Astronomical Regulator: Hardy


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Made by William Hardy (d.1832) and known as 'Hardy' since Airy's time, this particular regulator was delivered to the Observatory in 1811 and remained in continuous use as a Transit Clock until 1954. It is one of the most important clocks that the Observatory ever owned. During its lifetime, it underwent a number of significant alterations.

Until 1871, when Dent 1906 was brought into use, the Transit Clock was the Observatory's de-facto sidereal standard. Initially used to time transits with Troughton's 6-foot Mural Circle, Hardy was later used with Troughton's 10-foot Transit Instrument followed by the Airy Transit Circle.

Today, Hardy can be seen on the south side of the Airy Transit Circle in the same position that it has occupied since December 1850. It is cared for by the National Maritime Museum (Object ID: ZAA0591). A replica pier (erected by the Museum in the mid-1960s) alongside the Troughton Transit Instrument marks the position Hardy occupied from 1823 until 1850.

Hardy in use with the Airy Transit Circle. The observer is in a pit below the level of the floor. The dial can be seen towards the top left. From the 8 August 1885 edition of The Graphic (detail)


Brief history

Nevil Maskelyne, the fifth Astronomer Royal. Engraved from a pastel drawing by John Russell and published by J. Asperne, 1 March 1804

In the early 1800s, using an Altazimuth Circle at his Observatory in Westbury Sub Mendip in Somerset, the astronomer John Pond was able to show that the Greenwich Quadrants were defective. Shortly afterwards, in 1807, Nevil Maskelyne, the fifth Astronomer Royal, having consulted with Pond and the Council of the Royal Society, ordered a large Mural Circle for the Royal Observatory from the instrument maker Edward Troughton. This was done with the intention that it would supercsede both the Mural Quadrants and the 8-foot transit telescope. At around the same time, the chronometer maker William Hardy persuaded the Board of Longitude to test a clock containing a new form of escapement he had invented. The clock was put on trial at the Royal Observatory where Maskelyne was so impressed with its performance that in 1808, he ordered a clock from Hardy for use with the new Mural Circle. Maskelyne died before either instrument was delivered and it fell to Pond, who was appointed as his successor, to bring the new instruments into use. The clock was delivered in 1811 and the Mural Circle in 1812.

In the event, the Mural Circle proved insufficiently stable for making reliable transit observations, so in 1813, Pond ordered a new 10-foot Transit Instrument from Troughton. It was brought into use in 1816 and used initially with the existing Transit Clock, Graham 3. In 1821, Graham 3 was dismounted and replaced by a series of transit clocks in quick succession (some or all of which appear to have been supplied on a trial basis), starting with a clock by Molyneux and Cope. None appear to have been satisfactory. By late 1823, Hardy needed to be moved to make way for a second Mural Circle in the Circle Room and it was at this point, that it was transferred from the Circle Room to the Transit Room for use with the Transit Instrument.

In 1850, the Airy Transit Circle, replaced both the Transit Telescope and the Mural Circle. Hardy remained in use as the Transit Clock and continued to be used with the Transit Circle until the last observation was taken in 1954.


Four key features of the Greenwich Clock as originally supplied
  • Hardy's escapement (the first commercial clock to be fitted with one)
  • Accurately cut epi-cycloid shaped teeth on the wheels and pinions
  • All bearings jewelled
  • An integrated stone pier which formed part of the case

The epi-cycloid shaped teeth on the wheels and pinions of Hardy's regulators. Detail from plate 34 accompanying Hardy's description of his escapement. Reproduced from Transactions of the Society Instituted at London for the Encouragement of Arts, Manufactures and Commerce. Volume 38, courtesy of the Wellcome Library & Internet Archive


1807: Hardy's escapement is tested for the Board of Longitude at Greenwich

Trial results showing the rate of the clock. Reproduced under the terms of a Creative Commons Attribution-Non-Commercial 3.0 Unported License (CC BY-NC 3.0) courtesy of Cambridge Digital Library (see below)

On 8 January 1807, Hardy wrote to George Gilpin, the Secretary of the Board of Longitude, explaining how he had invented a new form of escapement that appeared to perform exceptionally well and requesting that the Astronomer Royal give it 'a more accurate trial at the Royal Observatory'. When put to the next meeting of the Board, on 5 March, Maskelyne assented to Hardy's request. Hardy records that

‘He accordingly called on me the day after the meeting of the Board, to see the escapement; and being pleased with it, desired me to send the clock to the Observatory for trial, as soon as I possibly could.’

For reasons that are unclear, it took until 27 April for Gilpin to write to Hardy to inform him in writing of the Board's decision. In his reply, dated 12 May, Hardy explained that Maskelyne had called on him to see the clock and that it was now in his care at the Observatory. He also informed Gilpin that he had:

'adapted to the timekeeper, the same principle of escapement, as the new regulator, by means of suspending the balance, different from the present mode, whereby its vibrations are as little disturbed, by any external cause, as those of the pendulum; should this method answer my expectation, I have every reason to believe, that the accuracy of the timekeeper, will be much improved, and rendered more steady, and uniform in its operation.'

The letter was read and minuted at the next meeting of the Board on 3 June. Exactly what Hardy meant remains unclear.

Hardy's clock was trialled at Greenwich for a period of three months beginning on 29 May and ending on 27 August. For reasons unknown the results were not tabled by Maskelyne at the next meeting of the Board on 3 December, but at the one after that on 3 March 1808, where it was the first item on the agenda. The minutes record that Maskelyne considered the escapement 'to be an essential improvement, and deserving encouragement.' It was therefore resolved:

'That the sum of £50 be given to Mr William Hardy as a Reward for the performance of his Clock, and to encourage him to proceed in the farther improvement of Clocks.'

The surviving papers of the Board of Longitude have been digiitised and those relevant to the trial can be viewed via the links below.

Hardy's letter to the Board of Longitude asking for his clock to be put on trial, 8 January 1807 (RGO14/23/239)

Minutes of the Board recording Hardy's request and the Board's decision, 5 March 1807 (RGO14/7/103)

Hardy's letter thanking the Board for accepting the clock for trial, 12 May 1807 (RGO14/23/241)

Minutes of the Board recording the receipt and reading of Hardy's letter of 12 May, 3 June 1807 (RGO14/7/107)

Trial Results of showing the rate of Hardy (RGO14/23/243)

The rate of Graham 3 during the same period (Greenwich Observations, 1807)

Minutes of the Board recording an award of £50 to Hardy for the performance of his clock, 3 March 1808 (RGO14/7/115)

The results of the trial are reproduced above. Against the entry for 15 & 16 June, Maskelyne has written 'Cleaned the pallets & teeth of the swing Wheel from dirty oil'. At the bottom of the page however, Maskelyne has also written:

'N.B. June 13 & 14 the Transit clock [Graham 3] appeared to be going irregular for want of the foul oil being cleaned out from the pallets and teeth of the swing wheel.'

An examination of the published observations shows that on 15 June Maskelyne recorded:

'At 6h24' stopped the Transit Clock, and cleaned away all the dirty oil from the swing wheel and pallets of the verge; then put a little of the best olive oil to them, and set the clock going again, exactly one minute faster than before. The clock was stopped 24 minutes.'

Having stopped Graham 3, it would have had to be re-rated before the rate of Hardy could be measured again. In light of this, it has to be asked, what exactly did Maskelyne mean by his entry for clock Hardy on 15 & 16 June? Was Hardy stopped and cleaned or was the entry a somwhat ambiguous reference to Graham 3 that was partially clarified by the note at the bottom of the page? If Hardy was cleaned, it was probably only done as a precaution while the trial was paused while Graham 3 was cleaned and re-rated. It also seems likely that Hardy would have been summoned to do it. There is no evidence that he was sent for.

Very few Hardy escapements still exist in their original form and there has been much debate about why this is. One of the downsides of the escapement (said by McEvoy to be its Achilles' heel) is that any build up of dirt on the pallets had a significant impact on the rate of the clock. In his book English Precision Pendulum Clocks (2003), Derek Roberts published a transcript of the trial results (with a shockingly large number of transcription errors) and wrote:

'Note that even at this time its going became irregular after just 10 weeks [days?] because of "foul oil"; however its overall performance was excellent, remaining within the same second'.

In December 2021, Bohams sold what was described as the trial clock for £25,250 (Bohnams Catalogue). Seemingly building on what Roberts had written, the catalogue entry states of the trial:

‘Overall the performance was very promising. The regulator maintained a rate of to within one second a day, but not before a problem in the middle of June when the performance became erratic due to the accumulation of dirt on the pallets. Hardy had to clean the pallets and "the teeth of the swing wheel" (escape wheel). It took two days to do this and reset the clock when it ran until the end of August to within one second a day.’

Neither Roberts nor Bonhams seem to have registered that there was a problem with the Transit Clock.

It is worth noting that as well as the Bonham's clock, it has also been suggested that the Hardy regulator now belonging to the PowerHouse Musuem in Australia was the trial clock (Object No: 9889). The former however seems to be the most likely candidate.


Contemporary descriptions of the escapement

In 1820, Hardy was awarded a gold medal and an award of fifty guineas for his escapement  design by the Society Instituted at London for the Encouragement of Arts, Manufactures and Commerce (the present Royal Society of Arts), who published a set of plates with an accompanying description together with an introductory letter from Hardy that set out the circumstances of the first clock's trial at Greenwich, his relationship with Maskelyne and the ordering of a clock by the Observatory. They can be viewed online via the following links:

Letter and description: Transactions of the Society Instituted at London for the Encouragement of Arts, Manufactures and Commerce. Volume 38, (1820) pp.168–185.

Plates: 34–38.

At the end of the description, Hardy made the following somewhat abiguous statement:

‘I think it proper to add, for the benefit of the time-piece and regulator makers, that I have enabled Mr. Thomas Leyland, clock-maker, of Prescot, in Lancashire, to cut wheels and pinions with teeth made truly epicycloidal, from patterns generated by myself, and also to make and fit up regulator movements complete.’

What he failed to state is who Leyland was authorised to make them for? We don't even know if he made them for Hardy himself.

There are an estimated 28 clocks thought to have been made by (or for?) Hardy, quite a number of which are still in existence. Although all are very similar there are significant variations between them. These include the number of pillars linking the front and back plates (some have five and others four), the train count, the precise detailing of the dial and the positioning of the four screws fastening the dial to the rest of the movement. Charles Allix has also noted inaccuracies in the published plates. In many ways, the Greenwich Clock was an overspecified prototype for those that followed and differed from them in a number of significant details. A proper comparative study is long overdue, but is regrettably beyond the scope of this website.

At the end of the 1820s, William Pearson (1767-1847), one of the founders of the Royal Astronomical Society (who owned a Hardy Regulator and had joined the Observatory's Board of Visitors in 1826) described Hardy's escapement in his magnum opus An introduction to practical astronomy, which was published in three volumes. His account and illustrations are largely adapted (without acknowledgement) directly from the account given by Hardy in 1820. Links to the relevant pages are provided below.

Description: An introduction to practical astronomy, Vol 2 pp.306-8

Illustrations: An introduction to practical astronomy, Vol 3, Plate 14, figs 5, 6, 7, 8, 9

Instructions on cleaning the mechanism: An introduction to practical astronomy Vol 2 p.315

Hardy is said to be the first (British?) Clock maker to use accurately cut epi-cycloid shaped teeth on the wheels and pinions of his clocks. Details of how they were cut were initially published in 1822 by Thomas Gill in Volume 1 of his Technical Repository: and elaborated on in 1839 in Volume 1 of his Machinery Improved.

