And likewise of things that do not burn, as, for instance, the warmth of the body; in a word, all heat that is sensible, whatever may be its degree, or the source from which it is derived.
CAROLINE.
What then are the other modifications of caloric? It must be a strange kind of heat that cannot be perceived by our senses.
MRS. B.
None of the modifications of caloric should properly be called heat; for heat, strictly speaking, is the sensation produced by caloric, on animated bodies; this word, therefore, in the accurate language of science, should be confined to express the sensation. But custom has adapted it likewise to inanimate matter, and we say the heat of an oven, the heat of the sun, without any reference to the sensation which they are capable of exciting.
It was in order to avoid the confusion which arose from thus confounding the cause and effect, that modern chemists adopted the new word caloric, to denote the principle which produces heat; yet they do not always, in compliance with their own language, limit the word heat to the expression of the sensation, since they still frequently employ it in reference to the other modifications of caloric which are quite independent of sensation.
CAROLINE.
But you have not yet explained to us what these other modifications of caloric are.
MRS. B.
Because you are not acquainted with the properties of free caloric, and you know that we have agreed to proceed with regularity.