6 
molecular attractions, and these may have some influence 
in the distribution ; in other words, it is possible to conceive 
that the particles will distribute themselves with some bias. 
Here again it seems to me that so far from such speculations 
on the intensity of colour of mixtures being fruitless, they 
may even extend the application of colorimetry ; for while 
experimental agreement with the theory would strengthen 
the theory, even negation would have its value, and an 
investigation into the departures from the law might lead 
to interesting results, and give some insight into the opera- 
tion of those molecular forces which separately elude 
observation, but whose joint effect must necessarily have 
some influence in determining the intensity of colour. 
Some of the above reasoning applies to the case of turbid 
liquids, and I was led to the conclusion that a carbon diffu- 
sion would behave with regard to the extinction of light in 
the same manner that it would do if the carbon were actu- 
ally in solution. The only difference in the reasoning is, 
that the different series of carbon points, instead of falling 
on one section, are distributed through a series of circular 
sections of the containing cylinder, these sections being 
parallel to the external white surface. As I have shown in 
another paper, the results of the experiments agree very 
well with the theory. So far I have considered the intensity 
of the residual whiteness when we mix black with white. 
The same course of reasoning might be applied to determine 
the residual colour when we mix black with any colour. 
Suppose, for instance, we take a mass M of yellow and let 
the initial yellow be Yo. Then, if we mix with it a mass 
m of black, we shall remove some fraction of the yellow ; 
let this be denoted by nYo, so that the residual yellow is 
Yo(l — n), or YoR After n repetitions according to the 
proportions laid down in the case of black and white, the 
intensity of the residual yellow will be YoR*. 
Another problem is the mixture of white with some 
