328 COSMOS. 



before the discovery of the elliptic orbit of the planets, he as- 

 cribed a rectilinear and not a closed revolving course, were 

 regarded by him, in 1608, in his '' new and singular discourse 

 on the hairy stars," as having originated from "celestial air," 

 He even added, in accordance with ancient fancies on sjion- 

 taneous generation, that comets arise " as an herb springs from 

 the earth without seed, and as fishes av jrmed in the sea by 

 a generatio s.ponta7iear 



Happier in his other cosmical conjectures, Kepler hazarded 

 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 cosmical island as to con- 

 stitute the center 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 discovered 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,t 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 propositions of this nature, felicitous 

 conjectures of that which was subsequently discovered, excit- 

 ed general interest, while none of Kepler's cotemporaries, in- 

 cluding Galileo, conferred any adequate praise on the discov- 

 ery of the three laws, which, since Newton and the promul- 



Nibuleuses et de la Matiire diffuse en Etoiles). Compare Cosmos, vol. 

 i., p. 144 and 152. 



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

 planetary system, vol. i., p. 141 ; also Struve, Etudes d'' Astronomie Stel- 

 laire, 1847, p. 4. 



t Apelt says {Epocken der Geschichte der Menschheit, bd. i., 1845, s. 

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

 under the name of Bode'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 librt 

 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, 

 PHny, Censorinus, and Achilles Tatius, in the Prolegomena to the 

 Aratus, are carefully collected in Fries, Geschichte der Philosophie, bd. 

 i., 1837, s. 146-150; in Martin, Etudes sur le Tim6e, t. ii., p. 38; and in 

 Brandis, Geschichte der Griechisch-Romischen Philosophie, th. ii., abth. 

 i., 1844. s. 364. 



