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it becomes faintly visible; stir into it a teaspoonful of milk, then
turn in the ray of sunlight, and it glows like a lamp, illuminating
the whole room. These experiments show how the straight rays of
the sun are diffused in every direction over the earth.

Set a small light near one edge of a mirror; then, by putting the
eye near the opposite edge, you see almost as many flames as you
please from the multiplied reflections. How can this be accounted
for?

Into your beam of sunlight, admitted through a half-inch hole,
put the mirror at an oblique angle; you can arrange it so as to
throw half a dozen bright spots on the opposite wall.

[Illustration: Fig. 10.--Manifold Reflections.]

In Fig. 10 the sunbeam enters at A, and, striking the mirror _m_
at _a_, is partly reflected to 1 on the wall, and partly enters
the glass, passes through to the silvered back at B, and is totally
reflected to _b_, where it again divides, some of it going to the
wall at 2, and the rest, continuing to make the same reflections
and divisions, causes spots 3, 4, 5, etc. The brightest spot is
at No.2, because the silvered glass at B is the best reflector
and has the most light.

When the discovery of the moons of Mars was announced in 1877,
it was also widely published that they could be seen by a mirror.
Of course this is impossible. The point of light mistaken for the
moon in this secondary reflection was caused by holding the mirror