134 EXPERIMENTS ON COLOUR, AS PERCEIVED BY THE EYE, 



But 78 pc must be divided by 1'97, to reduce it to PC, as was previously 

 explained. The result of calculation is, therefore, 



39 PC + '22 U + '39 Bk = '58 V + "42 EG, 

 the black being introduced simply to fill up the circle. 



This result differs very little from that of experiment (3), and it must be 

 recollected that these are single experiments, made independently of theory, and 

 chosen at random. 



Experiments made at Cambridge, with all the combinations of five colours, 

 shew that theory agrees with calculation always within - 012 of the whole, 

 and sometimes within 0'002. By the repetition of these experiments at the 

 numerous opportunities which present themselves, the accuracy of the results 

 may be rendered still greater. As it is, I am not aware that the judgments 

 of the human eye with respect to colour have been supposed capable of so 

 severe a test. 



Further consideration of the Diagram of Colours, 



We have seen how the composition of any tint, in terms of our three 

 standard colours, determines its position on the diagram and its proper coefficient. 

 In the same way, the result of mixing any other colours, situated at other 

 points of the diagram, is to be found by taking the centre of gravity of their 

 reduced masses, as was done in the last calculation (experiment 3). 



We have now to turn our attention to the general aspect of the diagram. 



The standard colours, V, U, and EG, occupy the angles of an equilateral 

 triangle, and the rest are arranged in the order in which they participate in 

 red, blue, and green, the neutral tint being at the point w within the triangle. 

 If we now draw lines through w to the different colours ranged round it, we 

 shall find that, if we pass from one line to another in the order in which they 

 lie from red to green, and through blue back again to red, the order will be 



Coefficient. Coefficient. 



Carmine ..... 0'4 



Vermilion . . . . . 1 



Red Lead 1-3 



Orange Orpiment . . . 1-0 



Orange Chrome . . . 1 -6 



Chrome Yellow . . . 1-5 



Gamboge 1-8 



Pale Chrome .... 2-0 



Mixed Green (U C) ... 0-4 



Brunswick Green . . . 0'2 



Emerald Green . . . . I/O 



Verditer Blue .... 0-8 



Prussian Blue . . . . " 1 



Ultramarine 1 '0 



