In the meantime it has turned one quarter of the way around its axis, and the spot marked by the cross is still directly under the earth.

For the lunar inhabitant standing on that spot the sun is now on the point of rising, and he sees the earth no longer in the shape of a full moon, but in that of a half-moon.

The lunar globe itself appears, at the same time from the earth, as a half-moon, being in the position or phase that we call first quarter.
Seven more days elapse, and the moon arrives at _C_, opposite to the position of the sun, and with the earth between it and the solar orb.

It is now high noon for our lunarian standing beside the cross, while the earth over his head appears, if he sees it at all, only as a black disk close to the sun, or--as would sometimes be the case--covering the sun, and encircled with a beautiful ring of light produced by the refraction of its atmosphere.

(Recall the similar phenomenon in the case of Venus.) The moon seen from the earth is now in the phase called full moon.
Another lapse of seven days, and the moon is at _D_, in the phase called third quarter, while the earth, viewed from the cross on the moon, which is still pointed directly at it, appears again in the shape of a huge half-moon.
During the next seven days the moon returns to its original position at _A_, and becomes once more new moon, with "full earth" shining upon it.
Now it is evident that in consequence of the peculiar law of the moon's rotation its days and nights are each about two of our weeks, or fourteen days, in length.