SCIENCE 
IS 
KNOWLEDGE. 
KNOWLEDGE 
IS 
POWER. 
A PRACTICAL JOURNAL OF 
HOME ARTS. 
Vol. IV. 
NEW YOKK, APEIL, 1881. 
No. 4. 
Color. 
F we admit a beam 
of ordinary white 
liglit (sunlight) into 
a darkened room, 
and let it fall upon 
a triangular prism, 
it will be separated 
into different kinds 
of light, and these 
received upon a 
white screen will 
give us the solar 
spectrum with its 
familiar rainbow 
colors. It is thus 
separated because the shortest light waves 
are deflected more from their original 
course by the prism than the longest 
waves. 
Accordingly we find the red light least 
refracted, and following it in succession 
come orange, yellow, green, blue, and 
violet, the last being at the opposite end 
from red. Indigo as a distinct color of the 
spectrum is now disregarded. If we select 
\y)j the most careful process a beam of one 
of the colored lights from the spectrum, 
and let it fall upon a second prism, we 
shall find that it remains unchanged ; 
therefore, these colors being incapable of 
further analysis, have been called primary 
colors. We can, however, produce any 
of these colors by a proper combination 
of three of them, viz. : red, green, and 
violet, which Dr. Young first pointed 
out as the true primary colors. It is still 
an open question whether violet or blue is 
to be considered as the third member of 
the group. Eed, blue, and yellow cannot 
be regarded as primary colors, for it is 
impossible to produce green light by the 
combination of blue and yellow light; 
they produce white light. On the other 
hand, yellow light results from the mix- 
ture of red and green light; blue light 
from the mixture of green and violet, and 
orange from red and yellow; so that we 
have thus all the colors of the rainbow. 
Since red, green, and violet can be thus 
combined, they can, of course, also be 
so combined as to reproduce white light ; 
but white light can be obtained not only 
by combining these three directly, but 
also by combining yellow and a proper 
hue of blue, since blue is composed of 
