**Cosserat** studied the deformation of surfaces which led him to a theory of elasticity.

- Eugène was only four years old when François Cosserat entered the École Polytechnique in 1870, and nine years old when Lucien-Constant Cosserat entered the same institution in 1875.
- Eugène was educated first in a primary school in Amiens, moving to the Lycée in Amiens for his secondary education which he entered in the autumn of 1877.
- During three years of study at the École Normale, Cosserat attended lectures by leading mathematicians including Paul Appell, Gaston Darboux, Gabriel Koenigs and Émile Picard.
- Cosserat graduated in 1886 and spent a short time teaching at the Lycée in Rennes before he was appointed as an assistant astronomer at the Observatory in Toulouse towards the end of 1886.
- In his doctoral dissertation, Cosserat extended Plücker's concept of generation by means of straight lines by considering infinitesimal properties of spaces generated by circles.
- Even before the award of his doctorate in 1889, Cosserat had begun teaching mathematics courses at the Faculty of Science at Toulouse.
- In 1908 Cosserat was appointed to the chair of astronomy at Toulouse, becoming director of the Observatory there for the rest of his life.
- The role of director of the Observatory was a demanding one, and Cosserat became almost totally occupied with administrative tasks from the time of his appointment and so was forced to essentially give up mathematical research from this time on.
- Although he was not living in Paris, Cosserat was elected to the Académie des Sciences as a corresponding member on 19 June 1911 and a full member on 31 March 1919.
- All these various contributions showed great skill and resulted in highly accurate data but much of Cosserat's work on astronomy was carried out at a time when he was also devoting much of his time to the study of mathematics.
- In his later work, Cosserat studied the deformation of surfaces which led him to a theory of elasticity.
- The Cosserats themselves recognised the value of oriented two-dimensional continua (i.e., curves and surfaces endowed with additional structure in the form of directors) for representing the deformations of rods and shells respectively.
- Exceptions are also colleagues of Eugène Cosserat in Toulouse, like L Ray and A Buhl.
- Relativity Theory and Quantum Physics overtook this period in science and the work of E and F Cosserat was almost rediscovered after 1950 because of the use of liquid crystals.
- Another aspect of Eugène Cosserat's work which we should mention is his contributions to the Annales de la faculté des sciences de Toulouse.
- This journal began publication in 1887 and, two years later, Cosserat joined the editorial board.
- In 1896 Cosserat became secretary to the editorial board of the Annals and he continued to hold this role until 1930.
- In addition to his administrative work for the Annals, Cosserat also translated articles from Russian and published French versions in the Annals.

Born 4 March 1866, Amiens, France. Died 31 May 1931, Toulouse, France.

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Astronomy

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive