlin1 and his parting words to me then were1 ',tell ,faraday that ,i entirely agree with him1 and that he has1 in my opinion1 completely explained the variation of the declination4' ,eminent men have since informed me that ,humboldt was hasty in expressing this opinion4 ,in fact1 ,faraday's memoirs on atmospheric magnetism lost much of their force--perhaps too much--through the important discovery of the relation of the variation of the declination to the number of the solar spots4 ,but ,i agree with him and ,m4 ,edmond ,becquerel1 who worked independently at this subject1 in thinking1 that a body so magnetic as oxygen1 swathing the earth1 and subject to variations of temperature1 diurnal and annual1 must affect the manifestations of terrestrial magnetism4#a ,the air that stands upon a single square foot of the earth's surface is1 according to ,faraday1 equivalent in magnetic force to #hafj lbs4 of crystallized protosulphate of iron4 ,such a substance cannot be absolutely neutral as regards the deportment of the magnetic needle4 ,but ,faraday's writings on this subject are so voluminous1 and the theoretic points are so novel and intricate1 that ,i shall postpone the complete analysis of these researches to a time when ,i can lay hold of them more completely than my other duties allow me to do now4 ,footnote to ,chapter #ab #a ,this persuasion has been greatly strengthened by the recent perusal of a paper by ,mr4 ,baxendell4 ,chapter #ac4 ,speculations3 nature of matter3 lines of force ,the scientific picture of ,faraday would not be complete without a reference to his speculative writings4 ,on ,friday1 ,january #ai1 #ahdd1 he opened the weekly evening-meetings of the ,royal ,institution by a discourse entitled ',a speculation touching ,electric ,conduction and the nature of ,matter4' ,in this discourse he not only attempts the overthrow of ,dalton's ,theory of ,atoms1 but also the subversion of all ordinary scientific ideas regarding the nature and relations of ,matter and ,force4 ,he objected to the use of the term atom3--',i have not yet found a mind1' he says1 'that did habitually separate it from its accompanying temptations2 and there can be no doubt that the words definite proportions1 equivalent1 primes1 c41 which did and do fully express all the facts of what is usually called the atomic theory in chemistry1 were dismissed because they were not expressive enough1 and did not say all that was in the mind of him who used the word atom in their stead4' ,a moment will be granted me to indicate my own view of ,faraday's position here4 ,the word 'atom' was not used in the stead of definite proportions1 equivalents1 or primes4 ,these terms represented facts that followed from1 but were not equivalent to1 the atomic theory4 ,facts cannot satisfy the mind3 and the law of definite combining proportions being once established1 the question 'why should combination take place according to that law8' is inevitable4 ,dalton answered this question by the enunciation of the ,atomic ,theory1 the fundamental idea of which is1 in my opinion1 perfectly secure4 ,the objection of ,faraday to ,dalton might be urged with the same substantial force against ,newton3 it might be stated with regard to the planetary motions that the laws of ,kepler revealed the facts2 that the introduction of the principle of gravitation was an addition to the facts4 ,but this is the essence of all theory4 ,the theory is the backward guess from fact to principle2 the conjecture1 or divination regarding something1 which lies behind the facts1 and from which they flow in necessary sequence4 ,if ,dalton's theory1 then1 account for the definite proportions observed in the combinations of chemistry1 its justification rests upon the same basis as that of the principle of gravitation4 ,all that can in strictness be said in either case is that the facts occur as if the principle existed4 ,the manner in which ,faraday himself habitually deals with his hypotheses is revealed in this lecture4 ,he incessantly employed them to gain experimental ends1 but he incessantly took them down1 as an architect removes the scaffolding when the edifice is complete4 ',i cannot but doubt1' he says1 'that he who as a mere philosopher has most power of penetrating the secrets of nature1 and guessing by hypothesis at her mode of working1 will also be most careful for his own safe progress and that of others1 to distinguish the knowledge which consists of assumption1 by which ,i mean theory and hypothesis1 from that which is the knowledge of facts and laws4' ,faraday himself1 in fact1 was always 'guessing by hypothesis1' and making theoretic divination the stepping-stone to his experimental results4 ,i have already more than once dwelt on the vividness with which he realised molecular conditions2 we have a fine example of this strength and brightness of imagination in the present 'speculation4' ,he grapples with the notion that matter is made up of particles1 not in absolute contact1 but surrounded by interatomic space4 ',space1' he observes1 'must be taken as the only continuous part of a body so constituted4 ,space will permeate all masses of matter in every direction like a net1 except that in place of meshes it will form cells1 isolating each atom from its neighbours1 itself only being continuous4' ,let us follow out this notion2 consider1 he argues1 the case of a non-conductor of electricity1 such for example as shell-lac1 with its molecules1 and intermolecular spaces running through the mass4 ,in its case space must be an insulator2 for if it were a conductor it would resemble 'a fine metallic web1' penetrating the lac in every direction4 ,but the fact is that it resembles the wax of black sealing-wax1 which surrounds and insulates the particles of conducting carbon1 interspersed throughout its mass4 ,in the case of shell-lac1 therefore1 space is an insulator4 ,but now1 take the case of a conducting metal4 ,here we have1 as before1 the swathing of space round every atom4 ,if space be an insulator there can be no transmission of electricity from atom to atom4 ,but there is transmission2 hence space is a conductor4 ,thus he endeavours to hamper the atomic theory4 ',the reasoning1' he says1 'ends in a subversion of that theory altogether2 for if space be an insulator it cannot exist in conducting bodies1 and if it be a conductor it cannot exist in insulating bodies4 ,any ground of reasoning1' he adds1 as if carried away by the ardour of argument1 'which tends to such conclusions as these must in itself be false4' ,he then tosses the atomic theory from horn to horn of his dilemmas4 ,what do we know1 he asks1 of the atom apart from its force8 ,you imagine a nucleus which may be called a1 and surround it by forces which may be called m2 'to my mind the a or nucleus vanishes1 and the substance consists in the powers of m4 ,and indeed what notion can we form of the nucleus independent of its powers8 ,what thought remains on which to hang the imagination of an a independent of the acknowledged forces8' ,like ,boscovich1 he abolishes the atom1 and puts a 'centre of force' in its place4 ,with his usual courage and sincerity he pushes his view to its utmost consequences4 ',this view of the constitution of matter1' he continues1 'would seem to involve necessarily the conclusion that matter fills all space1 or at least all space to which gravitation extends2 for gravitation is a property of matter dependent on a certain force1 and it is this force which constitutes the matter4 ,in that view matter is not merely mutually penetrable2#a but each atom extends1 so to say1 throughout the whole of the solar system1 yet always retaining its own centre of force4' ,it is the operation of a mind filled with thoughts of this profound1 strange1 and subtle character that we have to take into account in dealing with ,faraday's later researches4 ,a similar cast of thought pervades a letter addressed by ,faraday to ,mr4 ,richard ,phillips1 and published in the ',philosophical ,magazine' for ,may1 #ahdf4 ,it is entitled ',thoughts on ,ray-vibrations1' and it contains one of the most singular speculations that ever emanated from a scientific mind4 ,it must be remembered here1 that though ,faraday lived amid such speculations he did not rate them highly1 and that he was prepared at any moment to change them or let them go4 ,they spurred him on1 but they did not hamper him4 ,his theoretic notions were fluent2 and when minds less plastic than his own attempted to render those fluxional images rigid1 he rebelled4 ,he warns ,phillips moreover1 that from first to last1 'he merely threw out as matter for speculation the vague impressions of his mind2 for he gave