The Sun and Solar System. 275 



longitude of the fixed stars ; and this point also 

 constitutes the vernal equinox. This point, how- 

 ever, is found to recede westward every year about 

 50 seconds of a degree. The fixed stars, of course, 

 appear to have advanced every year in the same 

 proportion, by a movement which is general and 

 common to all, about the poles of the ecliptic. 

 Their longitude is therefore annually augmented 

 in this proportion. 



This general movement of the fixed stars, and 

 this difference of longitude, depend upon what 

 is called the precession of the equinoctial points ; 

 and this precession, physical astronomers say, is 

 produced by the modified attractions of the sun 

 and moon upon the spheroidal figure of the 

 earth, which is known to be not a perfect globe, 

 but rather flatted at the poles. By means of 

 these attractions acting more powerfully upon 

 the equatorial regions, the poles of the equator de- 

 scribe circles about the poles of the ecliptic, in 

 the long period of 25,748 years. Hence, if the 

 sun is one year in conjunction with a particular 

 star at the instant of the equinox, he ought the 

 succeeding year to be at the equinox before he 

 comes in conjunction with the same star. The 

 arrival of the sun at the equinoctial point there- 

 fore precedes the termination of his revolution, 

 and hence is derived the phrase the precession 

 of the equinoxes. The complete explication of 

 this interesting phenomenon is too recondite to 

 admit of introduction into a popular treatise like 



