Mudge Green Chronometer The Mudge Green Chronometer is a hugely important heritage object.[1] Completed in 1777, it encapsulates the perfectionism and technical excellence of its creator, Thomas Mudge, while also being a product of the competitive inventiveness that drove clock- and watchmaking during the late 1700s. This work ethos was part of a wider scientific movement. During this time, the race was on to win the Longitude Prize by producing a chronometer (a small, portable marine timekeeper) capable of working at sea. During the early 1770s, Mudge decided to commit himself wholly to this pursuit. He closed his London shop, ‘retired’ and moved to Plymouth, Devon in the southwest of England – an ideal location for testing chronometers at sea. During his so-called retirement, which encompassed the last 20 years of his life, Mudge focused exclusively on the improvement of chronometers to win the coveted Longitude Prize.[2] During this time, he produced three chronometers, including the Mudge Green. This is one of a pair of chronometers that were produced at the same time to fulfil the Board of Longitude’s requirements: that production be replicated, and that the two productions be tested together. Mudge’s retirement marked the end of a long, quietly successful career. He was well known and widely respected for the superior quality of his work. He was also patronised by royalty, specifically King George III and King Ferdinand VI of Spain, and was counted among London’s elite circle of groundbreaking master clock- and watchmakers. He had trained with the best of the best, apprenticing with George Graham, the protégé and successor of the great Thomas Tompion. In 1750, he opened his own shop on Fleet Street and in a year had also taken over Graham’s business upon his death. Mudge’s most significant contribution to horological development was the lever escapement , which he invented in 1755. This type of escapement is the most widely used escapement in watches and is still a feature of almost all mechanical watches today. Its design greatly informed and enhanced the design of the escapements in Mudge’s chronometers, as evidenced by the exceptional and intricately complex construction of the Mudge Green Chronometer’s mechanism (discussed below). Despite being beautifully presented and expertly crafted, the Mudge Green Chronometer (and its mate, the Mudge Blue Chronometer) proved to be less than practical for determining longitude on long voyages at sea, the raison d'être driving Mudge’s work. Still, it played an important role in the wider pursuit of the quest to solve the problem of longitude, the greatest scientific problem of its day. The pursuit of the Longitude Prize Navigation of the open sea had always been a dangerous business, and this danger was often down to navigational errors.[3] While determining latitude was relatively easy, early ocean navigators had to rely on dead reckoning to estimate longitude. This was especially inaccurate on long voyages without sight of land and could sometimes lead to calamity. From the 1400s, transoceanic travel had grown in significance due to the expansion of European empires and trade routes. By the 1700s, there was a pressing need to find a solution to the problem of how to determine longitude at sea. This was because there were fortunes to be made from the accumulation of resources from the ‘New World’. Thus, reliable navigation at sea was crucial to the financial success of the colonial endeavours of Britain, France, Portugal and Spain. The lives of those aboard their ships were also at stake. Scientific thinkers had been working on the problem of longitude for a long time. Most believed that the solution would be an astronomical one rather than a horological one. They thought that the reliable calculation of longitude could be achieved by measuring the position of the navigator relative to celestial bodies such as Jupiter’s moons, which had been discovered by Galileo Galilei in 1610. The first Royal Astronomer, John Flamsteed, shared this belief with his royal patron, King Charles II. Compelled by the worry that the French were close to solving the longitude problem, the King established the Royal Observatory by royal warrant in 1675 to further Flamsteed’s pursuit of an astronomical solution. Then, in 1707, the Scilly naval disaster occurred. This was a wreck in which four ships and around 2000 souls were lost, making it one of the worst naval disasters in British naval history. Because poor navigation contributed to the catastrophe, this and the desire to capitalise on global trade (specifically the trade of goods, raw materials and enslaved Africans trafficked by way of the transatlantic slave trade route) helped spur the British government into providing a formal response to the problem of longitude. In May 1714, a petition calling for endeavours to find an adequate solution to the longitude problem was presented to the Palace of Westminster (where the British Parliament convenes). Soon after, in July 1714, Parliament passed the Longitude Act. This included the establishment of the Board of Longitude and offered a prize of £20,000 (equivalent to £5 million today) for