Dame Kathleen Lonsdale ( Yardley; 28 January 1903 – 1 April 1971) was an Irish-born British pacifist, prison reformer and crystallographer. She proved, in 1929, that the benzene ring is flat by using X-ray diffraction methods to elucidate the structure of hexamethylbenzene. She was the first to use Fourier spectral methods while solving the structure of hexachlorobenzene in 1931. During her career she attained several firsts for female scientists, including being one of the first two women elected a Fellow of the Royal Society (FRS) in 1945 (along with Marjory Stephenson), first woman tenured professor at University College London, first woman president of the International Union of Crystallography, and first woman president of the British Association for the Advancement of Science. Early life and education She was born Kathleen Yardley at Newbridge, County Kildare, Ireland, the tenth child of Harry Yardley, the town postmaster, and Jessie Cameron. Kathleen's family was not wealthy, and her father was an alcoholic. As the Irish unrest became more severe and Kathleen's father was an alcoholic, Kathleen's mother divorced her father and took the rest of the family to England. Her family moved to Seven Kings, Essex, England, when she was five years old. Kathleen attended Downshall Elementary school from 1908 to 1914. She studied at Ilford County High School for Girls, then transferred to Ilford County High School for Boys to study mathematics and science, because the girls' school did not offer these subjects. Kathleen had the highest score in physics that any student at London University ever had. She earned her Bachelor of Science degree from Bedford College for Women in 1922, graduating in physics with an MSc from University College London in 1924. Career and research In 1924 she joined the crystallography research team headed by William Henry Bragg at the Royal Institution. Following her marriage in 1927, she moved to the University of Leeds, but continued to correspond with Bragg. From 1929 to 1934, she started a family and largely stayed at home while continuing her work calculating structure factors. Her husband Thomas Lonsdale was a textile chemist who supported his wife's research. He encouraged his wife to work from home and to go back to work when offered. He worked at Silk Research Association in Leeds after they were married. In 1934, Lonsdale returned to work with Bragg at the Royal Institution as a researcher. She was awarded a DSc