1809: Maskelyne places an order for a clock for the Observatory and a dispute over the final cost

Hardy's letter to the Board of Longitude containing the first mention of a clock being ordered for the Royal Observatory. It was written on 31 May 1808. Reproduced under the terms of a Creative Commons Attribution-Non-Commercial 3.0 Unported License (CC BY-NC 3.0) courtesy of Cambridge Digital Library (see below)

William Hyde Wollaston, by William Ward, after John Jackson. Mezzotint, early 19th century. National Portrait Gallery, London. Reproduced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported (CC BY-NC-ND 3.0) licence (see below)

Sir Joseph Banks. Engraving by W. Holl from the 1815 oil painting by Thomas Phillips. The Board of Trustees of the Science Museum. Reproduced under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence (CC BY-NC-SA 4.0), details below

In the early 1800s, the Observatory was funded by the Board of Ordnance and overseen by the Council of the Royal Society (acting in their role as Visitors).

Clearly impressed by the trial of Hardy's clock, Maskelyne ordered a similar one for the Observatory for use as a transit clock with the new Mural Circle. This had been ordered from Troughton in 1807, but not yet delivered. In the event, Maskelyne died in February 1811 before either instrument had arrived. The Mural Circle was erected in 1812, with the first published observations being made on 11 June. No record has yet been seen by this author to show when the clock was delivered. When the annual visitation took place on 19 July 1811, there is no mention of Hardy or  the clock in the minutes nor is there a record of the inventory having being checked as it normally had been in the past, making it impossible to tell if the clock had been delivered by then or not (RS/MS/600/66). It is reasonable however to surmise however that it was at the Observatory by 21 August 1811, as by then, questions were being asked about the enormous size of the £325 bill submitted by Hardy, which was to lead to a full-blown enquiry (RSMS/372/146). RGO5/222, which has not yet been examined may shed more light on the date of arrival.

The documentation surrounding the early history of the clock is incomplete and has lead to a number of false narratives coming into play. Most of the documentation that survives is contained in the Royal Society file RS/MS/372 and the minutes of the meetings of its Council.

Extracts from the minutes from 1710-1830 deemed relevant to the Royal Observatory were transcribed for George Airy and can be found in RGO6/21&22. What, if anything, was omitted is not known and a comparison with the originals would be needed to find out - a task that no researcher has yet undertaken. What is clear, is that information one would normally expect to find about the clock is not present in RGO6/22. In particular, there is no record of any discussion between Maskelyne and Council about ordering a clock from Hardy. Nor is there a record of Pond submitting Hardy's bill to Council for them to approve and then forward to the Board of Ordnance for payment in the normal way. Troughton's bill of £735 for the Mural Circle for example was discussed at Council on 14 January 1813, with 'the recommendation of the President and the Council that the same be paid'. Pond himself would have been aware of this procedure regarding the payment of bills before he became Astronomer Royal as he was present at the Council meeting on 13 December 1810 when Maskylene submitted a set of bills for approval (RGO6/22/63). Either the references to the clock were overlooked during the transcription process, or irregular procedures were being followed.

It is not known exactly when the clock was ordered, but it was apparently at some point before 31 May 1808 as Hardy mentions the order when writing to the Board of Longitude to thank them for the award of £50 (image above). The next record of the clock comes three years later in the form of a letter dated 21 August 1811 and sent by the Board of Ordnance to William Wollaston (who at that time was one of the Secretaries of the Royal Society). The text read:

‘Mr. Wm. Hardy having delivered a Bill amounting to £325 for the astronomical clock he has prepared for the Royal Observatory, and the Astronomer Royal having stated that the charge is much greater than was expected or thought reasonable by the Council of the Royal Society: I am directed to acquaint you therewith, and request you will move the Council to favour the Board with their opinion, what would be a reasonable sum to be allowed Mr. Hardy for the Clock alluded to.’ (RS/MS/172/146)

The letter was read at what appears to be the next meeting of Council which was held twelve weeks later on 14 November. There it was resolved that 'Mr Hardy be desired to attend a meeting of the Council on Thursday next [21 November]'. There is no mention of Hardy actually having attended in RGO6/22, so it is not known whether he did or not.

At this point, it is helpful to understand a little more about the relationship between the President of the Royal Society, Sir Joseph Banks, and Maskelyne and how things were handed over to Pond when he became Astronomer Royal. Banks and Maskelyne were both Commissioners of the Board of Longitude and Maskelyne was answerable to the Board of Visitors of which Banks, as Presidient of the Royal Society, was Chairman (and had been since 1778). Maskelyne also held high office at the Royal Society, having been a longstanding member of its Council. Their working relationship on the Board of Longitude came under severe strain in 1784 and an abrubt end in 1806 when Banks stopped attending meetings following a disagreement with his fellow Commisioners and in particular Maskelyne. Although Banks had stopped attending meetings of the Board of Longitude, Maskelyne who by then was in his mid 70s, continued to attend meetings of Council of the Royal Society.

It was during Bank's absence at the Board of Longitude that the seeds were sown that led to the Nautical Almanac being brought into disrepute in the 1810s. This was due in large part to a lack of succession planning for the replacement of the comparer Malachy Hitchins (1741-1809) or indeed of Maskelyne himself, both of whom died in post. The meeting of the Board of Longitude on 7 March 1811 was the first to be held following the death of Maseklyne and the first that Banks had attended since March 1806. There it was the resloved:

‘That the Astronomer Royal [Pond] be requested to conduct the business of the Nautical Almanac by superintending & paying the Computers and Comparer in the manner that has been heretofore done & that the Secretary be requested to allow him access to the Minutes of the Board in order that he may collect from them the mode in which that business has been hitherto carried on.’(RGO14/7/145)

What is striking is that Pond wasn’t handed a dossier by the Secretary setting out how the Almanac had been managed and what the present state of play was. He was required instead to extract this information from the Board’s minutes. This would have been an all but impossible task since the minutes, of which 800 pages had been accumulated since the Almanac was conceived in 1765, did not contain the information in the detail that Pond would have needed. So what of the handover to Pond of the Observatory business?

We know that Pond dined with Maskelyne at the Observatory on at least seven occassions between 1806 and 1809. He may also have dined after 1809, but there are no surviving records for this period. Pond was clearly familiar with some aspects of the way in which the Observatory was run during Maskelyne's time. But what if anything did he know about the clock? The catalogue of Maskelyne's papers (RGO4) makes no reference to either Hardy or the purchase of a new Transit Clock, suggesting that Pond would have little if any knowlege of what had been agreed between Maskelyne and Hardy. The fact that the catalogue also makes no reference to the Mural Circle suggests that Maskelyne did not keep his paperwork in good order and that neither he nor the visitors had considered what would happen if he suddenly died.

The extent to which the Royal Society and its President Sir Joseph Banks in particular were attempting to deflect blame for the Hardy fiasco away from themselves by being economical with the truth in the report that they sent to the Ordnance, is difficult to judge. After a brief introductory paragraph, the report continued:

'That having examined Mr Hardy on the reasons & calculations of his charge of £325 for an Astronomical Clock; and then inquired of all such persons as they thought able to give them information respecting the just value of & proper prices for such Instru­ments. Hence they are opinion That Mr Hardy has in consequence of a misconception of the verbal directions given to him by the late Astronomer Royal unnecessarily incurred a considerable expense in executing those parts of the clock which have no real influence on the correctness of its going. He appears to have finished those parts almost as highly as the principal movements. The labour and expense thus bestowed are of little or no value to the purchasers of a Clock as a measure of time. That he has employed more jewel work, than usual, in making this clock, more than they believe has before been thought expedient in the construction of any clock whatever. That he has been so inattentive to the interest of his employers, as to suffer the tradesmen, of whom he ordered those parts of the clock which the clockmaker does not usually supply (the case for instance) to charge for their work prices as unreason­ able as his own charge is deemed by the Council to be. That he has, in computing his charge for this clock, included the expense of some part of the tools with which it was made; a practice never customary with tradesmen of any kind, as the tools remain their property; and those of Mr Hardy have actually enabled him to make other clocks for the persons who now employ him. On considering the whole of the case, the general testimony of those who have inspected the Clock that it seems to be extremely well executed, and the report of the Astronomer Royal that it has gone with extraordinary exactness since it was put up in the Royal Observatory. The Council do resolve to recommend to the Board of Ordnance to pay Mr Hardy the sum of Two hundred guineas for the clock he has delivered; and they are of opinion that this sum, which is considerably larger than any that has been before paid for an Astro­nomical Clock, is a liberal compensation to Mr Hardy for his skill & labour in making the Clock as well as for the just and reasonable cost of the articles not furnished by himself.' (RGO6/22/69)

Only one individual can be indentified by name as having talked to Hardy – the clockmaker Alexander Cumming. Nowhere in either his report to the Royal Society or the Royal Society's report to the Board of Ordnance is there any mention of a written contract with Hardy – so did one actually exist? The real elephant in the room however is the signed but undated itemised estimate from Hardy for £269 3s 6d. for supplying the Greenwich clock. Held in the Royal Society archives (RS/MS/372/152) rather than those of the Observatory, there is no reference to it in Cumming's or the Royal Society's reports, (nor seemingly in most later accounts of the affair either).

Estimate of the Greenwich Clock

To ten months, and two weeks workmanship, and time £210-0-0

  Frames Mounting 8-0-0

  Brass Plate 6-10-0

  Wood work 20-0-0

  Varnishing D.o 1-0-0

  Pendulum and index 8-10-0

  Weight, and pulley work 1-11-6

  Dial place, and glass 2-10-0

  Engraving D.o afresh 1-0-0

  Jewelling 9-10-0

  Porterage and carriage 0-12-0

£269 3 6

     charge - £325 [written in another hand] W.m Hardy

After interviewing Hardy, Cumming wrote to Wollaston on 19 Jan 1812. In his letter, he explained how he had met with Hardy (apparently at the Council's request and at the suggestion of Hardy) to discuss the terms of the contract. Although the Ordnance letter of 21 August 1811 could be construed as meaning that Hardy appealed over Pond's head directly to the Ordnance for payment, this does not appear to be the case, as Cumming wrote that Hardy 'said that he understood that his Bill was sent to the Tower, and he supposed it was to be paid' (RS/MS/172/149).

The Council report was submitted around two weeks after Cumming wrote his letter. The first two-thirds of the section of the report reproduced above could easily have been written based on what Cumming had said – which does raise the question of who else, if anyone, the Royal Society consulted. Turner provides a transcript of both Cumming's letter (RS/MS/372/149) and what appears to be the final draft of the Report (RS/MS/172/153) in Volume 11/6 (Winter 1979) of Antiquarian Horology.

In the published letter of 1820, Hardy himself gave the following account of the agreement that had been made:

‘It was from the satisfactory performance of this clock [the one that had been on trial], that I was recommended by the Doctor [Maskelyne] to the Board of Ordnance as a fit person to furnish a clock on the same principle for the room in which the famous mural circle is placed, which circle was then making by the celebrated Edward Troughton. The order for the clock was unlimited in price, and directed me to consult the Doctor on every particular connected with it. I therefore waited on the Doctor to receive his instructions; his treatment to me was kind and hospitable, and he gave me every encouragement to exert myself, and to complete the clock in such a manner as to be durable and certain in its performance. As it was to accompany one of the most excellent instruments that ever was made, he wished the clock to be equally so in point of excellence. This excited me to use my utmost exertion, and to spare neither time nor expense in order to make it as perfect as possible. It was decided upon to jewel every action in the escapement and all the pivot holes. The teeth of the wheels and pinions were epicycloidal, and were all finished in the engine by cutters which I made for that purpose; and the whole of the clock was finished in a style equal to any of our first-rate chronometers.’

