The sixty-eight volumes of the papers of the Board of Longitude document in rich detail many of this public institution’s remarkably wide-ranging activities over more than a century (1714-1828). The 1714 Longitude Act nominated twenty-two Commissioners, including parliamentarians, administrators, scholars and naval officers. Their official tasks were to judge proposals for determining longitude at sea, fund experiments to try what seemed viable projects, and reward schemes judged successful according to the Act’s stringent criteria. The current disposition of these archives is mainly due to the nineteenth century astronomer George Airy, a member of the Board when it was abolished in 1828. Its papers were then divided up between the Admiralty and the Royal Society. In 1840 Airy arranged for all the papers to be brought to Greenwich Observatory, and by 1858 he’d ordered them into bound volumes with subject headings that reflect his own classification of the material.

The first volumes of the series therefore include copies of the legislation governing the Board, as well as draft and confirmed copies of the Board’s minutes, and some of its financial accounts. Other archives, such as the papers of Nevil Maskelyne, Astronomer Royal from 1765, document official and unofficial meetings of the Commissioners not mentioned in these minutes. The first recorded meeting of the Commissioners, minuted in RGO 14/5 , took place on 30 July 1737, when it was agreed to award £250 to the Humberside clockmaker John Harrison after a trial voyage of his sea clock to Lisbon. The Commissioners knew that, in principle, a marine clock that could keep time reliably over long voyages, combined with accurate determinations of the ship’s local time, could establish longitude at sea. It is possible that it was Harrison’s project that prompted the Commissioners to start their meetings. The minutes trace the Board’s negotiations with Harrison, large-scale funding for his work, followed by trials of his fourth sea clock in voyages to the West Indies in the 1760s and eventually payments to him of very considerable rewards.

The minutes also detail the Board’s concern in these decades with an alternative astronomical method for longitude at sea, involving computation of the Moon’s motion and observation from ships of the distance between the Moon and known stars. The early volumes record the Board’s receipt in 1755 and 1762 of accurate lunar tables made by the German mathematician Tobias Mayer. From 1767 Maskelyne produced a Nautical Almanac based on these tables that promised to allow mariners to determine their position by observation and calculation. Several volumes of the papers, especially RGO 14/22 , deal with the complex business of computing, publishing and correcting the Almanac. Other papers record the interest of the Board in increasingly precise devices for observing the position of the Moon and stars.

From 1774 new laws overhauled and widened the Board’s responsibilities. Records such as the accounts in RGO 14/15 - RGO 14/21 illustrate the Board’s reliance on the social networks of particularly important members, especially Maskelyne, Astronomer Royal until 1811, and the public servant and natural philosopher Thomas Young, the Board’s secretary from 1818. Most of the Board’s surviving papers deal with its activities from the 1770s onwards, including schemes for improvement and manufacture of marine chronometers, and sometimes controversial debates about the virtues of rival devices. These projects are detailed in RGO 14/23 - 28 . The Board also became a clearing-house for many navigational schemes, especially in improved optical instruments and precisely divided scales, magnetic compasses, and a range of survey methods. The archive has rich documentation from hosts of petitioners and makers offering newfangled improvements and seeking reward and sponsorship. Volumes of papers from the later eighteenth and early nineteenth century, RGO 14/29 - 30 , contain documents on instruments for observations at sea, while petitions and correspondence from the same decades, preserved in RGO 14/11 - RGO 14/12 and RGO 14/32 - RGO 14/41 , offer an invaluable record of the activities of a vast number of practitioners, often otherwise little-known, engaged in cartography, mathematics, astronomy, navigation and magnetism in the late Georgian period. Schemes that Airy labeled “impracticable”, collected in RGO 14/39 - RGO 14/40 , as well as groups of submissions on astronomical theories and on such topics as perpetual motion and circle squaring, held at RGO 14/53 - RGO 14/54 , offer a fascinating survey of the range of interests of several of these practitioners.

In order to test longitude methods, as well as make geodetic, magnetic and meteorological measurements, the Board hired astronomers for several voyages into the Pacific, including those of Cook in the 1770s, Vancouver in the 1790s and Flinders in 1801. RGO 14/56 - RGO 14/61 contain logbooks from Cook’s voyages, RGO 14/62 - RGO 14/63 logs kept by the astronomer William Gooch despatched to join Vancouver, and 14/64 - RGO 14/68 a range of important logs and correspondence related to later expeditions. Magnetic measures, many pursued as part of campaigns for global magnetic maps and surveys, formed a very significant part of the Board’s work. RGO 14/42 - RGO 14/43 hold an especially rich collection of papers on methods for securing and improving compasses and magnetic measures.

The final decade of the Board’s existence, a period of dramatic expansion as well as crisis, is well documented here. In 1818, at a period when the its remit and budget both grew, the Board was also charged with administering rewards for mariners who charted a north-west passage from the Atlantic to the Pacific, and for those navigators who came close to the North Pole. In 1822, the Board agreed to support the establishment of a new state observatory at the Cape of Good Hope, and the minutes, as well as correspondence in RGO 14/48 - RGO 14/49 , give some details of this decision and its consequences. In the 1820s, the Board planned collaboration with the Paris Observatory to determine the distance between the two Observatories, and papers in RGO 14/13 detail these plans. The papers also testify to the strenuous efforts exerted by the Board throughout its existence somehow to register, catalogue and control the worldwide distribution of instruments and personnel that formed a vital part of its activities.

Also included in this collection are two items closely related to the papers of the Board - Letters, memoranda and journal containing the history of Mr William Gooch and An account of John Harrison and his chronometer .

Simon Schaffer
History and Philosophy of Science
University of Cambridge

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