Description

A very rare and quite exceptionnal example of a miniature repeating circle signed “Lenoir à Paris” and numbered “35”.

In addition, the instrument bears the signature “Dépôt de l’école Imperial des Ponts et Chaussés n°1”.

This is a miniature form (circle of 12cm diamater and telescope of 12cm lenght) of the quite famous Etienne Lenoir repeating circle, here used only for geodesics uses.

According with the second signature, we can suppose this example was manufactured for teaching purposes at the Ponts et Chaussés School during the Napoleonic period.

The repeating circle was created around 1784 by Borda and Lenoir. It become the standard French instrument for the French surveyors.

“An instrument of this kind was typically employed by the French in geodesy. It is used to measures anglais by training the telescopic sights on either side of the divided circle on to the objects whose angular distance is required. By realigning the telescopes and repeating the observation a number of times, the cumulative angle can be divided by the number of observations, thus reducing the error involved with sighting.” (see Le citoyen Lenoir. Scientific instrument making in revolutionnary France, Whipple Museum, 1989, instruments number 65).

The instrument can be rotate in all sides, and the double joint of the foot in all sides vertically and horizontaly.

All the movements and screws work perfectly. The two telescopes give an sharp image and the optics is original.

A very rare instrument by Lenoir.