This chapter details the creation and management of the Nautical Almanac, one of the Board of Longitude’s most important concerns. Appointed Astronomer Royal and thus a Commissioner of Longitude in 1765, Nevil Maskelyne oversaw its publication and that of associated texts, directing the work of a group of mathematical computers overseen by comparers. Hierarchical organisation and increasing costs preoccupied much of the Board of Longitude’s subsequent affairs. Calculated up to a decade in advance, the Nautical Almanac became a symbol of the Board’s repute among foreign academies and observatories, although its accuracy was later subject to satire and criticism. After Maskelyne’s death, work seems to have suffered and its management was overhauled by the Longitude Act of 1818 that brought it under Thomas Young’s management. Controversy wracked the Board’s direction of the Nautical Almanac for the next decade. Its assignment from 1831 to the astronomer William Stratford as superintendent was a major element of the aftermath of the Board’s abolition.

This chapter offers a survey of the ways in which the British Board of Longitude handled the range of schemes and projects that were presented by mathematicians and mariners, inventors and entrepreneurs during its final decades to 1828. Labels of impracticality, eccentricity and derangement have long been assigned to many of these proposals, notably in the classification scheme imposed by Astronomer Royal George Airy in his reorganisation of the Board’s archives from the 1840s. This chapter favours close reading of the ways in which schemes were assessed and managed at the time. In the bulky correspondence received, schemes for new devices, calculation methods or navigation techniques were mixed with projects for squaring the circle or endless mechanical power. The Board distinguished between those projects reckoned impossible or unsound, and those it judged irrelevant or beyond its scope. It is shown how much discretionary power the Board exercised, and how its accumulated papers preserve a wide range of protagonists’ technical and scientific interests.

This chapter examines the Board of Longitude’s relationships with watchmakers in the five decades after their dealings with John Harrison. In this period in which the chronometer – a term brought into more common use in the period – began to develop into a stable technology, the Board still fielded proposals for schemes about mechanical timekeeping and actively engaged with a small number of makers. Acting within the remit of a new Longitude Act in 1774 that significantly changed the terms for testing and reward, the Board increasingly relied on land trials at the Royal Observatory, Greenwich, alongside a small number of long-distance voyages, which provided an additional arena for testing the nascent technology. During this period, the Board became embroiled in two debates that further shaped its horological dealings and saw its authority contested in Parliament. The first, over the work of Thomas Mudge, saw the Board’s authority undermined. The second, centring on a long and bitter dispute between watchmakers Thomas Earnshaw and John Arnold (and son), finally saw the Board’s authority recognised.

This chapter surveys the workings of the British Board of Longitude in the period from the mid-1770s, which saw expenditure and bureaucracy increase. The Longitude Act of 1774 cut rewards and tightened the criteria for success. Managed through a permanent secretary, the Board more resembled an office of state, while personal and patronage relations still played vital roles in its conduct. Both Astronomer Royal Nevil Maskelyne and Joseph Banks exploited the Board to further their own interests in policy and organisation in projects including management of the Nautical Almanac and its computers, supply of instruments to survey voyages, and trials of new kinds of optical glass. The chapter explains how Maskelyne used the Board to extend networks centred on the Royal Observatory, Greenwich, while Banks used his position as a Commissioner of Longitude to mend relations with the Admiralty and extend patronage. Although there were major tensions and conflicts with Maskelyne, Banks was able effectively to make the Board of Longitude an integral component of his system of public administration over the sciences.

This chapter reinterprets the demise of the Board of Longitude in 1828, which has been seen as resulting from reformist pressure or financial retrenchment. Such accounts underestimate continuation of the Board’s activities, notably managing chronometers, producing the Nautical Almanac and providing scientific advice. Changes were initially driven by Joseph Banks’s interests, notably the appointment of Royal Society fellows and Resident Commissioners including Thomas Young, who became secretary and a key organiser after Banks’s death. Schemes such as rewards for finding the Northwest Passage, improvement of optical glass, determining the figure of the Earth and the foundation of the Cape Observatory, were managed under Young’s aegis. The role of the Admiralty and its Secretaries John Wilson Croker and John Barrow were decisive. The Longitude Act of 1818 brought the Board under Admiralty control, and that of 1828 moved its work into the Admiralty. An Admiralty committee comprising Young and natural philosophers Michael Faraday and Edward Sabine was formed; the Nautical Almanac and chronometer testing remained within the Admiralty’s financial remit.

This brief epilogue considers the decades after the dissolution of the British Board of Longitude in 1828 and the ways in which its functions were subsumed by and distributed between other bodies, within the Admiralty and beyond.

This chapter scrutinises the British Longitude Act of 1714 and its immediate aftermath. It shows, first, the extent to which the wording of the Act drew on precedents from the previous century. Second, it argues that the Act was never intended to create a ‘Board of Longitude’ as a formal, standing committee with regular meetings. Rather, it nominated a number of individuals – by name or by virtue of their official role – seen fit to judge potential ideas. This is a powerful example of the way in which longitude legislation was revisable and open-ended. With this in mind, the chapter shows that the Act did indeed foster considerable activity and discussion around longitude matters over the next two decades. This activity was marked by considerable continuity in the persistence of schemes already being discussed before 1714: eclipses, lunar distances, artificial timekeepers, magnetic variation and dip, signalling, and dead reckoning.

Focusing on the period from the early 1760s to the resolution of the John Harrison affair in 1773, this chapter argues that it was only in this period that the ‘Board of Longitude’ came into being. This was largely in response to the debates surrounding the sea trials of Harrison’s fourth marine timekeeper (H4) and two other longitude schemes – Tobias Mayer’s tables and method for lunar distances and Christopher Irwin’s marine chair for observing Jupiter’s satellites. The transformation into a standing board manifested in regular rather than sporadic meetings and the appointment of a secretary to keep the Board’s papers in order as the Commissioners, for whom astronomer Nevil Maskelyne would become a central figure, sought to defend their decisions over the allocation of monetary rewards. The debates with Harrison, which focused on questions of adequate testing and the judging of trials, disclosure and replicability, and accusations of self-interest, would see the Board harden its stance through the use of legislation to ensure resolution. The Harrisons and their supporters, by contrast, sought to bolster support through lobbying and publication of their claims.

This chapter explores the long- and short-term roots of the British Longitude Act 1714, highlighting the degree of continuity with earlier precedents. It first explores the nature and impact of developments in navigational techniques and instruments, astronomy, timekeeping, the finding of longitude on land and the judging and funding of longitude proposals in sixteenth- and seventeenth-century Europe. It then delves into the chain of events and written and verbal discussions which gave rise to the new British rewards in 1713–1714. These saw the self-interested lobbying of two projectors gain momentum through a confluence of national and political interests, before becoming enshrined in law as rewards open to all comers.