GREAT PERSONALITIES IN THE FIELDS OF ELECTRICAL AND MAGNETICMEASUREMENTS

By Professor J. T. MACGREGOR-MORRIS , D.Sc.(Eng.), Member.

{Lecture delivered before the MEASUREMENTS SECTION, 21 st May, 1948.)

I very much appreciate the honour of being asked to give thislecture, but when I look at the names of previous lecturers Itremble and must ask for your indulgence.

I have chosen a subject which is different from all the others,partly because of the people of whom I shall speak I have metall but four, and have spoken to almost all of those, so that Ihave some knowledge of them; but to begin with I must gomuch further back, and I shall start with a quotation fromFleming's "Memories of a Scientific Life" in which he talksabout the work of Cavendish:

Maxwell repeated almost all the principal experiments describedby Cavendish. Cavendish had very few experimental appliances, andhis only method of comparing the electrical resistance of wires wasby taking electric shocks through them and adjusting them until theshocks appeared to be equal. To us that sounds rather rough onthe experimenter. Cavendish had a valet called Richard, who wasmade to add to his other duties that of acting as a shock-meter.Fleming writes "I remember assisting Maxwell in a similar capacityone afternoon to decide whether two electric shocks taken throughdifferent circuits were equal or different in intensity."That is the kind of background from which we have to start.

When you think of Galvani's experiments with a recently-killedfrog, a muscle of which was made to twitch by causing it to makecontact with a piece of copper and zinc, and remember thatthere was no galvanometer in those days, none of those familiarthings which we know so well, you can easily understand thatthe difficulties under which those early experimenters had towork were simply amazing. When we examine Cavendish'swork, we cannot but be astounded by the degree of precisionwith which he was able to equate two shocks.

Of course, one person had to suffer both shocks; a shockthrough one person and a shock through another might not be atall the same in their physiological effect. I had a friend, a NewZealander, who was terribly sensitive to shock, and a shockwhich I could not feel at all made him jump six inches off thefloor and scream. That happened in Professor Carey-Foster'slaboratory, and he looked round at us to see whether we weretrying to murder a fellow-student!

Let us pass now to a group of three men who independentlyhit upon the self-exciting principle of the dynamo. One wasWheatstone, and the two others were Werner von Siemens andS. F. Varley. Wheatstone was a very remarkable man. He wasa good scientist, and was Professor of Physics at King's Collegein the Strand at about the same time that Michael Faraday wasProfessor of Chemistry there. He did original work in manyfields, but most of us know him because his name is applied tothe bridge for measuring resistances which we call the Wheatstonebridge. My old chief used to say that it was called the Wheat-stone bridge because Wheatstone did not invent it and it is nota bridge. As a matter of fact it was invented by S. H. Christiein 1833, but Sir Charles Wheatstone did a useful piece of workin bringing the bridge to the notice of the people who were likelyto use it, and that is an important factor in any process ofdevelopment.

(U.D.C. 92:621.317)Prof. MacGregor-Morris was formerly at Queen Mary College and University

College, London.

Wheatstone was rather a timid man. He was once asked togive a lecture at the Royal Institution. He prepared the experi-ments beforehand, and in this case Faraday had helped him toget them ready; but at two minutes to nine o'clock Wheatstonewas not to be found. He had disappeared, being in a blue funk,and Faraday had to give the lecture. I have heard Sir WilliamBragg say that that is the origin of the custom at the RoyalInstitution of the Director waiting to see the lecturer enter thetheatre, before coming in himself by another door.

The second member of the trio was, as I have said, Werner vonSiemens. He was a pioneer in many branches of this subject.He invented measuring instruments, one of which [exhibited]was used very often in the early days of electric lighting. Mr.A. H. Walton in 1922, at one of the Commemoration Meetingsof The Institution,* described J. E. H. Gordon's system of electricsupply for the Great Western Railway at Paddington in 1884."In those early days," he said, "the only alternating-currentammeter we had was the Siemens dynamometer, a most excellentinstrument but unfit for everyday use with engine-room staff.The only voltmeter we had was the Cardew hot-wire instrument,which was also far from robust." The need for more practicalinstruments for everyday use was obvious, but such instrumentswere only beginning to be developed at that time.

