175px|thumb|right|Axial cross section of Carnot's heat engine. In this diagram, abgh is a cylindrical vessel, cd is a movable piston, and A and B are constant–temperature bodies. The vessel may be placed in contact with either body or removed from both (as it is here).Figure 1 in Carnot (1824, p. 17) and Carnot (1890, p. 63). In the diagram, the diameter of the vessel is large enough to bridge the space between the two bodies, but in the model, the vessel is never in contact with both bodies simultaneously. Also, the diagram shows an unlabeled axial rod attached to the outside of the piston.
175px|thumb|right|Axial cross section of Carnot's heat engine In this diagram abgh is a cylindrical vessel cd is a movable piston and A and B are constant–temperature bodies The vessel may be placed in contact with either body or removed from both (as it is here)Figure 1 in Carnot (1824 p 17) and Carnot (1890 p 63) In the diagram the diameter of the vessel is large enough to bridge the space between the two bodies but in the model the vessel is never in contact with both bodies simultaneously Also the diagram shows an unlabeled axial rod attached to the outside of the piston