215 



illumination, therefore it will appear relatively grey under any given 

 external illumination. 



The author then status, that the tri:ingular arrangement of colours 

 first proposed by Mayer, and farther carried out by Lambert, appears 

 to afford the clearest and truest mode of displaying at a glance the 

 modification of colour due to the varying proportion of the three 

 primary elements. In this triangle, perfect red, yellow, and blue, 

 occupy the three corners ; and these colours graduate into one another, 

 according to the simple law of the distance of any point in the tri- 

 angle from the three corners. The sides of the triangle are occupied 

 by binary colours or compounds, by two and two ; the interior is 

 occupied by triple compounds ; and the centre of gravity of the tri- 

 angle ought to be a neutral grey. 



Hence it will appear, that any hue not purposely diluted with 

 black or white, as composed of a compound of a binary colour with 

 neutral grey. Hence a convenient nomenclature suggests itself as 

 follows : the first column containing the binary colours. 



These colours are supposed to be of the standard or maximum at- 

 tainable intensity. 



They may be diluted with white on the one hand, forming tints; 

 or with black, forming shades. 



Mayer's triangle may be repeated with these modifications ; but 

 as the colour tends to extinction, either in the direction of perfect 

 blackness or perfect whiteness, the number of compartments in the 

 triangles may be diminished as the dilution of the colours increases. 

 Thus, the whole may be formed into a double pyramid of colour, con- 

 verging to white above and to black below. 



The author has been much indebted to Mr D. R. Hay, the inge- 

 nious author of the " Nomcnlature of Colours," and other works, not 



