Signed: BREVETS J.L. REUTTER No. 3875
Circa 1930

The spring-driven movement of this beautiful Atmos clock has a going train only. It has a large chrome-plated brass balance with torsion wire suspension, visible below the movement. The movement is wound by a temperature-sensitive mechanism. Should the temperature remain stable, the clock will continue to run for 90 days. The clock is numbered on a strip behind the spring barrel: 3875 and signed BREVETS J.L. REUTTER S.G.D.G. MADE IN FRANCE.

The circular silvered dial has a Arabic chapter ring. Above the middle of the dial the clock is marked ATMOS PENDULE PERPÉTUELLE. The time is indicated by a fine pair of blued-steel Breguet hands.

This Atmos clock by J.L. Reutter is made of chrome-plated brass with facetted glass panels on all sides so that the movement is entirely visible. There are doors to the front and back. The balance can be secured by a slide under the front door for transport purposes.

Duration Infinite, in case of no temperature differences 90 days.

Height: 24 cm
Width: 18 cm
Depth: 15.5 cm

– J. Zeeman, Het Klokkenlexicon, Zwolle, 2003, p. 17
– Jean Lebet, Von der Luft leben: die Geschichte der Pendeluhr Atmos, Jaeger-LeCoultre, 1997.
The maker
Jean-Léon Reutter (Neuchâtel, Switzerland, 1899-1971) is the inventor of Atmos clocks. In 1913 this engineer, based in Paris, started his experiments which would eventually result in the production of the Atmos clock. He actually developed ideas of James Cox who thought of a self-winding system as early as 1765. In 1926 the first commercially produced clock was introduced on the market. He applied for the first patent in 1929. Reutter made used of a U-shaped glass vessel, which is positioned in such a way that small deflections were possible which wound the main spring continually. The horizontal arm of the U and part of the vertical tubes are filled with mercury. In the vacuum above the mercury is a fast evaporating liquid and saturated vapour.
One of the vertical parts is insulated, whereas the other is not. When the temperature rises more in one leg than the other (because of the insulation) a small amount of mercury is moved, causing the U to slightly change shape, which is used to wind the main spring. A temperature fall has the same effect. Later models use an aneroid metal box which works like a barometer and causes mechanical displacements winding the main spring.

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