<p style='text-align: justify;'>A proposal for finding the longitude by <a target='_blank' class='externalLink' href='http://www.npg.org.uk/collections/search/portrait/mw06743/William-Whiston?LinkID=mp04796&role=sit&rNo=0'>William Whiston</a>, once Newton's successor as Lucasian Professor at Cambridge, but by the 1730s a somewhat infamous public lecturer in London. The manuscript describes an instrument and method proposed to the Royal Society in 1730 and there is, indeed, <a target='_blank' class='externalLink' href='http://royalsociety.org/DServe/dserve.exe?dsqIni=Dserve.ini&dsqApp=Archive&dsqCmd=Show.tcl&dsqDb=Catalog&dsqPos=13&dsqSearch=%28%28text%29%3D%27whiston%27%29'>a second copy</a> of this manuscript in the RS archives. It therefore helps to show how in these early years of the Board of Longitude the Royal Society was a parallel institution to which proposals were shown. The signature confirming receipt of this copy by Sir Charles Wager, Lord High Admiral, shows that it was sent to the Admiralty as a route to the Board.</p><p style='text-align: justify;'>Whiston's proposal is to find longitude at sea through observing the eclipses of Jupiter's satellites. This was the third main method of finding longitude that proposals to the Board investigated, after lunar distance and chronometers. Its two main inconveniences were the fact that Jupiter's satellites were not visible for about 2 months per year as their orbits drew close to Jupiter, and that the accurate observations necessary to use them were extremely difficult on a moving vessel. Whiston combatted the second in this proposal with his newly invented telescope. He proposed combining 7 eye glasses such that the observer could keep Jupiter and the satellites in view in at least one of the glasses despite standing on a rocking deck. He likewise argued that this telescope could be used to observe lunar appulses during the months when the eclipses couldn't be seen, even though this was more complicated. The telescope could also be used to observe for latitude.</p><p style='text-align: justify;'>One <a href='' onclick='store.loadPage(1);return false;'> comment (MSS/79/130.2:1)</a> by Whiston is particularly telling, where he explains that, 'I did not then carry this discovery any farther; because I was determined not to publish anything more about ye Longitude till I was fully satisfied ye method was not only right, but also would be practicable at sea.' This proposal was his fourth method for finding longitude since the suggestion of using bomb vessels, published jointly with Humphrey Ditton, which had launched the <a href='/view/MS-RGO-00014-00001/19'> Longitude Act (RGO 14/1:10r)</a> in 1714. He had also proposed using magnetic variation in 1719, and solar eclipses in 1724. His openly dissenting religious views and such intent pursuit of the longitude had turned Whiston into an established figure of satire by the 1730s, inextricably linked to jokes about madness and projecting. His comment here suggests that he was not impervious to such satire, and may even be reflected in Wager's <a href='' onclick='store.loadPage(4);return false;'> label (MSS/79/130.2:4)</a> of the manuscript as 'Mr Whiston's Project for finding the Longitude.'</p><p style='text-align: justify;'>Whiston's closing comment on the importance of accurate surveying of 'ports and havens' did at least cause the Board to take him seriously, however. It was undeniable that accurate mapping of the land was essential as the comparison point for navigation at sea, and Cassini had recently achieved this for the French coast. Jupiter's satellites were also the most accurate means of doing this on land. In 1741, the Board <a href='/view/MS-RGO-00014-00005/10'> awarded (RGO 14/5:6)</a> Whiston £500 for this project of surveying, at the same time as making John Harrison the second payment in support of developing his chronometers. </p><p style='text-align: justify;'>Katy Barrett<br />History and Philosophy of Science<br />University of Cambridge<br /></p>
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