Sextant

by David Barrie

  The old paper charts—which are bulky and expensive—are gradually disappearing as navigators rely increasingly on “electronic chart display and information systems” (ECDIS) that can be loaded on computers and readily updated. Connected directly to the GPS, these “moving map displays” show the vessel as a little ship moving across the surface of the “chart,” and provide very precise information about its course and speed, as well as the effects of currents and leeway, the state of the tide, not to mention distances to, and estimated times of arrival at, any chosen point. Nothing could be more convenient, but such “electronic charts” reduce the navigator’s role almost to that of a spectator—or perhaps, more precisely, a mere consumer of navigational data.

  In the light of these developments, there has been much debate in nautical circles about the continuing relevance and usefulness of celestial navigation. The U.S. Navy has taken the bold step of ceasing to train all officers in the use of the sextant: only navigational specialists now have that privilege. In most national navies and the merchant service, however, courses in celestial navigation are still required. Safety is usually advanced as the reason for retaining the old skills. At the simplest level, it is obvious that electronic systems—like GPS—can and often do break down, for example when electricity supplies fail or equipment is accidentally damaged. But there are other risks, too.5 Charged particles emitted by the sun can give rise to disturbances of the earth’s magnetosphere capable of disrupting electronic equipment in orbit—or even on the ground. Although we usually have some warning of such events, and the GPS network is designed to be resilient, there is always the possibility that some satellites might be accidentally disabled. The system is also vulnerable to acts of war, and those who control it can easily restrict access to it.

  Perhaps a more pressing danger, however, arises from inexpensive jamming devices designed to block the reception of the very weak signals emitted by GPS satellites. Drivers of commercial vehicles fitted with GPS trackers sometimes use such jammers to conceal from their employers exactly where they have been, but in so doing they may unintentionally block GPS coverage over a wide radius. Nor is the vulnerability of GPS of concern only to navigators: many of the electronic systems on which modern life depends—including cellular phones and the computers that manage international financial markets—rely on GPS time signals. In view of all these real or potential problems, an “enhanced” modern version of LORAN is being developed to provide a robust and accurate backup to GPS.6

  STRANGELY ENOUGH, THE work of an artist—James Turrell—has helped me understand why navigating with a sextant casts such a powerful spell over me. Turrell has spent half a lifetime turning an extinct volcano in a remote corner of the Painted Desert of Arizona into what can justly be described as a celestial work of art. Roden Crater is a naked-eye observatory, without telescopes or computers, where the only sounds are the wind in the juniper bushes and the crunch of the reddish pumice under foot. Turrell’s medium is light itself, and the “skyspaces” he has built within the crater are designed to help us catch sight of ourselves in the very act of seeing and to discover with freshly opened eyes the everyday wonders of light—especially the light that comes from beyond the “ocean of air” that is the earth’s atmosphere. To enter one of these skyspaces is revelatory. When I was lucky enough to meet him, I was not surprised to discover that Turrell is an aviator and a sailor, that he knows how to find his way by the light of the heavens. His art is embedded in his reverence for the natural world.

  Turrell describes the light that reaches us from outer space as “old,” in contrast to the “new” light that we generate ourselves. It is a nice distinction, though in cosmic terms the light from the stars we can see with our naked eyes is extremely young. Our Milky Way—filled with hundreds of billions of stars—is just one of countless galaxies, many of which are so distant that their light, when at last it reaches us, has been travelling since long before the earth coalesced out of a cloud of cosmic dust some 4.5 billion years ago, and the stars from which it comes may long since have died. In 2012 astronomers reported observing a galaxy formed not long after the Big Bang itself that is (or was when its light set out on its journey) more than 13 billion light-years distant from us.7 Thirteen billion years travelling through space at roughly 186,000 miles a second: that is a long, long way. Yet it was only when the first big reflecting telescopes were built early in the last century that anyone knew for sure that the Milky Way was not a solitary archipelago of light in a pitch-black, otherwise empty universe. The huge new mirrors resolved the mysterious blurry nebulae revealed by the old telescopes into vast congregations of stars. The known universe had just grown vastly bigger, and it has gone on growing as the reach of telescopes has continued to increase.

