COPERNICUS IN ITALY. 



399 



for them we cannot now stop to inquire. Dome- 

 nico Maria No vara combined the duties of Pro- 

 fessor of Astronomy at the university with those 

 of astrologer in ordinary to the Prince of Bologna. 

 Of the innumerable delusions to which mankind 

 has been subject, judicial astrology was perhaps 

 the most universally diffused, and it is difficult to 

 determine whether it should be classed as a 

 sporadic or an infectious disorder — whether it 

 spread from one centre, or sprang up spontane- 

 ously at many points. Like all popular errors, 

 too, it died hard. Only the most daring minds 

 of the fifteenth century, such as Pico della Mi- 

 randola, ventured to assail its principles ; and in 

 the sixteenth and seventeenth, Girolamo Cardano, 

 Giannantonio Magini, and other equally able men 

 of science, were slaves to its influence. If we 

 could imagine Zadkiel's Almanac and Ephemeris 

 edited by the astronomer-royal, we should have 

 a tolerably exact idea of the propwslicons which 

 Novara was, by virtue of his official position, 

 bound to publish at the beginning of every year. 

 To flatter the fortunes of the Bentivogli, and to 

 save the orthodox doctrine of free-will while 

 maintaining in full force the influence of the 

 stars, by which it was felt to be compromised, 

 was the somewhat complicated problem which 

 the court astrologer of Bologna had to solve. 

 His successor, Luca Gaurico, was a less prudent 

 courtier, though a more skillful seer. He predict- 

 ed the fall of the house of Bentivoglio in the be- 

 ginning of the very year (1506) in which, by 'a 

 singular coincidence, it actually took place, and 

 received the usual reward of prophets of evil — 

 imprisonment and torture. Novara was, however, 

 also a diligent laborer in the legitimate field of 

 his profession, and an observation recorded by 

 him in his prognosticon for 1489, although he 

 failed to read its meaning right, is remarkable 

 enough to deserve mention. 



The slow westerly movement which carries 

 the equinoctial points backward through all the 

 zodiacal signs in a period of 25,868 years, al- 

 though retrograde with regard to space, is called 

 precession, because it causes the equinoxes to 

 precede their due time by twenty minutes and 

 nineteen seconds — the amount of difference be- 

 tween the tropical and sidereal years. This grad- 

 ual process of change was known to the Greeks 

 from the time of Hipparchus, and the ancient 

 Hindoo astronomers were able to estimate its an- 

 nual value with a close approach to modern ac- 

 curacy. But the corresponding motion of the 

 earth's axis, the pole of which describes a circle 

 round the pole of the ecliptic in the same long 



period, had not been recognized until Novara, 

 comparing his observations with those of Ptole- 

 my, found that the pole of the heavens — which is 

 nothing more than the vanishing-point of the 

 earth's axis — had considerably changed its place 

 among the stars. Both these variations in celes- 

 tial relations — that of the equinoxes and that of 

 the pole — are in truth but different manifestations 

 of the same fact — the secular tilting of the earth 

 in its orbit, caused by the action of the sun and 

 moon on the protuberant mass at the equator. 

 The error of Novara's inference from his observa- 

 tion — namely, that the celestial pole was slowly 

 approaching the zenith — is now obvious enough; 

 the stability of the earth's axis in the earth itself, 

 and the consequent invariability of the distance 

 between the pole of the heavens and the zenith, 

 or representation in space of some given spot on 

 the earth's surface, being considered one of the 

 cardinal points in astronomical science. 



The intimate relations then customary be- 

 tween master and pupil were maintained un- 

 broken by Copernicus with Novara during the 

 two and a half years of his residence at Bologna. 

 He was sheltered by his roof, sat at his board, 

 shared all his ideas, learned all his methods, and 

 assisted him night after night in the laborious ob- 

 servations and calculations necessary for rede- 

 termining the positions of the 1,022 stars cata- 

 logued by Ptolemy, and estimating anew the in- 

 clination of the equator to the plane of the eclip- 

 tic. The cosmographical opinions of Novara are, 

 therefore, of primary importance in endeavoring 

 to estimate the influences within the reach of 

 which Copernicus came during his stay in Italy. 

 Two Ferrarese writers, Libanori and Barotti, as- 

 sert, although without alleging any definite proof 

 of their statement, that Novara first put forward 

 the theory afterward adopted by Galileo, that 

 the tides were caused by the earth's daily rota- 

 tion; and the question has lately been raised 

 whether his knowledge of the movement of the 

 pole was compatible with a sincere adherence 

 to Ptolemaic doctrines. This, in our opinion, 

 hardly admits of a decisive answer. The crystal 

 spheres of the celestial motions had been found 

 capable of containing so many anomalies, that 

 one additional fact would scarcely have sufficed 

 to shatter them. Moreover, it was not to be ex- 

 pected that the first innovators on the existing 

 system should be those whose emoluments and 

 honors depended en its maintenance. We should 

 be surprised to find railway directors engaged in 

 promoting aeronautic science, or publicans active 

 in the temperance movement; and astronomers 



