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EFFECT OF THE ADMIXTURE OF PIGMENTS 
 The Primary , Secondary, and Tertiary Colours , 
 Brewster s Theory. 
 
CASSELL’S TECHNICAL MANUALS. 
 
 C O L O U R. 
 
 BY 
 
 A. H. CHURCH, M.A., 
 
 OF LINCOLN COLLEGE, OXFORD. 
 
 PROFESSOR OF CHEMISTRY IN THE ROYAL AGRICULTURAL COLLEGE, 
 CIRENCESTER. 
 
 CASSELL, PETTER, AND GALPIN, 
 
 LONDON, PARIS, AND NEW YORK. 
 
CONTENTS. 
 
 FACE 
 
 Chapter I.—Introduction—Connection of the Science of Optics with 
 Colour—Luminous Bodies —The Undulatory Theory-—Refraction 
 of Light . 5 
 
 Chapter IL—Composition of Light—Complementary Colours—The 
 
 Spectrum—Diffraction of Light. 12 
 
 Chapter III.— Production of Colour by Transmission, Absorption, and 
 
 Reflection—Mutual Relation of Colours 21 
 
 Chapter IV.—Maxwell’s Theory of Primary Colours. 3* 
 
 Chapter V.—The Common Theory of the Primary Colours, tones, 
 Shades, Tints, and Scales—Primary Colours- Secondary Colours 
 —Tertiary Colours—Hues—Tones . 40 
 
 Chapter VI.—The Laws of Contrast—Contrasts of Tones—Contrasts 
 
 of Colour—Simultaneous Contrast . 49 
 
 Chapter VIL-Colours with White, Grey, and Black-Ocular Modifi¬ 
 cations of Colour—Persistence of Colour Impressions Irradiation 
 Subjective Colours—Contact and Separation of Colour .. .. 54 
 
 Chapter VIII.—The Cultivation of the Sense of Colour—Triple Com¬ 
 binations of Colour—Distribution, Balance, and Quality of Tone.. 65 
 
 Chapter IX.—Complex Colour-Combinations—Harmonies of Ana¬ 
 logy-Harmonies of Contrast — Harmonies of Seriation-Harmo¬ 
 nies of Change . 74 
 
iv 
 
 CONTENTS. 
 
 PAGE 
 
 Chapter X.—Cautions as to the true Primary Colours and Chromatic 
 Equivalents—Modifications of Colour by Illumination—Diffused 
 Daylight—Light of the Sky and Clouds—Sunlight—A Dominant 
 Coloured Light — Artificial Lights—Two Lights.84 
 
 Chapter XI.— Surface and Structure Modify Colour—Colours of 
 Metals—Damascening and Plating—Enamelling on Gold and 
 Silver—Lacquering — Colours of Gems—Coloured Marbles— 
 Mineral Pigments.96 
 
 Chapter XII.—Coloured Glass—Colours of Pottery and Porcelain 
 —Mineral Pigments.— Colours of Plants, Flowers, Woods, and 
 Vegetable Fibres —Colours of Animals and Animal Products .. 104 
 
COLOUR. 
 
 CHAPTER I. 
 
 INTRODUCTION—CONNECTION OF THE SCIENCE OF 
 OPTICS WITH COLOUR. 
 
 The fibres of the optic nerve if excited by pressure, elec¬ 
 tricity, internal causes, or above all, by light, r give rise to 
 the sensations of which we speak as colour. It is owing to 
 the general dependence of colour upon light that we must 
 begin our study of its laws and their applications by a 
 statement of two or three of the chief facts of Optics. 
 We wish now to direct our reader’s attention to the re¬ 
 flection, the emission, the transmission, the absorption, 
 the refraction, and the dispersion of light. 
 
 Everything that we can see is visible owing to its re¬ 
 flection of light, or to its emission of it: the former action 
 produces or characterises illuminated bodies ; the latter, 
 luminous bodies. Illuminated bodies are marked out and 
 distinguished from one another by the different amounts 
 and qualities of the light which they reflect. A piece of 
 black cloth on a white porcelain plate reflects but a very 
 small part of the light which falls upon it; the plate, on 
 the other hand, reflects much. Had the black cloth pos¬ 
 sessed no power of reflecting light, it would have been in¬ 
 visible 5 black velvet, which reflects less light, sometimes 
 produces to the eye the effect of absolute blackness that 
 is of an empty and dark space. Similarly, a sheet of 
 plate glass may appear lustrous and visible enough if the 
 light which falls on it is sent back to the eye ; but if we 
 are so placed in front of the glass that these rays escape 
 us, it ceases to be visible, and we may, perchance, 
 stretch out our hand to take something from behind the 
 
 B 
 
6 
 
 COLOUR. 
 
 glass, wholly unconscious of its existence. But it is pos¬ 
 sible to render a piece of polished glass permanently 
 visible. Crush it to powder, and then in whatever di¬ 
 rection the light falls upon its particles the surfaces of 
 those particles will turn back or reflect some of the rays, 
 and so render themselves visible. The clear glass has 
 become opaque. 
 
 For the very same reason dense clouds, which appear 
 black when between the observer’s eye and the sky, owing 
 to the complete way in which they cut off the light, may 
 become brilliantly white when the sun’s rays fall upon their 
 constituent particles, owing to the very same action ; for 
 the light, which cannot get through the cloud, ig con¬ 
 tinually reflected to and fro from the surfaces of its minute 
 parts, and so illuminates it. Thus it happens that the 
 lower half of a cloud against a dark mountain may appear 
 white, while the upper part of the same cloud against a 
 luminous sky may appear a dull grey. The lessening of 
 reflection, on the other hand, diminishes visibility. The 
 numerous small reflections which occur between the sur¬ 
 faces of the fibres in a piece of paper may be greatly 
 reduced by wetting or oiling the paper, when it becomes 
 less opaque and at the same time greyer and clearer : to 
 this cause the transparency of tracing paper and tracing 
 cloth is due. 
 
 We said above that bodies differ not only in the amount 
 but in the quality of the light which they reflect. N ow 
 one of the chief differences as to quality of light is the 
 difference of colour. Powdered vermilion reflects much 
 light to the eye ; this light, however, is chiefly red light, 
 though there is some white light mixed with it. A 
 stick of red sealing-wax shows in some positions a bar of 
 white reflected light in the direction of its length, while in 
 other positions we see only the red light reflected from the 
 particles of its surface and of a small depth below. Why 
 this light happens to be red in the vermilion we shall dis¬ 
 cuss further on : we would only point out here that while 
 the reflection from a polished surface is regular, that from 
 a rough surface is irregular, and that from a coloured 
 surface coloured. A polished plane metallic surface 
 affords an example of the first kind of reflection, a piece 
 of chalk of the second. So great is the difference in 
 
LUMINOUS BODIES. 
 
 7 
 
 effect produced by regular reflection from that produced 
 by irregular reflection, that if an illuminated polished body 
 could be found which was wholly incapable of irregularly 
 reflecting any part of the light falling upon it, that body 
 would be invisible. We may, therefore, say that we dis¬ 
 cern bodies by the aid of the light which they reflect irre¬ 
 gularly, or scatter ; a perfectly regular reflection gives, on 
 the contrary, an image of the source of light, not of the 
 object illuminated. It is only light which is regularly 
 reflected which can be shown to obey the great law of 
 reflection, which is this “The angle which an incident 
 ray of light makes with a perpendicular to the reflecting 
 surface, is equal to the angle which the reflected ray 
 makes with that perpendicular in other words, the angle 
 of incidence and the angle of reflection are equal. Another 
 law here to be mentioned is, that both the incident and 
 the reflected rays of light are in the same plane, which is 
 perpendicular to the reflecting surface. We shall have to 
 refer to these laws of reflection, to reflection at varying 
 angles and from different substances, and to the different 
 kinds of reflection enumerated above, when we proceed 
 to discuss the subject of Colour. 
 
 A few words may now be said on luminous bodies, or 
 those which emit light. A candle-flame, a glowing piece 
 of charcoal, and the sun, are examples of luminous bodies. 
 From these sources of light luminous rays are sent out; 
 these rays are the lines in which the light is propagated ; 
 luminous pencils are bundles of such rays. From such 
 luminous bodies as are near the eye the rays emitted are 
 divergent, but the rays from the sun and distant bright 
 bodies are practically parallel. Highly luminous bodies 
 can only be clearly seen when much of the light which 
 they emit is cut off by a special contrivance, such as a 
 piece of smoked or dark-green glass. It is thus quite pos¬ 
 sible to see the form and changes of the coke-points of 
 the electric lamp, intense as its light is. 
 
 The light emitted from bodies travels in straight lines, 
 and causes the production of shadows. The form and 
 sharpness of shadows is influenced not only by the shape 
 and the relative size of the opaque body which casts the 
 shadow, but by the form of the luminous body, the light 
 of which is intercepted. A luminous point gives a 
 
 B 2 
 
8 
 
 COLOUR. 
 
 sharply-defined shadow, while a luminous surface, on the 
 other hand, gives a dark shadow surrounded by a paler 
 and less definite one which goes by the name of a 
 penumbra. 
 
 We have so far spoken of the reflection and of the emis¬ 
 sion of light : the transmission of light has now to be con¬ 
 sidered. Bodies are said to be transparent when they 
 permit light freely to pass, so as to allow objects to be dis¬ 
 tinguished through them; translucent , when they allow 
 light to pass less perfectly, and objects on the other side 
 of them cannot be clearly discerned ; opaque , when light 
 is wholly cut off. But in reality no bodies are perfectly 
 transparent or perfectly opaque. The most colourless and 
 flawless polished glass cuts off some rays, while substances, 
 such as metals, which are commonly considered quite 
 opaque, become transparent when reduced to the form of 
 thin leaves. The sun may be conveniently viewed through 
 a glass thinly coated with silver, while the light transmitted 
 by an ordinary piece of gold-leaf is grass-green. 
 
 In addition to this, it may be remarked that different 
 transparent bodies permit the light to pass through them 
 with more or less facility, but they also variously affect the 
 light which finds its way into them. Suppose the case of 
 water. A beam of light made up, we will suppose, of 
 1,000 rays, strikes the water perpendicularly; 18 rays 
 will then be reflected towards the luminous source, while 
 982 will find their way through the water unchanged, un¬ 
 less the layer of water be of considerable thickness. Now 
 introduce into the water a drop of some red solution ; the 
 light transmitted will be filtered light, the red solution 
 having strained off some of the constituent rays and left 
 the others. The intensity of the light and its quality will 
 thus have been altered by transmission, just as they are 
 by reflection. Colour, in fact, may be produced from 
 white light, either by the absorption of some parts of the 
 luminous rays and the reflection of others, or by the 
 absorption of some parts and the transmission of others ; 
 but, as we shall point out presently, there are several 
 other ways of producing colour without the intervention of 
 an absorbent body. 
 
 Before, however, we can profitably study these ways, 
 and the curious phenomenon of absorption itself, we must 
 
THE UNDULATORY THEORY. 
 
 9 
 
 become acquainted with the main features of the theory of 
 light. This theory is called the imdulatory theory. 
 
 The undulatory theory supposes the existence, through¬ 
 out all space and throughout all matter, of an infinitely 
 thin, elastic medium called the luminiferous or light- 
 bearing ether. It must be supposed that this ether is not 
 only universally present, but present without break in its 
 continuity. It exists in space, in all solids, liquids, and 
 gases, and it cannot be excluded from what we call a 
 vacuum. It can hardly be material in the sense in which 
 the sixty-three elements of the chemist are material; but 
 to account for the properties of light, we must presume 
 the medium which conveys it to have some at least of the 
 properties of matter. The movement of this ether is 
 light. It undulates in waves, the undulations of the par¬ 
 ticles of the ether being across the direction in which the 
 light is propagated. Light is supposed to originate in the 
 following manner 'The particles or molecules which 
 constitute a luminous body are in a state of disturbance, 
 a state of intensely rapid motion. This motion of the 
 molecules is communicated to the ether and sets it in 
 vibration, and is propagated in all directions in the form 
 of spherical waves. Reaching the retina, this fine motion 
 of the ether excites vision and becomes sensible as light. 
 With these statements of the main assumptions of the 
 wave-theory of light before us, we shall be able to con¬ 
 sider with exactness not only the absorption and refrac¬ 
 tion of light, but the several modes of the production of 
 colour. 
 
 The waves of the ether are of different lengths ; in pure 
 white light, such as that emitted by the electric arc, waves 
 of all lengths occur between the limits of about to£oo °f an 
 inch on the one hand, and about emmo of an inch on the 
 other hand ; or we may measure the waves by their dura¬ 
 tion. Those which excite vision vary between T | r and 
 of a billionth of a second of time. Now the colour of 
 light is dependent upon the length of the wave. The 
 longest wave that is perceived by the retina is the red 
 wave, the shortest the violet. Longer waves than the red 
 wave possess a high heating power ; shorter waves than 
 the violet, invisible to the eye, and with scarcely any action 
 on the thermometer, are gifted with a great degree of 
 
10 
 
 COLOUR. 
 
 chemical energy : they are called actinic. If we use the 
 electric light, which is really a more perfect light than that 
 of the sun, we shall find that it emits or causes undula¬ 
 tions, the waves of which are of much wider differences as 
 to length than those of the red and violet lights above 
 mentioned. By means of various solutions we can absorb 
 some of the rays : those of light can, for instance, be 
 strained off, and those of heat and actinism transmittted. 
 Thus it has been found that waves of certain lengths can¬ 
 not undulate in a solution of iodine in carbon disulphide, 
 they are arrested or quenched thereby. Such a solution, 
 indeed, permits only the rays of dark heat to pass through 
 it ; but the undulations of this dark heat may be changed, 
 and their wave-lengths may be diminished by allowing the 
 invisible heat-rays to be concentrated in a focus and to fall 
 upon a solid, infusible body. This solid will become hot 
 and then luminous—heat has been changed into light. 
 This passage of calorific into luminous rays is known as 
 calorescence , and may be made so complete a change that 
 all the colours of the rainbow may be thus obtained from 
 a perfectly dark source of heat. But exactly the same 
 sort of change may be effected with the invisible actinic 
 rays, the wave-lengths of which are shorter even than those 
 of light. By using a solution of blue vitriol in ammonia, 
 dark rays of chemical energy may be transmitted and 
 freed from the visible rays. Receive these dark rays upon 
 a screen of fluor spar, or Canary glass, or solution of 
 quinine sulphate, light and colour are produced. The 
 wave-lengths of the actinic undulations have been in¬ 
 creased ; the invisible chemical rays have passed into 
 visible luminous rays ; this passage is called fluorescence. 
 Another name for the change in wave-length which we 
 have just described is change in refrangibility. 
 
 We will now proceed to describe the meaning of the 
 expressions refraction and refrangibility. 
 
 When a beam of light falls perpendicularly upon water, 
 more than 98 per cent, of the rays pursue a straight course 
 through the water. Let the incidence of the beam be ob¬ 
 lique, and then it will be found that fewer rays will penetrate 
 through the surface, and that those which do will not pass 
 the water in a straight line, but will be more or less bent 
 out of that line : this bending is called refraction. Refrac- 
 
 ( 
 
REFRACTION OF LIGHT. 
 
 II 
 
 tion takes place when a beam of light passes obliquely 
 from a rarer to a denser medium, or vice versa. Instances 
 of refraction are familiar no doubt to most of our readers, 
 perhaps the best known example being the case of a stick 
 half immersed in water, which appears broken owing to re¬ 
 fraction ; and of a coin, which, lying invisible at the bottom 
 of a basin, may be made to appear by pouring water upon it, 
 and so bending back the rays, which are reflected by the 
 coin, till they reach the eye. In passing from air into water 
 or glass the refracted ray is bent towards the perpendicular ; 
 in passing out of water or glass into air the reverse refraction 
 occurs, and to a precisely equivalent extent. If, therefore, 
 a beam of light enters obliquely a piece of glass, the faces 
 of which are parallel, the refraction towards the perpendi¬ 
 cular on entering the glass will be exactly compensated by 
 the refraction from the perpendicular on leaving the lower 
 surface, and so the emergent ray will necessarily be parallel 
 with the incident ray. But supposing we employ a prism 
 of glass instead of a flat plate, then the ray is permanently 
 refracted. The prism so much employed in Optics is a 
 wedge-shaped piece of flint glass, and is an indispensable 
 instrument in the study of colour. The angle enclosed by 
 two oblique sides of this prism is called the refracting 
 angle. If we place the prism so that this angle shall be 
 below, and the opposite side of the prism horizontal, then 
 a beam of light falling from above on to one of the oblique 
 sides will be refracted towards the refracting angle, and 
 passing across to the other oblique side will emerge, with 
 its path changed again, but now in an upward direction. 
 But something more will have commonly happened to the 
 beam besides its permanent refraction. If the light be 
 simple, if its wave-lengths be of one measure only, it will 
 be simply deflected ; but if, as is nearly always the case, 
 the light be compound—if its waves are of different 
 lengths—then the prism will differently affect them. It 
 will retard the short waves more than the long ones, and 
 so we shall find that these short waves are more refracted. 
 The more refrangible rays are then the short violet rays, 
 the less refrangible rays are the longer red rays. In every 
 case, therefore, where a luminous body emits rays of 
 various refrangibility, these rays can be separated from 
 each other by means of the prism. As solar light consists 
 
12 
 
 COLOUR . 
 
 of an enormous number of rays of different refrangibilities, 
 it may be decomposed, analysed, or split into an enormous 
 number of coloured lights, the wave-length of each of which 
 belongs to a particular ray. The electric light gives an 
 infinite number of such coloured lights, for there are no 
 breaks in its series of rays, such as exist in the light of the 
 sun. Usually, burning metals and glowing glasses emit, 
 on the other hand, fewer rays, and give fewer colours, 
 when their light is prismatically decomposed. The de¬ 
 composition, or splitting up of light by the prism, is called 
 the dispersion of light; the coloured image formed is 
 called a spectrum. We are enabled to study the origin, 
 the properties, and the changes of colours by means of 
 this spectrum. 
 
 CHAPTER II. 
 
 COMPOSITION OF LIGHT—COMPLEMENTARY COLOURS— 
 THE SPECTRUM. 
 
 It was Newton who first discovered the compound nature 
 of white light. In order to split up a ray of the solar light 
 into its constituent parts, the following contrivance (Fig. i) 
 may be adopted :—Through a hole in the shutter of a 
 darkened room a beam of light, s, is allowed to enter. 
 This small beam must fall upon a prism of flint glass, A, 
 so arranged that the side, P, opposite to its refracting angle 
 is uppermost and horizontal. The beam will be refracted 
 and dispersed, as described in the last chapter ; and if the 
 refracting angle of the prism be 6o°, a vertical band of 
 rainbow colours will be produced on a screen placed at a 
 distance of five yards or so from the prism, A. This band, 
 H I, is the solar spectrum. It consists of a very large 
 number of different tints, amongst which it is easy to dis¬ 
 tinguish seven principal colours. Beginning at the end of 
 the spectrum which is nearest to the spot, K, the beam 
 would have reached, had no prism bent it out of its path, 
 we find the order of the colours is as follows :—Red, 
 orange, yellow, green, blue, indigo, violet. Now the mode 
 
COMPOSITION OF LIGHT. 
 
 13 
 
 in which these colours have been separated from white 
 light is sufficient proof that they cannot be further sepa¬ 
 rated into other kinds of colour. This anticipation is 
 realised by actual trial; for if, as in Fig. 2, one of the 
 colours of the spectrum, v, be allowed to pass through a 
 hole in the screen, E, on which the band of decomposed 
 light has been received, it cannot be altered by being trans- 
 
 Fig. 1. 
 
 mitted through a second prism, B. The ray will be re¬ 
 fracted, of course, but it will show but one colour, as before, 
 and its image will not be elongated. 
 
 We have already learnt that every ray of coloured light 
 has its own wave-length, and therefore that all the colours 
 of the spectrum, however similar they may seem, are really 
 distinct tints. But this consideration does not take in all 
 the facts of the case. The green of the solar spectrum is 
 not compound, but simple ; and yet we know that many 
 substances of a green colour may be split into two com¬ 
 ponents, one blue and the other yellow. Supposing for a 
 moment we can exactly imitate the green of the solar spec¬ 
 trum by mixing yellow and blue pigments together, this 
 fact would not of itself suffice to prove that the solar green 
 was really a mixed hue ; but it would show that the sensa¬ 
 tion of vision is similarly excited by the waves that reach 
 the eye from these two colours—one simple, the other ap¬ 
 parently compound. Precisely the converse of this holds 
 
14 
 
 COLOUR. 
 
 good. We can, as might be expected, re-form white light 
 by re-uniting all the seven dispersed coloured lights of the 
 solar spectrum (we will describe how to do this presently); 
 but we can reach the same result by re-uniting merely 
 certain pairs of these coloured lights. Thus, the following 
 unions of two colours generate white, or nearly white 
 light :— 
 
 1. Red—greenish-blue. I 3. Yellow—ultramarine-blue. 
 
 2. Orange—Prussian blue. | 4. Greenish-yellow—violet. 
 
 There is no monochromatic complementary to the pure 
 green of the spectrum, but one may be made by the union 
 of red and violet. These pairs of colours, and many others 
 less easy to distinguish by intelligible names, when united 
 lose their respective colours and become white. They are 
 
 Fig. 2. 
 
 called complementary colours. It will be seen that we have 
 followed in our grouping of them the sequence of the 
 colours of the spectrum, beginning with the red or least 
 refrangible rays ; but in order to produce white light by 
 the combination of any couple of the above colours, two 
 conditions must be fulfilled—the intensity and the quantity 
 of the component rays must be adjusted with care. By 
 receiving two such coloured pencils of light upon a lens 
 which condenses and brings them to the same focus on a 
 white screen placed at a suitable distance, the result is a 
 perfectly white light; but, to secure this result, the con¬ 
 stituents of a coloured ray are as important as its apparent 
 quality of colour. Thus Helmholtz has found that the red 
 and bluish-green of the spectrum produce yellow, not white; 
 while red, with the bluish-green, or perhaps greenish-blue, 
 formed by the union of green and indigo, does yield white. 
 Green and red have indeed a relation to each other which 
 
THE SPECTRUM. 
 
 15 
 
 is different in some particulars from that of many other 
 pairs of colours. They, however, are often included among 
 the pairs of so-called complementary colours for reasons to 
 be hereafter noticed. That there is something very peculiar 
 in the relation of green to red may be also concluded from 
 the frequency with which these two colours are confounded 
 by persons who suffer from colour-blindness or Daltonism. 
 
 One of the most curious of all the results of studying the 
 re-composition of white light is the relation of yellow to 
 blue. It is a matter of observation that a yellow and blue 
 liquid and a yellow and blue powder, when mixed together, 
 produce respectively a green liquid and a green powder. 
 But a very different result ensues on mixing blue and yellow 
 light together. When the blue and yellow rays of the spec¬ 
 trum are mixed together, white light is produced. The 
 same effect results from receiving upon the eye the reflected 
 image of a disc painted with gamboge along with the 
 direct image of a second disc painted with cobalt-blue. 
 Though a disc painted with these two pigments mixed to¬ 
 gether would have appeared green, yet when the lights 
 these pigments respectively reflect are conveyed to the 
 retina as above described, then, where the two images 
 coincide, whiteness is the result. 
 
 We must now describe some of the peculiarities of dif¬ 
 ferent spectra, and afterwards a few of the more recondite 
 methods bv which colour is produced. 
 
 Our purest source of coloured light is a spectrum. We 
 may use the spectrum of the solar beams, or that from the 
 electric lamp : the latter is more convenient, and yields, 
 as we have previously stated, a light more complex than 
 the sun ; for in the solar spectrum there are some three 
 thousand or more gaps where rays are missing. These 
 are the black lines first noticed by Wollaston, in 1802, after¬ 
 wards mapped out by Fraunhofer, and at last explained by 
 Bunsen and Kirchhoff. These black lines indicate lost 
 rays—rays which have been blotted out by absorption. 
 The absorption takes place in the following manner :—In 
 the sun’s gaseous envelope certain vapours exist. These 
 vapours are opaque to certain rays of light : they do not 
 allow them to pass, but quench them. There is, for in¬ 
 stance, the metal sodium in the sun’s gaseous covering. 
 Now sodium vapour is opaque to a certain yellow ray 
 
i6 
 
 COLOUR. 
 
 which it itself originates when it is burnt. Consequently, 
 the place which should be occupied by a bright yellow 
 band in the solar spectrum is a dark line, or rather group 
 of lines, called D. In like manner the other black lines, or 
 many of them, have been traced to the special absorptive 
 powers possessed by the sun’s gaseous envelope, and exer¬ 
 cised upon certain rays of light emanating from within. 
 These black lines, however, in the solar spectrum, though 
 rendering it imperfect in continuity, are of great service in 
 referring to the localities of particular colours. Yet we 
 must not forget that the material of the prism exercises 
 some influence upon the position of the lines and the rela¬ 
 tive extent of the coloured bands. At page 28 a coloured 
 plate will be found in which are shown the positions occu¬ 
 pied by the most important of the black lines and coloured 
 spaces in the solar spectrum when obtained by means of 
 a flint-glass prism in the spectroscope. The conditions of 
 success in obtaining these lines distinctly are a narrow, 
 clean-edged slit, a collimating lens to make the luminous 
 rays parallel, and a prism of highly-refractive and disper¬ 
 sive glass, quite free from striae and flaws. The instru¬ 
 ments known as spectroscopes are, however, always of 
 more complicated construction than these conditions seem 
 to involve ; for it is desirable to use a battery of prisms 
 instead of one prism, and to obtain a magnified image of 
 the spectrum by means of a combination of lenses in a 
 telescope. Let us turn now to the consideration of the 
 spectra as obtained by means of the spectroscope. 
 
 Most of our sources of artificial light yield spectra with¬ 
 out lines. An oil-lamp, gas-flame, the electric light, are 
 instances of this kind. But it is easy to secure a flame 
 which shall yield a very simple spectrum, reduced by the 
 absence of so large a number of rays that it shall merely 
 consist of a few bright bands, or merely of one. Dissolve 
 a little common salt, for instance, in some methylated spirit 
 of wine, and introduce the solution into a spirit-lamp. 
 The flame will, to the eye, appear tolerably luminous and 
 distinctly yellow. The spectrum of this flame shows little 
 more than a single brilliant yellow band, occupying the 
 dark space of the solar spectrum called D. The metal 
 sodium is distinguished from other metals by its flame 
 emitting rays of that particular refrangibility only. If a 
 
THE SPECTRUM . 
 
 17 
 
 salt of lithium be taken, and dissolved in spirit, the flame 
 of the lamp will be crimson, and two coloured bands will 
 characterise the spectrum. One of them is red, and very 
 distinct; the other is of a faint orange tint. Other metals 
 produce different spectra, though in many cases the colour 
 which they impart to the flame of a Bunsen gas-burner or 
 a spirit-lamp may seem to the unassisted eye identical. 
 
 In trying experiments with coloured flames, in order to 
 study their effects on the appearance of different objects, 
 the following contrivance may be used :— A (Fig. 3) is a 
 
 Bunsen gas-bumer (which is best made of steatite); B is a 
 bundle of fine platinum wires, bound together by a spiral 
 coil of rather coarser wire of the same metal, and dipping 
 into a small vessel containing a mixture of a solution of 
 the metallic salt to be experimented with, and pure ammo¬ 
 nium chloride. A ball of pumice attached to a bundle of 
 asbestos fibres may be substituted for the platinum wires. 
 
i8 
 
 COLOUR. 
 