Having received a letter from the Ordnance that they were 'not disposed to allow the amount' of his bill, Hardy replied on 17 February 1812 asking 'for two or three superior chronometer makers' to arbitrate or 'to have permission to take back the clock' (RS/MS/372/150). Two days later on 19 February the Ordnance forwarded a copy of Hardy's letter to Wollaston and asking for the opinion of the Royal Society on the matter (RS/MS/372/151). Impatient for a reply, the Ordnance wrote again on 3 March asking for the Royal Society's response (RS/MS/372/148). Two days later, on 5 March, the letter was discussed at Council, who somewhat scathingly:

'Resolved. That the Council of the Royal Society do recommend to the Board of Ordnance that Mr. Hardy's proposal of submitting his bill to a reference be consented to; but since the matter iin question between the Board of Ordnance & Mr, Hardy is a clock and not a chronometer, the Council deem it a necessary condition that the referees be not mere Chronometer Makers but Clock makers.

Resolved Further. That the Council of the Royal Society would highly approve the momination of Mr. Alexander Cumming who was originally named to them by Mr. Hardy as a referee peculiarly qualified to judge of the merits and value of his workmanship.' (RGO6/22/70)

At this point, the record peters out so it is not known for sure how the situation was resolved. Clearly Hardy did not take the clock back as it remained at the Royal Observatory. It is usually stated that Hardy was paid 200 guineas for the Greenwich clock. This is despite the fact that no evidence has yet been uncovered to verify that this was actually the case. The best that can really be said is that he was probably paid 200 guineas.

What we do know however that in 1822, Hardy supplied a similar clock for the Observatory at the Cape. The cost to the Board of Longitude was 100 guineas (RGO14/7/391). See also RGO14/48/173 & RGO14/48/58 Unlike the Greenwich Clock, which had five pillars linking the front and back plates, that supplied to the Cape had just four.


The changing location of the clock, the form of the mounting and the design of the case

Although Pond published an engraving of the Mural Circle in his first volume of published observations, he failed to show the clock or where it was mounted relative to the telescope. The Circle Room as shown on the 1831 Observatory plan (RGO6/45) shows the room as it was some seven or more years earlier and predates the construction of the pier for the second Mural Circle (which began in January 1824). It shows an unlabelled structure, presumed to be the clock pier, close to the Circle Room wall immediately to the east of the centre of the Troughton Mural Circle. When Airy drew his manuscript plan of the Observatory in 1846 (ADM140/426), it included the pier for the second mural circle on the site previously occupied by the clock, and a new and rather smaller clock pier located against the south wall and roughly equidistant from the two Mural Circles to which a journeyman clock was originally fitted.

Detail from the plan published in 1847 as an addendum to the 1845 volume of Greenwich Observations (north at the top). It is based on Airy's 1846 manuscript plan (ADM140/426). Key: (c) Transit Room. (d) Circle Room. (4) the pier for the Transit Clock (Hardy from 1823–1850) – note the recess cut into it. (5) the pier for Troughton's Circle. (6) the Pier for Jones's Circle. (7) the pits for the convenience of reading the lower microscopes of the Circles. (8) the stage for reading the upper microscopes of the Circles. (9) the pier for the Circle Room Clock (probably erected here in 1823 or 1824 around the time Hardy was moved to the Transit Room). The large shaded area on the opposite side of the wall to (9) is marked on the manuscript plan as a buttress

The earliest evidence for how the clock Hardy was orginally mounted comes from Hardy himself in the letter that he wrote for publication in 1820:

‘The Doctor [Maskelyne] being sensible of the great importance of fixing up the clock upon a material that should be permanent and immoveable, I suggested that it should rest upon a strong brass plate screwed fast to the top of a stone pier, in which a recess or channel might be cut out to receive the weight and the pendulum, which was adopted.’

Detail of plate 35 accompanying Hardy's description of his escapement. It shows a side view of the lower half of the movement with the dial on the left. (A) is the brass plate (the seatboard) on which the movement rested. Half an inch thick, several inches deep and more than a foot in length, at Greenwich, it spanned the top of the recess of the stone pier to which it was bolted. It contained piercings through which the pendulum (x) and the cord (5) which supported the driving weight passed. Reproduced from Transactions of the Society Instituted at London for the Encouragement of Arts, Manufactures and Commerce. Volume 38, courtesy of the Wellcome Library & Internet Archive

In other words, the seatboard (also referred to as a rising-board) was made of brass and the pier was integral to the case and effectively the trunk of the clock. This was not the case for the twenty plus similar clocks Hardy made later. Although a brass seatboard is shown in the published plans (right), a wooden plate has been substituted in some clocks. The Greenwich clock presumably had a fairly conventional hood and some kind of framework and door attached to the pier to protect the pendulum and weight.

With its integral stone pier, the Greenwich Clock would not have been easy to move and this might well explain why instead of moving it to the Transit Room in 1816, Pond continued to use Graham 3 there. Eventually, starting in 1821, he dismounted Graham 3 and installed a series of transit clocks in quick succession (some or all of which appear to have been supplied on a trail basis), starting with a clock by Molyneux and Cope. Finally, in late 1823, with work shortly to begin on erecting the pier for the second circle, Pond had Hardy moved into the Transit Room. On 4 November, he recorded in Greenwich Observations: 'Took down the temporary transit clock, and removed Mr. Hardy's clock from the circle room into its place.' How long this took is not clear as no further observations were made until 9 November. Given that observations were made with the Circle on 6 November, it sounds as though the move took a minimum of three days. Given that in 1816, it took no more than eleven days to increase the height of the piers on which the Bird Transit Instrument had been mounted and to get the new Troughton Transit Insturment installed in its place, it is likely that as well as the clock being moved in 1823, the pier was as well, especially as the 1831 plan implies that the two clock piers had the same footprint and the 1846/7 plan (above) shows the pier with a recess cut into it. Further evidence that the pier was moved comes from Pond in his explanation to the Visitors of how Dent's name came to be inscribed on the dial in 1830. In it, he wrote:

'Another clock could not be permanently substituted, as the stone pier is constructed expressly for Mr. Hardy's Clock, so that in this emergency no method of proceeding with the observations appeared so advisable of availing ourselves of Mr. Dent's offer. (RS MS371/58)'

Normally when things needed doing to the clock, Hardy was involved and Pond recorded this in Greenwich Observations with phrases like 'Mr. Hardy took down the Clock to be cleaned.' or 'Mr. Hardy put up the Clock, and set it nearly with sidereal Time.' Although Hardy was not mentioned by name in the 4 November entry, there are two reasons to believe he was there. Firstly because on 22 November Pond recorded that Hardy had stopped the clock and fitted a new second hand (presumably because the original was damaged during the move). Secondly because in 1824, Thomas Gill wrote in his Volume 5 of his Technical Repository:

‘We were exceedingly gratified by Mr. Hardy's information, a few days since, that the teeth of the wheels and pinions of his time-piece at the Royal Observatory at Greenwich, were lately examined with magnifiers, by several of our most scientific men, and that not the slightest appearance of rubbing could be perceived upon them, after thirteen years' wear!

going on to say:

'This is, indeed, a most satisfactory example of the value of the epicycloid, when appled with accuracy to the teeth of wheels and pinions.'

Having been moved, the Clock Hardy was to remain in position for just 27 years before being moved again. Being a systematic man, Airy decided that he wanted observations with his new Transit Circle to commence on 1 January 1851 or as soon thereafter as weather permitted. To this end, he had Hardy moved from the Transit Room to the Transit Circle Room towards the end of December. He recorded the following in the 1850 volume of Greenwich Observations.

'December 27, 0h. The transit-clock (Hardy) was removed to the Transit-Circle Room, and a clock by Arnold (A2) was used in its stead.'

Although Airy informs us that Hardy was placed in a recess built into the brickwork of the pier supporting the south collimator of the Transit Circle, he failed to mention that the upper section where the movement sits is around 18 inches wide, whist the lower section, below the seatboard is roughly 14 inches wide. Nor did he mention that a massive cast iron seatboard was substituted for the brass one. In its new location, the movement was no longer accessible from above or from the side. On the assumption that Hardy made the clock in accordance with his published plans, this would also have necessitated altering the way in which the pendulum was suspended (more on this below).

The seatboard is slightly less wide than the upper part of the recess. Rather than being of a uniform thickness, it has two reinforcing ribs than run from side to side across the bottom. As a result, the thickness varies from around ½ an inch to more than three inches. The corners of the left and right hand edges extend beyond the central section and taper inwards. This presumably made it easier to remove when required. It is not currently known if the seatboard originally sat directly on the brickwork, nor if it was held in place solely by its own weight. Nor is it known if there was some kind of locating lug to ensure it was always returned to the same place.

Airy arranged things so that the dial was in clear view of the observer siting in the pit of the instrument (see image at the top of the page). As a result, most of the clock was below ground level, with the dial itself being about a foot above the floor of the room. When Airy published his description of the Transit Circle in  Appendix 1 of the 1852 volume of Greenwich Observations, he failed to mention how the pendulum was accessed for adjustment and maintenance. If as orignially conceived the section of flooring between the collimator pier and pit was removable, this is no longer the case, the floor having been replaced at least twice since the 1960s under the stewardship of the National Maritime Museum.

Hardy as seen from the pit of the Transit Circle. Photo 2005

The south collimator pier with the dial of Hardy at its northern end. Photo 2011


Ground plan of the Transit Circle Room and view of the Transit Circle etc. from above. Adapted from Plate 3 of Airy's description of the Transit Circle published as Appendix 1 of the 1852 volume of Greenwich Observations

Detail, showing the location of Hardy and the lamp used to illuminate it (key below). Reproduced courtesy of the Munich DigitiZation Center (MDZ) and the Bavarian State Library (BSB).

Key (adapted from Greenwich Observations):                  Complete Key to plate 3.

t. The pier for the south collimator. Made of brick, it was covered with a slab of sandstone.

u. (Dotted lines,) the recess in the brickwork of the pier below the stone slab, in which the transit clock is placed.

v. A small projection from the clock case, in which a chronometer was placed when it was being compared with the transit clock (no longer present).

n. A gas light with its smoke chimney fixed to W for illuminating the transit clock (no longer present).
x. Wooden box covering the collimator

W. Pillars supporting the roof.

In its new location Hardy was particularly vulnerable to damp, so much so, that in 1868 Airy was to tell the Visitors:

'I have given a new form to the head of the clock, for admission of small tin boxes in which a few lumps of quicklime will be placed, in order to keep the air about the wheel-work in a state of dryness.' (1868 Report)

The following year hear informed them that the quicklime was changed once a month (1869 Report). After this, there is no further mention of either quicklime or the tin boxes, meaning that it is not possible to know when the practice was discontinued.

The damp problem was not however solved as in 1874, the clock was absent from the Observatory for around ten to eleven weeks while being rerfurbished. Having 'become exceed­ingly rusty', it was absent again in 1878, this time for just over eight weeks as (more on these absences below). Later, in 1905, the then Astronomer Royal William Christie noted in his Report to the Board of Visitors:

'The Clock Hardy, which was much rusted owing to damp weather, has been cleaned by Messrs. Kullberg, who have made alterations in the case to protect the clock from damp as far as possible.'

