Guest blog by Alex Mordey
Look at almost any electrical device in your home. The phone charger, the kettle, the television, printed or moulded beside the voltage figures, you will find a small wavy line: ∿. The alternating current sinusoidal wave (or Sine wave). It is one of the most reproduced symbols on earth, stamped onto every mains appliance ever manufactured, and almost nobody knows its origin.
It was proposed in a single sentence, one evening, in a lecture theatre at the Institution of Electrical Engineers in 1889, by a self-taught telegraph clerk named William Morris Mordey. Ninety six years later the same Institution sat on the British committee that wrote his symbol into law. The AC Sine wave is only the most visible of his legacies. Behind it sits a body of work that helped build the modern electricity supply industry, and a man that history has largely forgotten.
The clerk who taught himself
Mordey was born in County Durham in 1856 and entered the Post Office telegraph service around 1870 at the age of fourteen, the year the service was nationalised. After a brief spell in London he was posted to Bradford, the Yorkshire wool town where he would spend his formative working years. He had no formal engineering education, and for a boy of his background there was almost no way to get one. Britain had no system of free secondary education in the 1870s. Universities and the few technical colleges there were, charged fees far beyond the reach of a telegraph clerk. The established route into the profession, a pupillage or apprenticeship under a senior engineer, had to be bought with a premium that working families simply did not have.
Mordey taught himself physics in the evenings, and as many self-taught men of the period did, he passed what he had learned on to others, running evening classes in telegraphy, magnetism and electricity for the Science and Art Department and for the City and Guilds of London Institute. This was how technical knowledge spread in Victorian Britain outside of universities, taught by men who had a genuine passion and aptitude in specific areas. In 1881, sitting the examination alongside the very students he had been teaching, he was awarded the second prize and medal of the City and Guilds Institute in the advanced stage of telegraphy. His academic excellence did not go unnoticed, and that same year he joined the Anglo-American Brush Electric Light Corporation, where he became chief electrician.
The evening of liveliest interest
By the late 1880s the great unsolved problem of alternating current was whether two or more alternators could be run in parallel. The consensus of nearly every major authority was that it could not reliably be done. Mordey had first contemplated the idea of an alternator with no iron in its armature in 1884 and concluded it impractical. By 1889 he had found a way to make it work, and he brought the finished machine to the Institution to prove it.
He read his paper, Alternate Current Working, on the evening of 23 May 1889 to a distinguished audience that included Lord Kelvin, the most eminent physicist in Britain, and Lord Rayleigh, who would later win the 1904 Nobel Prize in Physics for his discovery of argon gas. Mordey settled the parallel working question not with theory but with eight live demonstrations in front of them. The Electrician, the leading professional publication of the electrical industry, was unrestrained in its verdict. The paper declared it was “full of the liveliest interest from beginning to end,” and Mordey had “settled by direct and conclusive experiment the question of working alternators in parallel.” Two years later the same journal credited him as the first man to demonstrate parallel working “in an engineering fashion.” That principle, the running of synchronised alternators in parallel onto a shared supply, is the foundation on which every alternating current grid in the world, including the national grid, is built to this day.
It was in this same paper, almost in passing, that Mordey proposed the wavy line. He needed a quick way to write what engineers then called the periodicity of an alternating current, the property we now call frequency, the number of cycles it completes each second. “To save confusion I always write it thus, ∿,” he told the meeting, “and I would suggest that this sign be used unless a better one be forthcoming.” Lord Rayleigh pressed instead for the plain written word “frequency,” and Mordey replied with “a plea for the sign ∿ as rendering confusion impossible.” A better one was never forthcoming. That same wavy line is the character we now know as Unicode U+223F, the sine wave, and as IEC 60417-5032 sinusoidal wave, the international symbol for alternating current.
