The striking analogy which exists between the physio logical perception of colours and the phenomena associated with colour. Photography has convinced me that both the Ophthalmic surgeon and the physiologist who have taken up the study of colour blindness and colour vision, will find that the serious study of this fascinating science will illuminate many obscure phenomena connected with the physiology of vision and colour blindness, and will well repay them for the time spent In acquiring a practical knowledge of at least one of the leading processes described herein.