solving the problem of longitude. Up to that point, no clockmaker had been able to create a clock that could keep time accurately and reliably at sea. Existing clocks were simply unable to meet the Longitude Prize’s accuracy requirements, and the pendulum clock technology of the time was virtually useless at sea. Pendulum clocks were far too sensitive to fluctuations of movement and temperature, and the salty air and moisture wrought havoc with the regularity of their back-and-forth swing. Because of these considerations, the possibility of a horological solution was rejected by all the London clockmakers of the day. The vast majority of clockmakers assumed that they stood no chance of winning the prize, so they did not try. An exception was a self-taught clockmaker by the name of John Harrison. He made tremendous strides towards a solution by producing his series of sea clocks, and in 1759 his efforts culminated with the production of his groundbreaking H4 chronometer.[4] H4 was successfully tested at sea in 1761, and again in 1764. The chronometer proved to be Harrison’s masterpiece and fulfilled the requirements set out by the Board of Longitude for successfully determining longitude at sea. However, Harrison was not formally recognised for his achievement, and the Board did not award him the prize money for manufacturing H4 until 1773.[5] What is more, he was not awarded the full £20,000 prize (although he did manage to win the most money of all the contenders). Technically speaking, the ultimate prize was still up for grabs. Watchmaker and horological historian Rebecca Struthers points out that today we very much view Harrison as a horological hero whose invention saved countless lives at sea. While this is undoubtedly true, she explains that it is important to remember that while H4 was a momentous achievement, it was not the endgame when it came to reliably and efficiently determining longitude at sea.[6] Early chronometers were still imperfect, tending to accumulate inaccuracies over very long distances. This new technology was also extremely complicated and expensive to produce. Compounding the costs was the fact that multiple chronometers were needed for each voyage, many of which would be rendered useless by the end of a journey. As noted previously, temperature fluctuations, salty air and humidity damaged their mechanisms. Typically, they performed best at the start of a voyage and deteriorated over the course of the long journey. Once a chronometer began to lag, it was then switched out for a fresh one. Therefore, the most significant thing about H4 was not the instrument itself. Although Harrison had demonstrated that a chronometer had the capacity to reliably determine longitude at sea, there remained room for improvement. It was in this milieu of competitive inventiveness that Mudge removed himself to Plymouth, one of England’s busiest ports, to work towards producing a more practical chronometer. Definitively winning the Longitude Prize, and all the fame and riches that came with it, was surely a strong motivating factor. Trials and tribulations The Mudge Green, completed in 1777, is one of three chronometers that Mudge produced during his so-called retirement. Mudge’s first chronometer is known as Mudge No. 1.[7] It took three years to make and was completed in 1774.[8] To reinforce stability and avoid ‘poise problems’, Mudge used a horizontal balance.[9] He also used the same pallets that he used for his Huber timekeeper, the earliest known timekeeper with a ‘constant force’ escapement.[10] These pallets are driven via the spiral springs and provide the constant force. While Mudge greatly improved upon his constant force escapement design, the movement of this chronometer was so complex that Mudge was compelled to modify the amount of time that the chronometer could run without winding from 8 days down to 2 days before sending it off to be tested. Mudge No. 1 was tested at the Royal Observatory at Greenwich in 1774 by the Astronomer Royal, Nevil Maskelyne, who was also a member of the Board of Longitude. The tests did not go well. First, the chronometer’s drive springs were prone to failure. Second, that same year Parliament repealed the Longitude Act of 1714 and replaced it with far tougher conditions, which Mudge No. 1 did not meet. Now, the Board stipulated that any timekeeper considered for the cash prize must be reproduced by a third party, and that the two instruments must be tested together. The reasoning behind this was to establish whether an instrument could be reproduced with consistency and at reasonable cost. Mudge kept working on Mudge No. 1. Although he failed to replicate Mudge No. 1, he eventually tested it again. In 1777, he was able to report to the Board of Longitude that the chronometer had gained just one minute, nineteen seconds in a run of 109 days at sea - exceptional results. In fact, Mudge No. 1’s performance was so good during its second trial that it was not equalled for nearly a century. To Mudge’s great frustration, the Board awarded him £500 for his progress. This equated to nothing more than a firm nod of encouragement (albeit a very generous one). The complicated matter of the Mudge Green Disappointed at not winning the whole £20,000 prize, Mudge started production in 1776 on a pair of chronometers that could be tested together. These are known as the Mudge Green and the Mudge Blue, named as such because of the colour of their shagreen cases. Shagreen is a type of rawhide leather usually prepared from the skin of aquatic animals such as shark or stingrays.