INSENSIBILITY TO COLOURS. 115 



that he is sometimes baffled in distinguishing a full purple 

 from a deep blue, but that he knows light, dark, and 

 middle yellows, and all degrees of blue except sky-blue. 

 " I married my daughter to a genteel, worthy man, a few 

 years ago : the day before the marriage he came to my 

 house dressed in a new suit of fine cloth clothes. I was 

 much displeased that he should come, as I supposed, in 

 black ; and said that he should go back to change his 

 colour. But my daughter said, No No ; the colour is 

 very genteel ; that it was my eyes that deceived me. He 

 was a gentleman of the law, in a fine rich claret-coloured 

 dress, which is as much a black to my eyes as any black 

 that ever was dyed." Mr. Scott's father, his maternal 

 uncle, one of his sisters, and her two sons, had all the same 

 imperfection. Dr. Nichol has recorded a case where a 

 naval officer purchased a blue uniform coat and waistcoat 

 with red breeches to match the blue, and Mr. Harvey 

 describes the case of a tailor at Plymouth, who, on one 

 occasion, repaired an article of dress with crimson in place 

 of black silk, and on another, patched the elbow of a blue 

 coat with a piece of crimson cloth. It deserves to be 

 remarked that our celebrated countrymen the late Mr. 

 Dugald Stewart, Mr. Dalton, and Mr. Troughton, have a 

 similar difficulty in distinguishing colours. Mr. Stewart 

 discovered this defect when one of his family was admiring 

 the beauty of the Siberian crab-apple, which he could not 

 distinguish from the leaves but by its form and size. 

 Mr. Dalton cannot distinguish blue from pink, and the 

 solar spectrum consists only of two colours, yellow and 

 blue. Mr. Troughton regards red, ruddy pinks, and 

 brilliant oranges, as yellows, and greens as blues, so that 

 he is capable only of appreciating blue and yellow colours. 

 In all those cases which have been carefully studied, 

 at least in three of them in which I have had the advan- 

 tage of making personal observations, namely, those of 



