402 



TEE POPULAR SCIENCE MONTELY.— SUPPLEMENT. 



The details of his cosmical system are, it must be 

 admitted, open to much doubt ; but his design 

 was rather to expose prevalent errors than to 

 build up from the foundations a new structure. 

 The point important to be held in mind is that, 

 forty years before Copernicus was born, Cardinal 

 Cusa clearly apprehended and pointed out, at 

 least in principle, the difference between the real 

 and apparent motions of the heavenly bodies. 

 The same treatise contains some remarkable fore- 

 shadowings of subsequent discoveries, which, al- 

 though conclusions drawn from false premises, 

 show a singular intuition of scientific truth. Un- 

 til Kepler discovered his first law, it was taken 

 to be a necessary and fundamental principle of 

 Nature, that the orbits of all the heavenly bodies 

 were perfect circles. Even Copernicus did not 

 venture to impugn the truth of this axiom, and 

 was consequently compelled to impair the simple 

 beauty of his system by retaining in it some of 

 the rusty machinery of the Ptolemaic scheme. 

 Cardinal Cusa, however, rejected not only uniform 

 circular motion, but also perfect symmetry of 

 figure as inconceivable and impossible in the ex- 

 isting order of things, and maintained that the 

 figure of the earth, although closely approaching 

 sphericity, was not that of a perfect sphere, as 

 well as that its orbit departed to some extent 

 from the perfectly circular form. Another pas- 

 sage shows a close approximation to modern ideas 

 on the subject of the solar constitution : 



" To a spectator on the surface of the sun," 

 he says, " the splendor which appears to us would 

 be invisible, since it contains, as it were, an earth 

 for its central mass, with a circumferential en- 

 velope of light and heat, and between the two an 

 atmosphere of water and clouds and of ambient 

 air." 



A somewhat obscure passage which has been 

 generally considered to refer to the earth's orbi- 

 tal revolution seems to us to point rather to a 

 proper motion of the entire solar system in space 

 — or, as he describes it, round the poles of the 

 world — inferred erroneously from the apparent 

 movement of the stars really caused by preces- 

 sion. This curious book, which attracted much 

 attention in Italy, was printed at Corte Maggiore 

 in 1502 — two years, that is, before Copernicus 

 finally returned to his native land. It is there- 

 fore in the highest degree improbable that it es- 

 caped the notice of one whose faculties were, 

 there is little doubt, already beginning to concen- 

 trate themselves on the subjects mooted by the 

 philosophical cardinal. 



There is abundant evidence that the doctrine 



of the earth's rotation was extensively prevalent 

 in Italy when Copernicus took up his abode there, 

 and Signor Berti has done good service in point- 

 ing out this interesting and hitherto almost ig- 

 nored fact in the history of science. Girolamo 

 Tagliavia, a Calabrese poet, propounded the the- 

 ory in unequivocal terms toward the close cf the 

 fifteenth century; although the assertion of Za- 

 varrone that Copernicus not only saw the poem 

 in which these ideas were expressed, but bor- 

 rowed from it its precise words, rests on no suffi 

 cient evidence, and cannot therefore be admitted 

 to form part of history. In Bologna itself, how- 

 ever, during the residence of Copernicus, the sub- 

 ject was one of common discussion. We hear, 

 for instance, that Codrus Urceus, Professor of 

 Greek and Latin Letters at the university — an 

 eccentric character, who prided himself on the 

 poignancy of his sallies and the piquancy of his 

 wit — was accustomed to treat those who believed 

 in the earth's motion as favorite butts for his 

 satire. 



Somewhat later, probably about 1510, Leo- 

 nardo da Vinci included the notion in his theory 

 of falling bodies, rather as one already admitted 

 than as needing special proof. Some of the opin- 

 ions, indeed, of this miracle of genius are so far 

 in advance of those of his contemporaries as to 

 seem inspirations of prescience far more than in- 

 ferences of ordinary reason, and can therefore 

 hardly be treated as evidence of the common 

 standard of thought in his time. Finally, while 

 Copernicus, in the solitude of Frauenburg, was 

 slowly and laboriously completing his new cos- 

 mical system, another ecclesiastic was revolving 

 similar thoughts at the biilliant court of Ferrara. 

 Celio Calcagnini died in 1541 — tw r o years before 

 the great work of Copernicus saw the light — and 

 his treatise, " Quod Coelum stet, Terra autem 

 moveatur," seems to have been written some 

 years earlier. It is possible, although it does not 

 appear, that some rumors of impending innova- 

 tions in astronomical science may have reached 

 him from Rome, where, in 1533, Widmenstadt 

 expounded the doctrines of Copernicus with much 

 applause to Clement VII. and his court. Cal- 

 cagnini, at any rate, maintains his opinion stoutly, 

 declaring the immobility of the earth to be the 

 doctrine most repugnant to reason of any ever 

 taught by philosophers, and citing sundry an- 

 cient authorities — Hicetas of Syracuse, Herac- 

 lides and Ecphantus — in support of his view. He 

 gives no hint, however, of the earth's orbital 

 motion. Another man, of far higher genius than 

 the Apostolic Prothonotary of Ferrara, was busy 



