out, some being prolonged to a considerable distance.
And yet, from a little way off, does it not form the man's face above
indicated?

[Illustration: FIG. 67.--Woman's head in the Moon.]

From the earliest astronomical observations made with the aid of
instruments by Galileo, in 1609, people tried to find out what the dark
spots could represent, and they were called seas, because water absorbs
light, and reflects it less than _terra firma_. The Moon of itself
possesses no intrinsic light, any more than our planet, and only shines
by the light of the Sun that illuminates it. As it rotates round the
Earth, and constantly changes its position with respect to the Sun, we
see more or less of its illuminated hemisphere, and the result is the
phases that every one knows so well.

[Illustration: FIG. 68.--The kiss in the Moon.]

[Illustration: FIG. 69.--Photograph of the Moon.]

At the commencement of each lunation, the Moon is between the Sun and
the Earth, and its non-illuminated hemisphere is turned toward us. This
is the New Moon, invisible to us; but two days later, the slim crescent
of Diana sheds a gentle radiance upon the Earth. Gradually the crescent
enlarges. When the Moon arrives at right angles with ourselves and with
the Sun, half the illuminated hemisphere is presented to us. This is the
first quarter. At the time of Full Moon, it is opposite the Sun, and we
see the whole of the hemisphere illuminated. Then comes the decline: the
brilliant disk is slightly corroded at first; it diminishes from day to
day, and about a week before the New Moon our fair friend only shows her
profile before she once more passes in front of the Sun: this is the
last quarter.

[Illustration: FIG. 70.--The Moon's Phases.]

When the Moon is crescent, in the first evenings of the lunation, and
after the last quarter, the rest of the disk is visible, illuminated
feebly by a pale luminosity. This is known as the ashy light. It is due
to the shine of the Earth, reflecting the light received from the Sun
into space. Accordingly the ashy light is the reflection of our own sent
back to us by the Moon. It is the reflection of a reflection.

This rotation of the Moon round the Earth is accomplished in
twenty-seven days, seven hours, forty-three minutes, eleven seconds; but
as the Earth is simultaneously revolving round the Sun, when the Moon
returns to the same point (the Earth having become displaced relatively
to the Sun), the Moon has