THE PLANETS. 435 



of the discovery of Ceres, and the other so-caller! small 

 vlanets, first forcibly recalled to mind Kepler's Pythagorean 

 arguments, was his almost forgotten conjecture as to the pro- 

 bable existence of a yet unseen planet in the great planedess 

 chasm between Mars and Jupiter. (' k Motus semper distan- 

 tiam pone sequi videtur ; atque ubi magnus hiatus erat inter 

 orbes, erat et inter motus."*) tk I have become more daring." 

 he says, in the introduction to the Mysterium Cosmographicum, 

 " and place a new planet between Jupiter and Mars, as also (a 

 conjecture which was less fortunate, and remained long unno- 

 ticed,* 5 ) another planet between Venus and Mercury ; neither 



spheres, in which the planets were supposed to be fixed. 

 Kepler praised the undertaking, but he still adhered to the 

 opinion that the sphere of fixed stars was a solid globular shell 

 of two German miles in thickness, upon which are the twelve 

 fixed stars, which are all situated at equal distances from us, 

 and have a peculiar relation to the corners of an icosahedron. 

 The fixed stars ' lumina sua ab intus cmittunt;" "emit light 

 from their own bodies;" he also considered for a long time 

 that the planets were self-luminous, until Galileo taught him 

 better ! Although he, like many other of the ancients and 

 Giordano Bruno, considered the fixed stars to be suns like 

 our own, still he was not much inclined to entertain the 

 opinion, which he had well considered, that all fixed stars are 

 surrounded by planets, as I had formerly stated him to be. 

 (Cosmos, vol. ii. p. 711.) Compare Apelt. Commentary to the 

 Harmonice, pp. 21-24. 



* " There seems to be always a close relation between the 

 motion and the distance [of the planets] ; that is to say, 

 where there is a great interval between their orbs, the same 

 exists also between their motions." 



16 It was not until the year 1821 that Delambre, in the 

 Hist, de VAstron. Mod. torn. i. p. 314, directed attention to 

 the planets which Kepler conjectured to lie between Mercury 

 and Venus, in the extracts which are complete with regard 

 to astronomy, but not with regard to astrology, from Kepler's 

 collected works (pp. 314-615). ' ; On n'a fait aucune attention 

 a oette supposition de Kepler, quand on a forme des projcts 



VOL. IV. L 



