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Astronomical Regulator: Graham 3

 

page under construction

Known as Graham 3 since Airy's arrival at the Observatory in the mid 1830s, this particular clock was ordered in 1749 by the third Astronomer Royal, James Bradley as part of his re-equipping of the Observatory. It remained at the Observatory as a working clock until its closure in 1998 when it was transferred to the National Maritime Museum in whose care it remains (Object ID: ZBA0709).

Although signed Geo. Graham London. on the dial, the clock is known to have been made by his assistant John Shelton whose stamped signature is hidden on the underside of the back cock (McEvoy / Bonhams).

 

Brief history

Graham 3 served as the Transit Clock from 1750 until 1821 when it was replace by a series of clocks in quick succession, starting with a clock by Molyneux and Cope and culminating in 1824 with the Clock Hardy which remained in use as the Transit Clock until the last observation was made with the Airy Transit Circle in 1954.

Until 1871, the Transit Clock was the Observatory's de facto sidereal standard. Graham 3 was used with Bradley's 8-foot Transit Instrument from 1750 until 1816 when it was replaced by Troughton's 10-foot Transit Instrument which was erected in the same location on heightened piers. The first published observation made with the clock is dated 2 Sep 1750 (Greenwich Obs).

After 1821, Graham 3 was adjusted to Mean Solar Time (rather than sidereal time) and was located for a while in the newly set up Chronometer Room. By 1828, it had been transfered to the Quadrant Room where it was used by Captain Sabine for his experiments with Kater's pendulum swinging experiments:

Following the installation of the Time Ball in 1833 it was placed near the control mechanism where it was used by the Assistant charged with dropping the ball to ensure that it was dropped at the right time.

In the mid 1920s, Graham 3 was retired and transferred to the office of the Astronomer Royal. Over the years, the clock underwent numerous and significant alterations, many of these being carried out in the last three decades of the eighteenth century while Maskelyne was Astronomer Royal.

 

The naming of the Graham Clocks at Greenwich.

Over the years, George Graham supplied the Observatory with a total of four clocks. The first, a week clock with a simple pendulum, was bought by Edmond Halley in 1721. It's presence at the Observatory was last recorded in the 1818 inventory. The second and third clocks were bought in 1725 as part of the re-equipping of the Observatory. Both were month going and have movements which are numbered on the backplate (621 & 675). The fourth clock (this one) was bought by Halley's successor James Bradley and has a movement that is not numbered. In order to remove the ambiguity that had long existed in the Observatory inventories where all three of the Graham month going clocks were described in the same way, Airy decided during his first year at the Observatory to number them for the records – the two clocks from 1725 becoming known as Graham 1 and Graham 2, and the later clock as Graham 3. All three survive and are now in the collections of the National Maritime Museum.

 

The pendulum and the frequency of winding

Remarkably little is recorded about the early history of the clock. It is from the preface that the fifth Astronomer Royal Nevil Maskelyne wrote for his first volume of Greenwich Observations (p.ii & Vi) that we get the first details. These tell  us that it had a grid-iron pendulum and was month going, normally being wound on the first day of the Month. By Airy's time it (along with all the other clocks) was being wound weekly on a Monday, the first published record of this being in the Introduction to the 1838 volume of Greenwich Observations. In later years, it was wound twice a week on Mondays and Thursdays, the first published record of this coming in the Introduction to the 1880 volume of Greenwich Observations.

The 1831 inventory (RGO6/54/36) describes the clockt as:

'A Month Clock by Graham used by Cap[tain] Kater in Pendulum Experiments' with a later amendment saying 'Removed to the passage in Great Room for the time Ball'.

The 1840 inventory (RGO6/54/72) however describes it as follows:

'A clock, formally going a month, now going a week, by Graham, with mercurial pendulum: adjusted to Mean Solar Time: used in dropping the Time Signal Ball.'

It is not presently known if there was a material alteration to the clock or simply an alteration to the frequency of winding. Nor is it presently known why it began to be wound twice a week in later years. Today, the National Maritime Museum website describes the clock as being of eight-days duration.

