National Maritime Museum Manuscripts : Lunar-distance observations form by Robert Bishop

National Maritime Museum Manuscripts

<p>A printed form for entering handwritten computations for finding the longitude at sea by lunar-distance observations. One side is blank with the modern handwritten notation 'found loose in SEL 32' at the bottom, while the other side was completed in ink for 5 September 1767. The form was created by <a href='/search?keyword=Robert%20Bishop'>Robert Bishop</a>, a former <a href='/search?keyword=Naval'>Naval</a> master and pilot who repeatedly collaborated with the Board of Longitude and other nautical interests, and is said to have been printed by order of Act of <a href='/search?keyword=Parliament'>Parliament</a> on 9 December 1768. Similar forms can be seen in volume [<a href='/view/MS-RGO-00014-00067/1'>RGO 14/67</a>].</p> <p>Forms like this one were a vital part of the Astronomer Royal <a href='/search?keyword=Nevil%20Maskelyne'>Nevil Maskelyne</a>'s efforts from the 1760s onwards to put both the lunar-distance method and the annually published Nautical Almanac into wider use. On 12 March 1767, the Board of Longitude directed [<a href='/view/MS-RGO-00014-00005/79'>RGO 14/5:75</a>] that copies of the first <i>Almanac</i> be put on sale in British, European and colonial ports. On 12 November the following year, the Board decided [<a href='/view/MS-RGO-00014-00005/92'>RGO 14/5:88</a>] to advise the Admiralty to order ship's masters and commanders to learn how to use the <i>Almanac</i> with a Hadley's quadrant from specified teachers including Robert Bishop in London (a plan which experienced little success).</p> <p>Maskleyne also turned to Bishop in 1768 to design the first published lunar-distance forms, which were intended to guide those untutored in the method through making the necessary calculations and recording the results. One section refers to computation of refraction by Mr <a href='/search?keyword=%5BIsrael%5D%20Lyons'>[Israel] Lyons</a>'s table - the acceptance and encouragement of which by the Board is explained in the summary for volume [<a href='/view/MS-RGO-00004-00292/1'>RGO 4/292</a>]. Before this, Bishop had also published charts and sailing directions and had been one of the individuals examined by the Parliamentary committee of 1763 which considered the case of John Harrison, leading to the enactment of Act 3 George III c. 14.</p> <p>Alexi Baker<br />History and Philosophy of Science<br />University of Cambridge<br /> </p>


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