  Our species is thought to have first emerged about two hundred thousand years ago. Almost everything about our prehistory remains uncertain, but there is no doubt that until very recently our ancestors survived in the wild as hunter-gatherers, living off the land or sea. The details must have varied a good deal from place to place, as they do among the few groups that still survive in these ways, but in every case people were immersed in the natural world, and profoundly influenced by it, if not completely under its control. Survival depended on thoroughly understanding the environment in which they lived—when and where the food and water they needed could be found, the timing of migrations of birds and animals, the behavior of predators, seasonal weather patterns, and so on. With the development of agriculture and settled life in villages and towns over the last ten thousand years, humans have achieved a growing measure of independence from the vagaries of nature. But until the Industrial Revolution almost everyone was engaged directly or indirectly in the production of the raw materials of life: food, clothing, and shelter. Very few lived in towns, most of which were still so small that the countryside would never have felt remote.

  Over the last few hundred years the balance has gradually but decisively changed. Today most of the world’s population live in cities, many of which have grown so large that their inhabitants have little or no day-to-day contact with the natural world. They cannot even see the stars at night. The accelerating growth of urban culture has been closely associated with the development of new technologies, many of which have contributed to our growing alienation from “wild nature”: new methods of transport and communication, new kinds of food and drink, new forms of work. In short, we now have completely new ways of living. A frequently observed feature of modern life is that it makes fewer and fewer physical demands, with the result that more and more of us are suffering from illnesses associated with a sedentary existence. We are also being gradually relieved of the mental challenges that were once part of everyday life. Computers eliminate the burden of performing the simplest calculations, they correct our spelling and grammar, help us to remember what we have to do, “manage” the engines of our cars, help us take photographs, and much more besides. Now they even do our navigation for us.

  If asked, most sailors would probably agree that they endure the many discomforts of life at sea in order to find spiritual refreshment in the largest wilderness on the planet. They might also mention the attractions of self-sufficiency and independence. It is then ironic that so many navigators should now choose to find their way at sea by watching a little red ship moving over a bright blue screen rather than by using the natural cues around them. In doing so, they are not only turning their backs on the very things that make the whole undertaking worthwhile, but they are also denying themselves the precious rewards of agency—the use of hand, head, and eye to solve problems and overcome difficulties.8

  GPS and all the other electronic gadgetry certainly offer reassurance and convenience, but the solutions they provide are delivered without the slightest effort on our part, and often with as little understanding. And excessive reliance on such technology may actually weaken our natural navigational skills.9 As GPS threatens to return us all to the helpless dependency of
childhood, offshore sailors in particular run the risk of neglecting an older, more demanding, yet far more personally rewarding technology. I am not calling for electronic navigational tools to be abandoned, but we should avoid becoming exclusively dependent on them. It is time to rediscover the joys of celestial navigation, not merely as a safety net, but because using a sextant to find our way puts us in the closest possible touch with the natural world at its most sublime.

  Outside the abstract domain of mathematics, nothing better symbolizes the timeless order and perfection of the divine realm than the workings of the cosmos. When I recall learning how to handle a sextant all those years ago, I see myself, a transient speck of life, fixing my position on the surface of our small planet by taking the measure of vast, unimaginably distant suns whose lives are measured in billions of years. The chastening contrast between their calm majesty and my fretful pettiness was overwhelming. And yet, small as I was, when I caught the stars in the mirrors of my sextant, I felt as if I was entering into a strange communion with them. After crossing countless miles of space, light emitted by those colossal thermonuclear fires had at last reached my eyes, had told me exactly where I was. When I look up at the stars in the night sky that once showed me the way across an ocean, a sense of wonder engulfs me, and I bow my head.

  Acknowledgments

  For reasons that will be obvious, I should first record my thanks to my father and to Colin McMullen. I am also deeply grateful to my mother for encouraging me to embark on that life-changing voyage aboard Saecwen so many years ago.

  Special thanks are due to my agent, Catherine Clarke, for helping me to refine the original proposal for this book and for persuading HarperCollins to publish it. Arabella Pike, my editor, saw the point of what I was trying to do and has been very supportive throughout the book’s development while at the same time offering shrewd and constructive criticism. I am immensely grateful to her, and to the team who have put the book together—Jo Walker, who designed the cover; Katherine Josselyn and Tara Al Azzawi who have masterminded the PR and marketing; Peter James, the copy editor; Geraldine Beare who assembled the index; and especially Kate Tolley, who has overseen the whole process with such skill, patience, and good humour.

