LECTURE IV.the moon ( continued).
Full orb’d, and breaking through the scatter’d clouds,
Shows her broad visage in the crimson east,
Turn’d to the Sun directs her spotted disk,
Where mountains rise, umbrageous dales descendAnd caverns deep, as oblique tubes descry ;
A smaller earth, gives all his blaze again,
Void of its flame, and sheds a softer day.”
Thomson.
To many lovers of astronomy there is a charm in the studyof the physical condition of the Moon ’s surface, far surpassingany pleasure they may feel in the complicated theory of itsmovements. Even to the naked eye there is evidence ofthe existence of various configurations of form and feature,abundantly sufficient to excite a wish for a closer view;while in a good opera-glass many irregularities may be noticedin the inner edge of the lunar crescent,—mountain : peaks whichtower up to catch the Sun ’s beams, while the interveningvalleys lie invisible in the shade. But a small telescopediscloses a scene of marvellous beauty ; and one of greaterpower reveals innumerable details full of the deepest interest.
It is from three to eight days before, or after, it is new, that■the most striking views of the Moon are obtained; becausethe light of the Sun , at such times, shines so obliquelyupon the formations near to the edge of its bright crescent,that all inequalities of the surface are thrown into prominentrelief by the intensely black and sharply-defined shadows whichfall behind them. On the contrary, when the Moon is nearlyfull, although certain delicate markings are then best seen,