I am very curious to know of what nature they can be; for I have no notion of any kind of heat that is not perceptible to the senses.
MRS. B.
In order to enable you to understand them, it will be necessary to enter into some previous explanations.
It has been discovered by modern chemists, that bodies of a different nature, heated to the same temperature, do not contain the same quantity of caloric.
CAROLINE.
How could that be ascertained? Have you not told us that it is impossible to discover the absolute quantity of caloric which bodies contain?
MRS. B.
True; but at the same time I said that we were enabled to form a judgment of the proportions which bodies bore to each other in this respect. Thus it is found that, in order to raise the temperature of different bodies the same number of degrees, different quantities of caloric are required for each of them. If, for instance, you place a pound of lead, a pound of chalk, and a pound of milk, in a hot oven, they will be gradually heated to the temperature of the oven; but the lead will attain it first, the chalk next, and the milk last.
CAROLINE.
That is a natural consequence of their different bulks; the lead being the smallest body, will be heated soonest, and the milk, which is the largest, will require the longest time.