CALORESCENCE. When radiant energy is absorbed by a substance (i.e., when the sum of the reflected and transmitted energies is not equal to the incident energy) the absorbed energy is usually transformed into radiant energy of a different wave length or refrangibility, or into energy of another form. The conversion of the rays belonging to the dark (infra-red) portion of the spectrum into the shorter, more refrangible waves of visible light was demonstrated by John Tyndall and the term calorescence (from the Lat. calor, heat) was invented by him to describe this phenomenon.
Tyndall sifted out the long, dark, infra-red waves from the shorter, visible waves associated with them in the light from the sun or electric arc, and concentrated them to a focus. A piece of charcoal or blackened platinum placed at this focus was raised to incandescence. The emission of light (visible rays) by the charcoal or platinum is purely a temperature effect, therefore calorescence is not to be regarded as the strict converse of the phenomenon shown by Sir G. G. Stokes to occur in fluorescent bodies (see FLUORESCENCE and PHOSPHORESCENCE).
See also John Tyndall, Heat as a Mode of Motion.