The Diamond Pallets of John Harrison's Fourth Longitude Timekeeper—H4

Summary

John Harrison (1693–1776) is regarded as the father of chronometry. During his lifetime, he relentlessly pursued one of humankind's greatest and oldest challenges—that of finding the longitude at sea. In succeeding (according to the rules dictated by an Act of Parliament), he bequeathed to humankind the most accurate portable timekeeper the world had ever seen. It is a remarkable fact that his timekeeper, known today as H4, remains more accurate than the majority of expensive mechanical wristwatches manufactured today. Such accuracy required novel approaches to address the various difficulties that befall all mechanical watches, and Harrison overcame many of these with his own innovations. The reduction or elimination of friction is one such problem with clocks and watches, and from an early age Harrison demonstrated his mastery in this subject. This is typified by his choice of woods in his early clocks, and in later clocks by his ‘grasshopper’ escapement. In the 1750s, Harrison's attention switched from clocks to watches, necessitating a hardwearing, low friction material to be found for the pallets in the escapement of his timekeepers. He found these properties in diamond, and in utilizing this to great effect in H4's escapement, he became one of the first people to use diamond as a high-tech material. This paper describes a scientific investigation into the diamond pallets of H4 using Raman microscopy, X-ray diffraction and optical microscopy, to elucidate why diamond was used rather than a more conventional jewel such as ruby, and to gain some insight into how Harrison might have achieved their unconventional morphology. From the evidence presented here, together with evidence collected from primary sources, it is shown that his use of diamond as a hard, low friction material was nothing other than extraordinary, and should be regarded in the same high esteem as his other technological gifts to the world.

Acknowledgements

We would like to thank the countless people who have assisted with the research presented here. In particular, we are extremely grateful to Mr R. Clare, Director, National Maritime Museum for allowing this research to take place and MoD Art Collections for temporarily allowing the balance staff and pallets of H4 to be examined in Cambridge. We extend our gratitude to Prof. J. E. Field OBE FRS for his interest and for valuable advice he has given throughout the project. Our thanks also to Mr A. Taylor of the Diamond Trading Company, who has provided useful advice on diamond polishing and X-ray diffraction. For illustrations, we are extremely grateful to: National Maritime Museum, London, Ministry of Defence Art Collection for their permission to publish Figure 1; Mr D. Penney for allowing us to use his excellent illustration of H4's verge shown in Figure 2; the Syndics of Cambridge University Library for allowing us to reproduce Figure 3; Ms N. L. Ferguson for producing the schematic drawings of the pallets in shown in Figure 4a and 4b; and the Mineralogical Society of America for permission to use Figure 14. We would like to thank Spheric-Trafalgar for donating the high-carbon steel balls and are grateful to Dr M. Seal for originally suggesting this research.

Notes

¹H. Quill, John Harrison; the Man Who Found Longitude (London, 1966). Woolley's remarks are to be found in the Foreword.

²D. Sobel, Longitude: the True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time (New York, 1995).

³‘Longitude’; a television programme made by Granada television and shown on UK Channel Four on 02/01/00 and 03/01/00.

⁴R.T. Gould, The Marine Chronometer; Its History and Development (Woodbridge, UK, 1989), 54–99.

⁵Quill, op. cit. (note 1).

⁶H. Quill, ‘John Harrison, Copley Medallist, and £20 000 Longitude Prize’. Notes and Records of the Royal Society of London, 18 (1963), 146–60.

⁷Whether it can be said that Harrison technically ‘won’ the Longitude Prize is a moot point among scholars, since it was only by the intervention of Parliament in Board of Longitude matters that Harrison was awarded his money.

⁸Barometric error would also have to be considered, both for pendulum clocks and, to a lesser extent, to portable timekeepers.

⁹K.G. McLaren and D. Tabor, ‘The frictional properties of lignum vitae’. British Journal of Applied Physics, 12 (1961), 118–20. The indentation hardness of natural lignum vitae is c.23 kg mm⁻¹, whereas the value for PTFE lies in the region of 5 kg mm⁻¹.

¹⁰G. Amontons, Histoire de l'Académie Royale des Sciences avec les Mémoires de Mathématique et de Physique (1699), 206.

¹¹J.A. Williams, Engineering Tribology (Oxford, 1994), 29–30.

¹²T. Hatton, An Introduction to the Mechanical Part of Clock and Watch Work in Two Parts: Containing All the Arithmetic and Geometry Necessary, with Their Particular Application in the Said Branches. a Work Very Useful for the Working Mechanic, or Gentlemen Mechanically Inclined (London, 1773), 253–55.

