198 PHYSIOLOGICAL BOTANY. PART II. 



In these three mixtures of the binaries, we have respect- 

 ively the three original colours, Y, 11, B, combined with 

 N. And thus, if N be white light a restoration of the 

 three original primaries is effected, but if (N) represent 

 grey, obtained by mixing material colours, then the 

 three primaries will appear dull or "impure." This dull 

 appearance always results from the mixture of any two 

 material colours, however brilliant or "pure" they may 

 naturally be. These remarks are perhaps sufficient to 

 show that all brilliant or " pure " colours may be con- 

 sidered equally as primaries or binaries, combined with 

 a greater or less proportion of white light ; whilst all 

 dull or " impure " colours result from mixing pure 

 colours with grey. In order to obtain any truly bril- 

 liant tint we must procure our colour from some na- 

 tural substance and not form it by admixture. Such 

 pure colours are comparatively rare in nature, and even 

 those which approach the nearest to brilliancy gene- 

 rally contain more or less grey. Although it is par- 

 ticularly difficult to obtain either of the three colours 

 which we have adopted as our primaries perfectly pure 

 from admixture with one of the other two, we may 

 state our theory and then we must practically contrive 

 to make as close an approximation to such a scheme as 

 the nature of the case will admit. 



It will be evident, that any pure colour in nature, 

 when reduced to the same shade as those in our scale 

 {fig. 154.), will either exactly coincide with one of the 

 twelve basial colours or lie between two which are 

 contiguous. Thus a colour whose composition is 5 B 

 -f 3 Y, lies between (B + Y) and (2 B + Y), and its 

 exact position may be ascertained, by forming fresh 

 combinations between these two colours and their re- 

 sultants as before described. Thus, 



Since (2 B + Y) and (B + Y) are contiguous in the third circle, 



So will (2 B + Y) (3 B + 2 Y) (B + Y) be in the fourth, 



And (2 B + Y) (5 B -I- 3 Y) (3 B + 2 Y) (4 B + 3 Y) (B -4- Y) in 



the tilth, &c. 