William Siemens, the brother of Werner von Siemens, developeda process of electrolysis in Berlin. He was not at all a goodlinguist, but he came to England to try to place his patent. Hedid a good deal of walking about in London, but could not findwhat he wanted, and so finally he went to Birmingham. Therehe looked about for someone who would take up his patent, and,seeing the name "Undertaker" over a door, he went in to seewhether they would undertake the patent. That visit to Bir-mingham, however, was the beginning of Elkington's electro-plating work there.

Later William Siemens, who was the first President of TheInstitution, was knighted, and Punch published a cartoon withthe caption, "The Electric Knight-Light." You need to knowa good deal about the history of electrical engineering to under-stand it fully. William Siemens used electric arc lights in horti-cultural experiments on the growth of plants, and published theresults of these experiments.

Next let us turn to his nephew, Alexander Siemens, who wasPresident of The Institution in 1894, and again in 1904. Whenhe became President The Institution had no building of its own,and its meetings were held at The Institution of Civil Engineers,then on the north side of Great George Street, quite close toParliament Square. We had the hospitality of their building forvery many years, and were very grateful. When we could nothold our meetings there we went to the Royal Society of Arts.

I should now like to say a word about Carey-Foster, my oldProfessor of Physics at University College and a very charmingman. He was most approachable, and he and his wife used toinvite his senior students to their house at Hampstead; we hadmany very interesting and fairly rowdy evenings there, with sing-

* Meetings held on the 21st-23rd February, 1922, in commemoration of the firstordinary meeting of the Society of Telegraph Engineers, 28th February, 1872.

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502 MACGREGOR-MORRIS: GREAT PERSONALITIES IN THE

songs and so on. He had an aptitude for developing newmethods of doing things, and the Carey-Foster bridge was devisedby him in 1872.

He saw great possibilities in an old student of the Collegenamed John Ambrose Fleming, and he later asked the CollegeCouncil to invite Fleming to give a few lectures on electricaltechnology. That was in 1884. The following year, Flemingwas appointed Head of the Electrical Engineering Departmentthere, a position which he held for 41 years with outstandingsuccess. I have a portrait of Fleming taken in 1891 at the timewhen I was attending his lectures. He had a virile personalityand did not miss anything with his eyes, but he was a little deaf.He always tried to turn experiments into something that couldbe seen instead of something that could be heard. As previouslymentioned, Carey-Foster developed the idea of a bridge for com-paring resistances, especially low resistances, and Fleming work-ing at the Cavendish Laboratory made an arrangement of thatbridge for practical purposes.

Now I turn to the development of the potentiometer. On theFleming bridge many experiments were done in connection withthe standardizing of ohms, and Maxwell said that the CavendishLaboratory at Cambridge should not become a manufactory ofohms but should be used for the comparison of ohms. Thefather of the potentiometer was Poggendorff. The early text-books show his method of comparing e.m.f.'s. A cell is con-nected to the ends of a long straight-stretched thin wire, and thenthe cell whose e.m.f. is to be compared with another one isbalanced by connecting it between one end of the stretched wirethrough a galvanometer to a slider on the wire, and a point ofbalance is found. Then another cell is put in, the e.m.f. ofwhich is known, and another point of balance is found, the pro-portion between the readings giving the ratio of the e.m.f.'s.That was the original apparatus.

Later on, the standard of e.m.f. was developed, Fleming doingsomething towards that by developing the Daniell cell. Stilllater, Latimer Clark developed what is known as the Clark cell,which was used universally in connection with the potentiometer.The only alteration that Fleming made to the original PoggendorflFbridge was simply to add an adjustable resistance in series at oneend. It seems an extraordinarily simple thing to do, yet itbrought the apparatus out of the range of ordinary work forstudents in a physics laboratory into the range of use as anengineering tool.

I have had the opportunity and the privilege of going throughthe correspondence between Ambrose Fleming and ColonelCrompton, in which they tried to assess their respective shares incontributing to the success of the potentiometer. As far as Ican gather, it comes to this. Fleming's potentiometer was onein which there was a series of mercury cups, with devices forpulling down springy spiral resistors so that they were made todip into a mercury cup, thus bringing in any one one of a seriesof resistors into circuit. Crompton said: "This mercury businessis a mess, and engineers will not stand it; if anybody gives it aknock, the mercury will disappear," and so he converted theaccurate but inconvenient tool that Fleming had made into thepractical form of the potentiometer as we now know it.

