At the beginning of the 20th century timekeeping instruments of all kinds were still firmly based on the mechanical principles which had been exploited over the preceding three hundred years. The mechanisms developed and refined during those centuries had reached a high degree of precision. Yet well before the end of the new century mechanical watches and clocks belonged to history.
The development of electrical-mechanical clocks and, later,quartz driven timekeeping, set standards of accuracy which purely mechanical devices were pressed to match. Quartz technology in particular opened up precise timekeeping at extremely low prices and by the last quarter of the century accurate timekeeping was affordable for most people in a way never seen before. The original quartz clock was made by J.W Horton and Warren A. Marrison and took up the space of a small room. Today, however, quartz clocks are built into calculators, computers and watches and are by far the most popular form of timekeeping. Depending on the size, shape and vibration frequency of the quartz crystal, it can keep time accurately to about one second every ten years.
At the other end of the scale the development of atomic clocks, based on the rate at which nuclear particles (such as cesium) decay, enabled time to be partitioned with unprecedented precision on a hitherto unimaginably small scale. At this point the cutting edge of time measurement moves beyond horology into the realms of pure physics.
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Atmos Clock
Atmos Clock made by Jaeger-Le-Coultre in 1972.
In 1913 a French engineer named J E Reulter had the idea of using atmospheric pressure changes to wind up a clock, the principle having been put into practice by James Cox in 1765. This clock is an example of the technique.
Clocks today employ temperature rather than pressure changes, and need only a fall in temperature in order to wind themselves.
Electric Master Clock made by John Neale of Stowupland, Suffolk, c.1980
A floor standing electric master clock with skeleton movement.
Made by John Neale c.1980, Stowupland, Suffolk.
Master clock systems consist of one central clock, often externally regulated by radio signals, and a number of slave dials which are driven by the master clock, thereby keeping all dials showing the same time. In principle the idea was a development of the purely mechanical regulator, where one precision timepiece would be used to give the time to all the clocks in a house.
In clocks like this one however the master clock and the slave dials are connected together electrically, either in a series loop, or in a parallel configuration.
Radio Controlled Clock by Junghans
A radio controlled clock is monitored or impulsed by time transmission pulses which are broadcast by the British Telecom International Transmitter at Rugby, and are effective up to 900 miles.
Clocks or watches such as this one by Junghans are constantly checked for accurate time and automatically adjusted for daylight saving time in spring and autumn.
