This collection of essays, bringing together many of the established curators and historians in the field of scientific instruments and ranging widely over their interests, represents a branch of the history of science whose activity, output and significance within the discipline have blossomed in recent years. It is no longer possible to fence off a grand conceptual succession and represent this as the only essence of scientific development. Practices - in discovery, experiment, application and teaching - are integral parts of what science does and are therefore all part of what it is, and instruments were central to each of these varieties of scientific practice. The instrument historian comes in a number of guises - the scholar, the collector, the curator, the dealer - and the discipline is practised in a variety of settings. The university has very different priorities from the salesroom, the museum from the antiques fair, but the challenge of instrument history is to integrate connoisseurship, technical insight and historical sensitivity, while not neglecting the trade institutions and practices of the makers and remaining familiar with instrument populations in both the captivity of museums and the relative freedom of the market-place. This volume is presented to Gerard Turner, who has been at the forefront of promoting instrument studies in recent years. After a twenty-five-year association with the Museum of the History of Science at Oxford, a Visiting Professorship in the History of Scientific Instruments was established for him at the Imperial College, London, in 1988, from where he has been able to increase his research in this field. Gerard Turner has also been, amongst other positions in his distinguished career, the first Chairman of the Scientific Instrument Society, the President of the Royal Microscopical Society and the President of the British Society for the History of Science. In addition, he currently holds the position of Editor of the journal Annals of Science. The volume includes papers on instruments for mathematics, astronomy, navigation, horology, chemistry, physics, optics and medicine, together with studies of the instrument-making trade and reflections on the significance of such work for our understanding of the past.