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 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.