It's close to perpetual motion, but no cigar! It violates the Second Law of Thermodynamics, as well as the law of conservation of energy, since it fails to produce energy from nothing.
Not only that, but these clocks do require servicing, usually every 10 to 20 years.
Perpetual motion would mean the negation of friction and any other element that might stop the clock, meaning that there would never be the need for service of any kind.
There is an energy source, ethyl chloride gas, stored in the shape of a very powerful hollow spring, set in a large drum at the back of the clock.
Just one degree of temperature change has the effect of keeping the clock running for two days.
A plate covering this spring acts on another, much weaker spring, which in turn is connected to a chain attached to the mainspring.
In this way the clock is kept wound.
So whether the temperature rises or falls, the difference will always wind the clock.
Cornelius Drebbel made such a timepiece for James the First of England, and also one for Rudolf the Second of Bohemia.
These clocks relied on atmospheric pressure and temperature changes to keep them wound.
The Enlightenment saw an experimental clock made in 1760 by James Cox and Joseph Martin.
This clock relied simply on atmospheric pressure.
It wasn't until 1928 that the first Atmos appeared as we know it today.
Invented by a gentleman named Jean-Louis Reutter, it carries the unofficial name of Atmos 0.
This was followed by the Compagnie Generale de Radio, a French company, bringing out Atmos 1, using mercury and ammonia bellows to power it.
July 1935, Jaeger Le Coultre stepped in and developed the second design, Atmos 2.
A word about how Jaeger Le Coultre came into being.
The firm was originally started in 1833 by Antoine Le Coultre.
It took until 1903, however, that the company as we know it today was born.
Edmund Jaeger, of Paris, threw down the gauntlet and challenged the French watchmakers to produce pocket watches that were wafer thin.
Jacques-David Le Coultre, the grandson of Antoine, took him up and did indeed make a superb pocket watch of tiny cross section.
So the partnership came into being.
Now, they are situated in the Valee de Joux, in the Swiss Jura Mountains.
Reutter spent a long time examining the movement of the 400 day clock, and utilized the torsion pendulum and suspension spring for his Atmos.
This spring holds the heavy brass pendulum, considerably heavier than a 400 day, but the operation is very much the same.
The bellows filled with ethyl chloride occasionally need to be replaced.
When they come from the material house, they're bound tight with a thin steel strap.
To simply cut this strap and then expect to drop the bellows in place is an exercise fraught with despair.
The best way of fitting them is to place them in the freezing compartment of your refrigerator so that the bellows contract.
The strap will simply fall off, and you are then able to place the bellows in the drum and replace the back, which is a bayonet fitting.
The movement itself is small, delicate and fully jewelled.
I do not recommend placing the little plates in an ultra-sonic cleaner.
It's possible to shatter the jewels in this way.
Wash the plates by hand in a good cleaning solution and 'peg them out'- run pith wood through the holes until they're clean.
The pallet jewels should be examined and scraped clean, again with wooden slips.
Never apply oil.
The power is so delicate that oil will have a retarding effect There's no question that the Atmos is a remarkable clock - but not quite perpetual motion