Has Cecil Adams, whoever goes by that nom de guerre, found his way back to the phlogiston theory of fire (the Straight Dope, November 22, 2002)? Surely, "heat" as a substance received its quietus from the work of physicists such as Rudolf Clausius in Germany and Lord Kelvin in Great Britain, yet Cecil, offering his definition of "fire," speaks of a "rapid combination of oxygen with fuel in the presence of heat." Uh-uh!
Setting aside as less than germane such referents of "heat" as a powerful emotional state, the perception of physical heat, and so on, we're left with the term as a reference to an excitation of molecular or atomic particles measurable by physical instruments, i.e., any of various sorts of thermometer. Heat is the motion of particles. It is not a substance or chemical accompanying fire but, among other things, an aspect of fire.
I suppose this setting the record straight may generate unwonted heat in Cecil and his acolytes. Tant pis!
Stuart Jay Silverman
Hot Springs, Arkansas
Cecil Adams replies:
By "the presence of heat" I meant that a minimum temperature was necessary to initiate and then sustain combustion. No doubt there are people who can torture themselves into concluding from this that I think heat is a substance, just as there are people who can work "quietus" into a sentence without blushing. Tailoring your definitions to keep these people happy is a sure way to make them incomprehensible to anyone else.