A GLANCE AT THE STARS. 



149 



SUMMARY. 



The stars included in this list are not all visible to the naked eye. They are those 

 whose declination and right ascension have been accurately ascertained, and inserted 

 chiefly in Flamstead's catalogue. Declination is the distance of any heavenly body either 

 north or south of the equinoctial, measured on a meridian. Right ascension is its distance 

 east from the first point of Aries, measured on the equinoctial. The former corresponds 

 to terrestrial latitude, and the latter to terrestrial longitude ;' but while declination, like 

 latitude, may extend to 90, and no more, right ascension is reckoned only in one direc- 

 tion, and may therefore extend round the sphere, or to 360, whereas terrestrial longitude, 

 being reckoned east and west, can only extend to 180. 



Owing to the precession of the equinoxes, a change has occurred in the relation be- 

 tween the signs of the zodiac and their respective asterisms, which is somewhat puzzling 

 to the general reader, who is apt to confound the sign with the constellation called after 

 it. Two thousand years ago, in the days of Hipparchus, the zodiacal signs and asterisms 

 corresponded, so that when the sun entered the first point of the sign Aries, he entered 

 also the constellation of that name. Then the equinoctial colure, an imaginary great circle 



passing through the poles of the heavens and the 

 sun's place at the vernal equinox, intersected the 

 stellar ram, as some ancient representations testify. 

 But as the equinoctial points retrograde about 50" 

 annually, they have receded nearly 31 since the 

 time of Hipparchus, or more than a whole sign. 

 The effect has been to separate the asterisms from 

 their denominational signs, so that the constellation 

 Pisces is now in the sign Aries, the constellation 

 Aries in the sign Taurus, and the tropics of Cancer 

 and Capricorn, according to the sun's place among 

 the stars, have become the tropics of Gemini and 

 Sagittarius. Four thousand years back, anterior to 

 the time of the Hebrew patriarchs, the sun was in the asterism Taurus at the vernal 

 equinox, and the Bull opened the astronomical year ; and two thousand years hence, the 

 asterism Aquarius will occupy the present position of Pisces, and lead on the celestial 



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