From their invention by Christiaan Huygens in 1656 until the introduction of quartz clocks in the 1930s, pendulum clocks were the most accurate form of timekeeper available. During that time, precision regulators played a central role as accurate time-keeping instruments in astronomical observatories and in the related fields of navigation and surveying. During the 18th and 19th century, London makers were at the forefront of innovation, introducing new and better escapements as well as the compensated pendulum.
Most of the Observatory’s regulators still survive, with the majority still in full working order. Many are now in the care of the National Maritime Museum at Greenwich. A few were regrettably sold in the 1930s and are now in private hands.
Prior to 1835, many of the clocks listed in the inventories were not named and only a description was given. It was Airy who assigned names to the clocks. These include the three clocks made by George Graham, now known as ‘Graham 1’, ‘Graham 2’ and ‘Graham 3’ and the clocks ‘Arnold 1’ and ‘Arnold 2’. The clocks were not however given identifying marks.
Arnold (hour angle/degree clock)
Graham (Week Clock)
Grimaldi & Johnson
Mean Time (no name)
Molyneux (with flat steel pendulum)
Molyneux (with wooden pendulum)
Mudge & Dutton
Tompion (hour angle/degree clock)
Tompion Great Clocks (x2)
Tompion (sextant clock)
Tompion (arc house clock)
Earnshaw No. 1 (of the Armagh Observatory)
This clock by Earnshaw, which was destined for the new Observatory at Armagh, is said to have been delivered for trial at the Royal Observatory, Greenwich in February 1792 and to have remained there for two years until installed by Earnshaw at Armagh on 18 August 1794. For more information see A G Gunn’s article: Armagh’s Longcase Regulators, which was published in September 1993 (downloads as a pdf from the Armagh Observatory website). The Armagh website also has an excellent photograph of the clock together with an extensive description. Click here to view.
Arnold & Dent 708 (Dial Clock)