Regrettably, no records have yet been located that show showing how the seatboard sat within the recess prior to the clock being put on display by the National Maritime Museum in 1967. Conservation photos taken in 1969 show that at that time the brickwork surrounding the clock was painted black with the seatboard seemingly sitting directly on the brickwork below. At some point, possibly around 1990 when an attempt was made to increase the running time of the clock from 3¾ days to 8 days (more on this below), the recess was lined with what appears to be plywood. The seatboard no longer sits directly on the brickwork but on some kind of a wooden plinth that sits between them. Its left and right hand edges are now concealed by the lining that rises vertically above it. As a consequence, the dial is around 5cm higher above the floor than it was before and the seatboard can no longer be easily removed from the recess.

The piers which supported Troughton's Transit together with the pier on which the transit clock had been mounted were removed at the start of 1851. When the Observatory was turned into a museum, replica piers were erected on the site of the originals. The replica clock pier is rectangular in section and tapering towards the top, with a vertical face on which to mount the clock. It is suspected it was modelled on that shown in a late eighteenth century drawing of the Transit Room, when Graham 3 was mounted there. Purchased in 1966 (Object ID: PAF2956), a year before the building which houses the telescope was opened to the public, it was drawn by John Charnock, probably in the 1790s. The Museum however had a problem on its hands. Hardy, which was loaned by the Astronomer Royal was (rightfully) retained in its 1851 position with the Airy Transit Circle. and the Museum did not at that time own Graham 3 (it was acquired in 1998 when the Royal Greenwich Observatory (RGO) was shut down). The dilemma it faced, was what clock to mount on the replica pier given that it did not own any suitable clocks of its own (the RGO had also retained Graham 1 and Graham 2). To solve the problem, in 1966 the Museum borrowed a clock by Shelton from St John's College Cambridge. It remained on loan to the Museum until 1992. Today (2023), rather than supporting Graham 3, the replica pier in the Transit Room supports a clock by Hardy which although never used at the Observatory was purchased by the Museum in 1980 (Object ID:ZAA0606). Not only is the way in which this clock is mounted entirely different to the Greenwich Hardy, it also lacks the a brass seatboard, being supported instead by one of wood (view image). Interstingly, in 1967, the Museum also borrowed the regulator by Hardy that had been bought in 1824 by the Cambridge Observatory (now part of the Institute of Astronomy). It was returned to Cambridge in 1981 following the Museum's purchase of the clock mentioned above. It now forms part of the collections of the Whipple Museum (Accession Number 2800).

In 1975, volume 3 of Greenwich Observatory by Derek Howse was published. Although Howse was a curator at the National Maritime Museum and a key player in the 1960s in converting the Observatory into a museum, he seems to have believed that the clock was originally supplied and mounted in a conventional wooden case. In the book, he provides a table of key dates in the history of the clock. Against the year 1850 he has recorded 'Movement taken out of wooden case and mounted in Transit Circle Room pit as transit clock'. His successors seem to have taken much the same view and much the same information is currently (2023) given on the Museum's website. The error was compounded by Charles Allix in his article William Hardy and his spring-pallet regulators that was publsihed in Antiquarian Horology in 1990 (Vol 18/6). Although Howse may not have been aware of Hardy's 1820 letter, Allix most certainly was, though whether or not he had read it is uclear. Possibly influenced by what Howse had written in 1975 and what AJ Turner had written in the Horological Journal in 1979 (Vol 11/6), Allix failed to mention the recess or channel that had been cut out of the stone pier to receive the weight and the pendulum, writing:

'The clock had a wooden case when first set up in the Circle Room. This is clear from the Royal Society's Report quoted by Turner (M.S. 732, No.153) [This author diagrees]. The case presumably looked conventional; but since the movement of the clock was attached to the top of a stone pier, its case probably had neither backboard nor bottom. It would have needed to be specially made and braced. This perhaps accounts of a rather high cost of £20'

Where the figure of £20 came from is not mentioned by Allix, but would appear to have come from Hardy's estimate mentioned above (RS/MS/372/152).

When Hardy suppiled his clocks to (some?) purchasers, he also supplied intrstructions on how they should be mounted. Those republished by Pearson began:

'The case must be fixed up to a solid stone pier by the four blocks and screws. The screw holes must be made in the back of the case, where they are marked. The brass plate on which the clock is seated is to be made perfectly horizontal, by placing the spirit-level betwixt the pencil lines drawn thereon. ...'

By contrast, in the description published in 1820 Hardy wrote something completely different:

'AA, plate XXXV, represents the edge of a horizontal brass plate [the seatboard], which must be fixed on two brackets firmly screwed to a stone pedestal or wall, and quite independent of any part of the case of the clock.'

The three different mounting methods published in different locations at different times perhaps help explain the confusion that has existed for so many decades about the way in which the Greenwich Clock was mounted. A future examination of the correspondence between Airy and Dent as well as yielding details of changes Dent were asked to make, may also yield further details about how the clock was mounted.


The dial

Measuring 297mm across and 3mm thick, the dial was originally silvered brass. The large outer dial indicates the minutes, the small upper dial the seconds and the small lower dial the hours. At some point (date currently unknown), the dial was painted white. This was presumably to make it easier to read as the silvered dial would have been prone to tarnishing. Conservation photographs taken in the 1960s show that over the years, the markings around and beneath the winding hole had been worn or wiped away. This included the pair of outer tram lines of the seconds dial between the 34 and 40 marks and the outer circle of the hour dial between 19.5 & 22.5.  The outer circle of the hour dial was also missing between 13.5 & 14.5, whilst the inner circle was missing between 13.5 & 18.5 and 20 & 22.5. The y of Hardy and the numeral 22 on the hour dial also showed signs of crude retouching prior to the dial undergoing conservation treatment in 1984. Other areas may also have been retouched prior to 1984, but it is not possible to discern this from the photos. What caused the loss is unclear, but it may have been caused by contact with lubricant that was subsequently wiped off. This could have occured, if, as is believed to be the case, lubricant had been applied though the winding hole and had run down the dial.

Although the detailing is possibly the same as that of the original engraving beneath, it should be noted that the y of Hardy is quite unlike those that are found on the later clocks. So too, are a significant number of the other details, particularly the presence of the inner circle of the hour dial. Whether these differences are present in the orginal engraving cannot be determined. When Dent changed the clock's escapement for one of his own in 1830 (more on this below), Pond records that he added the following inscription: 'New deadbeat Escapement &c by Dent London A.D. 1830.' (RS/MS/171/58). This is not what is recorded on the dial today, the inscription being an abridged version and missing the words &c., London and the date. Perhaps Dent's inscription as originally engraved was aesthetically unpleasing and later altered for this reason.

The dial has nine drilled holes of varying diameters: four for securing the dial, three for the hands, one for the winding key and one viewing aperture which was probably cut in 1854 when electrical contacts were added (see below).

The dial also has two segmental appertures in the seconds dial that have been plugged with brass plates soldered into position. Located betwen the 10 and 20 and the 40 and 50 marks, their position can just made out in the image above. Further research is required to establish why and when the appertures were cut and why and when they were plugged. They may relate to alterations made by Dent in 1836 when Airy asked if he could make the beat of the clock louder and were possibly closed following the addition of electrical contacts in 1854 which rendered eye and ear observations with the clock obsolete. See below for information on these two sets of alterations.


Dust covers

Although later clocks by Hardy seem to have been supplied with internal wooden dust covers such as the one shown here, there is no evidence to suggest that such a cover was supplied for the Greenwich Clock. Its movement does however appear to have had cover plates (now missing) that were screwed to the sides and top, the evidence for this coming from the presence of screw holes drilled into the edge of the front and back plates (which were 7mm thick). It is not known either when they were added or when they were removed. The 1984 conservation report also states that a cover plate 'seems' to have once been present on the bottom of the movement, but does not state the evidence for this. Since the front and the back plates sat directly on the seatboard, and assuming that the statement was not made in errior is not clear why a cover plate would have been fitted in this location.

Once the Clock had moved for use with the Transit Circle, it was no longer possible to examine its movement without completely dismounting it. This would be true whether or not dust covers were fitted.


The Movement, the driving weight and the duration of the clock

Over the years the driving weight and its configuration appear to have been altered more than once. The following description is thought to show how the clock was configured when it underwent conservation work in 2010. It is taken from the Royal Museums Greenwich website:

‘The movement has exceptionally thick (7mm) arched brass plates [that] are united by five heavy pillars riveted to the backplate and secured by domed blued steel screws with shouldered brass washers. The finely constructed six-wheel train is driven by [a] brass cased weight with integral pulley and triple pulley system to compensate for the short drop of the pendulum chamber. The double line runs on a turned barrel with a sprung C-shaped stop iron mounted to the front flange with a chamfered push piece lying across the nineteenth turn. The barrel is also fitted with Harrison’s maintaining power, a great wheel and a second wheel driving the large hour wheel. All wheels have six straight crossings and are of light construction. The dead-beat escapement with jewelled brass pallets is mounted on the backplate; a sixty-tooth contact wheel with one blank division is mounted to escape wheel arbor between the frontplate and the dial with corresponding view aperture cut into the dial plate.’

It should be noted that in all his known later regulators Hardy bolted rather than rivetted the pillars to the backplate

Other information about the movement of the Greenwich Hardy is as follows:

Barrel grooved for 20 turns.

Train count :  140   128/14   120/16   30/16 

Wheel concentric with Great wheel 75. Wheel carrying hour hand 180.

The 1984 conservation report noted: 'Bottoming wear noticable in all pinions'.

In 1836, Airy asked Dent to make the beat of the clock louder. The correspondece between Dent and Airy suggest that the weight and possibly the pulley system was altered at that time. Mercer (1977) records that Dent on 2 December Dent wrote:

'I must then have a weight made with the pulley introduced into it; as it is now, it must be wound on the 7th day otherwise it goes down, and by the introduction of a pulley as stated, it will go the eight days.'

Conservation photographs taken in 1969, show a weight with a hook on the top hanging from a single pulley unit. The clock Hardy made for Brisbane (which dates from c1815) has a similar arrangement. Other clocks by Hardy for which images were availabe (three in total) show something different. All show a cylindrial weight with a pulley built into it. In the Skinners Clock and the so called Jensen Clock, the top of the pulley appears to be flush wit the top of the weight. In the Cape Clock, it appears to be slightly lower.

Prior to 1864, Airy indicated in the Introductions to the volumes of Greenwich Observations that the Clock was wound once a week on a Monday. From 1864 onwards, he recorded that it was wound twice a week on Mondays and Thursdays, though he didn't incicate why. We do know however from the published observations that the Clock was taken down on 29 April for cleaning and bought back into use on 3 June, suggesting that this may have been when the switch over occured.

Rate sheets from the National Maritime Museum from 1984 and 1985 record that the clock had a duration of approximately 3¾ days. In 1986, designs were drawn up 'for rendering the Hardy Transit Clock 8 day going'. The conservation records do not show the existing arrangement at that time and there is no clear statement that the plans were put into effect. The wording of records made in 1993 suggest that they were, but there is no clear indication as to when this might have happened. Nor does the design appear to have been successful as rate sheets for 1993 and 1994 record the duration as 6 days, 23 hours and 15 minutes. This figure however was revised upwards in February 1995. In practice however, the clock frequently stopped between its weekly windings and in mid 2006, the figure for the exact duration was revised once again; this time to 'Approx 7 days only'.

The Museum records indicate that there are two weights now associated with the Clock, but give no further information other than their dimensions (but not their wieght). Their object ID's are:

  • ZAA0591.1 which appears to be the one that was use in 1969 and a shorter weight
  • ZAA0591.8 which has neither a hook nor a pulley, is cylindrical and flattens towards the top


The pendulum

As supplied by Hardy, the clock came with a mercurial pendulum. The first modification came in 1828 when:  'Mr Hardy applied a new glass cylinder to the pendulum of the clock containing a column of quicksilver nearly half and inch longer than the former.' (Greenwich Observations,1828).

