The Longitude at the Eve of the Third...

Geneva, Hotel Des Bergues, Oct 23, 1999

LOT 64

L. Leroy & Cie., 7 Bd. de La Madeleine, Paris,No. 1403, Pendule à pression constante commissioned on January 27th 1930, delivered on December 2, the same year.Very fine and rare, centre seconds, Constant Pressure observatory precision regulator.

CHF 50,000 - 60,000

Sold: CHF 63,250

C. White painted bronze cylinder with cast-iron white painted wall bracket, glass dome over the brass bracket supporting the movement. D. Silvered with Arabic seconds ring and observation apertures over the remontoire and the escape wheel. Blued steel counterpoised hand. M. Brass trapezoidal full plate, marble finished, with cylindrical pillars, running in partial vacuum. Reid type escapement specially adapted by Leroy, the power supplied by the fall of a weighted arm, raised every 32 seconds byan electro-magnet. The invar pendulum beats 61 times in 60 seconds. A double contact is activated directly by the pendulum, and both circuits are closed momentarily with each oscillation, except on the 61st swing when they are by-passed by the action of a third breaker in order to mark the minute. By adjusting the internal pressure of the case, the rate can be adjusted, starting at 0 atmospheres. An increase of pressure of 1 mm of mercury, slows the rate by 0,018 of a second. The rateis adjusted so that the signals coincide with the hour precisely, once the small daily variations have been eliminated.Dim. 146 x 38 cm.


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Grading System
Grade:
Case: 3

Good
Movement: * 3
Dial: 3 - 01

Notes

Provenance: Commissioned by an important American collector, Mr. D., on January 27, 1930, with the deposit of10'000 Francs, requesting this Pendule à Pression Constante, with a glass dome according to his own sketch. The account was settled on August 8, 1930 for a total price 25'000 Francs. This regulator was delivered almost one year later, on December 2, the same year, at the Morgan Bank, 14 place Vendôme, Paris. It has always been serviced by his owner and remained in his family after his death.The Paris Observatory was equipped with three clocks of this design, fitted in the Catacombes beneath at a depth of26 meters, to eliminate fluctuations in temperature and atmospheric pressure. Electrical impulse signals were transmitted to the Service de l'Heure, to provide precise time and to service the radio broadcast time signals sent from the Eiffel Tower. Comparing the signals with those of 21 other Observatories, situated around the globe, enabled the fixing of exact time. The Observatory clocks are still operational, but for a number of years, Atomic clocks have been used to control global time signas.One of the Constant Pressure cloks of the Bureau International de l'Heure is illustrated in Pierre Le Roy et la Chronométrie byP. Ditisheim, R. Lallier, L. Reverchon and Commandant Vivielle, pl. XXXI, and described pp. 125 and 126.