,t£T. XIX. AND ABERRATION OF LIGHT. Zl^

Had no such atmosphere existed, the rays oflight would have come to us in straight lines,and the appearance and disappearance of the innwould have been instantaneous ; we should havehad a sudden transition from the brightest sun-shine to the most profound darkness, and fromthick darkness to a blaze of light. Refraction,therefore, is extremely useful, not only as it pre-pares us gradually for the light of the fun, butalso as it occasions twilight, and by that meansprolongs the duration of the day. Nature hasestablished these gradations, to heighten ourpleasures by variety; the scene is perpetuallychanging, but the order of things is immutableand eternal.

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“ Look nature through, ’tis revolution all,

All change, no death: day follows night; and nightThe dying day; stars rife, and set, and rise;

Earth takes th’ example: fee the Summer gay,

"With her green chaplet, and ambrosial flow’rs,

Droops into pallid Autumn ; Winter gray,

Horrid with frost, and turbulent with storm,

Blows Autumn and his golden fruits away,

Then melts into the Spring; soft Spring, with breath'Favonian, from warm chambers of the south,

Recalls the first: all, to reflourilh, fades;

As in a wheel, all sinks, to re-afcend.”

Young.

The refractive power of the atmosphere ap-pears to have been known to Astronomers be-fore the time of Ptolemy; but the first who de-termined