Go back to article: The life and material culture of Hertha Marks Ayrton (1854–1923): suffragette, physicist, mathematician and inventor

Arc angel: Ayrton’s research on electric arcs in the 1890s

Figure 4

IET Archives UK 108 IMAGE 1/1/0020 Hertha Ayrton head and shoulder portrait, n.d.

Arc lighting was developed in the early to mid-nineteenth century and by the mid-nineteenth century had found a use as the powerful light in lighthouses. By the late nineteenth century, direct-current electric arcs were widely used for public lighting and were replacing gaslights as street lighting. As such, electric arcs were of significant industrial, commercial and physical interest. However, the electric arc lighting systems of this time were temperamental and prone to problems: they flickered, hissed, rotated, and produced unsteady and inconsistent lighting. There were also further difficulties with the materials used: the intense heat produced made for excellent, large-scale public lighting but also made it difficult to manufacture insulators and design electrodes capable of dealing with the intense heat. Some research had been done into electric arcs but much of their operation and underlying principles remained unknown and so scientists were unable to advise manufacturers as to the best way to design and operate such lights.

In 1893, William Ayrton travelled to the Chicago Electric Congress to present the results of his research on electric arcs. William left the sole copy of his paper with the Secretary for publication but instead it was accidentally used as kindling for a fire (Ayrton, 1902, vi). No rough copy or abstract remained of the paper and while William was in the US attending the congress, his experiments, which were being conducted at South Kensington, were left under Ayrton’s supervision (Trotter, 1924). When William returned he had no inclination to rewrite the paper and so Ayrton took over the experiments previously conducted by her husband, at first replicating his research but quickly moving beyond it. Her husband moved onto other areas of research as he was keen not to be credited with his wife’s work.

Ayrton established two key points in relation to the working of electric arcs. Firstly, she discovered that the problems with electric arc lighting such as hissing, flickering and instability were the result of oxygen coming into contact with the carbon rods used to create the arc (Mason, 2004). Secondly, Ayrton discovered that when oxygen was excluded, a steady arc was obtained and hence she was able to establish a linear relationship between arc length, pressure, and potential difference, the ‘Ayrton equation’. Ayrton used her knowledge of electric arcs to patent a number of improvements in anti-aircraft searchlight carbons, which she developed for the British Admiralty; she also designed improved cinema projectors and more general arc lamp technology.

Between 1895 and 1896, Ayrton published a series of twelve articles on her analysis, research and technical advances in the field of electric arc lighting – commonly used for street lighting and powerful interior lights – in The Electrician, the premier electrical engineering periodical of the age. With these articles, she overtook her husband’s earlier work in this field and established her own credentials as an expert on the workings of the electric arc and in the field of electrical engineering more generally. This recognition led to increased opportunities including the invitation to deliver her own paper on electric arcs before the Institution of Electrical Engineers (IEE). She was the first woman to read her own paper before this prestigious engineering society, although the society was more progressive than many of their peers and had allowed women to attend their lectures since the institution was founded as the Society of Telegraph Engineers in 1871. In all of this, Ayrton was achieving rare progress for a woman but was also establishing a path which other women in science, technology, and engineering might and would follow.

Three of Ayrton’s earliest papers on electric arcs were delivered before the annual meetings of the British Association for the Advancement of Science (BAAS, now the British Science Association) in 1895, 1896 and 1898. All three papers were delivered before Section A – Mathematical and Physical Sciences and the two earliest papers were delivered immediately adjacent to papers of Ayrton’s husband, who was heavily involved in the BAAS. Ayrton was also a member of the ‘Brit. Ass.’, as it was affectionately known (Barrett, 2017, p 210). In 1895, Ayrton delivered a paper on ‘On the Equation Connecting the Potential Difference, Current, and Length of the Electric Arc’ for which no further details were provided in the report of the sixty-fifth annual BAAS meeting. The paper was presented immediately before a paper by Ayrton’s husband with T Maher, ‘On the back EMF and True Resistance of the Electric Arc’.[11] In 1897, Ayrton presented a paper ‘On the Relations between Arc Curves and Crater Ratios with Cored Positive Carbons’ before the BAAS annual meeting held at Toronto, Canada that year (the BAAS held every fourth meeting abroad). Again, Ayrton presented immediately adjacent to her husband: this time William Ayrton presented jointly with Professor J Viriamu Jones, FRS with a paper on ‘On a Determination of the Ohm made in Testing the Lorenz Apparatus’.[12]

