"Later, in 1830, Carnot appreciated that his comparison of... the waterwheel was not exact, and that some heat was converted into mechanical energy... Thereupon he abandoned the and adopted the view that heat was... motions of the particles of bodies, heat and mechanical energy being interconvertible... Carnot died... 1832, and his later views... were not published until 1878."
January 1, 1970
https://en.wikiquote.org/wiki/Nicolas_L%C3%A9onard_Sadi_Carnot