nothing as the result of sufficient consideration1 or as the settled conviction1 or even probable conclusion at which he had arrived4' ,the gist of this communication is that gravitating force acts in lines across space1 and that the vibrations of light and radiant heat consist in the tremors of these lines of force4 ',this notion1' he says1 'as far as it is admitted1 will dispense with the ether1 which1 in another view is supposed to be the medium in which these vibrations take place4' ,and he adds further on1 that his view 'endeavours to dismiss the ether but not the vibrations4' ,the idea here set forth is the natural supplement of his previous notion1 that it is gravitating force which constitutes matter1 each atom extending1 so to say1 throughout the whole of the solar system4 ,the letter to ,mr4 ,phillips winds up with this beautiful conclusion3-- ',i think it likely that ,i have made many mistakes in the preceding pages1 for even to myself my ideas on this point appear only as the shadow of a speculation1 or as one of those impressions upon the mind which are allowable for a time as guides to thought and research4 ,he who labours in experimental inquiries1 knows how numerous these are1 and how often their apparent fitness and beauty vanish before the progress and development of real natural truth4' ,let it then be remembered that ,faraday entertained notions regarding matter and force altogether distinct from the views generally held by scientific men4 ,force seemed to him an entity dwelling along the line in which it is exerted4 ,the lines along which gravity acts between the sun and earth seem figured in his mind as so many elastic strings2 indeed he accepts the assumed instantaneity of gravity as the expression of the enormous elasticity of the 'lines of weight4' ,such views1 fruitful in the case of magnetism1 barren1 as yet1 in the case of gravity1 explain his efforts to transform this latter force4 ,when he goes into the open air and permits his helices to fall1 to his mind's eye they are tearing through the lines of gravitating power1 and hence his hope and conviction that an effect would and ought to be produced4 ,it must ever be borne in mind that ,faraday's difficulty in dealing with these conceptions was at bottom the same as that of ,newton2 that he is in fact trying to overleap this difficulty1 and with it probably the limits prescribed to the intellect itself4 ,the idea of lines of magnetic force was suggested to ,faraday by the linear arrangement of iron filings when scattered over a magnet4 ,he speaks of and illustrates by sketches1 the deflection1 both convergent and divergent1 of the lines of force1 when they pass respectively through magnetic and diamagnetic bodies4 ,these notions of concentration and divergence are also based on the direct observation of his filings4 ,so long did he brood upon these lines2 so habitually did he associate them with his experiments on induced currents1 that the association became 'indissoluble1' and he could not think without them4 ',i have been so accustomed1' he writes1 'to employ them1 and especially in my last researches1 that ,i may have unwittingly become prejudiced in their favour1 and ceased to be a clear-sighted judge4 ,still1 ,i have always endeavoured to make experiment the test and controller of theory and opinion2 but neither by that nor by close cross-examination in principle1 have ,i been made aware of any error involved in their use4' ,in his later researches on magne-crystallic action1 the idea of lines of force is extensively employed2 it indeed led him to an experiment which lies at the root of the whole question4 ,in his subsequent researches on ,atmospheric ,magnetism the idea receives still wider application1 showing itself to be wonderfully flexible and convenient4 ,indeed without this conception the attempt to seize upon the magnetic actions1 possible or actual1 of the atmosphere would be difficult in the extreme2 but the notion of lines of force1 and of their divergence and convergence1 guides ,faraday without perplexity through all the intricacies of the question4 ,after the completion of those researches1 and in a paper forwarded to the ,royal ,society on ,october #bb1 #ahea1 he devotes himself to the formal development and illustration of his favourite idea4 ,the paper bears the title1 ',on lines of magnetic force1 their definite character1 and their distribution within a magnet and through space4' ,a deep reflectiveness is the characteristic of this memoir4 ,in his experiments1 which are perfectly beautiful and profoundly suggestive1 he takes but a secondary delight4 ,his object is to illustrate the utility of his conception of lines of force4 ',the study of these lines1' he says1 'has at different times been greatly influential in leading me to various results which ,i think prove their utility as well as fertility4' ,faraday for a long period used the lines of force merely as 'a representative idea4' ,he seemed for a time averse to going further in expression than the lines themselves1 however much further he may have gone in idea4 ,that he believed them to exist at all times round a magnet1 and irrespective of the existence of magnetic matter1 such as iron filings1 external to the magnet1 is certain4 ,no doubt the space round every magnet presented itself to his imagination as traversed by loops of magnetic power2 but he was chary in speaking of the physical substratum of those loops4 ,indeed it may be doubted whether the physical theory of lines of force presented itself with any distinctness to his own mind4 ,the possible complicity of the luminiferous ether in magnetic phenomena was certainly in his thoughts4 ',how the magnetic force1' he writes1 'is transferred through bodies or through space we know not2 whether the result is merely action at a distance1 as in the case of gravity2 or by some intermediate agency1 as in the case of light1 heat1 the electric current1 and 7as ,i believe7 static electric action4 ,the idea of magnetic fluids1 as applied by some1 or of ,magnetic centres of action1 does not include that of the latter kind of transmission1 but the idea of lines of force does4' ,and he continues thus3--',i am more inclined to the notion that in the transmission of the magnetic force there is such an action an intermediate agency external to the magnet1 than that the effects are merely attraction and repulsion at a distance4 ,such an affection may be a function of the ether2 for it is not at all unlikely that1 if there be an ether1 it should have other uses than simply the conveyance of radiations4' ,when he speaks of the magnet in certain cases1 'revolving amongst its own forces1' he appears to have some conception of this kind in view4 ,a great part of the investigation completed in ,october1 #ahea1 was taken up with the motions of wires round the poles of a magnet and the converse4 ,he carried an insulated wire along the axis of a bar magnet from its pole to its equator1 where it issued from the magnet1 and was bent up so as to connect its two ends4 ,a complete circuit1 no part of which was in contact with the magnet1 was thus obtained4 ,he found that when the magnet and the external wire were rotated together no current was produced2 whereas1 when either of them was rotated and the other left at rest currents were evolved4 ,he then abandoned the axial wire1 and allowed the magnet itself to take its place2 the result was the same4#b ,it was the relative motion of the magnet and the loop that was effectual in producing a current4 ,the lines of force have their roots in the magnet1 and though they may expand into infinite space1 they eventually return to the magnet4 ,now these lines may be intersected close to the magnet or at a distance from it4 ,faraday finds distance to be perfectly immaterial so long as the number of lines intersected is the same4 ,for example1 when the loop connecting the equator and the pole of his barmagnet performs one complete revolution round the magnet1 it is manifest that all the lines of force issuing from the magnet are once intersected4 ,now it matters not whether the loop be ten feet or ten inches in length1 it matters not how it may be twisted and contorted1 it matters not how near to the magnet or how distant from it the loop may be1 one revolution always produces the same amount of current electricity1 because in all these cases all the lines of force issuing from the magnet are once intersected and no more4 ,from the external portion of the circuit he passes in idea to the internal1 and follows the lines of force into the body of the magnet itself4 ,his conclusion is that there exist lines of force within the magnet of the