s an _eclipse of the moon_. It seems a great pity that custom
should oblige us to employ the one term "eclipse" for this and also for
the quite different occurrence, an eclipse of the sun; in which the
sun's face is hidden as a consequence of the moon's body coming directly
_between_ it and our eyes.

The popular mind seems always to have found it more difficult to grasp
the causes of an eclipse of the moon than an eclipse of the sun. As Mr.
J.E. Gore[4] puts it: "The darkening of the sun's light by the
interposition of the moon's body seems more obvious than the passing of
the moon through the earth's shadow."

Eclipses of the moon furnish striking spectacles, but really add little
to our knowledge. They exhibit, however, one of the most remarkable
evidences of the globular shape of our earth; for the outline of its
shadow when seen creeping over the moon's surface is always circular.

[Illustration: FIG. 3.--Total and Partial Eclipses of the Moon. The Moon
is here shown in two positions; i.e. _entirely_ plunged in the earth's
shadow and therefore totally eclipsed, and only _partly_ plunged in it
or partially eclipsed.]

_Eclipses of the Moon_, or Lunar Eclipses, as they are also called, are
of two kinds--_Total_, and _Partial_. In a total lunar eclipse the moon
passes entirely into the earth's shadow, and the whole of her surface is
consequently darkened. This darkening lasts for about two hours. In a
partial lunar eclipse, a portion only of the moon passes through the
shadow, and so only _part_ of her surface is darkened (see Fig. 3). A
very striking phenomenon during a total eclipse of the moon, is that the
darkening of the lunar surface is usually by no means so intense as one
would expect, when one considers that the sunlight at that time should
be _wholly_ cut off from it. The occasions indeed upon which the moon
has completely disappeared from view during the progress of a total
lunar eclipse are very rare. On the majority of these occasions she has
appeared of a coppery-red colour, while sometimes she has assumed an
ashen hue. The explanations of these variations of colour is to be found
in the then state of the atmosphere which surrounds our earth. When
those portions of our earth's atmosphere through which the sun's rays
have to filter on their way towards the moon are free from watery
vapour, the lunar surface will be tinged with a reddish light, such as
we ordinarily experience at sunset when our air is