Lescarbault, Edmond Modeste

BornChâteaudun, Eure-et-Loir, France, 11 August 1814

DiedOrgères, Orne, France, 1894

A single observation by Edmond Lescarbault set off a decade-long but futile search for Vulcan, supposedly orbiting the Sun closer than Mercury. As a student, Lescarbault studied medicine and produced a thesis on typhoid fever, enabling him to serve as a country physician in Orgères, 75 miles southwest of Paris, from 1848 until 1872. But his passion was astronomy, and for it he constructed an observatory equipped with a refractor, a pocket watch, and a seconds pendulum, as well as a wooden board on which he did his computations.

The discovery of Neptune had been prompted by calculations carried out by Urbain Le Verrier concerning the irregularities of Uranus’s orbit; Le Verrier also suggested that a similarly unknown planet could explain observed discrepancies in Mercury’s orbit. Lescarbault read of Le Verrier’s work, and informed him that on 26 March 1859, Lescarbault had observed an unusual black dot...