1835.] Composition of White Light. 177 



sion, and which is, consequently, of a lighter colour : the 

 experiments hefore described, being repeated in this light, 

 produced the same results. 



When the experiment was made with orange-yellow glass, 

 the accidental colour was violet ; with green glass, the acci- 

 dental colour was crimson ; and with crimson glass, green : 

 thus confirming, as far as I have proceeded, by a new and 

 unexpected method, the results of my former experiments. 



The principle upon which this explanation has been 

 attempted is applicable to a variety of other subjects. 



The effect of contrast in heightening colours is well 

 known ; but, I believe, not satisfactorily accounted for ; at 

 any rate, the combinations which produce the best effect 

 are not reduced to any fixed rules ; and as the subject is of 

 great importance to the artist, and to others who have any 

 thing to do with the arrangement of colours, I may be 

 excused, perhaps, if I lengthen this communication, by 

 shewing in what manner the principle upon which acci- 

 dental colours are formed is applicable to it. 



Objects, though they appear of a particular colour, gene- 

 rally reflect light of the three primitive colours ; and the 

 light thus reflected, forms white light until either one or 

 two of the colours are exhausted ; leaving the colour, or 

 colours, in excess, diluted with the white light thus formed, 

 to exhibit the proper colour of the body from which it is 

 reflected. 



If, then, we look, at a coloured body, when the eye has 

 been previously prepared by looking at its complementary 

 colour, we not only see the colour which distinguishes it, 

 with full effect, but we also see the white light which 

 accompanies it, converted to the same colour ; thus, adding 

 to the quantity of the coloured light in excess, and, at the 

 same time, increasing its intensity, by removing the effect 

 of the white light, by which, when the eye is not rendered 

 insensible to the complementary colour of the object, the 

 primary colour is diluted. 



On the contrary, if we prepare the eye by looking at the 

 same colour, instead of the complementary colour, or at 

 any compound colour of which it forms a part, the colour of 

 the body is lessened in intensity ; in some cases, so much so 

 as to be wholly lost, and even converted to its complemen- 



VOL. II. N 



