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let (Hoffman's violet-B. B.). If this color cannot be found, buy "Nuremberg violet." Get these shades, and no others, and then cut out three narrow strips of cardboard, and give one a coat of the red, one a coat of violet, and paint the other green. Take pains to give them a good thick coat, so as to hide the white paper. Study the solar spectrum on the screen carefully, and you will see that these shades of red, green, and violet, are in it. When the painted strips are dry, take the red vermilion strip and hold it in the spectrum at the left or red end, and you will see that it matches the red exactly. Tip the paper backward a trifle so that the surface of the paper will not shine or glisten in the light, and then move it slowly to the right, keeping it before the spectrum. As it passes the orange it grows dark; in the yellow it is darker still; opposite the green it is perfectly black. Move it to the very end, and everywhere the red strip is quite black. Place it before the red again, and its color comes out clear and bright. Try the violet strip in the same way. In the same manner, the green strip is green when it is in the green part of the spectrum, and black everywhere else.

This experiment shows that green, red, and violet, are visible in green, red, and violet light, and that in light of any other color they are invisible, and the

strip of card appears to be black. Hence, an object appears of its proper color because it absorbs all colors of the white light except its own color which it reflects.

Look at the spectrum closely, and you will notice that the red is at one end, the green near the middle, and violet is at the other end. Between the red and the green you will notice many shades of yellow, from deep-orange to yellowish-green, and between the green and the violet are many shades of blue, from greenish-blue to deep indigo.

It is thought that, when we see a red light, certain nerves in the eye are affected, and convey a peculiar sensation to the brain, that we call red. These nerves are sensitive to red light, but are not sensitive to any other light, except in a moderate degree. Another set of nerves in the eye are peculiarly sensitive to green light, and still another set are affected by violet light. Hence the sensations caused by these three colors are called the three elementary color sensations, and from the combinations of these sensations come all countless shades of color. When one of these colors falls on the eye, we see it distinctly. When two-say the red and greenmeet the eye, both sets of nerves are affected at

once, and we get a sensation that is neither red nor green, but yellow. In the same manner, when green and violet meet in the eye, the two sets of nerves are excited, and we see not green and violet, but blue. In the same manner, if red, green, and violet light enters the eye, all the nerves are excited at once, and we see not three colors, but one, which is white.

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This diagram will assist us to remember the relation the color sensations bear to each other. The red and the green combine to make yellow; the green and the violet unite to make blue; all three mingled

together give us white. We may also combine red and violet light, and get purple light.

THE COLOR-TOP.

This picture represents a common iron top, that may be found at the toy-shops. If you cannot find .

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one exactly like it, there are others having a straight handle at the top, instead of the curved handle.

Just under the flat part of the disk are two or three round pieces of drawing-paper, and under these is a thick disk of pasteboard. Each of these has a hole in the centre, so that it can be slipped over the leg of the top. In some tops, however, it may be easier to put these disks above on the handle. Such a top as this may be made to spin in a dinner-plate on the table by winding a string round the leg, and then pulling it away with the right hand, while the top is held upright by the left hand.

Get some thick drawing-paper, and cut out three disks, each 4 inches (10 centimetres) in diameter, and make a hole in the centre of each, so that it will slip over the leg of the top. Cut each disk open from the circumference to the centre with a pair of scissors. Paint one with the red vermilion, one with the emerald-green, and the other with the violet that we used in the last experiment, and then, while these are drying, make a disk of thick pasteboard, and cut a hole in the middle, so that it will slip tightly over the leg of the top.

When these are ready, take the red and green disks and hold them side by side with the cut places opposite, and slip one into the other, and then turn them round, so that the green covers the red. Then put them both on the leg of the top, and put the

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