Explain the following:
231. The alcohol formed by the yeast in making bread light is practically all gone by the time the bread is baked.
232. The oceans do not flow off the earth at the south pole.
233. Lamp globes often have frosted bottoms.
234. A damp dust cloth will take up the dust, without making it fly.
235. The stars twinkle when their light passes through the moving air currents that surround the earth.
236. Shears for cutting tin and metal have long handles and short blades.
237. A coin at the bottom of a glass of water seems raised when you look at it a little from one side.
238. You have to brace your feet to row well.
239. Light from the northern part of the sky, where the sun is not, does not make sharp shadows.
240. Pokers and lifters for stove lids often have open spiral handles.
Section 27. Color.
What makes the ocean look green in some places and blue in others?
What makes the sky blue?
What causes material to be colored?
What makes a rainbow?
What is color?
Fig. 90. Making a rainbow on the wall.
Color is merely a kind of light. We say that a sweater is red; really the sweater is not red, but the light that it reflects to our eyes is red. We speak of a piece of red glass, but the glass is not red; it is the light that it lets pass through it that is red.
White is not really a color; all colors put together make white. Experiments 50 and 51 will prove this.
