Note 63 — Chapter VI
Reading edition
From his experiments, the following conclusions were arrived at by M. Delaroche:—
1. Invisible radiant heat may, in some circumstances, pass directly through glass.
2. The quantity of radiant heat which passes directly through glass is so much greater, relative to the whole heat emitted in the same direction, as the temperature of the source of heat is more elevated.
3. The calorific rays which have already passed through a screen of glass, experience, in passing through a second glass screen of a similar nature, a much smaller diminution of their intensity than they did in passing through the first screen.
4. The rays emitted by a hot body differ from each other in their faculty to pass through glass.
5. A thick glass, though as much or more permeable to light than a thin glass of worse quality, allows a much smaller quantity of radiant heat to pass. The difference is so much the less as the temperature of the radiating source is more elevated.
6. The quantity of heat which a hot body yields in a given time, by radiation to a cold body situate at a distance, increases, cæteris paribus, in a greater ratio than the excess of temperature of the first body above the second.—Journal de Physique, vol. lxxv.