That is owing to the different power which various bodies possess for _conducting_ caloric, a property which we shall presently examine. Thus, although a metallic vessel feels warmer to the hand, a vessel of this kind is known to preserve the heat of the liquid within, better than one of any other materials; it is for this reason that silver teapots make better tea than those of earthen ware. EMILY. According to these experiments, light-coloured dresses, in cold weather, should keep us warmer than black clothes, since the latter radiate so much more than the former. MRS. B. And that is actually the case. EMILY. This property, of different surfaces to radiate in different degrees, appears to me to be at variance with the equilibrium of caloric; since it would imply that those bodies which radiate most, must ultimately become coldest. Suppose that we were to vary this experiment, by using two metallic vessels full of boiling water, the one blackened, the other not; would not the black one cool the first? CAROLINE. True; but when they were both brought down to the temperature of the room, the interchange of caloric between the canisters and the other bodies of the room being then equal, their temperatures would remain the same. EMILY. I do not see why that should be the case; for if different surfaces of the same temperature radiate in different degrees when heated, why should they not continue to do so when cooled down to the temperature of the room? MRS. B. You have started a difficulty, Emily, which certainly requires explanation. It is found by experiment that the power of absorption corresponds with and is proportional to that of radiation; so that under equal temperatures, bodies compensate for the greater loss they sustain in consequence of their greater radiation by their greater absorption; so that if you were to make your experiment in an atmosphere heated like the canisters, to the temperature of boiling water, though it is true that the canisters would radiate in different degrees, no change of temperature would be produced in them, because they would each absorb caloric in proportion to their respective radiation. EMILY. But would not the canisters of boiling water also absorb caloric in different degrees in a room of the common temperature? MRS. B. Undoubtedly they would. But the various bodies in the room would not, at a lower temperature, furnish either of the canisters with a sufficiency of caloric to compensate for the loss they undergo; for, suppose the black canister to absorb 400 rays of caloric, whilst the metallic one absorbed only 200; yet if the former radiate 800, whilst the latter radiates only 400, the black canister will be the first cooled down to the temperature of the room. But from the moment the equilibrium of temperature has taken place, the black canister, both receiving and giving out 400 rays, and the metallic one 200, no change of temperature will take place. EMILY.