Hertha Ayrton: pioneering inventor and suffragette

Physicist, mathematician, engineer, inventor and suffragette – Hertha Ayrton was many things at a time when women were expected to simply keep house and raise a family. Anita Chandran explores the life of this remarkable scientist, who died a century ago next year

Portrait of Hertha Ayrton in 1906 by Helena Darmesteter

The turn of the 20th century was defined by huge strides in engineering, automation and manufacturing. It was an era that gave us technologies such as radio transmission, air conditioning and the diesel engine, and saw the likes of Nikola Tesla, Thomas Edison and Alexander Bell at the forefront of innovation. But one often overlooked name is Hertha Ayrton.

Responsible for developments in fields as diverse as electricity, mathematics and the physics of liquids and gases; Ayrton is widely regarded as one of the most prolific female inventors in scientific history. Her work, which touched the lives of many, ranged from improving the standards of bulbs and lamps across society, to developing the technology used to combat chemical gas in the trenches of the First World War. 

Although Ayrton faced much opposition during her career due to her gender, she persevered, and forged a path for the many women who followed in her footsteps. Indeed, her involvement in the women’s suffrage movement only added to her rich legacy. As her close friend, writer and suffragist Evelyn Sharp wrote in a memoir of Ayrton: “She was a physicist, suffragist, democrat, humanitarian and very human woman – but never any of these things in a water-tight compartment.”

The birth of “Hertha”

Born Phoebe Sarah Marks on 28 April 1854 in Portsea, UK, Ayrton was the third child and eldest daughter of Jewish watchmaker and Polish immigrant, Levi Marks, and his wife Alice Theresa, a seamstress from Portsea. When Ayrton was seven, her father suddenly died, leaving her mother to raise seven children, with another on the way. 

Despite her family’s hardships, Ayrton thrived as a child and enjoyed unusual freedoms for girls at the time, being encouraged to think freely and play in the streets. It was Alice who safeguarded her daughter’s independence, believing that “women [had] the harder battle to fight in the world” and so needed a better education than men. This opinion propelled Ayrton’s mother to accept an offer from her sisters to send Ayrton to their school in London when she was nine years old – a decision that sharply contrasted with what was considered “the duty” of an eldest daughter in the 1860s. 

At school, Ayrton stood out as having a brilliant scientific mind and a strong personality, but given the freedoms she enjoyed at home, she had no patience for arbitrary discipline, rule-setting or the etiquette expected of young girls. “[Her upbringing] was not an upbringing that helped to make her at the age of nine a docile little schoolgirl,” wrote Sharp. Ayrton also did not tolerate injustice, once going on hunger strike for two days when wrongly accused of breaking school rules. 

Hertha Ayrton with a group of women who took the University of Cambridge entrance examination for women in 1874

Despite occasional clashes with her teachers, Ayrton excelled at school and by 16 was self-sufficient, working as a governess and supporting her family. During this time she met numerous influential thinkers, in particular associating herself with the early women’s suffrage movement. One new friend was Ottilie Blind, who gave Ayrton the nickname “Hertha”, inspired by Algernon Swinburne’s 1869 poem of the same name. Together, the pair attended women’s suffrage meetings and later coached each other for the University of Cambridge entrance examination for women. 

Life as a society governess wasn’t enough for Ayrton, who sought further education, and in 1873 she was introduced by Blind to Barbara Leigh Smith Bodichon. A leading feminist and co-founder of Cambridge’s first women’s college, Girton College, Bodichon became Ayrton’s mentor and confidant, encouraging her to apply to Cambridge. She also introduced Ayrton to Mary Ann Evans, author of Middlemarch who used the penname George Eliot. Indeed, Evans was so inspired by Ayrton that she based the character Mirah in her 1876 novel Daniel Daronda after her.

Ayrton passed the University of Cambridge entrance examination for women in 1874 with honours in English and maths, however, it wasn’t until 1876, sponsored by Bodichon and Evans among others, that she started studying mathematics at Cambridge.

Cambridge and Finsbury

In the 1870s, there were few, if any, classes at Cambridge open to women. Instead, Ayrton worked closely with the handful of other female students, establishing a small, separate study group. She was coached by Richard Glazebrook, a physicist with a specialty in aviation and electricity, both of which became pillars of Ayrton’s career. 

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Ayrton was beloved at Cambridge – it was impossible not to know her. Sharp quotes a classmate saying that Ayrton “gave one the impression that she was one of the students of her year with a future before her”. She was heavily involved in college life, establishing the Girton College Fire Brigade, leading the college choral society and forming a mathematics club.

Hertha Ayrton in the Girton College Fire Brigade in 1880

It was during her studies that Ayrton began her journey as an inventor, developing an early form of the sphygmomanometer – a device for measuring pulse beats. It consisted of an old watch-spring, fastened around the wrist with a paint brush attached to it. By drawing a piece of paper at a steady pace below the brush, a heartbeat could be recorded. We now know this device as the inflatable cuff doctors fit around an arm to measure blood pressure. The sphygmomanometer was formally patented in 1881 by the Austrian physician Samuel Siegfried Karl von Basch, but Ayrton is not credited in its development. 

