Additional Information Incredibly accurate moonphase requires no adjustment until the year 3821.

The Atmos clock obtains the energy it needs to run from small temperature changes in the environment, and can run for years without human intervention.

Its power source is a hermetically sealed capsule containing a mixture of gas and liquid ethyl chloride, which expands into an expansion chamber as the temperature rises, compressing a spiral spring; with a fall in temperature the gas condenses and the spring slackens. This motion constantly winds the mainspring. A variation in temperature of only one degree in the range between 15 and 30 degrees Celsius is sufficient for two days' operation.

In order to run the clock on this small amount of energy, everything inside the Atmos has to work in as friction-free a manner as possible. For timekeeping it uses a torsion pendulum, which consumes less energy than an ordinary pendulum. The torsion pendulum executes only two torsional oscillations per minute, which is 1/60th the rate of the pendulum in a conventional clock.

The first clock powered by changes in atmospheric pressure and temperature was invented by Cornelis Drebbel in the early seventeenth century. Drebbel built as many as 18 of these, the two most notable being for King James I of Britain, and Rudolf II of Bohemia. The King James clock was known as the Eltham Perpetuum, and was famous throughout Europe. It is mentioned in two works of Ben Jonson.

Experimental clocks powered by atmospheric pressure and temperature changes were next made during the Enlightenment. An early example is Cox's timepiece, a clock developed in the 1760s by James Cox and John Joseph Merlin. The oldest predecessor still extant is the 1864 Beverly Clock.

The first Atmos clock was designed by Jean-Léon Reutter, an engineer in Neuchâtel, Switzerland, in 1928. This noncommercial prototype, which predated the Atmos name but is now known unofficially as Atmos 0, was driven by a mercury-in-glass expansion device. The mechanism operated on temperature changes alone.

On June 1, 1929, Compagnie Générale de Radio (CGR) in France began manufacturing the first commercial model, Atmos 1, which used a mercury and ammonia bellows power source. On July 27, 1935 Jaeger-LeCoultre took over production of Atmos 1 while it developed a second design which used the present ethyl chloride power source. This model, later named the Atmos 2, was announced January 15, 1936, but problems delayed full production until mid 1939.

Today the Atmos clock is a refined hermetically sealed luxury timepiece, that, like time itself, marches along without interruption and without human interaction.