589 



LECTURE XLVIII. 



ON THE HISTORY OF ASTRONOMY. 



V\' E have now taken a general view of the most striking phenomena of the 

 universe at large, of the great features of the solar system, and of the pecu- 

 liarities of the planet which we inhabit, with respect both to its solid and to 

 its fluid parts. All these are departments of astronomy, and we shall con- 

 clude our examination of the subject with a summary of the history of the 

 science, principally extracted and abridged from Laplace's Exposition du 

 syst^me du monde. 



In all probability the astronomy of the earliest ages was confined to ob-- 

 servations of the obvious motions and eclipses of the sun and moon, the 

 rising, setting, and occultations of the principal stars, and the apparent mo- 

 tions of the planets. The progress of the sun was followed, by remarking 

 the stars as they were lost in the twilight, and perhaps also by the variation 

 of the length of the shadow- of a detached object, observed at the time of the 

 day when it was shortest. In order to recognise the fixed stars, and their 

 diflferent motions, the heavens were divided into constellations; and twelve 

 of these occupied the zone denominated the zodiac, within the limits of 

 which the sun and planets were always found; 



The entrance of the sun into the constellation aries, or the ram, denoted, 

 in the time of Hipparchus, the beginning of the spring; and as the season 

 advanced, the sun continued his progress through the bull, the twins, and 

 the other signs in order; some of which appear to have been denominated from 

 their relation to the agriculture and to the climates of the countries in which 

 they were imagined. and others from the celestial phenomena attending the sun's 

 passage through them; the crab, for example, denoting his retrograde motion 

 after the time of the solstice, and the balance the equality of day and 



VOL. r. 4 p 