What he built
If the sine wave was but a footnote, the machine he had come to demonstrate was his crowning achievement. The Mordey Victoria alternator became the dominant AC generator of Britain’s pioneer electricity age. Among its home’s was Bankside in London, where the first public AC supply in the capital was generated on the site that is now Tate Modern. Two further achievements rank alongside it. In 1893 Mordey named and defined the V curve of a synchronous motor. The relationship between field excitation and armature current that traces a characteristic V shape, a fundamental concept of electrical theory that has been taught in standard textbooks ever since. Then in 1895, working with the Hungarian engineer Ottó Bláthy, he showed that the steady growth of hysteresis loss in transformer cores was caused by the heating of the iron itself, the phenomenon known these days as magnetic or thermal ageing.
Mordey co-invented the Mordey-Fricker electricity meter, devised the Equaliser, and was the discoverer of the Mordey Effect. He filed at least thirty eight British patents, many of them abroad too, across a working life that ran from 1883 to a final patent in 1935 when he was seventy eight! The true impact of that work is easy to underestimate, his 1920 patent for electromagnetic mineral separation still being cited as prior art by General Electric in 1952 and by Raytheon in the 1970s. His Mordey Victoria alternators and transformers were installed at more than thirteen power stations in Britain and abroad, among them Bankside in London, Pandon Dene in Newcastle, Bath and Dover. In 1895 his machines lit two of the most public installations in the country: the incandescent lighting of the Great Northern Railway’s King’s Cross terminus, its passenger and goods stations, the Great Northern Hotel and the line out to Hornsey was generated by three Mordey Victoria alternators, and three more drove the lighting of the Indian Exhibition at Earl’s Court through the summer. His 250 kilowatt Mordey Victoria alternator was important enough to earn a dedicated illustrated article in Scientific American, and his transformer was listed as one of the principal modern types in the 1911 Encyclopaedia Britannica. In 1902 he co-authored a paper on electric traction on railways at the Institution of Civil Engineers, and the senior engineering institution in the country awarded him its Telford Medal for that work, quite an honour for a self taught telegraph clerk. And in 1908 he was elected president of the Institution of Electrical Engineers, a position he held through to 1909.
Lighting the Great Northern Railway
Among the many installations that used his machines, one stands out for its impact on rail and lighting. In 1895 the Great Northern Railway was powered from a single central works at Ashburton Grove in Holloway. The Engineer judged that the company had outstripped most of its rivals in the effort to illuminate so large an area.
From that one station the supply extended across the railway’s London suburbs including, King’s Cross terminus, the Great Northern Hotel, the passenger and goods stations, the cattle docks and carriage sidings, and the line northward through Finsbury Park, Harringay and Hornsey. The longest circuit ran nearly eight miles, and about forty miles of cable were laid beside the track. The outdoor yards were lit by some 350 arc lamps powered by Brush machines, but the incandescent lighting of the buildings was generated entirely by alternating current, from three Mordey Victoria alternators with two smaller machines beside them. The stationary iron-free armature he had brought before the Institution six years earlier, and the Equaliser of his own devising, were now lighting one of the busiest railway termini in the world.
The regard of his rivals
The measure of an engineer’s work is perhaps found in the challenge of their rivals. And for Mordey’s disc-armature alternator there was certainly competition. Mordey’s alternator was patented in Britain in April 1888 and in the United States in September 1890. His design and its priority were no secret on the other side of the Atlantic, The American engineer and editor T. C. Martin had set out the Mordey machine in print in the United States from 1888, crediting it explicitly, noting that a key precaution, that is alternators intended to work in parallel must have low self-induction in their armatures “was first pointed out by Mr. Mordey.” Six weeks after Mordey’s American patent was granted, Nikola Tesla filed a US patent for an architecturally similar disc-type alternator.
When Tesla lectured to a spellbound audience of some eight hundred people in February 1892, The Electrician publication described his machine in unmistakably Mordey-type terms. Tesla never claimed to have known Mordey’s work when he filed, and the records do not show that he did. But by December 1892 he was writing in The Electrician, in his own words, that in his first high-frequency trials he had “expected to obtain the best results with a machine of the Mordey type,” and that “with an armature without iron, as used by Mordey, the results obtained were excellent.” He used the phrase the Mordey type without explanation, plainly expecting readers to know it. The Mordey machine had become a recognised engineering term, a benchmark that the most celebrated electrical inventor of the age measured himself against.