 The following is a list of substances which give colours of 
 different hues to the flame of a burner under the circum¬ 
 stances described, the metallic salts most applicable being 
 those known as chlorides, chlorates, and nitrates :— 
 
 Substances. 
 
 Calcium nitrate . 
 
 Lithium chloride . 
 
 Strontium nitrate or chlorate 
 Sodium chloride . 
 
 Barium chloride or chlorate 
 Boracic acid 
 Thallium perchloride , 
 Copper chloride . 
 
 Indium chloride . 
 
 Potassium chloride 
 
 Colours of Flames. 
 
 Red. 
 
 Carmine. 
 
 Crimson. 
 
 Yellow. 
 
 Y ellowish-green. 
 Green. 
 
 Green. 
 
 Bluish-green. 
 
 Indigo-blue. 
 
 Violet. 
 
 The above substances give, for the most part, spectra 
 with many bright lines of different colours ; but the red 
 lines will dominate in one spectrum, and the green in 
 another. 
 
 Thus far we have been studying light and colour by 
 means of the prism : we will now see how the colours of 
 the spectrum may be separated without that instrument, 
 and yet without loss of any of their component parts. 
 Some of the most beautiful phenomena of colour are pro¬ 
 duced by a modification which light undergoes when it 
 passes the edge of an opaque body, or when it traverses 
 a small opening. Light then turns a corner, just as a 
 wave in water will turn the angle of a wall, or spread 
 itself on the further side of a hole in a plate through 
 which it has passed. This bending of the waves of light 
 has been termed diffraction. The source of light 
 in studying the phenomena of diffraction should be a 
 luminous or highly illuminated point. A silvered bead, 
 or steel globule, or the focus of rays obtained by the action 
 of a lens on a beam of light entering a dark chamber by 
 means of a small hole—all these contrivances furnish a 
 suitable light. If a narrow rectangular slit between two 
 metallic edges be placed in a beam of light, between the 
 focus of a lens and a screen, the space between the edges 
 will be occupied by bands of coloured light. If one colour 
 only be used, as by the interposition of a screen of red 
 
DIFFRACTION OF LIGHT. 
 
 19 
 
 glass, then alternate bands of that colour and black will 
 be seen. By using, instead of a simple rectangular slit, 
 apertures differing in size, number, and shape, very 
 beautiful chromatic appearances may be developed. 
 These may be obtained by looking at a bright point or 
 line of light through a bird’s feather mounted in a card- 
 frame, through a piece of glass dusted with lycopodium 
 spores, through a fine wire-grating, through a piece of very 
 fine cambric, or through a plate of smoked glass ruled 
 with fine lines. 
 
 The halo of colours sometimes seen round the moon 
 and the sun is usually a phenomenon of the same kind, 
 produced by the diffraction of light by the globules of 
 water constituting the fog. Imperfectly polished metals, 
 the feathers of many birds, and the surfaces of mother- 
 of-pearl, owe part, at least, of the peculiar coloured effects 
 which they exhibit, and which are known as iridescence, 
 to the diffraction of the light reflected from the small 
 strise, filaments, or folds of their surfaces. 
 
 Now, without entering into the minute particulars ne¬ 
 cessary to elucidate these appearances thoroughly, we 
 may state that the phenomena of diffraction are due to 
 two causes. One of these is the bending of light round 
 a comer, as waves of water bend round a rock in a 
 lake ; the other, the interference of the waves of the light- 
 rays so bent with one another. Interference of one set of 
 oscillations with those of another set may even extinguish 
 the light altogether. This takes place when the crests of 
 the undulations of a ray coincide with the hollows of the 
 undulations of another ray : thus there will be rays on 
 either side of a slit which, bent by diffraction, will by this 
 kind of interference exactly neutralise each other and 
 abolish the light. The dark bands and lines produced 
 by diffraction are explicable in this way. As to the cause 
 of the colours seen under the conditions just mentioned, 
 we may refer to the obliquity of the paths of the diffracted 
 rays. If red light be employed, black and red rings or 
 bars alternate ; but with violet light, black and violet rings 
 or bars are seen. The violet rings are nearer together 
 than the red, because their waves are smaller than the red. 
 We can obtain bands of colours intermediate in width 
 between red and violet by employing, for example, green 
 
20 
 
 COLOUR. 
 
 !«1 . H 2SSSfi!£ « 
 
 the constituent colours are not d 5 y Slde ’ becaus e 
 obliquity of the path of the rays aSdThe^-ff^ t0 the 
 
 ray which enters the\hin * by the mterference of the 
 fleeted from its second , * rans P a . r ent film, and is re- 
 directly reflected from^ts first^surfSe^ Which is 
 may be of such a thickness as to retard' SOa P- bubb] e 
 from its second surface hv lLlf o , 6 beam re A ec ted 
 number of half wavedenmhs In ?T length ’ 0r by any 
 found that the bubble is black £L h \ Case Jt wil1 he 
 beams are in complete discoiSrS :ause , the J two reflected 
 light follows. Then again cn nC u Yt? d a destru ction of 
 much in the thickness^ A-ff P "^ Ubbles ma y vary very 
 
 of light differ in length so th^ Pa ,? S - A$ the wav ^ 
 thicknesses to produc/accordan^7 wdl re fl u ire different 
 result of this fs tSurffil The 
 
 petent to extinguish one colour wilf Whlch is com - 
 colours. Thin films of variaS nS n° extmgulsh other 
 illuminated by white light will th cb , an £"?& thicknesses, 
 
 pf the precious opal are due tn The colours 
 
 internal reflections from its nterference of the 
 
 The colours of tar-films 7 6 vacuous Assures, 
 
 wings, and of lead-skimming due inSCCts ’ 
 
 ference. So also are the snlendid n d • lso to mter- 
 of certain crystals when vi?led in vSsed 
 
 fridescent? 311 ^ ** «*"» 
 
 colour by 1 “"deed™ absorption“to^th 116 production °f 
 
 of white light by the re-unfon of its scattered 0 'Ti P ° Sltl0n 
 
 elements, 11 t0 the “ ***»?TS£ 
 
PRODUCTION OF COLOUR. 
 
 21 
 
 CHAPTER III. 
 
 PRODUCTION OF COLOUR BY TRANSMISSION, ABSORP¬ 
 TION AND REFLECTION — MUTUAL RELATION CF 
 COLOURS. 
 
 The absorption and reflection of light are very closely 
 related, yet there are many coloured bodies which instead 
 of absorbing some rays and reflecting others, transmit 
 those rays which they do not reflect. Even a third con¬ 
 dition exists, in which a substance reflects some rays of 
 the incident light, transmits others, and absorbs the re¬ 
 mainder. We may now briefly consider the production 
 of colour by these three methods. 
 
 Let us suppose a substance which appears red by re¬ 
 flected light and red also by transmitted light. Of the 
 white light which has fallen upon it and which it has de¬ 
 composed, it has absorbed or quenched all the colours 
 save the red ; while of the red it has transmitted part and 
 reflected part. But the instances in which a substance 
 appears of a very distinct colour owing to reflection are 
 rare. A few metals may be cited as examples along with 
 such substances as murexide, magnesium platinocyanide, 
 potassium permanganate, and indigo. The yellow colour 
 of gold is due to selective reflection. A plate of this metal 
 reflects much of the incident light unchanged, but it 
 quenches in another portion much of the violet and other 
 very refrangible rays, and so leaves the residual red, orange, 
 and yellow rays to produce their colouring effect. It might 
 seem likely that gold would transmit when in sufficiently 
 thin leaves all those coloured rays which it does not 
 reflect. This is true to a great extent; still the grass- 
 green light which a leaf of gold transmits is not perfectly 
 complementary to the orange-yellow which it reflects, 
 some of the constituent rays of the original white light 
 having been absorbed. Solid indigo affords us a similar 
 example of selective absorption and reflection. If a lump 
 of pure indigo be pressed with an agate burnisher, a 
 copper-coloured streak makes its appearance. As long as 
 the substance of the indigo is not coherent—that is, as 
 
 C 
 
22 
 
 COLOUR. 
 
 long as it is in minute powdery particles—so long it shows 
 no symptom of a copper-coloured reflection, but is blue. 
 Now the blueness of powdered indigo thus seen by re¬ 
 flection is not really produced by or in reflection, but 
 rather during transmission of light from particle to particle 
 of the powder. A chromatic selection is thus made, and 
 the light finally reflected to the eye has been deprived 
 of several of its coloured elements. Increase the co¬ 
 herence of the blue indigo powder either by pressure, or 
 by the chemical process of sublimation, by which crystals 
 may be formed, and then, though the transmitted light 
 will remain blue as before, the reflected light will be chiefly 
 copper-coloured, having been deprived by reflection itself 
 of its blue and some other constituent rays. The foregoing 
 facts often suffice to explain the great difference in colour 
 between a solid substance and its powder. 
 
 Substances which are commonly regarded as transparent 
 are never perfectly so. N either water, nor flint glass, nor 
 rock crystal, permit all light-rays to travel freely through 
 them. Some substances, such as solutions of the rare 
 metal didymium, and certain specimens of the mineral 
 known as zircon, absorb or cut off several of the rays of 
 solar light, and yet do not appear perceptibly coloured. 
 The residual transmitted rays in such cases are of such 
 quality and exist in such proportion that they suffice to 
 produce white light. Very thin layers of coloured sub¬ 
 stances, such as films of tinted liquids, may seem colour¬ 
 less, and yet, when we increase their thickness, colour 
 becomes perceptible. Not only does colour become per¬ 
 ceptible, but the colour varies with the thickness. A 
 crystal of blue vitriol shows on its thinnest edges a greenish 
 tint, which alters to a pure blue in the mass. Such a 
 change as this is easily explained. A thin plate of blue 
 vitriol transmits all the blue, a good deal of the green, and 
 a very little of the remaining rays of the spectrum. If we 
 double the thickness of the plate the effect is increased, 
 not in arithmetical but in geometrical proportion. Ulti¬ 
 mately, by the extinction of all the rays save the blue, 
 the transmitted light becomes sensibly an homogeneous 
 blue. 
 
 A very easy mode of observing the striking differences 
 in colour between thin and thick layers was devised by 
 
PRODUCTION OF COLOUR. 
 
 23 
 
 Professor Stokes. A fine slit (one-fiftieth of an inch across) 
 between two blackened metallic edges is adjusted vertically 
 in a blackened piece of board ; behind the slit is a source 
 of light, such as a bright flame or the sky. Hold the 
 prism, having an angle of 6o°, against the eye ; by ad¬ 
 justing the position of the prism a pure spectrum will be 
 obtained, showing, if solar light be used, the principal 
 fixed lines. Now, to observe the absorption of any liquid, 
 fix a test tube or flat cell containing the liquid to be 
 examined behind the slit. Begin the experiment by using 
 a very pale solution, and then gradually increase the 
 strength, noting the gradual appearance of dark lines or 
 spaces in the spectrum and the blotting out of colour 
 after colour. If a wedge-shaped trough be used to hold 
 the coloured liquid behind the slit, it may be gradually 
 moved so as to interpose thicker and thicker layers of 
 the coloured liquids, and thus to produce the same results 
 as those obtained by gradually increasing the strength of 
 the solution. This method is of service when we wish to 
 know the result of diluting any coloured liquid which has 
 to be employed for artistic purposes. Thus, it will be 
 found that some reds, when diluted, instead of becoming 
 pink, pass through orange to yellow; while some blues, 
 instead of becoming paler blues when weakened, become 
 either green on the one hand or violet on the other. 
 
 We turn now to the re-composition of white light from 
 its constituent elements. There are several ways of ac¬ 
 complishing this result. If we receive the spectrum of 
 coloured rays produced by one prism, A, on another pre¬ 
 cisely similar prism, B, but inverted (Fig. 4), the emergent 
 beam, E, will be white. The concentration of a spectrum 
 
 Fig. 4. 
 
 by a bi-convex lens or a concave mirror gives a white and 
 not a variegated image. Or the seven so-called principal 
 colours of a spectrum may be received upon seven little 
 
 C 2 
 
24 
 
 COLOUR. 
 
 mirrors (as shown in Fig. 5), and then these mirrors may 
 be so adjusted that their separate images are superposed. 
 In this case also a single white image is obtained. 
 
 Fig. 5 - 
 
 A less perfect mode of re-uniting colours so as to form 
 white may be accomplished in the manner suggested by 
 Newton. A disc (Fig. 6) is painted in radiating segments 
 with the nearest approach afforded by pigments to the 
 seven colours of the spectrum, the centre and edges being 
 made black. The relative areas of the several colours 
 must be adjusted so as to correspond as far as possible 
 with the normal spectrum, introducing, however, such 
 
 Fig. 6. 
 
 differences as the imperfections of the pigments used may 
 demand. As red, green, and blue are the most prominent 
 colours of the spectrum, they should be used in larger 
 
MUTUAL RELATIONS OF COLOURS. 
 
 25 
 
 proportion than the orange, yellow, indigo, and violet. 
 Indeed, a very respectable kind of whitish grey may be 
 obtained by the use of fewer colours than seven ; but of 
 this point we shall have occasion to speak more definitely 
 further on. The best pigments, however, even when used 
 in proper proportions, do not produce a perfect white 
 when the disc painted with them is rapidly revolved (see 
 Fig. 7), so that the retina receives in quick succession the 
 impression of the whole series. All coloured bodies ab¬ 
 sorb much light and do not reflect really homogeneous 
 
 rays, and a grey is the result. If several series of similarly 
 coloured segments be painted on the disc the grey more 
 nearly approaches white. In the latter case the eye re¬ 
 ceives simultaneously the impressions of the several 
 colours, and so the effect does not wholly depend upon 
 the long persistence on the retina of these impressions. 
 
 We may now turn our attention to the mutual relations 
 of the several colours. 
 
 Reverting for a moment to the pure solar spectrum 
 obtained by means of a prism and a slit, and with the 
 exclusion of all extraneous light, we may first of all notice 
 
26 
 
 COLOUR. 
 
 that it consists mainly of three colours—red, green, and 
 blue. These coloured bands occupy by far the largest 
 area of its most brilliant portion. The orange, yellow, 
 and sea-green, though more brilliant, are very limited in 
 extent, while the indigo and violet region of the spectrum 
 is much less conspicuous. The gradual passage of one 
 colour into another observed in the case of the solar 
 spectrum and in the spectra of most ordinary lights 
 prevents us from easily marking off and naming many 
 of the constituent hues. But by means of a grating 
 of black bars interposed in the path of the coloured beams, 
 or by a sliding screen with a few slits in it capable of 
 adjustment, we may compare the solar colours with one 
 another and obtain something like a nomenclature for 
 those which are at first sight difficult to isolate and name. 
 The following list commences with the red, or least re¬ 
 frangible end of the spectrum, the most important colours 
 being printed in capitals :— 
 
 f Crimson. 
 
 Red. ) Scarlet. 
 
 1 Orange-red. 
 
 ( Orange. 
 
 / Y ellow. 
 
 | Greenish-yellow. 
 J Yellowish-green. 
 \ Green. 
 
 I Seagreen-green. 
 'Seagreen. 
 
 ( Seagreen-blue. 
 
 t>. ) Blue. 
 
 BLUE ‘ ) Indigo. 
 
 ( Deep violet. 
 
 In this list the true purple or red-violet does not find a 
 place. In point of fact this colour does not occur in the 
 solar spectrum, although it may be made by mixing the 
 red and blue, or red and violet together. It may also be 
 produced by receiving the red rays of one spectrum and 
 the blue rays of another upon the same surface. The true 
 purple is a redder colour than that known as violet: it 
 may be termed red-violet, an expression by which we may 
 have hereafter to designate it. Sometimes, when light 
 and brilliant, it has been called pink or almond-blossom, 
 
MUTUAL RELATIONS OF COLOURS, 27 
 
 —the latter name seems less liable to misconception than 
 the former. 
 
 There are certain colours in the spectrum of the sun’s 
 light, and of most ordinary lights, which are much more 
 rich, deep, or saturated in proportion to their brilliancy 
 than the rest; these are the richest and most characteristic 
 colours of the spectrum, red, green, and blue, and have 
 been selected from the remaining hues and called primary 
 colours. With them, in various admixtures, it is believed 
 that all other colours may be obtained. N ow for many 
 practical purposes the theory of the existence of only three 
 primary or elementary colours will be found very useful. 
 The selection of these primary colours has, however, been 
 far from unanimous, one set of observers choosing scarlet, 
 green, and blue, another yellow, red, and blue. Nearly 
 all writers on the artistic aspects of colours, such authors 
 as Chevreul, Field, Redgrave, and Hay, have accepted 
 the latter selection ; but though it undoubtedly affords 
 an easier means of studying the nature of the mixed 
 colours which pigments and paints afford, it is but par¬ 
 tially supported by experiments with the pure colours of 
 the spectrum, and in some points is positively contradicted 
 by them. The rival theory, in which the three primaries 
 assumed are scarlet, green, and blue, has been profoundly 
 studied by Maxwell, and has been made the basis of a 
 small treatise, most sumptuously illustrated, on the science 
 of colour, by Mr. W. Benson, a London architect, who has 
 done much to further the acceptance of this comparatively 
 modern theory. We shall proceed to give an outline of 
 both views as to the relations of the colours of the spec¬ 
 trum ; thus our readers will be able to form their own 
 judgments on the two theories. For our own part we 
 regard Maxwell’s experiments as conclusively proving 
 most of the positions he has laid down when pure coloured 
 lights are the subject of comparison and experiment. Yet 
 in actual work with pigments themselves, the older theory 
 affords a more immediate, though often a less exact, 
 answer to any question which may arise. 
 
 In order to study the primary or simple, and the second¬ 
 ary or mixed colours, several methods may be pursued. We 
 here name three of the most important of these methods. 
 
 Tint two pieces of paper with the two colours to be 
 
28 
 
 COLOUR. 
 
 examined, place the coloured pieces an inch or two apart 
 on a piece of black velvet, and set up, equidistant between 
 them, a slip of thin, colourless plate glass ; then adjust the 
 eye so that one coloured patch maybe seen by reflection 
 from the near surface of the glass, coincident with the 
 other patch as seen directly through the glass. By inclin¬ 
 ing the glass the reflected image of one colour may be 
 altered in intensity, and so the relative proportions of the 
 two colours may be varied at pleasure. The coloured 
 figures 8 and 9 are so arranged as to enable our readers to 
 perform this experiment for themselves, and at the same 
 time to note the different results of the mere commixture 
 of pigments. If the plate of glass above referred to be 
 erected along the middle of Fig. 8, and the reflection of the 
 blue stripe be properly combined with the image of the 
 yellow stripe, a greyish white, and not a green colour, will 
 be the result. Butwhere the two pigments have been printed 
 upon the same surface of paper we have a very distinct 
 green hue as the product. So in Fig. 9, the red and green 
 patches viewed by means of the glass give some approach 
 to a yellow or citrine colour, a good deal mixed with grey, 
 however : but a much duller and greyer hue is formed by 
 the superposition of the pigments, where at one side of 
 the figure the coloured triangles overlap. 
 
 Another plan, devised, like the last, by Helmholtz, con¬ 
 sists in obtaining two intersecting spectra. Two clean- 
 edged narrow slits, forming together a right angle, thus V, 
 are made in a metallic plate. When this compound slit, 
 brightly illuminated from behind, is viewed by means of a 
 prism about twelve feet off, two overlapping spectra will be 
 seen, the prism being held vertically. As each coloured 
 band of one spectrum crosses all the coloured bands of 
 the other, the result of combining two of the spectrum 
 colours together may be studied. For this purpose it is 
 desirable to employ solar light, the fixed lines of which 
 afford a means of identification of the several colours, and 
 may be readily seen in the above-named spectra by means 
 of a telescope. The telescope is furnished with cross wires, 
 and a diaphragm for limiting the field of view, placed a short 
 distance from the eye-piece of the telescope and close to 
 the eye. A third slit may be used, if it be desired, to 
 unite three coloured rays. A modification of this method 
 
Fig. VIrr. 
 

 
 
 
 
 
 
 
MUTUAL RELATIONS OF COLOURS. 
 
 29 
 
 of producing overlapping spectra consists in cutting out 
 from a piece of white cardboard three pieces of the shape 
 indicated in Fig. 10 by the black spaces. The perforated 
 cardboard, which should be of large size, is placed in a 
 bright light with a piece of black velvet below it. It is 
 then to be viewed six or seven yards off with a prism 
 having its refracting angle turned away from the eye, and 
 placed at right angles with the edge A B of the cardboard 
 figure. N0 description can give an idea of the beauty of the 
 overlapping spectra thus produced. The results obtained 
 by Helmholtz and Maxwell, by means of experiments con¬ 
 ducted by the method of overlapping spectra will be de¬ 
 scribed below. 
 
 A third method of combining colours is by means of a 
 revolving disc such as that represented in Fig. 7. The 
 disc may be painted with the colours it is desired to com¬ 
 bine, and then rotated. Of course the proportions of the 
 colours used may be varied not only by painted segments 
 having different areas, but by the superposition of a second 
 or third disc upon the original one, the 
 additional discs having segments of 
 different areas cut out, and being 
 themselves either white, black, or col¬ 
 oured. The various kinds of colour- 
 tops and kaleidoscopic tops may be 
 used for these experiments. We may 
 now give the chief results obtained by 
 Helmholtz and by Maxwell, by means 
 of the first and second methods above 
 described, premising that the state¬ 
 ments refer to the coloured rays of the 
 pure spectrum, and not to those of 
 pigments. 
 
 Helmholtz concludes that there are 
 five primary colours. These are red, 
 yellow, green, blue, and violet. With 
 these, two or three together, and in 
 various proportions, he obtained nearly perfect represen¬ 
 tations of the mixed colours. Many combinations of three 
 of them yielded white light. A great range of mixed 
 colours may be obtained by variously combining red, 
 green, and violet, the coloured elements originally selected 
 
30 
 
 COLOUR. 
 
 by Dr. Young. Helmholtz considers these three as af¬ 
 fording better results than red, green, and blue, which 
 Maxwell regards as the only essential primary colours, and 
 as infinitely preferable to the older selection of red, yellow, 
 and blue. With regard to the mixture of colours, it ap¬ 
 pears that the following are among the most important of 
 Helmholtz’s results :— 
 
 Red + bluish-green yellow. 
 
 Red + bluish-green + indigo 
 Red + greenish-blue 
 Yellow 4 indigo 
 Orange + blue 
 
 The two most remarkable of these results are the facts 
 that red and bluish-green make yellow, and that yellow 
 must therefore be regarded as a compound colour. When 
 this yellow is united with the deep blue called indigo, it 
 produces white. Here we have two conclusions quite 
 opposed to the result obtained by mixing pigments. When 
 vermilion and emerald green are mixed, a grey with merely 
 a suspicion of yellow is the product. When chrome yel¬ 
 low and indigo are mixed, a distinct green is the product. 
 We have before alluded to the causes of such discrepan¬ 
 cies, but may now explain them so far as relates to the 
 examples just cited, since these are typical cases of the 
 kind, and illustrate the two chief points in which the new 
 theory of primary colours differs from the old. Vermilion 
 reflects chiefly red and yellow light to the eye; emerald green 
 chiefly green, but also a little blue and yellow. Mix these 
 coloured powders together, and most of the red, green, and 
 blue they reflect, as long as separately viewed, is either ab¬ 
 sorbed or re-combined into whiteness, little else remaining 
 but the small quantity of residual yellow rays common to 
 both. Similarly with chrome yellow and indigo ; the chief 
 colour they reflect in common is green, and so most of the 
 other rays which they reflect when separate are either 
 quenched when they are mingled, or overpowered by the 
 combined and enhanced effect of the green common to 
 both pigments. 
 
 We shall proceed in our next chapter with the account 
 of the new theory of colour by giving some of Maxwell’s 
 results. 
 
 = white. 
 
maxwell's theory. 
 
 31 
 
 CHAPTER IV. 
 
 MAXWELL’S theory of primary colours. 
 
 In continuation of our remarks upon the various theories 
 which have been propounded as to the true primary colours, 
 we may now refer to the conclusions of Professor Clerk 
 Maxwell. According to this observer, the three primary 
 colours are scarlet, green, and blue. By the combination of 
 these colours he considers that all others may be formed ; 
 but at the same time he admits that the other colours of 
 the spectrum are due to simple or undecomposible rays, 
 though they excite the same sensations as those of certain 
 mixtures of rays. A bluish-green ray, for example, though 
 not compounded of blue and green rays, produces a sensa¬ 
 tion which may be regarded as compounded of those sen¬ 
 sations which are produced by blue and green. In their 
 selection of the three most important 
 colours of the spectrum, in their diverg¬ 
 ence from the ordinary theory as to the 
 primary colours, and in their views as to 
 complementary colours, Helmholtz and 
 Maxwell agree to a considerable extent : 
 it is as to the possibility of forming from 
 three colours all the others that they differ 
 —Maxwell affirming this, and Helmholtz 
 denying it. A few words as to the pri¬ 
 mary, secondary, and complementary 
 colours admitted by Maxwell may now 
 be given. In order to observe these 
 colours satisfactorily, the following con¬ 
 trivance should be adopted :—Two slips 
 of pure white unglazed paper should be 
 laid upon a piece of black velvet, after 
 the manner represented in Fig. 11. If 
 this diagram be thus copied in paper and 
 velvet on a large scale, and viewed from 
 a distance, by means of a prism having 
 its refracting edge turned away from the spectator, the 
 colours will be seen as indicated in the figure. These 
 
3 2 
 
 COLOUR. 
 
 colours are the two complementaries. By varying the 
 shape of the black and white spaces, new and instructive 
 effects may be developed, which we have not space to 
 describe particularly. One of these 
 variations is made by placing a narrow 
 white strip across the middle of a long 
 black band, and a similar narrow black 
 strip across a contiguous long white 
 band, and continuous with the white 
 strip. 
 
 According to the deductions of Max¬ 
 well, the most effective three primary 
 colours for the purpose of compounding 
 the largest numbers of other colours 
 have the following wave - lengths in 
 millionths of an inch, and the following 
 f ~ I- - —-I positions in the spectrum of the sun 
 
 (Figs. 12 and 13) :— 
 
 O ! I—. 53 Navies of Primaries. Wave-lengths. Positions. 
 
 0 Pure red or scarlet. 2,328 .-|fromlmeCtoD. 
 Pure green . . . 1,914 . J from line E to F. 
 
 Pure blue . . . 1,717 . \ from line F to G. 
 
 The secondary colours complementary 
 to these primaries are— 
 
 Sea-green complementary to Red. 
 
 Almond-blossom ,, Green. 
 
 Yellow ,, Blue. 
 
 Some authors call the colour we have 
 here named “almond-blossom” pink, 
 others peach-blossom: the term “purple” 
 might be used for it, had not this word 
 been employed to signify such a variety 
 of hues. It contains less blue than does 
 violet, which is not its true complemen¬ 
 tary. Perhaps the best representation of 
 the particular colour here meant is to be obtained by 
 burning the gas known to chemists as cyanogen—easily 
 obtained by heating a little mercuric cyanide in a short 
 test-tube fitted with a fine glass jet to s?rye as a burner. 
 
 c b 
 
 
Violet. 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
maxwell's theory. 
 
