432 ON THE THEORY OF COMPOUND COLOURS. 



another in the perception of colour. The standard colours are connected by the 

 following equation, as determined by six observations : 



18-l(24) + 27'5(44) + 37(68) = W* (17). 



The average errors in these observations were 



TABLE VIII. 



R, -28 

 G, -83 

 B, -16 



G + B, -83 

 B + R, -42 

 R + G, -95 



G - B, -83 

 B-R, -28 

 R-G, -72 



R + G + B, -95 



shewing that in this case, also, the power of distinguishing colour is more to be 

 depended on than that of distinguishing degrees of illumination. 



The average error in the other observations from the means was "64 for red, 

 76 for green, and 1'02 for blue. 



TABLE IX. 

 Observations by J., October 1859. 



XIII. Comparison of ResuUs by Newton's Diagram. 



The relations of the colours, as given by these observations, are laid down 

 in fig. 5, Plate VI., p. 444. It appears from this diagram, that the positions of 

 the colours lie nearly in a straight line from (24) to (44), and from (48) to (60). 

 The colours beyond (60) are crowded together, as in the other diagram, and 

 the observations are not yet sufficiently accurate to distinguish their relative 

 positions accurately. The colour (20) at the red end of the spectrum is further 