Today, the pendulum is suspended from a heavy cast iron Troughton frame mounted on the cast iron seatboard which is roughly 18 inches wide, the change being made when the clock was moved from the Transit Room into the recess in the collimator pier of the Transit Circle in December 1850. In this location, rather than being fitted with a removable hood, the covering above the movement was an imovable sandstone stab. By altering the suspension arrangement, the likelihood of damaging the movement would have been considerably reduced.

The present pendulum is a compensated one of zinc & steel. The earliest reference to Hardy having such a pendulum in the Observatory's own publications comes in the Introduction to the 1908 volume of Greenwich Observations and was repeated in the volume for 1909, which was the last volume to have an introduction. After this date, there appears to be no further mention of the pendulum in the published output of the Observatory.

Information about changes and repairs made to the more important clocks was normally published in the Reports of the Astronomer Royal. No such information about changes to Hardy's pendulum was ever published. The location of the more important clocks was also published in the Introductions to the volumes of Greenwich Observations (1836-1909). Unless a change had taken place, the same information was normally copied over from one year to the next. Information about the type of pendulum was often included as well. The nature of these entries tends to be inconsistent, particularly between 1881 and 1909 during the tenure of Christie as Astronomer Royal, who only mentioned Hardy's pendulum for the first time in the volume for 1907, when he stated that it was fitted with a gridiron pendulum. On this basis, it might seem reasonable to assume that a mercurial pendulum was replaced by a gridiron one in 1907 which was then changed for a zinc and steel one in 1908. But was this really the case, or did the Astronomer Royal simply fail to report the changes in the year in which they happened? What we do know is that Hardy still had its mercury pendulum in 1869 as Airy told the Visitors in his Annual Report that 'Two ounces of quicksilver' had been 'added to the bulb of the Transit-Clock-pendulum'. We also know from a list of clocks written out by Christie's hand and dated 21 January 1899, that a zinc and steel pendulum had been fitted by that date  (RGO7/45/C6).

The first clocks at the Observatory to have zinc & steel pendulums were all ordered by Airy and delivered in 1871. They were the new sidereal standard, Dent 1906, and the three clocks Dent 1914, 1915 & 1916, which were orderd for the forthcoming 1874 Transit of Venus expeditions. Airy also arranged for zinc & steel pendulums to be fitted to three of the existing Observatory clocks that were being loaned for the expeditions (Earnshaw, Graham 2 & Arnold 2). Prior to the 1882 Transit of Venus Expeditions, five and possibly six of the Dent clocks that had been supplied for the 1874 Expeditiion with wooden pendulums had them upgraded to zinc and steel. They were Dents 1916, 2010, 2011, 2012, 2016, 2017 and possibly 2015.

In his 1874 Report to the Board of Visitors Airy wrote:

'The clock Hardy, which was in a bad state, has been thoroughly renovated by Messrs. E. Dent & Co., the principal alterations being the substitution of new contact­ apparatus and of a new escape-pinion for the old parts. While these repairs were being executed, the clock Arnold 1 was placed in the Transit-Circle-pit for use in observations of Circumpolar Stars, &c. The rate of this clock would probably be improved by the substitution of a zinc and steel pendulum (which has been found to answer so well in the Sidereal Standard and Transit of Venus clocks) for its old grid­iron pendulum.'

Despite what Airy wrote, Arnold 1 still retained a gridiron pendulum on 1 January 1909 when Chrisitie compiled a list of clocks at the Observatory (RGO7/44). The published results show that Hardy was absent from the Observatory for around ten to eleven weeks in 1874, having been dismounted on 19 February and remounted at some point between 1 and 6 May. The exact date of its return was not recorded in either the published observations or the journal of the Astonomer Royal or his Chief Assistant.

In his 1878 Report, Airy wrote: 'The clock" Hardy" frequently used with the Transit-Circle, had become exceed­ingly rusty, and has received extensive repair.' The published results show that Hardy was absent from the Observatory for just over eight weeks, having been sent to Dent on 13 January 1878 and returned on 11 March.

Given that Airy clearly rated the zinc & steel pendulums, it has to be asked: did he have Hardy's pendulum changed for one of zinc & steel in 1874 or 1878, but fail to mention the fact? It seems that this may be what happened as in a letter published in the December 1886 issue of The Horological Journal, Thomas Buckney says of the clock:

'Some years ago this mercurial pendulum was replaced by a zinc and steel one, the change resulting in a most marked improvement in the going of the clock.'

As Buckney's statement cannot as yet be verified, the best that can presently be said about when a zinc and steel pendulum was fitted is that it was at some point between 1869 and 1899, with 1878 looking to be the most likely date. A search of the 'correspondence with tradesman' in the archives may shed more light on the the the timing as well as the accuracy of the information above.

Assuming that Christie was not in error when he recorded in 1907 that Hardy had a gridiron pendulm, one has to ask when was it first fitted and why.

Normally when pendulums of the Observatory clocks were replaced, the original pendulums were kept and their location recorded in the inventories. This does not appear to have happened in the case of Hardy. Also now lost is the beat scale, which can be seen to be missing in photographs from the 1960s.


The mysterious iron 'Mounting Stud'

The National Maritime Museum inventory records the presence of what is described as a 'Mounting Stud associated with the clock. Object ID: ZAA0591.4. Probably made of iron and somewhat coroded in the past, there is seemingly no record of where within the clock it was originally located. Since it is painted black, it may have been removed from the brickwork in which the clock was mounted when the wood lining was introduced in the 1990s.


Issues with the clock when used with the Mural Circle for transit observations

Transit observations with the Mural Circle began on June 1812, with regular observations ceasing on 3 March 1814  (Greenwich Obs 1814), ... but restarted later that month on 22 March (but were published in with the Observations of North Polar Distance made with two microscopes rather than separately as they had been previously. These observations ceased at the end of 1822.

From xxx Mural circle used for Transit Observations when Transit intrument was out of use until at least 1832 and used with a journeyman clock set to beat in time with Hardy


Table comparing the frequency of cleaning of Hardy and Graham 3, June 1812- Sep 1822

The data below is taken from the published volumes of Observations. The figures in brackets at the end of each entry give the number of days for which the clock was out of action. (NS) = Not stated.

Graham 3
1812 Oct 1 'The Circle clock was taken down to be cleaned' (NS)
Nov 9 'After having run irregularly of a day or two, Hardy was sent for who applied a little oil to the pallets' (0)
1814 Dec 9 'Took down the Clock to have it cleaned' (11)
1816 Jul 29 'Mr. Hardy took down the clock to be cleaned' (4)
Aug 5 'The Transit Clock was taken down to be cleaned' (0)
1817 Aug 8 'The Transit Clock was taken down and cleaned' (0)
1818 Jun 5 'Mr. Hardy took down the clock to be cleaned' (6)
Dec 28 'The Transit Clock was cleaned by Mr. Johnson' (0)
1819 Dec 30 'Mr. Hardy took down the clock to be cleaned' (36)
1821 Sep 10 The clock was taken down, in order to put up a new one, made by Messrs Molyneux and Cope.

The period considered is too short to be able to make any meaningful comparison about how frequently the two clocks needed cleaning. What is striking however is that when Hardy was cleaned it was usually out of action for days at a time. This is quite unlike Graham 3 which was always cleaned and put back into service the same day. Caution however is required before jumping to any conclusions. After 3 March 1814, there was no pressing need for the clock to be put back into use as after that date, transit observations made with the Mural Circle were downgraded in importance, with Pond relying on those made with the Transit Telescope instead. Once Hardy had been moved into the Transit Room however, it was important that it should be out of action for as short a time as possible. From them until Dent removed Hardy's escapement in February 1830, the clock seems to have been cleaned and set going on the same day.


Cleaning of the clock November 1824 - Feb 1830

As in the table above, the data below is taken from the published volumes of Observations. The figures in brackets at the end of each entry give the number of days for which the clock was out of action. The table covers the period from November 1823 (when Hardy was moved from the Circle Room to the Transit Room) to February 1830 (when Dent replaced Hardy's escapement with a deadbeat escapement of his own. Although there is no mention of the clock being cleaned during or immediately following it being moved to the Transit Room, logic would suggest that it is likely to have been cleaned around that time.

1825 May 18 'Mr. Hardy took down the clock to clean it, and on the 21st it was put up again' (3)
May 24 'Mr. Hardy stopped the clock to apply some oil; it was set going again nearly at sidereal time' (0)
1827 Feb 21 'Mr Hardy stopped the clock, to apply fresh oil and make some alterations in the springs of the escapement' (0?)
Jun 26 'Mr. Hardy cleaned the Clock' (0)
1828 May 5 'Mr. Hardy cleaned the clock' (0)

Roberts (English Precision Pendulm Clocks, 2003) states (p.86), but without quoting a source:

'Because Hardy's movements are very sensitive to any build up of dirt on the pallets; it can result in a gaining rate of several seconds a day; they have to be cleaned very regularly. In the case of  the Greenwich Clock this was  roughly every nine months.'

The 'roughly every nine months' comment is not borne out by the data in the two tables above. Although Pond may in error have omitted some occassions when the clock was cleaned, it seems unlikely that so many would have been omitted by accident. An examination of RGO5/222 and RGO5/4-16 may shed further light on any possible omissions.


Cleaning of the clock: Feb 1830 - Dec 1850

At the start of this period, Hardy's escapement was replaced with a deadbeat excapement. The period ends n 1850 when the clock was dismounted and moved to the room next door for use with the Airy Transit Circle. As the clock was away from the Observatory for xxx in 1830 having the escapement replaced, it seems likely that Dent also cleaned the rest of the clock at this time, even though the published record does not specifically say so

1831 Dec 13 'After the passage of the Sun, Mr.Dent took down the clock to clean it' (2)
1834 Apr 10 'On the 10th, Mr. Dent cleaned the clock and set it going again', but the clock was taken down on Apr 8 for this purpose (2)
1836 Nov 18
Dec 6 'Hardy was again taken away and Arnold 2 used' (4). This is when the 'jewelled holes' were removed. The clock was presumably also cleaned (4)
1839 Jun 10 (14/21)
1845 Nov 26 (14)
1850 Dec 27 Moved for use with Airy Transit Room and ready to use by 1 Jan

taken out of service in 19 Feb 1874, brought back into service 5 May 1874


Hardy's view of Maskelyne and Pond

Hardy's letter of 29 July 1818 complaining about the Observatory. Reproduced under the terms of a Creative Commons Attribution-Non-Commercial 3.0 Unported License (CC BY-NC 3.0) courtesy of Cambridge Digital Library (see below)

Hardy paints a poor picture of his relationship with Pond. Having got to a bad start as a result of the Hardy's bill, the relationship does not seem to have improved in the following years as evidenced by the letter written by Hardy in 1818 to the Secretary of the Board of Longitude. In it, he complained of the treatment he had received during a recent visit, going on to say 'ever since the late Dr. Maskelyne I have been treated with the greatest indifference when there on business and a great want of care has been showen towards the clock which I made ... (RGO14/23/244)'.

It was perhaps his ongoing annoyance about his treatment that caused him to include the introductory letter, dated 25 April 1820, that was published to accompany his paper in Transactions of the Society Instituted at London for the Encouragement of Arts, Manufactures and Commerce. Volume 38. In it, Hardy painted a rosy view of his relationship with Maskelyne:

‘The order for the clock was unlimited in price, and directed me to consult the Doctor on every particular connected with it. I therefore waited on the Doctor to receive his instructions; his treatment to me was kind and hospitable, and he gave me every encouragement to exert myself, and to complete the clock in such a manner as to be durable and certain in its performance.

