Papers of Nevil Maskelyne : Journal of voyage to Java Head

Bishop, Robert; Laudor, John

Papers of Nevil Maskelyne

An abstract of a journal of an East Indiaman compiled by Robert Bishop, former master and pilot in the West Indies who produced charts and sailing directions for the region. It was in his capacity as pilot for this region that Bishop was examined in 1763 by a Parliamentary committee with respect to John Harrison's fourth chronometer, noted by Derek Howse in Nevil Maskelyne: Seaman's Astronomer (Cambridge, 1989). He was also appointed by the Board of Longitude in 1768 to instruct and issue certificates to masters relating to their ability to use almanac and quadrant <a href='/view/MS-RGO-00014-00005/177'> Confirmed Minutes for 12 November 1768 (RGO 14/5:173)</a> and he compiled tables for the computation of longitude, some of which are held in <a href='/view/MS-RGO-00014-00067'> Observations on Voyage of Discovery (RGO 14/67)</a>. Bishop used the journals from routine East India Company voyages to compile his East India Navigator's Daily Assistant (London, 1773), a volume of sailing directions in which journal summaries such as this are reproduced alongside textual description.This journal summary is from the 1768 to 1769 voyage of the East India Company ship Duke of Gloucester from the Lizard to Java Head, originally recorded by the Captain John Lauder. Physically it is made up of four folded leaves and is approximately 23 by 30 cm in size. The summary is tabulated, with columns for recording the daily latitude and longitude 'by account', longitude corrected by observation and the difference between the tow longitude positions. A final column is for observations on magnetic variation. Remarks inserted, <a href='' onclick='store.loadPage();return false;'> transgressing the lines of the table (RGO 4/157:2)</a>, suggest the importance of navigational information extraneous to the form here proposed for describing the ship's passage, as well as the significance of recording particular experience, not only as part of shipboard bureaucratic practice but also in subsequent texts produced for use in the field. Remarks include notes on the current, soundings, sightings of land and the actions of departure and arrival. The 'difference' column frequently contains thermometrical observations, again showing the tension between the forms for description proposed and the forms of description executed.Interestingly, <a href='' onclick='store.loadPage();return false;'> a note (RGO 4/157:4)</a> on the 12th May 1769 records a corrected longitude which revealed the dead reckoning position to be 413 miles further East. Two weeks later a concluding note of the summary on the longitude by account and corrected by observation for the Scilly Isles highlights a difference of six degrees of longitude <a href='' onclick='store.loadPage();return false;'> 'which proves the Exactness of our reckonings since that time' (RGO 4/157:4)</a>. This note on the successful preservation of known error is significant more broadly because it shows a lack of interaction between the two longitude columns, the results of different methods for establishing longitude at sea kept independent of one another at the same time as the one was being used to judge the other. As a document produced during the construction of a set of sailing directions, the noting of where longitude by account differed radically from longitude by observation also potentially speaks to the importance of knowing whereabouts on a voyage longitude by account might be liable to slip. Along with the other journal summaries compiled by Bishop (<a href='/view/MS-RGO-00004-00155'> (RGO 4/155)</a>, <a href='/view/MS-RGO-00004-00156'> (RGO 4/156)</a> and <a href='/view/MS-RGO-00004-00158'> (RGO 4/158)</a>), this volume is significant as it contains some of the data from which his East India sailing directions were constructed, and speaks to the potential use and utility of shipboard inscriptions.Megan Barford History and Philosophy of Science University of Cambridge