The Longitude at the Eve of the Third...

Geneva, Hotel Des Bergues, Oct 23, 1999

LOT 10

Ferdinand Berthoud à Paris, circa 1770.Very fine and rare, month-going rose wood marquetry, weight-driven longcase regulator with equation of time.

CHF 220,000 - 250,000

C. Rectangular with glazed door, gilt bronze beaded decoration, applied five-pointed star on the base, with flambeau urn finial. D. White enamel by Coteau with Roman numerals, outer Arabic minute ring, gold paillonne five minute divisions, aperture below "XII" for the annual calendar. Pierced and engraved gilt brass hands with blued-steel centre-seconds and mean time minute hand. M. Rectangular brass with cylindrical pillars, weight-driven with Huygens endless rope winding, Graham dead-beat escaement, seconds beating pendulum with knife-edge suspension and Ferdinand Berthoud's special compensation with offset bob. The annual calendar ring with the equation cam, behind the dial.Signed on the dial and the back plate.Dim. 230 x 50 x 28 cm.


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Grading System
Grade: AAA

Excellent
Case: 3

Good
Movement: * 3
Dial: 3 - 01

Notes

Invented by Ferdinand Berthoud, the pendulum of this regulator is described in his Essai sur l'Horlogerie, 1763, vol. 2,pl. XXXIV, pp. 302 and 303. It is constructed from three bars only, two of steel, one in brass. In order to perfect the compensation, F. Berthoud devised an auxiliary adjustable compensation lever ("L" on the design), mounted between the bar of brass and one of the steel bars. The pendulum is also fitted with a thermometer. The bob is offset relative to the centre line of the pendulum, apparently to avoid any distortion of the bars. At rest, the gridiron is therefore at an angle from the vertica. This type of pendulum was soon abandoned in favour of the 9 rod gridiron pendulum. To date, only four regulators, including this lot, fitted with this form of pendulum are known, one of which is preserved in the Musée National des Techniques (C.N.A.M.), Paris.