¹³Gould, op. cit. (note 4), 70.

¹⁴British patent No. 371, 1704.

¹⁵In Harrison's time, the escape wheel was known as the balance wheel. In modern terms, the oscillating body is the balance and spring.

¹⁶ The Principles of Mr Harrison's Time-Keeper, with Plates of the Same. Published by Order of the Commissioners of Longitude (London, 1767).

¹⁷ The Principles of Mr Harrison's Time-Keeper, with Plates of the Same. Published by Order of the Commissioners of Longitude (London, 1767)., xv.

¹⁸J. Harrison, A Description Concerning Such Mechanism As Will Afford a Nice, or True Mensuration of Time; Together with Some Account of the Attempts for the Discovery of the Longitude by the Moon: As Also an Account of the Discovery of the Scale of Musick (London, 1775).

¹⁹J. Harrison, 1763 GUILDHALL MS 3972:1.

²⁰J. Harrison, 1771 GUILDHALL MS 3972:2.

²¹Principles, op. cit. (note 16), xvi.

²²Harrison, op. cit. (note 18), 49.

²³G. Lenzen, The History of Diamond Production and the Diamond Trade. Trans. from the German by F. Bradley (London, 1970).

²⁴C.R. Ashbee, The Treatises of Benvenuto Cellini on Goldsmithing and Sculpture: Made into English from the Italian of the Marcian Codex (London, 1898), 31–32.

²⁵V. Ball, Travels in India by Jean-Baptiste Tavernier (ed. W. Crooke), vol. 2 (Oxford, 1925), 41–49.

²⁶V. Ball, Travels in India by Jean-Baptiste Tavernier (ed. W. Crooke), vol. 2 (Oxford, 1925)., Valentine Ball's translation describes the scaifes used in and around Golconda fort as being made from steel. This is unusual as European accounts refer to scaifes made from iron (the preferred material today). The manufacture of steel is known to have originated in Sri Lanka c.300 bc and by 200 ad, the practice had spread to and evolved in southern India, where high-quality steel was being produced by the crucible technique. In contrast, steel making in Europe began in the early seventeenth century, and it is this fact that probably explains this difference in the materials used by Asian and European lapidaries.

²⁷J.R. Hird and J.E. Field, ‘Diamond Polishing’, Proceedings of the Royal Society of London Series A, 460 (2004), 3547–68.

²⁸F.M. van Bouwelen, ‘Electron Microscopy Analysis of Debris Produced During Diamond Polishing’, Philosophical Magazine, 83 (2003), 839–44.

²⁹M.S. Couto, W.J. P. van Enckvort and M. Seal, ‘Diamond Polishing Mechanisms: an Investigation by Scanning Tunnelling Microscopy’, Philosophical Magazine B, 69 (1994), 621–41.

³⁰Harrison, op. cit. (note 20), 19.

³¹E.M. Wilks and J. Wilks, Properties and Applications of Diamond (Oxford, 1991).

³²M. Yoshikawa, ‘Development and Performance of a Diamond Film Polishing Apparatus with Hot Metals’, SPIE Diamond Optics III 1325 (1990) 210–21.

³³K. Horio, M. Hyohdoh, and T. Kasai, ‘Tribo-Chemical Smoothing of Diamond Film’, Proceedings of the American Society of Precision Engineering, 20 (1999), 135–80.

³⁴H. Tokura, C-F Yang and M. Yoshikawa, ‘Study on the Polishing of Chemically Vapour Deposited Diamond Film’, Thin Solid Films 212 (1992), 49–55.

³⁵I. P Hayward, The Friction and Strength Properties of Diamond, Ph.D. thesis (Cambridge, 1987).

³⁶C.J. Freeman and J.E. Field, ‘Friction of Diamond, Syndite and Amborite Sliding on Various Alloys’, Journal of Materials Science, 24 (1989), 1069–72.

³⁷A.K. Gangopadhyay and M.A. Tamor, ‘Friction and Wear Behaviour of Diamond Films Against Steel and Ceramics’, Wear 169 (1993), 221–29.

³⁸I. Iliuc and M. Jokl, ‘A Comparative Investigation of the Sliding Wear Mechanism in Lubricated Steel-on-Steel and Diamond-on-Steel Friction Pairs’, Wear 176 (1994), 73–79.

³⁹A. L Yurkov, V.N. Skvortsov, I.A. Buyanovsky and R.M. Matvievsky, ‘Sliding Friction of Diamond on Steel, Sapphire, Alumina and Fused Silica with and Without Lubricants’, Journal of Materials Science Letters, 16 (1997), 1370–74.

