MRS. B.
The cold you experience consists in the loss of caloric that your hand sustains in an attempt to bring its temperature to an equilibrium with the marble. If you lay a piece of ice upon it, you will find that the contrary effect will take place; the ice will be melted by the heat which it abstracts from the marble.
CAROLINE.
Is it not in this case the air of the room, which being warmer than the marble, melts the ice?
MRS. B.
The air certainly acts on the surface which is exposed to it, but the table melts that part with which it is in contact.
CAROLINE.
But why does caloric tend to an equilibrium? It cannot be on the same principle as other fluids, since it has no weight?
MRS. B.
Very true, Caroline, that is an excellent objection. You might also, with some propriety, object to the term equilibrium being applied to a body that is without weight; but I know of no expression that would explain my meaning so well. You must consider it, however, in a figurative rather than a literal sense; its strict meaning is an equal diffusion. We cannot, indeed, well say by what power it diffuses itself equally, though it is not surprising that it should go from the parts which have the most to those which have the least. This subject is best explained by a theory suggested by Professor Prevost of Geneva, which is now, I believe, generally adopted.