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The deadbeat escapement invented in 1675 by Richard Towneley and popularized by George Graham around 1715 in his precision "regulator" clocks gradually replaced the anchor escapement and is now used in most modern pendulum clocks.Observation that pendulum clocks slowed down in summer brought the realization that thermal expansion and contraction of the pendulum rod with changes in temperature was a source of error.Some of the most accurate pendulum clocks: (left) Riefler regulator clock, that served as the US time standard from 1909 to 1929, (right) Shortt-Synchronome clock, the most accurate pendulum clock ever manufactured, which served as the time standard during the 1930s.These early clocks, due to their verge escapements, had wide pendulum swings of 80–100°.During the Industrial Revolution, daily life was organized around the home pendulum clock.More accurate pendulum clocks, called regulators, were installed in places of business and railroad stations and used to schedule work and set other clocks.The French Time Service used pendulum clocks as part of their ensemble of standard clocks until 1954.
Clockmakers' realization that only pendulums with small swings of a few degrees are isochronous motivated the invention of the anchor escapement around 1670, which reduced the pendulum's swing to 4–6°.A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element.The advantage of a pendulum for timekeeping is that it is a harmonic oscillator; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates.This was solved by the invention of temperature-compensated pendulums; the mercury pendulum by George Graham in 1721 and the gridiron pendulum by John Harrison in 1726.
With these improvements, by the mid-18th century precision pendulum clocks achieved accuracies of a few seconds per week.
The anchor became the standard escapement used in pendulum clocks.