PRODUCED BY ELECTRO-CHEMICAL ACTION. 113 
by a reference to the law of imaginary colours. It is necessary to give 
a brief development of the 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 always 
the same for the same tint. These colours, in some measure the off- 
spring of the real colours, are called imaginary by philosophers, and 
by others they are named fantastic or accidental. The following is a 
table of them :— 
Real Colour. Corresponding imaginary Colour. 
BERET eae renttcnesedon sacacs tensa Azure-green. 
5) oe) ie i lA A a oad br 
Green-yellow* .........ss0008 Violet. 
APMEE-SLCEN 3 idsieiap aun dacilavarees Red. 
RO oo can dob Satlch tags cansnany GOlGEN. 
WiGleb oo wacesceescoeeser<ainta dae reen-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 sensation of the other, is agreeable and harmonious.” 
“ Women of good taste know the colour of the trimming which has 
a good or a bad effect in combination with 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 nott+: 
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, 
Mollia luteola pingit vaccinia caltha. 
“ Mengs extols the union of violet and yellow; the same author says 
that the combination of red, yellow and azure is disagreeable}; 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. 
+ On Painting, chap. 89. t Mengs, Legons de Peinture. 
Vor. I—Parr I. I 