In 1898, Ayrton presented a third paper on electric arcs before the BAAS annual meeting, this time held in Bristol. In her paper ‘The drop of potential at the carbons of the electric arc’, Ayrton described her research into the constancy of the drop of potential at the carbons of the electric arc and noted that she hoped to find a more conclusive answer in her future research.[13] By now, Ayrton appears to have a found a new independence and confidence in the public presentation of her research: she no longer presented immediately adjacent to her husband and also submitted an abstract for the paper to The Electrician for publication; a corrected and annotated proof in Silvanus Thompson’s hand is held by the IET archives.[14] Ayrton’s papers before the BAAS were, in part, enabled by women being able to serve on the BAAS general and sectional committees and marked a changing relationship between the learned society and women, both as producers and consumers of scientific research and content.[15]

The following year in March 1899, Ayrton’s research and expertise, in particular that related to the electric arc, were recognised by the IEE: Ayrton was invited to give a paper before the IEE and she was elected a member of the institution (MIEE), a prestigious and widely recognised professional qualification. On 23 March 1899, Ayrton read a paper ‘The Hissing of the Electric Arc’ before the IEE which summarised her research into the sometimes eccentric behaviour of electric arcs. The paper and the post-paper discussion were published in the Journal of the Institution of Electrical Engineers (Ayrton, 1899).

Figure 5

Pen and ink illustration from a paper entitled the hissing of the electric arc

IET Archives UK 108 IMAGE 1/2/0084 Figure 8 (apparatus) from Hertha Ayrton’s paper, ‘The hissing of the electric arc’, Journal of the IEE Volume 28, Issue 140, June 1899, p 400 –436

Just two days after she delivered her paper, Ayrton was elected the first female member of the IEE, which then consisted of 3,300 members (Sharp, 1926, p 141). Ayrton remained the sole female full member of the institution until 1958, although Gertrude Entwisle became a student, graduate and associate member of the institution in the 1920s. Additionally, in March 1899, Ayrton was awarded an IEE premium (prize) to the value of £10 for her IEE paper on electric arcs. This was formally presented to her at the society’s annual general meeting the following November at which the new President, Silvanus Thompson, gave his inaugural address. Ayrton was in good company: among her fellow recipients of IEE premiums that evening was Guglielmo Marconi, for his paper ‘Wireless Telegraphy’, and Professor Oliver Lodge for his paper (also on wireless telegraphy), ‘Improvements in Space Telegraphy’.

In post-lecture correspondence with fellow electrical engineer Dr Silvanus P Thompson in late May 1899, Ayrton noted that she had received a copy of A P Trotter’s contribution to the post-lecture discussions.[16] Ayrton mentioned, in passing, Thompson’s Cantor Lecture, delivered a few months previously before the Royal Society of Arts, about the electric arc. Perhaps it was only in passing because her equation of the relationship between current and voltage disagreed with that of Thompson (Hong, 2001, p 162). The main focus of her letter to Thompson was to clarify that ‘while it was impossible that the slowly rotating figures should not have been observed before, but that [she] could find no description of [these] figures’ and that these figures observed from her electric arcs made in her laboratory had not been described by Thompson in his Cantor Lecture.[17] Ayrton lamented that she was unable to show Thompson ‘the clearly defined & comparatively slowly moving light & dark bands’ as she had been too busy since her IEE lecture in late March to get the apparatus in working order again.[18]

