154 cosmos. 



itself a proof of the interest which this natural phenomenon 

 could not fail to awaken, by calling forth many important 

 questions, in an epoch so brilliant in the history of astronomy. 

 For (notwithstanding the general rarity of the appearance of 

 new stars) similar phenomena, accidentally crowded togeth- 

 er within the short space of thirty-two years, were thrice re- 

 peated within the observation of European astronomers, and 

 consequently served to heighten the excitement. The im- 

 portance of star catalogues, for ascertaining the date of the 

 sudden appearance of any star, was more and more recog- 

 nized ; the periodicity^ (their reappearance after many cen- 

 turies) was discussed ; and Tycho Brahe himself boldly ad- 

 vanced a theory of the process by which stars might be 

 formed and molded out of cosmical vapor, which presents 

 many points of resemblance to that of the great William 

 Herschel. He was of opinion that the vapory celestial mat- 

 ter, which becomes luminous as it condenses, conglomerates 

 into fixed stars : " Coeli materiam tenuissimam, ubique nostro 

 visui et planetarum circuitibus perviam, in unum globum con- 

 densatam, stellam effingere." This celestial matter, which 

 is universally dispersed through space, has already attained 

 to a certain degree of condensation in the Milky Way, which 

 glimmers with a soft silvery brightness. Accordingly, the 

 place of the new star, as well as of those which became sud- 

 denly visible in 945 and 1264, was on the very edge of the 

 Milky Way (quo factum est quod nova stella in ipso galaxiaB 

 margine constiterit). Indeed, some went so far as to believe 

 that they could discern the very spot (the opening or hiatus) 

 whence the nebulous celestial matter had been drawn from 

 the Milky Way.f All this reminds one of the theories of 



the phenomenon of the new star by a concourse of country people, 

 need not, therefore, be here noticed. 



* Cardanus, in his controversy with Tycho Brahe, went back to the 

 star of the Magi, which, as he pretended, was identical with the star 

 of 1572. Ideler, arguing from his own calculations of the conjunctions 

 of Saturn with Jupiter, and from similar conjectures advanced by Kep- 

 ler on the appearance of the new star in Ophiucus in 1604, supposes 

 that the star of the Magi, through a confusion of aoTqp with uorpov, 

 which is so frequent, was not a single great star, but a remarkable con- 

 junction of stars — the close approximation of two brightly-shining plan- 

 ets at a distance of less than a diameter of the moon. — Tychonis Pro- 

 gymnasmata, p. 324-330 ; contrast with Ideler, Handbuch der Mathe- 

 matischen und Technischen Chronologie, bd. ii., s. 399-407. 



t Progymn., p. 324-330. Tycho Brahe, in his theory of the forma- 

 tion of new stars from the Cosmical vapor of the Milky Way, builds 

 much on the remarkable passages of Aristotle on the connection of the 



