comes from an object off to one side, naturally you think the thing
you are looking at is off to one side. Maybe the diagram (Fig. 65)
will make this clearer.

[Illustration: FIG. 65. In passing through the prism the light is bent
so that an object at _b_ appears to be at _c_.]

Here in _a_ is an object the same height as the eye. The light comes
straight to the eye, and one knows that the object is level with the
eye. In _b_ the object is in the same position as in _a_, but the
prism bends the light so that it strikes the eye with an upward slant.
So the person thinks the object is below the eye at _c_.

Here is another experiment with bending light:

EXPERIMENT 45. Fill a china cup with water. Put a pencil in
it, letting the pencil rest at a slant from left to right.
Lower your head until it is almost level with the surface of
the water. How does the pencil look?

[Illustration: FIG. 66. The pencil is not bent, but the light that
comes from it is.]

The reason the pencil looks bent is because the light from the part of
it under the water is bent when it passes from the water into the air
on its way to your eye; so the slant at which it comes to your eye is
the same slant at which it ordinarily would come from a bent pencil.

EXPERIMENT 46. Fill a glass with water. Put the pencil into
it in the same way you put it in the cup in the previous
experiment, letting the pencil slant from left to right. Lower
your head this time until it is on a level with the water in
the glass, and look through the glass and water at the pencil.
Notice what happens where the pencil goes into the water.

What you see is explained in the same way as are the things that took
place in the other experiments in refraction, or bending of light. The
light from the part of the pencil above the water comes straight to
your eye, of course; so you see it just as it is. But the light from
the part of the pencil in the water is bent when it comes out of the
water into the air on its way to your eye. This makes it come to your
eye from a different direction and makes the lower part of the pencil
seem to be in a place to one side of the place where it _really_ is.
The pencil, therefore, looks broken.

[Illustration: FIG. 67. The bending of the light by the water in the
glass causes the pencil to look broken.]

Whenever light passes first through something dense like water or
glass, and then through somet