Astronomical Regulators: Riefler 50 and Cottingham


Page under Construction


The two related clocks, Riefler 50 and Cottingham were both obtained in the early 1920s. The Riefler, which was bought second-hand, was sold in May 1938 to Professor Schönland.(RGO39/6/208). It's current location is unknown. The Cottingham, a copy of a different model of a Riefler, is named after its maker. It took over from Dent 1906 as the Sidereal Standard in October 1922. On 1 January 1925, it was superceeded by Shortt 3. It is now in the care of the National Maritime Musuem (Object I.D. ZAA0542).

Image: The two basic designs of Riefler Clocks. Riefler 50 was similar to the one on the right. The Cottingham was similar to the one on the left. From a German advert c.1910

Image: Riefler 50 in the Rugby Room in March 1929. The case has been removed for the purpose of photography. The G.P.O (General Post Office) who were responsible for the Rugby Transmitter, and it was they who took the photo. © BT Heritage. Reproduced under the terms of a Creative Commons Attribution-Non-Commercial-ShareAlike (CC BY-NC-SA) licence (see below)

Image: Close up of the dial and barometric compensation device of Riefler 50. Note the serial number which can be seen top right. © BT Heritage. Reproduced under the terms of a Creative Commons Attribution-Non-Commercial-ShareAlike (CC BY-NC-SA) licence (see below)

Image: The clock Cottingham (right) in the Clock Room at Greenwich. Dent 2016, can be seen to its right. From the 23 February 1924 edition of The Illustrated London News

Image: A wider angle view of the Clock Room taken on 7 May 1928. The Cottingham has been dismounted and presumably remounted elsewhere in the Clock Room as there is no indication that it was being serviced at this time (RGO39/4/222). From left to right, the three clocks visible are: Dent 2016, Dent 2 and the slave clock of Shortt 11



Dent 1906, which incorporated innovations by Airy, became the sidereal standard of the Observatory in August 1871. By the start of the twentieth century, clocks made by the German company Clemens Riefler had set a new standard in precision timekeeping and were being adopted as primary standards in observatories around the world. Riefler Clocks came in a number of different designs of increasing accuracy (and expense). The most accurate were Types A, D & E. In the D and E, versions, the pendulum swung inside an evacutated chamber in the form of a cylinder.  Both the Cape of Good Hope and the Royal Observatory Edinburgh had both acquired one by 1912. For reasons that are difficult to comprehend, especially given its global reputation, it took until the early 1920s for Greenwich to begin to play catch-up.

William Christie who joined the Observatory as Chief Assistant in 1870, became Astronomer Royal in 1881, retiring 29 years later in 1910. During his first 15 years as Astronomer Royal, there  was a massive increase in the number of large telescopes deployed. Funded in part by the taxpayer and in part from generous donations, there were seven in total: the Lassell 2-foot Reflector, the 13-inch Astrographic Refractor, the Thompson 9-inch Photographic Refractor, the 28-inch Refractor, the Thompson 26-inch Photographic Refractor, the Thompson 30-inch Photographic Reflector (1896) and Christie's Altazimuth. By the turn of the century, Christie’s programme of expansion at Greenwich had come to an end, but without a single new clock being purchased. Nor was one acquired during the remainder of his tenure.

With the new telescopes and facilities, came a significant increase in both the range and amount of work being done. Chrisitie's failure to secure in advance any sort of commitment from the Admiralty to increase the staffing levels combined with high turnover amongst the temporary computers, put him under considerable personal pressure which inevitably took its toll. In June 1905, he was ordered by his Doctor to give up his work immediately, leave Greenwich and live in the open air, giving up his duties and responsibilities altogether (ADM190/16). The physician’s report sent to the Chairman of the Board of Visitors, Sir William Huggins, stated amongst other things that his capacity for work was small and for sustained work was nil. Christie’s symptoms suggest he was suffering from a combination of stress and heart failure. They were listed in the report as follows:

  1. His pulse is rapid and feeble – the heart being irritable and tending to dilate
  2. The blood vessels throughout the body are slightly infected and the liver is a little swollen
  3. The nervous system is feeble and excitable and there is a marked tendency to insomnia.

According to Dyson, the illness was a repeat of one that he had had a few years earlier. Reading between the lines, it seems likely that Christie was afflicted throughout his last ten years as Astronomer Royal – the very period when the Rieflers were being adopted elsewhere.

