ilO cosmos. 



At the close of the sixteenth century, all the Pythagorean 

 and Platonic views of the system of the universe were again 

 reanimated in the person of the imaginative Kepler. He, in 

 the first instance, constructed the planetary system in the 

 Mysterium Cosmograjiliicum, in accordance with the prin- 

 ciple of the five regular solids, which may be imagined as 

 situated between the planetary spheres, then in the Harmo- 

 nice Mundi, according to the intervals of tone. ^ Convinced 

 of the regularity of the relative distances of the planets, he 

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

 nation of his earlier and later views. It is extremely re- 

 markable that Tycho Brahe, who in other respects is found 

 to be so strictly attached to actual observation, had already 

 expressed the opinion (controverted by Rothmann) that the 

 revolving cosmical bodies were capable of vibrating the ce- 

 lestial air (what we now call resisting medium) so as to pro- 

 duce tones. f But the analogies between the relations of tone 

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

 laboriously endeavored to trace out, remained, in his opinion, 

 as it appears to me, entirely with the domain of abstract 

 speculation. He congratulated himself upon having, to the 

 greater glorification of the Creator, discovered musical rela- 

 tions 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 expres- 

 sions, so frequently employed, Kepler says positively, "Jam 

 soni in ccelo nulli existunt, nee tarn turbulentus est motus, ut 

 ex attritu aurce, ccelestis eliciatur stridor. $ {Harmonice 

 Mundi, lib. v., cap. 4.) The thin and clear celestial air 

 (aura ccelestis) is also mentioned here again. 



The comparative consideration of the planetary intervals 

 with the regular bodies which would fill these intervals, en- 



uscript in Leyden, have been minutely treated of with critical erudition 

 by the younger Ideler (Hermapion, 1841, pars i., p. 198-214). Com- 

 pare also Lobeck, Aglaoph., torn, ii., p. 932. 



* On the gradual development of the musical ideas of Kepler, vide 

 Apelt's Commentary of the Harmonice Mundi, in his work ; Johann 

 Kepler's Weltansichl, 1849, p. 76-116. (Compare also Delambre, 

 Hist, de V Astronom. Mod., torn, i., p. 352-360.) 



t Cosmos, vol. ii., p. 316. 



t [Now there are no such things as sounds among the heavenly 

 bodies, nor is their motion so turbulent as to elicit noise from the at- 

 trition of the celestial air.] 