‘I cannot here refrain from saying a few words to the memory of the late Rev. Dr. Maskelyne. My first knowledge of the Doctor was at the period above mentioned ; at that time they were making great improvements at the Observatory, which engrossed the whole of the Doctor’s attention; the room for the new instruments was then building, and such was his perseverance, that he was out there in the most inclement weather, superintending the workmen, which I believe tended much to shorten his days: he was most indefatigable in his application to the interest of the Observatory, no doubt, for the great end of advancing the science of astronomy, in which he delighted. His attention to the business of the Observatory was punctual and strict, and he continued to transact it till within a week or two of his death, an event which, it will be allowed, was a great loss to the public, and to be regretted the more as he did not live to see the new instruments completed, in which he took such pride, and which he strove so much to accomplish.’

Roughly six weeks after writing this Hardy sent a signed manuscript copy of the last paragraph to Maskelyne's widow or daughter. Now preserved amongst the records of the National Maritime Museum, it can be viewed here: Hardy, in Memory of Maskelyne 7 June 1820 (REG09/37).

Hardy's 1818 letter suggest he was quite possessive about the clock and that he had failed to understand the exposed environment in which the clock would be required to operate. It should be noted that his comments about Maskelyne and the ordering of the clock were not written until after he had complained about Pond in 1818. Clearly frustrated, perhaps he then felt the need to put his massaged version of events on the public record, and deflect all responsibility for the expensive and unnecessary work he had carried out while making the clock onto Maskelyne on whom he heaped nothing but praise.

Despite Hardy's irritation with Pond, he continued to service the clock until 1830 when his ire was provoked again after Pond arranged for his escapement to be replaced with one made by Dent (see below).


1830: Dent replaces the escapement and an argument ensues

In February 1830, Dent replaced Hardy's escapement with a dead-beat one of his own and at the same time, signed his name on the dial. This incensed Hardy so much that he wrote to the Admiralty who by then had taken over all the Board of Ordnance's responsibilities for the funding of the Observatory. The minutes of the meeting of Council of the Royal Society on 28 June 1830 record:

'The Admirarlty having transmitted a letter from Mr. Hardy relative to certain alterations made in his clock at the Royal Observatory.
The Astronomer Royal communicated a written explanation on the subject.
Resolved that this explanation be transmitted to the Admiralty pursuant to the recommendation of the Visitors at the last Visitation [which had taken place on 29 May]'. (RGO6/22/197)

It would seem that Hardy was not satisfied with what the Admiralty told him as he wrote again on 14 October. This time his letter was forwarded to Pond who was asked for an explanation (RGO5/230/234). Pond's reply cannot be located, nor can the minutes of the Visitation. More unfortunately, neither can either of the letters from Hardy. A copy of Pond's 'written explanation', dated 17 June 1830 is however preserved in the Royal Society Archives (RS/MS371/58).

Whatever it was that Hardy was complaining about, in Pond's view, as expressed in the 17 June document, the only complaint deserving serious attention was the insertion of Dent's name on the dial. This was addressed by Pond who also provided an explanation as to why Dent was allowed to fit a new escapement. What follows below has been put together from what Pond wrote and the published volumes of Greenwich Observations.

Starting in 1827, Hardy's clock had begun to run somewhat eratically. Pond decided that the problem lay in the degree of compensation being provided by the mercury in the pendulum. In his 'written explanation', he wrote:

'About the month of February last, the clock after various unsuccessful experiments (made [over the past two years] by Mr. Hardy himself or by Mr. Taylor [the First Assistant] at Mr Hardy's suggestion,) on the quantity of compensating quicksilver, continued to go very indifferently. Mr Hardy though apprised, by my direction, of the imperfections of his clock not coming down frequently enough to remove or even palliate the inconvienience. And here it must be noticed, that to continue any of the Greenwich observations with an imperfect instrument is doing infinitely more micschief than omitting them altogether, since such observations, according to our peculiar method, vibrate the mean, and injure the result of other observations in themselves good. I became, therefore much alarmend at the continued irregularity of this clock.'

Pond did not publish details of how he calculated the rate of the clock. The figures in the two tables below from 1829 and 1830 differ from those listed in the transit observations. There is no evidence however that supports Roberts' (2003) assertion that 'In 1830 the clock's rate went up by nearly four seconds a day'. 

The table below shows the various interventions that were made starting in 1827.

1827 Feb 21: Mr. Hardy stopped the clock, to apply fresh oil and make some alterations in the springs of the escapement. A small quantity of mercury was likewise added to the pendulum weight (link)
Feb 24: Lowered the weight of the pendulum (link)
June 26: Mr. Hardy cleaned the clock (link)
Dec 28: Stopped the clock about 40 seconds, and lowered the weight of the pendulum (link)
1828 Apr 29: The daily rate of the clock for some time past having been compared with the state of the thermometer, indicated that the pendulum was not sufficiently compensated. The clock was stopped for some time to examine the mercury, and set going again nearly at the same time as before (link)
May 3: Mr. Hardy applied a new glass cylinder to the pendulum of the clock, containing a column of quicksilver nearly half an inch longer than the former (link)
May 5: Mr. Hardy cleaned the clock (link)
May 7: Raised the weight of the pendulum two divisions (link)
1829 Feb 18: From the observations made during the late cold weather, the want of compensation (before suspected) appeared so evident, that a quantity of quicksilver, about one eighth of an inch in height, was added. The clock was stopped on the occasion, and set going again nearly at the same deviation from sidereal time as before (link)
Feb 20: Raised the weight of the pendulum three divisions (link)
Feb 28: Stopped the clock about 40 seconds, and lowered the weight of the pendulum two divisions (link)
1830 Feb 13: After the passage of the Sun, the clock was taken down by Mr. Dent, in order to apply a new escapement, and a clock of his own substituted in the place thereof (link)

Tabulated account of the error and rate of the Transit Clock in 1829. Digitized by Google from the 1829 volume of Greenwich Observations at the University of Princeton

Tabulated account of the error and rate of the Transit Clock in 1830. Digitized by Google from the 1829 volume of Greenwich Observations at the University of Princeton

Pond continued his explanation by saying: 'At this time I saw Mr.Dent by accident in the transit room.' He then explained that Dent had won the previous year's chronometer trial and had also supplied a 'clock for the chronometer room of very superior excellence [Dent 2]'. When Dent offered to take Hardy's clock and 'make it perform as well' as Dent 2 Pond decided to take up the offer explaining that:

'Another clock could not be permanently substituted, as the stone pier is constructed expressly for Mr. Hardy's clock, so that in this emergency no method of proceeding with the observations appeared as advisable as availing ourselves of Mr. Dent's offer.'

This was all very well, but it leaves a lot of questions unanswered. Firstly, what was Dent doing in the Transit Room? Secondly, why did Pond not simply bring a clock from elsewhere in the Observatory for use temporarily while awaiting for Hardy to come and fix his clock? 

Whilst it was true that the way the Hardy Clock was mounted in the Transit Room prevented another clock from being mounted temporarily in its place on the same pier, there was nothing to stop one from being mounted on the south wall of the Transit Room in the same location that the Transit Clock (Graham 3) had occupied from 1750 until 1780. We know however that Graham 3 was not available as it was in use by Sabine for his pendulum experiments that were taking place at the far end of the building. Likewise, Dent 2 was in use in the chronometer Room and Earnshaw was in use in with Pond's 25-foot Great Zenith Tube. But what of the two clocks by Arnold or the other two clocks by Graham?

What Pond chose not to reveal in his 'written explanation' was that when Dent took Hardy away, a clock of his own was substituted as the Transit Clock. It remained in use for just over six weeks until clock Hardy was returned. This was the only time that anorther clock was substituted for Hardy during the whole of Pond's tenure, suggesting he was rather averse to the concept of a reserve Transit Clock. Airy had no such qualms, making use of both Graham 1 and Arnold 2 in the period 1836–1850.

As far as Dent putting his name on the dial was concerned, Pond did not either authorise it or condone it and believed that it was done 'in a manner likely to cause offence'. The inscription read: the inscription 'Escapement by Dent London A.D. 1830'. When Dent was challenged by Pond about this, he justified himself by 'contending that his escapement was entitled to a Public trial, and objected to the removal of his name without at the same time removing the escapement also'. With that threat in mind and no doubt recalling Hardy's own threat to remove the clock unless he was paid the full £325 asking price, Pond thought that the continuance of the observations without furher sources of interuption was more important than any other consideration, going on to comment that the clock had run well after the alteration and had continued to do so.

In his 1990 paper, Charles Allix writes (p.610):,

'the removal of Hardy's escapement by E.J. Dent might never have happened had only Hardy twice not failed to attend to his clock when given notice to do so.'

Much the same was repeated by Roberts (p.86) in 2003. Neither author quotes a source. In his 'written submission' Pond made no reference to Hardy having been summoned once let alone twice to sort out the clock. In addition to what he said above, what he said was:

'It should be further stated that the whole of the above transaction took place under the impression on my mind that Mr. Hardy was prevented by indisposion from giving the necessary attention [to the clock].'

If Allix is correct and Hardy did twice fail to show up, it is possible that his information came from RGO5/10 or RGO5/222 neither of which has yet been checked for this article.

Meanwhile, in the autumn of 1829  John Wrottesley, a founding member of the Royal Astronomical Society, began constructing an observatory at his house less than half a mile to the south of the Royal Observatory in Montpelier Row in Blackheath. He appears to have been on good terms with the staff at Greenwich as his published catalogue of stars tells us that the staff of the Royal Observatory helped him determine the longitude of his observatory. It also gives the following rather intriguing information about his transit clock:

‘On the 1st of December, 1829, a clock with the dead-beat escapement, and having a mercurial compensation pendulum, was fixed to the pier above described. The wheel-work of this instrument is by Hardy, but the pendulum was made by Mr. William Richardson of the Royal Observatory. The beat of this clock is remarkably clear and loud, and is heard distinctly in very stormy weather. The arc of vibration of the pendulum was, in June 1831, 4° 47':5, and in February 1835, and now (September 1835), it is 4° 55'. This clock was subjected to a severe trial, by being set up in a new and damp building immediately anterior to the commencement of a winter so intensely cold as that of 1829-30; but I have no ground to suspect that any portion of the works was permanently affected by it.’

As well as having knowledge of Wrottesley's clock, Richardson also observed from time to time with the Transit Telescope at Greenwich. This raises several intriguing questions:

  • Did Richardson's knowledge of Wrottesley's clock influence Pond's decision to allow Dent to change the escapement for a deadbeat one?
  • Why did Wrottesley's clock have a dead-beat escapement rather than Hardy's own?
  • Was Hardy's escapement more affected by the thickening of oil in cold weather than a dead-beat one?

An examination of the temperatures recorded at the Royal Obsevatory shows that the temperature inside the Circle Room was more or less permanently below 0oC (32oF) from the middle of January 1830 until at least 5 February. It seems highly likely that the temperature in the Transit Room was much the same. Although it is not known what oil Hardy had used to lubricate the Clock at Greenwich, we do know that Maskelyne applied an oil made of  'an equal Mixture of Olive Oil and Oil of Sweet Almonds' to the pallets of the Transit Clock (Grahm 3) in 1781 and that in 1807 he 'cleaned away all the dirty oil from the swing wheel and pallets of the verge; then put a little of the best olive oil to them'.

