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The three kinds were partially separated by a prism, the actinic rays being generally more refracted, and the thermal rays less refracted than the luminous.

Of or pertaining to actinism; as, actinic rays.

It is a very familiar fact that when material bodies are heated they emit electromagnetic radiations, in the form of thermal, luminous, and actinic rays, in appreciable quantities.

The peculiar property which it possesses, of darkening under the actinic rays of the sun, makes it essential that it be combined with other, more stable pigments to prolong its life when exposed to weather.

The glasses did not reduce the quantity of light, as do smoked glasses, but the quality; the actinic rays, which do the greatest harm, were eliminated.