By the late nineteenth century, Ayrton’s work in the field of electrical engineering began to be recognised more widely – domestically and internationally. In 1899, Ayrton presided over the physical science section at the International Congress of Women held in London and she was invited by the Royal Society to demonstrate her electric arc experiments at their annual conversazione (Byers and Williams, 2006, p 17). In 1900, she delivered a lecture in French about her electric arc research, L'intensité lumineuse de l'arc à courants continus (‘The luminous intensity of the direct-current arc’), at the International Electrical Congress in Paris.[19]

Her lecture was used by her cousin Marcus Hartog to persuade the British Association for the Advancement of Science to allow women on their committees (Mason, 2004). In 1901, her paper ‘The mechanism of the electric arc’ was delivered before the Royal Society by renowned electrical engineer Professor John Perry (Ayrton, 1901). Perry was an electrical engineer, former Professor of Engineering and Mathematics at Finsbury Technical College and had collaborated with William Ayrton for a number of years. Perry delivered Ayrton’s Royal Society paper as women were still unable to present papers before this prestigious and traditional scientific society.

In 1902, Ayrton published The Electric Arc, a comprehensive summary of her research and work on the electric arc, with origins in her earlier articles from The Electrician published between 1895 and 1896 (Ayrton, 1902). The title page was where the author laid out their qualifications and expertise. Here it said simply ‘Hertha Ayrton, Member of the Institution of Electrical Engineers’; no further qualification was needed. The Electric Arc, which remains in print into the twenty-first century, became the standard textbook on the subject until after the First World War and firmly established Ayrton’s reputation in electric arc lighting as well as electrical engineering.

Despite these many achievements in physics and electrical engineering, Ayrton remained marginalised by more traditional scientific societies such as the Royal Society and, with the exception of the IEE and the support of her husband, an outsider in the scientific community. In the aftermath of the publication of The Electric Arc in 1902, Ayrton was proposed as an FRS by Professor Perry (who had read Ayrton’s paper before the Royal Society a year previously in 1901) and other prominent scientists and Royal Society council members. The Society's council were divided on the issue: then Royal Society President and astronomer William Huggins was against women ‘trivialising’ his elite scientific institution and Ayrton’s increasingly outspoken commitment to women’s suffrage probably did not help matters (Jones, 2010). However, officially Ayrton’s application was turned down by the Council of the Royal Society based on legal advice that married women were ineligible to be Fellows of the Royal Society as they had no independent legal standing in law.[20]

Nonetheless in 1904 (and in the temporary absence of William Huggins) Ayrton became the first woman to deliver her own paper, ‘The Motion of Ripples in Sand and Wave’, before the Royal Society. She delivered further papers on this subject before the Royal Society, published in 1908 and 1910 (Ayrton, 1908; Ayrton, 1910). In 1906, Ayrton was awarded the Royal Society’s Hughes medal which was granted ‘without restriction of sex or nationality […] for an original discovery in the physical sciences, particularly as applied to the generation, storage and use of energy’ in recognition of her work on the electric arc and her later research on the motion of ripples in sand and water.[21] Although the Royal Society was a conservative and restricted institution – as indicated by their denial of the full participation of women for much of the twentieth century – the Hughes medal was prestigious within and without the society and eligibility for it was defined in progressive terms as being ‘without restriction of sex or nationality’. Despite these claimed lack of restrictions, Ayrton was the first woman awarded this prestigious medal: a rare achievement considering the gendered spaces she was working and not working in. Unlike her male scientific peers, Ayrton did not have access to any institutional laboratory in her own right and instead relied on the use of her husband's laboratory at the Central Institution in London (now Imperial College), until his death in 1908 (Jones, 2010).

