Pendulum from the English Reifler escapement astronomical clock designed by E. T. Cottingham, by Thomas Mercer & Co, St. Albans, England, 1923-1925

Record summary

Held and catalogued by Science Museum Group, London (object number 1940-15/6), this is a pendulum by Cottingham, E. T.; Thomas Mercer and Company, made in St Albans, Hertfordshire, England, United Kingdom, St Albans, dated 1923-1925. The Atlas places it in the Golden Age of Mechanical Watchmaking period (1900 – 1945) of its Movements & Components collection. The record is illustrated with 1 photograph.

Assembled from the source record's structured fields. Dates and attributions are given as the source states them; where a field is missing the Atlas leaves it blank rather than estimating.

Catalogue description

The source record does not include a narrative description. The structured fields above are reproduced from it.

Atlas type guide

Pendulums, balances and balance springs

The oscillator determines a timekeeper's rate. Galileo observed the near-isochronism of the pendulum; Huygens applied it to clocks in 1656 and the balance spring to watches in 1675. Temperature changes alter pendulum length and balance-spring elasticity, so eighteenth- and nineteenth-century makers devised compensation: Graham's mercury pendulum, Harrison's gridiron, bimetallic split balances for chronometers and watches, and Charles-Édouard Guillaume's invar and elinvar alloys (Nobel Prize in Physics, 1920).

Balance springs evolved from flat spirals to Breguet's overcoil (1795) and helical springs for chronometers; twentieth-century alloys (Nivarox) and twenty-first-century silicon springs largely solved temperature and magnetism problems.

General guidance written by the Atlas editors about this kind of object. It is not a statement about this particular piece; for that, rely on the source record above and on physical examination.

Read next:Balance spring (hairspring)Anchor (recoil) escapement