By the early 1890s Mordey’s standing among his peers was high. A technical survey in The Electrician in 1893 judged that, “from a purely electrical point of view the Mordey alternator is almost perfect, and certainly possesses the important feature of a high efficiency of conversion at light loads.” And named him alongside Gisbert Kapp and James Swinburne among those who had worked out the theory of exciting alternating current machines. His V curve results were already being reproduced in print as standard reference material.
No engineer engaged with Mordey’s work more publicly than Professor George Forbes, a consulting engineer to the Niagara scheme. In a Society of Arts lecture in 1892 Forbes singled out the Mordey type of alternator as he weighed the options for the great Niagara Falls project, and in his Niagara paper of late 1893 he named Mordey’s machines among the very best in the world for running in parallel. Of all the machine’s built, he said, those that worked best in parallel appeared to be those of Ganz, Mordey and Elwell-Parker. As that paper closed in December 1893 he set Mordey among the engineers to whom the whole field was indebted, naming him in the same breath as Tesla, Fleming, Hopkinson and Thomson.
And then, almost in the same season, the tone changed. At the Institution that winter, Forbes cast doubt on Mordey’s celebrated parallel-working experiments, and early in 1894, communicated from San Francisco via letter, he pressed Mordey to publish exactly how many breakdowns his machines had suffered in the City of London works. What is striking is not the attack but the response to it. The profession closed ranks around Mordey. Silvanus Thompson and James Swinburne backed his position openly at the Institution, and The Electrician, which had witnessed his parallel-working trials at Thames Ditton in 1891, defended him in print, observing that the offending paper should never have been presented to an engineering society. The journal was careful to separate two questions, conceding that nobody was claiming the Mordey alternators were the right machines for Niagara itself, while insisting that the validity of his experiments was beyond criticism. The Niagara contract went to Westinghouse, and the Adams Station generators that began turning in 1895 ran on Tesla’s polyphase alternators rather than Mordey’s single-phase disc; but the machine architecture chosen, a fixed armature with a revolving field, was the very principle Mordey’s disc alternator had been built on.
Courtesy of the IET Archives (OPC 01 034 04)
The first voice on the air
Of all the uses Mordey’s design was put to, the most extraordinary came at Brant Rock, Massachusetts, on Christmas Eve 1906. That night Reginald Fessenden made what is generally regarded as the world’s first radio broadcast of speech and music, and the machine that generated his continuous radio wave was an alternator of the Mordey type running at approximately 50,000 Hz to generate a continuous radio wave. The fixed iron free armature and revolving field that Mordey had built in 1889 to light streets and houses was now rotating fast enough to transmit a human voice and music across the airwaves. When Professor J. A. Fleming set out the engineering of early radio in his standard textbook, he singled out the Mordey type as the design selected for the work and explained precisely why it had been chosen. Fleming traced the line forward, too. Fessenden’s small Mordey-type machines led to the far more powerful high speed alternators developed by Ernst Alexanderson, and it was an Alexanderson alternator that powered the great transatlantic radio station Marconi built at New Brunswick, New Jersey, sending continuous wave signals across the ocean from 1918. The famous spark transmitters of Marconi’s first 1901 transatlantic signal had given way, within a generation, to the alternator, and the alternator that worked traced its design back to Mordey. A generator conceived for the electricity supply of Victorian Britain had become, almost incidentally, a founding instrument of broadcasting and long-range wireless.
The library he gave back
By 1916 Mordey was past sixty and his great industrial work was behind him, but when his old friend and champion Silvanus P. Thompson died that summer, he stepped forward. Thompson, an IEE President, Fellow of the Royal Society, author of Calculus Made Easy and the definitive biography of Lord Kelvin, had defended Mordey in print when others would not, calling him “my friend William M. Mordey, engineer and inventor.” Mordey was made chairman of the committee formed to buy Thompson’s extensive scientific library and present it to the IEE as a memorial. It was a collection of some nine hundred rare books and manuscripts reaching back to 1391, priced at four thousand pounds. Mordey was one of four trustees who saw it through wartime storage to its installation at Savoy Place in 1921. At the Annual General Meeting of 1923 he rose to present it, opening with the words: “I must resist the temptation to-night to speak of Thompson as a man, as a teacher and as a friend.”
