In 1849 the learned Swiss philosopher Wartmann stated, in his “Deuxième Mémoire sur le Daltonisme”, p. 40, that “the eye arrests the chemical radiations which accompany the more refrangible rays.” He founded this conclusion on experiments made with guaiac resin; but as this substance is by no means very sensitive to actinic influence, it seemed desirable to test the question whether the eye can transmit the chemical rays of light, by an appeal to those highly impressible actinolytes (as they may be called) which the recent progress of photography has revealed to us.