Hertha Marks Ayrton

English engineer and mathematician

• Born: April 28, 1854
• Birthplace: Portsea, England
• Died: August 26, 1923
• Place of death: North Lancing, Sussex, England

Ayrton made improvements to the electric arc, an important illumination source in the nineteenth century. She also invented a drafting tool and a manually operated fan.

Primary field: Electronics and electrical engineering

Primary inventions: Carbon electric arc; Ayrton fan

Early Life

Phoebe Sarah Marks was the third of eight children of Levi and Alice Theresa (Moss) Marks. Anti-Semitism had induced Levi to emigrate from his native Poland. He struggled to support his large family as a clockmaker and jeweler. In 1861, Levi died, leaving his family with debts. Alice, who was known for her civic and charitable activities, supported her children by selling needlework.

Sarah gained both mechanical talent and a compassionate concern for others from her parents. When she was nine years old, Sarah went to live with her maternal aunt in London, where she received her early education. Her cousin, a graduate of Cambridge University, taught mathematics to Sarah and introduced her to writers and other intellectuals. As a teenager, Sarah decided to leave the Jewish religion, though she remained proud of her heritage. The young agnostic took the name Hertha, the name of a Germanic earth goddess featured in a popular poem by Algernon Charles Swinburne.

Hertha Marks tutored students and sold embroidery to earn money, much of which she sent to her family. One of the founders of Girton College at Cambridge University, Barbara Leigh Smith Bodichon, offered to subsidize Marks’s education. Marks passed entrance examinations in mathematics and English with honors and entered the college in 1876. While she was a student, Marks invented an instrument for recording pulse beats, but after learning that others had preceded her, she did not continue working on it. She completed the Cambridge Tripos examinations in 1881. Since Cambridge did not grant degrees to women, Marks was not eligible.

After inventing a drafting tool that was well received, Marks realized that she might be able to pursue a scientific career. With financial support from Madame Bodichon, she began studying in 1884 at Finsbury Technical College in London under William Ayrton, professor of physics and prominent electrical engineer. Marks and Ayrton married the next year. They had one daughter, Barbara.

Life’s Work

Hertha Ayrton’s first invention was a device for dividing a line into equal parts. Her design was based on the principle that corresponding sides in similar triangles are proportional, and was somewhat related to the drawing compass. Marks patented this invention in 1884 and engaged a British manufacturer.

After marrying Professor Ayrton in 1885, she became involved with his investigations of the electric arc. At that time, arc lamps were an important source of illumination for streets, factories, stores, and other public places. Their intense, harsh light made them best suited for commercial purposes. The electric arc was also used for searchlights. Unfortunately, arc lamps were also noisy, producing unpleasant hissing, humming, and sputtering, and they rotated spontaneously, which changed the color and intensity of light. Arc lamps were temperamental and required many adjustments to keep them operating. During use, the arc’s high temperatures vaporized the carbon electrodes and melted most insulation materials. As the electrodes deteriorated, the distance between them changed, making corrections to the circuit and to positions of searchlight mirrors necessary.

The basic arc lamp consisted of two electrodes housed in a receptacle. When a high-voltage source was connected to the electrodes, molecules of the ambient air would break down into charged particles, or ions. A surge of current (discharge) resulted as the ions suddenly moved to the electrodes. The energy transmitted by these rapidly moving particles would heat the electrodes to incandescence. The electrodes were usually made of carbon, although other materials could be substituted.

The relationship of variables in the arc circuit were not well understood at that time, and Hertha Ayrton realized that this relationship was key to improving the arc. While experimenting with the arc circuit, she found that, for a constant current, the power required was directly proportional to the length of the arc. The current and electric potential were inversely proportional. Ayrton then turned to the question of the electrodes themselves. During the arc’s operation, depressions (craters) developed in the tips of the electrodes as the carbon dissipated. She found that variations in these craters affected the potential needed to maintain the arc discharge.

Next, Ayrton attacked the vexing problem of the hissing arc. Besides being annoying, hissing arcs were not stable. Ayrton found that when a carbon electrode oxidized instead of vaporizing, the crater would spread from the tip to the sides. This change in shape left a path for air to rush in, turn the electrode, and make the unwanted hissing sound. Ayrton realized that manufacturers were creating the conditions required for a hissing arc by placing grooves along the sides of the electrodes. She also recognized that electrodes with flat ends would better resist degradation than the tapered carbons being marketed.