 33 
 
 These three secondary colours, in order to be truly com¬ 
 plementary to their several primaries, must not only be of 
 the right quality and purity, but must be of the right intensity 
 or brightness. So the sea-green named above must have 
 the added brightness of its two components, blue and green; 
 the almond-blossom must have the added brightness of its 
 two components, red and blue ; and the yellow must have 
 the added brightness of its components, red and green. Of 
 course these statements refer only to Maxwell’s theory of 
 the colours of light. In the case of pigments we shall have 
 frequent occasion further on to repeat what we have in¬ 
 deed often stated before—that the complex nature of the 
 
 coloured rays they generally reflect does not permit these 
 simple relations of colours to each other to hold good. In 
 continuing our outline of some of the chief features of the 
 new.theory of colour, we may draw our readers’ attention 
 to the annexed diagrams (Figs. 14 and 15) by means of 
 which, when filled in with the colours named, they can re¬ 
 present for themselves the primary and secondary colours 
 of Maxwell’s theory. 
 
 In these diagrams the following abbreviations are 
 used :— 
 
 I. Primary Colour. —R, Red ; G, Green ; B, Blue. 
 
 II. Secondary Colour.— S G, Sea-green; A, Almond-blossom; 
 
 Y, Yellow. 
 
34 
 
 COLOUR . 
 
 When the diagrams are filled in with the purest pigments 
 attainable, then Fig. 14 should show the effect of taking 
 away the three primary colours from white, leaving three 
 overlapping circles of secondary colours where only one 
 colour is removed ; leaving three-sided spaces of primary 
 colours where two colours are removed ; and leaving also 
 a similar space of black or darkness in the centre, where 
 all three primaries are equally removed. The exact con¬ 
 verse of this effect is shown in Fig. 15, where the primary 
 colours are supposed to be represented in equal strength 
 upon a black ground. They form, by the overlapping of 
 two of the three circles or discs containing them, three 
 
 Fig. 15 - 
 
 spaces of the secondary colours, and where all three 
 circles overlap or coincide, a central space of white. 
 Coloured lights are, of course, alone competent to produce 
 secondary colours brighter or more luminous than their 
 constituent primaries. A similar but false imitation of 
 this effect is produced by mixing white with the secon¬ 
 dary colours used in preparing the above diagrams, as 
 this admixture destroys the saturation of the colour, re¬ 
 ducing its tone. 
 
 We have, however, made use of this contrivance in the 
 coloured diagrams, Figs. 17 and 18, which respectively 
 represent the taking away of the primary colours from 
 
MAXWELL’S theory . 
 
 35 
 
 white and the adding of these colours to black. In Fig. 
 17 we have, first of all, a white ground which we assume to 
 representamixture of equivalents of the primaries, red, green, 
 and blue. If from this white we take away the primary 
 green, the residual red and blue will remain, constituting 
 the secondary colour, almond-blossom or pink, which fills 
 the greater part of the upper surface in the diagram, and 
 has the brightness of both its constituents. Similarly the 
 two other circles are chiefly filled in with blue-green or 
 sea-green, and with yellow respectively. These colours 
 are the secondaries obtained by the removal of the primary 
 red and the primary blue, respectively, from white light. 
 The sea-green or blue-green has the brightness of both 
 green and blue, while the yellow is similarly more brilliant 
 than either of its constituents, for it has the brightness of 
 both red and green in it. The three small triangular 
 spaces, in Fig. 17, represent the primaries, or white from 
 which two out of its three coloured elements have been 
 removed ; while in the centre is a similar space of black 
 formed by the abstraction of all the primaries red, green, 
 and blue. Nowin Fig. 18 we have a representation of the 
 converse of all this. On a black ground we suppose three 
 overlapping discs of the primaries; then, where two of 
 these overlap, we have the resulting secondary colour pro¬ 
 duced, and in the centre of the diagram, in the space 
 common to all three discs, we have a triangular space of 
 white formed by the mixture of the three primaries. But 
 in our diagrams we can also see, opposite to each primary 
 colour, its proper complementary, forming the pairs :— 
 
 Red and Seagreen. 
 
 Green and Almond-blossom. 
 
 Blue and Yellow. 
 
 Perhaps, however, the best way of exhibiting, in a neat 
 and intelligible form, the relations of the primary and 
 secondary colours and hues, is by means of a chromatic 
 circle, Fig. 16, triangle or cube. Chevreul has adopted a 
 plan of this kind with reference to the common theory of 
 the primary colours, introducing moreover into his scheme 
 numerous modifications of hue, tone, shade, &c., produced 
 by the admixture of colours with white and with black as 
 well as with one another. But this arrangement requires 
 
COLOUR. 
 
 36 
 
 considerable alteration before it can be taken to repre¬ 
 sent the constitution of colours upon the true system. 
 The triangle of Maxwell represents many important truths 
 concerning colours and pigments as deduced in part from 
 experiments. The cubes of colours which Mr. Benson 
 employs in his two works on Colour afford excellent means 
 of developing and arranging the vasf numbers of modifica¬ 
 tions of hue and tone of which colours are susceptible. His 
 chromatic cube presents the full white at one solid angle, 
 pure black, or the absence of all colour, at the opposite 
 
 
 Fig. 16. 
 
 solid angle, while the six other similar points of the cube 
 are occupied by the primary colours and their secondaries, 
 blue being opposed to yellow, and so on with the other 
 pairs. On the plane surfaces of the cube and its 
 edges are duly placed the products obtained by the mix¬ 
 ture of the colours on the poles with each other, or with 
 white or with black, in various proportions, while towards 
 the centre of the figure the dull colours produced by ad¬ 
 mixture with grey will be found. Our present purpose 
 
maxwell's theory. 
 
 37 
 
 may, however, be sufficiently answered by a simpler 
 arrangement based on the chromatic circle of Dr. Briicke. 
 We print the primaries in a thick, and conspicuous type, 
 arranging them at equidistant points on the circumference 
 of the circle. Joined by thick lines, as diameters, to 
 these primaries are the three important secondaries, which 
 are distinguished by smaller letters. Then come the hues 
 in which the primaries are mingled together in proportions 
 different to those which constitute the secondaries. All 
 colours then, in this arrangement, which are complemen¬ 
 tary to one another will be found as pairs joined by dia¬ 
 meters of the circle. 
 
 In the above chromatic circle we have assigned no place 
 to black, though white will be found at some one point 
 or other upon each of the several diameters joining the 
 complementary pairs of colours. Theoretically this white 
 will be found at the centre of the circle where all these 
 lines intersect. But in practice the exact pairing of colours 
 is often impossible, for we have to take into account not 
 only their hue but also several other qualities, such as 
 saturation, brightness , and so forth. A few words on 
 these points may be fitly introduced in this place. 
 
 The brightness of a colour depends upon the quantity 
 of its light. It is sometimes spoken of as brilliancy. 
 
 The saturation or depth of a colour is another name 
 for its purity, fulness, or richness, the richness itself being 
 commensurate with the quantity of its unneutralised or 
 free light of particular colour. 
 
 The clearness of a colour depends upon the relation 
 between the quantity of its light and its saturation. A 
 colour which is at once clear and saturated is often said 
 to be intense. Very great brilliancy in a colour is not 
 generally compatible with saturation, as the effect of such 
 colours upon the eye is similar to that of a mixture of 
 white and coloured light. The ocular appreciation of 
 coloured surfaces is also much altered by the quantity of 
 light by which they are illuminated, the values of colours, 
 and the distinctions between different colours being more 
 easily obliterated in some cases than in others by the 
 diminished or increased quantity of the incident light. A 
 red, for example, which in a strong light appears brighter 
 than a blue, may in a weak light become darker. Thus it 
 
 D 
 
38 
 
 COLOUR. 
 
 happens that in a very weak light all, or nearly all, distinc¬ 
 tions of colour are lost before the objects have become 
 invisible, for the contrast between light and darkness, or 
 between white and black, being stronger than any other 
 possible contrast, remains as a residual effect. So in 
 twilight and moonlight we may often feel convinced that 
 the objects of a landscape are not wholly destitute of 
 colour, yet we find it very difficult to represent their ex¬ 
 tremely indefinite and obscure hues. 
 
 Connected with the subject of the quality of colours 
 and especially with the quality of saturation, is the con¬ 
 stitution of those minor pairs of complementary colours 
 where hues and not secondary colours are found to con¬ 
 stitute together white light. As hues are colours in which 
 the primaries are mixed in proportions other than their 
 equivalents, we may of course speak of bluish sea-green 
 as made up of two equivalents of blue and one equivalent 
 of green, or, using the symbols B and G for these primary 
 colours, we may formulate them thus : 
 
 Now the complementary hue to this hue will be made 
 up of those elements of white light which it lacks and in 
 the proportion in which they are deficient, and thus may 
 be formulated : 
 
 The truth of these propositions is at once seen when we 
 remember that on Maxwell’s theory, which we are now 
 discussing, white light (w) may be made up of equivalents 
 of red green blue light, its constitution being expressed 
 by the formula—R + G + B=W; while our bluish sea-green 
 and orange give together the same results, thus, 
 
 Bluish sea-green + orange=white ; or 
 2B + G + 2R + G=2W; or 
 
 b+ g +r+-=w 
 2 2 
 
Fig XVII. 
 
 Fig. XVIII. 
 
maxwell's theory. 
 
 39 
 
 But those of our readers who desire to pursue this sub¬ 
 ject are referred to the works of Mr. Benson for further 
 information on these and kindred matters. And we take 
 this opportunity of again acknowledging the obligations 
 we are under to this ardent apostle of the true theory 
 of colour as developed by Maxwell and Helmholtz. 
 
 This seems a suitable occasion for introducing some ac¬ 
 count of the physiology of colour-sensations of different 
 kinds and of the way in which they may be supposed to 
 originate. The researches of Helmholtz have rendered Dr. 
 Young’s idea of three sets of optical fibres in the nervous 
 structure of the retina very probable. These three sets of 
 fibres, which for brevity we will speak of as the red, green, 
 and blue fibres, respectively, are impressionable to these 
 three kinds of primary coloured light in different degrees. 
 If the light be red the red fibres by their responsive action 
 will transmit the corresponding message to the brain. If 
 the red and green fibres be equally affected, as by yellow 
 light, or by mixed green and red lights, the sensation of 
 yellow wili be produced. Green and blue lights will affect 
 more especially both the green and blue fibres, and sea- 
 green will be the sensation provoked. By admixture of 
 other coloured lights, and in various proportions, the com¬ 
 pound action of the optical fibres will, in a similar manner, 
 originate other secondary colours and hues. Colour 
 blindness, or Daltonism, in its varying degrees, may be 
 explained by an extension of the same theory. For we may 
 imagine the optical fibres to be less completely differen¬ 
 tiated from each other in the case of those persons who 
 have not the normal appreciation of colours. Rays of red 
 and green light, for instance, are often not distinguished 
 by the colour-blind, for both these colours affect the red 
 and green fibres of such persons in a similar manner. In 
 these cases the spectrum of the sun may be said to consist 
 of two and not of three distinct bands of colour, one extend¬ 
 ing from the red to the beginning of the blue, and possibly 
 appearing to persons suffering from Daltonism as some¬ 
 thing like a shaded stripe of yellow of normal vision, 
 while the rest of the spectrum may present the ordinary 
 series of blue colours. 
 
 D 2 
 
4o 
 
 COLOUR. 
 
 CHAPTER V. 
 
 THE COMMON THEORY OF THE PRIMARY COLOURS, TONES, 
 
 SHADES, TINTS, AND SCALES—PRIMARY COLOURS— 
 
 SECONDARY COLOURS—TERTIARY COLOURS—HUES. 
 
 Thus far we have been studying the constitution of colours 
 by means of experiments with coloured lights. And we 
 have arrived at some results, which, it will be presently 
 seen, are in striking discordance with those commonly ac¬ 
 cepted. Yet there is a sound basis of fact in the case of 
 Maxwell’s theory which the more popular view does not 
 possess in a nearly equal degree. We must, however, turn 
 our attention to the latter view as to the primary colours 
 —the “red-yellow-blue” theory, as it has been called. But 
 although, through subsequent chapters, we shall adopt 
 in the main the terms and explanations of this usual theory, 
 we shall take occasion to note, here and there, the more 
 serious difficulties which it involves. And it will be easy 
 to translate our language into the more correct forms de¬ 
 manded by Maxwell’s theory, if due use be made of our 
 explanation of that theory just given, and especially if 
 the chromatic circle of complementary colours be studied 
 with care. 
 
 One great advantage is possessed, we readily admit, by 
 the old theory—it works far better with actual pigments 
 than does the new one. It breaks down more or less 
 completely when tested, by the means we have already 
 mentioned, with coloured rays of light. Concerned as we 
 usually are with coloured materials and not with coloured 
 rays, we shall describe the old theory at some length, par¬ 
 ticularly as it affords an easy means of studying the mixed 
 colours which pigments afford. 
 
 In our coloured diagram* we have arranged the most 
 important colours in a six-pointed star made of twelve 
 equilateral triangles. The whole figure being regarded as 
 consisting of two intersecting triangles, the three primary 
 colours will be found in the angles of one of these, the 
 
 Frontispiece. 
 
TONES. 
 
 41 
 
 three secondary colours in the angles of the other, and 
 the more mixed hues in the area where the two triangles 
 coincide or overlap. However, before showing how the 
 compound colours may be supposed to originate from the 
 admixture of simple ones, it will be necessary to define the 
 meanings of a few words which we shall have frequent 
 occasion to employ. 
 
 Tones , often called shades, signify colours mixed with 
 varying proportions of white or black. In mixing a colour 
 with white we weaken or reduce its tone, but by the addi¬ 
 tion of black a colour has its tone broken or darkened, not 
 deepened. Red mixed with white in increasing propor¬ 
 tions gives weaker and weaker tones of red ; red mixed 
 with black in increasing proportions gives duller and duller 
 tones of red ; while red mixed in a similar manner with 
 both white and black—that is, grey—gives a series of tones 
 of red which are at the same time duller and weaker than 
 the original colour. 
 
 A scale is a regular series of such tones as those just de¬ 
 scribed. Every colour admits of three scales :— 
 
 1. The reduced scale—that is, the normal colour mixed 
 with white, thus forming tints. 
 
 2. The darkened scale—that is, the normal colour mixed 
 with black, thus forming shades. 
 
 3. The dulled scale—that is, the normal colour mixed 
 with both white and black, or, in one word, with grey. 
 
 Primary or elementary colours are usually regarded as 
 three in number, and are assumed to be capable of yield¬ 
 ing by combination all other colours. They are commonly 
 assumed to be yellow, red, and blue. 
 
 Secondary colours are mixtures of two primaries in equi¬ 
 valent proportions. Orange, green, and violet are the 
 three secondary colours. We say equivalent, not equal 
 proportions ; for it will be found that equal quantities of 
 yellow and red lights, or of the purest yellow and red pig¬ 
 ments attainable, will not produce the normal orange. In 
 making, therefore, such a secondary colour as orange, we 
 have to judge by the eye what quantities of its primary 
 constituents will produce a colour equally removed from 
 yellow on the one hand, and from red on the other. 
 
 Tertiary colours are mixtures of the three primary 
 colours in certain proportions, which will be noticed pre- 
 
42 
 
 COLOUR. 
 
 sently. All tertiary colours are dull, owing to the follow¬ 
 ing fact. All pigments representing the three primary 
 colours produce, when mixed together in equivalents, not 
 whiteness, but greyness or blackness. In tertiary colours, 
 therefore, the equivalents of yellow, red, and blue which 
 are present, unite to neutralise one another, and so to form 
 grey ; while it is only the unneutralised residue of the one 
 or two colours that are in excess which gives a special 
 character to the final result. The neutral grey of the ter- 
 tiaries, as thus produced, dulls all their tones, and dis¬ 
 tinguishes them at once from the primary colours, and from 
 all combinations of two primaries. Indeed, the six normal 
 tertiary colours are nothing more than the dulled tones of 
 the three primary and the three secondary colours. 
 
 H:tes include all tertiary colours, and all those colours 
 in which the primaries are mixed in other proportions than 
 are requisite to form the secondary colours. Yellowish- 
 orange and bluish-green are secondary hues ; reddish-grey 
 and violet-grey are tertiary hues. 
 
 With these definitions of terms before us, the con¬ 
 sideration of the chief colours, of the quality and optical 
 composition of coloured materials and of the pigments in 
 actual use, may be commenced. 
 
 The Common Primary Colours. — Yellow .—The 
 most luminous of all colours is the pure yellow. It occu¬ 
 pies a very narrow space in the solar spectrum, but is dis¬ 
 tinctly the brightest part of it. Most yellow pigments and 
 coloured materials reflect or transmit much orange and red 
 light, as well as yellow. Chrome yellow is an example of 
 this fact. Some transparent yellows on a white surface, 
 such as gamboge, allow the transmission of, or reflect much 
 white light, in addition to the yellow rays which charac¬ 
 terise them. They are in reality reduced yellows—yellow, 
 that is, mixed with white. Yellows occasionally verge 
 upon green, especially in their lighter tints. This effect is 
 partly due to their reflection of some green rays in place 
 of the red which they usually emit, and partly to the result 
 upon the eye of contrasting the lighter or reduced tones of 
 yellow with the darker tones which verge upon orange and 
 red. An orange or even a red tint is often perceived in 
 yellow pigments when they become dry, though they may 
 have appeared of a nearly pure yellow when wet. Fibres 
 
PRIMARY COLOURS. 
 
 43 
 
 of wool, silk, cotton, etc., dyed yellow, exhibit the same 
 appearances, as to the optical constituents of the colours 
 they reflect, as do other white surfaces of paper, canvas, 
 and porcelain, upon which opaque or transparent pigments 
 have been spread. In all cases varying proportions of 
 white light are reflected ; while of the light which is decom¬ 
 posed by the coloured surfaces, different but considerable 
 amounts of violet, indigo, blue, and, in a measure, green, 
 are quenched or absorbed. The remaining rays produce 
 the colour effect of the object, and will, of course, con¬ 
 sist mainly, but not entirely, of yellow light. With stained 
 glass and other transparent materials, such as coloured 
 gelatine and coloured liquids, similar groups of violet and 
 blue rays are on the one hand absorbed, while on the other 
 hand the less refrangible colours are transmitted. 
 
 Red .—The second primary colour in point of vividness 
 is red. It is less luminous than yellow, but warmer and 
 more retiring. All our ordinary red colours contain orange 
 and yellow, or else blue and violet. A stick of sealing-wax 
 examined by a prism is found to reflect all the rays up to 
 the line D in the yellow— that is, the colour which it pre¬ 
 sents is made up of much orange and a little yellow in 
 addition to the true red. The fugitive paint known as 
 geranium colour is a purer red than that just named, the 
 vermilion of sealing-wax, but it is not free from a tint of 
 orange. Carmine and crimson lake, with other similar pig¬ 
 ments, reflect to the eye a trace of the blue and violet, as 
 well as nearly all the red, and some of the orange rays of the 
 light which falls upon them. The best idea of pure red¬ 
 ness may be got from the bright and broad red band in the 
 spectrum of a burning lithium salt. Red glass, at least 
 that kind of red glass which is coloured by copper sub¬ 
 oxide, does not transmit unmixed red rays, but many 
 orange rays as well. Two or three thicknesses of it do, 
 however, transmit a purer red beam. 
 
 Blue .—The third and least vivid of the primary colours 
 is blue. It is also the most retiring and cool. We can¬ 
 not point to any tolerably pure blue pigment. Beautiful 
 as ultramarine undoubtedly is, its spectrum reveals the 
 existence of several colours besides blue. Yet it would be 
 hardly fair on this account to regard this or any other 
 colour as impure. If the various coloured rays which a pig- 
 
44 
 
 COLOUR . 
 
 ment reflects to the eye impart the sensation of blueness, it is 
 enough. They may contain red, violet, and other consti¬ 
 tuents, but the resultant effect of the combination may be 
 a blue indistinguishable in purity from the normal blue of 
 the solar spectrum. A difficulty does, however, arise when 
 such pigments as those above referred to are illuminated 
 by artificial light, or are mixed with others to form second¬ 
 ary and tertiary colours ; the anticipated result being oc¬ 
 casionally very far from being realised. Cobalt blue reflects 
 much green and violet light, as well as blue, and in fact 
 shows a very remarkable combination of colours when its 
 spectrum is examined. On mixing it with carmine, to form 
 a violet hue, the green constituent in its light interferes with 
 
 Fig. 19. 
 
 the purity of the resulting colour, which is much greyer 
 than one would have expected. By lamp-light cobalt-blue 
 appears violet. Prussian-blue and indigo absorb most of 
 the red, orange, and yellow rays, but emit a very large part 
 of the green, blue and indigo. A crystal of blue vitriol 
 (copper sulphate) cuts off all the red, orange, and yellow 
 rays, together with the green rays up to line E, and trans¬ 
 mits the remainder. 
 
SECONDARY COLOURS. 
 
 45 
 
 Secondary colours may now engage our attention. On 
 referring to the frontispiece, it will be seen that the 
 three primaries occupy the angles of the first triangle, 
 and the three secondaries the angles of the second. If we 
 represent the same arrangement without colour (Fig. 19), 
 we shall be able to point out very clearly the constituents 
 of each compound colour. The three small triangles 
 marked I. contain the three primary colours, while those 
 marked II. contain the three secondary colours. When 
 equivalent quantities of yellow and red are mixed, orange 
 is the result—a secondary colour equally distant from 
 yellow on the one side and red on the other. It is com¬ 
 monly held that, with material pigments, three parts (by 
 surface measurement) of a good yellow require five parts 
 of a good red to form the normal orange. The eight parts 
 of the normal orange formed in this way will serve as a 
 complementary equivalent to eight parts of the normal 
 blue. But, after all, these and similar numbers are merely 
 approximate, serving just to indicate the direction in which 
 one coloured constituent must preponderate over another 
 in such mixtures as the secondary colours. When yellow 
 and red are mixed in proportions differing from those 
 necessary to constitute the normal orange, the resulting 
 colour becomes a yellowish-orange or a reddish-orange, 
 according to the predominance of either of the constituent 
 primaries; countless variations of a secondary colour in 
 this direction are possible. Indeed, as we have already 
 shown, most of our coloured materials, usually regarded as 
 exhibiting primary colours, in reality furnish us with 
 secondary hues of this kind, though their mixed character 
 is not perceived by the unassisted vision. 
 
 The following list shows the imaginary or theoretical 
 composition of the three secondary colours, and their six 
 chief modifications or hues. The letters Y, R, and B re¬ 
 present the equivalent proportions of the three primaries— 
 yellow, red, and blue ; the equivalent of yellow being 
 assumed to be 3, of red 5, and of blue 8 :— 
 
 SECONDARY COLOURS. 
 
 Y + R = Orange. 
 
 R + B = Violet. 
 
 B + Y — Green. 
 
46 
 
 COLOUR. 
 
 SECONDARY HUES. 
 
 2Y + R = Yellowish-orange. 
 
 Y + 2R = Reddish-orange. 
 
 2R + B = Reddish-violet. 
 
 R + 2B = Bluish-violet. 
 
 2B + Y = Bluish-green. 
 
 B + 2Y = Yellowish-green. 
 
 Orange .—This colour is the most powerful and bril¬ 
 liant of the three normal secondaries. It is seen in the 
 pigment known as cadmium yellow (the cadmium sulphide) 
 and in the skin of a rich-coloured ripe orange. To make 
 a pure and bright orange by mixture, it is essential that the 
 yellow pigment should incline to red rather than to green, 
 and the red pigment to orange rather than to blue. If the 
 contrary be the case, and a greenish-yellow pigment be 
 mixed with a red, or a yellow with a violet-red, a certain 
 amount of grey is produced by the combination of the 
 three primaries present, and a dulled tone of orange is the 
 result. The worst effect of this kind is produced when a 
 greenish-yellow is mixed with a violet-red. Gamboge 
 and carmine form an orange far inferior in purity to 
 that produced by the admixture of chrome yellow and 
 vermilion. 
 
 Violet is the least powerful of the secondary colours. 
 The aniline dye known as mauve may be taken as some¬ 
 what near the normal violet. Many other artificial colour¬ 
 ing matters made from the products of coal-distillation 
 also approach this beautiful colour. Violet usually appears 
 much redder and duller by candle or gas light than by day¬ 
 light. The yellow and orange rays which are present in 
 peculiar abundance in most artificial lights, neutralise 
 some of the blue in the violet, forming therewith grey, and 
 at the same time setting free, as it were, the red element 
 of this secondary combination. To make a pure and bright 
 violet by mixture, it is essential that the red pigment should 
 incline to blue rather than to orange, and that the blue 
 pigment should incline to red rather than to green. Ver¬ 
 milion and cobalt produce a very dull and earthy-looking 
 combination, owing to the presence of orange in the former 
 colour and green in the latter. Carmine and ultramarine 
 afford a more satisfactory mixture. 
 
SECONDARY COLOURS. 
 
 47 
 
 Green is more vivid than violet, but less so than orange. 
 It occupies a considerable space in the solar spectrum, 
 where, however, much of the green light has a yellowish 
 hue, and some of it inclines towards blue. Emerald green 
 is in reality far from reflecting pure green light only to the 
 eye. Its spectrum is simply deficient in red and orange 
 rays, yet even these are by no means absent. The new 
 “ aniline green,” which retains its characteristic and bril¬ 
 liant colour by artificial light, absorbs, when of sufficient 
 purity and in sufficient amount, nearly all rays except the 
 green. When a piece of cotton dyed with this green is in¬ 
 terposed between a light and the spectroscope, it will be 
 found that about six thicknesses of the fabric are requisite 
 to strain off all the red rays. But this result may be ac¬ 
 complished more easily by a solution of the colouring 
 matter ; for in this case there are no interstices through 
 which light can pass, and thus escape the selective absorp¬ 
 tion of the pigment. Viridian, the beautiful and perma¬ 
 nent chrome green introduced recently, transmits the 
 green rays or green portion of the spectrum unchanged, 
 but along with them a small portion of the red and of 
 the blue rays. In producing a green by admixture of 
 yellow and blue, it is important to take a yellow and a blue 
 both free from red. A greenish-yellow and a greenish- 
 blue, or else a pure yellow and a pure blue, may be suc¬ 
 cessfully used. Notwithstanding its brilliancy, cadmium 
 yellow, which is really an orange, cannot be made to yield 
 a satisfactory green by the addition of any kind of blue 
 pigment. 
 
 Tertiary Colours have now to be considered. Referring 
 back to our diagram (Fig. 19), we find six spaces marked 
 III. Each of these spaces is immediately contiguous with 
 a space (marked I.) assigned to a primary, or to a space 
 (marked II.) assigned to a secondary colour. We have 
 already alluded to the fact that the so-called tertiary colours 
 ought, strictly speaking, to be regarded as nothing more 
 than dulled tones of the primary and secondary colours. 
 Indeed, it is impossible, on the theory of the three prima¬ 
 ries together forming grey, to have any colour which shall 
 exhibit the colour-effect of more than two of them together. 
 An examination of the composition of the tertiary colours 
 will explain this point. Using again our former symbols 
 
48 
 
 COLOUR. 
 
 for the primaries, and letting Gy stand for grey, we may 
 express the constituents of the six normal tertiaries thus :— 
 
 Gy = Yellow-grey, or citrine. 
 
 R + Gy = Orange-grey, or buff. 
 Gy = Reddish-grey, or russet. 
 
 B + Gy = Violet grey, or plum. 
 Gy = Bluish-grey, or slate. 
 
 R + 2B = Y+ B+ Gy = Greenish-grey, or sage. 
 
