The first pendulums appeared first on wall clocks. On these timepieces we can also call this organ oscillator pendulum. The distance between its attachment point and its center of gravity is the most important distance on a timepiece. If you lengthen it, it slows down and if you shorten it, it accelerates. A bit like a ruler vibrating on the corner of a table.

Some pendulums, also called wall clocks, have a thermal compensation system. It is sometimes a simple container filled with mercury at the base of the pendulum. So when it is colder the pendulum will shorten but the mercury will drop. If it is warmer the pendulum will get longer but the mercury will rise. Thus the distance between the attachment point and the center of gravity will remain the same and everything will compensate itself.

For a long time, timepieces remained objects that had to remain motionless to measure time. They became portable thanks to the invention of the balance spring.

Thanks to this invention we can now move a timepiece in all directions without it stopping. Like the pendulum, the most important distance on a balance wheel is the distance between its center and the outer ring of the balance wheel, which is called the serge of the balance wheel, but also the length of its balance spring.

As on the pendulum there are balances with thermal compensation. These balances with thermal compensation are cut at two places at the level of the serge whose blade is bi-metallic. It is in most cases of steel and brass and in its most prestigious version of steel and invar. This second most prestigious balance is called Guillaume balance. In homage to Charles Edouard Guillaume, inventor of invar and winner of the Nobel Prize in Physics in 1920.

The Guillaume balance is recognizable because unlike other bimetallic balances it is not cut at the arms but at an angle of about 30 degrees from the arms of the balance. Some of the balances are equipped with weights or other elements that can be moved to modify its inertia. The more the gravity is in the center the faster the balance will go and the more it is outside the slower it will go.