  I have benefited from conversations and email exchanges with Dr. Richard Dunn, Senior Curator and Head of Science and Technology at the National Maritime Museum, who has also kindly read and commented on parts of the manuscript. Richard’s colleagues on the Cambridge Digital Library Board’s Longitude Project have helped me with technical queries: Katy Barrett, Dr. Rebekah Higgitt, and Dr. Nicky Reeves. I am also grateful to the staff of the Caird Archive and Library at the National Maritime Museum, the National Archives, the United Kingdom Hydrographic Office, and the British Library.

  The Director of the Royal Institute of Navigation, Peter Chapman-Andrews, has been very helpful, and I have made extensive use of the Institute’s Cundall Library as well as the Institute’s online archives. Peter put me in touch with David Rydiard, staff author, Admiralty Manual of Navigation, who kindly read and commented on the technical parts of the manuscript. J. D. Hill of the British Museum gave me useful advice about the Nebra Sky Disc. I am also grateful to Professor Maya Jasanoff of Harvard University and Professor Claudio Aporta of Dalhousie University for helpfully responding to my queries.

  I would also like to thank Tristan Gooley and John Heilbron for their advice and encouragement, and Javier Mendez Alvarez of the Roque de Los Muchachos Observatory on La Palma in the Canary Islands, who showed me how a modern observatory works and patiently answered many questions. Warner Bros. kindly gave permission for me to quote from the screenplay of Mutiny on the Bounty.

  Heather Howard, Colin McMullen’s daughter, and Vanessa de Mowbray have generously allowed me to reproduce photographs of Colin and of Saecwen, while my sister Fiona Rogers, my nephew Kit Rogers, and his wife, Jessie Lane, have commented helpfully on the manuscript. My sister-in-law, Elizabeth Gibson, has given me valuable advice, and her husband, Rick Morgan, brought to my attention and translated the passage from the Lusiads quoted in Chapter 3. My wife’s cousin, Jane Kimber, and her husband, Jonny Clothier, have been extremely generous in allowing me to borrow their beautiful yacht, Brown Bear, in various parts of the world.

  My wife, Mary, and my daughters, Eleanor and Miranda, have cheerfully endured my enthusiasm for celestial navigation over many years and have encouraged me greatly during the writing of Sextant. But it is to Mary, above all, that I owe my deepest thanks—not least for her expert help in polishing the manuscript.

  Notes

  INTRODUCTION

  1 Beaglehole (1966) 41ff.

  2 Ibid. 36.

  3 Ibid. 57.

  4 According to Mendaña’s own estimate, the “Western Islands” lay some 5,000 nautical miles from Peru, but this was more than 2,000 miles short. Such large errors were by no means unusual: one of Magellan’s pilots was out in his estimate of the longitude of the Philippines by almost 53 degrees—equivalent to some 3,000 nautical miles. See Beaglehole (1966) 38.

  5 Beaglehole (1966) 80.

  6 Ibid. 317ff.

  7 Jean-Nicolas Buache was later to be custodian of the French hydrographic service—the Dépôt des Cartes et Plans de la Marine: Van der Merwe 45.

  8 The sextant was a development of Hadley’s “quadrant,” which continued in use for many years after the sextant was introduced. But the name sextant has long been used as a generic term for all instruments of this kind, and that is the sense in which I use it here.

  9 Lack of space prevented the inclusion of other remarkable hydrographers—like Alessandro Malaspina, who led the great Spanish expedition to the Pacific of 1789–94, or William Fitzwilliam Owen, who surveyed much of the coast of Africa in the 1820s while also conducting campaigns against slave traders.

  10 See, e.g., Lewis.

  11 GPS is in fact just one satellite navigation system, though by far the best known and most widely used. The generic term for all such systems is Global Navigation Satellite Systems, or GNSS.

