EXPERIMENT 52. (a) On a sunny day, take three bottles, all of the same size and shape, and pour water out of a pitcher or pan into each bottle. Do not run the water directly from the faucet into the bottle, because sometimes that which comes out of the faucet first is warmer or colder than that which follows; in the pitcher or pan it will all be mixed together, and so you can be sure that the water in all three bottles is of the same temperature to begin with. Wrap a piece of white cotton cloth twice around one bottle; a piece of red or green cotton cloth of the same weight twice around the second bottle, and a piece of black cotton cloth of the same weight twice around the third bottle, fastening each with a rubber band. Set all three bottles side by side in the sunlight, with 2 or 3 inches of space between them. Leave them for about an hour. Now put a thermometer into each to see which is warmest and which is least warm. From which bottle has most of the light been reflected back into the air by the cloth around it? Which cloth absorbed most of the light and changed it into heat? Does the colored cloth absorb more or less light than the white one? than the black one? [Illustration: FIG. 93. Which color is warmest in the sunlight?] (b) On a sunny day when there is snow on the ground, spread three pieces of cotton cloth, all of the same size and thickness, one white, one red or green, and one black, on top of the snow, where the sun shines on them. Watch them for a time. Under which does the snow melt first? The white cloth is white because it reflects _all_ colors back at once. It therefore absorbs practically no light. But the reason the black cloth looks black is that it reflects almost none of the colors--it absorbs them all and changes them to heat. The colored cloth reflects just the red or the green light and absorbs the rest. Maybe you will understand color better if it is explained in another way. Suppose I throw balls of all colors to you, having trained you to keep all the balls except the red ones. I throw you a blue ball; you keep it. I throw a red ball; you throw it back. I throw a green ball; you keep it. I throw a yellow ball; you keep it. I throw two balls at once, yellow and red; you keep the yellow and throw back the red. I throw a blue and yellow ball at the same time; you keep both balls.