8 4

BOOK n.

ECLIPSES AND THEIR ASSOCIATEDPHENOMENA.

CHAPTER I.

GENERAL OUTLINES.

Definition s. —Position of the Moon ’s Orbit as regards the Earth ’s. — Con-sequences resulting from their being inclined. —Betrograde Motion ofthe Bodes of the Moon’s Orbit. — Coincidences of 223 SynodicalPeriods with 19 Synodical Bevolutions of the Node. — Known as theSaros. — Statement of Diogenes Laertius . — Blustration of the Use ofthe Saros. — Number of Eclipses which can occur. — Solar Eclipsesmore frequent than Lunar ones.—Duration of Annular and TotalEclipses of the Sun .

The class of phenomena we are about to describe are thoseproduced by the interposition of celestial objects; for we knowwell that inasmuch as many of the heavenly bodies are con-stantly in motion, it follows that the direction of lines drawnfrom one to another will vary from time to time; and it mustoccasionally happen that three will come into the same line.“ When one of the extremes of the series of 3 bodies, whichthus assume a common direction, is the Sun , the interme-diate body deprives the other body, either wholly or par-tially, of the light which it habitually receives. When one ofthe extremes is the Earth , the intermediate body intercepts,wholly or partially, the other extreme body from the view ofobservers situate at places on the Earth which are in thecommon line of direction, and the intermediate body is seen

* See Appendix II.