Royal Astronomical Society. 529 



was printed from the manuscript furnished by Copernicus himself, 

 there is little doubt about the matter. There are but two passages 

 which bear or can bear upon the question. The first is in the ad 

 lectorem, in which the writer (Osiander, though even Delambre make 

 him Copernicus) asks whether any one acquainted with geometry or 

 optics can receive the Ptolemaic epicycle then used to explain the 

 motion in longitude of Venus ? But the meaning of the allusion to 

 optics is explained in the next sentence, by a reference (and by no 

 means a fortunate one) to the changes of apparent diameter of Venus 

 derived from that epicycle ; changes which, as they made the peri- 

 gean diameter more than four times as great as the apogean, were 

 assured to be falsified by common experience. The second passage 

 is the one on which this discussion must turn. In book i. chap, x., 

 after noting that some had theretofore believed Mercury and Venus to 

 come between the earth and sun, he mentions the difficulty arising 

 from the absence of the remarkable phase, which we now call the 

 transit over the sun's disc. He describes the opinion just mentioned 

 favourably, referring, not to his own view, but to that of those 

 others who had held it. This is not an uncommon idiom : persons 

 advocating an unpopular opinion are very apt to describe the main- 

 tainers of it in the third person, though themselves be of the number. 

 But when he comes to describe what he takes to be the necessary 

 consequence of the opinion, he lapses into the first person as fol- 

 lows : — " Non ergo fatemur in stellis opacitatem esse aliquam lunari 

 similem, sed vel proprio lumine, vel solari totis imbutas corporibus 

 fulgere, et idcirco solem non impediri " 



These are the words of the first edition (Nuremberg, 1543)* 

 That Copernicus could have answered any objection, either by word 

 or writing, is impossible, since he drew his last breath within a few 

 hours of the time when, not able to open it from weakness, he saw 

 the first printed copy. The second edition (Basle, 1566) is usually 

 said to have been edited by Rheticus. The reason of this is that the 

 name of Rheticus appears in the title-page. But this appearance 

 only arises from the Narratio, &c. of Rheticus being added to the 

 edition ; and it is only the description of this edition which brings 

 Rheticus into the title-page. There is no mark whatever of his 

 having been the editor ; and as the work was printed at Basle, where 

 I cannot find that Rheticus ever sojourned, and as the latter was 

 deeply engaged at the time in his enormous trigonometrical calcu- 

 lation, some proof of his editorship must be given before it is ad- 

 mitted. As the point is of importance, I will notice, that unless 

 Rheticus had made some stay at Basle, it is very unlikely he should 

 have edited a work printed there. He did not edite the first edition, 

 only because it was found convenient to print it at Nuremberg in- 

 stead of at Wittemberg ; and it was accordingly entrusted to Osiander. 

 Now, if ever there were a connexion between two men, and between 

 one of them and the book of the other, which made it desirable and 

 even necessary that the first should edite the second, it was the case 

 of Rheticus and the first editio.n of the De Revolutionibus, &c. ; and 

 yet no arrangement could be made by which the sheets printed at 



Phil. Mag, S. 3. No. 21 1 . Suppl. Vol. 3 1 . 2 M 



