The Morals of Measurement is a contribution to the social histories of quantification and electrical technology in nineteenth-century Britain, Germany and France. It shows how the advent of commercial electrical lighting stimulated the industrialization of electrical measurement from a skilled labour-intensive activity to a mechanized practice. Challenging traditional accounts that focus on the metrological standards used in measurement, this book shows the central importance of trust when measurement was undertaken in an increasingly complex division of labour. Alongside ambiguities about the very nature of measurement and the respective responsibilities of humans and technologies in generating error-free numbers, the book also addresses controversies over the changing identity of the measurer through the themes of body, gender and authorship. The reader will gain fresh insights into a period when measurement was widely treated as the definitive means of gaining knowledge of the world.