How to ensure a chronometer's accuracy. Josiah Emery timekeepers and their users

Precision was not a quality expected from ordinary watches in the eighteenth century, which required specific maintenance to function correctly. The precautions to be taken to ensure the accuracy of pocket chronometers, whose going would influence navigation or the results of scientific activities, were even more vital. However, the remarkable attention that horological studies have devoted to the origins of chronometry has neglected these aspects. It has erroneously assumed that the success of chronometers was guaranteed by their innovative impact and technological advancement. To illustrate the importance to examine the birth of chronometry from the point of view of manipulating technology and the user experience, my paper will discuss the case of the small series of pocket chronometers manufactured between 1782 and 1794 by the London workshop of the Swiss watchmaker Josiah Emery. The article shows that not all the users possessed the necessary technical knowledge nor training to handle and employ chronometers appropriately and that the instructions given by the artisan to his clients played a fundamental role.