Observations on Colours. 199 
with its opposite in the same way, it will produce as many va- 
rieties of gradations ; and by going thus round the whole circle, 
every tint that can be seen in nature, or imagined, will be formed. 
As it is of consequence that the peculiar tint of each of the 
three primary colours should be determined, I will endeavour to 
communicate my ideas of each of them by reference to flowers, 
or more particularly to those pigments used in (water colour) 
painting which approach the nearest to them. 
With respect to the primary colour of yellow, there is less un- 
certainty in the general application of the term than with either 
of the others; for the least tinge of orange readily procures it the 
name of orange or golden colour, and so likewise the slightest 
tinge of green gives it the name of green. This colour is pro- 
cured in all its different degrees of strength from gamboge. 
Blue, the name of the second primary colour, is applied with 
much less precision ; for we find that it is given to many of the 
gradations towards purple, and likewise when it falls into a 
greenish hue. From an attentive consideration of the colours of 
flowers, I have remarked that the most usual tints are different 
gradations of orange, purple, and red. The primary tint of yellow 
is seldom seen pure, and the plue still less, scarcely ever; the 
pigment approaching the nearest to which is Antwerp blue. 
Ultramarine and Prussian blue tend more or less to the purple. 
I come now to the third primary, red 5 and here we find the 
greatest uncertainty, as the term is given to all the shades of orange. 
This error is particularly adopted in the Newtonian theory. This 
arises from its being founded on the prismatic experiments : in 
the prismatic spectrum the third primary colour is not shown, 
the two ends of the spectrum are equally near to it: if there be 
any difference, I think the violet is more inclined to it than the 
other. Inthe figure, the colour which falls under the denomina- 
tion of orange is precisely that which is called red in the prismatic 
spectrum: its tint is between that of vermilion and red lead, 
and is of course, from what has been said, exactly neutralised by 
blue. In the same manner, the colour calied purple in the figure 
is nearly the same with the prismatic violet, and is neutralised 
by yellow. This will readily be proved likewise with the prism 5 
for, if the spectrum is thrown on a strong blue ground, the colour 
which is there called red will disappear ; and if on a pure yellow 
ground, the violet will be neutralised. 
The true primary colour of red is that which is called crim- 
son: this colour in its various degrees of strength is very fre- 
quent in flowers ; the rose gives it in its paler gradations ; but 
the pink or carnation shows it in all its gradations from the palest 
to the most deep. This colour is most nearly given by carmine. 
With gamboge, Antwerp plue, and carmine, an artist can most 
N4 certainly 