 2 Y 
 
 + 
 
 R 
 
 + 
 
 B = Y + 
 
 2 Y 
 
 + 
 
 2 R 
 
 + 
 
 B = Y + 
 
 Y 
 
 + 
 
 2 R 
 
 + 
 
 B = R + 
 
 Y 
 
 + 
 
 2 R 
 
 + 
 
 2B = R + 
 
 Y 
 
 + 
 
 R 
 
 + 
 
 2B = B + 
 
 2 Y 
 
 + 
 
 R 
 
 + 
 
 2 B = Y + 
 
 It is commonly stated that the tertiary colours are com¬ 
 pounded of the secondary colours. Thus the two second¬ 
 aries, orange and green, are assumed to give rise to the 
 tertiary colour known as citrine. This hue is really nothing 
 more than a yellow-grey ; for its orange constituent con¬ 
 tains yellow and red, and its green constituent yellow and 
 blue. Subtracting equivalents of the three primaries, so 
 as to form grey, we have, therefore, nothing but a residue 
 of the primary yellow, to produce the whole colour-effect 
 of the mixture of the secondaries orange and green. This 
 residual yellow is dulled by the presence of the grey which 
 is the product of mixing equivalents of pigments represent¬ 
 ing the three primaries. The colour complementary with 
 citrine or yellowish-grey is violet, which, of course, sup¬ 
 plies the blue and red which have been extinguished in 
 the former hue. 
 
 The secondary colours orange and violet produce, when 
 mixed together, the tertiary hue known as russet. It is 
 really a reddish grey. Some autumnal leaves present good 
 examples of this colour. Its complementary is green, which 
 supplies the yellow and blue which are wanting in russet. 
 
 The secondary colours green and violet produce, when 
 mixed together, the tertiary hue often called olive, but 
 which may, perhaps, be more correctly designated slate. 
 It is really a bluish-grey. The complementary colour is 
 orange, which supplies the missing red and yellow con¬ 
 stituents. 
 
 We may here name, as other and very useful tertiary 
 hues, those known as buff, plum, and sage. Buff, or orange 
 modified by grey, may be produced by the addition of red 
 to citrine, or by mixing the three primaries so that yellow 
 and red predominate. Sage-green is produced by the ad¬ 
 dition of yellow to slate-colour, or by mixing the three 
 
TERTIARY COLOURS. 
 
 49 
 
 primaries so that both yellow and blue predominate. Plum- 
 colour is a violet grey produced by the addition of blue to 
 russet, or by mixing the three primaries so that both blue 
 and red predominate. 
 
 Numerous other tertiary hues, besides the six just named, 
 are constantly observed in natural objects, and may be 
 reproduced with great advantage in decorative art. It is, 
 however, very difficult to describe the composition and 
 character of such colours. These tertiary hues are, how¬ 
 ever frequently used in modern art-manufactures with the 
 happiest effects, and, employed, say, as walls in pairs of 
 related or contrasted tints, or in two shades of the same 
 hue, afford a quiet background for the full development 
 of the beauty of the more vivid and elaborate contrasts of 
 colour, to be found in pictures and the higher works of 
 decoration. In subsequent chapters we shall point out 
 the extreme importance of these dulled colours, colours 
 mingled with grey, since they at once relieve the fatigue 
 experienced by the eye when occupied too exclusively with 
 colours of great brightness and saturation, and at the same 
 time enable such bright colours to give their maximum of 
 pleasurable sensation even when used sparingly. 
 
 CHAPTER VI. 
 
 THE LAWS OF CONTRAST—CONTRASTS OF TONE—CON¬ 
 TRASTS OF COLOUR—SIMULTANEOUS CONTRAST. 
 
 Contrasts of tone and of colour .—If there be the slightest 
 difference either of tone or of colour in two contiguous or 
 neighbouring coloured or shaded surfaces, that difference 
 will not be seen exactly as it really exists. Under such 
 conditions, either the retina of the eye receives an impres¬ 
 sion, which does not actually reproduce the facts of the 
 exterior phenomenon, or the message transmitted to the 
 brain is itself modified. Whatever the exact cause, the 
 study of the subjective modifications of tone and colour 
 is one of the most important branches of our subject. We 
 shall describe, first of all, contrasts of tone, and then 
 contrasts of colour. 
 
5° 
 
 COLOUR. 
 
 Contrasts of tone may be either successive or simulta¬ 
 neous. Of the first kind, we have examples in the facts 
 that a dark-toned piece of cloth or paper looks lighter if 
 we have immediately before been looking at a still darker 
 piece ; and that a light-toned piece looks darker, if we have 
 immediately before been looking at a still lighter piece. 
 The following are illustrations of the facts of the simulta¬ 
 neous contrast of tones:—We first take two strips of pale- 
 grey paper, and fix them a few inches apart towards one 
 side of a piece of linen stretched across a window. Two 
 similar strips are next prepared, but they are to be of a 
 considerably darker tone. One of these is placed so as to 
 touch one of the first strips ; the other is fixed at some few 
 inches’ distance. The following sketch shows the arrange¬ 
 ment of the strips :— 
 
 Pale. 
 
 A. 
 
 Pale. 
 
 Dark. 
 
 A' 
 
 B 
 
 Dark. 
 
 B' 
 
 Upon steadily looking at the four sheets for a short time, 
 it will be perceived that A' close to B seems lighter than A, 
 while B close to A' seems darker than B'. The effect of 
 contrast in altering the tone of the contiguous strips A' 
 and B may be further studied in this way. Make such 
 openings in a piece of card as to divide the strips A and B 
 each into three portions. It will then be noticed that the 
 two nearest portions are most contrasted in tone, and the 
 others less so in proportion to their distance from the line 
 of contact. But the effect of contrast of tone is still 
 better seen when a more complete series of toned strips 
 is placed in contiguity. In such a case the effect on all 
 the strips, save the end ones, is that of a double contrast. 
 The second strip, or second tone, has one side of it made 
 apparently darker by reason of the contiguity of the 
 lighter tone of strip i, while the other side seems lighter 
 by the contiguity of the darker tone of strip 3. The 
 general result of these double contrasts is that the whole 
 series or scale of tones presents the appearance of a 
 number of hollows, although, in fact, the apparent hollows 
 are perfectly flat spaces of shading or colouring. The 
 effect of this experiment is approximately represented in 
 
CONTRAST OF TONE. 
 
 51 
 
 Fig. 20, where the real flatness of each tone of the six 
 may be verified by covering up all the other spaces by a 
 card. The same diagram of contrast of tone may be 
 made more effective, by dividing a slip of card into several 
 
 Fig. 20. 
 
 equal sections—say, six—by faint pencil lines, and then 
 giving all six a light wash of Indian ink. Next, when 
 this is dry, five sections receive a second similar wash. 
 Afterwards the same process is repeated until the third 
 section has received three washes, the fourth section four, 
 the fifth section five, and the sixth section six. In carrying 
 out the process, all sections, except those being submitted 
 to the operation of washing, should be hid from view. 
 Without this precaution it is difficult to secure a flat tint 
 in each strip. If a series of pieces of grey paper of the 
 same colour, but of different tones, are obtainable, they 
 may be used in the construction of the same figure. They 
 should be of equal size, and be pasted close together on a 
 strip of cardboard ; or a strip of glass or gelatine may be 
 so arranged as to present at one end one thickness of the 
 material, and the other end six or more thicknesses. On 
 looking through the series, especially if a piece of white 
 enamel glass, or a sheet of white paper, be placed behind, 
 the effect of simultaneous contrast of tone will be clearly 
 perceived. It is scarcely necessary to state that the 
 tones of any particular colour may be used as well as 
 grey to illustrate this kind of contrast. Its characteristic 
 effect is not seen unless the contrasting tones differ con¬ 
 siderably in intensity, and are in close contiguity or ab¬ 
 solute contact. 
 
 Contrasts of colour are always more or less complex in 
 character. There is, to begin with, the actual or ob¬ 
 jective difference between two colours, and then, super- 
 
52 
 
 COLOUR. 
 
 added to this, we have certain subjective modifications, of 
 an ocular or mental kind, which all contrasted colours 
 produce. Further than this, it is rare to find any contrast 
 of colour in which the effects of contrast of tone are not 
 likewise present. We shall have to speak in a future 
 chapter, and with considerable detail, of the practical 
 results of all the circumstances which affect contrast of 
 colours, and so now we merely introduce this subject by 
 a few words on the successive and simultaneous contrast 
 of colour. 
 
 If the eyes have steadily regarded some coloured object, 
 and then look at a colourless object, the latter object will 
 assume a colour complementary to that of the former, or 
 will present an image of that object in the complementary 
 colour. If the second object be itself also coloured, but 
 differently from that first viewed, then the complementary 
 colour will mingle with that of the second object, and 
 modify its proper colour accordingly. But even a third 
 case of successive contrast may occur. Supposing we 
 look steadily at a series of pieces of scarlet cloth, 
 one after another being placed before us; the eye, 
 fatigued with the repeated calls on its perception and 
 appreciation of scarlet, becomes incapable of estimating 
 the series of identical specimens, and reports the last 
 specimen to be duller than the first. The eye has become 
 less appreciative of red, and more appreciative of the 
 other colours. It sees less red, and more green and blue 
 than before, which mixing with the red of the later speci¬ 
 mens of cloth, dull and modify them. The eye may be 
 rested and restored to its proper condition by gazing upon 
 a piece of green or bluish-green cloth, when its power of 
 appreciating red will once more return. 
 
 The simultaneous contrast of colours was first thoroughly 
 worked out by the French chemist, Chevreul. It is the 
 most fertile of all the laws of colour in the elucidation of 
 the actual phenomena of contrasts, and in the suggestion 
 of new combinations. When two coloured objects are 
 seen at the same time, they usually mutually affect each 
 other both in colour and tone. A yellow object, for ex¬ 
 ample, placed close to a blue one, will appear as if it 
 inclined to orange, while the blue object will seem to 
 incline towards violet. The reason of this, on the as- 
 
SIMULTANEOUS CONTRAST. 
 
 53 
 
 sumption that yellow, red, and blue are the primary 
 colours, is that the eye looking at yellow becomes less 
 able to appreciate it, and sees the remainder of the 
 primary' colours, red and blue, that is, violet. This violet 
 mixing with the contiguous blue colour tinges it with a 
 faint trace of red. So with the blue object : the eye 
 looking at the blue becomes less able to appreciate it, and 
 sees the remaining primaries, yellow and red, or orange, 
 the complementary of blue, which orange is imparted to 
 the yellow, giving it a reddish hue. But blue and yellow 
 differ much in their respective value as regards tone. 
 The luminous and brilliant yellow becomes still more 
 brilliant by contact with the richer and deeper blue, 
 which itself is at the same time deepened, so that under 
 ordinary circumstances these two colours afford a com¬ 
 bined example of simultaneous contrast of tone and colour. 
 But two complementary colours, such as red and green 
 are presumed to be according to the common theory, do 
 not modify one another’s colour by contiguity. Theo¬ 
 retically, they contain the three constituents of white 
 light, and the eye perceives no deficiency or excess of 
 any coloured elements in the combination. So red and 
 green merely enhance each other’s characteristics when 
 in contact. Thus it is with orange and its complementary 
 blue, and with other pairs of complementary colours. 
 
 By placing strips of coloured paper together, a few of 
 the chief phenomena of simultaneous contrast may be 
 easily observed. We here give a list of some of the modi¬ 
 fications of hue which coloured surfaces seem to undergo 
 when placed in contact in pairs :— 
 
 ( Red 
 
 < with 
 
 ( Orange 
 Red 
 
 < with 
 
 ( Yellow 
 Red 
 with 
 Blue 
 Red 
 with 
 Violet 
 
 to violet. 
 
 ,, yellow. 
 ,, violet. 
 
 ,, green. 
 „ orange. 
 
 „ green. 
 ,, orange. 
 
 ,, blue. 
 
 inclines 
 
 Orange 
 
 with 
 
 Yellow 
 
 Orange 
 
 with 
 
 Green 
 
 Orange 
 
 with 
 
 Violet 
 
 Yellow 
 
 with 
 
 Green 
 
 inclines to red. 
 
 ,, „ green. 
 
 „ „ red. 
 
 ,, „ blue. 
 
 „ „ yellow. 
 
 „ ,, blue. 
 
 „ ,, orange. 
 
 „ „ blue. 
 
 E 
 
54 
 
 COLOUR. 
 
 Yellow 
 
 inclines to orange. 
 
 with 
 
 
 
 Blue 
 
 99 
 
 ,, violet. 
 
 Green 
 
 99 
 
 ,, yellow. 
 
 with 
 
 
 Blue 
 
 99 
 
 „ violet. 
 
 Green 
 
 with 
 
 Violet 
 
 Blue 
 
 with 
 
 Violet 
 
 inclines to yellow. 
 
 „ ,, red. 
 
 ,, » green. 
 
 „ „ red. 
 
 CHAPTER VII. 
 
 COLOURS WITH WHITE, GREY, AND BLACK—OCULAR MO¬ 
 DIFICATIONS OF COLOUR—PERSISTENCE OF COLOUR- 
 IMPRESSIONS—IRRADIATION—SUBJECTIVE COLOURS— 
 CONTACT AND SEPARATION OF COLOURS. 
 
 We have seen, in the last lesson, that there are two kinds 
 of contrast—the contrast produced by difference of tone 
 and the contrast produced by difference of colour. We 
 have also seen that these contrasts are produced under 
 several conditions, and that they are modified through 
 the mode in which they are perceived by the eye and 
 impressed upon the mind. No sooner, in fact, are two 
 colours so placed as to be seen at the same time or in 
 quick succession, than they are apparently changed. The 
 change may be one of tone only, of colour only, or of both 
 tone and colour. Nor is it necessary, in such experi¬ 
 ments, that two colours should be used : we may employ 
 two tones of the same colour or a single tone of colour 
 with white, grey, or black. We have already studied the 
 apparent changes which the primary and secondary colours 
 mutually cause when placed in contiguity, and so may row 
 proceed to state what modifying influences white, grey, 
 and black respectively produce upon the most important 
 colours (see Figs. 27, 28, and 29, page 70). 
 
 1. Yellow. — Yellow with white is rendered darker, 
 less luminous, and less prominent, and acquires a faint 
 greenish hue. The lighter the tone of the yellow, the less 
 pleasing is the combination. 
 
 Yellow with grey is rendered darker, less luminous, 
 and perhaps a trifle more orange. When the grey is of 
 about the same intensity or tone as the yellow, the com- 
 
WHITE , GREY, AND BEACH. 
 
 ss 
 
 bination is not satisfactory; but it becomes so when the 
 grey is rather deep, the yellow then recovering brightness. 
 
 Yellow with black is rendered lighter or paler, more 
 luminous, and more prominent. The combination affords 
 the most intense contrast next to that of white with black. 
 The blackness of the black acquires a somewhat bluish- 
 violet hue, which has a tendency to enrich it. 
 
 2. Orange. — Orange with white is rendered darker, 
 and perhaps a trifle more reddish. The contrast between 
 orange and white is much greater than that between 
 yellow and white, and the combination is consequently 
 more effective. 
 
 Orange with grey, when the latter is pale, is darkened 
 and reddened. With deep tones of grey, orange becomes 
 more luminous, 
 
 Orange with black becomes more luminous and yel¬ 
 lower ; the contrast is next in intensity to that afforded by 
 yellow with black. 
 
 3. Red. — Red with white becomes more intense and of 
 a deeper tone. The combination, as to intensity of con¬ 
 trast, is similar to that of green with white ; being less 
 decided than that of blue and violet with white, but more 
 so than that of yellow and orange with white. 
 
 Red with grey, where the latter is pale, becomes more 
 intense, deeper, and occasionally acquires a slight bluish 
 hue. 
 
 Red with black becomes more luminous and slightly 
 yellower. 
 
 4. Violet. — Violet with white affords a contrast of 
 very decided character, owing to the great difference of 
 tone between a full violet and white. The violet is ren¬ 
 dered deeper in tone in this combination. 
 
 Violet with grey. —The distinctive colour of the violet 
 makes itself felt in this combination, which is a quiet and 
 agreeable one. 
 
 Violet with black affords an instance of the harmony of 
 analogy rather than of contrast. The violet is enriched 
 by its proximity with black ; but the latter thereby ac¬ 
 quires a rusty hue, which takes away from its richness. 
 
 5. Blue. — Blue with white constitutes a pleasing com¬ 
 bination. The contrast is very decided where the tone of 
 blue is deep. The effect of white clouds in deepening 
 
 E 2 
 
COLOUR. 
 
 56 
 
 the tone of the sky is a good example of one of the chief 
 characteristics of this combination. 
 
 Blue with grey .—Grey enhances the tone and quality 
 of blue, deepening it to a remarkable extent under certain 
 circumstances. 
 
 Blue with black .—This combination resembles that of 
 violet and black, but is less agreeable, especially where 
 the blue is of a deep tone. Light shades of blue'are ren¬ 
 dered paler and more luminous by contiguity with black. 
 
 6 . Green. —Green with white becomes more intense 
 and of a deeper tone ; green is distinctly improved by 
 the presence of white. 
 
 Green with grey becomes deeper in tone. 
 
 Green with black is rendered rather lighter in tone, and 
 more brilliant; but the'black suffers in purity, and becomes 
 slightly tinged with a ruddy hue—the result of adding to 
 the black, red, the complementary colour of the neigh¬ 
 bouring green. 
 
 From what has been said in the preceding paragraphs, 
 it will have been seen that the effect of white upon a 
 colour is to enhance its quality and deepen its tone ; for 
 white, presenting the maximum of brightness itself, 
 naturally lowers the apparent brightness of coloured sur¬ 
 face in contact with it. But the white is capable of en¬ 
 hancing the quality of a colour for a different reason 
 (explained already when speaking of “ Simultaneous Con¬ 
 trasts ”). In virtue of this principle, the white, in con¬ 
 tiguity with a colour, has a tendency to become tinctured 
 with the complementary of that colour ; the presence of 
 this trace of the complementary colour enhances the 
 quality of the original colour itself, in obedience to the 
 law of contrast : the same effect is observed, also, with 
 grey and black when placed in contiguity with colours. 
 
 This remarkable law of contrast, of which we are now 
 speaking, may, indeed, in its widest terms and most gene¬ 
 ral application, be summed up in the statement that 
 two differing colours or differing tones tend, when placed 
 together, to differ still more. Light tones and colours be¬ 
 come lighter, dark tones darker, complementary colours 
 are mutually enhanced in distinctness or saturation ; and 
 where a colour is present without its complementary, that 
 complementary is, as it were, evolved, owing to extra 
 
WHITE, GREY, AND BLACK. 
 
 57 
 
 sensibility of the eye for those colours which are not pre¬ 
 sented to it when it has been excited and fatigued by those 
 at which it has been gazing. Before studying the more 
 complex combinations of colours and their applications 
 in the arts, it will be expedient to develop a little more 
 fully some of those principles on which the “ subjective ” 
 or “ocular” modifications of colours depend. To such 
 phenomena we have just now, as well as on former occa¬ 
 sions, briefly alluded ; but we are now in a position to 
 extend and amplify our previous observations. 
 
 The subjective modifications which colours suffer arise 
 from at least three causes. 
 
 First of all, we have the persistence of the impression on 
 the retina of the eye. The discharge of a Leyden jar gives 
 a spark which is sensibly instantaneous, and yet the im¬ 
 pression which it makes upon the eye endures a distinct 
 fraction of a second. The spokes of a rapidly-revolving 
 wheel are seen with perfect distinctness and perfectly 
 separate if it be illuminated by an electric spark, although 
 in an ordinary light they may present a shadowy surface, 
 where all the elements of the wheel are blended together. 
 Yet the apparent solidity of this surface may be proved 
 to be unreal by its approximative transparency to objects 
 placed on the further side of it. These objects if properly 
 lighted, can be readily perceived through the shadowy 
 surface previously described. Similarly with a series of 
 flashes of electric sparks ; if these follow one another at 
 intervals less than the period during which the impression 
 of each spark remains upon the retina, the resultant effect 
 will be that of a continuous light. A familiar example of 
 this persistence of impressions upon the retina is to be 
 found in the experiment of rapidly whirling a glowing stick 
 or piece of red-hot charcoal; a continuous circle of light 
 being produced under these circumstances, if the rotation 
 be sufficiently rapid. Now the effect of this peculiarity of 
 the optical arrangements of the human eye is very marked 
 in the case of colours ; but it does not take place exactly 
 in the direction in which we might expect it. It would be 
 imagined that if one of the eyes has been looking at a 
 yellow disc or other yellow object it would perceive, when 
 directed upon a blue object, a mixture of yellow and blue, 
 or a colour lying between them. However, under such 
 
COLOUR. 
 
 S 8 
 
 circumstances the blue object, so far from acquiring a 
 greenish tinge, becomes rather tinctured with a violet hue. 
 This effect is really one of subjective colour, as well as 
 of persistent vision ; for the eye having seen a yellow 
 object is partially blinded or paralysed, so far as that 
 component of white is concerned ; acquiring, on the other 
 hand, greater sensitiveness to the perception of the com¬ 
 plementary of yellow—that is, violet. White surfaces, or 
 even coloured surfaces, which, of course, reflect much 
 white light, will then have their violet or red and blue 
 constituents brought into unusual prominence by the pre¬ 
 vious perception of yellow, and will be consequently 
 tinctured with violet. As it is difficult to carry out mentally, 
 from this principle, the whole scheme of alterations of 
 colour effected by the peculiar kind of contrast just de¬ 
 scribed, we shall here give a list of the principal colours 
 as modified by the previous perception of others. Before 
 doing so, it may be advisable to give our readers a method 
 of proving for themselves that such modifications really 
 occur. 
 
 Close the right eye, and then look steadily with the left 
 at a sheet of red paper. When the red paper appears 
 dull, owing to the special sort of fatigue it induces in the 
 eye, look immediately, still with the left eye, upon a sheet 
 of violet paper. The violet paper receiving the comple¬ 
 mentary of red—namely green—becomes much bluer. 
 To verify this observation it is only necessary, after having 
 closed the left eye, to open the right, and to look with it 
 upon the sheet of violet paper. The violet will be per¬ 
 ceived very differently now, and so far from being bluer 
 than in reality, may actually appear modified in the con¬ 
 trary direction—becoming more red, instead of more blue. 
 To be performed with successful and distinct results, such 
 experiments as these require great care and frequent repe¬ 
 tition. Moreover different individuals have very different 
 powers of appreciating colours and of recording their 
 impressions. One eye, also, will often be found to differ 
 from its fellow in many important particulars. Notwith¬ 
 standing the delicacy and difficulty which may be ex¬ 
 perienced in determining the special relations of contrast 
 (often called “ mixed contrast”) now under consideration, 
 they are of considerable importance in the practice of 
 the various kinds of decorative and pictorial art. 
 
OCULAR MODIFICATIONS OF COLOUR. 59 
 
 We now give our list of the modifications induced by 
 mixed contrasts of colour. 
 
 If the eye has first seen 
 
 and then looks at 
 
 the latter colour will appear 
 
 Yellow, 
 
 orange, 
 
 reddish-orange. 
 
 Yellow, 
 
 red, 
 
 reddish-violet. 
 
 Y ellow, 
 
 violet, 
 
 bluish-violet. 
 
 Y ellow, 
 
 blue, 
 
 violet-blue. 
 
 Y ellow, 
 
 green, 
 
 bluish-green. 
 
 Orange, 
 
 yellow, 
 
 greenish-yellow. 
 
 Orange, 
 
 red, 
 
 reddish-violet. 
 
 Orange, 
 
 violet, 
 
 bluish-violet. 
 
 Orange, 
 
 blue, 
 
 tinged with violet. 
 
 Orange, 
 
 green, 
 
 bluish-green. 
 
 Red, 
 
 yellow, 
 
 greenish-yellow. 
 
 Red, 
 
 orange, 
 
 yellow. 
 
 Red, 
 
 violet, 
 
 indigo-blue. 
 
 Red, 
 
 blue, 
 
 greenish-blue. 
 
 Red, 
 
 green, 
 
 bluish-green: 
 
 Violet, 
 
 yellow, 
 
 slightly greenish. 
 
 Violet, 
 
 orange, 
 
 yellowish-orange. 
 
 Violet, 
 
 red, 
 
 orange-red. 
 
 Violet, 
 
 blue. 
 
 greenish-blue. 
 
 Violet, 
 
 green, 
 
 yellowish-green. 
 
 Blue, 
 
 yellow, 
 
 orange-yellow. 
 
 Blue, 
 
 orange, 
 
 yellower. 
 
 Blue, 
 
 red, 
 
 orange-red. 
 
 Blue, 
 
 violet, 
 
 reddish-violet. 
 
 Blue, 
 
 green, 
 
 yellowish-green. 
 
 Green, 
 
 yellow, 
 
 orange-yellow. 
 
 Green, 
 
 orange, 
 
 reddish-orange. 
 
 Green, 
 
 red, 
 
 tinged with violet. 
 
 Green, 
 
 violet, 
 
 reddish-violet. 
 
 Green, 
 
 blue, 
 
 violet-blue. 
 
 It must not be forgotten that the above modifications 
 of colour arising from mixed contrast, differ not only in 
 intensity, but in persistence. The modification produced 
 by the successive view of violet and yellow is stronger 
 and more persistent than that produced by the successive 
 
6o 
 
 COLOUR. 
 
 view of blue and orange ; green is but slightly modified, 
 and for a brief space of time only, by the previous view of 
 red, and so on. And the above-described effects of contrast 
 are influenced, to a great degree, by the difference of tone 
 between the colours successively observed. A dark blue 
 viewed after orange may actually appear somewhat green¬ 
 ish, when the normal modification would be precisely in 
 the opposite direction—that is, towards violet ; yet this 
 change occurs most conspicuously when the blue is of not 
 too full a tone. Among the most important cases, con¬ 
 stantly occurring in common life or artistic practice, of 
 modifications of colours arising from persistence of the 
 impressions made on the retina, we may cite the difficulty 
 experienced by painters, from gazing too long at any 
 bright coloured object, natural or artificial, of reproducing 
 or matching its tone and hue. Again, we may allude to 
 the well-known instance of the purchaser of coloured 
 fabrics. If a series of bright yellow fabrics be displayed, 
 and then some pieces of orange or red stuff; this latter 
 is regarded as dull, and to have a crimson or even a violet 
 tinge. Under such circumstances, the retina, fatigued by 
 the sight of yellow, has a tendency to appreciate and pex - - 
 ceive violet, its complementary, more distinctly. Thus, 
 much of the yellow in the orange stuff is suppressed, and 
 it appears redder than it really is ; red similarly acquires 
 a violet tinge. Doubtless much of the weariness ex¬ 
 perienced by a long examination of the pictures in an 
 exhibition of modem works of art is due to eye-fatigue, 
 and the consequent ocular modifications of colour. 
 
 The second subjective or ocular cause of apparent 
 changes in the colours of objects is due to defects of the 
 organ of vision. The eye may suffer from what in optical 
 language is termed “ spherical aberration ”—a scattered 
 light, of varying degrees of intensity, always surrounding 
 the defined images of luminous and strongly illuminated 
 objects upon the retina. The result of this nebulous 
 border about such images is to increase their apparent 
 size ; but it is nearly always imperceptible under the 
 ordinary conditions of moderate illumination. When, how¬ 
 ever, we look at incandescent or glowing and luminous 
 bodies, the effect is very striking. A piece of charcoal no 
 thicker than one’s finger, if lighted at one end and plunged 
 
OCULAR MODIFICATIONS OF COLOUR. 
 
