[I]f we should find about us only bodies as hot as our furnaces, how can we condense steam? What should we do with it if once produced? - Nicolas Carnot

Nature, in providing us with combustibles on all sides, has given us the power to produce, at all times and in all places, heat and the impelling power which is the result of it. To develop this power, to appropriate it to our uses, is the object of heat-engines.

There is almost as great a distance between the first apparatus in which the expansive force of steam was displayed and the existing machine, as between the first raft that man ever made and the modern vessel.

[W]e have just described the re-establishment of equilibrium in the caloric, its passage from a... heated body to a cooler one.