Power Technologies and the Advance of Science, 1700–1825

The science of thermodynamics was one of the major intellectual achievements of the nineteenth century, and the origins of its basic principles must therefore be of great interest to the historian. The first two principles to be established were the statement of the mechanical equivalence of heat (Mayer and Joule) and the postulation by Sadi Carnot of an idealized heat engine which, when working in a precisely specified manner on a cycle that can be performed in the inverse sense, must obtain the maximum possible work from a given "fall" of heat from a furnace to a cold body, or condenser.' Carnot noticed that the cold body is as necessary for the production of work as the furnace: he thus imposed in advance an important limitation on the then unformulated doctrine of the mechanical equivalence of heat: work can be obtained only when heat flows from a hot to a cold body. It is hardly less important for the historian of science and technology to have some idea of the circumstances that led to the formulation of