ON THE HISTORY OF ASTRONOMY. 451 



4to, Pavia, 1773. On the Tides in the Adriatic, Ph. Tr. 1777, p. 144. Lalande, 

 Traite du Flux et du Reflux de la Mer, 4to, Paris, 1781. Laplace, Mec. Celeste, 

 lib. v. Lubbock, Ph. Tr. 1831, p. 379 ; 1832, pp. 51, 595 ; 1833, p. 19 ; 1834, 

 p. 143; 1835, p. 275 ; 1836, pp. 57, 217 ; 1837, p. 97. Whewell's Cotidal Lines, 

 Ph. Tr. 1833, p. 147. Researches on the Tides, ibid. 1834, p. 15 ; 1835, p. 83 ; 

 1836, pp. 1, 131, 289; 1837, pp. 75, 227; 1838, p. 231 ; 1839, pp. 151, 163; 

 1840, pp. 161,255. Palmer's Tide Gauge, Ph. Tr. 1831, p. 209. Bunt's, ibid. 

 1838, p. 249. Daussy, Connaissance des Temps, 1834 (a low barometer is accom- 

 panied with high tides). Bunt, Eleventh Report of Brit. Ass. 



LECTURE XLVIII. 



ON THE HISTORY OF ASTRONOMY. 



WE 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 

 peculiarities 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 

 conclude 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 

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

 rising, setting, and occupations of the principal stars, and the apparent 

 motions 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 different 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, denot- 

 ing his retrograde motion after the time of the solstice, and the balance 

 the equality of day and night at the autumnal equinox. But the motion 

 of the equinoctial points having changed in some degree the course of 

 the seasons with regard to the stars, the signs of the ecliptic, by which 

 the places of the sun and planets are described, no longer coincide pre- 

 cisely with the constellations of the zodiac from which they derive their 

 names. 



The most ancient observations of which we are in possession, that are 



2 G 2 



