331. Why, if a hot and a cold body were placed near to each other, would the cold one become warmer, and the hot one cooler?
Because free caloric (that is, caloric that is not latent,) always exhibits a tendency to establish an equilibrium. If twenty bodies, of different temperatures, were placed in the same atmosphere, they would all soon arrive at the same temperature. The caloric would leave the bodies of those of the highest, and find its way to those of the lowest temperature.
It travels in parallel rays in all directions with a velocity approximating to that of light; and it passes through various bodies with a rapidity proportionate to their power of conduction.
333. Why does melted metal run like a stream of fluid?
Because caloric has passed into its substance, and, repelling its particles, has separated them to that degree which produces fluidity.
334. How do we know that it is caloric passing into the substance of the metal which produces this effect?
Because, as soon as a bar of metal begins to be heated, it expands and lengthens. It continues to do so, until the heat arrives at that point which causes the metal to melt.
335. Why does the iron of an ironing-box sometimes become too large for the box to receive it?