  CHAPTER 1: SETTING SAIL

  1 Beaglehole (1974) 33–34.

  2 Ritchie 15.

  3 Beaglehole (1974) 54.

  4 Ibid. 58.

  5 Ibid. 71–72.

  6 Conrad 2.

  CHAPTER 2: FIRST SIGHT

  1 Hakluyt VI.38–42.

  2 Howse and Sanderson 109.

  3 Translations given in Bowditch 248.

  4 Mary Blewitt, Celestial Navigation for Yachtsmen (5th ed., 1973).

  5 Homer, The Odyssey, Book 5, lines 269–75: my translation.

  6 After making the necessary corrections to the reading (for sextant error, “height of eye,” atmospheric refraction, the sun’s semi-diameter and parallax), the sun’s altitude was subtracted from 90 degrees to give the “zenith distance.” To this figure was added the value of the sun’s (northerly) declination to yield the latitude. If the sun’s declination had been southerly—as it is between late September and late March—it would have been subtracted from the zenith distance. The sun’s declination should also be corrected for the approximate longitude of the ship, as even a difference of a few hours from Greenwich can make a small but significant difference.

  CHAPTER 3: THE ORIGINS OF THE SEXTANT

  1 Joshua Slocum, Sailing Alone Around the World (1956).

  2 James L. Gould, “Animal Navigation: A Galaxy of Cues,”Current Biology, vol. 23, 4 (2013) 149–50; Marie Dacke, Emily Baird, Marcus Byrne, Clarke H. Scholtz, and Eric J. Warrant, “Dung Beetles Use the Milky Way for Orientation,” ibid. 298–300.

  3 P. Kraft, C. Evangelista, M. Dacke, T. Labhart, and M. V. Srinivasan, “Honeybee Navigation: Following Routes Using Polarized-Light Cues,” Philosophical Transactions of the Royal Society B, vol. 366, 1565 (2011) 703–708.

  4 Jonathan T. Hagstrum, “Atmospheric Propagation Modeling Indicates Homing Pigeons Use Loft-Specific Infrasonic ‘Map’ Cues,” Journal of Experimental Biology, vol. 216 (2013) 687–99.
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  5 B. Mauck, N. Gläser, W. Schlosser, and G. Dehnhardt, “Harbour Seals (Phoca vitulina) Can Steer by the Stars,” Animal Cognition, vol.11, 4 (2008) 715–18.

  6 Aveni 87–92.

  7 Taylor 99–100.

  8 Cotter (1968) 35.

  9 Ibid. 56.

  10 Luís Vaz de Camões, The Lusiads, Canto V, verses 25–27, translation courtesy of Rick Morgan.

  11 Cotter (1968) 67.

  12 Newton’s bitter rival Robert Hooke had invented a simpler instrument, on similar lines and employing only a single mirror, as early as the 1660s, whereas Newton’s relied on the use of two mirrors: see Cotter (1968) 74–75.

  13 Ibid. 77ff.

  14 Ibid. 81.

  15 Ibid.

  16 Bruyns 106, for example.

  17 Melville 448–49.

  CHAPTER 4: BLIGH’S BOAT JOURNEY

  1 Beaglehole (1974) 498.

  2 Bligh 160.

  3 Bligh claimed in his published account of the voyage that he was allowed to take only a “quadrant,” but his journal shows that he actually had a sextant and navigational books.

  4 Bligh 156–64.

  5 Ibid. 177.

  6 Ibid. 180.

  7 Ibid. 182.

  8 Ibid. 192.

  9 Ibid. 197.

  10 Ibid. 220.

  11 Ibid. 227.

  12 Ibid. 234.

  13 Ritchie 190.

  CHAPTER 5: ANSON’S ORDEALS

  1 This famous sea battle took place in May 1941. The Bismarck was the largest European battleship of the day, and the pride of the German navy. She was attempting to break out into the North Atlantic with her consort, the heavy cruiser Prinz Eugen, when she was intercepted in the Denmark Strait by the elderly British battle cruiser Hood and the brand-new battleship Prince of Wales. Hood exploded and sank in a matter of minutes after being straddled by a German broadside that probably ignited one of her magazines. More than 1,400 men died—only a handful survived. A shell from Prince of Wales, however, punctured one of Bismarck’s fuel tanks, forcing her to cut short her mission and head for France. She was sunk two days later with heavy loss of life. Prince of Wales herself was later sunk by Japanese bombers off the Malay Peninsula. Colin, who was among the last to leave the ships, swam from the bridge as she turned over. He dryly commented that they were lucky not to have been attacked by sharks while they floated in the sea waiting to be rescued.