⁴⁰K. Miyoshi and D.H. Buckley, ‘Adhesion and Friction of Single-Crystal Diamond in Contact with Transition Metals’, Applied Surface Science, 6 (1980), 161–72.

⁴¹Y. Enomoto and D. Tabor, ‘The Friction Anisotropy of Diamond’, Proceedings of the Royal Society of London Series A, 373 (1981), 405–17.

⁴² Tribological: pertaining to Tribology; the study and science of friction and wear. From the Greek, τρβtσ, meaning to rub.

⁴³A.G. Randall ‘The Technology of John Harrison's Portable Timekeepers’ (Final Part). Antiquarian Horology, 18 (1989), 261–77.

⁴⁴LaueX is a software program dedicated to the solution and generation of Laue diagrams. http://www.iucr.org/sincris-top/logicel/laueX/en/LaueX_en.html

⁴⁵M. Tolkowsky, Research on the Abrading, Grinding, or Polishing of Diamond, D.Sc. thesis (Eng.) (City and Guilds College, University of London, 1920).

⁴⁶I.P. Hayward and J.E. Field, ‘A Computer-Controlled Friction Measuring Apparatus’, Journal of Physics E Scientific Instruments, 21 (1988), 753–56.

⁴⁷Principles, op. cit. (note 16), 31.

⁴⁸R.P. Steijn, ‘On the Wear of Sapphire’, Journal of Applied Physics, 32 (1961), 1951–58.

⁴⁹E.J. Durwell, ‘Friction and Wear of Single-Crystal Sapphire Sliding on Steel’, Journal of Applied Physics, 33 (1962), 2691–98.

⁵⁰Enomoto and Tabor, loc. cit. (note 41).

⁵¹Harrison, op. cit. (notes 18–20).

⁵²Lenzen, op. cit. (note 23), 68–131.

⁵³P. Grodzinski, ‘The History of Diamond Polishing’, Industrial Diamond Review (Special Supplement, 1) (1953) 1–13.

⁵⁴A. Heal, The London Goldsmith's, 1200–1800 (Cambridge, 1935). The lapidaries mentioned in this work are: Guilleaume Bonjonnier, High Moorfields, 1702, diamond cutter; George Robertson, Frith Street, Soho, 1774–1777, diamond merchant and jeweller; and Edward Woodcock, Bury Street (Nr. Aldgate), 1709, diamond cutter.

⁵⁵Lenzen, op. cit. (note 23), 89.

⁵⁶ Anon. ‘Diamond Polishing’, Engineering 45, 123–25 (1889).

⁵⁷Lewis Atkinson, letter to the Editor, The Times, 4 November 1887, 13, states that nearly 200 years ago (i.e. around the beginning of the eighteenth century) ‘Englishmen were the finest diamond cutters in the world, and the trade was nearly all carried on in London …’

⁵⁸The wills held under category PROB11 at the National Archives in Kew include the wills of twelve diamond cutters and twenty-four lapidaries who died between 1700 and 1800. All but two of these diamond cutters and one of the lapidaries lived in London. Many of the deaths occurred in the latter half of the century—the most being recorded in the ten years between 1771 and 1780. As the Prerogative Court of Canterbury dealt with the relatively wealthier sections of society, it is reasonable to assume that the actual number of people working in these trades exceeds the figures given here.

⁵⁹G. L'E Turner, ‘The Auction Sale of Larcum Kendall's Workshop 1790’, Antiquarian Horology, 269–74 (Sep. 1967). Curiously, this polishing bench was sold to John Smeaton FRS, the celebrated civil engineer who had a strong interest in horology.

⁶⁰I. Newton, Opticks (London, 1704).

⁶¹R. Boyle, Essay About the Origine & Virtues of Gems: Wherein Are Propos'd and Historically Illustrated Some Conjectures About the Consistence of the Matter of Precious Stones, and the Subjects Wherein Their Chiefest Virtues Reside (London, 1672).

⁶²Lenzen, op. cit. (note 23), 116.

⁶³D. Jeffries, A Treatise on Diamond and Pearls. In Which Their Importance Is Considered: and Plain Rules Are Exhibited for Ascertaining the Value of Both: and the True Method of Manufacturing Diamonds, 2nd edn. (London, 1751).

