"After the invention of the steam-engine in its present form by James Watt, the attention of engineers and of scientific men was directed to the problem of its further improvement. With this end in view, the young Sadi Carnot, in 1824, published the Réflexions sur la Puissance Motrice du Feu... Carnot examined the relations between heat and the work done by heat used in an ideal engine, and by reducing the problem to its simplest form... establish[ed] the conditions upon which the economical working of all heat-engines depends. ...[T]hough the proof was invalid, the proposition remained true, and carried with it the truth of such of Carnot’s deductions as were based solely upon it."