136 SPECIAL RESULTS IN THE URANOLOGICAL PORTION 



The detailed character of these statements ( 267 ) would of 

 itself suffice to show how great a stimulus to the considera- 

 tion of highly important questions must have been afforded, 

 by the occurrence of such a phenomenon at a period so 

 brilliant in the history of astronomy. The stimulus was the 

 stronger, because, notwithstanding the above^deseribed 

 general rarity of the appearance of new stars, it happened 

 that European astronomers witnessed phsenomena of this 

 kind three times within the short period of thirty-two years. 

 The importance of star-catalogues, determining with cer- 

 tainty the novelty of such stars, was more and more 

 recognised ; their periodical character, i. e. their reappear- 

 ance after the lapse of several centuries, was discussed ; ( 268 ) 

 and Tycho Brahe even boldly put forth a theory respecting 

 the process of formation of stars from cosmical vapour or 

 nebulosity, which had much analogy with that of the great 

 William HerscheL He believed that the nebulous celestial 

 matter, luminous in the course of its condensation, solidified 

 into fixed stars : " Cceli materiem tenuissimam, ubique 

 nostro visui et planetarum circuitibus perviam, in unum 

 globum condensatain, stellam effingere." He conceived this 

 everywhere-diffused celestial matter to have already a certain 

 degree of condensation in the Milky Way, where its dawning 

 luminosity produced a mild silvery brightness, and this he 

 thought the reason why the new star, like those of 945 and 

 1264, shone forth on the edge of the Milky Way itself (quo 

 factum est quod nova stella in ipso Galaxise margine 

 constiterit) ; and it even seemed possible to recognise the 

 place (the opening, hiatus) from whence the nebulous matter 

 of the Milky Way had been taken. ( 269 ) All this reminds us 

 of the transition of. cosmical vapour into clusters of stars, 



