PRECESSION OF THE EQUINOXES. 61 



time, the equinoctial point iias retrograded 30, or one sign, they 

 whole circle, 360, being divided into 12 signs of 30 each ; 

 consequently, the vernal equinox is now in what was then the 

 last constellation, Pisces, for the stars have not changed places, 

 only the intersecting point. Astronomers, however, have agreed 

 to call the point where the vernal equinox is situated, the first point 

 of Aries, forever, whatever may be the constellation where this 

 point is located, hence the sign Aries, is now in the constellation 

 Pisces, the sign Pisces, in the constellation Ag'tiarius, &c. The 

 annual amount of precession is small, being but 50.1" in a year, 

 hence the time occupied to make a complete revolution, will be 

 25,868 years. However, small as it is, it is quite palpable in the 

 course of a century, and has been of signal aid in Chronology as 

 we shall show in our chapter upon that subject. As the place of 

 equinox goes forward each year, to meet the sun, 50.1 seconds of 

 space, it is evident the tropical or equinoctial year will be as much 

 shorter than the siderial year, as it takes the sun to describe this 

 small space, which is 20m 20s, nearly, hence the length of the 

 equinoctial year is 365d, 5h, 48m, 51.6s, and this is the year which 

 most intimately concerns us. In ancient times, the days of th 

 summer and winter solstice were determined by means of the 

 shadow of a gnomon, or upright post, as the sun rose higher and 

 higher each day, at noon, the shadow became shorter and shorter, 

 until, having reached its limit, it began to lengthen, this was the 

 day of the summer solstice. The day of the winter solstice, was 

 the time of the longest shadow. When we look back, and think 

 of the ancient philosophers, with their shadow-sticks, and rude 

 dials, and see them trying, with these rough means, to measure 

 the distances of the heavenly bodies, and the size of the earth, we 

 may wonder that they ever approximated as near as they did. In 

 no Science has the advancement of general learning and civiliza- 

 tion been more apparent, than in Astronomy. Tables of the posi- 

 tions of the sun, moon and planets, in the heavens, are now given for 

 many years to come, with such accuracy, that the unassisted eye 

 cannot detect even their greatest errors, and in some cases, the 

 positions are given with more accuracy than even could be obtained 

 from observation itself. 