Nonetheless, Ayrton continued with her research and further developed theories informed by her body of experimental work, presenting before British and international audiences. In 1911, Ayrton travelled to Paris where she presented a paper on ‘Sand Ripples and Oscillating Water’ before the Société de Physique.[22] Ayrton began her paper, which summarised her experiments on, and theories of, the formation of ripples in sand and waves in water, with compliments to her audience of ‘distinguished and brilliant…scientists… Frenchmen [who] make the kindest and most indulgent audience in the world’.[23] Ayrton concluded her paper with a consideration of how her research on the formation of ripples would apply to propellers and aircraft adding an ‘urgent plea’ for mathematicians to take into consideration her research and theories and to modify their theories, in particular in hydrostatics, accordingly.[24]

While in Paris in 1911, Ayrton also visited Marie Curie and would always visit her when she came to the French capital. The two women of science first met during a visit by the Curies to the Royal Institution in London in 1903 after they won the Nobel Prize for Physics. Here, the two women became good friends and they had many shared commonalities: being part of a married collaborative couple; an independent dedication to scientific research, which both pursued against their social origins and gendered expectations of the time; and a strong sense of social justice especially for women (Ogilvie, 2011, pp 123–125). Such was the strength of their friendship that Marie Curie presented Ayrton with an author’s presentation copy of her 1903 thesis with the dedication, ‘A Madame Hertha Ayrton / Hommage d'une sympathie tres sincere / M. Curie’ (‘To Madame Hertha Ayrton/ in truly sincere homage / M.Curie’), now held by the IET library and archives.[25]

Ayrton’s visit to Paris in 1911 was particularly notable as, almost simultaneously in November 1911, Curie received her second Nobel Prize in Chemistry – for the discovery of radium and polonium – and her affair with fellow physicist and colleague Paul Langevin (who was married) was publicly revealed.[26] Later on in the summer of 1912, Curie secretly came to England with her daughters Irene and Eve and stayed with Ayrton for two months at a coastal English cottage when Curie needed somewhere to escape the brief scandal concerning her relationship with Langevin (Hemmungs Wirten, 2015, p 76). Ayrton was not the only the member of the scientific community to publicly support Curie when revelations of the affair came to light to much public criticism: Albert Einstein wrote a friendly and supportive private letter to Curie, expressing his admiration for ‘[her] intellect, [her] drive, and [her] honesty’ and considered himself lucky to have made her personal acquaintance at the 1911 Solvay Conference in Physics in Brussels.[27]

It would seem that Marie Curie, and the audience of French physicists to which Ayrton was so highly complimentary, provided a more welcoming audience than that of the British scientific establishment as represented by the Royal Society. Ayrton had, in turn, been an out-spoken champion and supporter of Curie when, after her husband’s death in 1909, Pierre Curie and not Marie Curie was claimed as the discoverer of radium, including by the British press. Perhaps reflecting on her personal experience of her scientific successes being attributed to her husband, Ayrton wrote a letter to the Westminster Gazette on 14 March 1909, noting ‘Errors are notoriously hard to kill, but an error that ascribes to a man what was actually the work of a woman has more lives than a cat’ (quoted in Sharp, 1926, p 117).

Between 1911 and 1913, Ayrton was kept busy with the suffragette movement, marching on many if not all of the most militant suffrage marches in London. She also continued her research into the scientific and mathematical understanding of motion of ripples in sand and motion, including a paper on the topic ‘On some new facts connected with the motion of oscillating water’, presented before the Royal Society in 1911. The paper was delayed from November 1910 to late January 1911 due to Ayrton’s involvement in the suffrage marches at this time and Ayrton felt her public involvement in these marches was the reason the paper was not published (Abir-Am and Outram, 1987, p 122 footnote 53). This was contradicted by a detailed three-page anonymous Royal Society reviewer’s comments about Ayrton’s paper which noted:[28]

Mrs Ayrton’s paper is rather difficult to criticise. She has brought to light a number of interesting facts and exhibited them in a very beautiful way, but the reasoning throughout appears defective. The essential fallacy has its source in treating the motion at any instant as if the water were at rest, and consequently neglecting the effect of the rate of change of momentum. […]

Despite the setback in terms of publication of her research, Ayton continued her experiments which led to further research on oscillations in water and air, a research topic she continued to pursue throughout the war years and one which had immense practical application in the First World War.[29]

Component DOI: http://dx.doi.org/10.15180/181002/004