a. [f. Gr. ἀκτῖν- ray + -IC.] Of or pertaining to actinism.
1844. Sir J. Herschel, Brit. Assoc. Report, 13. While the actinic influence is still fresh upon the face (i.e. as soon as it is removed from the light).
1845. Penny Cycl., I. 167/2. A beam of solar light is made up of three distinct sets of rays—the luminous, the calorific, and the chemical or actinic rays.
1859. Bentley’s Q. Rev., No. 3, 157. The actinic force, or that of the violet end of the spectrum, quickens germination much more than the luminous.
1870. Proctor, Other Worlds, x. 246. Besides light and heat, the stars emit actinic rays.
1871. H. Macmillan, True Vine, 124. We produce photographs by a power in the sunbeam called the chemical, or actinic power.
1874. Hartwig, Aer. World, vi. 68. These ultra violet, actinic, or Ritterian rays, as they have been named, after their discoverer Ritter.
