National Maritime Museum Manuscripts : Sixth voyage of Bombay Castle, Bombay and China: calculations of longitude, 1805

National Maritime Museum Manuscripts

<p>One of three documents from the papers of the East India Company <a href='/search?keyword=Captain%20Archibald%20Hamilton'>Captain Archibald Hamilton</a>, who from 1802 commanded two voyages in the East India Company Ship <a href='/search?keyword=Bombay%20Castle'>Bombay Castle</a> that sailed to <a href='/search?keyword=Bombay'>Bombay</a> and <a href='/search?keyword=China'>China</a> along the well-established trade networks as part of the East India Company's lucrative business in the Indian Ocean and the Pacific. The journey Bombay Castle has received most attention for is its involvement in the 1804 Battle of Pulo Aura - a confrontation initiated by French attempts to raid the cargo-laden British vessels at the <a href='/search?keyword=Straits%20of%20Malacca'>Straits of Malacca</a>.</p> <p> These records, however, do not contain information about military skirmishes, rather, they contain the instructions for, and attempts at, calculating longitude by lunar and stellar observation and by timekeeper. What is perhaps most interesting is the list of instructions contained in [<a href='/view/MS-HMN-00031/1'>HMN/31</a>] that outline in quite basic terms the method of calculating longitude by lunar or stellar observation. It should be remembered that these techniques were not necessarily 'new' but they were difficult, and by the early nineteenth century no standard procedure had been established of who should perform them or when they should be done: on British voyages of discovery, for instance, it was often Board of Longitude appointed astronomers who were tasked to carry out these actions. These techniques for finding longitude also ran up against a real reluctance by officers both from the Royal Navy and from the East India Company to attend naval schools and academies to learn the necessary mathematics.</p> <p> By comparing the instructions [<a href='/view/MS-HMN-00031/1'>HMN/31</a>] with the rough calculations (in [<a href='/view/MS-HMN-00029/1'>HMN/29</a>] and HMN/44), we can also see that the ongoing trialling of timekeepers was totally dependant upon astronomical technique in order to produce rates of the going of these timekeepers and to judge how well they were performing (and therefore how much they were to be trusted) - something which was still occurring in the early nineteenth century. This information tended to be used in three ways: by the clock and watchmakers themselves to promote their instruments both to the private market of officers on Royal Navy and East India Company ships; by the Board of Longitude in their attempt to discern between the quality of different timekeepers and the usefulness of timekeepers as a practical solution for finding longitude (even at the beginning of the nineteenth century); and by officers themselves who, by the early nineteenth century were demonstrating their capacity as conspicuous consumers of timekeepers by writing about the various advantages and/or deficiencies of timekeepers in magazines and journals such as the New Monthly Magazine.</p> <p>Eóin Phillips<br />History and Philosophy of Science<br />University of Cambridge<br /> </p>


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