218 On the Decomposition oJ'L^ght. 



green and violet, blue; the violet and red, purple: the 

 three together produce white; and lastly, the intermediate 

 shades are according to the proportional quantities of theit 

 elements. 



Bodies exercise a general action on all the rays of light, 

 and a particular one relative to their peculiar nature. If 

 the while pencil fall obliquely on the surface of a trans- 

 parent body, the rays, as they penetrate it, deviate from 

 their original direction, some more, others less, according 

 to their nature. Here we have a true analysis of white 

 light, in which its three simple elements may be found 

 separate, as well as combined, in different proportions. 

 It is thus that refraction exhibits a series of tints, which 

 differ, in different bodies, both with respect to their general 

 deflection, measured by its mean quantity, in the relative 

 dispersion of the rays, and in the particular position of 

 each colour. 



If the affinity of the body for the rays of light, be such 

 as to absorb some into its own substance, it will be coloured ; 

 and will exert a preferable ' or stronger action on certain 

 sorts of rays. In a small mass, the body will first absorb 

 these rays, to which it has a preferable affinity ; and, if its 

 action on the two simple kinds do not give a marked pre- 

 ponderance to one of them, it will be a nuxed combination, 

 that will first disappear. The mass of the body being 

 gradually increased, the destruction of the rays will go 

 by new mixtures, still progressively ; the kind least acted 

 upon will remain the last, and it will necessarily be one of 

 these three, red, green, or violet; after which no more light 

 will be transmitted. Such are the phajuoniena of absorp- 

 tion, and its different gradations. 



I shall give here one of the last results of my experiments, 

 which mioht h ive created some confusion had it been mixed 

 with the preceding considerations, yet lends to confirm their 

 principles. 



I had an inclination to try whether the light from a given 

 part of the single spectrum, combined with that of another 

 part chosen for the purpose, would produce white. 



To 



