Finding Longitude: How ships, clocks and stars helped solve the longitude problem. Rebekah Higgitt. Читать онлайн. Newlib. NEWLIB.NET

Автор: Rebekah Higgitt
Издательство: HarperCollins
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Жанр произведения: Историческая литература
Год издания: 0
isbn: 9780007525874
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75° W, compared with a modern value of 67° 43' W. The observations showed significant errors by modern reckoning, not surprising given the instruments and data available, but they did demonstrate that determinations of longitude could be made while on expedition. While the infrequency of eclipses meant that they would never be routinely useful, other observations of the Moon had the potential to be used on a more regular basis and, as discussed in Chapter 2, some attempts to try them out were made in this early period.

       Error and loss

      Shipwrecks had many causes, just as they do today. Storms were a persistent problem but human error, including navigational mistakes, was also common. In many cases this was not simply about longitude determination but arose from a range of factors causing uncertainty as to a ship’s position and surroundings. Without proper charts, no amount of position fixing could prevent disaster.

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      Fig. 15 – Sir Cloudisly Shovel in the Association with the Eagle, Rumney and the Firebrand, Lost on the Rocks of Scilly, October 22, 1707

      {National Maritime Museum, Greenwich, London}

      Problems could easily arise in relatively unfamiliar parts of the world, and might be compounded by hostile weather and unknown currents. This was something that William Dampier, the first person to circumnavigate the world on three separate occasions, discovered repeatedly in a turbulent seafaring life. Dampier ventured into the Pacific for the second time in 1703 in command of the St George, as part of an ill-fated privateering party with the Cinque Ports. As the ships rounded Cape Horn, storms hit with their expected venom. The St George attempted to crawl its way around the Cape but its position was soon uncertain as the winds took it wherever they wished. What happened next depends on whose account one believes. According to William Funnell, an officer whom Dampier later accused of desertion, Dampier ordered the ship north once he believed they were to the west of Cape Horn but two days later it turned out, ‘contrary to all our expectations’, that they were still five leagues east of Tierra del Fuego.11 Dampier saw it differently. While he conceded that there was some uncertainty about their east–west position, sighting Tierra del Fuego was not so unexpected:

      for it is well known the Evening before, I told them we should see Land the next Morning, that of Terra del Fuego, the South Part of it: Now I look upon that to be a greater Mistake, to take one side of the Land for the other, than ’tis to be mistaken that we were Westward of the whole Island, and miss his Longitude ...12

      In any case, they were forced to brave the Horn once more.

      Their troubles did not end there. Having separated from the Cinque Ports, the St George headed north towards the Juan Fernandez archipelago, off the coast of Chile, which was a regular rendezvous and watering spot for ships entering the Pacific. The typical approach to Juan Fernandez was to run down the latitude from the coast of Chile but, according to Funnell, the St George sailed right past because Dampier failed to recognize the islands. They finally returned after three days without sight of land, only to find the Cinque Ports safely anchored there. Dampier’s information and memory had led him astray. Incidentally, one of the sailors on board the Cinque Ports was Alexander Selkirk, the inspiration for Daniel Defoe’s Robinson Crusoe, who decided he would rather be abandoned alone on an uninhabited island in the archipelago than remain on the unseaworthy Cinque Ports. Despite the privations of life on the island, it proved to be wise decision as the Cinque Ports foundered later in its journey.

      Mariners feared Cape Horn with reason, and the same was true of the western coast of Australia, which is littered with offshore reefs and islands that saw the demise of many ships plying their trade between Europe and Asia. The most notorious incident followed the loss of the VOC ship Batavia on its maiden voyage. Batavia sailed from the Netherlands in October 1628 and was in the southern Indian Ocean eight months later, heading along the recommended route eastwards before turning north for Java once it reached the correct longitude. By 4 June, it was approaching the Houtman Abrolhos, a known hazard off the west coast of Australia named ten years earlier by Frederik de Houtman, from the Portuguese abre os olhos, meaning ‘open your eyes’. The Batavia’s pilot knew he was approaching the reefs but seems to have ignored the danger signs and the ship struck. Of 322 on board, forty drowned during the shipwreck, and more than 110 men, women and children were killed as they awaited rescue in a tale of mutiny and murder that made for sensationalist reading back in Europe.

      Remote, unknown waters presented obvious dangers but there were plenty closer to home as well. Indeed, the Royal Navy’s worst maritime disaster of this period occurred not hundreds or thousands of miles away, but off the Isles of Scilly. Having concluded naval operations in the Mediterranean, a fleet under the command of Admiral Sir Cloudesley Shovell set sail for England at the end of September 1707. It should have been a routine voyage in well-known waters, even though they hit gales as they headed home. Just over three weeks in, the Admiral ordered his ships to heave to and check their position, concluding that they were safely in the English Channel. On the evening of 22 October, however, five ships struck the outlying rocks of Scilly (Fig. 15). Within hours four had sunk and at least 1600 men, including Shovell, were dead. It was a national tragedy.

      Many causes have been cited: weather; tides and currents; compass error; even longitude. What the surviving log-books show is that variable navigational abilities and unreliable data were the main culprits. The officers’ latitude determinations from backstaff observations, for instance, had an average spread of 25.5 nautical miles (47.2 km), those by dead reckoning a spread of 73 nautical miles (135.2 km). More dangerously, their geographical data was flawed. Most of the fleet took Cape Spartel at the entrance to the Strait of Gibraltar as their point of departure. Its latitude and longitude were listed in manuals such as Colson’s New Seaman’s Kalendar and Seller’s Practical Navigation, but their figures varied widely. Combined with inaccurate charts (see Fig. 11) and generally moderate navigational skills, poor data landed the fleet in its perilous position.

       The drive to improve navigational knowledge

      The known hazards of the sea and the resulting losses were a spur to improve all aspects of seafaring, including navigation. Among Europe’s maritime states, possible improvements were of obvious interest to those wielding commercial and political power as they sought to strengthen naval and trading operations. As will be seen in Chapter 2, the various rewards offered for longitude solutions from the sixteenth century onwards, and the foundation of state observatories in the seventeenth, arose within this context.

      Identical motives lay behind initiatives to improve navigational training. State-backed schools to train and license navigators and pilots engaged in long-distance trade were founded in Spain and Portugal in the fifteenth and sixteenth centuries, and these inspired a number of French navigation schools in the second half of the seventeenth century. Britain was not far behind its rivals when, in 1672, Samuel Pepys, by then Clerk of the Acts of the Navy, led moves to create ‘a Nursery ... of Children to be educated in Mathematicks for the particular Use and Service of Navigacon’.13 Granted a charter by Charles II, the Royal Mathematical School at Christ’s Hospital took in forty boys each year, from 1673, to study mathematics and navigation to prepare them for life in the merchant service or Royal Navy.

      Significantly, the school had the support of Isaac Newton (1642–1727) and the astronomers John Flamsteed and Edmond Halley (1656–1742), who saw this as a way in which their work could have tangible public benefit. Flamsteed, who taught some of the boys at the Royal Observatory, wrote to Pepys of the school’s value, foreseeing a time when trained seamen would fix longitudes from astronomical observations, ‘whereby the faults of our present Mapps and Sea Charts ... will be corrected and a halfe the Business of navigation perfected’.14 Another school initiated in 1712 as part of Greenwich Hospital for Seamen followed similar lines, with pupils first taught (from 1715) by Thomas Weston, assistant to the Astronomer Royal.

      Pepys continued his