THE GREEK ASTRONOMY. 505 



CHAPTER I. 

 Earliest Stages of Astronomy 



The Globular Form of the Earth. 



THERE are parts of Plato's writings which have been adduced as 

 bearing upon the subsequent progress of science ; and especially 

 upon the globular form of the earth, and the other views which led to 

 the discovery of America. In the Timaius we read of a great conti- 

 nent lying in the Ocean west of the Pillars of Hercules, which Plato 

 calls Atlantis. He makes the personage in his Dialogue who speaks 

 of this put it forward as an Egyptian tradition. M. H. Martin, who 

 has discussed what has been written respecting the Atlantis of Plato, 

 and has given therein a dissertation rich in erudition and of the most 

 lively interest, conceives that Plato's notions on this subject arose from 

 his combining his conviction of the spherical form of the earth, with 

 interpretations of Homer, and perhaps with traditions which were cur- 

 rent in Egypt {Etudes sur le Timee, Note xiii. § ix.). He does not 

 consider that the belief in Plato's Atlantis had any share in the dis- 

 coveries of Columbus. 



It may perhaps surprise modern readers who have a difficulty in 

 getting rid of the persuasion that there is a natural direction uptvards 

 and a natural direction downwards, to learn that both Plato and Aris- 

 totle, and of course other philosophers also, had completely overcome 

 this difficulty. They were quite ready to allow and to conceive that 

 down meant nothing but towards some centre, and up, the opposite 

 direction. (Aristotle has, besides, an ingenious notion that-while heavy 

 bodies, as earth and water, tend to the centre, and light bodies, as fire, 

 tend from the centre, the fifth element, of which the heavenly bodies 

 are composed, tends to move round the centre.) 



Plato explains this in the most decided manner in the Timwus (62, 

 c). "It is quite erroneous to suppose that there are two opposite 

 regions in the universe, one above and the other below ; and that 

 heavy things naturally tend to ihe latter place. The heavens are 

 spherical, and every thing tends to the centre ; and thus above and be- 

 low have no real meaning. If there be a solid globe in the middle, 