Life at Cambridge was not easy for Ayrton, who often had the competing priorities of supporting her family and combatting her own insecurities. She was known to rush her mathematical work, having little time and support for mastering the fundamentals. Her friends at Cambridge often said that she tended to self-sabotage, a form of what we now might identify as imposter syndrome. During her studies she also suffered bereavements and a severe illness.

Yet despite her struggles, Ayrton fought hard to complete her degree. In 1880 she passed her Mathematical Tripos examinations – some of the hardest mathematics exams in the world – but placed relatively poorly in the university rankings, a fact that disappointed her for many years. Like all women of the period at Cambridge, she was prevented from sitting her finals in the exam halls, instead having to take them unofficially in a separate lecture room, and she was not allowed to receive a degree despite passing. Consequently, she took an external examination for the University of London – one of the few UK universities that granted women degrees – and received a BSc in mathematics in 1881.

After obtaining her degree, Ayrton began working in London as a maths teacher, first at Kensington High School and then at Wimbledon School. She soon switched to tutoring maths privately, and began devising and publishing mathematical problems for students that became popular among teachers. 

The cover page of one of Ayrton's US patents

Ayrton continued her scientific research while she worked, and in 1884 developed a new type of mathematical line divider that could split a line precisely into any number of equal parts. After months of work and numerous failed iterations, she patented the invention in the UK and abroad. The result generated a huge amount of press – in some part because she was a woman – being referenced in Nature in January 1885 (31 275) and in the French publication Revue Scientifique in May of that year.

The success of the patent not only drew congratulations from feminist circles – including leading suffragist Millicent Fawcett – it allowed Ayrton to present a paper before the Physical Society (a precursor to the Institute of Physics) and pushed her to consider pursuing scientific research full-time. With financial hardship holding her back, it was Bodichon – Ayrton’s benefactor at Cambridge – who provided a lifeline, donating a large sum of money to Ayrton so that she could teach fewer pupils and instead focus her energies on science.  

Committing herself to this pursuit, in the autumn of 1884 Ayrton began taking four nights of classes per week at Finsbury Technical College (later incorporated into Imperial College London), where she studied electro-technics (electricity and physics) as one of three women alongside 118 men. She was taught by William Ayrton, a physicist and fellow of the Royal Society. William, an ardent champion of women’s education, fought hard for opportunities for Ayrton. The two developed a deep connection, and William relied on Hertha’s expertise in both physics and in life. Their friendship quickly turned romantic, and the two married in 1885. Their daughter, Barbara Bodichon Ayrton, was born in 1886 and they raised her alongside William’s daughter Edith from a previous marriage. 

Luminous arc 

Following her marriage, Ayrton’s scientific pursuits were limited by ill health, and domestic and family responsibilities, but she persevered. In 1888, she gave a series of lectures on electricity to women at Finsbury Technical College – a progressive act at the time. “That a woman should lecture to women on such a subject…was regarded as a startling innovation,” says Sharp in her memoir of Ayrton.

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In June 1891 Ayrton’s mentor and friend Bodichon died. Although a great blow to Ayrton, Bodichon’s final act of generosity was to leave her with money enough to hire a housekeeper so she could once again focus on science. Her husband meanwhile was determined that Ayrton conduct independent research, knowing that if they shared authorship of papers, he would receive sole credit. He therefore ensured she had lab space for her own work and was careful not to directly collaborate with her. 

Hertha Ayrton in 1895

Through William, Ayrton developed an interest in carbon arc lamps, the first practical electric lights, which had been invented by Humphry Davy in the early 1800s. To ignite these lamps, a voltage is applied across two carbon conducting rods that are in contact. The conductors are then pulled apart, and the luminous arc is maintained by the carbon vapourizing as it heats up, acting as a bridge for the electrical current.

When her husband visited the US, Ayrton continued his research on arc lamps at the Central Technical College in Kensington (later incorporated into Imperial College London) where William was now a professor. Their resulting paper was one of the few pieces of research the couple collaborated on, but when the sole copy was accidentally destroyed, Ayrton took full ownership of the project.

At the time arc lamps were widely used in lighthouses and to illuminate public places, but their behaviour baffled scientists. They would hiss and flicker, seeming to defy the laws of electricity, and the materials used could not cope with the intense heat produced. Ayrton discovered that the cause of arc instability was oxygen coming into contact with the carbon rods. By excluding oxygen from the lamps, she was able to obtain a steady arc and establish the “Ayrton equation” relating arc length, pressure and potential difference. It was revolutionary work that led to better, more efficient and brighter lighting. Later she also investigated the carbon used in arc lamps, developing rods that lasted longer and were better suited to particular applications.

