<p>A notebook of observations by <a href='/search?keyword=Nevil%20Maskelyne'>Nevil Maskelyne</a>, comprising miscellaneous observations made in 1758 in <a href='/search?keyword=Barnet'>Barnet</a>, where Maskelyne held a curacy, and observations made in 1764 on the return voyage from <a href='/search?keyword=Barbados'>Barbados</a>.</p> <p>As a rough notebook, the beginning of the volume is in part interesting because of the heterogeneous nature of the observations: comparisons of barometers sit alongside calculations of requisite stationary<a href='' onclick='store.loadPage(3);return false;'>RGO 4/1:1r</a>, and a note on seconds lost from 'Mr <a href='/search?keyword=Harrison'>Harrison</a>'s watch' is found next to one about the want of a preface to Mr Scott Newlin's book.<a href='' onclick='store.loadPage();return false;'>RGO 4/1:inside cover</a> There is also a table comparing the positions of major stars<a href='' onclick='store.loadPage(4);return false;'>RGO 4/1:1v</a> in the 'British Catalogue' (the common name for <a href='/search?keyword=John%20Flamsteed'>John Flamsteed</a>'s 1725 Stellarum Inerrantium Catologus Britannicus) and in the <a href='/search?keyword=Abbe%20de%20la%20Caille'>Abbe de la Caille</a>'s positions from 1750.</p> <p>The bulk of the 1758 notes are comprised of barometrical observations in <a href='/search?keyword=Barnet'>Barnet</a>. These notes include details on the setting up and nature of the instruments used<a href='' onclick='store.loadPage(5);return false;'>RGO 4/1:2r</a>, and the people who took part in the observation process: Captain <a href='/search?keyword=Ashurst'>Ashurst</a> whose portable barometer was also used, as well as <a href='/search?keyword=John%20Bevis'>John Bevis</a> and <a href='/search?keyword=Mr%20Bennet'>Mr Bennet</a> who made observations using a portable barometer on a journey into London on Maskelyne's behalf. <a href='/search?keyword=Richard%20Hassell'>Richard Hassell</a>, with whom Maskelyne was then lodging, also features as the owner of space in which observations were made, for instance in 'Mr Hassell's garden'<a href='' onclick='store.loadPage(6);return false;'>RGO 4/1:2v</a> as well as other locations in the house.</p> <p>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 <a href='/search?keyword=Britannia'>Britannia</a> under Captain <a href='/search?keyword=Hesketh%20Davis'>Hesketh Davis</a>. Corrections to the adjustment of the sextant and quadrant used on the voyage<a href='' onclick='store.loadPage(53);return false;'>RGO 4/1:26r</a> again indicate the importance of attention to preparing equipment before use, and the noted height of the eye above the sea at different places on board the ship<a href='' onclick='store.loadPage(16);return false;'>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 time a particular computation has taken<a href='' onclick='store.loadPage(37);return false;'>RGO 4/1:18r</a> or the need to repeat a calculation due to a mistaken taking out of the sun's declination for a particular date.<a href='' onclick='store.loadPage(44);return false;'>RGO 4/1:21v</a> Less reflexively, but revealing of frustrated computation, is a page on which the majority of the work is crossed out<a href='' onclick='store.loadPage(21);return false;'>RGO 4/1:10r</a>.</p> <p>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 soundings<a href='' onclick='store.loadPage(130);return false;'>RGO 4/1:64v</a>, weather and sails<a href='' onclick='store.loadPage(100);return false;'>RGO 4/1:49v</a>, and sightings of and communications with other ships<a href='' onclick='store.loadPage(74);return false;'>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 loss of the shorter focus eye glass for the telescope mentioned, but the contingencies of weather also only alowed for a shortened observation period<a href='' onclick='store.loadPage(67);return false;'>RGO 4/1:33r</a>.</p> <p>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>Megan Barford<br />History and Philosophy of Science<br />University of Cambridge<br /> </p>
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