Prof. J. D. Forbes on the Classificalion of Colours. 178 



each *. The analysis he employs is the absorbing power of 

 media, for these colours are (as is well known) undecomposable 

 by refraction. 



Various attempts have been made to carry out Mayer's 

 principle of compounding colours from red, yellow and blue, 

 and some elaborate attempts have been made to obtain model 

 suites of colour. I shall at present only refer to Mr. D. R. 

 Hay's ingenious work called Nomenclature of Colours, which 

 he has illustrated by a very large number of selected hues and 

 shades all compounded from lied. Yellow and Blue, variously 

 diluted with Black and White, which, from Mr. Hay's skill 

 in the choice and use of colours, are probably as pure and 

 vivid as we can expect to produce in the present state of art. 

 It is unnecessary here to speak of the taste and skill with which 

 the harmony and contrasts of colour are used and illustrated 

 in the plates to iiis work. 



As a mere classification of colours, Mr. Hay's work does 

 not adopt the simplest form ; nor is the nomenclature, I con- 

 ceive, by any means free from objection. It would be difficult, 

 for instance, to refer any required colour to its place in a com- 

 plete system of hues and shades by merely looking over Mr. 

 Hay's plates. The specimens which have the closest affinity 

 are often widely separated ; but then the object, a purely 

 artistic one, was different from ours. The mixtures used by 

 Mr. Hay in his gradations of colour were made, I understand, 

 by the eye, and not by weight; but an experienced eye will 

 perhaps make a gradation at least as good as a quantitative 

 one. The dilutions with white (or tints, as Mr. Hay calls 

 them,) appear to be less perfect in this respect. 



The primary colours in Mr. Hay's work are red, yellow 

 and blue, or those which occupy the angles of Mayer's triangle, 

 fig. 1. They are composed of carmine, chrome-yellow, and 

 French ultramarine. 



The secondary colours, or orange, green and purple, with 

 their gradations into their component primaries, exhaust all 

 the combinations two and two of the primaries, embracing all 

 the colours of the spectrum, and are represented by the ex- 

 terior row of colours in Mayer's triangle. 



The combination of colours by three at a time leads to more 

 complexity, and the advantage of Mayer's system is here most 

 evident. Mr. Hay, following Field, calls tertiary colours 

 those produced by a union of the secondaries : thus — 

 Orange and green form Citrine, 

 Orange ... purple ... Russet, 

 Purple ... green ... Olive. 

 * Edinburgh Transactions, vol. xii. 



