This paper explores discussions centred on the activities of the British Board of Longitude to consider the ways in which some men of science, instrument makers and others thought about questions of precision and accuracy, both in principle and in terms of what was possible in practice when making observations at sea. It considers firstly the terminology used in some eighteenth- and early nineteenth-century texts, highlighting the concept of exactness, which was more commonly used to describe one of the desirable (...) qualities of instruments and methods. It then looks at some of the discussions and debates in which the Board of Longitude was involved from the 1760s to think about different actors’ expectations of what levels of exactness might be either desirable or possible for day-to-day navigation. The focus is on the ability to make accurate shipboard observations and on the question of what degree of exactness might have been accepted as good enough for routine navigational purposes when at sea. (shrink)

Sixteenth-century astrology was considered by its practitioners to be allied to a wide range of disciplines, including medicine, the magical arts and the mathematical arts. The last of these associations was particularly important, since it formed a cornerstone of the legitimation of the celestial art. Astrologers in late Tudor England sought to show, therefore, that astrology shared the characteristics of the increasingly strong and well-defined domain of the mathematical arts, and that it was an important ally of many of the (...) individual arts, such as astronomy, navigation, and instrument-making. This association was demonstrated in practice, where astrology and other mathematical arts were mastered by the same practitioners. (shrink)