LIGHT.
*43
The accompanying figure represents a chromatrope
with an arrange¬
ment for quickly
replacing one
disk by another
of different pat¬
tern. Rotation
is given by fric¬
tion pulleys.
With this form
there is a disk
with the so-called
seven primary
colors to illus¬
trate Newton’s
theory of colors, 3. & <3 4
one to illustrate Brewster’s theory, two to illustrate
Young’s theory, and a chameleon top, designed by
President Morton, of Stevens Institute, Hoboken.
The effects with all the forms of chromatropes are
due to persistence of vision.
Interesting subjective effects may be observed by
projecting in the ordinary way bits of colored glass an
inch or two square, so as to have upon the screen a large
patch of color with a boundary of white light. The eyes
must be fixed attentively upon the colored patch for
about half a minute, when the colored piece must be
quickly removed, the eyes to be kept meanwhile upon
the screen. To prevent the eyes from unconsciously
wandering while looking, it will be found advisable to
pin a large black button or a piece of black paper to
the screen in the middle of the disk. This is to be
kept in the centre of vision. The effects observed will
of course depend upon the color upon the screen, and