THE PLANETS. 99 



teenth century. The symbolizing habit of consecrating cer- 

 tain metals to the planets belongs, undoubtedly, to the new 

 Platonic doctrines of the Alexandrian school in the fifth cen- 

 tury, as is ascertained from passages in Proclus (ad Tim., ed. 

 Basil, p. 14), from Olympiodorus, as well as by a late scholium 

 to Pindar (Isthm., vol. ii.). (Compare Olympiod., Comment, 

 in Aristot., Meteorol., cap. 7, 3 in Ideler's edition of the Me- 

 teorol., torn, ii., p. 163 ; also torn, i., p. 199 and 25] .) 



Although the number of the visible planets amounted, ac- 

 cording to the earliest limitation, to five, and subsequently, 

 by the addition of the large disks of the Sun and Moon, in- 

 creased to seven, conjectures were prevalent, even in antiqui- 

 ty, that beyond these visible planets there were yet other less 

 luminous, unseen planets. This opinion is stated by Simpli- 

 cius to be Aristotelean. " It is probable that such dark cos- 

 mical bodies which revolve round the common center some- 

 times give rise to eclipses of the moon as well as the earth." 

 Artemidorus of Ephesus, whom Strabo often mentions as a 

 geographer, believed in the existence of an unlimited number 

 of such dark, revolving cosmical bodies. The old ideal body, 

 the anti-earth (avrixduv) of the Pythagoreans, does not be- 

 long to this class of conjectures. The earth and the anti- 

 earth have a parallel concentric motion ; and the anti-earth, 

 conceived in order to avoid the assumption of the rotatory 

 motion of the earth, moving in a planetary manner round 

 the central fire in twenty-four hours, can scarcely be any 

 thing else than the opposite hemisphere the antipodean 

 portion of our planet.* 



When from the 43 principal and secondary planets now 

 known (a number six times greater than that of the planet- 

 ary bodies known to the ancients), the 36 objects which have 

 been discovered since the invention of the telescope are chro- 

 nologically separated according to the succession of their dis- 

 covery, there is obtained for the seventeenth century nine, 

 for the eighteenth century also nine, and for the half of the 

 nineteenth century eighteen newly-discovered planets. 



* Bockh, Ueber Philolaus, p. 102 and 