same nature as those without4 ,what is more1 they are exactly equal in amount to those without4 ,they have a relation in direction to those without2 and in fact are continuations of them4444 ',every line of force1 therefore1 at whatever distance it may be taken from the magnet1 must be considered as a closed circuit1 passing in some part of its course through the magnet1 and having an equal amount of force in every part of its course4' ,all the results here described were obtained with moving metals4 ',but1' he continues with profound sagacity1 'mere motion would not generate a relation1 which had not a foundation in the existence of some previous state2 and therefore the quiescent metals must be in some relation to the active centre of force1' that is to the magnet4 ,he here touches the core of the whole question1 and when we can state the condition into which the conducting wire is thrown before it is moved1 we shall then be in a position to understand the physical constitution of the electric current generated by its motion4 ,in this inquiry ,faraday worked with steel magnets1 the force of which varies with the distance from the magnet4 ,he then sought a uniform field of magnetic force1 and found it in space as affected by the magnetism of the earth4 ,his next memoir1 sent to the ,royal ,society1 ,december #ca1 #ahea1 is 'on the employment of the ,induced ,magnetoelectro ,current as a test and measure of magnetic forces4' ,he forms rectangles and rings1 and by ingenious and simple devices collects the opposed currents which are developed in them by rotation across the terrestrial lines of magnetic force4 ,he varies the shapes of his rectangles while preserving their areas constant1 and finds that the constant area produces always the same amount of current per revolution4 ,the current depends solely on the number of lines of force intersected1 and when this number is kept constant the current remains constant too4 ,thus the lines of magnetic force are continually before his eyes1 by their aid he colligates his facts1 and through the inspirations derived from them he vastly expands the boundaries of our experimental knowledge4 ,the beauty and exactitude of the results of this investigation are extraordinary4 ,i cannot help thinking while ,i dwell upon them1 that this discovery of magneto-electricity is the greatest experimental result ever obtained by an investigator4 ,it is the ,mont ,blanc of ,faraday's own achievements4 ,he always worked at great elevations1 but a higher than this he never subsequently attained4 ,footnotes to ,chapter #ac #a ,he compares the interpenetration of two atoms to the coalescence of two distinct waves1 which though for a moment blended to a single mass1 preserve their individuality1 and afterwards separate4 #b ,in this form the experiment is identical with one made twenty years earlier4 ,see page #cd4 ,chapter #ad4 ,unity and convertibility of natural forces3 theory of the electric current4 ,the terms unity and convertibility1 as applied to natural forces1 are often employed in these investigations1 many profound and beautiful thoughts respecting these subjects being expressed in ,faraday's memoirs4 ,modern inquiry has1 however1 much augmented our knowledge of the relationship of natural forces1 and it seems worth while to say a few words here1 tending to clear up certain misconceptions which appear to exist among philosophic writers regarding this relationship4 ,the whole stock of energy or working-power in the world consists of attractions1 repulsions1 and motions4 ,if the attractions and repulsions are so circumstanced as to be able to produce motion1 they are sources of working-power1 but not otherwise4 ,let us for the sake of simplicity confine our attention to the case of attraction4 ,the attraction exerted between the earth and a body at a distance from the earth's surface is a source of working-power2 because the body can be moved by the attraction1 and in falling to the earth can perform work4 ,when it rests upon the earth's surface it is not a source of power or energy1 because it can fall no further4 ,but though it has ceased to be a source of energy1 the attraction of gravity still acts as a force1 which holds the earth and weight together4 ,the same remarks apply to attracting atoms and molecules4 ,as long as distance separates them1 they can move across it in obedience to the attraction1 and the motion thus produced may1 by proper appliances1 be caused to perform mechanical work4 ,when1 for example1 two atoms of hydrogen unite with one of oxygen1 to form water the atoms are first drawn towards each other--they move1 they clash1 and then by virtue of their resiliency1 they recoil and quiver4 ,to this quivering motion we give the name of heat4 ,now this quivering motion is merely the redistribution of the motion produced by the chemical affinity2 and this is the only sense in which chemical affinity can be said to be converted into heat4 ,we must not imagine the chemical attraction destroyed1 or converted into anything else4 ,for the atoms1 when mutually clasped to form a molecule of water1 are held together by the very attraction which first drew them towards each other4 ,that which has really been expended is the pull exerted through the space by which the distance between the atoms has been diminished4 ,if this be understood1 it will be at once seen that gravity may in this sense be said to be convertible into heat2 that it is in reality no more an outstanding and inconvertible agent1 as it is sometimes stated to be1 than chemical affinity4 ,by the exertion of a certain pull1 through a certain space1 a body is caused to clash with a certain definite velocity against the earth4 ,heat is thereby developed1 and this is the only sense in which gravity can be said to be converted into heat4 ,in no case is the force which produces the motion annihilated or changed into anything else4 ,the mutual attraction of the earth and weight exists when they are in contact as when they were separate2 but the ability of that attraction to employ itself in the production of motion does not exist4 ,the transformation1 in this case1 is easily followed by the mind's eye4 ,first1 the weight as a whole is set in motion by the attraction of gravity4 ,this motion of the mass is arrested by collision with the earth2 being broken up into molecular tremors1 to which we give the name of heat4 ,and when we reverse the process1 and employ those tremors of heat to raise a weight1 as is done through the intermediation of an elastic fluid in the steam-engine1 a certain definite portion of the molecular motion is destroyed in raising the weight4 ,in this sense1 and this sense only1 can the heat be said to be converted into gravity1 or more correctly1 into potential energy of gravity4 ,it is not that the destruction of the heat has created any new attraction1 but simply that the old attraction has now a power conferred upon it1 of exerting a certain definite pull in the interval between the starting-point of the falling weight and its collision with the earth4 ,so also as regards magnetic attraction3 when a sphere of iron placed at some distance from a magnet rushes towards the magnet1 and has its motion stopped by collision1 an effect mechanically the same as that produced by the attraction of gravity occurs4 ,the magnetic attraction generates the motion of the mass1 and the stoppage of that motion produces heat4 ,in this sense1 and in this sense only1 is there a transformation of magnetic work into heat4 ,and if by the mechanical action of heat1 brought to bear by means of a suitable machine1 the sphere be torn from the magnet and again placed at a distance1 a power of exerting a pull through that distance1 and producing a new motion of the sphere1 is thereby conferred upon the magnet2 in this sense1 and in this sense only1 is the heat converted into magnetic potential energy4 ,when1 therefore1 writers on the conservation of energy speak of tensions being 'consumed' and 'generated1' they do not mean thereby that old attractions have been annihilated and new ones brought into existence1 but that1 in the one case1 the power of the attraction to produce motion has been diminished by the shortening of the distance between the attracting bodies1 and that in the other case the power of producing motion has been augmented by the increase of the distance4 ,these remarks apply to all bodies1 whether they be sensible masses or molecules4 ,of the inner quality that enables matter to attract matter we know nothing2 and the law of conservation makes no statement regarding that quality4 ,it takes the facts of attraction as they stand1 and affirms only the constancy