[11] The Mudge Green Chronometer is beautifully presented. Its gilt dial is decorated with silver spandrels. These surround two enamel dials. The larger of the two is a regular mean solar time dial, indicating the hours and minutes. The smaller is a subsidiary seconds dial. The green cover on its drum form case is made from a warty chameleon skin, probably of the species Furcifer verrucosus, also known as the Madagascar Giant Chameleon. The complexity of the Mudge Green’s movement is astonishing and can be viewed in detail in the accompanying video here on Clocktime. The precision and attention to detail required to saw and file the hand-cut teeth of its wheels are incredible. For instance, the chronometer’s great wheel is comprised of 100 teeth, the centre wheel has 120 teeth and 20 leaves on the pinion, the third wheel has 120 teeth and 16 leaves on the pinion, the contrate wheel also has 120 teeth and 15 leaves on the pinion, and the smaller seconds and reversing wheels each have 45 teeth. The movement also features Mudge’s constant force escapement, with an escape wheel that has five crossings, 15 long teeth and 12 leaves on the pinion. Mudge also used Harrison’s maintaining power. The chronometer’s polished brass backplate features a mounted flat rim balance with three-arm crossing and counterpoise weight. This includes roller wheels to minimise friction, and jewelled end stones on the balance bridge and balance potence. On the backplate, Mudge also provided a temperature compensation mechanism featuring two straight bi-metal springs. It also included a finely pierced and foliate engraved balance bridge with griffin and scallop shells. There is also a dust exclusion pipe. Mudge’s signature with date, Tho. Mudge 1777, is engraved along the backplate’s circumference. The bottom plate features an easily accessible adjustment in the form of a small semicircular plate and blued-steel pointer for indexing adjustments. While Mudge achieved some success in terms of refinement of detail, the mechanisms of the Green and Blue Chronometers were even more complicated than that of Mudge No. 1. In fact, the Mudge Green and Blue mechanisms were so complex that Mudge reduced their duration further, from 2 days to 1 day. When tested at the Royal Observatory, they produced mixed results.[12] Mudge continued to adjust his chronometers over the remaining 17 years of his life (he died on 14 November 1794). His son, Thomas Mudge Jr, also tried to establish a factory to produce copies of his father’s timekeepers, but this endeavour ultimately ended in failure. In sum, the Mudge Green Chronometer was a high-quality, expertly engineered thing of beauty. It, along with the Mudge Blue and Mudge No. 1, was just too complex to provide a practical solution for determining longitude at sea. Lost and found The Mudge Green and Blue Chronometers disappeared at some point during the early 1800s and were thought to have been lost at sea. Their whereabouts remained unknown for over a century. The Mudge Blue eventually turned up in Russia in 1920. After being offered to the Worshipful Company of Clockmakers (who were unable to afford acquisitions at that time), it was sold to the Mathematisch-Physikalischer Salon in Dresden, Germany (Inventory number D IV b 11), where it is displayed today. The Mudge Green was ‘rediscovered’ by the horologist Charles Allix around 1950, when he came upon it in a private collection in Europe. Further details about the collector are not known. The chronometer officially re-entered the historical record in 1976, when it came up for auction at Christie’s in Geneva. Although the Longitude Prize eluded Mudge, Struthers rightly asserts that Mudge did more to advance the watch movement than any other maker. In her recent book Hands of Time, Struthers provides a fitting last word on Mudge and his chronometers. She writes: The leaps in accuracy achieved for the chronometer made a different kind of watch – and time – possible. And for this, Harrison should share his crown with Mudge. While Harrison’s legend overshadowed pretty much all of his golden age contemporaries, in fact no maker has left as lasting a mark on the advancement of the watch movement as Thomas Mudge. Mudge’s lever escapement watches turned out to be more accurate and more reliable even than Harrison’s, and he incorporated them into a chronometer just as Harrison won the Longitude Prize. Had Mudge succeeded a few years earlier, he likely would have beaten Harrison and claimed the prize, and lasting celebrity, for himself. Nevertheless, his legacy lives on in the watch. It is the descendant of Mudge’s lever escapement that is still ticking on your wrist.[13] The Mudge Green’s mechanism has been extensively illustrated and described in detail by numerous horologists over the years.