The Thompson Library is still at the IET today, one of two great rare book collections the Archives hold.
Legacy of the symbol
So follow the wavy line, the sine wave. Mordey proposed it in 1889. Fleming adopts it in 1891 and carries it on into his wireless textbooks. Ayrton and Sumpner are using it in The Electrician by 1892, where it soon settles into routine editorial use.9 The trail then runs, very likely from Fleming’s own use, into the formal standards process: in 1966 the Radiocommunications committee began the work of standardising graphical symbols for use on equipment. By 1973 the symbol was published as IEC 60417-5032. In 1985 it was written into British Standard BS 3939 Part 6, the graphical symbol for alternating current in every machine, generator, motor and transformer diagram in the land.
Among the bodies named on the technical committee that produced that standard was the Institution of Electrical Engineers, the very body Mordey had presided over in 1908 and 1909. Ninety six years after he offered the world a small wavy line “unless a better one be forthcoming,” his own Institution helped make it British law.
The recognition he deserves
When Mordey died at Warlingham in the summer of 1938, aged eighty two, The New York Times remembered him simply as an “engineer and magnetician” who had helped develop the modern dynamo, generator and transformer. At home, The Engineer marked his passing with words that read like a quiet warning about how the world would go on to forget him:
The death of Mr. W. M. Mordey, at the age of eighty two, removes from the electrical profession a man whose work in the early days of electricity supply scarcely seems to have received in recent times the recognition it deserves. Few of the younger generation of electrical engineers appear to appreciate the important part Mordey Victoria alternators played in the generation of single phase current or to what extent the originator of those machines contributed to the solution of the problems that presented themselves when electric lighting began to replace gas.
From the misfortunes of the period Mr. Mordey did not escape but although he had to face many difficulties he never published anything directly relating to them. The history of the technical side of electricity supply has been sadly neglected. Few seem to have considered it worth while to record at length their early experiments, and with the death of this pioneer who did so much in bygone days, scarcely anyone is left to do so.
Eighty seven years later, rigorous research across the IET Archives, the Science Museum Group collections, and the contemporary engineering press has begun to reclaim what an obituary once feared was lost.
His contributions paved the way for the modern electrical supply industry, leaving behind a physical legacy we still rely on today, even as his name faded into the annals of time. He sought no monuments, and he has none. Yet every time we plug in a device, flick a switch, or tune a radio, we are offered a silent and unwitting tribute. Perhaps the truest measure of his greatness lies not in how loudly his name is remembered, but in how deeply the legacy of his work is still felt.
IET film of William Mordey
You can see a film of William Mordey speaking about his time at IEE President, on the Film London website. Please note that the film begins at 01:30. This is part of a collection of short films produced by the IEE (now the IET).
References and further reading
1. W. M. Mordey, ‘Alternate-Current Working’, The Electrician, vol. XXIII, 31 May 1889, p. 94 (section ‘Periodicity’); same passage in Journal of the Institution of Electrical Engineers, vol. XVIII, p. 597. The paper in which the ∿ sign was proposed and parallel working demonstrated.
2. W. M. Mordey, ‘On Testing and Working Alternators’, Journal of the Institution of Electrical Engineers, vol. 22, 1893, pp. 110 to 134 (V curves at p. 128, equaliser at p. 131; parallel working at pp. 132 to 134). DOI: 10.1049/jiee-1.1893.0004.
3. ‘W. M. Mordey’, obituary, The Engineer, 8 July 1938, pp. 44 to 45. Source of the closing quotations and of the early-life and recognition material. Public scan via the Internet Archive; related entry at Grace’s Guide to British Industrial History.
4. ‘William Morris Mordey; British Engineer Who Developed Electro-Magnetic Machinery’, obituary, The New York Times, 2 July 1938. Records the ‘engineer and magnetician’ description and his Imperial College and Science Museum roles.
5. N. Tesla, ‘The Ewing High-Frequency Alternator and Parsons Steam Engine’, The Electrician, vol. 30, 17 December 1892, p. 391. Tesla’s own reference to ‘a machine of the Mordey type’. Volume scan at HathiTrust; transcription at Wikisource.
