Silbermann's heliostat (1843)

Copyright: Lebée Inventaire Général / École Polytechnique

For physicist Jean-Thiébault Silbermann, Jean-Baptiste Soleil manufactured a simpler and less expensive heliostat than the one in use at the time, designed by the French inventor Henri Gambey. This instrument allows the sun's rays to be projected in a fixed direction by means of mirrors, despite the rotation of the earth, in order to study its spectrum, for example. The principle is to compensate for the earth's rotational movement by a clockwork mechanism. The version developed by Jean-Baptiste Soleil was much appreciated and used until the beginning of the 20th century.