548 
SECOND REPORT -1832. 
ings on which it is founded; but he proceeds at once to analyse 
one leading phenomenon of colour, and he then applies this 
analysis as an experimentum crucis in determining the origin of 
all colours similarly produced. 
The colour chosen for this purpose was the green colour of 
the vegetable world, and this selection was made for the fol¬ 
lowing reasons : 
1. Because the green colour of plants is the one most preva¬ 
lent in nature; 
2. Because it is the colour of which Sir Isaac Newton has 
most distinctly described the nature and composition; 
3. Because its true composition is almost identically the same 
in all the variety of plants in which it appears. 
After determining the exact composition of this colour, the 
author concludes that the green colour of plants, whether it is 
examined in its original verdure, or in its decaying tints, has 
no relation whatever to the colours of thin plates. 
To the same mode of analysis the author submitted nearly 
150 coloured media, consisting of fluids extracted from the 
petals, the leaves, the seeds, and the rind of plants ; of the dif¬ 
ferent substances used in dyeing ; of coloured glosses of mine¬ 
rals ; of coloured artificial salts; and of different coloured gases: 
and in all these cases he obtained results which prove that their 
colours are not those of thin plates. 
From the experiments detailed in this paper, the author con¬ 
cludes that the second and leading proposition of Newton’s 
theory of colours is incompatible with the phenomena ; and he 
infers the incorrectness of the first proposition by stating the 
fact, that he has found red, yellow , green, and blue media 
which are absolutely incapable of reflecting or transmitting cer¬ 
tain definite rays of the same colour with themselves. 
The paper was concluded with a brief statement of what the 
author regards as the true theory of the colours of natural bo¬ 
dies. When light enters any body, and is either reflected or 
transmitted to the eye, a certain portion of it, of various re- 
frangibilities, is lost within the body, and the colour of the 
body, which evidently arises from part of the intermitted light, 
is that which is composed of all the rays which are not lost; or, 
which is the same thing, the colour of the body is that which, 
when combined with that of all the rays which are lost, com¬ 
poses the original light. Whether the lost rays are reflected or 
detained by a specific affinity for the material atoms of the body, 
has not been rigorously demonstrated. In some cases of opa¬ 
lescence they are either partly or wholly reflected; but the 
author considered it as almost capable of demonstration, that 
