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Papers of Nevil Maskelyne : Observations

Papers of Nevil Maskelyne

<p style='text-align: justify;'>A notebook of observations by Nevil Maskelyne, comprising miscellaneous observations made in 1758 in Barnet, where Maskelyne held a curacy, and observations made in 1764 on the return voyage from Barbados.</p><p style='text-align: justify;'>As a rough notebook, the beginning of the volume is in part interesting because of the heterogeneous nature of the observations: <a href='' onclick='store.loadPage(3);return false;'> comparisons of barometers sit alongside calculations of requisite stationary (RGO 4/1:1r)</a>, and <a href='' onclick='store.loadPage();return false;'> a note on seconds lost from 'Mr 's watch' is found next to one about the want of a preface to Mr Scott Newlin's book. (RGO 4/1:inside cover)</a> There is also a table comparing the <a href='' onclick='store.loadPage(4);return false;'> positions of major stars (RGO 4/1:1v)</a> in the 'British Catalogue' (the common name for John Flamsteed's 1725 Stellarum Inerrantium Catologus Britannicus) and in the Abbe de la Caille's positions from 1750.</p><p style='text-align: justify;'>The bulk of the 1758 notes are comprised of barometrical observations in Barnet. These notes include details on the <a href='' onclick='store.loadPage(5);return false;'> setting up and nature of the instruments used (RGO 4/1:2r)</a>, and the people who took part in the observation process: Captain Ashurst whose portable barometer was also used, as well as John Bevis and Mr Bennet who made observations using a portable barometer on a journey into London on Maskelyne's behalf. Richard Hassell, with whom Maskelyne was then lodging, also features as the owner of space in which observations were made, for instance in <a href='' onclick='store.loadPage(6);return false;'> 'Mr Hassell's garden' (RGO 4/1:2v)</a> as well as other locations in the house.</p><p style='text-align: justify;'>The second part of the volume is taken up with observations on the return voyage from Barbados between 30th August 1764 and 12th October 1764, on the ship Britannia under Captain Hesketh Davis. <a href='' onclick='store.loadPage(53);return false;'> Corrections to the adjustment of the sextant and quadrant used on the voyage (RGO 4/1:26r)</a> again indicate the importance of attention to preparing equipment before use, and <a href='' onclick='store.loadPage(16);return false;'> the noted height of the eye above the sea at different places on board the ship (RGO 4/1:7v)</a> demonstrates the importance of knowing one's hardware, since the error introduced if such heights were incorrectly known would be substantial. There are also a number of computations of longitude and notes on the difference between longitude computed and longitude by account. Sometimes these are accompanied by notes, for instance about the <a href='' onclick='store.loadPage(37);return false;'> time a particular computation has taken (RGO 4/1:18r)</a> or the <a href='' onclick='store.loadPage(44);return false;'> need to repeat a calculation due to a mistaken taking out of the sun's declination for a particular date. (RGO 4/1:21v)</a> Less reflexively, but revealing of frustrated computation, is a <a href='' onclick='store.loadPage(21);return false;'> page on which the majority of the work is crossed out (RGO 4/1:10r)</a>.</p><p style='text-align: justify;'>The form of the greater part of the notes from the return voyage is particularly interesting, since its presentation suggests the importance of routine shipboard activity to Maskelyne's own observation process. On each double page the verso is information copied out from the ship's log book, showing time, direction, course, and intermittent remarks on <a href='' onclick='store.loadPage(130);return false;'> soundings (RGO 4/1:64v)</a>, <a href='' onclick='store.loadPage(100);return false;'> weather and sails (RGO 4/1:49v)</a>, and <a href='' onclick='store.loadPage(74);return false;'> sightings of and communications with other ships (RGO 4/1:36v)</a>. The recto is taken up with Maskelyne's own observations, often concerned with establishing local time according to the time of the sunset. This is accompanied by the checking and adjustment of watches according to the local time of sunset as written in the 'Mariner's Calendar' and 'Mariner's Compass', referring to two volumes often bound together, Nathaniel Colson's Mariner's New Kalendar and the Mariner's Compass Rectified, originally compiled by Andrew Wakely, demonstrating how such works migh be put to use in the field. One of the longer notes here concerns the observation of the occultation of ω Sagittarii, an insight is given into some of the contingencies of observation: not only is the <a href='' onclick='store.loadPage(67);return false;'> loss of the shorter focus eye glass for the telescope mentioned, but the contingencies of weather also only alowed for a shortened observation period (RGO 4/1:33r)</a>.</p><p style='text-align: justify;'>This volume, as rough notebook, gives insight into the processes of observation and computation, and of such inscriptions as activity as well as product. It is also interesting because of what it shows of Maskelyne's activities at historiographically relatively underemphasised moments, for instance the observations made during the return voyage from Barbados.</p><p style='text-align: justify;'>Megan Barford<br />History and Philosophy of Science<br />University of Cambridge<br /></p>

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