 61 
 
 in oxygen, appears actually to swell as the combustion 
 becomes more intense and the light brighter. A spiral of 
 platinum wire heated to whiteness by a galvanic current 
 not only has its diameter, so far as the wire itself is con¬ 
 cerned, enormously increased, but the separate turns of 
 the spiral seem to approach and even to coalesce, if not 
 originally too distant. The crescent of the moon appears, 
 for the same reason, to belong to a much larger sphere 
 than the dimmer mass of the satellite which it clasps. 
 Much of the peculiar indefiniteness and mystery which 
 impart considerable beauty to flames of different kinds, 
 to strongly illuminated clouds and surfaces of water, and 
 to the intense reflected lights of metallic ornaments, is 
 due, in part at least, to irradiation, which, moreover, is 
 one of the chief causes by which coloured margins are so 
 frequently observed to surround coloured objects. A rim 
 of greenish light may be observed round a red wafer 
 placed on white paper, owing to the extension of the image 
 of the red wafer beyond its geometrical image on the 
 retina of the eye. Of course the rim is green, owing to 
 the effect of simultaneous contrast. With a pure yellow, 
 such as that of the spectrum, or that made by mixing 
 green and red lights together, the rim of irradiate colour 
 would be blue. This effect is roughly shown in Fig. 21. 
 
 There is another and entirely different kind of defect in 
 some eyes which causes modification of actual colours. 
 For it has recently been shown with great clearness by 
 Leibreich that the yellow colour which tints the lens of the 
 eyeinadvancingyears produces remarkable effects upon the 
 appreciation of blue and bluish colours. This aged condi¬ 
 tion of the eye is not always strongly marked, but occa¬ 
 sionally, as in the case of the painter Mulready, it has 
 produced very curious results. The later pictures of the 
 artist are often spoken of as too cold, too blue, or too purple. 
 If they are examined through a piece of glass tinted of a 
 pale sherry-yellow colour they re-assume a natural appear¬ 
 ance, and exhibit the same harmonious and natural system 
 of colouring which Mulready adopted in his earlier works. 
 Leibreich points out that we have an excellent illustration 
 of how Mulready saw his own works with the naked eye in 
 his later years, if we will only look through a yellow glass 
 at a picture of his in the South Kensington Museum called 
 
62 
 
 COLOUR. 
 
 “ The Young Brother.” Without the glass it is far too blue 
 to be natural, with the glass it closely resembles an earlier 
 and more accurately-coloured work by the same hand 
 which is preserved in the same collection. This latter 
 work was painted twenty-one years earlier, when the lenses 
 of the eyes of the artist were normal. Even when they 
 became yellow the objects of exterior nature were scarcely 
 modified in colour in consequence of the ocular change, 
 for the yellow medium could cut off but an infinitely small 
 proportion of the blue in the intense light and colour of 
 the day, while the eye through the constant presence of 
 this yellowness, became less appreciative of this colour, 
 and consequently more appreciative of its complementary 
 blue. But with pictures the case was entirely different. 
 The light reflected from pigments is so immeasurably less 
 in quantity and intensity than that of exterior nature that 
 a yellow lens will seriously interfere with the blues which 
 paints represent : it will intercept them. So the painter 
 will try to set this right by strengthening his blues and in¬ 
 creasing their proportions in his mixed colours. To his 
 yellow lens his pictures thus become right in harmony and 
 key of colour. To a normal lens they are too blue—his 
 reds, of course, too, being changed, becoming purple or 
 violet. If then we look at one of Mulready’s later pictures 
 through a sherry-yellow glass it recovers in a great degree 
 its truthfulness of hue, and appears to us as it appeared to 
 him: but if we look at one of his early pictures through the 
 same medium we see that it is altered in nearly every re¬ 
 spect for the worse: no wonder then that the artist himself 
 became dissatisfied with his earlier colouring as his lens 
 grew yellower. 
 
 The third ocular cause of the modification of colour 
 has been already dwelt upon at some length, and in dif¬ 
 ferent places, in the present series of lessons : it is the 
 production of subjective complementary colours. We 
 may just allude to the phenomenon here, in order that 
 this most important and fundamental fact may be tho¬ 
 roughly impressed upon the minds of our readers. Simply 
 stated, the cause of the phenomenon may be traced to the 
 impaired sensibility to light temporarily caused by the 
 action of light upon the optic nerve. Not only is this 
 true of white light, but of light of every colour. Not only 
 
CONTACT AND SEPARATION OF COLOURS. 63 
 
 does a moderately lighted room appear dark when we first 
 enter it from broad sunshine, but, as we have before 
 stated, the last piece of yellow or red cloth we look at 
 will seem duller than the first, though they have all been 
 cut from the same roll. When light of any particular 
 colour falls upon the eye, it becomes less sensitive to, and 
 less appreciative of, that colour ; it is partially blinded to 
 its perception. So, not only will a red wafer placed upon 
 a sheet of white paper be surrounded by a rim of colour 
 through irradiation, but that rim will be green ; and if the 
 wafer be moved away, a green spot will occupy its former 
 position. For the eye, by gazing at the red wafer, has had 
 its sensibility to red light temporarily impaired, and so 
 the white light received on that particular spot of the 
 retina previously occupied by the red image of the wafer 
 will have its red constituent virtually removed, and will 
 produce the effect of the residual rays—namely, a green 
 image, the complementary of the previous red one. Seve¬ 
 ral other contrivances for producing subjective comple¬ 
 mentary colours have been devised. One of the most 
 satisfactory of these is to view a surface of white, grey, or 
 coloured paper, moderately illuminated, through an aper¬ 
 ture in another sheet of paper of a different colour, and 
 placed at a little distance above or before it. The lower 
 surface, as seen through the aperture, will be tinged with 
 the complementary of the coloured surface above. So, 
 also, the shadow of an object interposed in a beam o 
 coloured light will, if received on a screen slightly illumi¬ 
 nated with white light, appear to have assumed the colour 
 complementary to that of the beam ; and, for the same 
 reason, a beam of daylight finding its way into a room 
 illuminated with yellowish light from candle-flames, will 
 appear violet. The importance of this fact, as regards 
 the proper treatment of shadows in painting, will have to 
 be insisted on and illustrated in a subsequent chapter. 
 
 We have now studied the mutual effects of many pairs 
 of colours, the effects of white, grey, and black upon single 
 colours, and the effect on a second colour of the previous 
 perception of another. We have then passed to the causes, 
 dependent upon the structure of the human eye, which 
 modify the natural appearance of coloured objects. We 
 may fitly close this chapter with a few remarks on the uses 
 
6 4 
 
 COLOUR . 
 
 which may be made of some of the facts and laws which 
 have just been stated, confining our attention at present, 
 however, to those effects of the apposition and separation 
 of coloured spaces which are illustrated in our coloured 
 figures. 
 
 We have before stated that yellow is the most for¬ 
 cible, luminous, and prominent of the primary colours. 
 It will appear nearer to the eye than either red or blue. 
 In Fig. 22 (coloured plate) a yellow leaf pattern is repre¬ 
 sented upon a ground partially red and partially blue. 
 While there is no doubt of the prominence of the yellow, 
 it will probably be allowed that the red ground appears 
 nearer than the blue ; and if the blue had been of a purer 
 and fuller tone still, the retiring effect which it possesses 
 would have been yet more perceptible. How far the 
 retiring effect of blue is due to association or fancy, to 
 our constant view of the sky and the hazy distance of a 
 landscape, it is difficult to determine. But there can be 
 no doubt that we are obliged, in decorative and pictorial 
 art, to recognise the idea of distance conveyed by blue 
 and bluish hues, and that such colours afford means of 
 attaining effects of mystery, obscurity, hollowness, etc., 
 which other hues do not furnish. Another association 
 with the colour blue is that of coolness, just as red recalls 
 the glowing warmth of a fire, and yellow the bright 
 shining of the sun. Another feature of our diagram 
 (Fig. 22) is the distinctness of the sensation imparted by 
 the three colours, yellow, red, and blue. If the red ap¬ 
 proaches the yellow rather more closely than the latter 
 does the blue, it arises from the impossibility of repre¬ 
 senting by actual pigments these three colours. 
 
 Figs. 23 and 24 teach another fact relating to coloured 
 spaces in contact. Often when we attempt to mix pigments, 
 our mixture is anything but successful. The difficulty of 
 getting a good violet by adding blue and red together is 
 well known. The result may be achieved in a different 
 way. If lines or dots of red and blue be distributed 
 suitably over a surface, the effect of violet will be pro¬ 
 duced—at all events, when the figure is held at some dis¬ 
 tance. One mode of accomplishing this result is seen 
 in Fig. 24, where the distinction of the two colours is lost, 
 and a mixed colour effect produced, in obedience to the 
 
CULTIVATION OF THE SENSE OF COLOUR. 65 
 
 laws of subjective colours already announced. In Fig. 23 
 the two colours retain their distinctness at ordinary small 
 distances. 
 
 When two colours of about the same intensity and 
 tone, as the blue and yellowish or leaf-green in the 
 central stripes of Figs. 25 and 26, are in contact, there is 
 a want of distinctness and purity about the margins of 
 the contiguous colours, which renders the combination by 
 no means a pleasing or favourite one. Yet a bright leaf- 
 green is often seen in Nature against the deep blue of a 
 summer sky, and no one dreams of quarrelling with this 
 arrangement of colour. There are, however, delicate 
 differences between the natural and artificial appositions 
 of green and blue. The green leaves of trees are full 
 of minute variations of tone, structure, and form, and 
 they are further helped to contrast with the more uniform 
 blue beyond them by the reflected illumination of some of 
 the edges and the shading or darkening of others. The 
 latter modification may be represented to us roughly in 
 Fig. 25. Here we see the enormous importance of white 
 and of black, even in the narrowest lines and smallest 
 quantities, in separating related colours. Such colours, 
 difficult as they are to harmonise successfully under many 
 ordinary conditions, afford by the aid of black or white, 
 combinations of great delicacy and beauty. 
 
 CHAPTER VIII. 
 
 THE CULTIVATION OF THE SENSE OF COLOUR—TRIPLE 
 COMBINATIONS OF COLOUR—DISTRIBUTION, BALANCE, 
 AND QUALITY OF COLOUR. 
 
 Having described with some fulness of detail the rela¬ 
 tions of colours amongst themselves and to white, black, 
 and grey, we may now extend and apply the knowledge 
 gained to several of its practical uses in the decorative arts. 
 Directly we begin to study combinations of three or more 
 colours, and the important subjects of the harmony, con¬ 
 trast, and balance of colours, we find our ground less sure, 
 for not only do many subjective influences come in to 
 
66 
 
 COLOUR. 
 
 modify the objective realities, of complex colour combina¬ 
 tions, but the element of taste —to some extent a personal 
 element peculiar to the individual—introduces fresh diffi¬ 
 culties in reaching a right judgment. Yet it must not 
 be forgotten that taste in great measure depends upon 
 knowledge, association, and culture, and may be developed 
 from very small rudiments by proper study. Never was 
 there a time when the opportunities for such study, in re¬ 
 lation to taste in colour, were more abundant. Commenc¬ 
 ing with the acquirement of the knowledge of the theory 
 and the laws of light and colour, we may proceed to study 
 and to analyse the most pleasing and attractive colour- 
 combinations to be found in the works of Nature and of 
 art. Here it is that our parks and gardens, our museums of 
 specimens of natural history and ornamental art, as well as 
 such art libraries as that at South Kensington, become of 
 such special use. The dwellers in a great city, if shut out 
 from the pure blue of the sky, and the foaming white of the 
 ocean, if debarred from the wide beauties of the open 
 landscape, yet have an opportunity of studying the wonder¬ 
 ful colours of Nature. Such are shown in the softened 
 tones, and tender hues, and metallic lustres of flowers, 
 birds, shells, and minerals, in the pictures which represent 
 outward facts as interpreted by the intelligence and skill 
 of man, and in the thousand and one forms of decorative 
 art which so often express, in various degrees, the de¬ 
 velopment, historical and national, of the appreciation of 
 colour. 
 
 We may suitably commence to apply the laws of colour 
 by a reference to the effect of certain triple combinations 
 of primary and other colours. Some details of this kind 
 have been already furnished when we were describing the 
 value of black and white in separating related colours. 
 Orange and red do not accord well together, for they are 
 closely related by the possession of many qualities in 
 common, being bright, warm, and exciting to the eye, and so 
 similar as to have their boundaries confused when placed 
 together. A white line placed between a red and an orange 
 space or device of colour, not only serves to separate them, 
 but to deepen and enrich their tone, by virtue of the law of 
 contrast. But it does not do this so effectually as a line 
 of black, which, affording very nearly the strongest possible 
 
TRIPLE COMBINATIONS OF COLOUR. 
 
 67 
 
 contrast with orange and a powerful contrast with red, 
 brightens both of these colours considerably, without ac¬ 
 tually causing the whole combination to reflect more light 
 to the eye, but rather less. Now, if we wish to separate 
 two related colours from each other by the use of white or 
 black, and these colours should happen to be, like blue and 
 violet, of a cool retiring quality, and less exciting than 
 orange and red, black will prove itself much inferior to 
 white. Deep tones of blue and violet are so closely related 
 to black that the latter effects little towards their separa¬ 
 tion, while it is itself injured by contact with them, acquir¬ 
 ing a rusty hue. But white, on the other hand, while it 
 deepens these colours, renders them purer, and by itself 
 acquiring a faint tinge of the complementary yellow or 
 orange (in obedience to the law of simultaneous contrast) 
 causes their differences to appear more distinctly. Still 
 there is a triple combination slightly preferable to that of 
 blue, white, and violet; it is formed by the substitution of 
 grey for white. The contrast becomes less violent, and is 
 undoubtedly more agreeable. Without going through the 
 whole series of primary and secondary colours in their re¬ 
 lations to one another, and to grey, white, and black, it 
 will be useful to furnish an outline of the principles by 
 which such combinations may be classified and valued. 
 Triple assortments of this kind may be arranged in three 
 groups :— 
 
 1. Two primary colours, with (a) white, (b) grey, (r) black. 
 
 2. One primary and one secondary colour, with white grey, or 
 
 black. 
 
 3. Two secondary colours, with white, grey, or black. 
 
 1. Of the first species of triple assortments there maybe 
 nine varieties, even if we limit the list to those varieties 
 in which the colours are separated by the white, grey, or 
 black:— 
 
 Yellow—with white, grey, or black—and red (three varieties). 
 
 Red—with white, grey, or black—and blue (ditto). 
 
 Blue, with white, grey, or black—and yellow (ditto). 
 
 2. Of the second species of triple assortments there may 
 be twenty-seven varieties :— 
 
 Yellow—with white, grey, or black—and orange (three varieties.) 
 Yellow—with white, grey, or black—and violet (ditto). 
 
68 
 
 COLOUR . 
 
 Yellow—with white, grey, or black—and green (three varieties.) 
 
 Red—with white, grey, or black—and orange (ditto). 
 
 Red—with white, grey, or black—and violet (ditto). 
 
 Red—with white, grey, or black—and green (ditto). 
 
 Blue—with white, grey, or black—and orange (ditto). 
 
 Blue—with white, grey, or black—and violet (ditto). 
 
 Blue—with white, grey, or black—and green (ditto). 
 
 3. Of the third species of triple assortments there may 
 be nine varieties :— 
 
 Orange—with white, grey, or black—and violet (three varieties). 
 Violet—with white, grey, or black—and green (ditto). 
 
 Green—with white, grey, or black—and orange (ditto). 
 
 In these lists we have presented the simplest kinds of 
 triple assortments in their baldest forms. Before we can 
 form any just idea of their relative merit, so far as the de¬ 
 gree of pleasure they convey to the eye is concerned, it 
 will be necessary to look a little more closely at the various 
 conditions under which these assortments of colours may 
 be made or met with. Supposing our colours to be pro¬ 
 duced by the purest pigments, and each one of them to 
 present its characteristic depth of tone (which we have 
 previously described as its equivalent), we shall yet find 
 that the effect of any one of our series, above given, of 
 simple triple colour-assortments depends upon many mi¬ 
 nute particulars. Amongst these we may name, as the 
 most important, the relations of the colour-elements of 
 each assortment, so far as concerns their— 
 
 1. Distribution, as to form and surface. 
 
 2. Proportion or balance. 
 
 3. Quality, as to warmth, brilliancy, saturation, etc. 
 
 The consideration of the texture of the coloured material, 
 
 its lustre, transparency, and similar physical character, 
 together with the modifications of colour produced by 
 different kinds of illumination, being deferred for the pre¬ 
 sent, we proceed now to say a few words as to the distri¬ 
 bution of the constituents in combinations of three colours. 
 The simplest case is the presence of the three elements on 
 three equal and similar spaces, such as a square space of 
 yellow separated by a similar square space of white from 
 one of red ; or we may have a disc of red, surrounded by 
 a ring of white, and that bordered by a second ring of 
 
DISTRIBUTION, BALANCE, AND QUALITY. 69 
 
 yellow, each surface being of equal area. Differences of 
 area, as well as of form, may also be taken into considera¬ 
 tion. The white space may be reduced to a narrow band 
 separating the yellow and red, or it may be increased so 
 as to form several strips, and then arranged in the order 
 —white yellow, white red, and so on. This is not only an 
 alteration in the relative space occupied by one of the 
 elements in a triple assortment, but it involves an altera¬ 
 tion in the way in which the element is distributed. The 
 mode of distributing colours, however, belongs rather to 
 another branch of the subject, although it undoubtedly 
 influences to a great extent the quality of the colour- 
 effects produced in any assortment of hues. We will, 
 however, say a few more words about the effects of tbt 
 mode of distributing colour on a surface when we have 
 touched upon the two allied subjects of the balance ot 
 colour and the quality of colour. 
 
 The balance of colour has been already alluded to in 
 Chapter IV., and need not be discussed at length in 
 this place. The principle which underlies the idea of 
 the balance or proportion of colour is that the eye and 
 mind demand for their satisfaction the presence of the 
 several elements of the chromatic scale in some form 
 or other of combination, and in such proportions as 
 shall be competent to re-constitute white light, white¬ 
 ness, or greyness. But there are three facts which must 
 not be lost sight of in studying the balance of colour 
 in any actual composition. The first of these facts is that 
 our purest pigments are far from representing the several 
 colours of the spectrum, and so we can only approximate 
 our groups of coloured surfaces very roughly to the propor¬ 
 tions required by theory. The next fact is that this theory 
 itself is merely a provisional one. For, as we have already 
 pointed out (see Chapter IV.), Professor Maxwell and other 
 observers have shown that the commonly received theory 
 as to the primary colours is not altogether true or compe¬ 
 tent to explain some of the most important phenomena of 
 colour. Convenient this ordinary theory certainly is, while 
 its defects do not obtrude themselves upon our notice when 
 we examine the impressions produced by coloured terres¬ 
 trial objects. We will not go over this ground again 
 here, but merely mention the inherent defectiveness of the 
 
70 
 
 COLOUR . 
 
 usual theory of the coloured constituents of the white light, 
 in order to point out how it is that we feel unable to claim 
 any real or complete scientific basis for our present views 
 as to the balance of colour in a composition. We must, 
 however, for the present accept and utilise these views in 
 default of better ; yet it would be improper to claim for 
 them an unhesitating acceptance or adoption. But even 
 supposing the theory of the balance of colour to have 
 greater pretensions to truth than it really possesses, there 
 is a third fact which tends to lessen still further its value 
 and applicability—we refer to the satisfactory and agree¬ 
 able nature of many colour-combinations which glaringly 
 transgress its demands. Yet the fact that the contempla¬ 
 tion of a single pure and bright colour viewed alone gives 
 us pleasure no more negatives the idea of the greater and 
 more complex kind of pleasure derived from an assortment 
 of colours than the sweet quality of a particular note in 
 the human voice, or a musical instrument disproves the 
 superior beauty of a chord. So, too, just as some airs have 
 but a very limited range of musical tones, yet possess a 
 simple and quiet beauty of their own, so a few colour- 
 tones of the same scale, or a series of three or four closely- 
 related colours, may give us great pleasure, and seem to 
 employ and satisfy the eye. There can be no doubt, then, 
 that while the colour-elements are beautiful by themselves 
 and in a ,large number of simple combinations, fresh beau¬ 
 ties of other and less obvious sorts are brought out by as¬ 
 sorting colours in obedience to certain principles. So far 
 as balance or proportion is concerned, we may say that of 
 the most brilliant and luminous colours, such as yellow, 
 we need least in any assortment; of colours of interme¬ 
 diate power, such as red, a larger quantity may be used ; 
 while the deep and more retiring blue demands a space at 
 least equal to that occupied by both the yellow and the 
 red. White will be used most sparingly, as being more 
 brilliant than yellow ; and black will likewise be employed 
 temperately, as the deepest of all tones, and giving the 
 most violent constrasts possible. Here it is that the im¬ 
 mense value of grey and the tertiary hues is especially felt. 
 For suppose we desire to convey some particular impres¬ 
 sion by a colour-assortment, we can often do so, without 
 widely departing from the balance of colour, by introducing 
 
XIXX 
 

 
 
 
 
 
 
 
DISTRIBUTION, BALANCE, AND QUALITY , 
 
 71 
 
 grey into the assortment, either by itself or mixed with a 
 colour, so as to produce a “ broken tone.” Thus, if we 
 desire a quiet, but not cold assortment of colours, we may 
 mix with our yellow enough grey to turn it into citrine, 
 and then the complementary violet, which in a binary as¬ 
 sortment is the other necessary constituent, will not pro¬ 
 duce so striking a contrast as with the original yellow. 
 We may, also, then increase the proportion of surface 
 covered by the citrine, so as to lighten the whole effect. 
 In such a combination, white, too, may be introduced with 
 more satisfactory effect, as it accords better with yellow 
 when the latter has been made less brilliant by admixture 
 with grey than it does with pure yellow, which too much 
 resembles it in brilliancy. In considering the balance or 
 proportion of this or any such arrangement, or of those 
 arrangements in which there is a manifest deficiency of 
 some one colour-element, it should not be forgotten that 
 we have continually occasion to devise combinations of 
 colour which are not intended to stand alone; indeed, 
 it is usually impossible, even if it were desirable, to 
 isolate the colour-assortments of natural or artificial 
 origin. Thus the very elements which may be needed 
 to supply the chromatic balance in, say, an old blue 
 and white jar of the porcelain of Nankin may be furnished 
 by the deep brown stand on which it is placed, or by 
 the furniture or paper of the room. We must not, then, 
 expect in all the fixed or movable decorations of a house 
 that perfectly balanced proportion which the whole of them 
 taken together may offer. The position, use, and material 
 of each coloured object will necessitate a particular pre¬ 
 ponderance of certain colours, while a perfect colour- 
 balance in each part would constantly lead to a very im¬ 
 perfect one in the whole system or arrangement. 
 
 Something has already been said of the quality of 
 colours, as influencing our estimation of the value of their 
 several assortments. We here return for a short space to 
 this subj ect. In describing the primary and secondary colour, 
 we have shown that their fullest and purest tones differ 
 greatly in different cases. No tone of yellow can be ob¬ 
 tained of equal depth with the corresponding tone of blue. 
 The brightness or brilliancy of the yellow will always 
 cause it to contrast, not only so far as the tone is con- 
 
72 
 
 COLOUR. 
 
 cerned, but also in relation to colour, with the blue. To 
 deepen the yellow we must mix black with it, turning it 
 into brown. Colours such as green and red may be ob¬ 
 tained of full tones and yet equal intensities, so as to offer 
 no contrast of tone, only one of colour. The inherent 
 brightness or sombreness of colours forms, then, one of 
 their most important qualities when they are introduced 
 into combinations or assortments. Of course, the quality 
 of colours is variously modified by admixture with other 
 colours, or with white, grey, or black. Combinations of 
 secondary and tertiary colours and hues, while influenced 
 by the same principles of distribution and balance as 
 those just laid down, are less capable of yielding dis¬ 
 cordant and unsatisfactory assortments. The contrasts 
 between them are less violent, while their assortments 
 admit of more varied treatment and more subtle expres¬ 
 sion. We shall have occasion to notice the great value of 
 several of the more indefinite and mixed hues in the re¬ 
 maining papers of this series. 
 
 We may now proceed to illustrate by a few examples 
 the application of the principles of the distribution, 
 balance, and quality of colours to their triple assortments, 
 which are of three series. 
 
 Series I .—Assortments of two primary colours with 
 white, grey, or black constitute the first series. They are 
 generally preferable to assortments in which one primary 
 and one secondary colour occur, unless these happen to 
 be complementary, when the effect is more agreeable still. 
 The more brilliant colour must be used in moderation, 
 and may be distributed in narrow lines or delicate forms. 
 The deeper colour usually requires a broader treatment, 
 and to be present in larger quantity. In separating the 
 two bright primaries, yellow and red, from each other, 
 black is preferable to white ; while in separating blue and 
 red, white is preferable to black. In such instances we 
 have to pay attention to the balance of tone, and must 
 not allow the bright or the deep elements of colour to 
 preponderate. Grey is very often of use in colour assort¬ 
 ments, where white or black might produce too marked a 
 contrast. 
 
 Series II .—Assortments of one primary and one se¬ 
 condary colour with white, grey, or black. It is needless 
 
DISTRIBUTION, BALANCE, AND QUALITY . 73 
 
 to say that in the cases belonging to Series II. the effect 
 of a primary with its complementary secondary is far 
 superior to all the other combinations. Thus yellow and 
 violet constitute a more agreeable assortment than yellow 
 and orange. But yellow and violet cannot be much im¬ 
 proved by the introduction of black, which too much 
 resembles the violet, and differs too much from the 
 yellow ; while white is liable to an objection precisely the 
 converse of this. Nor does grey produce a very satis¬ 
 factory effect in this arrangement. The more agreeable 
 the combination of two colours when in contiguity the less 
 improvement do they require, and the less do they ex¬ 
 perience from the introduction of white, grey, or black. 
 Such assortments as that of yellow and orange are, on 
 the other hand, greatly improved by the introduction of 
 another element to define or emphasise them. The ar¬ 
 rangement yellow, black, and orange is vastly superior 
 to that with yellow and orange alone. When white is 
 used in an assortment of this nature containing two bright 
 colours, it often produces a happier effect when introduced 
 so as not to separate the colours, but to precede the 
 brighter of them—thus, white, yellow, orange. If white 
 be also inserted between the yellow and the orange, the 
 effect is impoverished. When two deep colours are used 
 together, and in combination with black, the black may 
 advantageously follow the deeper colour, but such an as¬ 
 sortment as blue, violet, and black is a sombre one ; yet 
 to many eyes it will appear more satisfactory than one in 
 which alternate spaces of white are introduced, in order 
 to restore the balance of tone 
 
 Series III .—Assortments of Two Secondary Colours. 
 —Orange and green may be advantageously separated by 
 black, orange and violet by grey, and violet and green by 
 white. 
 
 We hope the examples just given will be sufficient to 
 enable our readers, with the aid of actual experimental 
 trials, to judge of the merit of any triple assortment of 
 colour, and to arrange many agreeable combinations 
 suitable for special purposes. We may just allude here 
 to one of the applications flowing out of the principles 
 which we have been enunciating. It is an application 
 of great service to ornamental designers, and has been 
 
74 
 
 COLOUR. 
 
 extensively carried out in practice. It may be briefly 
 stated in three rules or propositions:—i. If in an orna¬ 
 mental design the ground be of a deep tone of colour, 
 and the forms or figures upon it be of a less intense or 
 lighter complementary colour, then these forms should be 
 outlined with white, or with a light tone of grey, or, in 
 any event, with some colour of a tone lighter either than 
 the ground or the pattern. 2. If in an ornamental design 
 the ground be of a light tone of colour, and the forms or 
 figures upon it be of a more intense or deeper comple¬ 
 mentary colour, then these forms should be outlined with 
 black, or with a deep tone of grey, or, in any event, with 
 some colour of a tone deeper than either the ground or 
 pattern. 3. In painting with tones of one colour, or 
 monochrome, the same rule must be observed, varying 
 the depth or tone of the outline according to the relations 
 as to tone of the pattern and the ground, as in the pre¬ 
 ceding rules. 
 
