wn shining, for we give light to the moon, as she does to us. The sun's
rays strike on the earth, and are reflected on to the moon, so that the
moon is lighted by earthshine as we are lighted by moonshine, and it is
these reflected earth-rays that light up the dark part of the moon and
enable us to see it. What a journey these rays have had! They travel
from the sun to the earth, and the earth to the moon, and then back to
the earth again! From the moon the earth must appear a much bigger and
more glorious spectacle than she does to us--four times wider across and
probably brighter--for the sun's light strikes often on our clouds,
which shine more brilliantly than her surface.

Once again we must use an illustration to explain the subject. Set a
lamp in the middle of a dark room, and let that be the sun, then take a
small ball to represent the earth and a smaller one for the moon. Place
the moon-ball between the lamp and the earth-ball. You will see that the
side turned to the earth-ball is dark, but if you move the moon to one
side of the earth, then from the earth half of it appears light and half
dark; if you put it right away from the lamp, on the outer side of the
earth, it is all gloriously lit up, unless it happens to be exactly
behind the earth, when the earth's shadow will darken it. This is the
full explanation of all the changes of the moon.

[Illustration: AN ECLIPSE OF THE MOON.]

Does it ever fall within the earth's shadow? Yes, it does; for as it
passes round the earth it is not always at the same level, but sometimes
a little higher and sometimes a little lower, and when it chances to
pass exactly behind it enters the shadow and disappears. That is what we
call an eclipse of the moon. It is nothing more than the earth's shadow
thrown on to the moon, and as the shadow is round that is one of the
proofs that the earth is round too. But there is another kind of
eclipse--the eclipse of the sun; and this is caused by the moon herself.
For when she is nearest to the sun, at new moon--that is to say, when
her dark side is toward us, and she happens to get exactly between us
and the sun--she shuts out the face of the sun from us; for though she
is tiny compared with him, she is so much nearer to us that she appears
almost the same size, and can blot him right out. Thus the eclipses of
both sun and moon are not difficult to understand: that of the moon can
only happen at full moon, when she is furthest from the