GENERAL ORISMOLOGY. 21 



He considered three of the seven prismatic colours as simple primary 

 colours ; viz. blue, red, and yellow, and adopted them as the basis of 

 his whole system, seeking their correspondent affinities in nature. Blue 

 conducts on the one side to black, yellow to white. From the admix- 

 ture of equal parts of the approximate colours, two new ones arise ; viz. 

 violet, from blue and red, and orange, from red and yellow ; green is 

 excluded, it being treated as the unnatural and irregular union of two 

 colours removed from their true places (!). Thence we have the fol- 

 lowing series : 



Black, blue, violet, red, orange, yellow, white. 



This series he inscribes upon a scale, divided into sixty equal parts ; 

 he places white at 0, and proceeding from 10 to 10, consecutively 

 arranges them all. The modification, in the union of two approximate 

 colours, is determined by their relative numerical power ; for example, 

 five parts black, and five blue, give black-blue ; eight parts black, and 

 two blue, give a very deep black-blue (bleu noir triple), &c. By this 

 means, he obtains sixty different gradations of colour, which, we admit, 

 frequently suffice for the description of natural colours, but do not cer- 

 tainly extend to all, for all unions of black and red, red and white, 

 black and white, are wanting. This table is also rendered excessively 

 defective by the entire omission of green, one of the most prevailing 

 colours, and in the most variable gradations, throughout nature. 



28. 



Eight primary colours are generally adopted in Natural History ; 

 viz. white, grey, black, brown, red, blue, green and yellow. Each of 

 these colours admit of being mixed with others, and even some of those 

 named are produced by the union of two of the rest. It is, therefore, 

 evident, how excessively variable must be the effect of such mixtures 

 of colours, and how very closely they approach to and pass into each 

 other, so that the precise distinction of each change would be an 

 ungrateful and useless task. 



The degrees and intensity of colour are also very variable. 



The following terms are in use to express some of them : 



DEEP (saturate), when colour is very intense or thickly laid on. 



PALE (dilute), when but slightly coloured. 



BRIGHT (Icete), when the colour is clear and vivacious. 



FADED (obsolete), when it appears as if faded by the air. 



SORDID (sordide), when the colouring is impure, and as if clouded 

 by the admixture of another. 