6. T. C. Martin and J. Wetzler, The Electric Motor and Its Applications, 3rd edition, New York: W. J. Johnston Company, 1892, pp. 107 to 108. Early American attribution of priority to Mordey. archive.org/details/electricmotorits01martuoft.
7. J. A. Fleming, The Principles of Electric Wave Telegraphy, 2nd edition 1910, p. 12; and The Principles of Electric Wave Telegraphy and Telephony, 3rd edition, London: Longmans, Green and Co., 1916, pp. 12 to 13. Fessenden’s and the later Alexanderson alternators as ‘the Mordey type’.
8. G. Forbes, on Niagara, The Electrician: a Society of Arts lecture reported at vol. XXVIII, 12 February 1892, p. 388 (reported speech, not a transcript); and his Niagara paper and the ensuing IEE discussion in vol. 32, 1893 to 1894, naming Mordey’s machines among the best for parallel working (p. 119), listing Mordey alongside Tesla, Fleming, Hopkinson and Thomson (p. 123), and reporting the Westinghouse contract (p. 74). His defenders, including Silvanus Thompson and James Swinburne, are recorded in the discussion (pp. 194 to 196); The Electrician’s editorial defence of Mordey, and its note that nobody claimed the Mordey alternators suited Niagara, is at pp. 177 to 178. Forbes’s contribution pressing Mordey on breakdowns was communicated from San Francisco in 1894.
9. Contemporary technical assessment of the Mordey alternator (‘from a purely electrical point of view the Mordey alternator is almost perfect’) and of Mordey as a theorist of alternating-current machine excitation, alongside Kapp and Swinburne, in a serialised article in The Electrician, vol. 32, 1893 (pp. 69, 87 and 88), which also reproduces Mordey’s V curve results.
10. W. M. Mordey and B. M. Jenkin, ‘Electrical Traction on Railways’, Minutes of Proceedings of the Institution of Civil Engineers, vol. CXLIX, Paper No. 3331, 18 February 1902, p. 40, with discussion at p. 87 (Lord Kelvin); award reported in ‘Scientific Notes and News’, Science, new series, vol. 16, no. 413, 28 November 1902, pp. 876 to 879 (Mordey, Telford Medal; Jenkin, George Stephenson Medal).
11. W. M. Mordey, ‘Inaugural Address’, Journal of the Institution of Electrical Engineers, 1909. DOI: 10.1049/jiee-1.1909.0001. Delivered as IEE President for the 1908 to 1909 session.
12. British patent GB5162 (priority 7 April 1888), the foundational Mordey disc alternator, with United States equivalent US437501A; and US1463713A (1923), electromagnetic mineral separation. Patent activity confirmed against Grace’s Guide (‘at least 38 British patents’) and an Espacenet export. Tesla’s architecturally similar US447921A was filed 15 November 1890 and granted 10 March 1891.
13. IEC 60417, symbol 5032, alternating current; and British Standard BS 3939: Part 6: 1985 (identical with IEC 617-6: 1983). The same wavy form, standardised as the international equipment symbol for alternating current.
14. Holdings of the IET Library and Archives, Savoy Place, London, including the Silvanus P. Thompson Library; Mordey objects in the Science Museum Group collections; and ‘250-Kilowatt Mordey-Victoria Alternator’, Scientific American.
15. W. M. Mordey, ‘Some Prejudicial Actions in Dynamo Machines’, Journal of the Society of Telegraph Engineers and Electricians, 1884, pp. 160 to 168. DOI: 10.1049/jste-3.1884.0023. His debut paper, in which he considered and set aside the iron-free armature he would later build; it received honourable mention from the Council.
16. The Mordey-Fricker electricity meter, co-invented with Guy Carey Fricker. British patents GB190002710A (application 10 February 1900) and GB190201251A (application 16 January 1902, patent 1251 of 1902), patents.google.com/patent/GB190201251A/en. Recorded and described in The Engineer, vol. 93, January to June 1902: the patent at p. 127 (‘1251. Electricity Meters, W. M. Mordey and G. C. Fricker, London’), and at p. 546 as a new and simple meter suitable for direct or alternating currents, intended especially for small consumers with only a few lamps; archive.org/details/sim_engineer_january-2-june-27-1902_93. Shown at a Royal Society conversazione per Grace’s Guide, gracesguide.co.uk/Mordey-Fricker_Electricity_Meter_Co.
