Nicolas Léonard Sadi Carnot was a French physicist and military engineer who gave the first successful theoretical account of heat engines, now known as the Carnot cycle, thereby laying the foundations of the second law of thermodynamics. Technically, he is the world's first thermodynamicist, being responsible for such concepts as Carnot efficiency, Carnot theorem, Carnot heat engine, and others. Wikipedia
The definitive Wikipedia entry for Nicolas Léonard Sadi Carnot. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Nicolas_L%c3%a9onard_Sadi_Carnot