 

Contemporary images of Graham 3

Although there are no known contemporary photographs that include Graham 3, it does appear (at least in part) in a late eighteenth century drawing of the Transit Room made by John Charnock which was purchased by the National Maritime Museum in 1966 (Object ID: PAF2956). Although the form of the case is clearly shown, the key markings on the dial are out of view.

In its later life, when Graham 3 was used to determine the exact moment at which to drop the time ball, schematic representations were used to illustrate the various published descriptions. Two are reproduced below. That on the left dates from 1835 and is taken from the Volume 4 of Nautical Magazine. That on the right is taken from the 9 November 1844 edition of The Illustrated London News where it is described as being from The Illustrated London Almanack for 1845, which had just been published. Whilst neither of the dials is anything like the real thing, the hood of the image on the left does bear some resemblance. No other images are known.

 

Comparing the observatory clocks

An inspection of the published observations indicates that form the arrival of Graham 3 in 1750 Bradley normally wound it and the two other month going clocks by Graham on the first day of the month. Within the volume there are also references to the three clocks being compared. The published references are patchy until May 1763, when Bradley started to use a code to display the information. In the preface to the second volume (which covers the Transit Observations made by both him and his successor Bliss between 1756 and 1765), the code was explained as follows:

'That the reader may fully understand some remarks, it may be necessary to inform him, that N. stands for the new Clock in the Transit Room [Graham 3], Q. for the Clock in the Quadrant Room [Graham 2], and G. for the Clock in the Great Room [Graham 1]. When the times by any two of these are compared, the comparison is expressed thus, N. Q. 4", meaning that the Transit Clock was 4" before the Quadrant Clock.'

No explanation was given however as to how the clocks compared. Although Maskelyne *who arrived as Astronomer Royal in 1765)  continued to normally wind the clocks on the first day of the month, he used a different method of comparing them which he explained in the preface to his first volume of Observations:

'In the year 1766, two assistant clocks, with a loud beat, were provided, and set up; one in the transit room and the other in the great room; principally designed to be used in windy weather, when the beats of the other clocks could not be well heard at a distance: in which case the assistant clock was first set to beat exactly with the principal or astronomical clock. Moreover, by the help of the bell of the assistant clock, which rings exactly every minute, when the second-hand comes to 60, and which may be heard from the great room to the transit room, when a window in each is left open, the astronomical clocks standing in these rooms are readily compared together, and their difference noted, in order to reduce the observations made in the great room to the time of the transit clock.'

In later years, other methods were used to compare the sidereal clocks notably, with a mean solar time chronometer and the method of beats - a practice that partially ended with the introduction of the chronograph in 1854.

Comparisons were also made between the transit clock and others set to mean solar time using a special device by Hardy which was described by Sabine in the write up of his pendulum experiments as follows:

'The comparison of the clock [Graham 3] with the Greenwich transit clock [Hardy] was effected by means of a machine constructed by HARDY for the purpose, it being capable of indicating 0".05 in time; and from the mean of 5 comparisons which was always employed, it is hoped the comparisons never err 0.03 from the truth these comparisons were made at or near the time the observations were making for the rate of the transit clock, on the accurate determination of which must rest the accuracy of the rate of the clock used in the experiment.'

 

Graham 3 today

The following description is taken from the National Maritime Museum's website (which also has numerous photographs of the clock and its various elements):

'The movement has typical Graham/Shelton chamfered corners to the tops of the plates which are united by six latched and knopped pillars. The four wheel train is driven by a black painted cylindrical weight suspended on a double line on a narrow diameter going barrel (19 turns) which carries the great wheel and Harrison’s maintaining power. All wheels have four curved crossings except for the light steel escape wheel which has six straight crossings. The escapement is fully jewelled; the long shank pallets have ruby nibs and are attached to the pallet arbor by a long brass collet. The crutch is fitted by a split collet allowing for beat adjustment and runs between two guard pins mounted on a plate screwed to the backplate. All of the rear pivots are fitted with double screwed brass end plates. The movement is screwed down to the seatboard via four brackets, and fixed to the backboard by two further brackets.

