COLOR. 
Definition. 
Color is a visual sensation, caused by waves of 
incomplete light acting upon the eye. 
Cause of 
color. 
Most objects have the property of reflecting certain 
rays of light and absorbing all others. The color of 
an object is the remaining portion of white light after the abstraction 
of those rays which are extinguished by absorption. 
Source of 
color. 
Light is the source of all colors, and where there is 
no light there is no color ; an effect of color is, how- 
ever, sometimes produced by unduly exciting the optic nerve, either 
by electricity, pressure, or a blow upon the eye. In teaching color 
we have nothing to do with this phenomenon, as it belongs entirely 
to the realm of the physicist. 
Light. 
Light is a vibratory wave motion of a medium called 
ether, which fills all space. Its motion is similar to 
that caused by throwing a stone into a pond, only the waves of light 
are infinitely small and of short duration, there being for red about 
39,000 of them in the space of an inch, and about 667 trillions of 
them are executed in a second of time. '* These waves break upon 
the surface of the retina and cause the sensation of sight." 
Ray of light . * 
Beam of light. 
A ray of light is a small linear portion of light. It 
may be of any color. 
A beam of light is a linear portion of light composed 
of a number of ravs. 
Prismatic 
colors. 
White light, that is, sunlight, is composed of vaiious 
colors, as is easily shown by placing a prism in the 
path of a small beam of sunlight. The prism separates the different 
colors that compose white light, and produces what is known as the 
prismatic or solar spectrum, as shown in the illustration. 
ORANGE 
These colors are the same, and their arrangement is in the same 
order, as in the rainbow. 
Objects have no color in themselves, but they possess the power 
of reflecting waves of light ; and it is the waves of light of varying 
lengths that give us the effect of color. 
It is the amount of motion of the ether, or height of the wave, that 
produces the intensity or brightness of the light, and the length of 
the wave that produces the color ; thus red has a wave length of 
about 2 5o 7 oo°o ooo of an inch, orange ^somoooo, yellow s^ooooo, green 
__ 6 27 2 _ 
250000009 1 
blue 2 50000000; and violet ^soodoooo' 
