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H9890 Regulator clock, Breguet mean-time regulator clock, metal / wood / paper, made by Breguet and Sons, Paris, France, 1818, used at the Parramatta and Sydney Observatory's, Parramatta and Sydney, New South Wales, Australia. Click to enlarge.

Breguet mean-time regulator clock

Made by Breguet & Son in France, 1815-1820.

In 1818 Lieutenant-General Thomas Brisbane a keen amateur astronomer purchased this regulator clock from the Paris clockmaker Breguet. It appears that Breguet had originally made the clock for the French Commission of Longitude but sold it to Brisbane for use in his observatory at Largs in Scotland. This clock cost Brisbane the not inconsiderable sum of 2,500 francs and the fact Brisbane chose to buy French rather British, even in the nationalistic climate of the early nineteenth century gives u...


Object No.


Object Statement

Regulator clock, Breguet mean-time regulator clock, metal / wood / paper, made by Breguet and Sons, Paris, France, 1818, used at the Parramatta and Sydney Observatory's, Parramatta and Sydney, New South Wales, Australia

Physical Description

A longcase astronomical regulator clock. The clock has a double weight driven gear train with a double adjustable escapement, which is directly connected to the pendulum. Also includes perspex case made for exhibition. The clocks mechanism fits into a wooden long case consisting of a rectangular wooden box with a hinged door at the front. At the top of the door is a square window in a hinged wooden frame. There is a keyhole in the wooden frame. At the bottom of the door is an oval glass window. The clock case sits on a removable square wooden base that is open at the back and bottom. Additional components associated with the clock include a winder key, clock weights and pulleys and a certificate

Observatory stock number 28.



2080 mm


530 mm


530 mm



Clocks are essential tools for astronomical measurement and their precision defines the accuracy with which the time of a transit can be recorded. In their construction the astronomical clock differs from others mainly in the care with which the parts are produced. For this reason many people regard these clocks as occupying a pre-eminent position in the art of clock making.

There are two main kinds of astronomical clock a common feature of which is their separate hour, minute and second hands. One measures the true mean solar time and the second measures sidereal time which has no direct connection with solar time and instead keeps pace with the apparent movement of the stars and indicates the position of the stars in the sky.

The tilt of the earth on its axis means the earth's orbit is not exactly circular and as a result solar days vary in length throughout the year. To avoid this complication astronomers calculate the time of days by the passage of stars. To do this they measure the time between two successive transits of a star across the meridian. This is known as sidereal time.

Astronomical clocks were made to beat exact seconds of time which depended on the length of the pendulum. The exact length of a pendulum which calculates true seconds was formulated by Huygens at an amount approximating to 39 inches. However this length is slightly different at different parts of the globe and the pendulums themselves can expand or contract depending on the temperature. To overcome this compensated pendulums such as the one invented by the clockmaker Graham contained mercury which expanded and contracted to keep the clock beating exact time.

In 1675 the first Astronomer Royal at the Greenwich Observatory, John Flamsteed, commissioned Thomas Tompion to build two clocks. These were wound once a year and had 13 foot pendulums and are thought to be the first year movements ever made. The pursuit of greater accuracy led to many improvements in astronomical clocks and in some cases, such as Clement's anchor escapement, their innovations were incorporated into other timekeeping devices.

In the early nineteenth century there was a great increase demand for astronomical clocks among private and government institutions in Britain. The maker of this clock Abraham Louis Bréguet was born in 1747 and died in 1823. He founded his watch and clock making company in Paris in 1775 and sold many of his works to European Royalty and the leading scientists of the age. He is acknowledged as one of the primary inventors of many of the technical innovations which lead to the development of modern clock and watches and for over two centuries the business has continued to maintain the reputation he established.

William Hardy, along with Robert Pennington and John Roger Arnold, was one of best known and respected makers of astronomical clocks in this period. His major innovations included the detached clock escapement and a clock balance.

Howse, D., Greenwich Time; the discovery of the longitude, Oxford University Press, 1980
Lloyd, H.A., 'Timekeeping Mechanisms and Clocks for Scientific Purposes', in the catalogue of the British Clockmakers Heritage Exhibition, Science Museum, London, 1952
Peck, W., A Popular Handbook and Atlas of Astronomy, Gall and Inglis, London, 1890
Wood, C., 'Robert Molyneux's Astronomical Clocks and Chronometers', in Antiquarian Horology, Number 4, Volume 9, September 1975
Wood, C., 'What's Wrong with Hardy's Escapement?', in Antiquarian Horology, Number 8, Volume 9, September 1976


Breguet & Son France 1815-1820



This Breguet longcase regulator clock arrived in Australia with Governor Brisbane in late 1821 and was used at Australia's first permanent observatory at Parramatta, New South Wales. Brisbane, a keen amateur astronomer, bought this clock in 1818 for 2,500 francs and it, along with the three others he brought to Australia, must be amongst the earliest regulators to arrive in on these shores.

The instrument was put into storage after the Parramatta observatory was closed down in 1847 and remained so until the new Sydney Observatory was built above the Rocks. The opening of the new observatory in 1858 saw many of the original Brisbane instruments taken out of storage for use. This clock was one of the few instruments which the new Government Astronomer Rev. W. Scott felt was good enough to use in the new observatory.

Sometime around 1928 the base of the Hardy clock [H9889] was removed and placed on the base of the Breguet clock [H9890].

In 1987 the local Sydney Company 'Clocks of Distinction' did restoration work on the Clock. Under the supervision of Mr. Carl Parker original clock components, including brass pulleys, steel plates, brass weight and escape wheel, were removed [these are now stored in the museum as separate parts along with the case]. 'Clocks of Distinction' also felt the case of the clock was not original and as a result the mechanism was rehoused in a Perspex case. The original case was replaced at an earlier date as it was probably destroyed by white ants sometime after its arrival at the Parramatta Observatory. A certificate of authenticity was also purchased from the original maker in France by 'Clocks of Distinction' at this time giving the precise date of purchase from the company.

Powerhouse Museum, H9890 Blue File Object Record
Scott, W., Astronomical Observations made at the The Sydney Observatory in the Year 1860, Thomas Richard, Government Printer, Sydney, 1861
Antiquorum Catalogue, The Longitude at the Eve of the Third Millennium, Antiquorum, Geneva, 1999

Cite this Object


Breguet mean-time regulator clock 2018, Museum of Applied Arts & Sciences, accessed 21 March 2019, <>


{{cite web |url= |title=Breguet mean-time regulator clock |author=Museum of Applied Arts & Sciences |access-date=21 March 2019 |publisher=Museum of Applied Arts & Sciences, Australia}}
This object is currently on display at the Sydney Observatory.


This object record is currently incomplete. Other information may exist in a non-digital form. The Museum continues to update and add new research to collection records.

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