  It is a great pity that exquisitely beautiful facts and mysteries are wrapped up in the crack-jaw terms of foreign languages, and so made to appear ugly. There is no branch of knowledge more fascinating than light. To follow up its study is like walking along a shady lane, where at certain distances apart the wayfarer lights upon jewels of great brilliance. It has been said above that white light is formed by the union or combination of seven colors. When a ray of light passes through a prism it is split up into the parts of which it is composed, and seven colors as in the rainbow appear. These colors shade off into one another with every variety of tint, like a band of rainbow-colored ribbon. This band is called a spectrum. Now, where science classes are held there may be seen a complicated instrument, which is used to show how the seven colors unite to form white light. It is a disc on which the colors of the spectrum are painted, and it is made to spin round with great rapidity. The impression received by the eye, when looking at the revolving disc is total abstinence of color. In other words it is white light. Fortunately, you can satisfy yourselves on this point without any other materials than a cardboard disc and a piece of string. On this disc paint in small sections the That the experiment may be entirely successful, the sections must be marked off according to the following scale of width of section. Let orange, next to the circumference represent 2: then
Now, in any diameter of the disc bore two holes not too near the edge. Through them pass a piece of string, and knot the two ends together. Take hold of the string with both hands, and make the disc spin round. Then extend and approach the hands alternately to give a very rapid movement to the disc. When revolving rapidly enough you will not be able to distinguish the separate colors. They all become blended into white light. | |||||||||||||||||||||
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