§ 46. NUMBER OF THE PRIMARIES. 69 



enumerating the secondary ones, there seems to be no reason 

 for subdividing one of them, as the purple — into two, " purple 

 and violet ; " one of these being a gradation of the secondary- 

 colour composed of red and blue, instead of the one result of 

 that union. Though it has been determined by philosophical 

 experiments that the prism, or the rainbow, contains seven 

 colours, it is much more simple for practical purposes to con- 

 fine the number to six, viz. the three primaries and their 

 three intermediate compounds. Indeed, if two be admitted 

 between red and blue, two should be admitted between red 

 and yellow ; and also between blue and yellow ; which would 

 increase the number to nine. The actual number, however, 

 is of little importance in the use of colours ; a more essential 

 point is to define the character of each, that we may under- 

 stand what we mean in mentioning its name ; and that, in 

 speaking of a red or a yellow, we may not convey the idea of a 

 pink, or of a canary-colour. 



Experiments which prove that the prismatic colours are 

 "red, green, blue, and violet," or according to Dr. Young, 

 that " red, green, and violet are the fundamental colours," and 

 that " the perfect sensations of yellow and blue may be pro- 

 duced, the former by a mixture of red and green, and the 

 latter by green and violet," can be of no use in the har- 

 monious combination of colours for ornamental purposes ; nor 

 can any observations on the relative position and quantity of 

 colour resulting from philosophical speculation be taken as 

 guides in polychrome decoration. 



orange into yellow," and so on with the rest. For a body to exhibit truly its 

 colour it must be placed in white light. " A red wafer," as Brewster observes, 

 appears red in the white light of day because it reflects red light more copiously 

 than any of the other colours. If we place a red wafer in yellow light it can 

 no longer appear red, because there is not a particle of red light in the yellow 

 light which it could reflect." In like manner any other coloured body reflects 

 the rays corresponding to its own colour. " The colours therefore of bodies 

 arise from their property of reflecting or transmitting to the eye certain rays of 

 white light, while they stifle or stop the remaining rays." 



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