An illustration in the Crompton catalogue of 1892 shows thepotentiometer in the form of a long, straight-stretched wire.There were two schools of thought, one favouring the long,straight-stretched wire and the other a number of tiny coils, allequally adjusted. Those who have watched the developmentof the potentiometer have seen that battle going on. Some firmshave carried it too far, but in essence -both come to the samething, the only point being that the long wire is more apt to bedamaged than the coils, as they are protected from damage, beingunderneath the ebonite top.

At University College we had a potentiometer exactly like thatshown in the Crompton catalogue, and someone dropped ahammer on it, denting the wire badly. I remember the grief thatFleming expressed about it. I carried out an experiment to seewhether we could find out that dent electrically. The wire wasreduced to half its thickness, but we could not show it electricallyat all; the metal had spread out sideways, thus compensating forthe amount of the reduction in the dimension downwards, sothat, although it did not look pretty, it still worked.

The trouble with the Clark cell was that it had a temperaturecoefficient of which it was necessary to take account, and a tablegiving the value of the e.m.f. for different temperatures wasplaced at the right-hand end of the potentiometer. Later on acadmium cell was used, in which the temperature effect is sosmall as to be not worth talking about. Now almost everyinstrument firm of repute makes a potentiometer, and every goodlaboratory must have at least one.

The next branch with which I want to deal is that of standards,and we will begin with Rayleigh (the father of the Lord Rayleighwho died a short time ago), as he had so much to do with them.1 have often heard him give lectures at the Royal Institution.His method of lecturing was not impressive; but his experimentswere extraordinarily well worth seeing, and his brilliance incontributing to the foundations of so many subjects is almostpast comprehension.

There is a photograph in the possession of The Institutionshowing on the right Lord Rayleigh and on the left Sir JosephThomson. Rayleigh was very keen on the development ofelectrical standards, standards of voltage, of current and ofresistance. Fleming read a paper before The Institution about1888 on the need for a standardizing laboratory to test electricalinstruments, and at the end of it he suggested that The Institutionshould go forward with this idea. It was, however, very difficultto get The Institution to move in the direction of anything whichaffected industry; in those days it was thought that such movesmight warp its scientific attitude. We have, of course, gone along way from that, and we realize that there should be fullcollaboration between industry and science; but in those daysthe prejudice was hard to overcome.

Fleming, however, was undoubtedly the man who set the ballrolling, and so there was set up the Standardizing Laboratory ofthe Board of Trade, of which Major Cardew was the firstDirector.

During some experiments which I was doing for Fleming atUniversity College we were trying to test the accuracy of aKelvin balance. We had a copper voltameter in series with itand had to keep the current going for two hours, but before ithad been going for an hour the smell of paraffin wax was con-siderable. We drew Fleming's attention to this and finallystopped the test. Next morning we found that the balance wasstuck solid; much of the paraffin wax had melted out of the coil.By a surgical operation we carved out all the loose paraffin wax,and then, on Fleming's instructions, we took the balance to theBoard of Trade to see what Cardew had to say about it. It wasfound to be accurate to 1 part in 1 000, even after that treatment,which shows the good design that Kelvin had put into it, apartfrom the fact that it was not intended to be used for such lengthyperiods at full current.

When I went to Whitehall Gardens, where the StandardizingLaboratory then was, I was surprised to see an enormous arrayof the now old-fashioned Cardew voltmeters, which were seen inevery electric lighting station 60 years ago. There were no high-voltage voltmeters in those days, so that, in order to measure2 000 volts, 20 of these instruments had been screwed on thewall, the whole wall being covered by them. The 20 instrumentsbeing connected in series, the readings of all were totalled. That

FIELDS OF ELECTRICAL AND MAGNETIC MEASUREMENTS 503

did not contribute towards accuracy, but in those days theSiemens electro-dynamometer and the Cardew voltmeter werealmost the only means of measuring alternating current andvoltage. Each of the voltmeters took 30 watts, so that 20 ofthem took 600 watts, which means nearly 1 h.p. going in thevoltmeters alone.

