OO THE WORLD. 



stars to which it formerly gave a name, for the shifting of the 

 equinox cannot carry forward the stars with "it. The vernal equi- 

 noctial point is now situated in the constellation Pisces, having 

 altered its position about 30 since the constellations were grouped 

 and named in their present order. As we know the annual 

 amount of the precession, we can determine how long ago the 

 present zodiac was formed, viz : 



50.2" : 1 year : : 30 (=108,000"): 2155.6 years, 

 that is, about 300 years before the Christian era, when the most 

 celebrated astronomical school of antiquity, flourished under the 

 auspices of the Ptolemies, and the labors of the astronomers of 

 that school, the most celebrated of whom was Hipparchus, who 

 formed a catalogue of the stars, were recorded in the Ahnagest of 

 Ptolemy, and constituted the chief knowledge upon this subject, 

 until the times of Kepler, Tycho Brahe and Copernicus. The 

 conclusions which we may come to, from ancient astronomical 

 observations, are necessarily liable to some error, from the im- 

 perfect manner in which their observations were made, most of 

 them having been 1?ut approximations, and not very close ones, 

 to the truth. We have illustrated, (page 60), in what manner 

 the precession of the equinoxes causes the pole of the heavens to 

 revolve around the pole of the ecliptic, the effect of which is, that 

 successive stars, which lie in the circumference of the circle 

 which the pole of the heavens thus describes, will, in succession, 

 become the pole star. The present polar star was not always the 

 pole star, nor is it as near the true pole of the heavens now, as it 

 will be. In about 240 years, it will be but 29' 55" distant from 

 the pole. At the time of the earliest catalogues, it was 12 dis- 

 tant, and now, 1848, its distance is about 1 25'. About 2900 

 years before the commencement of the Christian era, the bright 

 star in the tail of Draco, called Alpha, was the polar star, and was 

 then only 10' from the pole ; and in 11,600 years, the bright 

 star Lyra, will become the polar star, and will then be but 5 from 

 the pole, whereas, its distance now is upwards of 51. We give 

 on the next page, a representation of that part of the heavens 

 where the north pole of the ecliptic is situated. 



Here we have the pole of the ecliptic fh the centre, and the 



