330 Prof. Tyndall on a peculiar case of Colour Blindness. 



covevy, at finding that a favourite damask rose had become in all 

 its parts, petals, leaves, and stem, of one uniform dull colour ; 

 and that variegated flowers, such as carnations, had lost their 

 characteristic tints." 



The case of Captain C, which I have to describe, is one of 

 these rare instances. The sufferer is a seaman, and ten or twelve 

 years ago was accustomed, when time lay heavy on his hands, to 

 occupy it by working at embroidery. Being engaged one after- 

 noon upon a piece of work of this description, and anxious to finish 

 a flower (a red one, he believes), he prolonged his labours until 

 twilight fell, and he found it difficult to select the suitable colours. 

 To obtain more light he went into the companion, or entrance 

 to the cabin, and there continued his needlework. While thus 

 taxing his eyes, his power of distinguishing the colours suddenly 

 vanished. He went upon deck, hoping that an increase of light 

 would restore his vision. In vain. From that time to the pre- 

 sent he has remained colour blind. 



My first examination of Captain C. took place in the house of 

 Mr. Cooper. Being furnished with specimens of Berlin wool, 

 such as that with which the patient had been accustomed to 

 woi'k, I placed before him a skein which he at once, and cor- 

 rectly, pronounced to be blue. For this colour he has a keen 

 appreciation, and I have never known him make a mistake re- 

 garding it. Two bundles of worsted, one a light green and the 

 other a vivid scarlet, were next placed before him : he pronounced 

 them to be both of the same colour; a diff'erence of shade was 

 perceptible, but both to him were drab. A green glass and a 

 red glass were placed side by side between him and the window : 

 he could discern no difference between the colours. A very dark 

 green he pronounced to be black ; the purple covering of the 

 chairs were also black ; a deep red rose on the wall of the room 

 was a mere blotch of black ; fruit, partly of a bright red and 

 partly of a deep green, were pronounced to be of the same uni- 

 form colour. A cedar pencil and a stick of sealing-wax placed 

 side by side were nearly alike ; the former was rather brown, the 

 latter a drab. Time, I found, made a difference : slate colour 

 and red were placed side by side; on first looking at them 

 Captain C. thought them different shades of the same colour, 

 but after looking at them for half a minute even this difiference 

 of shade disappeared. By the production of subjective efi"ects, 

 such as looking long at an object through a coloured glass, and 

 then removing the latter, his judgement of colours could also be 

 made to vary in a slight degree. 



My second examination of Captain C. took place in the theatre 

 of the Royal Institution ; and on the day he called upon me I 

 happened to be using the electric light, rendered continuous by 