The large brass suspension block is screwed to the wall with a corresponding cut-out to the backboard of the case. The mercurial temperature compensated pendulum has a steel rod and glass jar held within a stirrup, the lower section of which is signed ‘RICHARDSON, Royal Observatory’ with blued steel pointer to the silvered pendulum scale reading 0-2.5 degrees.

The 12 inch square silvered-brass regulator dial has outer minute circle with arabic five-minute marks enclosed by an outer scribe line and inner minute track. The subsidiary seconds dial with observatory marks at five second intervals also has arabic numerals enclosed by an outer line and inner track. Situated above the cursive signature, ‘Geo. Graham, London’, is the twenty-four hour subsidiary dial, recessed within an elliptical aperture, which runs counter clockwise. The blued steel hands to the seconds and hour subsidiaries are counter-poised, the minute hand is round sectioned and tapering and secured by a domed brass collet and taper pin. There is a filled circular hole next to the twenty second mark. The rear of the dial has been refinished, curled and lacquered. The dial is screwed to four dial feet, each riveted to chamfered plates fixed to the front plate by means of a screw and steady pin.

The case is veneered in straight grain mahogany. The flat topped hood has a concave moulding to the cornice, panelled sides and locking front door with internal turn buckle locking the hood to the trunk. The trunk has a moulded rectangular door (270 x 845 mm) with three strap hinges, on a rectangular base with moulded double plinth.'

 

The 24 hour subsiduary dial

 

Published records of Graham 3's rate

Bradley Vol 1 Page 116 (Link)

Bradley Vol 2 p 308 &  p413

Maskelyne from 1793 onwards Vol 3

Pond, likewise

 

