CAROLINE.
Certainly. But how can you reverse this experiment?
MRS. B.
It may be done by cooling the several bodies to the same degree in an apparatus adapted to receive and measure the caloric which they give out. Thus, if you plunge them into three equal quantities of water, each at the same temperature, you will be able to judge of the relative quantity of caloric which the three bodies contained, by that, which, in cooling, they communicated to their respective portions of water: for the same quantity of caloric which they each absorbed to raise their temperature, will abandon them in lowering it; and on examining the three vessels of water, you will find the one in which you immersed the lead to be the least heated; that which held the chalk will be the next; and that which contained the milk will be heated the most of all. The celebrated Lavoisier has invented a machine to estimate, upon this principle, the specific heat of bodies in a more perfect manner; but I cannot explain it to you, till you are acquainted with the next modification of caloric.
EMILY.
The more dense a body is, I suppose, the less is its capacity for caloric?
MRS. B.
This is not always the case with bodies of different nature; iron, for instance, contains more specific heat than tin, though it is more dense. This seems to show that specific heat does hot merely depend upon the interstices between the particles; but, probably, also upon some peculiar constitution of the bodies which we do not comprehend.
EMILY.
But, Mrs. B., it would appear to me more proper to compare bodies by measure, rather than by weight, in order to estimate their specific heat. Why, for instance, should we not compare pints of milk, of chalk, and of lead, rather than pounds of those substances; for equal weights may be composed of very different quantities?