49 
group. The deepest degree of it must be placed at B and JE in the deepest 
shade, there to oppose the brightest yellow; and if some of it inclined to red, 
that would oppose the green leaves. But all these colours, both in this and in 
every other instance of composition, must be very carefully brought in, so that 
not one of them shall interfere with the principal colour, or exceed the prismatic 
proportion in quantity. 
It is not necessary, however, to portion out colours in a picture by 
prismatic degrees, for that is impossible; but it would be very easy to form a 
scale by them, and for every degree to allow such a certain part, or measure, a 
square inch for instance, and let that be divided into ten equal parts, as might 
be convenient for the purpose ; for it matters not how large or how small the 
scale is: but when once fixed upon, it would be very easy to remember that 
there should be, for instance, double the quantity of violet to that ot indigo; 
that there should be equal quantities of blue and green, and the different 
proportions of the other colours also; in short, that each colour in the gioup, 
or picture, should bear the same proportion to one another. The effect would 
then be precisely the same as in the prismatic Spectrum; and for want of this 
measure, or proportion, being observed, the eye is often hurt in examining 
paintings (otherwise admirable), where an over quantity of one colour often 
destroys the value of the rest; and makes one wish, at least, to throw a shade 
over some part of the exceeding tint, which would, in a certain measure, har¬ 
monize the whole; but in no degree be equal to that of preserving the true 
proportion pointed out in the rainbow, which if strictly attended to, would, I 
may confidently say, produce unvarying harmony in every imitation of it with 
the pencil. By the blot it may be seen, that some yellow of a much lower tone 
should be placed near the extremity of the group at D, on the shaded side, 
in order to produce the reflected tint, without which no roundness or projection 
will ever be obtained; besides the necessity of distributing the colours generally 
throughout the whole. 
