434 COSMOS. 



believed that he had solved the problem by a happy com- 

 bination of his earlier and later views. It is extremeiy 

 remarkable that Tycho Brahe, who in other respects is founo 

 to be so strictly attached to actual observation, had already 

 expressed the opinion (controverted by Rothman), that the re- 

 volving cosmical bodies were capable of vibrating the celestial 

 air (what we now call resisting medium,) so as to produce 

 tones. 86 But the analogies between the relations of tone nnd 

 the distances of the planets, which Kepler so long and labo- 

 riously endeavoured to trace out, remained, in his opinion, as 

 it appears to me, entirely with the domain of abstract specu- 

 lation. He congratulated himself upon having, to the greattf 

 glorification of the Creator, discovered musical relations of 

 number in the relations of cosmical space ; as if in poetic 

 enthusiasm, he makes " Venus, together with the Earth, sound 

 sharp in aphelion and flat in perihelion ; the highest tone 

 of Jupiter and that of Venus must coincide in flat accord." 

 In spite of these merely symbolical expressions, so frequently 

 employed, Kepler says positively : " Jam soni in coclo nulli 

 existunt, nee tarn turbulentus est motus, ut ex attritu aura 

 ccelestis eliciatur stridor.* (Harmonice Mundi, lib. v. cap. 4.) 

 The thin and clear celestial air (aura ccelestis) is also men- 

 tioned here again. 



The comparative consideration of the planetary intervals 

 with the regular bodies which would fill these intervals, 

 encouraged Kepler to extend his hypothesis even so far as the 

 region of fixed stars. 95 The circumstance which on the occa- 



Kepler, vide Apelt's Commentary of the Harmonice Mundi, 

 in his work ; Johann Keppler's Weltansicht, 1849, p. 76-1 16. 

 (Compare also Delambre, Hist, de VAstronom. mod. torn. i. 

 pp. 352-360.) 



** Cosmos, vol. ii. p. 697. 



* Now there are no such things as sounds among the 

 heavenly bodies, nor is their motion so turbulent, as to elicit 

 uoise from the attrition of the celestial air. 



25 Tycho had denied the existence of the crystalli'flo 



