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jhffhz ^traced it through the whole ^prismatic range; that it begins in the 
invisible rays, before it reaches the red, from whence it extends to the utmost 
limits of the violet rays, and that it is gradually impaired as the rays grow 
more refrangible; by which it appears, that it is not equally distributed 
among them, hut is chiefly resident in the red rays, and may be proportionally 
so in all: however, till that is fully ascertained, we cannot judge whether 
it would afford us a better guide, or not. But it appears to me, that if the 
relative degree^oj' heat, as well as illuminating power, which colour bears 
to another, were exactly known, a scale might be formed, shewing the proper 
accompanying tints, both in a pure and compound state, to whatever principle 
one was fixed upon for the centre of a group : till then, we must make use of 
the best guide we have, which is certainly that of the prismatic proportions, 
0t. flta- <)r< ^c^hc^stam^«, as to degree of illumination; and possibly none will 
ever be iffiwUJ thatwill increase the harmony. But though the colours, in 
a great measure, may be arranged, and proportioned by those rules, the 
qualities of the colours should be considered, as they all differ in their natures, 
and produce different effects. There is a strong analogy between them and 
the note^ip music, for each of them has its separate part to perform in a 
group, that the different notes have in a piece of music; and till their power, 
and province are fully considered, a painter has as little chance of producing* 
harmony in a group of flowers, as a musician, who has not studied the 
theory of music, and considered the effect each note would have in a full 
chorus. 
Yellows from its brilliancy, and affinity to light, is fittest to come next it in 
the light quarter, lied, from its warmth, is fit for a prominent place of 
power, and force. Orange stands next to it, hut has less power. Blue, from 
its coldness, is fittest for a retiring place in the shade quarter. Indigo, from 
its affinity to black, is fit for the deepest shade. Violet, from its weakness, is 
only fit for a retiring situation. Green has a double quality; it is equal to 
yellow m point of illumination, comes next it in the light, and yet from its 
cold nature is equally fit for the shadow. But though blue, indigo, and violet, 
are capable of distinct illumination, and blue equally with red’, not one of them 
