408 HISTORY OF FORMAL ASTRONOMY. 



supported by sound physical considerations; and 

 it must be allowed, that at the period of which we 

 are speaking, this had not yet been done in favour 

 of the Copernican hypothesis. We may add, how- 

 ever, that it is not quite clear that Bacon was 

 in full possession of the details of the astronomical 

 systems which that of Copernicus was intended to 

 supersede ; and that thus he, perhaps, did not see 

 how much less harsh were these fictions, as he 

 called them, than those which were the inevitable 

 alternatives. Perhaps he might even be liable to a 

 little of that indistinctness, with respect to strictly 

 geometrical conceptions, which we have remarked 

 in Aristotle. We can hardly otherwise account 

 for his not seeing any use in resolving the appa- 

 rently irregular motion of a planet into separate 

 regular motions. Yet he speaks slightingly of this 

 important step 4 . "The motion of planets, which 

 is constantly talked of as the motion of regression, 

 or renitency, from west to east, and which is 

 ascribed to the planets as a proper motion, is not 

 true ; but only arises from appearance, from the 

 greater advance of the starry heavens towards the 

 west, by which the planets are left behind to the 

 east." Undoubtedly those who spoke of such a 

 motion of regression, were aware of this ; but they 

 saw how the motion was simplified by this way of 

 conceiving it, which Bacon seems not to have seen. 

 Though, therefore, we may admire Bacon for the 

 4 Thema Cceli, p. 246. 



