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COMBINATION OF LIGHT WITH DIFFERENT BODIES.

SECT. VI.

COMBINATION OF LIGHT

WITH

DIFFERENT BODIES.

PHILOSOPHERS have ascertained that various bodies, if ex-posed to light, either at a high or low temperatnre, combinewith it and emit it again, without alteration, under certain cir-cumstances.

Substances of this kind have been calledSOLAR PHOSPHORI,

Or substances which shine in the dark without emitting heat,after having been exposed to the light.

The world is stocked with an immense variety of bodies ofthis kind. All terrestrial objects not only possess a power of ab-sorbing light, but they likewise emit it again. The eyes of cats,owls, and several other animals, are constructed so as to collectlight, to enable them to find their food in the dark. Water con-densed into the form of ice or snow emits light remarkably.This accounts for the light afforded by snow, even when theheavens are involved in extreme darkness. The snow on theground absorbs light, by being exposed to it all the day, andemits a considerable quantity again in the dark.

The principal bodies of this kind are the following :