L\'ART DE L\'HORLOGERIE EN FRANCE DE ...

Geneva, Hotel Des Bergues, Nov 14, 1993

LOT 75

Julien Le Roy à Paris, Invenit et Fecit, No. 4732, made by his son Pierre, circa 1774. Extremely rare and important movement of a centre-seconds watch, so called "Petite Ronde", divised by Pierre Le Roy à l'usage des astronomes et des marins.

CHF 4,000 - 6,000

Sold: CHF 10,350

D. Later white enamel with Roman numerals and outer Arabic minute ring. Gold Louis XV hands. M. Gilt brass full plate with cylindrical pillars, fusee with chain, frictional rest escapement of Sully type, improved by Pierre Le Roy, with the typical "spider" escape wheel, three-arm balance with gold studs, flat balance spring regulation with unusual index, small cock with one foot only and ruby end-stone. The traces of a compensation device reveal the system devised by Pierre Le Roy for this timekeeper which evidently belongs to the very rare group of the so called La Petite Ronde, intended for use at sea. The bimetallic compensation consists of two blades acting through ail arm upon the regulating index. In good condition.


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Notes

This type of watches was presented to the Académie Royale des Sciences on 6 September 1771 in a Mémoire sur une Nouvelle Montre à l'usage des Astronomes et des Marins, with a plate. One of them was tried by MM. Verdun de la Crenne, De Borda and Pingré in 1771 and 1772 and published in the Histoire de l'Académie Royale des Sciences. "Operations carried out on board the King's frigate La Flore and in various ports and harbours of Europe, Africa and America, for testing instruments and methods for determining the longitude". In their report, MM. Le Monnier and De Montigny wrote on 10 May 1773: Qu'elle (the Academie) ne pouvait que savoir gré à M. Le Roy de lui avoir fourni les moyens de s'assurer du dérangement des montres causé par l'humidité, dérangement qu'on ne connaissait point jusqu'ici, de reconnaître en même temps qu'il est difficile de diminuer beaucoup le volume des montres marines sans qu'elles perdent de leur précision et que l'on ne pouvait trop inviter M. Le Roth à continuer ses tentatives pour approcher de plus en plus la perfection dans la mesure du temps. For the only known example in original state, see G. Brusa : L'Arte dell' Orologeria .... 1979 and 1982, fig. 589-591. Described and illustrated by Ch. Allix and G. Brusa : Antiquarian Horology, March 1971, an offprint copy is coming with the watch.