Jaeger-LeCoultre Atmos

Atmos is the collection of table clocks from the Swiss manufacture Jaeger-LeCoultre that wind themselves from changes in room temperature. The mechanism was invented by the engineer Jean-Léon Reutter in 1928.

Inside the case is a sealed capsule filled with a gas mixture: as it warms the gas expands, as it cools it contracts, and this movement winds the mainspring. A change of just one degree Celsius is enough for 48 hours of running, so the clock needs neither a battery nor manual winding. The mechanism uses very little energy: its torsion balance makes only two oscillations per minute.

The classic model is the Atmos Classique: a rectangular case with glass panels through which the slow rotation of the balance can be seen, and a white dial with Roman numerals. The brass case is rhodium-plated or gilded, and there is also a moon phase version, the Atmos Classique Phases de Lune.