MRS. B.
Undoubtedly. I will now show you the very simple and ingenious apparatus, by means of which he made these experiments. This cubical tin vessel or canister, has each of its sides externally covered with different materials; the one is simply blackened; the next is covered with white paper; the third with a pane of glass, and in the fourth the polished tin surface remains uncovered. We shall fill this vessel with hot water, so that there can be no doubt but that all its sides will be of the same temperature. Now let us place it in the focus of one of the mirrors, making each of its sides front it in succession. We shall begin with the black surface.
CAROLINE.
It makes the thermometer which is in the focus of the other mirror rise considerably. Let us turn the paper surface towards the mirror. The thermometer falls a little, therefore of course this side cannot emit or radiate so much caloric as the blackened side.
EMILY.
This is very surprising; for the sides are exactly of the same size, and must be of the same temperature. But let us try the glass surface.
MRS. B.
The thermometer continues falling, and with the plain surface it falls still lower; these two surfaces therefore radiate less and less.
CAROLINE.
I think I have found out the reason of this.