PRECESSION OF THE EQUINOXES. 



meridian called the equinoctial colure, or meridian which passes 

 through the equinoxes, a part of which meridian is seen at P O, its 



declination and latitude will be pretty near the same, but if the 

 star happens to be in the solstitial colure, the latitude will vary 

 from the declination, by the amount due to the obliquity of the 

 ecliptic, being either more, or less, according to the position of 

 the star, and whether the latitude is reckoned north or south. It 

 will also appear that the latitude of a star is not altered by preces- 

 sion. Imagine, for a moment, the system of meridians, and the 

 ecliptic and equator, entirely detached from the stars, and moved 

 slowly around, not the pole of the earth, which we will imagine 

 within it, but the pole of the ecliptic H. It is easy to conceive 

 that a star which is in the equator, say at the point 2, would no 

 longer be in it, but a star at II, in the ecliptic, although its distance 

 from the vernal equinox would be increased, would still be in the 

 ecliptic. The same is true of all small circles parallel to the 

 equator and ecliptic, the former called declination circles, and the 

 latter parallels of latitude. Perhaps we have been tediously mi- 

 nute, but there is some satisfaction in understanding a difficult 

 subject, and if the reader has had like patience with ourselves, 

 we trust the time will not be spent in vain. The grand point at 

 which we have been aiming, after all, is this : if we can find any 

 ancient records of observations which give the longitudes of the 

 stars, we can tell the dates of the observations. It is well known 

 Chat the ancients did not. possess a uniform system of chronology 



