Nov. 20, 1884] 



NA TURE 



59 



based entirely upon the study of colouring matters, and 

 ignore altogether the fundamental distinction between 

 colour as a property of such matter, and colour in the 

 physiological sense of a particular affection of the organ 

 of sight. It is to the study of colour by means of colour- 

 sensations that our attention is directed ; and it is to the 

 synthesis and analysis of the retinal impressions that we 

 are to look for exact views on the relationships of the 

 colours. The distinction in question once stated is so 

 obvious that the author's claim for recognition of the new 

 system or method as the necessary complement of the 

 older will be at once admitted. But the author's aim is 

 not so much to obtain the intellectual assent of those 

 accustomed to the propositions of abstract science, as 

 rather to convince colour-artists of every denomination 

 of the direct utility of the method — to show them, in 

 fact, that it supplies the means of solving problems in 

 colouring with rapidity and certainty, and furnishes 

 valuable criteria with which to strengthen the aesthetic 

 judgment. 



The chief obstacles to the general acceptance of the 

 method lie in the erroneous views which underlie the 

 well-worn proverb, " II ne faut pas disputer des gouts et 

 des couleurs." While, in opposition to these tenets, the 

 author contends for the admission of more positive views, 

 and of the experimental method upon which they are 

 based, he very distinctly disclaims the idea of substituting 

 taste and artistic inspiration by a set of mathematical 

 rules. " Taste," he says, " must ever remain the supreme 

 judge of the aesthetic value of any combination of 

 colours." 



It is true that the artistic instinct confers upon its 

 possessor a comparative independence of the methodical 

 selection of colour ; but this instinct, or intuitive percep- 

 tion of harmony, is by no means an unerring guide, nor 

 without the influence of prevailing ideas. Most of these 

 are of necessity incomplete, and many are demonstrably 

 false : and the artistic instinct therefore needs develop- 

 ment and correction. In the abstract which we shall give 

 of the author's treatise, we shall give due prominence to 

 the evidences of these shortcomings. 



The elaboration of the empirical system still prevalent 

 we owe to Chevreul. It is based entirely upon the study 

 of colouring-matters, and its scales of colour-relationships 

 are purely arbitrary. The theoretical treatment of colour, 

 on the other hand, has been chiefly, and indeed neces- 

 sarily, confined to the investigations of the spectrum. 

 Early in this century, Young, the father of our modern 

 science of light, formulated a theory of colour-sensation, 

 a theory, that is to say, which co-ordinated the physical 

 phenomena of coloured light with the phenomena of its 

 appreciation by the eye. Colour, we know, is the expres- 

 sion of wave-length ; the sense of colour was referred by 

 Young to the agency of distinctive retinal nerves, each 

 endowed w ith the capacity of selective excitation by rays 

 of certain wave-lengths. He recognised, further, three 

 primary divisions of wave-lengths, corresponding to red, 

 blue, and yellow light. The later researches of Maxwell 

 have given results confirmatory of this view, and addi- 

 tional testimony to the wonderful insight of this great 

 philosopher. But we are not concerned at this moment 

 with the theories and speculations of pure science so 

 much as with the more practical question of the advan- 

 tage to the colourist of correcting impressions derived 

 from the empirical study of pigments, by the study of 

 colour in the light of their main results and consequences. 

 A very praiseworthy effort to bridge over the gap which 

 had so long existed between the science and the art of 

 colouring has been made by Prof, von Bezold in the pub- 

 lication of his work on the " Science of Colour." This 

 excellent treatise, in spite of its translation into English, 

 has, we think, not received the attention in this country 

 which it deserves ; this is accounted for in part by its 

 publication in America, but an equally powerful cause is 



to be found in the conservatism of those to whom it 

 appeals, in the jealousy of invasion by the forces of a new 

 method of a territory rendered sacred by inheritance. 



In both treatises considerable importance is attached 

 to the reduction of the various terms in conventional use 

 to the accurate expression of the ideas involved in the 

 scientific investigation of colour. This is a task of con- 

 siderable difficulty. 



M. Rosenstiehl finds the French terms especially diffi- 

 cult to handle. The three principal substantives nuance^ 

 teinte, and ton, he assigns — though with a confession that 

 his choice is somewhat arbitrary — to the three variables 

 respectively which determine a colour, viz. kind or quality 

 ifspece), intensity, and purity. In this choice he admits 

 that the terms ton and nuance may be said to have an 

 inverse relationship to that which they occupy in musical 

 language, but at the same time justifies the selection as 

 most in accordance with present usage, pointing out, 

 moreover, that the analogy between the ear and the eye 

 is so slender that it is not to be sought in the terms which 

 express their sensations. The translator of Bezold finds 

 himself called upon to accommodate himself in his treat- 

 ment of the subject to the use of the terms hue, tint, 

 shade. To avoid prolixity we give as the result of a 

 careful consideration of the terminology of both authors 

 the following definitions of essential terms : — 



(1) Colour in the sense of wave-length must be deno- 

 minated by hue. 



(2) The degree of brightness (French, intensite) we may 

 express by tint. 



(3) The degree of purity, i.e. non-admixture with white, 

 may be rendered by tone. 



It is obvious that (2) and (3) are, in regard to the 

 ordinary conditions of vision, interdependent variables, 

 for, as the intensity or illumination increases, the propor- 

 tion of white increases. 



It will be found on trial that, by means of these three 

 substantives, the essential factors of any colour may be 

 expressed. It is clear that habit will prevent our special- 

 ising the use of the word colour ; but we may limit its 

 use scientifically to the general expression of primary 

 distinctions, reserving the term hue to indicate specially 

 wave-length and variations in wave-length. There still 

 remains, however, the important word shade to dispose of, 

 amongst the substantives in conventional use, as well as 

 the numerous adjectives with which they have been 

 conjoined. 



The more general use of shade has been to express the 

 idea contained in (3), i.e. the toning of colours by addition 

 or removal of white, and this use may be retained. At 

 the same time, in order that our nomenclature may be 

 precise, we must obviously avoid such expressions as a 

 " red shade of orange, using instead " red-orange hue," or 

 even " red hue of orange," or again, " dark shade of 

 green," meaning thereby a green of medium tone perhaps, 

 but of low illumination ; the correct expression here would 

 be " a green, a dark or low tint " (couleur foncie). 



The term couleur sali/ree is applied by M. Rosenstiehl to 

 a pure colour, or the corresponding visual sensation : such 

 colours are obviously never met with in the arts ; those 

 which approximate to saturation he terms couleurs /ranches. 

 These adjectives are perhaps best translated by integral 

 and full respectively. 



The spectral hues are integral ; full colours or tones 

 are those which give the impression of quantity of colour. 



The term gamut or scale is used in two senses : first, 

 to indicate a graduated succession of tones, i.e. the 

 gradations of a given hue through its several tones to 

 white ; and second, a graduated succession of tints, or 

 the gradations of a given hue through its several tints to 

 black. 



The aesthetic samut or scale is the term applied by the 

 author to graduated modifications of one and the same 

 colour- sensation ; its special significance will become 



