Mercury compensation
The mercury compensation was a way to compensate the temperature error in mechanical watches of the 18th century.
The great thermal expansion and the strong reaction of mercury to temperature changes were used in watchmaking to increase the accuracy of the clocks , which were then quite imprecise .
As early as 1726, the Englishman George Graham developed a pendulum filled with mercury which, when heated, compensated for the expansion of the pendulum rod and thus contributed to the compensation. A container with mercury served as a pendulum weight; the expansion of the mercury when it is warm (and thus the rise in the mercury level in the container) shifts the center of gravity upwards. The mercury thus compensates for the thermal expansion of the pendulum rod (and thus the downward shift in the center of gravity). The dimensions of the pendulum parts, the materials used and the amount of mercury must be coordinated in such a way that the two effects cancel each other out as desired. Glass tubes, in which the shiny silver mercury also had a decorative effect, were often used as containers for the mercury.
Compensation pendulums were later built from metal rods ( rust pendulum ).
Even with clocks that did not work with a pendulum, a compensation could be achieved with mercury: Since the unrest at that time was made of simple metals, which expanded or contracted due to the influence of temperature, the problem arose of a not inconsiderable inaccuracy of the time measurement. Around 1770 the Frenchman Pierre Le Roy developed a compensation balance with a closed metal ring on which two small mercury thermometers were attached for increased compensation.
It was not until 1880, with the introduction of bimetal balance, that the temperature error of balance escapements became easier to control.
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- The watch lexicon, Heel Verlag 2005, ISBN 3-89880-430-5
- The right Time, Austin Books London 1882