In 1842, Wrottesley relocated his observatory to Wrottesley Hall in Staffordshire taking his transit clock by Hardy wiith him. In 1854, he described it as follows:

'The Hardy or transit clock has behaved exceedingly well during the whole course of the observations; the rate has been remarkably steady, and the beat is, as before loud and distinct. This is, indeed an admirable mechanism, and of all the instruments in my observatory has given me the most unalloyed satisfaction.' (Journal of Science and Art)

Most ot the Wrottesley family papers were destroyed when Wrottesley Hall burnt down in 1897, meaning that significant further information on the history of the clock is unlikely to come to light. Following Wrottesley's death in 1867, his clock and observatory seem to disappear from the records.

As an aside, it is worth recording that as well as making the pendulum for Wrottesley's clock, Richardson made a similar pendulum that was fitted to Graham 3. Signed: RICHARDSON Royal Observatory, but undated, it was still in use at Herstmonceux in 1975 (Howse 1975), it is now in the care of the National Maritime Museum, a photo of it can be seen here.


Clock Makers: their signatures and the work of others

Looking back to the trial of Hardy's escapement in 1807, it is worth asking if Hardy was guilty of a similar naming offence to that of which he accused Dent? We know from what he wrote in 1820 that he fitted his own escapement onto an exisiting clock by another maker. That clock is believed to be one that is very clearly signed 'Raymond London' on the backplate, but has a dial signed 'Willm. Hardy/ Invt. et Fecit/ London/ No.2'. Click here to view.

Prior to this and long before Hardy had launched himself onto the clock-making scene, Maskelyne had asked the chronometer maker Thomas Earnshaw to make a clock for the observatory in Armagh. The clock he produced performed exceedingly well when put on trial at the Royal Observatory in 1792 before being shipped to Armagh in 1794. As McEvoy has pointed out (Maskelyne, 2014), given the success of the clock, it is perhaps surprising that Earnshaw was not immediately commissioned to make a similar clock for Greenwich to replace Graham 3 which had undergone several alterations over the years. Some years later, in 1808, in Longitude: an appeal to the public: stating Mr Thomas Earnshaw's claim to the original invention of the improvements in his timekeepers, ... (p.48), Earnshaw wrote:

'After I had pointed out to Dr. Maskelyne the absurd manner in which the famous Mr. Arnold had jewelled the transit clock [Graham 3] at Greenwich, he wanted me to re-jewel it, and do any thing else I thought necessary; I refused, saying, that let me do what I might, it was still Graham's clock, and his name was on it, and it the Royal Society, after the proofs I had given of my superiority, did not choose to order as good a clock of me, as I could make, they might keep their old one as it was, as a standing monument of disgrace to Mr. Arnold and others, who had botched it up in the manner it now is.'

Whether or not Dent was aware of this is not known by this author, but one can't help suspect that he was.

In his appeal, it would appear that Earnshaw was being somewhat economical with the truth as he claims on p.47 that the Amargh clock was the first that he had ever made and on p.40 that prior to then he had 'never made a clock, and did not know how many wheels were in one'.  It is hard to see how this can be true as the Board of Longitude bought a clock from him in 1791. It was sent with the astronomer William Gooch on H.M.S. Daedalus for transfer to H.M.S. Discovery (which was under the command of George Vancouver) where it was used during the mapping of the coast of north-west America. It was later used by Matthew Flinders to map Austrailia during his circumnavigation on the H.M.S Investigator. In 1828 it was transferred to the Royal Observatory and during its time there was known as Earnshaw. Earnshaw also refers to another earlier clock on p.45, though it is possible that the date given is in error, as others have been later corrected in the text.


1836: Dent is asked to make the beat of the clock louder

One of the unintnended consequences of substituting a dead-beat escapement was that the beat appears to have become much quieter and could not be heard by the observers in certain observing conditions. Although nothing is recorded that directly states this, there are three reasons to believe that this was so:

  1. There is no publshed record of the clock being hard to hear prior to 1830
  2. Although this seems to be the first reference to the loudness of the clock, the clock Hardy later supplied to the Cambridge Observatory (which still has its original escapement) was recorded by Airy as being noteworthy 'for the general steadiness of its rate, as [well as] for the loudness and unusual distinctness of its beat' (Cambridge Observations, Vol 1, 1829)
  3. In 1836, Airy asked Dent to try and make the Greenwich clock louder (See correspondence and Airy's Journal (RGO6/24))


The preservation of Hardy's escapement and the parts removed by Dent in 1836

Once Dent had removed Hardy's escapement, it was returned to the Observatory where it was preserved. Likewise, the items removed by Dent in 1836. Both the escapement and the other items are now lost. The former survived until at least 1933 and the latter until at least 1864.

For reasons yet to be established, the Admiralty instructed Airy to send Hardy's escapement to them during the reporting year 1839/40 (Visitors Report 1840). It was eventually returned in 1843/44 (Visitors Report 1844).

The various inventories record the following:

1840, May 15 Inventory, In the Octagon Room: Hardy's escapement (item 83); 'Old work of the transit clock, removed in 1836' (item 96). (RGO6/54/77 & RGO39/1/6).

1864 Inventory. In lower room of Great Equatorial Building (which at this time was a bit of a dumping ground): Escapement (item 79);  'Old work' (item 112).

1911 Inventory, escapement recorded as being in 'New Chronometer Room' in the Great Equatorial Building (RGO39/4/131). 'Old work' not found.

1926 Inventory. Escapement still present in the 'New Chronometer Room' (RGO39/5/233). 'Old work' not found.

1933 inventory (RGO39/6/221), Escapement still present in the 'New Chronometer Room', but the location of  has been later crossed out and altered to 'Time Depart[ment]'.


1854: The introduction of a chronograph and the subsequent alterations made to Hardy

Looking northwards in the Chronograph Room. The chronograph is standing on the table in the centre, its conical pendulum being independently supported by a bracket attached to the telescope pier. The person on the right appears to be loading a new recording sheet onto the drum, whilst the one on the left appears to be transcribing the results from another. Originally published in the 1862 volume of The Leisure Hour, the image was later reused in the 1891 edition of Dunkin's The Midnight Sky, which is where this copy comes from

In 1854, a chronograph was installed at the Observatory. Before looking at how Hardy was altered to provide it with electrical impulses at one second intervals, it is helpful to know more about how the chronograph worked. Airy provided a detailed account of its construction in the 1856 volume of Greenwich Observations. He also provided a brief description in the introductions to Greenwich Observations from 1854 onwards. In his series of articles in the Leisure Hour in 1862, his Assistant Edwin Dunkin used this as the basis of a more basic description:

'Before describing the recording apparatus, it is necessary, however, to state that the original method of observing transits consists in counting the beats of a clock, and estimating the fraction of a second when the object passed one of the wires in the telescope. The clock-time is then entered into the observer's book, the operation being repeated as many times as the number of wires. The new method of observation, or the chronographic method, is much more simple when the registering apparatus is in good working order.

The chronographic recording apparatus is placed in the ground floor of the north dome [i.e. the eastern summerhouse]. The clock, which is of peculiar construction, the motion being governed by the conical rotation of a pendulum, gives a sensibly uniform motion to a revolving brass barrel, which is in connection with it. The barrel is covered with woollen cloth, upon which a sheet of paper is folded, the ends of the paper being gummed together. A spindle which is attached to the clock turns two long screws, causing a travelling frame to traverse the whole length of the barrel. This frame carries two levers, each armed at one end with a pricking point, mounted in such a way that, when the opposite end of the lever is pulled away from the barrel, the pricking end is pushed against it, and makes a permanent puncture on the paper. Two galvanic magnets are fixed on the travelling frame, so as to attract the lever ends opposite to the pricking points. All that is required, therefore, to cause those points to make punctures upon the paper, is to send galvanic currents through the magnets.

One of the prickers is devoted to the registration of the seconds of the clock in the transit-circle room, the communication being made by wires connecting the clock with the travelling frame. The other pricker is used for the registration of the times of observation when a star passes behind a wire in the telescope, a similar communication with wires being made. For the proper generation of the galvanic force, a voltaic battery is included in the circuit of each course of wires.

On this recording instrument, therefore, nearly all transits observed with the transit-circle, altazimuth, or great equatorial, are permanently registered. They are extracted from the sheets, and converted into figures on the following morning-an operation requiring care, but which, in skilled readers, is not considered a very difficult proceeding.'

When first introduced, Airy had hoped that the pendulum of the chronograph could be used for marking intervals of a second on the sheet. This proved unsuitable and Hardy was adapted to provide the signals instead. This too was not straight forward as Airy had to change to make two subsequent changes to the way he did it. The last of these was made in 1856. Airy explained what had appened prior to 26 May 1854 in his Report to the Board of Visitors:

'The Barrel-Apparatus for the American method of Transits has been practically brought into use: not, however, without a succession of difficulties, arising sometimes from causes very hard to discover. When the instrument was approaching to a serviceable state, there still remained an imperfection in the ill-defined form of the punctures on the paper. At this juncture, Lieutenant Maury, U.S.N., paid me a brief visit, and in the course of inspection of the instruments he alluded to this very defect, and to the method which had been used in America for its remedy. Although my apparatus did not admit of the same application, yet, possessed of the principle, I had no difficulty in embodying it in a form adapted to my wants; the prickers were mounted on springs, and now the punctures are perfectly round. The paper on which the punctures are to be made is folded in a wet state, upon a brass cylinder covered with a single thickness of tailor's woollen cloth, and has its edges united by glue.

The punctures, it will be remembered, are produced by two systems of prickers, which have nothing in common except that they are carried by the same travelling frame, which moves slowly in the direction of the barrel-axis while the barrel revolves beneath it. These require separate notice.

One pricker is driven by a galvanic magnet whose galvanic circuit is completed at every second of sidereal time. It was at first intended by me that the completion of the circuit should be effected by the same smooth-motion clock (regulated by a conical pendulum) which drives the barrel. I found, however, that I could not ensure such a constancy in the radial arc of the pendulum as would make its rate sufficiently uniform to entitle it to be considered as the fundamental clock; and, moreover, there was a little difficulty in referring its indications to those of the transit-clock (which must be used in some cases). I, therefore, carried wires from the pricker-magnet to the transit-clock, connected there with springs whose contact is made at every second by the transit-clock. At first, the contact was made by the touch of a pin fixed in the pendulum-rod; and this construction for a time answered well. But it so happens that, in our transit-clock, the pendulum is carried by one frame, and the point of attachment of the galvanic springs by a different frame: it was impossible to maintain these in steady adjustment; and the rate of the clock was sensibly disturbed. I have now adopted the following construction, which promises to succeed better. A wheel of 60 teeth is fixed on the escape-wheel-axis, and the teeth of this wheel in succession make momentary contacts of the galvanic springs.
The position of the springs is so adjusted that the effort of the wheel-tooth upon them occurs only when one escape-tooth has passed the sloping surface of the pallet, and the other escape-tooth is dropping upon its bearing; and thus the resistance of the springs does in no way affect the legitimate action of the train upon the pendulum.

The other pricker is driven by a galvanic magnet, whose circuit is completed by an arbitrary touch- made by an observer's finger upon a contact-piece. Of contact-pieces there are three. One is upon the eye-end of the Transit Circle: it effects the contact of two brass rings which (by means of wires passing in the interior of the tubes) are connected with two other brass rings surrounding the axis and touched respectively by two springs on the pier leading to the galvanic wires. The other two contact-pieces are upon the rotating base-plate of the Altazimuth (one to be used with Vertical Face to the Right, the other with Vertical Face to the Left); the parts which they bring together carry springs which touch two large horizontal rings on the fixed base; and these rings are connected with branches of the same pair of wires which communicate with the Altazimuth. Thus Altazimuth observations are referred absolutely to the same time-record as Transit-Circle observations.

