FOUCAULT, Léon (1819-1868). ''Démonstration physique du movement de rotation de la terre au moyen du pendule.'' In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Volume 32, Number 5. Paris: Bachelier, 3 February 1851.
FOUCAULT, Léon (1819-1868). "Démonstration physique du movement de rotation de la terre au moyen du pendule." In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Volume 32, Number 5. Paris: Bachelier, 3 February 1851.
4o (279 x 225 mm). (Light spotting.) Original pink-brown printed wrappers (backstrip lacking, other edges chipped with minor loss); cloth folding box.
THE FIRST MECHANICAL DEMONSTRATION OF THE EARTH'S ROTATION
FIRST EDITION. Copernicus had explained the daily diurnal rotation of the earth on its polar axis in the first book of his De Revolutionibus (see lot 60), however it was Foucault who first demonstrated it. The first public experiment "was a splendid affair which took place in the Pantheon in 1851 before a fashionable audience. A heavy ball was suspended from the dome on a wire 220 feet long; beneath the ball was a table 12 feet in diameter covered with sand on which the ball would leave a mark. This is known as 'Foucault's pendulum'. It soon became apparent that the plane in which the pendulum was swinging moved in a clockwise direction and in about thirty-two hours the plane of vibration had completed a full circuit... The audience in the Pantheon was greatly impressed; some ladies fainted with excitement, while other spectators maintained that they could feel the earth move beneath them." Published as an offprint under the title Sur Divers Signes Sensibles du Mouvement Diurne de la Terre. (PMM 330). RARE: American Book Prices Current records only two copies sold at auction in the last thirty years.