Blue and Grey.

(68.) The Grey appears tinged with Orange, by receiving the influence of the complementary of Blue. The Blue appears brighter,-greener, perhaps.

Indigo and Grey.

(69.) The same as the above (68.).

Violet and Grey.

(70.) The Grey appears tinged with Yellow, by receiving the influence of the complementary of Violet.

The Violet appears purer, less tarnished.

(70.bis.) The Grey used in the preceding experiments was as free as possible from all colouring matter foreign to black. It belonged to the scale of normal black (see 2nd Part, 164.), that is to say, it resulted from a mixture of black and white substances as pure as could possibly be obtained: in contact with white it rendered it lighter and apparently brighter, while juxtaposed with black, it heightened it, and made it appear lighter and more rusty.

(70.ter.) One result of the complementaries of colours juxtaposed with grey being more apparent than when these colours are juxtaposed with white or even with black, is, that if instead of a normal grey we juxtapose a tinted grey, either red, orange, yellow, &c., these tints will be singularly heightened by the complementaries which will be added to them. For example, a bluish-grey will receive a very palpable exaltation of blue from its contiguity to orange, and a yellowish-grey will take a decided green tint from the same contiguity.

CHAPTER VII.

THE CHEMICAL COMPOSITION OF COLOURED SUBSTANCES HAS NO INFLUENCE ON THE PHENOMENA OF SIMULTANEOUS CONTRAST.

(71.) ALL the experiments I have made with the view of ascertaining if the chemical nature of bodies, when placed beside each other, has any influence on the modification of

their colours, have, as I expected, led me to an absolutely negative conclusion. Whatever happened to be the chemical composition of the coloured substances, provided they were identical in colour, they gave the same results. I will cite the following examples:

Indigo or prussian-blue, cobalt, ultramarine, as nearly alike as possible, gave the same kind of modification.

Orange prepared with red lead, with annotto, or with the mixture of woad and madder, gave the same modification to the colours with which they were juxtaposed.

CHAPTER VIII.

ON THE JUXTAPOSITION OF COLOURED SUBSTANCES BELONGING TO THE COLOURS OF THE SAME GROUP OF COLOURED RAYS.

(72.) WHENEVER there is a great difference between two contiguous colours, the difference is rendered more appreciable by bringing the same colour successively in contact with different colours belonging to the same group. For example:

Orange and Red.

When we place near Orange a scarlet-red, a pure red, or a crimson-red, we shall see that the Red acquires a purple, and the Orange a yellow tint.

Violet and Red.

Analogous results are obtained with Violet placed in contact with scarlet-red, carmine-red, and crimson-red. The Violet always appears bluer, and the Red yellower, or less purple.

(73.) These observations clearly explain the cause of our obtaining results conformable to the formula, although we may have made use of coloured substances, such as stained papers or stuffs, which are far from exhibiting very pure colours.

(74.) The juxtaposition of coloured bands is a means of

demonstrating the difficulty of fixing the types of pure colours by our pigments, at least if we do not take into consideration the law of simultaneous contrast. For instance:

1. Take Red, and place it in contact with orange-red, the first will appear purple, and the second yellower, as I have before stated; but if we put the first Red in contact with a purple-red, this latter will appear bluer, and the other yel lower, or orange; so that the same Red will appear purple in one case, and orange in the other.

2. Take Yellow, and place it near orange-yellow, it will appear greenish, and the other redder; but if we put the first Yellow in contact with a greenish-yellow, this latter will appear greener, and the former more orange; so that the same Yellow will incline to green in one case, and to orange in the other.

3. Take Blue, put it in contact with a greenish-blue; the first will incline to violet, and the second will appear yellower. Put the same Blue in contact with a violet-blue, the first will incline to green, and the second will appear redder, so that the same Blue will in one case appear violet, and in the other greenish.

(75.) Thus we perceive that the colours which painters term simple or primary, Red, Yellow, and Blue, pass insensibly by their juxtaposition to the state of secondary or compound colours. Since the same Red becomes purple or orange, the same Yellow is orange or green, and the same Blue is green or violet.

CHAPTER IX.

ON THE APPLICATION OF THE LAW OF CONTRAST TO THE HYPOTHESIS, THAT RED, YELLOW, AND BLUE ARE THE ONLY PRIMARY COLOURS, AND THAT ORANGE, GREEN, INDIGO, AND VIOLET ARE SECONDARY OR COMPOUND COLOURS.

(76.) THE experiments to which I have applied the principle of the modification that colours undergo by their juxtaposition, and the explanation which results therefrom, according to the manner in which we consider the physical com

position of white light, are also clearly explained in the language used by painters and dyers, who only admit of three primary colours-red, yellow, and blue; and, as it may occur to many persons, who, partaking of the same opinion, will, nevertheless, desire to understand the phenomena resulting from the juxtaposition of colours, I will now proceed to explain them in conformity with their language; and, for greater perspicuity, I will take five groups of juxtaposed colours, commencing with those which include the observations to which the preceding law most readily applies. I will suppose, then, that Orange is formed of red and yellow, Green of blue and yellow, and Indigo and Violet of blue and red.

FIRST GROUP.-Two Compound Colours having one Simple Colour for their Common Element.

It is very easy to verify the law by observing two colours comprehended in this group. We see that by their reciprocal influence they lose more or less of the colour which is common to both. It is therefore evident that they will differ from each other in proportion to this loss.

1. Orange and Green.

These two colours having Yellow for a common element, lose some by juxtaposition: the Orange will appear redder, and the Green bluer.

2. Orange and Indigo.

These two colours having Red for a common element, lose some by juxtaposition: the Orange appearing yellower, and the Indigo bluer.

3. Orange and Violet.

The same as the preceding.

4. Green and Indigo.

These two colours having Blue for a common element, lose some by juxtaposition: the Green appears yellower, and the Indigo redder.

As the preceding.

5. Green and Violet.

SECOND GROUP.-A Compound Colour and a Simple Colour which is found in the Compound.

1. Orange and Red.

The Orange loses its Red, and appears yellower; and the Red becomes more Blue, differing as much as possible from Orange.

2. Violet and Red.

Violet loses its redness, and appears bluer; the Red becomes yellow, differing as much as possible from Violet.

3. Indigo and Red.

The same as the preceding.

4. Orange and Yellow.

Orange loses some yellow, and appears redder; the Yellow becomes bluer, differing as much as possible from Orange.

5. Green and Yellow.

Green loses some yellow, and appears bluer; the Yellow becomes redder, and differs as much as possible from Green.

6. Green and Blue.

The Green loses some blue, and appears yellower; the Blue becomes redder, differing as much as possible from Green.

7. Violet and Blue.

The Violet loses some blue, and appears redder; the Blue becomes yellow, and differs as much as possible from Violet.

As the preceding.

8. Indigo and Blue.