Ayrton’s work on arc lamps led to several patents, a series of papers and a book. Not only did her research improve general arc lamp technology and street lighting, but also cinema projectors and military searchlights. Her papers were considered exceptional even by her critics, and she became established as a leading expert on electrical arcs, boosting opportunities for her in the scientific community. Ayrton was asked to present her papers in various fora, including the British Association for the Advancement of Science (later renamed the British Science Association), although in the early years she often had to do this immediately before or after her husband.

In March 1899 the Institution of Electrical Engineers (IEE, a precursor to the Institution of Engineering and Technology), which then consisted of 3300 men, defied precedence by inviting Ayrton to read her well-regarded paper “The hissing of the electric arc” – making her the first woman to present her own work to the society, and she went on to become the institution’s first female member. Her advocacy at the International Electrical Congress in 1900 led to women being allowed to serve on general scientific committees in the UK for the first time in history. 

Helping women in and out of science

Ayrton later formed a friendship with the Nobel-prize winning scientist Marie Curie, whose reputation she vocally defended in public and in the press in the coming years. For instance, when Pierre Curie died, many UK newspapers proclaimed him to have discovered radium, a feat actually achieved by Marie. As Ayrton wrote in a letter correcting the Westminster Gazette: “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.”

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

She and Curie were close, with Ayrton even tutoring Curie’s daughter, Irène Joliot-Curie, in mathematics. She also brought Curie into the women’s suffrage movement, influencing her to sign an international petition to free British suffragettes who were in jail and on hunger strikes. 

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Throughout her career, Ayrton profoundly felt the impact of combative attitudes towards women. For example, she was denied fellowship of the Royal Society because married women were not eligible at the time, and her early work had to be presented to the Society by male colleagues. Despite the opposition, Ayrton became the first woman to present a paper in front of the Royal Society in 1904, and she was later awarded the society’s prestigious Hughes Medal, which only two other women have won since.

Ayrton was heavily involved in women’s rights beyond science too. As Sharp describes in her memoir of Ayrton, she had “always been a suffragist as a matter of course…she never required any conversion to the principle of votes for women”. Initially, Ayrton considered her best contribution to the cause was to show, through her own scientific achievements, that women were fit to vote. Her involvement mostly came through attending meetings and giving the campaign the support of her name.

Later, however, she went on to join the more radical “suffragette” branch of the movement, the Women’s Social and Political Union (WSPU). Ayrton donated funds and took part in the demonstrations – including “Black Friday” on 18 November 1910 that saw police and male bystanders violently attack the protesting women. She even sheltered the suffragettes who were recovering from hunger strikes in jail, which meant her home was constantly surrounded by police.

From the beach to the battle field

While on holiday in Kent, Ayrton became interested in sand ripples on the beach, and began a new programme of work experimenting on sand and water to examine coastal erosion. Following William Ayrton’s death in 1908, she turned inwards, increasingly spending time carrying out research from home. She moved their home laboratory from the top storey of the house to the drawing room, equipping it with glass tanks filled with water and sand. Here she made great strides in the study of waves and vibrations, and, although her work began out of pure curiosity, it took on real significance following the outbreak of the First World War. 

Hertha Ayrton in her laboratory in 1910

Poison gas was first used in April 1915, and Ayrton immediately began applying her study of rippling water to devise a method of repelling it. She even constructed a fake “battlefield” complete with trenches in one of her sand tanks, using smoke from paper fires to simulate the gas. Before long, Ayrton had invented a fan device that released a puff of air when hit against a hard surface, thereby displacing the advancing gas. By May 1915 she approached the army with her design, but the government would not be persuaded, insisting that Ayrton’s design was too simple to be taken seriously. In large part, despite her renown as an inventor, this was due to her being a woman and a suffragette. But Ayrton persisted, and her fan was accepted over a year later. 

More than 100,000 “Ayrton Flapper Fans” were deployed in France and Belgium, and they were known for their use in rolling back large clouds of heavy, toxic gases. The late uptake of her device plagued Ayrton, however, who was aware of the number of lives that might have been saved if the fans had been adopted earlier. She continued working on the fan, in conjunction with a budding interest in the labour movement, and her device was later used to improve modern industrial conditions for workers in factories. 

Hertha Ayrton died aged 69 on 26 August 1923, from septicaemia caused by an infected insect bite. In her final years, she turned her considerable intellect to advancing the causes she cared most deeply about: women’s suffrage, the rights of working people, and protections for children. She continued her work in science with no sign of slowing down, publishing papers right up until her death, the last of which was read posthumously to the Royal Society. Through her life, she was awarded 26 patents, and her untimely death meant she left behind unfinished research. Ayrton was beloved by the many people whose lives she intersected with, all of whom remarked on her quick wit, passion, and her favourite mantra, often written on her notebooks, to “prove all things; hold fast that which is good”. 

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