M.E. Chevreul. Photograph by Nadar.

Michel Eugène Chevreul was employed for most of his career as a chemist at the Muséum national d'Histoire naturelle in Paris, where he investigated the chemistry of fats: his work contributed both to the invention of margarine and to the industrial manufacture of soap. He was also director of the Gobelins tapestry works, where, as a chemist, he was expected to improve the dyes used to colour the fabrics. He discovered that the intensity of colours as they appear to the eye depended largely on their neighbouring colours, and he designed a wheel of 72 colours scientifically arranged, which could be used by designers and painters. Chevreul was also remarkable for his great age: born in 1786 (before the French Revolution), he celebrated his 100th birthday in 1886 and died at the age of 102 in 1889. On his 100th birthday he was interviewed by the Parisian celebrity photographer Nadar, while Nadar's son Paul took photographs. The Wellcome Library has the complete set of 27 photographs, of which this is one