Sur une experience relative a la vitesse de propagation de la lumiere [Fizeau]. WITH: Determination experimentale de la vitesse de la lumiere; parallaxe du Soleil [AND] description des appareils [Foucault]. ARMAND-HIPPOLYTE-LOUIS FIZEAU, JEAN-BERNARD-LEON FOUCAULT.

Sur une experience relative a la vitesse de propagation de la lumiere [Fizeau]. WITH: Determination experimentale de la vitesse de la lumiere; parallaxe du Soleil [AND] description des appareils [Foucault]

FIRST EDITION of the report of Fizeau’s famous experiment to determine the speed of light, the first accurate results obtained from a terrestrial experiment. WITH: FIRST EDITION of his rival FOUCAULT’S refinement (two papers), resulting in a measurement of the speed of light within 0.6% of the present-day value. FINE COPIES IN ORIGINAL VOLUME WRAPPERS.

“By 1849 Fizeau had developed his own method for measuring the speed of light in air. On the peak of a hill he set up a light source and a spinning gear, arranged so that the light would shine through the gear’s teeth. As it spun, the gear would alternately block and unblock the light, so that it would flash. On another hilltop 5 miles (8 km) away he positioned a mirror that reflected the light back to its source. Fizeau spun the gear very fast, so that light passing through one gap in the gear’s teeth would travel to the mirror, bounce back, and reenter through the next gap. By using a timer, he was able to determine the amount of time it took light to travel 10 miles (16 km)--the distance between the two hilltops...

“Fizeau arrived at the figure of 195,615 miles (315,000 km) per second--a number slightly higher, by about 5%, than that obtained by astronomical means (192,600 mps) but certainly far more accurate than any previous terrestrial method had yielded. The modern figure for the speed of light is approximately 186,000 miles (299,700 km) per second...

“In 1862, Foucault outdid his former friend Fizeau when he used Charles Wheatstone’s revolving mirror to obtain an improved value for the speed of light in air. Foucault’s experiements were conducted from the ‘La Salle de Meridienne’ in the Paris Observatory. His value of 298,000 km/s (about 185,000 miles/sec) is only 0.6% different from the currently accepted value and more importantly for Foucault a considerable improvemnet on the efforts of his arch rival Hippolyte Fizeau” (Stefan Hughes, Catchers of the Light).

"Foucault’s first experiment, carried out in 1850 and written up in full in his doctoral thesis of 1853, was purely comparative; he announced no numerical values until 1862. Then, with an improved apparatus, he was able to measure precisely the velocity of light in air. This result, significantly smaller than Fizeau’s of 1849, changed the accepted value of solar parallax and vindicated the higher value which Le Verrier had calculated from astronomical data. Foucault’s turning-mirror apparatus was the basis for the later determinations of the velocity of light by A. A. Michelson and Simon Newcomb"
(Dictionary of Scientific Biography).

IN: Comptes rendus hebdomadaires des seances de l’Académie des sciences, Vol 29, pp. 90-92. Paris: Bachelier, 1849 (the entire volume, July - December). WITH: (ibid.) Vol 55, pp. 501-503; pp. 792-796. Paris: Mallet-Bachelier, 1862 (the entire volume, July - December). Quarto, original wrappers; custom cases. Occasional foxing, a small circle of dampstaining on first few volume leaves on 1862 volume. Beautiful, uncut and unopened copies in original wrappers.

Price: $3,900 .