It is necessary to mark upon the revolving barrel the beginnings of some minutes and the numeration of some hours and minutes. This is done by arbitrary punctures given by the observer's touch, upon a simple system which scarcely merits detailed description.

In order to guide the eye through the multitude of dots upon the sheet, lines of ink are traced by means of a glass pen, which is attached to the same frame as that by which the prickers are carried.

I have only to add that this apparatus is now generally efficient. It is troublesome in use; consuming much time in the galvanic preparations, the preparation of the paper, and the translation of the puncture-indications into figures. But among the observers who use it there is but one opinion on its astronomical merits—that, in freedom from personal equation and in general accuracy, it is very far superior to the observation by eye and ear.'

The final alteration took place in 1856. Allthough significant, Airy did not report it to the Board.

‘The opportunity was taken of the Transit-Clock being removed for repair in the month of November 1856, to have one of the teeth in the wheel before mentioned cut away, so that once in each minute no contact of the two springs takes place. The omission of the corresponding puncture on the revolving barrel thus marks with certainty the commencement of each minute.’ Intro to Greenwich Obs 1856

The timing of the various alterations to Hardy (as extracted from the volumes of published observations to which links are given) was as follows:

1853 Chronograph intstalled
1854, Jan 6 'An apparatus was attached to the pendulum of the Transit-Clock, for the purpose of closing a galvanic circuit in the middle of each oscillation'. (Link)
1854, Feb Removed for cleaning on Feb 17 and returned on Feb 23, Mudge and Dutton used in the meantime. (Link)
1854, Apr 11 Taken down and Graham substituted (Graham 3?). (Link)
1854, Apr 12 Taken down and Mudge 'temporarily set up'. This would suggest that the Apr 11 entry was incorrect though it does not appear to have been corrected in the errata lists published in the suceeding years (Link)
1854, May 15 Hardy brought back into use. Airy records: 'To the clock is attached a supplementary wheem with sixty teeth, on the prolongation of the Axis of the scape wheel, so that at every beat of the clock one of the teeth presses upon the upper of two springs a, and closes the galvanic circuit'. (Link)
1855, Jul 11-14 Clock out of action whicle galvanic contact springs altered. (Link)
1856, Nov 18 Dismounted on November 18 for cleaning and Mudge and Dutton used in its stead. (Link)
1856, Nov 24 Remounted. While being cleaned, Airy took the opportunity to have one of the teeth in the wheel cut away, so that once in each minute no mark was placed on the chronograph drum. (Link)


The reserve Transit Clocks from 1823 onwards

Arnold 2

Mudge & Dutton

Arnold 1


Historical summary with references
1807 Hardy's escapement trialled at Royal Observatory for the Board of Longitude
1808? Clock ordered for Greenwich from Hardy by Nevil Maskelyne for use as a transit clock with the new Mural Circle that is on order.
1811 Clock delivered and Hardy submits his bill for £325, which is then disputed.
1812 The Council of the Royal Society recommends to the Ordnance that that Hardy be paid a sum of £200 guineas for the clock. (RS MS 372/153 & RGO6/22/68).
1816 New 10-foot Transit Instrument by Troughton replaces Bradley's 8-foot Transit Instrument of 1750 on raised piers in the same location.
1823 4 Nov: Hardy Moved from Circle Room to Transit Room for use as the Transit Clock, with the new Transit Telescope. (Greenwich Observations 1823)
22 Nov: New second hand fitted (Greenwich Observations 1823)
1828 3 May: First recorded alteration to the pendulum 'Mr Hardy applied a new glass cylinder to the pendulum of the clock containing a column of quicksilver nearly half and inch longer than the former.' (Greenwich Obs 1828)
1830 13 Feb: 'After the passage of the Sun the clock was taken down by Mr. Dent in order to apply a new escapment, and a clock of his own substituted in place thereof.' (Greenwich Observations 1830). This was done because the The rate of the clock had become extremely unsteady (Intro to Greenwich Obs 1836)
30 Mar: 'Hardy's clock was put up again by Mr.Dent, having had a dead-beat escapement applied (Greenwich Observations 1830).
Hardy later complained to the Royal Society as Dent also inscribed the dial (in keeping), with the words 'New Dead Beat Escapement by Dent
1836 In Airy's first year in office, a number of clocks were altered by Dent. in December 1836 Hardy had its jewelled holes removed by Dent. After the alterations the pivots turned in brass holes (Intro to Greenwich Obs 1836)
1850 The Troughton 10-foot Transit Instrument replaced by the Airy Transit Cicle which had been erected in the Circle Room which had been adapted to receive it. In December, Hardy transferred to the Transit Circle Room for use as the Transit Clock. To this end, it was dismounted from its case and mounted so that the dial was in the lower part of the south collimator pier facing nothwards, in which position it remains today. The telescope was bought into use at the start of 1851
1854 Chronograph introduced.
6 Jan: 'An apparatus was attached to the pendulum of the Transit-Clock, for the purpose of closing a galvanic circuit in the middle of each oscillation'.
By 26 May,  Removed for cleaning on 17 Feb and returned on 23 Feb, Mudge and Dutton used in the meantime.
Taken down on 11 Apr and Graham substituted (Graham 3?). Hardy taken down on 12 Apr and Mudge 'temporarily set up'. 15 May, Hardy brought back into use Gren Obs records: 'To the clock is attached a supplementary wheem with sixty teeth, on the prolongation of the Axis of the scape wheel, so that at every beat of the clock one of the teeth presses upon the upper of two springs a, and closes the galvanic circuit
1855 11-14 Jul. Clock out of action whicle galvanic contact springs altered (Gren Obs)
1856 Dismounted on November 18 for cleaning and Mudge and Dutton used in its stead. Eye and Ear method used until Hardy remounted on 24 November (Greenwich Obs 1856). While being cleaned, Airy took the opportunity to have one of the teeth in the wheel cut away, so that once in each minute no mark was placed on the chronograph drum (Intro to Greenwich Obs 1856).
1864 Clock cleaned taken down on 29 April for cleaning and bougth back into use on 3 June (Greenwich Observations 1864). Winding of the clock switched from one a week (Mondays) to twice a week (Mondays and Thursdays).
1867/8 'I have given a new form to the head of the clock, for admission of small tin boxes in which a few lumps of quicklime will be placed, in order to keep the air about the wheel-work in a state of dryness.' (1868 Report). The quicklime was replaced monthly
1871 Dent 1906 installed in Magnetic Basement as the new sidereal standard providing impulses for the chrononograph and reducing Hardys role to that of a reserve clock.
1893 Described in 1893 inventory (RGO39/10/29) as 'Clock by Hardy' and being in the Transit Circle Room, with no infromation about the pendulum. Nor is there any reference to an earlier pendulum being stored in either of the two Chronometer Rooms or the Museum that had been set up in the partially constructed New  Physical Building.
1954 30 March: last published observation made with the Airy Transit Cicle taken by Gilbert Saterthwaite (Greenwich Observations 1954). By November, the movement and driving weight were being stored in the East Library at Greenwich (Inventory, Nov 1954). The location of the pendulum was not recorded
1967 Refurbished Meridian Building opens to the public for the first time. Hardy on display in 1851 location, but on loan from the Astronomer Royal
1975 Clock running (Howse, 1975)
1984 Conservation work carried out at the National Maritime Museum
1991 Disassembled and lightly cleaned prior to reassembly ready
1990s? Clock running, but sometimes set to mean solar time and sometime sidereal time
1998 Hardy transferred to the National Maritime Museum on closure of RGO
2010 Dismounted for examination and oiling on 21 January, Remounted 9 March and set running
c.2018 Removed duing floor replacement and other building works
Articles and chapters on Hardy Regulators

Antiquarian horology

What’s Wrong With Hardy’s Escapement? Christopher Wood, Volume 9/8 (September 1976)

William Hardy’s Regulator. A.J. Turner, Volume 11/6 (Winter 1979)

William Hardy and His Spring Pallet Regulators. Charles Allix, Volume 18/6 (Summer 1990)

Design Analysis of a William Hardy Regulator Spring Detent. Leslie Paton, Volume 19/2 (Winter 1990)

What’s Wrong With Hardy’s Escapement? A Re-Appraisal. Christopher Wood, Volume 20/4 (Winter 1992)

English Precision Pendulum Clocks. Derek Roberts (2003), pp. 83-94.

Masklyne, Astronomer Royal. Rory McEvoy, Ed. Higgitt (2014), chapter 5


Hardy regulators with images online or in Antiquarian Horology

All the regulators below were originally fitted with Hardy's escapement.

Ordered by/for etc.
Other information
c.1807 Board of Longitude trial Dead-beat Bohnams Catalogue Marked 'No.2' on the dial
1808-11 Royal Observatory, Greenwich Dead-beat n/a
c.1814 Garnett Hill Observatory, Glasgow Hardy (1989)
National Museums Scotland, Object: T.1988.96
1814 Unknown Hardy (by Redfern / Stevenson) See Derek Roberts (2003)
c.1815? Brisbane's Observatory, Largs Scotland. Taken by him to Austrailia in 1821 (Paramatta Observatory)
Dead-beat PowerHouse Musuem, Object No: 9889)
1819-20 Military Academy Sandhurst Hardy (20th century) Chrisite's Catalogue Movement shown is from a different clock
1821 Royal Observatory Cape of Good Hope Dead-beat
c.1824? Cambridge Observatory Hardy (original) Whipple Museum, Accession Number 2800
c.1825? Unknown Hardy (Spring pallets restored 1993) Bonhams Skinner Catalogue
c.1825?? Unknown Hardy (19th century by Lecluse) National Maritime Museum, Object ID:ZAA0606) See also A.H.

Allix records that the Wrottesley clock was 'apparently' acquired by Durham University and implies a date of 1841 for when this happened. This is manifestly incorrect. It would appear that Allix muddled his notes. He quotes as his source an article by Howse published in Antiquarian Horology, (Autumn 1987,32). This was based on The Greenwich List of Observatories, published in 1986. Both the Howse articles record that it was Hussey's Hardy Regulator that ended up at Durham. Allix's incorret information was later repeated by Roberts in 2003.

No information has yet come to light about what happened to Wrottesley's Observatory following his death in 1867. Wrottesley hall burnt down in 1897, destroying almost all the Wrottesley family papers.

See also


Further Reading

Desccription of the two clocks supplied to Hassler by Hardy for his survey of the coast of the  United States. Papers on various subjects connected with the survey of the coast of the United States, Ferdinand Hassler, 1824

Hardy's obituary: Gentleman's Magazine, December 1832


Image licensing

The images reproduced courtesy of Cambridge Digital Library are more compressed than the originals and have been reproduced under the terms of a Creative Commons Attribution-NonCommercial 3.0 Unported License. Links to the individual images are as follows:

Image 1: Trial Results of showing the rate of Hardy (RGO14/23/243)

Image 2: Hardy's letter to the Board of Longitude, 31 May 1808 (RGO14/1/200).

Image 3: Hardy's letter to the Board of Longitude, 29 July 1818 (RGO14/23/244)

The following images are © National Portrait Gallery, London and are reproduced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported (CC BY-NC-ND 3.0) licence.

William Hyde Wollaston, by William Ward, after John Jackson. Mezzotint, early 19th century. National Portrait Gallery Object ID: NPG D36339

The following images are reproduced under the terms of a Creative Commons Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence (CC BY-NC-SA 4.0) courtesy of The Board of Trustees of the Science Museum.

Sir Joseph Banks (cropped from the original. Object Number: 1982-333/3


Working notes

See also RGO5/4,6,7,8,9, 10, 12, 12, 15, 16,  & RGO5/222