Carnot, << kahr NOH, >> Nicolas Leonard Sadi (1796-1832), a French engineer, is considered the founder of the science of thermodynamics. In his Reflections on the Motive Power of Heat and on Proposed Machines to Develop That Power, published in 1824, he used the “Carnot cycle” to show that the efficiency of a reversible engine depends on the temperatures between which it works. Carnot was born in Paris.