After Cardew, A. P. Trotter carried on the work very ably inthis Whitehall Gardens laboratory. Trotter used to talk of thebirth of the ampere as taking place in 1881. Before that timewhat we now call the ampere was called a weber. We use"weber" for other purposes now. Trotter related that the name"ampere" for the unit of current was instituted at a restaurantin Paris, where, over a cup of coffee, Kelvin proposed throwingover the name "weber" and replacing it by "ampere." Helm-holtz was there at the time and agreed, and Mascart, who wasthe Chairman, was charged with the task of carrying the proposalthrough at the next meeting of the International Congress. Thatwas done on the 21st September, 1881, when the ampere wasreally born.

I must mention the name of one other man who gave a greatdeal of his life to most valuable work in this field of standards.Many of you revere Sir Richard Glazebrook for the unselfishand devoted work that he did in this field; he was the firstDirector of the National Physical Laboratory, which has de-veloped out of the Board of Trade Standardizing Laboratory,and which is of international reputation. The expansion inlayout which has gone on there is enormous.

We must now turn to another branch, inductance and mag-netism. Joseph Henry, an American, was a man of greatability. He worked quite independently of Michael Faraday.It was a neck-and-neck race between them for the discovery ofthe induction of electric currents. Which of thdm actually didthe experiment first it is not easy to say, but undoubtedly Faradaypublished his work first, and Henry bowed to the decision thatthe publication of any research work must be the test of priority.We can justly honour Henry, however, for the independentclarity of thought which led him to do the work he did. Hewas the first to show that an oscillatory discharge may occur incircuits which have inductance as well as capacitance andresistance.

As we pass on to the testing of iron we come to a remarkablefigure, Charles Proteus Steinmetz. He was a dwarf and ahunchback, not more than four feet in height. At the St. LouisExposition in America, to which a party went from this Institutionand to which I had the privilege of going, we were in the con-ference room when somebody said, "There's Steinmetz." Icould not see anybody, but as I crossed the room 1 saw a cloudof smoke, and when I got closer I could see this little man withhis dark beard, puffing away at a big cigar. It would not havebeen Steinmetz if he had not been smoking. At one time thesmoking habit became so serious in the works of the GeneralElectric Company of America that the directors decided to putup notices throughout the buildings that smoking was prohibited.Such a notice was put in Steinmetz's room. Steinmetz came innext morning, saw the notice, lit his cigar and got on with hiswork. One of the directors came into the room, said "Goodmorning," and then led the conversation round to the fact thatthere was a notice in the room. "Have you seen it?" he asked."Yes," said Steinmetz. "Well, what about it?" "Steinmetzsmokes or Steinmetz goes," was the reply. So Steinmetz wasallowed to smoke, the only man to do so in the whole of thatenormous works.

I once heard Steinmetz give a lecture on rotary convertors,and it was amazing to hear him rattle out equations and thensay, "This means 3% more copper," "This means so-and-so,"turning each part of the equation into quantitative figures for a

given case, so that a practical man could realize at once what itmeant. At first sight it was quite a shock to see him, butchildren loved him and ran into his arms; there was a humanityabout him which was perfect, in spite of his deformities.

There is a photograph in The Institution of which I shouldlike to show you a portion. It shows some of the memberstaking part in the Conference of 1881 in Paris. On the right isSteinmetz, standing, with his cigar. Next to him is AlexanderSiemens, and the man behind is Elihu Thomson, of the Thomson-Houston Company of America. Then comes a man who wasalways to the fore, Professor Ayrton, who usually wore a frockcoat. The man behind is Silvanus Thompson, the Head ofFinsbury Technical College, who published such wonderfultreatises on electrical engineering. The next is Kennelly; I do notknow who the last but one is, but the last is Sir William Preece.

Elihu Thomson touched on a great many things—electric arcs,electric welding, electricity meters, dynamos, alternators and soforth—and made very distinct advances in their design.

I should now like to refer to another of the men of King'sCollege, London—Dr. John Hopkinson. Hopkinson was thefirst Professor of Electrical Engineering at King's, and ErnestWilson followed him; and now Professor Greig, who is with usthis evening, is a kind of electrical grandson of this man.Hopkinson was, I think, the first to study the magnetic propertiesof iron at high temperatures, and he and his brother Edwardwere the first to put the theory of dynamo design on a soundfoundation.

