On 2 January 1860 he announced the discovery of Vulcan to a meeting of the Académie des Sciences in Paris.
Na hitro je izmeril njegovo lego in smer gibanja ter s pomočjo stare ure in nihala, s katerima je pacientom meril srčni utrip, ocenil čas prehoda na 1 uro 17 minut in 9 sekund.