ON THE HISTORY OF ASTRONOMY. 453 



brated author, who has been mentioned, has sought to establish, in his 

 treatise on Indian astronomy, that the former of these epochs is founded on 

 observation. But if we calculate from our own improved tables, we shall 

 find that the general conjunction of the sun, moon, and planets, which the 

 Indian tables suppose, in reality never happened, although it may be 

 deduced, according to those tables, by ascending from the later series. The 

 equation of the sun's centre, depending on the eccentricity of the earth's 

 orbit, appears indeed to indicate a still higher antiquity ; but its magni- 

 tude, as deduced from eclipses, must have been affected by a contrary error 

 with respect to the moon's place : and the determination of the mean motion 

 of the moon seems to make it probable that these tables are even of a later 

 date than Ptolemy." 



In astronomy, as well as in other sciences, the Greeks were the disciples 

 of the Egyptians ; they appear to have divided the stars into constellations 

 13 or 1400 years before Christ. Newton attributes this arrangement to 

 Chiron,* and he supposes that he made the middle of the constellations cor- 

 respond to the beginning of the respective signs. But until the time of the 

 foundation of the school of Alexandria, the Greeks treated astronomy as a 

 science purely speculative, and indulged themselves in the most frivolous 

 conjectures respecting it. It is singular that amidst the confusion of sys- 

 tems heaped up on each other, without affording the least information to 

 the mind, it should never have occurred to men of so great talents, that th 

 only way to become accurately acquainted with nature, is to institute 

 experimental inquiries throughout her works. 



Thales of Miletus, who was born in the year 640 before Christ, having tra- 

 velled and studied in Egypt, founded, on his return, the Ionian school of 

 philosophy, in. which he taught the sphericity of the earth,f and the obli- 

 quity of the ecliptic with respect to the equator.^ He also explained 

 the true causes of eclipses, which he was even able to foretel,|| unques- 

 tionably by means of the information that he had obtained from the Egyp- 

 tian priests. 



Pythagoras of Samos was born 590 years before Christ ; he probably 

 profited by the information which Thales had acquired, and travelled also 

 into Egypt for his further improvement.^ It is conjectured that he was 

 acquainted with the diurnal and annual motions of the earth,** but he did 

 not publicly profess the true system of the world. It was taught after his 

 death, by his disciple Philolaus, about the year 450, as well as by Nicetas,ft 

 and by others of the school. They considered all the planets as revolving 

 round the sun,^ and as inhabited globes ; and they understood that the 



* Chronology, p. 25. 



t Plutarch, de Placit. Philos. 1. 2, c. 9, 10. 



t Diogenes Laertius, Life of Thales. Plutarch, Conviv. Sept. Sapient. Proclus, 

 Comm. in Euc. 1. 1. 



Plutarch, de Placit. 1. 2, c. 21, 24, 28. 



|| Herod, l.-l, &c. Pliny, Nat. Hist. 1. 2, c. 12. Riccioli, Almagest. Nov. i. 

 363. Costard, Ph. Tr. xlviii. 17. Baily, ibid. 1811. 



fl Jamblichus, Vita Pythag. ** Aristotle, de Coelo, 1. 2, c. 13. 



* ft Cicero, Qusest Acad. 1. 4, 39. 



Jt Plin. Hist. Nat. 1. 2, c. 22. Macrob. in Somn. Scip. 1. 1. c. 19. Greeorii 

 Prtef. ad Ast. &c. 



