Heat can evidently be a cause of motion only by virtue of the changes of volume or of form which it produces in bodies. - Nicolas Carnot

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.

Notwithstanding the work of all kinds done by steam-engines... their theory is very little understood, and the attempts to improve them are still directed almost by chance.

The production of motion in steam-engines is always accompanied by... the re-establishing of equilibrium in the caloric; that is, its passage from a body in which the temperature is more or less elevated, to another in which it is lower.