Royal Greenwich Wall Clock
The Shepherd Gate Clock is the wall clock mounted on the wall outside the gate of the Royal Greenwich Observatory building in Greenwich, 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.
In 1849, Charles Shepherd, of 53 Leadenhall Street, London, had patented a system for controlling a network of master and slave clocks using electricity (or galvanism, as it was called). Shepherd, an engineer and son of a clockmaker, had installed the public clocks for the Great Exhibition which opened in May 1851. In October, 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 its descent at 13:00 was synchronized with the master clock inside the observatory.
By August 1852, Shepherd had built and installed the network of clocks and cables in the observatory. Costs were considerably higher than the original estimates. Shepherd had estimated £40 for the master clock and time ball apparatus, and £9 for each sympathetic clock. The total costs included £70 for the master clock, and £75 for the wall clock by the gate.