of working-power4 ,that power may exist in the form of ,,motion2 or it may exist in the form of ,,force1 with distance to act through4 ,the former is dynamic energy1 the latter is potential energy1 the constancy of the sum of both being affirmed by the law of conservation4 ,the convertibility of natural forces consists solely in transformations of dynamic into potential1 and of potential into dynamic1 energy1 which are incessantly going on4 ,in no other sense has the convertibility of force1 at present1 any scientific meaning4 ,by the contraction of a muscle a man lifts a weight from the earth4 ,but the muscle can contract only through the oxidation of its own tissue or of the blood passing through it4 ,molecular motion is thus converted into mechanical motion4 ,supposing the muscle to contract without raising the weight1 oxidation would also occur1 but the whole of the heat produced by this oxidation would be liberated in the muscle itself4 ,not so when it performs external work2 to do that work a certain definite portion of the heat of oxidation must be expended4 ,it is so expended in pulling the weight away from the earth4 ,if the weight be permitted to fall1 the heat generated by its collision with the earth would exactly make up for that lacking in the muscle during the lifting of the weight4 ,in the case here supposed1 we have a conversion of molecular muscular action into potential energy of gravity2 and a conversion of that potential energy into heat2 the heat1 however1 appearing at a distance from its real origin in the muscle4 ,the whole process consists of a transference of molecular motion from the muscle to the weight1 and gravitating force is the mere go-between1 by means of which the transference is effected4 ,these considerations will help to clear our way to the conception of the transformations which occur when a wire is moved across the lines of force in a magnetic field4 ,in this case it is commonly said we have a conversion of magnetism into electricity4 ,but let us endeavour to understand what really occurs4 ,for the sake of simplicity1 and with a view to its translation into a different one subsequently1 let us adopt for a moment the provisional conception of a mixed fluid in the wire1 composed of positive and negative electricities in equal quantities1 and therefore perfectly neutralizing each other when the wire is still4 ,by the motion of the wire1 say with the hand1 towards the magnet1 what the ,germans call a ,scheidungs-,kraft--a separating force--is brought into play4 ,this force tears the mixed fluids asunder1 and drives them in two currents1 the one positive and the other negative1 in two opposite directions through the wire4 ,the presence of these currents evokes a force of repulsion between the magnet and the wire2 and to cause the one to approach the other1 this repulsion must be overcome4 ,the overcoming of this repulsion is1 in fact1 the work done in separating and impelling the two electricities4 ,when the wire is moved away from the magnet1 a ,scheidungs-,kraft1 or separating force1 also comes into play2 but now it is an attraction that has to be surmounted4 ,in surmounting it1 currents are developed in directions opposed to the former2 positive takes the place of negative1 and negative the place of positive2 the overcoming of the attraction being the work done in separating and impelling the two electricities4 ,the mechanical action occurring here is different from that occurring where a sphere of soft iron is withdrawn from a magnet1 and again attracted4 ,in this case muscular force is expended during the act of separation2 but the attraction of the magnet effects the reunion4 ,in the case of the moving wire also we overcome a resistance in separating it from the magnet1 and thus far the action is mechanically the same as the separation of the sphere of iron4 ,but after the wire has ceased moving1 the attraction ceases2 and so far from any action occurring similar to that which draws the iron sphere back to the magnet1 we have to overcome a repulsion to bring them together4 ,there is no potential energy conferred either by the removal or by the approach of the wire1 and the only power really transformed or converted1 in the experiment1 is muscular power4 ,nothing that could in strictness be called a conversion of magnetism into electricity occurs4 ,the muscular oxidation that moves the wire fails to produce within the muscle its due amount of heat1 a portion of that heat1 equivalent to the resistance overcome1 appearing in the moving wire instead4 ,is this effect an attraction and a repulsion at a distance8 ,if so1 why should both cease when the wire ceases to move8 ,in fact1 the deportment of the wire resembles far more that of a body moving in a resisting medium than anything else2 the resistance ceasing when the motion is suspended4 ,let us imagine the case of a liquid so mobile that the hand may be passed through it to and fro1 without encountering any sensible resistance4 ,it resembles the motion of a conductor in the unexcited field of an electro-magnet4 ,now1 let us suppose a body placed in the liquid1 or acting on it1 which confers upon it the property of viscosity2 the hand would no longer move freely4 ,during its motion1 but then only1 resistance would be encountered and overcome4 ,here we have rudely represented the case of the excited magnetic field1 and the result in both cases would be substantially the same4 ,in both cases heat would1 in the end1 be generated outside of the muscle1 its amount being exactly equivalent to the resistance overcome4 ,let us push the analogy a little further2 suppose in the case of the fluid rendered viscous1 as assumed a moment ago1 the viscosity not to be so great as to prevent the formation of ripples when the hand is passed through the liquid4 ,then the motion of the hand1 before its final conversion into heat1 would exist for a time as wave-motion1 which1 on subsiding1 would generate its due equivalent of heat4 ,this intermediate stage1 in the case of our moving wire1 is represented by the period during which the electric current is flowing through it2 but that current1 like the ripples of our liquid1 soon subsides1 being1 like them1 converted into heat4 ,do these words shadow forth anything like the reality8 ,such speculations cannot be injurious if they are enunciated without dogmatism4 ,i do confess that ideas such as these here indicated exercise a strong fascination on my mind4 ,is then the magnetic field really viscous1 and if so1 what substance exists in it and the wire to produce the viscosity8 ,let us first look at the proved effects1 and afterwards turn our thoughts back upon their cause4 ,when the wire approaches the magnet1 an action is evoked within it1 which travels through it with a velocity comparable to that of light4 ,one substance only in the universe has been hitherto proved competent to transmit power at this velocity2 the luminiferous ether4 ,not only its rapidity of progression1 but its ability to produce the motion of light and heat1 indicates that the electric current is also motion4#a ,further1 there is a striking resemblance between the action of good and bad conductors as regards electricity1 and the action of diathermanous and adiathermanous bodies as regards radiant heat4 ,the good conductor is diathermanous to the electric current2 it allows free transmission without the development of heat4 ,the bad conductor is adiathermanous to the electric current1 and hence the passage of the latter is accompanied by the development of heat4 ,i am strongly inclined to hold the electric current1 pure and simple1 to be a motion of the ether alone2 good conductors being so constituted that the motion may be propagated through their ether without sensible transfer to their atoms1 while in the case of bad conductors this transfer is effected1 the transferred motion appearing as heat4#b ,i do not know whether ,faraday would have subscribed to what is here written2 probably his habitual caution would have prevented him from committing himself to anything so definite4 ,but some such idea filled his mind and coloured his language through all the later years of his life4 ,i dare not say that he has been always successful in the treatment of these theoretic notions4 ,in his speculations he mixes together light and darkness in varying proportions1 and carries us along with him through strong alternations of both4 ,it is impossible to say how a certain amount of mathematical training would have affected his work4 ,we cannot say what its influence would have been upon that force of inspiration that urged him on2 whether it would have daunted him1 and prevented him