So, then, the sensation I feel on touching a cold body, is in proportion to the rapidity with which my hand yields its heat to that body?
MRS. B.
Precisely; and, if you lay your hand successively on every object in the room, you will discover which are good, and which are bad conductors of heat, by the different degrees of cold you feel. But, in order to ascertain this point, it is necessary that the several substances should be of the same temperature, which will not be the case with those that are very near the fire, or those that are exposed to a current of cold air from a window or door.
EMILY.
But what is the reason that some bodies are better conductors of heat than others?
MRS. B.
This is a point not well ascertained. It has been conjectured that a certain union or adherence takes place between the caloric and the particles of the body through which it passes. If this adherence be strong, the body detains the heat, and parts with it slowly and reluctantly; if slight, it propagates it freely and rapidly. The conducting power of a body is therefore, inversely, as its tendency to unite with caloric.
EMILY.
That is to say, that the best conductors are those that have the least affinity for caloric.
MRS. B.