506 ADDITIONS. 



and if a person walk re and it, he will become the antipodes to him- 

 self, and the direction which is up at one time will be down at an- 

 other." 



The notion of antipodes, the inhabitants of the part of the globe of 

 the earth opposite to ourselves, was very familiar. Thus in Cicero's 

 Academic Questions (ii. 39) one of the speakers says, "Etiam dicitis 

 esse e regione nobis, e contraria parte terrse, qui adversis vestigiis stant 

 contra nostra vestigia, quos Antipodas vocatis." See also Tusc. Disp. 

 i. 28 and v. 24. 



The Heliocentric System among the Ancients. 



As the more clear-sighted of the ancients had overcome the natural 

 prejudice of believing that there is an absolute up and down, so had 

 they also overcome the natural prejudice of believing that the earth is 

 at rest. Cicero says (Acad. Quest, ii. 39), "Hicetas of Syracuse, as 

 Theophrastus tells us, thinks that the heavens, the sun, the moon, the 

 stars do not move ; and that nothing does move but the earth. The 

 earth revolves about her axis with immense velocity ; and thus the 

 same effect is produced as if the earth were at rest and the heavens 

 moved ; and this, he says, Plato teaches in the Timceus, though some- 

 what obscurely." Of course the assertion that the moon and planets 

 do not move, was meant of the diurnal motion only. The passage re- 

 ferred to in the Timceus seems to be this (40, c) "As to the Earth, 

 which is our nurse, and which clings to the axis which stretches through 

 the universe, God made her the producer and preserver of day and 

 night." The word elhkofjievrjv, which I have translated clings to, some 

 translate revolves ; and an extensive controversy has prevailed, both in 

 ancient and modern times (beginning with Aristotle), whether Plato 

 did or did not believe in the rotation of the earth on her axis. (See 

 M. Cousin's Note on the Timceus, and M. Henri Martin's Dissertation, 

 Note xxxvii., in his JStudes sur le Timee.) The result of this discus- 

 sion seems to be that, in the Timcvus, the Earth is supposed to be at 

 rest. It is however related by Plutarch (Platonic Questions, viii. 1), 

 that Plato in his old age repented of having given to the Earth the 

 place in the centre of the universe which did not belong to it. 



In describing the Prelude tc the Epoch of Copernicus (Book v. 

 Chap, i.), I have spoken of Philolaus, one of the followers of Pythag- 

 oras, who lived at the time of Socrates, as having held the doctrine 

 that the earth revolves about the sun. This has been a current opin- 