from driving his adits into places where no theory pointed to a lode4 ,if so1 then we may rejoice that this strong delver at the mine of natural knowledge was left free to wield his mattock in his own way4 ,it must be admitted1 that ,faraday's purely speculative writings often lack that precision which the mathematical habit of thought confers4 ,still across them flash frequent gleams of prescient wisdom which will excite admiration throughout all time2 while the facts1 relations1 principles1 and laws which his experiments have established are sure to form the body of grand theories yet to come4 ,footnotes to ,chapter #ad #a ,mr4 ,clerk ,maxwell has recently published an exceedingly important investigation connected with this question4 ,even in the non-mathematical portions of the memoirs of ,mr4 ,maxwell1 the admirable spirit of his philosophy is sufficiently revealed4 ,as regards the employment of scientific imagery1 ,i hardly know his equal in power of conception and clearness of definition4 #b ,one important difference1 of course1 exists between the effect of motion in the magnetic field1 and motion in a resisting medium4 ,in the former case the heat is generated in the moving conductor1 in the latter it is in part generated in the medium4 ,chapter #ae4 ,summary4 ,when from an ,alpine height the eye of the climber ranges over the mountains1 he finds that for the most part they resolve themselves into distinct groups1 each consisting of a dominant mass surrounded by peaks of lesser elevation4 ,the power which lifted the mightier eminences1 in nearly all cases lifted others to an almost equal height4 ,and so it is with the discoveries of ,faraday4 ,as a general rule1 the dominant result does not stand alone1 but forms the culminating point of a vast and varied mass of inquiry4 ,in this way1 round about his great discovery of ,magneto-electric ,induction1 other weighty labours group themselves4 ,his investigations on the ,extra ,current2 on the ,polar and other ,condition of ,diamagnetic ,bodies2 on ,lines of ,magnetic ,force1 their definite character and distribution2 on the employment of the ,induced ,magneto-electric ,current as a measure and test of ,magnetic ,action2 on the ,revulsive ,phenomena of the magnetic field1 are all1 notwithstanding the diversity of title1 researches in the domain of ,magneto-electric ,induction4 ,faraday's second group of researches and discoveries embrace the chemical phenomena of the current4 ,the dominant result here is the great law of definite ,electro-chemical ,decomposition1 around which are massed various researches on ,electro-chemical ,conduction and on ,electrolysis both with the ,machine and with the ,pile4 ,to this group also belongs his analysis of the ,contact ,theory1 his inquiries as to the ,source of ,voltaic ,electricity1 and his final development of the ,chemical ,theory of the pile4 ,his third great discovery is the ,magnetization of ,light1 which ,i should liken to the ,weisshorn among mountains--high1 beautiful1 and alone4 ,the dominant result of his fourth group of researches is the discovery of ,diamagnetism1 announced in his memoir as the ,magnetic ,condition of all ,matter1 round which are grouped his inquiries on the ,magnetism of ,flame and ,gases2 on ,magne-crystallic action1 and on ,atmospheric ,magnetism1 in its relations to the annual and diurnal variation of the needle1 the full significance of which is still to be shown4 ,these are ,faraday's most massive discoveries1 and upon them his fame must mainly rest4 ,but even without them1 sufficient would remain to secure for him a high and lasting scientific reputation4 ,we should still have his researches on the ,liquefaction of ,gases2 on ,frictional ,electricity2 on the ,electricity of the ,gymnotus2 on the source of ,power in the ,hydro-electric machine1 the last two investigations being untouched in the foregoing memoir2 on ,electro-magnetic ,rotations2 on ,regelation2 all his more purely ,chemical ,researches1 including his discovery of ,benzol4 ,besides these he published a multitude of minor papers1 most of which1 in some way or other1 illustrate his genius4 ,i have made no allusion to his power and sweetness as a lecturer4 ,taking him for all in all1 ,i think it will be conceded that ,michael ,faraday was the greatest experimental philosopher the world has ever seen2 and ,i will add the opinion1 that the progress of future research will tend1 not to dim or to diminish1 but to enhance and glorify the labours of this mighty investigator4 ,chapter #af4 ,illustrations of ,character4 ,thus far ,i have confined myself to topics mainly interesting to the man of science1 endeavouring1 however1 to treat them in a manner unrepellent to the general reader who might wish to obtain a notion of ,faraday as a worker4 ,on others will fall the duty of presenting to the world a picture of the man4 ,but ,i know you will permit me to add to the foregoing analysis a few personal reminiscences and remarks1 tending to connect ,faraday with a wider world than that of science--namely1 with the general human heart4 ,one word in reference to his married life1 in addition to what has been already said1 may find a place here4 ,as in the former case1 ,faraday shall be his own spokesman4 ,the following paragraph1 though written in the third person1 is from his hand3--',on ,june #ab1 #ahba1 he married1 an event which more than any other contributed to his earthly happiness and healthful state of mind4 ,the union has continued for twenty-eight years and has in no wise changed1 except in the depth and strength of its character4' ,faraday's immediate forefathers lived in a little place called ,clapham ,wood ,hall1 in ,yorkshire4 ,here dwelt ,robert ,faraday and ,elizabeth his wife1 who had ten children1 one of them1 ,james ,faraday1 born in #agfa1 being father to the philosopher4 ,a family tradition exists that the ,faradays came originally from ,ireland4 ,faraday himself has more than once expressed to me his belief that his blood was in part ,celtic1 but how much of it was so1 or when the infusion took place1 he was unable to say4 ,he could imitate the ,irish brogue1 and his wonderful vivacity may have been in part due to his extraction4 ,but there were other qualities which we should hardly think of deriving from ,ireland4 ,the most prominent of these was his sense of order1 which ran like a luminous beam through all the transactions of his life4 ,the most entangled and complicated matters fell into harmony in his hands4 ,his mode of keeping accounts excited the admiration of the managing board of this ,institution4 ,and his science was similarly ordered4 ,in his ,experimental ,researches1 he numbered every paragraph1 and welded their various parts together by incessant reference4 ,his private notes of the ,experimental ,researches1 which are happily preserved1 are similarly numbered3 their last paragraph bears the figure #af1jda4 ,his working qualities1 moreover1 showed the tenacity of the ,teuton4 ,his nature was impulsive1 but there was a force behind the impulse which did not permit it to retreat4 ,if in his warm moments he formed a resolution1 in his cool ones he made that resolution good4 ,thus his fire was that of a solid combustible1 not that of a gas1 which blazes suddenly1 and dies as suddenly away4 ,and here ,i must claim your tolerance for the limits by which ,i am confined4 ,no materials for a life of ,faraday are in my hands1 and what ,i have now to say has arisen almost wholly out of our close personal relationship4 ,letters of his1 covering a period of sixteen years1 are before me1 each one of which contains some characteristic utterance2--strong1 yet delicate in counsel1 joyful in encouragement1 and warm in affection4 ,references which would be pleasant to such of them as still live are made to ,humboldt1 ,biot1 ,dumas1 ,chevreul1 ,magnus1 and ,arago4 ,accident brought these names prominently forward2 but many others would be required to complete his list of continental friends4 ,he prized the love and sympathy of men--prized it almost more than the renown which his science brought him4 ,nearly a dozen years ago it fell to my lot to write a review of his ',experimental ,researches' for the ',philosophical ,magazine4' ,after he had read it1 he took me by the hand1 and said1 ',tyndall1 the sweetest reward of my work is the sympathy and good will which it has caused to flow in upon me from all quarters of the world4' ,among his letters ,i find little sparks of kindness1 precious to no one but myself1 but more precious to me than all4 ,he would peep into the laboratory when he thought me weary1 and take me upstairs with him to rest4 ,and if ,i happened to be