Kathleen Lonsdale, Irish crystallographer and prison reformer (born 1903)

Dame Kathleen Lonsdale was an Irish crystallographer, pacifist, and prison reform activist. 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, first female 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.

April 1 is the 91st day of the year in the Gregorian calendar; 274 days remain until the end of the year.