William John Macquorn Rankine (1820-1872) is a major figure in the history of nineteenth-century science and engineering. As well as being a successful railway and hydraulic engineer, he was largely responsible for the establishment of 'engineering science' as the core of a new academic discipline separate from that of practical engineering. Beginning with his birth in Edinburgh in 1820 this book - the first full length biography of Rankine - traces his Scottish schooling, his engineering apprenticeship in Ireland, his early years as railway and hydraulic engineer in the 1840s, his emergence as a distinctive scientific voice in the 1850s, and his career as a university professor in Glasgow. It places his idiosyncratic formulation of thermodynamics in the context of Scottish common sense philosophy and the exigencies of heat engineering; and examines his role as the engineers' advocate of the new science of energy, and of a science of 'energetics', during the 1850s and 1860s. Through his role as a man of science and as an engineer, the book demonstrates how he laboured with local captains of Scottish industry in the business of power-engineering and shipbuilding, helping foster the philosophical reform of commerce and industry that was to underpin Britain's empire.