532 ADDITIONS. 



tomed to assert that the immensely rapid motion of the sphere of the 

 Fixed Stare graduates by a slower and slower motion of Planets, 

 Comets, Air, and Ocean, into the immobility of the Earth. So that 

 the conditions are not satisfied on which he hypothetically says, " turn 

 abnegandus est motus terrae." 



With regard to the proper motions of the planets, this passage seems 

 to me to confirm what I have already said of him ; that he does not 

 appear to have seen the full value and meaning of what had been done, 

 up to his time, in Formal Astronomy. 



We may however fully agree with Mr. De Morgan ; that the whole 

 of what he has said on this subject, when put together, does not jus- 

 tify Hume's assertion that he rejected the Copernican system " with 

 the most positive disdain." 



Mr. De Morgan, in order to balance the Copernican argument de- 

 rived from the immense velocity of the stars in their diurnal velocity 

 on the other supposition, has reminded us that those who reject this 

 great velocity as improbable, accept without scruple the greater velo- 

 city of light. It is curious that Bacon also has made this comparison, 

 though using it for a different purpose ; namely, to show that the 

 transmission of the visual impression may be instantaneous. In Apho- 

 rism xlvi. of Book ii. of the Novum Organoid he is speaking of what 

 he calls Tnstantice curriculi, or Instantice ad aquam, which we may 

 call Instances by the clock: and he says that the great velocity of the 

 diurnal sphere makes the marvellous velocity of the rays of light more 

 credible. 



" Immeusa ilia velocitas in ipso corpore, quse cernitur in motu 

 diurno (quse etiam viros graves ita -obstupefecit ut mallent credere mo- 

 tum terrce), facit motum ilium ejaculationis ab ipsis [stellis] (licet 

 celeritate ut diximus admirabilem) magis credibilem." This passage 

 shows an inclination towards the opinion of the earth's being at rest, 

 but not a very strong conviction. 



Kepler persecuted. 



We have seen (p. 280) that Kepler writes to Galileo in 1597 — "Be 

 trustful and go forwards. If Italy is not a convenient place for the 

 publication of your views, and if you are likely to meet with any ob- 

 stacles, perhaps Germany will grant us the necessary liberty." Kepler 

 however had soon afterwards occasion to learn that in Germany also, 

 the cultivators of science were exposed to persecution. It is true that 



