OA MEMOIR ON COLOURED SHADOWS. 



obferved ; thefe are capable of Aiewing all the colours of 

 the prifm ; in fad, we fee red, orange, yellow, green, blue, 

 indigo and violet, more or lefs blackened. 

 Number of The number of thefe thadows is almoft always two or three, 



ihadows. fometimes four or five; it has even happened that we have 



didingu idled fix. 



When thefe fhadows are two in number, the colours they 

 prefent are always thofe called complemmtary colours. 

 Combination of The infinite variety' of colours obferved in the folar fpec- 

 tTtrthe follT' ^'■""^ *"^y ^® imperfeaiy imitated by combining different pro- 

 fpeftrum. portions of the natural colours, red, yellow and blue ; and, 



according to the obfervations of Newton, an artificial white 

 may be formed, by mixing thefe^three colours. Tjpofe co- 

 Complementary lours are denominated complementary, which muft be made 

 colours. ^jj^j^ one or two of the tiiree colours cited, to produce an ar- 



tificial white with a given colour. 



To obtain an artificial white with a red, the yellow and 



blue muft be mixed with it. The yellow and blue make a 



green, green is therefore the complementary colour of red, 



and vice vcrfu. 



The complementary colour of the orange formed by yellow 



, and red is the blue. 



The complementary colour of yellow is violet. 

 The term does As the complementary colours meet together in a great 

 Ne J?o^nTa« '^^ number of cafes, we have thought it neceOary in the outfct 

 theory oi the to give them that denomination, which makes no change in 

 folar light, ^^^Q rgfults, by which Newton proves that the folar ray is 



compofed of an infinity of homogeneous coloured rays. 



If the fpe6lrum is divided into two parts at the point where 

 the green commences, all the homogeneous rays of the lower 

 part, that is tq hy, from the beginning of the red to the be- 

 ginning of the green, are complementary to thofe of the upper 

 part, that is to fay, from the green to the violet ; and that in 

 the natural order of their appearance. 



The denomination of complementary colours has no other 



object but to point out two colours which are found together 



very frequently ; and to avoid, by this fimple medium, the 



circumlocution which their diftinc^ion would lead to. 



Complementary Whenever two coloured fhadows are feen, they are nearly 



colours of tsvo ajy^^ays complementary to each other; that is to fay, if the 



* fliade of one is red, orange, or yellow, that of the other is 



green, blue, or violet, 



5 When 



