ABSTRACT
Richard Hills, a Member and former Council Member of the Society, has pointed out that eighteenth and early nineteenth century engineers thought of the steam-engine as a vapour pressure engine and not as a heat engine. Accordingly, John Farey's article on the steam-engine, in Rees' Cyclopaedia, asserted, as a general principal, that: The force of the steam-engine is derived from the property of water to expand itself, in an amazing degree, when heated above the temperature at which it becomes steam. The most efficient engines in the world were, as Carnot acknowledged, to be found in the English county of Cornwall. The performance of Cornish pumping engines had improved remarkably since the beginning of the nineteenth century and, what was quite unique, meticulous public records were kept of the duty - that is the work done for the combustion of a given amount of coal—of practically every engine in the area.
