PRODUCED BY ELECTRO-CHEMICAL ACTION. 113 



by a reference to the law of imaginaiy colours. It is necessarj- to give 

 a brief development of tlie principle of this theory. 



Let any colour whatsoever be exposed to some given degree of light 

 and let the eyes be kept steadily fixed on it for some time : if the eyes be 

 afterwards closed we have the impression of a different colour, which 

 though it is never the same for one tint that it is for another, is ahvaj's 

 the same for the same tint. These colours, in some measure the off- 

 spring of the real colours, are called imaginary by pliilosophers, and 

 by others they are named fantastic or accidental. The following is a 

 table of them : — 



Real Colour. Corresponding imaginary Colour. 



Red , Azure-green. 



Golden Indigo. 



Green-yellow* Violet. 



Azure-green Red. 



Indigo Golden. 



Violet Green-yellow. 



After this table I cannot do better in reference to the present topic 

 than give the following extract from Venturi. 



" The combination or succession of those colours which have such a 

 mutual correspondence, that the perception of the one is followed by the 

 imaginary seJisation of the otiier, is agreeable and harmo7iious" 



" Women of good taste know the colour of the trimming which has 

 a good or a bad effect in combination Avith the fundamental colour of 

 their dress. Leonardo da Vinci promised to give a table showing the 

 colours which harmonize with one another and those which do notf : 

 but he did not fulfill the promise, and no other painter that I know has 

 pointed out precise rules for the harmony of colours. Several have 

 observed merely that red combined with green has an agreeable effect ; 

 Newton apprises us that orange agrees with indigo ; and Virgil was per- 

 haps of the same opinion when he put this verse into the mouth of his 

 Naiad, 



MoUia luteola pingit vaccinia caltba. 



" Mengs extols the union of violet and yellow ; the same author says 

 that the combination of red, yellow and azure is disagreeable J; but that 

 each of them should rather be joined with the colour intermediate be- 

 tween the two others ; the red with the green, the yellow with the violet, 

 and the azure with the orange." 



" These different opinions have their origin and foundation in the 

 transitions from the real to the imaginary state, which, as we have seen, 

 naturally follow the involuntary movement of the retina ; so that the 



* When the names of two colours are thus joined, the idea intended to be 

 conveyed is that of the intermediate tint. 



t On Painting, chap. 89, J Mengs, Lemons cle Peinture. 



Vol. I — Part I. i 