Next I should like to mention James Alfred Ewing, who wrotethe first textbook on magnetic induction in iron and othermetals, which even now has points that are well worth thestudy of every magnetician, although of course a great deal of itis obsolete. On one occasion The Institution held a meeting atthe Royal Society of Arts at which Alfred Ewing demonstratedhis hysteresis tester. My brother and I were there, and we sawour chief, Dr. Ambrose Fleming, and Dr. John Hopkinson—that is, University College and King's College—sitting togetherin the front row. Hopkinson was a little hard of hearing, andFleming decidedly so, and so we could hear every word theysaid to each other. They were very interested to hear how Ewing

. was going to develop his tester.One man to whom not much credit has been given in this

field is Evershed. He read two very important papers beforeThe Institution on the magnetic properties of permanent magnets,and on magnetic materials and iron, and these are well worthstudying even now. He was one of the pioneers of a number ofmeasuring instruments. I have here a paper taken from theProceedings of The Institution of Civil Engineers (1892) written byJames Swinburne (to whom I shall refer later) which gives a verygood general survey of the state of the art at that time.

Now we come to a unique man, David Edward Hughes. Heand Edison ran one another very close in connection with anumber of developments. Both, apparently, invented themicrophone independently, and Hughes actually discoveredwireless telegraphy 20 years before Marconi. In fact, he hadachieved telegraphy over a distance of quarter of a mile alongGreat Portland Street, and showed the experiments to Sir GeorgeGabriel Stokes, Sir Charles Wheatstone and others. Those twomembers of the Royal Society were at first very much impressed,but later they felt that all the experiments that Hughes had showncould be predicted from existing knowledge. Hughes was muchdisappointed by this statement, and he decided to try to work upthe experiments to a point where they were impossible to refute.He never did so, and it was not until 20 years later, after he hadwatched all the developments of Hertz and Marconi and others,that Fahie and Campbell Swinton persuaded him to publish thework that he had done.

504 MACGREGOR-MORRIS: GREAT PERSONALITIES IN THE

The notebooks recording these early wireless-telegraphy experi-ments are very precious, but we cannot give to him the honourof the discovery, because he was not the first to publish hisresults, and, as mentioned previously, we must have some meansof deciding who is the first in any field. Hughes was a remark-able man; he touched on so many things and generally made areal contribution to each. If at a meeting of The Institution,with two or three hundred people present, someone made a joke,one would know at once whether Hughes was there, because hislaugh was unique; it made one feel that one had tickled a sheepinto laughter, if you can imagine how that would sound. It wasso characteristic that nobody could miss it.

I am going to show you Hughes's induction balance of 1879in operation. While this is being prepared, there are someacknowledgments that I should like to make. In preparing thislecture I have received a great deal of help from the Librarianof The Institution in sorting out the apparatus shown on the tableand in obtaining slides. Most of those that I have shown wereprepared for The Institution. I also wish to express my thanksto Professor Barlow, of University College, for arranging forthis Hughes induction balance to be overhauled by their expertassistant, Mr. Effemey, who has put this ancient piece of apparatusinto working order.

It can be worked with a microphone, and an arrangement canbe used to give a pulsing current round the circuit, but we aregoing to demonstrate it by means of a cathode-ray oscillograph,so as to make its operation visible to everyone. There are twocoils which are opposed to one another. We are going to usean audio-frequency current, of 3 000 c/s, through the two pairsof exciting coils. Those coils surround the pair which are con-nected to the oscillograph in this case but could be connectedto a telephone. This pair of coils is in opposition, so that ifthe magnetic flux coming through the two coils is equal thereshould be no response, but if* you upset the inductance of onecircuit by dropping a shilling into one of the coils, as we proposeto do, it will upset the balance. The cathode-ray oscillograph,which is connected to an amplifier, will show the magnitude ofthe effect.

[The apparatus was then demonstrated by inserting a nickelshilling, a silver shilling, and discs of high-conductivity copper,commercial copper and German silver, and an ordinary pin.]

Doing the experiment in this way has enabled us to see it,instead of listening to a buzzer.

I am grateful to Mr. Lance, of Cinema Television, Ltd., forsupplying this magnificent cathode-ray oscillograph on loan forthis lecture and to Mr. Walker for its efficient operation. HereI should like to make a plea for the Measurements Section Com-mittee to think over. There is a hole in the wall at the back ofthis lecture theatre for a lantern, and that is accepted as part ofthe essential equipment of The Institution; should not there bea hole in the wall at the other end of the theatre for a cathode-ray oscillograph as part of the permanent equipment of thetheatre? Preparing for experimental lectures at present is apainful business. The time has come for this proposition tobe seriously considered.

