FOUCAULT, Jean Bernard Lon (1819-1868). Thse prsente la facult de Paris ... Sur les vitesses rlatives de la lumire dans l'air et dans l'eau. Paris: Bachelier, 1853.

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FOUCAULT, Jean Bernard Lon (1819-1868). Thse prsente la facult de Paris ... Sur les vitesses rlatives de la lumire dans l'air et dans l'eau. Paris: Bachelier, 1853.

4o (279 x 214 mm). Folding engraved plate (slight marginal spotting to plate, some very faint browning to margins of text). Original printed wrappers (spine renewed, slight soiling and a few small chips to edges); black cloth folding case.

FIRST EDITION. Foucault's doctoral thesis on the speed of light, in which he provided a convincing proof for the wave theory of light. Foucault had initially been working with Armand Hippolyte Fizeau (1819-1896) in his experiments to determine the velocity of light, but the two argued and continued their work separately, as rivals. Fizeau was the first to announce, in 1849, an exact measurement of the velocity, but Foucault was the first to discover, in 1850, that light travels faster in air than in water, further evidence in favour of the wave theory of light which by the mid-nineteenth century was extremely popular. Foucault's doctoral thesis was a detailed account of his experiments. He did not arrive at a numerical value for the speed of light until 1862. His figure of 298,000 kilometers per second was both smaller and much more accurate than Fizeau's. RARE. En franais dans le texte 270; Norman 820.

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