Tettje Clay-Jolles

Tettje Clay-Jolles (1881–1972) was one of the first female Dutch physicists. She studied the variation of atmospheric radiation with geographic latitude with her husband Jacob Clay.

Clay-Jolles was born in 1881 in Assen, Netherlands to Eva Dina Halbertsma and Maurits Aernout Diedrick Jolles. She was the only girl to attend the local secondary school, passing both the alpha and beta series exams at the end of her studies there. These exams tested her knowledge of the humanities and science, respectively.

After secondary school, Clay-Jolles attended the University of Groningen. She commuted each day from Assen by train until 1903 when she transferred to the University of Leiden. She was one of the few women who studied physics at the university. There she began her doctoral research on low-temperature physics under Heike Kamerlingh Onnes. She worked on her thesis until December 1908 when she left her studies to devote herself to her family.

Clay-Jolles met and fell in love with Jacob Clay, another of Kamerlingh Onnes's students, and in 1908 the two were married. Later that year she left school to focus on her family. She spent the next twelve years raising the couple's three children. In 1920 the family moved to Bandung, Java when Jacob Clay was hired as a professor of physics at the Institute of Technology.

In Java, Clay-Jolles returned to research, working as an assistant in a laboratory researching vacuum pumps. During this time she also edited and typed all of her husband's publications. In 1921 she was hired to edit a series of lectures by Nobel laureate Hendrik Antoon Lorentz. Clay-Jolles worked with her husband during the 1920s studying cosmic rays, radiation in the ultraviolet solar spectrum, and the intensity of atmospheric radiation. The two discovered that atmospheric radiation depended on geographic latitude. They did this by comparing the ultraviolet light at their location in Java to the ultraviolet light at the Batavia Observatory. Clay-Jolles published their findings in 1933 in the East Indian scientific journal, Natuurkundig Tijdshrift voor Nederlandsch-Indië. Later that year Clay-Jones and her husband published an article in the Proceedings of the Amsterdam Academy of Sciences entitled "Measurements of Ultraviolet Sunlight in the Tropics." In 1929 the family moved to Amsterdam where Clay-Jones died in 1972.