There is only one living man whose portrait I wish to showyou, and that is the portrait of Sir James Swinburne. In theearly days of electric lighting he was a very prominent man, andalmost no meeting of The Institution was complete if he did nottake part in the discussion. What often happened was thatsomeone would describe a new measuring instrument, and itwould be lauded considerably, and then Swinburne would get upin his suave manner and say it was very nice, but ten years ago. . . and so on and so on; he had done much of the work before.I do not say that to blame him, but just to show you that he wasahead of his time. He had great talent in that field. He

became our leading scientific expert, and a judge once said ofhim that he was the only scientific expert who had never misleda judge. That says something for his character.

The brilliance of Kelvin in that field was certainly amazing.When the Atlantic cable was first laid there was an engineerin charge who was not a sailor by any means, nor very distin-guished in the theory of the operation of cables, and the cablebroke down, apparently owing to the use of induction coils tospark messages into it—rather a brutal treatment. It "died"after only 2\ months' work, and William Thomson (LordKelvin), then a young man, was appointed Chief Engineer. Toappoint such a man was a risky thing to do, but Sir CharlesBright and his colleagues were right; they had the foresight tosee that this man was worthy of trust. He began by inventingthe mirror galvanometer. Nobody thinks about who invented itnowadays, but in fact Kelvin did. The needle of the swingingapparatus which the previous engineer had used weighed about£ lb, and for a needle like that to have to swing to get messagesthrough a cable quickly is absurd. Kelvin, instead, had twovery short pieces of steel or watchspring stuck on to the back ofa mirror, the whole weighing only a few grains, and thus it wasso light that it could respond quickly to the signals. I have nottime to elaborate this matter further.

In addition to Kelvin's mirror galvanometer (1858) we havetwo of his electrostatic voltmeters on view.

I should like to refer again to Silvanus Thompson, a man soversatile that just because of his brilliant versatility he was notable to do a tremendous amount in any one field. He was awriter of several technical books and a first-class teacher; hecould have succeeded as a doctor, as an examiner in music, asa good artist or as a first-rate linguist. I have heard him speakin French, German, Italian, and in American too. He alsowrote an excellent Life of Lord Kelvin in two volumes. I havea photograph of a group showing Silvanus Thompson on theleft, Sir William Ramsay (the discoverer of neon, krypton,xenon and other rare gases) in the centre, and Trotter on theright.

I must also mention Professor Ayrton. Many years ago, theJapanese sent a Commission to study education in various partsof the world. They came to the conclusion that the Englishmethod was best suited for their purpose, and when TokyoUniversity was founded they appointed four professors: Ayrton,Perry, Milne and Ewing. These four men went to Tokyo anddeveloped the University there, Ewing dealing with magnetismand mechanical engineering, Milne with earthquakes (from which,as you know, Japan suffers a good deal), Ayrton with physicsand Perry with mechanics. They laid such firm foundationsthat the work which was carried on afterwards was a real creditto them. In magnetism there was Nagaoka, who did brilliantwork, and later Honda and others have done very good work inthe field of permanent magnets.

I have a photograph of two very well-known men, ProfessorPerry and Colonel Crompton, which is entitled "Theory andPractice."

I have left myself very little time, but there are two other menwhom I must mention. One is William Duddell. I have nevermet a man more skilful with his fingers and more inventive thanDuddell. It was a real joy to see him at work and to talk tohim. He was bristling with ideas, but unfortunately he had tofight all the time against ill-health; he suffered from asthmawhen quite young, and finally his war work broke him downand he died during the First World War. We owe to him theDuddell oscillograph and the Duddell thermal galvanometer, andthere are certain papers of his full of ideas and still worthyof study by instrument makers who wish to improve theirapparatus.

FIELDS OF ELECTRICAL AND MAGNETIC MEASUREMENTS 505

Lastly, I must mention Ferranti. About 1895 there was abattle going on in The Institution between direct current andalternating current. My brother and I used to enjoy the fight;we liked to see these big men hammering away at one anotherand hurling arguments to and fro. Ayrton was very active;Swinburne was suave, but equally effective; Colonel Cromptonwas the champion of direct current; and Kelvin said that whilehe admired the extraordinary ingenuity of the alternating-currentengineer he could not but believe that the simplicity of directcurrent would win in the long run. As far as the battle hasgone, he does not appear to have been right, but that was hisconsidered opinion.