 CHAPTER IX. 
 
 COMPLEX COLOUR-COMBINATIONS—HARMONIES OF ANA¬ 
 LOGY-HARMONIES OF CONTRAST — HARMONIES OF 
 SERIATION—HARMONIES OF CHANGE. 
 
 Hitherto our studies of colours have been confined 
 almost entirely to those which are considered elementary 
 and those which are compounded with equivalents of 
 their constituent primaries. We have alluded once and 
 again to the existence and use of the vast series of mixed 
 hues. It is however, chiefly in the employment of these 
 colours that the higher chromatic developments, consti¬ 
 tuting the poetry of colour, are manifested. The obvious 
 assortments of the primary and secondary colours, with 
 their contrasts, resemblances, and harmonies, are not 
 difficult to understand ; but it requires a well-trained eye 
 to discern the subtle differences and concords of com¬ 
 position in which several mixed hues preponderate, and a 
 well-cultivated imagination to appreciate and to pursue 
 their intricate delights. Here, where aid from descriptions 
 is most desirable, it is most difficult. Endeavours to 
 reproduce the more recondite harmonies of hues by me- 
 
COMPLEX COLOUR-COMBINATIONS. 
 
 75 
 
 chanical processes are never wholly successful, and usually 
 are even less useful than accurate verbal descriptions 
 combined with references to natural examples. An illus¬ 
 tration strikes us as we write. Many an observant 
 student of Nature must have noticed the triple combination 
 of hues presented by an old beech or elm tree as seen 
 against the sky or clouds in early spring. We have 
 the yellowish grey-green of the moss and lichen-grown 
 trunk and branches standing out relieved against the dull 
 grey of the shifting and variable clouds beyond; and 
 this tender green of the moss and grey of the cloud are 
 not flat or uniform, as they too often appear in our imi¬ 
 tations of them, but fluctuating with a hundred variations 
 of texture, quality, and tone. A few dead leaves per¬ 
 chance remain, suggesting, if not completing, by their 
 brown or russet hues, the balance of colour, which just 
 needed such idea of warmth and ruddiness as they convey. 
 
 But let us regard a little more minutely, a little longer, 
 this natural combination of hues, which we commend, 
 with countless others in the world around us, to every 
 student of decorative art; let us see whether it does not 
 possess other elements of beauty than those which we 
 have recorded. Yes ; if we look a little closer we shall 
 doubtless see some delicate portion of nearly pure primary 
 or secondary colour, some stray fragment of brightness— 
 perchance an early flower or insect—just as the ancient 
 pines of the unbroken American forest have been described 
 as bearded with hoary lichens, yet touched with grace by 
 the violets at their feet. So, too, there will be observed 
 in the outermost twigs of our tree that hopeful thickening 
 by myriads of leaf-buds, neither purple-russet nor clove- 
 brown, nor any colour which we can definitely fix, but 
 very beautiful in themselves and promising the verdure ot 
 summer. Deep hollows of shade, and the brightness of 
 light will be seen too, yet sparingly, and so, like the 
 simpler colours, made the more precious. From this 
 example, of which nothing but the original work of a 
 master in the art of painting could convey an adequate 
 notion, most important deductions may be drawn. It 
 will help us to realise, in a thoughtful, artistic way, the 
 value of temperance in colour, as well as of balance and 
 distribution. It will lead us to introduce, among our blues 
 
76 
 
 COLOUR. 
 
 and reds and yellows, some of "those rarer tints which 
 we cannot exactly name, but which the watchful student 
 of Nature may see trembling on the leaves of the willow, 
 or paving the autumnal paths of the forest, or shining 
 at eventide from the cloudy but splendid pavilions of 
 the sun. 
 
 It behoves us now, passing from this somewhat pictorial 
 treatment of the obscure subject of the complex combina¬ 
 tions of mixed hues and colours, to attempt the description 
 and classification of harmonies of colour. 
 
 It is usual to divide harmonies of colour into two 
 classes—those of analogy and those of contrast. Having 
 already described the conditions under which assortments 
 of colours become more or less harmonious, we need here 
 do little more than illustrate by an example or two the 
 several kinds of harmony of contrast here referred to. 
 But it must be remembered that the distinction of har¬ 
 monies into two classes is rather arbitrary. Some dif¬ 
 ference always exists between any two colours and any 
 two tones, so that collocation, whether agreeable or other¬ 
 wise, inevitably includes the element of contrast. Har¬ 
 monies differ in degree or in complexity, but not in kind, 
 so far as contrast is concerned. The ordinary harmonies 
 of analogy pass by insensible degrees into distinct un¬ 
 doubted harmonies of contrast. We here cite M. Chevreul’s 
 classification of harmonies, a classification which has been 
 adopted by most writers on colour :— 
 
 I.—HARMONIES OF ANALOGY. 
 
 1. The Harmony of Analogy of Scale .—This harmony 
 is essentially the harmony of a series, or the harmony of 
 gradation. It is produced by the simultaneous view of 
 several tones of the same scale, and is obtained in varying 
 degrees of perfection according to the number of the tones 
 present and the intervals between them. When the tones 
 are not easily separable by the eye, and run into one 
 another, then the effect commonly called “shading” is 
 produced. 
 
 2. The Harmony of Analogy of Tones .—When two or 
 more tones of the same depth, or nearly the same depth, 
 but belonging to different but neighbouring or related 
 scales, are viewed together, the harmony of tone is pro- 
 
HARMONIES OF SERI A TION. 
 
 77 
 
 duced. Many such assortments, however, are displeasing 
 to the educated eye unless they be so selected as to fall 
 into a series with a gradually increasing quantity of some 
 one of their colour-elements, when they may be ranged in 
 the third kind of harmonies of analogy— 
 
 3. The Harmony of a Dominant Colour. —This har¬ 
 mony is produced by viewing a landscape, a bouquet of 
 flowers, or any contrasted colour-assortment, through a 
 piece of glass so slightly tinctured with a colour as not to 
 obliterate but merely to modify the natural colours of the 
 arrangement or composition. 
 
 II.—HARMONIES OF CONTRAST. 
 
 1. The harmony of contrast of scale is produced by the 
 simultaneous view of two very distant tones of the same 
 scale. 
 
 2. The harmony of contrast of tones is produced by the 
 simultaneous view of two or more tones of different depths, 
 belonging to neighbouring or related scales. 
 
 3. The harmony of co?itrast of colours is produced by 
 the simultaneous view of colours belonging to very dis¬ 
 tant scales, and assorted in accordance with the laws of 
 contrast. This kind of contrast includes also those cases 
 in which the effect is still further increased by differences 
 of tone as well as of colour. 
 
 It must be confessed that the above classification of 
 colour-harmonies is forced and imperfect; for every har¬ 
 mony depends to a greater or less extent upon contrast, 
 either of tone or of colour, or of both ; and our harmonies 
 of analogy will be found to be derived from the milder 
 and less startling kinds of contrast. Two ruling ideas 
 will, however, be apparent in colour-arrangements, and 
 upon the recognition of these ideas we may, perhaps, 
 found a more satisfactory classification of colour-harmo¬ 
 nies than that of Chevreul. These two fundamental ideas 
 are those of seriation and change. Of the first we have 
 an example in the assortment yellow, orange, red ; of the 
 latter in the assortment yellow, red, blue. Seriation or 
 succession corresponds in some measure to the scales, 
 and change to the chords, of musical composition. Seria¬ 
 tion may be succession of tones or of colours, or of both ; 
 
78 
 
 COLOUR. 
 
 but in all cases the idea of a series, of steps, of orderly 
 succession, with the presence of a pervading and dominant 
 element, is the leading feature of the arrangement. In 
 harmonies of change, on the other hand, an element com¬ 
 mon to all the members or a majority of the members is 
 wanting ; nor is there any distinct idea of orderly succes¬ 
 sion or of development in those harmonies which convey 
 very distinctly the notion of change, more or less abrupt. 
 Between harmonies of seriation and harmonies of change 
 there are numberless connecting links, so that the one 
 kind may imperceptibly slide into the latter. For beyond 
 the regulating principles of balance, distribution, appro¬ 
 priateness, harmony, etc., no rigid rules, as of cast iron, 
 need trammel the imagination of the colourist, and so no 
 precisely-defined classes can be arranged to receive all 
 the possible harmonies of assorted colours and hues. 
 What further remarks we have to make with reference 
 to this subject we now proceed to give under the two heads 
 of harmonies of series and harmonies of change. 
 
 Seriation, succession, development, sequence, gradation, 
 or shading includes many cases of the harmony of analogy, 
 and is of two kinds. The tones of a scale succeeding 
 one another in regular order furnish one example of shad¬ 
 ing ; another is seen in a series of assorted colours so ar¬ 
 ranged as to convey the notion of a gradual increase of 
 some quality in the series. The gradual development of 
 the full leaf-green of a plant in the spring furnishes an 
 example of gradation, not only of tones but of colours. 
 A greenish-yellow passes into yellowish-green, this into 
 green, and this finally acquires both depth and a greater pro¬ 
 portion of blue. Leaves in autumn may often be observed to 
 reverse this order, passing through various tones and hues 
 of russet, red, orange, and yellow. The open country con¬ 
 tinually offers illustrations of the two kinds of gradation 
 we have named, and the landscape painter, apprehending 
 the value of this fact, is enabled to realise the relations to 
 each other of the different parts of the view spread before 
 him, both as regards gradation of tone and gradation of 
 colour. In the near objects constituting the foreground 
 he notices the extensive range of the scales both of tone 
 and colour, and the preponderance of those hues which 
 imply the notions of brightness and warmth. In the 
 
HARMONIES OF SERI ATI ON. 
 
 79 
 
 middle distance the range of tones and colours is more 
 abridged ; while the far distance is commonly distin¬ 
 guished by retiring and cold colours, with a very limited 
 range of scale as well as of colour. From these natural 
 examples of gradation we may take many hints useful 
 in applying colour to decorative purposes. Supposing we 
 wish to conventionalise a compound leaf, we may do so not 
 only so far as its details and form are concerned, but also 
 in reference to its colour. Fig. 30 represents such a con¬ 
 ventional colour arrangement—an arrangement the key to 
 which is to be found in a natural sequence of colours often 
 occurring in plants. 
 
 What is called a harmony of analogy runs through the 
 series of colours in Fig. 30. The four colours there as¬ 
 sumed to be present resemble in kind and in order those 
 
 found in the spectrum of the sun to lie between the yellow 
 and the green. The arrangement of the series conveys 
 the idea of an increasing brightness and warmth as we des¬ 
 cend from the pure green terminal leaflet to the smallest 
 pair of leaflets close to the leaf-stalk. Fig. 31 represents 
 the same series of colours in a diagrammatic way, but 
 inverted, and furnishes us with a scientific analysis of the 
 effects observed. The full green is represented, in accord¬ 
 ance with the common theory, at the base of Fig. 31 as 
 
8o 
 
 COLOUR. 
 
 containing eight parts of blue and three of yellow. The 
 yellowish-green comes next, with one-third less blue and 
 the same amount of yellow as before. The greenish-yellow 
 contains only one-third the amount of blue of the original 
 green. Then we reach the pure yellow, which is to be re¬ 
 garded as the common element of the series, bringing all 
 its members into relation. On Maxwell’s theory we are to 
 suppose increasing additions of red as we ascend from 
 green to yellow. 
 
 Fig- 31- 
 
 In our next illustration (Fig. 32) the range of colour is 
 more extensive. The series is not for general use in deco¬ 
 rative assortments, but there are several useful lessons to 
 be drawn from it and applied in practice. The contrasts 
 between contiguous colours in the present example are 
 much more startling than in Fig. 30, the intervals are 
 larger, while the harmony is one which must be said to 
 lie between those of analogy and those of contrast. The 
 element of serial succession or development is weak here, 
 and that of change very apparent. The gradation in the 
 assortment depends upon the increasing brightness of the 
 colours as we ascend, and upon the link which connects 
 each group of three neighbouring colours together—the 
 presence of a common element. We arrive at this result 
 
HARMONIES OF SERI A TION. 
 
 8l 
 
 by interposing a secondary between its constituent prima¬ 
 ries all through the arrangement. Thus orange is placed 
 between yellow and red, which latter is succeeded by vio¬ 
 let, the compound of red and blue. Blue follows, and after 
 this green ; then we should recommence the series by re¬ 
 turning to the yellow with which it began. The analysis 
 of the colour-series in Fig. 32 is represented roughly in 
 Fig. 33, where the thin lines represent yellow, a thicker 
 line red, and the thickest line blue. Where two lines over¬ 
 lap, a compound colour appears. 
 
 We may, however, learn some¬ 
 thing more from Fig. 32 than is here 
 put down. The greater development 
 of the stalks and leaflets towards the 
 base, with the gradually increasing 
 pointed character of the latter to¬ 
 wards the summit, helps to carry out 
 the idea of series suggested by the 
 succession of the colours. If in some 
 minor details, such as the larger size 
 of the second pair of leaflets, we find 
 a break in the symmetry of the series, 
 this is just the common feature of 
 vegetable and animal growths by 
 which they are in part distinguished 
 from the mathematically accurate, but 
 less interesting products of mere 
 mechanism; for very often the poetry, the mystery, of 
 beautiful organic forms lies hid in such seeming exceptions 
 to law. 
 
 We must not fail to notice that there exist several 
 methods of more completely harmonising the contrasted 
 colours of such a series as that shown in Figs. 32 and 33. 
 In copying the former figure in colours for the sake of the 
 instruction this exercise affords, we recommend our readers 
 to try the following generally applicable methods of bring¬ 
 ing greater unity into such a series :— 
 
 1. An outline and veining of black, common to all the leaflets. 
 
 2. An outline and veining of gold, common to all the leaflets. 
 
 3. The addition of grey to the whole of the colours used, the 
 largest proportion being added to the green, the least to the 
 yellow. 
 
82 
 
 COLOUR. 
 
 Yellow 
 
 Red. 
 
 Blue 
 
 Yellow -■ 
 
 Red. 
 
 Violet. 
 
 Blue. 
 
 4. Instead of making the secondary colours by mixture, intro¬ 
 duce their constituent primaries by dots placed side by side. 
 
 Splendid examples of such grada¬ 
 tions of colour as those we have 
 been describing are to be found in 
 Orange, numerous specimens of decorative 
 art and manufacture in the fabrics 
 of India, the silks of Damascus, the 
 faience of Persia, the lacquer-ware 
 of Japan, and the porcelain of China. 
 To take a single example, we may 
 refer our readers to the peculiar but 
 beautiful selection and sequence of 
 colours upon such plates of the so- 
 Green. called “ Persian ware” as may be 
 seen in the Ceramic Gallery at 
 South Kensington. The particular 
 Fig. 33 variety of this ware which we have 
 now in view is known as “ Damas,” 
 “ Lindus,” or more generally “ Rho¬ 
 dian.” The range of colours is limited except so far as one 
 series is concerned—the series beginning with green, and 
 passing through turquoise blue, to a pure deep cobalt, 
 and thence to a lilac hue. The most conspicuous of the 
 remaining colours is a dull brick-red, opaque and much 
 raised in relief above the others. A chocolate-brown, and 
 a black or grey like that of Indian-ink complete the list, 
 except that now and then a specimen of the ware is found 
 with a little yellow on it. On a ground of creamy white, 
 conventionalised forms derived from the hyacinth, the 
 tulip, and a few other plants occur. The leaves are filled 
 in with a copper-green, some flowers are of deep blue 
 touched with turquoise, others of a lilac hue. On some 
 specimens no other colours are found than these four, yet 
 these establish so lovely a series that it is doubtful whether 
 the specimens which exhibit these colours only are not 
 equal or even superior to the others. The colours of the 
 plants represented probably suggested, in cases like the 
 present one, some of the predominant harmonies in which 
 the dull red, with its yellowish tincture, balances the cooler 
 blues and greens, while the Indian-ink colour, in light cir¬ 
 cles and delicate spirals of smoke-grey, tones down the 
 
HARMONIES OF CHANGE. 
 
 83 
 
 whole composition, and actually brightens and purifies its 
 dominant series of colours. We ought not to fail to notice 
 a most precious quality of these Persian wares—that fluc¬ 
 tuation of colour, that absence of mechanical hardness of 
 outline and uniformity of tone which distinguishes human 
 handiwork of the thoughtful kind from the perfectly correct 
 and thoroughly insipid work of a machine. But we must not 
 linger any more over our illustrations of the harmonies of 
 series or relation, but conclude our present lesson with a 
 word or two on the “ harmonies of change.” 
 
 Harmonies in which the sequence or relationship of the 
 constituent colours is indistinct or absent include most 
 varieties of the harmonies of contrast. The change of 
 tone or colour in them may vary greatly in abruptness : 
 in the more complex assortments of this class it is very 
 difficult to attain anything like an agreeable unity, for if 
 there be many startling changes or contrasts, the effect 
 becomes tiresome and spotty. The harmonies of change 
 become more agreeable the more closely the rules of ju¬ 
 dicious distribution and balance of colour and tone are 
 followed. The free use of separating lines of white, grey, 
 gold, or black is often indispensable. The value of re¬ 
 duced tones of colour, and of the mixed and tertiary hues 
 to modify the crudeness of a startling contrast, is very re¬ 
 markable. But we have already described at considerable 
 length, in Chapters V., VI., and VII., the principles upon 
 which harmonious contrasts depend, and so here simply 
 confine our attention to two illustrative examples derived 
 from the floral world. 
 
 We might turn to the splendid family of the orchids, 
 with their quaint forms and complex systems of colour, or 
 we might choose one of the Malvacce, such as the Abutilon 
 megapotamicum —a plant in which the green of the leaves 
 offers a violent contrast with the red of the swollen calyces, 
 and the five bright yellow petals of the corolla contrast 
 again very forcibly with the violet hue of the central 
 branch of clustered stamens—a startling assortment, very 
 rich in effect, when completed by the opening of the flower. 
 In this example, besides the mere notion of contrast, we 
 have the idea of repetition which resembles that of seria- 
 tion ; red contrasting with its complementary, green, and 
 yellow with its complementary, violet, both the comple- 
 
8 4 
 
 COLOUR. 
 
 mentaries having, therefore, the third element, blue, in 
 them. But every flower presenting three different colours 
 may serve to illustrate the harmony of contrast, and we 
 need not go far for an example. Even the quiet violet, 
 with its minute orange-tinted eye, the faint green bases of 
 its petals and their own chief hue, somewhere between 
 blue and red, affords a colour-assortment of the kind un¬ 
 der discussion, the balance of which is in a measure com¬ 
 pleted when the leaves of the plant are included in the 
 series. Similar studies of other plants should be made ; 
 it will surprise many persons to discover what a world of 
 instruction, as well as of enjoyment, is to be derived from 
 what we may call the chromatic analysis of flowers. 
 
 The next subjects to be discussed are the modifications 
 of colour arising from methods of illumination and differ¬ 
 ences of structure and surface. 
 
 CHAPTER X. 
 
 CAUTIONS AS TO THE TRUE PRIMARY COLOURS AND CHRO¬ 
 MATIC EQUIVALENTS—MODIFICATIONS OF COLOUR 
 Y ILLUMINATION—DIFFUSED DAYLIGHT—LIGHT OF 
 THE SKY AND CLOUDS — SUNLIGHT — A DOMINANT 
 
 COLOURED LIGHT—ARTIFICIAL LIGHTS—TWO LIGHTS. 
 
 / 
 
 Before entering upon the consideration of the changes 
 produced in coloured objects, by the nature of the light 
 which falls upon them, it is desirable to repeat a caution 
 which we have given our readers more than once as to the 
 value to be put upon our supposed set of three primary 
 colours and their chromatic equivalents ; for, in discussing 
 the laws of harmonious assortments of colours, we have 
 assumed the truth of both these doctrines, because we 
 were dealing with pigments or dyes, and not with coloured 
 lights (see Chapters VI., VII., and VIII.), and because for 
 pigments, the conclusions reached by Field, and generally 
 adopted, so far as regards the relations and equivalents of 
 colours, are of no small service. Field’s conclusions were 
 indeed obtained by imperfect methods, and relate, so far 
 as they are true, only to colours produced by absorption ; 
 but it is, of course, precisely with this mode of producing 
 colours that we are concerned when occupied with pig- 
 
TRUE PRIMARY COLOURS. 
 
 35 
 
 ments. It will be well, however, to point out the special 
 convenience of the primary triad of colours in general use 
 by painters and ornamental colourists. Yellow, red, and 
 blue have been selected, for artistic as well as practical 
 reasons. With these colours, unmixed, but properly dis¬ 
 tributed over a painted surface, it is perfectly possible to 
 get that kind of “ neutralised bloom” which all satisfac¬ 
 tory colour-combinations should exhibit when viewed at a 
 sufficient distance ; just as a similar result may be secured 
 by the mingling, through rotation or otherwise, of the same 
 three colours. A second artistic or aesthetic reason for 
 the selection of this triad lies in the variety thus secured. 
 Yellow represents to the eye nearness, lightness, and bril¬ 
 liancy, and does not actually admit of anything like the in¬ 
 tensity of the purest red. Red imparts an idea of warmth 
 and richness, and is as far removed, in its several qualities 
 and the sensation it awakens, from yellow as it is from 
 blue. Blue gives us the element of coolness and retire¬ 
 ment, and is less brilliant and more intense even than red. 
 If we take the triad red, green, and blue, we have not the 
 same range of effect at our disposal, red and green being 
 removed from each other by a far greater interval than that 
 which separates green and blue. As to the practical uses 
 of the two rival triads, there can be little hesitation in 
 preferring the common one ; for red and green pigments 
 when mixed do indeed produce grey, and blue and yellow 
 pigments, green ; though were lights, not pigments, con¬ 
 cerned, red and green would yield a yellow, and blue and 
 yellow a white light. Any one, however, who will turn to 
 the exquisite colour-arrangements, founded on Maxwell’s 
 theory, which are given in Mr. Benson’s “ Principles of 
 Colour,” will see that even with pigments, some most 
 charming combinations may be regularly deduced from 
 the more correct but less popular theory. 
 
 We have already explained how the mixed nature of 
 the rays reflected and absorbed by pigments causes this 
 difference, this departure from the anticipated result; but 
 the only thing we have to do under the circumstances is 
 the adoption, for the special purpose, of a plan of mixing 
 colours which can be successfully carried out in practice. 
 The impressions which the retina of the eye receives, and 
 which become translated by the brain into sensations of 
 
 G 
 
86 
 
 COLOUR. 
 
 colour, are certainly produced in different ways. The 
 mingled rays, for example, of red and bluish-green light 
 produce a colour-sensation absolutely identical with that 
 produced by the perfectly simple and pure yellow light of 
 the spectrum ; but it would be grossly incorrect to regard 
 yellow as of necessity a compound colour for this reason, 
 since we know it to be incapable of any kind of decom¬ 
 position as it occurs in the solar spectrum and in most 
 pigments. It is quite possible, also, to produce the colour- 
 sensation of blue by the mingling on the retina of certain 
 green and violet rays, yet this does not warrant us in 
 regarding the solar blue rays as being otherwise than 
 simple. But when we come to mix pigments on a palette 
 we find that very different results occur, yet that in no 
 case is a pure yellow, or red, or blue colour produced by 
 any mingling of other colours. So our practical treatment 
 of the colour-relations of pigments must differ from that of 
 coloured lights. 
 
 We are also compelled to lay but little stress on the 
 doctrine of chromatic equivalents. When pure coloured 
 rays are experimented with, it is possible to learn the 
 proportions in which they must be mingled to produce 
 certain effects ; but when the same problem is attempted 
 to be solved in the case of pigments, the complexity of 
 the subject baffles us, and our results are scarcely more 
 than very rough approximations to the truth. Still, there 
 is an obvious propriety in the more sparing use of 
 luminous and brilliant colours, such as yellow, as compared 
 with those of great depth and intensity, such as blue; and 
 if we find that mixtures in certain proportions of particular 
 coloured pigments give colours [approximating to certain 
 standards, or produce neutral greys, we may consider 
 such proportions as corresponding in some measure to the 
 chromatic equivalents of the pigments in question. Thus 
 it is found by experiment that two grains of nickel in the 
 form of chloride yield a bluish-green solution, which is 
 perfectly competent to neutralise the rose-pink colour of 
 a solution of chloride of cobalt containing one'grain of 
 cobalt. In this instance, the nickel-green is related to 
 the cobalt-pink in the proportion of 2 to i. We trust 
 that, without further dwelling upon these subjects of the 
 primary colours and chromatic equivalents, we have said 
 
DIFFUSED DAYLIGHT. 
 
 87 
 
 enough to show at once not only the use of our expla¬ 
 nations in Chapters VIII. and IX. of colour-proportion 
 balance, and harmony, but also the reserve under which 
 these explanations must be accepted. In passing on to 
 the study of the modifying influences of different kinds 
 of illumination upon the colours of objects, we would 
 premise that the remarks just made must likewise be kept 
 in view. 
 
 The quality and intensity of the light by which objects 
 and their colours are discerned are liable to great varia¬ 
 tions, and produce corresponding changes in the colours 
 reflected from the surfaces which they illuminate. Putting 
 on one side, for the present, the variations produced by 
 the nature of the substance or surface on which the light 
 falls, we may consider the condition of a plane and uni¬ 
 formly-coloured surface as illuminated by 
 
 1. Diffused daylight, and sunlight ; 
 
 2. A dominant coloured light; 
 
 3. Artificial lights, as candles, lamps, fire ; 
 
 4. Two lights, of different quality or intensity. 
 
 § 1. It is scarcely necessary to state that the light of 
 day varies greatly in colour; the causes, however, of its 
 variations may not be at once apparent. In reality, there 
 is one chief active cause which originates its chromatic 
 changes— the air is not perfectly transparent , it is more 
 or less cloudy or troubled. Now even if the sun’s luminous 
 rays be purely white, they will suffer change by passing 
 through a cloudy medium. The ease with which they 
 pass will vary with the more or less complete approach 
 to transparency of the atmosphere and its depth. Let 
 us study in succession the blue light of the sky, the ap¬ 
 parently white light of clouds, and the [reddish light of 
 direct sunshine. 
 
 How does the blueness of an unclouded sky originate? 
 We may best explain it by means of an experimental 
 illustration. 
 
