2748 x 3617 px | 23,3 x 30,6 cm | 9,2 x 12,1 inches | 300dpi
Aufnahmedatum:
18. Januar 2012
Weitere Informationen:
The Shepherd Gate Clock is the clock mounted on the wall outside the gate of the Royal Greenwich Observatory building in Greenwich, Greater London. The clock, an early example of an electric clock, was a slave mechanism controlled by electric pulses transmitted by a master clock inside the main building. The network of master and slave clocks was constructed and installed by Charles Shepherd in 1852. The clock by the gate was probably the first to display Greenwich Mean Time to the public, and is unusual in using the 24-hour analogue dial. The original idea for the clock network came from the Astronomer Royal, George Airy. With the arrival of the railway network, a single time standard was needed to replace the various incompatible local times then in use across the country. Airy proposed that this standard time would be provided by the Royal Observatory. His idea was to use what he called "galvanism" or electric signalling to transmit time pulses from Greenwich to slave clocks throughout the country, and perhaps to Europe and the colonies too. The new undersea cable recently installed between Dover to Calais in 1851 raised the possibility of sending time signals between England and France - this would allow longitude differences to be measured very accurately, for the first time In 1849, Charles Shepherd Junior (1830–1905), an engineer and son of a clockmaker, patented a system for controlling a network of master and slave clocks using electricity (or galvanism, as it was called). Shepherd installed the public clocks for the Great Exhibition which opened in May 1851. In October 1851, Airy wrote to Charles Shepherd asking for proposals and estimates, including a request for the following clocks: One automatic clock. One clock with large dial to be seen by the Public, near the Observatory entrance, and three smaller clocks, all to be moved sympathetically with the automatic clock. Airy also wanted the existing Greenwich time ball to be electrically operated, so that
