Kelvin diagram of Carnot engine

Diagram of carnot heat engine originally from thomson, w. (1849). "an account of carnot's theory of the motive power of heat; with numerical results deduced from regnault's experiments on steam". Transactions of the royal society of edinburgh 16 (part v): page 546. Doi:10. 1017/s0080456800022481 also in carnot, sadi; thomson, william; thurston, robert henry (editor and translator) (1890). Reflections on the motive power of heat. New york: j. Wiley & sons. Page 142.