absent1 he would leave a little note for me1 couched in this or some other similar form3--',dear ,tyndall1--,i was looking for you1 because we were at tea--we have not yet done--will you come up8' ,i frequently shared his early dinner2 almost always1 in fact1 while my lectures were going on4 ,there was no trace of asceticism in his nature4 ,he preferred the meat and wine of life to its locusts and wild honey4 ,never once during an intimacy of fifteen years did he mention religion to me1 save when ,i drew him on to the subject4 ,he then spoke to me without hesitation or reluctance2 not with any apparent desire to 'improve the occasion1' but to give me such information as ,i sought4 ,he believed the human heart to be swayed by a power to which science or logic opened no approach1 and1 right or wrong1 this faith1 held in perfect tolerance of the faiths of others1 strengthened and beautified his life4 ,from the letters just referred to1 ,i will select three for publication here4 ,i choose the first1 because it contains a passage revealing the feelings with which ,faraday regarded his vocation1 and also because it contains an allusion which will give pleasure to a friend4 ',royal ,institution4 this is crossed out by ,faraday ',ventnor1 ,isle of ,wight1 ,june #bh1 #ahed4 ',my ,dear ,tyndall1--,you see by the top of this letter how much habit prevails over me2 ,i have just read yours from thence1 and yet ,i think myself there4 ,however1 ,i have left its science in very good keeping1 and ,i am glad to learn that you are at experiment once more4 ,but how is the health8 ,not well1 ,i fear4 ,i wish you would get yourself strong first and work afterwards4 ,as for the fruits1 ,i am sure they will be good1 for though ,i sometimes despond as regards myself1 ,i do not as regards you4 ,you are young1 ,i am old4444 ,but then our subjects are so glorious1 that to work at them rejoices and encourages the feeblest2 delights and enchants the strongest4 ',i have not yet seen anything from ,magnus4 ,thoughts of him always delight me4 ,we shall look at his black sulphur together4 ,i heard from ,schonbein the other day4 ,he tells me that ,liebig is full of ozone1 i4e41 of allotropic oxygen4 ',good-bye for the present4 ',ever1 my dear ,tyndall1 ',yours truly1 ',m4 ,faraday4' ,the contemplation of ,nature1 and his own relation to her1 produced in ,faraday a kind of spiritual exaltation which makes itself manifest here4 ,his religious feeling and his philosophy could not be kept apart2 there was an habitual overflow of the one into the other4 ,whether he or another was its exponent1 he appeared to take equal delight in science4 ,a good experiment would make him almost dance with delight4 ,in ,november1 #ahej1 he wrote to me thus3--',i hope some day to take up the point respecting the magnetism of associated particles4 ,in the meantime ,i rejoice at every addition to the facts and reasoning connected with the subject4 ,when science is a republic1 then it gains3 and though ,i am no republican in other matters1 ,i am in that4' ,all his letters illustrate this catholicity of feeling4 ,ten years ago1 when going down to ,brighton1 he carried with him a little paper ,i had just completed1 and afterwards wrote to me4 ,his letter is a mere sample of the sympathy which he always showed to me and my work4 ',brighton1 ,december #i1 #aheg4 ',my ,dear ,tyndall1--,i cannot resist the pleasure of saying how very much ,i have enjoyed your paper4 ,every part has given me delight4 ,it goes on from point to point beautifully4 ,you will find many pencil marks1 for ,i made them as ,i read4 ,i let them stand1 for though many of them receive their answer as the story proceeds1 yet they show how the wording impresses a mind fresh to the subject1 and perhaps here and there you may like to alter it slightly1 if you wish the full idea1 i4e41 not an inaccurate one1 to be suggested at first2 and yet after all ,i believe it is not your exposition1 but the natural jumping to a conclusion that affects or has affected my pencil4 ',we return on ,friday1 when ,i will return you the paper4 ',ever truly yours1 ',m4 ,faraday4' ,the third letter will come in its proper place towards the end4 ,while once conversing with ,faraday on science1 in its relations to commerce and litigation1 he said to me1 that at a certain period of his career1 he was forced definitely to ask himself1 and finally to decide whether he should make wealth or science the pursuit of his life4 ,he could not serve both masters1 and he was therefore compelled to choose between them4 ,after the discovery of magneto-electricity his fame was so noised abroad1 that the commercial world would hardly have considered any remuneration too high for the aid of abilities like his4 ,even before he became so famous1 he had done a little 'professional business4' ,this was the phrase he applied to his purely commercial work4 ,his friend1 ,richard ,phillips1 for example1 had induced him to undertake a number of analyses1 which produced1 in the year #ahcj1 an addition to his income of more than a thousand pounds2 and in #ahca a still greater addition4 ,he had only to will it to raise in #ahcb his professional business income to #ejjj,l4 a year4 ,indeed double this sum would be a wholly insufficient estimate of what he might1 with ease1 have realised annually during the last thirty years of his life4 ,while restudying the ,experimental ,researches with reference to the present memoir1 the conversation with ,faraday here alluded to came to my recollection1 and ,i sought to ascertain the period when the question1 'wealth or science1' had presented itself with such emphasis to his mind4 ,i fixed upon the year #ahca or #ahcb1 for it seemed beyond the range of human power to pursue science as he had done during the subsequent years1 and to pursue commercial work at the same time4 ,to test this conclusion ,i asked permission to see his accounts1 and on my own responsibility1 ,i will state the result4 ,in #ahcb1 his professional business income1 instead of rising to #ejjj,l41 or more1 fell from #ajij,l4 #ds4 to #aee,l4 #is4 ,from this it fell with slight oscillations to #ib,l4 in #ahcg1 and to zero in #ahch4 ,between #ahci and #ahde1 it never1 except in one instance1 exceeded #bb,l42 being for the most part much under this4 ,the exceptional year referred to was that in which he and ,sir ,charles ,lyell were engaged by ,government to write a report on the ,haswell ,colliery explosion1 and then his business income rose to #aab,l4 ,from the end of #ahde to the day of his death1 ,faraday's annual professional business income was exactly zero4 ,taking the duration of his life into account1 this son of a blacksmith1 and apprentice to a bookbinder1 had to decide between a fortune of #aej1jjj,l4 on the one side1 and his undowered science on the other4 ,he chose the latter1 and died a poor man4 ,but his was the glory of holding aloft among the nations the scientific name of ,england for a period of forty years4 ,the outward and visible signs of fame were also of less account to him than to most men4 ,he had been loaded with scientific honours from all parts of the world4 ,without1 ,i imagine1 a dissentient voice1 he was regarded as the prince of the physical investigators of the present age4 ,the highest scientific position in this country he had1 however1 never filled4 ,when the late excellent and lamented ,lord ,wrottesley resigned the presidency of the ,royal ,society1 a deputation from the council1 consisting of his ,lordship1 ,mr4 ,grove1 and ,mr4 ,gassiot1 waited upon ,faraday1 to urge him to accept the president's chair4 ,all that argument or friendly persuasion could do was done to induce him to yield to the wishes of the council1 which was also the unanimous wish of scientific men4 ,a knowledge of the quickness of his own nature had induced in ,faraday the habit of requiring an interval of reflection1 before he decided upon any question of importance4 ,in the present instance he followed his usual habit1 and begged for a little time4 ,on the following morning1 ,i went up to his room and said on entering that ,i had come to him with some anxiety of mind4 ,he demanded its cause1 and ,i responded3--',lest you should have decided against the wishes of the deputation that waited on you yesterday4' ',you would not urge me to undertake this responsibility1' he said4 ',i not only urge you1' was my reply1 'but ,i consider it your bounden duty to accept it4' ,he spoke of the labour that it would involve2 urged that it was not in his nature to take things easy2 and that if he became president1 he would surely have to stir many new questions1 and agitate for some changes4 ,i said that in such