17. John S. Belrose, ‘Fessenden and the Early History of Radio Science’, The Radioscientist, volume 5, number 3, September 1994, ewh.ieee.org/reg/7/millennium/radio/radio_radioscientist.html. On Fessenden’s machine for the first broadcast of speech and music, Christmas Eve 1906 at Brant Rock, Massachusetts: ‘The Fessenden high frequency alternator was a small machine of the Mordey type, having a fixed armature in the form of a thin disc, or ring, and a revolving field magnet with 360 teeth, or projections. At a speed of 139 revolutions per second, an alternating current of 50,000 Hz and a terminal EMF of 65 volts was generated. The maximum output of the alternator at the above speed was about 300 watts.’ Belrose draws on Fleming’s 1910 textbook (p. 849).
18. W. M. Mordey, presentation address, 51st Annual General Meeting, Journal of the Institution of Electrical Engineers, vol. 61, issue 320, July 1923, pp. 1146 to 1147. The Thompson Memorial Library presentation, with Mordey’s opening words.
19. The Mordey Effect, the difference in hysteresis loss between iron carried through its magnetic cycle by rotation in a machine and iron in a periodically reversed field. Named in professional discussion by 1891 (W. E. Ayrton, reported as ‘what Mr. Vignoles called the Mordey effect’, The Electrician, vol. XXVII, 1891, p. 112). Described by Silvanus P. Thompson, Dynamo-Electric Machinery, 4th edition, 1892, recording that ‘Mordey has found the losses by hysteresis to be somewhat smaller’ in the rotating case (quoted in T. O’Conor Sloane, The Standard Electrical Dictionary, 1892, gutenberg.org/cache/epub/26535/pg26535-images.html). Confirmed experimentally by F. G. Baily, ‘The Hysteresis of Iron and Steel in a Rotating Magnetic Field’, Philosophical Transactions of the Royal Society A, vol. 187, 1896, pp. 715 to 746, DOI: 10.1098/rsta.1896.0018.
20. Power-station installations of the Mordey Victoria alternator, per Grace’s Guide to British Industrial History, which records the type as installed at ‘more than 13’ stations in Britain and abroad. Confirmed UK sites include Bankside, London (first public AC supply in the capital, now the site of Tate Modern), gracesguide.co.uk/Bankside_Power_Station; Pandon Dene, Newcastle, gracesguide.co.uk/Pandon_Dene_Power_Station; Bath (three Mordey Victoria 75 kW dynamos), gracesguide.co.uk/Bath_Power_Station; and Dover, gracesguide.co.uk/Dover_Power_Station.
21. Bankside power station, London: the first public alternating-current supply in the capital, generated with Mordey alternators on the site now occupied by Tate Modern. Grace’s Guide to British Industrial History, gracesguide.co.uk/Bankside_Power_Station.
22. ‘The Engineer’, vol. 80, July to December 1895: the Great Northern Railway electric lighting installation, pp. 384 to 386 (18 October 1895), recording that ‘the incandescent-lamp lighting is all carried out by alternate current, generated by three A14 Mordey-Victoria machines’, serving from King’s Cross to Hornsey, including the Great Northern Hotel and the King’s Cross passenger and goods stations; and the Indian Exhibition at Earl’s Court, p. 550 (6 December 1895), three engine sets ‘driving Mordey alternators… throughout the summer’. archive.org/details/sim_engineer_july-5-december-27-1895_80.
23. ‘Great Northern Electric Light Station, Holloway’, The Engineer, vol. 80, 18 October 1895, pp. 384 to 386, recording that ‘the incandescent-lamp lighting is all carried out by alternate current, generated by three A14 Mordey-Victoria machines’ serving the Great Northern Railway from King’s Cross to Hornsey. archive.org/details/sim_engineer_july-5-december-27-1895_80.