Ferranti came to the fore when still very young, about 19 yearsof age. He was very good at explaining things to people whohad money, telling them that if they did so-and-so it was boundto be successful. Whenever trouble occurred Ferranti rose tothe occasion and invented something to get over it. His ideaof having the power station a long way from the place wherethe supply was going to be used was right, and he put down theDeptford power station to supply current six miles away atBlackfriars Bridge. There were no cables in those days whichcould be used for 10 000 volts, so he said, "If there are none,let us start making them," and he set to work with candle-greaseand paper and copper and got his cables to work, although therewere joints every 25 feet, or every 25 yards—I am not sure which.The amazing fact is that some of those cables worked for 20 or

30 years without breakdown. The youthfulness of the man, hispowers of persuasion and his vision were outstanding.

In conclusion, I should not be true to my colours if I did notadd one word about the spiritual side of these men. It is notusual to talk about such things here, but I have taken a broadsubject, and, as I say, I must be true to my colours. I shouldlike to read an extract from an ode which Hans Andersen, theauthor of the fairy tales, wrote on Oersted, the discoverer ofthe magnetic effect of an electric current, and which RolloAppleyard translated from Danish into English—

When to thy mind there flashed the lightning thought,The realm of science, wondrous in the blaze,Revealed such treasures in the truth you taughtThat men before its beauty bowed and soughtA path to its Creator by your ways.

Turning now to Professor Silvanus Thompson—he was amember of the Society of Friends, and wrote a book called "ANot Impossible Religion." Lord Kelvin was a humble com-municant. Sir Ambrose Fleming, my old chief, though he didnot let us know it at college, was an earnest Christian, as wasalso Professor Clerk Maxwell. Here are five names that shouldmake those who doubt wonder whether truth does not lie in thatdirection. What we seek for scientifically is truth, and we mustseek for truth also in the moral and spiritual world. Let usreach out towards it as far as we can.

ABSTRACTS OF PAPERS

ANISOTROPIC STRAINS PRODUCED BY SURFACE ABRASION, AND THEIR EFFECTON THE MAGNETIC PROPERTIES OF SILICON SHEET STEEL

By R. G. MARTINDALE, M.SC, Associate Member.(ABSTRACT of a Measurements Section paper which was published in October, 1948, in Part H of the Journal.)

It is shown that surface abrasion of electrical sheet steel withemery cloth by hand results in the formation of high internalstrains in the material which are markedly anisotropic incharacter, even though the depth of cut may be only about100 micro-inches. Such treatment produces compression of thesurface layers, with the result that abrasion of the steel on bothsides leads to the formation of a tensile stress in the centrallayers of the sheet. This stress is a maximum in a direction atright angles to that of abrasion, and has a pronounced effect onthe magnetic properties of cold-rolled silicon steel possessing ahigh degree of preferred grain orientation, and also to a lesserextent on those of ordinary hot-rolled 4% silicon transformersteel.

Measurements of magnetostriction and permeability in therolling direction are given for samples of these materials beforeand after abrasion in different directions relative to the appliedfield, and Fig. 1 shows values of permeability obtained for sixsamples of a cold-rolled steel, 0-012 in thick and containing2 • 39 % of silicon, in which a large proportion of the grains areoriented with a [100] cube edge in the rolling direction and a(110) plane in the plane of the sheet. Longitudinal abrasionrefers to abrasion parallel to, and transverse at right angles to,the field direction.

The changes in magnetic properties arising from surfaceabrasion are explained qualitatively in terms of the domaintheory of ferromagnetism, and an estimation of the initialdomain distribution in the abraded samples of cold-rolled steel

Mr. Martindale is with the Metropolitan-Vickers Electrical Co., Ltd.

20000As received

beforeabrasion

After stransverse abrasion

After longitudinaabrasion

i5 10 15

Flux density i3,kilogaussFig. 1.—Variation of permeability with flux density for six samples

of cold-rolled silicon steel, showing the effect of surface abrasionin different directions relative to the applied field.

indicates that about two-thirds of the domains are initiallyoriented at right angles, and about 25 % parallel to, the directionof abrasion in the plane of the sheet, the remainder being orientedperpendicular to the plane of the sheet.