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Leon Foucault (1819-1868). Two significant papers on the improved design of telescopes. (1) "Essai d'un nouveau télescope parabolique en verre argenté" (Essay on a New Parabolic Telescope with Silvered Glass) Comptes Rendus de l'Academie es Sciences, Paris, 11 July 1859, vol 49 no. 2, the full weekly issue of pp 57-100 with the Foucault on pp 85-87. Very nice condition, bright and clean and crisp. This issue is extracted from a larger bound volume though the spine has been beautifully rebacked. Fine copy. [++] Foucault's "Essai d'un nouveau télescope parabolique en verre argenté" (Essay on a New Parabolic Telescope with Silvered Glass) presented his new and innovative design for a new parabolic mirrored telescope that utilized silvered glass for its mirrors. This was a major advance in the construction of telescope mirrors, allowing the user to focus light more effectively and aiding the overall performance and efficiency of the instruments. (Henry Draper son of John William Draper--would improve on these designs in his influential paper published in 1864 in the USA, "On the Construction of a Silver-Glassed Telescope." A longer paper on this topic "Mémoire sur la construction des télescopes en verre argenté," by Foucault appears in "Annales de l'Observatoire impériale de Paris," vol. 5, pages 197-237 (1859). [++] Plus: (2) "Télescopes en verre argenté, miroirs à surface ellipsoïde et parabolique de révolution, application au ciel" (Telescopes with Silvered Glass, Mirrors with Ellipsoidal and Parabolic Surfaces, Application to the Sky) in the Comptes Rendus de l'Academie des Sciences, Paris, 2 August 1858, vol 47 no. 8, the full weekly issue of pp 169-244 with the Foucault on pp 205-207. This issue is somewhat browned and has a bit of foxing. This issue is extracted from a larger bound volume though the spine has been beautifully rebacked. GOOD copy, overall. [++] "Foucault is best-known for two of the most significant experiments of the mid-nineteenth century-the laboratory determination of the velocity of light (1850, 1862) and the mechanical demonstration of the earth s rotation (1851, 1852)-and for his advancement of the technology of the telescope.None of these inventions, however, was as significant for science as Foucault s introduction of the modern technique for silvering glass to make mirrors for reflecting telescopes (1857) and his simple but accurate methods for testing and correcting the figure of both mirrors and lenses (1858). Glass proved much superior to the speculum metal previously used in reflecting telescopes because it is much lighter in weight, easier to grind and figure, and easier to resurface if it becomes tarnished or damaged."--Complete DSB online (Foucault) He is also of course his popular fame rests on his famous pendulum experiment, which beautifully demonstrated the rotation of the Earth.
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