 Upon a sheet of black glass or a surface of black 
 japanned metal, place a drop of milk, diluted, if necessary 
 —which will seldom be the case—with a drop of water. 
 The milk is a cloudy medium; its minute particles 
 reflect certain rays of very short wave-length—those 
 towards the more refrangible or blue end of the spectrum ; 
 
 G 2 
 
88 
 
 COLOUR. 
 
 therefore, by reflected light, a drop of milk on a dark 
 background appears blue. So, through a delicate skin, 
 and a series of translucent but not transparent membranes, 
 the light reflected where the dark background of a vein 
 filled with venous blood exists, is blue. So, also, the 
 translucent, but not absolutely transparent, tissue of the 
 iris of the eye often reflects a blue light, there being in 
 this instance also a background of a black pigment, but 
 no real blue colouring matter whatever. The blueness 
 of the sky has a similar origin. Against the dark back¬ 
 ground of infinite space, a translucent medium is placed ; 
 this medium is the atmosphere. It is never transparent, 
 countless millions of minute particles, chiefly of water, 
 being suspended in it. When these particles are of a 
 certain degree of minuteness, and uniformity, they arrest 
 the free passage of white light; this they do by a peculiar 
 kind of “interference” (see Chapter II.) Each minute 
 foreign particle of water gives rise to two reflections, one 
 on each surface—one external, on the anterior surface; 
 one internal, on the posterior. These reflected rays, 
 passing from air into water, and from water into air, 
 suffer different retardations, and, on emergence, cause 
 the usual phenomenon of interference, namely, the pro¬ 
 duction of colour. When the particles thus affecting the 
 incident light are sufficiently minute and sufficiently 
 numerous, the proportion of reflected green, blue, and 
 violet rays, which together give the colour-sensation of 
 blue, predominates greatly over the red, orange, and 
 yellow rays, with their longer undulations. Thus, the 
 reflected light of the open sky is blue ; but let the thick¬ 
 ness of the reflecting layer, or the number of the reflecting 
 particles increase, and the blueness of the light decreases, 
 for the solar light, which has been deprived by the kind 
 of reflection just described of a great proportion of its 
 more refrangible rays of short vibration, has become 
 yellowish, or orange-tinted, and is no longer capable of 
 furnishing an excess of blue rays. From this cause we 
 see that while the light of the zenith is a distinct blue, 
 it becomes gradually of a less pronounced tint towards 
 the horizon, where it would be white if other conditions 
 did not there produce other modifications of the reflected 
 light. This exquisite gradation of tone in the sky is 
 
LIGHT OF THE SKY AND CLOUDS. 
 
 89 
 
 often missed by unobservant painters, who think that 
 the same mixing of some blue pigment will do to re¬ 
 present the colour of the whole sky shown in their 
 pictures. 
 
 Now if the reflected light of the blue sky owes its colour 
 to a sort of sifting of the solar rays, it will be rightly con¬ 
 cluded that the transmitted light, deprived by this process 
 of its green, blue, and violet elements will partake more 
 or less distinctly of the colours of the residual rays of the 
 solar spectrum. Such is the case. The light transmitted 
 through a turbid medium shows a predominance of yellow, 
 orange, or even red light. Direct sunlight partakes of 
 this character, but it is generally more distinctly seen 
 when the same object is illuminated by two lights, which 
 can be compared and contrasted together. Yet there are 
 cases in which the redness of sunlight is manifest enough. 
 Not only is bright sunshine spoken of by painters as warm 
 in an artistic sense, because of its ruddiness, but the light 
 of the sun, transmitted through a great thickness of a 
 turbid atmosphere, often appears, as at sunset, of an in¬ 
 tense red or crimson colour. The street lamps in a fog 
 illustrate, by their gradually increasing redness as they 
 become more distant, the same fact. 
 
 While, then, the light reflected from the sky is bluish, 
 and that transmitted directly from the sun through an 
 aqueous atmosphere reddish, the light of day is often 
 white. The particles suspended in the air may be either 
 too large or too small to produce the effect we have been 
 discussing. Thus, through certain kinds of fog and mist 
 the light of the sun reaches us, reduced in intensity it is 
 true, but unchanged as to its quality of whiteness. So, 
 also, the light reflected from dense masses of cloud is 
 often nearly white, and at other times is grey, owing to a 
 comparatively deficient illumination or to absorption. It 
 will not be necessary to detail here the modifications of 
 colour which objects undergo when illuminated by direct 
 sunshine, or by the light reflected by the blue firmament 
 or white clouds, as it may be readily learnt from the next 
 succeeding paragraph, in which we treat of the effects of a 
 dominant coloured light. 
 
 § 2. When a landscape is viewed through a piece of 
 neutral-tinted or grey glass, the rays of different colours 
 
90 
 
 COLOUR . 
 
 belonging to different parts of the spectrum are intercepted 
 to a nearly equal extent; when the glass itself is coloured, 
 a different result ensues. Through a deep yellow glass all 
 objects at first acquire a yellowish tinge, not because the 
 yellow glass actually adds any yellow rays to the light 
 which it reflects, but because it cuts off the other coloured 
 constituents of the light in different degrees, and so in¬ 
 creases the proportion of yellow light conveyed to the 
 eye. Objects which are originally yellow remain virtually 
 unchanged, but relatively intensified ; those which are red 
 lose a small part of their red rays ; those which are green 
 assume a yellowish-green hue, since some of their green 
 and blue rays are cut off; while blue objects acquire a 
 greyish-green hue, owing to the suppression of many of 
 their proper blue rays, and of the further sifting which the 
 white light they reflect suffers. When a painting is viewed 
 through a yellow glass the smaller amount of light which 
 it reflects renders the changes more startling and per¬ 
 manent. When, on the other hand, objects variously 
 coloured are illuminated by a pure light of one colour, 
 that is, monochromatic light, the results are different. 
 All objects reflect naturally, if they have the opportu¬ 
 nity, as in daylight they have, some white light; but 
 when a pure coloured light is thrown upon objects 
 usually distinctly coloured, they can either reflect no light 
 at all, or only that which is incident upon them. But, in 
 point of fact, when experimenting with coloured illumina¬ 
 tion of this kind, we have not to deal with pure red, or 
 orange, or green lights. It will be most serviceable for 
 the purposes of the practical application of our principles 
 if we give some clue as to the modifications produced in 
 the colours of objects by different qualities of light, in 
 which certain rays severally preponderate, but, neverthe¬ 
 less, do not wholly constitute the light. Illuminated by a 
 light in which yellow rays predom inate, yellow objects be¬ 
 come less distinctively yellow when put by the side of white 
 objects, which then assume a yel low tint. Pale yellow 
 gloves by the yellow light of a lam p are hardly to be dis¬ 
 tinguished from white gloves. Orange-coloured objects 
 become, if anything, rather more yellowish in yellow light. 
 Vermilion increases in brilliancy if the light be not very 
 largely composed of yellow rays, but merely have them in 
 
ARTIFICIAL LIGHTS. 
 
 91 
 
 preponderating number. Reddish and bluish violets be¬ 
 come duller and redder, losing a part of their blue. Blue 
 itself, when pale, becomes paler, and inclines towards a 
 greenish blue ; while dark and rich blues lose somewhat 
 in intensity and purity. If, instead of white light tinged 
 with yellow, we try the effects of yellow light accompanied 
 by a small amount of white light, the effects are still more 
 decided. 
 
 The following is, in the main, Chevreul’s list of the modi¬ 
 fications experienced by various coloured surfaces, when 
 viewed in coloured light nearly pure, or in a dim diffused 
 light with an intense coloured direct illumination :— 
 
 Yellow rays falling on 
 
 •white make 
 
 it appear pale yellow. 
 
 99 
 
 99 
 
 99 
 
 yellow ,, 
 
 99 
 
 orange-yellow. 
 
 99 
 
 99 
 
 99 
 
 orange ,, 
 
 99 
 
 yellower. 
 
 99 
 
 99 
 
 99 
 
 red ,, 
 
 99 
 
 orange-brozvn. 
 
 99 
 
 99 
 
 99 
 
 violet ,, 
 
 9 9 
 
 brownish-violet. 
 
 99 
 
 99 
 
 99 
 
 deep blue ,, 
 
 99 
 
 greenish -slate. 
 
 99 
 
 99 
 
 99 
 
 green ,, 
 
 99 
 
 yellowish-green. 
 
 99 
 
 99 
 
 99 
 
 black ,, 
 
 99 
 
 blackish-olive. 
 
 Red 
 
 rays falling on 
 
 white make it appear 
 
 red. 
 
 99 
 
 99 
 
 99 
 
 yellow ,, 
 
 9 9 
 
 orange. 
 
 99 
 
 99 
 
 99 
 
 orange „ 
 
 9 9 
 
 redder. 
 
 9 9 
 
 99 
 
 99 
 
 red ,, 
 
 9 9 
 
 redder. 
 
 99 
 
 99 
 
 99 
 
 violet ,, 
 
 9 9 
 
 reddish-violet. 
 
 99 
 
 99 
 
 99 
 
 blue ,, 
 
 99 
 
 violet. 
 
 99 
 
 99 
 
 99 
 
 green ,, 
 
 9 9 
 
 reddish-g7-ey. 
 
 9 9 
 
 99 
 
 99 
 
 black ,, 
 
 9 9 
 
 rusty black. 
 
 Blue 
 
 rays falling on white make 
 
 it appear 
 
 blue. 
 
 99 
 
 99 
 
 99 
 
 yellow ,, 
 
 99 
 
 green. 
 
 99 
 
 9 9 
 
 99 
 
 orange ,, 
 
 9 9 
 
 plum-brown. 
 
 99 
 
 9 9 
 
 99 
 
 red ,, 
 
 9 9 
 
 violet. 
 
 99 
 
 99 
 
 9 9 
 
 violet ,, 
 
 9 9 
 
 reddish-violet. 
 
 99 
 
 99 
 
 9 9 
 
 blue ,, 
 
 99 
 
 bhier. 
 
 99 
 
 99 
 
 99 
 
 green ,, 
 
 9 9 
 
 bluish-green. 
 
 99 
 
 99 
 
 99 
 
 black ,, 
 
 9 9 
 
 bluish-black. 
 
 Orange rays falling on 
 
 white make 
 
 it appear orange 
 
 99 
 
 99 
 
 99 
 
 yellow ,, 
 
 99 
 
 orange-yellow. 
 
 99 
 
 99 
 
 99 
 
 orange ,, 
 
 99 
 
 reddish-orange. 
 
 99 
 
 99 
 
 99 
 
 red „ 
 
 99 
 
 scarlet. 
 
 9 9 
 
 99 
 
 99 
 
 violet ,, 
 
 99 
 
 reddish-brown. 
 
 9 9 
 
 99 
 
 99 
 
 blue ,, 
 
 9 9 
 
 greyish-orange. 
 
 99 
 
 9 9 
 
 99 
 
 green „ 
 
 99 
 
 greyish-green. 
 
 99 
 
 99 
 
 99 
 
 black ,, 
 
 99 
 
 brown. 
 
92 
 
 COLOUR. 
 
 Violet rays falling on 
 
 9 9 9 9 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 white make 
 yellow ,, 
 orange „ 
 red ,, 
 
 violet ,, 
 blue ,, 
 green „ 
 black ,, 
 
 it appear violet. 
 
 ,, brown, rather reddish. 
 ,, light greyish-red. 
 
 ,, reddish-violet. 
 
 ,, deeper tone of violet. 
 
 ,, bluish-violet. 
 
 )> greyish-violet, \yiolet. 
 
 ,, slightly tinged, with 
 
 Green rays falling 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 99 99 99 
 
 on white make it appear green. 
 yellow ,, ,, yellowish-green, 
 
 orange ,, ,, greyish leaf-green. 
 
 red ,, ,, brown, 
 
 violet ,, ,, greenish-slate, 
 
 blue ,, ,, bluish-green, 
 
 green ,, ,, more intense a green, 
 
 black ,, ,, dark greenish-grey. 
 
 The above results were originally obtained by Chevreul 
 by exposing pieces of coloured cloth to diffused daylight, 
 and illuminating half of each piece also by the light pass¬ 
 ing through glasses of the several colours named. The 
 effects are consequently partly due to contrast, and are only 
 true for the special conditions of the experiments performed. 
 They, however, give us some notion of the various direc¬ 
 tions in which different coloured lights affect the colours 
 of objects already moderately illuminated by diffused day¬ 
 light. On this point see the statements given under § 4 
 further on. 
 
 § 3 . In considering the effects on coloured surfaces of 
 yellow light, we have in point of fact considered the effects 
 of the light of gas, oil lamps, and candles upon them, for 
 all the ordinary kinds of artificial light possess a super¬ 
 abundance of yellow rays. This preponderance is less 
 marked in the case of paraffin oils and solid paraffin can¬ 
 dles, the light of which, though far from white, is not so 
 yellow as that emitted by burning stearine or tallow. By 
 the side of objects illuminated by direct daylight, which 
 is, we know, slightly reddish, the light of a candle, though 
 really yellow, may appear orange, while direct sunlight 
 itself may, by contrast, appear positively violet or blue. 
 Now the general results of the yellow illumination of 
 artificial lights upon coloured surfaces may be learnt by 
 reference to the table given above, but it may be interest- 
 
ARTIFICIAL LIGHTS. 
 
 93 
 
 ing to give in fuller detail one particular and familiar in¬ 
 stance of the sort of effect thus produced. We allude to 
 the strange effect of artificial light in altering the colour of 
 certain violet colours, and of blues which possess a tinge of 
 violet. Take as an example the precious stone known as 
 the amethyst. A good specimen of this mineral presents 
 by daylight almost the same tint as that of the flower of 
 the violet, but at night, illuminated by lamp or candle¬ 
 light, it loses much of its blueness, and acquires so dis¬ 
 tinct a reddish hue that it might be mistaken for a red gar¬ 
 net or carbuncle. This change is due to the deficiency of 
 blue in the artificial light, while ordinarily the red of these 
 stones is annulled partially by the greenish-blue element 
 of daylight. A similar instance of a change in colour has 
 been observed with some sapphires. The saphir merveil- 
 leux in the Hope Collection, South Kensington Museum, 
 presents a clear blue tint by daylight, but by candlelight 
 it appears violet. Certain flowers show a still more curi¬ 
 ous property. The flowers of the viper’s bugloss (Echium 
 vulgare ) and of the marsh forget-me-not (Myosotispalus- 
 tris) are rose-coloured in the bud and when they begin to 
 open, but, afterwards, on fully expanding, become blue as 
 viewed by daylight. By artificial light, however, the 
 change appears not to have taken place, at all events, to 
 any great extent, since a spray of one of these plants thus 
 seen by candlelight shows its buds red or rose-coloured 
 indeed, but its fully-opened flowers are not blue, but only 
 pink or a pale purplish-red. The difference between red 
 and a blue verging on purple is thus partially annulled. 
 So also, as regards blues and greens ; the ordinary green 
 and blue pigments, with very few exceptions (eg., aniline 
 green), are hard to distinguish by candlelight. Those 
 blues which verge on green do so, of course, by the special 
 absorptive power which they possess for the yellow, orange, 
 and red rays, and their power of reflecting the green, the 
 blue, and the violet. Now, as candlelight is deficient in 
 blue and violet, the green of these blue pigments then 
 comes out in unusual force. Such serious changes are ex¬ 
 perienced by some blues under artificial illumination that 
 it is often advisable to substitute green for blue in colour- 
 combinations which are to be viewed at night by gas or 
 candles. The triad— red — yellow—green becomes under 
 
94 
 
 COLOUR. 
 
 such circumstances superior in effect to the triads red — 
 yellow—ultramarine blue, and crimson — yellow—Prussian 
 blue. So yellow, to be seen well and effectively by candle¬ 
 light, must incline towards orange or a golden hue ; but 
 white, on the other hand, if it be meant to appear white, 
 must by no means be tinted with a shade of blue, with the 
 intention of purifying it, and neutralising the yellowness 
 of the illumination on the material. This plan in day¬ 
 light is effective, but by candlelight dulls the brilliancy of 
 the white, by the absorption of certain rays cf light which 
 it causes. 
 
 § 4 . A double illumination, where the lights are of 
 different quality, produces some striking effects of con¬ 
 trast. Such effects are often seized upon and reproduced, 
 with varying degrees of fidelity, by those artists who 
 delight in painting forges, candlelight scenes, and confla¬ 
 grations. In order to study the conditions and effects 
 of double illuminations, the following experiment may be 
 made. Place a sheet of pure white paper in such a 
 position that it may be illuminated at the same time by 
 diffused daylight and by the light of a candle. Now 
 arrange an opaque rod vertically, so that it may throw 
 two shadows upon the paper. The shadow thrown by 
 the daylight will be tinged with yellow, while that pro¬ 
 duced by the candle will be bluish; the doubly illuminated 
 surface being itself white. Now we have before pointed 
 out (see § 3 ,) that candlelight possesses a superabun¬ 
 dance of yellow rays, and is therefore more yellow than 
 the light of day. In consequence of this, the shadow 
 of the rod, as cast by the light of diffused daylight, and 
 illuminated therefore only by candlelight, appears yellow. 
 Conversely, as the light of day is bluish compared with 
 that of a candle, the shadow of the rod as cast by the 
 light of the candle, and illuminated therefore only by day¬ 
 light, appears blue. Of course the contrast between the 
 colours of the two shadows is enhanced in accordance 
 with the laws of contrast, as previously pointed out in 
 Chapters V. and VI. Similar results are met with every 
 day in the case of objects illuminated at the same time by 
 a natural and by an artificial light. The lamps of a church 
 may illuminate some parts of the furniture and floor with 
 a yellowish light, overpowered and contrasted in other 
 
SURFACE AND STRUCTURE MODIFY COLOUR. 95 
 
 parts by the apparently purplish light of day. A re¬ 
 markable effect of this kind is seen when strong sunlight 
 illuminates a room through a window partly screened by 
 a yellow or buff-coloured blind. Here the contrast and 
 relativeness of the colours seen become very distinct. 
 The light transmitted through the material in common 
 use for blinds of this sort is of an orange tint, and it will 
 be seen that the direct rays escaping filtration through 
 this medium, are of a beautiful reddish-purple colour. 
 More complicated effects of the same nature may be 
 observed in the case of stained glass windows. The 
 simplest case of this kind that we can recall just now is, 
 perhaps, that of windows glazed with a pale greenish glass, 
 but bordered with strips of white glass, when the latter 
 
 I will appear pinkish under some conditions of natural 
 illumination. The effect here is, of course, not wholly due 
 to the proper or intrinsic colour of the daylight, but to the 
 effect of complementary contrast between the white glass 
 which admits the natural rays almost unaltered, and the 
 
 I greenish glass which very materially affects them. But 
 the most magnificent and beautiful effects of this order are 
 to be watched in the phenomena of sunrise and sunset. 
 When a range of distant mountains is seen against the 
 sky about the time of sunset, the effects produced may 
 be readily explained. If the sun be sinking behind the 
 mountains, the shadows which it casts will be illuminated 
 moderately by scattered and reflected lights of a blue or 
 bluish-violet hue, produced by the minute particles dis¬ 
 seminated throughout the atmosphere. These hues will 
 be to a certain extent real and objective, derived from the 
 peculiarity of the light itself, and the colours of the objects 
 and surfaces which it discloses. If’these objects be grey, 
 as many rocks, or white, as snow, then the blue or violet 
 hue will be distinct, but it may be modified by the local 
 colouring of the rocks or trees of the landscape. Still 
 further, it will be changed or intensified by subjective 
 contrast with the colour of the sky, for the light from the 
 sky will reach an observer modified by its passage through 
 a turbid medium, the air, and it will thus be yellow, orange, 
 or red, according to the amount of blue, or more refrangi¬ 
 ble rays, which it cuts off. So the sky near the western 
 horizon will often be of an apple-green colour, with clouds 
 
96 
 
 COLOUR . 
 
 of greyish-purple edged with scarlet, all these variations 
 being produced by the decomposition of solar light by its 
 passage through a medium which is not perfectly trans¬ 
 parent, and the consequent conveyance to the eye, in 
 varying proportions, of lights of higher refrangibility which 
 have been reflected, and of lights of lower refrangibility, 
 which, escaping complete absorption, have been trans¬ 
 mitted. 
 
 Hitherto we have regarded the colours of objects as 
 they are modified by the quality of the light which falls 
 upon them. We have to study in the next place the 
 influence of the structure, surface, and material of the 
 objects themselves upon their apparent colours. 
 
 CHAPTER XI. 
 
 SURFACE AND STRUCTURE MODIFY COLOUR—COLOURS 
 OF METALS—DAMASCENING AND PLATING—ENAMEL¬ 
 LING ON GOLD AND SILVER—LACQUERING—COLOURS 
 OF GEMS—COLOURED MARBLES. 
 
 The colour of objects is influenced not only by the nature 
 of the light by which they are illuminated, but also by 
 their own peculiarities of texture, structure, and surface. 
 The coloured light reflected from satin is different from 
 that of velvet, though the silk used in the manufacture of 
 these fabrics may have been dyed in the same bath. In 
 explaining modifications of colour produced by texture, 
 etc., we shall select a series of illustrative examples from 
 the mineral, vegetable, and animal kingdoms. We shall 
 then proceed to explain their colour-peculiarities, and the 
 manner in which these may be utilised, in decorative art 
 more particularly. 
 
 Metallic colours first claim our attention. Polished 
 metals are distinguished for their intense power of reflect¬ 
 ing light, and for an almost complete opacity. An intense 
 reflection of light is also observed with other than metallic 
 surfaces, such, for instance, as the neck feathers of the 
 peacock, and that beautiful chemical salt, the magnesium 
 platinocyanide. But there are some points in which these 
 
COLOURS OF METALS. 
 
 97 
 
 lustrous colours differ from those of the true metals. We 
 have alluded to this subject in Chapter I., and may here 
 proceed to apply the principles of absorption and reflection 
 of colour there laid down to the special case of metallic 
 colours. Now it will be allowed that, under ordinary 
 circumstances, metals do not appear highly coloured, 
 though their brilliancy is often intense. The angle of 
 incidence of the light has much to do with this. When 
 we take a polished and level plate of gold or copper, and 
 look along its surface, we shall see it appear very brilliant, 
 but nearly white. In such a case, the rays of light which 
 illuminate it almost graze the surface, making an angle of 
 nearly i 8 o° with the reflected rays that reach the eye. 
 But let this angle be reduced to one of a few degrees 
 only, then the proper colour of the metal will be conspicu¬ 
 ous. It may be still further developed and enriched by 
 repeated reflections at a small angle of incidence. F>g. 34 
 
 illustrates the mode in which a beam of light may become 
 in this way more highly saturated with colour by numerous 
 reflections from two polished surfaces of metal. From 
 this cause chased gold and “ granulated” gold appear of a 
 far richer colour than burnished gold. And by so shaping 
 the grooves or lines of chasing upon any piece of coloured 
 metal, that repeated reflections at small angles of incidence 
 occur in them, very rich colour-effects may be produced. 
 The splendid colours inside gold or gilt goblets arise from 
 this cause. Many metals which lack distinctive colour 
 under common conditions may thus be made to develop 
 it. Yet the colour thus produced not only changes in 
 tone or saturation as it becomes enriched, but its quality 
 
9 8 
 
 COLOUR. 
 
 is also modified. Thus copper may be made to yield 
 ultimately a nearly pure or monochromatic red light by 
 repeated reflections. The colour is more distinct, it is 
 purer; but there is less light. 
 
 The colour of a pure metal may be greatly altered by 
 alloying it, even slightly, with another. Thus, gold 22 
 parts, with 2 parts of silver, produces a metal of a green¬ 
 ish colour, which may be rendered still more decided by 
 a small further addition of silver. Copper on the other 
 hand, to the extent of 10 or 12 per cent., reddens gold ; 
 while a small admixture of both copper and silver does 
 not materially affect its colour, though it makes it rather 
 paler. A large proportion of silver, varying from 20 to 50 
 per cent., produces electrum, some specimens of which, 
 where the silver exists in nearly equal proportion with the 
 gold, are almost white. Ancient and modern coins, as 
 well as jewellery, furnish interesting examples of the 
 variations in the colour of gold produced by alloy. The old 
 Roman gold coins, with less than 1 per cent, of alloy, 
 show the rich characteristic orange tint of the pure metal; 
 while in a handful of modern sovereigns the yellowish- 
 orange ones indicate the presence in the alloy of copper and 
 silver ; the greenish ones indicate silver alone, and the 
 reddish ones copper alone. Slight as these differences 
 of colour would appear did they belong to ordinary pig¬ 
 ments, yet, in the case of the metals, the intensity of their 
 reflection enables us to use with effect coloured varieties 
 of gold in ornamental jewellery. Gold, if not alloyed very 
 much (not more than 9 parts in 24 ), may be made to 
 assume its proper colour by a process of “ pickling” or 
 “ colouring.” Gold articles plunged when warm into 
 nitric acid lose a portion of their superficial alloy, be it 
 copper or silver, the pure metal being left with a some¬ 
 what matt, or dead surface, and a rich orange colour. Or 
 a mixture of equal parts of borax, nitre, and sal-ammoniac 
 may be made, ground into fine powder, mixed with a 
 little water, and applied as a thin coating to the metal. 
 The metallic object is then heated till a faint discoloura¬ 
 tion appears on the coating ; afterwards, the paste being 
 washed off, the pure gold film will appear beneath. With 
 a film thus prepared, and with some of those films which 
 are obtained by electro-metallurgical processes, the bril- 
 
COLOURS OF METALS. 
 
 99 
 
 liancy of the metallic reflection is much impaired, though 
 its characteristic colour may remain. This alteration 
 arises from the loss of continuity of the metallic surface. 
 Silver, in fact, may be so precipitated from a solution as 
 to present a surface almost indistinguishable from a sheet 
 of cream-wove white paper; and gold may be obtained 
 by similar processes in a state which presents a close 
 resemblance to yellow ochre. Some of the most beautiful 
 effects in the decorative employment of metals may be 
 secured by the partial polishing or burnishing, with an 
 agate or steel tool, of such matt or dead surfaces as these. 
 When silver is deposited by Liebig’s silvering liquid on 
 glass, it may be made to assume a most perfect or “ black,” 
 lustre, and is then applicable for use in mirrors or in the 
 reflectors of telescopes. Here the continuity of surface is 
 practically perfect. 
 
 The delicate and subtle contrasts between metallic 
 colours has led to the association of two or more metals 
 in several kinds of decorative work. We have already 
 referred to the varieties of coloured gold. In jewellery 
 red gold may be used for flowers, with white gold or 
 electrum ; green gold may be employed for leaves; while 
 the ornamental spray itself may be laid upon a chased or 
 granulated surface of pure orange-coloured gold. By the 
 process of parcel-gilding on silver, a more decided differ¬ 
 ence of colour may be secured; while the methods of 
 metallic inlaying and damascening enable us to obtain 
 the more marked contrasts between iron and gold and 
 iron and silver. In these latter cases we have not only a 
 considerable difference of colour between the two metals, 
 but a very distinct difference in reflecting power. Iron or 
 steel covered, by an easy chemical method, with a film of 
 platinum, is preserved from corrosion, and still furnishes 
 an excellent combination with silver or gold, or with both 
 of these metals, as inlays. 
 
 Before giving a list of the colours of a few metals in 
 their pure and unalloyed state, we may remark that other 
 metals besides gold are remarkably modified in hue by 
 the presence of alloy. Perhaps copper shows this effect 
 more commonly and more distinctly than any other. An 
 alloy of 85 parts of copper with 15 parts of tin, or with 15 
 parts of a mixture of tin and zinc, constitutes a mixed 
 
IOO 
 
 COLOUR . 
 
 metal of a rich yellow colour, the pink colour of the 
 copper being then much altered. So 5 parts of the bluish- 
 white metal aluminium will similarly modify the colour of 
 95 parts of copper, an effect seen in the so-called alumi¬ 
 nium gold, or aluminium bronze, which is thus constituted. 
 If the copper be mixed with tin in the proportion of 70 of 
 the former metal to 30 of the latter, then the alloy is no 
 longer yellow, but greyish-white, forming what is known 
 as speculum metal. 
 