cases he would find himself supported by the youth and strength of the ,royal ,society4 ,this1 however1 did not seem to satisfy him4 ,mrs4 ,faraday came into the room1 and he appealed to her4 ,her decision was adverse1 and ,i deprecated her decision4 ',tyndall1' he said at length1 ',i must remain plain ,michael ,faraday to the last2 and let me now tell you1 that if ,i accepted the honour which the ,royal ,society desires to confer upon me1 ,i would not answer for the integrity of my intellect for a single year4' ,i urged him no more1 and ,lord ,wrottesley had a most worthy successor in ,sir ,benjamin ,brodie4 ,after the death of the ,duke of ,northumberland1 our ,board of ,managers wished to see ,mr4 ,faraday finish his career as ,president of the ,institution1 which he had entered on weekly wages more than half a century before4 ,but he would have nothing to do with the presidency4 ,he wished for rest1 and the reverent affection of his friends was to him infinitely more precious than all the honours of official life4 ,the first requisite of the intellectual life of ,faraday was the independence of his mind2 and though prompt to urge obedience where obedience was due1 with every right assertion of manhood he intensely sympathized4 ,even rashness on the side of honour found from him ready forgiveness1 if not open applause4 ,the wisdom of years1 tempered by a character of this kind1 rendered his counsel peculiarly precious to men sensitive like himself4 ,i often sought that counsel1 and1 with your permission1 will illustrate its character by one or two typical instances4 ,in #ahee1 ,i was appointed examiner under the ,council for ,military ,education4 ,at that time1 as indeed now1 ,i entertained strong convictions as to the enormous utility of physical science to officers of artillery and engineers1 and whenever opportunity offered1 ,i expressed this conviction without reserve4 ,i did not think the recognition1 though considerable1 accorded to physical science in those examinations at all proportionate to its importance2 and this probably rendered me more jealous than ,i otherwise should have been of its claims4 ,in ,trinity ,college1 ,dublin1 a school had been organized with reference to the ,woolwich examinations1 and a large number of exceedingly well-instructed young gentlemen were sent over from ,dublin1 to compete for appointments in the artillery and the engineers4 ,the result of one examination was particularly satisfactory to me2 indeed the marks obtained appeared so eloquent that ,i forbore saying a word about them4 ,my colleagues1 however1 followed the usual custom of sending in brief reports with their returns of marks4 ,after the results were published1 a leading article appeared in ',the ,times1' in which the reports were largely quoted1 praise being bestowed on all the candidates1 except the excellent young fellows who had passed through my hands4 ,a letter from ,trinity ,college drew my attention to this article1 bitterly complaining that whereas the marks proved them to be the best of all1 the science candidates were wholly ignored4 ,i tried to set matters right by publishing1 on my own responsibility1 a letter in ',the ,times4' ,the act1 ,i knew1 could not bear justification from the ,war ,office point of view2 and ,i expected and risked the displeasure of my superiors4 ,the merited reprimand promptly came4 ',highly as the ,secretary of ,state for ,war might value the expression of ,professor ,tyndall's opinion1 he begged to say that an examiner1 appointed by ,his ,royal ,highness the ,commander-in-,chief1 had no right to appear in the public papers as ,professor ,tyndall has done1 without the sanction of the ,war ,office4' ,nothing could be more just than this reproof1 but ,i did not like to rest under it4 ,i wrote a reply1 and previous to sending it took it up to ,faraday4 ,we sat together before his fire1 and he looked very earnest as he rubbed his hands and pondered4 ,the following conversation then passed between us3-- ,f4 ,you certainly have received a reprimand1 ,tyndall2 but the matter is over1 and if you wish to accept the reproof1 you will hear no more about it4 ,t4 ,but ,i do not wish to accept it4 ,f4 ,then you know what the consequence of sending that letter will be8 ,t4 ,i do4 ,f4 ,they will dismiss you4 ,t4 ,i know it4 ,f4 ,then send the letter6 ,the letter was firm1 but respectful2 it acknowledged the justice of the censure1 but expressed neither repentance nor regret4 ,faraday1 in his gracious way1 slightly altered a sentence or two to make it more respectful still4 ,it was duly sent1 and on the following day ,i entered the ,institution with the conviction that my dismissal was there before me4 ,weeks1 however1 passed4 ,at length the well-known envelope appeared1 and ,i broke the seal1 not doubting the contents4 ,they were very different from what ,i expected4 ',the ,secretary of ,state for ,war has received ,professor ,tyndall's letter1 and deems the explanation therein given perfectly satisfactory4' ,i have often wished for an opportunity of publicly acknowledging this liberal treatment1 proving1 as it did1 that ,lord ,panmure could discern and make allowance for a good intention1 though it involved an offence against routine4 ,for many years subsequently it was my privilege to act under that excellent body1 the ,council for ,military ,education4 ,on another occasion of this kind1 having encouraged me in a somewhat hardy resolution ,i had formed1 ,faraday backed his encouragement by an illustration drawn from his own life4 ,the subject will interest you1 and it is so sure to be talked about in the world1 that no avoidable harm can rise from its introduction here4 ,in the year #ahce1 ,sir ,robert ,peel wished to offer ,faraday a pension1 but that great statesman quitted office before he was able to realise his wish4 ,the ,minister who founded these pensions intended them1 ,i believe1 to be marks of honour which even proud men might accept without compromise of independence4 ,when1 however1 the intimation first reached ,faraday in an unofficial way1 he wrote a letter announcing his determination to decline the pension2 and stating that he was quite competent to earn his livelihood himself4 ,that letter still exists1 but it was never sent1 ,faraday's repugnance having been overruled by his friends4 ,when ,lord ,melbourne came into office1 he desired to see ,faraday2 and probably in utter ignorance of the man--for unhappily for them and us1 ,ministers of ,state in ,england are only too often ignorant of great ,englishmen--his ,lordship said something that must have deeply displeased his visitor4 ,all the circumstances were once communicated to me1 but ,i have forgotten the details4 ,the term 'humbug1' ,i think1 was incautiously employed by his ,lordship1 and other expressions were used of a similar kind4 ,faraday quitted the ,minister with his own resolves1 and that evening he left his card and a short and decisive note at the residence of ,lord ,melbourne1 stating that he had manifestly mistaken his ,lordship's intention of honouring science in his person1 and declining to have anything whatever to do with the proposed pension4 ,the good-humoured nobleman at first considered the matter a capital joke2 but he was afterwards led to look at it more seriously4 ,an excellent lady1 who was a friend both to ,faraday and the ,minister1 tried to arrange matters between them2 but she found ,faraday very difficult to move from the position he had assumed4 ,after many fruitless efforts1 she at length begged of him to state what he would require of ,lord ,melbourne to induce him to change his mind4 ,he replied1 ',i should require from his ,lordship what ,i have no right or reason to expect that he would grant--a written apology for the words he permitted himself to use to me4' ,the required apology came1 frank and full1 creditable1 ,i thought1 alike to the ,prime ,minister and the philosopher4 ,considering the enormous strain imposed on ,faraday's intellect1 the boy-like buoyancy even of his later years was astonishing4 ,he was often prostrate1 but he had immense resiliency1 which he brought into action by getting away from ,london whenever his health failed4 ,i have already indicated the thoughts which filled his mind during the evening of his life4 ,he brooded on magnetic media and lines of force2 and the great object of the last investigation he ever undertook was the decision of the question whether magnetic force requires time for its propagation4 ,how he proposed to attack this subject we may never know4 ,but he has left some beautiful apparatus behind2 delicate wheels and pinions1 and associated mirrors1 which were to have been employed