The present "Atmos" clock is a very early example with its movement driven by a mercury in glass expansion device rotating a cylinder which winds the mainspring by ratchet. In the late 1920s the young engineer Jean-Leon Reutter experimented with a clock which would not need direct mechanical or electrical intervention to keep it wound, a clock powered only by Perpetual Motion. His idea of a Perpetual Motion timepiece led him to make a clock with a mechanism designed to consume the smallest possible amount of power to keep it running. His design included a device powering the movement independently, using mercury - a substance which would react to the most sensitive changes in temperature and atmospheric conditions. Reutter developed a specially designed glass tube similar to that of a thermometer for the mercury and encased it all inside a metal cylinder, known as the Bellows. The result was an ingenious new clock unlike any other, past or present, a timepiece that would run independently and continuously, so incredibly sensitive that it could be rewound by the slightest fluctuations in the atmosphere or by the slightest changes in temperature, hence the name: "Atmos Clock". The first models, such as the present clock, were called Reutter Atmos I. Later, due to dangers in handling and instability, the mercury in the Bellows powering the Atmos Clock was changed to a more stable saturated gas, ethyl chloride. Reutter's system was patented in 1928 and improved by Jaeger-LeCoultre.