 The colours of some of the metals, in a few cases ascer¬ 
 tained and determined by two or more reflections, are 
 here given :— 
 
 Copper . . 
 
 Gold . . 
 
 Lead . . 
 
 Mercury 
 Potassium . 
 
 • red. 
 
 . orange. 
 
 . bluish-grey. 
 
 . slaty-grey. 
 
 . lavender-grey. 
 
 Silver . . 
 
 Sodium . 
 Steel. . . 
 
 Tin . . . 
 
 Zinc. 
 
 . orange-yellow. 
 . rosy-pink. 
 
 . neutral-grey. 
 
 • greyish-yellow. 
 . bluish-white. 
 
 There is one remarkable and important property enjoyed 
 by metals, and particularly by gold, of at once harmonising 
 with and setting off ordinary coloured materials. Two 
 instances of such a use of gold will occur to every one— 
 the gilt frame of a picture, and the gold threads in embroi¬ 
 dery. Gold, in fact, is removed from the series of ordinary 
 paints and dyes by the intensity of its metallic lustre, and 
 so combines into agreeable assortments with all colours, 
 even with those with which yellow and orange pigments 
 do not associate well. In a picture-frame this peculiarity 
 of its metallic lustre prevents its yellow colour from inter¬ 
 fering with the similar hues of the picture, while its colour 
 being luminous and “near,” gives the idea of some degree 
 of distance to the picture itself. We seem to look through 
 an opening into the scene represented. 
 
 Gold, and other metals as well, may have their lustre 
 made use of as a brilliant background for the development 
 of colour. A transparent film of some sort is often placed 
 upon metals, and when this film is coloured, such part of 
 the light as escapes reflection at its surface passes through 
 it, is reflected from the metal behind, and again passes 
 outwards, leaving the film strongly tinctured with its 
 colour. Films of this kind are of two sorts, one kind 
 
ENAMELLING ON GOLD AND SILVER, 101 
 
 belonging to the vitreous or glassy series of materials, and 
 the other being resinous, that is, essentially similar to a 
 varnish. These transparent films are applied to metals 
 for three purposes—to protect the surface, to cause an 
 inferior metal to assume the aspect of a more precious 
 one, and to produce certain colour-effects not otherwise 
 attainable. Silver, when varnished with white lac, loses 
 some of its brilliancy, but is no longer liable to tarnish. 
 Iron and brass may be protected from corrosion, and 
 improved in appearance, by a lacquer in which the red 
 resin known as dragons 1 blood is an ingredient. With 
 this preparation, silver assumes something of the rich 
 aspect of gold, and iron resembles bronze. Resinous 
 substances may be applied to metals either in the form 
 of varnishes—that is, of solutions which dry and leave a 
 continuous film or coating of the resins they contain—or 
 by means of fusion. In the latter case the finely-powdered 
 resin may be introduced in a pasty form mixed with a 
 little water into the grooves, etc., prepared to receive it, 
 and then heated to the temperature necessary to produce 
 fusion. True translucid enamels of the vitreous class, on 
 the other hand, require a much higher temperature 
 than the resin, and yield far superior and more varied 
 results. They consist essentially of different kinds of 
 glass, coloured suitably with metallic oxides. Blue 
 enamels thus contain cobalt; puce and violet enamels 
 are furnished by manganese ; grass green by chromium 
 sesqui-oxide, and so forth. Such enamels appear on 
 silver of their proper colour, but on gold the hue of the 
 metallic background produces a change of colour, some¬ 
 times advantageous, sometimes the contrary. But as the 
 colour of gold may be greatly modified by a little alloy, it 
 is easy to select or prepare a quality of gold suitable for the 
 several coloured enamels in use. The following list gives 
 the most appropriate metals for a few colours 
 
 Green .—Gold of 20 carats with 4 carats of silver alloy. 
 
 Red .—Gold of 22 with 2 carats copper, or a mixed alloy. 
 
 Violet, rose, white , yellow. —Silver, or, less suitably, white 
 electrum. 
 
 Puce .—Electrum of 16 carats gold, 6 carats silver, 2 carats 
 copper, or gold 20 carats fine. 
 
 Brown .—Gold of 20 to 22 carats. 
 
 H 
 
102 
 
 COLOUR. 
 
 The subject of translucid enamels naturally leads us to 
 the consideration of gems and glass. It ought scarcely 
 to be necessary to vindicate for the natural precious stones 
 a very high position amongst decorative coloured ma¬ 
 terials. Besides the hardness of the more esteemed sorts 
 of jewels, they present beauties and singularities of colour 
 and optical effect which are, to a great extent, quite 
 inimitable by artificial methods. Yet amongst a certain 
 clique of artists and amateurs it has become the fashion 
 to depreciate their excellence, and, further, to insist upon 
 their being cut, if used at all, in a way which is usually 
 fatal to the development of those qualities upon which 
 the beauty of precious stones depends. This method is 
 known as the cutting eti cabochon or “ tallow-topped,” and 
 is applicable or appropriate, as a rule, only to those 
 stones which are not perfectly transparent—opals, cats’- 
 eyes, chrysoprases, etc. When applied to transparent 
 gems, it prevents the full play of light and colour proper 
 to them, internal reflection is imperfect, and the marvel¬ 
 lous dispersive power often present does not show its 
 effect in producing the so-called fire of the stone. Ana¬ 
 lysed with a prism, the colour of gems is often found 
 to differ from that of the nearest approach in artificial 
 “paste”—that is, glass—that can be manufactured to 
 represent them. Then, too, gems often exhibit peculiar 
 optical properties which no fused artificial substances can 
 possess. The minute internal fissures, to which the 
 splendid play of colours in the precious opal of Hungary 
 and Mexico is due, cannot be imitated, though there is 
 another mineral, spliene, which possesses this remarkable 
 quality in a high degree. The opal is seen best upon a 
 black or dark-blue background of enamel, and is still 
 further enhanced in beauty by a border of small diamonds, 
 which form a delicate yet effective contrast, through their 
 perfect transparency and purity, and their almost metallic 
 lustre, with the milkiness and variegation of the opal. 
 The stones known as star-stones have also optical pe¬ 
 culiarities, which are quite inimitable. These gems are 
 essentially crystallised alumina, and are known as star or 
 asterias rubies or sapphires, according to their colour : 
 they are translucent only, and owe their beauty to a 
 peculiarity of their minute crystalline structure. This is 
 
MINERAL PIGMENTS. 
 
 I03 
 
 revealed when one of these crystals is cut across its 
 principal axis, and left with its top en cabochon. Then a 
 six-rayed star makes its appearance, best seen in sunlight, 
 or by the light of a small brilliant flame, or in the focus 
 of a condensing lens. It is due to the symmetrically dis¬ 
 posed layers of which the crystal is built up. The less 
 transparent varieties of red garnet, when cut as carbuncles, 
 occasionally show a star, but it has only four rays, owing 
 to the simpler crystalline structure of the stone in this 
 case. Among other chatoya7it stones with a play of light 
 upon or in them, the moonstone, a species of nearly 
 colourless and transparent felspar, is one of the most 
 familiar. Its light is more diffused than that of the star- 
 stones, and has a pearly whiteness. Moonstones may be 
 very effectively combined with dark-coloured clear ame¬ 
 thysts, the contrast being one not only of colour but of lustre. 
 The stones called cats’-eyes are of two species : one of 
 them, the more precious, is yellow or yellowish-green, hard, 
 and shows a pale bluish line of light when properly cut; 
 this is due wholly to the optical structure of the crystal 
 itself. But in the commoner variety we merely have 
 quartz penetrated with fine fibres of asbestos, which catch 
 and reflect the light. There is one peculiarity of precious 
 stones which we cannot pass over, a property known as 
 dichroism. A crystal which is greenish in one direction 
 may appear rose-pink when seen in another. A ray of 
 light is affected differently according to the direction in 
 which it passes through the crystal. The tourmaline is 
 an excellent example of this, a grass-green specimen 
 of this stone appearing dark brown or even black 
 when viewed along the principal axis of the crystal 
 instead of across it. The emerald, also, shows two hues 
 of green : one, verging on yellow-green, is seen when a 
 crystal is viewed along the principal axis, the other hue is 
 more bluish and is observed in directions at right angles 
 to that just named. This, again, is a quality of some 
 natural gems which cannot be imitated exactly in artificial 
 mixtures. 
 
 We may here find occasion to introduce a word or two 
 concerning the commoner sorts of ornamental and coloured 
 minerals, ranging from agates down to tinted building 
 stones. There are two points of special importance con- 
 
 H 2 
 
io4 
 
 COLOUR. 
 
 nected with such materials. One of these points is the 
 undesirability of mixing natural with artificial materials 
 in walls and pavements. It is very difficult to combine 
 satisfactorily tiles and marbles. There is a faint approach 
 to translucency in many marbles, with which the dull, dry, 
 opaque surface of unglazed tiles contrasts unpleasantly ; 
 and glazed tiles are coarsely artificial in their gloss. 
 Then, again, we have, in the second place, to remind our 
 readers that marbles with natural veinings and mottlings 
 of colour do not allow of sculptured ornament. Your 
 surface decoration in relief will interfere with Nature’s 
 prior decoration in colour. The wildness and almost 
 infinite variations of the natural tones of brown in a piece 
 of Derbyshire alabaster are broken up when its surface 
 is diapered with a conventional carved ornament—the 
 natural picturesqueness and the artificial are incongruous. 
 A surface in a tessera of mottled or veined marble, or a 
 pillar, displays its beauties, but in a sculptured capital of 
 the same material they are disfigured, while the light and 
 shade of the ornamental design do not come out properly 
 in the variegated material. 
 
 There still remain for study among mineral products 
 glass, porcelain, and pottery. Opalescence and iride¬ 
 scence, as well as several other peculiarities influencing 
 their colour-effect, are common in a measure to some 
 kinds of all these artificial products, and we may, there¬ 
 fore, group them together for consideration in the next 
 chapter. 
 
 CHAPTER XII. 
 
 COLOURED GLASS—COLOURS OF POTTERY AND PORCE¬ 
 LAIN — MINERAL PIGMENTS — COLOURS OF PLANTS, 
 FLOWERS, WOODS, AND VEGETABLE FIBRES—COLOURS 
 OF ANIMALS AND ANIMAL PRODUCTS. 
 
 We have now to consider the peculiarities of coloured 
 glass. Glass, being a vitreous and not a crystallised sub¬ 
 stance, does not present that extensive variety of optical 
 properties which characterises many natural gems. It is 
 
COLOURED GLASS. 
 
 I°S 
 
 probably on this account that the most perfect and uniform 
 coloured glass is not by any means satisfactory or in¬ 
 teresting from an artistic point of view. Very instructive 
 examples of the bad effect of such glass are to be seen in 
 many painted glass windows, especially in those which 
 belong to the earlier period of the recent revival of Gothic 
 art in this country. The blue and other glass is deep 
 enough in colour, but lacks real richness ; it is thin and 
 flat, though staring. There is no fluctuation of colour, 
 no breaking up and scattering of the transmitted beams 
 of light. The glass to accomplish this must be less per¬ 
 fect as a mechanical product of manufacture. If the 
 colour be uniformly diffused throughout the glass, the 
 glass must vary in thickness, its surfaces must be uneven; 
 and striae and blebs only improve the effect. A glass 
 which is absolutely perfect as glass may be rightly devoted 
 to the construction of optical instruments, but is incapable 
 of completely realising the poetry of colour. 
 
 The colours of glass may arise from several causes. A 
 fine white powder—say oxide of tin—diffused through 
 clear glass gives it the opalescence of a cloudy medium ; 
 a bluish colour being produced by reflected light, and a 
 yellow or red colour by transmitted light. Opal glass 
 may vary from a faint cloudiness to milky and nearly 
 opaque white. Another glass, owing its peculiarity to 
 solid matter, is known as aventurine glass ; it contains 
 glistening crystals of copper. But the colours of most 
 transparent glasses are due to the presence of metallic 
 silicates, such as those of iron, copper, cobalt, and man¬ 
 ganese. These metals give to glass various tints of green, 
 orange, blue, and violet. One metal, uranium, imparts 
 not only a distinct yellow colour, but the interesting pro¬ 
 perty called fluorescence. The common “canary” glass 
 is a glass of this kind. Viewed by transmitted light it is 
 yellow; but when the solar beams fall upon a piece of 
 this glass, the actinic rays are modified, and are reflected 
 back to the eye as green light. 
 
 The method of using coloured glass in windows should 
 be limited very strictly by the nature of the material, as 
 well as by the office of a window. The glass must not 
 pretend to be a picture, nor must it contain large shaded 
 or obscured portions, opaque or nearly so to light. Minute 
 
io6 
 
 COLOUR. 
 
 lines and details of drawing are out of place and useless. 
 A mosaic work of small pieces of glass, separated by bold 
 and firm lead lines, is most effective. If the window is 
 required to let in unmodified daylight, the glass may be 
 decorated with firmly-drawn outlines in dark maroon or 
 brown upon a white or grey ground, the pattern extending 
 through a large number of quarries. Here and there a 
 medallion of richer colour may be symmetrically intro¬ 
 duced. Where highly-coloured windows are considered 
 desirable, some of the richest and happiest effects are to 
 be obtained by the use of blue glass in preponderating 
 quantity, as in the ancient glass of Canterbury Cathedral, 
 or of ruby-red with blue and a golden yellow, as in the 
 windows of La Sainte Chapelle, at Paris. Some portions 
 of the latter glass may be studied at South Kensington. 
 Where the pieces of glass are small, the effect of the con¬ 
 tiguous beams of red and blue light is to produce a result 
 similar to that of violet glass, but infinitely richer, more 
 brilliant, and more “ bloomywhile the lead lines prevent 
 a confused mingling of the colours when seen more closely. 
 Mosaic work in coloured glass is most appropriate and 
 effective. Painting in chiaro-oscuro , especially in mono¬ 
 chrome, is radically bad in theory, and unpleasant, to say 
 the least, in result. 
 
 The peculiarity of the colours of porcelain and pottery 
 consists mainly in the mode in which they are applied to 
 the wares. In the case of delft, faience, and majolica w^are, 
 the colours are painted, as enamel colours, upon an opaque 
 white or nearly white stanniferous enamel. Transparent 
 or translucent colours on this opaque ground come out 
 with great force ; while opaque colours appear less, cha¬ 
 racteristic than they do upon porcelain, and upon trans¬ 
 lucent bodies generally. Upon earthenware and porcelain, 
 designs may be either printed or painted, either under or 
 over the glaze. Colours printed or painted over the glaze 
 lire generally better defined and more brilliant than those 
 which are below it. In the decoration of pottery and 
 porcelain, besides the use of enamel colours, other 
 decorative effects may be produced by means of pre¬ 
 parations of gold and platinum, and by means of colours 
 mixed with the body of the ware or the glaze. Some 
 of the most remarkable effects of the latter sort are to be 
 
GLASS, POTTERY, AND PORCELAIN. 107 
 
 seen upon the old Italian lustre-ware plates, and upon 
 the modern porcelain of M. Brianchon, imitated at 
 Worcester and Belleek, in which recent instances the 
 iridescent glaze contains a considerable amount of bismuth 
 in its composition. 
 
 A very important series of coloured materials is pro¬ 
 duced directly or indirectly from minerals. Most of the 
 native mineral pigments are of a useful and permanent 
 character. The compounds of iron, chiefly oxides and 
 hydrates, have always been largely employed in the arts, 
 and afford a wide range of useful colours—yellows, reds, 
 browns, maroons, etc. The colours derived from copper, 
 such as verdigris and malachite, are more liable to change 
 by conversion into the black oxide and dark brown 
 sulphide of this metal. Pigments made out of coloured 
 glass or frit—such pigments, for instance, as smalt and 
 ultramarine—are commonly difficult to manipulate and 
 mix, but yet are endowed with considerable fixity. Pre¬ 
 parations of lead, such as the carbonate and the chromate, 
 white lead and chrome yellow respectively, are subject 
 to one great drawback. This is their sensitiveness to 
 sulphuretted hydrogen, which darkens and destroys all 
 the more delicately-coloured preparations containing this 
 metal with considerable rapidity. The protection of these 
 materials from change is partially affected by covering 
 the particles of which they consist by a film of oil-varnish, 
 wax, paraffin, or gum, as in the ordinary methods of 
 painting in oil, encaustic, or water. In fresco and dis¬ 
 temper painting, where lime or size serves to bind or cover 
 the pigmentary granules, the action of injurious substances 
 upon sensitive materials is more rapid. In stereochromy, 
 and other methods of silicious painting, the colours are 
 liable to change. But then the range of colours is rather 
 limited, owing to another consideration, namely this, that 
 water-glass, and the alkaline silicates in general, which 
 constitute the medium with which the pigments are mixed 
 in stereochromy, or with which they are fixed, alter and 
 destroy many mineral colours, such as emerald green, 
 Prussian blue, and chrome yellow. If we exclude such 
 alterable pigments, including most preparations of lead 
 and copper, and then further eliminate, for the same 
 reason, some of the most beautiful vegetable and animal 
 
io8 
 
 COLOUR. 
 
 colouring matters, the residue of available pigments is 
 indeed small. The point, however, to which we now 
 wish to draw attention is not the modification of colour 
 by injurious atmospheric or other influences, but the 
 colour-peculiarities caused by the nature of the medium 
 with which the pigments are incorporated, or by the 
 optical qualities of the pigment itself. The most im¬ 
 portant general characters of pigments reside in their 
 translucency, or opacity, as regards light. A transparent 
 pigment need be much less saturated or intense to produce 
 a given colour-effect than an opaque one. The reason of 
 this will be clear when the statements made in former 
 chapters are recalled. The light reflected from the ground 
 on which a transparent colour is laid has to pass twice 
 through that colour; while an opaque colour often reflects, 
 or at least scatters, much unaltered white light. The use 
 of clear colours upon opaque grounds or painted surfaces 
 is often called glazing by artists, and gives a depth, in¬ 
 tensity, and richness which cannot be exactly attained in 
 other ways. Scumbling is the precise opposite of this, 
 for in it an opaque colour or white, mixed with some oil 
 or other medium, is used to cover partially, and so to 
 modify, the clear or mixed colours which have been 
 previously laid on. It conveys an idea of distance, or 
 mystery, or cloudiness. 
 
 The binding material which unites the particles of a pig¬ 
 ment together, or which retains them on the painted sur¬ 
 face, may be either opaque or transparent. In all ordinary 
 water-colour and oil-colour painting, the binding material 
 is practically transparent; but in fresco painting it would 
 seem that the freshly-covered surface acquires a film of 
 carbonate of lime (calcium carbonate), which gives dead¬ 
 ness and opacity to the surface of pictures executed by 
 this method. Something of the same kind of effect is 
 produced in the several methods of silicious painting, of 
 which the only one which is of any importance, and has 
 been practically employed, is the stereochromy of Fuchs. 
 In this process the pigments are bound to the wall, and 
 acquire coherence by the changes which the soluble potas¬ 
 sium and sodium silicates used in the process undergo. 
 They appear to enter into direct combination with the zinc 
 oxide or calcium carbonate laid on as a ground or mixed 
 
FLOWERS AND VEGETABLE PRODUCTS. 109 
 
 with the pigment. The silicate must not be saturated with 
 silica, but should be, contrary to the usual opinion, strongly 
 alkaline; otherwise an irremovable silicious bloom will 
 shortly disfigure the mural painting executed by this pro¬ 
 cess. The wall, slate, plaster, or stone to be decorated 
 should be wetted with baryta-water, painted with the pre¬ 
 viously-tested colours, and then, when dry, syringed with 
 a fine spray of the fixing silicious solution. This syringing 
 is repeated at short intervals, until no trace of colour can 
 be removed with a dry or wet hard brush applied to the 
 painting. If a saline bloom appear after a time, it should 
 be removed by means of sponging with distilled water. 
 If a hard white silicious bloom mar the brilliancy of the 
 colours, no chemical or mechanical method is com¬ 
 petent to remove it. But in this case the appearance of 
 the injured fresco or stereochrome picture may be greatly 
 improved by a process which the writer of this volume in¬ 
 vented in 1856. It consists in the use of paraffin, driven 
 into the picture by heat, or applied in the form of solution, 
 by a brush or in spray. The solvent used may be either 
 benzole or mineral turpentine. Some fine copal or dam¬ 
 mar varnish is a desirable addition. In this way old dis¬ 
 temper paintings may be preserved from destruction. The 
 effects of damp and decay are arrested, and the colours 
 may actually acquire more than their pristine beauty. In 
 fact, this process converts the opaque binding materials of 
 the painting into transparent or translucent ones. It is 
 scarcely necessary to say that all colours, oils, and var¬ 
 nishes should be tested before they are used, if their colours 
 and appearances are to remain unchanged. No soluble 
 saline matters should remain in pigments ; they ought to 
 be tried alone and mixed with others, to see if they alter or 
 fade when exposed to sunlight. The oils and varnishes 
 must be examined to see whether they darken, or if they 
 irregularly contract on drying, and so forth. But we must 
 not dwell further on the chemistry of pigments, of grounds, 
 and of the media and methods of painting, for this subject 
 requires a volume for its adequate treatment. Yet we 
 must add a word or two on a subject of the utmost import¬ 
 ance to artists, and to those who are engaged in copying 
 pictures. As the colours which we see are modified 
 subjectively, it is necessary that they should not be repro- 
 
no 
 
 COLOUR. 
 
 duced as we see them, but as they actually exist. The 
 high lights of a blue robe may appear yellow or orange to 
 us, and yet could be copied only by the use of a lighter 
 tone of blue. So the high lights of a face may give by 
 way of contrast a greenish hue to its shaded parts, although 
 this effect would not be reproduced, but grossly exaggera¬ 
 ted, by mixing some green with the grey of these parts. 
 
 The most conspicuous colours belonging to flowers are 
 usually very fleeting, and cannot be utilised for decorative 
 purposes. Generally, too, they are particularly liable to 
 alteration by acids or alkalies—becoming red under the 
 influence of the former agents, and blue or green by the 
 action of the latter. This property has been turned to ac¬ 
 count in chemical testing; one of the best test-papers 
 being prepared from that beautiful crimson-foliaged plant, 
 the Coleus Vershaffeltii. The stems of the plant are 
 bruised and extracted with spirit; then white blotting-paper 
 is soaked in the solution. The lavender-grey of this paper 
 becomes red with acids, and green with soda and other 
 alkalies. In the copper-beech and the dark portions of 
 some zonal geraniums, we have the ordinary green colour¬ 
 ing matter of leaves, called chlorophyll, mixed with a crim¬ 
 son colouring matter, the combination producing a kind 
 of deep maroon. The extreme beauty of many flowers 
 depend in part upon their peculiarities of structure. The' 
 cell-walls within which the vegetable pigments occur are 
 often extremely thin, and present a soft yet glistening 
 aspect, which enhances and varies the colour-effects of 
 their contents. This aspect, though often called crystalline, 
 in no degree arises from any structure to which this term 
 can be applied. Some very beautiful and yet permanent 
 colouring matters are, however, obtained from plants, 
 though these do not always contain them ready-formed. 
 As instances in point, we may cite indigo and some of the 
 madder colours. 
 
 The vegetable fibrous materials used in the manufacture 
 of textile fabrics are generally white or pale yellow, but 
 may be dyed of any colour by suitable processes. In some 
 cases the dyeing material may be made to enter a central 
 cavity in the fibre ; but usually colouring substances can 
 be made to adhere permanently to vegetable fibres only by 
 means of a mordant. First of all, a substance such as tin 
 
ANIMALS AND ANIMAL PRODUCTS. Ill 
 
 peroxide, having an attraction for colouring matter, is 
 precipitated upon the fibre, and then it is immersed in a 
 dye-bath. The colouring matter is withdrawn from the 
 liquid, and adheres firmly to the mordanted fibre. The 
 lustre of vegetable fibres is usually not very marked, and 
 is diminished in the process of dyeing them. Linen, the 
 woven fibres of flax, does, however, reflect the light which 
 falls upon it with considerable power, particularly in cer¬ 
 tain positions. A pattern may thus be made in which the 
 strands which form the warp may be contrasted, not only 
 as regards colour, but as regards lustre, with those of the 
 woof. Under these conditions damasked linen, just like 
 silk damask, may exhibit a curious optical illusion. If a 
 white warp and a red woof be associated, it will be noticed 
 that in certain lights the white parts of the fabric assume 
 a bluish-green tint, acquiring, very distinctly, the tint com¬ 
 plementary to the dyed threads, the effect being enhanced 
 by the difference of lustre dependent upon the way which 
 the light falls upon the fabric. Similar but still more decided 
 effects are seen in fabrics where lustrous silk and dull cot¬ 
 ton or wool are associated. Nor should we here neglect 
 to allude to the peculiar mingled tones produced by the re¬ 
 peated recurrence at short intervals of similarly coloured 
 strands in a fabric. 
 
 The colours of woods are usually subdued, but varied. 
 Much of the beauty of some woods depends, however, 
 rather upon texture and lustre than upon colour. In fur¬ 
 niture and the general decorative treatment of wooden 
 construction, much maybe made out of the combined use 
 of these two qualities of lustre and colour. One wood 
 dark in colour, and of lustrous texture, may be introduced 
 in the form of bosses, panels, or mouldings into a framework 
 of an opaque and light wood. So woods of distinct patterns 
 may be associated with those which possess a uniform 
 appearance. The colours of woods are, indeed, brought 
 out by varnishing and oiling ; but the former of these pro¬ 
 cesses has a tendency to check those alterations of tint 
 which often render old specimens of woodwork far more 
 beautiful than new. 
 
 The colours of animal products are usually less change¬ 
 able than those of vegetable products. In some cases, 
 notably in the case of the humming-birds, the brilliant, 
 
112 
 
 COLOUR. 
 
 almost metallic colours of the animals are due rather to 
 the optical structure of the coloured substance and surface 
 than to any actual colouring matter. Instances, however, 
 do occur, as in the plantain-eaters, or touracous of Africa, 
 where a colouring matter may be actually extracted from 
 the brilliant plumage of birds. The colouring matter of 
 these birds was discovered by the present writer, and found 
 to resemble the red colouring matter of arterial blood 
 in some respects. It is especially remarkable as contain¬ 
 ing a fixed per-centage of the metal copper. White feathers, 
 like other animal products, may be dyed without any mor¬ 
 dant, silk and wool being also particularly characteristic 
 examples of this fact; ivory, bone, and horn may be noticed 
 in the same connection. 
 
 We trust that the principles laid down in this manual 
 will at least serve to furnish a suggestive guide in the 
 arrangement and study of coloured compositions, both 
 pictorial and decorative. Further information may be 
 gained, both as to textile fabrics and paintings, from “ The 
 Laws of the Contrast of Colour,” by M. Chevreul; while 
 Dr. E. Briicke’s treatise on “ Colours,” which maybe read 
 in the French translation of Dr. Schutzenberger, enters 
 more fully into the physical and physiological matters 
 connected with this subject. Besides the papers of the 
 late Dr. George Wilson, of Helmholtz, and of Professor 
 Clerk Maxwell, we have two excellent works from the 
 pen of Mr. W. Benson. These latter are entitled, re¬ 
 spectively, the “ Principles of the Science of Colour,” and 
 a “ Manual of Colour,” and deserve careful study. Nearly 
 all these works contain something about the singular con¬ 
 dition, to which we have been able to allude but cursorily, 
 known as Daltonism, or colour-blindness. 
 
 THE END. 
 
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