Historical summary

	1748		Aug 10: Board of Visitors supports Bradley's petition for re-equiping the Observatory. (RGO6/21/29) Oct 17: Visitors support application for a grant. The estimated total of £1,000 included £40 for a new transit clock (RGO6/21/29-33 & RGO6/21/40)
	1749		'In the year 1749, 1000l. [£1000] was given by his majesty, to be paid by the treasurer of the navy out of money arising from the old stores of the navy, (upon the representation of the lords of the admiralty, and principally upon Lord Anson's recommendation,) to buy some astronomical instruments for the use of the Royal Observatory (Miscellaneous Works and Correspondence of the Rev. James Bradley). The final cost of the clock is recorded as £39 (RGO6/21/44 & Miscellaneous Works ...)
	1750		Sep 2: First published observation made using the clock (Greenwich Obs)
	1771		Jul 9: 'In the Afternoon the [transit] Clock was taken down, to have Ruby Escapements applied to the Pallets. In the mean time, till the clock is set up again, the Observations are continued by the time of the Assistant-Clock standing in the same Room, which had been previously brought to keep time with the Transit-Clock. Whenever this is wound up, to prevent its losing time, the Wheels are kept going round by pushing the Second Hand forward with the Finger, which answers the Purpose very well.' (Greenwich Obs) Jul 15: 'The Observations are now continued by the Time of the Transit-Clock, as usual, which was set up again Yesterday about Noon, having been cleaned and had a Pair of highly-polished hard Ruby Escapements applied to the Pallets by Mr. JOHN ARNOLD, Watchmaker, which it is apprehended will require no Oil, and produce a much more regular Going of the Clock ... with the present [Ruby] Pallets it goes faster in 24 Hours than with the former [Steel] ones … The former Pallets, which had been going with the Clock for about Twenty-one Years, were somewhat wore, and that unequally, which seemed owing to their Shape, not having been made perfectly exact. Great Care was taken in forming the Ruby Pallets. (Greenwich Obs)                 No references to this work found in RGO6/21. The cost may have been included in Arnold's invoice for £84.16.0. which is believed to relate to the purchase of two new clocks and other works at the Observatory and which was approved by Council on 22 Dec 1774 (RGO6/21/129)
	1774		Dec 14 (inventory): Refered to as 'A month clock by Shelton with a compound pendulum and ruby palletts' (RGO4/309/4)
	1778		Jul 13 (at the visitation): 'A new contrivance to be put to the transit clock to keep it going while it is winding up - 2 guineas (estimate) And the pendulum altered so as to adjust it more accurately  for changes of heat & cold & a steel wheel to be substituted instead of the brass swing wheel & the pivot holes of the verge to be jewelled - 10 guineas [estimate]' (RGO6/21/156)
	1779		On 20 Jan, the clock was taken down to have some alterations made. It was replaced on 28 Feb, having had: 'a new steel Swing-wheel applied to it; the Pivot Holes of the Pallets and Swing-wheel jewelled; the Support of the Pendulum strengthened by brass pieces; and a perpetual Ratchet added to keep the Clock going in winding up, instead of the former machinery for that purpose, which had been found to fail for some Time. The whole by Mr. Arnold.' From Greenwich Observations, p.145 & p.148 'A bill for work done to the clocks by M.r John Arnold' for £23.4.0. probably included the work mentioned above. (RS/MS172/174)
	1780		On 13 Jan, 'taken down from the Wall on the South Side of the Room, to which it was fixed by Pieces of Wood let in, and was fixed up to a new stone pier lately built for it, nearer to the Transit Instrument. The pendulum is fixed to the Pier, independent of the Clock-case, by Means of a large and strong Plate of Brass, to which the Pendulum is attached, and which was firmly wedged in the Pier by running in melted Pewter. The new Clock was fixt up in the former Place of the Transit Clock, and the Observations will be made by it for a few days till the Transit Clock is brought to keep sidereal Time.' On 8 February, Maskelyne records that in its new position, the clock was found to be going very irregularly 'owing to the Spring having got bent, which gave the Pendulum a wabling Motion.' The 'new Clock' was therefore used for the transit observations until a new Spring could be fitted. Observations using Graham 3 restarted on 22 Feb. From Greenwich Observations, p.167 & p.169 & 170. The clock referred to as the 'new Clock' was probably one of the two Arnolds Arnold 1 or Arnold 2. These were ordered in 1772 for installation in the East and West Domes (formerly the East and West Summerhouses) and had been delivered by Dec 1774 (RGO4/309/4). Although they had been present in the domes for a while, by 1779 they were still awaiting the installation of proper fixings to secure them to. This was probably because the two Equatorial Sectors that they were supposed to be used with which were supplied by Sisson in 1773 were deemed unusable on account of structural weaknesses
	1789		May 27: 'The clock was stopped in order to be cleaned and have some alterations made to it. The clock from the advanced building was cleaned and set up in the Transit room, in order to continue the observations by.' (Greenwich Obs) Jul 15: 'The Transit clock having been cleaned, and had a solid brass bob substituted instead of a leaden one covered with brass, and that supported at the centre instead of the bottom, as before, and had a circle applied to shew the hours up to 24 hours instead of 12 hours only, and had a provision made at the bottom of the rod of the pendulum to regulate it with respect to heat and cold, for any small imperfection that might be found in the performance of the gridiron part, and a small regulating ball put at the bottom to adjust the clock exactly to the rate of the sidereal time without touching the bob of the pendulum, by Mr. Kendal, was set going nearly with sidereal time.' (Greenwich Obs)
	1790		Apr 29: At a Council of the Royal Society the following were amongst the items approved and transmitted to the Board of Ordnance with the Council's recommendation that it be paid (RGO6/22/22). 1) 'Mr John Arnold's receipt for cleaning the transit clock in 1786' – £1.1.0. 2) 'Mr Larcum Kendall's receipt for work done to and cleaning the clocks of the Royal Observatory' – £12.1.0.
	1792		Aug 6: The Clock, having been going 3 years, since its last cleaning, was now cleaned. The Regulating Ball was taken away from the Bottom of the Pendulum. the Regulating Nut being thought sufficient for regulating the Clock.' (Greenwich Obs)
