was not quite sure which. While he was trying to recall his
aunt's directions, his sister said that he could use soap and
water to take the grease out; then his brother told him to
scrape the spot with a knife. Which would have been the right
thing for him to do?

INFERENCE EXERCISE

Explain the following:

31. A pen has a slit running down to the point.

32. When a man smokes, the smoke goes from the cigar into his
mouth.

33. A blotter which has one end in water soon becomes wet all
over.

34. Cream comes to the top of milk.

35. It is much harder to stand on stilts than on your feet.

36. Oiled shoes are almost waterproof.

37. City water reservoirs are located on the highest possible
places in or near cities.

38. You can fill a self-filling fountain pen by squeezing the
bulb, then letting go.

39. The oceans do not flow off the world.

40. When you turn a bottle of water upside down the water
gurgles out instead of coming out in a smooth, steady stream.

SECTION 7. _How things stick to one another: Adhesion._

Why is it that when a thing is broken it will not stay
together without glue?

Why does chalk stay on the blackboard?

Now that you have found out something about capillary attraction,
suppose that you should go to the imaginary switchboard again and
tamper with some other law of nature. An innocent-looking switch,
right above the capillary attraction switch, would be labeled
ADHESION. Suppose you have turned it off:

In an instant the wall paper slips down from the walls and crumples to
a heap on the floor. The paint and varnish drop from the woodwork like
so much sand. Every cobweb and speck of dust rolls off and falls in a
little black heap below.

When you try to wash, you cannot wet your hands. But they do not need
washing, as the dirt tumbles off, leaving them cleaner than they ever
were before. You can jump into a tank of water with all your clothes
on and come out as dry as you went in. You discover by the dryness of
your clothes that capillary attraction stopped when the adhesion was
turned off, for capillary attraction is just a part of adhesion.
But you are not troubled now with the clamminess of unabsorbed
perspiration. The perspiration rolls off in little drops, not wetting
anything but running to the ground like so much quicksilver.

Your hair is fluffier than after the most