These infinitesimally small ultra-violet or actinic waves, as they are called, are the principal agents in photography, and the great waves of wireless telegraphy are able to carry a force across the Atlantic which can sensibly affect the apparatus on the other side; therefore we see that the ether of space affords a medium through which energy can be transmitted by means of vibrations.
"The Law and the Word"
Thomas Troward
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.
"My Attainment of the Pole"
Frederick A. Cook
This was the first comet which was successfully photographed, and it may be remarked that comets possess very little actinic power.
"The Story of the Heavens"
Robert Stawell Ball