This work investigates the rise and eventual decline of the caloric theory of heat, tracing its development from the late eighteenth century through the mid-nineteenth century. Robert Fox, a historian of science, examines how the concept of heat as a weightless fluid shaped early thermodynamic research. By analyzing the transition from Lavoisier’s chemical framework to the experimental precision of Regnault, the book argues that caloric theory provided a necessary, albeit flawed, structure for early gas physics.

Historians of science regard this text as a definitive account of the caloric theory's influence on nineteenth-century physics. Scholars frequently cite the book for its meticulous documentation and its clear explanation of the shift toward modern thermodynamics.