94 Mr Dalton on the Vision of Colours. 



have a great affinity to green, as may be imagined from what 

 I have said of greens. Browns seem to me to be very diver- 

 sified ; some I should call red : — dark brown woollen cloth I 

 should call black. 



The light of the rising or setting sun has no particular ef- 

 fect ; neither has a strong or weak light. Pink appears rather 

 duller, all other circumstances alike, in a cloudy day. 



All common combustible substances exhibit colours to me in 

 the same light ; namely, talloiv, oil, wax, pit-coal. 



My vision has always been as it is now. 



II. An account of others whose vision has been found similar 

 to mine. — It has been already observed that my brother per- 

 ceived the change in the colour of the geranium such as myself. 

 Since that time having made a great number of observations on 

 colours, by comparing their similarities, &c. by day-light and 

 candle-light, in conjunction with him, I find that we see as 

 nearly alike as any other persons do. He is shorter sighted 

 than myself. 



As soon as these facts were ascertained, I conceived the de- 

 sign of laying our case of vision before the public, apprehend- 

 ing it to be a singular one. I remembered, indeed, to have 

 read in the Philosophical Transactions for 1777, an account 

 of Mr Hams of Maryport in Cumberland, who, it was said, 

 " could not distinguish colours ;" but his case appeared to be 

 different from oui's. Considering, however, that one anomaly 

 in vision may tend to illustrate another, I reperused the ac- 

 count ; when it appeared extremely probable that, if his vi- 

 sion had been fully investigated, and a relation of it given in 

 the first person, he would have agreed with me. There were 

 four brothers in the same predicament, one of whom is now 

 living. Having an acquaintance in Maryport, I solicited him 

 to propose a few queries to the survivor, which he readily did, 

 (in conjunction with another brother, whose vision has no- 

 thing peculiar,) and from the answers transmitted to me, I 

 could no longer doubt of the similarity of our cases. To ren- 

 der it still more circumstantial, I sent about twenty specimens 

 of different coloured ribbands, with directions to make obser- 



