100

CAPACITY OF BODIES FOR CONTAINING HEAT.

tities contained in equal volumes, we still find that the same dif-ference takes place. Thus it is found by experiment, that thequantity of caloric necessary to raise the temperature of a givenvolume of water any number of degrees, is to that necessary toraise an equal volume of mercury the same number of degreesas 2 to 1. This is therefore the proportion between the compara-tive quantities of caloric which these two bodies contain, esti-mated by their volumes; and similar differences exist withrespect to every other kind of matter.

From the nature of the experiments by which the quantitiesof caloric which bodies contain are ascertained, it is evident thatwe discover merely the comparative, not the absolute quantities.Hence water has been chosen as a standard, to which other bo-dies may be referred; its capacity is stated as the arbitrary termof 1000, and with this the capacities of other bodies are com-pared.

It need not be told that pains have been taken to estimate onthese experiments that portion of heat which diffuses itself intothe air or into the vessel where the mercury and water areblended together. As however such valuations cannot be madewith complete accuracy, the numbers stated above are only anapproximation to truth.