630 Royal Astronomical Society. 



Nuremberg could be revised at Wittemberg. It is very unlikely, 

 then, that Rheticus should have edited the second edition, when, as 

 far as we know, a similar impediment existed. 



The third edition, by MUler (Amsterdam, 1617), has no authority 

 as to the text above that of the second. 



Now both the second and third editions change the wox6^ fatemur 

 into fatentur, thus causing Copernicus to throw the opinion in 

 question upon his predecessors, instead of directly making it his 

 own. Not that it would be conclusive, even if the emendation were 

 adopted : for, as I have said, Copernicus is evidently speaking with 

 approbation of the opinions which he describes ; and it would be 

 difficult to say why comperiunt or putant in one sentence should 

 imply approbation, and fatentur, in the next, should be at least dis- 

 avowal, if not disapprobation. If Rheticus, who knew the mind of 

 Copernicus better than any one, had been the editor, I can conceive 

 that stress ought to be laid upon the change of the first into the 

 third person as an emendation ; that is, I should be somewhat stag- 

 gered by Rheticus having thought it necessary to make such an 

 alteration. 



But, Rheticus not being in the question, as I think, for the rea- 

 sons given above, the next best authority on an opinion of Coper- 

 nicus is Galileo. Now the latter, in speaking of the phases of Venus, 

 expressly attributes to Copernicus the maintenance of one of the 

 two alternatives, — that the planet is either self-luminous or perfo- 

 rated by the solar rays. Of these alternatives, he says, in his letter 

 to Velser (Works, vol. ii. pp. 88, 89), " Al Copernico medesimo 

 convien amettere come possibile, anzi pur come necessaria una delle 

 dette posizioni." And that such was the opinion of Copernicus is 

 also assumed by the writer of the note on the Sydereus Nuncius in 

 the volume just mentioned, and by others, even down to our own 

 time ; as by Mr. Drinkwater Bethune, in his life of Galileo. In fact, 

 with the exception of the unsupported story mentioned at the be- 

 ginning of this paper, there is nowhere, that I can find, anything 

 against my conclusion. And it is to be remembered, that Copernicus 

 nowhere shows any of that acumen in matters of phj^sics, apart from 

 mathematics, which has often enabled the cultivators of the former 

 to make steps more than proportionate to their knowledge of the 

 latter. Ptolemy, the great promoter of the old theory, and Coper- 

 nicus, its destroyer, were both mathematicians in a peculiar sense ; 

 Ptolemy being far the more sagacious in questions of pure experi- 

 ment. Their grounds of confidence are mathematical ; and Coper* 

 nicus, in particular, dares to face his own physics (for there is no 

 reason to suppose he was beyond his age in mechanical philosophy) 

 with reasons drawn entirely from probabilities afforded by mathe- 

 matics. 



There is much reason to regret the practice of associating with 

 the names of those who have led the way in great discovery the 

 glory which is due to their followers. The disadvantage is twofold. 

 In the first place, it introduces into the history of science an index 

 error of from one to two centuries ; secondly, those who come to in- 



