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will the eye, in looking on a green objed, be at once afFcded by 

 blue and yellow raysj and therefore become infenfible to them 

 both; and confequently the fpedrum will appear red. But if 

 green be a primitive, original colour, generated by its own peculiar 

 green-making rays, the eye in contemplating a green objed, will 

 become infenfible only to the green rays ; and therefore the other 

 fix prifmatic colours, which are fpecifically different from the 

 green, ought to be fenfible, and produce their proper compound 

 effed-, but this would not be the fenfation of red. In like 

 manner, if the obje(5l be yellow, the eye will at length become 

 infenfible to the yellow-making rays, and the fpedlrum will be 

 violet. Now fince on the hypothefis of feven original colours, 

 the orange and green are primitive, though the eye be rendered 

 infenfible to the yellow rays, it will not be fo to the orange and 

 green, which therefore, together with the red, blue, violet and 

 indigo will produce their compound efi'ecfl ; but the colour re- 

 fulting from this joint adion is not violet, which neverthelefs is 

 the colour of the ocular fpedlrum. On the other hand, if there 

 be but three primitive colours, red, yellow and blue, when the 

 eye is infenfible to the yellow-making rays, the fpedrum mufl 

 necefiarily be violet, which is the colour that refults from the 

 mixture of red and blue. If it be objeded, that the eye is not 

 only infenfible to the unmixed yellow rays, but likewife to the 

 yellow of the orange and the green, then it is admitted that 

 orange and green are compound colours. Ecfides, finq^ the co- 

 lour which would refult from the mixture of red, orange, green, 



blue, 