The U.S. Naval Observatory acquired a Riefler in 1904. Three years later, on 22 March 1907, William Eichelberger published a paper in which he compared its rate with that of Dent 1906 at Greenwich. Click here to read. By his analysis the mean deviation of the daily clock rate of the Riefler was 0.015 compared to 0.051 for Dent 1906. Thomas Lewis, the Head of the Time Department at Greenwich refuted this analysis in a letter published on 31 May. Click here to read. Not to be cowed, Eichelberger responded with a letter that was published on 28 June. Click here to read. What, at the very least, ought to have been a wake up call to Greenwich to properly investigate the merits or otherwise of the Rieflers, seems, on the face of it, to have been been ingnored.

Christie retired in 1910 and Lewis in 1917. It took until 1920 for the new Astronomer Royal to take action. What prompted it then, is unknown, but the idea may have been seeded by the clockmaker Edwin Cottingham while he was staying with Dyson for a couple of nights in March 1919 before setting off on the 1919 eclipse expedition with Eddington. In his Report to the Board of Visitors which he completed on 22 May, Dyson wrote:

‘Much time has been spent during the last few months on the sidereal standard clock. The room in which it is mounted is dry, and a constant tempera­ture is satisfactorily maintained. The barometric adjustment has been overhauled and appears to be working satisfactorily. But the going of the clock is not up to the standard of the best modern clocks, and it will be necessary to obtain a new one.’

He was supported in this by the Board at their meeting on 14 June when it was ‘Proposed by General Hills, seconded by Admiral Sir John Parry and carried:– That it is desirable that the Royal Observatory should possess three standard clocks in good working order.’ (ADM190/6/188)


The acquisition of an orginal Type A and a copy of Type D (E?) by the Royal Observatory

In 1920, the Observatory purchased a second-hand Type A Riefler Clock (serial number 50) from the Victoria University, Manchester (University of Manchester). At around the same time, a copy of a Type D?/E? Riefler was ordered from Cottingham.

The Riefler (which was made c.1900) arrived at Greenwich on 23 June 1920, and was set up in the Clock Room at the western end of the Meridian Building on the 30 July (RGO39/10/61 and Report). The Cottingham was delivered on 25 February 1921. It too was installed in the Clock Room in the Meridian Building. It was adopted as the sidereal standard in place of Dent 1906 on 24 October 1922.


The purpose of the two clocks

Whilst the records show that the Cottinham Clock was ordered with the specific intention (subject to perfomance) of it replacing Dent 1906 as the Sidereal Standard, Dyson's intentions regarding Riefler 50 are less clear.  The inventory records contradict the photographic record and in the Reports of the Astronomer Royal to the Board of Visitors, there are no mentions of the clock following the announcement of the clock's arrival in 1920.

The three relevant inventories (1911, 1926 and 1933) consistently list the Riefler as being in the Clock Room. However, there are photos from 1929 showing it mounted in the Rugby Room (in the eastern summerhouse) which record it as the Riefler Standard Mean-time Clock.

The riefler was overhauled by Cottingham at the end of 1920 (28/XII/1920) and again in February 1923. Shortt 16 Shortt 16, was purchased to take over the role of mean solar standard and to regulate the distribution of radio timesignals (the ‘six pip’ signal transmitted by the BBC and the Rugby rhythmic time signals transmitted by the Post Office) and to regulate other clocks at the Observatory. It arrived at the Observatory about a year after Shortt 11 on 26 October 1927 (RGO39/5/223), and set up in the newly established Rugby Room on the ground floor of the of what had been Flamsteed's eastern summerhouse. Around the same time, various alterations were made to the Riefler which was clearly intended to be part of the new installation. The 1926 inventory (RGO39/5/222) gives the following information:

19270/4/26      Magnetic control applied. Order No, 137
1927/08/27      Contact apparatus fitted to give ½ minute signals. Order No.161
1927/12/17      escapement cleaned and adjusted. Order No. 302

That it was modified to give ½ minute signals suggest that it may have been intended as a reserve for the Shortt 16 slave. If so, it would have taken over in October 1929 when the Shortt slave was overhauled (RGO39/4/224).



Further reading

The Engineer of Precision Time: Pendulum Clocks by Sigmund Riefler. Bernard Huber (downloads as a pdf). Alternative link

Rugby Radio Station website


Image licensing

The two photographs of the Riefler in the Rugby Room are © BT Heritage. They have been obtained from The BT Digital Archives and are reproduced under the terms of a Creative Commons Attribution-Non-Commercial-ShareAlike (CC BY-NC-SA) licence. They are more compressed than the originals.