Sir Isaac Newton first divided a white ray of light, and found it to
consist of an assemblage of coloured rays, which formed an image upon a
wall, and in which were displayed the following colours: red, orange,
yellow, green, blue, indigo, and violet. Sir Isaac then showed that
these seven colours, when again put together or combined, recomposed
white light. This may be proved by painting a card wheel in circles
with the above colours, and whirling it rapidly upon a pin, when it
will appear white.
Light may also be decomposed by the following beautiful experiment:
Form a tube about ten inches long and one inch in diameter, of paper,
one side of which is of a bright blue colour. This may be done by
wrapping the paper once round a cylinder of wood, and securing the
edges of the paper with paste. The coloured side of the paper must be
the interior of the tube. Apply this tube to one eye, the other being
closed, and on looking at the ceiling, a circular orange spot will be
seen, which is the result of decomposition: the white light from the
ceiling enters the tube, the blue is retained, and the red and yellow
rays enter the eye, and produce the impression of orange.