The Morals of Measurement is a contribution to the social histories of quantification and of electrical technology in nineteenth-century Britain, Germany, and France. It shows how the advent of commercial electrical lighting stimulated the industrialisation of electrical measurement from a skilled labour-intensive activity to a mechanised practice relying on radically new kinds of instruments. Challenging traditional accounts that focus on metrological standards, this book shows instead the centrality of trust when measurement was undertaken in an increasingly complex division of labour with manufactured hardware. Case studies demonstrate how difficult late Victorians found it to agree upon which electrical practitioners, instruments, and metals were most trustworthy and what they could hope to measure with any accuracy. Subtle ambiguities arose too over what constituted 'measurement' or 'accuracy' and thus over the respective responsibilities of humans and technologies in electrical practice. Running alongside these concerns, the themes of body, gender, and authorship feature importantly in controversies over the changing identity of the measurer. In examining how new groups of electrical experts and consumers construed the fairness of metering for domestic lighting, this work charts the early moral debates over what is now a ubiquitous technology for quantifying electricity. Accordingly readers will gain fresh insights, tinged with irony, on a period in which measurement was treated as the definitive means of gaining knowledge of the world.