Ayrton’s analysis and solution for the hissing arc quickly brought professional recognition. This achievement transformed Ayrton’s public image from helpmate to established independent researcher. The Institution of Electrical Engineers broke tradition and permitted Ayrton to read her own paper in 1899 rather than requiring a man to present it. The institution awarded her a prize of œ10 and made her its first female member.

After this feat, Ayrton was invited to participate in other meetings and conferences. She compiled her researches into a book on the electric arc that was published in 1902. The British Admiralty consulted with Ayrton on methods to improve carbons in searchlights. She also designed improvements for movie projectors. Ayrton patented many of her inventions.

In 1901, Ayrton noticed sand ripple patterns formed by ocean waves at the beach. Her curiosity led her to investigate water vortices and waves, resulting in several publications. She devised a pressure-difference gauge to confirm her analysis. In 1906, the Royal Society of London awarded Ayrton the prestigious Hughes Medal for her work on the electric arc and on sand ripples. Unlike the Institution of Electrical Engineers, the Royal Society did not grant her membership, deciding instead that a married woman was not eligible.

During World War I, dismayed by the deaths and suffering unleashed by poisonous gas warfare, Ayrton transferred her knowledge of sand ripples and hydrodynamics to the behavior of air. Soon she had invented a fan to move toxic gases out of the trenches, which she offered free of charge and hoped would save many lives. A frustrating combination of indifference and bureaucratic bungling prevented the fan’s timely deployment, a source of deep pain to Ayrton. In 1917, she devised a mechanical version of her fan but apparently did not pursue this. Ayrton died in North Lancing, Sussex, on August 26, 1923.

Impact

Ayrton’s work was part of an engineering tradition that attacked concrete physical problems without using abstract models or theories. Her work on the electric arc was significant for the electric lighting industry. Though electric arcs became less important for lighting after the invention of the incandescent lamp, they continued to be used in searchlights, in projectors, and for welding. Because arcs produce high temperatures, they were used in furnaces to make steel.

The electric arc was especially interesting for physical theory, as scientists recognized that the arc discharge took place in a special state of matter, an assemblage of ions. Investigations of electrical discharges in ionized gases occupied many physicists during the late nineteenth century. Now called plasma physics, the study of ionized gases has applications in physics, astrophysics, and meteorology.

Ayrton’s line divider was patented and marketed for engineers, architects, artists, and other professionals, and her fan for removing toxic gases from trenches proved useful during World War I. However, Ayrton may be best remembered for her personal achievement in rising beyond her economically straitened origins and excelling in a field dominated by men. Ayrton struggled against economic, social, and cultural barriers to pursue her career. Her life is both an inspiration for young people and a case study for exceptional women. As with many women of her era, Ayrton’s path was smoothed by an influential man. Like most successful scientists and engineers of either gender, she had supportive mentors and gained the necessary financial means to pursue her goals. Ayrton was also aided by her enthusiasm, charm, and sociability. She was a trailblazer, making way for other women to pursue careers in engineering and science.

Bibliography

Blühm, Andreas, and Louise Lippincott. Light! The Industrial Age, 1750-1900. New York: Thames and Hudson, 2000. Original, attractive book that places technological developments in their social and historical settings. The authors, curators from the Van Gogh Museum in Amsterdam and the Carnegie Museum of Art in Pittsburgh, emphasize implications of lighting for art. Illustrations, bibliographical references, index.

Bowers, Brian. Lengthening the Day: A History of Lighting Technology. New York: Oxford University Press, 1998. Informative book by the science curator of London’s Science Museum that traces lighting from antiquity to modern times. Includes a chapter on the electric arc. Illustrations, bibliographical references, index.

Malley, Marjorie. “Hertha Marks Ayrton.” In Women in Chemistry and Physics, edited by Louise S. Grinstein, Rose K. Rose, and Miriam H. Rafailovich. Westport, Conn.: Greenwood Press, 1993. Based on original publications, this essay relates and interprets major aspects of Ayrton’s life and work. Part of a collection featuring many lesser-known scientists. Notes, bibliography.

Mason, Joan. “Hertha Ayrton (1854-1923).” In Out of the Shadows: Contributions of Twentieth Century Women to Physics, edited by Nina Byers and Gary Williams. New York: Cambridge University Press, 2006. Engaging sketch of Ayrton that includes several of her extrascientific activities, as well as an overview of her scientific work. Notes, portrait, bibliography.

Sharp, Evelyn. Hertha Ayrton, 1854-1923. London: Edward Arnold, 1926. Written by a friend, the only full length biography of Ayrton paints a portrait of a warm, spirited, resourceful woman of broad interests and endeavors. Illustrations.