The Shepherd Gate Clock is mounted on an external wall to the right of the double gates leading into the Observatory Courtyard. Since its original installation in 1852, it has been one of the most photographed objects at the Observatory. It is the public face of Greenwich Mean Time and today serves as a symbol of standardised timekeeping. It is unusual because of its 24 hour dial. Because of its importance, the Clock (together with the wall on which it is mounted), was given a Grade I listing on 8 June 1973.
A description of the principles behind the clock was published by Charles Thomlinson in Volume 2 of his Cyclopaedia of useful arts, mechanical and chemical, manufactures, mining, and engineering, (1854), pp.41–3.
According to the Journal of the Astronomer Royal (RGO6/25), the frame of the Gate Clock was inserted into the wall on 20 May 1852, with the Clock coming into use on Friday 13th August. The cost was £75.
When originally installed, the Gate Clock displayed astronomical time (which was reckoned from one midday to the next) rather than civil time (which was reckoned from midnight). Following the International Meridian Conference in 1884, the Clock was altered to show civil time with effect from 1 January 1885. Since its inception, the Clock has always shown Greenwich Mean Time, no adjustment ever having been made for it to show daylight saving time (also known as summer time).
On June 11, as the Clock was being installed, Alexander Bain (who had invented the first electrical clock in 1840 and taken out a number of patents soon after), called upon Airy to discuss certain patent issues, having taken exception to the fact that the Clock contained Shepherd’s name as patentee. This was followed up by a letter which Airy received and answered on 14 June. After much correspondence with Bain and his solicitor, Airy agreed to remove Shepherd’s name until Bain had legally established his claim. This however was never done: and in 1853 Shepherd’s name was restored.
An entry in Airy’s Journal (RGO6/27) for 25 July 1881 states: ‘The Dial of the entrance gate restored after repair.’ There is no reference to the repair in the Reports to the Board of Visitors, and it is not presently known what this work might have consisted of.
In about 1910, towards the end of Christie’s term in office as Astronomer Royal, the dial of the Shepherd Gate Clock was repainted. A number of changes were made to both the numbering and fonts, the result of which was a dial with a more clunky appearance. In detail, the changes were:
At some point between the early 1900s and the early 1930s, (possibly in 1927 when a new master clock was brought into use), the number of solenoids in the Clock was reduced from eight to four. The 1911 inventory (RGO39/4/62) states that on 27 April 1922, the coils were rewound, the armature remagnetised and ‘adjustable resistance supplied’. It also states that 15 resistance bobbins (25 ohms each), 8 mounted heat coils and 8 unmounted heat coils (25 amp) were supplied, the order for them having been made on 22 April 1922.
On 15 October 1940, the Courtyard gates were destroyed by a direct hit. The wall above the Gate Clock collapsed, and the dial (which was somewhat battered by the blast), bowed outwards. The mechanism itself however was largely undamaged. The site was secured with temporary gates, which were eventually replaced on new piers after the war had ended.
A replica of the dial was made without charge by Messrs. James Cooke and Son, of Stechford, Birmingham. Not realising that the dial had originally been flat, the one they supplied had a domed surface, matching that of the damaged dial which they had been sent to copy. A second dial was made and fitted in 1947. Said by the Astronomer Royal, Spencer Jones, to be an exact copy of the original, the two hyphens in the word galvano-magnetic-clock were in fact omitted. It is not known why this was.
By 1981, the paint was blistering badly due to poor original preparation of the copper base and in desperate need of repainting. The bezel, hands, dial and movement were removed on 17 February 1981. The dial was stripped on 8 Sept 1981 and repainted by David Penney. It was reinstalled 19 Feb 1982. Penney’s estimate for work was £150. Early 20th century images and postcards were used as a guide. With the exception of the tram lines around the minute marks, the dial was restored to the appearance it had when first installed in the 1850s.
On 20 August 1982, it was reported that the second hand had ‘broken again’. At this point, a new hand was made by Jonathan Betts.
The following clocks and electronic systems have been used to control the Gate Clock:
1852–1893 Shepherd Master Clock
1893–1925 Dent No. 2012
1925–1927 ?Dent No. 2012 / Dent No. 2016
1927–1935 ?Short No. 16 via Dent No. 2012 / Dent No. 2016
1935–1939 ?Short No. 49 via Dent No. 2012 / Dent No. 2016
1940–1947 Gate Clock out of service due to wartime damage
1960–1991 Synchronome Pendulum Clock
1991–present Controllers based on MSF signals
Special thanks to Douglas Bateman who kindly provided the photograph of The Syncronome Clock in 1990 and to Eugen Denkel for drawing attention to the drawing by Shepherd in Thomlinson’s Cyclopaedia of useful arts, mechanical and chemical, manufactures, mining, and engineering.