	1793		Jun 19: 'The Transit Clock was taken down to be cleaned, and to have some alterations made to it. A clock of Mr Earnshaw's construction, was set up in its stead' (Greenwich Obs) Jun 20: 'The Astronomer Royal represented to the Council [of the Royal Society] that the Transit Clock was liable to sudden starts in its going on change of weather that this was probably owing to an occasional small bending of the brass and steel rods of which the pendulum is composed by their being pressed by the great weight of the bob. That this might probably be removed by putting 3 new cross stays to confine the rods laterally without hindering ther perpendicular motion there being only one such stay at present and that with too much play to confine the rods sufficiently. That if the Council shall approve this alteration, he desires to recommend Mr. Earnshaw to make it, and at the same time to clean the clock. That Mr. Earnshaw produces the same motion of the hour hand of his clocks with one wheel, which other clocks do with 3 wheels; which eases the clock of unnecessary work to be put in motion and has some advantage attending it. That he therefore requests that this alteration may also be made to the clock. That the expense of these alteration is estimated at between three and five guineas. The Council directed them to be carried into execution. (RGO6/22/29) Jun 29: 'The Transit Clock had been cleaned, and three new stays had been put to the bars of the pendulum instead of the single one there before, and applied to fit them more closely, in order to steady them; and the wheel work for moving the hour hand, had been reduced by Mr. Earnshaw. At 15h 40' the Clock was set going exactly 38 seconds faster than Mr. Earnshaw's clock, and nearly with sidereal time.' (Greenwich Obs) Maskelyne's former Assistant Thomas Evans records that the alterations to the pendulum were made 'so as to prevent the clock from making those sudden starts which it formerly did of a second per day in its daily rate' The juvenille tourist (1804)
	1795		Mar 19: At a Council of the Royal Society ''Mr Thomas Earnshaw's bill for work to the Clock and time keepers at the Royal Observatory [for] £14.3.6' was approved and transmitted to the Board of Ordnance with the Council's recommendation that it be paid. (RGO6/22/31). This would have included the work done to Graham 3 in 1793
	1816		16 Jul: the 10-foot Transit Instrument by Troughton replaces Bradley's 8-foot Transit Instrument of 1750 on raised piers in the same location. First published observation made with Graham 3 on Jul 21. (Greenwich Obs)
	1821		Sep 10: Last observation made with Graham 3 as a transit clock. Later that day 'The Clock was taken down, in order to put up a new one, made by Messrs. Molyneux and Cope.' Greenwich Observations 1821. Exactly where it went after that is unclear
	1824?		'The Transit Clock which had a Gridiron pendulum was placed in the circle room [when?], and is now called the ball clock a mercurial pendulum was substituted about 1824'. (Post 1835 note made by Airy based on info from John Belville: RGO6/4/4). The new pendulum is believed to be the present one signed by Richardson. A later note added to the inventory of 4 June 1824 (RS MS/371/70) records that Graham 3 had been moved to the Chronometer Room (where it would presumably have been adjusted to mean solar time. From other notes in the inventory, it would appear that this occured before the inventory was taken. An amendent in an undated rough inventory also states Graham 3 was removed to the Chronometer Room (RS/MS372/171/2). The entry however is problematic in that it states 'Removed to the Chronometer Room & Mr Hardy's Clock substituted for it' We know however that following Graham 3's dismounting four other clocks were tried as Transit Clocks before Clock Hardy was moved into the Transit Room in Nov 1823 An undated, but later inventory (RGO6/54/22-29) seems to  imply that it was later moved to the Great Room and then to the Quadrant Room. There is consdierable doubt as to Graham 3's exact location at different times from being taken down in 1821 and placed in the Quadrant Room in 1828
	1828		Used in the Quadrant Room by Edward Sabine in pendulum swinging experiments: Experiments to Determine the Difference in the Number of Vibrations Made by an Invariable Pendulum in the Royal Observatory at Greenwich, and in the House in London in Which Captain Kater's Experiments Were Made. Edward Sabine, Philosophical Transactions of the Royal Society of London, Vol. 119 (1829), pp. 83-102
	1829		Used in the Quadrant Room by Sabine in further pendulum swinging experiments: Experiments on the Length of the Seconds Pendulum at the Royal Observatory of Greenwich. Edward Sabine and Thomas Glanville Taylor. Philosophical Transactions of the Royal Society of London, Vol. 121 (1831), pp. 459-488
	1833		Time ball brought into use. Graham 3 moved to landing outside Octagon Room (Great Room) to be used to ensure that it was dropped at the right time
	1856		'Graham 3. formerly used for the daily dropping of the 'Time Signal Ball at 1h, but employed since the middle of the month of March for facilitating the regulation of the galvanic motor clock' (Intro to Greenwich Obs). This presumably required the clock to be modified. The work does not appear to have been done by  Dent, so it was possibly done by Shepherd (further research is required in RGO6/730). The clock was also relocated alongside the Shepherd Motor Clock to the newly created 'ball lobby' at the foot of the Octagon Room staircase
	1869		'The Ball Clock (Graham 3) has been cleaned' (1869 Report)
	1880		First published record of Graham 3 being wound twice a week (on Monday's and Thursdays rather than weekly on a Monday) (Intro to Greenwich Obs)
	1911		In Ball Lobby (at foot of stairs leading to the Octagon Room). The 1911 Inventory (RGO39/4) lists it as the Ball Clock
	1914		Moved to the recently set up clock room at the western end of the Meridian Building along with the Shepherd Master Clock (1914 Report). The 1911 inventory (RGO39/4/60) was not however updated to reflect this
	1926		In Astronomer Royal's Office in the north wing on the main floor of the South Building. Cleaned and overhauled (Order No. 938 of 3 Sep). (1926 Inventory: RGO39/5). 1926 was the year the second Shortt Clock (No.11) arrived at the Observatory. As space in the Clock Room was in short supply, it seems likely that Graham 3 was moved in order to make way for the slave clock of Shortt 11 to be mounted in its place
	1927		Cleaned and overhauled (Order No. 245 of 14 Oct). (1926 Inventory: RGO39/5)
	1948?		Moved to Astronomer Royal's new office in Herstmonceux Castle
	1954		The 1954 inventory compiled by Roy Tucker mentions only Graham 1 and Graham 2 (RGO71/1/3/1). It would appear that the clock identified as Graham 2 was in fact Graham 3
	1981		In Director's Office at Herstmonceux
	1988		Mounted in Conference Ante-Room, Herstmonceux Castle
	1990		Transfered to new site at Cambridge
	1996		Erected in office of KPT the Head of Astronomy (Room F48, first floor, southwest corner of the RGO building)
	1998		Aug 4: Transferred to National Maritime Museum (Museum records)

