When the moon is between us and the sun, the side towards us must of course be dark. Then it is that we do not see the moon at all.
But as the moon moves gradually to one side we begin to see a little strip of the bright portion as you notice in Fig. [1]. This represents the moon in its first phase.
I suppose you have noticed at such times, when the new moon is very small, that we can often see the whole disk of the moon, although the principal portion of it is very dim indeed. Still we can see a faint light shining upon it which makes it comparatively easy for us to discern its outlines.
FIG. 1. FIRST PHASE OF MOON.
This pale light is “earth-light.” The earth is then “full” to the moon-folk, (if there be any such creatures who can live without air,) and its brilliancy is partially reflected back to us from the surface of the moon.
The bright portion of the moon now grows larger and larger until, in about seven or eight days, we see it as it is shown in Figure [2]. Then it is said to be in its first quarter.
At this time the spots and various markings on its surface are generally seen very distinctly.
For seven days the bright portion of the moon continues to grow larger and larger, and during a part of this time it presents the appearance shown in Figure [3].
