EXPERIMENTS IN CONTRASTED COLORS.

Cut out three pieces of drawing-paper about 2 inches (5.1 centimetres) square, and paint one red, another green, and another violet, using the paints we bought for the color-top. If these are not at hand, cut out squares of red, green, and violet paper, and squares of yellow, pink, blue, or any other colors you can obtain. Lay a piece of black cloth on a table, near the window, and then sit before it with your back to the light, and place the red square of paper on the cloth. Take a sheet of white or, still better, lightgray blotting-paper in the right hand, and hold it just above the red square in such a position that it can be quickly slipped over it, so as to hide it from sight. Now look steadily at the red square for a minute or two, and then slip the gray paper over it. In a few seconds there will appear on the gray paper a curious image just the size and shape of the red square, but of a bluish-green color. It will grow brighter quickly, and then fade away, leaving nothing but the gray paper. Put the green square on the black ground, and, after looking at it for a moment, cover it with the gray paper, and a pink image of the square will seem to shine out of the gray paper for a moment, and then fade away. Look at the violet square, and

then suddenly hide it, and a pale, greenish-yellow image will be seen. Get a square of yellow paper, and repeat the experiment, and you will see a violetblue image. In the same way try an orange square and get a violet image; try greenish-yellow, and get a pink image.

These strange, ghostly after-images that linger after any color has been suddenly removed, result from an action in the eye. Having looked at red till the eye becomes weary, and then having suddenly taken the red away and replaced it by a white surface, the nerves of the eye send us another sensation that we call bluish-green. The nerves sensitive to red having become fatigued, the nerves sensitive to green and violet are fresh and fully sensitive to the green and violet rays in the white light reflected from the paper.

Every color gives a particular after-image, and this image is always of a color that is said to be complementary to it. Red is complementary to bluish-green, orange to sky-blue, yellow to violet-blue, green to pink, and so on through all the colors.

To vary this experiment, you may take a small bit of green paper, say about the size of a wafer, and lay it on the middle of a square of orange-colored paper, and then, after looking at the two colors for a moment, hide them both with the gray paper, and the

after-image will be blue, with an orange spot in the centre. Take off the green wafer and put on a blue one, and make the experiment. Put a large spot of ink in the centre of this orange square, and the blue after-image will have a gray spot in the centre. Black, we know, is the absence of color, and on looking at the black spot the eye is not excited at all, and the blue image appears to have a hole in the middle through which we see the gray paper. If we put a white wafer on the orange square, we shall see a blue after-image with an orange spot.

These strange and curious after-images, appearing like colored ghosts on the gray paper, may afford both amusement and instruction, and will give us the complementary color of any color we use in the experiments. These complementary colors, when placed side by side, always give the eye a pleasing sensation, and we say that the colors look well together.

room.

Take a piece of red cloth or paper and hang it up before a white screen, or upon a white wall, in a dark Stand near the window and look at the red cloth, and you will not be able to see it. Then slowly open the window-shutter, and permit a little light to enter the room. Now the red cloth looks like a black patch on a gray wall. Let in a little more light, and it turns to a deep, dark red. Gradu

ally let in more and more light, and the deep-red cloth will change to a lighter and lighter shade, till the room is fully lighted, when it will appear in its real color. Bring the red cloth into the full sunlight, or throw a beam from the heliostat upon it, and it assumes a still lighter shade of red. Close the shutters again, and it will change back from red to dark-red, and through every shade to perfect black. Try any other color in the same manner, and you will produce precisely the same effects. This experiment may be tried in the night by turning the gas (or other lamp) slowly down till the light disappears, and turning it up again, while you watch the changing shades of color as the light decreases and increases.

Here we have quite a different matter, showing that the shade or brightness of a color depends upon the amount of light it receives. If it has plenty of light, it appears of its normal shade; if it has less light, it takes a darker shade; if more, it has a brighter shade. If, in using our color-top, we put a bit of black cloth or paper on the colors, the ring of color, when the top spins, will take a darker shade. If we put on a piece of white paper, we shall get rings of a lighter shade.

When the sunlight falls on any object, the object

absorbs part of the light and reflects the rest. If it absorbs all the light and reflects nothing, the eye sees no reflected rays, and we say the object is black, or is invisible. If it reflects all the light, all colors enter the eye, and we say it is white. If it absorbs all the rays of the spectrum except red, our eyes receive these red-reflected rays, and we call the object red. If it absorbs all the rays except red and green, the eye receives these two rays, two sets of nerves are excited at once, and we say that the object is yellow. It is in this manner that we see the things about us, and are enabled to recognize the colors in which they appear to be clothed.