49 
scriptions; which is the less a wonder, as everyone endeavouring at the 
same effect hits on tliu same causes : but a trifling mistake in conjec- 
ture, liowever, keeps us in that darkness which time alone disperses 
to show true light and colours, 
C. A. Prieur says, " I remarked that, under certain circumstances, 
the colours exhibited by refraction were almost wholly these three, 
red, green, and violet; that sometimes yellow appeared to arise from 
a mixture of red and green ; and blue from a mixture of green and 
violet." This is, in my opinion, really unmixing what were previously 
mixed ; or, properly, substituting a broader light, naturally or arthi- 
cially, instead of a narrow one: see it partly expressed in (ab. 4. c. d. 
He in another place observes, " How is it that the rays, when taken 
in pairs from the extremities of every diameter of the dial, that is, 
from any two opposite points, shall always form the same white ? 
A certain red with a green gives white; and an orange with a bhie, 
the same ; and a violet with a yellow, also." It will be found that it 
is easy to make either or all of them produce white, if it is proper to 
call it white, which will depend much upon the velocity, or something 
else ; and in material colours they may be more simply termed, and all 
formed of yellow, red, and blue. 
First, Red with green, which is formed of yellow and blue, give 
white. 
Second, Orange, which is formed of red and yellow, and blue, 
which mixing with the yellow of the orange make a green like the 
first, so that orange and blue are tantamount to red and green. 
Third, A violet with a yellow. Red and blue form violet, the 
blue of which mixed with the yellow are green; and therefore each 
being in the same proportion, when mixed, form the same colour. 
This is so distinct and simple, that it is amazing that there should 
appear any ditHculty to so discerning a gentleman. 
I must further observe that each mixture would be a light or 
darker grayish, brownish or blackish white, depending upon the 
H 