[14] For a complete overview of its features, see the Mudge Green’s specifications on Clocktime. Dr Kristin Leith, Senior Curator of Clocktime April 2025 End notes [1] Betts 2018, 48 and 228; Britten 1982, 128, 192–193; Carter 2021, 224–229; Chamberlain 1978, 337–339; Daniels 1981; Garver 1992, 11; Good 1955; Gould 1999, 107–125; Hutchinson 1978; Mudge Jr 1799; Penney 1993; Randall and Good 1990, 181–185. [2] Apparently, Mudge’s decision to retire in Devon was also partly due to failing health (Carter 2021, 228). The move back to Devon must also have been something of a homecoming for Mudge, who was born in Exeter in September 1717. [3] Sobel 2011, 1–33. [4] Betts 2023, 86–118; Sobel 2011, 99–174; Struthers 2023, 68–71. [5] Sobel 2011, 148. [6] Struthers 2023, 71–75. [7] Mudge No. 1 is currently on display in the British Museum (Museum Number 1958,1006.2119). [8] Carter 2021, 228; Thompson 2004, 128. [9] ‘Poise problems’ refers to an imbalance in the weight of the balance wheel. If the weight of the balance wheel is not correctly distributed, this leads to a ‘heavy spot’. This uneven distribution of weight can cause positional errors and compromise accuracy. Uneven balance wheels are often described as being ‘unpoised.’ [10] Mudge’s Huber timekeeper is a chronometer that was made between 9 June and 31 October 1755. It is known as the Huber Timekeeper because Mudge followed the instructions and design of the Basle mathematician and astronomer Johann Jakob Huber (b. 1733, d. 1798). In summer 1755, Huber was in London and commissioned Mudge to build the clockwork. Huber brought the chronometer back with him to Basel. It was left to the scientific 'cabinet' of the University in 1829 by his son, the mathematician Daniel Huber, and is now in the Historisches Museum Basel in Switzerland (Inv. 1960.20.). [11] The original blue shagreen case of the Mudge Blue Chronometer has not survived. It now has a later purpose-made display case. For a photograph, see Carter 2021, 229. [12] The records of the sea trials for all three of Mudge’s chronometers are archived in the Royal Museums Greenwich. [13] Struthers 2023, 75. [14] Betts 2018, 48 and 228; Britten 1982, 128, 192–193; Carter 2021, 224–229: Chamberlain 1978, 337–339; Daniels 1981; Garver 1992, 11; Good 1955; Gould 1999, 107–125; Hutchinson 1978; Mudge Jr 1799; Penney 1993; Randall and Good 1990, 181–185. References Betts, J. 2018. Marine Chronometers at Greenwich: A catalogue of marine chronometers at the National Maritime Museum, Greenwich. Oxford: Oxford University Press. Betts, J. 2023. John Harrison and the Quest for Longitude (2nd edition). Greenwich, London: National Maritime Museum. Britten, F. J. 1986. Britten’s Old Clocks and Watches and Their Makers: A history of styles in clocks and watches and their mechanisms (9th edition). London: Bloomsbury Books. Carter, J. 2021. The John C Taylor Collection: Part I (Selling Exhibition Catalogue, Carter Marsh & Co.). Winchester: Carter Marsh & Co. Chamberlain, P. 1978. It’s About Time. London: Littlehampton Book Services. Daniels, G. 1981. "Thomas Mudge: The complete horologist." Antiquarian Horology 13: 150–173. Garver, H. 1992. ‘Keeping Time’ in The Time Museum Brochure (reprinted from Invention & Technology, p. 11. Good, R. 1955. ‘The Mudge marine timekeeper’ in Pioneers of Precision Timekeeping. London: Antiquarian Horological Society, pp.75–91. Gould, R.T. 1999. The Marine Chronometer, Its History and Development (new edition). London: ACC Art Books. Hutchinson, 1978. ‘Some observations on the timekeepers of Thomas Mudge’ in Antiquarian Horology 11: 715–719. Mudge, T Jr. 1799 [reprinted 1977]. A Description, with Plates of The Time-keeper Invented by the Late Mr. Thomas Mudge. London: National Maritime Museum. Penney, David. 1993. ‘Thomas Mudge and the longitude: A reason to excel’ in J. H. Andrewes (editor) Quest for Longitude. Cambridge, MA: Collection of Historical Scientific Instruments, pp. 294–308, pl. 18. Randall, A. G. and R. Good. 1990. Catalogue of watches in the British Museum VI: Pocket chronometers, marine chronometers and other portable precision timekeepers. London: British Museum Publications. Sobel, D. 2011. Longitude: The true story of a lone genius who solved the greatest scientific problem of his time. London: Harper Perennial. Struthers, R. 2023. Hands of Time: A watchmaker’s history of time. Great Britain: Hodder & Stoughton. Thompson, D. 2004. Clocks. London: British Museum Press. Further reading Dunn R. and R. Higgit. 2014. Ships, Clocks, and Stars: The quest for longitude, p.162 illustration pp.164–166. Köberer, W. 2016. ‘On the first use of the term 'Chronometer'' in The Mariner's Mirror 102(2): 203–206. Mudge Jr, T. 1791. A reply to the Answer of the Rev. Dr. Maskelyne, Astronomer Royal, to A narrative of facts, relating to some time-keepers, constructed by Mr. Thomas ... at sea, &c. By Thomas Mudge, jun. ... London: printed for Thomas Payne. Randall, A. G. 2006. ‘Thomas Mudge and the Swiss contribution to his inventions (lecture synopsis)’ in Horological Journal, January: 16–17. Rogers, P. 3 April 2009. ‘Letter following up Jeremy Thacker: Longitude fake?’ in Times Literary Supplement.
