Director of the International Bureau of Weights and Measures.
Nobel Prize for physics.
Development of anibal, a steel and nickel alloy, for the production of the integral balance wheel or Guillaume balance wheel: bi-metallic balance wheel (anibal-brass) where the secondary error is practically eliminated.
Developed invar (abbreviation of invariable, name proposed by Genevan professor, Marc Thury), a steel and nickel alloy, to make precision pendulums: pendulums with an invar shaft.
Development of elinvar, steel and nickel allow containing chromium and tungsten, to make self-compensating spirals.