THE GREEK ASTRONOMY. 507 



ion ; — so current, indeed, that the Abbe Bouillaud, or Bullialdus, as 

 we more commonly call him, gave the title of Philolaus to the defence 

 of Copernicus which he published in 1639 ; and Chiaramonti, an Aris- 

 totelian, published his answer under the title of Antiphilolaus. In 

 1645 Bullialdus published his Astronomia Philolaica, which was an- 

 other exposition of the heliocentric doctrine. 



Yet notwithstanding this general belief, it appears to be tolerably 

 certain that Philolaus did not hold the doctrine of the earth's motion 

 round the sun. (M. H. Martin, Etudes sur le Timee, 1841, Note 

 xxxvii. Sect. i. ; and Bceckh, De vera Indole Astronomice Philolaicce, 

 1810.) In the system of Philolaus, the earth revolved about the cen- 

 tral fire ; but this central fire was not the sun. The Sun, along with 

 the moon and planets, revolved in circles external to the earth. The 

 Earth had the Antichthon or Counter-Earth between it and the cen- 

 tre ; and revolving round this centre in one day, the Antichthon, being 

 always between it and the centre, was, during a portion of the revolu- 

 tion, interposed between the Earth and the Sun, and thus made night; 

 while the Sun, by his proper motion, produced the changes of the 

 year. 



When men were willing to suppose the earth to be in motion, in 

 order to account for the recurrence of day and night, it is curious that 

 they did not see that the revolution of a spherical earth about an axis 

 passing through its centre was a scheme both simple and quite satis- 

 factory. Yet the illumination of a globular earth by a distant sun, and 

 the circumstances and phenomena thence resulting, appear to have 

 been conceived in a very confused manner by many persons. Thus 

 Tacitus (Agric. xii.), after stating that he has heard that in the north- 

 ern part of the island of Britain, the night disappears in the height of 

 summer, says, as his account of this phenomenon, that " the extreme 

 parts of the earth are low and level, and do not throw their shadow 

 upwards ; so that the shade of night falls below the sky and the stars." 

 But, as a little consideration will show, it is the globular form of the 

 earth, aud not the level character of the country, which produces this 

 effect. 



It is not in any degree probable that Pythagoras taught that the 

 Earth revolves round the Sun, ov that it rotates on its own axis. Nor 

 did Plato hold either of these motions of the Earth. They got so far 

 as to believe in the Spherical Form of the Earth ; and this was appar- 

 ently such an effort that the human mind made a pause before going 

 any further. " It required," says M. H. Martin, " a great struggle for 



