rror is facing the sun, the back gets hot.
(e) If you put your hand in front of a mirror held in the sun,
the mirror reflects heat to your hand. (f) If you put a plate
on a steam radiator, the top of the plate gradually becomes
hot. (g) If anything very hot or cold touches a gold or
amalgam filling of a sensitive tooth, you feel it decidedly.
(h) The handle of your soup spoon becomes hot when the bowl of
it is in the hot soup. (i) The moon is now very cold, although
it probably was once very hot.

INFERENCE EXERCISE

Explain the following:

181. Trees bend in the wind, then straighten up again. Why do
they straighten up?

182. A cloth saturated with kerosene and placed in the bottom
of a clock will oil the clockworks above it.

183. In cold weather the doorknob _inside_ the front door is
cold.

184. It is cool in the shade.

185. Clothes get hot when you iron them.

186. Potatoes fried in deep fat cook more quickly than those
boiled in water.

187. If you hold your hand near a vacuum electric lamp globe
that is glowing, some of the heat will go out to your hand at
once.

188. Rubbing silver with fine powder polishes it.

189. A mosquito can suck your blood.

190. A hot-water tank becomes hot at the top first, then
gradually heats downward. When you light the gas under an
ordinary hot-water heater, the hot water circulates to the
top of the boiler, while the cold water from the boiler pushes
into the bottom part of the heater, as shown in Figure 59.
What causes this circulation?

SECTION 22. _Reflection._

How is it that you can see yourself in a mirror?

What makes a ring around the moon?

Why can we see clouds and not the air?

Why is a pair of new shoes or anything smooth usually shiny?

If we turn off a switch labeled REFLECTION OF LIGHT on our imaginary
switchboard, we think at first that we have accidentally turned off
RADIATION again, for once more everything instantly becomes dark
around us. We cannot see our hands in front of our faces. Although it
is the middle of the day, the sky is jet black. But this time we see
bright stars shining in it. And among them is the sun, shining as
brightly as ever and dazzling our eyes when we look at it. But its
light does no good. When we look down from the sky toward the earth,
everything is so black that we shou