 

The changes to the Observatory's Transit Clock between 1821 and 1823 as recorded in Greenwich Observations

The table below lists entries from the published volumes of Greenwich Observations. Only once does Pond state why a chage was made

	Date	Text as published in Greenwich Observations	Reference
	1821 Sep 10	The Clock was taken down, in order to put up a new one, made by Messrs. Molyneux and Cope.	Greenwich Observations 1821
	1822 Nov 24	Mr. Molyneux took down the Clock. The observations were continued with the Counter set to beat with Hardy's Clock in the Circle Room.	Greenwich Observations 1822
	1822 Nov 28	The Observations will now be continued with a Clock put up by Mr. Johnson.	Greenwich Observations 1822
	1823 Mar 2	After the passage of the Sun, the Clock was taken down, and another put up by Captain Kater.	Greenwich Observations 1823
	1823 Mar 12	The clock was removed, and another put up by Molyneux and Cope.*     *Captain KATER'S Clock was removed on account of its being very indistinct and irregular in beat.	Greenwich Observations 1823
	1823 Nov 4	Took down the temporary transit clock, and removed Mr. Hardy's clock from the circle room into its place,	Greenwich Observations 1823

 

Earnshaw declines the offer to upgrade Graham 3

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.'

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 Australia 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.

 

Image licensing

The portrait of George Graham is reproduced under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence courtesy of The Board of Trustees of the Science Museum. Object Number: 1868-249