⁶⁴D. Jeffries, A Treatise on Diamond and Pearls. In Which Their Importance Is Considered: and Plain Rules Are Exhibited for Ascertaining the Value of Both: and the True Method of Manufacturing Diamonds, 2nd edn. (London, 1751), It is of passing interest to note that among the subscribers of this work, a Mr John Jeffries is listed. Due to the inconsistency of spelling at this time, Jeffries is often also spelt Jefferies or Jefferys, and so the possibility exists (at least in theory) that this is same the John Jefferys who was the workman who built and signed Harrison's pocket watch—the forerunner of H4. It is also of note that the copy of the book belonging to Cambridge University Library is autographed with the name ‘Morton’. It is very likely that this book belonged either to Charles Morton FRS (one of the signatories of William Harrison's fellowship proposal) or to the Earl of Morton, whose signature is similar to the latter.

⁶⁵J. Horrins, Memoirs of a Trait in the Character of George III. of Theses United Kingdoms; Authenticated by Official Papers and Private Letters in Possession of the Author: with and Appendix of Illustrative Tracts, &C. Abridged from the Original Work in Manuscripts (London, 1835), iv (in preface).

⁶⁶L. Kendall, British Library MS Add. 39822 (1770).

⁶⁸Kendall, op. cit. (note 66).

⁶⁷L. Kendall, British Library MS Add. 39822 (1770)., Kendall's figures for the cost of the diamond pallets do not tally with the cost of diamonds at the time. Both the 1756 and 1800 editions of Jeffries’ treatise op. cit. (note 63) put the price of a 1 carat rough diamond of medium quality at £2. If roughly spherical, a stone of this mass would have a diameter of around 4.77 mm. Using the density of diamond (3.51×10³ kg m⁻³) and the rectangular dimensions of the pallets (2×1×0.3 mm), this gives an overestimate of the pallet weight at 0.012223 carats (2.4456 mg) each. Although Jeffries does not assign values to ‘small’ stones of under a carat, it is still difficult to arrive at Kendall's figure of £10 for the total cost of the diamonds when the price of cutting a diamond to a brilliant was just £1, in addition to using a mark-up of 150 per cent. It is possible then, that Kendall included the cost of polishing the diamonds in his breakdown which made them seem so expensive. Thus, the cost of the timekeepers of his own invention—K2 and K3—which use ruby pallets, would be economically more favourable in comparison. See also J. Betts, ‘The Transits of Venus, the Voyages of Cook and the Marine Chronometer’, Antiquarian Horology, XX (1993), 60–69.

⁶⁹Gould, op. cit. (note 4), 107.

⁷⁰Harrison, op. cit. (note 19), 47.

⁷¹Harrison, op. cit. (note 20), 19.

⁷²Principles, loc. cit. (note 16).

⁷³E.H. Kraus and C.B. Slawson, ‘Variation of hardness in the diamond’, American Mineralogist, 24 (1939), 661–76.

⁷⁴The smoothing technique used to finish facets on diamond is known as ‘zoeting’—from the Dutch verb zoeten, to smooth.

⁷⁵Harrison, op. cit. (note 20).

⁷⁶One of the authors (DP), has succeeded in manufacturing perfectly formed diamond pallets for a full-scale replica of H4, using a new technique based on modern knowledge of the crystal structure of diamond and of the wear mechanisms involved. The details of how this was achieved will form the subject of a future paper.

⁷⁷Quoted from G. Lenzen, Diamonds and Diamond Grading. Trans. from the German by P.B. Lapworth (London, 1983), 65.

⁷⁸Quoted from G. Lenzen, Diamonds and Diamond Grading. Trans. from the German by P.B. Lapworth (London, 1983), 65.

⁷⁹For an explanation of Mohs’ number and indentation hardness, see D. Tabor, ‘Moh's Hardness Scale—a Physical Interpretation’ Proc. Phys. Soc. B 67, 249–57, 1954. Sapphire is assigned a value of 9 on Mohs’ hardness scale, while diamond is ascribed a value of 10. The scale is misleading for diamond since between 1 and 9, the indentation hardness H increases by c. sixty per cent for each step: viz. log H nM, where n is assigned a value of 1.6, and M is the hardness number on Moh's scale. Diamond is an anomaly because it has an indentation hardness which lies in the range 5700—10,400 kg mm⁻² (depending on the crystallographic plane, load, and direction of indentation) compared with the value for sapphire c.2000 kg mm⁻². See also C.A. Brooks, Properties and Applications of Diamond, edited by J.E. Field (London, 1992), 515–46.

⁸⁰Principles, op. cit. (note 16).

⁸¹Harrison, op. cit. (note 19), 57.

⁸²T. Delfs, ‘Diamond balance springs’, Horological Journal 49–50 (2004).