CHROMOLOGY. 87 



CHAPTER VII. 



Chronology. 



44 Brightly ye burn on heaven's brow ; 

 Ye shot a ray as bright as now, 

 When mirrored on the unruffled wave 

 That whelmed earth's millions to one grave." 



E. P. Mason. 



WK have more than once mentioned the importance of the 

 movements of the heavenly bodies, in determining certain chro- 

 nological questions, and will now give some farther illustrations 

 of this subject. The precession of the equinoxes, and the occur- 

 rence of solar and lunar eclipses, are the two astronomical 

 events which have been of most essential service. We have, 

 in the preceding pages, illustrated the precession of the equinoxes, 

 showing that the places of vernal and autumnal equinox, or the 

 points where the ecliptic intersects the plane of the equator, moved 

 westward at the rate of 50| seconds of arc in one year. The 

 phenomena of solar and lunar eclipses, we have not explained, 

 nor does it fall within the limits w r e have prescribed to our little 

 volume, to embrace them. We shall, therefore, only refer at 

 present, to the service which chronology has received from the 

 knowledge of the retrogradatioii of the nodes of the earth's orbit, 

 on the ecliptic. As already shown, the path of the ecliptic in the 

 heavens, is divided into 12 equal parts, of 30 each, called signs, 

 and these signs formerly gave the names to the constellations, or 

 groups of stars near which they were located, when the ecliptic 

 was thus first divided or portioned out. That point in the ecliptic 

 where the vernal equinox is located, was then, and has been 

 always, designated as the first point of Aries, but as this equi- 

 noctial point changes its position, moving contrary to the order of 

 the signs in the ecliptic, at the rate of 50.2 seconds a year, the first 

 point of the sign Aries no longer corresponds with that group of 



