Kathleen Yardley Lonsdale, co-developer of the space group tables in crystallography and the scientist who determined the structure of benzene, was born on January 28, 1903 in Newbridge, near Dublin, Ireland.

When Kathleen Lonsdale was young her parents separated, and her mother took the children to the London area. Her father, who was an avid reader and a self-taught mathematician, positively influenced Lonsdale.

Kathleen Lonsdale finished high school with an all around excellent record. She went on to complete a B.Sc. degree in physics at Bedford College, a women's college that is part of the University of London. Her performance on the University's written exam, the highest in 10 years, resulted in Nobel laureate Professor W. Henry Bragg inviting her to work at the Royal Institution under him for a master of science degree. Here she earned both an M.Sc. (1924) and later a D.Sc. (1927).

Yardley married Thomas Lonsdale on August 27, 1927. They raised three children, and Thomas was very supportive of Kathleen's professional career.

While working with Bragg, Lonsdale began her lifelong work of developing space group tables, which are invaluable to crystallographers. During a few years at Leeds, she determined the structure of benzene. Data obtained from some large crystals of hexamethylbenzene given to her by Professor Christopher K. Ingold irrefutably showed that benzene was planar.

The Lonsdale family returned to London in 1930. Kathleen resumed working with Bragg at the Royal Institution and remained there until her death in 1971. Lonsdale's other professional achievements included experimental proof that the concept of molecular orbitals was a reality, and research in which the lattice constants of synthetic and natural diamonds were determined. For this latter work, a rare hexagonal form of diamond was named "lonsdaleite" after her.

Lonsdale was one of the first two women to be elected a Fellow of the Royal Society. Lonsdale applied and was appointed Reader in Crystallography at University College, London in 1946. Within three years she was promoted to Professor of Chemistry and Head of the Department of Crystallography. She was the first female professor at University College. She was also the first woman president of both the International Union of Crystallography and the British Association for the Advancement of Science. In addition to her significant scientific achievements, Lonsdale was an active advocate for world peace and prison reform.

Lonsdale died of bone marrow cancer on April 1, 1971.

1. Contributions of 20th Century Women to Physics: Kathleen Yardley Lonsdale

1. Julian, M. M. Women in Crystallography. In Women of Science: Righting the Record; Kass-Simon, G., Farnes, P., Eds.; Indiana University Press: Bloomington, 1993; pp 342-343, 355-357.
2. Rayner-Canham, M.; Rayner-Canham, G. Kathleen Yardley Lonsdale (1903-1971). In Women in Chemistry: Their Changing Roles from Alchemical Times to the Mid-Twentieth Century; American Chemical Society and the Chemical Heritage Foundation: Washington, DC, 1998; pp 71-75.