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Show WHY FOAM IS WHITE. No one can have failed to notice that the foam along the shore of the sea or of a lake is white. No matter how deep the blue of the water may be, there is the same whiteness of the froth at its edge. If the blackest ink in the world is beaten into foam, the foam will be as white as the froth of milk. The reason for this is that we see all objects by reflected light. If they reflect all the rays, they appear white; if they absorb all the rays, they seem to be black. When beaten into a froth the bubbles reflect all the light from their surfaces, for their extreme thinness thin-ness makes them practically nothing but smface and thus they are white. For the same reason any colored stone shows white when It Is ground to a powder. Take the blackest mar- BBBiMiiiiShfc ble and reduce it to small grains and these will appear white, because their surfaces now all reflect the same light. If the polished surface of the same marble be only a little scratched as with a nail or drill-point the effect will be ,a light-colored streak. The same point is illustrated in the appearance of the tiny particles of dew on the spider's -web as compared with the larger drops suspended from the tips of blades of grass. All the more striking is the difference when the cold has converted Jew and water into frost and ice. The frost sparkles from the innumerable faces of the crystals, while the ice shows a uni- IH formly shining surface. jH Frost and snow are white because M of the Bmallness of their particles and M the great number of their reflecting jH surfaces. H |