DISCOVERIES IN THE CELESTIAL SPACES. 711 



the earth without seed, and as fishes are formed in the sea by 

 a generatio spontanea 



Happier in his other cosmical conjectures, Kepler ha- 

 zarded the following propositions: that all the fixed stars 

 are suns like our own luminary, and surrounded by planetary 

 systems ; that our sun is enveloped in an atmosphere which 

 appears like a white corona of light during a total solar 

 eclipse; that our sun is so situated in the great cosmicai 

 island as to constitute the centre of the compressed stellar 

 ring of the milky way ;* that the sun itself, whose spots had 

 not then been discovered, together with all the planets and 

 fixed stars, rotates on its axis ; that satellites, like those dis- 

 covered by Galileo round Jupiter, will also be discovered 

 round Saturn and Mars; and that in the much too great 

 interval of space between Mars and Jupiter, f where we are 

 now acquainted with seven asteroids (as between Venus and 

 Mercury), there revolve planets which, from their smallness 

 alone, are invisible to the naked eye. Presentient proposi- 

 tions of this nature, felicitous conjectures of that which was 

 subsequently discovered, excited general interest, whilst none 

 of Kepler's cotcmporaries, including Galileo, conferred any 

 adequate praise on the discovery of the three laws, which, 

 since Newton and the promulgation of the theory of gravita- 

 tion, have immortalised the name of Kepler. J Cosmical con- 

 siderations, even when based merely on feeble analogies and 



* Compare the ideas of Sir John Herschel on the position of our 

 planetary system, vol. i. p. 141, also Strave, Etudes d' Astronomic 

 stellaire, 1847, p. 4. 



f .A pelt says (Epoclien der Geschichte der Mcmchheit, bd. i. 1845, 

 s. 223) : " The remarkable law of the distances, which is usually known 

 under the name of Bo4e's law (or that of Titius), is the discovery of 

 Kepler, who, after many years of persevering industry, deduced it from 

 the observations of Tycho de Brahe." See Harmonices Mundi libri 

 quinque, cap. 3. Compare also Cournot's Additions to his French 

 Translation of Sir John Herschel's Astronomy, 1834, 434, p. 324, and 

 Fries, Vorlesungen uber die Sternkunde, 1813, s. 325 (On the Law of 

 the distances in the secondary planets). < The passages from Plato, Pliny, 

 Censorinus, and Achilles Tatius, in the Prolegomena to the Aratus, are 

 carefully collected in Fries, Geschichte der Philosophic, bd. i. 1837, 

 s. 146-150; in Martin, Etudes sur le Timee, t. ii. p. 38; and in 

 Brandis. Geschichte der Griechisch- Romisclien Philosophic, th. ii. abth. 

 i. 1844, s. 364. 



J Delambre, Hist, de VAstronomie moderne, t. i. p. 360. 



