Reflections on the motive power of heat : $b and on machines fitted to develop that power

Reflections on the Motive Power of Fire and on Machines Fitted to Develop that Power (French: Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissance) is a scientific treatise written by the French military engineer Sadi Carnot. Published in 1824 in French, the short book (118 pages in the original) sought to advance a rational theory of heat engines. At the time, heat engines had acquired great technological and economic importance, but very little was understood about them from the point of view of physics. Carnot's Reflections is now widely regarded as a key document in the development of modern thermodynamics, and Carnot himself (who published nothing else during his lifetime) has often been identified as the "father of thermodynamics". The book introduced such concepts as thermodynamic efficiency, reversible processes, the thermodynamic cycle, and Carnot's theorem. (This summary is from Wikipedia.)