On the Invisibility of certain Colours to certain Eyes. 85 



Art. XV— CONTRIBUTIONS TO POPULAR SCIENCE. 

 No. V. On the Invisibility of certain Colours to certain Eyes. 



A variety of cases have been recorded, where persons with 

 sound eyes, capable of performing all their ordinary functions, 

 were incapable of distinguishing certain colours, and what is 

 still more remarkable, this imperfection runs in particular fa- 

 milies. Mr Huddart mentions the case of one Harris, a shoe- 

 maker at Maryport in Cumberland, who could only distinguish 

 black and white, and he had two brothers almost equally defec- 

 tive, one of whom always mistook orange for green. Harris 

 observed this defect when he was four years old, and, chief- 

 ly from his inability to distinguish cherries on a tree like his 

 companions. He had two other brothers and sisters, who, as 

 well as their parents, had no such defect. Another case of a 

 Mr Scott is recorded in the Philosophical Trmisactions, in 

 which full reds and full greens appeared alike, while yellows 

 and dark blues were very easily distinguished. Mr Scott's fa- 

 ther, his maternal uncle, one of his sisters, and her two sons, 

 had all the same imperfection. Our celebrated chemist, Mr Dal- 

 ton, cannot distinguish blue from pink by daylight ; and in the 

 solar spectrum the red is scarcely visible, the rest of it appear- 

 ing to consist of two colours, yellow and blue. Dr Butters, in 

 a fetter addressed to the editor of this work, has described the 

 case of Mr R. Tucker, son of Dr Tucker of Ashburton, who 

 mistakes orange for green, like one of the Harrises. Like Mr 

 Dalton, he could not distinguish blue from pink ; but he always 

 knew yellow. The colours in the spectrum he describes as 

 follows: 



1 . Red mistaken for • • brown, 



2. Orange .... g»ecn, 



3. Yellow, generally known, but sometimes taken for orange, 



4. Green mistaken for ... orange, 



5. Blue . P il,k » 



6. Indigo . P ur P lc > 



7. Violet . • • purple. 



