k in tightly, pull out the pin. Screw the
cap on the bottle so as to hold the cork fast. Put the bottle
in a pail or box, and pack ice and salt around it. Within an
hour you should be able to see what the freezing water does to
the bottle.

_APPLICATION 27._ Explain why ice is lighter than water; why
we have no snow in summer.

INFERENCE EXERCISE

Explain the following:

141. Sealing wax is held over a candle flame before it is
applied to a letter.

142. Automobile tires tighten upon a sudden change from cold
weather to hot.

143. When paper has been rolled, it tends to curl up again
after being unrolled.

144. Seats running across a car are much more comfortable
when a car starts and stops, than are seats running along the
sides.

145. You cannot siphon water from a low place to a higher one.

146. Candles get soft in hot weather.

147. Meteorites fall to the earth from the sky.

148. When you preserve fruit and pour the hot fruit into
the jars, you fill the jars brim full and screw on the cap
air-tight; yet a few hours later the fruit does not fill the
jars; there is some empty space between the top of the fruit
and the cover.

149. Water pipes burst in the winter when it is very cold.

150. When people want to make iron castings, they first melt
the iron, then pour it into molds. They leave it in the molds
until cold. After that the iron holds the shape of the molds.
Explain why the iron changes from a liquid to a solid.

SECTION 18. _Evaporation._

Why is it that when ink is spilled it dries up, but when it is
in the bottle it does not dry up?

What put the salt into the ocean?

Why do you feel cold when you get out of the bathtub?

Wet clothes get dry when they are hung on the clothes-line. The water
in them _evaporates_. It turns to invisible vapor and disappears into
the air. Water and all liquids evaporate when they are long exposed to
the air. If they didn't--well, let us imagine what the world would be
like if all evaporation should suddenly stop:

You find that your face is perspiring and your hands as well. You wipe
them on your handkerchief, but soon they are moist again, no matter
how cool the weather. After wiping them a few more times your
handkerchief becomes soaking wet, and you hang it up to dry. There may
be a good breeze stirring, yet your