in the investigation4 ,the mere conception of such an inquiry is an illustration of his strength and hopefulness1 and it is impossible to say to what results it might have led him4 ,but the work was too heavy for his tired brain4 ,it was long before he could bring himself to relinquish it and during this struggle he often suffered from fatigue of mind4 ,it was at this period1 and before he resigned himself to the repose which marked the last two years of his life1 that he wrote to me the following letter--one of many priceless letters now before me--which reveals1 more than anything another pen could express1 the state of his mind at the time4 ,i was sometimes censured in his presence for my doings in the ,alps1 but his constant reply was1 ',let him alone1 he knows how to take care of himself4' ,in this letter1 anxiety on this score reveals itself for the first time4 ',hampton ,court1 ,august #a1 #ahfd4 ',my ,dear ,tyndall1--,i do not know whether my letter will catch you1 but ,i will risk it1 though feeling very unfit to communicate with a man whose life is as vivid and active as yours2 but the receipt of your kind letter makes me to know that1 though ,i forget1 ,i am not forgotten1 and though ,i am not able to remember at the end of a line what was said at the beginning of it1 the imperfect marks will convey to you some sense of what ,i long to say4 ,we had heard of your illness through ,miss ,moore1 and ,i was therefore very glad to learn that you are now quite well2 do not run too many risks or make your happiness depend too much upon dangers1 or the hunting of them4 ,sometimes the very thinking of you1 and what you may be about1 wearies me with fears1 and then the cogitations pause and change1 but without giving me rest4 ,i know that much of this depends upon my own worn-out nature1 and ,i do not know why ,i write it1 save that when ,i write to you ,i cannot help thinking it1 and the thoughts stand in the way of other matter4 99 99 99 99 99 ',see what a strange desultory epistle ,i am writing to you1 and yet ,i feel so weary that ,i long to leave my desk and go to the couch4 ',my dear wife and ,jane desire their kindest remembrances3 ,i hear them in the next room3444 ,i forget--but not you1 my dear ,tyndall1 for ,i am ',ever yours1 ',m4 ,faraday4' ,this weariness subsided when he relinquished his work1 and ,i have a cheerful letter from him1 written in the autumn of #ahfe4 ,but towards the close of that year he had an attack of illness1 from which he never completely rallied4 ,he continued to attend the ,friday ,evening ,meetings1 but the advance of infirmity was apparent to us all4 ,complete rest became finally essential to him1 and he ceased to appear among us4 ,there was no pain in his decline to trouble the memory of those who loved him4 ,slowly and peacefully he sank towards his final rest1 and when it came1 his death was a falling asleep4 ,in the fulness of his honours and of his age he quitted us2 the good fight fought1 the work of duty--shall ,i not say of glory8--done4 ,the ',jane' referred to in the foregoing letter is ,faraday's niece1 ,miss ,jane ,barnard1 who with an affection raised almost to religious devotion watched him and tended him to the end4 ,i saw ,mr4 ,faraday for the first time on my return from ,marburg in #ahej4 ,i came to the ,royal ,institution1 and sent up my card1 with a copy of the paper which ,knoblauch and myself had just completed4 ,he came down and conversed with me for half an hour4 ,i could not fail to remark the wonderful play of intellect and kindly feeling exhibited by his countenance4 ,when he was in good health the question of his age would never occur to you4 ,in the light and laughter of his eyes you never thought of his grey hairs4 ,he was then on the point of publishing one of his papers on ,magnecrystallic action1 and he had time to refer in a flattering ,note to the memoir ,i placed in his hands4 ,i returned to ,germany1 worked there for nearly another year1 and in ,june1 #ahea1 came back finally from ,berlin to ,england4 ,then1 for the first time1 and on my way to the meeting of the ,british ,association1 at ,ipswich1 ,i met a man who has since made his mark upon the intellect of his time2 who has long been1 and who by the strong law of natural affinity must continue to be1 a brother to me4 ,we were both without definite outlook at the time1 needing proper work1 and only anxious to have it to perform4 ,the chairs of ,natural ,history and of ,physics being advertised as vacant in the ,university of ,toronto1 we applied for them1 he for the one1 ,i for the other2 but1 possibly guided by a prophetic instinct1 the ,university authorities declined having anything to do with either of us4 ,if ,i remember aright1 we were equally unlucky elsewhere4 ,one of ,faraday's earliest letters to me had reference to this ,toronto business1 which he thought it unwise in me to neglect4 ,but ,toronto had its own notions1 and in #ahec1 at the instance of ,dr4 ,bence ,jones1 and on the recommendation of ,faraday himself1 a chair of ,physics at the ,royal ,institution was offered to me4 ,i was tempted at the same time to go elsewhere1 but a strong attraction drew me to his side4 ,let me say that it was mainly his and other friendships1 precious to me beyond all expression1 that caused me to value my position here more highly than any other that could be offered to me in this land4 ,nor is it for its honour1 though surely that is great1 but for the strong personal ties that bind me to it1 that ,i now chiefly prize this place4 ,you might not credit me were ,i to tell you how lightly ,i value the honour of being ,faraday's successor compared with the honour of having been ,faraday's friend4 ,his friendship was energy and inspiration2 his 'mantle' is a burden almost too heavy to be borne4 ,sometimes during the last year of his life1 by the permission or invitation of ,mrs4 ,faraday1 ,i went up to his rooms to see him4 ,the deep radiance1 which in his time of strength flashed with such extraordinary power from his countenance1 had subsided to a calm and kindly light1 by which my latest memory of him is warmed and illuminated4 ,i knelt one day beside him on the carpet and placed my hand upon his knee2 he stroked it affectionately1 smiled1 and murmured1 in a low soft voice1 the last words that ,i remember as having been spoken to me by ,michael ,faraday4 ,it was my wish and aspiration to play the part of ,schiller to this ,goethe3 and he was at times so strong and joyful--his body so active1 and his intellect so clear--as to suggest to me the thought that he1 like ,goethe1 would see the younger man laid low4 ,destiny ruled otherwise1 and now he is but a memory to us all4 ,surely no memory could be more beautiful4 ,he was equally rich in mind and heart4 ,the fairest traits of a character sketched by ,paul1 found in him perfect illustration4 ,for he was 'blameless1 vigilant1 sober1 of good behaviour1 apt to teach1 not given to filthy lucre4' ,he had not a trace of worldly ambition2 he declared his duty to his ,sovereign by going to the levee once a year1 but beyond this he never sought contact with the great4 ,the life of his spirit and of his intellect was so full1 that the things which men most strive after were absolutely indifferent to him4 ',give me health and a day1' says the brave ,emerson1 'and ,i will make the pomp of emperors ridiculous4' ,in an eminent degree ,faraday could say the same4 ,what to him was the splendour of a palace compared with a thunderstorm upon ,brighton ,downs8--what among all the appliances of royalty to compare with the setting sun8 ,i refer to a thunderstorm and a sunset1 because these things excited a kind of ecstasy in his mind1 and to a mind open to such ecstasy the pomps and pleasures of the world are usually of small account4 ,nature1 not education1 rendered ,faraday strong and refined4 ,a favourite experiment of his own was representative of himself4 ,he loved to show that water in crystallizing excluded all foreign ingredients1 however intimately they might be mixed with it4 ,out of acids1 alkalis1 or saline solutions1 the crystal came sweet and pure4 ,by some such natural process in the formation of this man1 beauty and nobleness coalesced1 to the exclusion of everything vulgar and low4 ,he did not learn his gentleness in the world1 for he withdrew himself from its culture2 and still this land of ,england contained no truer gentleman than he4 ,not half his greatness was incorporate in his science1 for science could not reveal the bravery and delicacy of his heart4 ,but it is time that ,i should end these weak words1 and lay my poor garland on the grave of this ,just and faithful knight of ,god4