7 
respecting the number of prismatic colours, also whether each is 
an original colour of itself, or only produced by a mixture of 
the two contiguous ones, not being of importance to the subject 
in question, I shall only observe, that painters reckon but three 
primitive colours, Yellow, Red, and .Blue; and that an examina¬ 
tion of the prismatic spectrum has led to the consideration and 
knowledge of the different powers and qualities of these three 
colours, which essentially differ from each other. 
They may be considered as three distinct heads of three 
distinct families of colours; each comprehending all the Yellows, 
all the Reds, and all the Blues, from the lightest to the darkest tints; 
and these families are no ways related to each other, but per¬ 
form different offices in the prismatic system. Yellow illuminates, 
Red warms, Blue is opposite to both these, and is of a cold re¬ 
tiring nature; these at least are the effects that our corresponding 
material colours produce when applied to the purposes of paint- 
ting; and what makes it remarkable is, that although any one 
of these three colours will unite and mix with either of the other 
two separately, so as to form another pure brilliant prismatic 
tint, yet no one of them will unite with the other two together. 
B 
