Julien LE ROY (1686-1759) and Claude LANGLOIS (1690-1756) - Lot 497

Lot 497
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Estimation :
800 - 1000 EUR
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Julien LE ROY (1686-1759) and Claude LANGLOIS (1690-1756) - Lot 497
Julien LE ROY (1686-1759) and Claude LANGLOIS (1690-1756) Universal horizontal sundial or meridian dial in brass Marked "INVENTÉ PAR JULIEN LE ROYDE LA SOCIETE DES ARTS" and "ÉXECUTÉ PAR LANGLOIS AUX GALLERIES DU LOUVRE". With latitude indications for 30 cities (Paris, Bayeux, Besançon, Marseille, Mainz, Brest, Orleans, Chartres, London and Genoa) and Arabic numerals around the circumference. The dial also features a three-part latitude scale with four adjustable feet, and was created for the 49-degree latitude. The massive gnomon has four "holes" for operating the device Our model features a compass and western declination, which differ from Le Roy's original invention of 1735 Important dial in the history of horology France, circa 1740-1760 L. 24 cm - W. 17.5 cm - H. 11 cm Note: The meridian dial is an atypical sundial created by Julien Le Roy (watchmaker to King Louis XV) and described in September 1735 in the "Mercure de France" and in 1737 in Henry Sully's Revue. In his memoir "Description et usage d'un nouveau cadran horizontal, universel, et propre à tracer des méridiennes" (Description and use of a new universal horizontal sundial, suitable for tracing meridians), Julien Leroy explains precisely how his new sundial worked, and how it was designed to calculate meridians (the North-South axis of a given location). The accuracy of a sundial depends on its correct positioning on the meridian of the place of orientation and on the latitude of the place. As a result, this type of sundial enables greater precision and the development of new models. The first examples of this sundial were created by Jacques Le Maire (1720-1740) around 1740, then other manufacturers perfected the system, culminating in Claude Langlois. In his memoir, Le Roy points out that contrast can be improved with a dark room, a feature developed by Langlois for the Château de La Roche Guyon (the dial is still in place) in 1750. Two examples of meridian dials are preserved at the Musée des Arts et Métiers in Paris (nos. 10485 and 925).
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