The Eternal Clock

by Thomas Byczkowski

This year Jaeger-LeCoultre not only celebrates its 175th birthday, but also the anniversary of one of its most mysterious products as well: the Atmos. This clock collection, now 80 years old, is a symbol for the ingenuity with which this manufacture tackles the challenges of time measurement. The slow and steady movement of the unusual horizontal pendulum, which seems to move without any effort, lifts the spectator into a state of tranquility, if not hypnosis.

With two specialist lines, the Atmos Metiers Rares and the Atmos Astronomique, the company this year pays tribute to one of the most pure and perfectly considered timepieces.

The Atmos impressed the Swiss watchmaking industry so much that in the 1950s the Swiss Confederation presented its guests with the clock as the official gift of the state: in this manner the Atmos found its home with statesmen, royals and renowned people from John F. Kennedy to Winston Churchill, Charles De Gaulle and King Hussein of Jordan, among many others. In the Vatican alone there are said to be sixty of the pieces ticking the time away.

And tick they surely do, though they never need to be wound up.

This fact is the magic of the Atmos. It’s truly in the air. The Atmos gets its energy from changes in the temperature and air pressure of its surroundings, and its spring winds up without human interference. Together with a maximum power reserve of one year, it virtually can run forever.

The secret behind this almost perpetual movement lies in the very slow motion of the movement—the pendulum needs a whole minute for one full turn, hence it consumes only an extremely small amount of energy.

From poisoning to detonation

The power is generated through temperature-induced contractions of an expandable metal container, which is filled with gas. The winding barrel is consequently wound up, triggered by the changing shape of the container, thereby delivering the small amounts needed for the clock to run.

Jean-Louis Reutter, an engineer from Neuchatel, developed the concept. He built the first prototypes in 1928, but with a movement that consumed too much energy. In addition, the perfect substance for the expansion process was not yet found. Reutter could not find his way to the eternal motion he was expecting from his timekeeper.

As Antoine LeCoultre stumbled upon the project, he immediately sensed the uniqueness of the concept, but soon found the weakness of Reutter’s construction. In his company LeCoultre gave the Atmos a complete overhaul, perfecting the movement and considering new approaches to the “breathing-capabilities” of the metal container, which is the source of the winding mechanism.

Legend has it that in the beginning of the 1930s some minor detonations occurred in the Jaeger-LeCoultre workshops in Le Sentier—rattling windows and leaving watchmakers startled at their desks—when they tried to fill up the gas container with a substance called ethyl chloride. That was the point at which the watchmakers came to the realization that trying to replace the highly toxic mercury Reutter had used with ethyl chloride meant jumping out of the frying pan into the fire: the gas is extremely flammable.

If one scrutinizes the very old Atmos movements in the company’s heritage gallery, an engraving can be discerned on the back of the containers. It reads, “don’t open, danger!” in English, German and French. The clocks built before 1932 were equipped with mercury, the only fluid metal to perform visible volume changes at temperatures close to room temperature (as one can observe in many thermometers.)

In the 1930s, the company succeeded with the new substance. It made well-sealed containers that it filled with exactly 1.3 grams of ethyl chloride. They no longer posed any threat of explosion.

The Atmos atelier

The danger of explosion of course was not the reason for the Atmos atelier to be moved to another building some five minutes up the road from Jaeger-LeCoultre’s headquarters. Atmos production takes up a lot of space, not available in the halls of the manufacture today. With a new building already in progress, the company will bring the Atmos home by the end of the decade.

Until then the atelier can be found in the fourth floor of a long building in which Patek Philippe also has an atelier. Taking a freight elevator to the fourth floor one walks into the world of Atmos: shiny bodies of clocks in every production stage throw back sunrays as they are laid out on the workbenches in a light-flooded atelier.

At the end of the large room is another hall, where four rows of glass-fronted cabinets tower, each filled to the top with eighty years of Atmos history. Altogether 800 Atmos of all eras, from art nouveau to the present day, are annually tested for accuracy after they have gone through maintenance.

In the left corner of the room, located under a specially prepared extractor hood, the ethyl chloride filling station for the gas cylinders can be found. Each container gets its exact amount (1.3 grams) of gas from a tank under the desk that is then, while still freezing cold, sealed by a soldering iron. The containers are then joined to another 150 pieces in a refrigerator, where they are tested for proper function. The containers themselves are produced by another Swiss manufacturer and delivered to the workshop.

While looking at this production set-up, Rene Lamotte, a tall shorthaired man in his fifties and the master watchmaker in the atelier, explains the reason for the almost perpetual movement of the clock. He notes that this 80-year-old concept is probably the closest product to a perpetual-motion machine in the watch world. It is a device that delivers mechanical work generated from a thermal energy source without a need for attention from outside.

Of course, while a true perpetual machine would defy physical law, there is at least one example inside the offices here that comes close. It’s an Atmos that resides in the manufacture itself. In 1996 former Jaeger-LeCoultre CEO Guenther Blumlein had an Atmos walled into a newly erected building. That clock is still working flawlessly, and can be seen through a peephole in the walls of the basement of the manufacture.