550 



THEORY OF COLORS. 



In the same manner, throughout the whole extent of the three uniform spec- 

 tra thus intermingled the tints of color will correspond to the intensities of the 

 spectra at the same point. 



In this manner the succession of colors exhibited by the prismatic spectrum 

 is explained. The orange, for example, is only the intermixture of a consid- 

 erable quantity of red and yellow, qualified by a small quantity of blue. The 

 green, in the same manner, is a mixture of a considerable quantity of blue and 

 yellow, qualified by a very small quantity of red. 



There is a certain proportion in which these three elementary colors may 

 be mixed together so as to produce white. If any one of them, the red, for 

 example, be in excess above this proportion, the other two observing it, the re- 

 sulting color will be a red diluted with white. If, on the other hand, there be 

 a deficiency of the proper proportion of red, the tint will be green diluted with 

 white, produced by the excess of blue and yellow. 



In general, if we take the actual proportion in which these three elementary 



Now, if we suppose a beam of white light, like the natural light of the sun, 

 which is composed of these three constituent elementary lights, to be transmit- 

 ted through the prism, we ought to expect these three spectra of the element- 

 ary colors, red, yellow, and blue, to be simultaneously produced, the maximum 

 of each being at the place already assigned to it. The combination of these is ] 

 represented in the diagram, fig. 7, and the tint of color at each point of the } 

 spectrum will be that which would result from the corresponding mixture of col- 

 ors. Thus at R N, where the red is most intense, a portion of blue, represent- 

 ed by N b, and of yellow, represented by N a, are mixed with it, and the re- 

 sulting tint will be that which will be produced by the mixture ; in like man- 

 ner at Y N, where the yellow is most intense, a portion of blue, represented 

 by N b' and a portion of yellow, represented by N a', will be mingled 

 with it. 



Fig. 7. 



