Green and Indigo. No. 13.

(24.) Red, the complementary of Green, added to Indigo, makes it redder, or more violet.

The complementary of Indigo (Orange-Yellow), added to Green, makes it yellower.

Green and Violet. No. 14.

(25.) Red, the complementary of Green, added to Violet, makes it redder.

The complementary of Violet (Greenish-Yellow), added to Green, makes it yellower.

Orange and Red. No. 1.

(26.) Blue, the complementary of Orange, added to Red, makes it incline to violet or crimson.

The complementary of Red (Green), added to Orange, makes the latter incline to yellow.

Violet and Red. No. 5.

(27.) Greenish-Yellow, the complementary of Violet, added to Red, makes it yellower, or inclining to orange. The complementary of Red (Green), added to Violet, makes the latter incline to indigo.

Indigo and Red. No. 4.

(28.) Orange-Yellow, the complementary of Indigo, added to Red, makes it incline to orange.

The complementary of Red (Green), makes the Indigo

bluer.

Orange and Yellow. No. 6.

(29.) Blue, the complementary of Orange, added to Yellow, makes it incline to green.

The complementary of Yellow (Indigo inclining to violet), makes the Orange redder.

(30.) Red, the complementary of Green, added to Yellow, makes it incline to orange.

Indigo inclining to violet, the complementary of Yellow, added to Green, makes it bluer.

Green and Blue. No. 12.

(31.) Red, the complementary of Green, added to Blue, makes the latter incline to indigo.

The complementary of Blue (Orange), added to Green, makes it yellower.

Violet and Blue. No. 16.

(32.) Greenish-Yellow, the complementary of Violet, added to Blue, causes it to become greenish.

The complementary of Blue (Orange), added to Violet, makes it redder.

Indigo and Blue. No. 15.

(33.) Orange-Yellow, the complementary of Indigo, added to Blue, makes it incline to green.

The complementary of Blue (Orange), added to Indigo, makes it incline to violet.

Red and Yellow. No. 2.

(34.) Green, the complementary of Red, added to Yellow, makes it incline to green.

The complementary of Yellow (Indigo inclining to violet), added to Red, makes it incline to violet.

Red and Blue. No. 3.

(35.) Green, the complementary of Red, added to Blue, causes it to incline to green.

The complementary of Blue (Orange), added to Red, makes it incline to orange.

Yellow and Blue. No. 11.

(36.) Indigo, the complementary of Orange-Yellow, added to Blue, makes the latter incline to indigo.

The complementary of Blue (Orange), added to Yellow, makes it incline to orange.

Indigo and Violet. No. 17.

(37.) Orange-Yellow, the complementary of Indigo, added to Violet, makes it incline to red.

The complementary of Violet (Greenish-Yellow), added to Indigo, causes it to appear bluer.

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(38.) It is evident that, other things being equal, the greater the difference that exists between a colour and the complementary (c or c') which is added to it, the more striking will be the modification of the juxtaposed colour; for when the complementary c' is added to the colour o it will be identical with it, as the complementary c is identical with the colour P to which it is added; and the modifications of o and P are limited to a simple augmentation of intensity of colour. But do we know, at the present day, of two coloured bodies which are capable of exhibiting to the observer two perfectly pure colours complementary to each other? Certainly not! All those substances which appear coloured by reflection, reflect, as I have said (7.), besides white light, a great number of differently coloured rays. Therefore we cannot instance a red pigment and a green, or an orange pigment and a blue, or an orange-yellow pigment and an indigo, or, lastly, a greenish-yellow pigment and a violet, which reflect simple or compound colours absolutely complementary to each other, so that their juxtaposition would produce only a simple augmentation of intensity in their respective colours. If, therefore, it be generally less easy to verify the law of contrast with red and green, or orange and blue substances, &c., than it is with those which have been the object of the seventeen observations mentioned above (15.); yet in endeavouring to verify the first, we shall see that the colours will acquire a most remarkable brilliancy, strength, and purity, and this result, in perfect conformity with the law, is easily understood. For example, an orange-coloured object reflects blue rays, just as a blue object reflects orange rays (7.). Therefore, when we put a blue stripe beside an orange stripe, whether we admit that the first appears to the eye to receive some blue from the proximity of the second, as this latter appears to acquire orange through the vicinity of the blue stripe,-or, which is the same thing, whether we admit that the blue stripe ap

pears to destroy the effect of the blue rays of the second stripe, as this latter appears to destroy the effect of the orange rays of the blue stripe,-it is evident that the colours of the two objects in contact will purify each other, and become more vivid. But it may happen that the Blue will appear to incline to green or to violet, and the Orange to yellow or to red, that is to say, the modification acts not only upon the intensity of the colour, but also upon its physical composition: whatever it be, if the latter effect takes place, it is undoubtedly always much feebler than the first. Besides, if we look a certain number of times at these same coloured bands we shall see that the blue, which at first appeared greener, will soon appear more violet, and that the orange, which at first appeared yellower, will become redder, so that the phenomenon of modification, dependent upon the physical composition of colour, will not be so constant as those which are the subject of the seventeen preceding observations (15.). I will now explain the previous remarks on substances, the colours of which are as nearly as possible complementary to each other.

Red and Green.

(39.) Red, the complementary of Green, added to Red, increases its intensity.

Green, the complementary of Red, added to Green, augments its intensity.

Such is the theoretical conclusion; and experiment confirms it.

When we place a Green inclining more to Yellow than to Blue in contact with

1o a Red slightly Orange,
2° a Red slightly Crimson,
3° an intermediate Red,

and then make a certain number of observations upon each of these groups of colours, we shall witness different results; that is to say, while in one case the Red will appear more orange, and the Green yellower; in another, the Red will appear more violet, and the Green bluer; and we may remark, that the change is attributable as much to a dif

also

ference in the intensity of the light illuminating the colours, as to fatigue of the eyes.

When we place a Green inclining more to Blue than to Yellow in juxtaposition with

1° a Red slightly Orange,
2° a Red slightly Crimson,
3° an intermediate Red,

the results are the same as with the first green, with this difference, however, that in the combination of bluish-green and crimson-red, looked at for a certain number of times, the Green and the Red almost always appear yellower than when viewed separately, a result easily anticipated.

Orange and Blue.

(40.) Blue, the complementary of Orange, added to Blue, increases its intensity.

Orange, the complementary of Blue, added to Orange, augments its intensity.

On repeating these observations with a deep Blue and an Orange which is not too red, both colours will frequently appear redder than otherwise.

Orange-Yellow and Indigo.

(41.) Orange-Yellow, the complementary of Indigo, added to Orange-Yellow, imparts to it greater intensity.

Indigo, the complementary of Orange-Yellow, added to Indigo, increases its intensity.

The result of observation is almost always in conformity with theory.

Greenish-Yellow and Violet.

(42.) Greenish-Yellow, the complementary of Violet, added to Greenish-Yellow, imparts to it greater intensity.

Violet, the complementary to Greenish-Yellow, added to Violet, increases its intensity.

The result of observation is almost always in conformity with the law.