The Earth goddess and the electric arc
Name: Hertha Marks Ayrton
Fields: Mathematics and engineering
Claim to fame: Expert on the electric arc
Hertha Marks Ayrton (1854-1923) was a dedicated suffragette, enduring physical and verbal abuse during demonstrations between 1906 and 1914, and nursing hunger strikers back to health under duress from the police and press. Over her lifetime, Hertha made substantial contributions to the understanding of the direct-current arc and patented several inventions.
A sense of self
When she was a teenager, Phoebe Sarah Marks (1854-1923), the third of eight children in a poor Jewish family that had fl ed Poland to build a new life in the UK, changed her name to Hertha, inspired by the heroine of a best-selling feminist novel by Fredrika Bremer. The agnostic and vivacious Hertha maintained her mother‘s values of generosity and self-suffi ciency throughout her life.
Hertha went to London when she was nine to be educated by her aunt. She aspired to a university education but needed to support herself – and help her family – by tutoring and doing embroidery work. Her dream was fi nally made financially possible in 1876 by one of the founders of the University of Cambridge‘s Girton College, Barbara Leigh Smith Bodichon, a passionate supporter of women in higher education.
She received her BSc from the University of London because the University of Cambridge did not give degrees to women at the time.
Engineering a brighter future
After graduating, Hertha supported herself by teaching maths, although her real passion lay in experimental mathematics and engineering. In 1884, she invented a device that could divide a line into any number of equal parts, which was to prove very useful for architects, engineers and surveyors. With renewed confi - dence and financial backing from Bodichon, she continued her studies at the Technical College in Finsbury.
The field of electricity caught Hertha‘s interest, and she decided to study under William Edward Ayrton, who was a supporter of women‘s rights. They developed a strong relationship and married in 1885, after which Hertha continued to experiment with and lecture on electricity. But the pressures of poor health and increasing domestic responsibilities at home left her with little time for research.
When Hertha‘s friend and benefactor Barbara Leigh Smith Bodichon died in 1891, she left Hertha enough money to support her mother and get help around the house. This enabled her to resume her scientific investigations, and she happily took on some of her husband’s work on the electrical breakdown of gas, known as the electric arc.
Over the next few years, Hertha made a number of important discoveries about the nature of the electric arc, and published a series of papers that she incorporated into a book in 1902. In 1899, she read her own paper on the hissing arc at the Institution of Electrical Engineers and became their first female member. In that same year, she made several presentations and demonstrations, notably at the International Electric Congress in Paris.
Toxic winds of war
During World War I, poisonous, clear chlorine gas was the cause of death or lingering torture to soldiers in the trenches. In 1915, Ayrton drew on her knowledge of air vortices to invent a simple fan that could dispel the gas from the trenches. She campaigned strongly for its use and invented an adapted version in 1917 that was even better. Despite the demonstrable effectiveness of the device and her well-known personal charms, Hertha was unable to convince the wartime bureaucrats to put the Ayrton fan into general use.
Hertha‘s work on the electric arc preceded the emergence of the field of plasma physics. Direct-current arcs, which at the time were a commercially important source of lighting, break down gas and produce a continuous plasma discharge; the arc is generated between two carbon electrodes that are then consumed. The problem was that because of this, the length of the arc was continually changing. Also, the heat generated by the arc melted most materials.
Ayrton‘s work illuminated the relationship between power supply, current and arc length and determined that the shape and size of the positive carbon electrode were among the most important factors in the arc’s behaviour. Her findings led directly to improvements in searchlight carbons and in lamp houses for cinema projectors. She also produced original works on hydrodynamics and, based on her knowledge of air vortices, invented the Ayrton fan, a cheap and simple device that could be used to clear poisonous gas from trenches.