In 1855, Le Verrier hired a physicist known for his pendulum, which demonstrated the rotation of the Earth: Léon Foucault (1819-1868). Foucault revolutionized astronomical observation by replacing the poorly reflecting bronze mirrors then used in telescopes by silvered glass mirrors, which could be easily resurfaced when tarnished. He built many telescopes, including that of the Marseilles Observatory, which, with its 80-centimetre mirror, was for many years the largest in the world, and served well for a century.

caption : Foucault 20 cm telescope - credits : Observatoire de Paris