dt Prof. Maxwell’s Account of Experiments on 
from the mean of that group was -92. No observation was 
attempted to be registered nearer than one degree of the top, 
or gp Of a circle ; so that this set of observations agrees with 
the theory of three primary colours quite as far as the observa- 
tions can warrant us in our calculations; and I think that the 
human eye has seldom been subjected to so severe a test of its 
power of distinguishing colours. My eyes are by no means so 
accurate in this respect as many eyes I have examined, but a little 
practice produces great improvement even in inaccurate observers. 
I have laid down, according to Newton’s method, the relative 
positions of the five positive colours with which I worked. It 
will be seen that W lies within the triangle V U G, and Y out- 
side that triangle. 
The first combination, equation I., consisted of blue, yellow 
and green, taken in such proportions that their centre of gravity 
falls at W. 
In equation II. a mixture of red and green, represented in 
the diagram by the point 2, is seen to be equivalent to a mixture 
of white and yellow, also represented by 2, which isa pale yel- 
low tint. 
Equation III. is between a mixture of blue and yellow and 
another of white and red. The resulting tint is at the inter- 
section of YU and W V;; that is, at the point 3, which repre- 
sents a pale pink grey. 
Equation IV. is between V G and U Y, that is, at 4, a dirty 
yellow. 
Equation V. is between a mixture of white, red, and green, 
and a mixture of blue and yellow at the point 5, a pale dirty 
yellow. 
Equation VI. has W for its resulting tint. 
Blue, U. 
G, Green, 
Of all the resulting tints, that of equation IV. is the furthest 
Oe 
