THE PLJLNETS. 419 



increased to seven; conjectures were prevalent, even in anti- 

 quity, that beyond these visible planets, there were yet other 

 less luminous, unseen planets. This opinion is stated by 

 Simplicitis, to be Aristotelean. ' It is probable that 

 such dark cosmical bodies which revolve round the common 

 centre, sometimes 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 (iarrv)fmf) of the Pytha- 

 goreans, does not belong to this class of conjectures. The 

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

 and the anti-earth was conceived in order to avoid the assump- 

 tion of the rotatory motion of the earth moving in a plane- 

 tary manner round the central fire in twenty-four hours, can 

 scarcely be anything else than the opposite hemisphere the 

 antipodean portion of our planet. 1 * 



When from the 43 principal and secondary planets now 

 known (a number six times greater than that of the planetary 

 bodies known to the ancients) the 36 objects which have been 

 discovered since the invention of the telescope are chronolo- 

 gically separated according to the succession of their disco- 

 very, 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. 



cilaso de la Vega himself corrects his previous statement 

 (parte i. lib. ii. c. 35,) by distinctly saying, there were three 

 festivals in each of the months, which were reckoned after 

 the moon, and that the people should work eight days and 

 rest upon the ninth (parte i. lib. vi. cap. 23). The so-called 

 Peruvian weeks, therefore, consisted of nine days. (See my 

 Vues des CordilUres, torn. i. p. 341-343). 

 n Bockh, uber Philolaus, p. 102 and 117. 



VOL. IV. K . 



