CHAPTER XXVII.

COLOR.

[Sidenote: Why the sun’s light is white.]

[Sidenote: Made up of seven colors, as Newton showed.]

The light that comes from the sun is, you know, a white light. Now in this white light are the different colors of the rainbow. Indeed, it is these colors mixed together that make the white color of the sun’s light. This was proved by Sir Isaac Newton in this way: He had a hole in a shutter through which he let a very little of the sun’s light into a dark room. He had a screen for it to strike upon, and on this it made a bright white spot. He then let it shine through a three-cornered piece of glass, called a prism. This turned the ray of light out of its way, and made it shine upon another part of the screen; and, besides this, the spot of light on the screen, instead of being round, as it was before, was now lengthened out, and had seven different colors in it.

All this is represented on this figure. At O is the hole in the shutter, and _m_ is a mirror by which a little of the bright sunlight is thrown into this hole. Without the prism it would go straight to the screen, S _r_, and make a round white spot where the word _white_ is. But with the prism, P, the beam of light is turned out of its straight path, and is divided into the different colors as marked in the figure. The reason that these colors are seen so distinct from each other is, that they are bent out of their way in different degrees--the orange a little more than the red, the yellow a little more than the orange, and so on, the violet being most bent of all. You see this represented on the figure.

[Sidenote: Colors in ice.]

This and various other experiments, tried by Newton and others, show that the white light of the sun is not a simple thing. It can be cut up, as we may say, into different parts. The glass prism does this. You have often seen it done without thinking much about it. You have seen it done by ice. When there has been a rain, and the rain, as it fell, froze upon the branches of the trees, and the wind and the sun have together broken the ice on the trees, and strewed the ground with it, you have seen these pieces of the ice brilliant with all the colors into which they have divided the bright light of the sun. It seemed as if the ground was covered with gems of every hue; and as you looked up into the tree, it seemed to you that every twig also was strung with gems.

[Sidenote: The rainbow.]

[Sidenote: Colors in dew-drops.]

You see the same thing in the rainbow. The white light of the sun is separated by the drops of rain into its different colors just as is done by the glass prism, and thus the bow is made. Exactly how this is done you are not old enough yet to understand. What you see in the rainbow and in the scattered pieces of ice you can also sometimes see in the dew-drops in the morning. They sparkle with all the different colors. The grass seems to be filled with gems of every variety. The drops of dew do this by dividing up the sunlight, as the drops of rain do when the rainbow is made.

[Sidenote: Black no color.]

Now see how it is that different things have different colors. When a thing is white it is because all the different parts or colors of the light are reflected from it to our eyes. On the other hand, when a thing is perfectly black, it is because none of the colors are reflected. Black is, then, no color at all, while in white all the colors are mixed together.

[Sidenote: Newton’s experiments with a wheel and with powders.]

Newton proved that white is a mixture of all colors in a very pretty way. He made a wheel, on the edge of which he painted all the seven colors. When he whirled it round very fast indeed he could not see the colors separate from each other. The colors all went to his eye mixed up together, and being mixed, they made a white color, just as they do in a beam of light. The rim of the wheel then looked to him as if it was white.

He proved the same thing in another way. He took powders of these seven different colors, and ground them together very finely. The colors all disappeared. The mixed powder was almost white. It would have been entirely white if he could have mixed the powders as thoroughly as the colors are mixed by the Creator in the light of the sun.

But I have not yet told you how one thing looks green, another yellow, another blue, etc. I have only told you why one thing is black and another white. When a thing looks blue, it is because none but the blue part of the light is reflected to your eye. All the rest of the colors stop right there in the thing. They do not bound off from it as the blue does. So, when a thing is green, the green part of the light is reflected to your eye. When a thing is orange color, the orange part of the light is reflected, and so on.

[Sidenote: Why things have different colors explained.]

If you have pieces of glass, and let the light come through them, you see the same thing in another way. Light coming through blue glass comes to your eye blue, because all the other colors stop in the glass, while the blue passes on; and light coming through green glass is green for the same reason.

Now what is done with the colors that stay in things that they come to we do not know. If a thing looks blue, only one color out of the whole seven in the light is thrown off from it. The other six colors, red, orange, yellow, green, indigo, and violet, stop right there in the thing. What it does with them is a mystery. It puts them out of sight in some way, and sends only one of the seven colors to our eyes.

_Questions._--What makes the color of the sun’s light white? How many colors are there in a ray of the sun? Mention Sir Isaac Newton’s experiment. Tell what is represented by the figure. What does the glass prism do to the light? Tell about the colors of the scattered ice. How is the rainbow formed? Tell about the colors in the dew. When is a thing white? When is a thing black? Tell about Newton’s painted wheel. Tell about his mixture of powders. Explain how it is that one thing is blue, another green, another yellow, etc. How is it when light comes through things, as colored pieces of glass? What is said about the parts of the light that are not reflected by things that we see?