48

THE BEAUTY OP THE HEAVENS.

has advanced a little farther in her orbit, as to y, her inhabitants then see asmall portion of the earth’s disc illuminated ; the earth’s phase is then to themwhat the moon’s phase is to us when it is in the position x ; we may be calledto them their new earth (as we term her our new moon). In every part of thelunation, or of the moon’s course round the earth, that portion of her discwhich, in any stage, we see illuminated, is exactly the portion of the earth whichto an inhabitant of the moon appears in shadow ; or, which is the same, thatportion of the moon’s disc which to us does not appear, or is not illuminated,exactly corresponds with the portion of the earth which appears to the inhabi-tant of the moon to be illuminated, and, therefore, constitutes the phase of theearth, for him, in that position.

It must be understood that, in strictness, the darkened portions of themoon are not absolutely invisible to the earth, nor are the unilluminated por-tions of the earth invisible to the moon; a small quantity of light is reflectedfrom the brightly illuminated part of the one, upon the unilluminated part ofthe other: although, in the case of the moon, we perceive this only when sheis in her conjunction, or near the position a. In the other parts of her orbither darkened portion is invisible to us, sometimes by the greater, and, there-fore, overpowering light of the sun ; and, at others, by the greater, and, there-fore, overpowering light from those parts of herself which are fully illuminated.This phenomenon is most remarkable at the new moon, and is the subject of adistinct scene.

Scene No. XVI.— The Crescent Moon. No. 1.

The phases of the moon, and the motions that produce them, are alreadydescribed in a former scene.

If we observe the moon, on a clear evening, a little after sun-set, when sheis about three or four days old, that part of her disc which is not enlightenedby the sun is faintly illuminated by the light that is reflected from the earth ;and the horns of the enlightened part appear, as it were, to project beyond theremaining parts of the moon, as if they actually formed a portion of a sphere con-siderably larger in diameter than the unenlightened portion. It was formerly,and even now is sometimes, deemed a sufficient explanation of this appearance,to say, that bright objects affect the eye to a greater extent than those which areless luminous ; and that, therefore, the bright part of the moon, expanding onthe sight, presents the appearance of part of a large circle projecting beyondthe darker portion of her disc. This phenomenon has, however, been betterexplained. The human eye does not view objects with sufficient distinctness atsuch a distance as that of the moon: and the moon is the most distant objectwhich can present itself to us in a clear and distinct form—the sun being fartoo bright for our eyes ; the stars too distant to be seen distinctly.

It has been suggested, and it is generally received as a circumstance greatly